Sample records for pulse width modulation

  1. Wireline equalization using pulse-width modulation

    Schrader, J.H.R.; Klumperink, Eric A.M.; Visschers, J.L.; Nauta, Bram


    Abstract-High-speed data links over copper cables can be effectively equalized using pulse-width modulation (PWM) pre-emphasis. This provides an alternative to the usual 2-tap FIR filters. The use of PWM pre-emphasis allows a channel loss at the Nyquist frequency of ~30dB, compared to ~20dB for a

  2. Global synchronization of parallel processors using clock pulse width modulation

    Chen, Dong; Ellavsky, Matthew R.; Franke, Ross L.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Jeanson, Mark J.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Littrell, Daniel; Ohmacht, Martin; Reed, Don D.; Schenck, Brandon E.; Swetz, Richard A.


    A circuit generates a global clock signal with a pulse width modification to synchronize processors in a parallel computing system. The circuit may include a hardware module and a clock splitter. The hardware module may generate a clock signal and performs a pulse width modification on the clock signal. The pulse width modification changes a pulse width within a clock period in the clock signal. The clock splitter may distribute the pulse width modified clock signal to a plurality of processors in the parallel computing system.

  3. Analysis of Pulse Modulated Control Systems (Ⅲ) Stability of Systems with Pulse Frequency Modulation and Systems with Combined Pulse Frequency and Pulse Width Modulation



    Sufficient conditions for finite pulse stability of interconnected systems with combined pulse frequency and pulse width modulation are developed in this paper using a direct method. The stability criteria established provide upper bounds on the number of pulses emitted by each modulator. The results are also applicable to those systems which contain a finite number of pulse frequency modulators and a finite number of combined pulse frequency and pulse width modulators

  4. Energy detection UWB system based on pulse width modulation

    Song Cui


    Full Text Available A new energy detection ultra-wideband system based on pulse width modulation is proposed. The bit error rate (BER performance of this new system is slightly worst than that of a pulse position modulation (PPM system in additive white Gaussian noise channels. In multipath channels, this system does not suffer from cross-modulation interference as PPM, so it can achieve better BER performance than PPM when cross-modulation interference occurs. In addition, when synchronisation errors occur, this system is more robust than PPM.

  5. Pulse-Width-Modulating Driver for Brushless dc Motor

    Salomon, Phil M.


    High-current pulse-width-modulating driver for brushless dc motor features optical coupling of timing signals from low-current control circuitry to high-current motor-driving circuitry. Provides high electrical isolation of motor-power supply, helping to prevent fast, high-current motor-driving pulses from being coupled through power supplies into control circuitry, where they interfere with low-current control signals.

  6. Pulse-width modulated DC-DC power converters

    Kazimierczuk, Marian K


    This book studies switch-mode power supplies (SMPS) in great detail. This type of converter changes an unregulated DC voltage into a high-frequency pulse-width modulated (PWM) voltage controlled by varying the duty cycle, then changes the PWM AC voltage to a regulated DC voltage at a high efficiency by rectification and filtering. Used to supply electronic circuits, this converter saves energy and space in the overall system. With concept-orientated explanations, this book offers state-of-the-art SMPS technology and promotes an understanding of the principle operations of PWM converters,

  7. Fractal Reference Signals in Pulse-Width Modulation

    Lurie, Boris; Lurie, Helen


    A report proposes the use of waveforms having fractal shapes reminiscent of sawteeth (in contradistinction to conventional regular sawtooth waveforms) as reference signals for pulse-width modulation in control systems for thrusters of spacecraft flying in formation. Fractal reference signals may also be attractive in some terrestrial control systems - especially those in which pulse-width modulation is used for precise control of electric motors. The report asserts that the use of fractal reference signals would enable the synchronous control of several variables of a spacecraft formation, such that consumption of propellant would be minimized, intervals between thruster firings would be long (as preferred for performing scientific observations), and delays in controlling large-thrust maneuvers for retargeting would be minimized. The report further asserts that whereas different controllers would be needed for different modes of operation if conventional pulsewidth modulation were used, the use of fractal reference signals would enable the same controller to function nearly optimally in all regimes of operation, so that only this one controller would be needed.

  8. Compact Pulse Width Modulation Circuitry for Silicon Photomultiplier Readout

    Bieniosek, M F; Olcott, P D; Levin, C S


    The adoption of solid state photo-detectors for positron emission tomography (PET) system design and the interest in 3D interaction information from PET detectors has lead to an increasing number of readout channels in PET systems. To handle these additional readout channels, PET readout electronics should be simplified to reduce the power consumption, cost, and size of the electronics for a single channel. Pulse width modulation (PWM), where detector pulses are converted to digital pulses with width proportional to the detected photon energy, promises to simplify PET readout by converting the signals to digital form at the beginning of the processing chain, and allowing a single time-to-digital converter to perform the data acquisition for many channels rather than routing many analog channels and digitizing in the back end. Integrator based PWM systems, also known as charge-to-time converters (QTC), are especially compact, reducing the front-end electronics to an op-amp integrator with a resistor discharge, and a comparator. QTCs, however, have a long dead-time during which dark count noise is integrated, reducing the output signal to noise ratio. This work presents a QTC based PWM circuit with a gated integrator that shows performance improvements over existing QTC based PWM. By opening and closing an analog switch on the input of the integrator, the circuit can be controlled to integrate only the portions of the signal with a high signal-to-noise ratio. It also allows for multiplexing different detectors into the same PWM circuit while avoiding uncorrelated noise propagation between photodetector channels. Four gated integrator PWM circuits were built to readout the spatial channels of two position sensitive solid state photomultiplier (PS-SSPM). Results show a 4×4 array 0.9mm×0.9mm×15mm of LYSO crystals being identified on the 5mm×5mm PS-SSPM at room temperature with no degradation for 2-fold multiplexing. In principle, much larger multiplexing ratios are

  9. A New Selective Harmonic Elimination Pulse- Width and Amplitude Modulation (SHEPWAM) for Drive Applications

    Ghoreishy, Hoda; Varjani, Ali Yazdian; Mohamadian, Mustafa


    Compared to the conventional selective harmonic elimination-pulse width modulation (SHE-PWM), the selective harmonic elimination-pulse width and amplitude modulation (SHE-PWAM) control strategy results in significant improvements in the performance of CHB inverters. This fact is due to considerin...

  10. Pulse width tunable subpicosecond pulse generation from an actively modelocked monolithic MQW laser/MQW electroabsorption modulator

    Takada, A.; Sato, K.; Saruwatari, M.; Yamamoto, M.


    Actively modelocked pulses are generated from a 1.59 micron MQW laser integrated with an MQW electroabsorption modulator driven at the monolithic cavity frequency. The pulse width is controlled from 39 ps to 0.55 ps by changing the inverse bias voltage applied to the electroabsorption modulator and by linear pulse compression using a fiber.

  11. Total Ionizing Dose Test Report for the UC1823A Pulse Width Modulator

    Chen, Dakai; Forney, James


    The purpose of this study is to examine the total ionizing dose susceptibility for the UC1823A pulse width modulator manufactured by Texas Instruments, Inc. The part is suspected to be vulnerable to enhanced low dose rate sensitivity (ELDRS).

  12. Comparative study of SVPWM (space vector pulse width modulation) & SPWM (sinusoidal pulse width modulation) based three phase voltage source inverters for variable speed drive

    Ahmed, Waheed; Usman Ali, Syed M.


    We have performed comparative studies of Space Vector Pulse Width Modulation (SVPWM) and Sinusoidal Pulse Width Modulation (SPWM) techniques utilizing MATLAB tools. During these investigations, we carried out intensive simulations, comprehensively analyzed the obtained results and compared the harmonic density, power factor (PF), & switching losses of SVPWM and SPWM. It has been observed during investigations that if the switching frequency is high then losses due to harmonics are negligible, thus based on obtained results we suggested that the SVPWM technique is a more reliable solution. Because SVPWM utilizes DC bus voltage more efficiently, generates less Total Harmonic Distortion (THD) and has higher output quality it provides flexible control of output voltage and output frequency for Variable Speed Drive (VSD).

  13. Current mode pulse width modulation/pulse position modulation based on phase lock loop

    Wisartpong, Pichet; Silaphan, Vorapong; Kurutach, Sunee; Wardkein, Paramote


    In this paper, the fully integrated CMOS current mode PLL with current input injects at the place of input or output of the loop filter without summing amplifier circuit. It functions as PPM and PWM circuit is present. In addition, its frequency response is an analysis which electronic tuning BPF and LPF are obtained. The proposed circuit has been designed with 0.18 μm CMOS technology. The simulation results of this circuit can be operated at 2.5 V supply voltage, at center frequency 100 MHz. The linear range of input current can be adjusted from 43 μA to 109 μA, and the corresponding duty cycle of pulse width output is from 93% to 16% and the normalized pulse position is from 0.93 to 0.16. The power dissipation of this circuit is 4.68 mW with the total chip area is 28 μm × 60 μm.

  14. Analysis of Symmetrical Pulse Width Modulation Strategies for Matrix Converters

    Larsen, K.B.; Jorgensen, A.H.; Helle, Lars


    This paper presents a new and easy way to understand the derivation of the modulation functions for matrix converters. It is shown how the duty cycles can be calculated using techniques known from the back-to-back (B2B) voltage source inverter (VSI), thus making the subject accessible to people...... with prior knowledge in standard drives. A new modulation strategy is presented minimizing harmonic distortion compared to the standard double-sided space vector modulation for matrix converters. An improvement to an existing modulator is also presented where the proposed modification improves the harmonic...... performance. The strategies are compared both analytically and by the use of both simulations and measurements on a 12 kW matrix converter prototype.It is found that the proposed modulator has superior performance compared to modulators with equal switching frequencies and an equal number of switchings....

  15. Optimized Pulse Width Modulation for transformerless active-NPC inverters

    Achilladelis, Nikolaos; Koutroulis, Eftichios; Blaabjerg, Frede


    The transformerless DC/AC inverter topologies are employed in Photovoltaic systems in order to improve the power conversion efficiency, power density and cost. The Active-Neutral Point Clamped (Active-NPC) transformerless inverters have the advantage of achieving better thermal balance among...... their power semiconductors. In this paper, a new modulation technique is proposed for optimally controlling the power switches employed in transformerless Active-NPC inverters. The design results demonstrate that compared to the existing PWM strategies, using the proposed method results in lower total power...

  16. Equalization of Skin Effect Loss Dominated Channels using Pulse-Width Modulation (PWM) Pre-Emphasis

    Schrader, J.H.R.; Klumperink, Eric A.M.; Visschers, J.L.; Nauta, Bram

    A digital transmitter pre-emphasis technique is presented that is based on pulse-width modulation, instead of finite impulse response (FIR) filtering. The technique fits well to future high-speed low-voltage CMOS processes. A 0.13μm CMOS transmitter achieves more than 5Gb/s (2-PAM) over 25m of

  17. Pulse Width Modulator Controller Design for a Brushless DC Motor Position Servo.


    performance. This thesis involves computer aided design of a functionally robust brushless dc motor position controller using pulse width modulation...Recent interest in positioning cruise missile flight control surfaces using electromechanical actuation has prompted a detailed study of brushless dc ... motor performance in such an application. While the superior response characteristics of these electronically commutated motors are particularly well

  18. Red and blue pulse timing control for pulse width modulation light dimming of light emitting diodes for plant cultivation.

    Shimada, Aoi; Taniguchi, Yoshio


    A pulse width modulation (PWM) light dimming system containing red and blue light emitting diodes was designed and constructed. Cultivation of the plant Arabidopsis thaliana under various light dimming wave patterns was compared. Control of the pulse timing (phase of wave pattern) between red and blue light in PWM light dimming was examined. Different plant growth was obtained by changing the phase of red and blue pulses. Pulse timing control of PWM light dimming for plant cultivation has the potential to act as a method for probing photosynthesis. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. Variable Voltage Source Inverter with controlled frequency spectrum based on Random Pulse Width Modulation

    Muhammad Farrukh Yaqub


    Full Text Available This paper presents a new method for single phase variable voltage inverter based on Random Pulse Width Modulation. In Random Pulse Width Modulation based inverter, the frequency spectrum of the output current and voltage waveforms becomes continuous because of the randomization of the switching function of the devices controlling the output voltages. This paper establishes a theory that if the distributions of the random numbers generated by the random source are kept within certain limit with respect to the peak value of reference sinusoidal waveform, the frequency spectrum can be controlled. On the basis of the results, a novel drive using variable tap changing transformer (optional and adaptive random number generator, to control the ratio between the numbers generated by the random source and the reference waveform has been suggested that will guarantee a better power quality profile for a broad range of output voltages.

  20. Isolated PDM and PWM DC-AC SICAMs[Pulse Density Modulated; Pulse Width Modulated

    Ljusev, P.


    In this report a class of isolated PDM and PWM DC-AC SICAMs is described, which introduce the audio reference only in the output stage. AC-DC power supply is implemented in its simplest form: diode rectifier followed by a medium-size charge-storage capacitor. Isolation from the AC mains is achieved using a high frequency (HF) transformer, receiving the HF voltage pulses from the input 'inverter' stage and transferring them to the output 'rectifier+inverter' stage, which can use either PDM or PWM. The latter stage is then interfaced to the load using an output low-pass filter. Each of the dedicated stages is discussed in detail. Measurements on the master/slave PWM DC-AC SICAM prototype are presented to help benchmarking the performance of this class of SICAMs and identify the advantages and drawbacks. (au)

  1. Dynamic Voltage Restorer Based on Space Vector Pulse Width Modulation Technique

    B.N S P Venkatesh


    Full Text Available Power Quality problems encompass a wide range of disturbances such as voltage sags, swells, flicker,harmonics distortion and interruptions. The strategic deployment of custom power devices has been proposed asone of the means to protect sensitive loads from power quality problems such as voltage sags and swells. The Dynamic Voltage Restorer (DVR is a power electronic device that is used to inject 3-phase voltage in series and in synchronism with the distribution feeder voltages in order to compensate voltage sag and similarly itreacts quickly to inject the appropriate voltage component (negative voltage magnitude in order to compensate voltage swell. The principal component of the DVR is a voltage source inverter that generates three phase voltages and provides the voltage support to a sensitive load during voltage sags and swells. Pulse Width Modulation Technique is very critical for proper control of DVR. Sinusoidal Pulse Width Modulation (SPWM and Space Vector Pulse Width Modulation (SVPWM control techniques are used for controlling the DVR. Inthis work, the operation of DVR is presented and the control technique used for voltage source inverter is Space Vector PWM technique. Space vector PWM can utilize the better dc voltage and generates the fewer harmonic in inverter output voltage than Sinusoidal PWM technique. This work describes the DVR based on Space Vector PWM which provides voltage support to sensitive loads and is simulated by using MATLAB/SIMULINK. Simulation results show that the control approach is able to compensate for any type of voltage sags and swells.

  2. Prototype of Pulse Width Modulation Generator Based on Timer 555 and IRF 40

    Wahyu Sapto Aji


    Full Text Available In many applications such of DC motor speed regulation commonly needed DC to DC voltage conversion. The method that frequently use for DC to DC conversion is using chopper circuit. In chopper circuit a DC voltage source being chopped at constant frequency but with variable duty cycle (in this case it’s called as Pulse Width Modulation, PWM. In this research a circuit chopper has been design successfully. The circuit uses 555 timer IC as PWM pulse shaper and IRF 40 power Mosfet as switch device. This circuit prototype successfully tested to drive a 12 watt DC motor at 1200 rpm with voltage at 12 V.

  3. Sliding mode pulse-width modulation technique for direct torque controlled induction motor drive

    Bounadja, M.; Belarbi, A. W.; Belmadani, B.


    This paper presents a novel pulse-width modulation technique based sliding mode approach for direct torque control of an induction machine drive. Methodology begins with a sliding mode control of machine's torque and stator flux to generate the reference voltage vector and to reduce parameters sensitivity. Then, the switching control of the three-phase inverter is developed using sliding mode concept to make the system tracking reference voltage inputs. The main features of the proposed methodologies are the high tracking accuracy and the much easier implementation compared to the space vector modulation. Simulations are carried out to confirm the effectiveness of proposed control algorithms.

  4. Attitude Control of Satellite With Pulse-Width Pulse- Frequency (PWPF Modulator Using Generalized Incremental Predictive Control

    Ehsan Chegeni


    Full Text Available In this paper, we use generalized incremental predictive control (GIPC to stabilize attitude of satellite. We compare Generalized Predictive Control (GPC with GIPC algorithm and present that GIPC has better performance. The three-axis attitude control systems are activated in pulse mode. Consequently, a modulation of the torque command is compelling in order to avoid high non-linear control action. This work considers the Pulse-Width Pulse-Frequency modulator (PWPF is composed of a Schmitt trigger, a first order filter, and a feedback loop. PWPF modulator has several advantages over classical bang-bang controllers such as close to linear operation, high accuracy, and reduced propellant consumption

  5. Sensorless Modeling of Varying Pulse Width Modulator Resolutions in Three-Phase Induction Motors

    Marko, Matthew David; Shevach, Glenn


    A sensorless algorithm was developed to predict rotor speeds in an electric three-phase induction motor. This sensorless model requires a measurement of the stator currents and voltages, and the rotor speed is predicted accurately without any mechanical measurement of the rotor speed. A model of an electric vehicle undergoing acceleration was built, and the sensorless prediction of the simulation rotor speed was determined to be robust even in the presence of fluctuating motor parameters and significant sensor errors. Studies were conducted for varying pulse width modulator resolutions, and the sensorless model was accurate for all resolutions of sinusoidal voltage functions. PMID:28076418

  6. Laboratory manual for pulse-width modulated DC-DC power converters

    Kazimierczuk, Marian K


    Designed to complement a range of power electronics study resources, this unique lab manual helps students to gain a deep understanding of the operation, modeling, analysis, design, and performance of pulse-width modulated (PWM) DC-DC power converters.  Exercises focus on three essential areas of power electronics: open-loop power stages; small-signal modeling, design of feedback loops and PWM DC-DC converter control schemes; and semiconductor devices such as silicon, silicon carbide and gallium nitride. Meeting the standards required by industrial employers, the lab manual combines program

  7. DC link current simulation of voltage source inverter with random space vector pulse width modulation

    Chen Guoqiang


    Full Text Available Aiming at analysis complexity, a simulation model is built and presented to analyze and demonstrate the characteristics of the direct current (DC link current of the three-phase two-level inverter with the random space vector pulse width modulation (SVPWM strategy. The developing procedure and key subsystems of the simulation model are given in detail. Several experiments are done using the simulation model. The results verify the efficiency and convenience of the simulation model and show that the random SVPWM scheme, especially the random switching frequency scheme, can efficiently suppress the harmonic peaks of the DC link current.

  8. Improved Switching Performance Analysis of Space Vector Pulse Width Modulation on Field Programmable Gate Array

    Nagalingam RAJESWARAN


    Full Text Available Nowadays VLSI (Very Large Scale Integration technology is being successfully implemented by using Pulse Width Modulation (PWM in applications like power electronics and drives. The main problems in PWM viz. harmonic distortion and switching speed are overcome by implementing the Space-Vector PWM (SVPWM technique by using the Xilinx tool VHDL (Verilog High Speed Integrated Circuit (VHSIC Hardware Description Language and tested in programmable Integrated Circuits of Field Programmable Gate Array (FPGA. The results are provided along with simulation analysis in terms of hardware utilization and schematic, power report, computing time and usage of memory.

  9. Enhancement of mosquito trapping efficiency by using pulse width modulated light emitting diodes

    Liu, Yu-Nan; Liu, Yu-Jen; Chen, Yi-Chian; Ma, Hsin-Yi; Lee, Hsiao-Yi


    In this study, a light-driving bug zapper is presented for well controlling the diseases brought by insects, such as mosquitoes. In order to have the device efficient to trap the insect pests in off-grid areas, pulse width modulated light emitting diodes (PWM-LED) combined with a solar power module are proposed and implemented. With specific PWM electric signals to drive the LED, it is found that no matter what the ability of catching insects or the consumed power efficiency can be enhanced thus. It is demonstrated that 40% of the UV LED consumed power and 25.9% of the total load power consumption can be saved, and the trapped mosquitoes are about 250% increased when the PWM method is applied in the bug zapper experiments.

  10. Controlling DC-DC converters by chaos-based pulse width modulation to reduce EMI

    Li Hong [Department of Mathematics and Computer Science, FernUniversitaet in Hagen, 58084 Hagen (Germany)], E-mail:; Zhang Bo [School of Electric Power, South China University of Technology, Guangzhou (China); Li Zhong; Halang, Wolfgang A. [Department of Mathematics and Computer Science, FernUniversitaet in Hagen, 58084 Hagen (Germany); Chen Guanrong [Department of Electronic Engineering, City University of Hong Kong, Hong Kong (China)


    In this paper, periodic and chaotic behaviors of DC-DC converters under certain parametric conditions are simulated, experimentally verified, and analyzed. Motivated by the work of J.H.B. Deane and D.C. Hamill in 1996, where chaotic phenomena are useful in suppressing electromagnetic interference (EMI) by adjusting the parameters of the DC-DC converter and making it operate in chaos, a chaos-based pulse width modulation (CPWM) is proposed to distribute the harmonics of the DC-DC converters continuously and evenly over a wide frequency range, thereby reducing the EMI. The output waves and spectral properties of the EMI are simulated and analyzed as the carrier frequency or amplitude changes with regard to different chaotic maps. Simulation and experimental results are given to illustrate the effectiveness of the proposed CPWM, which provides a good example of applying chaos theory in engineering practice.

  11. Voltage Sag Mitigation Using Pulse Width Modulation Switched Autotransformer through Matlab Simulation

    P. Shyam Kiran


    Full Text Available In this paper, a new voltage sag compensator for critical loads in electrical distribution system discussed. The proposed scheme employs a Pulse width modulation ac-ac converter along with a auto transformer. During a disturbance such as voltage sag, the proposed scheme supplies the missing voltage and helps in maintaining the rated voltage at the terminals of the critical load. Under normal condition the approach work in bypass mode and delivering utility power directly to load. The proposed system has less number of switching devices and has good compensating capability in comparison to commonly used compensators. Simulation analysis of three-phase compensator is performed in MATLAB/SIMULINK and performance analysis of the system is presented for various levels of sag and swell.



    A switch mode pulse width modulated DC-DC power converter comprises at least one first electronic circuit on a input side (1) and a second electronic circuit on a output side (2). The input side (1) and the output side (2) are coupled via at least two power transformers (T1, T2). Each power...... transformer (T1, T2) comprises a first winding (T1a, T2a) arranged in a input side converter stage (3, 4) on the input side (1) and a second winding (T1 b, T2b) arranged in a output side converter stage (5) on the output side (2), and each of the windings (T1a, T1 b, T2a, T2b) has a first end and a second end...

  13. Harmonics Reduction of Multilevel Inverter Drive Using Sine Carrier Pulse Width Modulation Techniques

    S. Ebanezar Pravin


    Full Text Available The main objective of this paper is to control the speed of an induction motor by using seven level diode clamped multilevel inverter and improve the high quality sinusoidal output voltage with reduced harmonics. The presented scheme for diode clamped multilevel inverter is sine carrier Pulse Width Modulation control. An open loop speed control can be achieved by using V/ƒ method. This method can be implemented by changing the supply voltage and frequency applied to the three phase induction motor at constant ratio. The presented system is an effective replacement for the conventional method which has high switching losses, its result ends in a poor drive performance. The simulation result portrays the effective control in the motor speed and an enhanced drive performance through reduction in total harmonic distortion (THD. The effectiveness of the system is verified through simulation using PSIM6.1 Simulink package.

  14. Space Vector Pulse Width Modulation Strategy for Single-Phase Three-Level CIC T-source Inverter

    Shults, Tatiana E.; Husev, Oleksandr O.; Blaabjerg, Frede


    This paper presents a novel space vector pulse-width modulation strategy for a single-phase three-level buck-boost inverter based on an impedance-source network. The case study system is based on T-source inverter with continuous input current. To demonstrate the improved performance of the inver......This paper presents a novel space vector pulse-width modulation strategy for a single-phase three-level buck-boost inverter based on an impedance-source network. The case study system is based on T-source inverter with continuous input current. To demonstrate the improved performance...... of the inverter, the strategy was compared the traditional pulse-width modulation. It is shown that the approach proposed has fewer switching states and does not suffer from neutral point misbalance....

  15. Evaluation of functional reliability indices for DC-link capacitors in pulse-width modulation converters

    Gorpinich Alexander


    Full Text Available The impact of kHz range harmonics on the power losses, thermal stress, and lifetime reduction of the dc-link capacitors in pulse-width modulation (PWM converters was investigated. Expressions to evaluate the mean time to failure, survival probability, and unavailability of aging failure for dc-link capacitors are presented. The dc-link capacitors failures due to accelerated insulation aging were modeled using Weibull and normal distribution. A case study with the Siemens SINAMICS S120 frequency converter for driving of rolling mill leveler shows that the failures of motor modules due to breakdown of electrolytic dc-link capacitors registered for the time frame from May 2012 to October 2012 can be caused by the increased ambient temperature and additional heating due to high-frequency components of the ripple current. As a possible solution to improve reliability of motor modules, the four AVX FFVE4I0227K film capacitors instead of nine EPCOS B43564 electrolytic capacitors in dc-link were recommended.

  16. Pulse width and height modulation for multi-level resistance in bi-layer TaOx based RRAM

    Alamgir, Zahiruddin; Beckmann, Karsten; Holt, Joshua; Cady, Nathaniel C.


    Mutli-level switching in resistive memory devices enables a wide range of computational paradigms, including neuromorphic and cognitive computing. To this end, we have developed a bi-layer tantalum oxide based resistive random access memory device using Hf as the oxygen exchange layer. Multiple, discrete resistance levels were achieved by modulating the RESET pulse width and height, ranging from 2 kΩ to several MΩ. For a fixed pulse height, OFF state resistance was found to increase gradually with the increase in the pulse width, whereas for a fixed pulse width, the increase in the pulse height resulted in drastic changes in resistance. Resistive switching in these devices transitioned from Schottky emission in the OFF state to tunneling based conduction in the ON state, based on I-V curve fitting and temperature dependent current measurements. These devices also demonstrated endurance of more than 108 cycles with a satisfactory Roff/Ron ratio and retention greater than 104 s.

  17. Implementations of artificial neural networks using current-mode pulse width modulation technique.

    El-Masry, E I; Yang, H K; Yakout, M A


    The use of a current-mode pulse width modulation (CM-PWM) technique to implement analog artificial neural networks (ANNs) is presented. This technique can be used to efficiently implement the weighted summation operation (WSO) that are required in the realization of a general ANN. The sigmoidal transformation is inherently performed by the nonlinear transconductance amplifier, which is a key component in the current integrator used in the realization of WSO. The CM-PWM implementation results in a minimum silicon area, and therefore is suitable for very large scale neural systems. Other pronounced features of the CM-PWM implementation are its easy programmability, electronically adjustable gains of neurons, and modular structures. In this paper, all the current-mode CMOS circuits (building blocks) required for the realization of CM-PWM ANNs are presented and simulated. Four modules for modular design of ANNs are introduced. Also, it is shown that the CM-PWM technique is an efficient method for implementing discrete-time cellular neural networks (DT-CNNs). Two application examples are given: a winner-take-all circuit and a connected component detector.

  18. Control Scheme of Z-Source Inverter Based BLDC Motor Drive System Using Modified Pulse Width Modulation Techniq

    S. Suresh Kumar,


    Full Text Available A modified pulse width modulation technique for Z-source inverter based BLDC motor is proposed and analyzed in this project.The Z-source inverter can be used as Buck/Boost converter with lower cost and high efficiency. BLDC motors are used in electric vehicles where portability and efficiency are required. This drive system provides advantages of both BLDC motors and Z-source inverter, and can be used in fuel cell system and other adjustable speed drive application. In this project principle of modified pulse width modulation technique is implemented and simulated. The model of a three phase Z-source inverter has been discussed based on modified pulse with modulation technique. The simulation of Z-source inverter based BLDC motor is done using the MATLAB/SIMULINK.

  19. Pulse width modulation-based temperature tracking for feedback control of a shape memory alloy actuator.

    Ayvali, Elif; Desai, Jaydev P


    This work presents a temperature-feedback approach to control the radius of curvature of an arc-shaped shape memory alloy (SMA) wire. The nonlinear properties of the SMA such as phase transformation and its dependence on temperature and stress make SMA actuators difficult to control. Tracking a desired trajectory is more challenging than controlling just the position of the SMA actuator since the desired path is continuously changing. Consequently, tracking the desired strain directly or tracking the parameters such as temperature and electrical resistance that are related to strain with a model is a challenging task. Temperature-feedback is an attractive approach when direct measurement of strain is not practical. Pulse width modulation (PWM) is an effective method for SMA actuation and it can be used along with a compensator to control the temperature of the SMA. Using the constitutive model of the SMA, the desired temperature profile can be obtained for a given strain trajectory. A PWM-based nonlinear PID controller with a feed-forward heat transfer model is proposed to use temperature-feedback for tracking a desired temperature trajectory. The proposed controller is used during the heating phase of the SMA actuator. The controller proves to be effective in tracking step-wise and continuous trajectories.


    Hiram Ponce


    Full Text Available Most of machine-operated industrial processes implement electric machinery as their work sources, implying the necessary improvement of control techniques and power electronics drivers. Many years have passed since the control conflicts related to induction motors have been overcome through torque-flux control techniques so their advantages over direct current motors have made them to be the most common electric actuator found behind industrial automation. In fact, induction motors can be easily operated using a Direct Torque Control (DTC. Since, it is based on a hysteresis control of the torque and flux errors, its performance is characterized by a quick reaching of the set point, but also a high ripple on both torque and flux. In order to enhance that technique, this study introduces a novel hybrid fuzzy controller with artificial hydrocarbon networks (FMC that is used in a Space Vector Pulse Width Modulation (SVPWM technique, so-called FMC-SVPWM-DTC. In fact, this study describes the proposal and its design method. Experimental results over a velocity-torque cascade topology proved that the proposed FMC-SVPWM-DTC responses highly effective almost suppressing rippling in torque and flux. It also performed a faster speed response than in a conventional DTC. In that sense, the proposed FMC-SVPWM-DTC can be used an alternative approach for controlling induction motors.

  1. Analysis and Minimization of Output Current Ripple for Discontinuous Pulse-Width Modulation Techniques in Three-Phase Inverters

    Gabriele Grandi


    Full Text Available This paper gives the complete analysis of the output current ripple in three-phase voltage source inverters considering the different discontinuous pulse-width modulation (DPWM strategies. In particular, peak-to-peak current ripple amplitude is analytically evaluated over the fundamental period and compared among the most used DPWMs, including positive and negative clamped (DPWM+ and DPWM−, and the four possible combinations between them, usually named as DPWM0, DPWM1, DPWM2, and DPWM3. The maximum and the average values of peak-to-peak current ripple are estimated, and a simple method to correlate the ripple envelope with the ripple rms is proposed and verified. Furthermore, all the results obtained by DPWMs are compared to the centered pulse-width modulation (CPWM, equivalent to the space vector modulation to identify the optimal pulse-width modulation (PWM strategy as a function of the modulation index, taking into account the different average switching frequency. In this way, the PWM technique providing for the minimum output current ripple is identified over the whole modulation range. The analytical developments and the main results are experimentally verified by current ripple measurements with a three-phase PWM inverter prototype supplying an induction motor load.

  2. Liquid mixing enhanced by pulse width modulation in a Y-shaped jet configuration

    Xia, Qingfeng; Zhong, Shan


    In this paper, mixing between two fluid streams, which are injected into a planar mixing channel via a Y-shaped confluence section at the same volume flow rate, is studied experimentally. The injection of the two fluid streams is controlled by two separate solenoid valves, which are operated with a phase difference of 180°, using pulse width modulation. The experiments are conducted using water at a mean Reynolds number between 83 and 250, a range of pulsation frequencies and two duty cycles (25 and 50%). Both particle-image velocimetry and planar laser-induced fluorescence technique are used to visualize the flow patterns and to quantify the mixing degree in the mixing channel. This experiment shows that the pulsation of each jet produces vortical structures, which promotes mixing via vortex entrainment and vortex breakup, and at the same time the mixing is also greatly enhanced by sequential segmentation produced by a 180° out-of-phase pulsation of the two jets. This mixing enhancement method is effective at a Reynolds number greater than 125 with a mixing degree of 0.9 being achieved. For the Reynolds numbers studied in the present experiments, an optimal frequency exists, which corresponds to a Strouhal number in the range of 0.5-2. Furthermore, at a given mean Reynolds number a lower duty cycle is found to produce a better mixing due to the resultant higher instantaneous Reynolds number in the jet flow. It is also found that pulsation of only one jet can produce a similar mixing effect.

  3. PSCAD modeling of a two-level space vector pulse width modulation algorithm for power electronics education

    Ahmet Mete Vural


    Full Text Available This paper presents the design details of a two-level space vector pulse width modulation algorithm in PSCAD that is able to generate pulses for three-phase two-level DC/AC converters with two different switching patterns. The presented FORTRAN code is generic and can be easily modified to meet many other kinds of space vector modulation strategies. The code is also editable for hardware programming. The new component is tested and verified by comparing its output as six gating signals with those of a similar component in MATLAB library. Moreover the component is used to generate digital signals for closed-loop control of STATCOM for reactive power compensation in PSCAD. This add-on can be an effective tool to give students better understanding of the space vector modulation algorithm for different control tasks in power electronics area, and can motivate them for learning.

  4. Optimum design of phase opposition disposition pulse width modulation logic circuit for switching seven level cascaded half bridge inverter

    Nentawe Y. Goshwe


    Full Text Available Theevolution of multilevel inverters (MLIs has made it possible to extract power from direct current (DC sources to alternating current (AC power. This paper presents the design of a novel phase opposition disposition pulse width modulation scheme (PODPWM logic circuit for a conventional single phase seven level cascaded H-Bridge (CHB inverter using Matlab/Simulink. The minimum switching logic circuit for the single phase seven level CHB inverter was obtained by modeling the logic equations that could be used with any number of levels depending on the number of modulating and carrier signals involved. The reduction in total harmonic distortion (THD of the output voltage for the MLI using low switching frequency at different modulation indixes is also investigated. The logic equations have made it easier to design a PODPWM circuit for any CHB inverter and the logic gates designed gave an optimum THD value of 16.73 % at modulation index of 0.20.

  5. Isolated PWM DC-AC SICAM with an active capacitive voltage clamp[Pulse Density Modulated; Pulse Width Modulation

    Ljusev, P.


    In this report an isolated PWM DC-AC SICAM with an active capacitive voltage clamp is presented. AC-DC power supply is implemented in its simplest form: diode rectifier followed by a medium-size charge-storage capacitors and possibly with an EMC filter on the mains entrance. Isolation from the AC mains is achieved using a high frequency (HF) transformer, whose voltages are not audio-modulated. The latter simplifies the design and is expected to have many advantages over the approach where the transformer voltages are modulated in regards to the audio signal reference. Input stage is built as a DC-AC inverter (push-pull, half-bridge or a full-bridge) and operated with 50% duty cycle, with all the challenges to avoid transformer saturation and obtain symmetrical operation. On the secondary side the output section is implemented as rectifier+inverter AC-AC stage, i.e. a true bidirectional bridge, which operation is aimed towards amplification of the audio signal. In order to solve the problem with the commutation of the load current, a dead time between the incoming and outgoing bidirectional switch is implemented, while a capacitive voltage clamp is used to keep the induced overvoltage to reasonable levels. The energy stored in the clamping capacitor is not wasted as in the dissipative clamps, but is rather transferred back to the primary side for further processing using an auxiliary isolated single-switch converter, i.e. an active clamping technique is used. (au)

  6. 软开关脉宽调制变频技术%Soft-Switching Technique in Pulse Width Modulation Inverters

    陈国呈; 谷口胜则; 中村博人


    In this paper, a new soft-switching inverter using a minimum number of devices, and a new PWM (pulse-width modulation)method suitable for 3-phase soft-switching inverters are proposed. The circuit is used as an interface between the DC supply and the conventional voltage source of a PWM inverter. The number of switching operations can be reduced by using the PWM strategy. Increasing the amplitude of the fundamental component contained in the output waveform results in an effective utilization of the DC supply, a reduction of nominated capacity of the inverter elements, and a reduction of switching loss in the switching devices.

  7. Swarming Speed Control for DC Permanent Magnet Motor Drive via Pulse Width Modulation Technique and DC/DC Converter

    A.S. Oshaba


    Full Text Available This study presents an approach for the speed control of a permanent magnet DC motor drive via Pulse Width Modulation (PWM technique and a DC/DC converter. The Particle Swarm Optimization (PSO technique is used to minimize a time domain objective function and obtain the optimal controller parameters. The performance of the proposed technique has been evaluated using various types of disturbances including load torque variations. Simulation results illustrate clearly the robustness of the controller and validity of the design technique for controlling the speed of permanent magnet motors.

  8. Application of chaotic pulse width modulation control for suppressing electromagnetic interference in a half-bridge converter

    Yuhong Song


    Full Text Available It was proposed in the former research that chaos control can be used to suppress electromagnetic interference (EMI in DC–DC converters. Analysis on a half-bridge converter is detailed in this study. Here, the practical example of the power supply of personal computers is given to show that, with an external chaotic signal to a pulse width modulation control circuit, the proposed approach can reduce EMI by reducing the amplitudes of power signals such as transformer current and output inductor currents at multiples of fundamental frequency.

  9. Design and Simulation of Control Technique for Permanent Magnet Synchronous Motor Using Space Vector Pulse Width Modulation

    Khan, Mansoor; Yong, Wang; Mustafa, Ehtasham


    After the rapid advancement in the field of power electronics devices and drives for last few decades, there are different kinds of Pulse Width Modulation techniques which have been brought to the market. The applications ranging from industrial appliances to military equipment including the home appliances. The vey common application for the PWM is three phase voltage source inverter, which is used to convert DC to AC in the homes to supply the power to the house in case electricity failure, usually named as Un-interrupted Power Supply. In this paper Space Vector Pulse Width Modulation techniques is discussed and analysed under the control technique named as Field Oriented Control. The working and implementation of this technique has been studied by implementing on the three phase bridge inverter. The technique is used to control the Permanente Magnet Synchronous Motor. The drive system is successfully implemented in MATLAB/Simulink using the mathematical equation and algorithm to achieve the satisfactory results. PI type of controller is used to tuned ers of the motothe parametr i.e. torque and current.

  10. Resolution enhancement using pulse width modulation in digital micromirror device-based point-array scanning pattern exposure

    Kuo, Hung-Fei; Huang, Yi-Jun


    Digital-mask lithography systems, with a digital micromirror device (DMD) as their central piece, have been widely used for defining patterns on printed circuit board (PCB). This study designed optical module parameters for point-array projection lithography based on field tracing technique to improve the quality of the aerial image on the exposure plane. In the realized optical module for the point-array projection lithography, a DMD was used as the dynamic digital-mask, and a 405-nm-wavelength laser was used to illuminate the DMD. The laser was then focused through the micro-lens array in the optical module to form a point array and was projected onto a dynamic scanning stage. By calculating the beam-overlapping rate, stage velocity, spot diameter, and DMD frame rate and programming them into the stage- and DMD-synchronized controller, the point array formed line patterns on the photoresist. Furthermore, using pulse width modulation (PWM) technique to operate the activation periods of the DMD mirrors effectively controlled the exposure and achieved a feature linewidth of less than 10 μm.


    M. Shankar


    Full Text Available This study proposes a novel control design of Unified Power Quality Conditioner (UPQC. This design is enabled by a control framework that employs Genetic Algorithm which determines optimum points and angle for filtering and Space Vector Pulse Width Modulation Technique (SVPWM to offer significant flexibility to optimize waveform. In addition the same framework integrates the major functions of the UPQC with ease to unify the treatments of several power quality problems including system harmonics in the supply voltage and load current, sags/swells in the supply voltage, variations in the load demands and poor power factor at the supply side. Simulation studies on a three phase power distribution system are used to verify the performance and implementation of this control design with the UPQC.

  12. Impact Of The Pulse Width Modulation On The Temperature Distribution In The Armature Of A Solenoid Valve

    Goraj R.


    Full Text Available In order to estimate the inductive power set in the armature of the high-speed solenoid valve (HSV during the open loop control (OLC using pulse width modulation (PWM an analytical explicit formula has been derived. The simplifications taken both in the geometry and in the physical behavior of the HSV were described. The inductive power was calculated for different boundary conditions and shown as a function of the frequency of the coil current. The power set in the armature was used as an input to the thermal calculation. The thermal calculation had an objective to estimate the time dependent temperature distribution in the armature of the HSV. All the derivation steps were presented and the influence of different boundary conditions was shown and discussed. The increase of the temperature during the heating with inductive power has been evaluated both in the core and on the side surface of the HSV.

  13. Impact Of The Pulse Width Modulation On The Temperature Distribution In The Armature Of A Solenoid Valve

    Goraj, R.


    In order to estimate the inductive power set in the armature of the high-speed solenoid valve (HSV) during the open loop control (OLC) using pulse width modulation (PWM) an analytical explicit formula has been derived. The simplifications taken both in the geometry and in the physical behavior of the HSV were described. The inductive power was calculated for different boundary conditions and shown as a function of the frequency of the coil current. The power set in the armature was used as an input to the thermal calculation. The thermal calculation had an objective to estimate the time dependent temperature distribution in the armature of the HSV. All the derivation steps were presented and the influence of different boundary conditions was shown and discussed. The increase of the temperature during the heating with inductive power has been evaluated both in the core and on the side surface of the HSV.

  14. A simplified method for estimation of iron loss in wound toroidal cores energised by pulse width modulated voltage sources

    Tutkun, Nedim; Moses, Anthony J.


    Recently the strip wound toroidal cores have increasingly been used in switching mode and uninterruptible power supplies for a wide range of industrial applications. Therefore, the prediction of iron loss increase in such magnetic cores energised by non-sinusoidal voltage excitation is important step in the design of electromagnetic devices. In this investigation, a loss increase was estimated by determination of unknown constants in a previously developed loss separation model using genetic algorithms. Also the skin effect of flux density was taken into account for estimation of power loss under pulse width modulated voltage sources. The results obtained are in good agreement with the measured results in wound toroids at various flux densities.

  15. Time-Domain Quaternary-Weighted Pulse Width Modulation Driving Method for Active Matrix Organic Light-Emitting Diode Displays

    Park, Hyun-Sang; Kuk, Seung-Hee; Han, Min-Koo


    We proposed a new digital driving method and its pixel structure for active matrix organic light-emitting diode (AMOLED) displays employing time-domain quaternary-weighted pulse width modulation. In the new digital driving method, the luminance of AMOLED displays is accurately determined by averaging photon flux to the desired level over a frame period. The proposed pixel was verified by spice simulation and the output linearity between the grayscale and the OLED current was successfully achieved. In the proposed digital driving pixel, the timing margin was increased and the effect on luminance of AMOLED displays by the troublesome variation of the thin-film transistors (TFTs) was suppressed without additional compensation schemes.

  16. Automatic Frequency Identification under Sample Loss in Sinusoidal Pulse Width Modulation Signals Using an Iterative Autocorrelation Algorithm

    Alejandro Said


    Full Text Available In this work, we present a simple algorithm to calculate automatically the Fourier spectrum of a Sinusoidal Pulse Width Modulation Signal (SPWM. Modulated voltage signals of this kind are used in industry by speed drives to vary the speed of alternating current motors while maintaining a smooth torque. Nevertheless, the SPWM technique produces undesired harmonics, which yield stator heating and power losses. By monitoring these signals without human interaction, it is possible to identify the harmonic content of SPWM signals in a fast and continuous manner. The algorithm is based in the autocorrelation function, commonly used in radar and voice signal processing. Taking advantage of the symmetry properties of the autocorrelation, the algorithm is capable of estimating half of the period of the fundamental frequency; thus, allowing one to estimate the necessary number of samples to produce an accurate Fourier spectrum. To deal with the loss of samples, i.e., the scan backlog, the algorithm iteratively acquires and trims the discrete sequence of samples until the required number of samples reaches a stable value. The simulation shows that the algorithm is not affected by either the magnitude of the switching pulses or the acquisition noise.

  17. Paralleled Phase Shifted Carrier Pulse Width Modulation (PSCPWM) Schemes - A Fundamental Analysis

    Christensen, Frank Schwartz; Frederiksen, Thomas Mansachs; Nielsen, Karsten


    The paper presents a fundamental analysis of modulation schemes and their spectral aspects for a range of powerstage topologies, from a simple 2-level switching leg to more complex multi-level switching topologies. A family of modulation schemes are introduced and the double Fourier series based...

  18. Modular space-vector pulse-width modulation for nine-switch converters

    Dehghan, Seyed Mohammad; Amiri, Arash; Mohamadian, Mustafa


    Recently, nine-switch inverter (NSI) has been presented as a dual-output inverter with constant frequency (CF) or different frequency (DF) operation modes. However, the CF mode is more interesting because of its lower switching device rating. This study proposes a new space-vector modulation (SVM...

  19. Pulse-Width-Modulation of Neutral-Point-Clamped Sparse Matrix Converter

    Loh, P.C.; Blaabjerg, Frede; Gao, F.


    literature. Addressing the afore-described issues, this paper focuses on the operational mode analysis of a three-level sparse matrix converter implemented using a neutral-point-clamped inversion stage, and  the design of a number of PWM and modulation ratio compensation schemes for controlling the converter...

  20. A pulse-width modulated, high reliability charge controller for small photovoltaic systems

    Gerken, K. [Morningstar Corp., Olney, MD (United States); Welsh, D. [Morningstar Corp., Encinitas, CA (United States)


    This report presents the results of a development effort to design, test and begin production of a new class of small photovoltaic (PV) charge controllers. Sandia National Laboratories provided technical support, test data and financial support through a Balance-of-System Development contract. One of the objectives of the development was to increase user confidence in small PV systems by improving the reliability and operating life of the system controllers. Another equally important objective was to improve the economics of small PV systems by extending the battery lifetimes. Using new technology and advanced manufacturing techniques, these objectives were accomplished. Because small stand-alone PV systems account for over one third of all PV modules shipped, the positive impact of improving the reliability and economics of PV systems in this market segment will be felt throughout the industry. The results of verification testing of the new product are also included in this report. The initial design goals and specifications were very aggressive, but the extensive testing demonstrates that all the goals were achieved. Production of the product started in May at a rate of 2,000 units per month. Over 40 Morningstar distributors (5 US and 35 overseas) have taken delivery in the first 2 months of shipments. Initial customer reactions to the new controller have been very favorable.

  1. FPGA Based Sinusoidal Pulse Width Modulated Waveform Generation for Solar (PV) Rural Home Power Inverter

    Singh, S N


    With the increasing concern about global environmental protection and energy demand due to rapid growth of population in developing countries and the diminishing trend of resources of conventional grid supply, the need to produce freely available pollution free natural energy such as solar/wind energy has been drawing increasing interest in every corner of the world. In an effort to utilize these energies effectively through Power converter, a great deal of research is being carried out by different researchers / scientist and engineers at different places in the world to meet the increasing demand of load. The study presents methodology to integrate solar (PV) energy (which is freely available in every corner of the world) with grid source and supplement the existing grid power in rural houses during its cut off or restricted supply period. In order to get consistency in supply a DG is also added as a standby source in the proposed integration of network. The software using novel Direct PWM modulation strate...

  2. Pulse-Width Jitter Measurement for Laser Diode Pulses

    TANG Jun-Hua; WANG Yun-Cai


    @@ Theoretical analysis and experimental measurement of pulse-width jitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced.

  3. Virtual-vector-based space vector pulse width modulation of the DC-AC multilevel-clamped multilevel converter (MLC2)

    Rodriguez, Pedro; Busquets-Monge, Sergio; Blaabjerg, Frede;


    This work presents the development of the space vector pulse width modulation (SVPWM) of a new multi-level converter topology. First, the proposed converter and its natural space vector diagram are presented. Secondly, a modified space vector diagram based on the virtual-vectors technique is show...

  4. A frequency and pulse-width co-modulation strategy for transcutaneous neuromuscular electrical stimulation based on sEMG time-domain features

    Zhou, Yu-Xuan; Wang, Hai-Peng; Bao, Xue-Liang; Lü, Xiao-Ying; Wang, Zhi-Gong


    Objective. Surface electromyography (sEMG) is often used as a control signal in neuromuscular electrical stimulation (NMES) systems to enhance the voluntary control and proprioceptive sensory feedback of paralyzed patients. Most sEMG-controlled NMES systems use the envelope of the sEMG signal to modulate the stimulation intensity (current amplitude or pulse width) with a constant frequency. The aims of this study were to develop a strategy that co-modulates frequency and pulse width based on features of the sEMG signal and to investigate the torque-reproduction performance and the level of fatigue resistance achieved with our strategy. Approach. We examined the relationships between wrist torque and two stimulation parameters (frequency and pulse width) and between wrist torque and two sEMG time-domain features (mean absolute value (MAV) and number of slope sign changes (NSS)) in eight healthy volunteers. By using wrist torque as an intermediate variable, customized and generalized transfer functions were constructed to convert the two features of the sEMG signal into the two stimulation parameters, thereby establishing a MAV/NSS dual-coding (MNDC) algorithm. Wrist torque reproduction performance was assessed by comparing the torque generated by the algorithms with that originally recorded during voluntary contractions. Muscle fatigue was assessed by measuring the decline percentage of the peak torque and by comparing the torque time integral of the response to test stimulation trains before and after fatigue sessions. Main Results. The MNDC approach could produce a wrist torque that closely matched the voluntary wrist torque. In addition, a smaller decay in the wrist torque was observed after the MNDC-coded fatigue stimulation was applied than after stimulation using pulse-width modulation alone. Significance. Compared with pulse-width modulation stimulation strategies that are based on sEMG detection, the MNDC strategy is more effective for both voluntary muscle

  5. An Efficient Space Vector Pulse Width Modulation with BFO Based Self Tuning PI Controller for Shunt Active Power Filter

    P. Saravanan


    Full Text Available This research study mainly focuses on using an efficient control strategy for extracting reference currents of shunt active filters under non linear load conditions. In recent decades, the utilization of highly automatic electric equipments has resulted in enormous economic loss. Thus, the power suppliers as well as the power consumers are very much concerned about the power quality issues and compensation approaches. In order to deal with this issue, Active Power Filter (APF has been considered as an attractive solution due to its significant harmonic compensation. But, the performance of APF is not consistent and is varies based on the output of the controller techniques. An efficient (id-id control strategy is used in this approach for attaining utmost profit from grid-interfacing inverters installed in transmission systems. The voltages are controlled through the PI controller which is further tuned by an optimization approach. Bacterial Forge Optimization (BFO is used in this approach for tuning the PI controller for the optimal value. The inverter used in this approach can be considered as a Shunt Active Power Filter (SAPF to compensate non linear load current harmonics. In order to improve the overall performance of the system, Space Vector Pulse Width Modulation (SVPWM is used in this proposed approach which regulates power frequency and produces good circularity through DC-AC part. SVPWM also eliminates the 3rd order harmonics and minimizes the 5th order harmonics effectively. The integration of (id-id control strategy and SVPWM has been proposed in this research study. Simulation results are carried out in MATLAB/Simulink and the performance of the proposed approach is compared with other control strategies. This research studies shows unique approach for attaining maximum benefits from RES with suppression of current harmonics.

  6. An optical pulse width modulation generator based on the injection-locking property of single mode FP-LD

    Tran, Quoc Hoai; Nakarmi, Bikash; Won, Yong Hyub


    A novel simple optical pulse width modulation generator (OPWMG) based on injection-locking property of a single mode FP-LD (SMFP-LD) has been proposed and experimentally verified. The OPWMG consists of a SMFP-LD (which acts as comparator), an optical sinusoidal wave source (analog input), and a continuous optical beam (control signal). The power required for fully injection-locking the SMFP-LD acts as the referent power whereas the combination power of continuous optical beam and analog optical sinusoidal signals work as control signals for changing the duty cycle of the proposed OPWMG. The presence of only continuous optical beam is not sufficient to suppress the dominant mode of SMFP-LD with high ON/OFF contrast ratio; however, the application of additional sinusoidal wave of constant amplitude and frequency, the dominant mode of SMFP-LD can be suppressed for the certain time window. Since, injection-locking power is dependent with the combined power of input injected continuous beam and sinusoidal optical wave, the time window of injection-locking can be varied by changing input beam power which provides different duty cycle of 13% to 68% at the output. Current available schemes for generating PWM signals are in electrical domain, hence, they need to convert electrical signals into optical domain by using expensive O/E converters for application in optical control and signal processing. The proposed OPWMG scheme has several advantages, such as low cost, low power consumption (~0.5 mW) which can be used for various applications where the effect of EMI/EMR is considered as an important factor such as control circuit for high voltage converters in power plant and electrical vehicles.

  7. Virtual-vector-based space vector pulse width modulation of the DC-AC multilevel-clamped multilevel converter (MLC2)

    Rodriguez, Pedro; Busquets-Monge, Sergio; Blaabjerg, Frede


    This work presents the development of the space vector pulse width modulation (SVPWM) of a new multi-level converter topology. First, the proposed converter and its natural space vector diagram are presented. Secondly, a modified space vector diagram based on the virtual-vectors technique is shown....... Simulation results by using a space vector approach are presented. Special emphasis is given on the total harmonic distortion (THD) by making a comparison with those of the classical NPC topologies....

  8. Research on Internal Relation Between Virtual Space Vector Pulse Width Modulation Strategy and Carrier Sinusoidal Pulse Width Modulation Strategy for Three-Level Neutral Point Clamped Converter%三电平NPC变流器虚拟空间矢量调制策略与载波调制策略的内在关系研究

    李宁; 王跃; 蒋应伟; 雷万钧; 王兆安


    分析了虚拟空间矢量调制(virtual space vector pulse width modulation,VSVPWM)策略的基本原理,推导了三电平 VSVPWM 策略与单相双调制波三电平正弦脉冲宽度调制(sinusoidal pulse width modulation,SPWM)策略的内在联系,建立了两者间的调制波等效关系。应用调制波等效关系分析了 VSVPWM 策略的输出电压总谐波畸变率(total harmonic distortion,THD)、直流电压利用率和开关器件损耗。最后,提出了基于调制波等效关系的三电平VSVPWM快速实现方案。仿真和实验结果验证了理论分析的正确性。%In the modulation strategies for three-level NPC converter, neutral point voltage control under the entire modulation index and full power factor can be achieved by virtual space vector pulse width modulation (VSVPWM) strategy. In this paper the basic principle of VSVPWM is analyzed, then the internal relation between three-level VSVPWM strategy and single-phase dual modulation based three-level sinusoidal pulse width modulation (SPWM) strategy is derived and the modulation-wave equivalence between the two modulation strategies is established. Using the established modulation-wave equivalent relation, the total harmonic distortion (THD) of output voltage, DC voltage utilization rate and switch device losses under VSVPWM strategy are analyzed. Finally, a fast implementation of three-level VSVPWM strategy based on modulation-wave equivalence is proposed. The correctness of the theoretical analysis is verified by both results from simulation and experiments.

  9. PWM脉宽调制实现电机的恒速驱动%The Driver of Constant Speed Motor Based on PWM Pulse Width Modulation



    现在许多单片机具有PWM脉宽调制功能,结合单片机的定时器、计数器,我们可以很方便的实现电机的恒速驱动。本文以编码器为反馈信号,构成了电机恒速转动的闭环系统。%Now many Single Chip Microcomputer with PWM pulse width modulation,combined with Single Chip Microcomputer timer and counter,we can easily achieve the constant speed drive motor.In this paper,encoder acts as feedback signal,constitutes a constant speed motor rotating closed-loop system.

  10. Analysis and Speed Ripple Mitigation of a Space Vector Pulse Width Modulation-Based Permanent Magnet Synchronous Motor with a Particle Swarm Optimization Algorithm

    Xing Liu


    Full Text Available A method is proposed for reducing speed ripple of permanent magnet synchronous motors (PMSMs controlled by space vector pulse width modulation (SVPWM. A flux graph and mathematics are used to analyze the speed ripple characteristics of the PMSM. Analysis indicates that the 6P (P refers to pole pairs of the PMSM time harmonic of rotor mechanical speed is the main harmonic component in the SVPWM control PMSM system. To reduce PMSM speed ripple, harmonics are superposed on a SVPWM reference signal. A particle swarm optimization (PSO algorithm is proposed to determine the optimal phase and multiplier coefficient of the superposed harmonics. The results of a Fourier decomposition and an optimized simulation model verified the accuracy of the analysis as well as the effectiveness of the speed ripple reduction methods, respectively.

  11. Transient analysis and control of bias magnetic state in the transformer of on-line pulse-width-modulation switching full bridge direct current-direct current converter

    Chen, Jiaxin; Guo, Youguang; Zhu, Jianguo; Wei Lin, Zhi


    This paper presents a finite element analysis (FEA) based method for analyzing and controlling the bias magnetic state of the transformer of a pulse-width-modulation (PWM) switching full bridge dc-dc converter. A field-circuit indirect coupling method for predicting the transient bias magnetic state is introduced first. To increase flexibility of the proposed method, a novel transformer model which can address not only its basic input-output characteristic, but also the nonlinear magnetizing inductance, is proposed. Both the asymmetric characteristic and the variable laws of the current flowing through the two secondary windings during the period of PWM switching-off state are highlighted. Finally, the peak magnetizing current controlled method based on the on-line magnetizing current computation is introduced. Analysis results show that this method can address the magnetic saturation at winding ends, and hence many previous difficulties, such as the start-up process and asymmetry of power electronics, can be easily controlled.

  12. Pulse-width modulation for small heat pump installations - Phase 4; Pulsbreitenmodulation fuer Kleinwaermepumpenanlagen. Phase 4: Erweiterung der PBM-Regler fuer Kombianlagen

    Bianchi, M.; Shafai, E. [Eidgenoessische Technische Hochschule (ETH), Institut fuer Mess- und Regeltechnik, Zuerich (Switzerland); Gabathuler, H.R.; Mayer, H. [Gabathuler AG, Beratende Ingenieure, Diessenhofen (Switzerland)


    This final report for the Swiss Federal Office of Energy (SFOE) presents the results of the fourth phase of a project that investigated three types of pulse-width modulation (PWM) controllers that were developed during its first two phases. A third phase monitored the controllers when used in a simulated environment and for a real-life heat pump. The report discusses the fourth phase of the project, in which the controller was further developed and tested using the building emulation developed in the third phase. The functioning of the self-regulating controller and its use of meteorological data is described and the savings to be made in heating costs are discussed.

  13. Reduce Adverse Effects of Laparoscopic Cholecystectomy with Pulse Width Modulated LED Light (625 nm, 76 Hz, 23% Duty Cycle).

    Redkin, Alexander V; Vdovin, Victor V; Vakhtel, Victor M; Lukyanovich, Pavel A; Malkina, Natalia A


    Reducing adverse effects in laparoscopic cholecystectomy (LCE) is important to avoid complications. After removal, the porta hepatis and gallbladder bed of liver were treated with pulse width modulated (PWM) red LED light with parameters λ = 625 ± 5 nm, full width at half maximum 17 nm, 76 Hz, duty cycle 23%, 15-30 mW/cm(2), and 0.9-1.8 J/cm(2). The changes of eight blood parameters were studied: red blood cell, hemoglobin, white blood cell, erythrocyte sedimentation rate (ESR), bilirubin, aspartate transaminase (AST), alanine transaminase (ALT), and amylase. Other current methods of reducing undesirable effects of LCE significantly affect surgery and are not commonly used in practice. Before LCE, 263 patients were randomized into the control and test groups. Patients in the test group were treated with light radiated for 2 min during the surgery on the bed of the removed gallbladder and porta hepatis. Blood samples were taken before surgery and on the third day after surgery, studied, and compared by nonparametric statistical methods. The test group revealed significant reduction in postsurgery gain of levels of ALT, AST, and ESR compared with the control group. Treatment of the removed gallbladder bed and porta hepatis by red LED PWM radiation during LCE significantly reduces the adverse effects of surgery while increasing its time insignificantly and does not affect the surgical best practices deployed.

  14. High-frequency modelling of a three-phase pulse width modulation inverter towards the dc bus considering line and controller harmonics

    Saeid Haghbin


    Full Text Available Closed-form analytical formulas are provided to calculate the dc bus harmonics of a three-phase sinusoidal pulse width modulation (SPWM inverter. The harmonic analysis is performed by using a double Fourier series approach to determine the dc bus current frequency spectrum. For an arbitrary modulation index and load power factor, the full harmonic components of the inverter dc side current are calculated. Based on the developed analytical model, an equivalent circuit is proposed for the inverter harmonic analysis towards the dc bus. Moreover, the impacts of line harmonics and zero sequence injection in controller towards the dc bus are presented. The results show that the 5th and 7th ac line harmonics on the dc side current is appearance of the 6th harmonic in the dc side. The impact of zero sequence injection to the controller on the dc side is negligible. In addition to analytical formulation, different simulations and extensive measurements performed which the results verified the presented analytical framework.

  15. A Sliding Surface-Regulated Current-Mode Pulse-Width Modulation Controller for a Digital Signal Processor-Based Single Ended Primary Inductor Converter-Type Power Factor Correction Rectifier

    Hsin-Jang Shieh; Ying-Zuo Chen


    To efficiently supply wide-range DC voltage from a pulse-width modulation (PWM) rectifier, this paper presents a single-phase, full-wave, diode-bridge, single-ended primary-inductor converter-type (SEPIC-type...

  16. Pulse-width modulation pre-emphasis applied in a wireline transmitter, achieving 33 dB loss compensation at 5-Gb/s in 0.13-/spl mu/m CMOS

    Schrader, J.H.R.; Klumperink, E.A.M.; Visschers, J.L.; Nauta, B.


    A transmitter pre-emphasis technique for copper cable equalization is presented that is based on pulse-width modulation (PWM). This technique is an alternative to the usual 2-tap symbol-spaced FIR (SSF) pre-emphasis. The technique uses timing resolution instead of amplitude resolution to adjust the

  17. An adaptive neuro fuzzy inference system controlled space cector pulse width modulation based HVDC light transmission system under AC fault conditions

    Ajay Kumar, M.; Srikanth, N.


    In HVDC Light transmission systems, converter control is one of the major fields of present day research works. In this paper, fuzzy logic controller is utilized for controlling both the converters of the space vector pulse width modulation (SVPWM) based HVDC Light transmission systems. Due to its complexity in the rule base formation, an intelligent controller known as adaptive neuro fuzzy inference system (ANFIS) controller is also introduced in this paper. The proposed ANFIS controller changes the PI gains automatically for different operating conditions. A hybrid learning method which combines and exploits the best features of both the back propagation algorithm and least square estimation method is used to train the 5-layer ANFIS controller. The performance of the proposed ANFIS controller is compared and validated with the fuzzy logic controller and also with the fixed gain conventional PI controller. The simulations are carried out in the MATLAB/SIMULINK environment. The results reveal that the proposed ANFIS controller is reducing power fluctuations at both the converters. It also improves the dynamic performance of the test power system effectively when tested for various ac fault conditions.

  18. 基于SVPWM的VIENNA整流器研究%Study on the VIENNA Rectifier Based on Space Vector Pulse Width Modulation

    王正; 谭国俊; 曾维俊; 柳萌


    分析了三相三开关三电平(VIENNA)整流器的工作原理,研究了其空间矢量脉宽调制(SVPWM)的实现方法,提出了此整流器的矢量控制策略.采用电压外环和电流内环的双闭环控制,实现了VIENNA整流器的高性能特性.基于Matlab仿真平台,搭建了VIENNA整流器的仿真模型,仿真结果表明,该整流器能实现良好的动态性能和稳态性能.%The working principle of three-phase three-switch three-level (VIENNA) rectifier was analyzed, and its implement method of space vector pulse width modulation (SVPWM) was researched. On that basis, the vector control strategy of VIENNA was proposed. It achieved the high performance characteristics of VIENNA rectifier by using dual closed loop with voltage outer loop and current inner loop. Furthermore, based on the platform of Matlab simulation,the simulation model of VIENNA rectifier was built. The simulation results show that the rectifier can achieve both good dynamic performance and good static performance.

  19. Development of microheaters for gas sensor with an AT-Mega 8535 temperature controller using a PWM (pulse width modulation) method

    Megayanti, Meti; Panatarani, Camellia; Joni, I. Made


    Microheater is the main component in gas sensor characterized by their sensitivity, selectivity, and time response of gas sensor which is depend on the microheater temperature stability. A Cu microheater was developed and utilized AT-Mega 8535 controller using a PWM (pulse width modulation) method. This control system is interfaced to the PC to observe the real time temperature response of the microheater. Three initial resistance (R0) variations of microheater were developed in an open loop control system. The power characteristic of designed microheater depends on the specified microheater initial resistance. The smaller R0, the less power required to reach a temperature setting value. The developed microheater was designed to reach a temperature setting value of 250°C having resistance 0.531 Ω for 1.979 Watt and 0.265 Ω for 1.072 Watt respectively. The results of the investigation on the control performances shows microheater-control system achieved operating temperature up to 250°C. The response of the temperature control shows smallest R0 resulted in a high stability with short settling time, short delay time and small ripple for temperature setting values higher than 150°C. The obtained error of microheater temperature with R0 = 0.265 is 8.596 %. It is concluded that the developed microheater can be utilized as a component of a gas sensor.

  20. 基于脉冲跳变的空间矢量脉冲宽度调制策略%Novel space vector pulse width modulation based on pulse-shifting

    林城美; 王公宝; 汪光森; 李卫超; 崔小鹏


    针对二极管钳位型单相九电平逆变器,分析其工作原理,提取了逆变器工作的有效开关状态。根据伏秒平衡原理和两矢量三段式调制规律,提出了一种基于脉冲跳变的空间矢量脉冲宽度调制( space vector pulse width modulation,SVPWM)策略。通过分析所有开关周期脉冲的跳变情况,给出了脉冲类型的判断条件,并根据脉冲类型计算起始和终止电压矢量及其作用时间;同时,应用FPGA设计了模块化SVPWM控制系统,并对该控制系统进行了时钟与资源消耗评估。性能分析结果表明,该调制策略计算速度快、资源消耗小。最后,仿真与实验结果验证了所提调制策略的正确性和有效性,而且能够有效地均衡电容电压。%The operating principle of diode-clamped single phase 9-level inverter was analyzed firstly, and its useful switching vectors of the inverter were obtained. A novel space vector pulse width modulation ( SVPWM) was presented based on pulse-shifting, according to volt-second balance principle and two-vector modulation rule. By analyzing the pulse-shifting condition within one normal switching period, the criterion for judging pulse type was also proposed. Based on different pulse type, the computing method of the start and end voltage vector were different, and their dwell time were also different. The SVPWM control system was implemented using a field programmable gate array ( FPGA) circuit as the hardware simulation platform, whose clock and resource utilization are evaluated. The simulation and experimental results demonstrate that the presented control strategy has good control effect, and balances the capacitor voltages better.

  1. Comparison of Two Fast Space Vector Pulse Width Modulation Algorithms%两种快速的空间矢量脉宽调制算法比较

    范必双; 谭冠政; 樊绍胜; 王玉凤


    A comparison is made between two fast space vector pulse width modulation (SVPWM) algorithms: the 60° non-orthogonal coordinate SVPWM and the 45° rotating coordinate SVPWM. New general methods of the 60° and 45° algorithms for any level SVPWM are also provided, which need only the angle and the modulation depth to generate and arrange the final vector sequence. The analysis shows the latter offers better flexibility with fewer calculations and is well suited for digital implementation. Both methods are implemented in a field programmable gate array (FPGA) with very high speed integrated circuit hardware description language (VHDL) and compared on the basis of implementation complexity and logic resources required. Simulation results show the overwhelm in advantages of the 45° rotating coordinate SVPWM in brevity and efficiency. Finally, the experimental test results for a three-level neutral-point-clamped (NPC) inverter are presented.%对60°非正交坐标系和45°旋转坐标系这两种快速空间矢量脉宽调制算法(space vector pulse width modulation, SVPWM)进行比较,目的是为工程技术人员在这两种SVPWM算法之间选择时提供一个理论和实践的参考。提出了一种新的针对这两种方法的任意多电平调制通用算法,只需角度和调制比两个信号就能够决定最终的矢量开关顺序。理论分析结果表明,45°旋转坐标系 SVPWM 比60°非正交坐标系SVPWM更简单,计算量小,更适合于数字实现。两种算法都以硬件的方式在FPGA上用VHDL语言编程实现,并对实现的复杂度和逻辑资源占用这两方面进行比较。仿真结果表明,45°旋转坐标系下的SVPWM算法比60°坐标系下的SVPWM算法在简洁性和资源占用方面具有明显的优势。最后,在一个三电平中点箝位型逆变器上对所提的两种通用算法进行了实验验证。

  2. Pulse width modulation algorithm and simulation based on linear motor%直线电机脉宽调制算法及仿真研究

    林峰; 邓小雷


    为解决目前常规空间矢量脉宽调制( SVPWM)算法存在的计算繁琐、难以数字化实现的缺点,在综合分析永磁直线同步电机(PMLSM)控制原理的基础上,提出了一种用于永磁直线同步电机的新型SVPWM快速算法.该算法通过永磁直线同步电机位移传感器的检测值完成扇区判断与开关工作时间的计算.最后,通过Matlab/Simulink建立了仿真模型.仿真结果表明,该算法效果良好,解决了常规SVPWM算法由于反正切函数运算而导致系统响应慢、控制精度低的问题,具有一定的实用性与可行性.%In order to solve the problem of computational complexity and reduce the difficulty on implementing digitization with space vector pulse width modulation (SVPWM) , a novel rapid algorithm for SVPWM was proposed based on the comprehensive analysis of the control principle of permanent magnet linear synchronous motor (PMLSM). The sector judgment and the calculation of switching time can be calculated based on the data from the displacement sensor of PMLSM. Finally, the model of the algorithm was established in Matlab/ Simulink. The simulation results show that the novel algorithm is practical and feasible, the problems of low response and low control accuracy from inverse tangent calculation in conventional SVPWM is solved.

  3. Logic Pulse Width Modulation Method for Converter%变换器的逻辑脉冲宽度调制方法

    魏毅立; 周金生; 罗家涛; 张自雷


    分析了单相半桥DC-AC变换器的逻辑脉冲宽度调制( LPWM)控制方法,阻感负载电流为正和为负情形下IGBT的导通状态,进而分别给出了等效电路。其方法是根据负载的电流的正负而开放或封锁对应的IGBT的门极脉冲。在单相半桥DC-AC变换器的LPWM基础上,分析了三相桥式DC-AC变换器的LPWM控制方法和SVPWM的LPWM控制方法, LPWM控制方法的优点是减少了一半的门极驱动损耗,除电流过零点以外无需再加死区,提高了开关频率,增强了系统的安全性。然后再通过Matlab仿真软件对LPWM仿真,验证了LPWM控制方法正确性。%The logic pulse width modulation ( LPWM) control method for single-phase half bridge DC-AC convert-er, and the on-off state of IGBT under the circumstance of inductive load with the load current as positive and nega-tive respectively have been analyzed in this paper, so as to present the equivalent circuits.This method is to open or close the corresponding IGBT trigger pulse according to the load current being positive or negative.In addition, based on the LPWM control method for the single-phase half bridge DC-AC converter, LPWM control methods for the three-phase bridge DC-AC converter and SVPWM control method have been also analyzed.The advantage of LP-WM control method is to reduce half of the switching loss.No dead zone is need to add up except for the current pass-ing through the zero point, so as to improve the switch frequency and enhance the system safety.Simulation results based on Matlabverify the correctness of LPWM control method.

  4. Advanced Pulse Width Technique in Impedance Source Cascaded Multilevel Inverter with Asymmetric Topology

    Rajnish Kumar Sharma


    Full Text Available In this research, a single phase Z-source cascading Multilevel Inverter, Nine-level inverter topologies with a trinary DC sources are offered. The recommended topologies are expanded by cascading a full bridge inverter with dissimilar DC sources. This paper recommends advanced pulse with modulation technique as a switching scheme. In this PWM technology, trapezoidal modulation technique is used as variable amplitude pulse width modulation. These topologies compromise reduced harmonics present in the output voltage and superior root mean square (RMS values of the output voltages linked with the traditional trapezoidal pulse width modulation. The simulation of proposed circuit is carried out by using MATLAB/SIMULINK.

  5. 二极管钳位式三电平逆变器SVPWM控制策略研究%Control Strategy Study of Diode-Clamp Three-Level Inverter Based on Space Vector Pulse Width Modulation



    空间矢量脉宽调制在多电平逆变器的控制中应用广泛,但是随着电平数增加,控制算法渐趋复杂化。提出了三电平空间矢量脉宽调制控制方法,将三电平电压矢量区变换为由两电平空间矢量区构成,从而通过使用两电平空间矢量脉宽调制方法简化了控制算法。该方法理论上可应用于更高电平逆变器的控制中,仿真验证了方法的可行性。%Space vector pulse width modulation is widely applied in control of multi-level inverters, but following increasing of level number, the control algorithm becomes more and more complicated. Three-level space vector pulse width modulation control method was raised to transfer three-level voltage vector zone to two-level space vector zones, so as to simplify the control algorithm with two-level space vector pulse modulation method. The method on the theory can be used to control much higher level inverters and simulation has verified feasibility of the method.

  6. Statistical study of the pulse width distribution for radio pulsars


    Pulse widths of standard pulse profiles for 262 pulsars were measured by using the Urumqi 25 m radio telescope at 1.54 GHz.For the simplest case of circular emission beam,we applied Monte Carlo simulations to the pulse width distribution.Different density functions of magnetic inclination angle α and observer angle ξ were considered.Using Kolmogorov-Smirnov tests,we derived the most probable distribution for α and ξ.

  7. Optical antennas with sinusoidal modulation in width.

    Dikken, Dirk Jan; Segerink, Frans B; Korterik, Jeroen P; Pfaff, Stefan S; Prangsma, Jord C; Herek, Jennifer L


    Small metal structures sustaining plasmon resonances in the optical regime are of great interest due to their large scattering cross sections and ability to concentrate light to subwavelength volumes. In this paper, we study the dipolar plasmon resonances of optical antennas with a constant volume and a sinusoidal modulation in width. We experimentally show that by changing the phase of the width-modulation, with a small 10 nm modulation amplitude, the resonance shifts over 160 nm. Using simulations we show how this simple design can create resonance shifts greater than 600 nm. The versatility of this design is further shown by creating asymmetric structures with two different modulation amplitudes, which we experimentally and numerically show to give rise to two resonances. Our results on both the symmetric and asymmetric antennas show the capability to control the localization of the fields outside the antenna, while still maintaining the freedom to change the antenna resonance wavelength. The antenna design we tested combines a large spectral tunability with a small footprint: all the antenna dimensions are factor 7 to 13 smaller than the wavelength, and hold potential as a design element in meta-surfaces for beam shaping.

  8. Theoretical analysis of pulse modulation of semiconductor lasers

    Xu Baoxi; Zhan Yushu; Guo Siji


    Rate equations of Gaussian shape pulse modulated semiconductor lasers are solved by Runge--Kutta method, and the results are analyzed. The formulae for calculating the delay time, pulse width of laser pulse and maximum bit-rate of Gaussian shape pulse modulation are derived. The experimental results of modulation pattern effects are given.

  9. Capacitor charging FET switcher with controller to adjust pulse width

    Mihalka, A. M.


    A switching power supply includes an FET full bridge, a controller to drive the FETs, a programmable controller to dynamically control final output current by adjusting pulse width, and a variety of protective systems, including an overcurrent latch for current control. Power MOSFETS are switched at a variable frequency from 20 to 50 kHz to charge a capacitor load from 0 to 6 kV. A ferrite transformer steps up the dc input. The transformer primary is a full bridge configuration with the FET switches and the secondary is fed into a high voltage full wave rectifier whose output is connected directly to the energy storage capacitor. The peak current is held constant by varying the pulse width using predetermined timing resistors and counting pulses. The pulse width is increased as the capacitor charges to maintain peak current. A digital ripple counter counts pulses, and after the desired number is reached, an up-counter is clocked. The up-counter output is decoded to choose among different resistors used to discharge a timing capacitor, thereby determining the pulse width. A current latch shuts down the supply on overcurrent due to either excessive pulse width causing transformer saturation or a major bridge fault, i.e., FET or transformer failure, or failure of the drive circuitry.


    Ekaterina Alexandrovna Shershunova


    Full Text Available The paper deals with the realization and the diagnostics of the volume diffuse dielectric barrier discharge in 1-mm air gap when applying high voltage rectangular pulses to the electrodes. The effect of the applied pulse width on the discharge dissipated energy was studied in detail. It was found experimentally, the energy stayed nearly constant with the pulse elongation from 600 ns to 1 ms.

  11. 一种带约束的电压空间矢量脉宽调制方法%A Novel Method of Space Vector Pulse Width Modulation With Constraints

    吴德会; 夏晓昊; 李钷


    为解决传统调制方法中的最小脉宽问题,提出了一种带约束的电压空间矢量脉宽调制(space vector pulse width modulation,SVPWM)方法。首先,建立新的三相桥臂坐标,取消了扇区的划分和判断;其次,将基本电压空间矢量由8个减小为3个,并将其作用时间与三相桥臂的导通时间一一对应;再次,通过增加约束条件,将传统 SVPWM 方法的调制过程及其结果离散化,从而避免了窄脉宽的出现;最后,给出了一种快速的计算策略,其计算量仅与 SVPWM方法一个扇区的计算量基本相同。相对于 SVPWM 方法,所提方法调制的基波与杂波在频谱上的分布更清晰,低次谐波较少,有利于进行低通滤波处理,更适合较高电压和较大电流的逆变要求。仿真及实验结果均验证了该方法的可行性。%To solve the problem of the minimum pulse width in traditional modulation methods, a space vector pulse width modulation (SVPWM) method with constraints is proposed. Firstly, a three-phase bridge-arm coordinate is established to cancel the traditional sector division and the judgment;secondly, the number of basic voltage space vectors is reduced from 8 to 3, and their actuation durations correspond to the on-times of three-phase bridge-arms respectively;thirdly, by means of adding constraint conditions the modulation process of traditional SVPWM and modulation results are discretized to prevent the appearance of narrow pulse width;finally a fast computational strategy is given and its calculated amount is basically same as to the calculated amount for one sector by SVPWM method. Relative to SVPWM method, the distribution of the fundamental wave and clutters modulated by the proposed method on the frequency spectrum is more clear and there are less low-order harmonics, so it is favorable to implement low-pass filtering, thus the proposed method is more suitable for PV inverters with higher voltage and

  12. Research of reduced common-mode voltage technique with nonzero vector pulse width modulation for three-phase inverters%三相逆变器的无零矢量共模电压抑制技术研究

    章勇高; 邝光健; 龙立中


    The common-mode suppression techniques with nonzero vector pulse width modulation (NZPWM) for three-phase inverters are studied. They are random state pulse width modulation (RSPWM), active zero state PWM1 (AZSPWM1), active zero state PWM3 (AZSPWM3) and near state PWM (NSPWM). Firstly, the operation areas of modulation factor and reference voltage vector with different modulation strategies are analyzed. The results show that RSPWM has a smaller operation area than other three NZPWM and is suitable for the application with lower modulation ratio. Secondly, the DC voltage utilization rate and output harmonic of different NZPWM are researched and compared with that of traditional space vector modulation (SVM) by using theoretical analysis and simulation. The results show that AZPWM1, AZPWM3 and NSPWM can not only suppress the common mode voltage of three-phase inverters efficiently, but also maintain high DC voltage utilization rate. However, three-phase inverters with NSPWM have the higher output harmonic comparing with the traditional SVM. The research results provide theoretical basis and instruction for the selection of common mode voltage suppression technique with NZPWM for three-phase inverters and its further study.%  研究了三相逆变器的 RSPWM、AZSPWM1、AZSPWM3和 NSPWM 无零矢量共模电压抑制技术。首先,分析了不同调制策略的调制因数和参考电压矢量的工作区间,说明了 RSPWM 的工作区间较小,适用于低调制比工作场合。再次,利用理论分析和仿真方法,研究了无零矢量调制策略的直流电压利用率和输出谐波特性,并与传统 SVM 调制策略比较。结果表明,AZSPWM1、AZSPWM3和 NSPWM 调制策略能够有效地抑制三相逆变器共模电压,同时保持了较高的直流电压利用率。但相对 SVM 调制策略,三相逆变器的输出谐波含量有所增大。研究结果为三相逆变器的无零矢量共模电压抑制技术的选用及进一步研究提供了理论依据和指导。

  13. Design of Cascading Pulse Width Modulation Rectifier Based on CPS-SPWM%基于CPS-SPWM级联型脉冲宽度调制整流器设计

    于鹏; 季振东; 赵剑锋


    在建立级联型H桥脉冲宽度调制(pulse width modulation,PWM)变换器的平均模型的基础上,对单极性和双极性调制算法谐波特性进行分析,提出基于左、右桥臂独立调制的级联型调制算法;分析了级联型直流侧电压不均衡的原理及调节方法,给出基于调制比重构的直流侧平衡控制算法.MATLAB/Simulink软件仿真验证了所提出调制策略以及控制策略的有效性.

  14. 空间矢量脉宽调制( SVPWM)技术的仿真与分析%Simulation and Analysis of Space Vector Pulse Width Modulation Technique

    张成; 王心坚; 李良璋; 孙泽昌


      By analyzing the basic principle of flux tracking and voltage space vector synthesis , the DC voltage utilization ratio of space vector pulse width modulation (SVPWM) was analyzed theoretically.The PMSM speed regulating system model adopting SVPWM technique was built in Matlab /Simulink environment.And the simulation results show that SVPWM yields a circular magnetic field in motor space .The harmonics of output voltage distribute mainly around integer multiples of carrier frequency , and higher modulation index yields a low-er voltage total harmonic distortion.%  基于SVPWM的磁链跟踪和电压矢量合成原理,理论分析了SVPWM的直流电压利用率,在Matlab/Simulink中建立SVPWM及永磁同步电机调速系统的仿真模型。仿真结果表明, SVPWM可在电机空间实现圆形磁场,输出电压谐波集中在载波频率整数倍附近,较高的调制比可获得较小的电压谐波畸变。

  15. Pulse width control loop as a duty cycle corrector

    Jovanović Goran


    Full Text Available The clock distribution and generation circuitry forms a critical component of current synchronous digital systems. A digital system’s clocks must have not only low jitter, low skew, but also well-controlled duty cycle in order to facilitate versatile clocking techniques. In high-speed CMOS clock buffer design, the duty cycle of a clock is liable to be changed when the clock passes through a multistage buffer because the circuit is not pure digital [8]. In this paper, we propose a pulse width control loop referred as MPWCL (modified pulse width control loop that adopts the same architecture as the conventional PWCL, but with a new pulse generator and new charge pump circuit as a constituent of the duty cycle detector. Thanks to using new building blocks the proposed pulse width control loop can control the duty cycle in a wide range, and what is more important it becomes operative in saturation region too, what provides conditional for fast locking time. For 1.2 µm double-metal double-poly CMOS process with Vdd = 5 V and operating frequency of 133 MHz, results of SPICE simulation show that the duty cycle can be well controlled in the range from 20 % up to 80 % if the loop parameters are properly chosen.

  16. 基于延迟锁定环技术的数字脉宽调制器的设计与实现%The Design and Implementation of a Delay Lock Loop Digital Pulse Width Modulator

    宋慧滨; 梁雷; 王永平; 李菲; 孙伟峰


    A novel digital pulse width modulator( DPWM) architecture that based on DLL technology is introduced, which applies to switched-mode power supply( SMPS) . The delay line of this DPWM take advantage of the program-mable delay unit(PDU)and the DLL technology to eliminate the influence of process,temperature and voltage, which improve the linearity of PWM dramatically. This DPWM is well suited for FPGA or custom chip implementa-tion. The IC occupying only 0.045 7 mm2 silicon area is implemented in a CMOS 0.18μm process,the measure re-sults meet with the demand and the DPWM can fit the engineering application.%介绍了一种新型的基于数字延迟锁定环DLL( Delay Lock Loop)技术的混合数字脉宽调制器DPWM( Digital Pulse Width Modulator)结构,该结构用可编程延迟单元PDU( Programmable Delay Unit)构成延迟线,通过DLL调节算法,动态地调整PDU的延迟时间,从而消除了延迟线的延迟时间受工艺、温度、工作电压的影响,提高了PWM的调节线性度,适用于数字控制开关式电源SMPS( Switched-Mode Power Supply),可以大幅度的提升系统的性能。同时,此种结构的DPWM适合FPGA验证和流片实现。采用CMOS 0.18μm工艺对所提出的结构进行了设计与实现,DPWM占用面积0.0457 mm2,芯片测试结果非常好,可以进行工程应用。

  17. A Space Vector Pulse Width Modulation Based Optimization Control Strategy for Hybrid Cascaded 7-Level Inverter%基于SVPWM调制的混合级联七电平逆变器优化控制策略

    耿俊利; 梁晖; 金渊


    The working modes of hybrid cascaded 7-level inverter with dead zone are analyzed and analysis results show that there are different jumping situations of inverter voltage under different working modes. On this basis, based on space vector pulse width modulation (SVPWM) strategy an optimal control method is proposed. In the premise that the supporting capacitor voltage is under the control, through analyzing the jumping of output voltage level and the valve action times corresponding to the charging/discharging process of supporting capacity voltage switching in each interval an optimal control strategy to reduce the jumping of output voltage is put forward; besides, the output voltage loss due to the existence of dead zone time is analyzed and calculated according to the principle of volt-second balance, and the dead zone compensation for its modulation wave is performed. The effectiveness of the proposed control strategy is validated by results of simulation and experiments.%分析混合级联七电平逆变器带死区时的工作模式,不同工作模式下其逆变器电压的跳变情况不同。在此基础上,提出了基于空间矢量脉冲调制(space vector pulse width modulation,SVPWM)策略的优化控制方法。以控制支撑电容电压为前提,通过对每个区间支撑电容充放电切换过程所对应的开关动作次数、输出电压电平跳变情况的分析,提出了一种减小输出电压跳变的优化控制策略;此外,分析了死区时间的存在所带来的输出电压损失,根据伏秒平衡原理进行计算,并对其调制波进行死区补偿。仿真及实验结果验证了该控制策略的有效性。

  18. Implementation of Carrier-Based Simple Boost Pulse Width Modulation (PWM) for Z-Source Inverter (ZSI) using Field Programming Gate Array (FPGA)

    Muhammad, M.; Rasin, Z.; Jidin, A.


    In recent years, the research on the Z-source inverter (ZSI) has received a wide acceptance due to its attractive solution for example in the renewable energy interface that requires voltage boost capability. The conventional inverter circuit based on the SPWM technique for example does not able to fully utilize its DC input voltage to produce a greater output voltage. The ZSI shoot-through implementation in high switching frequency requires a processor with fast sampling and high precision. In simulation, this can be easily carried out with the available advanced engineering software. In the hardware implementation however, the processor used is not only handle the switching, but also needs to read the data obtained by the sensor, voltage and current control, information display etc. This limits the capacity that can be used to implement the switching fast sampling with high precision. The aims of this work are to implement high precision of carrier-based simple boost PWM for ZSI using FPGA and to verify its real time hardware implementation. The high precision of PWM control algorithm based on the FPGA platform is verified by comparing the simulation results with the experimental results for different modulation index and boost factor, and a good agreement is concluded. It is observed that the application of FPGA reduces complexity, increases speed and the design of the switching technique can be altered without having to modify the hardware implementation.

  19. Microsecond pulse width, intense, light-ion beam accelerator

    Rej, D. J.; Bartsch, R. R.; Davis, H. A.; Faehl, R. J.; Greenly, J. B.; Waganaar, W. J.


    A relatively long-pulse width (0.1-1 μs) intense ion beam accelerator has been built for materials processing applications. An applied Br, magnetically insulated extraction ion diode with dielectric flashover ion source is installed directly onto the output of a 1.2 MV, 300-kJ Marx generator. The diode is designed with the aid of multidimensional particle-in-cell simulations. Initial operation of the accelerator at 0.4 MV indicates satisfactory performance without the need for additional pulse shaping. The effect of a plasma opening switch on diode behavior is considered.

  20. Direct Torque Control of Asynchronism Motor Based on Space Vector Pulse Width Modulation%基于SVPWM的感应电机直接转矩控制方法的研究

    高中臣; 张爱玲; 陈晨


    To reduce the low speed torque ripple of induction motor and keep constant switch frequency, this paper proposed a new control strategy on the basis of direct torque control (DTC),which uses Space Vector Pulse Width Modulation instead of switch table.The experiment and simulation results show that it can reduce the torque ripple,and improve the waveform of stator flux and current.%针对传统直接转矩控制开关频率不恒定及低速时的转矩脉动大的缺点,采用了基于SVPWM的直接转矩控制方法.根据转矩和定子磁链的误差确定应该施加的参考电压矢量,然后利用电压空间矢量脉宽调制(SVPWM)的方法合成该矢量.仿真和实验结果表明,基于SVPWM的直接转矩控制(SVPWM-DTC)能够有效减小转矩脉动,改善磁链和电流波形.

  1. Non-Fragile H∞Control for Random Pulse Width Modulation of DCM Boost Converter%DCM Boost变换器随机PWM非脆弱H∞控制

    冉华军; 李翔; 肖鹏


    引入两模态马尔科夫链随机PWM策略到DCM Boost变换器,推导建立了变换器的离散随机跳变模型,并基于随机跳变系统非脆弱H∞控制理论为Boost变换器设计了非脆弱H∞控制器,利用Simulink软件平台设计仿真电路进行验证。仿真分析表明,设计的控制器改善了Boost变换器的EMI品质,对控制器参数摄动表现出非脆弱性,使整个变换器系统具有较好的鲁棒性。%The two-state-Markov-chain random pulse width modulation (PWM) scheme was introduced into the DCM Boost converter. This paper derived the random discrete-time jumping model of the converter and designed the non-fragile H∞ con-troller based on non-fragile H∞ control theory of stochastic jumping system. The simulation was done to check the validity of non-fragile H∞controller on the Simulink platform. The simulation analysis indicates that the designed controller has improved the EMI quality of Boost converter along with non-fragility to its parameters uncertainty, and with better robust for the whole converter system.

  2. Design of fuzzy' pulse width modulation controller with accuracy and energy retrenchment applied to spacecraft%航天器精确节能模糊脉冲调宽控制器的设计

    周尹强; 徐炼新; 姜玉宪


    为实现航天器精确、节能的姿态或轨道控制,提出一种采用脉冲宽度调制PWM(Pulse Width Modulation)与模糊比例微分PD(Proportional Differential)控制相结合的模糊PD-PWM控制器.其中PWM能将开关型控制转化为相应的精确线性控制,而模糊PD控制在能量消耗限制不同情况下可实现两种快速、节能的控制过程.在分析大气层外拦截器EKV(Extra-atmospheric Kill Vehicle)处于目标捕获和末制导阶段对姿控系统的不同性能要求的基础上,以EKV姿控系统为例介绍了模糊PD-PWM控制器的设计和优化过程.说明了模糊PD控制器隶属度函数的设计、待优化参数的选择以及模糊控制规则的设计,重点叙述了遗传算法GA(Genetic Algorithms)中适应度函数的设计方法,并对隶属度函数进行了优化.仿真结果证明优化后的控制器能满足EKV不同阶段姿态控制要求,具有精确、节能的特点.

  3. Digital-Analog Converter Based on Pulse Width Modulated Force Feedback in Sigma-Delta Accelerometer%Σ△微加速度计中基于脉宽调制的力反馈回路

    陶呈瑶; 邓康发


    针对微加速度计接口电路的Sigma-Delta(撞驻)数字反馈系统,提出了一种基于脉宽调制( PWM)的力反馈回路:利用模拟低通滤波器将PWM波解调成模拟输出信号,具有滤波和数模转换功能。首先建立微加速度计撞驻闭环反馈系统的Simulink模型并进行了系统级仿真。之后采用Filter Solutions滤波器设计软件确定三阶低通巴特沃斯滤波器,并采用Pspice仿真软件进行电路级仿真。最后将制作的PCB版电路进行测试:PWM波通过力反馈回路能还原成高保真度的模拟信号,输出信号和输入信号的频率相对误差小于0.36%,等效DAC分辨率为8 bit。试验表明,此方案结构简单、成本低,能以较低电路复杂度实现高精度的模拟信号输出。%Aiming at the Sigma-Delta(Σ△) digital force feedback system in Mcro-accelerometer interface circuit,this paper presents a force feedback loop based on Pulse Width Modulator(PWM). The PWM wave can be translated into output analog singal using low pass filter,indicating that this circuit has a dual function of filter and digital to analog conversion( DAC) . Firstly,Σ△closed loop feedback system was simulated in Simulink model for system level simulation,then Filter Solutions software was used for designing three-order Butterworth low pass filter,and Pspice software was adopted for circuit level simulation. Finally electronic circuit was made by PCB and then tested. Through the force back loop,the wave can be successfully translate to undistorted analog signal,and the maximun relative error is below 0. 36% compared to the input signal,the equivalent DAC resolution is 8 bit. This experiment shows that this method has the advantages of simple structure,low cost,and easy way to produce high precise output analog signal.

  4. A Novel Transcranial Magnetic Stimulator Inducing Near Rectangular Pulses with Controllable Pulse Width (cTMS)

    Jalinous, Reza; Lisanby, Sarah H.


    A novel transcranial magnetic stimulation (TMS) device with controllable pulse width (PW) and near rectangular pulse shape (cTMS) is described. The cTMS device uses an insulated gate bipolar transistor (IGBT) with appropriate snubbers to switch coil currents up to 7 kA, enabling PW control from 5 μs to over 100 μs. The near-rectangular induced electric field pulses use 22–34% less energy and generate 67–72% less coil heating compared to matched conventional cosine pulses. CTMS is used to stimulate rhesus monkey motor cortex in vivo with PWs of 20 to 100 μs, demonstrating the expected decrease of threshold pulse amplitude with increasing PW. The technological solutions used in the cTMS prototype can expand functionality, and reduce power consumption and coil heating in TMS, enhancing its research and therapeutic applications. PMID:18232369

  5. Safe Operation and Alignment of the Variable Pulse Width Laser at the US Army Research Laboratory


    ARL-TN-0736 ● FEB 2016 US Army Research Laboratory Safe Operation and Alignment of the Variable Pulse Width Laser at the US Army...Laboratory Safe Operation and Alignment of the Variable Pulse Width Laser at the US Army Research Laboratory by Jennifer L Gottfried...TITLE AND SUBTITLE Safe Operation and Alignment of the Variable -Pulse Width Laser at the US Army Research Laboratory 5a. CONTRACT NUMBER 5b

  6. Measurement of Pulse Width from a Bubble Cloud under Multibubble Sonoluminescence Conditions

    Ko, Ilgon; Kwak, Ho-Young


    The pulse width from a bubble cloud under multibubble sonoluminescence (MBSL) conditions was measured for the first time using a time-correlated single photon counting technique (TC/SPC). The measured pulse width from several thousand bubbles in water was approximately 250.9 ps, with scattered pulses occurring 1.5 ns before and after the maximum light pulse intensity. The observed pulse width from a bubble cloud, which appears to be comparable to that of the single bubble sonoluminescence, indicates that the clouds of bubbles collapse simultaneous to emitting a light that is synchronized with the applied ultrasound. Also, pulse widths from clouds of multibubbles in water-surfactant and water-alcohol solutions were measured to investigate the surfactant and alcohol effect on the sonoluminescence intensity and pulse width. Size distribution of the bubble cloud at the multibubble conditions was also measured by phase-Doppler technique.

  7. Pulse-width tunable multi-channel NRZ-to-RZ conversion with duplicate output

    Yu, Yu; Zhang, Xinliang; Huang, Dexiu


    We demonstrate multi-channel non-return-to-zero (NRZ) to return-to-zero (RZ) conversions with tunable output pulse-width and single-to-dual function, using a phase modulator and an array waveguide grating (AWG), which acts both detuned multi-channel filter and demultiplexer. Four-channel NRZ signals after transmission can be converted to eight-channel RZ signals with timing jitter and extinction ratio improvement. Further transmission and bit error ratio (BER) measurements for the converted RZ signal show a good performance compared with conventional one.

  8. Pulse shaping using a spatial light modulator

    Botha, N


    Full Text Available Femtosecond pulse shaping can be done by different kinds of pulse shapers, such as liquid crystal spatial light modulators (LC SLM), acousto optic modulators (AOM) and deformable and movable mirrors. A few applications where pulse shaping...

  9. Nonlinear Pulse Compression and Reshaping Using Cross-Phase Modulation in a Dispersion-Shifted Fiber

    S.; W.; Chan; K.; K.; Chow; C.; Shu


    Nonlinear pulse compression has been demonstrated by cross-phase modulation in a dispersion-shifted fiber. The output is obtained from filtering of the broadened optical spectrum and a pulse width reduction from 61 to 28 ps is achieved.

  10. Picosecond optical pulse generation at gigahertz rates by direct modulation of a semiconductor laser

    Auyeung, J.


    We report the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser. Pulse width of 28 ps is achieved at a repetition frequency of 2.5 GHz. Pulse width dependence on the experimental parameters is described.

  11. Correlation between pulse-width and peak luminosity of single-pulse long gamma-ray bursts


    With a sample of 21 single-pulse GRBs with redshift measurement and a sample of 65 single-pulse GRBs with pseudo redshift estimated by the luminosity-spectral lag relation,we show that the peak luminosities of GRB pulses are anti-correlated with pulse width,indicating that longer-pulses tend to be dimmer in the gamma-ray band.The anti-correlation is accessible with an internal shock scenario.

  12. New pulse modulator with low switching frequency

    Golub V. S.


    Full Text Available The author presents an integrating pulse modulator (analog signal converter with the pulse frequency and duration modulation similar to sigma-delta modulation (with low switching frequency, without quantization. The modulator is characterized by the absence of the quantization noise inherent in sigma-delta modulator, and a low switching frequency, unlike the pulse-frequency modulator. The modulator is recommended, in particular, to convert signals at the input of the class D power amplifier.

  13. Numerical simulation of different pulse width of long pulsed laser on aluminum alloy

    Li, Mingxin; Jin, Guangyong; Zhang, Wei; Chen, Guibo; Bi, Juan


    Established a physical model to simulate the melt ejection induced by long pulsed laser on aluminum alloy and use the finite element method to simulate the whole process. This simulation is based on the interaction between single pulsed laser with different pulse width and different peak energy and aluminum alloy material. By comparing the theoretical simulation data and the actual test data, we discover that: the theoretical simulation curve is well consistent with the actual experimental curve, this two-dimensional model is with high reliability; when the temperature at the center of aluminum alloy surface increases and evaporation happens after the surface temperature at the center of aluminum alloy surface reaches boiling point and later the aluminum alloy material sustains in the status of equilibrium vaporization; the keyhole appears on the surface of the target, an increment of the keyhole, the maximum temperature at the center of aluminum alloy surface gradually moves inwardly. This research may provide the theoretical references to the understanding of the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application of the laser materials processing and military field.

  14. Long-pulse-width narrow-bandwidth solid state laser

    Dane, C.B.; Hackel, L.A.


    A long pulse laser system emits 500-1000 ns quasi-rectangular pulses at 527 nm with near diffraction-limited divergence and near transform-limited bandwidth. The system consists of one or more flashlamp-pumped Nd:glass zig-zag amplifiers, a very low threshold stimulated-Brillouin-scattering (SBS) phase conjugator system, and a free-running single frequency Nd:YLF master oscillator. Completely passive polarization switching provides eight amplifier gain passes. Multiple frequency output can be generated by using SBS cells having different pressures of a gaseous SBS medium or different SBS materials. This long pulse, low divergence, narrow-bandwidth, multi-frequency output laser system is ideally suited for use as an illuminator for long range speckle imaging applications. Because of its high average power and high beam quality, this system has application in any process which would benefit from a long pulse format, including material processing and medical applications. 5 figs.

  15. Solid-state pulse forming module with adjustable pulse duration

    Wang, Langning; Liu, Jinliang; Qiu, Yongfeng; Chu, Xu; Zhang, Qingmeng


    A new solid-state pulse forming module is described in this paper. The pulse forming module is fabricated on a glass ceramic substrate, with the dimension of 250 mm × 95 mm × 4 mm. By changing the copper strips used in the pulse forming modules, the pulse duration of the obtained pulsed can range from 80 ns to 140 ns. Both the simulation and tests show that the pulse forming module has a good pulse forming ability. Under a high voltage in microsecond's time, the new pulse forming modules can hold off a voltage up to 25 kV higher than that of the previous study. In addition, future optimization for the field enhancement near the thin electrode edge has been proposed and simulated.

  16. Pulse width effect on the dissociation probability of CH4+ in the intense femtosecond laser field

    WANG Gao; SONG Di; LIU Yuyan; KONG Fan'ao


    The laser pulse width effect on the dissociation probability of CH4+ irradiated by an ultrafast laser has been investigated experimentally and theoretically. The femtosecond laser at 800 nm with an intensity of 8.0 × 1013 W/cm2 was used. The observed relative yield of the primary fragment ion CH3+ increases with increasing pulse width and tends to saturate when the pulse width is longer than 120 fs. The field-assisted dissociation (FAD) model and quasi-classical trajectory (QCT) calculation were applied to predicting the dissociation probability of CH4+.The calculated probability is corrected with the molecular orientation effect and the spatial distribution of laser intensity. The modified results show that the dissociation requires at least 23 fs and saturates with long pulse widths (≥100 rs). The result is approximately consistent with the experimental observation.

  17. The effect of laser pulse width on laser-induced damage at K9 and UBK7 components surface

    Zhou, Xinda; Ba, Rongsheng; Zheng, Yinbo; Yuan, Jing; Li, Wenhong; Chen, Bo


    In this paper, we investigated the effects of laser pulse width on laser-induced damage. We measured the damage threshold of K9 glass and UBK7 glass optical components at different pulse width, then analysis pulse-width dependence of damage threshold. It is shown that damage threshold at different pulse width conforms to thermal restriction mechanism, Because of cm size laser beam, defect on the optical component surface leads to laser-induced threshold decreased.

  18. Pulse amplitude modulated chlorophyll fluorometer

    Greenbaum, Elias; Wu, Jie


    Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

  19. Pulse-Width Control in Ladder Structure Four-Phase Rectifier for AC-Electromotive

    Ivanov, V. V.; Myatez, S. V.; Langeman, E. G.; Schurov, N. I.


    Based on these studies the ways of power factor of the single-phase rectifiers operating in a single-phase AC network improving are suggested. The ladder four-phase rectifier is offered as a technical mean using a pulse-width method of controlling the rectified voltage. The pulse-width control efficiency as a way of the power factor rectifier with a ladder structure for AC electromotive improving is evaluated.

  20. Modeling and analysis of the HPM pulse-width upset effect on CMOS inverter

    Xinhai, Yu; Changchun, Chai; Liping, Qiao; Yintang, Yang; Yang, Liu; Xiaowen, Xi


    We derive analytical models of the excess carrier density distribution and the HPM (high-power microwave) upset susceptibility with dependence of pulse-width, which are validated by the simulated results and experimental data. Mechanism analysis and model derivation verify that the excess carriers dominate the current amplification process of the latch-up. Our results reveal that the excess carrier density distribution in P-substrate behaves as pulse-width dependence. The HPM upset voltage threshold Vp decreases with the incremental pulse-width, while there is an inflection point which is caused because the excess carrier accumulation in the P-substrate will be suppressed over time. For the first time, the physical essence of the HPM pulse-width upset effect is proposed to be the excess carrier accumulation effect. Validation concludes that the Vp model is capable of giving a reliable and accurate prediction to the HPM upset susceptibility of a CMOS inverter, which simultaneously considers technology information, ambient temperature, and layout parameters. From the model, the layout parameter LB has been demonstrated to have a significant impact on the pulse-width upset effect: a CMOS inverter with minor LB is more susceptible to HPM, which enables us to put forward hardening measures for inverters that are immune from the HPM upset. Project supported by the National Natural Science Foundation of China (No. 60776034) and the State Key Development Program for Basic Research of China (No. 2014CB339900).

  1. Design of compact Marx module with square pulse output

    Liu, Hongwei; Xie, Weiping; Yuan, Jianqiang; Wang, Lingyun; Ma, Xun; Jiang, Ping


    Compact pulsed power system based on compact Marx generator is widely used in terms of drive resistance and capacitive loads. This system usually adopts high performance components such as high energy density capacitors, compact switches, and integrated structure. Traditional compact Marx generator can only output double-exponential pulse profile. In this paper a compact, low-impedance Marx module which can output rectangular pulse profile is design and tested. This module has multiple circuits of different discharge frequencies in parallel to generate quasi-rectangular pulse. Discharge characteristic of an ideal module with infinite branches is calculated theoretically. A module with two branches has been designed and tested. Test results show that the impedance of the module is 1.2 Ω. When charging voltage is 100.6 kV and load resistance is 1 Ω, the peak output pulse is 45.2 kV voltage, the peak power is about 2 GW, the pulse width is about 130 ns, and the rise time is about 35 ns. The energy density and power density of the module are 15 kJ/m3 and 140 GW/m3, respectively.

  2. Simulation calculation of 24kV long pulse TESLA modulator

    TAO Xiao-Ping; Stefan CHOROBA


    A 24 kV long pulse modulator is designed for DESY's TESLA Test Facility (TIF). This modulator,with a 120 kV, 1.7 ms width pulse output, is used to drive a Thomson TH1801 multibeam klystron. In order to make waveform flatness of the klystron voltage less than ±0.5%, it is necessary to use a bouncer circuit. This paper gives the Pspice simulation results of the 24 kV long pulse TESLA modulator.

  3. Broadband supercontinuum generation with femtosecond pulse width in erbium-doped fiber laser (EDFL)

    Rifin, S. N. M.; Zulkifli, M. Z.; Hassan, S. N. M.; Munajat, Y.; Ahmad, H.


    We demonstrate two flat plateaus and the low-noise spectrum of supercontinuum generation (SCG) in a highly nonlinear fiber (HNLF), injected by an amplified picosecond pulse seed of a carbon nanotube-based passively mode locked erbium-doped fiber laser. A broad spectrum of width approximately 1090 nm spanning the range 1130-2220 nm is obtained and the pulse width is compressed to the shorter duration of 70 fs. Variations of the injected peak power up to 33.78 kW into the HNLF are compared and the broad spectrum SCG profiles slightly expand for each of the injected peak powers. This straightforward configuration of SCG offers low output power and ultra-narrow femtosecond pulse width. The results facilitate the development of all fiber time-domain spectroscopy systems based on the photoconductive antenna technique.

  4. Frequency Properties Research of Elevator Drive System with Direct Torque Control-Pulse with Modulation

    A. S. Koval


    Full Text Available In the article problems of frequency properties research for electric drive system with direct torque control and pulse width modulator are described. The mathematical description of elevator is present. Simplified mathematical description of direct torque control - pulse width modulator electric drive system is shown. Transfer functions for torque and speed loops are determined. Logarithmic frequency characteristics are computed. Damping properties of elevator drive system are estimated.

  5. Existence and stabilizability of steady-state for semilinear pulse-width sampler controlled system

    JinRong Wang


    Full Text Available In this paper, we study the steady-state of a semilinear pulse-width sampler controlled system on infinite dimensional spaces. Firstly, by virtue of Schauder's fixed point theorem, the existence of periodic solutions is given. Secondly, utilizing a generalized Gronwall inequality given by us and the Banach fixed point theorem, the existence and stabilizability of a steady-state for the semilinear control system with pulse-width sampler is also obtained. At last, an example is given for demonstration.

  6. Very-short-pulse modulator using asymmetric thyristors

    Perol, P.


    The development of a semiconductor delay-line modulator for a 40-nsec/pulse 10-kHz-repetition-rate coaxial magnetron radar used to monitor airport runway traffic is reported and illustrated with circuit diagrams, output spectra, and photographs. The problems presented by the design specifications are indicated, and the solutions adopted (asymmetric press-packed thyristors and ferrite pulse transformer) are explained. Pulse widths and peak powers with 16 nf of delay line and a 2.5-kV charge at the level of the modulator are found to be 120 nsec and 58 kW without truncation and 40 nsec and 50-51 kW with truncation, the latter corresponding to an efficiency of 17 percent. The pulse leading edges have dI/dt at the transformer primary = 1.8 kA/microsec and dV/dt at the magnetron = 160 kV/microsec.

  7. Tissue effects of Ho:YAG laser with varying fluences and pulse widths

    Vari, Sandor G.; van der Veen, Maurits J.; Pergadia, Vani R.; Shi, Wei-Qiang; Duffy, J. T.; Weiss, Andrew B.; Fishbein, Michael C.; Grundfest, Warren S.


    We investigated the effect of varying fluence and pulse width on the ablation rate and consequent thermal damage of the Ho:YAG (2.130 micrometers ) laser. The rate of ablation on fresh bovine knee joint tissues, fibrous cartilage, hyaline cartilage, and bone in saline was determined after varying the fluence (160 - 640 J/cm2) and pulse width (150, 250, 450 microsecond(s) ec, FWHM) at a repetition rate of 2 Hz. A 400/440 micrometers fiber was used. The ablation rate increased linearly with the fluence. In fibrocartilage, different pulse durations generated significant changes in the ablation rates, but showed minor effects on hyaline cartilage and bone. The heat of ablation for all three tissue types decreased after lengthening the pulse.

  8. Design of a variable width pulse generator feasible for manual or automatic control

    Vegas, I.; Antoranz, P.; Miranda, J. M.; Franco, F. J.


    A variable width pulse generator featuring more than 4-V peak amplitude and less than 10-ns FWHM is described. In this design the width of the pulses is controlled by means of the control signal slope. Thus, a variable transition time control circuit (TTCC) is also developed, based on the charge and discharge of a capacitor by means of two tunable current sources. Additionally, it is possible to activate/deactivate the pulses when required, therefore allowing the creation of any desired pulse pattern. Furthermore, the implementation presented here can be electronically controlled. In conclusion, due to its versatility, compactness and low cost it can be used in a wide variety of applications.

  9. Testing a scale pulsed modulator for an IEC neutron source into a resistive load

    Dale, Gregory E [Los Alamos National Laboratory; Wheat, Robert M [Los Alamos National Laboratory; Aragonez, Robert [Los Alamos National Laboratory


    A 1/10th scaled prototype pulse modulator for an Inertial Electrostatic Confinement (IEC) neutron source has been designed and tested at Los Alamos National Laboratory (LANL). The scaled prototype modulator is based on a solid-state Marx architecture and has an output voltage of 13 kV and an output current of 10 A. The modulator has a variable pulse width between 50 {micro}s and 1 ms with < 5% droop at all pulse widths. The modulator operates with a duty factor up to 5% and has a maximum pulse repetition frequency of 1 kHz. The use of a solid-state Marx modulator in this application has several potential benefits. These benefits include variable pulse width and amplitude, inherent switch overcurrent and transient overvoltage protection, and increased efficiency over DC supplies used in this application. Several new features were incorporated into this design including inductorless charging, fully snubberless operation, and stage fusing. The scaled prototype modulator has been tested using a 1 k{Omega} resistive load. Test results are given. Short (50 {micro}s) and long (1 ms) pulses are demonstrated as well as high duty factor operation (1 kHz rep rate at a 50 {micro}s pulse width for a 5% duty factor). Pulse agility of the modulator is demonstrated through turning the individual Marx stages on and off in sequence producing ramp, pyramid, and reverse pyramid waveforms.

  10. Improving Stability of Pulse Modulator Technology

    ZHANG; Li-feng; ZHU; Zhi-bin; LIU; Bao-jie; YANG; Sheng


    In high voltage pulse modulator,the RD loop and the primary winding of the pulse transformer is parallel,and the negative peak loop and the PFN is parallel.When the modulator is running,the resistor temperature of RD loops and the resistor temperature of reverse peak loop are too high,exceeding 100℃.It can work normally,

  11. Predicted effects of pulse width programming in spinal cord stimulation: a mathematical modeling study.

    Lee, Dongchul; Hershey, Brad; Bradley, Kerry; Yearwood, Thomas


    To understand the theoretical effects of pulse width (PW) programming in spinal cord stimulation (SCS), we implemented a mathematical model of electrical fields and neural activation in SCS to gain insight into the effects of PW programming. The computational model was composed of a finite element model for structure and electrical properties, coupled with a nonlinear double-cable axon model to predict nerve excitation for different myelinated fiber sizes. Mathematical modeling suggested that mediolateral lead position may affect chronaxie and rheobase values, as well as predict greater activation of medial dorsal column fibers with increased PW. These modeling results were validated by a companion clinical study. Thus, variable PW programming in SCS appears to have theoretical value, demonstrated by the ability to increase and even 'steer' spatial selectivity of dorsal column fiber recruitment. It is concluded that the computational SCS model is a valuable tool to understand basic mechanisms of nerve fiber excitation modulated by stimulation parameters such as PW and electric fields.

  12. High-Quality Ultrashort Pulse Generation Utilizing a Self-Phase Modulation-Based Reshaper


    An ultrashort 10-GHz pulse generation scheme was successfully demonstrated using a bulk material InGaAsP electroabsorption modulator to generate the seed pulse. A self-phase modulation-based reshaper was used after the adiabatic soliton compression in a comb-like dispersion profiled fiber. Experiments and simulations confirm that the reshaper effectively removes the pulse pedestal and improves the pulse extinction ratio. As a result, the 10-GHz pulse had no pedestal, a high extinction ratio, and a pulse width of only 1.4 ps.

  13. Nanosecond pulse-width electron diode based on dielectric wall accelerator technology

    Zhao, Quantang, E-mail: [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Z.M.; Yuan, P.; Cao, S.C.; Shen, X.K.; Jing, Y. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Yu, C.S. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Z.P.; Liu, M.; Xiao, R.Q. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zong, Y.; Wang, Y.R. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, H.W. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)


    An electron diode using a short section of dielectric wall accelerator (DWA) has been under development at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. Tests have been carried out with spark gap switches triggered by lasers. The stack voltage efficiency of a four-layer of Blumleins reached about 60–70% with gas filled spark gap switching. The generated pulse voltage of peak amplitude of 23 kV and pulse width of 5 ns is used to extract and accelerate an electron beam of 320 mA, measured by a fast current transformer. A nanosecond pulse width electron diode was achieved successfully. Furthermore, the principle of a DWA is well proven and the development details and discussions are presented in this article. -- Highlights: •The key technology of DWA, including switches and pulse forming lines were studied. •The SiC PCSS obtained from Shanghai Institute were tested. •Two layers ZIP lines (new structure) and four layers Blumlein lines were studied with laser triggered spark gap switches. •A nanosecond pulse-width electron diode based on DWA technologies is achieved and studied experimentally. •The principle of DWA is also proved by the diode.

  14. Effects of finite pulse width on two-dimensional Fourier transform electron spin resonance

    Liang, Zhichun; Crepeau, Richard H.; Freed, Jack H.


    Two-dimensional (2D) Fourier transform ESR techniques, such as 2D-ELDOR, have considerably improved the resolution of ESR in studies of molecular dynamics in complex fluids such as liquid crystals and membrane vesicles and in spin labeled polymers and peptides. A well-developed theory based on the stochastic Liouville equation (SLE) has been successfully employed to analyze these experiments. However, one fundamental assumption has been utilized to simplify the complex analysis, viz. the pulses have been treated as ideal non-selective ones, which therefore provide uniform irradiation of the whole spectrum. In actual experiments, the pulses are of finite width causing deviations from the theoretical predictions, a problem that is exacerbated by experiments performed at higher frequencies. In the present paper we provide a method to deal with the full SLE including the explicit role of the molecular dynamics, the spin Hamiltonian and the radiation field during the pulse. The computations are rendered more manageable by utilizing the Trotter formula, which is adapted to handle this SLE in what we call a "Split Super-Operator" method. Examples are given for different motional regimes, which show how 2D-ELDOR spectra are affected by the finite pulse widths. The theory shows good agreement with 2D-ELDOR experiments performed as a function of pulse width.

  15. Nanosecond pulse-width electron diode based on dielectric wall accelerator technology

    Zhao, Quantang; Zhang, Z. M.; Yuan, P.; Cao, S. C.; Shen, X. K.; Jing, Y.; Yu, C. S.; Li, Z. P.; Liu, M.; Xiao, R. Q.; Zong, Y.; Wang, Y. R.; Zhao, H. W.


    An electron diode using a short section of dielectric wall accelerator (DWA) has been under development at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. Tests have been carried out with spark gap switches triggered by lasers. The stack voltage efficiency of a four-layer of Blumleins reached about 60-70% with gas filled spark gap switching. The generated pulse voltage of peak amplitude of 23 kV and pulse width of 5 ns is used to extract and accelerate an electron beam of 320 mA, measured by a fast current transformer. A nanosecond pulse width electron diode was achieved successfully. Furthermore, the principle of a DWA is well proven and the development details and discussions are presented in this article.

  16. Simple autocorrelator for ultraviolet pulse-width measurements based on the nonlinear photoelectric effect.

    Takagi, Y


    An optical pulse-width measurement in the ultraviolet spectral region has been performed in a simple manner by introducing into the second-order autocorrelator a nonlinear response of the optical detector based on the two-photon photoelectric effect. The pulse widths of the third, fourth, and fifth harmonics of a mode-locked Nd:YAG laser were measured by the use of a photomultiplier with a cesium iodide photocathode with a minimum required pulse energy of 10 nJ and a power density of 10 kW/cm(2). The effect of transient interband optical excitation with different photon energies on the intensity correlation profile was also studied for the case of a copper iodide photocathode, and the result provides a background-free intensity correlation in a part of the ultraviolet spectral region.

  17. Pulse width shaping of passively mode-locked soliton fiber laser via polarization control in carbon nanotube saturable absorber.

    Jeong, Hwanseong; Choi, Sun Young; Rotermund, Fabian; Yeom, Dong-Il


    We report the continuous control of the pulse width of a passively mode-locked fiber laser via polarization state adjustment in a single-walled carbon nanotube saturable absorber (SWCNT-SA). The SWCNT, coated on the side-polished fiber, was fabricated with optimized conditions and used for stable mode-locking of the fiber laser without Q-switching instabilities for any polarization state of the laser intra-cavity. The 3-dB spectral bandwidth of the mode-locked pulses can be continuously tuned from 1.8 nm to 8.5 nm with the polarization control for a given laser cavity length and applied pump power. A pulse duration varying from 470 fs to 1.6 ps was also observed with a change in the spectral bandwidth. The linear and the nonlinear transmission properties of the SA were analyzed, and found to exhibit different modulation depths depending on the input polarization state in the SA. The largest modulation depth of the SA was observed at the polarization state of the transverse electric mode that delivers shortest pulses at the laser output.

  18. Soft demodulation to the optical pulse position modulated signals

    Zhou, Tian-hua; Chen, Wei-biao


    The optical Pulse Position Modulation (PPM) is applied widely in Free Space Optical communication (FSO) with the low average power and the high peak power. The transmitted PPM information depends on the location of the coming optical pulse signals in fixed period. Both receiver and transmitter should been kept in time slot synchronization and frame synchronization in demodulation. Because the channel is very complex, the received optical pulse width will be stretched randomly. We design and realize one digital PPM modulation receiver with high sensitivity using the technology of PMT, A/D converter, and DSP. It is suitable to the total digital optical receiver with random time slots and random pulse width. The paper will mainly discuss the realization of the soft demodulation behind A/D converter. The key of PPM digital soft modulation is the establishment of the synchronization that involves the segment synchronization, the fame synchronization and the bit synchronization. The synchronization can be obtained by seeking for the frame head in data frames. Based on the estimation of received waveform characteristics, we adopt a matched filter without the best factors firstly. Thereafter, their errors will be self-adapted while finding the synchronization head. Considering the real-time need, we choose the reduced mode of maximum likelihood function judgment finally. In the experiments, results with high sensitivity and low bit error rate have been achieved.

  19. 两电平空间矢量脉宽调制的简化算法和电压谐波分析方法%A Simplified Algorithm and A Method of Voltage Harmonic Analysis for Two-Level Space Vector Pulse Width Modulation

    于心宇; 魏应冬; 姜齐荣


    传统的两电平空间矢量脉宽调制(space vector pulse width modulation,SVPWM)算法流程复杂,计算量较大。从传统算法的伏秒平衡方程出发,推导并求解了三相上开关器件脉宽时间所满足的线性方程组,提出了一种无需坐标变换和扇区判断的两电平 SVPWM 简化算法。该算法流程简单,计算量少,且在参考电压含不对称分量时仍与传统算法等价。在此基础上,针对采用同步 SVPWM 的两电平变流器,提出了一种电压谐波分析方法,给出了在不同零矢量分配方式下通用的电压谐波频谱计算公式,并定性分析了电压谐波的频谱分布特性。基于PSCAD/EMTDC的仿真结果验证了所提的两电平 SVPWM 简化算法和电压谐波分析方法的准确性。%The traditional algorithm for 2-level space vector pulse width modulation (SVPWM) is complicated with large computation. In this paper, based on the volt-second balance equation of traditional algorithm, the linear equations of the pulse time of switching devices in 3-phase upper arms are set up and solved, thus a simplified algorithm for 2-level SVPWM without coordinate transformation and sector judgment is proposed, which reduces a lot of computation and is much easier to implement. Based on the simplified algorithm, a method of voltage harmonic analysis for synchronous SVPWM is proposed, which presents the generic expressions of the voltage harmonic spectrum when the distribution of zero vectors is varied, and explains the distribution characteristics of voltage harmonics qualitatively. The accuracy of the simplified algorithm and the novel method of voltage harmonic analysis for 2-level SVPWM are verified by the simulation results based on PSCAD/EMTDC.

  20. Bit rate and pulse width dependence of four-wave mixing of short optical pulses in semiconductor optical amplifiers

    Diez, S.; Mecozzi, A.; Mørk, Jesper


    We investigate the saturation properties of four-wave mixing of short optical pulses in a semiconductor optical amplifier. By varying the gain of the optical amplifier, we find a strong dependence of both conversion efficiency and signal-to-background ratio on pulse width and bit rate....... In particular, the signal-to-background ratio can be optimized for a specific amplifier gain. This behavior, which is coherently described in experiment and theory, is attributed to the dynamics of the amplified spontaneous emission, which is the main source of noise in a semiconductor optical amplifier....

  1. Optimal pseudorandom pulse position modulation ladar waveforms.

    Fluckiger, David U; Boland, Brian F; Marcus, Eran


    An algorithm for generating optimal pseudorandom pulse position modulation (PRPPM) waveforms for ladar ranging is presented. Bistatic ladar systems using Geiger-mode avalanche photodiodes require detection of several pulses in order to generate sufficient target statistics to satisfy some detection decision rule. For targets with large initial range uncertainty, it becomes convenient to transmit a pulse train with large ambiguity range. One solution is to employ a PRPPM waveform. An optimal PRPPM waveform will have minimal sidelobes: equivalent to 1 or 0 counts after the pulse correlation filter (compression). This can be accomplished by generating PRPPM pulse trains with optimal or minimal sidelobe autocorrelation.

  2. A Hybrid Fiber/Solid-State Regenerative Amplifier with Tunable Pulse Widths for Satellite Laser Ranging

    Coyle, Barry; Poulios, Demetrios


    A fiber/solid-state hybrid seeded regenerative amplifier, capable of achieving high output energy with tunable pulse widths, has been developed for satellite laser ranging applications. The regenerative amplifier cavity uses a pair of Nd:YAG zigzag slabs oriented orthogonally to one another in order to make thermal lensing effects symmetrical and simplify optical correction schemes. The seed laser used is a fiber-coupled 1,064-nm narrowband (1 mJ) was measured. This corresponds to a nonlinear conversion efficiency of >60%. Furthermore, by pulse pumping this system, a single pulse per laser shot can be created for the SLR (satellite laser ranging) measurement, and this can be ejected into the instrument. This is operated at the precise frequency needed by the measurement, as opposed to commercial short-pulsed, mode-locked systems that need to operate in a continuous fashion, or CW (continuous wave), and create pulses at many MHz. Therefore, this design does not need to throw away or dump 99% of the laser energy to produce what is required; this system can be far smaller, more efficient, cheaper, and readily deployed in the field when packaged efficiently. Finally, by producing custom diode seed pulses electronically, two major advantages over commercial systems are realized: First, this pulse shape is customizable and not affected by the cavity length or gain of the amplifier cavity, and second, it can produce adjustable (selectable) pulse widths by simply adding multiple seed diodes and coupling each into commercial, low-cost fiber-optic combiners.

  3. Effects of finite laser pulse width on two-dimensional electronic spectroscopy

    Leng, Xuan; Yue, Shuai; Weng, Yu-Xiang; Song, Kai; Shi, Qiang


    We combine the hierarchical equations of motion method and the equation-of-motion phase-matching approach to calculate two-dimensional electronic spectra of model systems. When the laser pulse is short enough, the current method reproduces the results based on third-order response function calculations in the impulsive limit. Finite laser pulse width is found to affect both the peak positions and shapes, as well as the time evolution of diagonal and cross peaks. Simulations of the two-color two-dimensional electronic spectra also show that, to observe quantum beats in the diagonal and cross peaks, it is necessary to excite the related excitonic states simultaneously.

  4. Dual-Pulse Pulse Position Modulation (DPPM) for Deep-Space Optical Communications: Performance and Practicality Analysis

    Li, Jing; Hylton, Alan; Budinger, James; Nappier, Jennifer; Downey, Joseph; Raible, Daniel


    Due to its simplicity and robustness against wavefront distortion, pulse position modulation (PPM) with photon counting detector has been seriously considered for long-haul optical wireless systems. This paper evaluates the dual-pulse case and compares it with the conventional single-pulse case. Analytical expressions for symbol error rate and bit error rate are first derived and numerically evaluated, for the strong, negative-exponential turbulent atmosphere; and bandwidth efficiency and throughput are subsequently assessed. It is shown that, under a set of practical constraints including pulse width and pulse repetition frequency (PRF), dual-pulse PPM enables a better channel utilization and hence a higher throughput than it single-pulse counterpart. This result is new and different from the previous idealistic studies that showed multi-pulse PPM provided no essential information-theoretic gains than single-pulse PPM.

  5. Study on Pulse Skip Modulation Mode in Smart Power Integrated Circuits and Its Test Technology

    LUO Ping


    @@ Up to now, the popular control modes for smart power integrated circuit (SPIC) are PWM and PFM.PWM bases on constant frequency variable width (CFVW) control pulse, whereas, PFM bases on constant width variable frequency (CWVF) control pulse. PWM converter has low efficiency with light loads and high amplitude harmonic. On the other hand,the control circuit and filter for PFM are much complex. This dissertation proposes a novel modulation mode named pulse skip modulation (PSM)for SPIC converter, which bases on constant width constant frequency (CWCF) control pulse. It is shown that PSM converter would improve its efficiency and suppress EMI. It also has quick response speed, good interfere rejection and strong robust. Furthermore, it is easy to realize PSM control circuit. The modulating theories of PSM are firstly studied in the world according to the author's investigation.

  6. Effects of Pulse Width and Electrode Placement on the Efficacy and Cognitive Effects of Electroconvulsive Therapy

    Sackeim, Harold A.; Prudic, Joan; Nobler, Mitchell S.; Fitzsimons, Linda; Lisanby, Sarah H.; Payne, Nancy; Berman, Robert M.; Brakemeier, Eva-Lotta; Perera, Tarique; Devanand, D. P.


    BACKGROUND While electroconvulsive therapy (ECT) in major depression is effective, cognitive effects limit its use. Reducing the width of the electrical pulse and using the right unilateral electrode placement may decrease adverse cognitive effects, while preserving efficacy. METHODS In a double-masked study, we randomly assigned 90 depressed patients to right unilateral ECT at 6 times seizure threshold or bilateral ECT at 2.5 times seizure threshold, using either a traditional brief pulse (1.5 ms) or an ultrabrief pulse (0.3 ms). Depressive symptoms and cognition were assessed before, during, and immediately, two, and six months after therapy. Patients who responded were followed for a one-year period. RESULTS The final remission rate for ultrabrief bilateral ECT was 35 percent, compared with 73 percent for ultrabrief unilateral ECT, 65 percent for standard pulse width bilateral ECT, and 59 percent for standard pulse width unilateral ECT (all P’s<0.05 after covariate adjustment). The ultrabrief right unilateral group had less severe cognitive side effects than the other 3 groups in virtually all primary outcome measures assessed in the acute postictal period, and during and immediately following therapy. Both the ultrabrief stimulus and right unilateral electrode placement produced less short- and long-term retrograde amnesia. Patients rated their memory deficits as less severe following ultrabrief right unilateral ECT compared to each of the other three conditions (P<0.001). CONCLUSIONS The use of an ultrabrief stimulus markedly reduces adverse cognitive effects, and when coupled with markedly suprathreshold right unilateral ECT, also preserves efficacy. ( number, NCT00487500.) PMID:19756236

  7. Femtosecond pulse-width dependent trapping and directional ejection dynamics of dielectric nanoparticles

    Chiang, Weiyi


    We demonstrate that laser pulse duration, which determines its impulsive peak power, is an effective parameter to control the number of optically trapped dielectric nanoparticles, their ejections along the directions perpendicular to polarization vector, and their migration distances from the trapping site. This ability to controllably confine and eject the nanoparticle is explained by pulse width-dependent optical forces exerted on nanoparticles in the trapping site and ratio between the repulsive and attractive forces. We also show that the directional ejections occur only when the number of nanoparticles confined in the trapping site exceeds a definite threshold. We interpret our data by considering the formation of transient assembly of the optically confined nanoparticles, partial ejection of the assembly, and subsequent filling of the trapping site. The understanding of optical trapping and directional ejections by ultrashort laser pulses paves the way to optically controlled manipulation and sorting of nanoparticles. © 2013 American Chemical Society.

  8. Pulse-Width Saturation and Kelly-Sideband Shift in a Graphene-Nanosheet Mode-Locked Fiber Laser with Weak Negative Dispersion

    Yang, Chun-Yu; Lin, Yung-Hsiang; Chi, Yu-Chieh; Wu, Chung-Lun; Lo, Jui-Yung; Lin, Gong-Ru


    The optimized soliton mode locking of the erbium-doped fiber laser (EDFL) and its pulse-shortening dynamic with the graphene nanosheet is demonstrated by precisely detuning the weakly negative group-delay dispersion (GDD) and maintaining strong self-phase-modulation (SPM), to obtain the shortest pulse width of 449 fs with a spectral linewidth of 6.02 nm. The pulse evolution with the mode-locking mechanism changing from the self-amplitude-modulation of the saturable absorber, to the soliton compression caused by the GDD and SPM is experimentally and numerically investigated in detail. Under high pumping powers, the enlarged up-chirp inside the EDFL cavity can induce a significant Kelly-sideband shift of up to 0.5 nm. The passively-mode-locked EDFL pulse width is controllable by detuning the GDD and SPM parameters, so that the pulse width can be compressed from 642 to 449 fs while reducing the negative GDD from -0.354 to -0.154 ps2 . The compression ratio can be also improved by strengthening the SPM at this stage.

  9. Enhanced soliton-effect pulse compression by cross-phase modulation in optical fibers

    曹文华; 刘颂豪


    A new method is proposed to enhance the soliton-effect compression of optical pulses. It consists of copropagating two optical pulses with close wavelengths in the anomalous group-velocity dispersion regime of single-mode fibers. Numerical simulations show that, as compared with the traditional single pulse compression method, cross-phase modulation can not only dramatically increase the compression ratio but also decrease the optimum fiber length. The effects of initial pulse-width mismatch, Raman self-scattering, and pulse walk-off on the pulse compression are also discussed.

  10. On the pulse-width statistics in radio pulsars. III. Importance of the conal profile components

    Maciesiak, K; Melikidze, G


    This work is a continuation of two previous papers of a series, in which we examined the pulse-width statistics of normal radio pulsars. In the first paper we compiled the largest ever database of pulsars with interpulses in their mean profiles. In the second one we confirmed the existence of the lower boundary in the scatter plot of core component pulse-widths versus pulsar period W50 sim 2.5 P^{-0.5}[deg], first discovered by Rankin using much smaller number of interpulse cases. In this paper we show that the same lower boundary also exists for conal profile components. Rankin proposed a very simple method of estimation of pulsar inclination angle based on comparing the width W50 of its core component with the period dependent value of the lower boundary. We claim that this method can be extended to conal components as well. To explain an existence of the lower boundary Rankin proposed that the core emission originates at or near the polar cap surface. We demonstrated clearly that no coherent pulsar radio e...

  11. Inferences from the Distributions of Fast Radio Burst Pulse Widths, Dispersion Measures and Fluences

    Katz, J I


    The widths, dispersion measures, dispersion indices and fluences of Fast Radio Bursts (FRB) impose coupled constraints that all models must satisfy. Observation of dispersion indices close to their low density limit of $-2$ sets a model-independent upper bound on the electron density and a lower bound on the size of any dispersive plasma cloud. The non-monotonic dependence of burst widths (after deconvolution of instrumental effects) on dispersion measure excludes the intergalactic medium as the location of scattering that broadens the FRB in time. Temporal broadening far greater than that of pulsars at similar high Galactic latitudes implies that scattering occurs close to the sources, where high densities and strong turbulence are plausible. FRB energetics are consistent with supergiant pulses from young, fast, high-field pulsars at cosmological distances. The distribution of FRB dispersion measures is inconsistent with expanding clouds (such as SNR). It excludes space-limited distributions (such as the loc...

  12. A new pulse modulation adaptive controller (PMAC) applied to HVAC systems

    Salsbury, T.I. [Johnson Controls Inc., Milwaukee (United States)


    The paper proposes a new switching control law (pulse modulation adaptive controller, PMAC) that implements pulse-width-pulse-frequency modulation. Pulse durations are determined to maintain the amplitude of variation in the controlled variable at or below a user-defined level. In addition to providing quantifiable control performance, PMAC can reduce component wear by issuing fewer switches than conventional control schemes. The control law is developed around a first-order system characterization but incorporates an adaptive loop, which allows application to a wide range of non-first-order and also time-variant systems. Test results are presented from applying PMAC to both simulated and real HVAC systems. (author)

  13. New autocorrelation technique for the IR FEL optical pulse width measurements

    Amirmadhi, F.; Brau, K.A.; Becker, C. [Vanderbilt Univ., Nashville, TN (United States)] [and others


    We have developed a new technique for the autocorrelation measurement of optical pulse width at the Vanderbilt University FEL center. This method is based on nonlinear absorption and transmission characteristics of semiconductors such as Ge, Te and InAs suitable for the wavelength range from 2 to over 6 microns. This approach, aside being simple and low cost, removes the phase matching condition that is generally required for the standard frequency doubling technique and covers a greater wavelength range per nonlinear material. In this paper we will describe the apparatus, explain the principal mechanism involved and compare data which have been acquired with both frequency doubling and two-photon absorption.

  14. A novel approach for pulse width measurements with a high precision (8 ps RMS) TDC in an FPGA

    Ugur, C.; Linev, S.; Michel, J.; Schweitzer, T.; Traxler, M.


    High precision time measurements are a crucial element in particle identification experiments, which likewise require pulse width information for Time-over-Threshold (ToT) measurements and charge measurements (correlated with pulse width). In almost all of the FPGA-based TDC applications, pulse width measurements are implemented using two of the TDC channels for leading and trailing edge time measurements individually. This method however, requires twice the number of resources. In this paper we present the latest precision improvements in the high precision TDC (8 ps RMS) developed before [1], as well as the novel way of measuring ToT using a single TDC channel, while still achieving high precision (as low as 11.7 ps RMS). The effect of voltage, generated by a DC-DC converter, over the precision is also discussed. Finally, the outcome of the temperature change over the pulse width measurement is shown and a correction method is suggested to limit the degradation.

  15. Controllable pulse width of bright similaritons in a tapered graded index diffraction decreasing waveguide

    Prakash, S. Arun [Department of EEE, Anna University, Ramanathapuram 623513 (India); Malathi, V. [Department of EEE, Anna University, Regional office, Madurai (India); Mani Rajan, M. S., E-mail: [Department of Physics, Anna University, Ramanathapuram 623513 (India); Loomba, Shally [Department of Physics, Panjab University, Chandigarh 160014 (India)


    We obtain the bright similariton solutions for generalized inhomogeneous nonlinear Schrödinger equation (GINLSE) which governs the pulse propagation in a tapered graded index diffraction decreasing waveguide (DDW). The exact solutions have been worked out by employing similarity transformations which involve the mapping of the GINLSE to standard NLSE for the certain conditions of the parameters. By making use of the exact analytical solutions, we have investigated the dynamical behavior of optical similariton pairs and have suggested the methods to control them as they propagate through DDW. Moreover, pulse width of similariton is controlled through various profiles. These results are helpful to understand the similaritons in DDW and can be potentially useful for future experiments in optical communications which involve optical amplifiers and long-haul telecommunication networks.

  16. Relationship between width of pulses and Lorentz factor expected from the light curve of fireball sources

    Zhang Fu-Wen; Qin Yi-Ping


    Time profiles of many gamma-ray bursts consist of distinct pulses, which provides a possibility of characterizing the temporal structure of these bursts. We employ a simple model of highly symmetric fireballs to analyse the effect of the expansion speed on the light curve arising from different forms of local pulses. The relationship between the ratio r of the FWHM width of the rising phase of the light curve to that of the decaying phase and the Lorentz factor is investigated. The analysis shows that, when the rest frame radiation form is ignored, temporal profiles of the light curve arising from pulses of fireballs will not be affected by the expansion speed (that is, r is almost a constant) as long as the fireball expands relativistically. When the rest frame radiation form is taken into account, there will be a break in the curves of r - log Γ. The location of the break depends mainly on the adopted value of the rest frame peak frequency v0,p. One would reach almost the same result when a jet is considered. In addition, we utilize a sample of 48individual GRB pulses to check the relationship between the ratio r and the expansion speed Γ. We find no significant correlation between them, and this is consistent with the theoretical analysis.

  17. [Doppler effect on width of characteristic line in plasma induced by pulsed laser ablating Al].

    Song, Yi-Zhong; He, An-Zhi


    Aluminum (Al) plasma was induced with a pulsed Nd: YAG laser beam ablating Al target in Ar. Time-resolved information of the plasma radiation was taken with time-resolved technique, and the spectra of the radiation were recorded with an optical multi-path analyzer (OMA III ), whereupon, time-resolved spectra of the plasma radiation induced by pulsed laser were acquired. Based on the experiment data, Al resonant double lines, Al I 396.15 nm, Al I 394.40 nm, were respectively fitted with Lorentz, Gauss and their linear integrated function (abbr. Integrated function), whereupon, Lorentz and Gauss elements were separated from the experiment data profile curve. By contrasting Lorentz with Gauss curve separated, it was found that the experiment curve mainly consisted of Lorentz element, a with little Gauss. By contrasting Lorentz with Integrated fitting curve for experiment data, a visual picture of the characteristic lines broadened by Doppler effect was exhibited. According to the visual picture, the increase of full half-high width of the characteristic line broadened by Doppler effect was estimated. It was about 2 x 10(-)3 -8 x 10(-3) nm, approximating the theoretical value 6.7 x 10(-)3 nm. As a result, Doppler effect on the width of characteristic lines in the plasma could be reasonably explained by curve fitting analysis and theoretical calculation.

  18. Coherent pulse position modulation quantum cipher

    Sohma, Masaki; Hirota, Osamu [Quantum ICT Research Institute, Tamagawa University, 6-1-1 Tamagawa-gakuen, Machida, Tokyo 194-8610 (Japan)


    On the basis of fundamental idea of Yuen, we present a new type of quantum random cipher, where pulse position modulated signals are encrypted in the picture of quantum Gaussian wave form. We discuss the security of our proposed system with a phase mask encryption.

  19. 基于空间矢量脉宽调制的三电平逆变器滤波器参数设计%Parameter design of LCL filter for three-level converter based on space vector pulse width modulation

    张国荣; 李讯; 周同路


    The neutral-point-clamped (NPC) three-level inverter is used more and more in the grid-connected renewable energy generation system. In order to achieve the lower current harmonic, an LCL filter is also widely utilized due to its superior filtering performance. The LCL filter has the advantages of a high-frequency stopband with good performance and low-frequency compensation ability, but the parameters of LCL are hard to design. Especially the different modulation methods between three-level and two-level inverters, and the different ripple current, all these factors lead to a more difficult design of the parameters. The key of LCL design is the arm-side inductance design, due to the fact that an improper design of arm-side inductance will conduct to a completely different ripple current of the inverter, power loss of the filter components, and larger stress switch stress, thus resulting in poor performance of output current. Moreover, the control of the inverter will be affected. In the design of arm-side inductance, the most important thing is to strike a maximum ripple current. On the basis of establishing the mathematical model of a three-level grid-connected inverter, this paper takes output current control under the unity power factor into consideration, combining with the characters of space vector pulse width modulation (SVPWM) to reach the arm-side ripple current’s variation regularity. The maximum ripple current could be obtained at the peak of a grid side current based on this research. There will always be three latest vectors for the synthesis of the reference vector in accordance with the principle of the Nearest Three Vectors (NTV). In addition, seven-segment modulation on the action time allocation of each vector was applied. Considering the worst case, the value of max ripple current can be obtained when the middle vector was neglected , coupled with the engineering demand for ripple current, and upper limits of arm-side inductance can be given

  20. SEMICONDUCTOR INTEGRATED CIRCUITS: A 1.25 Gb/s laser diode driver with pulse width optimization

    Huan, Wang; Zhigong, Wang; Jian, Xu; Rong, Wang; Peng, Miao; Yin, Luo


    A 1.25 Gb/s laser diode driver (LDD) with pulse width optimization has been implemented in a 0.6-μm BiCMOS process. This paper illustrates the relation between the pulse width distortion (PWD) of the output eye diagram and the driving amplitude from the second pre-amplifier. Also, a specific current setting circuit working together with an LDD is proposed to generate the optimum driving amplitude and to avoid device nonlinearity, temperature variation and process deviation. The measured results show a maximum crossing deviation of -3% and indicate the desired independence and stability.

  1. Pulse-Width Dependence of the Cooling Effect on Sub-Micrometer ZnO Spherical Particle Formation by Pulsed-Laser Melting in a Liquid.

    Sakaki, Shota; Ikenoue, Hiroshi; Tsuji, Takeshi; Ishikawa, Yoshie; Koshizaki, Naoto


    Sub-micrometer spherical particles can be synthesized by irradiating particles in a liquid with a pulsed laser (pulse width: 10 ns). In this method, all of the laser energy is supposed to be spent on particle heating because nanosecond heating is far faster than particle cooling. To study the cooling effect, sub-micrometer spherical particles are fabricated by using a pulsed laser with longer pulse widths (50 and 70 ns). From the increase in the laser-fluence threshold for sub-micrometer spherical particle formation with increasing pulse width, it is concluded that the particles dissipate heat to the surrounding liquid, even during several tens of nanoseconds of heating. A particle heating-cooling model considering the cooling effect is developed to estimate the particle temperature during laser irradiation. This model suggests that the liquid surrounding the particles evaporates, and the generated vapor films suppress heat dissipation from the particles, resulting in efficient heating and melting of the particles in the liquid. In the case of small particle sizes and large pulse widths, the particles dissipate heat to the liquid without forming such vapor films. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Single pulse TMS differentially modulates reward behavior.

    Stanford, Arielle D; Luber, Bruce; Unger, Layla; Cycowicz, Yael M; Malaspina, Dolores; Lisanby, Sarah H


    Greater knowledge of cortical brain regions in reward processing may set the stage for using transcranial magnetic stimulation (TMS) as a treatment in patients with avolition, apathy or other drive-related symptoms. This study examined the effects of single pulse (sp) TMS to two reward circuit targets on drive in healthy subjects. Fifteen healthy subjects performed the monetary incentive delay task (MID) while receiving fMRI-guided spTMS to either inferior parietal lobe (IPL) or supplemental motor area (SMA). The study demonstrated decreasing reaction times (RT) for increasing reward. It also showed significant differences in RT modulation for TMS pulses to the IPL versus the SMA. TMS pulses during the delay period produced significantly more RT slowing when targeting the IPL than those to the SMA. This RT slowing carried over into subsequent trials without TMS stimulation, with significantly slower RTs in sessions that had targeted the IPL compared to those targeting SMA. The results of this study suggest that both SMA and IPL are involved in reward processing, with opposite effects on RT in response to TMS stimulation. TMS to these target cortical regions may be useful in modulating reward circuit deficits in psychiatric populations.

  3. Solid-state pulse modulator using Marx generator for a medical linac electron-gun

    Lim, Heuijin; Hyeok Jeong, Dong; Lee, Manwoo; Lee, Mujin; Yi, Jungyu; Yang, Kwangmo; Ro, Sung Chae


    A medical linac is used for the cancer treatment and consists of an accelerating column, waveguide components, a magnetron, an electron-gun, a pulse modulator, and an irradiation system. The pulse modulator based on hydrogen thyratron-switched pulse-forming network is commonly used in linac. As the improvement of the high power semiconductors in switching speed, voltage rating, and current rating, an insulated gate bipolar transistor has become the more popular device used for pulsed power systems. We propose a solid-state pulse modulator to generator high voltage by multi-stacked storage-switch stages based on the Marx generator. The advantage of our modulator comes from the use of two semiconductors to control charging and discharging of the storage capacitor at each stage and it allows to generate the pulse with various amplitudes, widths, and shapes. In addition, a gate driver for two semiconductors is designed to reduce the control channels and to protect the circuits. It is developed for providing the pulsed power to a medical linac electron-gun that requires 25 kV and 1 A as the first application. In order to improve the power efficiency and achieve the compactness modulator, a capacitor charging power supply, a Marx pulse generator, and an electron-gun heater isolated transformer are constructed and integrated. This technology is also being developed to extend the high power pulsed system with > 1 MW and also other applications such as a plasma immersed ion implantation and a micro pulse electrostatic precipitator which especially require variable pulse shape and high repetition rate > 1 kHz. The paper describes the design features and the construction of this solid-state pulse modulator. Also shown are the performance results into the linac electron-gun.

  4. Scaling behavior of the thermal conductivity of width-modulated nanowires and nanofilms for heat transfer control at the nanoscale.

    Zianni, Xanthippi; Jean, Valentin; Termentzidis, Konstantinos; Lacroix, David


    We report on scaling behavior of the thermal conductivity of width-modulated nanowires and nanofilms that have been studied with the phonon Monte Carlo technique. It has been found that the reduction of the thermal conductivity scales with the nanostructure transmissivity, a property entirely determined by the modulation geometry, irrespectively of the material choice. Tuning of the thermal conductivity is possible by the nanostructure width-modulation without strict limitations for the modulation profile. In addition, a very significant constriction thermal resistance due to width-discontinuity has been identified, in analogy to the contact thermal resistance between two dissimilar materials. The constriction thermal resistance also scales with the modulated nanostructure transmissivity. Our conclusions are generic indicating that a wide range of materials can be used for the modulated nanostructures. Direct heat flow control can be provided by designing the nanostructure width-modulation.

  5. Chaotic carrier pulse position modulation communication system and method

    Abarbanel, Henry D. I.; Larson, Lawrence E.; Rulkov, Nikolai F.; Sushchik, Mikhail M.; Tsimring, Lev S.; Volkovskii, Alexander R.


    A chaotic carrier pulse position modulation communication system and method is disclosed. The system includes a transmitter and receiver having matched chaotic pulse regenerators. The chaotic pulse regenerator in the receiver produces a synchronized replica of a chaotic pulse train generated by the regenerator in the transmitter. The pulse train from the transmitter can therefore act as a carrier signal. Data is encoded by the transmitter through selectively altering the interpulse timing between pulses in the chaotic pulse train. The altered pulse train is transmitted as a pulse signal. The receiver can detect whether a particular interpulse interval in the pulse signal has been altered by reference to the synchronized replica it generates, and can therefore detect the data transmitted by the receiver. Preferably, the receiver predicts the earliest moment in time it can expect a next pulse after observation of at least two consecutive pulses. It then decodes the pulse signal beginning at a short time before expected arrival of a pulse.

  6. Line Width Narrowing with 14N Nuclear Quadrupole Resonance Lines at 296 K and 77 K Using a High Powered Pulsed Spectrometer

    Trepanier, R. J.; Whitehead, M. A.


    The dependence of the NQR line width on the RF pulse intensity and period using a continuous steady state pulse train for polycrystalline 14N compounds shows a dependence on the asymmetry parameter η, the temperature, and the crystal structure.

  7. Laser pulse modulation instabilities in partially stripped plasma

    Hu Qiang-Lin; Liu Shi-Bing; Jiang Yi-Jian


    The laser pulse modulation instabilities in partially stripped plasma were discussed based on the phase and group velocities of the laser pulse and the two processes that modulation instabilities excited. The excitation condition and growth rate of the modulation instability were obtained. It was found that the positive chirp and competition between normal and abnormal dispersions play important roles in the modulation instability. In the partially stripped plasma,the increased positive chirp enhances the modulation instability, and the dispersion competition reduces it.

  8. A driving pulse edge modulation technique and its complex programming logic devices implementation

    Xiao CHEN; Dong-chang QU; Yong GUO; Guo-zhu CHEN


    With the continual increase in switching speed and rating of power semiconductors, the switching voltage spike becomes a serious problem. This paper describes a new technique of driving pulse edge modulation for insulated gate bipolar transistors (IGBTs). By modulating the density and width of the pulse trains, without regulating the hardware circuit, the slope of the gate driving voltage is controlled to change the switching speed. This technique is used in the driving circuit based on complex programmable logic devices (CPLDs), and the switching voltage spike of IGBTs can be restrained through software, which is easier and more flexible to adjust. Experimental results demonstrate the effectiveness and practicability of the proposed method.

  9. Kv1.1 channelopathy abolishes presynaptic spike width modulation by subthreshold somatic depolarization.

    Vivekananda, Umesh; Novak, Pavel; Bello, Oscar D; Korchev, Yuri E; Krishnakumar, Shyam S; Volynski, Kirill E; Kullmann, Dimitri M


    Although action potentials propagate along axons in an all-or-none manner, subthreshold membrane potential fluctuations at the soma affect neurotransmitter release from synaptic boutons. An important mechanism underlying analog-digital modulation is depolarization-mediated inactivation of presynaptic Kv1-family potassium channels, leading to action potential broadening and increased calcium influx. Previous studies have relied heavily on recordings from blebs formed after axon transection, which may exaggerate the passive propagation of somatic depolarization. We recorded instead from small boutons supplied by intact axons identified with scanning ion conductance microscopy in primary hippocampal cultures and asked how distinct potassium channels interact in determining the basal spike width and its modulation by subthreshold somatic depolarization. Pharmacological or genetic deletion of Kv1.1 broadened presynaptic spikes without preventing further prolongation by brief depolarizing somatic prepulses. A heterozygous mouse model of episodic ataxia type 1 harboring a dominant Kv1.1 mutation had a similar broadening effect on basal spike shape as deletion of Kv1.1; however, spike modulation by somatic prepulses was abolished. These results argue that the Kv1.1 subunit is not necessary for subthreshold modulation of spike width. However, a disease-associated mutant subunit prevents the interplay of analog and digital transmission, possibly by disrupting the normal stoichiometry of presynaptic potassium channels.

  10. Excitation of spin echo by pulses with linear frequency modulation

    Baruzdin, S. A.


    The excitation of a spin echo by two pulses with linear frequency modulation, upon which the pulse parameters ensure maximal compression of the response in time, is considered. The frequency of the excitation pulses was changed by a step law, approximating its linear rise. The transfer matrix of the state of the spin system for pulses with linear frequency modulation is found by solving the Bloch equations. The shape of the envelope of the spin echo in thin magnetic cobalt films, as well as the dependence of the echo amplitude on the parameters of the excitation pulses, is determined. The amplitudes of the excitation pulses, which ensure the excitation of the echo maximal amplitude for various values of the frequency deviation, are found. It is shown that the use of pulses with linear frequency modulation makes it possible to obtain the same echo amplitude as with the use of simple excitation pulses for a substantially smaller amplitude and power of excitation pulses.

  11. A Time-Domain Reflectometry Method with Variable Needle Pulse Width for Measuring the Dielectric Properties of Materials

    Andrzej Wilczek


    Full Text Available Time-domain reflectometry (TDR methods used for measuring the dielectric properties of materials mostly utilize step or needle electrical pulses of constant amplitudes and shapes. Our novel approach enables determining the dielectric relaxation time of a sample using the analysis of the amplitudes of reflected pulses of two widths, in addition to bulk dielectric permittivity and electrical conductivity commonly obtained by the TDR technique. The method was developed for various values of electrical conductivity and relaxation time using numerical simulations of a five-rod probe placed in a material with complex dielectric permittivity described by the Debye model with an added electrical conductivity term. The characterization of amplitudes of two pulses of selected widths was done with regard to the dielectric parameters of simulated materials. The required probe parameters were obtained solely from numerical simulations. Verification was performed for the probe placed in aqueous KCl solutions with 14 different electrical conductivity values. The determined relaxation time remained roughly constant and independent of electrical conductivity. The obtained electrical conductivity agreed with the reference values. Our results indicate that the relaxation time, dielectric permittivity and electrical conductivity of the tested solutions can be simultaneously determined using a simple analysis of the amplitude and reflection time of two needle pulses of different widths.

  12. Design and development of a prototype 25 kV, 10 A long pulse Marx modulator for high power klystron

    Acharya, Mahesh; Shrivastava, Purushottam


    Research, design, and development of high average power modulators for the proposed Indian Spallation Neutron Source are in progress at Raja Ramanna Centre for Advanced Technology. With this objective, a prototype of 25 kV, 10 A, 1 ms Marx modulator at repetition rate of 1 Hz has been designed and developed which serves as a proof of principle and technology assessment stage for further development of high repetition rate high voltage high average power modulators. Insulated Gate Bipolar Transistor (IGBT) based modules of 2.8 kV switching capability have been used as main modules. The modulator had 8.2% droop in output voltage pulse without any droop compensation circuit. A droop compensation involving 15 corrector modules has been used to reduce the droop up to 1%. We have used IGBT based 250 V switches to realize the corrector module. A microcontroller based control unit was designed and developed for triggering the main and corrector modules. With this control unit, programmable output pulse has been achieved. Electrical isolation between high voltage circuits and control circuit has been achieved by the use of fiber optic based control signal transmission. Output pulses of 1 ms pulse width, 800 ns rise time, and 5 μs fall time have been achieved. The modulator has advantages of modular design, adjustable pulse width, adjustable rise time, and fall time.

  13. Modeling and Analysis of Pulse Skip Modulation


    The state space average model and the large signal models of Pulse Skip Modulation (PSM) mode are given in this paper. Farther more, based on these models and simulations of PSM converter circuits, the analysis of the characteristics of PSM converter is described in this paper, of which include efficiency, frequency spectrum analysis, output voltage ripple, response speed and interference rejection capability. Compared with PWM control mode, PSM converter has high efficiency, especially with light loads, quick response, good interference rejection and good EMC characteristic. Improved PSM slightly, it could be a kind of good independent regulating mode during the whole operating process for a DC-DC converter. Finally, some experimental results are also presented in this paper.

  14. Atmospheric velocity spectral width measurements using the statistical distribution of pulsed CO2 lidar return signal intensities

    Ancellet, Gerard M.; Menzies, Robert T.; Grant, William B.


    A pulsed CO2 lidar with coherent detection has been used to measure the correlation time of backscatter from an ensemble of atmospheric aerosol particles which are illuminated by the pulsed radiation. The correlation time of the backscatter of the return signal, which is directly related to the velocity spectral width, can be used to study the velocity structure constant of atmospheric turbulence and wind shear. Various techniques for correlation time measurement are discussed, and several measurement results are presented for the technique using the information contained in the statistical distribution of a set of lidar return signal intensities.

  15. Influence of segment width on plan quality for volumetric modulated arc based stereotactic body radiotherapy.

    Nithiyanantham, Karthikeyan; Kadirampatti Mani, Ganesh; Subramani, Vikraman; Karukkupalayam Palaniappan, Karrthick; Uthiran, Mohanraj; Vellengiri, Sennniandavar; Raju, Sambasivaselli; Supe, Sanjay S; Kataria, Tejinder


    To study the influence of segment width on plan quality for volumetric modulated arc based stereotactic body radiotherapy. The redundancy of modulation for regularly shaped small volume tumors results in creation of many small segments and an increase of monitor units, with a consequent prolongation of treatment and uncertainty in treatment delivery. Six cases each in lung, abdomen and liver were taken for the study. For each case, three VMAT SBRT plans were generated with different penalties on minimum segment width of 0.5, 1.0 and 1.5 cm. A comparison was made on the metrics of dose volume histogram, dosimetric indices, monitor units (MUs) and delivery accuracy. The mean reduction of total MUs when compared with 0.5 cm plan was observed as 12.7 ± 6.0% and 17.5 ± 7.2% for 1.0 cm and 1.5 cm of minimum segment width, respectively. The p value showed a significant degradation in dosimetric indices for 1.5 cm plans when compared with 0.5 cm and 1.0 cm plans. The average deviation of measured dose with TPS calculated was 3.0 ± 1.1%, 2.1 ± 0.84% and 1.8 ± 0.9% for 0.5, 1.0 and 1.5 cm, respectively. The calculated gamma index with pass criteria of 2% dose difference and 2 mm distance to agreement was 95.9 ± 2.8%, 96.5 ± 2.6% and 97.8 ± 1.6% as calculated for 0.5, 1.0 and 1.5 cm of penalties, respectively. In view of the trade off between delivery efficiency and plan quality, 1 cm minimum segment width plans showed an improvement. VMAT SBRT plans with increased optimal value of minimum segment width showed better plan quality and delivery efficiency for stereotactic body radiotherapy.

  16. Modulational instability of short pulses in long optical fibers

    Shukla, P. K.; Juul Rasmussen, Jens


    The effect of time-derivative nonlinearity is incorporated into the study of the modulational instability of heat pulses propagating through long optical fibers. Conditions for soliton formation are discussed......The effect of time-derivative nonlinearity is incorporated into the study of the modulational instability of heat pulses propagating through long optical fibers. Conditions for soliton formation are discussed...

  17. Coherence control of pulse trains by spectral phase modulation

    Ding, Chaoliang; Koivurova, Matias; Turunen, Jari; Setälä, Tero; Friberg, Ari T.


    We propose a technique to control the spectral and temporal coherence properties of pulsed beams of light via time-dependent manipulation of the spectral phase. Modulation schemes for the generation of partially coherent pulse trains from a train of fully coherent pulses are presented. The feasibility of experimental realization of the method is confirmed by numerical estimates.

  18. 单相H桥逆变器单极性正弦脉宽调制下的分岔及混沌行为研究%Study on bifurcation and chaos in single-phase H-bridge inverter modulated by unipolar sinusoidal pulse width modulation

    刘洪臣; 杨爽


    The unipolar SPWM has been widely used in H-bridge inverter because of its superiority for lower switching loss and less electromagnetic interference as compared with bipolar SPWM. However, the nonlinear phenomena in it have not been reported. In this paper, the bifurcation and chaos in the H-bridge inverter modulated by unipolar SPWM is studied. The one-dimensional discrete iterated mapping model under proportional control is established. Effects of the proportional coefficient k on the system performance are analyzed by using bifurcation diagram, folded diagram, and Lyapunov index spectrum. The time-domain waveforms with different proportional coefficients are obtained by Matlab/Simulink, which verify the correctness of theoretical analysis. Finally, the nonlinear behavior in the inverter caused by the variation of other circuit parameters like input voltage E , load resistance R, and inductance L is investigated through bifurcation diagrams. This paper turns the chaotic research of single-phase H-bridge inverter from bipolar SPWM to unipolar SPWM, So that the proposed approach is more practical. The results have important guiding significance and application value for designing and debugging the single-phase H-bridge inverter correctly.%本文研究了单相H桥逆变器在单极性正弦脉宽调制下的分岔和混沌行为,建立了系统在比例控制下的一阶离散映射模型,采用分岔图、折叠图和Lyapunov指数谱分析了比例系数k对系统性能的影响,通过Matlab/Simulink仿真得到了不同比例系数下的时域波形图,验证了理论分析的正确性。最后运用分岔图研究了输入电压E、负载电阻R和电感L等外部参数变化时变换器中存在的非线性行为。本文将单相H桥逆变器的混沌研究从双极性正弦脉宽调制转向单极性正弦脉宽调制,使之更具实用性,研究结果对于正确设计和调试单相H桥逆变器具有重要的指导意义和应用价值。

  19. Broadly wavelength- and pulse width-tunable high-repetition rate light pulses from soliton self-frequency shifting photonic crystal fiber integrated with a frequency doubling crystal.

    Lanin, Aleksandr A; Fedotov, Andrei B; Zheltikov, Aleksei M


    Soliton self-frequency shift (SSFS) in a photonic crystal fiber (PCF) pumped by a long-cavity mode-locked Cr:forsterite laser is integrated with second harmonic generation (SHG) in a nonlinear crystal to generate ultrashort light pulses tunable within the range of wavelengths from 680 to 1800 nm at a repetition rate of 20 MHz. The pulse width of the second harmonic output is tuned from 70 to 600 fs by varying the thickness of the nonlinear crystal, beam-focusing geometry, and the wavelength of the soliton PCF output. Wavelength-tunable pulses generated through a combination of SSFS and SHG are ideally suited for coherent Raman microspectroscopy at high repetition rates, as verified by experiments on synthetic diamond and polystyrene films.

  20. Effects of the pulse width on the reactive species production and DNA damage in cancer cells exposed to atmospheric pressure microsecond-pulsed helium plasma jets

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Kang, Tae Hong; Chung, T. H.


    Plasma-liquid and plasma-cell interactions were investigated using an atmospheric pressure dc microsecond-pulsed helium plasma jet. We investigated the effects of the electrical parameters such as applied voltage and pulse width (determined by the pulse frequency and duty ratio) on the production of reactive species in the gas/liquid phases and on the DNA damage responses in the cancer cells. The densities of reactive species including OH radicals were estimated inside the plasma-treated liquids using a chemical probe method, and the nitrite concentration was detected by Griess assay. Importantly, the more concentration of OH resulted in the more DNA base oxidation and breaks in human lung cancer A549 cells. The data are very suggestive that there is strong correlation between the production of OH in the plasmas/liquids and the DNA damage.

  1. Nanosecond Pulse Shaping with Fiber-Based Electro-Optical Modulators and a Double-Pass Tapered Amplifier

    Rogers, Charles E


    We describe a system for generating frequency-chirped and amplitude-shaped pulses on time scales from sub-nanosecond to ten nanoseconds. The system starts with cw diode-laser light at 780 nm and utilizes fiber-based electro-optical phase and intensity modulators, driven by an arbitrary waveform generator, to generate the shaped pulses. These pulses are subsequently amplified to several hundred mW with a tapered amplifier in a delayed double-pass configuration. Frequency chirps up to 5 GHz in 2 ns and pulse widths as short as 0.15 ns have been realized.

  2. Research and Development of ns Pulse Width Ultrafast Pulsed Power Supply%ns 级快脉冲电源研制

    陈锦晖; 韩谦


    高重复频率ns级快脉冲电源是粒子加速器超快 kicker注入引出技术中有待攻克的关键技术难题。本工作利用计算机仿真和桌面实验等手段从理论上研究了感应叠加技术、射频MOSFET开关及驱动电路技术,并在此基础上设计研制了1台10级感应叠加的快脉冲电源性能样机。经初步测试,10级叠加性能样机在500 Hz低频工作条件下,输出脉冲幅度>4.3 kV ,脉冲前沿<2.8 ns ,脉冲宽度<9 ns ,基本达到了预期目标。%High repetition rate ,nanosecond pulse width fast pulsed power supply is a key technology to be overcome for particle accelerator fast kicker injection and ejection . In this paper ,inductive adder topology ,the RF MOSFET and its driver circuit were studied by computer simulation and table circuit experiment .On the basis of theory research ,a ten-grade inductive adder pulsed power supply evaluating prototype was developed .The preliminary test of the prototype was completed .A ten-grade adder can produce a short pulse of pulse amplitude>4.3 kV ,front edge<2.8 ns ,and pulse width<9 ns into 50 Ω at 500 Hz repetition rate .

  3. Neuron self-learning PSD control for backside width of weld pool in pulsed GTAW with wire filler

    张广军; 陈善本; 吴林


    In this paper, the weld pool shape control by intelligent strategy was studied. A neuron self-learning PSD controller for backside width of weld pool in pulsed GTAW with wire filler was designed. The PSD control arithmetic was analyzed, simulating experiment by MATLAB software was done, and the validating experiments on varied heat sink workpiece and varied gap workpiece were successfully implemented. The study results show that the neuron self-learning PSD control method can attain a perfect control effect under different set values and conditions, and is suitable for the welding process with the varied structure and coefficients of control model.

  4. Modulation of tibialis anterior muscle activity changes with upright stance width.

    Lemos, Thiago; Imbiriba, Luís A; Vargas, Claudia D; Vieira, Taian M


    When individuals stand with their feet apart, activation of tibialis anterior (TA) muscle seems to slightly exceed rest levels. In narrow stances, conversely, the stabilization of body lateral sways may impose marked, active demand on ankle inversors/eversors. In this study we investigate how much the modulation in TA activity, associated to center of pressure (COP) lateral sways, changes when stance width reduces. Surface EMG and COP coordinates were collected from 17 subjects at three different stances: feet apart, feet together and tandem. Pearson correlation analysis was applied to check whether the expected greater modulations in TA activity corresponded to a stronger association between fluctuations in EMG amplitude and COP lateral sways. When standing at progressively narrower stances participants showed larger fluctuations in COP lateral sways (pEMG-COP association (pmodulations in TA activity were observed for subjects showing greater association between EMG amplitude and COP sways in feet together and tandem stance (Pearson R>0.56, p<0.02), though not when standing with feet apart (R=-0.22, p=0.40). These results indicate that the contribution of TA activity to lateral sway control increases for narrower stances.

  5. Determination of the stochastic layer width induced by magnetic perturbations via heat pulse experiments in ASDEX upgrade

    Brida, D. [Max-Planck-Institut fuer Plasmaphysik, 17491 Greifswald (Germany); Physik-Department E28, Technische Universitaet Muenchen, 85747 Garching (Germany); Lunt, T.; Wischmeier, M.; Birkenmeier, G.; Faitsch, M.; Fischer, R.; Kurzan, B.; Schubert, M.; Sieglin, B.; Suttrop, W.; Wolfrum, E. [Max-Planck-Institut fuer Plasmaphysik, 17491 Greifswald (Germany); Cahyna, P. [Institute of Plasma Physics CAS, v.v.i. Prague (Czech Republic); Feng, Y. [Max-Planck-Institut fuer Plasmaphysik, 17491 Greifswald (Germany); Collaboration: the ASDEX Upgrade Team


    Magnetic Perturbations (MP) are studied on a number of tokamaks, due to their mitigating effect on Edge Localized Modes (ELMs), which pose a serious risk for the plasma facing components. MPs can lead to the creation of a stochastic layer in the plasma edge. Theory predicts, however, that the plasma screens the MP field, but the measurement of this screening effect remains elusive. In this contribution we present an experimental approach to measure the stochastic layer width, by the localized deposition of Electron Cyclotron Resonance Heating pulses in the edge region. Simulations with the 3D transport code EMC3-Eirene for ASDEX Upgrade (AUG) indicate that the propagation time to the target decreases with decreasing screening. A corresponding heat pulse L-mode experiment on AUG was carried out where no decrease of the propagation time between the case with and without MPs could be measured within the error bars, indicating strong screening.

  6. Laser pulse spectral shaping based on electro-optic modulation

    Yanhai Wang; Jiangfeng Wang; You'en Jiang; Yan Bao; Xuechun Li; Zunqi Lin


    A new spectrum shaping method, based on electro-optic modulation, to alleviate gain narrowing in chirped pulse amplification (CPA) system, is described and numerically simulated. Near-Fourier transform-limited seed laser pulse is chirped linearly through optical stretcher. Then the chirped laser pulse is coupled into integrated waveguide electro-optic modulator driven by an aperture-coupled-stripline (ACSL) electricalwaveform generator, and the pulse shape and amplitude are shaped in time domain. Because of the directrelationship between frequency interval and time interval of the linearly chirped pulse, the laser pulse spectrum is shaped correspondingly. Spectrum-shaping examples are modeled numerically to determine the spectral resolution of this technique. The phase error introduced in this method is also discussed.

  7. Evaluation of Methods to Increase Beam Pulse Width on the DARHT Axis-II Accelerator


    MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY...Hickman, J. S. Sullivan, and C. A. Brooksby, ”Solid-State Kicker Pulser for DARHT-2,” Pulsed Power Plasma Science, Vol. 1, pp. 632-635 (2001). [6

  8. Modulational instability of few cycle pulses in optical fibers

    Sarma, Amarendra K


    We investigate the modulational instability of a mathematical model [based on the model proposed by T. Brabec and F. Krausz, Phys.Rev. Lett. 78, 3282(1997)] appropriate for few cycle optical pulses with pulse duration as short as one carrier oscillation cycle in the context of a standard silica fiber operating at the telecommunication wavelength 1550 nm.

  9. Optical Pulse Generation with Self-Cascaded Electroabsorption Modulator

    WU Jian; QiU Ji-Fang; ZHOU Guang-Tao; XU Kun; LIN Jin-Tong


    A novel scheme for pulse generation with a self-cascaded electroabsorption modulator is presented and experi mentally demonstrated at 10 GHz.In the case of optimal tuning of time delay in the fibre loop,the improvement of 50% on pulsewidth with improved extinction ratio is obtained and the narrowest pulse generated with this method is about 11 ps.

  10. Performance characteristics of an induction linac magnetic pulse compression modulator at multi-kilohertz pulse repetition frequencies

    Sampayan, S.E.; Chambers, F.W.; Deadrick, F.J. [and others


    The ETA-II linear induction accelerator utilizes four pulse power conditioning chains. Magnetic pulse compression modulators (MAG1-Ds) form the last stage of each chain. A single power conditioning chain is used to drive the injector; the remaining three are used to drive 60 accelerator cells. Nominal parameters of the MAG1-D are an output voltage of greater than 120 kV, pulse width of 70 ns, and an output impedance of 2 ohms. Our operations goal for ETA-II is stable high average power operation at 5 kHz PRF. We have begun upgrading and characterizing the power conditioning chain on our High Average Power Test Stand (HAPTS). On HAPTS, the pulse to pulse amplitude stability has been improved to less than 0.7% (one sigma) and of order 3-5 ns random jitter about a systematic timing variation. In this paper we describe the status of our work to achieve the this paper we describe the status of our work to achieve the average power operation of ETA-II

  11. High-power pulse trains excited by modulated continuous waves

    Wang, Yan; Li, Lu; Malomed, Boris A


    Pulse trains growing from modulated continuous waves (CWs) are considered, using solutions of the Hirota equation for solitons on a finite background. The results demonstrate that pulses extracted from the maximally compressed trains can propagate preserving their shape and forming robust arrays. The dynamics of double high-power pulse trains produced by modulated CWs in a model of optical fibers, including the Raman effect and other higher-order terms, is considered in detail too. It is demonstrated that the double trains propagate in a robust form, with frequencies shifted by the Raman effect.

  12. Data acquisition electronics for gamma ray emission tomography using width-modulated leading-edge discriminators

    Lage, E; Tapias, G; Villena, J; Desco, M; Vaquero, J J, E-mail: desco@mce.hggm.e [Unidad de Medicina y CirugIa Experimental, Hospital General Universitario Gregorio Maranon, Madrid (Spain)


    We present a new high-performance and low-cost approach for implementing radiation detection acquisition systems. The basic elements used are charge-integrating ADCs and a set of components encapsulated in an HDL (hardware definition language) library which makes it possible to implement several acquisition tasks such as time pickoff and coincidence detection using a new and simple trigger technique that we name WMLET (width-modulated leading-edge timing). As proof of concept, a 32-channel hybrid PET/SPECT acquisition system based on these elements was developed and tested. This demonstrator consists of a master module responsible for the generation and distribution of trigger signals, 2 x 16-channel ADC cards (12-bit resolution) for data digitization and a 32-bit digital I/O PCI card for handling data transmission to a personal computer. System characteristics such as linearity, maximum transmission rates or timing resolution in coincidence mode were evaluated with test and real detector signals. Imaging capabilities of the prototype were also evaluated using different detector configurations. The performance tests showed that this implementation is able to handle data rates in excess of 600k events s{sup -1} when acquiring simultaneously 32 channels (96-byte events). ADC channel linearity is >98.5% in energy quantification. Time resolution in PET mode for the tested configurations ranges from 3.64 ns FWHM to 7.88 ns FWHM when signals from LYSO-based detectors are used. The measured energy resolution matched the expected values for the detectors evaluated and single elements of crystal matrices can be neatly separated in the acquired flood histograms.

  13. Data acquisition electronics for gamma ray emission tomography using width-modulated leading-edge discriminators

    Lage, E.; Tapias, G.; Villena, J.; Desco, M.; Vaquero, J. J.


    We present a new high-performance and low-cost approach for implementing radiation detection acquisition systems. The basic elements used are charge-integrating ADCs and a set of components encapsulated in an HDL (hardware definition language) library which makes it possible to implement several acquisition tasks such as time pickoff and coincidence detection using a new and simple trigger technique that we name WMLET (width-modulated leading-edge timing). As proof of concept, a 32-channel hybrid PET/SPECT acquisition system based on these elements was developed and tested. This demonstrator consists of a master module responsible for the generation and distribution of trigger signals, 2 × 16-channel ADC cards (12-bit resolution) for data digitization and a 32-bit digital I/O PCI card for handling data transmission to a personal computer. System characteristics such as linearity, maximum transmission rates or timing resolution in coincidence mode were evaluated with test and real detector signals. Imaging capabilities of the prototype were also evaluated using different detector configurations. The performance tests showed that this implementation is able to handle data rates in excess of 600k events s-1 when acquiring simultaneously 32 channels (96-byte events). ADC channel linearity is >98.5% in energy quantification. Time resolution in PET mode for the tested configurations ranges from 3.64 ns FWHM to 7.88 ns FWHM when signals from LYSO-based detectors are used. The measured energy resolution matched the expected values for the detectors evaluated and single elements of crystal matrices can be neatly separated in the acquired flood histograms.

  14. Continuous modulations of femtosecond laser-induced periodic surface structures and scanned line-widths on silicon by polarization changes.

    Han, Weina; Jiang, Lan; Li, Xiaowei; Liu, Pengjun; Xu, Le; Lu, YongFeng


    Large-area, uniform laser-induced periodic surface structures (LIPSS) are of wide potential industry applications. The continuity and processing precision of LIPSS are mainly determined by the scanning intervals of adjacent scanning lines. Therefore, continuous modulations of LIPSS and scanned line-widths within one laser scanning pass are of great significance. This study proposes that by varying the laser (800 nm, 50 fs, 1 kHz) polarization direction, LIPSS and the scanned line-widths on a silicon (111) surface can be continuously modulated with high precision. It shows that the scanned line-width reaches the maximum when the polarization direction is perpendicular to the scanning direction. As an application example, the experiments show large-area, uniform LIPSS can be fabricated by controlling the scanning intervals based on the one-pass scanned line-widths. The simulation shows that the initially formed LIPSS structures induce directional surface plasmon polaritons (SPP) scattering along the laser polarization direction, which strengthens the subsequently anisotropic LIPSS fabrication. The simulation results are in good agreement with the experiments, which both support the conclusions of continuous modulations of the LIPSS and scanned line-widths.

  15. 双波长皮秒脉冲与可调谐脉宽产生的实验研究%Experimental study about generation of picosecond pulses with dual-wavelengths and tunable pulse-widths

    郭志华; 罗春娅; 李丹; 凌福日


    In order to improve the practicability of multi-wavelength optical pulse equipment , a stable dual-wavelength semiconductor fiber ring laser was proposed and demonstrated by using dual-wavelength principle . Effects of ring cavity dispersion, filter pulse-width and modulation depth on output pulse were discussed .Experimental results are that repetition rate of dual-wavelength pulses is 5.0GHz and typical pulse-width is 20ps.Dual-wavelength pulses have good side-mode suppression ratios of 29.1dB ( at 1554.75nm) and 29.7dB ( at 1557.21nm) with typical output powers of -6.7dBm and -6.1dBm respectively.Output spectra are very stable with peak power fluctuation less than 0.5dB.This study is of great significance for the study of terahertz source and multi-wavelength optical pulse equipment .%为了提高多波长光脉冲设备的实用性,采用双波长工作原理,设计了一种稳定的双波长半导体环形光纤激光器. 讨论了环形腔色散、滤波器脉宽以及调制深度等对输出脉冲的影响. 结果表明,双波长光脉冲的重复率为5.0GHz,典型脉宽为20ps,双波长光脉冲具有良好的边模抑制比,当输出波长为1554.75nm和1557.21nm时,边模抑制比分别为29.1dB和29.7dB,其典型的输出功率分别为-6.7dBm和-6.1dBm,输出光谱的峰值功率波动小于0.5dB. 这项研究对太赫兹源和多波长光脉冲设备的研究具有借鉴意义.

  16. Electro-Optical Modulator Bias Control Using Bipolar Pulses

    Farr, William; Kovalik, Joseph


    An improved method has been devised for controlling the DC bias applied to an electro-optical crystal that is part of a Mach-Zehnder modulator that generates low-duty-cycle optical pulses for a pulse-position modulation (PPM) optical data-communication system. In such a system, it is desirable to minimize the transmission of light during the intervals between pulses, and for this purpose, it is necessary to maximize the extinction ratio of the modulator (the ratio between the power transmitted during an "on" period and the power transmitted during an "off" period). The present method is related to prior dither error feedback methods, but unlike in those methods, there is no need for an auxiliary modulation subsystem to generate a dithering signal. Instead, as described below, dither is effected through alternation of the polarity of the modulation signal. The upper part of Figure 1 schematically depicts a Mach-Zehnder modulator. The signal applied to the electro-optical crystal consists of a radio-frequency modulating pulse signal, VRF, superimposed on a DC bias Vbias. Maximum extinction occurs during the off (VRF = 0) period if Vbias is set at a value that makes the two optical paths differ by an odd integer multiple of a half wavelength so that the beams traveling along the two paths interfere destructively at the output beam splitter. Assuming that the modulating pulse signal VRF has a rectangular waveform, maximum transmission occurs during the "on" period if the amplitude of VRF is set to a value, V , that shifts the length of the affected optical path by a half wavelength so that now the two beams interfere constructively at the output beam splitter. The modulating pulse signal is AC-coupled from an amplifier to the electro-optical crystal. Sometimes, two successive pulses occur so close in time that the operating point of the amplifier drifts, one result being that there is not enough time for the signal level to return to ground between pulses. Also, the

  17. Modulated Pulses Based High Spatial Resolution Distributed Fiber System for Multi-Parameter Sensing

    Zhang, Jingdong; Zhou, Huan; Li, Yang; Liu, Min; Huang, Wei


    We demonstrate a hybrid distributed fiber sensing system for multi-parameter detection. The integration of phase-sensitive optical time domain reflectometry ({\\Phi}-OTDR) and Brillouin optical time domain reflectometry (B-OTDR) enables measurement of vibration, temperature and strain. Exploiting the fast changing property of vibration and the static property of temperature and strain, the laser pulse width and intensity are modulated and then injected into the single-mode sensing fiber proportionally, so that the three concerned parameters can be extracted simultaneously by only one photo-detector and data acquisition channel. Combining with advanced data processing methods, the modulation of laser pulse brings additional advantages because of trade and balance between the backscattering light power and nonlinear effect noise, which enhances the signal-to-noise ratio, and enables sub-meter level spatial resolution together with long sensing distance. The proposed method realizes up to 4.8 kHz vibration sensin...

  18. The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

    Pommer, Tobias; Falk, Marianne; Poulsen, Per Rugaard


    Purpose: Intensity modulated arc therapy (IMAT) is commonly used to treat prostate cancer. The purpose of this study was to evaluate the impact of leaf width and plan complexity on dynamic multileaf collimator (DMLC) tracking for prostate motion management during IMAT treatments.Methods: Prostate...

  19. A Simulation of the Effects of Varying Repetition Rate and Pulse Width of Nanosecond Discharges on Premixed Lean Methane-Air Combustion

    Moon Soo Bak


    Full Text Available Two-dimensional kinetic simulation has been carried out to investigate the effects of repetition rate and pulse width of nanosecond repetitively pulsed discharges on stabilizing premixed lean methane-air combustion. The repetition rate and pulse width are varied from 10 kHz to 50 kHz and from 9 ns to 2 ns while the total power is kept constant. The lower repetition rates provide larger amounts of radicals such as O, H, and OH. However, the effect on stabilization is found to be the same for all of the tested repetition rates. The shorter pulse width is found to favor the production of species in higher electronic states, but the varying effects on stabilization are also found to be small. Our results indicate that the total deposited power is the critical element that determines the extent of stabilization over this range of discharge properties studied.

  20. Modulation techniques for deep-space pulse-position modulation (PPM) optical communication

    Rayman, Marc D.; Robinson, Deborah L.


    The extremely energy-efficient pulse-position modulation (PPM) format is being actively developed as a basis for optical communications with deep-space probes. Attention is presently given to different modulation schemes for the efficient production of laser pulses over a broad range of repetition rates. Both Q-switching and cavity dumping modulation methods are available for the envisioned diode-pumped Nd:YAG laser source. Numerical calculation results are presented for cavity-dumping.

  1. Modulated coupled nanowires for ultrashort pulses

    Solntsev, Alexander S


    We predict analytically and confirm with numerical simulations that inter-mode dispersion in nanowire waveguide arrays can be tailored through periodic waveguide bending, facilitating flexible spatio-temporal reshaping without break-up of femtosecond pulses. This approach allows simulta- neous and independent control of temporal dispersion and spatial diffraction that are often strongly connected in nanophotonic structures.

  2. A Simple Method for the Evaluation of the Pulse Width of an Ultraviolet Femtosecond Laser Used in Two-Photon Ionization Mass Spectrometry

    Tomoko Imasaka


    Full Text Available A simple method was proposed for on-site evaluation of the pulse width of an ultraviolet femtosecond laser coupled with a mass spectrometer. This technique was based on measurement of a two-photon ionization signal in mass spectrometry by translation of the prism in the pulse compressor of the femtosecond laser. The method was applied to optical pulses that were emitted at wavelengths of 267, 241, and 219 nm; the latter two pulses were generated by four-wave Raman mixing using the third harmonic emission of a Ti:sapphire laser (267 nm in hydrogen gas. The measurement results show that this approach is useful for evaluation of the pulse width of the ultraviolet femtosecond laser used in mass spectrometry for trace analysis of organic compounds.

  3. Modulated Pulsed Laser Sources for Imaging Lidars


    manufactured by QPC. This C-mount device has a monolithic semiconductor amplifier allowing the package to output up to 1.5 Watts at 1064 nm with linewidths ɘ.1...pulsed driver based on the avalanche transistor circuit being used for gain switching, a 1064 nm DFB laser manufactured by QPC and a DBR -style laser...available now that may provide the needed power. An example of such a laser is the QPC C-mount monolithic oscillator/amplifier which can output 1.5

  4. Impacts of cross-phase modulation on modulation instability of Airy pulses

    Cheng, Yingkai; Fu, Xiquan; Bai, Yanfeng


    The modulation instability (MI) of Airy pulses with the influence of cross-phase modulation is studied based on the coupled nonlinear Schrödinger equations in nonlinear media. The main lobe of Airy pulses can be manifested as breakup of MI under interaction with higher power pumped solitons, although the power of Airy pulses is small. By comparing the main lobe's gain spectrum of MI, the gain spectrum has gradually improved with the increase of power of pumped solitons. The gain spectrum of MI of the main lobe is inversely proportional to the truncation coefficient, and then it gradually approaches to that of Gauss pulses with the truncation coefficient increasing to 1. For the side lobes of Airy pulses, there are similar MI but smaller gain spectrum than the main lobe when the pumped solitons is overlapping with corresponding ones of Airy pulses.

  5. Morphometric comparison of the acute rabbit corneal response to 1540-nm laser light following in-vitro exposure to millisecond or nanosecond pulse widths

    Eurell, Thomas E.; Johnson, Thomas E.; Roach, William P.


    Significant damage to rabbit corneal tissue was produced by a single pulse, in vitro exposure of 1540 m infrared laser light operating in either millisecond or nanosecond pulse widths. Millisecond pulse widths of infrared laser light produced a marked coagulative necrosis of both the corneal epithelium and stroma. We also noted histologic alterations in the stromal matrix within the beam path that we interpreted as matrix remodeling. To test this interpretation, we used an indirect immunohistochemical procedure to detect Matrix Metalloproteinase-2 (MMP-2) activity. Immunohistochemistry revealed that the MMP-2 reaction was mostly limited to the margins of the beam path. In addition, the MMP-2 reaction was less intense than expected given the significant tissue changes observed in the histologic sections. Exposure of rabbit corneal tissue to the nanosecond pulse widths produced a less severe coagulative necrosis of the tissue when compared to the millisecond exposures. However, a markedly stronger immunohistochemical pattern than would have been predicted from the histologic sections was observed, with approximately half of the beam path filled with MMP-2 reaction product. These data suggest an association between infrared laser pulse width and the degree of extracellular matrix remodeling in rabbit corneal tissue.

  6. Spatially modulated laser pulses for printing electronics.

    Auyeung, Raymond C Y; Kim, Heungsoo; Mathews, Scott; Piqué, Alberto


    The use of a digital micromirror device (DMD) in laser-induced forward transfer (LIFT) is reviewed. Combining this technique with high-viscosity donor ink (silver nanopaste) results in laser-printed features that are highly congruent in shape and size to the incident laser beam spatial profile. The DMD empowers LIFT to become a highly parallel, rapidly reconfigurable direct-write technology. By adapting half-toning techniques to the DMD bitmap image, the laser transfer threshold fluence for 10 μm features can be reduced using an edge-enhanced beam profile. The integration of LIFT with this beam-shaping technique allows the printing of complex large-area patterns with a single laser pulse.

  7. Absolute frequency synthesis of pulsed coherent light waves through phase-modulation active optical feedback.

    Shimizu, K; Horiguchi, T; Koyamada, Y


    A novel method for the broadband absolute frequency synthesis of pulsed coherent lightwaves is demonstrated. It is based on pulse recirculation around an active optical feedback ring containing a delay-line fiber, an external phase modulator, an acousto-optic frequency shifter (AOFS), and a high-finesse Fabry-Perot étalon. The modulation frequency F(M) and the frequency shift F(AO) that are due to AOFS are designed so that their sum or difference equals the free-spectral range of the étalon and F(AO) is set at larger than the half-width at full maximum of its resonant peaks. If one of the peak frequencies is tuned to the frequency of the initial pulse, the frequency of the recirculating pulse jumps to the next peak for each round trip. In the experiment the absolute frequency is synthesized over a frequency span of 700 GHz around the initial stabilized frequency of the master laser.

  8. Digital Pulse Modulation Amplifier (PMA) systems based on PEDEC control

    Nielsen, Karsten


    The paper extends previous research and presents a suite of novel high efficiency digital PMA topologies based on Pulse Edge Delay Error Correction (PEDEC). The practical results are very encouraging, showing that digital modulator performance is maintained throughout the subsequent power convers...... conversion. The topologies are believed to be the first implemented digital PMA systems including effective power stage error correction....

  9. Spatiotemporal vector pulse shaping of femtosecond laser pulses with a multi-pass two-dimensional spatial light modulator.

    Esumi, Y; Kabir, M D; Kannari, F


    A novel non-interferometric vector pulse-shaping scheme is developed for femtosecond laser pulses using a two-dimensional spatial light modulator (2D-SLM). By utilizing spatiotemporal pulse shaping obtainable by the 2D-SLM, we demonstrate spatiotemporal vector pulse shaping for the first time.

  10. Two-mode dynamics in pulse-modulated control systems

    Zhusubaliyev, Z.T.; Yanochkina, O.O.; Mosekilde, Erik


    as an example the paper provides a survey of three new mechanisms of torus bifurcation that can be observed in pulse-modulated control systems. The paper concludes with a discussion of the influence that operation in the torus regimes will have on the efficiency of the converter......Pulse-modulated converter systems play an important role in modern power electronics. Systems of this type also deserve considerable theoretical interest because of the complex interplay they exhibit between ordinary (smooth) bifurcations and so-called border-collision bifurcations generated...... by the switching dynamics. Particularly interesting are the unusual transitions to torus dynamics, i.e., to a mode of behavior in which the regular switching dynamics is modulated by another oscillatory mode that may arise through instability in the feedback control. Using the model of a two-level DC/DC converter...

  11. Investigation on Nyquist pulse generation using a single dual-parallel Mach-Zehnder modulator.

    Wu, Jian; Zang, Jizhao; Li, Yan; Kong, Deming; Qiu, Jifang; Zhou, Siyuan; Shi, Jindan; Lin, Jintong


    The generation of Nyquist pulses with a dual parallel Mach-Zehnder modulator (DPMZM) driven by a single RF signal is demonstrated theoretically and experimentally. A complete theoretical analysis is developed and the limitation of the proposed scheme is also discussed. It is theoretically proved that Nyquist pulses with a spectrum of 5 flat comb lines can be generated using a single DPMZM, which is also verified with simulation. 7 flat comb lines in frequency domain can also be obtained if a large RF driving voltage is applied to DPMZM but the generated waveforms won't present a sinc-shape. This scheme is further investigated experimentally. 40 GHz Nyquist pulses with full-width-at-half-maximum (FWHM) less than 4.65 ps, signal-to-noise ratio (SNR) better than 29.5 dB, and normalized root-mean-square error (NRMSE) less than 2.4% are generated. It is found that a tradeoff exists between the insertion loss of the DPMZM and the deviation of generated pulses. The tunability of repetition rate is experimentally verified by generation of 1 GHz to 40 GHz Nyquist pulses with SNR better than 28.4 dB and NRMSE less than 6.15%.

  12. Femtosecond pulse shaping by modulating the refractive index modulation of volume holographic grating.

    Yan, Xiaona; Dai, Ye; Gao, Zixuan; Chen, Yuanyuan; Yang, Xihua; Ma, Guohong


    Based on the modified Kogelnik's coupled-wave theory, time- and frequency-domain diffractions of a femtosecond pulse from transmitted volume holographic gratings (VHGs) are theoretically studied. Results show that when the refractive index modulation of the VHG changes in a certain range, the number of temporal diffracted pulse will evolve from one to two, then to three, and this pulse number evolution is periodic. This particular phenomenon can be explained by diffraction intensity spectrum and the overmodulation effect of refractive index modulation of transmitted VHG. Moreover, we find centers of all temporal diffracted pulses translate along the negative time axis, and the translation is irrelevant to the refractive index modulations. We will use time delay of volume grating to give a reasonable explanation.

  13. Overview of Space Vector Pulse Width Algorithm of Dual Three-phase Motor%双三相感应电机空间矢量脉冲宽度调制算法综述

    李洪亮; 贺诚; 田明; 许奔


      空间矢量脉冲宽度(SVPWM)调制算法将逆变器和电动机视为一个整体,着眼于使电动机获得幅值恒定的旋转磁场。与正弦脉冲宽度(SPWM)算法相比,SVPWM 可使功率开关器件的开关次数减少1/3,直流电压利用率提高15%,能获得较好的谐波抑制效果。本文分析了双三相感应电机常用的SVPWM调制算法,讨论了它们各自的优缺点,并给出了仿真和实验验证。%The algorithm of space vector pulse width modulation (SVPWM) regards the inverter and motor as a whole model to make the motor acquire a rotating magnetic field with constant amplitude. Comparing with the algorithm of sine pulse width modulation (SPWM), SVPWM can achieve a good harmonic control effect with less than 30 percent action times of the power switching devices and more than 15 percent DC voltage utilization. This paper analyzes the SVPWM’s common modulation algorithm of the three-phase motor and discusses their advantages and disadvantages. Simulation and experimental verification are given in the last.

  14. Optimal space communication techniques. [a discussion of delta modulation, pulse code modulation, and phase locked systems

    Schilling, D. L.


    Encoding of video signals using adaptive delta modulation (DM) was investigated, along with the error correction of DM encoded signals corrupted by thermal noise. Conversion from pulse code modulation to delta modulation was studied; an expression for the signal to noise ratio of the DM signal derived was achieved by employing linear, 2-sample, interpolation between sample points. A phase locked loop using a nonlinear processor in lieu of a loop filter is discussed.

  15. Pulse Power Hybrid Energy Storage Module Development Program


    simulation results were shown in Fig. 11.) 28 14. One of the two reference MatLab Simulink models for the study of the effect of HESMs and a pulsed load...the Megawatt Power Module 44 25 Block diagram of the MPM system - two flywheels per skid configuration 45 26 MatLab Simulink model of a two...Network McKttile Fig. 14. One of the two reference MatLab Simulink models for the study of the effect of HESMs and a pulsed load on a ship’s power

  16. Diffraction leveraged modulation of X-ray pulses using MEMS-based X-ray optics

    Lopez, Daniel; Shenoy, Gopal; Wang, Jin; Walko, Donald A.; Jung, Il-Woong; Mukhopadhyay, Deepkishore


    A method and apparatus are provided for implementing Bragg-diffraction leveraged modulation of X-ray pulses using MicroElectroMechanical systems (MEMS) based diffractive optics. An oscillating crystalline MEMS device generates a controllable time-window for diffraction of the incident X-ray radiation. The Bragg-diffraction leveraged modulation of X-ray pulses includes isolating a particular pulse, spatially separating individual pulses, and spreading a single pulse from an X-ray pulse-train.

  17. Healthy younger and older adults control foot placement to avoid small obstacles during gait primarily by modulating step width

    Schulz Brian W


    Full Text Available Abstract Background Falls are a significant problem in the older population. Most falls occur during gait, which is primarily regulated by foot placement. Variability of foot placement has been associated with falls, but these associations are inconsistent and generally for smooth, level flooring. This study investigates the control of foot placement and the associated gait variability in younger and older men and women (N=7/group, total N=28 while walking at three different speeds (slow, preferred, and fast across a control surface with no obstacles and surfaces with multiple (64 small (10cm long ×13mm high visible and hidden obstacles. Results Minimum obstacle distance between the shoe and nearest obstacle during each footfall was greater on the visible obstacles surface for older subjects because some of them chose to actively avoid obstacles. This obstacle avoidance strategy was implemented primarily by modulating step width and to a lesser extent step length as indicated by linear regressions of step width and length variability on minimum obstacle distance. Mean gait speed, step length, step width, and step time did not significantly differ by subject group, flooring surface, or obstacle avoidance strategy. Conclusions Some healthy older subjects choose to actively avoid small obstacles that do not substantially perturb their gait by modulating step width and, to a lesser extent, step length. It is not clear if this obstacle avoidance strategy is appropriate and beneficial or overcautious and maladaptive, as it results in fewer obstacles encountered at a consequence of a less efficient gait pattern that has been shown to indicate increased fall risk. Further research is needed on the appropriateness of strategy selection when the environmental demands and/or task requirements have multiple possible completion strategies with conflicting objectives (i.e. perceived safety vs. efficiency.

  18. Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer.

    Hong, Chae-Seon; Ju, Sang Gyu; Kim, Minkyu; Kim, Jung-In; Kim, Jin Man; Suh, Tae-Suk; Han, Youngyih; Ahn, Yong Chan; Choi, Doo Ho; Nam, Heerim; Park, Hee Chul


    The authors evaluated the effects of multileaf collimator (MLC) leaf width (2.5 vs. 5 mm) on dosimetric parameters and delivery efficiencies of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck (H&N) cancers. The authors employed two types of mock phantoms: large-sized head and neck (LH&N) and small-sized C-shape (C-shape) phantoms. Step-and-shoot IMRT (S&S_IMRT) and VMAT treatment plans were designed with 2.5- and 5.0-mm MLC for both C-shape and LH&N phantoms. Their dosimetric characteristics were compared in terms of the conformity index (CI) and homogeneity index (HI) for the planning target volume (PTV), the dose to organs at risk (OARs), and the dose-spillage volume. To analyze the effects of the field and arc numbers, 9-field IMRT (9F-IMRT) and 13-field IMRT (13F-IMRT) plans were established for S&S_IMRT. For VMAT, single arc (VMAT1) and double arc (VMAT2) plans were established. For all plans, dosimetric verification was performed using the phantom to examine the relationship between dosimetric errors and the two leaf widths. Delivery efficiency of the two MLCs was compared in terms of beam delivery times, monitor units (MUs) per fraction, and the number of segments for each plan. 2.5-mm MLC showed better dosimetric characteristics in S&S_IMRT and VMAT for C-shape, providing better CI for PTV and lower spinal cord dose and high and intermediate dose-spillage volume as compared with the 5-mm MLC (p 0.05). Further, beam delivery efficiency was not observed to be significantly associated with leaf width for either C-shape or LH&N. However, MUs per fraction were significantly reduced for the 2.5-mm MLC for the LH&N. In dosimetric error analysis, absolute dose evaluations had errors of less than 3%, while the Gamma passing rate was greater than 95% according to the 3%/3 mm criteria. There were no significant differences in dosimetric error between the 2.5- and 5-mm MLCs. As compared with MLC of 5-mm leaf

  19. Giant peak to valley ratio in a GaN based resonant tunnel diode with barrier width modulation

    Sankaranarayanan, Sandeep; Saha, Dipankar


    A barrier width modulated GaN based resonant tunnel diode is theoretically proposed which exhibits a giant peak to valley current ratio as high as 60 and a high negative differential conductance (NDC) of 1.77 × 106 S/cm2 with very low valley current density of 3 mA/cm2. This is achieved by the unique characteristic of the device current which monotonically decreases for applied voltages greater than the valley voltage in our simulation window. This is in contrast to all the other negative differential conductance based devices which experience an immediate exponential increase in current after the NDC region. The proposed device is also the first bidirectional tunneling diode which shows negative differential conductance for both polarity of the applied bias which is normally not observed with the conventional GaN/AlGaN double barrier structures due to the strong asymmetry arising from the internal electric fields due to polarization. The unique characteristics of the device can be attributed to the use of a modulated barrier width which is made possible by a polarization modulating InGaN layer and efficient utilization of internal electric fields in III-nitrides.

  20. Pit Depth and Width Modulation Multilevel Run-Length Limited Read-Only Optical Storage

    SONG Jie; PEI Jing; XU Duan-Yi; XIONG Jian-Ping; CHEN Ken; PAN Long-Ea


    When the techniques of integrating the variation of the pit depth and width simultaneously are adopted to conventional DVD, the high-density multilevel run-length limited read-only optical storage method is achieved. The dynamic range of readout signal is greatly enlarged in comparison with keeping one parameter varied, and the recording levels number can be obviously increased. The discs can be manufactured using standard photoresist mastering and replication techniques with great compatibility to conventional binary read-only discs. Experimental results show that eight-level read-only optical disc can be realized and the capacity can be increased to 20 GB.

  1. 10 GHz pulse source for 640 Gbit/s OTDM based on phase modulator and self-phase modulation

    Hu, Hao; Mulvad, Hans Christian Hansen; Peucheret, Christophe


    to compensate the chirp. The non-linear pulse compression stages are based on self-phase modulation (SPM) in dispersion-flattened highly non-linear fibers (DF-HNLF). The pulse source is tunable over the C-band with negligible pedestal. © 2011 Optical Society of America....... the high pulse quality. The pulse source is based on a linear pulse compression stage followed by two polarization-independent non-linear pulse compression stages. The linear pulse compression stage relies on a phase modulator, which is used to generate linear chirp and followed by a dispersive element...

  2. Short-pulse cross-phase modulation in an electromagnetically-induced-transparency medium

    Feizpour, Amir; Steinberg, Aephraim M


    Electromagnetically-induced transparency (EIT) has been proposed as a way to greatly enhance cross-phase modulation, with the possibility of leading to few-photon-level optical nonlinearities. This enhancement grows as the transparency window width, \\Delta_EIT, is narrowed. Decreasing \\Delta_EIT, however, increases the response time of the effect, suggesting that for pulses of a given duration, there could be a fundamental limit to the strength of the nonlinearity. We show that in the regimes of most practical interest - narrow EIT windows perturbed by short signal pulses- the enhancement offered by EIT is not only in the magnitude of the nonlinear phase shift but in fact also in its increased duration. That is, for the case of signal pulses much shorter (temporally) than the inverse EIT bandwidth, the narrow window serves to prolong the effect of the passing signal pulse, leading to an integrated phase shift that grows linearly with \\Delta_EIT even though the peak phase shift may saturate; the continued grow...

  3. Pulse plasma sintering of a tungsten/steel divertor module

    Kruszewski, Mirosław J., E-mail:; Ciupiński, Łukasz; Rosiński, Marcin; Michalski, Andrzej; Kurzydłowski, Krzysztof J.


    Highlights: • W/WL10 and WL10/steel joints were fabricated via pulse plasma sintering. • Fe interlayer successfully compensated thermal stresses at the WL10/steel joint. • Maximum temperature of a single stage sintering of the module was established. • Better accuracy in machining of W and WL10 elements is needed. -- Abstract: The paper presents the preliminary evaluation of the potential of a pulse plasma sintering (PPS) technique for the fabrication of a He-cooled modular divertor with a multiple-jet cooling module. In this work the W and WL10 elements were directly bonded by PPS. Examination of the microstructure revealed some minor defects at the interface, but the overall quality of the joint was good with no cracks or delamination being detected. To reduce the thermal stress gradient a thin transition layer of iron was used at the WL10/steel interface. In addition an attempt was made to fabricate the complete module by a single sintering process. The microstructures of the fabricated modules were examined and the findings were reported.

  4. A Q-Swicthed All-Solid-State Single-Longitudinal-Mode Laser with Adjustable Pulse-Width and High Repetition Rate

    ZHOU Jun; XU Shi-Zhong; HOU Xia; WEI Hui; CHEN Wei-Biao


    A single-longitudinal-mode (SLM) laser-diode pumped Nd: YAG laser with adjustable pulse width is developed by using the techniques of pre-lasing and changing polarization of birefingent crystal. The Q-switching voltage is triggered by the peak of the pre-lasing pulse to achieve the higher stability of output pulse energy. The output energy of more than 1mJ is obtained with output energy stability of 3% (rms) at 100 Hz. The pulsewidth can be adjusted from 30ns to 300ns by changing the Q-switching voltage. The probability of putting out single-longitudinal-mode pulses is almost 100%. The laser can be run over four hours continually without mode hopping.

  5. Pulse width modulated buck-boost five-level current source inverters

    Blaabjerg, Frede; Gao, F.; Loh, P.C.;


    This paper presents new five-level current source inverters (CSIs) with voltage/current buck-boost capability. Being different from the existing multilevel CSI, the proposed CSIs were first designed to regulate the flowing path of dc input current by controlling two additional active switches, re...

  6. Bifurcation and Chaos in a Pulse Width modulation controlled Buck Converter

    Kocewiak, Lukasz; Bak, Claus Leth; Munk-Nielsen, Stig


    by a system of piecewise-smooth nonautonomous differential equations. The research are focused on chaotic oscillations analysis and analytical search for bifurcations dependent on parameter. The most frequent route to chaos by the period doubling is observed in the second order DC-DC buck converter. Other...... bifurcations as a complex behaviour in power electronic system evidence are also described. In order to verify theoretical study the experimental DC-DC buck converter was build. The results obtained from three sources were presented and compared. A very good agreement between theory and experiment was observed....

  7. utility interfaced pulse-width modulation of solar fed voltage source ...

    solar energy into electrical energy; boosting the dc power; inversion of the dc to ac and then synchronization of .... rent error δ is compared with the hysteresis band as shown in fig.5b. .... mental period, T - fundamental period. 7. Modeling And ...

  8. On the Myth of Pulse Width Modulated Spectrum in Theory and Practice

    Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael Andreas E.


    Switch-mode audio power amplifiers are commonly used in sound reproduction. Their well known drawback is the radiation of high frequent energy, which can disturb radio and TV receivers. The designer of switch-mode audio equipment therefore needs to make arrangements to prevent this coupling which...... approaches by comparing them with reality from both the time and the frequency domain perspective. For validation a switch-mode audio power amplifier was built, delivering the contents material with less than 0.06 % distortion across the audio band at 50 W. The switch-mode signals have been evaluated very...

  9. Space Vector Pulse Width Modulation Scheme for a Seven-Phase Voltage Source Inverter

    Mohd. Arif Khan


    Full Text Available This paper analyses a simple space vector PWM (SVPWM scheme for a seven-phase voltage source inverter. At first the conventional method of producing sinusoidal output voltage  by utilizing six active and a zero space vectors are used to synthesis the input reference and then new PWM scheme called time equivalent space vector PWM is presented.  A comparison of the proposed scheme with the conventional scheme is presented based on various performance indices. Extensive Simulation results are provided to validate the findings

  10. Pengaruh Penambahan PWM (Pulse Width Modulation Pada Generator HHO Tipe Dry Cell

    Fungky Dyan Pertiwi


    Full Text Available Generator HHO memanfaatkan proses elektrolisis air agar mendapatkan gas H2. Namun, pada praktiknya pemakaian arus dari aki yang besar dan temperatur tinggi membuat bejana generator menjadi cepat rusak, sehingga dibutuhkan tambahan rangkaian elektronika PWM pada pengujian generator HHO guna mengatasi permasalahan tersebut. Penelitian menggunakan elektroda plat berjumlah 9 berdimensi 120mm 120mm, tebal 1mm dan dibatasi oleh o-ring dengan diameter 126mm, tebal 3mm. Pengujian dilakukan secara eksperimen dengan 2 kelompok yaitu kelompok control yang mana pengujian tanpa menggunakan PWM serta kelompok uji dimana pengujian menggunakan PWM dengan variasi duty cycle 30%, 50% dan 70%. Pengujian dilakukan hingga temperatur elektrolit 93oC. Hasil uji didapatkan bahwa arus, laju produksi dan efisiensi terbesar didapatkan pada pengujian tanpa PWM yang mencapai 60,6A, 6,033 10-6kg/s dan 25,69%. Namun, pada pengambilan data kedua efisiensi turun menjadi 19,74%. Penambahan PWM pada pengujian berpengaruh pada arus dan temperatur yang stabil meskipun laju produksi dan efisiensi lebih kecil daripada pengujian tanpa PWM. Pengujian dengan PWM pada duty cycle 70% menghasilkan laju produksi dan efisiensi terbesar yang mencapai 1,843 10-6 kg/s dan 15,19%.

  11. On the Myth of Pulse Width Modulated Spectrum in Theory and Practice

    Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael Andreas E.


    Switch-mode audio power amplifiers are commonly used in sound reproduction. Their well known drawback is the radiation of high frequent energy, which can disturb radio and TV receivers. The designer of switch-mode audio equipment therefore needs to make arrangements to prevent this coupling which...... precisely in time and spectral domain to enlighten the assumptions about the PWM spectra and decrypt this myth....

  12. Analysis of intra-pulse frequency-modulated, low probability of interception, radar signals



    In this paper, we investigate the problem of analysis of low probability of interception (LPI) radar signals with intra-pulse frequency modulation (FM) under low signal-to-noise ratio conditions from the perspective of an airborne electronic warfare (EW) digital receiver. EW receivers are designed to intercept andanalyse threat radar signals of different classes, received over large dynamic range and operating independently over large geographical spread to advice host aircraft to undertake specified actions. For an EW receiver, primary challenges in interception and analysis of LPI radar signals are low received power, intra-pulse modulations,multi-octave frequency range, wide signal bandwidth, long pulse width, vast and multi-parametric search space, etc. In the present work, a method based on match filterbank localization and Taylor’s seriesapproximation for analysing the entire family of intra-pulse FM radar signals is proposed. The method involves progressive, joint time–frequency (TF) localization of the signal of interest (SOI), under piecewise linearity andcontinuity assumptions on instantaneous frequency, to effectively capture local TF signatures. Detection is by information-theoretic criterion based hypotheses testing, while estimation and classification are based on polynomial approximation. Fine signal analysis is followed by synthetic reconstruction of the received signal slope. Detection, estimation and classification performances for the prominent FM radar signal classes are quantified based on simulation study statistics. Stagewise implementation of analysis and FM slope reconstruction,in realistic radar threat scenarios, is demonstrated for the potential SOIs. Subject discussion is organized from the perspective of practical EW system design and presented within the realm of signal processing architecture of concurrent EW digital receivers.Keywords. Digital receiver (DRx); electronic warfare (

  13. High extinction amplitude modulation in ultrashort pulse shaping

    Lin, Yen-Wei


    We explored the issues related to the resolution and the modulation extinction when filtering the spectrum of a UV femtosecond laser with a standard ultrashort pulse shaper. We have learned that a higher pulse shaping resolution often requires a larger working beam size or a higher density grating for greater dispersion. However, these approaches also introduce more optical errors and degrade the extinction. In this work, we examined specifics of each component to determine the best configuration of our spectral filtering setup. As a proof-of-concept demonstration, we utilized elements available as standard products and achieved 100 GHz filtering resolution with high extinction at the UV-A wavelength, which is superb in this wavelength range. The high extinction spectral filtering is especially important while modifying a broadband laser for the optical control of molecule's internal state.

  14. Three-dimensional optical storage in fused silica using modulated femtosecond pulses

    Qing Liu(刘青); Guanghua Cheng(程光华); Yishan Wang(王屹山); Zhao Cheng(程昭); Wei Zhao(赵卫); Guofu Chen(陈国夫)


    Three-dimensional bitwise optical recording with a density of 500 Gb/cm3 in fused silica using a Ti:sapphire femtosecond laser modulated by binary digits is demonstrated. Laser pulses modulation is realized by modulating two circuits of trigger pulses signal which are used to control laser pulses trapping and switching out from cavity, respectively. Bits are optically readout in both a parallel reading (phase-contrast) and a serial reading (confocal-type) methods. The method for modulating laser pulses can also be used in all of pulsed laser systems which operate in cavity-dumping configuration.

  15. The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

    Pommer, Tobias; Falk, Marianne; Poulsen, Per Rugaard; Keall, Paul J.; O’Brien, Ricky T.; Munck af Rosenschöld, Per


    Purpose: Intensity modulated arc therapy (IMAT) is commonly used to treat prostate cancer. The purpose of this study was to evaluate the impact of leaf width and plan complexity on dynamic multileaf collimator (DMLC) tracking for prostate motion management during IMAT treatments. Methods: Prostate IMAT plans were delivered with either a high-definition MLC (HDMLC) or a Millennium MLC (M-MLC) (0.25 and 0.50 cm central leaf width, respectively), with and without DMLC tracking, to a dosimetric phantom that reproduced four prostate motion traces. The plan complexity was varied by applying leaf position constraints during plan optimization. A subset of the M-MLC plans was converted for delivery with the HDMLC, isolating the effect of the different leaf widths. The gamma index was used for evaluation. Tracking errors caused by target localization, leaf fitting, and leaf adjustment were analyzed. Results: The gamma pass rate was significantly improved with DMLC tracking compared to no tracking (p < 0.001). With DMLC tracking, the average gamma index pass rate was 98.6% (range 94.8%–100%) with the HDMLC and 98.1% (range 95.4%–99.7%) with the M-MLC, using 3%, 3 mm criteria and the planned dose as reference. The corresponding pass rates without tracking were 87.6% (range 76.2%–94.7%) and 91.1% (range 81.4%–97.6%), respectively. Decreased plan complexity improved the pass rate when static target measurements were used as reference, but not with the planned dose as reference. The main cause of tracking errors was leaf fitting errors, which were decreased by 42% by halving the leaf width. Conclusions: DMLC tracking successfully compensated for the prostate motion. The finer leaf width of the HDMLC improved the tracking accuracy compared to the M-MLC. The tracking improvement with limited plan complexity was small and not discernible when using the planned dose as reference. PMID:24320425

  16. A dosimetric analysis of volumetric-modulated arc radiotherapy with jaw width restriction vs 7 field intensity-modulated radiotherapy for definitive treatment of cervical cancer.

    Huang, B; Fang, Z; Huang, Y; Lin, P; Chen, Z


    Radiation therapy treatment planning was performed to compare the dosimetric difference between volumetric-modulated arc radiotherapy (RapidArc™ v. 10; Varian® Medical Systems, Palo Alto, CA) and 7-field intensity-modulated radiotherapy (7f-IMRT) in the definitive treatment of cervical cancer. 13 patients with cervical cancer were enrolled in this study. Planning target volume (PTV) 50 and PTV60 were prescribed at a dose of 50 and 60 Gy in 28 fractions, respectively. The dose to the PTV60 was delivered as a simultaneous integrated boost to the pelvic lymph nodes. Owing to the mechanical limitation of the multileaf collimator in which the maximum displacement was limited to 15 cm, two types of RapidArc with different jaw width restrictions (15 and 20-23 cm) were investigated to evaluate their dosimetric differences. The RapidArc plan type with dosimetric superiority was then compared against the 7f-IMRT on the target coverage, sparing of the organs at risk (OARs), monitor units, treatment time and delivery accuracy to determine whether RapidArc is beneficial for the treatment of cervical cancer. The 15-cm jaw width restriction had better performance compared with the restrictions that were longer than 15 cm in the sparing of the OARs. The 15-cm RapidArc spared the OARs, that is, the bladder, rectum, small intestine, femoral heads and bones, and improved treatment efficiency compared with 7f-IMRT. Both techniques delivered a high quality-assurance passing rate (>90%) according to the Γ3mm,3% criterion. RapidArc with a 15-cm jaw width restriction spares the OARs and improves treatment efficiency in cervical cancer compared with 7f-IMRT. This study describes the dosimetric superiority of RapidArc with a 15-cm jaw width restriction and explores the feasibility of using RapidArc for the definitive treatment of cervical cancer.

  17. Inactivation of L. plantarum in a PEF microreactor The effect of pulse width and temperature on the inactivation

    Fox, M.B.; Esveld, D.C.; Mastwijk, H.C.; Boom, R.M.


    This article describes the inactivation of Lactobacillus plantarum by pulsed electric fields (PEF) in a microfluidic reactor. The microreactor has the specific advantage that the field intensity can be extremely high with accurate control and measurement of the pulse shape, combined with good

  18. Pulse Power Modulator development for the CLIC Damping Ring Kickers

    Holma, Janne


    The Compact Linear Collider (CLIC) study is exploring the scheme for an electron-positron collider with high luminosity (10-34 – 10-35 cm-2s-1) and a nominal centre-of-mass energy of 3 TeV: CLIC would complement LHC physics in the multi-TeV range. The CLIC design relies on Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve the very low emittance, through synchrotron radiation, needed for the luminosity requirements of CLIC. To limit the beam emittance blow-up due to oscillations, the pulse power modulators for the DR kickers must provide extremely flat, high-voltage pulses: the 2 GHz specification called for a 160 ns duration flat-top of 12.5 kV, 250 A, with a combined ripple and droop of not more than ±0.02 %. In order to meet these demanding specifications, a combination of broadband impedance matching, optimized electrical circuit layout and advanced control techniques is required. A solid-state modulator, the inductive adder, is the most promising approach to meeting the demanding specifications...

  19. Arbitrary waveform modulated pulse EPR at 200 GHz

    Kaminker, Ilia; Barnes, Ryan; Han, Songi


    We report here on the implementation of arbitrary waveform generation (AWG) capabilities at ∼200 GHz into an Electron Paramagnetic Resonance (EPR) and Dynamic Nuclear Polarization (DNP) instrument platform operating at 7 T. This is achieved with the integration of a 1 GHz, 2 channel, digital to analog converter (DAC) board that enables the generation of coherent arbitrary waveforms at Ku-band frequencies with 1 ns resolution into an existing architecture of a solid state amplifier multiplier chain (AMC). This allows for the generation of arbitrary phase- and amplitude-modulated waveforms at 200 GHz with >150 mW power. We find that the non-linearity of the AMC poses significant difficulties in generating amplitude-modulated pulses at 200 GHz. We demonstrate that in the power-limited regime of ω1 10 MHz) spin manipulation in incoherent (inversion), as well as coherent (echo formation) experiments. Highlights include the improvement by one order of magnitude in inversion bandwidth compared to that of conventional rectangular pulses, as well as a factor of two in improvement in the refocused echo intensity at 200 GHz.

  20. Phase matching of high order harmonic generation using dynamic phase modulation caused by a non-collinear modulation pulse

    Cohen, Oren; Kapteyn, Henry C.; Mumane, Margaret M.


    Phase matching high harmonic generation (HHG) uses a single, long duration non-collinear modulating pulse intersecting the driving pulse. A femtosecond driving pulse is focused into an HHG medium (such as a noble gas) to cause high-harmonic generation (HHG), for example in the X-ray region of the spectrum, via electrons separating from and recombining with gas atoms. A non-collinear pulse intersects the driving pulse within the gas, and modulates the field seen by the electrons while separated from their atoms. The modulating pulse is low power and long duration, and its frequency and amplitude is chosen to improve HHG phase matching by increasing the areas of constructive interference between the driving pulse and the HHG, relative to the areas of destructive interference.

  1. Spectral Compression of Intense Femtosecond Pulses by Self Phase Modulation in Silica Glass

    Iwaszczuk, Krzysztof; Zhou, Binbin; Bache, Morten


    We experimentally demonstrate spectral compression of mJ fs pulses by self phase modulation in silica glass. Spectral narrowing by factor 2.4 of near-transform-limited pulses is shown, with good agreement between experiment and numerical simulation.......We experimentally demonstrate spectral compression of mJ fs pulses by self phase modulation in silica glass. Spectral narrowing by factor 2.4 of near-transform-limited pulses is shown, with good agreement between experiment and numerical simulation....

  2. Pulse-modulated second harmonic imaging microscope quantitatively demonstrates marked increase of collagen in tumor after chemotherapy

    Raja, Anju M.; Xu, Shuoyu; Sun, Wanxin; Zhou, Jianbiao; Tai, Dean C. S.; Chen, Chien-Shing; Rajapakse, Jagath C.; So, Peter T. C.; Yu, Hanry


    Pulse-modulated second harmonic imaging microscopes (PM-SHIMs) exhibit improved signal-to-noise ratio (SNR) over conventional SHIMs on sensitive imaging and quantification of weak collagen signals inside tissues. We quantify the spatial distribution of sparse collagen inside a xenograft model of human acute myeloid leukemia (AML) tumor specimens treated with a new drug against receptor tyrosine kinase (ABT-869), and observe a significant increase in collagen area percentage, collagen fiber length, fiber width, and fiber number after chemotherapy. This finding reveals new insights into tumor responses to chemotherapy and suggests caution in developing new drugs and therapeutic regimens against cancers.

  3. Pulse width and energy influence on laser micromachining of metals in a range of 100 fs to 5 ps

    Le Harzic, R. [Institut fuer Strahlwerkzeuge (IFSW), Universitaet Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart (Germany) and Laboratoire Traitement du Signal et Instrumentation (TSI), UMR CNRS 5516, Bat F, 10 rue Barrouin, 42000 Saint Etienne (France)]. E-mail:; Breitling, D. [Institut fuer Strahlwerkzeuge (IFSW), Universitaet Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart (Germany); Weikert, M. [Institut fuer Strahlwerkzeuge (IFSW), Universitaet Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart (Germany); Sommer, S. [Institut fuer Strahlwerkzeuge (IFSW), Universitaet Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart (Germany); Foehl, C. [Forschungsgesellschaft fuer Strahlwerkzeuge mbH (FGSW), Nobelstrasse 15, 70569 Stuttgart (Germany); Valette, S. [Laboratoire Traitement du Signal et Instrumentation (TSI), UMR CNRS 5516, Bat F, 10 rue Barrouin, 42000 Saint Etienne (France); Donnet, C. [Laboratoire Traitement du Signal et Instrumentation (TSI), UMR CNRS 5516, Bat F, 10 rue Barrouin, 42000 Saint Etienne (France); Audouard, E. [Laboratoire Traitement du Signal et Instrumentation (TSI), UMR CNRS 5516, Bat F, 10 rue Barrouin, 42000 Saint Etienne (France); Dausinger, F. [Institut fuer Strahlwerkzeuge (IFSW), Universitaet Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart (Germany)


    Micromachining of steel, Cu and Al is studied. Ablation depths per pulse are deduced for laser pulse durations between 100 fs and 5 ps for fluences in the range of 150 mJ cm{sup -2} to 20 J cm{sup -2}. The evolution of ablation rates allows to evidence a low and a high fluence regime. Ablation thresholds and penetration depths are deduced as functions of pulse duration. While in the low fluence regime the penetration depth is close to the theoretical optical penetration depth, at higher fluences the effective heat penetration depth is 10-20 times bigger with also higher ablation thresholds. Even in the femtosecond range thermal ablation processes occur and reduce quality, accuracy and efficiency of micromachining. Additionally, the latter are influenced by strong beam distortions due to nonlinear interaction between the radiation and the atmospheric gas. In the case of steel and Cu, the pulse duration seems not to affect microprocessing, but it is demonstrated to play a role for Al for pulses between 1 and 5 ps.

  4. On an assessment of surface roughness estimates from lunar laser altimetry pulse-widths for the Moon from LOLA using LROC narrow-angle stereo DTMs.

    Muller, Jan-Peter; Poole, William


    Neumann et al. [1] proposed that laser altimetry pulse-widths could be employed to derive "within-footprint" surface roughness as opposed to surface roughness estimated from between laser altimetry pierce-points such as the example for Mars [2] and more recently from the 4-pointed star-shaped LOLA (Lunar reconnaissance Orbiter Laser Altimeter) onboard the NASA-LRO [3]. Since 2009, the LOLA has been collecting extensive global laser altimetry data with a 5m footprint and ?25m between the 5 points in a star-shape. In order to assess how accurately surface roughness (defined as simple RMS after slope correction) derived from LROC matches with surface roughness derived from LOLA footprints, publicly released LROC-NA (LRO Camera Narrow Angle) 1m Digital Terrain Models (DTMs) were employed to measure the surface roughness directly within each 5m footprint. A set of 20 LROC-NA DTMs were examined. Initially the match-up between the LOLA and LROC-NA orthorectified images (ORIs) is assessed visually to ensure that the co-registration is better than the LOLA footprint resolution. For each LOLA footprint, the pulse-width geolocation is then retrieved and this is used to "cookie-cut" the surface roughness and slopes derived from the LROC-NA DTMs. The investigation which includes data from a variety of different landforms shows little, if any correlation between surface roughness estimated from DTMs with LOLA pulse-widths at sub-footprint scale. In fact there is only any perceptible correlation between LOLA and LROC-DTMs at baselines of 40-60m for surface roughness and 20m for slopes. [1] Neumann et al. Mars Orbiter Laser Altimeter pulse width measurements and footprint-scale roughness. Geophysical Research Letters (2003) vol. 30 (11), paper 1561. DOI: 10.1029/2003GL017048 [2] Kreslavsky and Head. Kilometer-scale roughness of Mars: results from MOLA data analysis. J Geophys Res (2000) vol. 105 (E11) pp. 26695-26711. [3] Rosenburg et al. Global surface slopes and roughness of the

  5. Study of lower ionosphere by pulse cross-modulation method

    Chernogor, L. F.


    Three installations in the U.S.S.R. use cross-modulation to study the lower ionosphere from the Earth. Soviet work developed in the following directions: (1) simultaneous use of a number of independent methods; (2) use of broadband apparatus operating in the 1 to 6 MHz band; (3) utilization of both stationary and mobile installations; and (4) utilization of high powers (10 to 100 MW per pulse). Theoretical principle, as well as measurement and processing methods are described. Possibilities and errors of the method are considered. Information on the lower portion of the ionosphere, including the C layer can be collected in the daytime as well as the base of the ionosphere at 75 km at night. A better method for systematic studies of the D region is the partial reflections method.

  6. Pulse-modulation imaging-review and performance analysis.

    Chen, D G; Matolin, D; Bermak, A; Posch, C


    In time-domain or pulse-modulation (PM) imaging, the incident light intensity is not encoded in amounts of charge, voltage, or current as it is in conventional image sensors. Instead, the image data are represented by the timing of pulses or pulse edges. This method of visual information encoding optimizes the phototransduction individually for each pixel by abstaining from imposing a fixed integration time for the entire array. Exceptionally high dynamic range (DR) and improved signal-to-noise ratio (SNR) are immediate benefits of this approach. In particular, DR is no longer limited by the power-supply rails as in conventional complementary metal-oxide semiconductor (CMOS) complementary metal-oxide semiconductor active pixel sensors, thus providing relative immunity to the supply-voltage scaling of modern CMOS technologies. In addition, PM imaging naturally supports pixel-parallel analog-to-digital conversion, thereby enabling high temporal resolution/frame rates or an asynchronous event-based array readout. The applications of PM imaging in emerging areas, such as sensor network, wireless endoscopy, retinal prosthesis, polarization imaging, and energy harvesting are surveyed to demonstrate the effectiveness of PM imaging in low-power, high-performance machine vision, and biomedical applications of the future. The evolving design innovations made in PM imaging, such as high-speed arbitration circuits and ultra-compact processing elements, are expected to have even wider impacts in disciplines beyond CMOS image sensors. This paper thoroughly reviews and classifies all common PM image sensor architectures. Analytical models and a universal figure of merit - image quality and dynamic range to energy complexity factor are proposed to quantitatively assess different PM imagers across the entire spectrum of PM architectures.

  7. 用于微弱信号放大的高性能窄线宽纳秒脉冲光纤放大器%High-performance and narrow line-width nanosecond pulse laser amplifier for weak signal

    戚刚; 熊水东; 梁迅; 林惠祖


    A single mode, linearly polarized, narrow line-width, nanosecond pulsed fiber laser in master oscillator power amplifier (MOPA) configuration was demonstrated and the experimental results agreed with the theory. A single-frequency continuous wave laser operating at 1 064 nm was modulated by an acousto-optic modulator(AOM) to obtain pulses as the seed of the master amplifier. The repetition rate of the pulsed seed was 50 kHz and the average power was 25μW. In the pre-amplification stage, the effect of nonlinear effect, amplified spontaneous emission (ASE), parasitic lasing and pump saturation were analyzed by simulation. By optimizing the parameters of the MOPA system, the parasitic lasing was suppressed and the enlargement factor was increased effectively. In the experiment, the laser with pulse width of 64 ns and average power of 75 mW was achieved. Finally, the key factors that affect the performance of the sub-milli-watt weak signal amplifier were discussed.%搭建了一台主振荡功率放大(MOPA)结构的单模线偏振窄线宽纳秒脉冲全光纤放大器,理论仿真和实验结果较为吻合.通过声光调制器(AOM)对连续单频1 064 nm激光进行调制,获得了重复频率50 kHz、平均功率25μW的脉冲激光,作为放大器的种子源.对预放大过程中非线性效应、放大自发辐射、自激振荡及泵浦饱和问题进行了仿真分析.随后对种子光进行功率放大,通过光纤内参数的有效优化,进一步抑制了自激振荡,提升了弱信号的放大倍率.实验实现了脉冲宽度64 ns、平均功率75 mW的脉冲激光输出.最后,对亚毫瓦弱信号放大器中决定系统性能的关键因素进行了总结.

  8. Characterization of a High Efficiency, Ultrashort Pulse Shaper Incorporating a Reflective 4096-Element Spatial Light Modulator.

    Field, Jeffrey J; Planchon, Thomas A; Amir, Wafa; Durfee, Charles G; Squier, Jeff A


    We demonstrate pulse shaping via arbitrary phase modulation with a reflective, 1×4096 element, liquid crystal spatial light modulator (SLM). The unique construction of this device provides a very high efficiency when the device is used for phase modulation only in a prism based pulse shaper, namely 85%. We also present a single shot characterization of the SLM in the spatial domain and a single shot characterization of the pulse shaper in the spectral domain. These characterization methods provide a detailed picture of how the SLM modifies the spectral phase of an ultrashort pulse.

  9. Impact of Spectral Filter on Phase Modulation Pulse in Fiber Front End System

    LI Jing; JING Feng; WANG Jian-Jun; XU Dang-Peng; LIN Hong-Huan; GENG Yuan-Chao; LI Ming-Zhong; DENG Ying; ZHU Na; ZHANG Rui


    The transmission characteristics of phase modulation pulse transmitted through the filter in the power amplifier are investigated theoretically and experimentally. The narrow bandpass filter can induce large temporal modula-tion depth for the phase modulation pulse and induce double amplitude modulation(AM)if the frequency shift is lower than half bandwidth of the signal spectrum. We should choose a wider bandwidth filter to minimize the impact of the filter on the output pulse and suppress the amplified spontaneous emission(ASE) for the power fiber amplifier. These results are of benefit to the design of the fiber front end system.

  10. A new pulse width signal processing with delay-line and non-linear circuit (for ToT)

    Orita, Tadashi, E-mail: [Department of Nuclear Engineering and Management, Graduate School of Engineering, University of Tokyo (Japan); Takahashi, Hiroyuki; Shimazoe, Kenji; Fujiwara, Takeshi; Boxuan, Shi [Department of Nuclear Engineering and Management, Graduate School of Engineering, University of Tokyo (Japan)


    Traditional pulse-height-analysis systems suffer from the complexity arising from ADC circuits. In particular, it is difficult to be applied to a large format array of pixilated detectors. Each channel of such an energy resolving multichannel system must be low power consumption and therefore it must be composed of simple circuits. The time-over-threshold (ToT) method provides an inexpensive way in such a system. However, ToT method suffers from a poor linearity. We now propose a method to improve the linearity with the dynamic time-over-threshold method that relies on a dynamic threshold voltage and the trapezoidal shaping method.

  11. Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module


    Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module by Gregory K Ovrebo ARL-TR-7210...ARL-TR-7210 February 2015 Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module Gregory K... Bipolar Transistor (IGBT) Power Module 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Gregory K Ovrebo 5d

  12. Pulsed klystrons with feedback controlled mod-anode modulators

    Reass, William A [Los Alamos National Laboratory; Baca, David M [Los Alamos National Laboratory; Jerry, Davis L [Los Alamos National Laboratory; Rees, Daniel E [Los Alamos National Laboratory


    This paper describes a fast rise and fall, totem-pole mod-anode modulators for klystron application. Details of these systems as recently installed utilizing a beam switch tube ''on-deck'' and a planar triode ''off-deck'' in a grid-catch feedback regulated configuration will be provided. The grid-catch configuration regulates the klystron mod-anode voltage at a specified set-point during switching as well as providing a control mechanism that flat-top regulates the klystron beam current during the pulse. This flat-topped klystron beam current is maintained while the capacitor bank droops. In addition, we will review more modern on-deck designs using a high gain, high voltage planar triode as a regulating and switching element. These designs are being developed, tested, and implemented for the Los Alamos Neutron Science Center (LANSCE) accelerator refurbishment project, ''LANSCE-R''. An advantage of the planar triode is that the tube can be directly operated with solid state linear components and provides for a very compact design. The tubes are inexpensive compared to stacked semiconductor switching assemblies and also provide a linear control capability. Details of these designs are provided as well as operational and developmental results.

  13. Study on carrier trapping and emission processes in InAs/GaAs self-assembled quantum dots by varying filling pulse width during DLTS measurements

    Kim, Jin Soak; Kim, Eun Kyu; Kim, Jun Oh; Lee, Sang Jun; Noh, Sam Kyu


    The carrier trapping and emission processes of InAs self-assembled quantum dots (QDs) on GaAs substrates were measured and analyzed using capacitance-voltage techniques and deep-level transient spectroscopy (DLTS). We used different applied biases and filling pulse widths. This allowed the determination of the activation energies of defect/electronic states of the QDs within a range of 0.08-0.59 eV. These values represent the energy levels of the QDs with respect to the host matrix, showing that QDs have band-like interacting energy levels and that DLTS signals are largely affected by the electron density of states of QDs.

  14. Flow cytometry pulse width data enables rapid and sensitive estimation of biomass dry weight in the microalgae Chlamydomonas reinhardtii and Chlorella vulgaris.

    Maurizio Chioccioli

    Full Text Available Dry weight biomass is an important parameter in algaculture. Direct measurement requires weighing milligram quantities of dried biomass, which is problematic for small volume systems containing few cells, such as laboratory studies and high throughput assays in microwell plates. In these cases indirect methods must be used, inducing measurement artefacts which vary in severity with the cell type and conditions employed. Here, we utilise flow cytometry pulse width data for the estimation of cell density and biomass, using Chlorella vulgaris and Chlamydomonas reinhardtii as model algae and compare it to optical density methods. Measurement of cell concentration by flow cytometry was shown to be more sensitive than optical density at 750 nm (OD750 for monitoring culture growth. However, neither cell concentration nor optical density correlates well to biomass when growth conditions vary. Compared to the growth of C. vulgaris in TAP (tris-acetate-phosphate medium, cells grown in TAP + glucose displayed a slowed cell division rate and a 2-fold increased dry biomass accumulation compared to growth without glucose. This was accompanied by increased cellular volume. Laser scattering characteristics during flow cytometry were used to estimate cell diameters and it was shown that an empirical but nonlinear relationship could be shown between flow cytometric pulse width and dry weight biomass per cell. This relationship could be linearised by the use of hypertonic conditions (1 M NaCl to dehydrate the cells, as shown by density gradient centrifugation. Flow cytometry for biomass estimation is easy to perform, sensitive and offers more comprehensive information than optical density measurements. In addition, periodic flow cytometry measurements can be used to calibrate OD750 measurements for both convenience and accuracy. This approach is particularly useful for small samples and where cellular characteristics, especially cell size, are expected to vary

  15. Suppression of stimulated Brillouin scattering with phase modulator in soliton pulse compression

    Bo Lü; Taorong Gong; Ming Chen; Muguang Wang; Tangjun Li; Genxiang Chen; Shuisheng Jian


    A phase modulator is employed in the scheme of soliton pulse compression with dispersion shifted fiber (DSF). Stimulated Brillouin scattering (SBS) effect, as a negative influence here, can be dramatically suppressed after optical phase modulation. The experimental result shows that the launched power required for high-order soliton pulse compression has been significantly increased by 11 dB under the condition of 100-MHz phase modulation. Accordingly, the experiment of picosecond pulse compression generated from electro-absorption sampling window (EASW) has also been implemented.

  16. Modulation of ionization on laser frequency in ultra-short pulse intense laser-gas-target

    Hu Qiang-Lin; Liu Shi-Bing


    Based on the dispersion relation of intense laser pulse propagating in gradually ionized plasma, this paper discusses the frequency modulation induced by ionization of an ultra-short intense laser pulse interacting with a gas target.The relationship between the frequency modulation and the ionization rate, the plasmas frequency variation, and the polarization of atoms (ions) is analysed. The numerical results indicate that, at high frequency, the polarization of atoms (ions) plays a more important role than plasma frequency variation in modulating the laser frequency, and the laser frequency variation is different at different positions of the laser pulse.

  17. Anisotropy modulations of femtosecond laser pulse induced periodic surface structures on silicon by adjusting double pulse delay.

    Han, Weina; Jiang, Lan; Li, Xiaowei; Wang, Qingsong; Li, Hao; Lu, YongFeng


    We demonstrate that the polarization-dependent anisotropy of the laser-induced periodic surface structure (LIPSS) on silicon can be adjusted by designing a femtosecond laser pulse train (800 nm, 50 fs, 1 kHz). By varying the pulse delay from 100 to 1600 fs within a double pulse train to reduce the deposited pulse energy, which weakens the directional surface plasmon polarition (SPP)-laser energy coupling based on the initial formed ripple structure, the polarization-dependent geometrical morphology of the LIPSS evolves from a nearly isotropic circular shape to a somewhat elongated elliptical shape. Meanwhile, the controllable anisotropy of the two-dimensional scanned-line widths with different directions is achieved based on a certain pulse delay combined with the scanning speed. This can effectively realize better control over large-area uniform LIPSS formation. As an example, we further show that the large-area LIPSS can be formed with different scanning times under different pulse delays.

  18. Tandem electro-absorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short-pulse generation

    Zhao, Q.; Pan, J. Q.; Zhang, J.; Zhou, G. T.; Wu, J.; Wang, L. F.; Wang, W.


    A novel device of tandem multiple quantum wells (MQWs) electroabsorption modulators (EAMs) monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 mbar) selective area growth (SAG) MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio when coupled into a single mode fiber. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10GHz repetition rate pulse with a width of 13.7 ps without any compression elements is obtained.

  19. Control of high power pulse extracted from the maximally compressed pulse in a nonlinear optical fiber

    Yang, Guangye; Jia, Suotang; Mihalache, Dumitru


    We address the possibility to control high power pulses extracted from the maximally compressed pulse in a nonlinear optical fiber by adjusting the initial excitation parameters. The numerical results show that the power, location and splitting order number of the maximally compressed pulse and the transmission features of high power pulses extracted from the maximally compressed pulse can be manipulated through adjusting the modulation amplitude, width, and phase of the initial Gaussian-type perturbation pulse on a continuous wave background.

  20. GPU-based parallel clustered differential pulse code modulation

    Wu, Jiaji; Li, Wenze; Kong, Wanqiu


    Hyperspectral remote sensing technology is widely used in marine remote sensing, geological exploration, atmospheric and environmental remote sensing. Owing to the rapid development of hyperspectral remote sensing technology, resolution of hyperspectral image has got a huge boost. Thus data size of hyperspectral image is becoming larger. In order to reduce their saving and transmission cost, lossless compression for hyperspectral image has become an important research topic. In recent years, large numbers of algorithms have been proposed to reduce the redundancy between different spectra. Among of them, the most classical and expansible algorithm is the Clustered Differential Pulse Code Modulation (CDPCM) algorithm. This algorithm contains three parts: first clusters all spectral lines, then trains linear predictors for each band. Secondly, use these predictors to predict pixels, and get the residual image by subtraction between original image and predicted image. Finally, encode the residual image. However, the process of calculating predictors is timecosting. In order to improve the processing speed, we propose a parallel C-DPCM based on CUDA (Compute Unified Device Architecture) with GPU. Recently, general-purpose computing based on GPUs has been greatly developed. The capacity of GPU improves rapidly by increasing the number of processing units and storage control units. CUDA is a parallel computing platform and programming model created by NVIDIA. It gives developers direct access to the virtual instruction set and memory of the parallel computational elements in GPUs. Our core idea is to achieve the calculation of predictors in parallel. By respectively adopting global memory, shared memory and register memory, we finally get a decent speedup.

  1. A theoretical analysis for gigabit/second pulse code modulation of semiconductor lasers

    Danielsen, Magnus


    Investigation of the rate equations of a semiconductor laser suggests that bit rates of 3-4 Gbit/s can be achieved. Delay, ringing transients, and charge-storage effects can be removed by adjusting the dc-bias current and the peak and width of the current pulse to values prescribed by simple...

  2. Transmission Bandwidth Expansion of SI-POF Using WDM-Pulse-Position Modulations

    Katsumi; Takano; Eiji; Matsumoto; Kiyoshi; Nakagawa


    WDM-Pulse-position modulation technique in SI-POF transmission is proposed to overcome the limitation from mode dispersion. It can expand the flat transmission bandwidth to 80MHz with 100m-fiber length.

  3. Short optical pulse generation at 40 GHz with a bulk electro-absorption modulator packaged device

    Langlois, Patrick; Moore, Ronald; Prosyk, Kelvin; O'Keefe, Sean; Oosterom, Jill A.; Betty, Ian; Foster, Robert; Greenspan, Jonathan; Singh, Priti


    Short optical pulse generation at 40GHz and 1540nm wavelength is achieved using fully packaged bulk quaternary electro-absorption modulator modules. Experimental results obtained with broadband and narrowband optimized packaged modules are presented and compared against empirical model predictions. Pulse duty cycle, extinction ratio and chirp are studied as a function of sinusoidal drive voltage and detuning between operating wavelength and modulator absorption band edge. Design rules and performance trade-offs are discussed. Low-chirp pulses with a FWHM of ~12ps and sub-4ps at a rate of 40GHz are demonstrated. Optical time-domain demultiplexing of a 40GHz to a 10GHz pulse train is also demonstrated with better than 20dB extinction ratio.

  4. A Waveguide Based, High Power Pockels Cell Modulator for Sub-Nanosecond Pulse Slicing Project

    National Aeronautics and Space Administration — The Goal of this STTR is to develop a high speed, high power, waveguide based modulator (phase and amplitude) and investigate its use as a pulse slicer. The key...

  5. A megawatt solid-state modulator for high repetition rate pulse generation

    Wang, Y.; Pribyl, P.; Gekelman, W.


    A novel solid-state modulator capable of generating rapid consecutive power pulses is constructed to facilitate experiments on plasma interaction with high power microwave pulses. The modulator is designed to output a 100 kHz tone burst, which consists of up to 10 pulses, each with 1 μs duration and 1 MW peak power. The pulses are formed by discharging a total of 480 μF capacitors through 24 synchronized MOSFETs and 6 step-up transformers. The highly modular design, as a replacement of an old single-pulse version used in earlier experiments which employs a pulse forming network, brings great flexibility and wide potential to its application. A systematic cost-effectiveness analysis is also presented.

  6. Synchronization and Coherent Combining of Two Pulsed Fiber Ring Lasers Based on Direct Phase Modulation

    WANG Xiao-Lin; ZHOU Pu; MA Hao-Tong; CHEN Zi-Lun; LI Xiao; XU Xiao-Jun; LIU Ze-Jin


    We demonstrate a scalable architecture for coherent combining of pulsed fiber ring lasers based on mutual injection and direct phase modulation. By direct phase modulation in the common arm of two ring lasers, synchronous pulsed lasers can be generated and coherent combining of the two synchronous lasers is obtained. Two pulsed fiber ring lasers are coherently combined with 0.55 μJ pulse energy and 10μs pulse duration at a repetition rate of 27.5 kHz. Experimental results show that the two fiber ring lasers are phase locked with an invariable phase difference of π and have good temporal synchronization and spatial coherence. The combining efficiency of the two pulsed fiber laser reaches 90% and the fringe contrast is larger than 40%. Neither active phase control nor polarization control is used in our experiment and this method can be extended to combine more beams and higher repetition rate scaling up to higher power.

  7. Experimental Demonstration of the Effectiveness of Electromagnetically Induced Transparency for Enhancing Cross-Phase Modulation in the Short-Pulse Regime

    Dmochowski, Greg; Feizpour, Amir; Hallaji, Matin; Zhuang, Chao; Hayat, Alex; Steinberg, Aephraim M.


    We present an experiment using a sample of laser-cooled Rb atoms to show that cross-phase modulation schemes continue to benefit from electromagnetically induced transparency (EIT) even as the transparency window is made narrower than the signal bandwidth (i.e., for signal pulses much shorter than the response time of the EIT system). Addressing concerns that narrow EIT windows might not prove useful for such applications, we show that while the peak phase shift saturates in this regime, it does not drop, and the time-integrated effect continues to scale inversely with EIT window width. This integrated phase shift is an important figure of merit for tasks such as the detection of single-photon-induced cross-phase shifts. Only when the window width approaches the system's dephasing rate γ does the peak phase shift begin to decrease, leading to an integrated phase shift that peaks when the window width is equal to 4 γ .

  8. Self-phase modulation of a single-cycle THz pulse

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, M. C.


    We demonstrate self-phase modulation (SPM) of a single-cycle THz pulse in a semiconductor, using bulk n-GaAs as a model system. The SPM arises from the heating of free electrons in the electric field of the THz pulse. Electron heating leads to an ultrafast reduction of the plasma frequency, which...

  9. Control of high power IGBT modules in the active region for fast pulsed power converters

    Cravero, J M; Garcia Retegui, R; Maestri, S; Uicich, G


    At CERN, fast pulsed power converters are used to supply trapezoidal current in different magnet loads. These converters perform output current regulation by using a high power IGBT module in its ohmic region. This paper presents a new strategy for pulsed current control applications using a specifically designed IGBT driver.

  10. Equal pulse width chopping control based on plugged pulse principle in three-phase AC/AC system%基于脉冲阻塞原理的三相AC/AC系统等脉宽斩波控制

    郑诗程; 陈玲; 曹小虎


    A circuit topology of three-phase AC/AC system is presented,which needs only six power devices to realize the three-phase AC/AC frequency conversion. The traditional phase-shifted control strategy is replaced by the equal pulse width chopping control strategy based on plugged pulse principle to regulate the amplitude and frequency of output voltage separately or simultaneously. The equal pulse width chopping control strategy is analyzed in detail and the mathematic expression of duty cycle is deduced based on the area equivalent rule according to different frequency and amplitude of anticipant output voltage. Under the environment of PSPICE,the three-phase AC/AC system with the equal pulse width chopping control strategy is simulated. Its main circuit and FPGA-based control circuit are designed and tested. The experimental results are consistent with the simulative results,completely same as the theoretical analysis,which verifies the correctness and feasibility of the introduced control strategy.%针对传统的三相AC/AC变频电路特点,提出了一种新的电路拓扑,仅用6个功率器件即可实现三相AC/AC变频功能.提出基于脉冲阻塞原理的等脉宽斩波控制策略,取代传统的移相控制策略施加于该电路拓扑,实现了三相输出电压幅值、频率分别可调或同时可调.对等脉宽斩波控制策略进行了详细的理论分析.根据期望输出电压的不同频率和幅值.利用面积等效原则,推导出相应占空比的数学表达式.在PSPICE环境下根据脉冲阻塞原理.对三相AC/AC系统进行等脉宽斩波控制仿真.并设计了三相AC/AC系统主电路和基于FPGA的控制电路,完成了相关实验.仿真和实验结果一致,与文中的理论分析结果也完全一致,验证了该AC/AC变频控制策略的正确性及可行性.

  11. Frequency Stepped Pulse Train Modulated Wind Sensing Lidar

    Olesen, Anders Sig; Pedersen, Anders Tegtmeier; Rottwitt, Karsten


    In this paper a wind sensing lidar utilizing a Frequency Stepped Pulse Train (FSPT) is demonstrated. One of the advantages in the FSTP lidar is that it enables direct measurement of wind speed as a function of distance from the lidar. Theoretically the FSPT lidar continuously produces measurements...... as is the case with a CW lidar, but at the same time with a spatial resolution, and without the range ambiguity originating from e.g. clouds. The FSPT lidar utilizes a frequency sweeping source for generation of the FSPT. The source generates a pulse train where each pulse has an optical carrier frequency...... of frequency shifts corresponding to a specific distance. The spatial resolution depends on the repetition rate of the pulses in the pulse train. Directional wind measurements are shown and compared to a CW lidar measurement. The carrier to noise ratio of the FSPT lidar compared to a CW lidar is discussed...

  12. Dual temporal pitch percepts from acoustic and electric amplitude-modulated pulse trains.

    McKay, C M; Carlyon, R P


    Two experiments examined the perception of unmodulated and amplitude-modulated pulse trains by normally hearing listeners and cochlear implantees. Four normally hearing subjects listened to acoustic pulse trains, which were band-pass filtered between 3.9 and 5.3 kHz. Four cochlear implantees, all postlinguistically deaf users of the Mini System 22 implant, listened to current pulse trains produced at a single electrode position. In the first experiment, a set of nine loudness-balanced unmodulated stimuli with rates between 60 and 300 Hz were presented in a multidimensional scaling task. The resultant stimulus spaces for both subject groups showed a single dimension associated with the rate of the stimuli. In the second experiment, a set of ten loudness-balanced modulated stimuli was constructed, with carrier rates between 140 and 300 Hz, and modulation rates between 60 and 150 Hz. The modulation rates were integer submultiples of the carrier rates, and each modulation period consisted of one higher-intensity pulse and one or more identical lower-intensity pulses. The modulation depth of each stimulus was adjusted so that its pitch was judged to be higher or lower 50% of the time than that of an unmodulated pulse train having a rate equal to the geometric mean of the carrier and modulation rates. A multidimensional scaling task with these ten stimuli resulted in two-dimensional stimulus spaces, with dimensions corresponding to carrier and modulation rates. A further investigation with one normally hearing subject showed that the perceptual weighting of the two dimensions varied systematically with modulation depth. It was concluded that, when filtered appropriately, acoustic pulse trains can be used to produce percepts in normal listeners that share common features with those experienced by subjects listening through one channel of a cochlear implant, and that the central auditory system can extract two temporal patterns arising from the same cochlear location.

  13. All-optical DAC using counter-propagating optical and electrical pulses in a Mach-Zehnder modulator.

    Lowery, Arthur James


    A novel method of converting binary-level electrical pulses into multi-level optical pulses using only a conventional traveling-wave optical modulator is presented. The method provides low inter-pulse interference due to the counter-propagating pulses, low amplitude noise, and a timing jitter determined chiefly by the quality of the optical pulse source. The method only requires one electrical drive per modulator and provides low-jitter variable-amplitude optical pulses that are suitable for shaping into a wide variety of modulation formats using a programmable optical filter.

  14. A novel variable polarity welding power based on high-frequency pulse modulation

    Qiu Ling; Yang Chunli; Fan Chenglei; Lin Sanbao; Wu Yun


    A new type of variable polarity welding power modulated with high-frequency pulse current is developed.Series of high-frequency pulse current is superimposed on direct-current-electrode-negative (DCEN), which can improve the crystallization process in the weld bead as a result of the electromagnetic force generated by pulse current.Digital signal processor (DSP) is used to realize the closed-loop control of the first inverter, variable polarity output of the second inverter and high-frequency pulse current superposition.

  15. Temporally modulated phase retrieval method for weak temporal phase measurement of laser pulses

    Qiao, Zhi; Wang, Xiaochao; Jing, Yuanyuan; Fan, Wei; Lin, Zunqi


    The measurement of weak temporal phase for picosecond and nanosecond laser pulses is important but quite difficult. We propose a simple iterative algorithm, which is based on a temporally movable phase modulation process, to retrieve the weak temporal phase of laser pulses. This unambiguous method can achieve a high accuracy and simultaneously measure the weak temporal phase and temporal profile of pulses, which are almost transform-limited. Detailed analysis shows that this iterative method has valuable potential applications in the characterization of pulses with weak temporal phase.

  16. Amplification of Frequency-Modulated Similariton Pulses in Length-Inhomogeneous Active Fibers

    I. O. Zolotovskii


    Full Text Available The possibility of an effective gain of the self-similar frequency-modulated (FM wave packets is studied in the length-inhomogeneous active fibers. The dynamics of parabolic pulses with the constant chirp has been considered. The optimal profile for the change of the group-velocity dispersion corresponding to the optimal similariton pulse amplification has been obtained. It is shown that the use of FM pulses in the active (gain and length-inhomogeneous optical fibers with the normal group-velocity dispersion can provide subpicosecond optical pulse amplification up to the energies higher than 1 nJ.

  17. Extending the high-order harmonic generation cutoff by means of self-phase-modulated chirped pulses

    Neyra, E.; Videla, F.; Pérez-Hernández, J. A.; Ciappina, M. F.; Roso, L.; Torchia, G. A.


    In this letter we propose a complementary approach to extend the cutoff in high-order harmonic generation (HHG) spectra beyond the well established limits. Inspired by techniques normally used in the compression of ultrashort pulses and supercontinuum generation, we show this extension can be achieved by means of a nonlinear phenomenon known as self-phase-modulation (SPM). We demonstrated that relatively long optical pulses, around 100 fs full-width half maximum (FWHM), non linearly chirped by SPM, are able to produce a considerable extension in the HHG cutoff. We have also shown it is possible control this extension by setting the length of the nonlinear medium. Our study was supported by the numerical integration of the time-dependent Schrödinger equation joint with a complete classical analysis of the electron dynamic. Our approach can be considered as an alternative to the utilization of optical parametric amplification (OPA) and it can be easily implemented in usual facilities with femtosecond laser systems. This technique also preserves the harmonic yield in the zone of the plateau delimited by I p   +  3.17Up law, even when the driven pulses contain larger wavelength components.

  18. Modulated heat pulse propagation and partial transport barriers in chaotic magnetic fields

    del-Castillo-Negrete, D


    Direct numerical simulations of the time dependent parallel heat transport equation modeling heat pulses driven by power modulation in 3-dimensional chaotic magnetic fields are presented. The numerical method is based on the Fourier formulation of a Lagrangian-Green's function method that provides an accurate and efficient technique for the solution of the parallel heat transport equation in the presence of harmonic power modulation. The numerical results presented provide conclusive evidence that even in the absence of magnetic flux surfaces, chaotic magnetic field configurations with intermediate levels of stochasticity exhibit transport barriers to modulated heat pulse propagation. In particular, high-order islands and remnants of destroyed flux surfaces (Cantori) act as partial barriers that slow down or even stop the propagation of heat waves at places where the magnetic field connection length exhibits a strong gradient. Results on modulated heat pulse propagation in fully stochastic fields and across m...

  19. Shaping the output pulse of a linear-transformer-driver module.

    Long, Finis W.; McKee, G. Randall; Stoltzfus, Brian Scott; Woodworth, Joseph Ray; McKenney, John Lee; Fowler, William E.; Mazarakis, Michael Gerrassimos; Porter, John L.; Stygar, William A.; Savage, Mark Edward; LeChien, Keith, R.; Van De Valde, David M. (EG& G, Albuquerque, NM)


    We demonstrate that a wide variety of current-pulse shapes can be generated using a linear-transformer-driver (LTD) module that drives an internal water-insulated transmission line. The shapes are produced by varying the timing and initial charge voltage of each of the module's cavities. The LTD-driven accelerator architecture outlined in [Phys. Rev. ST Accel. Beams 10, 030401 (2007)] provides additional pulse-shaping flexibility by allowing the modules that drive the accelerator to be triggered at different times. The module output pulses would be combined and symmetrized by water-insulated radial-transmission-line impedance transformers [Phys. Rev. ST Accel. Beams 11, 030401 (2008)].

  20. Acousto-optic modulation by pulsed optical excitation: implications to imaging in turbid media.

    Paul, Joseph S; Sen, Deep; Dokos, Socrates


    We show that the transient response of acoustically modulated optical flux in a turbid medium irradiated by a pulsed point source of light is delayed in time relative to the light-alone flux obtained in the absence of acoustic modulation. The time delay is shown to result from an initial phase of flux reversal, as determined by the time point of the input pulse onset with reference to the ultrasound cycle. Both the time delay and amplitude of modulation are shown to be dependent on the effective attenuation coefficient of the medium. Application of a periodic train of excitation pulses spaced at equal intervals at, or in multiples of, the ultrasound period enables a time-locked detection of the modulated light, without the deleterious effects caused by speckle artifacts.

  1. Photonic Crystal Fano Laser: Terahertz Modulation and Ultrashort Pulse Generation

    Mørk, Jesper; Chen, Yaohui; Heuck, Mikkel


    We suggest and analyze a laser with a mirror realized by Fano interference between a waveguide and a nanocavity. For small-amplitude modulation of the nanocavity resonance, the laser can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers....

  2. Effects of continuous-wave, pulsed, and sinusoidal-amplitude-modulated microwaves on brain energy metabolism.

    Sanders, A P; Joines, W T; Allis, J W


    A comparison of the effects of continuous-wave, sinusoidal-amplitude-modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague-Dawley rats (175-225 g). Brain NADH fluorescence, adenosine triphosphate (ATP) concentration, and creatine phosphate (CP) concentration were determined as a function of modulation frequency. Brain temperatures of animals were maintained between -0.1 and -0.4 degrees C from the preexposure temperature when subjected to as much as 20 mW/cm2 (average power) CW, pulsed, or sinusoidal-amplitude modulated 591-MHz radiation for 5 min. Sinusoidal-amplitude-modulated exposures at 16-24 Hz showed a trend toward preferential modulation frequency response in inducing an increase in brain NADH fluorescence. The pulse-modulated and sinusoidal-amplitude-modulated (16 Hz) microwaves were not significantly different from CW exposures in inducing increased brain NADH fluorescence and decreased ATP and CP concentrations. When the pulse-modulation frequency was decreased from 500 to 250 pulses per second the average incident power density threshold for inducing an increase in brain NADH fluorescence increased by a factor of 4--ie, from about 0.45 to about 1.85 mW/cm2. Since brain temperature did not increase, the microwave-induced increase in brain NADH and decrease in ATP and CP concentrations was not due to hyperthermia. This suggests a direct interaction mechanism and is consistent with the hypothesis of microwave inhibition of mitochondrial electron transport chain function of ATP production.

  3. Nanosecond electric pulses modulate skeletal muscle calcium dynamics and contraction

    Valdez, Chris; Jirjis, Michael B.; Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.


    Irreversible electroporation therapy is utilized to remove cancerous tissues thru the delivery of rapid (250Hz) and high voltage (V) (1,500V/cm) electric pulses across microsecond durations. Clinical research demonstrated that bipolar (BP) high voltage microsecond pulses opposed to monophasic waveforms relieve muscle contraction during electroporation treatment. Our group along with others discovered that nanosecond electric pulses (nsEP) can activate second messenger cascades, induce cytoskeletal rearrangement, and depending on the nsEP duration and frequency, initiate apoptotic pathways. Of high interest across in vivo and in vitro applications, is how nsEP affects muscle physiology, and if nuances exist in comparison to longer duration electroporation applications. To this end, we exposed mature skeletal muscle cells to monopolar (MP) and BP nsEP stimulation across a wide range of electric field amplitudes (1-20 kV/cm). From live confocal microscopy, we simultaneously monitored intracellular calcium dynamics along with nsEP-induced muscle movement on a single cell level. In addition, we also evaluated membrane permeability with Yo-PRO-1 and Propidium Iodide (PI) across various nsEP parameters. The results from our findings suggest that skeletal muscle calcium dynamics, and nsEP-induced contraction exhibit exclusive responses to both MP and BP nsEP exposure. Overall the results suggest in vivo nsEP application may elicit unique physiology and field applications compared to longer pulse duration electroporation.

  4. Effect of Negative Pulse Width on Compactness of Plasma Electrolytic Oxidation Coatings on Mg-Gd-Y Alloy%负向脉宽对Mg-Gd-Y合金微弧氧化膜致密性的影响

    郭泉忠; 杜克勤; 朱秀荣; 王荣; 徐永东; 王福会


    通过在特定的电参数下改变负向脉宽,在Mg-Gd-Y合金表面制备了不同的微弧氧化膜.利用扫描电镜和电化学方法研究氧化膜的显微组织和电化学行为.结果表明:负向脉宽对于微弧氧化膜的致密性具有重要影响,适当的负向脉宽可以有效地提高膜层致密性,而稍低或者过高的负向脉宽都会降低氧化膜的致密性,从而降低涂层的耐腐蚀性.%The effect of negative pulse width of asymmetric bipolar pulse on the compactness of plasma electrolytic oxidation (PEO) coating on Mg-Gd-Y alloy is not yet revealed nowadays. Here, PEO coatings on Mg-Gd-Y alloy were prepared by means of bipolar pulse whose negative pulse width was changed within a desired range. The microstructure and corrosion performance of the coatings were examined by scanning electron microscope (SEM) and electrochemical measure ments respectively. The results show that negative pulse width plays an important role on compact ness of PEO coatings; and with negative pulse width within a suitable range the compactness of coatings can be surely enhanced, as a sequence, the corrosion resistance of the coatings is evidently increased.

  5. Spectral Phase Modulation and chirped pulse amplification in High Gain Harmonic Generation

    Wu, Zilu; Krinsky, Sam; Loos, Henrik; Murphy, James; Shaftan, Timur; Sheehy, Brian; Shen, Yuzhen; Wang, Xijie; Yu Li Hua


    High Gain Harmonic Generation (HGHG), because it produces longitudinally coherent pulses derived from a coherent seed, presents remarkable possibilities for manipulating FEL pulses. If spectral phase modulation imposed on the seed modulates the spectral phase of the HGHG in a deterministic fashion, then chirped pulse amplification, pulse shaping, and coherent control experiments at short wavelengths become possible. In addition, the details of the transfer function will likely depend on electron beam and radiator dynamics and so prove to be a useful tool for studying these. Using the DUVFEL at the National Synchrotron Light Source at Brookhaven National Laboratory, we present spectral phase analyses of both coherent HGHG and incoherent SASE ultraviolet FEL radiation, applying Spectral Interferometry for Direct Electric Field Reconstruction (SPIDER), and assess the potential for employing compression and shaping techniques.

  6. Tandem electroabsorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short pulse generation

    Zhao, Q.; Pan, J. Q.; Zhang, J.; Zhou, G. T.; Wu, J.; Wang, L. F.; Wang, W.


    A novel device of tandem MQW EAMs monolithically integrated with a DFB laser is fabricated by an ultra-low-pressure (22 mbar) selective area growth MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio when coupled to a single mode fibre. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10 GHz repetition rate pulse with an actual width of 13.7 ps without any compression elements is obtained.

  7. A Pulse Power Modulator System for Commercial High Power Ion Beam Surface Treatment Applications

    Barrett, D.M.; Cockreham, B.D.; Dragt, A.J.; Ives, H.C.; Neau, E.L.; Reed, K.W.; White, F.E.


    The Ion Beam Surface Treatment (lBESTrM) process utilizes high energy pulsed ion beams to deposit energy onto the surface of a material allowing near instantaneous melting of the surface layer. The melted layer typically re-solidifies at a very rapid rate which forms a homogeneous, fine- grained structure on the surface of the material resulting in significantly improved surface characteristics. In order to commercialize the IBESTTM process, a reliable and easy-to-operate modulator system has been developed. The QM-I modulator is a thyratron-switched five-stage magnetic pulse compression network which drives a two-stage linear induction adder. The adder provides 400 kV, 150 ns FWHM pulses at a maximum repetition rate of 10 pps for the acceleration of the ion beam. Special emphasis has been placed upon developing the modulator system to be consistent with long-life commercial service.

  8. Detecting Fleeting MRI Signals with Frequency-Modulated Pulses

    Kobayashi, Naoharu; Idiyatullin, Djaudat; Corum, Curtis; Moeller, Steen; Chamberlain, Ryan; O'Connell, Robert; Nixdorf, Donald R.; Garwood, Michael


    We describe a fundamentally different approach to MRI referred to as SWIFT (sweep imaging with Fourier transformation). SWIFT exploits time-shared RF excitation and signal acquisition, allowing capture of signal from spins with extremely short transverse relaxation time, T2*. The MR signal is acquired in gaps inserted into a broadband frequency-swept excitation pulse, which results in acquisition delays of only 1 – 2 microseconds. In SWIFT, 3D k-space is sampled in a radial manner, whereby one projection of the object is acquired in the gaps of each frequency-swept pulse, allowing a repetition time (TR) on the order of the pulse length (typically 1 – 3 milliseconds). Since the orientation of consecutive projections varies in a smooth manner (i.e., only small increments in the values of the x, y, z gradients occur from view to view), SWIFT scanning is close to inaudible and is insensitive to gradient timing errors and eddy currents. SWIFT images can be acquired in scan times similar to and sometimes faster than conventional 3D gradient echo techniques. With its ability to capture signals from ultrashort T2* spins, SWIFT promises to expand the role of MRI in areas of research where MRI previously played no or negligible role. In this article, we show wood and tooth images obtained with SWIFT as examples of materials with ultrashort T2*. Early experience suggests SWIFT can play a role in materials science and porous media research. PMID:22661791

  9. Health Related Quality of Life after ECT for depression: A study exploring the role of different electrode-placements and pulse-widths.

    Gálvez, Verònica; Li, Adrienne; Oxley, Cristal; Waite, Susan; De Felice, Nick; Hadzi-Pavlovic, Dusan; Kumar, Divya; Page, Andrew C; Hooke, Geoff; Loo, Colleen K


    Prior research has shown large improvements in HRQOL after a course of ECT for depression. However, the effect of different types of ECT on HRQOL outcomes has not been explored. This is important due to the considerable range of ECT treatment modalities that currently exist in clinical practice. HRQOL data from 355 depressed patients in three Australian clinical hospitals, who received ECT given with a range of treatment modalities (combinations of pulse-width and electrode-placement), were analysed. HRQOL was measured at baseline and after ECT, using the Quality of Life Enjoyment and Satisfaction Questionnaire-Short Form (Q-LES-Q-SF). The association between type of ECT and HRQOL after ECT was examined by regression analysis, controlling for variables that may affect HRQOL outcomes. There was a significant increase in HRQOL scores after ECT (p.0001; t=-23.4). The magnitude of change was large (54% increase, Cohen's d=1.43). Multiple regression analysis yielded a significant model (P.001, R(2)=0.18). Baseline HRQOL score (t=4.83; p.0001), age (t=2.75, p.01) and type of ECT received [Right Unilateral brief vs Bitemporal Ultrabrief (t=-2.99; p.01) and Right Unilateral brief vs Bifrontal Ultrabrief (t=-2.70; p.01)] were significant predictors of HRQOL after the ECT course. Data was collected naturalistically from clinical services, thus ECT modality was not randomly assigned. Site could have confounded results. An acute course of ECT for depression produced statistically and clinically significant improvements in HRQOL. ECT treatment modality can substantially impact HRQOL outcomes, with the possibility of bilateral ultrabrief forms of ECT being less beneficial. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Optical 40 GHz pulse source module based on a monolithically integrated mode locked DBR laser

    Huettl, B.; Kaiser, R.; Kroh, M.; Schubert, C.; Jacumeit, G.; Heidrich, H.


    In this paper the performance characteristics of compact optical 40 GHz pulse laser modules consisting of a monolithic mode-locked MQW DBR laser on GaInAsP/InP are reported. The monolithic devices were fabricated as tunable multi-section buried heterostructure lasers. A DBR grating is integrated at the output port of an extended cavity in order to meet the standardized ITU wavelength channels allocated in the spectral window around 1.55 μm in optical high speed communication networks. The fabricated 40 GHz lasers modules not only emit short optical pulses (< 1.5 ps) with very low amplitude noise (<1.5 %) and phase noise levels (timing jitter: 50 fs) but also enable good pulse-to-pulse phase and long-term stability. A wavelength tuning range of 6 nm is possible and large locking bandwidths between 100 ... 260 MHz are observed. All data have been achieved by operating the lasers in a hybrid mode-locking scheme with a required minimum micro-wave power of only 12 dBm for pulse synchronization. Details on laser chip architecture and module performance are summarized and the results of a stable and error free module performance in first 160 Gb/s (4 x 40 Gb/s OTDM) RZ-DPSK transmission experiments are presented.

  11. Self-phase modulation of a single-cycle THz pulse

    Hoffmann M. C.


    Full Text Available We demonstrate self-phase modulation (SPM of a single-cycle THz pulse in a semiconductor, using bulk n-GaAs as a model system. The SPM arises from the heating of free electrons in the electric field of the THz pulse. Electron heating leads to an ultrafast reduction of the plasma frequency, which results in a strong modification of the THz-range dielectric function of the material. THz SPM is observed directly in the time domain as a characteristic reshaping of single-cycle THz pulse. In the frequency domain, it corresponds to a strong frequency-dependent refractive index nonlinearity of n-GaAs, which is found to be both positive and negative within the broad spectrum of the THz pulse. The spectral position of zero nonlinearity is defined by the electron momentum relaxation rate. Nonlinear spectral broadening and compression of the single-cycle THz pulse was also observed.

  12. Hybrid Design Optimization of High Voltage Pulse Transformers for Klystron Modulators

    Sylvain, Candolfi; Davide, Aguglia; Jerome, Cros


    This paper presents a hybrid optimization methodology for the design of high voltage pulse transformers used in klystron modulators. The optimization process is using simplified 2D FEA design models of the 3D transformer structure. Each intermediate optimal solution is evaluated by 3D FEA and correction coefficients of the 2D FEA models are derived. A new optimization process using 2D FEA models is then performed. The convergence of this hybrid optimal design methodology is obtained with a limited number of time consuming 3D FEA simulations. The method is applied to the optimal design of a monolithic high voltage pulse transformer for the CLIC klystron modulator.

  13. 用一般脉宽调制器构造的变频式脉宽调制器%A Variable Frequency Type of Pulse Width Modulator Constructed of Using General Pulse Width Modulator

    孙定浩; 赵长春





    (v¿e?); a state feedback block A with compensation; a reference shaping block $i(R) to modify the pulsed reference $i(v¿r?) for optimized error estimation; a difference block to generate an error signal and a compensator $i(C) to shape this error. The invention makes it possible to implement practical digital...

  15. Pulse modulators for the VEPP-5 injection complex klystron power supply

    Akimov, A V; Bak, P A; Kot, N H; Yudin, V D


    In the complex VEPP-5 preinjector the klystrons are supplied by the modulators with a pulse power of 150 MW,a voltage of 47.5 kV, a primary current of 6.3 kA and a pulse duration of 3.5 mu s. During the long time operation some disadvantages in the design have been revealed and proper improvements were made. The modulator design with the taking into account all the resent changes is described and test results are presented. At present,three modulators are supplying three klystrons 5045 (production of SLAC Lab.,USA) and the forth modulator is tested with a dummy load in the nominal mode of operation.

  16. A scheme of pulse compression lidar with enhanced modulated bandwidth for detection through scattering media

    Yang, Cheng-hua; Zhang, Yong; Jin, Chen-fei; Xu, Lu; Yang, Xu; Wang, Qiang; Liu, Yue-hao; Zhao, Yuan


    This paper presents a scheme of pulse compression lidar with enhanced electrical modulated bandwidth. An ultra-wideband linear frequency modulated signal with a bandwidth of 50 GHz is generated using femtosecond laser and superimposed linear chirp fiber Bragg gratings in the transmitter, which separates the echo of the target from the backward scattered noise with low modulated frequency. An optical pulse compression system based on a negative dispersion fiber Bragg grating is used to compress the ultra-wideband linear frequency modulated signal in the receiver. SNR and range resolution of the proposed scheme are numerically simulated to prove its feasibility. The simulation results indicate that an enhancement of SNR by 15.8 dB can be achieved using the scheme, and the range resolution of the scheme increases from 0.68 m to 0.0027 m. It is therefore concluded that the proposed scheme is suitable for detection through scattering media.

  17. Transformation of the frequency-modulated continuous-wave field into a train of short pulses by resonant filters

    Shakhmuratov, R N


    The resonant filtering method transforming frequency modulated radiation field into a train of short pulses is proposed to apply in optical domain. Effective frequency modulation can be achieved by electro-optic modulator or by resonant frequency modulation of the filter with a narrow absorption line. Due to frequency modulation narrow-spectrum CW radiation field is seen by the resonant filter as a comb of equidistant spectral components separated by the modulation frequency. Tuning narrow-bandwidth filter in resonance with $n$-th spectral component of the comb transforms the radiation field into bunches of pulses with $n$ pulses in each bunch. The transformation is explained by the interference of the coherently scattered resonant component of the field with the whole comb. Constructive interference results in formation of pulses, while destructive interference is seen as dark windows between pulses. It is found that the optimal thickness of the resonant filter is several orders of magnitude smaller than the...

  18. Numerical Simulation of Ultrafast Laser Pulse Propagation in Tenuous Plasmas:Envelope Evolving and Modulation

    WANG Hong-Yu; XIE Bai-Song


    We propose an effective and useful numerical simulation scheme for the investigation of the ultra-fast laser pulses in tenuous plasmas. The accuracy of the method is tested by numerical examples. We check some special examples to investigate the laser envelope evolving and modulation in plasmas. Asymmetric two-peak modulation structure is found and its underlying physics is analyzed. The advantages and shortages of the method are also discussed.

  19. Characterization of pulse amplitude and pulse rate modulation for a human vestibular implant during acute electrical stimulation

    Nguyen, T. A. K.; DiGiovanna, J.; Cavuscens, S.; Ranieri, M.; Guinand, N.; van de Berg, R.; Carpaneto, J.; Kingma, H.; Guyot, J.-P.; Micera, S.; Perez Fornos, A.


    Objective. The vestibular system provides essential information about balance and spatial orientation via the brain to other sensory and motor systems. Bilateral vestibular loss significantly reduces quality of life, but vestibular implants (VIs) have demonstrated potential to restore lost function. However, optimal electrical stimulation strategies have not yet been identified in patients. In this study, we compared the two most common strategies, pulse amplitude modulation (PAM) and pulse rate modulation (PRM), in patients. Approach. Four subjects with a modified cochlear implant including electrodes targeting the peripheral vestibular nerve branches were tested. Charge-equivalent PAM and PRM were applied after adaptation to baseline stimulation. Vestibulo-ocular reflex eye movement responses were recorded to evaluate stimulation efficacy during acute clinical testing sessions. Main results. PAM evoked larger amplitude eye movement responses than PRM. Eye movement response axes for lateral canal stimulation were marginally better aligned with PRM than with PAM. A neural network model was developed for the tested stimulation strategies to provide insights on possible neural mechanisms. This model suggested that PAM would consistently cause a larger ensemble firing rate of neurons and thus larger responses than PRM. Significance. Due to the larger magnitude of eye movement responses, our findings strongly suggest PAM as the preferred strategy for initial VI modulation.

  20. Information Width

    Ratsaby, Joel


    Kolmogorov argued that the concept of information exists also in problems with no underlying stochastic model (as Shannon's information representation) for instance, the information contained in an algorithm or in the genome. He introduced a combinatorial notion of entropy and information $I(x:\\sy)$ conveyed by a binary string $x$ about the unknown value of a variable $\\sy$. The current paper poses the following questions: what is the relationship between the information conveyed by $x$ about $\\sy$ to the description complexity of $x$ ? is there a notion of cost of information ? are there limits on how efficient $x$ conveys information ? To answer these questions Kolmogorov's definition is extended and a new concept termed {\\em information width} which is similar to $n$-widths in approximation theory is introduced. Information of any input source, e.g., sample-based, general side-information or a hybrid of both can be evaluated by a single common formula. An application to the space of binary functions is con...



    A digital switching power amplifier with Multivariable Enhanced Cascade Controlled (MECC) includes a modulator, a switching power stage and a low pass filter. In the first preferred embodiment an enhanced cascade control structure local to the switching power stage is added, characterised by havi...... and feedback path A to determine stable self-oscillating conditions. An implemented 250W example MECC digital power amplifier has proven superior performance in terms of audio performance (0.005 % distortion, 115 dB dynamic range) and efficiency (92 %).......A digital switching power amplifier with Multivariable Enhanced Cascade Controlled (MECC) includes a modulator, a switching power stage and a low pass filter. In the first preferred embodiment an enhanced cascade control structure local to the switching power stage is added, characterised by having...

  2. Analysis and Simulation of Minor Hysteresis Characteristic for Ferromagnetic Material Under Pulsed Current Excitation Considering Frequency and Pulsed Width%计及频率和脉宽脉冲电流激励下铁磁材料局部磁滞特性的分析与模拟



    Excitation frequency and pulsed width were two important factors in the study of the minor hysteresis characteristics of ferromagnetic materials under pulsed current excitation. With pulsed current peak remaining unchanged, different minor hysteresis curves were obtained through changing frequency and pulsed width. The higher frequency is and the narrower pulsed width is, the more pulsed numbers of excitation current were needed to stabilize minor hysteresis curves. This phenomenon was caused by the magnetic aftereffect of magnetic flux density. To describe the impact of frequency and pulsed width on the minor hysteresis characteristics, the curve fitting method was used to establish mathematic relation between fitting functions of different minor hysteresis curves according to the change law of frequency, pulsed width and the magnetic flux density turning points values. Compared with experimental results, in a certain range, the simulation results prove that the mathematic expression can effectively reflect the influence law of frequency and pulsed width, and accurately simulate the minor hysteresis characteristics of ferromagnetic material when frequency and pulsed width of pulsed current are varied.%激励频率和脉宽是研究脉冲电流激励下铁磁材料局部磁滞特性的两个重要因素。脉冲电流峰值保持不变,改变频率和脉宽,得到不同的局部磁滞曲线。由于磁通密度具有磁后效应,频率越高,脉宽越小,磁后效应越明显,局部磁滞曲线达到稳定所需要的激励电流脉冲数越多。为描述频率和脉宽对铁磁材料局部磁滞特性的影响,根据频率、脉宽和转折点磁通密度值的变化规律,采用曲线拟合的方法建立不同局部磁滞曲线拟合函数间的数学关系。模拟结果和实验结果表明,在一定范围内,拟合的数学式能够有效地反映频率和脉宽的影响规律,较准确地模拟频率和脉宽不同的脉冲电流激

  3. On the trade-off between mainlobe width and peak sidelobe level of mismatched pulse compression filters for linear chirp waveforms

    Cilliers, Jacques E


    Full Text Available In previous paper the authors introduced a technique for generating mismatched pulse compression filters for linear frequency chirp signals. The technique minimizes the sum of the pulse compression sidelobes in an Lp norm sense. It was shown...

  4. Design of a CMOS Pulse Width Modulator%一种CMOS脉宽调制器的设计

    肖坤光; 苏玲



  5. Quality Assessment of Soft-Switching Based Single-phase Pulse Width Modulated Voltage Source Inverter (PWM VSI

    Z.A. Jaffery


    Full Text Available The authors present the design, simulation and analysis of a single phase voltage source inverter using soft switching techniques. The performance of the inverter has been compared in terms of harmonic contents present in output voltage and current. The research works for a PWM inverter along with a LLCC filter has been investigated. This paper also investigated the performance of the same inverter with a feedback controller with a closed loop feedback path to maintain rated output voltage. This work is helpful for the inverter used in application where high quality ac wave is prime requirement

  6. A Pulse Width Modulation Scheme With Zero-sequence Voltage Injection for Single Phase Three-level NPC Rectifiers


    A single phase three-level converter (shown in Fig. 1) has been widely applied in high-speed railway electrical traction drive systems. But the main technical drawback of the three-level converter is DC-link neutral point voltage drift. In order to solve this problem, it is important to understand the cause of DC-link neutral point voltage drift.

  7. Energy Efficiency of Induction Motors Running Off Frequency Converters with Pulse-Width Voltage Modulation{sup 1}

    Shvetsov, N. K., E-mail: [V. I. Lenin Ivanovo State Power University (Russian Federation)


    The results of calculations of the increase in losses in an induction motor with frequency control and different forms of the supply voltage are presented. The calculations were performed by an analytic method based on harmonic analysis of the supply voltage as well as numerical calculation of the electromagnetic processes by the finite-element method.

  8. Investigation on a Novel Discontinuous Pulse-Width Modulation Algorithm for Single-phase Voltage Source Rectifier

    Qu, Hao; Yang, Xijun; Guo, Yougui


    -sequence component injection, in order to reduce power loss and increased overall efficiency. And then by reconstructing the other two phase input voltages and currents, the transformation from stationary frame (abc) to rotating frame (dq frame) is designed. Finally, a PI regulator based controller for single......Single-phase voltage source converter (VSC) is an important power electronic converter (PEC), including single-phase voltage source inverter (VSI), single-phase voltage source rectifier (VSR), single-phase active power filter (APF) and single-phase grid-connection inverter (GCI). Single-phase VSC...

  9. Clipper circuit of pulse modulator used for klystron-5045 power supply

    Akimov, A V


    While the operation of modulator to the pulsed transformer of klystron-5045, current through the primary winding of the pulse transformer (PT) continues to flow even upon the end of the klystron voltage operating pulse. This is determined by an energy stored in magnetizing inductance. The prolongation of magnetizing current passing process simultaneously with the premature choking of thyratron can cause high voltage of inverse polarity at the klystron, which cause the destruction of the cathode. We have considered the possibility of shortening time of magnetizing current passage for the charge of reasonable choice of clipper circuit parameters. The behavior of clipper circuit was studied in modulators used for the VEPP-5 (BINP, Russia) preinjector klystron power supply. The optimum operation run of the circuit was selected and its design features are described.

  10. Adaptive Light Modulation for Improved Resolution and Efficiency in All-Optical Pulse-Echo Ultrasound.

    Alles, Erwin J; Colchester, Richard J; Desjardins, Adrien E


    In biomedical all-optical pulse-echo ultrasound systems, ultrasound is generated with the photoacoustic effect by illuminating an optically absorbing structure with a temporally modulated light source. Nanosecond range laser pulses are typically used, which can yield bandwidths exceeding 100 MHz. However, acoustical attenuation within tissue or nonuniformities in the detector or source power spectra result in energy loss at the affected frequencies and in a reduced overall system efficiency. In this work, a laser diode is used to generate linear and nonlinear chirp optical modulations that are extended to microsecond time scales, with bandwidths constrained to the system sensitivity. Compared to those obtained using a 2-ns pulsed laser, pulse-echo images of a phantom obtained using linear chirp excitation exhibit similar axial resolution (99 versus 92 μm, respectively) and signal-to-noise ratios (SNRs) (10.3 versus 9.6 dB). In addition, the axial point spread function (PSF) exhibits lower sidelobe levels in the case of chirp modulation. Using nonlinear (time-stretched) chirp excitations, where the nonlinearity is computed from measurements of the spectral sensitivity of the system, the power spectrum of the imaging system was flattened and its bandwidth broadened. Consequently, the PSF has a narrower axial extent and still lower sidelobe levels. Pulse-echo images acquired with time-stretched chirps as optical modulation have higher axial resolution (64 μm) than those obtained with linear chirps, at the expense of a lower SNR (6.8 dB). Using a linear or time-stretched chirp, the conversion efficiency from optical power to acoustical pressure improved by a factor of 70 or 61, respectively, compared to that obtained with pulsed excitation.

  11. Switching of 800 nm femtosecond laser pulses using a compact PMN-PT modulator.

    Adany, Peter; Price, E Shane; Johnson, Carey K; Zhang, Run; Hui, Rongqing


    A voltage-controlled birefringent cell based on ceramic PMN-PT material is used to enable fast intensity modulation of femtosecond laser pulses in the 800 nm wavelength window. The birefringent cell based on a PMN-PT compound has comparatively high electro-optic response, allowing for a short interaction length of 3 mm and thus very small size, low attenuation of 0.16 dB, and negligible broadening for 100 fs optical pulses. As an application example, agile wavelength tuning of optical pulses is demonstrated using the soliton self-frequency shift in a photonic crystal fiber. By dynamically controlling the optical power into the fiber, this system switches the wavelength of 100 fs pulses from 900 nm to beyond 1120 nm with less than 5 micros time. In addition, a feedback system stabilizes the wavelength drift against external conditions resulting in high wavelength stability.

  12. Operation Mode on Pulse Modulation in Atmospheric Radio Frequency Glow Discharges

    Zhang, Jie; Guo, Ying; Huang, Xiaojiang; Zhang, Jing; Shi, Jianjun


    The discharge operation regime of pulse modulated atmospheric radio frequency (RF) glow discharge in helium is investigated on the duty cycle and frequency of modulation pulses. The characteristics of radio frequency discharge burst in terms of breakdown voltage, alpha(α)-gamma(γ) mode transition voltage and current are demonstrated by the discharge current voltage characteristics. The minimum breakdown voltage of RF discharge burst was obtained at the duty cycle of 20% and frequency of 400 kHz, respectively. The α-γ mode transition of RF discharge burst occurs at higher voltage and current by reducing the duty cycle and elevating the modulation frequency before the RF discharge burst evolving into the ignition phase, in which the RF discharge burst can operate stably in the γ mode. It proposes that the intensity and stability of RF discharge burst can be improved by manipulating the duty cycle and modulation frequency in pulse modulated atmospheric RF glow discharge. supported by National Natural Science Foundation of China (Nos. 11475043 and 11375042)

  13. UWB multi-pulse position modulation for high data-rate wireless application

    WANG Ye-qiu; LU Ying-hua; ZHANG Hong-xin; HE Peng-fei; ZHANG Li-kun


    A new ultra-wide band (UWB) modulation scheme called L-ary ultra-wide band time hopping multi-pulse position modulation (UWB-TH-MPPM) is proposed for high data-rate wireless application, which can provide better communication performance. The constant weight code is introduced to construct the MPPM signal and the comparison between MPPM and single pulse position modulation (SPPM) is done in three aspects, namely, power efficiency, bandwidth efficiency, and probability of symbol error, respectively. The theoretical analysis and the numerical results show that when the constant weight code is appropriately chosen, MPPM can achieve lower probability of symbol error and higher power efficiency than SPPM at the cost of more bandwidth under the same condition.The proposed MPPM can be a good candidate in UWB system design.

  14. 基于喷油脉宽测试法的汽车油耗智能测试技术%Automobile fuel consumption intelligent testing technology based on fuel injection pulse-width test method

    付百学; 胡胜海


    injections is detected by the single-chip microcomputer, the fuel injection pulse width is obtained, and the relationship between the quality of engine fuel consumption and the injection pulse width is determined. According to EFI controller principles, we determined the testing method for automobile fuel consumption. Based on fuel consumption testing principles, we built a mathematical model of an automobile fuel-consumption testing system, and corrected the mathematical model in standard conditions. According to the function requirements of the fuel-consumption testing system, we determined the single chip microcomputer model and modules function of automobile fuel consumption test controlling system, and designed the injection pulse signal acquisition system and the main program for the automobile fuel-consumption test system. We structured the trial system on a testing prototype using the automotive fuel consumption prototype and the automotive dynamometer test bench. Through analyzing and processing the trial data, the testing precision of the automobile fuel consumption prototype is up to 0.46%. Engine speed has an important impact on injector characteristics parameters, and it will influence automobile fuel consumption testing accuracy. Injector characteristics parameters under different engine speed conditions were amended using a linear regression method that will further improve automobile fuel-consumption testing accuracy. The research will provide the reference to develop high-precision, intelligent automobile fuel-consumption test equipment.%针对汽车油耗测试存在的问题,采用单片机控制技术,通过直接测试喷油器喷油脉宽测试汽车油耗,研制汽车油耗智能测试仪器。根据汽车发动机喷油器喷油控制原理,确定汽车油耗测试方法。基于油耗测试原理构建汽车油耗测试系统的数学计算模型,并在标准状态下对该数学模型进行修正。根据油耗测试系统的功能要求


    刘永平; 许贵桥


    This paper concerns the problem of the Kolmogorov n-width, the linear n-width, the Gel'fand n-width and the Bernstein n-width of Sobolev classes of the periodicmultivariate functions in the space Lp(Td) and the average Bernstein σ-width, averageKolmogorov σ-widths, the average linear σ-widths of Sobolev classes of the multivariatequantities.

  16. Higher-order modulations of fs laser pulses for GHz frequency domain photon migration system.

    Lin, Huang-Yi; Cheng, Nanyu; Tseng, Sheng-Hao; Chan, Ming-Che


    Except the fundamental modulation frequency, by higher-order-harmonic modulations of mode-locked laser pulses and a simple frequency demodulation circuit, a novel approach to GHz frequency-domain-photon-migration (FDPM) system was reported. With this novel approach, a wide-band modulation frequency comb is available without any external modulation devices and the only electronics to extract the optical attenuation and phase properties at a selected modulation frequency in FDPM systems are good mixers and lock-in devices. This approach greatly expands the frequency range that could be achieved by conventional FDPM systems and suggests that our system could extract much more information from biological tissues than the conventional FDPM systems. Moreover, this demonstration will be beneficial for discerning the minute change of tissue properties.

  17. High efficiency WCDMA power amplifier with Pulsed Load Modulation (PLM) technique

    Liao, Shu-Hsien

    In wireless communication, high data rate complex modulation is used for spectral efficiency. However, power efficiency of power amplifier degrades when complex modulation is applied. Therefore, efficiency enhancement is necessary to maintain the performance. However, conventional efficiency enhancement schemes are nonlinear and performance improvement can only be optimized over a small range of power level. In order to preserve linearity and power efficiency, we propose a new digital power amplification technique "Pulsed Load Modulation (PLM)" for high efficiency and linear amplification. The PLM technique realizes load impedance modulation in digital fashion which is insensitive to device nonlinearity. Furthermore, the optimum power efficiency can be maintained over a wide range of output power. In this work, a PLM power amplifier module has been fabricated and to demonstrate the ability of PLM to provide high efficiency and linear amplification.

  18. SU-E-T-534: Dosimetric Effect of Multileaf Collimator Leaf Width On Volumetric Modulated Arc Stereotactic Radiotherapy for Spine Tumors

    Amoush, A; Djemil, T [Cleveland Clinic Foundation, Cleveland, OH (United States); Subedi, L [Cleveland State University, Cleveland, Ohio (United States); Huang, L [Huntsman Cancer Hospital, Salt Lake City, UT (United States); Xia, P [Cleveland Clinic, Cleveland, OH (United States)


    Purpose: To study the dosimetric impact of MLC leaf width in patients treated with Volumetric Modulated Arc Therapy (VMAT) for spine Stereotactic Body radiation Therapy (SBRT). Methods: Twelve spine SBRT patients were retrospectively selected for this study. The patients were treated with IMRT following the RTOG-0631 of spine metastasis. The prescription dose was 16 Gy in one fraction to 90% of the target volume (V16 > 90%). The maximum spinal cord dose of 14 Gy and 10% of the cord receiving < 10 Gy (V10) were set as dose constraints. For purpose of this study, three dual arc VMAT plans were created for each patient using three different MLC leaf widths: 2.5 mm, 4mm, and 5mm. The compliance to RTOG 0631, conformal index (CI), dose gradient index (DGI), and number of monitor units (MUs) were compared. Results: The average V16 of the target was 91.91±1.36%, 93.73±2.38%, and 92.25±2.49% for 2.5 mm, 4 mm, and 5 mm leaf widths, respectively (p=0.39). Accordingly, the average CI was 1.36±0.39, 1.36±0.34, and 1.41±0.3 (0.96), respectively. The average DGI was 0.24 ± 0.05, 0.22 ± 0.05, and 0.23 ± 0.04, respectively (p=0.86). The average spinal cord maximum dose was 12.10 ± 0.88 Gy, 12.52 ± 1.15 Gy, and 12.05 ± 1.12 (p=0.75) and V10 was 2.69 ± 1.71 cc, 5.43 ± 2.16 cc, and 3.71 ± 2.34 cc (p=0.15) for 2.5 mm, 4 mm, and 5 mm leaf widths, respectively. According, the average number of MUs was 4255 ± 431 MU, 5049 ± 1036 MU, and 4231 ± 580 MU respectively (p=0.17). Conclusion: The use of 2.5 mm, 4 mm, and 5 mm MLCs achieved similar VMAT plan quality as recommended by RTOG-0631. The dosimetric parameters were also comparable for the three MLCs.

  19. Short optical pulse generated by integrated MQW DBR laser/EA-modulator

    Chen, Young-Kai; Tanbun-Ek, Tawee; Logan, Ralph A.; Tate, A. R.; Sergent, A. M.; Wecht, K. W.; Sciortino, Paul F., Jr.; Raybon, Gregory; Froberg, Nan M.; Johnson, Anthony M.


    We report on the generation of short optical pulses by utilizing the non-linear absorption characteristics of a multiple quantum well (MQW) electro-absorption modulator, which is monolithically integrated with a MQW wavelength-tunable distributed Bragg reflector (DBR) laser on a single chip. Optical pulses as short as 39 ps and 15 ps have been generated at a repetition rate of 3 GHz and 10 GHz, respectively, with a broad tuning range of 5.4 nm near 1554 nm lasing wavelength.

  20. Single-shot laser pulse reconstruction based on self-phase modulated spectra measurements

    Anashkina, Elena A.; Ginzburg, Vladislav N.; Kochetkov, Anton A.; Yakovlev, Ivan V.; Kim, Arkady V.; Khazanov, Efim A.


    We report a method for ultrashort pulse reconstruction based only on the pulse spectrum and two self-phase modulated (SPM) spectra measured after pulse propagation through thin media with a Kerr nonlinearity. The advantage of this method is that it is a simple and very effective tool for characterization of complex signals. We have developed a new retrieval algorithm that was verified by reconstructing numerically generated fields, such as a complex electric field of double pulses and few-cycle pulses with noises, pedestals and dips down to zero spectral intensity, which is challenging for commonly used techniques. We have also demonstrated a single-shot implementation of the technique for the reconstruction of experimentally obtained pulses. This method can be used for high power laser systems operating in a single-shot mode in the optical, near- and mid-IR spectral ranges. The method is robust, low cost, stable to noise, does not require a priori information, and has no ambiguity related to time direction.

  1. Periodic modulation in pulse arrival times from young pulsars: a renewed case for neutron star precession

    Kerr, Matthew; Johnston, Simon; Shannon, Ryan


    In a search for periodic variation in the arrival times of pulses from 151 young, energetic pulsars, we have identified seven cases of modulation consistent with one or two harmonics of a single fundamental with time-scale 0.5-1.5 yr. We use simulations to show that these modulations are statistically significant and of high quality (sinusoidal) even when contaminated by the strong stochastic timing noise common to young pulsars. Although planetary companions could induce such modulation, the large implied masses and 2:1 mean motion resonances challenge such an explanation. Instead, the modulation is likely to be intrinsic to the pulsar, arising from quasi-periodic switching between stable magnetospheric states, and we propose that precession of the neutron star may regulate this switching.

  2. Multiple-load series resonant inverter for induction cooking application with pulse density modulation



    Multiple-load induction cooking applications are suitable used when multi-output inverters or multi-inverters are needed for multiple-load operation. Some common approaches and modifications are needed in inverter configuration for multiple-load application. This paper presents an inverter configuration with two loads by using pulse density modulation control technique. It allows the output power control of each load independently with constant switching frequency and constant duty ratio. The pulse density modulation control technique is obtained using phase on–off control between two legs of the inverter to reduce acoustic noise. Thetwo-load three-leg inverter configuration provides reduction of the component count for extension of multiple loads. The control technique provides a wide range of output power control. In addition, it can achieve efficient and stable zero voltage switching operation in the whole load range. The proposed control scheme is simulated and experimentally verified with two-load inverter configuration.

  3. Hierarchical classification of dynamically varying radar pulse repetition interval modulation patterns.

    Kauppi, Jukka-Pekka; Martikainen, Kalle; Ruotsalainen, Ulla


    The central purpose of passive signal intercept receivers is to perform automatic categorization of unknown radar signals. Currently, there is an urgent need to develop intelligent classification algorithms for these devices due to emerging complexity of radar waveforms. Especially multifunction radars (MFRs) capable of performing several simultaneous tasks by utilizing complex, dynamically varying scheduled waveforms are a major challenge for automatic pattern classification systems. To assist recognition of complex radar emissions in modern intercept receivers, we have developed a novel method to recognize dynamically varying pulse repetition interval (PRI) modulation patterns emitted by MFRs. We use robust feature extraction and classifier design techniques to assist recognition in unpredictable real-world signal environments. We classify received pulse trains hierarchically which allows unambiguous detection of the subpatterns using a sliding window. Accuracy, robustness and reliability of the technique are demonstrated with extensive simulations using both static and dynamically varying PRI modulation patterns. Copyright © 2010 Elsevier Ltd. All rights reserved.

  4. Novel Active Bouncer Topology for Klystron Modulators based on Pulsed Transformers

    AUTHOR|(CDS)2079689; Aguglia, Davide; Viarouge, Philippe; Cros, Jérôme


    Active droop compensation systems, so called active bouncers, for klystron modulators based on monolithic pulse transformers perform the regulation of the output pulse voltage while simultaneously withstand all the primary current of the modulator. This imposes the utilization of high power semiconductors which can produce high switching losses and degrade the overall system efficiency. In order to overcome this issue, this paper proposes a new active bouncer topology based on the parallel connection of two different power converters: the first one is in charge of handling the majority of the primary current at high efficiency, and the second one is used to fine tune the bouncer voltage via a high bandwidth converter rated at a fraction of the first parallel connected converter. Detailed comparison between a classical active bouncer and two variants of the proposed topology are presented and based on numerical simulations.

  5. All-optical short pulse translation through cross-phase modulation in a VO₂ thin film.

    Fardad, Shima; Das, Susobhan; Salandrino, Alessandro; Breckenfeld, Eric; Kim, Heungsoo; Wu, Judy; Hui, Rongqing


    VO2 is a promising material for reconfigurable photonic devices due to the ultrafast changes in electronic and optical properties associated with its dielectric-to-metal phase transition. Based on a fiber-optic, pump-probe setup at 1550 nm wavelength window, and by varying the pump-pulse duration, we show that the material phase transition is primarily caused by the pump-pulse energy. For the first time, we demonstrate that the instantaneous optical phase modulation of probe during pump leading edge can be utilized to create short optical pulses at probe wavelength, through optical frequency discrimination. This circumvents the impact of long recovery time well known for the phase transition of VO2.

  6. Analisys of alternatives for sidelobe reduction in linearly frequency modulated pulses

    Jorge Torres Gómez


    Full Text Available Taking The present article deals with the topic of windowing techniques for sidelobe reduction inlinearly frequency modulated (LFM pulses compressed by an adapted filter. Main characteristics ofwindow´s techniques are presented; focusing on those that improves the window´s performance. Designsare simulated in a Graphic User Interface in MatLab and Simulink to conform it on FPGA. Simulationof carried out softwares allows the selection of the best choice as the case of interest.

  7. Effect of stochastic modulation of inter-pulse interval during stimulated isokinetic leg extension

    Efe Anil Aksöz; Marco Laubacher; Stuart Binder-Macleod; Hunt, Kenneth J


    Recumbent cycling exercise achieved by functional electrical stimulation (FES) of the paralyzed leg muscles is effective for cardiopulmonary and musculoskeletal conditioning after spinal cord injury, but its full potential has not yet been realized. Mechanical power output and efficiency is very low and endurance is limited due to early onset of muscle fatigue. The aim of this work was to compare stochastic modulation of the inter-pulse interval (IPI) to constant-frequency stimulation during ...

  8. Decoupling of excitation and receive coils in pulsed magnetic resonance using sinusoidal magnetic field modulation

    Tseytlin, Mark; Epel, Boris; Sundramoorthy, Subramanian; Tipikin, Dmitriy; Halpern, Howard J.


    In pulsed magnetic resonance, the excitation power is many orders of magnitude larger than that induced by the spin system in the receiving coil or resonator. The receiver must be protected during and immediately after the excitation pulse to allow for the energy stored in the resonator to dissipate to a safe level. The time during which the signal is not detected, the instrumental dead-time, can be shortened by using magnetically decoupled excitation and receive coils. Such coils are oriented, with respect to each other, in a way that minimizes the total magnetic flux produced by one coil in the other. We suggest that magnetically decoupled coils can be isolated to a larger degree by tuning them to separate frequencies. Spins are excited at one frequency, and the echo signal is detected at another. Sinusoidal magnetic field modulation that rapidly changes the Larmor frequency of the spins between the excitation and detection events is used to ensure the resonance conditions for both coils. In this study, the relaxation times of trityl-CD3 were measured in a field-modulated pulsed EPR experiment and compared to results obtained using a standard spin echo method. The excitation and receive coils were tuned to 245 and 256.7 MHz, respectively. Using an available rapid-scan, cross-loop EPR resonator, we demonstrated an isolation improvement of approximately 20-30 dB due to frequency decoupling. Theoretical analysis, numerical simulations, and proof-of-concept experiments demonstrated that substantial excitation-detection decoupling can be achieved. A pulsed L-band system, including a small volume bi-modal resonator equipped with modulation coils, was constructed to demonstrate fivefold dead-time reduction in comparison with the standard EPR experiment. This was achieved by detuning of the excitation and receive coils by 26 MHz and using sinusoidal modulation at 480 kHz.

  9. Single pulse TMS-induced modulations of resting brain neurodynamics encoded in EEG phase.

    Stamoulis, Catherine; Oberman, Lindsay M; Praeg, Elke; Bashir, Shahid; Pascual-Leone, Alvaro


    Integration of electroencephalographic (EEG) recordings and transcranial magnetic stimulation (TMS) provides a useful framework for quantifying stimulation-induced modulations of neural dynamics. Amplitude and frequency modulations by different TMS protocols have been previously investigated, but the study of stimulation-induced effects on EEG phase has been more limited. We examined changes in resting brain dynamics following single TMS pulses, focusing on measures in the phase domain, to assess their sensitivity to stimulation effects. We observed a significant, approximately global increase in EEG relative phase following prolonged (>20 min) single-pulse TMS. In addition, we estimated higher rates of phase fluctuation from the slope of estimated phase curves, and higher numbers of phase resetting intervals following TMS over motor cortex, particularly in frontal and centro-parietal/parietal channels. Phase changes were only significantly different from their pre-TMS values at the end of the stimulation session, which suggests that prolonged single-pulse TMS may result in cumulative changes in neural activity reflected in the phase of the EEG. This is a novel result, as prior studies have reported only transient stimulation-related effects in the amplitude and frequency domains following single-pulse TMS.

  10. The influence of pre-melting in laser drilling with temporally modulated pulse

    Duan, Wenqiang; Wang, Kedian; Dong, Xia; Mei, Xuesong; Wang, Wenjun; Fan, Zhengjie; Lv, Jing


    Laser drilling by temporally modulated pulse is a promising technique and has many advantages compared with normal pulse drilling. In this work, the effect of modulated pulse comprising pre-heating front and sharp trail was mainly studied. The function of the former was to pre-melt the radiated material, and the latter was to expel the liquid melt from the molten pool, thus to form a blind hole. While the trail subpulse was kept constant, the difference in the pre-heating subpulse parameter could cause a considerable influence on the hole quality and drilling efficiency. The depth and volume of the molten pool were proportional to the pre-heating energy, and inversely proportional to the pre-heating duration. With pre-heating subpulses of proper parameters, the sharp trail subpulse was very effective in expelling the melt liquid, leaving only a small quantity of melt to re-solidify as the recast layer, which was observably thinner compared with the holes drilled using the normal pulse mode. In the pre-melting process, the directional melt flow and heat conduction were found to be the reasons why the deep melting phenomenon had occurred.

  11. Pulse re-shaping by using a liquid crystal spatial light modulator and deflector for producing a specific waveform

    Jun Kang; Wei Zhang; Hui Wei; Shaohe Chen; Jianqiang Zhu


    @@ A new shaping method for producing nanosecond pulses with specific shape is introduced. When a Gaussian laser pulse passes through an electro-optic deflector, it has been scanned as a line on the focal plane according to time precedence. Through controlling the intensity of transmitted light on each pixel of the liquid crystal spatial light modulator (LCSLM), various complicated pulses can be easily produced. Using this method, various specific shaped pulses with pulse duration varying from 750 ps to 5 ns are achieved.

  12. Pulse

    ... resting for at least 10 minutes. Take the exercise heart rate while you are exercising. ... pulse rate can help determine if the person's heart is pumping. Pulse ... rate gives information about your fitness level and health.




    This paper describes the pulse modulator power supplies used to drive the kicker magnets that inject the muon beam into the 8-2 storage ring that has been built at Brookhaven National Laboratory. Three modulators built into coaxial structures consisting of a series circuit of an energy storage capacitor, a damping resistor and a fast thyratron switch are used to energize three magnets that kick the beam into the proper orbit. A 100 kV charging power supply is used to charge the capacitor to 95kV. The damping resistor shapes the magnet current waveform to a 450 nanosecond half-sine to match the injection requirements. This paper discusses the modulator design, construction and operation.

  14. Pulse position modulation for a subcarrier-multiplexed optical fiber transmission system

    Wickramasinghe, V. R.; Ghassemlooy, Zabih F.


    Subcarrier multiplexed (SCM) optical network s offer a near to medium term alternative solution over high cost, evolving digital technology to distribute broadband services. Majority of existing systems are based on analogue optical transmission techniques and their principle disadvantage is the sensitivity to noise and system nonlinearities. Therefore, conventional SCM systems impose stringent noise and linearity requirements and as a result their performance is limited. A simple and attractive solution is to introduce an appropriate second stage modulator in order to improve the receiver sensitivity, hence the system performance.In this paper a SCM optical transmission system employing pulse position modulation as a second stage modulator, for transmission of video, audio and data channels is reported. Signal to noise ratio measurements obtained shows an improvement in optical receiver sensitivity compared with standard SCM systems.

  15. [An integral chip for the multiphase pulse-duration modulation used for voltage changer in biomedical microprocessor systems].

    Balashov, A M; Selishchev, S V


    An integral chip (IC) was designed for controlling the step-down pulse voltage converter, which is based on the multiphase pulse-duration modulation, for use in biomedical microprocessor systems. The CMOS technology was an optimal basis for the IC designing. An additional feedback circuit diminishes the output voltage dispersion at dynamically changing loads.

  16. Self-phase modulation of a single-cycle terahertz pulse by nonlinear free-carrier response in a semiconductor

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias C.


    We investigate the self-phase modulation (SPM) of a single-cycle terahertz pulse in a semiconductor, using bulk n-GaAs as a model system. The SPM arises from the heating of free electrons in the electric field of the terahertz pulse, leading to an ultrafast reduction of the plasma frequency, and ...

  17. Design of a 20 kV Solid State Marx Pulse Modulator%20 kV固态Marx脉冲调制器研制

    冯宗明; 冯元伟; 李洪涛; 丁明军


    A 20 kV solid-state Marx pulse modulator is developed.The modulator is com-posed of eight-stage Marx modules in series,each of which adopts two independently con-trolled insulated gate bipolar transistors (ICBTs) for charging and discharging to its energy storage capacitor.It takes high voltage silicon stack for capacitor charging isolation and switch-driven isolation for each stage of the Marx module.With push/pull PCB structure, the Marx modules are easy to maintenance and replacement.Experimental results show that the 20 kV solid-state Marx modulator can generate output pulse with voltage more than 20 kV,pulse width of 10μs,raise/fall time of 300 ns at a load of 20 kΩ.Without strengthen cool,the pulse repetition rate is up to 1 kHz in burst mode.%阐述了20 kV固态Marx脉冲调制器的设计原理、结构特点及驱动控制方法。该系统由8级模块串联而成,每级模块的储能电容、高压充电和固态开关驱动供电均采用高压硅堆隔离,Marx模块采用两只独立控制的高压绝缘栅双极型晶体管(insulated gate bipolar tran-sistor,IGBT)对模块的储能电容实现充电和放电。IGBT 驱动电路采用高压硅堆隔离供电、光纤传输触发脉冲和高性能IGBT驱动模块TD350设计构成。驱动电路具备完善的欠压、过流和过压保护功能。Marx模块采用插拔式结构,维护快捷简便。脉冲源在无强化散热措施条件下,输出方形高压脉冲幅度大于20 kV,脉冲宽度为10μs,脉冲前后沿均为300 ns,重复频率可达1 kHz。

  18. PHz-wide Supercontinua of Nondispersing Subcycle Pulses Generated by Extreme Modulational Instability

    Tani, F.; Travers, J. C.; Russell, P. St. J.


    Modulational instability (MI) of 500 fs, 5μJ pulses, propagating in gas-filled hollow-core kagome photonic crystal fiber, is studied numerically and experimentally. By tuning the pressure and launched energy, we control the duration of the pulses emerging as a consequence of MI and hence are able to study two regimes: the classical MI case leading to few-cycle solitons of the nonlinear Schrödinger equation; and an extreme case leading to the formation of nondispersing subcycle pulses (0.5 to 2 fs) with peak intensities of order 1014Wcm-2. Insight into the two regimes is obtained using a novel statistical analysis of the soliton parameters. Numerical simulations and experimental measurements show that, when a train of these pulses is generated, strong ionization of the gas occurs. This extreme MI is used to experimentally generate a high energy (>1μJ) and spectrally broad supercontinuum extending from the deep ultraviolet (320 nm) to the infrared (1300 nm).

  19. Pulsed ytterbium-doped fibre laser with a combined modulator based on single-wall carbon nanotubes

    Khudyakov, D. V.; Borodkin, A. A.; Lobach, A. S.; Vartapetov, S. K.


    This paper describes an all-normal-dispersion pulsed ytterbium-doped fibre ring laser mode-locked by a nonlinear combined modulator based on single-wall carbon nanotubes. We have demonstrated 1.7-ps pulse generation at 1.04 μm with a repetition rate of 35.6 MHz. At the laser output, the pulses were compressed to 180 fs. We have examined an intracavity nonlinear modulator which utilises nonlinear polarisation ellipse rotation in conjunction with a saturable absorber in the form of a polymer-matrix composite film containing single-wall carbon nanotubes.

  20. Pulsed ytterbium-doped fibre laser with a combined modulator based on single-wall carbon nanotubes

    Khudyakov, D V; Borodkin, A A; Vartapetov, S K [Physics Instrumentation Center, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Troitsk, Moscow Region (Russian Federation); Lobach, A S [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)


    This paper describes an all-normal-dispersion pulsed ytterbium-doped fibre ring laser mode-locked by a nonlinear combined modulator based on single-wall carbon nanotubes. We have demonstrated 1.7-ps pulse generation at 1.04 μm with a repetition rate of 35.6 MHz. At the laser output, the pulses were compressed to 180 fs. We have examined an intracavity nonlinear modulator which utilises nonlinear polarisation ellipse rotation in conjunction with a saturable absorber in the form of a polymer-matrix composite film containing single-wall carbon nanotubes. (lasers)

  1. Development of Pulse Position Modulation/Optical CDMA (PPM/O-CDMA) for Gb/s Fiber Optic Networking

    Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V; Lennon, W J


    Pulse position modulation (PPM) in lasercom systems is known to provide potential advantages over other modulation schemes. [1]. In PPM, a periodic time frame is established and data is transmitted by placing a pulse in any one of several subintervals (or ''slots'') within each frame. In PPM/O-CDMA all users use the same frame structure and each transmits its unique address code in place of the PPM pulse. The advantage of PPM as a pulsed signal format is that (1) a single pulse can transmit multiple bits during each frame; (2) decoding (determining which subinterval contains the pulse) is by comparison rather than threshold tests (as in on-off-keying); (3) each user transmits in only a small fraction of the frame, hence the multi-access interference (MAI) of any user statistically spreads over the entire frame time, reducing the chance of overlap with any other user; and (4) under an average power constraint, increasing frame time increases the peak pulse power (i.e., PPM trades average power for peak power). The most straightforward approach to implementing PPM/O-CDMA data modulator inserts the PPM pulse modulation first, then imposes the O-CDMA coding. A pulsed PPM modulator converts bits (words) into pulse positions. In the case of wavelength/time (W/T) matrix codes, multi-wavelength pulses are generated at the beginning of each frame, at the frame rate. For M-ary PPM, a block of k bits represents M = 2{sup k} unique interval positions in the frame corresponding to M-l specific time delays (the zero delay is also a position). PPM modulation is achieved by shifting the initial pulse into an interval position with delay D(i) (i=0,1,2,..,M-1). The location of a pulse position (selection of a delay) therefore identifies a unique k-bit word in the frame. At the receiver, determining which delay occurs relative to the frame start time decodes the data word. The probability of pulse overlap between two users decreases with M, which therefore

  2. RF-modulated pulsed fiber optic lidar transmitter for improved underwater imaging and communications

    Kimpel, F.; Chen, Y.; Fouron, J.-L.; Akbulut, M.; Engin, D.; Gupta, S.


    We present results on the design, development and initial testing of a fiber-optic based RF-modulated lidar transmitter operating at 532nm, for underwater imaging application in littoral waters. The design implementation is based on using state-of-the-art high-speed FPGAs, thereby producing optical waveforms with arbitrary digital-RF-modulated pulse patterns with carrier frequencies >= 3GHz, with a repetition rate of 0.5-1MHz, and with average powers >=5W (at 532nm). Use of RF-modulated bursts above 500MHz, instead of single optical pulse lidar detection, reduces the effect of volumetric backscatter for underwater imaging application, leading to an improved signal-to-noise-ratio (SNR) and contrast, for a given range. Initial underwater target detection tests conducted at Patuxent River Naval Air Station, MD, in a large water-tank facility, validates the advantages of this hybrid-lidar-radar (HLR) approach for improved underwater imaging, over a wide range of turbidity levels and both white and black targets. The compact, robust and power-efficient fiber laser architecture lends very well to lidar sensor integration on unmanned-underwater-vehicle (UUV) platforms. HLR transmitters can also provide similar advantages in active-sensing situations dominated by continuous backscatter, e.g. underwater communications, imaging through smoke and fire environment, rotor-craft landing in degraded visual environment, and pointing-tracking of active-EO sensors through fog.

  3. Compact MEMS mirror based Q-switch module for pulse-on-demand laser range finders

    Milanović, Veljko; Kasturi, Abhishek; Atwood, Bryan; Su, Yu; Limkrailassiri, Kevin; Nettleton, John E.; Goldberg, Lew; Cole, Brian J.; Hough, Nathaniel


    A highly compact and low power consuming Q-switch module was developed based on a fast single-axis MEMS mirror, for use in eye-safe battery-powered laser range finders The module's 1.6mm x 1.6mm mirror has cost than the traditional Electro-Optical Q-Switch. Because pulse-on-demand capability is required, resonant mirrors cannot be used to achieve the needed performance. Instead, a fast point-to-point analog single-axis tilt actuator was designed with a custom-coated high reflectance (HR) mirror to withstand the high intra-cavity laser fluence levels. The mirror is bonded on top of the MEMS actuator in final assembly. A compact MEMS controller was further implemented with the capability of autonomous on-demand operation based on user-provided digital trigger. The controller is designed to receive an external 3V power supply and a digital trigger and it consumes ~90mW during the short switching cycle and ~10mW in standby mode. Module prototypes were tested in a laser cavity and demonstrated high quality laser pulses with duration of ~20ns and energy of over 3mJ.

  4. Scaling in film growth by pulsed laser deposition and modulated beam deposition.

    Lee, Sang Bub


    The scalings in film growth by pulsed laser deposition (PLD) and modulated beam deposition (MBD) were investigated by Monte Carlo simulations. In PLD, an atomic pulse beam with a period t(0) were deposited instantaneously on a substrate, whereas in MBD, adatoms were deposited during a short time interval t(1) (0≤t(1)≤t(0)) within each period. If t(1)=0, MBD will be identical to PLD and, if t(1)=t(0), MBD will become usual molecular beam epitaxy (MBE). Specifically, logarithmic scaling was investigated for the nucleation density reported for PLD, and the scaling of island density was studied regarding the growth for 0MBE growth was observed as t(1) increased. The phase diagram was also presented.

  5. Phase-Modulated Nonresonant Laser Pulses Can Selectively Convert Enantiomers in a Racemic Mixture

    Thomas, Esben Folger; Henriksen, Niels Engholm


    Deracemization occurs when a racemic molecular mixture is transformed into a mixture containing an excess of a single enantiomer. Recent advances in ultrafast laser technology hint at the possibility of using shaped pulses to generate deracemization via selective enantiomeric conversion; however......-modulated, nonresonant, linearly polarized Gaussian laser pulses that can selectively deracemize a racemic mixture of 3D-oriented, 3,5-difluoro-3',5'-dibromobiphenyl (F2H3C6-C6H3Br2) molecules, the laser-induced dynamics of which are well studied experimentally. These results strongly suggest that designing a closed......-loop coherent control scheme based on this methodology may lead to the first-ever achievement of enantiomeric conversion via coherent laser light in a laboratory setting....

  6. High-fidelity pulse density modulation in neuromorphic electric circuits utilizing natural heterogeneity

    Utagawa, Akira; Asai, Tetsuya; Amemiya, Yoshihito

    Hospedales et al. have recently proposed a neural network model of the “vestibulo-ocular reflex” (VOR) in which a common input was given to multiple nonidentical spiking neurons that were exposed to uncorrelated temporal noise, and the output was represented by the sum of these neurons. Although the function of the VOR network is equivalent to pulse density modulation, the neurons' non-uniformity and temporal noises given to the neurons were shown to improve the output spike's fidelity to the analog input. In this paper, we propose a CMOS analog circuit for implementing the VOR network that exploits the non-uniformity of real MOS devices. Through extensive laboratory experiments using discrete MOS devices, we show that the output's fidelity to the input pulses is clearly improved by using multiple neuron circuits, in which the non-uniformity is naturally embedded into the devices.

  7. 40 Gb/s Pulse Generation Using Gain Switching of a Commercially Available Laser Module

    Nørregaard, Jesper; Hanberg, Jesper; Franck, Thorkild


    between the microwave substrate and the RF feed-through in the wall of the module. The module is build as a 14 pin butterfly package with the RF feed-through designed as a coplanar 50 ohm impedance port. Included in the module are a built-in optical isolator, a thermistor, a thermo-electric cooler...... to ease RF connection. The laser die is connected to a gold plated AlN microwave substrate that also acts as a heat spreader. The microwave substrate contains an impedance matching resistor for the RF signal as well as a bias-T for the DC bias. 50 ohm Flexguide technology is used for the interconnection......, and a photodiode for optical power monitoring.The RF input port was connected to the driver circuit using a coplanar microwave probe. A DC bias and a large signal modulation at 10 GHz was applied to the module to generate chirped pulses. A linear as well as a non-linear soliton compression was used with optical...

  8. Current-pulse-width control of degradation in II-VI and III-N compound blue-UV-white LEDs

    Harada, Y.; Ando, K.; Nakagawa, S.; Sakamoto, H.; Abe, T.; Kasada, H. [Electrical and Electronic Department, Tottori Univ., Koyama 4-101, Tottori 680-8550 (Japan)


    We have studied the cause of shortened lifetime and reduced brightness of wide-gap semiconductor LEDs, and found that generation/enhancement of microscopic point defects have strong association with device lifetime. A pulse-drive technology controlling defect enhancement has been proven new to extend life span of UV-blue-white-LEDs in high efficiency and high brightness operation. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Laser drilling of via micro-holes in single-crystal semiconductor substrates using a 1070nm fibre laser with millisecond pulse widths

    Maclean, Jessica O.; Hodson, Jonathan R.; Voisey, K. T.


    Micro-machining of semiconductors is relevant to fabrication challenges within the semiconductor industry. For via holes for solar cells, laser drilling potentially avoids deep plasma etching which requires sophisticated equipment and corrosive, high purity gases. Other applications include backside loading of cold atoms into atom chips and ion traps for quantum physics research, for which holes through the semiconductor substrate are needed. Laser drilling, exploiting the melt ejection material removal mechanism, is used industrially for drilling hard to machine materials such as superalloys. Lasers of the kind used in this work typically form holes with diameters of 100's of microns and depths of a few millimetres in metals. Laser drilling of semiconductors typically uses short pulses of UV or long wavelength IR to achieve holes as small as 50 microns. A combination of material processes occurs including laser absorption, heating, melting, vaporization with vapour and dust particle ejection and resolidification. An investigation using materials with different fundamental material parameters allows the suitability of any given laser for the processing of semiconductors to be determined. We report results on the characterization of via holes drilled using a 2000 W maximum power 1070 nm fibre laser with 1-20 ms pulses using single crystal silicon, gallium arsenide and sapphire. Holes were characterised in cross-section and plan view. Significantly, relatively long pulses were effective even for wide bandgap substrates which are nominally transparent at 1070 nm. Examination of drilled samples revealed holes had been successfully generated in all materials via melt ejection.

  10. Receiver Architecture for 12.5 Gb/s 16-ary Pulse Position Modulation (PPM) Signaling

    Mendez, A J; Gagliardi, R M; Hernandez, V J; Bennett, C V


    PPM is a signaling scheme that enables the transmission of multiple bits per symbol [1]. It has found favor in the regime of free space optical communications ('FSO' or 'Lasercom'); however, PPM has yet to be widely applied to fiber optic-based communications. Its limitation in fiber results from the exceedingly high bandwidth requirements needed to electronically process a directly detected pulse, especially as the symbol rate increases and the pulse width correspondingly decreases. As a solution, we introduced the concept of a virtual quadrant receiver for receiving 1.25 Gb/s 4-ary PPM, where photonic processing reduced the number of required electronic components [2]. In this paper, we extend these photonic process techniques to a 16-ary, 12.5 Gb/s (10 Gb/s plus 8B/10B line coding) PPM communications system for fiber optic avionics, wherein much of the receiver processing is enabled by techniques based on planar lightwave circuits (PLCs). The architecture is applicable to higher input data rates and M-ary PPM. In the following, we present the PPM encoding and decoding architectures and numerically simulated results.

  11. Transference & Retrieval of Pulse-code modulation Audio over Short Messaging Service

    Khan, Muhammad Fahad


    The paper presents the method of transferring PCM (Pulse-Code Modulation) based audio messages through SMS (Short Message Service) over GSM (Global System for Mobile Communications) network. As SMS is text based service, and could not send voice. Our method enables voice transferring through SMS, by converting PCM audio into characters. Than Huffman coding compression technique is applied in order to reduce numbers of characters which will latterly set as payload text of SMS. Testing the said method we develop an application using J2me platform

  12. Implementation of pulse interval modulation based on dualmapping technique for optical wireless communications

    ZHANG Tie-ying; WANG Hong-xing; HU Hao; CONG Pei-sheng


    Aiming at implementing the digital pulse interval modulation (DPIM) for optical wireless communications (OWC), a dual-mapping technique is presented. The scheme of DPIM train based upon the dual-mapping technique is given. Its slot error rate is derived for the avalanche photonic diode (APD) receiver model, and is compared with that of classical DPIM. Simulation results show that the dual-mapping DPIM (D-DPIM), which has a fixed slot length, only has marginally inferior error performance, but can solve waiting slots or buffer overflowing in comparison with DPIM. Hence, it is suitable for the optical wireless communication systems.

  13. Effect of stochastic modulation of inter-pulse interval during stimulated isokinetic leg extension

    Efe Anil Aksöz


    Full Text Available Recumbent cycling exercise achieved by functional electrical stimulation (FES of the paralyzed leg muscles is effective for cardiopulmonary and musculoskeletal conditioning after spinal cord injury, but its full potential has not yet been realized. Mechanical power output and efficiency is very low and endurance is limited due to early onset of muscle fatigue. The aim of this work was to compare stochastic modulation of the inter-pulse interval (IPI to constant-frequency stimulation during an isokinetic leg extension task similar to FES-cycling. Seven able-bodied subjects participated: both quadriceps muscles were stimulated (n = 14 with two activation patterns (P1-constant frequency, P2-stochastic IPI. There was significantly higher power output with P2 during the first 30 s (p = 0.0092, the last 30 s (p = 0.018 and overall (p = 0.0057, but there was no overall effect on fatiguability when stimulation frequency was randomly modulated.

  14. Effect of Stochastic Modulation of Inter-Pulse Interval During Stimulated Isokinetic Leg Extension

    Aksöz, Efe Anil; Laubacher, Marco; Binder-Macleod, Stuart; Hunt, Kenneth J.


    Recumbent cycling exercise achieved by functional electrical stimulation (FES) of the paralyzed leg muscles is effective for cardiopulmonary and musculoskeletal conditioning after spinal cord injury, but its full potential has not yet been realized. Mechanical power output and efficiency is very low and endurance is limited due to early onset of muscle fatigue. The aim of this work was to compare stochastic modulation of the inter-pulse interval (IPI) to constant-frequency stimulation during an isokinetic leg extension task similar to FES-cycling. Seven able-bodied subjects participated: both quadriceps muscles were stimulated (n = 14) with two activation patterns (P1-constant frequency, P2-stochastic IPI). There was significantly higher power output with P2 during the first 30 s (p = 0.0092), the last 30 s (p = 0.018) and overall (p = 0.0057), but there was no overall effect on fatiguability when stimulation frequency was randomly modulated. PMID:27990242

  15. Highly precise and accurate terahertz polarization measurements based on electro-optic sampling with polarization modulation of probe pulses.

    Nemoto, Natsuki; Higuchi, Takuya; Kanda, Natsuki; Konishi, Kuniaki; Kuwata-Gonokami, Makoto


    We have developed an electro-optic (EO) sampling method with polarization modulation of probe pulses; this method allows us to measure the direction of a terahertz (THz) electric-field vector with a precision of 0.1 mrad in a data acquisition time of 660 ms using a 14.0-kHz repetition rate pulsed light source. Through combination with a THz time-domain spectroscopy technique, a time-dependent two-dimensional THz electric field was obtained. We used a photoelastic modulator for probe-polarization modulation and a (111)-oriented zincblende crystal as the EO crystal. Using the tilted pulse front excitation method with stable regeneratively amplified pulses, we prepared stable and intense THz pulses and performed pulse-by-pulse analog-to-digital conversion of the signals. These techniques significantly reduced statistical errors and enabled sub-mrad THz polarization measurements. We examined the performance of this method by measuring a wire-grid polarizer as a sample. The present method will open a new frontier of high-precision THz polarization sensitive measurements.

  16. Negative Kerr Nonlinearity of Graphene as seen via Chirped-Pulse-Pumped Self-Phase Modulation

    Vermeulen, Nathalie; Castelló-Lurbe, David; Cheng, JinLuo; Pasternak, Iwona; Krajewska, Aleksandra; Ciuk, Tymoteusz; Strupinski, Wlodek; Thienpont, Hugo; Van Erps, Jürgen


    We experimentally demonstrate a negative Kerr nonlinearity for quasiundoped graphene. Hereto, we introduce the method of chirped-pulse-pumped self-phase modulation and apply it to graphene-covered silicon waveguides at telecom wavelengths. The extracted Kerr-nonlinear index for graphene equals n2 ,gr=-10-13 m2 /W . Whereas the sign of n2 ,gr turns out to be negative in contrast to what has been assumed so far, its magnitude is in correspondence with that observed in earlier experiments. Graphene's negative Kerr nonlinearity strongly impacts how graphene should be exploited for enhancing the nonlinear response of photonic (integrated) devices exhibiting a positive nonlinearity. It also opens up the possibility of using graphene to annihilate unwanted nonlinear effects in such devices, to develop unexplored approaches for establishing Kerr processes, and to extend the scope of the "periodic poling" method often used for second-order nonlinearities towards third-order Kerr processes. Because of the generic nature of the chirped-pulse-pumped self-phase modulation method, it will allow fully characterizing the Kerr nonlinearity of essentially any novel (2D) material.

  17. Optical Receiver for Coherently Detected Pulse-Position Modulated Signals in the Presence of Atmospheric Turbulence

    Munoz Fernandez, M.; Vilnrotter, V. A.


    Performance analysis and experimental verification of a coherent free-space optical communications receiver in the presence of simulated atmospheric turbulence is presented. Bit-error rate (BER) performance of ideal coherent detection is analyzed in Section II, and the laboratory equipment and experimental setup used to carry out these experiments are described. The key components include two lasers operating at a 1064-nm wavelength for use with coherent detection, a 16-element (4 x 4) focal-plane detector array, and a data acquisition and signal processing assembly needed to sample and collect the data and analyze the results. The detected signals are combined using the least-mean-square (LMS) algorithm. In Section III, convergence of the algorithm for experimentally obtained signal tones in the presence of atmospheric turbulence is demonstrated. In Section IV, adaptive combining of experimentally obtained heterodyned pulse-position modulated (PPM) signals with pulse-to-pulse coherence, in the presence of simulated spatial distortions resembling atmospheric turbulence, is demonstrated. The adaptively combined PPM signals are phased up via an LMS algorithm suitably optimized to operate with PPM in the presence of additive shot noise. A convergence analysis of the algorithm is presented, and results with both computer-simulated and experimentally obtained PPM signals are analyzed.

  18. Adaptive Bessel-autocorrelation of ultrashort pulses with phase-only spatial light modulators

    Huferath-von Luepke, Silke; Bock, Martin; Grunwald, Ruediger


    Recently, we proposed a new approach of a noncollinear correlation technique for ultrashort-pulsed coherent optical signals which was referred to as Bessel-autocorrelator (BAC). The BAC-principle combines the advantages of Bessellike nondiffracting beams like stable propagation, angular robustness and self-reconstruction with the principle of temporal autocorrelation. In comparison to other phase-sensitive measuring techniques, autocorrelation is most straightforward and time-effective because of non-iterative data processing. The analysis of nonlinearly converted fringe patterns of pulsed Bessel-like beams reveals their temporal signature from details of fringe envelopes. By splitting the beams with axicon arrays into multiple sub-beams, transversal resolution is approximated. Here we report on adaptive implementations of BACs with improved phase resolution realized by phase-only liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs). Programming microaxicon phase functions in gray value maps enables for a flexible variation of phase and geometry. Experiments on the diagnostics of few-cycle pulses emitted by a mode-locked Ti:sapphire laser oscillator at wavelengths around 800 nm with 2D-BAC and angular tuned BAC were performed. All-optical phase shift BAC and fringe free BAC approaches are discussed.

  19. Modeling and calibration of pulse-modulation based ToF imaging systems

    Süss, Andreas; Varga, Gabor; Marx, Michael; Fürst, Peter; Gläsener, Stefan; Tiedke, Wolfram; Jung, Melanie; Spickermann, Andreas; Hosticka, Bedrich J.


    Conversely to the continuous wave indirect time-of-flight (CW-iToF) imaging scheme, pulsed modulation ToF (PM-iToF) imaging is a promising depth measurement technique for operation at high ambient illumination. It is known that non-linearity and finite charge-transfer speed impact trueness and precision of ToF systems.1-3 As pulses are no Eigenfunctions to the shutter system, this issue is especially pronounced in pulsed modulation.2, 3 Despite these effects, it is possible to find analytical expressions founded on physical observations that map scenery parameters such as depth information, reflectance and ambient light level to sensor output.3, 4 In the application, the inverse of this map has to be evaluated. In PM-iToF, an inverse function cannot be yielded in a direct manner, as models proposed in the literature were transcendental.3, 4 For a limited range an approximating linearization can be performed to yield depth information.5 To extend the usable range, recently, an alternative approach that indirectly approximates the inverse function was presented.6 This method was founded on 1D doping concentration profiles, which, however, are typically not made available to end users. Also, limitations of the 1D approximation as well as stability are yet to be explored. This work presents a calibration methodology that copes with detector insufficiencies such as finite charge transfer speed. Contrarily to the state of the art, no prior knowledge on details of the underlying devices is required. The work covers measurement setup, a benchmark of various calibration schemes and deals with issues such as overfitting or defect pixels.

  20. Non-photic modulation of phase shifts to long light pulses.

    Antle, Michael C; Sterniczuk, Roxanne; Smith, Victoria M; Hagel, Kimberly


    Circadian rhythms can be reset by both photic and non-photic stimuli. Recent studies have used long light exposure to produce photic phase shifts or to enhance non-photic phase shifts. The presence or absence of light can also influence the expression of locomotor rhythms through masking; light during the night attenuates locomotor activity, while darkness during the day induces locomotor activity in nocturnal animals. Given this dual role of light, the current study was designed to examine the relative contributions of photic and non-photic components present in a long light pulse paradigm. Mice entrained to a light/dark cycle were exposed to light pulses of various durations (0, 3, 6, 9, or 12 h) starting at the time of lights-off. After the light exposure, animals were placed in DD and were either left undisturbed in their home cages or had their wheels locked for the remainder of the subjective night and subsequent subjective day. Light treatments of 6, 9, and 12 h produced large phase delays. These treatments were associated with decreased activity during the nocturnal light and increased activity during the initial hours of darkness following light exposure. When the wheels were locked to prevent high-amplitude activity, the resulting phase delays to the light were significantly attenuated, suggesting that the activity following the light exposure may have contributed to the overall phase shift. In a second experiment, telemetry probes were used to assess what effect permanently locking the wheels had on the phase shift to the long light pulses. These animals had phase shifts fully as large as animals without any form of wheel lock, suggesting that while non-photic events can modulate photic phase shifts, they do not play a role in the full phase-shift response observed in animals exposed to long light pulses. This paradigm will facilitate investigations into non-photic responses of the mouse circadian system.

  1. Discharge conditions for CW and pulse-modulated surface-wave plasmas in low-temperature sterilization

    Xu, L [Department of Electrical and Electronic Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561 (Japan); Terashita, F [Department of Electrical and Electronic Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561 (Japan); Nonaka, H [Department of Electrical and Electronic Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561 (Japan); Ogino, A [Department of Electrical and Electronic Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561 (Japan); Nagata, T [Department of Microbiology and Immunology, Hamamatsu University School of Medicine, 1-20-1 Handa-yama, Hamamatsu 431-3192 (Japan); Koide, Y [Department of Microbiology and Immunology, Hamamatsu University School of Medicine, 1-20-1 Handa-yama, Hamamatsu 431-3192 (Japan); Nanko, S [Nissin Inc., 10-7 Kamei-cho, Takarazuka 665-0047 (Japan); Kurawaki, I [GMA Co. Ltd., 3898-1, Asaba, Fukuroi, 437-1101 (Japan); Nagatsu, M [Department of Electrical and Electronic Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561 (Japan)


    The discharge conditions required for low-temperature plasma sterilization were investigated using low-pressure surface-wave plasma (SWP). The discharge conditions for both continuous wave (CW) and pulse-modulated SWPs in low-temperature sterilization of Geobacillus stearothermophilus with a population of 1.5 x 10{sup 6} and 3.0 x 10{sup 6} were studied by varying the microwave input power from 500 W to 3 kW, and the effective plasma treatment time from 40 to 300 s. Results showed that sterilization was possible in a shorter treatment time using a higher microwave power for both CW and pulse-modulated SWPs. Pulse-modulated SWPs gave effective sterilization at a temperature roughly 10 to 20 deg. C below that of CW SWPs under the same average microwave power.

  2. Discharge conditions for CW and pulse-modulated surface-wave plasmas in low-temperature sterilization

    Xu, L.; Terashita, F.; Nonaka, H.; Ogino, A.; Nagata, T.; Koide, Y.; Nanko, S.; Kurawaki, I.; Nagatsu, M.


    The discharge conditions required for low-temperature plasma sterilization were investigated using low-pressure surface-wave plasma (SWP). The discharge conditions for both continuous wave (CW) and pulse-modulated SWPs in low-temperature sterilization of Geobacillus stearothermophilus with a population of 1.5 × 106 and 3.0 × 106 were studied by varying the microwave input power from 500 W to 3 kW, and the effective plasma treatment time from 40 to 300 s. Results showed that sterilization was possible in a shorter treatment time using a higher microwave power for both CW and pulse-modulated SWPs. Pulse-modulated SWPs gave effective sterilization at a temperature roughly 10 to 20 °C below that of CW SWPs under the same average microwave power.

  3. Experimental research of pulsed chirp effect on the small-scale self-focusing


    The chirped optical pulses undergoing self-focusing and splitting into multiple filamentation passing through a Kerr medium-carbon disulfide (CS2) are studied experimentally and numerically. At the particular spatial position, modulation growth takes place from the experimental result. The process of modulation growth with different pulsed chirp is analyzed. It is found that with the pulsed chirp in-creasing (equal to the pulse width increasing), modulation growth of chirped opti-cal pulses is delayed and the average input power also increases. The simulation results are in agreement with the experimental results.

  4. Frequency modulated few-cycle optical pulse trains induced controllable ultrafast coherent population oscillations in three-level atomic systems

    Kumar, Parvendra


    We report a study on the ultrafast coherent population oscillations (UCPO) in sodium atoms induced by the frequency modulated few-cycle optical pulse trains. The phenomenon of UCPO is investigated by numerically solving the appropriate density matrix equations beyond the rotating wave approximation. We demonstrate that the quantum state of the atoms and the frequency of UCPO may be controlled by controlling the number of pulses in the pulse trains and the pulse repetition time respectively. Moreover, the robustness of population transfer against the variation of laser pulse parameters is also investigated. The proposed scheme may be useful for the creation of atomic beam in selected quantum state for desired time duration and may have potential applications in ultrafast optical switching.

  5. Pulse intensity modulation and the timing stability of millisecond pulsars: A case study of PSR J1713+0747

    Shannon, Ryan M


    Most millisecond pulsars, like essentially all other radio pulsars, show timing errors well in excess of what is expected from additive radiometer noise alone. We show that changes in amplitude, shape and pulse phase for the millisecond pulsar J1713+0747 cause this excess error. These changes appear to be uncorrelated from one pulse period to the next. The resulting time of arrival variations are correlated across a wide frequency range and are observed with different backend processors on different days, confirming that they are intrinsic in origin and not an instrumental effect or caused by strongly frequency dependent interstellar scattering. Centroids of single pulses show an rms phase variation \\approx 40 microsec, which dominates the timing error and is the same phase jitter phenomenon long known in slower spinning, canonical pulsars. We show that the amplitude modulations of single pulses are modestly correlated with their arrival time fluctuations. We also demonstrate that single-pulse variations are ...

  6. Dual-loss-modulated Q-switched Tm:LuAG laser with AOM and monolayer graphene.

    Luan, Chao; Yang, Ke Jian; Zhao, Jia; Zhao, Sheng Zhi; Qiao, Wen Chao; Li, Tao; Feng, Tian Li; Liu, Cheng; Qiao, Jun Peng; Zheng, Li He; Xu, Jun; Wang, Qing Guo; Su, Liang Bi


    A laser-diode-pumped dual-loss-modulated Q-switching Tm:LuAG laser with an acousto-optic modulator (AOM) and monolayer graphene saturable absorber (SA) around 2 μm is presented for the first time to the best of our knowledge. The average output power and the pulse widths for different repetition rates have been measured. In comparison with the singly Q-switching laser with AOM or with monolayer graphene SA, the dual-loss-modulated Q-switching laser could generate shorter pulse width and higher peak power. The maximum pulse width compression ratio was found to be 3.11, and the highest peak power was enhanced 97.4 times. The experimental results show that the dual-loss-modulated technology is an efficient method for compressing the pulse width, improving the peak power, and enhancing the pulse stability for the Q-switched lasers at 2 μm.

  7. Spectral broadening of 25 fs laser pulses via self-phase modulation in a neon filled hollow core fibre

    Weichert, Stefan


    The goal of this work was the realisation of a setup for spectral broadening and subsequent compression of 25 fs laser pulses provided by a commercial Ti:Sapphire based CPA laser system by means of the hollow core fibre chirped mirror compressor technique. For the spectral broadening a vessel containing the hollow waveguide filled with a noble gas serving as the nonlinear medium was set up and an alignment procedure was developed. Neon was chosen as the nonlinear medium for the self-phase modulation of the pulses. With this setup spectral broadening, sufficient for supporting sub 5 fs pulses, was observed. The spectra at different input energies and neon gas pressures were measured and the stability of these and their respective Fourier transform-limited pulses determined in order to find an operating point. For the compression of the self-phase modulated pulses a chirped mirror compressor was designed and set up, but not tested yet. The layout of a single-shot intensity autocorrelator capable of estimating the pulse duration of sub 10 fs pulses was given.

  8. Supercontinuum generation enhanced by conventional Raman amplification at pumping by nanosecond pulses from a directly modulated DFB laser

    Rojas-Laguna, Roberto; Gutiérrez-Gutiérrez, Jaime; Kuzin, Evgeny A.; Ibarra-Escamilla, Baldemar; Mendoza-Vázquez, Sergio; Estudillo-Ayala, Julián Moisés; Haus, Joseph W.


    We investigated spectral broadening in a standard fiber using a nanosecond directly modulated DFB laser (λ=1549 nm), amplified by a two stage Erbium-doped fiber amplifier. The amplifier provided amplification of 2-mW peak power input pulses to 100-W peak power output pulses. In other hand, the directly modulation of DFB lasers caused transient oscillations at the beginning of pulses. In our case pulses consisted of a 2-ns transient part followed by a steady-state plateau. We used a monochromator to measure the spectrum at the fiber output. A fast photodetector was placed at the monochromator output and pulse shapes were measured for different wavelengths. This technique allowed the separate measurement of different parts in output pulses spectrum. We used the SMF-28 fiber with the standard dispersion of 20 ps/nm-km for our wavelength. We made measurements of the output spectra for three fiber lengths: 0.6-km, 4.46-km and 9.15-km; finding that the initial transient part of a pulse shows supercontinuum generation whereas the plateau results in conventional Raman amplification of this supercontinuum.

  9. Ultrafast pulse generation from erbium-doped fiber laser modulated by hybrid organic-inorganic halide perovskites

    Jiang, Guobao; Miao, Lili; Yi, Jun; Huang, Bin; Peng, Wei; Zou, Yanhong; Huang, Huihui; Hu, Wei; Zhao, Chujun; Wen, Shuangchun


    We report the nonlinear optical responses of organic-inorganic halide perovskite CH3NH3PbI3 and its application in ultrafast pulse generation from an erbium-doped fiber laser in the optical communication band. By adopting the Z-scan technique, the third-order nonlinear optical responses of the organic-inorganic halide perovskites have been characterized. An ultrafast optical pulse with a pulse width of 661 fs centered at a wavelength of 1555 nm has been delivered via the nonlinear optical material introduced into the fiber laser cavity. Our experimental results confirm that the organic-inorganic halide perovskite possesses obvious third-order nonlinear optical responses in the C-band window and manifests its application potential in nonlinear optoelectronic devices.

  10. Near-Nyquist optical pulse generation with fiber optical parametric amplification.

    Vedadi, Armand; Shoaie, Mohammad Amin; Brès, Camille-Sophie


    A novel method using optical fiber parametric amplification and phase modulation is proposed in order to generate Nyquist pulses. Using parabolic pulses as a pump, we show theoretically that it is possible to generate Nyquist pulses. Furthermore, we show that by using a sinusoidal pump (pump intensity modulated by an RF tone), it is possible to obtain pulses with characteristics that are close to Nyquist limited pulses. We demonstrate experimentally the generation of bandwidth limited pulses with full width half maximum of 14 ps at 10 GHz repetition rate. We also discuss limitations of this method and means to overcome these limitations.

  11. Research on Modulation Strategies Based on Multilevel Inverter Universal Hybrid Topology

    Zhou Jinghua; Su Yanmin; Shen Chuanwen; Zhang Lin


    Based on multi-module-cascaded inverter topology, this study presented a universal multilevel inverter hybrid topology and unified the researches on multilevel inverter topology. According to the freedom of this universal topology, several new hybrid topologies were constructed. Also, based on conventional modulation strategies- multi-carrier SPWM (Sinusoidal Pulse Width Modulation), hybrid modulation strategies were introduced corresponding to hybrid topologies, and a multilevel SVPWM (Space Vector Pulse Width Modulation) technique based on phase-shifted theory was naturally produced. Simulation and experiment results prove that hybrid topologies and corresponding modulation strategies are valid, which lay a foundation for practical application of hybrid multilevel inverter topologies.

  12. A Long-Pulse Modulator for the TESLA Test Facility (TTF)

    Kaesler, W


    The long-pulse (1.6 ms) klystron modulator for TTF is a hardtube pulser using a Bouncer-circuit for droop compensation. It is built up with new advanced components representing industrial standards. The on-/off switch is a rugged 12 kV IGCT-stack with a fast 4kA turn-off capability. The 100 kJ storage capacitor bank contains only three capacitors with self-healing, segmented PP-foil technology. A new 100 kA solid-state switch based on light triggered thyristors (LTT) replaced the standard ignitrons as crowbar switches. The 300 kW high voltage power supply is based on modern switched mode technology.

  13. A dynamic CMOS multiplier for analog VLSI based on exponential pulse-decay modulation

    Massengill, Lloyd W.


    A clocked, charge-based, CMOS modulator circuit is presented. The circuit, which performs a semilinear multiplication function, has applications in arrayed analog VLSI architectures such as parallel filters and neural network systems. The design presented is simple in structure, uses no operational amplifiers for the actual multiplication function, and uses no power in the static mode. Two-quadrant weighting of an input signal is accomplished by control of the magnitude and decay time of an exponential current pulse, resulting in the delivery of charge packets to a shared capacitive summing bus. The cell is modular in structure and can be fabricated in a standard CMOS process. An analytical derivation of the operation of the circuit, SPICE simulations, and MOSIS fabrication results are presented. The simulation studies indicate that the circuit is inherently tolerant to temperature effects, absolute device sizing errors, and clock-feedthrough transients.


    LIU Rong; PAN Huachen; CHEN Ying


    A hybrid control strategy has been designed and developed for the electro-hydraulic position servo control system with generalized Pulse code modulation (GPCM), which is suitable for the area where the work condition is poor and a large flow rate is required. It is difficult to control the GPCM system because the system is discrete. With consideration of the stability and speediness of the GPCM position servo control system, a control strategy is developed through the theoretical and experimental analyses. The control strategy integrates the merits of Bang-Bang control, PID control and fuzzy control. With this hybrid control strategy, the electro hydraulic control system has good performances, and the servo control is carried out with GPCM through on-offvalves.

  15. A pulse-frequency modulation sensor using memristive-based inhibitory interconnections.

    Kavehei, Omid; Lee, Sang-Jin; Cho, Kyoung-Rok; Al-Sarawi, Said; Abbott, Derek


    This paper proposes a programmable inhibitory interconnection network between pixels in an array of novel low-voltage Schmitt-trigger-based PFM sensors that will be of interest for future applications in memristor-based early vision processing. In addition, a new low-power inverter-based pulse-frequency modulation (PFM) design and its integration with the network is also presented. To ensure no change in the memristors conductance in the network, the CMOS imager was designed for low voltage operation. That has resulted in a significant power reduction, better than 60%, and a comparable linear dynamic range when compared to published designs in the literature. The design was performed using a 0.13 um Samsung Electronics standard CMOS process, using 0.75 V supply voltage.

  16. Ultra-low-power wireless transmitter for neural prostheses with modified pulse position modulation.

    Goodarzy, Farhad; Skafidas, Stan E


    An ultra-low-power wireless transmitter for embedded bionic systems is proposed, which achieves 40 pJ/b energy efficiency and delivers 500 kb/s data using the medical implant communication service frequency band (402-405 MHz). It consumes a measured peak power of 200 µW from a 1.2 V supply while occupying an active area of 0.0016 mm(2) in a 130 nm technology. A modified pulse position modulation technique called saturated amplified signal is proposed and implemented, which can reduce the overall and per bit transferred power consumption of the transmitter while reducing the complexity of the transmitter architectures, and hence potentially shrinking the size of the implemented circuitry. The design is capable of being fully integrated on single-chip solutions for surgically implanted bionic systems, wearable devices and neural embedded systems.

  17. Predictive Pulse Pattern Current Modulation Scheme for Harmonic Reduction in Three-Phase Multidrive Systems

    Davari, Pooya; Yang, Yongheng; Zare, Firuz


    of them can lead to the cancellation of specific harmonics. This paper proposes a new cost-effective harmonic mitigation solution for multi-drive systems using a predictive pulse pattern current modulation control strategy. The proposed technique applies suitable interaction among parallel drive units......The majority of the industrial motor drive systems are equipped with the conventional line-commutated front-end rectifiers, and being one of the main sources of harmonics in the power line. While a parallel combination of these drive units elevates current quality issues, a proper arrangement...... at the rectification stage to synthesize sinusoidal input currents. The input voltage sensing is avoided in order to minimize the number of required sensors, and the grid synchronization also has been implemented based on a common Phase-Locked-Loop (PLL) using the DC-link capacitor voltage ripple. Experimental results...

  18. Comparison of WDM/Pulse-Position-Modulation (WDM/PPM) with Code/Pulse-Position-Swapping (C/PPS) Based on Wavelength/Time Codes

    Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V


    Pulse position modulation (PPM) signaling is favored in intensity modulated/direct detection (IM/DD) systems that have average power limitations. Combining PPM with WDM over a fiber link (WDM/PPM) enables multiple accessing and increases the link's throughput. Electronic bandwidth and synchronization advantages are further gained by mapping the time slots of PPM onto a code space, or code/pulse-position-swapping (C/PPS). The property of multiple bits per symbol typical of PPM can be combined with multiple accessing by using wavelength/time [W/T] codes in C/PPS. This paper compares the performance of WDM/PPM and C/PPS for equal wavelengths and bandwidth.

  19. Inter-island optical link demonstration using high-data-rate pulse-position modulation

    Bacher, Michael; Arnold, Felix; Thieme, Björn


    The growing data-rate demand on satellite communication systems has led to the increased interest in optical space communication solutions for uplinks and downlinks between satellites and ground stations. As one example for applications that benefit from higher data-rates offered by optical links, RUAG Space studied an uplink scenario from an Unmanned Aerial Vehicle (UAV) to a Geostationary Orbit (GEO), under the European Space Agency project formally known as "Optical Communications Transceiver for Atmospheric Links" (OCTAL). Particularly suitable for optical links through turbulent atmospheres are robust Pulse Position Modulation (PPM) schemes. Communication electronics using a Multi-Pulse PPM (MPPM) scheme have been developed, increasing the data-rate compared to traditional PPM at a constant peak-to-average ratio while allowing a widely configurable data-rate range. The communication system was tested together with a newly developed receiver and transmitter at a wavelength of 1055nm in a field test campaign on the Canary Islands, where the transmitter telescope was located on La Palma while the receiver was installed within the ESA Optical Ground Station on Tenerife. The nearly horizontal link between the two islands with a link distance of 142km allowed validation of relevant system performances under stringent atmospheric conditions. A data-rate of more than 360Mbps could be demonstrated using MPPM, while nearly 220Mbps could be achieved with traditional PPM, well exceeding the targeted data-rate of the studied UAV-to-GEO scenario. Following an introduction on the applied MPPM schemes, the architecture of the test setup is described, different modulation schemes are compared and the test results of this Inter-Island Test Campaign performed in October 2012 are presented.

  20. Pulse on Pulse

    Schmidt, Ulrik; Carlson, Merete


    Pulse on Pulse” investigates the relation between signifying processes and non-signifying material dynamism in the installation Pulse Room (2006-) by Mexican Canadian artist Rafael Lozano-Hemmer. In Pulse Room the sense of pulse is ambiguous. Biorhythms are transmitted from the pulsing energy...... and pulsating ‘room’. Hence, the visitors in Pulse Room are invited into a complex scenario that continuously oscillates between various aspects of signification (the light bulbs representing individual lives; the pulse itself as the symbolic ‘rhythm of life’) and instants of pure material processuality...... a multilayered sense of time and space that is central to the sensory experience of Pulse Room as a whole. Pulse Room is, at the very same time, an anthropomorfized archive of a past intimacy and an all-encompassing immersive environment modulating continuously in real space-time....

  1. Noise-immunity processing of digital multilevel pulse-amplitude modulation signals

    A. S. Makarenko


    Full Text Available Introduction. The main properties and features of spectral-effective multi-level pulse amplitude modulation digital signals at coherent reception are presented. It is shown that the phase locked loop circuit (PLL circuit used in the receiver is able to work at SNR > 5 dB.Object of the paper. We propose a new scheme of noise compensator at an intermediate frequency, allowing us to obtain increasing of SNR on 15–25 dB when error of PLL is equal zero. The noise compensator has the gain 8–18 dB at error of PLL = 33° that is able to work at SNR = 5 dB. As result, we can obtain a required SNR for determined BER in systems with multi-level PAM.Conclusions. This technical solution makes a spectrally-efficient system using multi-level amplitude modulation is also energy efficient, forward-looking and competitive. The power transmitters of cell phones and radio relay lines of mobile communication systems can be reduced by 10 times or at the same transmitter power improvement the quality of communication or range is presented.

  2. Coherent lidar modulated with frequency stepped pulse trains for unambiguous high duty cycle range and velocity sensing in the atmosphere

    Lindelöw, Per Jonas Petter; Mohr, Johan Jacob


    Range unambiguous high duty cycle coherent lidars can be constructed based on frequency stepped pulse train modulation, even continuously emitting systems could be envisioned. Such systems are suitable for velocity sensing of dispersed targets, like the atmosphere, at fast acquisition rates...

  3. Microprocessor-Controlled Pulsed NQR Spectrometer for Automatic Acquisition of Zeeman Perturbed Nuclear Quadrupole Spin Echo Envelope Modulations (ZSEEM )

    Reddy, Narsimha; Bhavsar, Arun; Narasimhan, P. T.


    A simple microprocessor-controlled pulsed NQR spectrometer system has been developed with the capability to acquire Zeeman perturbed spin echo envelope modulations (ZSEEM). The CPU of the system is based on the Intel Corporation 8085 A microprocessor. The performance of the spectrometer is illustrated with the presentation of ZSEEM spectra of NaClO3 and KClO3.

  4. A new method for compensation of the effect of charging transformer's leakage inductance on PFN voltage regulation in Klystron pulse modulators

    Patel, Akhil; Kale, Umesh; Shrivastava, Purushottam


    The Line type modulators have been widely used to generate high voltage rectangular pulses to power the klystron for high power RF generation. In Line type modulator, the Pulse Forming Network (PFN) which is a cascade combination of lumped capacitors and inductors is used to store the electrical energy. The charged PFN is then discharged into a klystron by firing a high voltage Thyratron switch. This discharge generates a high voltage rectangular pulse across the klystron electrodes. The amplitude and phase of Klystron's RF output is governed by the high voltage pulse amplitude. The undesired RF amplitude and phase stability issues arises at the klystron's output due to inter-pulse and during the pulse amplitude variations. To reduce inter-pulse voltage variations, the PFN is required to be charged at the same voltage after every discharge cycle. At present, the combination of widely used resonant charging and deQing method is used to regulate the pulse to pulse PFN voltage variations but the charging transformer's leakage inductance puts an upper bound on the regulation achievable by this method. Here we have developed few insights of the deQing process and devised a new compensation method to compensate this undesired effect of charging transformer's leakage inductance on the pulse to pulse PFN voltage stability. This compensation is accomplished by the controlled partial discharging of the split PFN capacitor using a low voltage MOSFET switch. Theoretically, very high values of pulse to pulse voltage stability may be achieved using this method. This method may be used in deQing based existing modulators or in new modulators, to increase the pulse to pulse voltage stability, without having a very tight bound on charging transformer's leakage inductance. Given a stable charging power supply, this method may be used to further enhance the inter-pulse voltage stability of modulators which employ the direct charging, after replacing the direct charging with the

  5. Propagation of pulse fluctuations in single-mode fibers.

    Marcuse, D


    An earlier paper [Applied Optics 19, 1653 (1980)] dealt with the ensemble averages of pulses propagating in single-mode fibers. In this paper we discuss pulse fluctuations. The light pulses are generated by modulation of the power of a continuously operating light source consisting of N discrete sinusoidal frequencies randomly phased relative to each other. The fixed amplitudes of the sinusoidal frequency components of the source are adjusted to fit into a Gaussian envelope, and the modulating pulse has a Gaussian distribution in time. This mathematical model approximates a laser light source operating in several free-running longitudinal modes. We find that the fluctuations of the modulated light pulses can die out if the pulses travel a long distance in a dispersive fiber, provided the spacings between the sinusoidal frequency components of the light source are larger than the spectral width of the modulating signal. If the source frequency components are spaced more closely than the spectral width of the modulating pulse, fluctuations persist indefinitely independent of fiber length. However, in a practical system, whose input pulse is only about half as short as the output pulse, fluctuations are practically unaffected by transmission through a fiber.

  6. Exposure to ELF-pulse modulated X band microwaves increases in vitro human astrocytoma cell proliferation.

    Pérez-Castejón, C; Pérez-Bruzón, R N; Llorente, M; Pes, N; Lacasa, C; Figols, T; Lahoz, M; Maestú, C; Vera-Gil, A; Del Moral, A; Azanza, M J


    Common concern about the biological effects of electromagnetic fields (EMF) is increasing with the expansion of X-band microwaves (MW). The purpose of our work was to determine whether exposure to MW pulses in this range can induce toxic effects on human astrocytoma cells. Cultured astrocytoma cells (Clonetics line 1321N1) were submitted to 9.6 GHz carrier, 90% amplitude modulated by extremely low frequency (ELF)-EMF pulses inside a Gigahertz Transversal Electromagnetic Mode cell (GTEM-cell). Astrocytoma cultures were maintained inside a GTEM-incubator in standard culture conditions at 37+/-0.1 degrees C, 5% CO2, in a humidified atmosphere. Two experimental conditions were applied with field parameters respectively of: PW 100-120 ns; PRF 100-800 Hz; PRI 10-1.25 ms; power 0.34-0.60 mW; electric field strength 1.25-1.64 V/m; magnetic field peak amplitude 41.4-54.6 microOe. SAR was calculated to be 4.0 x 10-4 W/Kg. Astrocytoma samples were grown in a standard incubator. Reaching 70-80% confluence, cells were transferred to a GTEM-incubator. Experimental procedure included exposed human astrocytoma cells to MW for 15, 30, 60 min and 24 h and unexposed sham-control samples. Double blind method was applied. Our results showed that cytoskeleton proteins, cell morphology and viability were not modified. Statistically significant results showed increased cell proliferation rate under 24h MW exposure. Hsp-70 and Bcl-2 antiapoptotic proteins were observed in control and treated samples, while an increased expression of connexin 43 proteins was found in exposed samples. The implication of these results on increased proliferation is the subject of our current research.

  7. Modulated Pulse Generations in a Laser-diode-pumped Passively Q-switched Intracavity-frequency-doubling Nd∶YVO4 Laser

    郑加安; 赵圣之; 陈磊


    The investigative results of modulated pulse output from an LD end-pumped passively Q-switched intracavity-frequency-doubling Nd∶YVO4/KTP laser with Cr4+∶YAG saturable absorber are presented. The numerical stimulations of these modulated pulses are carried out basing on the rate equations. It indicated that the modulations are attribute to the frequency beating of two eigenstates of the resonant polarized modes. The theoretical calculations are in good agreement with the experimental observations.

  8. 人眼安全高重频窄脉宽单模全光纤激光器特性研究%Characteristics of eye-safe high repetition frequency narrow pulse width single mode all fiber laser

    张鑫; 刘源; 贺岩; 杨燕; 侯霞; 陈卫标


    介绍了基于主振荡功率放大结构的人眼安全全光纤激光器。首先对比了电光调制及直接调制产生的种子激光在百kHz重复频率、纳秒级脉冲宽度的激光放大器中优缺点,综合系统需求选择直接调制方式;之后对窄脉冲单模放大中出现的脉冲分裂现象进行了研究,选用10μm纤芯的双包层铒镱共掺光纤,仅通过两级放大即获得了1550 nm,重复频率为200 kHz,脉冲宽度为4.07 ns,峰值功率为1.02 kW的单模激光输出。具有结构紧凑、稳定可靠的特点,可用于三维视频激光雷达。%An eye-safe, all fiber, single mode, fiber laser based on master oscillator power amplifier configuration was presented. The advantages and disadvantages were compared between using a directly modulated diode laser and an electro-optical modulated continuous-wave diode as seed laser in sub-Mega Hertz, nanosecond fiber amplifier. The main restriction of power scaling in nanosecond fiber laser was pulse split. 10μm core double cladding erbium ytterbium co-doped fiber was employed as gain fiber of power amplifier. The directly modulated seed laser was then amplified by only two stage amplifiers. Finally, a peak power of 1.02 kW with 4.07 ns pulse duration at 200 kHz pulse repetition frequency with single-mode output was obtained and it is applicable in three dimensional video imaging lidar system.

  9. Multi-pulse frequency shifted (MPFS) multiple access modulation for ultra wideband

    Nekoogar, Faranak [San Ramon, CA; Dowla, Farid U [Castro Valley, CA


    The multi-pulse frequency shifted technique uses mutually orthogonal short duration pulses o transmit and receive information in a UWB multiuser communication system. The multiuser system uses the same pulse shape with different frequencies for the reference and data for each user. Different users have a different pulse shape (mutually orthogonal to each other) and different transmit and reference frequencies. At the receiver, the reference pulse is frequency shifted to match the data pulse and a correlation scheme followed by a hard decision block detects the data.

  10. High power microwave system based on power combining and pulse compression of conventional klystrons

    Xiong, Zheng-Feng; Cheng, Cheng; Ning, Hui; Tang, Chuan-Xiang


    A high power microwave system based on power combining and pulse compression of conventional klystrons is introduced in this paper. This system mainly consists of pulse modulator, power combiner, driving source of klystrons and pulse compressor. A solid state induction modulator and pulse transformer were used to drive two 50 MW S-band klystrons with pulse widths 4 {\\mu}s in parallel, after power combining and pulse compression, the tested peak power had reached about 210 MW with pulse widths nearly 400 ns at 25 Hz, while the experimental maximum output power was just limited by the power capacity of loads. This type of high power microwave system has widely application prospect in RF system of large scale particle accelerators, high power radar transmitters and high level electromagnetic environment generators.

  11. A micropower supervisor for wireless nodes with a digital pulse frequency modulator battery monitor

    Carloni, Mirko; d'Aparo, Rocco; Scorrano, Pierpaolo; Naticchia, Berardo; Conti, Massimo


    In the last few years the increased development of wireless technologies led to the development of micropower devices with power management and real time power control, aimed to maximize the battery life time.1 The main and simplest method to estimate residual battery life time is by voltage measurement. This kind of measurement is simple but is useless in many cases, especially when long term Lithium-Thionyl chloride batteries are used, since its voltage is flat for more than 90% of the battery discharge. In this case, a current control should be used. However, these kinds of devices have various problems as a limited range of measurement and not negligible quiescent current that may distort the measurements. In this work we developed a micropower supervisor for wireless sensor nodes with a charge battery monitor, whose features are aimed at solving the problems just described. The current measured by a sense resistor, is filtered by a super-capacitor, amplified by a current sense amplifier and then fed to a voltage to pulse frequency modulator. In this way, the charge consumption can be estimated without the saturation of the current sense amplifier, even if the wireless node consumes time limited high current spikes, for example during transmission.

  12. A monolithic 56 Gb/s silicon photonic pulse-amplitude modulation transmitter

    Xiong, Chi; Proesel, Jonathan E; Orcutt, Jason S; Haensch, Wilfried; Green, William M J


    Silicon photonics promises to address the challenges for next-generation short-reach optical interconnects. Growing bandwidth demand in hyper-scale data centers and high-performance computing motivates the development of faster and more-efficient silicon photonics links. While it is challenging to raise the serial line rate, further scaling of the data rate can be realized by, for example, increasing the number of parallel fibers, increasing the number of wavelengths per fiber, and using multi-level pulse-amplitude modulation (PAM). Among these approaches, PAM has a unique advantage because it does not require extra lasers or a costly overhaul of optical fiber cablings within the existing infrastructure. Here, we demonstrate the first fully monolithically integrated silicon photonic four-level PAM (PAM-4) transmitter operating at 56 Gb/s and demonstrate error-free transmission (bit-error-rate < 10$^{-12}$) up to 50 Gb/s without forward error correction. The superior PAM-4 waveform is enabled by optimizatio...

  13. Negative Kerr nonlinearity of graphene as seen via chirped-pulse-pumped self-phase modulation

    Vermeulen, Nathalie; Cheng, JinLuo; Pasternak, Iwona; Krajewska, Aleksandra; Ciuk, Tymoteusz; Strupinski, Wlodek; Thienpont, Hugo; Van Erps, Jurgen


    We experimentally demonstrate a negative Kerr nonlinearity for quasi-undoped graphene. Hereto, we introduce the method of chirped-pulse-pumped self-phase modulation and apply it to graphene-covered silicon waveguides at telecom wavelengths. The extracted Kerr-nonlinear index for graphene equals n2,gr = -10^(-13) m^2/W. Whereas the sign of n2,gr turns out to be negative in contrast to what has been assumed so far, its magnitude is in correspondence with that observed in earlier experiments. Graphene's negative Kerr nonlinearity strongly impacts how graphene should be exploited for enhancing the nonlinear response of photonic (integrated) devices exhibiting a positive nonlinearity. It also opens up the possibility of using graphene to annihilate unwanted nonlinear effects in such devices, to develop unexplored approaches for establishing Kerr processes, and to extend the scope of the "periodic poling" method often used for second-order nonlinearities towards third-order Kerr processes. Because of the generic na...

  14. Investigating emotional top down modulation of ambiguous faces by single pulse TMS on early visual cortices

    Zachary Adam Yaple


    Full Text Available Top-down processing is a mechanism in which memory, context and expectation are used to perceive stimuli. For this study we investigated how emotion content, induced by music mood, influences perception of happy and sad emoticons. Using single pulse TMS we stimulated right occipital face area (rOFA, primary visual cortex (V1 and vertex while subjects performed a face-detection task and listened to happy and sad music. At baseline, incongruent audio-visual pairings decreased performance, demonstrating dependence of emotion while perceiving ambiguous faces. However, performance of face identification decreased during rOFA stimulation regardless of emotional content. No effects were found between Cz and V1 stimulation. These results suggest that while rOFA is important for processing faces regardless of emotion, V1 stimulation had no effect. Our findings suggest that early visual cortex activity may not integrate emotional auditory information with visual information during emotion top-down modulation of faces.

  15. Analysis of LAPAN-IPB image lossless compression using differential pulse code modulation and huffman coding

    Hakim, P. R.; Permala, R.


    LAPAN-A3/IPB satellite is the latest Indonesian experimental microsatellite with remote sensing and earth surveillance missions. The satellite has three optical payloads, which are multispectral push-broom imager, digital matrix camera and video camera. To increase data transmission efficiency, the multispectral imager data can be compressed using either lossy or lossless compression method. This paper aims to analyze Differential Pulse Code Modulation (DPCM) method and Huffman coding that are used in LAPAN-IPB satellite image lossless compression. Based on several simulation and analysis that have been done, current LAPAN-IPB lossless compression algorithm has moderate performance. There are several aspects that can be improved from current configuration, which are the type of DPCM code used, the type of Huffman entropy-coding scheme, and the use of sub-image compression method. The key result of this research shows that at least two neighboring pixels should be used for DPCM calculation to increase compression performance. Meanwhile, varying Huffman tables with sub-image approach could also increase the performance if on-board computer can support for more complicated algorithm. These results can be used as references in designing Payload Data Handling System (PDHS) for an upcoming LAPAN-A4 satellite.

  16. Study on self-frequency-shift of femtosecond pulse in nonlinear dispersion medium using time-resolved cross-phase modulation method

    赵应桥; 朱鹤元; 刘建华; 孙迭篪; 李富铭


    A time-resolved cross-phase modulation method combined with a modified nonlinear Schrodinger equation is used to study the effects of nonlinear response time on the propagation of ultrashort pulses in nonlinear dispersion media. Evolution of cross-phase modulation spectrum with the different time delay between the probe pulse and pump pulse is simulated using split-step Fourier method. It is shown that both normal self-frequency-shift-red-shift and abnormal self-frequency-shift-blue-shift can occur in the frequency domain for the probe pulse, and a satisfactory theoretical interpretation is given.

  17. Control over few-photon pulses by a time-periodic modulation of the photon emitter coupling

    Pletyukhov, Mikhail; Pedersen, Kim G. L.; Gritsev, Vladimir


    We develop a Floquet scattering formalism for the description of quasistationary states of microwave photons in a one-dimensional waveguide interacting with a nonlinear cavity by means of a periodically modulated coupling. This model is inspired by the recent progress in engineering of tunable coupling schemes with superconducting qubits. We argue that our model can realize the quantum analog of an optical chopper. We find strong periodic modulations of the transmission and reflection envelopes in the scattered few-photon pulses, including photon compression and blockade, as well as dramatic changes in statistics. Our theoretical analysis allows us to explain these nontrivial phenomena as arising from nonadiabatic memory effects.

  18. Generation of ultrahigh frequency air microplasma in a magnetic loop and effects of pulse modulation on operation

    Taghioskoui, Mazdak; Perlow, Joshua; Zaghloul, Mona; Montaser, Akbar


    An atmospheric pressure air microplasma (APAMP) source was developed under ambient conditions using a magnetic loop at an operating frequency of 740 MHz. A self-igniting, stable APAMP was generated at 9.5 W. Pulse modulation (PM) was applied to the ultra high frequency signal. The effects of PM on self-ignition and operation of the APAMP source were studied by using a square wave modulating signal in the frequency range of 5-30 KHz. With the application of PM on the APAMP, in the best case, the plasma self-ignites and is sustained at 2.5 W.

  19. Observation of a Long-Wavelength Hosing Modulation of a High-Intensity Laser Pulse in Underdense Plasma

    Kaluza, M. C.; Mangles, S. P. D.; Thomas, A. G. R.; Najmudin, Z.; Dangor, A. E.; Murphy, C. D.; Collier, J. L.; Divall, E. J.; Foster, P. S.; Hooker, C. J.; Langley, A. J.; Smith, J.; Krushelnick, K.


    We report the first experimental observation of a long-wavelength hosing modulation of a high-intensity laser pulse. Side-view images of the scattered optical radiation at the fundamental wavelength of the laser reveal a transverse oscillation of the laser pulse during its propagation through underdense plasma. The wavelength of the oscillation λhosing depends on the background plasma density ne and scales as λhosing˜ne-3/2. Comparisons with an analytical model and two-dimensional particle-in-cell simulations reveal that this laser hosing can be induced by a spatiotemporal asymmetry of the intensity distribution in the laser focus which can be caused by a misalignment of the parabolic focusing mirror or of the diffraction gratings in the pulse compressor.

  20. Mask-Free Patterning of High-Conductivity Metal Nanowires in Open Air by Spatially Modulated Femtosecond Laser Pulses.

    Wang, Andong; Jiang, Lan; Li, Xiaowei; Liu, Yang; Dong, Xianzi; Qu, Liangti; Duan, Xuanming; Lu, Yongfeng


    A novel high-resolution nanowire fabrication method is developed by thin-film patterning using a spatially modulated femtosecond laser pulse. Deep subwavelength (≈1/13 of the laser wavelength) and high conductivity (≈1/4 of the bulk gold) nanowires are fabricated in the open air without using masks, which offers a single-step arbitrary direct patterning approach for electronics, plasmonics, and optoelectronics nanodevices.

  1. GABAergic inhibition modulates intensity sensitivity of temporally patterned pulse trains in the inferior collicular neurons in big brown bats.

    Luan, Rui-Hong; Wu, Fei-Jian; Jen, Philip H-S; Sun, Xin-De


    The echolocating big brown bats (Eptesicus fuscus) emit trains of frequency-modulated (FM) biosonar signals with duration, amplitude, repetition rate, and sweep structure changing systematically during interception of their prey. In the present study, the sound stimuli of temporally patterned pulse trains at three different pulse repetition rates (PRRs) were used to mimic the sounds received during search, approach, and terminal stages of echolocation. Electrophysiological method was adopted in recordings from the inferior colliculus (IC) of midbrain. By means of iontophoretic application of bicuculline, the effect of GABAergic inhibition on the intensity sensitivity of IC neurons responding to three different PRRs of 10, 30 and 90 pulses per second (pps) was examined. The rate-intensity functions (RIFs) were acquired. The dynamic range (DR) of RIFs was considered as a criterion of intensity sensitivity. Comparing the average DR of RIFs at different PRRs, we found that the intensity sensitivity of some neurons improved, but that of other neurons decayed when repetition rate of stimulus trains increased from 10 to 30 and 90 pps. During application of bicuculline, the number of impulses responding to the different pulse trains increased under all stimulating conditions, while the DR differences of RIFs at different PRRs were abolished. The results indicate that GABAergic inhibition was involved in modulating the intensity sensitivity of IC neurons responding to pulse trains at different PRRs. Before and during bicuculline application, the percentage of changes in responses was maximal in lower stimulus intensity near to the minimum threshold (MT), and decreased gradually with the increment of stimulus intensity. This observation suggests that GABAergic inhibition contributes more effectively to the intensity sensitivity of the IC neurons responding to pulse trains at lower sound level.

  2. The High Time Resolution Universe Survey - V: Single-pulse energetics and modulation properties of 315 pulsars

    Burke-Spolaor, S; Bailes, M; Bates, S D; Bhat, N D R; Burgay, M; Champion, D J; D'Amico, N; Keith, M J; Kramer, M; Levin, L; Possenti, S Milia A; Stappers, B; van Straten, W


    We report on the pulse-to-pulse energy distributions and phase-resolved modulation properties for catalogued pulsars in the southern High Time Resolution Universe intermediate-latitude survey. We selected the 315 pulsars detected in a single-pulse search of this survey, allowing a large sample unbiased regarding any rotational parameters of neutron stars. We found that the energy distribution of many pulsars is well-described by a log-normal distribution, with few deviating from a small range in log-normal scale and location parameters. Some pulsars exhibited multiple energy states corresponding to mode changes, and implying that some observed "nulling" may actually be a mode-change effect. PSRJ1900-2600 was found to emit weakly in its previously-identified "null" state. We found evidence for another state-change effect in two pulsars, which show bimodality in their nulling time scales; that is, they switch between a continuous-emission state and a single-pulse-emitting state. Large modulation occurs in many ...

  3. Hybrid pulse position modulation and binary phase shift keying subcarrier intensity modulation for free space optics in a weak and saturated turbulence channel.

    Faridzadeh, Monire; Gholami, Asghar; Ghassemlooy, Zabih; Rajbhandari, Sujan


    In this paper a hybrid modulation scheme based on pulse position modulation (PPM) and binary phase shift keying subcarrier intensity modulation (BPSK-SIM) schemes for free-space optical communications is proposed. The analytical bit error rate (BER) performance is investigated in weak and saturated turbulence channels and results are verified with the simulation data. Results show that performance of PPM-BPSK-SIM is superior to BPSK-SIM in all turbulence regimes; however, it outperforms 2-PPM for the turbulence variance σ(1)(2)>0.2. PPM-BPSK-SIM offers a signal-to-noise ratio (SNR) gain of 50 dB in the saturation regime compared to BPSK at a BER of 10(-6). The SNR gain in comparison to PPM improves as the strength of the turbulence level increases.

  4. Design and Simulation of Dc-Dc Converter for Fuel Cell Operated Vehicle with Single Reference Six Pulse Modulation



    Full Text Available : Even though electrical vehicle concept is introduced in early 1800’s, it gained importance in past couple of decades due to growing conscience on environmental aspects. Different types of electrical vehicles are manufactured in the past centuries and now onboard generation is seems to be promising by fulfilling the needs of a vehicle. Fuel cells or fuel cell stack produces typically 32-68V of EMF, which has to be conditioned before it fed to motor. The conditioning involves two stages DCDC conversion and then to DC-AC conversion .DC-AC conversion is done through inverter. For DC-DC to conversion various topologies are proposed such as fly back, forward, buck-boost are proposed. This paper deals with the front end DC-DC converter and inverter switching. A hybrid modulation scheme is used to produce pulses to switch the source end full bridge rectifier and inverter at load end. In this modulation scheme high frequency pulses given to full bridge rectifier and 33% modulation scheme based pulses are produced for inverter switching.

  5. Pulse oximeter using a gain-modulated avalanche photodiode operated in a pseudo lock-in light detection mode

    Miyata, Tsuyoshi; Iwata, Tetsuo; Araki, Tsutomu


    We propose a reflection-type pulse oximeter, which employs two pairs of a light-emitting diode (LED) and a gated avalanche photodiode (APD). One LED is a red one with an emission wavelength λ = 635 nm and the other is a near-infrared one with that λ = 945 nm, which are both driven with a pulse mode at a frequency f (=10 kHz). Superposition of a transistor-transistor-logic (TTL) gate pulse on a direct-current (dc) bias, which is set so as not exceeding the breakdown voltage of each APD, makes the APD work in a gain-enhanced operation mode. Each APD is gated at a frequency 2f (=20 kHz) and its output signal is fed into a laboratory-made lock-in amplifier that works in synchronous with the pulse modulation signal of each LED at a frequency f (=10 kHz). A combination of the gated APD and the lock-in like signal detection scheme is useful for the reflection-type pulse oximeter thanks to the capability of detecting a weak signal against a large background (BG) light.

  6. Repetition rate tunable ultra-short optical pulse generation based on electrical pattern generator

    Xin Fu; Hongming Zhang; Meng Yan; Minyu Yao


    @@ An actively mode-locked laser with tunable repetition rate is proposed and experimentally demonstrated based on a programmable electrical pattern generator.By changing the repetition rate of the electrical patterns applied on the in-cavity modulator, the repetition rate of the output optical pulse sequences changes accordingly while the pulse width of the optical pulse train remains almost constant.In other words, the output ultra-short pulse train has a tunable duty cycle.In a proof-of-principle experiment, optical pulses with repetition rates of 10, 5, 2.5 and 1.25 GHz are obtained by adjusting the electrical pattern applied on the in-cavity modulator while their pulse widths remain almost unchanged.

  7. 空间矢量脉宽调制在离散VSC-HVDC中的应用%Space Vector Pulse Width Modulation Applied in Discrete VSC-HVDC




  8. 基于PSCAD/EMTDC的空间矢量PWM仿真研究%Simulation study of space vector pulse width modulation based on PSCAD/EMTDC

    戴武昌; 尚尔发; 王健; 陶晶涛



  9. A Time-Domain Asymptotic Approach to Predict Saddle-Node and Period Doubling Bifurcations in Pulse Width Modulated Piecewise Linear Systems

    El Aroudi A.


    Full Text Available In this paper closed-form conditions for predicting the boundary of period-doubling (PD bifurcation or saddle-node (SN bifurcation in a class of PWM piecewise linear systems are obtained from a time-domain asymptotic approach. Examples of switched system considered in this study are switching dc-dc power electronics converters, temperature control systems and hydraulic valve control systems among others. These conditions are obtained from the steady-state discrete-time model using an asymptotic approach without resorting to frequency-domain Fourier analysis and without using the monodromy or the Jacobian matrix of the discrete-time model as it was recently reported in the existing literature on this topic. The availability of such design-oriented boundary expressions allows to understand the effect of the different parameters of the system upon its stability and its dynamical behavior.

  10. Realization and Development of Application of Digital Pulse Width Modulation%数字PWM技术的实现及应用进展

    张怡; 姜岩峰



  11. Study on Method of the Digital Pulse Width Modulation%数字脉宽调制方法的研究



    Based on introduction of the integrated DSP motor controller ADMC331 and its PWM controller, this paper made analysis and comparision of the single and double digital PWM modes, and put forward the basic principles on the choice of the criterion of the PWM modes.Finally, it gives the corresponding results of the experiment that is done on a three-phase ACmotor voltage source inverter.%借鉴集成DSP电机控制器ADMC331及其PWM控制器结构,对单边和双边数字脉宽调制方式进行了比较,提出了脉宽调制方式选择的基本原则,以三相交流电机电压型逆变器做实验研究,得出了相应的实验结果.

  12. Effect of selective area growth mask width on multi-quantum-well electroabsorption modulated lasers investigated by synchrotron radiation X-ray microprobe

    Mino, Lorenzo, E-mail: [Department of Inorganic, Materials and Physical Chemistry, NIS Centre of Excellence and INSTM Unit, University of Turin, Via P. Giuria 7, I-10125 Turin (Italy); Agostino, Angelo [Department of General and Organic Chemistry, NIS Centre of Excellence, University of Turin, Massimo D' Azeglio 48, I-10125 Turin (Italy); Codato, Simone [Avago Technologies Italy S.r.l., Torino Technology Centre, Via G. Schiaparelli 12, 10148 Turin (Italy); Martinez-Criado, Gema [ESRF, 6 rue Jules Horowitz, BP220, F-38043 Grenoble CEDEX (France); Lamberti, Carlo [Department of Inorganic, Materials and Physical Chemistry, NIS Centre of Excellence and INSTM Unit, University of Turin, Via P. Giuria 7, I-10125 Turin (Italy)


    High performance optoelectronic devices require monolithic integration of different functions at chip level. This is the case of multi-quantum well (MQW) electroabsorption modulated laser (EML), employed in long-distance, high-frequency optical fiber communication applications, which is realized exploiting the selective area growth (SAG) technique. Optimization of the growth parameters is carried out by empirical approaches since a direct characterization of the MQW is not possible with laboratory X-ray sources, owing to the micrometer-variation of composition and thickness inherent to the SAG technique. In this work we combined micrometer-resolved photoluminescence with synchrotron radiation micrometer-resolved X-ray fluorescence to study the effect of different SAG masks on the electronic properties and chemical composition of the SAG MQW EML device.

  13. Development of a Novel Non-Equilibrium Pulsed Plasma Ignition Module for High Altitude Turbojets Project

    National Aeronautics and Space Administration — An experimental research program focusing on design, development, and testing of a novel nonequilibrium plasma ignition module is proposed. The ignition module will...

  14. A Pulsed Coding Technique Based on Optical UWB Modulation for High Data Rate Low Power Wireless Implantable Biotelemetry

    Andrea De Marcellis


    Full Text Available This paper reports on a pulsed coding technique based on optical Ultra-wideband (UWB modulation for wireless implantable biotelemetry systems allowing for high data rate link whilst enabling significant power reduction compared to the state-of-the-art. This optical data coding approach is suitable for emerging biomedical applications like transcutaneous neural wireless communication systems. The overall architecture implementing this optical modulation technique employs sub-nanosecond pulsed laser as the data transmitter and small sensitive area photodiode as the data receiver. Moreover, it includes coding and decoding digital systems, biasing and driving analogue circuits for laser pulse generation and photodiode signal conditioning. The complete system has been implemented on Field-Programmable Gate Array (FPGA and prototype Printed Circuit Board (PCB with discrete off-the-shelf components. By inserting a diffuser between the transmitter and the receiver to emulate skin/tissue, the system is capable to achieve a 128 Mbps data rate with a bit error rate less than 10−9 and an estimated total power consumption of about 5 mW corresponding to a power efficiency of 35.9 pJ/bit. These results could allow, for example, the transmission of an 800-channel neural recording interface sampled at 16 kHz with 10-bit resolution.

  15. Reaching white-light radiation source of ultrafast laser pulses with tunable peak power using nonlinear self-phase modulation in neon gas

    Tawfik, Walid


    A source of white-light radiation that generates few-cycle pulses with controlled peak power values has been developed. These ultrafast pulses have been observed by spectral broadening of 32 fs pulses through nonlinear self-phase modulation in a neon-filled hollow-fiber then compressed with a pair of chirped mirrors for dispersion compensation. The observed pulses reached transform-limited duration of 5.77 fs and their peak power values varied from 57 GW up to 104 GW at repetition rate of 1 kHz. Moreover, the applied method is used for a direct tuning of the peak power of the output pulses through varying the chirping of the input pulses at different neon pressures. The observed results may give an opportunity to control the ultrafast interaction dynamics on the femtosecond time scale and facilitate the regeneration of attosecond pulses.

  16. Transient features in nanosecond pulsed electric fields differentially modulate mitochondria and viability.

    Stephen J Beebe

    Full Text Available It is hypothesized that high frequency components of nanosecond pulsed electric fields (nsPEFs, determined by transient pulse features, are important for maximizing electric field interactions with intracellular structures. For monopolar square wave pulses, these transient features are determined by the rapid rise and fall of the pulsed electric fields. To determine effects on mitochondria membranes and plasma membranes, N1-S1 hepatocellular carcinoma cells were exposed to single 600 ns pulses with varying electric fields (0-80 kV/cm and short (15 ns or long (150 ns rise and fall times. Plasma membrane effects were evaluated using Fluo-4 to determine calcium influx, the only measurable source of increases in intracellular calcium. Mitochondria membrane effects were evaluated using tetramethylrhodamine ethyl ester (TMRE to determine mitochondria membrane potentials (ΔΨm. Single pulses with short rise and fall times caused electric field-dependent increases in calcium influx, dissipation of ΔΨm and cell death. Pulses with long rise and fall times exhibited electric field-dependent increases in calcium influx, but diminished effects on dissipation of ΔΨm and viability. Results indicate that high frequency components have significant differential impact on mitochondria membranes, which determines cell death, but lesser variances on plasma membranes, which allows calcium influxes, a primary determinant for dissipation of ΔΨm and cell death.

  17. Transient features in nanosecond pulsed electric fields differentially modulate mitochondria and viability.

    Beebe, Stephen J; Chen, Yeong-Jer; Sain, Nova M; Schoenbach, Karl H; Xiao, Shu


    It is hypothesized that high frequency components of nanosecond pulsed electric fields (nsPEFs), determined by transient pulse features, are important for maximizing electric field interactions with intracellular structures. For monopolar square wave pulses, these transient features are determined by the rapid rise and fall of the pulsed electric fields. To determine effects on mitochondria membranes and plasma membranes, N1-S1 hepatocellular carcinoma cells were exposed to single 600 ns pulses with varying electric fields (0-80 kV/cm) and short (15 ns) or long (150 ns) rise and fall times. Plasma membrane effects were evaluated using Fluo-4 to determine calcium influx, the only measurable source of increases in intracellular calcium. Mitochondria membrane effects were evaluated using tetramethylrhodamine ethyl ester (TMRE) to determine mitochondria membrane potentials (ΔΨm). Single pulses with short rise and fall times caused electric field-dependent increases in calcium influx, dissipation of ΔΨm and cell death. Pulses with long rise and fall times exhibited electric field-dependent increases in calcium influx, but diminished effects on dissipation of ΔΨm and viability. Results indicate that high frequency components have significant differential impact on mitochondria membranes, which determines cell death, but lesser variances on plasma membranes, which allows calcium influxes, a primary determinant for dissipation of ΔΨm and cell death.

  18. Modulations in the light of the firefly

    Anurup Gohain Barua


    Continuous light could be produced from the firefly by making it inhale vapours of ethyl acetate. Here we perform such a control experiment on the Indian species of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera : Lampyridae : Luciolinae), and analyse the light in the microsecond time scale. The amplitude of the continuous train of triangular pulses is apparently altered in accordance with the instantaneous values of a hypothetical signal, which exhibits pulse amplitude modulation (PAM). In addition to sampling in amplitude, this scheme apparently provides sampling in time, representing pulse width modulation (PWM). A Fourier transform spectrum of this waveform shows the `carrier’ frequency and the accompanying `side bands’.

  19. A novel scheme to generate 40-GHz CSRZ pulse trains using a 10-GHz dual-parallel Mach-Zehnder modulator

    Yanfei Xing; Caiyun Lou


    A new technique to generate 40-GHz carrier-suppressed return-to-zero (CSRZ) optical pulse trains using only a 10-GHz dual-parallel Mach-Zehnder modulator (MZM) is presented and experimentally demonstrated. The spectrum of the generated CSRZ pulses is calculated by simulation and compared with conventional MZM-based RZ and CSRZ pulse trains. The experimental results demonstrate that CSRZ pulse trains are obtained, and that the carrier and the unwanted 20-GHz low-frequency component are suppressed by 25 dB. The technique can also be extended to 160-GHz CSRZ pulse generation when 40-GHz devices are employed.%@@ A new technique to generate 40-GHz carrier-suppressed return-to-zero (CSRZ) optical pulse trains using only a 10-GHz dual-parallel Mach-Zehnder modulator (MZM) is presented and experimentally demonstrated. The spectrum of the generated CSRZ pulses is calculated by simulation and compared with conventional MZM-based RZ and CSRZ pulse trains. The experimental results demonstrate that CSRZ pulse trains are obtained, and that the carrier and the unwanted 20-GHz low-frequency component are suppressed by 25 dB. The technique can also be extended to 160-GHz CSRZ pulse generation when 40-GHz devices are employed.

  20. Visualization and analysis of modulated pulses in magnetic resonance by joint time-frequency representations.

    Köcher, S S; Heydenreich, T; Glaser, S J


    We study the utility of joint time-frequency representations for the analysis of shaped or composite pulses for magnetic resonance. Such spectrograms are commonly used for the visualization of shaped laser pulses in optical spectroscopy. This intuitive representation provides additional insight compared to conventional approaches, which exclusively show either temporal or spectral information. We focus on the short-time Fourier transform, which provides not only amplitude but also phase information. The approach is illustrated for broadband inversion pulses, multiple quantum excitation and broadband heteronuclear decoupling. The physical interpretation and validity of the approach is discussed.

  1. The matching pursuit approach based on the modulated Gaussian pulse for efficient guided-wave damage inspection

    Hong, Jin-Chul; Sun, Kyung Ho; Kim, Yoon Young


    The success of the guided-wave damage inspection technology depends not only on the generation and measurement of desired waveforms but also on the signal processing of the measured waves, but less attention has been paid to the latter. This research aims to develop an efficient signal processing technique especially suitable for the current guided-wave technology. To achieve this objective, the use of a two-stage matching pursuit approach based on the Gabor dictionary is proposed. Instead of truncated sine pulses commonly used in waveguide inspection, Gabor pulses, the modulated Gaussian pulses, are chosen as the elastic energy carrier to facilitate the matching pursuit algorithm. To extract meaningful waves out of noisy signals, a two-stage matching pursuit strategy is developed, which consists of the following: rough approximations with a set of predetermined parameters characterizing the Gabor pulse, and fine adjustments of the parameters by optimization. The parameters estimated from measured longitudinal elastic waves can be then directly used to assess not only the location but also the size of a crack in a rod. For the estimation of the crack size, in particular, Love's theory is incorporated in the matching pursuit analysis. Several experiments were conducted to verify the validity of the proposed approach in damage assessment.

  2. High-power Microwave Pulse Compression of Klystrons by Phase-Modulation of High-Q Storage Cavities

    Bossart, Rudolf; Mourier, J; Syratchev, I V; Tanner, L


    At the CERN linear electron accelerators LIL and CTF, the peak RF power from the 3GHz-klystrons was doubled by means of LIPS microwave pulse compressors. To produce constant RF power from the cavity-based pulse compressors, the klystrons were driven by a fast RF-phase modulation program. For the CLIC Test Facility CTF3, a new type of a Barrel Open Cavity (BOC) with a high quality factor Q0 has been developed. Contrary to LIPS with two resonant cavities, BOC operates with a single cavity supporting two orthogonal resonant modes TM 10,1,1 in the same cavity. For both LIPS and BOC storage cavities, it is important that the RF power reflected back to the klystron is minimal. This implies that the resonant frequencies, Q-factors and coupling factors of the two resonant modes of a pulse compressor are closely matched, and that the resonant frequencies are accurate to within a few KHz. The effects of small differences between the two orthogonal modes of the BOC cavity have been investigated. The dynamic pulse respon...

  3. Zero-Chirp Return-to-Zero Pulses Generation with Two Single-Driver z-Cut Mach-Zehnder Modulators

    QIN Xi; CAO Ji-Hong; ZHANG Feng; WANG Mu-Guang; ZHANG Jian-Yong; JIAN Shui-Sheng


    A novel method is proposed to suppress the frequency chirp of single-driver z-cut Mach-Zehnder modulators.Theoretical analysis shows that by multiplying the output pulses of a half clock frequency driving single-driver z-cut modulator with the one delayed odd multiple bit duration,the frequency chirp can be removed entirely,and return-to-zero(RZ)pulses with duty cycles of about 25% and 56% are obtained.An experimental scheme is proposed to validate the proposed method.The experimental results show that perfect 40 GHz zero-chirp RZ pulses can be obtained by using this scheme.

  4. Experimental study of propagation characteristics of a pulse-modulated surface-wave argon plasma at atmospheric pressure

    Chen, Chuan-Jie; Li, Shou-Zhe; Wu, Yue; Li, Zhen-Ye; Zhang, Jialiang; Wang, Yong-Xing


    An atmospheric-pressure, pulse-modulated surface wave argon plasma is investigated with respect to its propagation of the ionization front. The time-resolved photographs about the advance of the ionization front are taken using a high speed camera. The ionization front velocity and its rise time when propagating along the discharge tube are measured with respect to a series of values of input power, duty ratio, and the pulse repetition frequency. The interpretations are given on the basis of the ionization and diffusion processes. And it is also found that the reduced electric field and memory effect from previous discharge impose the influence on both the ionization front velocity and its rise time strongly.

  5. New space vector modulation technique for single-phase multilevel converters

    León Galván, José Ignacio; Portillo Guisado, Ramón Carlos; García Franquelo, Leopoldo; Vázquez Pérez, Sergio; Carrasco Solís, Juan Manuel; Domínguez, E


    Single-phase multilevel converters are suitable for medium power applications as photovoltaic systems and switched reluctance machines. An overview of possible modulation methods including carrier-based pulse width modulation and space vector modulation techniques for multilevel single-phase converters is presented. A new space vector modulation for this type of converters is proposed. This space vector modulation method is very simple presenting low computational cost. Different solutions fo...

  6. Broadband atomic-layer MoSsub>2sub> optical modulators for ultrafast pulse generations in the visible range.

    Zhang, Yuxia; Yu, Haohai; Zhang, Rui; Zhao, Gang; Zhang, Huaijin; Chen, Yanxue; Mei, Liangmo; Tonelli, Mauro; Wang, Jiyang


    Visible lasers are a fascinating regime, and their significance is illustrated by the 2014 Noble prizes in physics and chemistry. With the development of blue laser diodes (LDs), the LD-pumped solid-state visible lasers become a burgeoning direction today. Constrained by the scarce visible optical modulators, the solid-state ultrafast visible lasers are rarely realized. Based on the bandgap structure and optoelectronic properties of atomic-layer MoSsub>2sub>, it can be proposed that MoSsub>2sub> has the potential as a visible optical modulator. Here, by originally revealing layer-dependent nonlinear absorption of the atomic-layer MoSsub>2sub> in the visible range, broadband atomic-layer MoSsub>2sub> optical modulators for the visible ultrafast pulse generation are developed and selected based on the proposed design criteria for novel two-dimensional (2D) optical modulators. By applying the selected MoSsub>2sub> optical modulators in the solid-state praseodymium lasers, broadband mode-locked ultrafast lasers from 522 to 639 nm are originally realized. We believe that this Letter should promote the development of visible ultrafast photonics and further applications of 2D optoelectronic materials.

  7. Hybrid Asymmetric Space Vector Modulation for inverter based direct torque control induction motor drive

    Nandakumar Sundararaju


    Full Text Available This paper proposes novel hybrid asymmetric space vector modulation technique for inverter operated direct torque control induction motor drive. The hybridization process is performed by the combination of continuous asymmetric space vector modulation pulse width technique (ASVPWM and fuzzy operated discontinuous ASVPWM technique. Combination process is based on pulse mismatching technique. Pulse mismatching technique helps to reduce the active region of the switch. Finally, optimal pulses are applied to control the inverter. The optimal hybrid pulse condense switching losses of the inverter and also improves the operating performance of the direct torque control (DTC based drive system like smooth dynamic response in speed reversal, minimum torque error, settling time of speed. Simulation results of proposed hybrid asymmetric space vector pulse width modulation technique to direct torque control (HASVPWM-DTC approach has been carried out by using Matlab-Simulink environment.

  8. High Yield NiO Nanocubes from Bulk Nickel by Millisecond Pulse Width Laser Ablation%毫秒激光烧蚀镍靶高效率制备NiO纳米立方体

    田飞; 安俊超; 曹宏梅; 郭世珍; 孙景


    Long-pulse-width laser was used to ablate bulk nickel target immersed in circulating water to obtain NiO nanocubes in high yield.Transmission electron microscopy (TEM),X-ray diffraction (XRD),selected area electron diffraction(SAED) and energy dispersive spectromety (EDS) were employed to characterize the morphology and structure of the NiO nanocubes.The formation of NiO nanocubes is ascribed to the high temperature and high pressure (HTHP) conditions produced by high power density laser.The results show that when the laser power density is above 104 W/cm2,NiO nanocubes can be fabricated under laser ablation.The metal droplet is first generated by the laser with a power density higher than 104 W/cm2,which boil the surrounding liquid and produce a HTHP vapor due to the confinement of the liquid layer,and finally the surface reaction between the metal droplet and liquid take place to form NiO nanocubes.The laser ablating of bulk nickel target immersed in circulating water is a simple,green,high efficient method for the preparation of NiO nanocubes.%利用长脉宽毫秒激光烧蚀浸没在循环水中的金属镍靶制备了大量的氧化镍(NiO)纳米立方体,通过透射电子显微镜(TEM)、选区电子衍射(SAED)、X射线衍射(XRD)和能量色散谱(EDS)等手段表征了产物的形貌和结构.结果表明,高功率密度激光产生的高温高压条件是形成NiO纳米立方体的最重要因素.激光功率密度高于104 W/cm2时可以生成NiO纳米立方体,当功率高于该阈值时激光首先将镍靶烧蚀为金属液滴,高温的金属液体加热周围液体,并由于液体的限制效应使得压力进一步升高,最后金属液滴与液体发生表面反应生成NiO纳米立方体.

  9. Solid-State Modulators for RF and Fast Kickers

    Cook, Edward; Brooksby, Craig A; Cassel, Richard; De Lamare, Jeffrey E; Gower, Edward J; Hawkins, Steven; Hickman, Bradley C; Nguyen, Minh N; Pappas, Chris


    As the capabilities of solid-state devices increase, these devices are being incorporated into modulator designs for high voltage accelerator applications. Solid-state modulators based on inductive adder circuit topology have demonstrated great versatility with regard to pulse width and pulse repetition rate while maintaining fast pulse rise and fall times. Additionally, these modulators are capable of being scaled to higher output voltage and power levels. An explanation of the basic circuit operation will be presented as well as test data of several different hardware systems.

  10. Pulse-Density Modulation with an Ensemble of Single-Electron Circuits Employing Neuronal Heterogeneity to Achieve High Temporal Resolution

    Kikombo, Andrew Kilinga; Asai, Tetsuya; Amemiya, Yoshihito

    We investigated the implications of static noises in a pulse-density modulator based on Vestibulo-ocular Reflex model. We constructed a simple neuromorphic circuit consisting of an ensemble of single-electron devices and confirmed that static noises (heterogeneity in circuit parameters) introduced into the network indeed played an important role in improving the fidelity with which neurons could encode signals whose input frequencies are higher than the intrinsic response frequencies of single neurons. Through Monte-Carlo based computer simulations, we demonstrated that the heterogeneous network could corectly encode signals with input frequencies as high as 1 GHz, twice the range for single (or a network of homogeneous) neurons.

  11. High Energy, Short Pulse Fiber Injection Lasers at Lawrence Livermore National Laboratory

    Dawson, J W; Messerly, M J; Phan, H H; Crane, J K; Beach, R J; Siders, C W; Barty, C J


    A short pulse fiber injection laser for the Advanced Radiographic Capability (ARC) on the National Ignition Facility (NIF) has been developed at Lawrence Livermore National Laboratory (LLNL). This system produces 100 {micro}J pulses with 5 nm of bandwidth centered at 1053 nm. The pulses are stretched to 2.5 ns and have been recompressed to sub-ps pulse widths. A key feature of the system is that the pre-pulse power contrast ratio exceeds 80 dB. The system can also precisely adjust the final recompressed pulse width and timing and has been designed for reliable, hands free operation. The key challenges in constructing this system were control of the signal to noise ratio, dispersion management and managing the impact of self phase modulation on the chirped pulse.

  12. [Pulse-modulated Electromagnetic Radiation of Extremely High Frequencies Protects Cellular DNA against Damaging Effect of Physico-Chemical Factors in vitro].

    Gapeyev, A B; Lukyanova, N A


    Using a comet assay technique, we investigated protective effects of. extremely high frequency electromagnetic radiation in combination with the damaging effect of X-ray irradiation, the effect of damaging agents hydrogen peroxide and methyl methanesulfonate on DNA in mouse whole blood leukocytes. It was shown that the preliminary exposure of the cells to low intensity pulse-modulated electromagnetic radiation (42.2 GHz, 0.1 mW/cm2, 20-min exposure, modulation frequencies of 1 and 16 Hz) caused protective effects decreasing the DNA damage by 20-45%. The efficacy of pulse-modulated electromagnetic radiation depended on the type of genotoxic agent and increased in a row methyl methanesulfonate--X-rays--hydrogen peroxide. Continuous electromagnetic radiation was ineffective. The mechanisms of protective effects may be connected with an induction of the adaptive response by nanomolar concentrations of reactive oxygen species formed by pulse-modulated electromagnetic radiation.

  13. Noise signals and carrier modulation arising in electrical cables during nuclear pulse irradiation

    Both, E.; Bruemmer, H. P.; Lascaro, C. P.; Newberg, J.; Schlosser, W.


    Electrical noise signals generated in coaxial and other cables by pulsed nuclear radiation were measured as a function of applied voltage and exposure history. In consecutive exposures the signal magnitude and polarity was found to be strongly affected by training and memory effects. Unexpectedly large signals in the cable shield were identified as the cause for oscillatory signals in the center conductor and for the occurrence of parasitic leakage currents in nearby conductors. A r-f signal transmitted through RG62 A/U cable undergoes a temporary attenuation during the radiation pulse while it passes through RG59 B/U without measurable degradation. Definite rules are given for minimizing cable noise signals in nuclear pulse radiation measurements. (auth)

  14. Enhanced pulse compression induced by the interaction between the third-order dispersion and the cross-phase modulation in birefringent fibres

    徐文成; 陈伟成; 张书敏; 罗爱平; 刘颂豪


    In this paper, we report on the enhanced pulse compression due to the interaction between the positive third-order dispersion (TOD) and the nonlinear effect (cross-phase modulation effect) in birefringent fibres. Polarization soliton compression along the slow axis can be enhanced in a birefringent fibre with positive third-order dispersion. while the polarization soliton compression along the fast axis can be enhanced in the fibre with negative third-order dispersion.Moreover, there is an optimal third-order dispersion parameter for obtaining the optimal pulse compression.Redshifted initial chirp is helpful to the pulse compression, while blueshifted chirp is detrimental to the pulse compression. There is also an optimal chirp parameter to reach maximum pulse compression. The optimal pulse compression for TOD parameters under different N-order solitons is also found.

  15. Realization of ICA for Pulsed Neural Networks Based on Delta-Sigma Modulation and Their Hardware Implementation

    Hotta, Hirohisa; Murahashi, Yoshimitsu; Doki, Shinji; Okuma, Shigeru

    In order to ride on the strength of paralell operation a feature of neural network, it is preferable that all neuron is implemented on hardware. Formerly, we combine Neural Network and ΔΣ modulation, which is a method of converting to 1bit pulsed signal. Then we succeeded to configurate “a Pulsed Neural Network based on ΔΣ modulation(DSM-PNN)", which keep the circuit scale as same as to operate precisely. In last paper, we proposed hardware implementation methods of DSM-PNN with GHA learning rule and show its availability in linear operation. However, since neural networks are characterized by nonlinear map, signals needs to be treated with sufficient precision, also in nonlinear operation. In this paper, in order to shows that the 1-bit signal processing by DSM-PNN can be available, even when it includes nonlinear operation, we proposed the technique of realizing algorithm of ICA including nonlinear operation in DSM-PNN and confirm the performance of it.

  16. Thermal NDE of thick GRP panels by means of a Pulse Modulated Lock-In Thermography technique

    Pitarresi G.


    Full Text Available This work describes the development and implementation of an infrared thermal NDE procedure for the evaluation of subsurface defects. The approach is called Pulse-Modulated Lock-In Thermography (PMLT and is based on the analysis of the frequency response of the measured temperature and comparison with the carrier frequencies launched by the external heat delivering source. The heat deposited on the object is in particular modulated as a train of square waves. This is easily achieved by periodically shuttering the heat source. The temperature is then sampled throughout the deposition of a few square waves. A lock-in algorithm is then implemented able to selectively filter out components at the main carrier frequencies of the heating signal and evaluate the phase information. Defected areas at different depths can be marked based on phase contrast, by using data from a single experiment as in Pulsed-Phase Thermography. An artificially defected thick GRP panel typical of naval monolithic hull structures, is investigated to validate the proposed technique. Experimental data have confirmed the potentials of PMLT as a flexible IR NDT approach, and its ability to be implemented by means of low cost heating and IR equipments.

  17. Shaping frequency correlations of ultrafast pulse-pumped modulational instability in gas-filled hollow-core PCF

    Finger, Martin A; Russell, Philip St J; Chekhova, Maria V


    We vary the time-frequency mode structure of ultrafast pulse-pumped modulational instability (MI) in an argon-filled hollow-core kagom\\'e-style PCF by adjusting the pressure, pump pulse chirp, fiber length and parametric gain. Compared to solid-core systems, the pressure dependent dispersion landscape brings increased flexibility to the tailoring of frequency correlations. The resulting mode content is characterized by measuring the multimode second-order correlation function g(2) and by directly observing frequency correlations in single-shot MI spectra. We show that, from such measurements, the shapes and weights of time-frequency Schmidt (TFS) modes can be extracted and that the number of modes directly influences the shot-to-shot pulse-energy and spectral-shape fluctuations in MI. Using this approach we are able to change the number of TFS modes from 1.3 (g(2) = 1.75) to 4 (g(2) = 1.25) using only a single fiber.

  18. High-temperature potentiometry: modulated response of ion-selective electrodes during heat pulses.

    Chumbimuni-Torres, Karin Y; Thammakhet, Chongdee; Galik, Michal; Calvo-Marzal, Percy; Wu, Jie; Bakker, Eric; Flechsig, Gerd-Uwe; Wang, Joseph


    The concept of locally heated polymeric membrane potentiometric sensors is introduced here for the first time. This is accomplished in an all solid state sensor configuration, utilizing poly(3-octylthiophene) as the intermediate layer between the ion-selective membrane and underlying substrate that integrates the heating circuitry. Temperature pulse potentiometry (TPP) gives convenient peak-shaped analytical signals and affords an additional dimension with these sensors. Numerous advances are envisioned that will benefit the field. The heating step is shown to give an increase in the slope of the copper-selective electrode from 31 to 43 mV per 10-fold activity change, with a reproducibility of the heated potential pulses of 1% at 10 microM copper levels and a potential drift of 0.2 mV/h. Importantly, the magnitude of the potential pulse upon heating the electrode changes as a function of the copper activity, suggesting an attractive way for differential measurement of these devices. The heat pulse is also shown to decrease the detection limit by half an order of magnitude.

  19. Tandem-pulsed acousto-optics: an analytical framework of modulated high-contrast speckle patterns

    Resink, S.G.; Steenbergen, W.


    Recently we presented acousto-optic (AO) probing of scattering media using addition or subtraction of speckle patterns due to tandem nanosecond pulses. Here we present a theoretical framework for ideal (polarized, noise-free) speckle patterns with unity contrast that links ultrasound-induced optical

  20. Urinary (1)H Nuclear Magnetic Resonance Metabolomic Fingerprinting Reveals Biomarkers of Pulse Consumption Related to Energy-Metabolism Modulation in a Subcohort from the PREDIMED study.

    Madrid-Gambin, Francisco; Llorach, Rafael; Vázquez-Fresno, Rosa; Urpi-Sarda, Mireia; Almanza-Aguilera, Enrique; Garcia-Aloy, Mar; Estruch, Ramon; Corella, Dolores; Andres-Lacueva, Cristina


    Little is known about the metabolome fingerprint of pulse consumption. The study of robust and accurate biomarkers for pulse dietary assessment has great value for nutritional epidemiology regarding health benefits and their mechanisms. To characterize the fingerprinting of dietary pulses (chickpeas, lentils, and beans), spot urine samples from a subcohort from the PREDIMED study were stratified using a validated food frequency questionnaire. Urine samples of nonpulse consumers (≤4 g/day of pulse intake) and habitual pulse consumers (≥25 g/day of pulse intake) were analyzed using a (1)H nuclear magnetic resonance (NMR) metabolomics approach combined with multi- and univariate data analysis. Pulse consumption showed differences through 16 metabolites coming from (i) choline metabolism, (ii) protein-related compounds, and (iii) energy metabolism (including lower urinary glucose). Stepwise logistic regression analysis was applied to design a combined model of pulse exposure, which resulted in glutamine, dimethylamine, and 3-methylhistidine. This model was evaluated by a receiver operating characteristic curve (AUC > 90% in both training and validation sets). The application of NMR-based metabolomics to reported pulse exposure highlighted new candidates for biomarkers of pulse consumption and the impact on energy metabolism, generating new hypotheses on energy modulation. Further intervention studies will confirm these findings.

  1. Modulation of the characteristics of complex holographic gratings under an additional laser pulse

    Kucherenko, M G; Rusinov, A P; Fedorov, D S [Orenburg State University, Orenburg (Russian Federation)


    Recording of elementary holographic gratings in polymer films and solutions coloured with organic dyes has been investigated. Possible mechanisms of modifying a recorded grating by an additional laser pulse are considered. A theoretical model is proposed to describe the processes of recording/relaxation and modification of gratings recorded on triplet states of photochrome molecules; the predictions of this model are found to be in good agreement with the experimental data. (holography)

  2. Spectrum of the nonstationary electromyographic signal modelled with integral pulse frequency modulation and its application to estimating neural drive information.

    Jiang, Ning; Parker, Philip A; Englehart, Kevin B


    The spectrum of nonstationary electromyographic signal (EMG) is investigated, from which the error for neural drive information estimation from nonstationary EMG is studied in terms of signal-to-noise ratio (SNR), in analytical, numerical simulation, and experimental work. The signal refers to the neural drive information embedded within the nonstationary EMG, and noise refers to other portions of EMG that induce error in the estimation. The analytical expressions for the SNRs of force-modulated EMG with both single and multiple motor units (MU) are derived based on a sinusoidal integral pulse frequency modulation (IPFM) model. It is shown that the previously developed SNR expressions for stationary (unmodulated) EMG are special cases of the formulas presented here. The SNR results obtained from numerical simulated EMG agree very well with the analytical result. Results from nonstationary (modulated) surface EMG obtained from seven subjects also match the analytical and simulation results reasonably well. The results obtained from this work establish an analytical framework in studying and estimating the neural drive information contained in the EMG in the context of anisotonic and isometric contractions. Through the analytical study, the effects of different physiological parameters are identified, thus providing theoretical guidelines for developing advanced signal processing methods for nonstationary EMG in applications such as prosthesis control.

  3. Very long pulse high-RF power test of a lower hybrid frequency antenna module

    Goniche, M.; Brossaud, J.; Barral, C.; Berger-By, G.; Bibet, Ph.; Poli, S.; Rey, G.; Tonon, G. [Association Euratom-CEA, Centre d`Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Seki, M.; Obara, K. [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment] [and others


    Outgassing, induced by very long RF waves injection at high power density was studied in a module, able to be used for a lower hybrid frequency antenna. Good RF properties of the module are reported, however, resonance phenomena with strong absorption of RF power (15%) was observed at high temperature (T>400 deg C). A large outgassing data base is provided by the 75 shots cumulating 27 hours of RF injection. The comparison with previous experiments (Tore Supra and TdV prototype modules) confirm the effect of baking and results are consistent. Outgassing increases exponentially with -1/T, and a desorption model with an activation energy Ed {approx} 0.35 eV fits the data up to 400 deg C. In order to design vacuum pumping system for large lower hybrid frequency antenna, outgassing rates are given for different working temperatures. (author). 11 refs., 55 figs.

  4. Novel Scheme for Multiple Channel Pulse Generation from a Single Laser Diodefor 10 Gbit/s Based WDM Systems Using RZ Modulation Format

    H.; C.; Bao; Y.; J.; Wen; H.; F.; Liu


    A new technique for the generation of multi-channel optical pulse from a single laser diode (LD) is presented in this paper. 35 channel pulse source with 6.5 GHz repetition rate per channel and 32.5 GHz channel spacing was generated from a subharmonically hybrid mode-locked two section monolithic laser with enhanced amplitude modulation. The obtained pulse source exhibits high extinction ratio (>10 dB) and low level of root mean square (RMS) phase noise (<0.11 rad) over all channels from 1556 nm to 1565...

  5. Novel Scheme for Multiple Channel Pulse Generation from a Single Laser Diodefor 10 Gbit/s Based WDM Systems Using RZ Modulation Format

    H. C. Bao; Y. J. Wen; H. F. Liu


    A new technique for the generation of multi-channel optical pulse from a single laser diode (LD) is presented in this paper. 35 channel pulse source with 6.5 GHz repetition rate per channel and 32.5 GHz channel spacing was generated from a subharmonically hybrid mode-locked two section monolithic laser with enhanced amplitude modulation. The obtained pulse source exhibits high extinction ratio (>10 dB) and low level of root mean square (RMS)phase noise (<0.11 rad) over all channels from 1556 nm to 1565 nm.

  6. Enhancement of LED indoor communications using OPPM-PWM modulation and grouped bit-flipping decoding.

    Yang, Aiying; Li, Xiangming; Jiang, Tao


    Combination of overlapping pulse position modulation and pulse width modulation at the transmitter and grouped bit-flipping algorithm for low-density parity-check decoding at the receiver are proposed for visible Light Emitting Diode (LED) indoor communication system in this paper. The results demonstrate that, with the same Photodetector, the bit rate can be increased and the performance of the communication system can be improved by the scheme we proposed. Compared with the standard bit-flipping algorithm, the grouped bit-flipping algorithm can achieve more than 2.0 dB coding gain at bit error rate of 10-5. By optimizing the encoding of overlapping pulse position modulation and pulse width modulation symbol, the performance can be further improved. It is reasonably expected that the bit rate can be upgraded to 400 Mbit/s with a single available LED, thus transmission rate beyond 1 Gbit/s is foreseen by RGB LEDs.

  7. Comparison of three different Modulators for Power Converters with Respect to EMI Optimization

    Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael Andreas E.


    Switch-mode Power Converters are well known for emissions in the band of electromagnetic interference (EMI) interest. The spectrum shape depends on the type of modulator and its purpose. This paper gives design guidelines to choose the optimum topology depending on requirements of different...... applications. Spectral measurements on prototypes of a pulse width modulator (PWM), a -modulator and a hysteretic self-oscillating modulator are shown, which are verifying their simulations, with respect to different EMI challenges....

  8. Redesign of the SNS Modulator H-Bridge for Utilization of Press-Pack IGBTs

    Kemp, Mark A.; Burkhart, Craig; /SLAC; Anderson, David E.; /Oak Ridge


    The power conversion group at SLAC is currently redesigning the H-bridge switch plates of the High Voltage Converter Modulators at the Spallation Neutron Source. This integral part to the modulator operation has been indentified as a source of several modulator faults and potentially limits reliability with pulse width modulation operation. This paper is a presentation of the design and implementation of a redesigned switch plate based upon press-pack IGBTs.

  9. Level Width Broaden Effect

    ZHANG Jing-Shang


    In fitting the double-differential measurements thelevelwidth broadening effect should be taken into account properly due to Heisenberg uncertainty.Besides level width broadening effect the energy resolution in the measurements is also needed in this procedure.In general,the traditional normal Gaussian expansion is employed.However,the research indicates that to do so in this way the energy balance could not hold.For this reason,the deformed Gaussian expansion functions with exponential form for both the single energy point and continuous spectrum are introduced,with which the normalization and energy balance conditions could hold exactly in the analytical form.

  10. Passive decoy-state quantum key distribution using weak coherent pulses with modulator attenuation

    李源; 鲍皖苏; 李宏伟; 周淳; 汪洋


    Passive decoy-state quantum key distribution is more desirable than the active one in some scenarios. It is also affected by the imperfections of the devices. In this paper, the influence of modulator attenuation on the passive decoy-state method is considered. We introduce and analyze the unbalanced Mach–Zehnder interferometer, briefly, and combining with the virtual source and imaginary unitary transformation, we characterize the passive decoy-state method using a weak coherent photon source with modulator attenuation. According to the attenuation parameterδ, the pass efficiencies are given. Then, the key generation rate can be acquired. From numerical simulations, it can be seen that modulator attenuation has a non-negligible influence on the performance of passive-state QKD protocol. Based on the research, the analysis method of virtual source and imaginary unitary transformation are preferred in analyzing passive decoy state protocol, and the passive decoy-state method is better than the active one and is close to the active vacuum+weak decoy state under the condition of having the same modulator attenuation.

  11. Passive decoy-state quantum key distribution using weak coherent pulses with modulator attenuation

    Li, Yuan; Bao, Wan-Su; Li, Hong-Wei; Zhou, Chun; Wang, Yang


    Passive decoy-state quantum key distribution is more desirable than the active one in some scenarios. It is also affected by the imperfections of the devices. In this paper, the influence of modulator attenuation on the passive decoy-state method is considered. We introduce and analyze the unbalanced Mach-Zehnder interferometer, briefly, and combining with the virtual source and imaginary unitary transformation, we characterize the passive decoy-state method using a weak coherent photon source with modulator attenuation. According to the attenuation parameter δ, the pass efficiencies are given. Then, the key generation rate can be acquired. From numerical simulations, it can be seen that modulator attenuation has a nonnegligible influence on the performance of passive-state QKD protocol. Based on the research, the analysis method of virtual source and imaginary unitary transformation are preferred in analyzing passive decoy state protocol, and the passive decoy-state method is better than the active one and is close to the active vacuum + weak decoy state under the condition of having the same modulator attenuation. Project supported by the National Natural Science Foundation of China (Grant No. 11304397).

  12. Pulse-density modulation control of chemical oscillation far from equilibrium in a droplet open-reactor system.

    Sugiura, Haruka; Ito, Manami; Okuaki, Tomoya; Mori, Yoshihito; Kitahata, Hiroyuki; Takinoue, Masahiro


    The design, construction and control of artificial self-organized systems modelled on dynamical behaviours of living systems are important issues in biologically inspired engineering. Such systems are usually based on complex reaction dynamics far from equilibrium; therefore, the control of non-equilibrium conditions is required. Here we report a droplet open-reactor system, based on droplet fusion and fission, that achieves dynamical control over chemical fluxes into/out of the reactor for chemical reactions far from equilibrium. We mathematically reveal that the control mechanism is formulated as pulse-density modulation control of the fusion-fission timing. We produce the droplet open-reactor system using microfluidic technologies and then perform external control and autonomous feedback control over autocatalytic chemical oscillation reactions far from equilibrium. We believe that this system will be valuable for the dynamical control over self-organized phenomena far from equilibrium in chemical and biomedical studies.

  13. One-Dimensional Fluid Model of Pulse Modulated Radio-Frequency SiH4/N2/O2 Discharge

    王燕; 刘相梅; 宋远红; 王友年


    Driven by pulse modulated radio-frequency plasma in capacitively coupled discharge are studied by source, the behavior of SiH4/N2/02 using a one-dimensional fluid model. Totally, 48 different species (electrons, ions, neutrals, radicals and excited species) are involved in this simulation. Time evolution of the particle densities and electron temperature with different duty cycles are obtained, as well as the electronegativity nsiH-3 /ne of the main negative ion (Sill3 ). The results show that, by reducing the duty cycle, higher electron temperature and particle density can be achieved for the same average dissipated power, and the ion energy can also be effectively reduced, which will offer evident improvement in plasma deposition processes compared with the case of continuous wave discharge.

  14. 基于并联SOA的全光广播式超宽带脉冲形状调制技术%Research on all-optical broadcasting ultra-wideband pulse shape modulation based on multiple semiconductor optical amplifiers

    马晓璐; 李培丽; 郑加金; 张一; 朱天阳


    基于半导体光放大器(SOA)中交叉增益调制(XGM)效应,采用SOA的并联结构,提出了一种全光产生广播式超宽带(UWB)脉冲形状调制(PSM)信号的方案.该方案同时产生三路超宽带PSM信号,具有多用户传输数据的能力,可为多址通信作理论基础;采用相向的工作方式可以改善输出信号的消光比.利用OptiSystem7.0软件对方案进行仿真,分析了输入信号脉冲宽度、输入光功率和波长对产生的超宽带PSM信号的影响,对信号的传输特性进行了研究.结果表明,本文方案对输入信号脉冲宽度和输入光波长具有良好的容忍度,并且给出了输入光功率的优化范围.%An all-optical broadcasting ultra-wideband (UWB) pulse shape modulation (PSM) technology based on the cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) has been demonstrated.In this novel scheme,two wideband traveling wave SOAs are used,and the structure of the parallel SOAs is adopted to generate the PSM signals.and three kinds of ultra-wideband PSM signals are generated at the smae time.As a consequence,this new scheme has the ability to transmit data among multiple users,and can be used as a theoretical basis of multiple accuess communication.As the opposite working way is used.the scheme has an advantage in improving the extinction ratio (ER) of the output three ultra-wideband PSM signals.By using the software of OptiSystem7.0,the impacts of the input signal pulse width,the optical power and the wavelength of the laser on the generated three kinds of ultrawideband PSM signal are numberically simulated and studied.In addition,the transmission characteristics of the generated PSM signal are discussed.The results show that the PSM signal has a good toleration to the pulse width,and the optimized ranges of other parameters are presented.

  15. A 13.56-mbps pulse delay modulation based transceiver for simultaneous near-field data and power transmission.

    Kiani, Mehdi; Ghovanloo, Maysam


    A fully-integrated near-field wireless transceiver has been presented for simultaneous data and power transmission across inductive links, which operates based on pulse delay modulation (PDM) technique. PDM is a low-power carrier-less modulation scheme that offers wide bandwidth along with robustness against strong power carrier interference, which makes it suitable for implantable neuroprosthetic devices, such as retinal implants. To transmit each bit, a pattern of narrow pulses are generated at the same frequency of the power carrier across the transmitter (Tx) data coil with specific time delays to initiate decaying ringing across the tuned receiver (Rx) data coil. This ringing shifts the zero-crossing times of the undesired power carrier interference on the Rx data coil, resulting in a phase shift between the signals across Rx power and data coils, from which the data bit stream can be recovered. A PDM transceiver prototype was fabricated in a 0.35- μm standard CMOS process, occupying 1.6 mm(2). The transceiver achieved a measured 13.56 Mbps data rate with a raw bit error rate (BER) of 4.3×10(-7) at 10 mm distance between figure-8 data coils, despite a signal-to-interference ratio (SIR) of -18.5 dB across the Rx data coil. At the same time, a class-D power amplifier, operating at 13.56 MHz, delivered 42 mW of regulated power across a separate pair of high-Q power coils, aligned with the data coils. The PDM data Tx and Rx power consumptions were 960 pJ/bit and 162 pJ/bit, respectively, at 1.8 V supply voltage.

  16. Self-phase modulation of an ultra-short laser pulse from laser breakdown plasma

    Zhang, Yongsheng; Yan, Lixin; Zheng, Guoxin; Wang, Lijun; Liu, Jingru


    The detailed dynamic of an atom in a laser field with strength comparable to the atomic electric field is rich in physics and potential applications. Laser-breakdown plasma-induced spectral shifting in supersonic rare gases jet has been investigated with a sub-picosecond KrF excimer laser focused to peak intensity in the region of 10 15W/cm2. A 1.4mm diameter gas jet target was used in the experiment to minimize the refraction of the laser beam and thus a well-defined focused region was obtained. The typical quasi-periodic spectral shifting structures for helium and argon have been measured at various gas densities. For gas densities below 1x10 20cm -3,both spectral red-shift and blue-shift were observed, indicating the gas is partially ionized, in contrast to the predominantly blue shifted as the gas densities grows high and fully ionized. Compared to the other ultra-short pulse measurement methods, qualitative information about the pulse can be deduced by observing their spectrum after interacting with rare gas.

  17. Phase-dependent spectral control of pulsed modulation instability via dichromatic seed fields

    Brinkmann, Maximilian; Fallnich, Carsten


    We investigated experimentally and numerically the spectral control of modulation instability (MI) dynamics via the initial phase relation of two weak seed fields. Specifically, we show how second-order modulation instability dynamics exhibit phase-dependent anti-correlated growth rates of adjacent spectral sidebands. This effect enables a novel method to control MI-based frequency conversion: in contrast to first-order MI dynamics, which exhibit a uniform phase dependence of the growth rates, second-order MI dynamics allow to redistribute the spectral energy, leading to an asymmetric spectrum. Therefore, the presented findings should be very attractive to different applications, such as phase-sensitive amplification or supercontinuum generation initiated by MI.

  18. Fabrication of High-Voltage Bridge Rectifier Modules for Pulse Power Applications


    ORGANIZATION NAME(S) AND ADDRESS(ES) U.S. Army Research Laboratory ATTN: RDRL-SED-P 2800 Powder Mill Road Adelphi, MD 20783-1138 8. PERFORMING...3 Table 2 Version 3 module encapsulants & adhesives ..................................................................15 1 1. Introduction...substrate to the heat sink. A set of holes was drilled through the heat sink to allow the resulting pocket to be partially filled with encapsulant for

  19. Spectral Shearing of Quantum Light Pulses by Electro-Optic Phase Modulation.

    Wright, Laura J; Karpiński, Michał; Söller, Christoph; Smith, Brian J


    Frequency conversion of nonclassical light enables robust encoding of quantum information based upon spectral multiplexing that is particularly well-suited to integrated-optics platforms. Here we present an intrinsically deterministic linear-optics approach to spectral shearing of quantum light pulses and show it preserves the wave-packet coherence and quantum nature of light. The technique is based upon an electro-optic Doppler shift to implement frequency shear of heralded single-photon wave packets by ±200  GHz, which can be scaled to an arbitrary shift. These results demonstrate a reconfigurable method to controlling the spectral-temporal mode structure of quantum light that could achieve unitary operation.

  20. Intrinsic modulation of pulse-coupled integrate-and-fire neurons

    Coombes, S.; Lord, G. J.


    Intrinsic neuromodulation is observed in sensory and neuromuscular circuits and in biological central pattern generators. We model a simple neuronal circuit with a system of two pulse-coupled integrate-and-fire neurons and explore the parameter regimes for periodic firing behavior. The inclusion of biologically realistic features shows that the speed and onset of neuronal response plays a crucial role in determining the firing phase for periodic rhythms. We explore the neurophysiological function of distributed delays arising from both the synaptic transmission process and dendritic structure as well as discrete delays associated with axonal communication delays. Bifurcation and stability diagrams are constructed with a mixture of simple analysis, numerical continuation and the Kuramoto phase-reduction technique. Moreover, we show that, for asynchronous behavior, the strength of electrical synapses can control the firing rate of the system.

  1. Calculus of the Power Spectral Density of Ultra Wide Band Pulse Position Modulation Signals Coded with Totally Flipped Code

    DURNEA, T. N.


    Full Text Available UWB-PPM systems were noted to have a power spectral density (p.s.d. consisting of a continuous portion and a line spectrum, which is composed of energy components placed at discrete frequencies. These components are the major source of interference to narrowband systems operating in the same frequency interval and deny harmless coexistence of UWB-PPM and narrowband systems. A new code denoted as Totally Flipped Code (TFC is applied to them in order to eliminate these discrete spectral components. The coded signal transports the information inside pulse position and will have the amplitude coded to generate a continuous p.s.d. We have designed the code and calculated the power spectral density of the coded signals. The power spectrum has no discrete components and its envelope is largely flat inside the bandwidth with a maximum at its center and a null at D.C. These characteristics make this code suited for implementation in the UWB systems based on PPM-type modulation as it assures a continuous spectrum and keeps PPM modulation performances.

  2. Functional design and implementation with on-line programmable technology in optical fiber communication pulse code modulation test system

    Xu, Yuan; Ding, Huan; Gao, Youtang


    In order to complete the functional design in the fiber optical communication pulse code modulation test system, taking advantage of CPLD / FPGA and SOPC technology, software solutions used to design system hardware features and control functions, thereby the whole system could attain optimisation in the logic control as well as encoding and decoding functional designs on the motherboard, enabling this system fulfill the capacities varying from simple digital simulation transmission modulate to the high speed fiber optical communication network information encoding and decoding functions. Simultaneously the application of logarithmic pressure companding technique, PCM encoding and decoding system to improve the small signal quantizing SNR(Signal-to-Noise Ratio), TP3067 adopting A rate thirteen broken lines to carry on signal pressure companding. When the signal at a certain stage, the quantizing SNR is invariable(as signal receives uniform quantization in this phase, therefore the quantizing SNR drops along with signal amplititude decreasing). Test results are as follows: ideal various signal encoding and decoding system waveforms, high performance parameters , achieve the desired designing aim, a entirely new approach to realize different kinds of information encoding and decoding model building and implementation, saving development costs, improving design efficiency, satisfactory actual results, stable operation.

  3. Modulation properties of VCSEL with intracavity modulator

    van Eisden, J.; Yakimov, M.; Tokranov, V.; Varanasi, M.; Mohammed, E. M.; Young, I. A.; Oktyabrsky, S.


    We have studied the modulation properties of VCSEL with intracavity multiple quantum well (MQW) electroabsorption modulator integrated into the top distributed Bragg reflector (DBR) [1]. Small signal analysis of rate equations for loss modulation shows an intrinsic high-frequency roll-off slope of 1/ω instead of 1/ω2 in directly modulated laser diodes, and consequently bandwidths in excess of 40 GHz are obtainable with this configuration [2]. Possible limiting factors to high bandwidth were examined by fitting high frequency characteristics to a multi-pole transfer function, and include RC delay and carrier drift-limited time of flight (TOF) in the modulator intrinsic region. Intracavity loss modulation shows a strong (+20dB) relaxation oscillation resonant feature in both theory and experiment. As demonstrated, this feature can be significantly reduced in amplitude using parasitics. We have extracted relative contribution of TOF and parasitic capacitance by varying the modulator intrinsic region width (105 and 210 nm) and lateral size of the modulator (18 and 12μm). It was estimated that the small size modulator exhibits parasitics f -3dB at 8GHz. To estimate the carrier TOF contribution to bandwidth limits, low temperature growth of a 210 nm absorber i-region and MQW was employed to reduce photogenerated carrier lifetime. Bandwidth limitations were found to be mostly due to diode and metallization capacitances, in addition to one pole set by the optoelectronic resonance frequency. We have used p-modulation doping of the gain region to increase the relaxation frequency. Pronounced active Q-switching was observed, yielding pulse widths of 40 ps at a 4 GHz rate.

  4. rTPPM: Towards Improving Solid-State NMR Two-Pulse Phase-Modulation Heteronuclear Dipolar Decoupling Sequence by Refocusing

    Equbal, Asif; Paul, Subhradip; Mithu, Venus Singh


    We present here a simple refocused modification, r TPPM, of the Two-Pulse Phase-Modulation (TPPM) heteronuclear decoupling method, which improves decoupling and makes the sequence much more robust with respect to essential experimental parameters. The modified sequence is compared with the establ...

  5. Repetitive transcranial magnetic stimulator with controllable pulse parameters

    Peterchev, Angel V.; Murphy, David L.; Lisanby, Sarah H.


    The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10-310 µs and positive/negative phase amplitude ratio of 1-56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation up to 82% and 57% and decreases coil heating up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications and could lead to clinical applications with potentially enhanced potency.

  6. Analysis of nonlinear optical and dynamic gain effects of moderate-power, pulse-position-modulated, erbium-doped fiber amplifiers for deep-space applications.

    Yao, Haomin; Wright, Malcolm W; Marciante, John R


    Lasers for use in deep-space applications such as interplanetary optical communications employ multiwatt resonantly pumped dual-clad erbium-doped fiber amplifiers and the pulse-position modulation scheme. Nonlinear optical effects and dynamic gain effects often impair their performance and limit their operational range. These effects are analyzed theoretically and numerically with a time-dependent two-level propagation model, respectively. Self-phase modulation and stimulated Raman scattering are found to limit the usable data format space. In operational regimes free from nonlinear effects, dynamic gain effects such as the variation in the output pulse energy and square-pulse distortion are quantified. Both are found to primarily depend on the symbol duration and can be as large as 28% and 21%, respectively.

  7. Programmable pulse generator

    Xue Zhi Hua; Duan Xiao Hui


    The author introduces the design of programmable pulse generator that is based on a micro-controller and controlled by RS232 interface of personal computer. The whole system has good stability. The pulse generator can produce TTL pulse and analog pulse. The pulse frequency can be selected by EPLD. The voltage amplitude and pulse width of analog pulse can be adjusted by analog switches and digitally-controlled potentiometers. The software development tools of computer is National Instruments LabView5.1. The front panel of this virtual instrumentation is intuitive and easy-to-use. Parameters can be selected and changed conveniently by knob and slide

  8. Colossal magneto-optical modulation at terahertz frequencies by counterpropagating femtosecond laser pulses in Tbsub>3sub>Gasub>5sub>Osub>12sub>.

    Mikhaylovskiy, Rostislav V; Subkhangulov, Ruslan R; Rasing, Theo; Kimel, Alexey V


    Single-frequency terahertz modulation of the magneto-optical Faraday effect with a record amplitude of the polarization rotation of ∼0.5° is achieved using a slab of the etalon Faraday rotator crystal Tbsub>3sub>Gasub>5sub>Osub>12sub>. The modulation is the result of the interaction of two counterpropagating laser pulses via the optical Kerr effect. The frequency of the modulation is determined by the applied magnetic field and is continuously tunable in a terahertz frequency range between 0 and 0.7 THz.

  9. Bandwidth and repetition rate programmable Nyquist sinc-shaped pulse train source based on intensity modulators and four-wave mixing.

    Cordette, S; Vedadi, A; Shoaie, M A; Brès, C-S


    We propose and experimentally demonstrate an all-optical Nyquist sinc-shaped pulse train source based on intensity modulation and four-wave mixing. The proposed scheme allows for the tunability of the bandwidth and the full flexibility of the repetition rate in the limit of the electronic bandwidth of the modulators used through the flexible synthesis of rectangular frequency combs. Bandwidth up to 360 GHz at 40 GHz rate and up to 45 frequency lines at 5 GHz rate are demonstrated with 40 GHz modulators.

  10. Pulse source requirements for OTDM systems

    Clausen, Anders; Poulsen, Henrik Nørskov; Oxenløwe, Leif Katsuo


    A simulation model for investigating the impact of incoherent crosstalk due to pulse tail overlapping is proposed. Requirements to pulse width and pulse tail extinction ratio introducing a maximum of 1 dB penalty is extracted....

  11. High power solid state laser modulator

    Birx, Daniel L.; Ball, Don G.; Cook, Edward G.


    A multi-stage magnetic modulator provides a pulse train of .+-.40 kV electrical pulses at a 5-7 kHz repetition rate to a metal vapor laser. A fractional turn transformer steps up the voltage by a factor of 80 to 1 and magnetic pulse compression is used to reduce the pulse width of the pulse train. The transformer is fabricated utilizing a rod and plate stack type of construction to achieve a high packing factor. The pulses are controlled by an SCR stack where a plurality of SCRs are electrically connected in parallel, each SCR electrically connected to a saturable inductor, all saturable inductors being wound on the same core of magnetic material for enhanced power handling characteristics.

  12. Tailored RF Pulse Modulation for RF Refocussed Variable Flip Angle MRI

    Shah, Ajit S.; Ortendahl, Douglas A.; Carlson, Joseph W.; Kramer, David M.; Crooks, Larry E.


    Advances in Magnetice Resonance Imaging (MRI) techniques have recently made MRI the imaging modality of choice for many applications of clinical imaging. MRI provides the diagnosing clinician a non-invasive method for obtaining soft tissue differentiation with sub-millimeter resolution. Clinical MRI techniques include 3-dimensional imaging, spectroscopic imaging, arterial angiography and cardiac imaging. One MRI technique which has recently gained popularity is a class of protocols known as variable/partial flip angle MRI. Partial flip angle MRI techniques are useful because of their ability to vary contrast between tissues and/or maintain a particular level of contrast with a reduction in acquisition time [1]. Variable flip angle techniques differ from conventional MRI protocols in that the initial RF excitation/rotation pulse is not constrained to a 90 degree rotation of the longitudinal magnetization. Instead, the initial excitation flip angle is calculated to provide improved contrast between two tissues and/or maximize the intensity of a particular tissue. For tissues with reduced TR/T1 ratios, variable flip angle techniques may also be used to increase the image signal to noise within a localized region.

  13. On the Pulse Intensity Modulation of PSR B0823+26

    Young, N J; Weltevrede, P; Lyne, A G; Kramer, M


    We investigate the radio emission behaviour of PSR B0823+26, a pulsar which is known to undergo pulse nulling, using an 153-d intensive sequence of observations. The pulsar is found to exhibit both short (~min) and unusually long-term (~hours or more) nulls, which not only suggest that the source possesses a distribution of nulling timescales, but that it may also provide a link between conventional nulling pulsars and longer-term intermittent pulsars. Despite seeing evidence for periodicities in the pulsar radio emission, we are uncertain whether they are intrinsic to the source, due to the influence of observation sampling on the periodicity analysis performed. Remarkably, we find evidence to suggest that the pulsar may undergo pre-ignition periods of 'emission flickering', that is rapid changes between radio-on (active) and -off (null) emission states, before transitioning to a steady radio-emitting phase. We find no direct evidence to indicate that the object exhibits any change in spin-down rate between ...

  14. Receiver Signal to Noise Ratios for IPDA Lidars Using Sine-wave and Pulsed Laser Modulation and Direct Detections

    Sun, Xiaoli; Abshire, James B.


    seeder lasers, one on-line and one offline that are intensity modulated by two different frequency sine-waves signals before being amplified by a common laser amplifier. The receiver uses narrowband amplitude demodulation, or lock-in, Signal processing at the given laser modulation frequencies [3,4]. The laser transmitter operates in a quasi CW mode with the peak power equal to twice the average power. The on-line and off-line lasers can be transmitted at the same time without interference. Another direct detection technique uses a low duty cycle pulsed laser modulation [5,6] with the laser wavelengths alternating between on-line and off-line on successive pulses. The receiver uses time resolved detection and can also provide simultaneous target range measurement. With a lower laser duty cycle it requires a much higher peak laser power for the same average power.

  15. Phase-dependent spectral control of pulsed modulation instability via dichromatic seed fields

    Brinkmann, Maximilian; Kues, Michael; Fallnich, Carsten


    We investigated experimentally and numerically the spectral control of modulation instability (MI) dynamics via the initial phase relation of two weak seed fields. Specifically, we show how second-order MI dynamics exhibit phase-dependent anti-correlated growth rates of adjacent spectral sidebands. This effect enables a novel method to control MI-based frequency conversion: in contrast to first-order MI dynamics, which exhibit a uniform phase dependence of the growth rates, second-order MI dynamics allow to redistribute the spectral energy, leading to an asymmetric spectrum. Therefore, the presented findings should be very attractive to different applications, such as phase-sensitive amplification or supercontinuum generation initiated by MI.

  16. 柴油机喷油脉宽和喷油压力变化对喷油器流量系数的影响%Influence of changed fuel injection pulse width and pressure on discharge coefficient in diesel engine

    杜慧勇; 张紫微; 刘建新; 李民; 王站成; 徐斌


    In order to obtain the law of the impact of fuel injection pulse width and injection pressure change on the discharge coefficient and understand the causes of this law, this article designed and completed the experiment with commonly used fuel injection pulse width (1 000-2 500μs) and large scope of injection pressure (40-180 MPa). The momentum method was adopted to measure the fuel injection law in experiment, and the fuel injection quantity in different periods of injection process could be figured out at the same time, with the purpose of calculating the maximum discharge coefficient which corresponded to the duration of needle valve open completely, and the average discharge coefficient in the fuel injection duration in all conditions. The two parameters were used to explore the law of their own variation when the fuel injection pulse width and the injection pressure changed and to find their relationship and difference. With the purpose of obtaining more general results, the ratio of the duration of valve open fully and the injection duration was introduced as a dimensionless parameterτ, through which we could easily know the deviation value of discharge coefficient according to the curve of the mean discharge coefficient deviating from the maximum discharge coefficient. A lot of research has been made on discharge coefficient change in terms of external cause at home and abroad. But most of these studies were based on fluid simulation, or through Nurick simplified model to analyze, or just discussed the impacts of some physical parameters such as nozzle geometry, needle valve lift, Reynolds number and surface roughness inside the nozzle, fuel density and viscosity on discharge coefficient. Just discussing how much effect the conditions would have on the discharge coefficient was not enough, we must study why. This paper introduced the theory of flow loss analysis of nozzle discharge coefficient. Changes of discharge coefficient with the fuel injection pulse

  17. A hybrid pulse combining topology utilizing the combination of modularized avalanche transistor Marx circuits, direct pulse adding, and transmission line transformer.

    Li, Jiangtao; Zhao, Zheng; Sun, Yi; Liu, Yuhao; Ren, Ziyuan; He, Jiaxin; Cao, Hui; Zheng, Minjun


    Numerous applications driven by pulsed voltage require pulses to be with high amplitude, high repetitive frequency, and narrow width, which could be satisfied by utilizing avalanche transistors. The output improvement is severely limited by power capacities of transistors. Pulse combining is an effective approach to increase the output amplitude while still adopting conventional pulse generating modules. However, there are drawbacks in traditional topologies including the saturation tendency of combining efficiency and waveform oscillation. In this paper, a hybrid pulse combining topology was adopted utilizing the combination of modularized avalanche transistor Marx circuits, direct pulse adding, and transmission line transformer. The factors affecting the combining efficiency were determined including the output time synchronization of Marx circuits, and the quantity and position of magnetic cores. The numbers of the parallel modules and the stages were determined by the output characteristics of each combining method. Experimental results illustrated the ability of generating pulses with 2-14 kV amplitude, 7-11 ns width, and a maximum 10 kHz repetitive rate on a matched 50-300 Ω resistive load. The hybrid topology would be a convinced pulse combining method for similar nanosecond pulse generators based on the solid-state switches.

  18. A hybrid pulse combining topology utilizing the combination of modularized avalanche transistor Marx circuits, direct pulse adding, and transmission line transformer

    Li, Jiangtao; Zhao, Zheng; Sun, Yi; Liu, Yuhao; Ren, Ziyuan; He, Jiaxin; Cao, Hui; Zheng, Minjun


    Numerous applications driven by pulsed voltage require pulses to be with high amplitude, high repetitive frequency, and narrow width, which could be satisfied by utilizing avalanche transistors. The output improvement is severely limited by power capacities of transistors. Pulse combining is an effective approach to increase the output amplitude while still adopting conventional pulse generating modules. However, there are drawbacks in traditional topologies including the saturation tendency of combining efficiency and waveform oscillation. In this paper, a hybrid pulse combining topology was adopted utilizing the combination of modularized avalanche transistor Marx circuits, direct pulse adding, and transmission line transformer. The factors affecting the combining efficiency were determined including the output time synchronization of Marx circuits, and the quantity and position of magnetic cores. The numbers of the parallel modules and the stages were determined by the output characteristics of each combining method. Experimental results illustrated the ability of generating pulses with 2-14 kV amplitude, 7-11 ns width, and a maximum 10 kHz repetitive rate on a matched 50-300 Ω resistive load. The hybrid topology would be a convinced pulse combining method for similar nanosecond pulse generators based on the solid-state switches.

  19. Study Pulse Parameters versus Cavity Length for Both Dispersion Regimes in FM Mode Locked

    Bushra Razooky Mhdi


    Full Text Available To demonstrate the effect of changing cavity length for  FM mode locked on pulse parameters and make comparison for both dispersion regime , a plot for each pulse parameter as Lr function are presented for normal and anomalous dispersion regimes. The analysis is based on the theoretical study and the results of numerical simulation using MATLAB. The effect of both normal and anomalous dispersion regimes on output pulses is investigate Fiber length effects on pulse parameters are investigated by driving the modulator into different values. A numerical solution for model equations using fourth-fifth order, Runge-Kutta method is performed through MATLAB 7.0 program. Fiber length effect on pulse parameters is investigated by driving the modulator into different values of lengths. Result shows that, the output pulse width from the FM mode locked equals to τ= 501ns anomalous regime and τ=518ns in normal regime.

  20. Response Analysis on Electrical Pulses under Severe Nuclear Accident Temperature Conditions Using an Abnormal Signal Simulation Analysis Module

    Kil-Mo Koo


    Full Text Available Unlike design basis accidents, some inherent uncertainties of the reliability of instrumentations are expected while subjected to harsh environments (e.g., high temperature and pressure, high humidity, and high radioactivity occurring in severe nuclear accident conditions. Even under such conditions, an electrical signal should be within its expected range so that some mitigating actions can be taken based on the signal in the control room. For example, an industrial process control standard requires that the normal signal level for pressure, flow, and resistance temperature detector sensors be in the range of 4~20 mA for most instruments. Whereas, in the case that an abnormal signal is expected from an instrument, such a signal should be refined through a signal validation process so that the refined signal could be available in the control room. For some abnormal signals expected under severe accident conditions, to date, diagnostics and response analysis have been evaluated with an equivalent circuit model of real instruments, which is regarded as the best method. The main objective of this paper is to introduce a program designed to implement a diagnostic and response analysis for equivalent circuit modeling. The program links signal analysis tool code to abnormal signal simulation engine code not only as a one body order system, but also as a part of functions of a PC-based ASSA (abnormal signal simulation analysis module developed to obtain a varying range of the R-C circuit elements in high temperature conditions. As a result, a special function for abnormal pulse signal patterns can be obtained through the program, which in turn makes it possible to analyze the abnormal output pulse signals through a response characteristic of a 4~20 mA circuit model and a range of the elements changing with temperature under an accident condition.

  1. Tribological and structural properties of titanium nitride and titanium aluminum nitride coatings deposited with modulated pulsed power magnetron sputtering

    Ward, Logan

    The demand for economical high-performance materials has brought attention to the development of advanced coatings. Recent advances in high power magnetron sputtering (HPPMS) have shown to improve tribological properties of coatings. These coatings offer increased wear and oxidation resistance, which may facilitate the use of more economical materials in harsh applications. This study demonstrates the use of novel forms of HPPMS, namely modulated pulsed-power magnetron sputtering (MPPMS) and deep oscillation magnetron sputtering (DOMS), for depositing TiN and Ti1-xAlxN tribological coatings on commonly used alloys, such as Ti-6Al-4V and Inconel 718. Both technologies have been shown to offer unique plasma characteristics in the physical vapor deposition (PVD) process. High power pulses lead to a high degree of ionization compared to traditional direct-current magnetron sputtering (DCMS) and pulsed magnetron sputtering (PMS). Such a high degree of ionization was previously only achievable by cathodic arc deposition (CAD); however, CAD can lead to increased macroparticles that are unfavorable in high friction and corrosive environments. MPPMS, DOMS, and other HPPMS techniques offer unique plasma characteristics and have been shown to produce coatings with refined grain structure, improved density, hardness, adhesion, and wear resistance. Using DOMS and MPPMS, TiN and Ti1-xAlxN coatings were deposited using PMS to compare microstructures and tribological performance. For Ti1-xAlxN, two sputtering target compositions, Ti 0.5Al0.5 and Ti0.3Al0.7, were used to evaluate the effects of MPPMS on the coating's composition and tribological properties. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize microstructure and crystallographic texture. Several tribological properties were evaluated including: wear rate, coefficient of friction, adhesion, and nanohardness. Results show that substrate

  2. Active mode locking at 50 GHz repetition frequency by half-frequency modulation of monolithic semiconductor lasers integrated with electroabsorption modulators

    Sato, Kenji; Kotaka, Isamu; Kondo, Yasuhiro; Yamamoto, Mitsuo


    Active mode locking achieved at a 50 GHz repetition frequency by modulation at half (25 GHz) the cavity resonance frequency using a monolithic mode-locked InGaAsP laser integrated with an electroabsorption modulator is described. A pulse width of around 3 ps and a high suppression ratio of more than 33 dB of the intensity modulation at the driving frequency are obtained.

  3. Encoding of the amplitude modulation of pulsatile electrical stimulation in the feline cochlear nucleus by neurons in the inferior colliculus; effects of stimulus pulse rate

    McCreery, Douglas; Han, Martin; Pikov, Victor; Yadav, Kamal; Pannu, Satinderpall


    Objectives. Persons without a functional auditory nerve cannot benefit from cochlear implants, but some hearing can be restored by an auditory brainstem implant (ABI) with stimulating electrodes implanted on the surface of the cochlear nucleus (CN). Most users benefit from their ABI, but speech recognition tends to be poorer than for users of cochlear implants. Psychophysical studies suggest that poor modulation detection may contribute to the limited performance of ABI users. In a cat model, we determined how the pulse rate of the electrical stimulus applied within or on the CN affects temporal and rate encoding of amplitude modulation (AM) by neurons in the central nucleus of the inferior colliculus (ICC). Approach. Stimulating microelectrodes were implanted chronically in and on the cats' CN, and multi-site recording microelectrodes were implanted chronically into the ICC. Encoding of AM pulse trains by neurons in the ICC was characterized as vector strength (VS), the synchrony of neural activity with the AM, and as the mean rate of neuronal action potentials (neuronal spike rate (NSR)). Main results. For intranuclear microstimulation, encoding of AM as VS was up to 3 dB greater when stimulus pulse rate was increased from 250 to 500 pps, but only for neuronal units with low best acoustic frequencies, and when the electrical stimulation was modulated at low frequencies (10-20 Hz). For stimulation on the surface of the CN, VS was similar at 250 and 500 pps, and the dynamic range of the VS was reduced for pulse rates greater than 250 pps. Modulation depth was encoded strongly as VS when the maximum stimulus amplitude was held constant across a range of modulation depth. This ‘constant maximum’ protocol allows enhancement of modulation depth while preserving overall dynamic range. However, modulation depth was not encoded as strongly as NSR. Significance. The findings have implications for improved sound processors for present and future ABIs. The performance of

  4. Packet error rate analysis of digital pulse interval modulation in intersatellite optical communication systems with diversified wavefront deformation.

    Zhu, Jin; Wang, Dayan; Xie, Wanqing


    Diversified wavefront deformation is an inevitable phenomenon in intersatellite optical communication systems, which will decrease system performance. In this paper, we investigate the description of wavefront deformation and its influence on the packet error rate (PER) of digital pulse interval modulation (DPIM). With the wavelet method, the diversified wavefront deformation can be described by wavelet parameters: coefficient, dilation, and shift factors, where the coefficient factor represents the depth, dilation factor represents the area, and shift factor is for location. Based on this, the relationship between PER and wavelet parameters is analyzed from a theoretical viewpoint. Numerical results illustrate the validity of theoretical analysis: PER increases with the depth and area and decreases if location gets farther from the center of the optical antenna. In addition to describing diversified deformation, the advantage of the wavelet method over Zernike polynomials in computational complexity is shown via numerical example. This work provides a feasible method for the description along with influence analysis of diversified wavefront deformation from a practical viewpoint and will be helpful for designing optical systems.

  5. A Pulsed Electromagnetic Field Protects against Glutamate-Induced Excitotoxicity by Modulating the Endocannabinoid System in HT22 Cells

    Li, Xin; Xu, Haoxiang; Lei, Tao; Yang, Yuefan; Jing, Da; Dai, Shuhui; Luo, Peng; Xu, Qiaoling


    Glutamate-induced excitotoxicity is common in the pathogenesis of many neurological diseases. A pulsed electromagnetic field (PEMF) exerts therapeutic effects on the nervous system, but its specific mechanism associated with excitotoxicity is still unknown. We investigated the role of PEMF exposure in regulating glutamate-induced excitotoxicity through the endocannabinoid (eCB) system. PEMF exposure improved viability of HT22 cells after excitotoxicity and reduced lactate dehydrogenase release and cell death. An eCB receptor 1 (CB1R) specific inhibitor suppressed the protective effects of PEMF exposure, even though changes in CB1R expression were not observed. Elevation of N-arachidonylethanolamide (AEA) and 2-arachidonylglycerol (2-AG) following PEMF exposure indicated that the neuroprotective effects of PEMF were related to modulation of the eCB metabolic system. Furthermore, CB1R/ERK signaling was shown to be an important downstream pathway of PEMF in regulating excitotoxicity. These results suggest that PEMF exposure leads to neuroprotective effects against excitotoxicity by facilitating the eCB/CB1R/ERK signaling pathway. Therefore, PEMF may be a potential physical therapeutic technique for preventing and treating neurological diseases. PMID:28220060

  6. Modulation of conidia production and expression of the gene bbrgs1 from Beauveria bassiana by oxygen pulses and light.

    Rodriguez-Gomez, Divanery; Marcial-Quino, Jaime; Loera, Octavio


    Light and oxidant states affect the conidiation in diverse fungi, although the response has not been described when both stimuli are applied simultaneously. Conidial production and quality in Beauveria bassiana were analysed under four conditions for a wild-type (wt) strain and a previously isolated mutant (mt): normal atmosphere (21% O2; NA) or oxygen-enriched pulses (26% O2; OEP), with either light (L) or darkness (D). The response was complemented by following the expression of the bbrgs1 gene, encoding a regulator of the G-protein signal associated to conidia production. Conidiation was not significantly affected in the mutant strain by any condition (highest value with NA-L: 2.7×10(8)concm(-2)). Relative to maximal levels under NA (NA-D: 4×10(7)concm(2)), the wt strain diminished conidiation by 34-fold under OEP. The expression of bbrgs1 was higher (up to 188 times) in the mutant strain in every condition relative to the wt strain, in fact expression levels were consistent with the conidiation yields between strains. Viability and hydrophobicity were less affected by culture conditions, although pathogenicity parameters improved in conidia from OEP. The response to OEP, either with light or darkness, was strain-dependent for conidial production, viability, hydrophobicity and infectivity of conidia, then these parameters could be modulated in mass production processes. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Dynamics of wide and snake-like pulses in coupled Schrödinger equations with full-modulated nonlinearities

    Yomba, Emmanuel, E-mail:; Zakeri, Gholam-Ali, E-mail:


    We investigate the existence of various solitary wave solutions in coupled Schrödinger equations with specific cubic and quintic nonlinearities. This system arises in wave propagation in fiber optics with focusing and defocusing with modulated nonlinearities. We obtain front–front, bright–bright, dark–dark, and dark–bright like solitons using a direct approach, and then, by reducing the system of equations to a single auxiliary equation of a Duffing-type ordinary differential equation, we provide a large class of Jacobi-elliptic solutions. These solutions are presented in the exact form and analyzed. We find a class of wide localized and snake-like (in both space and time) vector solitons. One of the novel aspects of this study is that we have shown that the qualitative behavior of the solutions is independent of the choice of similarity variables. Numerical results show that the solutions of the above system are stable with up to 10% white noises. - Highlights: • Dynamics of wide and snake-like pulses is analyzed for coupled Schrödinger equations. • Qualitative appearance of solutions is analyzed using various similarity variables. • Effect of change in parameter-values on dynamics of the solutions is investigated. • Vectors front–front, bright–bright, dark–dark and dark–bright solitons are obtained.

  8. Optimised dispersion management and modulation formats for high speed optical communication systems

    Tokle, Torger


    This thesis studies dispersion management and modulation formats for optical communication systems using per channel bit rates at and above 10 Gbit/s. Novel modulation formats—including recently proposed multilevel phase modulation—are investigated and demonstrated at bit rates up to 80 Gbit/s. New...... system performance. Differential phase shift keying (DPSK) has recently been showed to be a promising modulation format for optical communication. We study DPSK with focus on differential quadrature phase shift keying (DQPSK). In a 12.5 Gbit/s WDM system, we demonstrate the suitability of DQPSK for ultra......-channel system, the optimum pulse width is very narrow. We find that a pulse width equal to 5% of the bit slot results in optimum performance for the system studied here. These narrow RZ pulses offer good receiver sensitivity and excellent tolerance to the nonlinear effect self phase modulation (SPM). However...

  9. An All Solid-State Pulsed Power Generator for Plasma Immersion Ion Implantation (PⅢ)

    LIU Kefu; QIU Jian; WU Yifan


    An all solid-state pulsed power generator for plasma immersion ion implantation (PⅢ) is described. The pulsed power system is based on a Marx circuit configuration and semi-conductor switches, which have many advantages in adjustable repetition frequency, pulse width modulation and long serving life compared with the conventional circuit category, tube-based technologies such as gridded vacuum tubes, thyratrons, pulse forming networks and transformers.The operation of PⅢ with pulse repetition frequencies up to 500 Hz has been achieved at a pulse voltage amplitude from 2 kV to 60 kV, with an adjustable pulse duration from 1 μs to 100 μs.The proposed system and its performance, as used to drive a plasma ion implantation chamber,axe described in detail on the basis of the experimental results.

  10. Pulse distortion in single-mode fibers. 3: Chirped pulses.

    Marcuse, D


    The theory of pulse distortion in single-mode fibers is extended to include laser sources that suffer a linear wavelength sweep (chirp) during the duration of the pulse. The transmitted pulse is expressed as a Fourier integral whose spectral function is given by an analytical expression in closed form. The rms width of the transmitted pulse is also expressed in closed form. Numerical examples illustrate the influence of the chirp on the shape and rms width of the pulse. A somewhat paradoxical situation exists. A given input pulse can be made arbitrarily short by a sufficiently large amount of chirping, and, after a given fiber length, this chirped pulse returns to its original width. But at this particular distance an unchirped pulse would be only [equiation] times longer. Thus chirping can improve the rate of data transmission by only 40%.

  11. 不同频率和脉宽的方波激励下无线电能传输效果分析%Effect Analysis of Wireless Power Transmission Under Excitation of Square Wave with Different Frequencies and Pulse Widths

    宋显锦; 刘国强; 张超; 张瑞华; 徐小宇


    Magnetic resonant wireless power transmission is a new type of technology for conducting non-radiative,mid-range power transmission using the near magnetic field based on resonant coupling phenomena.Many research findings were achieved through calculating the coupling voltage and power with the sinusoidal alternating current as the exciting source.The pulse current can also produce alternating magnetic field which induces the alternating current,and wireless power transmission excited by the pulse current has its own features.The circuit response process and the mechanism of resonant coupling excited by the pulse current are discussed,and the conclusion that the coupling process using pulse excitation is in essence also the sine wave coupling is drawn.With this transmission method,higher power can be transmitted to the load compared with sinusoidal excitation.The transfer effects of pulse waves with different pulse widths are compared by experiment and high-frequency resonant coils can be controlled by low frequency pulse signals,by which even more effective wireless power transfer can be achieved.%磁谐振式无线电能传输技术是基于磁谐振耦合现象利用近区磁场进行非辐射性、中距离输电的新技术。许多结果采用正弦交变电流作为激励,计算耦合电压和传输功率。脉冲激励也可以产生交变磁场从而感生交变电流,此方式下的无线电能传输有其自身特点。文中分析了脉冲激励下的电路响应过程及谐振耦合机理,其耦合过程本质上也是正弦波的耦合。在同一输出电压的情况下,与正弦激励相比,用脉冲方波做激励,负载可以获得较大的传输功率。最后,通过实验比较了几种脉宽和频率不同的方波激励的传输效果。实验结果表明,可以使用低频脉冲信号控制高频谐振线圈,从而实现更为有效的无线电能传输。

  12. Simplified flexible-PON upstream transmission using pulse position modulation at ONU and DSP-enabled soft-combining at OLT for adaptive link budgets.

    Liu, Xiang; Effenberger, Frank; Chand, Naresh


    We demonstrate a flexible modulation and detection scheme for upstream transmission in passive optical networks using pulse position modulation at optical network unit, facilitating burst-mode detection with automatic decision threshold tracking, and DSP-enabled soft-combining at optical line terminal. Adaptive receiver sensitivities of -33.1 dBm, -36.6 dBm and -38.3 dBm at a bit error ratio of 10(-4) are respectively achieved for 2.5 Gb/s, 1.25 Gb/s and 625 Mb/s after transmission over a 20-km standard single-mode fiber without any optical amplification.

  13. Investigation of the effects of continuous-wave, pulse- and amplitude-modulated microwaves on single excitable cells of Chara corallina.

    Liu, L M; Garber, F; Cleary, S F


    Single internodal excitable cells of Chara corallina were exposed to CW, pulse-modulated and sinusoidally modulated S-band microwave fields in a temperature-controlled waveguide exposure chamber. All electrical measurements were made external to the waveguide (ie, under no impressed microwave field). The dependent variables measured before, during, and after exposure to the S-band microwave fields included: resting potential, amplitude of the action potential, rise and decay time of the action potential, conduction velocity, and excitability. Cells maintained at 22 +/- 0.1 degrees C during exposure showed no consistent or statistically significant microwave-dependent alterations in any of the dependent variables.

  14. Ergodic channel capacity of spatial correlated multiple-input multiple-output free space optical links using multipulse pulse-position modulation

    Wang, Huiqin; Wang, Xue; Cao, Minghua


    The spatial correlation extensively exists in the multiple-input multiple-output (MIMO) free space optical (FSO) communication systems due to the channel fading and the antenna space limitation. Wilkinson's method was utilized to investigate the impact of spatial correlation on the MIMO FSO communication system employing multipulse pulse-position modulation. Simulation results show that the existence of spatial correlation reduces the ergodic channel capacity, and the reception diversity is more competent to resist this kind of performance degradation.

  15. Intra-pulse Raman frequency shift versus conventional Stokes generation of diode laser pulses in optical fibers.

    Kuzin, Evgeny; Mendoza-Vazquez, Sergio; Gutierrez-Gutierrez, Jaime; Ibarra-Escamilla, Baldemar; Haus, Joseph; Rojas-Laguna, Roberto


    We report experimental observations of stimulated Raman scattering in a standard fiber using a directly modulated DFB semiconductor laser amplified by two erbium-doped fibers. The laser pulse width was variably controlled on a nanosecond-scale; the laser emission was separated into two distinct regimes: an initial transient peak regime, followed by a quasi steady-state plateau regime. The transient leading part of the pump pulse containing fast amplitude modulation generated a broadband Raman-induced spectral shift through the modulation instability and subsequent intra-pulse Raman frequency shift. The plateau regime amplified the conventional Stokes shifted emission expected from the peaks of the gain distribution. The output signal spectrum at the end of a 9.13 km length of fiber for the transient part extends from 1550 nm to 1700 nm for a pump pulse peak power of 65 W. We found that the Raman-induced spectral shift is measurable about 8 W for every fiber length examined, 0.6 km, 4.46 km, and 9.13 km. All spectral components of the broadband scattering appear to be generated in the initial kilometer of the fiber span. The Stokes shifted light generation threshold was higher than the threshold for the intra-pulse Raman-induced broadened spectra. This fact enables the nonlinear spectral filtering of pulses from directly modulated semiconductor lasers.

  16. Intra-pulse Raman frequency shift versus conventional Stokes generation of diode laser pulses in optical fibers

    Kuzin, Evgeny A.; Mendoza-Vazquez, Sergio; Gutierrez-Gutierrez, Jaime; Ibarra-Escamilla, Baldemar; Haus, Joseph W.; Rojas-Laguna, Roberto


    We report experimental observations of stimulated Raman scattering in a standard fiber using a directly modulated DFB semiconductor laser amplified by two erbium-doped fibers. The laser pulse width was variably controlled on a nanosecond-scale; the laser emission was separated into two distinct regimes: an initial transient peak regime, followed by a quasi steady-state plateau regime. The transient leading part of the pump pulse containing fast amplitude modulation generated a broadband Raman-induced spectral shift through the modulation instability and subsequent intra-pulse Raman frequency shift. The plateau regime amplified the conventional Stokes shifted emission expected from the peaks of the gain distribution. The output signal spectrum at the end of a 9.13 km length of fiber for the transient part extends from 1550 nm to 1700 nm for a pump pulse peak power of 65 W. We found that the Raman-induced spectral shift is measurable about 8 W for every fiber length examined, 0.6 km, 4.46 km, and 9.13 km. All spectral components of the broadband scattering appear to be generated in the initial kilometer of the fiber span. The Stokes shifted light generation threshold was higher than the threshold for the intra-pulse Raman-induced broadened spectra. This fact enables the nonlinear spectral filtering of pulses from directly modulated semiconductor lasers.

  17. FPGA techniques based new hybrid modulation strategies for voltage source inverters.

    Sudha, L U; Baskaran, J; Elankurisil, S A


    This paper corroborates three different hybrid modulation strategies suitable for single-phase voltage source inverter. The proposed method is formulated using fundamental switching and carrier based pulse width modulation methods. The main tale of this proposed method is to optimize a specific performance criterion, such as minimization of the total harmonic distortion (THD), lower order harmonics, switching losses, and heat losses. The proposed method is articulated using fundamental switching and carrier based pulse width modulation methods. Thus, the harmonic pollution in the power system will be reduced and the power quality will be augmented with better harmonic profile for a target fundamental output voltage. The proposed modulation strategies are simulated in MATLAB r2010a and implemented in a Xilinx spartan 3E-500 FG 320 FPGA processor. The feasibility of these modulation strategies is authenticated through simulation and experimental results.

  18. Probabilistic Analysis of Crack Width

    J. Marková


    Full Text Available Probabilistic analysis of crack width of a reinforced concrete element is based on the formulas accepted in Eurocode 2 and European Model Code 90. Obtained values of reliability index b seem to be satisfactory for the reinforced concrete slab that fulfils requirements for the crack width specified in Eurocode 2. However, the reliability of the slab seems to be insufficient when the European Model Code 90 is considered; reliability index is less than recommended value 1.5 for serviceability limit states indicated in Eurocode 1. Analysis of sensitivity factors of basic variables enables to find out variables significantly affecting the total crack width.

  19. A deterministic width function model

    C. E. Puente


    Full Text Available Use of a deterministic fractal-multifractal (FM geometric method to model width functions of natural river networks, as derived distributions of simple multifractal measures via fractal interpolating functions, is reported. It is first demonstrated that the FM procedure may be used to simulate natural width functions, preserving their most relevant features like their overall shape and texture and their observed power-law scaling on their power spectra. It is then shown, via two natural river networks (Racoon and Brushy creeks in the United States, that the FM approach may also be used to closely approximate existing width functions.

  20. A dual-loss-modulated intra-cavity frequency-doubled Q-switched and mode-locked Nd:Lu0.15Y0.85VO4/KTP green laser with a single-walled carbon nanotube saturable absorber and an acousto-optic modulator

    Zhang, Gang; Zhao, Shengzhi; Yang, Kejian; Li, Guiqiu; Li, Dechun; Cheng, Kang; Han, Chao; Zhao, Bin; Wang, Yonggang


    By using both a single-walled carbon nanotube saturable absorber (SWCNT-SA) and an acousto-optic (AO) modulator, a dual-loss-modulated intra-cavity frequency-doubled Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4/KTP (KTiOPO4) green laser was demonstrated for the first time. The QML green laser characteristics such as the pulse width and single-pulse energy have been measured for different modulation frequencies of the AO modulator (fp). In particular, in comparison with the solely passively QML green laser with an SWCNT-SA, the dual-loss-modulated QML green laser can generate a more stable pulse train, a shorter pulse width of the Q-switched envelope, a greater pulse energy and a higher average peak power. For the dual-loss-modulated QML green laser, at a pump power of 7.9 W and a repetition rate of 10 kHz, the pulse width and the pulse energy of the Q-switch envelope and the average peak power of the QML green laser are 50 ns, 20.34 µJ and 15.5 kW, respectively, corresponding to a pulse width compression of 77%, a pulse energy improvement factor of six times and a QML peak power increase factor of 16 times when compared with those for the solely passively QML green laser. The experimental results show that the dual-loss modulation is an efficient method for the generation of a stable QML green laser with an SWCNT-SA.