WorldWideScience
 
 
1

Dc SQUID small signal analysis  

International Nuclear Information System (INIS)

This paper presents a Small Signal Analysis for the dc SQUID (Superconducting Quantum Interference Device). This analysis involves the linearization of the SQUID equations for a given flux and current bias. Considering the SQUID to be a two port device, an impedance matrix can be determined for a SQUID coupled to a general input circuit. Also, the two intrinsic noise sources referred to the input are computed. One advantage of this analysis over other models of the dc SQUID is that an analytic expression can be determined for the cross-correlation power spectral density of the noise sources. These results should be useful in determining the signal-to-noise ratio of low-noise SQUIDs for a given application. Other differences and similarities of the Small Signal Analysis to other dc SQUID models are discussed

2

Small-signal analysis of a rectangular helix structure traveling-wave-tube  

International Nuclear Information System (INIS)

This paper investigates the properties of traveling wave-beam interaction in a rectangular helix traveling-wave-tube (TWT) for a solid sheet electron beam. The 'hot' dispersion equation is obtained by means of the self-consistent field theory. The small signal analysis, which includes the effects of the beam parameters and slow-wave structure (SWS) parameters, is carried out by theoretical computation. The numerical results show that the bandwidth and the small-signal gain of the rectangular helix TWT increase as the beam current increases; and the beam voltage not obviously influences the small signal gain. Among different rectangular helix structures, the small-signal gain increases as the width of the rectangular helix SWS increases, however, the bandwidth decreases whether structure parameters a and L or ? and L are fixed or not. In addition, a comparison of the small-signal gain of this structure with a conventional round helix is made. The presented analysis will be useful for the design of the TWT with a rectangular helix circuit. (classical areas of phenomenology)

3

Small-Signal Amplifier with MOSFET and BJT in Triple Darlington Configuration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new circuit model of a small-signal narrow-band amplifier is proposed and analyzed on the qualitative scale. Proposed amplifier uses two MOSFETs and a BJT in Triple Darlington configuration with two additional biasing resistances in the circuit. With low distortion percentage (1.28%), the proposed circuit successfully amplifies small-signals of 1-10mV range and simultaneously provides high voltage gain (311.593) and current gain (13.971K) with narrow bandwidth (9.665KHz). Variations of maxi...

SUSMRITA SRIVASTAVA; NARESH KUMAR CHAUDHARY; SACHCHIDANAND SHUKLA

2013-01-01

4

Spectral dependence of the small-signal gain around 1.5 ?m in erbium doped silica fiber amplifiers  

International Nuclear Information System (INIS)

A simple theoretical analysis of a small-signal Er3 + doped silica fiber amplifier is presented which compares the efficiency of the 800, 980, and 1500 nm pump bands, and also demonstrates that wide bandwidth and high gains can be achieved simultaneously by a suitable choice of pump power and fiber length

5

A New Circuit Model of Small-Signal Sziklai Pair Amplifier  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new circuit model of RC coupled small-signal Sziklai pair amplifier is proposed and qualitatively analyzed for the first time. The circuit of proposed amplifier uses a Sziklai pair with NPN driver and crops high voltage gain (237.916), moderate bandwidth (15.10KHz), fairly high current gain (712.075) and considerably low THD (0.73%) at 1mV, 1KHz input AC signal. This circuit can be tuned in specific audible frequency range, extending approximately from 1Hz to 20KHz. Tuning performance makes...

SachchidaNand Shukla and Susmrita Srivastava

2013-01-01

6

Thermal Effects and Small Signal Modulation of 1.3-?m InAs/GaAs Self-Assembled Quantum-Dot Lasers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate the influence of thermal effects on the high-speed performance of 1.3-?m InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth...

Zhao, Hx; Yoon, Sf; Tong, Cz; Liu, Cy; Wang, R.; Cao, Q.

2010-01-01

7

Analysis of the large and small signal direct current modulation response up to 60GHz of metal-clad nano-lasers  

Science.gov (United States)

The response of metal clad nano-lasers to direct current modulation has been analysed in both the small signal and large signal regimes. Calculations have been performed using rate equations which include the Purcell cavity-enhanced spontaneous emission factor, F, and the spontaneous emission coupling factor ?. Calculations of both the small signal and large signal direct modulation response of nano-lasers indicate opportunities to achieve modulation bandwidth up to 60 GHz with peak responses at resonant frequencies of order 40 GHz and 30 GHz respectively.

Sattar, Z. A.; Shore, K. Alan

2014-09-01

8

Small-signal model for the series resonant converter  

Science.gov (United States)

The results of a previous discrete-time model of the series resonant dc-dc converter are reviewed and from these a small signal dynamic model is derived. This model is valid for low frequencies and is based on the modulation of the diode conduction angle for control. The basic converter is modeled separately from its output filter to facilitate the use of these results for design purposes. Experimental results are presented.

King, R. J.; Stuart, T. A.

1985-01-01

9

Correcting the minimization bias in searches for small signals  

International Nuclear Information System (INIS)

We discuss a method for correcting the bias in the limits for small signals if those limits were found based on cuts that were chosen by minimizing a criterion such as sensitivity. This type of bias is commonly present when a 'minimization' and an 'evaluation' are done at the same time. We propose to use a variant of the statistical bootstrap to adjust the limits. A Monte Carlo study shows that these new limits have correct coverage

10

Correcting the Minimization Bias in Searches for Small Signals  

CERN Document Server

We discuss a method for correcting the bias in the limits for small signals if those limits were found based on cuts that were chosen by minimizing a criterion such as sensitivity. Such a bias is commonly present when a "minimization" and an "evaluation" are done at the same time. We propose to use a variant of the bootstrap to adjust the limits. A Monte Carlo study shows that these new limits have correct coverage.

Rolke, W A; Rolke, Wolfgang A.; Lopez, Angel M.

2003-01-01

11

Small-signal modulation and differential gain of red-emitting (??=?630?nm) InGaN/GaN quantum dot lasers  

International Nuclear Information System (INIS)

We report small-signal modulation bandwidth and differential gain measurements of a ridge waveguide In0.4Ga0.6N/GaN quantum dot laser grown by molecular beam epitaxy. The laser peak emission is at ??=?630?nm. The ?3?dB bandwidth of an 800??m long device was measured to be 2.4?GHz at 250?mA under pulsed biasing, demonstrating the possibility of high-speed operation of these devices. The differential gain was measured to be 5.3?×?10?17?cm2, and a gain compression factor of 2.87?×?10?17?cm3 is also derived from the small-signal modulation response

12

Small-signal modulation and differential gain of red-emitting (??=?630?nm) InGaN/GaN quantum dot lasers  

Energy Technology Data Exchange (ETDEWEB)

We report small-signal modulation bandwidth and differential gain measurements of a ridge waveguide In{sub 0.4}Ga{sub 0.6}N/GaN quantum dot laser grown by molecular beam epitaxy. The laser peak emission is at ??=?630?nm. The ?3?dB bandwidth of an 800??m long device was measured to be 2.4?GHz at 250?mA under pulsed biasing, demonstrating the possibility of high-speed operation of these devices. The differential gain was measured to be 5.3?×?10{sup ?17}?cm{sup 2}, and a gain compression factor of 2.87?×?10{sup ?17}?cm{sup 3} is also derived from the small-signal modulation response.

Frost, Thomas; Banerjee, Animesh; Bhattacharya, Pallab, E-mail: pkb@eecs.umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)

2013-11-18

13

Small-signal analysis for dc SQUID amplifiers  

International Nuclear Information System (INIS)

A small-signal analysis is presented for the dc SQUID (Superconducting QUantum Interference Device) coupled to a general-input impedance. This method differs from previous calculations by introducing perturbations of the SQUID variables into all of the equations describing a dc SQUID rather than just those describing the input circuit and the continuity of the wave function phase around the SQUID loop. From this method, one is able to determine analytic expressions for the impedance matrix, the power spectral densities of the two conjugate noise sources, and the cross-correlation power spectral density in terms of the well-known solutions of an isolated dc SQUID. Results presented are compared with the results of other techniques

14

Thermal Effects and Small Signal Modulation of 1.3-?m InAs/GaAs Self-Assembled Quantum-Dot Lasers  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract We investigate the influence of thermal effects on the high-speed performance of 1.3-?m InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C. Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.

Tong CZ

2011-01-01

15

Thermal Effects and Small Signal Modulation of 1.3-?m InAs/GaAs Self-Assembled Quantum-Dot Lasers  

Science.gov (United States)

We investigate the influence of thermal effects on the high-speed performance of 1.3-?m InAs/GaAs quantum-dot lasers in a wide temperature range (5-50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.

Zhao, Hx; Yoon, Sf; Tong, Cz; Liu, Cy; Wang, R.; Cao, Q.

2011-12-01

16

Small-signal impedance characteristics of quantum-well laser structures  

Energy Technology Data Exchange (ETDEWEB)

Small-signal impedance characteristics of quantum-well laser structures are analyzed. A simple analytical expression for the frequency dependence of below-threshold small-signal impedance is derived and verified experimentally. It is shown that the differential carrier lifetime and quantum-well transport and capture times can be extracted from electrical impedance measurements. {copyright} 2001 American Institute of Physics.

Giudice, G. E.; Kuksenkov, D. V.; Temkin, H.

2001-06-25

17

Characterization and application of a broad bandwidth oscillator for the HELEN laser facility  

Science.gov (United States)

Preliminary investigations of a potential broad band oscillator for the HELEN laser facility and its proposed upgrade are described. The reasons for the need of broad bandwidth and the choice of commercial technology to achieve it are discussed. The characterization of the device and the diagnostics used for the investigations are described. Small signal amplification of the bandwidth by a glass amplifier was also performed along with investigations of the effect of various bandwidths on the far field beam quality when using random phase plates.

Andrew, James E.; Stevenson, R. M.; Bett, Thomas H.

1995-12-01

18

Characterization and application of a broad bandwidth oscillator for the HELEN laser facility  

International Nuclear Information System (INIS)

Preliminary investigations of a potential broad band oscillator for the HELEN laser facility and its proposed upgrade are described. The reasons for the need of broad bandwidth and the choice of commercial technology to achieve it are discussed. The characterization of the device and the diagnostics used for the investigations are described. Small signal amplification of the bandwidth by a glass amplifier was also performed along with investigations of the effect of various bandwidths on the far field beam quality when using random phase plates

19

The Bandwidth Exchange Architecture  

CERN Document Server

New applications for the Internet such as video on demand, grid computing etc. depend on the availability of high bandwidth connections with acceptable Quality of Service (QoS). There appears to be, therefore, a requirement for a market where bandwidth-related transactions can take place. For this market to be effective, it must be efficient for both the provider (seller) and the user (buyer) of the bandwidth. This implies that: (a) the buyer must have a wide choice of providers that operate in a competitive environment, (b) the seller must be assured that a QoS transaction will be paid by the customer, and (c) the QoS transaction establishment must have low overheads so that it may be used by individual customers without a significant burden to the provider. In order to satisfy these requirements, we propose a framework that allows customers to purchase bandwidth using an open market where providers advertise links and capacities and customers bid for these services. The model is close to that of a commoditi...

Turner, D M; Keromytis, A D; Turner, David Michael; Prevelakis, Vassilis; Keromytis, Angelos D.

2005-01-01

20

Small-signal analysis of dc-dc converters with sliding mode control  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with small-signal analysis of dc-dc converters with sliding mode control. A suitable small-signal model is developed which allows selection of control coefficients, analysis of parameter variation effects, characterization of the closed-loop behavior in terms of audiosusceptibility, output and input impedances, and reference to output transfer function. Unlike previous analyses, the model includes effects of the filters used to evaluate state variable errors. Simulated and experimental results demonstrate model potentialities.

Mattavelli, P.; Rossetto, L.; Spiazzi, G. [Univ. of Padova (Italy)

1997-01-01

 
 
 
 
21

Small-signal Amplifier with Three Dissimilar Active Devices in Triple Darlington Topology  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new circuit model of a small-signal amplifier is proposed and analyzed on the qualitative scale. Apart from routine biasing components, the proposed amplifier circuit uses two additional biasing resistances and three dissimilar active devices namely MOSFET, JFET and BJT in Triple Darlington configuration. Having a considerably low amount of distortion (0.71%), the proposed circuit successfully amplifies small-signals of 1-5mV range (at 1 KHz frequency) and simultaneously provides high volta...

DR. SACHCHIDANAND SHUKLA; SUSMRITA SRIVASTAVA

2013-01-01

22

Small-Signal Stability Analysis of Full-Load Converter Interfaced Wind Turbines  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Power system stability investigations of wind farms often cover the tasks of low-voltage-fault-ride-through, voltage and reactive power control, and power balancing, but not much attention has yet been paid to the task of small-signal stability. Small-signal stability analysis needs increasing focus since the share of wind power increases substituting power generation from conventional power plants. Here, a study based on modal analysis is presented which investigate the effect of large scale...

Knu?ppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nyga?rd; Jensen, Kim H.; Dixon, Andrew; Østergaard, Jacob

2009-01-01

23

Bandwidth in bolometric interferometry  

CERN Document Server

Bolometric Interferometry is a technology currently under development that will be first dedicated to the detection of B-mode polarization fluctuations in the Cosmic Microwave Background. A bolometric interferometer will have to take advantage of the wide spectral detection band of its bolometers in order to be competitive with imaging experiments. A crucial concern is that interferometers are presumed to be importantly affected by a spoiling effect known as bandwidth smearing. In this paper, we investigate how the bandwidth modifies the work principle of a bolometric interferometer and how it affects its sensitivity to the CMB angular power spectra. We obtain analytical expressions for the broadband visibilities measured by broadband heterodyne and bolometric interferometers. We investigate how the visibilities must be reconstructed in a broadband bolometric interferometer and show that this critically depends on hardware properties of the modulation phase shifters. Using an angular power spectrum estimator ...

Charlassier, R; Hamilton, J -Ch; Kaplan, J; Malu, S

2009-01-01

24

Small Signal Stability Improvement of Power Systems Using Optimal Load Responses in Competitive Electricity Markets  

DEFF Research Database (Denmark)

Since the hourly spot market price is available one day ahead in Denmark, the price could be transferred to the consumers and they may shift some of their loads from high price periods to the low price periods in order to save their energy costs. The optimal load response to an electricity price for demand side management generates different load profiles and may provide an opportunity to improve the small signal stability of power systems with high wind power penetrations. In this paper, the idea of power system small signal stability improvement by using optimal load response to the electricity price is proposed. A 17-bus power system with high wind power penetrations, which resembles the Eastern Danish power system, is chosen as the study case. Simulation results show that the optimal load response to electricity prices is an effective measure to improve the small signal stability of power systems with high wind power penetrations.

Hu, Weihao; Su, Chi

2011-01-01

25

Study on Small Signal Stability Improvement by PSS of the Large-Scale Wind Power Integration  

Directory of Open Access Journals (Sweden)

Full Text Available With the increasing penetration of wind energy generation into power system, the impact of wind farms on power grids performance and stability control is of growing concern. Firstly there is a introduction of basic principles related to small signal stability analysis. Then a new method of improving small signal stability is proposed in this paper. The method, based on optimization adjustment of time constant of the phase shift link of PSS, is verified to be effective by an instance analysis of simulation in DIgSILENT/Power Factory. Three-machine Nine Nodes Model is used in this simulation.

Zi Lan Zhao

2013-04-01

26

Analytical Expressions for Small-Signal and Saturation Processes of Optical Parametric Chirped-Pulse Amplification  

Science.gov (United States)

Analytical expressions corresponding to the small-signal and saturation processes of optical parametric chirped-pulse amplification are derived from the elliptic integration obtained by nonlinear-wave equations. The analytical expressions are simple and practical for the optimization of optical parametric chirped-pulse amplification even under the saturation process.

Harimoto, Tetsuo; Yamakawa, Koichi

2009-09-01

27

Cutter Connectivity Bandwidth Study  

Science.gov (United States)

The goal of this study was to determine how much bandwidth is required for cutters to meet emerging data transfer requirements. The Cutter Connectivity Business Solutions Team with guidance front the Commandant's 5 Innovation Council sponsored this study. Today, many Coast Guard administrative and business functions are being conducted via electronic means. Although our larger cutters can establish part-time connectivity using commercial satellite communications (SATCOM) while underway, there are numerous complaints regarding poor application performance. Additionally, smaller cutters do not have any standard means of underway connectivity. The R&D study shows the most important factor affecting web performance and enterprise applications onboard cutters was latency. Latency describes the time it takes the signal to reach the satellite and come back down through space. The latency due to use of higher orbit satellites is causing poor application performance and inefficient use of expensive SATCOM links. To improve performance, the CC must, (1) reduce latency by using alternate communications links such as low-earth orbit satellites, (2) tailor applications to the SATCOM link and/or (3) optimize protocols used for data communication to minimize time required by present applications to establish communications between the user and the host systems.

2002-10-01

28

Bandwidth of Gaussian weighted Chirp  

DEFF Research Database (Denmark)

Four major time duration and bandwidth expressions are calculated for a linearly frequency modulated sinusoid with Gaussian shaped envelope. This includes a Gaussian tone pulse. The bandwidth is found to be a nonlinear function of nominal time duration and nominal frequency excursion of the chirp signal.

Wilhjelm, Jens E.

1993-01-01

29

Small-Signal Stability of Wind Power System With Full-Load Converter Interfaced Wind Turbines  

DEFF Research Database (Denmark)

Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants (WPP). In this paper a comprehensive analysis is presented which assesses the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind turbine (WT) model with all grid relevant control functions is used in the study. The WT is, furthermore, equipped with a park level WPP voltage controller and comparisons are presented. The WT model for this work is a validated dynamic model of the 3.6 MW Siemens Wind Power WT. The study is based on modal analysis which is complemented with time domain simulations on the nonlinear system.

Knüppel, Thyge; Nielsen, JØrgen Nygaard

2012-01-01

30

Resolving small signal measurements in experimental plasma environments using calibrated subtraction of noise signalsa)  

Science.gov (United States)

The performance of many diagnostic and control systems within fusion and other fields of research are often detrimentally affected by spurious noise signals. This is particularly true for those (such as radiation or particle detectors) working with very small signals. Common sources of radiated and conducted noise in experimental fusion environments include the plasma itself and instrumentation. The noise complicates data analysis, as illustrated by noise on signals measured with the heavy ion beam probe (HIBP) installed on the Madison Symmetric Torus. The noise is time-varying and often exceeds the secondary ion beam current (in contrast with previous applications). Analysis of the noise identifies the dominant source as photoelectric emission from the detectors induced by ultraviolet light from the plasma. This has led to the development of a calibrated subtraction technique, which largely removes the undesired temporal noise signals from data. The advantages of the technique for small signal measurement applications are demonstrated through improvements realized on HIBP fluctuation measurements.

Fimognari, P. J.; Demers, D. R.; Chen, X.; Schoch, P. M.

2014-11-01

31

Small-signal analysis of OOFDM signal transmission with directly modulated laser and direct detection.  

Science.gov (United States)

This work presents a small-signal analysis for investigating the transmission performance of optical orthogonal frequency division multiplexing signals with a directly modulated DFB laser (DML). The analysis shows the positive chirp of DMLs can intensify power fading after transmission with positive dispersion and provide power gain instead with negative dispersion. The power of subcarrier-to-subcarrier intermixing interference after square-law direct detection, however, is independent on the sign of dispersion. PMID:21263483

Wei, Chia-Chien

2011-01-15

32

Uncertainty Estimation in SiGe HBT Small-Signal Modeling  

DEFF Research Database (Denmark)

An uncertainty estimation and sensitivity analysis is performed on multi-step de-embedding for SiGe HBT small-signal modeling. The uncertainty estimation in combination with uncertainty model for deviation in measured S-parameters, quantifies the possible error value in de-embedded two-port parameters (Y and Z - parameters). The analysis is applied to a 0.35 ?m 60 GHz fT SiGe HBT in frequency range 45 MHz to 26 GHz.

Johansen, Tom Keinicke; Vidkjær, Jens

2005-01-01

33

A new small-signal model for asymmetrical AlGaN/GaN HEMTs  

Energy Technology Data Exchange (ETDEWEB)

A new small-signal model for anisomerous AlGaN/GaN high electron mobility transistors (HEMTs) is proposed for accurate prediction of HEMT behavior up to 20 GHz. The parasitic elements are extracted from both cold-FET and pinch-off bias to obtain more precise results and the intrinsic part is directly extracted. All the parameters needed in this process are determined by the device structure rather than optimization methods. This guarantees consistency between the parameter values and the component's physical meaning. (semiconductor devices)

Ma Teng; Hao Yue; Chen Chi; Ma Xiaohua, E-mail: mateng03@gmail.co [National Key Laboratory of Wide Band-Gap Semiconductor Technology, Department of Microelectronics, Xidian University, Xi' an 710071 (China)

2010-06-15

34

A New Circuit Model of Small-Signal Amplifier using JFETs in Darlington pair Configuration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A small-signal amplifier with two identical JFETs in Darlington pair is proposed and qualitatively analyzed perhaps for the first time. Unlike CS-JFET amplifiers, the voltage gain of this amplifier is significantly higher than unity. In addition, this amplifier can also be tuned in the specific range of audible frequency extended from 90Hz to 19KHz. Tuning performance makes this amplifier suitable to use in Radio and TV receivers. An additional biasing resistance RA, ranging in 3K? to 1M?, ...

DR. SACHCHIDANAND SHUKLA; SUSMRITA SRIVASTAVA

2013-01-01

35

Numerical Analysis of Alternating-Current Small-Signal Response in Graphene Nanoribbons  

International Nuclear Information System (INIS)

Alternating-current small-signal admittances of armchair graphene nanoribbons are investigated using the method of non-equilibrium Green's function. The calculated ac admittances show an oscillatory response between inductive and capacitive behaviors, which is a result of the finite length of the graphene nanoribbon. The effects of hydrogen-passivated edges on ac response are demonstrated. At low frequency, the edge effects transform the inductive behavior in a metallic graphene nanoribbon into a capacitive one. Finally, the effects of variations in the width and bandgap of a graphene nanoribbon on its dynamic response are investigated. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

36

A linearised small-signal model of an HVDC converter for harmonic calculation  

Energy Technology Data Exchange (ETDEWEB)

In this paper a new method is presented for calculation of the harmonics in the ac current and dc voltage of a six-pulse HVDC converter. Instead of fast Fourier transform, FFT, the Fourier series is used in this method. The HVDC converter is represented by a linearised small-signal model in mixed time- frequency domain in which the effects of on and off states resistances, forward voltage drop, and snubber circuits of the thyristors are taken into account. RL series circuits are used for modeling of the converter transformer and ac system. To validate the method a comparison is made with PSCAD/EMTDC time domain simulation program. (author)

Seifossadat, Ghodratollah [Shahid Chamran University, Ahwaz (Iran); Shoulaie, Abbas [Iran University of Science and Technology (Iran)

2006-04-15

37

Black Holes, Bandwidths and Beethoven  

CERN Document Server

It is usually believed that a function whose Fourier spectrum is bounded can vary at most as fast as its highest frequency component. This is in fact not the case, as Aharonov, Berry and others drastically demonstrated with explicit counter examples, so-called superoscillations. The claim is that even the recording of an entire Beethoven symphony can occur as part of a signal with 1Hz bandwidth. Superoscillations have been suggested to account e.g. for transplanckian frequencies of black hole radiation. Here, we give an exact proof for generic superoscillations. Namely, we show that for every fixed bandwidth there exist functions which pass through any finite number of arbitrarily prespecified points. Further, we show that the behavior of bandlimited functions can be reliably characterized through an uncertainty relation for the standard deviation of the signals' samples taken at the Nyquist rate. This uncertainty relation generalizes to time-varying bandwidths.

Kempf, A

2000-01-01

38

ANNs in Bias Dependant Small-Signal and Noise Modeling of Microwave FETs  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper an efficient procedure for determination of small-signal and noise behavior of microwave transistors for various bias conditions is proposed. An empirical transistor noise model based on an equivalent circuit (improvement of Pospieszalski’s noise model is considered. Since it is necessary to extract values of the model equivalent circuit for each bias point (which requires the measured data acquiring and repeated time consuming extraction procedures, it is proposed to use an artificial neural network to model the bias dependence of the equivalent circuit parameters. In that way, it is necessary to acquire the measured data and extract the equivalent circuit parameters only for several operating biases used for the network training. Once the neural network is trained, the device small-signal scattering and noise parameters are easily obtained for an arbitrary bias point from the device operating range without changes in the model. The proposed modeling approach is exemplified by modeling of a specific MESFET device in a packaged form.

V. Markovi?

2010-06-01

39

Tenotomy does not affect saccadic velocities: support for the "small-signal" gain hypothesis.  

Science.gov (United States)

We investigated the effects of four-muscle tenotomy on saccadic characteristics in infantile nystagmus syndrome (INS) and acquired pendular nystagmus (APN). Eye movements of 10 subjects with INS and one with APN were recorded using infrared reflection, magnetic search coil, or high-speed digital video. The expanded nystagmus acuity function (NAFX) quantified tenotomy-induced foveation changes in the INS. Saccadic characteristics and peak-to-peak nystagmus amplitudes were measured. Novel statistical tests were performed on the saccadic data. Six out of the 10 INS subjects showed no changes in saccadic duration, peak velocity, acceleration, or trajectory. In the other four, the differences were less than in peak-to-peak amplitudes (from 14.6% to 39.5%) and NAFX (from 22.2% to 162.4%). The APN subject also showed no changes despite a 50% decrease in peak-to-peak amplitude and a 34% increase in NAFX. The "small-signal" changes (peak-to-peak nystagmus amplitude and NAFX) were found to far exceed any "large-signal" changes (saccadic). Tenotomy successfully reduced INS and APN, enabling higher visual acuity without adversely affecting saccadic characteristics. These findings support the peripheral, small-signal gain reduction (via proprioceptive tension control) hypothesis. Current linear plant models, limited to normal steady-state muscle tension levels, cannot explain the effects of the tenotomy. PMID:16497352

Wang, Z; Dell'Osso, L F; Zhang, Z; Leigh, R J; Jacobs, J B

2006-07-01

40

Black holes, bandwidths and Beethoven  

Science.gov (United States)

It is usually believed that a function ?(t) whose Fourier spectrum is bounded can vary at most as fast as its highest frequency component ?max. This is, in fact, not the case, as Aharonov, Berry, and others drastically demonstrated with explicit counterexamples, so-called superoscillations. It has been claimed that even the recording of an entire Beethoven symphony can occur as part of a signal with a 1 Hz bandwidth. Bandlimited functions also occur as ultraviolet regularized fields. Their superoscillations have been suggested, for example, to resolve the trans-Planckian frequencies problem of black hole radiation. Here, we give an exact proof for generic superoscillations. Namely, we show that for every fixed bandwidth there exist functions that pass through any finite number of arbitrarily prespecified points. Further, we show that, in spite of the presence of superoscillations, the behavior of bandlimited functions can be characterized reliably, namely through an uncertainty relation: The standard deviation ?T of samples ?(tn) taken at the Nyquist rate obeys ?T>=1/4?max. This uncertainty relation generalizes to variable bandwidths. For ultraviolet regularized fields we identify the bandwidth as the in general spatially variable finite local density of degrees of freedom.

Kempf, Achim

2000-04-01

 
 
 
 
41

Impact of Large-Scale Wind Power Integration on Small Signal Stability Based on Stability Region Boundary  

Directory of Open Access Journals (Sweden)

Full Text Available Up until now, study results on the impact of large-scale wind power integration on small signal stability have often been in conflict. Sometimes, the conclusions are even completely opposite, making people unable to agree on which is right. The reason behind this phenomenon is that most of these studies are based on a certain grid and typical working conditions, so conclusions are reached by comparing changes in oscillation mode, one by one. This study method lacks a broader perspective, and often reflects only a part of the grid conditions. However, the small signal stability region boundary describes the critical operating range of power system small signal stability as a whole, making possible an overall evaluation of the system from a more macro perspective. Thus it is more suitable for analysis of the impact of large-scale wind power integration on small signal stability. Based on the above, using the model of wind farm integration to the single-machine infinite bus power system, this paper studies the impact of wind power integration scale and the coupling strength with synchronous generator on small signal stability through the comparison of the stability region boundaries, thus providing a new method and support for analyzing the impact of wind power integration on small signal stability.

Wenying Liu

2014-11-01

42

T3DB: an integrated database for bacterial type III secretion system  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Type III Secretion System (T3SS, which plays important roles in pathogenesis or symbiosis, is widely expressed in a variety of gram negative bacteria. However, lack of unique nomenclature for T3SS genes has hindered T3SS related research. It is necessary to set up a knowledgebase integrating T3SS-related research data to facilitate the communication between different research groups interested in different bacteria. Description A T3SS-related Database (T3DB was developed. T3DB serves as an integrated platform for sequence collection, function annotation, and ortholog classification for T3SS related apparatus, effector, chaperone and regulatory genes. The collection of T3SS-containing bacteria, T3SS-related genes, function annotation, and the ortholog information were all manually curated from literature. BPBAac, a highly efficient T3SS effector prediction tool, was also implemented. Conclusions T3DB is the first systematic platform integrating well-annotated T3SS-related gene and protein information to facilitate T3SS and bacterial pathogenecity related research. The newly constructed T3 ortholog clusters may faciliate effective communication between different research groups and will promote de novo discoveries. Besides, the manually-curated high-quality effector and chaperone data are useful for feature analysis and evolutionary studies of these important proteins.

Wang Yejun

2012-04-01

43

Wide-Area Assessment of Aperiodic Small Signal Rotor Angle Stability in Real-Time  

DEFF Research Database (Denmark)

This paper presents the details of a new real-time stability assessment method. The method assesses a particular mechanism of stability: each generator’s capability to generate sufficient steady state electromechanical torque. The lack of sufficient steady state torque causes aperiodic increase in rotor angle and a loss of synchronism, referred to as aperiodic small signal instability. The paper provides the theoretical background of the method and an analytical assessment criterion. Furthermore, a mathematical mapping of the generators’ operating points that enables informative visualization of multiple operating points is derived in the paper. Finally, results from time-domain simulation of instability scenarios in the Nordic32 test system are presented and results used for testing the assessment method. The results illustrate the method’s capability to efficiently identify the location of the emerging problem and to quantify margins to stability boundary.

Jóhannsson, Hjörtur; Nielsen, Arne Hejde

2013-01-01

44

A small-signal generator based on a multi-layer graphene/molybdenum disulfide heterojunction  

International Nuclear Information System (INIS)

In this work, we fabricate a heterojunction small-signal generator (HSSG) based on a graphene-molybdenum disulfide (MoS2) heterojunction. The HSSG is fundamentally different from any analog device developed previously. The HSSG is composed of two quasi-2D heterojunctions and has three terminals named injector (I), recombinator (R), and generator (G). MoS2 serves as I and G, and graphene works as R in the HSSG. The scale coefficient (??=?IG/IR) of the HSSG is 1.14?×?10?4 (VIG,?IR?=?0.2?V) to 1.95?×?10?4 (VIG,?IR?=?1?V). The current generated from G could be as low as pA scale, which reveals the good performance of the HSSG

45

3-D effects on small signal gain for undulators with variable parameters  

International Nuclear Information System (INIS)

A new explanation on the quadrature expression for small signal gain (SSG) in a variable parameter undulator is given in terms of Madey's theorem and analogy between the FEL and a phased antenna array and the spontaneous emission spectrum is derived. The generalization of the SSG expression from one to three dimensions is carried out and the effect on SSG due to the collimation error among the axes of the optical, electron beam and undulator is included as well. It shows at three dimensional effects will reduce SSG severely. The comparison with Boeing's FEL experiment is carried out and it is also pointed out that a better operation condition may be obtained if the first uniform section of the Boeing's undulator is reduced a little to make the optimum energy mismatch shifted towards zero

46

Influence of Wind Plant Ancillary Voltage Control on System Small Signal Stability  

DEFF Research Database (Denmark)

As a common tendency, large-scale wind farms are increasingly connected to the transmission system of modern power grids. This introduces some new challenges to the connected power systems, and the transmission system operators (TSOs) have to put some new requirements as part of the grid codes on the integration of wind farms. One common requirement to wind farms is the function of system voltage control which can be implemented in the grid-side convertor controller of a variable speed wind turbine. This ancillary voltage control provided by wind farms could have some influence on the system small signal stability. This paper implements an ancillary voltage control strategy on a direct-drive-full-convertor-based wind farm and studies its influence on the damping ratio values of the dominant oscillation mode within the connected power system. All the calculations and simulations are conducted in DIgSILENT PowerFactory 14.0.

Su, Chi; Chen, Zhe

2012-01-01

47

Two neural approaches for small-signal modelling of GaAs HEMTs  

Directory of Open Access Journals (Sweden)

Full Text Available Focus of this paper is on the neural approach in small-signal modelling of GaAs HEMTs. Two modelling approaches based on artificial neural networks are discussed and compared. The first approach is completely based on artificial neural networks, while the second is a hybrid approach putting together artificial neural networks and an equivalent circuit representation of a microwave transistor. Both models consider the device gate width and therefore both are scalable. Results of modelling of three different AlGaAs/GaAs HEMTs in a wide range of operating bias conditions using the considered approaches are given. Different modelling aspects are discussed. A special attention is paid to the model development procedure and accuracy of the models.

Marinkovi? Zlatica

2010-01-01

48

Influence of Wind Plant Ancillary Frequency Control on System Small Signal Stability  

DEFF Research Database (Denmark)

Since large-scale wind farms are increasingly connected to modern power grids, the transmission system operators put more requirements as part of the grid codes on the integration of wind farms. System frequency control which is normally provided by conventional synchronous generators becomes a common requirement to wind farms. This ancillary frequency control provided by wind farms could have some influence on the system small signal stability. This paper implements an ancillary frequency control strategy on a directdrive- full-convertor-based wind farm and studies its influence on the damping ratio values of the dominant oscillation modes within the connected power system. All the calculations and simulations are conducted in DIgSILENT PowerFactory 14.0.

Su, Chi; Chen, Zhe

2012-01-01

49

Comparison Study of Power System Small Signal Stability Improvement Using SSSC and STATCOM  

DEFF Research Database (Denmark)

A static synchronous series compensator (SSSC) has the ability to emulate a reactance in series with the connected transmission line. A static synchronous compensator (STATCOM) is able to provide the reactive power to an electricity network. When fed with some supplementary signals from the connected power system, both SSSC and STATCOM are able to participate in the power system inter-area oscillation damping by changing the compensated reactance or the provided reactive power. This paper analyses the influence of SSSC and STATCOM on power system small signal stability. The damping controller schemes for SSSC and STATCOM are presented and discussed. The IEEE 39-bus New England system model as the test system is built in DIgSIELNT PowerFactory, in which the damping control strategies for both SSSC and STATCOM are validated by time domain simulations and modal analysis. Furthermore, comparison studies show that the SSSC is a better solution in term of equipment capabilities and costs.

Hu, Weihao; Su, Chi

2013-01-01

50

Radon transform and bandwidth compression.  

Science.gov (United States)

A bandwidth-compression scheme for two-dimensional data is presented that incorporates the Radon transform. There are three advantages to this approach: only one-dimensional operations are required, the dynamic range requirements of the compression are reduced by a filtering step associated with the inverse Radon transform, and the technique is readily adaptive to the data structure. A rectilinear object is compressed to demonstrate the algorithm. PMID:19718126

Smith, W E; Barrett, H H

1983-07-01

51

Bandwidth theorem for sparse graphs  

CERN Document Server

A graph $G$ is said to have \\textit{bandwidth} at most $b$, if there exists a labeling of the vertices by $1,2,..., n$, so that $|i - j| \\leq b$ whenever $\\{i,j\\}$ is an edge of $G$. Recently, B\\"ottcher, Schacht and Taraz verified a conjecture of Bollob\\'as and Koml\\'os which says that for every positive $r,\\Delta,\\gamma$, there exists $\\beta$ such that if $H$ is an $n$-vertex $r$-chromatic graph with bounded degree $\\Delta$ which has bandwidth at most $\\beta n$, then any graph $G$ on $n$ vertices with minimum degree at least $(1 - 1/r + \\gamma)n$ contains a copy of $H$ for large enough $n$. In this paper, we extend this theorem to random graphs. Let $H$ be a $r$-chromatic graph on $n$ vertices with bounded degree $\\Delta$ and bandwidth at most $\\beta n$ with respect to a labeling of vertices by $1,2,...,n$. Suppose also that for every interval $[a, a + \\beta^2 n] \\subset [1, n]$, there exists a vertex $v \\in [a, a+ \\beta^2 n]$ such that its neighbors form an independent set. We show that for every $r, \\Delt...

Huang, Hao; Sudakov, Benny

2010-01-01

52

47 CFR 101.109 - Bandwidth.  

Science.gov (United States)

...authorized bandwidth specified for each frequency band, the Commission reserves the...applicant's intended communications. Frequency band (MHz) Maximum authorized bandwidth...5 MHz 2,130 to 2,150 800 or 1600 KHz 1 2,150 to...

2010-10-01

53

Algorithms and Requirements for Measuring Network Bandwidth  

Energy Technology Data Exchange (ETDEWEB)

This report unveils new algorithms for actively measuring (not estimating) available bandwidths with very low intrusion, computing cross traffic, thus estimating the physical bandwidth, provides mathematical proof that the algorithms are accurate, and addresses conditions, requirements, and limitations for new and existing algorithms for measuring network bandwidths. The paper also discusses a number of important terminologies and issues for network bandwidth measurement, and introduces a fundamental parameter -Maximum Burst Size that is critical for implementing algorithms based on multiple packets.

Jin, Guojun

2002-12-08

54

Dynamic bandwidth allocation in GPON networks  

DEFF Research Database (Denmark)

Two Dynamic Bandwidth Allocation algorithms used for coordination of the available bandwidth between end users in a GPON network have been simulated using OPNET to determine and compare the performance, scalability and efficiency of status reporting and non status reporting dynamic bandwidth allocation. Results show that the status reporting is more efficiently using the bandwidth while non-status reporting provides better QoS for real time services.

Ruepp, Sarah Renée; Dittmann, Lars

2009-01-01

55

On Small-Signal Stability of Wind Power System with Full-Load Converter Interfaced Wind Turbines  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants. In this paper an analysis is presented which assess the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind tu...

Knu?ppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nyga?rd; Jensen, Kim H.; Dixon, Andrew; Østergaard, Jacob

2010-01-01

56

Small signal thermal analysis of local multibarrier behaviour in SiC Schottky diodes  

Science.gov (United States)

A nickel-based silicon carbide Schottky barrier diode presenting multibarrier behaviour was inspected by Small sIgnal Modulation for Thermal Analysis (SIMTA) to detect the weak spots responsible for this behaviour. SIMTA thermally modulates in frequency such weak spots with a small signal voltage while the device is electrically biased in an operating point of its static I/V curve (20 A-1 kV capability). This allows for quantitative studying of them in a thermal steady state as heat sources by lock-in thermography depending on the device operating regime. Using SIMTA, the barrier height and the area of each weak spot were determined by thermal means, yielding to an electrical model that fits the observed multibarrier behaviour. Results suggest that these spots were caused by surface areas of high density of states (due to 3C-SiC stacking faults) created during the wire bonding process, which locally shifted the Schottky barrier due to Fermi level pinning. Their origin was confirmed by scanning electron microscope inspections after milling these locations with a focused on beam, detecting Schottky metal contact degradation at weak spot locations due to an excessive bonding pressure.

León, J.; Perpiñà, X.; Vellvehi, M.; Jordà, X.; Berthou, M.; Godignon, P.

2014-09-01

57

Chasing Small Signals Using Global Spatial Filtering (GSF) of GNSS Coordinates  

Science.gov (United States)

GNSS station coordinate time series have spatially-correlated variations that are the sum of real geophysical signals plus non-local systematic errors. For certain geophysical applications, the signal of interest can be over a limited spatial scale (e.g., for strain modeling, co-seismic displacements, transient detection), in which case, the real geophysical signal can be enhanced by filtering out the non-local systematic errors of a much larger spatial scale. Indeed, there are examples of geophysical transients in GNSS time series that may have gone undetected without some form of spatial filtering. Global spatial filtering (GSF) was introduced by Rius et al. [1995], who applied the method globally to geocentric radial coordinate time series without any reference frame alignment. Unlike the regional common-mode error (CME) correction method of Wdowinski et al. [1997], which is broadly used with some modifications today, Rius et al. [1995] applied corrections to coordinates using a different 7-parameter transformation at each station i, computed from the residuals of all stations j with distance rij GSF method with those that are (1) unfiltered (with a common global transformation), and (2) spatially filtered by the CME method for specified regions. We also explore tuning the spatial scale R of the filter and on the choice of weighting function. Finally, we discuss the application of this method to the global detection and monitoring of small signals from a variety of possible geophysical phenomenon.

Blewitt, G.; Kreemer, C. W.; Goldfarb, J. M.; Plag, H.; Hammond, W. C.

2011-12-01

58

Study of Small Signal of 4H-SiC Static Induction Transistor  

Directory of Open Access Journals (Sweden)

Full Text Available Silicon carbide (SiC SITs were fabricated using home-grown epi structures. The gate is a recessed gate - bottom contact (RG - B. We designed that the mesa space 2.5 ?m and the gate channel is 1.5 ?m. One cell has 400 source fingers and each source finger width is 50 ?m. 0.5 mm gate periphery SiC SIT yielded a maximum drain current density of 160 mA/mm at a drain voltage of 80 V and a gate voltage of 2.5 V. The device blocking voltage with a gate bias of -16 V was 400 V. Packaged 0.5-mm devices were evaluated using amplifier circuits designed for class AB operations. Small signal of SIT was studied. the maximum stable gain (MSG were 11.2 dB at 500MHz and 7.85 dB at L band 1 GHz with Vds = 80V and Vg = 2V.

Gang Chen

2013-05-01

59

A methodology for performance evaluation of LEDs based on ac small signal analysis  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english This paper shows fundamentals and results that support a promising methodology for evaluation in locus of a LED from its own radiating signal, and that allows monitoring of its aging by remote inference on which degradation mechanism is acting internally to the device's structure. It brings out also [...] an alternative route for estimation of parameters of the Shockley's equation directly from small-signal ac analysis in a simple bench circuit. This last approach is shown to be effective and advantageous relatively to methods which take near a hundred points to achieve good estimations, while it uses only two points of the I-V static characteristic. Both approaches __ referred to as remote inference method (RIM) and two-points method (TPM) __ are applied together to show that external quantum efficiency (EQE) can be closely correlated to the injection process assumed to take place in that emitting device, meanwhile overvalued serial resistances due to neutral layers and ohmic contacts in electrodes affect only its electrical performance.

Isnaldo J. Souza, Coêlho; James N. da, Silva.

2013-12-01

60

Electron mobility characterization in OLEDs from ac small signal optical modulation  

International Nuclear Information System (INIS)

This paper investigates the field dependence of electron mobility in tris(8-hydroxyquinolinato)aluminium (Alq3) and bathocuproine (BCP) through ac small signal optical modulation on green light (ITO/PEDOT/NPD/Alq3/Ba/Ag) and blue light (ITO/PEDOT/NPD/BCP/Alq3/Ba/Ag) OLED. The electroluminescence (EL) transient time delay for the blue light OLED is much longer than for the green one. The electron mobility in BCP was extracted based on a Poole-Frenkel-like equation and EL transient time delay measurement, which is in the range (7-9) x 10-8 cm2 V-1 s-1 at an external electric field of 1530-1830 (V cm-1)1/2, comparable to the results from other published reports (Muckl et al 2000 Synth. Met. 111-112 91; Barth et al 2001 J. Appl. Phys. 89 3711; Nakamura H et al 1996 Int. Symp. on Inorganic and Organic Electroluminescence ed R H Mauch and H-E Gumlich (Berlin: Wissenschaft und Technik) p 95; Xie et al 2002 Appl. Phys. Lett. 80 1477). The difference in EL transient time delay and electron mobility for green and blue light OLEDs was demonstrated by the results of direct modulation. The electron transit time shows similar field dependence in both Alq3 layers in green and blue OLEDs. Unlike Alq3, the field dependence of electron mobility in BCP did not fit the conventional organic semiconductor characteristics ??exp(?E1/2), and the excitons form1/2), and the excitons formation at the NPD/BCP interface for the blue OLEDs was demonstrated through the EL spectrum.

 
 
 
 
61

S3DB core: a framework for RDF generation and management in bioinformatics infrastructures  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Biomedical research is set to greatly benefit from the use of semantic web technologies in the design of computational infrastructure. However, beyond well defined research initiatives, substantial issues of data heterogeneity, source distribution, and privacy currently stand in the way towards the personalization of Medicine. Results A computational framework for bioinformatic infrastructure was designed to deal with the heterogeneous data sources and the sensitive mixture of public and private data that characterizes the biomedical domain. This framework consists of a logical model build with semantic web tools, coupled with a Markov process that propagates user operator states. An accompanying open source prototype was developed to meet a series of applications that range from collaborative multi-institution data acquisition efforts to data analysis applications that need to quickly traverse complex data structures. This report describes the two abstractions underlying the S3DB-based infrastructure, logical and numerical, and discusses its generality beyond the immediate confines of existing implementations. Conclusions The emergence of the "web as a computer" requires a formal model for the different functionalities involved in reading and writing to it. The S3DB core model proposed was found to address the design criteria of biomedical computational infrastructure, such as those supporting large scale multi-investigator research, clinical trials, and molecular epidemiology.

Deus Helena F

2010-07-01

62

Small Signal Frequency Response of laser diodes using a femtosectond frequency comb  

Science.gov (United States)

A novel method to measure the optical modulation response of laser diodes that uses as the modulation source the output of a femtosecond optical parametric oscillator (OPO) is described. The femtosecond OPO generates a train of ~ 150 fs pulses tunable between 1.03 and 1.35 ?m with an average power of 12 mW at a repetition rate of 81 MHz. With such a narrow pulse a rich frequency spectrum of flat intensity distribution that easily surpasses the 2000 GHz 3 dB-bandwidth is obtained. To perform modulation response measurements the OPO is selectively tuned to modulate the carrier population in either the well or separate confinement region of the laser diode. Modulation traces obtained with this method in 1.3 ?m InAsP lasers are presented and compared with those obtained from electrical modulation at the same operating conditions.

Anton, Ovidio; Vaschenko, G.; Patel, Dinesh; Pikal, Jon M.; Menoni, Carmen S.

2002-12-01

63

Optimal dynamic bandwidth allocation for complex networks  

Science.gov (United States)

Traffic capacity of one network strongly depends on the link’s bandwidth allocation strategy. In previous bandwidth allocation mechanisms, once one link’s bandwidth is allocated, it will be fixed throughout the overall traffic transmission process. However, the traffic load of every link changes from time to time. In this paper, with finite total bandwidth resource of the network, we propose to dynamically allocate the total bandwidth resource in which each link’s bandwidth is proportional to the queue length of the output buffer of the link per time step. With plenty of data packets in the network, the traffic handling ability of all links of the network achieves full utilization. The theoretical analysis and the extensive simulation results on complex networks are consistent. This work is valuable for network service providers to improve network performance or to do reasonable network design efficiently.

Jiang, Zhong-Yuan; Liang, Man-Gui; Li, Qian; Guo, Dong-Chao

2013-03-01

64

High bandwidth vapor density diagnostic system  

Energy Technology Data Exchange (ETDEWEB)

This patent describes a high bandwidth atomic vapor density diagnostic system. It comprises: means for generating a high bandwidth laser beam, means for amplitude modulating the high bandwidth laser beam, means for propagating the modulated laser beam through an atomic vapor during one or more photoionization events, means for detecting the propagated laser beam to form a detected signal, and lock-in amplifier means for removing pickup noise from the detected signal.

Globig, M.A.; Story, T.W.

1992-10-06

65

Improving the Bandwidth Utilization by Recycling the Unused Bandwidth in IEEE 802.16 Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The Physical and MAC layers have been specified in IEEE 802.16 networks. The quality of service is ensured by the bandwidth reservation. The subscriber station should reserve the bandwidth more than its demand. But the bandwidth is fully utilized by SS but not all the time. So the bandwidth has recycled by the process of recycling the unused bandwidth. The main objective of the proposed scheme is to utilize the unused bandwidth by recycling and maintain the QOS service. By recycling the throughput can be improved which maintains the QOS in the proposed scheme. During this recycling process to maintain the QOS services, the amount of reserved bandwidth is not changed. The proposed scheme can utilize the unused bandwidth up to 70% on average. Protocols and the scheduling algorithms are used to improve the utilization and throughput.

Gowri T

2012-03-01

66

Effect of Er+3 Concentration on the Small Signal Gain Coefficient and the Gain in the Erbium Doped Fiber Amplifier  

Directory of Open Access Journals (Sweden)

Full Text Available The small signal gain coefficient and the gain of Erbium-Doped Fiber Amplifier (EDFA in the wavelength range (1400-1700 nm for different erbium concentrations and different amplifier lengths are calculated and studied. A core graded-index and erbium-doped concentration, are optimized for an EDFA in simplified two-level model. There is evidence to show that, the gain increases with the erbium concentration and the amplifier length. Where the relation between the gain and the amplifier length at different wavelengths is linear with the maximum gain at &lambda = 1530 nm. Also the temperature dependence of the small signal gain coefficient and the gain at the peak wavelength of EDFA was studied which shows, slightly increase in the values of both with temperature. The value of the signal wavelength was chosen in the gain window of EDFA at 1530 nm.

O. Mahran

2014-04-01

67

Small-signal analysis and controller design for an isolated zeta converter with high power factor correction  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the small-signal model of a proposed isolated zeta converter operating in discontinuous conduction mode (DCM). Based on the derived model, a classical controller is thus designed to tightly regulate the output voltage despite variations in the line voltage and load resistance. The experimental results validate the dynamics and performances of the proposed model. Moreover, the loss-free resistor (LFR) model is applied to verify that the isolated zeta converter exhibits a unity power factor. The operating principle and design considerations are also presented in this work. For the rectifier applications, a low total harmonic distortion (THD) of 9% in the input line current is also obtained. It meets the harmonic regulations of IEC 1000-3-2 Class D standards. (author) [Loss-free resistor model; High power factor correction; Isolated zeta converter; Small-signal model].

Lin, Jong-Lick; Yang, Sung-Pei; Lin, Pao-Wei [Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan (ROC)

2005-09-15

68

47 CFR 2.202 - Bandwidths.  

Science.gov (United States)

...depending on the quality desired Speech and music, M=4000, Bandwidth: 8000 Hz= 8 kHz...depending on the quality desired Speech and music, M=4000, Bandwidth: 4000 Hz= 4 kHz...lowest modulation frequency Speech and music, M=4500, lowest modulation...

2010-10-01

69

Gain and noise properties of small-signal erbium-doped fiber amplifiers pumped in the 980-nm band  

DEFF Research Database (Denmark)

The authors have experimentally and theoretically investigated the effects of detuning the pump wavelength on the gain and noise properties of small-signal, erbium-doped fiber amplifiers codirectionally pumped in the 980-nm band. While the pump wavelength can be varied over a wide range with little impact on the gain, a noise penalty is incurred. For amplifiers saturated by amplified spontaneous emission, it is possible to increase the gain by detuning the pump wavelength

1992-01-01

70

Bandwidth Allocation Algorithm of Heterogeneous Network  

Directory of Open Access Journals (Sweden)

Full Text Available In order to reasonable and effective distribute bandwidth to giving full play to the advantages of network resources and improve the efficiency of network data flow in heterogeneous network, this paper puts forward a heterogeneous network bandwidth allocation algorithm. The algorithm is adopted connection bandwidth constraint mechanism in the flow model, starting from the data transmission in the network key topological properties, and combines with routing strategy, using the connection bandwidth allocation to regulate the flow of the network data flow, to achieve ease network congestion, increase network load capacity, at the same time, the qualitatively analyses the process and cause of the change of the flow. Finally in scale-free network and small-world network on the network topology platform made simulating experiment, the experimental results show that: The algorithm optimizes the network bandwidth resource allocation, regulates the network traffic, increased the network load capacity

Zhijun Hu

2014-03-01

71

Bandwidth enhancement in disordered metamaterial absorbers  

Science.gov (United States)

In this letter, we show numerically and experimentally that a positional disorder of a collection of absorbing electromagnetic wave resonators operating in the long wavelength regime dramatically enhances the absorption bandwidth. The demonstration is performed by using single-size ring-shaped thin metal pieces periodically or randomly positioned onto a back-grounded dielectric layer. For periodic array, an optimum in the periodicity is pointed out with a narrow bandwidth, while the increasing influence of coupling effects for resonators in close vicinity explains a three-fold bandwidth enhancement in the case of positional disorder.

Hao, Jianping; Lheurette, Éric; Burgnies, Ludovic; Okada, Étienne; Lippens, Didier

2014-08-01

72

High bandwidth control of precision motion instrumentation  

Science.gov (United States)

This article presents a high-bandwidth control design suitable for precision motion instrumentation. Iterative learning control (ILC), a feedforward technique that uses previous iterations of the desired trajectory, is used to leverage the repetition that occurs in many tasks, such as raster scanning in microscopy. Two ILC designs are presented. The first design uses the motion system dynamic model to maximize bandwidth. The second design uses a time-varying bandwidth that is particularly useful for nonsmooth trajectories such as raster scanning. Both designs are applied to a multiaxis piezoelectric-actuated flexure system and evaluated on a nonsmooth trajectory. The ILC designs demonstrate significant bandwidth and precision improvements over the feedback controller, and the ability to achieve precision motion control at frequencies higher than multiple system resonances.

Bristow, Douglas A.; Dong, Jingyan; Alleyne, Andrew G.; Ferreira, Placid; Salapaka, Srinivas

2008-10-01

73

Center frequency and bandwidth tunable HTS filter  

International Nuclear Information System (INIS)

We have developed a bandwidth and a center frequency tuning method for use in high-temperature superconducting microstrip filters. Several ?-shaped waveguides are placed between the resonators, and the bandwidth is adjusted by changing the switch states of the waveguides. Additional electrical pads are placed open ends of the resonators for tuning the center frequency. Pads are also placed around the input/output coupled-line elements to enable the coupling strength between the coupled-line and resonator to be adjusted, thereby reducing the insertion loss caused by tuning. A prototype three-pole tunable bandpass filter was designed and analyzed using an electromagnetic simulator based on the moment method. The filter was designed at a center frequency of 5.00 GHz and a bandwidth of 150 MHz. The simulated bandwidth and center frequency of the filter were tuned from 150 to 300 MHz and 4.5-5 GHz without degradation of the insertion loss, respectively.

74

Small-signal analysis of 1.3/spl mu/m microcavity light-emitting diodes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

THE MODULATION SPEED OF 1.3-MU M MICROCAVITY LIGHT-EMITTING DIODES (MCLED'S) HAS BEEN MEASURED USING A SMALL-SIGNAL MODULATION ANALYSIS, A SPEED OF 260 MHZ USING A 25-MU M DIAMETER SAMPLE AT CURRENT DENSITY OF 10 KA/CM(2) HAS BEEN ACHIEVED, THE CARRIER CONFINEMENT HAS BEEN CALCULATED FOR SEVERAL CARRIER DENSITIES IN ORDER TO INVESTIGATE THE ORIGIN OF THE SPEED LIMITATION. BY COMPARING THE PERFORMANCE OF THE 1.3-MU M MCLED'S WITH THAT OF THE 990-NM DEVICES WE CONCLUDE THAT THE LIMITING FACTOR ...

Hegarty, John

1999-01-01

75

1.3 microm quantum dot laser in coupled-cavity-injection-grating design with bandwidth of 20 GHz under direct modulation.  

Science.gov (United States)

Using a multi section laser in coupled cavity injection grating design based on 1.3 microm InGaAs/GaAs quantum dot (QD) active region we were able to enhance the 3 dB modulation bandwidth well beyond the inherent material modulation bandwidth. The material bandwidth was determined by measurements on distributed feedback (DFB) devices to approximately 8 GHz. The special multisectional design allows interaction between the lasing mode and a second mode used as catalyst and enables a high resonance frequency of the device. Based on active QD material this approach allowed us to reach a cut off frequency of 20 GHz in the small signal response of the device. PMID:18542663

Gerschütz, F; Fischer, M; Koeth, J; Krestnikov, I; Kovsh, A; Schilling, C; Kaiser, W; Höfling, S; Forchel, A

2008-04-14

76

Design and characterization of a 30-GHz bandwidth low-power silicon traveling-wave modulator  

Science.gov (United States)

We present the design and characterization of a silicon PN junction traveling-wave Mach-Zehnder modulator near 1550 nm wavelength. The device shows 30 GHz bandwidth at 1 V reverse bias, with a 2.7 V-cm V?L? and accordingly a 9-V small-signal V?. The insertion loss of the phase shifter is 3.6 dB±0.4 dB. The device performance metrics in combination show significant improvement compared to the state-of-the-art in the sense that lower phase shifter loss and higher bandwidth are achieved for the same V? or vice versa. We demonstrated low modulation power of 640-fJ/bit at 40 Gb/s with a 1.6-Vpp differential-drive and 0-V DC bias, raising the prospect of direct compatibility with CMOS drive-voltages. Critical design tradeoffs are analyzed and design models are validated with measurement results. We proposed a new figure-of-merit (FOM) V?L?RpnC2pn as the junction design merit for high-speed traveling-wave modulators, and utilized 6 implants to achieve an optimal FOM with lower insertion loss. Several key RF design issues are addressed for the first time using simulation and measurement results. In particular, we discussed bandwidth extension using mismatched termination and closely matched experimental results. A bandwidth-limiting RF multi-mode behavior is noted, which also exists in other results in the literature; we suggested a widely applicable design remedy.

Ding, Ran; Liu, Yang; Li, Qi; Yang, Yisu; Ma, Yangjin; Padmaraju, Kishore; Lim, Andy Eu-Jin; Lo, Guo-Qiang; Bergman, Keren; Baehr-Jones, Tom; Hochberg, Michael

2014-06-01

77

Consequence and impact of electric utility industry restructuring on transient stability and small-signal stability analysis  

International Nuclear Information System (INIS)

The electric utility industry is undergoing unprecedented changes in its structure worldwide. With the advent of an open market environment and competition in the industry, and restructuring of the industry into separate generation, transmission, and distribution entities, new issues in power system operation and planning are inevitable. One of the major consequences of this new electric utility environment is the greater emphasis on reliability and secure operation of the power system. This paper examines the impact of restructuring on power system dynamic analysis. It specifically addresses issues related to transient stability analysis and small-signal stability analysis. Four major topics to examine the effect on the nature of studies conducted are considered. These topics are (1) system adequacy and security, (2) system modeling data requirements, (3) system protection and control, and (4) system restoration. The consequences and impact of each of these topics on the nature of the studies conducted are examined and discussed. The emphasis on greater reliability has led to a clearer enunciation of standards, measurements, and guides in some countries. These requirements will result in: (1) more measurements on existing systems, (2) rigorous analysis of transient stability and small-signal stability to determine operating limits and plan systems, (3) greater emphasis on studies to verify coordination and proper performance of protection and controls, and (4) develoof protection and controls, and (4) development of a detailed plan for system restoration in the case of wide-spread outages

78

Design Of Power System Stabilizer To Improve Small Signal Stability By Using Modified Heffron-Phillip’s Model  

Directory of Open Access Journals (Sweden)

Full Text Available One of the major problems in power system operation is related to small signal instability caused by insufficient damping in the system. The most effective way of countering this instability is to use auxiliary controllers called Power System Stabilizers, to produce additional damping in the system. Generally Heffron-phillip’s Model of a synchronous machine is commonly used for the small signal stability analysis. A Modified Heffron-Phillip’s (KconstantModel is derived for the design of Power System Stabilizers; knowledge of external parameters, such as equivalent infinite bus voltage and external impedance value are required for designing a conventional power system stabilizer, Modified Heffron-Phillip’s Model power system stabilizer. The efficiency of the proposeddesign technique and the performance of the stabilizer has been evaluated over a range of operating and system conditions and the performance of the proposed Modified Heffron-Phillip’s Model is much better than the conventional power system stabilize.. The proposed work describes the ‘Design of Power System Stabilizer by using Modified Heffron-Phillip’s model’ is simulated by using MATLAB/SIMULINK.

G. Sai Sudheer,

2011-06-01

79

Bandwidth Analysis of Smart Meter Network Infrastructure  

DEFF Research Database (Denmark)

Advanced Metering Infrastructure (AMI) is a net-work infrastructure in Smart Grid, which links the electricity customers to the utility company. This network enables smart services by making it possible for the utility company to get an overview of their customers power consumption and also control devices in their costumers household e.g. heat pumps. With these smart services, utility companies can do load balancing on the grid by shifting load using resources the customers have. The problem investigated in this paper is what bandwidth require-ments can be expected when implementing such network to utilize smart meters and which existing broadband network technologies can facilitate this smart meter service. Initially, scenarios for smart meter infrastructure are identified. The paper defines abstraction models which cover the AMI scenarios. When the scenario has been identified a general overview of the bandwidth requirements are analysed. For this analysis the assumptions and limitations are defined. The results obtained by the analysis show, that the amount of data collected and transferred by a smart meter is very low compared to the available bandwidth of most internet connections. The results show the bandwidth provided by GPRS technology is sufficient. However, from a delay point of view, GPRS has its limits, therefore, xDSL or 3G can be used for faster transfer but will rarely utilize the available bandwidth from these technologies. The aggregator or concentrator which is responsible to collect all the data from the different smart meters can become a bottleneck as the aggregated amount of data is high, thus the bandwidth for the data concentrator has to be high. These results are interesting to look at as it is a common misunderstanding that smart grid service requires high bandwidth.

Balachandran, Kardi; Pedersen, Jens Myrup

2014-01-01

80

Large scale probabilistic available bandwidth estimation  

CERN Document Server

The common utilization-based definition of available bandwidth and many of the existing tools to estimate it suffer from several important weaknesses: i) most tools report a point estimate of average available bandwidth over a measurement interval and do not provide a confidence interval; ii) the commonly adopted models used to relate the available bandwidth metric to the measured data are invalid in almost all practical scenarios; iii) existing tools do not scale well and are not suited to the task of multi-path estimation in large-scale networks; iv) almost all tools use ad-hoc techniques to address measurement noise; and v) tools do not provide enough flexibility in terms of accuracy, overhead, latency and reliability to adapt to the requirements of various applications. In this paper we propose a new definition for available bandwidth and a novel framework that addresses these issues. We define probabilistic available bandwidth (PAB) as the largest input rate at which we can send a traffic flow along a pa...

Thouin, Frederic; Rabbat, Michael

2010-01-01

 
 
 
 
81

Heterodyne spectrometers with very wide bandwidths  

Science.gov (United States)

New astronomical and remote-sensing instruments require microwave spectrometers with modest spectral resolution over many gigahertz of instantaneous bandwidth. Applications include millimeter-wave searches for distant objects with poorly known redshifts, submillimeter and far-infrared observations of Doppler-broadened spectral lines from galaxies, and observations of pressure-broadened atmospheric lines. Wide bandwidths and the consequent stability requirements make it difficult to use general-purpose receiver and spectrometer architectures in these applications. We discuss analog auto- and cross-correlation lag spectrometers that are optimized for these observations. Analog correlators obtain their wide bandwidths by a combination of transmission line delays and direct voltage multiplication in transistor or diode mixers. We show results from a new custom transistor multiplier with bandwidth to 25 GHz. Stability becomes increasingly important as bandwidths broaden. We discuss system requirements for single-dish correlation radiometers, which have intrinsic high stability, and present results showing that analog cross-correlators are suitable backends for these receivers.

Harris, Andrew I.

2003-02-01

82

Reconstruction in Time-Bandwidth Compression Systems  

CERN Document Server

Recently it has been shown that the intensity time-bandwidth product of optical signals can be engineered to match that of the data acquisition instrument. In particular, it is possible to slow down an ultrafast signal, resulting in compressed RF bandwidth - a similar benefit to that offered by the Time-Stretch Dispersive Fourier Transform (TS-DFT) - but with reduced temporal record length leading to time-bandwidth compression. The compression is implemented using a warped group delay dispersion leading to non-uniform time stretching of the signal's intensity envelope. Decoding requires optical phase retrieval and reconstruction of the input temporal profile, for the case where information of interest is resides in the complex field. In this paper, we present results on the general behavior of the reconstruction process and its dependence on the signal-to-noise ratio. We also discuss the role of chirp in the input signal.

Chan, Jacky; Asghari, Mohammad H; Jalali, Bahram

2014-01-01

83

High bandwidth differential amplifier for shock experiments.  

Science.gov (United States)

We developed a high bandwidth differential amplifier for gas gun shock experiments of low-resistance metals. The circuit has a bandwidth up to 1 GHz, and is capable of measuring signals of ?1.5 V with a common mode rejection of 250 V. Conductivity measurements of gas gun targets are measured by flowing high currents through the targets. The voltage is measured across the target using a technique similar to a four-point probe. Because of the design of the current source and load, the target voltage is ?250 V relative to ground. Since the expected voltage change in the target is common mode rejection. Various amplifying designs are shown, although the increased amplification decreases bandwidth. Bench tests show that the amplifier can withstand significant common mode dc voltage and measure 10 ns, and 50 mV signals. PMID:23126892

Ross, P W; Tran, V; Chau, R

2012-10-01

84

High bandwidth differential amplifier for shock experimentsa)  

Science.gov (United States)

We developed a high bandwidth differential amplifier for gas gun shock experiments of low-resistance metals. The circuit has a bandwidth up to 1 GHz, and is capable of measuring signals of ?1.5 V with a common mode rejection of 250 V. Conductivity measurements of gas gun targets are measured by flowing high currents through the targets. The voltage is measured across the target using a technique similar to a four-point probe. Because of the design of the current source and load, the target voltage is ˜250 V relative to ground. Since the expected voltage change in the target is common mode rejection. Various amplifying designs are shown, although the increased amplification decreases bandwidth. Bench tests show that the amplifier can withstand significant common mode dc voltage and measure 10 ns, and 50 mV signals.

Ross, P. W.; Tran, V.; Chau, R.

2012-10-01

85

Teleoperation over low bandwidth communication links  

International Nuclear Information System (INIS)

Teleoperation is well established for many areas of hazardous environment working. Where such environments are well structured and contained, such as within a working plant, communications bandwidths need not be a constraining factor. However where the worksite is remote, large, poorly structured or damaged communications rapidly become a critical factor in the efficient deployment and use of teleoperation equipment. The paper justifies and describes means which we are exploring to reduce the required communications bandwidth for teleoperation whist retaining full functionality. Techniques involved include incorporation of local intelligence at the worksite, with bandwidth devoted to high-level up-link control signals and down-link feedback, and the use of highly compressed video feeding 'virtual reality type' HMDs to provide maximum system transparency for the operator. The work is drawing on previous experience with an 'anthropomorphic robot heat' for telepresence work, and proprietary algorithms capable of compressing full colour video to standard telephone modem data rates. (Author)

86

Improved space bandwidth product in image upconversion  

DEFF Research Database (Denmark)

We present a technique increasing the space bandwidth product of a nonlinear image upconversion process used for spectral imaging. The technique exploits the strong dependency of the phase-matching condition in sum frequency generation (SFG) on the angle of propagation of the interacting fields with respect to the optical axis. Appropriate scanning of the phase-match condition (?k=0) while acquiring images, allow us to perform monochromatic image reconstruction with a significantly increased space bandwidth product. We derive the theory for the image reconstruction process and demonstrate acquisition of images with >10 fold increase in space bandwidth product, i.e. the number of pixel elements, when compared to upconversion of images using fixed phase-match conditions.

Dam, Jeppe Seidelin; Pedersen, Christian

2012-01-01

87

Improving Bandwidth of Yagi-Uda Arrays  

Directory of Open Access Journals (Sweden)

Full Text Available A novel approach for improving antenna bandwidth is described using a 6-element Yagi-Uda array as an example. The new approach applies Central Force Optimization, a deterministic metaheuristic, and Variable Z0 technology, a novel, proprietary design and optimization methodology, to produce an array with 33.09% fractional impedance bandwidth. This array’s performance is compared to its CFO-optimized Fixed Z0counterpart, and to the performance of a 6-ele- ment Dominating Cone Line Search-optimized array. Both CFO-optimized antennas exhibit better performance than the DCLS array, especially with respect to impedance bandwidth. Although the Yagi-Uda antenna was chosen to illustrate this new approach to antenna design and optimization, the methodology is entirely general and can be applied to any antenna against any set of performance objectives.

Richard A. Formato

2012-01-01

88

High Bandwidth Differential Amplifier for Shock Experiments  

Energy Technology Data Exchange (ETDEWEB)

We developed a high bandwidth differential amplifier for gas gun shock experiments. The circuit has a bandwidth up to 1 GHz, and is capable of measuring signals of ?1.5 V with a common mode rejection of 250 V. Conductivity measurements of gas gun targets are measured by flowing high currents through the targets. The voltage is measured across the target using a technique similar to a four-point probe. Because of the design of the current source and load, the target voltage is approximately 250 V relative to ground. Since the expected voltage change in the target is < 1 V, the differential amplifier must have a large common mode rejection. Various amplifying designs are shown, although the increased amplification decreases bandwidth. Bench tests show that the amplifier can withstand significant common mode DC voltage and measure 10 ns, and 50 mV signals.

Ross, P., Tran, V., Chau, R.

2012-10-01

89

1 MHz bandwidth true NMR SQUID amplifier  

Energy Technology Data Exchange (ETDEWEB)

We have developed an integrated dc SQUID magnetometer with additional positive feedback (APF) for low frequency true NMR applications. The APF scheme allows direct coupled read out from the SQUID to room temperature electronics and eliminates the need for the conventional modulation scheme, thereby greatly simplifying the flux-locked loop electronics. We have configured our SQUID system for the specific needs of sensitive NMR measurements which include large bandwidth and high slew rate. We have achieved a bandwidth of 1.2 MHz and a slew rate greater than 10{sup 5}{Phi}{sub 0}/s for frequencies above 10 kHz.

Thomasson, S.L.; Gould, C.M. [Univ. of Southern California, Los Angeles, CA (United States)

1995-10-01

90

1 MHz bandwidth true NMR SQUID amplifier  

Science.gov (United States)

We have developed an integrated dc SQUID magnetometer with additional positive feedback (APF) for low frequency true NMR applications. The APF scheme allows direct coupled read out from the SQUID to room temperature electronics and eliminates the need for the conventional modulation scheme, thereby greatly simplifying the flux-locked loop electronics. We have configured our SQUID system for the specific needs of sensitive NMR measurements which include large bandwidth and high slew rate. We have achieved a bandwidth of 1.2 MHz and a slew rate greater than 105?0/s for frequencies above 10 kHz.

Thomasson, S. L.; Gould, C. M.

1995-10-01

91

Reconfigurable silicon filter with continuous bandwidth tunability.  

Science.gov (United States)

We present the design and the fabrication of compact tunable silicon-on-insulator bandpass filters based on the integration of a Mach-Zehnder interferometer with ring resonators and activated via thermo-optic phase shifters. The proposed architecture provides wide filter bandwidth tunability from 10% to 90% of the free spectral range preserving the filter off-band rejection. Possible applications are channel subset selection in wavelength division multiplexing optical systems, adaptive filtering to signal bandwidth, and reconfigurable filters for gridless networking. PMID:22940985

Orlandi, Piero; Ferrari, Carlo; Strain, Michael John; Canciamilla, Antonio; Morichetti, Francesco; Sorel, Marc; Bassi, Paolo; Melloni, Andrea

2012-09-01

92

Investigation of spectral bandwidth of optical parametric amplification  

Science.gov (United States)

The spectral bandwidth of three-wave-mixing optical parametric amplification has been investigated. A general mathematical model for evaluating the spectral bandwidth of optical parametric amplification is developed with parametric bandwidth and gain bandwidth via three-wave noncollinear interactions. The spectral bandwidth is determined by expanding the wave-vector mismatch in a Taylor series and retaining terms through second order. The model takes into account the effects of crystal length, noncollinear angle, group velocity, group-velocity dispersion and gain coefficient. The relation between parametric bandwidth and gain bandwidth is clearly defined. The model is applied to a BBO OPA, a LBO OPA and a CLBO OPA.

Hongjun, L.; Wei, Z.; Guofu, C.; Yishan, W.; Zhao, C.; Chi, R.

2004-09-01

93

Improvements to the extraction of an AlGaN/GaN HEMT small-signal model  

International Nuclear Information System (INIS)

The accurate extraction of AlGaN/GaN HEMT small-signal models, which is an important step in large-signal modeling, can exactly reflect the microwave performance of the physical structure of the device. A new method of extracting the parasitic elements is presented, and an open dummy structure is introduced to obtain the parasitic capacitances. With a Schottky resistor in the gate, a new method is developed to extract Rg. In order to characterize the changes of the depletion region under various drain voltages, the drain delay factor is involved in the output conductance of the device. Compared to the traditional method, the fitting of S 11 and S 22 is improved, and fT and fmax can be better predicted. The validity of the proposed method is verified with excellent correlation between the measured and simulated S-parameters in the range of 0.1 to 26.1 GHz. (semiconductor devices)

94

Millimeter-wave small-signal modeling with optimizing sensitive-parameters for metamorphic high electron mobility transistors  

International Nuclear Information System (INIS)

In this paper, we present a simple and reliable technique for determining the small-signal equivalent circuit model parameters of the 0.1 µm metamorphic high electron mobility transistors (MHEMTs) in a millimeter-wave frequency range. The initial eight extrinsic parameters of the MHEMT are extracted using two S-parameter (scattering parameter) sets measured under the pinched-off and zero-biased cold field-effect transistor conditions by avoiding the forward gate biasing. Furthermore, highly calibration-sensitive values of the Rs, Ls and Cpd are optimized by using a gradient optimization method to improve the modeling accuracy. The accuracy enhancement of this procedure is successfully verified with an excellent correlation between the measured and calculated S-parameters up to 65 GHz

95

High bandwidth vapor density diagnostic system  

Energy Technology Data Exchange (ETDEWEB)

A high bandwidth vapor density diagnostic system for measuring the density of an atomic vapor during one or more photoionization events. The system translates the measurements from a low frequency region to a high frequency, relatively noise-free region in the spectrum to provide improved signal to noise ratio.

Globig, Michael A. (Antioch, CA); Story, Thomas W. (Oakley, CA)

1992-01-01

96

A long range full bandwidth Ethernet bridge  

Energy Technology Data Exchange (ETDEWEB)

An Ethernet Bridge has been built which has both a range which exceeds 39 kilometers and a full bandwidth of 10 Mbaud. The bridge is transparent to all Ethernet packets and is suitable for distant system control, distant high speed data collection and for all normal Ethernet use.

Thompson, M.A.; Lackey, J.L.; Nissen, K.H.; Thielman, D.J.; Hiulian, Z. (Physical Sciences Lab., Univ. of Wisconsin - Madison, 3725 Schneider Dr., Stoughton, WI (US))

1988-02-01

97

47 CFR 2.202 - Bandwidths.  

Science.gov (United States)

...Digital Information Continuous wave telegraphy Bn =BK, K=5 for fading circuits...5, Bandwidth: 100 Hz 100HA1A Telegraphy by on-off keying of a tone modulated...11 kHz 2K11H2B Direct-printing telegraphy using a frequency shifted...

2010-10-01

98

Bandwidth Enhancement Techniques of Dielectric Resonator Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available The paper briefly reviews the historical background of dielectric resonator antenna and its bandwidth enhancement techniques. The main focus is on a compact DRA that can offer broad band operation. It has been illustrated that dual resonance and multi resonance operation can be much effective to give wide band characteristics of DRA.

ARCHANA SHARMA

2011-07-01

99

Small signal audio design  

CERN Document Server

Learn to use inexpensive and readily available parts to obtain state-of-the-art performance in all the vital parameters of noise, distortion, crosstalk and so on. With ample coverage of preamplifiers and mixers and a new chapter on headphone amplifiers, this practical handbook provides an extensive repertoire of circuits that can be put together to make almost any type of audio system.A resource packed full of valuable information, with virtually every page revealing nuggets of specialized knowledge not found elsewhere. Essential points of theory that bear on practical performance are lucidly

Self, Douglas

2014-01-01

100

Bandwidth tunable amplifier for recording biopotential signals.  

Science.gov (United States)

This paper presents a low noise, low power, bandwidth tunable amplifier for bio-potential signal recording applications. By employing depletion-mode pMOS transistor in diode configuration as a tunable sub pA current source to adjust the resistivity of MOS-Bipolar pseudo-resistor, the bandwidth is adjusted without any need for a separate band-pass filter stage. For high CMRR, PSRR and dynamic range, a fully differential structure is used in the design of the amplifier. The amplifier achieves a midband gain of 39.8dB with a tunable high-pass cutoff frequency ranging from 0.1Hz to 300Hz. The amplifier is fabricated in 0.18?m CMOS process and occupies 0.14mm(2) of chip area. A three electrode ECG measurement is performed using the proposed amplifier to show its feasibility for low power, compact wearable ECG monitoring application. PMID:21096549

Hwang, Sungkil; Aninakwa, Kofi; Sonkusale, Sameer

2010-01-01

 
 
 
 
101

DBAS: A Deployable Bandwidth Aggregation System  

CERN Document Server

The explosive increase in data demand coupled with the rapid deployment of various wireless access technologies have led to the increase of number of multi-homed or multi-interface enabled devices. Fully exploiting these interfaces has motivated researchers to propose numerous solutions that aggregate their available bandwidths to increase overall throughput and satisfy the end-user's growing data demand. These solutions, however, have faced a steep deployment barrier that we attempt to overcome in this paper. We propose a Deployable Bandwidth Aggregation System (DBAS) for multi-interface enabled devices. Our system does not introduce any intermediate hardware, modify current operating systems, modify socket implementations, nor require changes to current applications or legacy servers. The DBAS architecture is designed to automatically estimate the characteristics of applications and dynamically schedule various connections or packets to different interfaces. Since our main focus is deployability, we fully i...

Habak, Karim; Harras, Khaled A

2012-01-01

102

Maximum-Bandwidth Node-Disjoint Paths  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a new method for finding the node-disjoint paths with maximum combined bandwidth in communication networks. This problem is an NP-complete problem which can be optimally solved in exponential time using integer linear programming (ILP. The presented method uses a maximum-cost variant of Dijkstra algorithm and a virtual-node representation to obtain the maximum-bandwidth node-disjoint path. Through several simulations, we compare the performance of our method to a modern heuristic technique and to the ILP solution. We show that, in a polynomial execution time, our proposed method produces results that are almost identical to ILP in a significantly lower execution time

Mostafa H. Dahshan

2012-03-01

103

High Bandwidth Differential Amplifier for Shock Experiments  

Energy Technology Data Exchange (ETDEWEB)

We developed a high bandwidth differential amplifier for gas gun shock experiments/applications. The circuit has a bandwidth > 1 GHz, and is capable of measuring signals of ?1.5 V with a common mode rejection of 250 V. Conductivity measurements of gas gun targets are measured by flowing high currents through the targets. The voltage is measured across the target using a technique similar to a four-point probe. Because of the design of the current source and load, the target voltage is approximately 250 V relative to ground. Since the expected voltage change in the target is < 1 V, the differential amplifier must have a large common mode rejection. High pass filters suppress internal ringing of operational amplifiers. Results of bench tests are shown.

Ross, P. W., Tran, V., Chau, R.

2012-04-30

104

Effective File I/O Bandwidth Benchmark  

Energy Technology Data Exchange (ETDEWEB)

The effective I/O bandwidth benchmark (b{_}eff{_}io) covers two goals: (1) to achieve a characteristic average number for the I/O bandwidth achievable with parallel MPI-I/O applications, and (2) to get detailed information about several access patterns and buffer lengths. The benchmark examines ''first write'', ''rewrite'' and ''read'' access, strided (individual and shared pointers) and segmented collective patterns on one file per application and non-collective access to one file per process. The number of parallel accessing processes is also varied and well-formed I/O is compared with non-well formed. On systems, meeting the rule that the total memory can be written to disk in 10 minutes, the benchmark should not need more than 15 minutes for a first pass of all patterns. The benchmark is designed analogously to the effective bandwidth benchmark for message passing (b{_}eff) that characterizes the message passing capabilities of a system in a few minutes. First results of the b{_}eff{_}io benchmark are given for IBM SP and Cray T3E systems and compared with existing benchmarks based on parallel Posix-I/O.

Rabenseifner, R.; Koniges, A.E.

2000-02-15

105

Fixed Innovative Bandwidth Utilization in TDM EPON  

Directory of Open Access Journals (Sweden)

Full Text Available PON can be used by two technologies, which were developed APONs (ATM Passive Optical Networks and EPONs (Ethernet Passive Optical Networks.With the development of services offered by the Internet, the last mile bottleneck problems continue to increase day by day. Many algorithms were developed for making TDM EPON efficient like IPACT, Scheduling, Priority swapping etc. These all algorithms have problems like starvation, QoS, latency and channel under-utilization. We focused the efficient bandwidth utilization in TDM EPON by managing time slots within ONUs and reducing latency, starvation and increasing quality of service. Our Fixed Innovative Bandwidth Algorithm is an intra-ONU bandwidth allocation algorithm, which is used to enhance the network performance by evaluating the parameters like channel underutilization, starvation, delay and Quality of Service. The issues which are lacking in the already made algorithms are being resolved with our proposed solution. The main problem is that the other solutions didn't use the time slots which are guaranteed to their classes efficiently. In FIB Algorithm this issue is being resolved.

Muhammad Bilal

2011-03-01

106

Improvements to the extraction of an AlGaN/GaN HEMT small-signal model  

Energy Technology Data Exchange (ETDEWEB)

The accurate extraction of AlGaN/GaN HEMT small-signal models, which is an important step in large-signal modeling, can exactly reflect the microwave performance of the physical structure of the device. A new method of extracting the parasitic elements is presented, and an open dummy structure is introduced to obtain the parasitic capacitances. With a Schottky resistor in the gate, a new method is developed to extract R{sub g}. In order to characterize the changes of the depletion region under various drain voltages, the drain delay factor is involved in the output conductance of the device. Compared to the traditional method, the fitting of S {sub 11} and S {sub 22} is improved, and f{sub T} and f{sub max} can be better predicted. The validity of the proposed method is verified with excellent correlation between the measured and simulated S-parameters in the range of 0.1 to 26.1 GHz. (semiconductor devices)

Pu Yan; Pang Lei; Wang Liang; Chen Xiaojuan; Li Chengzhan; Liu Xinyu, E-mail: puyan_66721@hotmail.co [Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

2009-12-15

107

Extended bandwidth management mechanism among multi-OLTs  

Science.gov (United States)

Passive optical networks (PON) is being considered as a promising solution for next generation broadband access network due to the convergence of broad bandwidth and low-cost fiber infrastructure along with its ability to successfully support IP-based multimedia applications. PON system has its individual bandwidth allocation mechanism compared with core network allocating bandwidth based on service priority level. However, no uniform bandwidth allocation mechanism from access network to care network. In this paper we propose a novel method of extended bandwidth allocation mechanism among multi-PON systems; then extended dynamic bandwidth allocation (DBA) algorithm in a Gigabit-capable PON (GPON) system for core network is presented. The bandwidth management mechanism among multi-optical line terminals (OLTs) can provide an end-to-end bandwidth guarantee for data transmission. We conduct detailed simulation experiments to study the performance and validate the effectiveness of the proposed method.

Zhang, Na; Yoshiuchi, Hideya

2007-11-01

108

Monolithic wideband linear power amplifier with 45% power bandwidth using pseudomorphic high-electron-mobility transistors for long-term evolution application  

Science.gov (United States)

A fully integrated, monolithic, wideband linear power amplifier using pseudomorphic high-electron-mobility transistor (pHEMT) technology has been developed for long-term evolution (LTE) applications. Implemented through the stacked field-effect transistor (stacked-FET) configuration, the amplifier exhibited a small signal gain of 15 dB and an output power of 25 dBm at 1 dB compression (P1dB) with a power-added efficiency (PAE) of 36% from 1.7 to 2.7 GHz yielding 45% power bandwidth. Moreover, when tested under a 10 MHz LTE-modulated signal, the amplifier achieved a 3% error-vector-magnitude (EVM) at 23 dBm output power over the entire power bandwidth.

Chiang, Che-Yang; Hsu, Heng-Tung; Chang, Edward Y.

2014-11-01

109

Effects of finite-bandwidth pump on ion heating  

International Nuclear Information System (INIS)

The effect of finite-bandwidth pump on the ion heating is investigated experimentally. The r.f. pump frequency is broadened by amplitude modulation with a white noise source. The finite-bandwidth pump enhances the ion heating drastically compared with a monochromatic pump. There is an optimum bandwidth for the ion heating. (author)

110

Molecular dissociation of HD^+ by broad bandwidth chirped laser pulses: a molecular bandwidth filter  

Science.gov (United States)

We employ a coincidence 3D momentum imaging method to study the fragmentation of HD^+ following interaction with an intense, 800 nm, 25 fs Fourier transform-limited (FTL) laser pulse. The broad bandwidth of our FTL pulse prevents us from observing vibrational peaks that one would expect to see using longer FTL laser pulses ˜100 fs. However, by chirping the pulse either positively or negatively, while maintaining a fixed bandwidth, we were able to measure vibrational structure. The kinetic energy release of these vibrational peaks are shifted up or down depending on the sign of the chirp.ootnotetextV. S. Prabhudesai et al., Phys. Rev. A 81, 023401 (2010). We will address the question of why the vibrational structure is observed in spite of the broad bandwidth of the chirped laser pulses.

Zohrabi, M.; Ablikim, U.; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I.

2012-06-01

111

Narrow bandwidth tunable optical parametric generator  

Science.gov (United States)

The output of a periodically poled lithium niobate (PPLN) optical parametric generator (OPG) is filtered using an off axis Fabry-Perot etalon. The filtered output is then parametrically amplified in the same PPLN crystal resulting in a tunable narrow-band infrared source. The PPLN OPG is pumped with a10 nsec pulse duration, 1.064 ?m singlefrequency pump laser, with an output signal and idler determined by the PPLN periodicity. The polarization of the pump laser is rotated so that only a portion of it is phase matched on the first pass through the PPLN crystal. The portion that is phase matched generates a signal that is directed to an off-axis Fabry-Perot etalon, which, in the off-axis configuration has a narrow bandwidth reflection. The pump beam is transmitted through a quarter wave plate and reflected with a mirror so that when passed back through the PPLN crystal, its polarization is rotated 90 degrees with respect to the input. Hence the portion of the pump not phase matched on the first pass is now phase matched for the second pass. The reflected and filtered signal is co-aligned with the pump resulting in a narrow bandwidth amplified signal. This system is capable of generating narrow bandwidth over the tuning range of the PPLN crystal and is only restricted by the etalon reflectivity range. We demonstrate tunability in the 1.4 ?m -1.6 ?m signal range (3.0 ?m-4.4 ?m idler range), which is restricted by our etalon reflectivity.

Dolasinski, Brian; Powers, Peter

2013-03-01

112

Bandwidth Efficient OFDM Transmitter Diversity Techniques  

Directory of Open Access Journals (Sweden)

Full Text Available Space-time block-coded orthogonal frequency division multiplexing (OFDM transmitter diversity techniques have been shown to be efficient means of achieving near-optimal diversity gain in frequency-selective fading channels. However, these known techniques all require a cyclic prefix to be added to the transmitted symbols, resulting in bandwidth expansion. In this paper, iterative space-time and space-frequency block-coded OFDM transmitter diversity techniques are proposed that exploit spatial diversity to improve spectral efficiency by eliminating the need for a cyclic prefix.

King F. Lee

2004-09-01

113

An octave bandwidth frequency independent dipole antenna  

CERN Document Server

Precision measurements of the spectrum of the cosmic radio background require frequency independent antennas of small electrical dimensions. We describe the design of a wide-band fat-dipole antenna with a sinusoidal profile having a frequency independent performance over the octave band 87.5 to 175 MHz. The input return loss exceeds 15 dB and the radiation power pattern is frequency invariant and close to cosine square over the octave bandwidth. The structure has been optimized using electromagnetic modeling, and the design has been validated by constructing a prototype.

Raghunathan, Agaram; Subrahmanyan, Ravi

2013-01-01

114

Achievement of arbitrary bandwidth of a narrow bandpass filter.  

Science.gov (United States)

By adjusting the coating parameters to vary the refractive index of the thin film material, we are able to fine tune the bandwidth of a narrow bandpass filter to an arbitrary value. The relation between the varied index Deltan and the maximum arbitrary bandwidth was analyzed. A 4-skip-0 bandpass filter for a 100 GHz DWDM system was designed and fabricated. In addition, the relation between the tolerance of the index and the bandwidth was also analyzed to avoid broadening or narrowing the bandwidth. The final results showed that the arbitrary bandwidth met the requirements very well. PMID:19550806

Lee, Cheng-Chung; Chen, Sheng-Hui; Kuo, Chien-Cheng; Wei, Ching-Yi

2007-11-12

115

Enhanced dynamic bandwidth allocation in WDM-PON  

Science.gov (United States)

WDM based passive optical network (PON) upgrades current TDM based PON at the architecture, protocol and dynamic bandwidth allocation algorithms to provide higher bandwidth in the access networks. Various Dynamic Wavelength and Bandwidth Allocation algorithms for WDM-PON have been studied. These DWBA algorithms exploit both inter-channel and intra-channel statistical multiplexing in order to achieve better performance, especially when the load on various channels is not symmetric. However, these algorithms let all ONUs share all wavelengths equally, and decouple bandwidth allocation from the wavelength assignment, which may cause bandwidth fragmentation across different wavelengths, and these algorithms further strictly limit the ONUs only to use one wavelength per allocation cycle, hence, leading to the underutilized network performance. To overcome the above limitation, we propose an enhanced dynamic wavelength and bandwidth allocation (EDBA) algorithm, which integrates wavelength assignment with bandwidth allocation process. We use extensive simulation to compare the performance of EDBA to another DWBA algorithm in 3.

Ye, Xin; Sana, Ajaz; Assi, Chadi M.; Ali, Mohamed A.

2007-09-01

116

Bandwidth Estimation For Mobile Ad hoc Network (MANET  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we presents bandwidth estimation scheme for MANET, which uses some components of the two methods for the bandwidth estimation: 'Hello Bandwidth Estimation 'Listen Bandwidth Estimation. This paper also gives the advantages of the proposed method. The proposed method is based on the comparison of these two methods. Bandwidth estimation is an important issue in the Mobile Ad-hoc Network (MANET because bandwidth estimation in MANET is difficult, because each host has imprecise knowledge of the network status and links change dynamically. Therefore, an effective bandwidth estimation scheme for MANET is highly desirable. Ad hoc networks present unique advanced challenges, including the design of protocols for mobility management, effective routing, data transport, security, power management, and quality-of-service (QoS provisioning. Once these problems are solved, the practical use of MANETs will be realizable.

Rabia Ali

2011-09-01

117

Recycling of Bandwidth in Metropolitan Area Networks(MAN  

Directory of Open Access Journals (Sweden)

Full Text Available In case of variable bite rate application, the subscriber station requires bandwidth for downlink anduplink of data transmission. As subscriber station cant estimate how much data it wants and to ensurethe QOS guaranteed services, It may reserve more bandwidth than its demand. As a result, the reservedbandwidth may not be fully utilized all the time. Hence there is a wastage of bandwidth. This paperconsists of a scheme named as ‘Bandwidth Recycling’, to recycle the unused bandwidth without changingthe existing bandwidth reservation. In this scheme the subscriber station will used the available unusedbandwidth. By this system throughput can also increase while maintain the same quality of services. Inthis scheme we use mathematical analysis and simulation. And this results in the scheme can recycle35% of unused bandwidth on average. The extension for this project can also be showed by the threescheduling algorithms. Thus the simulation results to improve overall throughput by 40% in a steadynetwork.

Bhargava Devana

2012-01-01

118

Ptychography with broad-bandwidth radiation  

Science.gov (United States)

Ptychography, a scanning Coherent Diffractive Imaging (CDI) technique, has quickly gained momentum as a robust method to deliver quantitative images of extended specimens. A current conundrum for the development of X-ray CDI is the conflict between a need for higher flux to reach higher resolutions and the requirement to strongly filter the incident beam to satisfy the tight coherence prerequisite of the technique. Latest developments in algorithmic treatment of ptychographic data indicate that the technique is more robust than initially assumed, so that some experimental limitations can be substantially relaxed. Here, we demonstrate that ptychography can be conducted in conditions that were up to now considered insufficient, using a broad-bandwidth X-ray beam and an integrating scintillator-based detector. Our work shows the wide applicability of ptychography and paves the way to high-throughput, high-flux diffractive imaging.

Enders, B.; Dierolf, M.; Cloetens, P.; Stockmar, M.; Pfeiffer, F.; Thibault, P.

2014-04-01

119

Tunable bandwidth of the terahertz metamaterial absorber  

Science.gov (United States)

We propose a broadband terahertz metamaterial absorber that utilizes the coupling effect of the sub-unit elements of the structure consisted of two asymmetric metallic square rings and a metallic ground plane separated by a dielectric layer. The bandwidth of the absorber is tunable over a range from 0.88 to 1.28 THz by the coupling distance of the two patterned square rings. The proposed absorber has the tunability from broadband to single-band by the polarization angle of the system. Moreover, the proposed concept also applies to other types of asymmetric absorber structure and can be readily extended to other frequency regimes for a host of applications such as detection, imaging and solar cell.

Wang, Ben-Xin; Wang, Ling-Ling; Wang, Gui-Zhen; Huang, Wei-Qing; Zhai, Xiang; Li, Xiao-Fei

2014-08-01

120

A high-bandwidth spintronic position sensor.  

Science.gov (United States)

Position sensing with resolution down to the scale of a single atom is of key importance in nanoscale science and engineering. However, only optical-sensing methods are currently capable of non-contact sensing at such resolution over a high bandwidth. Here, we report a new non-contact, non-optical position-sensing concept based on detecting changes in a high-gradient magnetic field of a microscale magnetic dipole by means of spintronic sensors. Experimental measurements show a sensitivity of up to 40 ?/?m, a linear range greater than 10 ?m and a noise floor of 0.5 pm/?[Hz]. Also shown is the use of the sensor for position measurements for closed-loop control of a high-speed atomic force microscope with a frame rate of more than 1 frame/s. PMID:25148257

Tuma, Tomas; Pantazi, Angeliki; Sahoo, Deepak R; Eib, Philipp; Salis, Gian; Pozidis, Haris; Sebastian, Abu

2014-09-19

 
 
 
 
121

Ptychography with broad-bandwidth radiation  

Energy Technology Data Exchange (ETDEWEB)

Ptychography, a scanning Coherent Diffractive Imaging (CDI) technique, has quickly gained momentum as a robust method to deliver quantitative images of extended specimens. A current conundrum for the development of X-ray CDI is the conflict between a need for higher flux to reach higher resolutions and the requirement to strongly filter the incident beam to satisfy the tight coherence prerequisite of the technique. Latest developments in algorithmic treatment of ptychographic data indicate that the technique is more robust than initially assumed, so that some experimental limitations can be substantially relaxed. Here, we demonstrate that ptychography can be conducted in conditions that were up to now considered insufficient, using a broad-bandwidth X-ray beam and an integrating scintillator-based detector. Our work shows the wide applicability of ptychography and paves the way to high-throughput, high-flux diffractive imaging.

Enders, B., E-mail: bjoern.enders@ph.tum.de; Dierolf, M.; Stockmar, M.; Pfeiffer, F. [Lehrstuhl für Biomedizinische Physik, Physik-Department and Institut für Medizintechnik, Technische Universität München, 85747 Garching (Germany); Cloetens, P. [European Synchrotron Radiation Facility, 38043 Grenoble (France); Thibault, P. [Department of Physics and Astronomy, University College London, London (United Kingdom)

2014-04-28

122

Ptychography with broad-bandwidth radiation  

International Nuclear Information System (INIS)

Ptychography, a scanning Coherent Diffractive Imaging (CDI) technique, has quickly gained momentum as a robust method to deliver quantitative images of extended specimens. A current conundrum for the development of X-ray CDI is the conflict between a need for higher flux to reach higher resolutions and the requirement to strongly filter the incident beam to satisfy the tight coherence prerequisite of the technique. Latest developments in algorithmic treatment of ptychographic data indicate that the technique is more robust than initially assumed, so that some experimental limitations can be substantially relaxed. Here, we demonstrate that ptychography can be conducted in conditions that were up to now considered insufficient, using a broad-bandwidth X-ray beam and an integrating scintillator-based detector. Our work shows the wide applicability of ptychography and paves the way to high-throughput, high-flux diffractive imaging

123

Plasmonic photodetector with terahertz electrical bandwidth  

Science.gov (United States)

We propose and investigate a surface plasmon photodetector concept, based on the enhancement of electrical near-field in low-defect, low-doped In0.53Ga0.47As detection volumes located in the gaps of an array of metal nanodipole antennas. We report enhancement in responsivity in the presence of nanodipoles and predict a maximum responsivity of ˜100 mA/W at wavelengths near 1550 nm. The 3 dB electrical bandwidth of the device is estimated based on its RC rise time and the hole transit time through the detection volume for the cases of conventional and ballistic transport in InGaAs and is found to range from ˜0.7 to 4 THz. Also, trends are observed relating the responsivity to the gap dimensions, revealing a trade-off between the field-enhancement in the gap and its volume, and leading to an optimum gap length producing the maximum responsivity.

Mousavi, Saba Siadat; Stöhr, Andreas; Berini, Pierre

2014-04-01

124

Optimal filter bandwidth for pulse oximetry  

Science.gov (United States)

Pulse oximeters contain one or more signal filtering stages between the photodiode and microcontroller. These filters are responsible for removing the noise while retaining the useful frequency components of the signal, thus improving the signal-to-noise ratio. The corner frequencies of these filters affect not only the noise level, but also the shape of the pulse signal. Narrow filter bandwidth effectively suppresses the noise; however, at the same time, it distorts the useful signal components by decreasing the harmonic content. In this paper, we investigated the influence of the filter bandwidth on the accuracy of pulse oximeters. We used a pulse oximeter tester device to produce stable, repetitive pulse waves with digitally adjustable R ratio and heart rate. We built a pulse oximeter and attached it to the tester device. The pulse oximeter digitized the current of its photodiode directly, without any analog signal conditioning. We varied the corner frequency of the low-pass filter in the pulse oximeter in the range of 0.66-15 Hz by software. For the tester device, the R ratio was set to R = 1.00, and the R ratio deviation measured by the pulse oximeter was monitored as a function of the corner frequency of the low-pass filter. The results revealed that lowering the corner frequency of the low-pass filter did not decrease the accuracy of the oxygen level measurements. The lowest possible value of the corner frequency of the low-pass filter is the fundamental frequency of the pulse signal. We concluded that the harmonics of the pulse signal do not contribute to the accuracy of pulse oximetry. The results achieved by the pulse oximeter tester were verified by human experiments, performed on five healthy subjects. The results of the human measurements confirmed that filtering out the harmonics of the pulse signal does not degrade the accuracy of pulse oximetry.

Stuban, Norbert; Niwayama, Masatsugu

2012-10-01

125

Routing Bandwidth Guaranteed Paths with Restoration in Label Switched Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Label switched networks have become increasingly attractive to both network providers and customers. By creating aggregate, bandwidth-reserved flows, these networks are known for their routing flexibility, predictable bandwidth usage, and quality-of-service (QoS) provisioning. This flexibility in routing enables fault-persistent QoS reservations, where connectivity and allotted bandwidth remains available, even if some links or network nodes fail. The automatic switch-over from a now-defunct ...

Norden, Samphel; Buddhikot, Milind M.; Waldvogel, Marcel; Suri, Subhash

2001-01-01

126

Optical delay control of large-spectral-bandwidth laser pulses  

International Nuclear Information System (INIS)

In this Rapid Communication we report an experimental observation of temporal delay control of large-spectral-bandwidth multimode laser pulses by means of electromagnetically induced transparency. We achieved optically controllable retardation of laser pulses with an input spectral bandwidth of 3.3 GHz with limited temporal distortion and excellent values of the delay-bandwidth product. The experimental results compare favorably with a theoretical analysis.

127

Compact antenna arrays with wide bandwidth and low sidelobe levels  

Energy Technology Data Exchange (ETDEWEB)

Highly efficient, low cost, easily manufactured SAR antenna arrays with lightweight low profiles, large instantaneous bandwidths and low SLL are disclosed. The array topology provides all necessary circuitry within the available antenna aperture space and between the layers of material that comprise the aperture. Bandwidths of 15.2 GHz to 18.2 GHz, with 30 dB SLLs azimuthally and elevationally, and radiation efficiencies above 40% may be achieved. Operation over much larger bandwidths is possible as well.

Strassner, II, Bernd H.

2014-09-09

128

Bandwidth selection for continuous-time Markov processes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We propose a theoretical approach to bandwidth choice for continuous-time Markov processes. We do so in the context of stationary and nonstationary processes of the recurrent kind. The procedure consists of two steps. In the first step, by invoking local Gaussianity, we suggest an automated bandwidth selection method which maximizes the probability that the standardized data are a collection of normal draws. In the case of diffusions, for instance, this procedure selects a bandwidth which onl...

Bandi, Federico; Corradi, Valentina; Moloche, Guillermo

2009-01-01

129

Increase of the grating coupler bandwidth with a graphene overlay  

International Nuclear Information System (INIS)

We present theoretical and experimental results that demonstrate an increase in the grating bandwidth by placing a graphene on the chip. A focusing subwavelength grating with coupling efficiency of ?4.3?dB and 1?dB bandwidth of ?60?nm was demonstrated. After a graphene sheet was transferred onto the chip, the maximum 1?dB bandwidth was increased to ?72?nm. Experimental results are consistent with the calculated graphene induced waveguide refractive index and dispersion changes, and the bandwidth improvement may be attributed to the reduction of grating dispersion. This study may be of interest for graphene-on-silicon photonic integrated circuit applications

130

Frequency Bandwidth Optimization of Left-Handed Metamaterial  

Science.gov (United States)

Recently, left-handed metamaterials (LHM s) have been demonstrated with an effective negative index of refraction and with antiparallel group and phase velocities for microwave radiation over a narrow frequency bandwidth. In order to take advantage of these characteristics for practical applications, it will be beneficial to develop LHM s with increased frequency bandwidth response and lower losses. In this paper a commercial three-dimensional electromagnetic simulation code is used to explore the effects of geometry parameter variations on the frequency bandwidth of a LHM at microwave frequencies. Utilizing an optimizing routine in the code, a geometry was generated with a bandwidth more than twice as large as the original geometry.

Chevalier, Christine T.; Wilson, Jeffrey D.

2004-01-01

131

Increase of the grating coupler bandwidth with a graphene overlay  

Energy Technology Data Exchange (ETDEWEB)

We present theoretical and experimental results that demonstrate an increase in the grating bandwidth by placing a graphene on the chip. A focusing subwavelength grating with coupling efficiency of ?4.3?dB and 1?dB bandwidth of ?60?nm was demonstrated. After a graphene sheet was transferred onto the chip, the maximum 1?dB bandwidth was increased to ?72?nm. Experimental results are consistent with the calculated graphene induced waveguide refractive index and dispersion changes, and the bandwidth improvement may be attributed to the reduction of grating dispersion. This study may be of interest for graphene-on-silicon photonic integrated circuit applications.

Cheng, Zhenzhou; Li, Zhen; Xu, Ke; Tsang, Hon Ki, E-mail: hktsang@ee.cuhk.edu.hk [Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin (Hong Kong)

2014-03-17

132

BANDWIDTH EFFICIENCY IN MAC PROTOCOL FOR AD HOC NETWORK?  

Directory of Open Access Journals (Sweden)

Full Text Available Bandwidth, power and collision are considered as three important resources in wireless networks. Therefore, how to manage these resources becomes a effect on wireless ad hoc network. These effects are not present in wire line networks, and evaluation of available bandwidth in wireless networks a difficult task. Furthermore, in wireless medium the available resources also vary with the protocol and its central network i.e. ad hoc network. In this thesis, a collision-aware spectrum assignment scheme has been proposed for Bandwidth Optical Networks allocates the available bandwidth and increases energy efficiency in multi hop collection networks compared to the traditionally used random back off. We improve the MAC protocols with details about the bandwidth, power and collision used and their limitations. However, the MAC is utilizing in link layer, the channel is easy to access by the CSMA/CD scheme. All channels to establish the channels’ situation and avoid collision, in the process of the frame duration access the TDMA, i.e. time slots are required in frame duration, and FDMA (Scheduled protocol access the bandwidth allocation which every node gets a permanent allocation of bandwidth. The aim of this thesis is to initiate multiple channels in medium for FDMA, which constrain the collision of number of channel (N and utilized bandwidth (W. Therefore, how to increase a MAC protocol to improve the bandwidth efficiency and decrease the energy utilization is necessary.

Mayank Sharma

2014-07-01

133

Optimal resource allocation in random networks with transportation bandwidths  

International Nuclear Information System (INIS)

We apply statistical physics to study the task of resource allocation in random sparse networks with limited bandwidths for the transportation of resources along the links. Recursive relations from the Bethe approximation are converted into useful algorithms. Bottlenecks emerge when the bandwidths are small, causing an increase in the fraction of idle links. For a given total bandwidth per node, the efficiency of allocation increases with the network connectivity. In the high connectivity limit, we find a phase transition at a critical bandwidth, above which clusters of balanced nodes appear, characterized by a profile of homogenized resource allocation similar to the Maxwell construction

134

Schottky Heterodyne Receivers With Full Waveguide Bandwidth  

Science.gov (United States)

Compact THz receivers with broad bandwidth and low noise have been developed for the frequency range from 100 GHz to 1 THz. These receivers meet the requirements for high-resolution spectroscopic studies of planetary atmospheres (including the Earth s) from spacecraft, as well as airborne and balloon platforms. The ongoing research is significant not only for the development of Schottky mixers, but also for the creation of a receiver system, including the LO chain. The new receivers meet the goals of high sensitivity, compact size, low total power requirement, and operation across complete waveguide bands. The exceptional performance makes these receivers ideal for the broader range of scientific and commercial applications. These include the extension of sophisticated test and measurement equipment to 1 THz and the development of low-cost imaging systems for security applications and industrial process monitoring. As a particular example, a WR-1.9SHM (400-600 GHz) has been developed (see Figure 1), with state-of-the-art noise temperature ranging from 1,000-1,800 K (DSB) over the full waveguide band. Also, a Vector Network Analyzer extender has been developed (see Figure 2) for the WR1.5 waveguide band (500 750 GHz) with 100-dB dynamic range.

Hesler, Jeffrey; Crowe, Thomas

2011-01-01

135

Optimal Bandwidth Selection in Observed-Score Kernel Equating  

Science.gov (United States)

The selection of bandwidth in kernel equating is important because it has a direct impact on the equated test scores. The aim of this article is to examine the use of double smoothing when selecting bandwidths in kernel equating and to compare double smoothing with the commonly used penalty method. This comparison was made using both an equivalent…

Häggström, Jenny; Wiberg, Marie

2014-01-01

136

Bandwidth Allocation and Reservation - End-to-End Specification  

CERN Document Server

The Bandwidth Allocation and Reservation (BAR) activity within JRA4 of the EGEE project specified and implemented the necessary components and interfaces to enable the EGEE Grid middleware to request and use guaranteed bandwidth services. This report describes the components and interfaces required for an end-to-end BAR service and how they interact.

Kavoussanakis, K; Palansuriya, C; Patil, A; Scharinger, F; Tziouvaras, C; Phipps, A; Vuagnin, G; Trew, A

2006-01-01

137

Dynamic Bandwidth Allocation Strategy for Marine VHF Communications  

Directory of Open Access Journals (Sweden)

Full Text Available In order to achieve the efficient management of marine VHF communications bandwidth resources under the battlefield environment and to maximize the bandwidth utilization while ensuring high-priority business access channel, the context puts forward a kind of dynamic bandwidth allocation strategy based on business priorities. When the bandwidth resources are sufficient, the system can accommodate more business, otherwise it can call the dynamic allocation strategy in order to ensure high-priority business is processed. The simulation results show that this strategy can effectively reduce the blocking rate of the high priority business and can ensure high-priority business transmit timely and efficiently through releasing the business of low priority and using bandwidth seriously.

Ding Yuan-Ming

2013-01-01

138

Microstrip antenna array with multi-octave bandwidth  

Science.gov (United States)

Up to the present time, electronic warfare (EW) systems have employed spiral antennas, wide bandwidth horns, or log periodic dipole arrays to meet the multioctave bandwidth antenna requirements. In the context of requirements to mount such antennas conformally on the bodies of missiles and aircraft, investigations have been conducted regarding the wide bandwidth capabilities of microstrip antennas. However, the bandwidths achieved so far have been limited. Attention is given to the possibility of multioctave operation on the basis of the formation of a log periodic array of patch elements. The basic action of a log periodic array is discussed, and the design of the log periodic overlaid patch array is described. It is pointed out that the log periodic microstrip patch array can now be considered for wide bandwidth EW application where the low profile, ruggedness, and conformal mounting properties of microstrip are important system advantages.

Hall, P. S.

1986-03-01

139

NETWORK BANDWIDTH ADAPTATION FOR AUDIO VIDEO STREAMING SYSTEMS  

Directory of Open Access Journals (Sweden)

Full Text Available The two major problems in the network includes streaming and playout.Synchronization has to be maintained in the streaming. In this paper the audio visual data are segmented based on time and length. The segmented data are then transmitted. The transmitted audiovisual segments are then played out synchronously. The proposed system transmits the bit streams considering various network bandwidth. The proposed system maintains the quality of audiovisualdata under variable network bandwidth. The system has its advantage in maintaining synchronization and channel bandwidth. The audiovisual data maintains the same quality throughout streaming process anddelay is reduced.

U.Rahamathunnisa

2010-11-01

140

Evaluation of dynamic bandwidth allocation algorithms in GPON networks  

DEFF Research Database (Denmark)

In this paper, two approaches for Dynamic Bandwidth Allocation in GPON networks are proposed, and validated through simulations in the OPNET modeler. One approach address a Status Reporting scheme, where the bandwidth allocation originates from the client request. The second use a centralized Non Status Reporting scheme. Furthermore, parameters to cope with variances in the traffic pattern is quantified. The results on performance, scalability and efficiency show that Status Reporting is utilizing the bandwidth more efficient while the Non Status Reporting provides better QoS for real time services.

Ruepp, Sarah Renée; Dittmann, Lars

2010-01-01

 
 
 
 
141

Large bandwidth RGC transimpedance preamplifier design in SCA  

International Nuclear Information System (INIS)

A Large Bandwidth RGC Transimpedance Preamplifier is designed for amplifying the high-fidelity timing signal in Switch Capacitance Array chip application. This amplifier have characteristics of low input impedance, large bandwidth, high transimpedance. It will be made under TSMC 0.25?m CMOS technology, and the supply voltage is single 2.5 V. Simulation results indicate: the transimpedance is 5000 ohm, -3dB BW is 953 MHz, and the detector output capacitance have litter effect on the bandwidth in some range. (authors)

142

Energy efficiency in elastic-bandwidth optical networks  

DEFF Research Database (Denmark)

The forecasted growth in the Internet traffic has made the operators and industry to be concerned about the power consumption of the networks, and to become interested in alternatives to plan and operate the networks in a more energy efficient manner. The introduction of OFDM, and its property of elastic bandwidth allocation, opens new horizons in the operation of optical networks. In this paper, we compare the network planning problem in an elastic bandwidth CO-OFDM-based network and a fixed-grid WDM network. We highlight the benefits that bandwidth elasticity and the selection of different modulation formats offer in terms of energy efficiency.

Vizcaino, Jorge Lopez; Ye, Yabin

2011-01-01

143

A NOVEL µ-NEGATIVE METAMATERIAL WITH ENHANCED REJECTION BANDWIDTH  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, a novel planar µ-Negative (MNG metamaterial structure based on Split Ring Resonators (SRRs with improved rejection bandwidth is presented. A bridging technique is used to connect two SRR unit cells at the center to emulate a cascaded filter. The proposed structure achieved a -20 dB rejection bandwidth of 15.5% compared to 4.5% for the conventional SRRs which makes it a good candidate for integration with antennas and RF circuits that require large operational bandwidth.

Haider Raad

2013-01-01

144

Elimination of bandwidth effect in attenuation measurement with picosecond ultrasonics  

Science.gov (United States)

We study the broadening effect of probing pulse light on the apparent attenuation of the Brillouin oscillation measured with picosecond ultrasonics. We observe experimentally that the attenuation of the Brillouin oscillation is sensitive to the bandwidth, and the apparent attenuation coefficient increases as the bandwidth increases, being far from the intrinsic attenuation coefficient. Theoretical calculation is performed to reconstruct the observed oscillations, and it is confirmed that there are several factors affecting the apparent attenuation in addition to the bandwidth. We finally propose equations that deduce the contribution of the broadening to the apparent attenuation of the Brillouin oscillation.

Maehara, Atsushi; Nakamura, Nobutomo; Ogi, Hirotsugu; Hirao, Masahiko

2014-08-01

145

Ultra-broad bandwidth parametric amplification at degeneracy.  

Science.gov (United States)

We report on a novel approach of ultra-broad bandwidth parametric amplification around degeneracy. A bandwidth of up to 400 nm centered around 800 nm is amplified in a BBO crystal by using chirped pump pulses with a bandwitdth as broad as 10 nm. A supercontinuum signal is generated in a microstructured fiber, having to first order a quadratic chirp, which is necessary to ensure temporal overlap of the interacting waves over this broad bandwidth. Furthermore, we discuss the potential of this approach for an octave-spanning parametric amplification. PMID:19498762

Limpert, J; Aguergaray, C; Montant, S; Manek-Hönninger, I; Petit, S; Descamps, D; Cormier, E; Salin, F

2005-09-19

146

On the Functional Relation Between Quality Factor and Fractional Bandwidth  

CERN Document Server

The functional relation between the fractional band-width and the quality factor of a radiating system is investigated in this note. Several widely used definitions of the quality factor are compared on two examples of RLC circuits that serve as a simplified model of a single resonant antenna tuned to its resonance. It is demonstrated that for a first-order system, only the quality factor based on differentiation of input impedance has unique proportionality to the fractional bandwidth, whereas e.g. the classical definition of the quality factor, i. e. the ratio of the stored energy to the lost energy per one cycle, is not uniquely proportional to the fractional bandwidth. In addition, it is shown that for higher-order systems the quality factor based on differentiation of the input impedance ceases to be uniquely related to the fractional bandwidth.

Capek, Miloslav; Hazdra, Pavel

2014-01-01

147

Available Bandwidth Estimation Strategy Based on the Network Allocation Vector  

Directory of Open Access Journals (Sweden)

Full Text Available Available bandwidth is of great importance to network Quality of Service assurance, network load balancing, streaming media rate control, routing, and congestion control, etc.. In this paper, the available bandwidth estimation strategy based on the Network Allocation Vector for Wireless Sensor Networks is proposed. According to the size of the average contention window, network nodes predict the probability of collision in process of frame transmission, and then estimate the number of retransmission. Through the collection of Hello packets periodically sent by neighbors, nodes obtain their Network Allocation Vector, and then estimate the available bandwidth. The simulation results show that the strategy is simple and effective, can accurately estimate the collision of data frames as well as the available bandwidth of Wireless Sensor Networks.

Hongtao Liu

2012-12-01

148

Feasibility Study of Bandwidth Reduction Technique for LORETS System.  

Science.gov (United States)

The purpose of this feasibility study and test demonstration was to conduct analysis for a bandwidth reduction technique to be incorporated in a LORAN Retransmission (LORETS) System. The design concept resulting from the analysis was then breadboarded and...

E. J. Dalabakis, G. R. Shoubridge

1971-01-01

149

MULTILAYER MICROSTRIP ANTENNA QUALITY FACTOR OPTIMIZATION FOR BANDWIDTH ENHANCEMENT  

Directory of Open Access Journals (Sweden)

Full Text Available The impedance bandwidth, one of the important characteristics of microstrip patch antennas, can be significantly improved by using a multilayer dielectric configuration. In this paper the focus is on bandwidth enhancement technique of a multilayer patch antenna for X-band applications. In order to enhance the bandwidth, antenna losses are contained by controlling those quality factors which can have a significant impact on the bandwidth for a given permittivity and thickness of the substrate. This has been achieved by conformal transformation of the multidielectric microstrip antenna. For the ease of analysis Wheelers transformation is used to map the complex permittivity of a multilayer substrate to a single layer. Method of Moments and Finite Difference Time Domain approaches are used for the computation of results.

M.C. SRIVASTAVA

2012-12-01

150

An adaptive scheduling scheme for fair bandwidth allocation  

Science.gov (United States)

Class-based service differentiation is provided in DiffServ networks. However, this differentiation will be disordered under dynamic traffic loads due to the fixed weighted scheduling. An adaptive weighted scheduling scheme is proposed in this paper to achieve fair bandwidth allocation among different service classes. In this scheme, the number of active flows and the subscribed bandwidth are estimated based on the measurement of local queue metrics, then the scheduling weights of each service class are adjusted for the per-flow fairness of excess bandwidth allocation. This adaptive scheme can be combined with any weighted scheduling algorithm. Simulation results show that, comparing with fixed weighted scheduling, it effectively improve the fairness of excess bandwidth allocation.

Liu, Wei; Cheng, Wenqing; He, Jianhua; Le, Chunhui; Yang, Zongkai

2005-02-01

151

Ultra Wideband Microstrip Diamond Slotted Patch Antenna with Enhanced Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available An Ultra Wideband (UWB microstrip diamond slotted patch antenna with enhanced bandwidth is presented in this paper. The proposed antenna is simulated in CST Microwave Studio and fabricated for measurements. Its simulated result displays impedance bandwidth from 3.28 GHz to 19.64 GHz, whereas the measured result displays the frequency region from 2.01 GHz to 18.67 GHz. The antenna complies with the return loss of S11 < –10 dB and Voltage Standing Wave Ratio (VSWR < 2 throughout the impedance bandwidth. Details of the antenna design and related results such as phase angle, input impedance and radiation patterns are discussed in this paper. This antenna has surpassed the bandwidth of UWB requirement, which is from 3.1 GHz to 10.6 GHz, and exhibits good UWB characteristics.

Chia Ping Lee

2011-07-01

152

Equivalent statistical bandwidths of conventional low-pass filters  

Science.gov (United States)

Values of the equivalent statistical bandwidths of Butterworth up to ten poles and Chebyshev up to eight poles low-pass filters for six different passband ripple levels have been computed and tabulated along with the corresponding noise bandwidths. The results obtained can be used for estimating the mean-square error resulting from power spectrum measurements employed in the sensitivity analysis of microwave radiometer systems.

Stanley, W. D.; Peterson, S. J.

1979-01-01

153

Asymptotics and optimal bandwidth selection for highest density region estimation  

CERN Document Server

We study kernel estimation of highest-density regions (HDR). Our main contributions are two-fold. First, we derive a uniform-in-bandwidth asymptotic approximation to a risk that is appropriate for HDR estimation. This approximation is then used to derive a bandwidth selection rule for HDR estimation possessing attractive asymptotic properties. We also present the results of numerical studies that illustrate the benefits of our theory and methodology.

Samworth, R J; 10.1214/09-AOS766

2010-01-01

154

Bandwidth-Aware AODV based Routing Protocol in MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available A wireless ad hoc network is a collection of mobile nodes that dynamically form a temporary network and communicate with each other without any physical networking infrastructure . Many real time applications have quality of Service (QoS requirements like bandwidth, end-to-end delay and jitter. So,to support these applications it is important to have QoS mechanism. In this paper we propose a bandwidth-aware routing protocol, which is based on the reactive ad-hoc distance vector (AODV routing protocol therefore we named it BAAODV protocol. In this Protocol, we include one of the important issue of ad hoc networks which is the bandwidth where the bandwidth-aware route discovery process discover a route in which each intermediate node has bandwidth greater than the required bandwidth. We compare our proposed bandwidthaware AODV routing (BA-AODV protocol to the existing traditional AODV routing protocol. The simulation results show the effectiveness and correctness of our proposed method in terms of increased network load in the scenarios consisting of mobile nodes as well as static nodes.

Richa Jain#1 , Chetan Kumar#2, Pankaj Jain

2013-06-01

155

Demand-based bandwidth assignment MAC protocol for wireless LANs  

Science.gov (United States)

Wireless networks are being rapidly installed in enterprise networks. There are several issues that are critical with the current specifications and the prominent ones are bandwidth utilization, cell capacity, propagation delay, power efficiency and quality of service aspects of the IEEE802.11 Medium Access Control (MAC) layer. IEEE 802.11 specifications for wireless LAN use Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme. Although this scheme is widely successful due to its simplicity, it is inefficient in utilizing the physical bandwidth. Wireless media being highly limited in bandwidth and power, a Time Division Multiple Access (TDMA) may help to increase the utilization of the channel bandwidth. Many satellite networks have used Demand Assignment Multiple Access-TDMA (DAMA-TDMA), where the time slots are allocated dynamically. In this paper, a variation of this protocol has been proposed, called as Demand Based Bandwidth Assignment (DBBA) protocol. One of the main challenges that this protocol resolves is to avoid collision to the maximum extent during the demand request contention period. In order to analyze the DBBA, a test bench has been developed to simulate the traffic. Based on the simulation result, it has been observed that the proposed DBBA protocol has higher bandwidth utilization, supports larger number of stations in one cell, lesser propagation delay, more power efficient and has the ability to provide better quality of service. Since there is no collision, the efficiency of the system can be increased without affecting the overall throughput of the system.

Murugan, K.; Dushyanth, B.; Gunasekaran, E.; Arivuthokai, S.; Bhuvaneswaran, R. S.; Shanmugavel, S.

2004-04-01

156

Frequency response and bandwidth enhancement in Ge/Si avalanche photodiodes with over 840 GHz gain-bandwidth-product.  

Science.gov (United States)

In this work we report a separate-absorption-charge-multiplication Ge/Si avalanche photodiode with an enhanced gain-bandwidth-product of 845 GHz at a wavelength of 1310 nm. The corresponding gain value is 65 and the electrical bandwidth is 13 GHz at an optical input power of -30 dBm. The unconventional high gain-bandwidth-product is investigated using device physical simulation and optical pulse response measurement. The analysis of the electric field distribution, electron and hole concentration and drift velocities in the device shows that the enhanced gain-bandwidth-product at high bias voltages is due to a decrease of the transit time and avalanche build-up time limitation at high fields. PMID:19654668

Zaoui, Wissem Sfar; Chen, Hui-Wen; Bowers, John E; Kang, Yimin; Morse, Mike; Paniccia, Mario J; Pauchard, Alexandre; Campbell, Joe C

2009-07-20

157

Design of a ×4 subharmonic sub-millimeter wave diode mixer, based on an analytic expression for small-signal conversion admittance parameters  

DEFF Research Database (Denmark)

Instead of using frequency multipliers before a fundamental mixer, subharmonic mixers can be used. In order to develop novel subharmonic mixer architectures it is necessary to know the exact signal phase at the nonlinear element. The purpose of this paper is to generalize the description of the small-signal admittance in a Schottky-diode mixer where the phase can be set arbitrarily. It is shown that only for the case of a fundamental frequency mixer this admittance becomes a purely real valued conductance. To test the theory a ×4 subharmonic sub-millimeter wave mixer is designed and simulated. With an RF frequency of 640 GHz, this design achieves a conversion gain of ?13.5 dB with a LO-power of only ?2.5 dBm.

Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke

2013-01-01

158

Wide-bandwidth and high-power 1.3 ?m InGaAsP buried crescent lasers with semi-insulating Fe-doped InP current blocking layers  

International Nuclear Information System (INIS)

By the use of Fe-doped InP layer as the only current blocking layer, 8.3 GHz bandwidth and 30 mw/facet output has been achieved on 1.3 ?m buried crescent lasers. Conventional 1.3 ?m buried crescent lasers are attractive as light sources for optical fiber communication systems because of their high output power, single transverse mode, and good reliability. However, their small signal modulation bandwidth is rather limited due to excess parasitic capacitance from the current blocking reverse-biased p-n junction. Recently, the modulation bandwidth of InGaAsP buried crescent lasers has been extended to 4 GHz by the use of Fe-doped semi-insulating InP blocking layers grown by metal organic vapor phase epitaxy (MOVPE). In this previous work, a stripe geometry contact defined by a SiO/sub 2/ mask in addition to the semi-insulating InP layer was used to restrict the current flow laterally. In the present work, the authors report 1.3 ?m In GaAsP buried crescent lasers using similar semi-insulating InP as the current blocking layer, but without the SiO/sub 2/ current confining layer. The lasers with the broad area metal contacts exhibit both wide bandwidth and high power capabilities simultaneously

159

Performance Comparison of Selected Bandwidth-Efficient Coded Modulations  

Science.gov (United States)

Bandwidth-efficient modulations may be used to reduce the possibility of future congestion in the deep-space frequency bands due to a growing demand for higher data rates and to an increasing number of simultaneous missions. High-rate error-correcting codes such as punctured turbo codes and low-density parity-check (LDPC) codes can improve bandwidth usage while still providing large coding gains essential for deep-space communications. This article examines the throughput and bit-error rate performance of various coding and modulation combinations. As the number of such combinations is unlimited, the study concentrates upon bandwidth-efficient quadrature modulations compatible with the DSN Block V Receiver and selected turbo and LDPC codes. Capacity limits are derived for modulations under bandwidth constraints, and a comparison of selected uncoded and coded modulation schemes on the basis of bandwidth-normalized throughput and bit-error rate performance, obtained via theory and/or simulation, is presented. The effect of nonlinear amplifier operation is also analyzed. Finally, candidates for high-data-rate Mars missions are identified.

Andrews, K.; Lee, D.; Pollara, F.; Srinivasan, M.

2002-07-01

160

Statistical Multiplexing of Homogeneous Streams results in Linear Bandwidth Gains  

Directory of Open Access Journals (Sweden)

Full Text Available Statistical multiplexing of traffic streams results in reduced network bandwidth requirement. The resulting gain increases with the increase in the number of streams being multiplexed together. However, the exact shape of the gain curve, as more and more streams are multiplexed together, is not known.

In this paper, we first present the generalized result that the statistical gain of combining homogeneous traffic streams, of any traffic type, is a linear function of the number of streams being multiplexed. That is, given a fixed Quality of Service (QoS constraint, like percentile delay, D, the bandwidth requirement of n streams to satisfy the delay constraint D is n x R x c where R is the bandwidth requirement of a single stream that satisfies the constraint D and c e (0,1]. We present the linear bandwidth gain result, using an extensive simulation study for video traces, specifically, streaming video (IPTV traces and interactive video (CISCO Telepresence traces.

The linear bandwidth gain result is then verified using analytical tools from two different domains. First, we validate the linearity using Queueing Theory Analysis, specifically using Interrupted Poisson Process (IPP and Markov Modulated Poisson Process (MMPP modeling. Second, we formally prove the linear behavior using the Asymptotic Analysis of Algorithms, specifically, the Big-O analysis.

2013-01-01

 
 
 
 
161

A novel dynamic wavelength bandwidth allocation scheme over OFDMA PONs  

Science.gov (United States)

With rapid growth of Internet applications, supporting differentiated service and enlarging system capacity have been new tasks for next generation access system. In recent years, research in OFDMA Passive Optical Networks (PON) has experienced extraordinary development as for its large capacity and flexibility in scheduling. Although much work has been done to solve hardware layer obstacles for OFDMA PON, scheduling algorithm on OFDMA PON system is still under primary discussion. In order to support QoS service on OFDMA PON system, a novel dynamic wavelength bandwidth allocation (DWBA) algorithm is proposed in this paper. Per-stream QoS service is supported in this algorithm. Through simulation, we proved our bandwidth allocation algorithm performs better in bandwidth utilization and differentiate service support.

Yan, Bo; Guo, Wei; Jin, Yaohui; Hu, Weisheng

2011-12-01

162

Optical computing for image bandwidth compression: analysis and simulation.  

Science.gov (United States)

Image bandwidth compression is dominated by digital methods for carrying out the required computations. This paper discusses the general problem of using optics to realize the computations in bandwidth compression. A common method of digital bandwidth compression, feedback differential pulse code modulation (DPCM), is reviewed, and the obstacles to making a direct optical analogy to feedback DPCM are discussed. Instead of a direct optical analogy to DPCM, an optical system which captures the essential features of DPCM without optical feedback is introduced. The essential features of this incoherent optical system are encoding of low-frequency information and generation of difference samples which can be coded with a small number of bits. A simulation of this optical system by means of digital image processing is presented, and performance data are also included. PMID:20203902

Hunt, B R

1978-09-15

163

Performance Investigation of Virtual Private Networks with Different Bandwidth Allocations  

CERN Document Server

A Virtual Private Network (VPN) provides private network connections over a publicly accessible shared network. The effective allocation of bandwidth for VPNs assumes significance in the present scenario due to varied traffic. Each VPN endpoint specifies bounds on the total amount of traffic that it is likely to send or receive at any time. The network provider tailors the VPN so that there is sufficient bandwidth for any traffic matrix that is consistent with these bounds. The approach incorporates the use of Ad-hoc On demand Distance Vector (AODV) protocol, with a view to accomplish an enhancement in the performance of the mobile networks. The NS2 based simulation results are evaluated in terms of its metrics for different bandwidth allocations, besides analyzing its performance in the event of exigencies such as link failures. The results highlight the suitability of the proposed strategy in the context of real time applications.

Natarajan, Mahalakshmi Chidambara; Nachiappan, Alamelu

2010-01-01

164

Bandwidth characteristics and comparisons of surface texture measuring instruments  

International Nuclear Information System (INIS)

In this review we will discuss many of the problems that are encountered when designing and carrying out comparisons of surface texture measuring instruments. Previous comparisons are discussed to highlight some of the key issues. The limitations of stylus and optical instruments are identified with a focus on the spatial bandwidths in which they operate. Guidance is given on how to design comparisons to avoid variations in the results that are due to the operating principles and bandwidth limitations of the instruments involved. Methods for matching the bandwidths of different instruments are presented and some examples are given that highlight potential problems. The software aspects of instrument comparisons are also discussed. Finally, some advice is given on how to compare profile and areal surface texture measurements. (topical review)

165

A low power wide bandwidth CMOS folded-cascode amplifier  

Science.gov (United States)

To solve the problem of traditional amplifiers that high unity-gain bandwidth is obtained in exchange of big-power, a low power wide band-width folded-cascode fully differential amplifier with cascode current-mirrors load is designed based on Smic0.18 um rf CMOS technology. Transitional capacitor and Miller capacitor are applied to enhance the stability of frequency-characteristic; Common-mode feedback circuit is added to stabilize the common-mode output voltage of differential structure; Test results show, with the power supply of 1.8V, the circuit has an open-loop gain of 76.07dB, a phase margin of 50.6°, a unity-gain bandwidth of 215.7MHz and a CMRR of 120dB, while consuming 1.75mW of power.

Sun, Jin; Zhang, Xiaolin

2009-12-01

166

Delivery of very high bandwidth with ATM switches and SONET  

Energy Technology Data Exchange (ETDEWEB)

To deliver high bandwidth, a ubiquitous inter-/intra-building cable plant consisting of single mode and multimode fiber as well as twisted pair copper is required. The selection of the ``glue`` to transport and interconnect distributed LANs with central facility resources over a pervasive cable plant is the focus of this paper. A description of the traditional problems that must be overcome to provide very high bandwidth beyond the narrow confines of a computer center is given. The applicability of Asynchronous Transfer Mode (ATM) switching (interconnection) and Synchronous Optical NETwork (SONET) (transport) for high bandwidth delivery is described using the environment and requirements of Sandia National Laboratories. Other methods for distributing high data rates are compared and contrasted. Sandia is implementing a standards based foundation utilizing a pervasive single mode fiber cable plant, SONET transport, and ATM switching to meet the goals of gigabit networking.

Gossage, S.A.

1993-08-01

167

A Modified Adaptive Algorithm for Formant Bandwidth in Whisper Conversion  

Directory of Open Access Journals (Sweden)

Full Text Available The whisper conversion technology is to transform undistinguished whispers with lower SNR into clear normal speech, and it has important application prospect in mobile communication. Because the whisper speech is stirred by the yawp source, its formant position shifts and its bandwidth increases, which induces the problem of formant combination occurs in the whisper conversion. By analyzing the power spectrum, in this article, we proposed a modified adaptive algorithm for formant bandwidth. Based on the rule that the pole power does not change, the algorithm has resolved the problem of formant combination by modifying the formant bandwidth of whisper before implementing formant conversion. The experimental results with six Chinese mandarin monophthong phoneme conversions proved the validity of the algorithm.

Gang Lv

2009-02-01

168

Large bandwidth, highly efficient optical gratings through high index materials  

CERN Document Server

We analyze the diffraction characteristics of dielectric gratings that feature a high index grating layer, and devise, through rigorous numerical calculations, large bandwidth, highly efficient, high dispersion dielectric gratings in reflection, transmission, and immersed transmission geometry. A dielectric TIR grating is suggested, whose -1dB spectral bandwidth is doubled as compared to its all-glass equivalent. The short wavelength diffraction efficiency is additionally improved by allowing for slanted lamella. The grating surpasses a blazed gold grating over the full octave. An immersed transmission grating is devised, whose -1dB bandwidth is tripled as compared to its all-glass equivalent, and that surpasses an equivalent classical transmission grating over nearly the full octave. A transmission grating in the classical scattering geometry is suggested, that features a buried high index layer. This grating provides effectively 100% diffraction efficiency at its design wavelegth, and surpasses an equivalen...

Rathgen, Helmut

2008-01-01

169

Wavelength and bandwidth tunable photonic stopband of ferroelectric liquid crystals.  

Science.gov (United States)

The chiral smectic C phase of ferroelectric liquid crystals (FLCs) has a self-assembling helical structure which is regarded as a one-dimensional pseudo-photonic crystal. It is well known that a stopband of a FLC can be tuned in wavelength domain by changing temperature or electric field. We here have demonstrated an FLC stopband with independently tunable wavelength and bandwidth by controlling temperature and incident angle. At highly oblique incidence, the stopband does not have polarization dependence. Furthermore, the bandwidth at highly oblique incidence is much wider than that at normal incidence. The mechanism of the tunable stopband is clarified by considering the reflection at oblique incidence. PMID:22418500

Ozaki, Ryotaro; Moritake, Hiroshi

2012-03-12

170

A meta-substrate to enhance the bandwidth of metamaterials  

Science.gov (United States)

We propose the concept of a meta-substrate to broaden the bandwidth of left-handed metamaterials. The meta-substrate, which behaves like an inhomogeneous magnetic substrate, is composed of another kind of magnetic metamaterials like metallic closed rings. When conventional metamaterial rings are printed on this kind of meta-substrate in a proper way, the interaction of the metamaterials units can be greatly enhanced, yielding an increased bandwidth of negative permeability. An equivalent circuit analytical model is used to quantitatively characterize this phenomenon. Both numerical and experimental demonstrations are carried out, showing good agreement with theoretical predictions.

Chen, Hongsheng; Wang, Zuojia; Zhang, Runren; Wang, Huaping; Lin, Shisheng; Yu, Faxin; Moser, Herbert O.

2014-06-01

171

A meta-substrate to enhance the bandwidth of metamaterials  

Science.gov (United States)

We propose the concept of a meta-substrate to broaden the bandwidth of left-handed metamaterials. The meta-substrate, which behaves like an inhomogeneous magnetic substrate, is composed of another kind of magnetic metamaterials like metallic closed rings. When conventional metamaterial rings are printed on this kind of meta-substrate in a proper way, the interaction of the metamaterials units can be greatly enhanced, yielding an increased bandwidth of negative permeability. An equivalent circuit analytical model is used to quantitatively characterize this phenomenon. Both numerical and experimental demonstrations are carried out, showing good agreement with theoretical predictions. PMID:24919678

Chen, Hongsheng; Wang, Zuojia; Zhang, Runren; Wang, Huaping; Lin, Shisheng; Yu, Faxin; Moser, Herbert O.

2014-01-01

172

SATELLITE BANDWIDTH ALLOCATION FOR SATELLITE ROUTED SENSOR NETWORKS?  

Directory of Open Access Journals (Sweden)

Full Text Available Next Generation Satellite Routed Sensor Systems is expected to provide disaster detection system with high real time performance. By using Satellite Networks SRSS realizes data collection from multiple sensor terminals deployed in a wide area. However an efficient access control scheme is needed to achieve multiple access from numerous sensor terminals to the satellite with its limited bandwidth. In order to efficiently resolve these problems we propose a new scheme which utilizes a divide and conquer approach for efficient bandwidth allocation. Numerical results demonstrate the effectiveness of proposal.

Ambika Telkar

2014-06-01

173

Ultra Wideband Microstrip Diamond Slotted Patch Antenna with Enhanced Bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An Ultra Wideband (UWB) microstrip diamond slotted patch antenna with enhanced bandwidth is presented in this paper. The proposed antenna is simulated in CST Microwave Studio and fabricated for measurements. Its simulated result displays impedance bandwidth from 3.28 GHz to 19.64 GHz, whereas the measured result displays the frequency region from 2.01 GHz to 18.67 GHz. The antenna complies with the return loss of S11 < –10 dB and Voltage Standing Wave Ratio (VSWR) < 2 throughout the i...

Chia Ping Lee; Chandan Kumar Chakrabarty

2011-01-01

174

Search-Free Codebook Mapping for Artificial Bandwidth Extension  

Science.gov (United States)

A new codebook mapping algorithm for artificial bandwidth extension (ABE) is introduced in this paper. We design a wideband line spectrum pair (LSP) codebook which is coupled with the same index as the LSP codebook of a narrowband speech codec. The received narrowband LSP codebook indices are used to directly induce wideband LSP codewords. Thus, the proposed scheme eliminates codebook search processing to estimate the wideband spectrum envelope. We apply the proposed scheme to bandwidth extension in adaptive multi-rate (AMR) compressed domain. Its performance is assessed via the perceptual evaluation of speech quality (PESQ), informal listening tests, and weighted million operations per second (WMOPS) calculations.

Park, Heewan; Yoon, Byungsik; Kang, Sangwon; Spanias, Andreas

175

Bandwidth of excitons in LH2 bacterial antenna chromoproteins  

Science.gov (United States)

The bandwidth of the exciton manifold in LH2 peripheral antenna complexes from the photosynthetic bacterium Rhodobacter sphaeroides has been determined using polarized fluorescence excitation spectroscopy and model simulations. It is shown that the fluorescence anisotropy spectra reveal a hidden structure of the exciton band that is correlated with its boundaries. The estimated exciton coupling energy and exciton bandwidth in the native complex is ˜360 and ˜1620 cm -1, respectively. The corresponding numbers in a mutant with the B800 bacteriochlorophyll molecules absent are somewhat larger (˜420 and ˜1890 cm -1), probably due to tightening of the protein structure.

Timpmann, Kõu; Trinkunas, Gediminas; Olsen, John D.; Neil Hunter, C.; Freiberg, Arvi

2004-11-01

176

Fabrication of high frequency ultrasonic probe with wide bandwidth  

International Nuclear Information System (INIS)

This paper is about fabrication of a wide band 2 MHz ultrasonic probe for NDT application. The piezoelectric material used is PZT. To achieve wide band operation, a backing layer is attached to the rear face and a matching/ protective layer is attached to the rear face. Backing layer is a mixture of epoxy and tungsten powder while matching layer is white alumina. The fabricated probe shows bandwidth of 53 % with centre frequency of 2.13 MHz. The pulse width at 50 % amplitude is 2.47 ?s. A wide bandwidth probe was successfully fabricated. (author)

177

A meta-substrate to enhance the bandwidth of metamaterials.  

Science.gov (United States)

We propose the concept of a meta-substrate to broaden the bandwidth of left-handed metamaterials. The meta-substrate, which behaves like an inhomogeneous magnetic substrate, is composed of another kind of magnetic metamaterials like metallic closed rings. When conventional metamaterial rings are printed on this kind of meta-substrate in a proper way, the interaction of the metamaterials units can be greatly enhanced, yielding an increased bandwidth of negative permeability. An equivalent circuit analytical model is used to quantitatively characterize this phenomenon. Both numerical and experimental demonstrations are carried out, showing good agreement with theoretical predictions. PMID:24919678

Chen, Hongsheng; Wang, Zuojia; Zhang, Runren; Wang, Huaping; Lin, Shisheng; Yu, Faxin; Moser, Herbert O

2014-01-01

178

An EC-branch in the decay of 27-s sup 2 sup 6 sup 3 Db evidence for the isotope sup 2 sup 6 sup 3 Rf  

CERN Document Server

27-s sup 2 sup 6 sup 3 Db was produced in the sup 2 sup 4 sup 9 Bk ( sup 1 sup 8 O, 4n) reaction at 93 MeV.The activity was transported by a He/KCl-jet to the laboratory where it was collected for 15 min and then subjected to a chemical separation specific for group-4 elements. The activity was dissolved in 0.5 M unbuffered alpha-HiB and eluted from a cation-exchange column. The effluent was made 9 M in HCl and group-4 tetrachlorides were extracted into TBP/Cyclohexane which was evaporated to dryness on a Ta disc. The Ta discs were assayed for alpha and SF activity. A SF activity with a half life on the order of 20 min was observed and assigned to the nuclide sup 2 sup 6 sup 3 Rf. It is formed by electron-capture decay of sup 2 sup 6 sup 3 Db with a decay branch of 3 sup + sup 4 sub - sub 1 %.

Kratz, J V; Rieth, U; Kronenberg, A K; Kuczewski, B; Strub, E; Brüchle, W; Schädel, M; Schausten, B; Türler, A; Gäggeler, H W; Jost, D T; Gregorich, K E; Nitsche, H; Laue, C; Sudowe, R; Wilk, P A

2003-01-01

179

Narrow-bandwidth holographic reflection filters with photopolymer films.  

Science.gov (United States)

Narrow-bandwidth holographic reflection filters are demonstrated that use volume gratings in 100-mum-thick photopolymer films. A full width at half-maximum of 0.09 nm can be achieved with ~35% peak reflectance near the 900-nm region. Detailed fabrication procedures and filter performances are described. PMID:18357250

Zhang, G; Montemezzani, G; Günter, P

2001-05-20

180

Bandwidth utilization maximization of scientific RF communication systems  

Energy Technology Data Exchange (ETDEWEB)

A method for more efficiently utilizing the frequency bandwidth allocated for data transmission is presented. Current space and range communication systems use modulation and coding schemes that transmit 0.5 to 1.0 bits per second per Hertz of radio frequency bandwidth. The goal in this LDRD project is to increase the bandwidth utilization by employing advanced digital communications techniques. This is done with little or no increase in the transmit power which is usually very limited on airborne systems. Teaming with New Mexico State University, an implementation of trellis coded modulation (TCM), a coding and modulation scheme pioneered by Ungerboeck, was developed for this application and simulated on a computer. TCM provides a means for reliably transmitting data while simultaneously increasing bandwidth efficiency. The penalty is increased receiver complexity. In particular, the trellis decoder requires high-speed, application-specific digital signal processing (DSP) chips. A system solution based on the QualComm Viterbi decoder and the Graychip DSP receiver chips is presented.

Rey, D. [Sandia National Lab., Albuquerque, NM (United States); Ryan, W. [New Mexico State Univ., Las Cruces, NM (United States); Ross, M.

1997-01-01

 
 
 
 
181

Effective Communication and File-I/O Bandwidth Benchmarks  

Energy Technology Data Exchange (ETDEWEB)

We describe the design and MPI implementation of two benchmarks created to characterize the balanced system performance of high-performance clusters and supercomputers: b{_}eff, the communication-specific benchmark examines the parallel message passing performance of a system, and b{_}eff{_}io, which characterizes the effective 1/0 bandwidth. Both benchmarks have two goals: (a) to get a detailed insight into the Performance strengths and weaknesses of different parallel communication and I/O patterns, and based on this, (b) to obtain a single bandwidth number that characterizes the average performance of the system namely communication and 1/0 bandwidth. Both benchmarks use a time driven approach and loop over a variety of communication and access patterns to characterize a system in an automated fashion. Results of the two benchmarks are given for several systems including IBM SPs, Cray T3E, NEC SX-5, and Hitachi SR 8000. After a redesign of b{_}eff{_}io, I/O bandwidth results for several compute partition sizes are achieved in an appropriate time for rapid benchmarking.

Koniges, A E; Rabenseifner, R

2001-05-02

182

47 CFR 2.1049 - Measurements required: Occupied bandwidth.  

Science.gov (United States)

...emission bandwidth limitation curve, the seventh and ninth order...35 dB step of the referenced curve and the eleventh and all higher...35 dB step of the referenced curve. (5) Independent sideband...level is established for the characteristic baseband frequency....

2010-10-01

183

Transit Time Enhanced Bandwidth in Nanostructured Terahertz Emitters  

Science.gov (United States)

Monte-Carlo simulations are used to show that the transit time in ˜100 nm gap photoconductive emitters of terahertz radiation is short enough to produce broad-bandwidth pulses. Furthermore, with these calculations we demonstrate that nanostructured contacts remove the need for low-temperature-grown or ion-implanted materials for broad-band terahertz devices.

Corzo-Garcia, S. C.; Alfaro, M.; Castro-Camus, E.

2014-09-01

184

Small signal AC-surface photovoltage technique for non-contact monitoring of near surface doping and recombination-generation in the depletion layer[Alternating Current  

Energy Technology Data Exchange (ETDEWEB)

Small signal non-contact ac-SPV method for monitoring near surface doping (NSD) in silicon has recently been introduced in commercial diagnostic tools. High chopping frequency light with a submicron penetration depth is used to generate small SPV signal and this signal is in turn monitored using a transparent pickup electrode. This technique has the advantage of producing fast, non-destructive full wafer measurement. Under certain conditions, the magnitude of this ac-SPV signal is inversely proportional to the depletion layer capacitance. if a depletion layer barrier height is known this allows the calculation of the concentration of ionized donors or acceptors in the depletion layer. NSD measurements by ac-SPV method were typically done for doping concentrations up to about 10{sup 16} cm{sup {minus}3}. Only recently this range has been extended to 10{sup 18} cm{sup {minus}3}, making it a very attractive technique for monitoring low and medium dose implants and especially for wafer scale mapping of implant uniformity and activation efficiency. In addition, the frequency dependence of the SPV signal provides a mean for evaluating the minority carrier lifetime in the near surface region of bulk and epitaxial wafers. The influence of surface/interface traps upon small ac-SPV signal has never been fully understood. This paper quantifies the role of interface traps in the monitoring of NSD. The effect of typical surface treatments such as HF, SC1 and SC1+SC2 wafer cleans are examined.

Marinskiy, D.; Lagowski, J.; Wilson, M.; Savtchouk, A.; Jastrzebski, L.; DeBusk, D.

2000-07-01

185

Impact of Wind Power Plants with Full Converter Wind Turbines on Power System Small-Signal Stability : Inherent Characteristics and Potential for Power Oscillation Damping Control  

DEFF Research Database (Denmark)

Wind power is being developed in power systems all around the world, and already today wind power covers more than 20 % of the electricity consumption in some countries. As the size of each wind power plant (WPP) increases and as the levels of penetration reaches certain magnitudes, the inclusion of the dynamic properties of the WPPs in the power system stability studies become important. The work presented in this report deal with the impact of WPPs based on full converter wind turbines (WTs) on the power system small-signal rotor angle stability. During small disturbances in the power system, the rotor speed of the synchronous machines will eventually return to its steady state if the power system is small-signal stable. The dynamic properties of a WPP are fundamentally dierent from those of a synchronous machine, and the interaction of WPPs with the synchronous machines in power system oscillations has not yet been fully claried. The participation of the WPP in the power system oscillations was investigated for a number of WPP penetration levels and for dierent WPP modes of operation. It was generally found that the inter-area modes were largely unaected by the WPP penetration level and mode of operation. The participation of the WT mechanical system in the inter-area modes were found to be orders of magnitudes smaller than the participation of the synchronous generators. The reactive power controller of the WPP and the WT were found have the highest participation among the WPP and WT states. WPPs based on converter interfaced WTs oer a high degree of controllability due to the rapid response of the converter and the ability to control both the active and the reactive power output. During this project, it has been explored how these properties could be utilized to actively contribute to the modal damping of weakly damped power oscillations through WPP power oscillation damping control (POD). Emphasis has been put on WPP level PODs due to its simplicity as compared to individual WT PODs, and since this oers a single point of access if the operation of the POD is to be controlled by a wide-area measurement system. The ndings encourage that a WPP level POD is feasible, since the WTs in a 150 WT WPP required very similar control signals to optimally contribute to an increased modal damping, and since time domain simulations showed that the interaction between the WTs did not adversely eect the ability of the WTs to generate an aligned WPP response. The theoretical ndings are supported with eld test results on a small 13 WT WPP that has been subject to open-loop tests of both active and reactive power modulations in the frequency range of 0:1 to 1:0 Hz. With the eld tests it has been shown that it was possible to control the WTs to deliver a common WPP response that was consistent in both frequency and phase. This was achieved for both active and reactive power modulation.

Knüppel, Thyge

2012-01-01

186

A wide-bandwidth and high-sensitivity robust microgyroscope  

International Nuclear Information System (INIS)

This paper reports a microgyroscope design concept with the help of a 2 degrees of freedom (DoF) sense mode to achieve a wide bandwidth without sacrificing mechanical and electronic sensitivity and to obtain robust operation against variations under ambient conditions. The design concept is demonstrated with a tuning fork microgyroscope fabricated with an in-house silicon-on-glass micromachining process. When the fabricated gyroscope is operated with a relatively wide bandwidth of 1 kHz, measurements show a relatively high raw mechanical sensitivity of 131 µV (° s?1)?1. The variation in the amplified mechanical sensitivity (scale factor) of the gyroscope is measured to be less than 0.38% for large ambient pressure variations such as from 40 to 500 mTorr. The bias instability and angle random walk of the gyroscope are measured to be 131° h?1 and 1.15° h?1/2, respectively

187

GHz bandwidth noise eater hybrid optical amplifier: design guidelines.  

Science.gov (United States)

This Letter describes the design of an optical amplifier system optimized to reduce the relative intensity noise (RIN) of the input signal, and discloses its performance in terms of intensity noise reduction and bandwidth, without phase noise degradation. This polarization-maintaining amplifier is composed of an erbium-doped fiber amplifier (EDFA) cascaded with a semiconductor optical amplifier (SOA). The EDFA is sized to feed the SOA with a constant power corresponding to the optimal saturation level for noise reduction, through coherent population oscillations. When properly optimized, such an amplifier provides, simultaneously, 17 dB optical gain, 5.4 dB noise factor, and 20 dB reduction of the input-RIN across a 3 GHz bandwidth, without any electronics feedback loop. PMID:25121696

Danion, Gwennaël; Bondu, François; Loas, Goulc'hen; Alouini, Mehdi

2014-07-15

188

Available Network Bandwidth Schema to Improve Performance in TCP Protocols  

Directory of Open Access Journals (Sweden)

Full Text Available The TCP congestion control mechanism in standard implementations presents several problems, for example, large queue lengths in network routers and packet losses, a misleading reduce of the transmission rate when there are link failures, among others. This paper proposes a schema to congestion control in TCP protocols, called NGWA, witch is based on the network bandwidth. The NGWA provides information considering the available bandwidth of the network infrastructure to the endpoints of the TCP connection.Hence, it helps in choosing a better transmission rate for TCP improving its performance. Simulation results show superior performance of the proposed scheme when compared to those obtained by TCP New Reno and standard TCP. A physical implementation in the Linux kernel was performed to prove the correct operation of the proposal.

Marcos Talau

2013-09-01

189

Dynamic bandwidth allocation on a slotted ring with integrated services  

Science.gov (United States)

The authors discuss what they consider the fundamental issue of bandwidth allocation on an integrated local area network. An approach is introduced for dynamic bandwidth allocation which is based on traffic prediction concepts. It is especially well suited for real-time services such as video and voice. Using a control model formulated here, two allocation schemes are proposed: the first is based on an analytical model of the traffic flow; the second is a simpler version that can be easily implemented on very high-speed systems. The results of simulation studies indicate a marked improvement in performance. The presented approach is especially effective when used in systems with large transmission path latencies as the network performance does not deteriorate with increasing latency. This is very useful if the network is to be used as a metropolitan area network.

Li, San-Qi; El Zarki, Magda

1988-07-01

190

IMAGE AUTHENTICATION THROUGH ZTRANSFORM WITH LOW ENERGY AND BANDWIDTH (IAZT  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper a Z-transform based image authentication technique termed as IAZT has been proposed to authenticate gray scale images. The technique uses energy efficient and low bandwidth based invisible data embedding with a minimal computational complexity. Near about half of the bandwidth is required compared to the traditional Z–transform while transmitting the multimedia contents such as images with authenticating message through network. This authenticating technique may be used for copyright protection or ownership verification. Experimental results are computed and compared with the existing authentication techniques like Li’s method [11], SCDFT [13], Region-Based method [14] and many more based on Mean Square Error (MSE, Peak Signal to Noise Ratio (PSNR, Image Fidelity (IF, Universal Quality Image (UQI and Structural Similarity Index Measurement (SSIM which shows better performance in IAZT.

Madhumita Sengupta

2013-09-01

191

Modeling of Bandwidth Aggregation over Heterogeneous Wireless Access Networks  

DEFF Research Database (Denmark)

Motivated by the multihomming capability of the mobile devices and the fact that the heterogeneous wireless access networks overlap in coverage, mobile operators are looking for solutions that will benefit by simultaneous use of the available multiple access interfaces. Multipath or multilink transfer deals with the problem on how to effectively aggregate the bandwidth by simultaneous usage of heterogeneous networks that a host is attached to in order to improve the throughput. This paper deals with a simulation based analysis of bandwidth aggregation techniques and their impact on higher layer applications. The analysis is performed on a multipath model developed with OPNET Modeler, which is an advanced research tool that supports modeling and integration of various kinds of built-in networks.

Popovska Avramova, Andrijana; Dittmann, Lars

2012-01-01

192

Bandwidth and Energy Management in Wireless Sensor Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The emergence of sensor networks as one of thedominant technology trends in the coming decades has posednumerous problems regarding the Quality of Service (QoSparameter to researchers. These QoS parameters are oftenfound to be as limited resources. Hence to effectively utilizethese limited resources, we propose a technique to manage twoof the most basic QoS parameters of sensor networks, they arebandwidth and energy. We propose bandwidth management byimplementing rules that guide the data streams to a specificdata rate, so as to treat different data to its own credit. Tomanage energy we present GAF algorithm that effectivelyreduces energy consumption of the nodes keeping a constantlevel of routing fidelity. The simulation is run on NS-2.34 with35 nodes in total. The simulation results obtained show that thecombination of the both bandwidth and energy in managementperforms better than the existing protocols.

Ashish Talikoti, Jayashree A

2012-10-01

193

Plasma density profiles and finite bandwidth effects on electron heating  

International Nuclear Information System (INIS)

Intense, p-polarized microwaves are incident on an inhomogeneous plasma in a cylindrical waveguide. Microwaves are mainly absorbed by resonant absorption near the critical surface (where the plasma frequency, ?/sub pe/, equals the microwave frequency, ?/sub o/). The localized plasma waves strongly modify the plasma density. Step-plateau density profiles or a cavity are created depending on the plasma flow speed. Hot electron production is strongly affected by the microwave bandwidth. The hot electron temperature varies as T/sub H/ is proportional to (? ?/?)-025. As the hot electron temperature decreases with increasing driver bandwidth, the hot electron density increases. This increase is such that the heat flux into the overdense region (Q is proportional to eta/sub H/T/sub H/32) is nearly constant

194

Coherent temporal imaging with analog time-bandwidth compression  

CERN Document Server

We introduce the concept of coherent temporal imaging and its combination with the anamorphic stretch transform. The new system can measure both temporal profile of fast waveforms as well as their spectrum in real time and at high-throughput. We show that the combination of coherent detection and warped time-frequency mapping also performs time-bandwidth compression. By reducing the temporal width without sacrificing spectral resolution, it addresses the Big Data problem in real time instruments. The proposed method is the first application of the recently demonstrated Anamorphic Stretch Transform to temporal imaging. Using this method narrow spectral features beyond the spectrometer resolution can be captured. At the same time the output bandwidth and hence the record length is minimized. Coherent detection allows the temporal imaging and dispersive Fourier transform systems to operate in the traditional far field as well as in near field regimes.

Asghari, Mohammad H

2013-01-01

195

A Contemporary Methodology for Bandwidth Reservation in Wireless Cellular Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The emerging technologies in wireless communication under the next generation have pulled many scientists and researchers towards them. The wireless cellular network, which is a widely used technology, has various issues regarding Quality of Service (QoS. The major issues that ever attract people are resource reservation, call admission control mechanisms and user mobility patterns. In this paper, various resource reservation schemes with their unique features are discussed and compared. One of the best-suited schemes would be the Tier- Based Bandwidth Reservation Scheme with better resource utilization. The simulation results have shown the better resource utilization and conservation when compared to one of the traditional schemes. The enhancement with the bandwidth borrowing concept is also simulated and the results are compared.

Malathi Balaji

2013-04-01

196

BANDWIDTH ENHANCEMENT USING PARASITIC PATCH FOR KU BAND  

Directory of Open Access Journals (Sweden)

Full Text Available - A design of microstrip patch antenna with prime focused of increasing bandwidth using various techniques of probe feed, parasitic patch around the main patch and two layer of substrate. The simulation process has been done using HFSS (High frequency Structural Simulator. In this paper, authors cover six aspect of microstrip antenna designs. The first is analysis of single element narrowband rectangular microstrip antenna which operates at central frequency of 14.3 GHz. The second/third aspect is design of two gap/direct coupled patch along main patch. The fourth/fifth aspect is analysis and design of four gap/direct coupled parasitic patch along main patch and in sixth aspect is analysis and design of two layer of substrate in parasitic patch design. The properties of antenna such as bandwidth, S parameter, VSWR, Gain has been investigated and compared

Kalpesh B. Barad

2014-04-01

197

Spacer Optimization and Accurate Small-Signal Modeling of 90nm Gate Underlap SOI-MOSFETs for Low Power GHz Applications  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the significance of gate-source/drain extension region (also known as underlap design optimization in 90nm single gate (SG Silicon-on-Insulator (SOI MOSFET for low power GHz frequency applications. Using an optimal spacer s (? 0.8×LG, where LG is gate length, it has been found that the device exhibits intrinsic gain of ? 25 dB in low-moderate inversion region (VOD =VGS – VTH ? 90 mV, where VOD, VGS and VTH are the overdrive, gate and threshold voltages, respectively at operating frequency of 20 GHz. An accurate (including non-quasi-static and extrinsic parasitics effects small-signal model for the optimized device has been presented. The comparison of Y-parameters of 2D ATLAS with overall modeled value (up to 20 GHz has shown an excellent matching (with an average error of ?5%, whereas results from quasi-static (QS predictive technology model (PTM differ significantly (>20%. Optimized underlap device shows transit frequency fT and maximum frequency of oscillation fMAX, ~108 and ~130 GHz respectively, with noise figure (NF ~2.8 dB and exhibits unilateral power gain (ULG ~38 dB (VOD =90mV, drain-to-source current IDS ? 0.64mA and drain-to-source voltage VDS = 1V at 20 GHz. Comparison with limited measured data suggest that simulated results are in well conformity, which suggest the possibility of use of underlap device technology in the design of key blocks such as low noise amplifier LNA and mixer for GHz applications. Key Words: Gate Underlap, silicon-on-Insulator, Non-Quasi-Static, Transconductance-to-Net-Charge Ratio (TCR, Low Power.

Indra Vijay Singh

2013-02-01

198

High bandwidth second-harmonic generation in partially deuterated KDP  

International Nuclear Information System (INIS)

We have experimentally determined the spectrally noncritical phasematching behavior of Type I frequency doubling in KDP and its dependence on deuteration level in partially deuterated KDP. The first order wavelength sensitivity parameter??k/?? for Type I doubling of 1.053 ?m light vanishes for a KD*P crystal with a deuteration level between 10 and 14%. Very high bandwidth frequency doubling of Nd:glass lasers is possible with such a crystal

199

High-speed and broad optical bandwidth silicon modulator  

Science.gov (United States)

A high-speed silicon modulator with broad optical bandwidth is proposed based on a symmetrically configured Mach—Zehnder interferometer. Careful phase bias control and traveling-wave design are used to improve the high-speed performance. Over a broadband wavelength range, high-speed operation up to 30 Gbit/s with a 4.5 dB-5.5 dB extinction ratio is experimentally demonstrated with a low driving voltage of 3 V.

Xu, Hao; Li, Xian-Yao; Xiao, Xi; Li, Zhi-Yong; Yu, Yu-De; Yu, Jin-Zhong

2013-11-01

200

Bandwidth considerations for binary phase-only filters  

International Nuclear Information System (INIS)

A binary phase-only filter (BPOF) bandwidth and, correspondingly, the performance with respect to stochastic noise are introduced as filter design parameters. A BPOF figure of merit is defined which references the matched filter. Analytical bounds on the BPOF signal-to-noise ratio are derived. The noise performance is illustrated with simulation results. It is demonstrated through analysis and simulation that BPOFs can be designed to perform well with respect to stochastic noise

 
 
 
 
201

Optimization of bandwidth in 60^o photonic crystal waveguide bends  

DEFF Research Database (Denmark)

A systematic scheme utilizing 2D and 3D finite-difference time-domain calculations to design 60^o photonic crystal waveguide bends is presented. The method results in an improved transmission bandwidth from 70 to 160 nm in 2D simulations, and from 50 to 100 nm in 3D simulations. The design principles involve displacements and enlargements of selected holes in the bend regions.

Xing, P. F.; Borel, Peter Ingo

2005-01-01

202

TUNNEL-BASED IPV6 TRANSITION WITH AUTOMATIC BANDWIDTH MANAGEMENT  

Directory of Open Access Journals (Sweden)

Full Text Available The Internet will soon be sailing in very rough as it is about to run out of the current Internet Protocol Version four (IPV4. Moving from Internet Protocol version Four (IPv4 to Internet Protocol version six (IPv6 is not straightforward because IPv4 and IPv6 are incompatible protocols. To enable the smooth transition between IPv4 and IPv6, several transition mechanisms have been proposed by IETF IPng Transition Working Group (NGTrans such as Tunneling, dual stack, Translation. Tunneling supports ?like-to-like? IP connectivity across an ?unlike? network, whereas translation supports ?like-to-unlike? IP interconnectivity. No comprehensive strategy exists to address all possible scenarios. Because tunneling can keep the end-to-end model that the Internet is built on. Tunneling enables IPv6 connectivity across an IPv4 network and vice versa. Although tunneling can’t achieve direct interworking between IPv4 and IPv6, but broadly adopting it as the foundation for IPv6 transition will accelerate IPv6 adoption, and retain the legacy IPv4 connectivity, and let operators leverage their existing IPv4 assets during the transition period. The key concern is that tunneling retains the end-to-end notion and IP like-to-like affinity on which the Internet is built. Bandwidth allocation is an important factor to be considered in networking. Efficient bandwidth management technique is important in satisfying the requested services. In this project, the emphasis is laid on developing a tunnel-based framework that solves the transition problems in backbone and allocation of bandwidth efficiently by allocating the requested bandwidth as per the demand.

Srinidhi K S

2014-06-01

203

Efficient Upload Bandwidth Estimation and Communication Resource Allocation Techniques  

CERN Document Server

In this paper we address two problems, for which we present novel, efficient, algorithmic solutions. The first problem is motivated by practical situations and is concerned with the efficient estimation of the upload bandwidth of a machine, particularly in the context of a peer-to-peer content sharing and distribution application. The second problem is more of a theoretical nature and considers a constrained communication resource allocation situation.

Andreica, Mugurel Ionut

2010-01-01

204

Terahertz bandwidth integrated radio frequency spectrum analyzer via nonlinear optics  

CERN Document Server

We report an integrated all-optical radio frequency spectrum analyzer based on a ~ 4cm long doped silica glass waveguide, with a bandwidth greater than 2.5 THz. We use this device to characterize the intensity power spectrum of ultrahigh repetition rate mode-locked lasers at repetition rates up to 400 GHz, and observe dynamic noise related behavior not observable with other techniques.

Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Clerici, Matteo; Caspani, Lucia; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Moss, David J

2014-01-01

205

Flexible bandwidth DGD estimation for coherent optical OFDM system.  

Science.gov (United States)

A Stokes vector based non-data-aided (NDA) differential group delay (DGD) estimation scheme with flexible bandwidth requirements is investigated. The scheme is demonstrated in both experiments and simulations for 40-Gb/s polarization-multiplexed coherent optical OFDM systems with up to 1000-km long haul transmission with an estimation error of less than 2.5 ps after 1000-km standard single-mode fiber transmissions. PMID:24216805

Do, Cuong C; Tran, An V; Chen, Simin; Anderson, Trevor; Hewitt, Don; Skafidas, Efstratios

2013-11-01

206

Dynamic Bandwidth Provisioning and Malleable Bulk Data Transfer Scheduling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To address the anticipated sporadic terabyte demands generated by high-end time-constrained applications, dynamically reconfigurable optical networks services are envisioned. However, the time and rate granularities of a bandwidth reservation service and those of transfer tasks using the reserved capacity is not necessarly in the same order of magnitude. This may lead to poor resource utilisation and overprovisionning. Transfer request aggregation is able to limit this problem. This paper exp...

Soudan, Se?bastien; Cade?re?, Christian; Barth, Dominique; Primet, Pascale

2008-01-01

207

Bandwidth and Energy Management in Wireless Sensor Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The emergence of sensor networks as one of thedominant technology trends in the coming decades has posednumerous problems regarding the Quality of Service (QoS)parameter to researchers. These QoS parameters are oftenfound to be as limited resources. Hence to effectively utilizethese limited resources, we propose a technique to manage twoof the most basic QoS parameters of sensor networks, they arebandwidth and energy. We propose bandwidth management byimplementing rules that guide the data st...

Ashish Talikoti, Jayashree A.

2012-01-01

208

Lateral loss effects on modulation bandwidth in VCSELs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Intensity noise and chromatic fiber dispersion in analog optical communication systems are attributed to harmonic and inter-modulation distortion in the amplitude modulation of semiconductor lasers. In addition, maximum usable bandwidth of the communication systems is limited by harmonic distortion. Due to the use of Fabry Perot type resonator, second harmonic distortion exists in both edge-emitting devices and VCSELs. However the distortion caused by lateral loss may be more so in VCSELs bec...

Chui, Pc; Yu, Sf

1999-01-01

209

Performance aspects of the adjustable bandwidth concept (ABC) predetection processor  

Science.gov (United States)

There are a variety of domains in which signal channelization has proven to be useful, including the time, frequency, spatial and polarization domains. These partitioning techniques are necessary for the proper management and effective utilization of the overall channel resource. The term "multi-channel" is used to describe this partitioning of these domains. However, there are other "domains" in which channelization techniques can be employed. These include the coding domain (as in code-division multiple-access) and the less obvious steganographic domain. One can argue that these latter examples of domains lack the physical interpretation of their counterparts, or that they are each in fact a clever use of the standard domains. But from the view of the overall channel resource, very effective utilization and management tools can be developed, operated and described in these domains. In this paper, a technique is studied which is based upon a novel utilization of the signal bandwidth domain, for pre-processing prior to detection and parameter estimation. Experimental and theoretical results will be given for assessment of device performance. The studied technique is referred to as the Adjustable Bandwidth Concept (ABC) signal energy detector. When implemented digitally, this device is essentially a cepstral-based pre-processor for generating multiple channels for the analysis and detection of signal components of distinguishable bandwidths. The ABC device processes an input log-magnitude spectrogram and results in a multi-channel output. Each output channel contains information regarding the input spectrogram which is sorted or partitioned based on the bandwidth of signal components within the spectrogram. A primary application of such a device is as a pre-processing step prior to detection and estimation, for automated spectral survey and characterization.

Noga, Andrew J.

2003-08-01

210

High-bandwidth polarimeter for a high density, accelerated spheromak  

Energy Technology Data Exchange (ETDEWEB)

A three-beam heterodyne polarimeter has been built to diagnose the PI-1 plasma injector at General Fusion, Inc. The polarimeter measures plasma density and Faraday rotation, which can provide estimates of magnetic field magnitude and direction. Two important calibration steps are required for the polarimeter to produce reasonable Faraday rotation signals. Beam polarization ellipticity must be measured to ensure there is a linear Faraday rotation response. In addition, the two beams travelling through the plasma must be collinear to reduce error due to differences in plasma density. Once calibrated, the Faraday rotation signals are in much better agreement with other diagnostics. For a null signal, the Faraday rotation measurement noise floor is 0.1° at 0.5 MHz bandwidth. Comparing preliminary spheromak Faraday rotation measurements to a model, the maximum error is about 0.3° at 0.5 MHz bandwidth, which is primarily due to electrical noise during the injector's capacitor discharge and limitations of the model. At a bandwidth of 0.5 MHz, the polarimeter has an axial resolution between 6 cm and 30 cm depending on the speed of the spheromak, which varies between 30 km/s and 150 km/s. The spheromak length ranges from 0.75 m to 2 m. Additional polarimeter chords will be added in future upgrades.

Carle, Patrick J. F.; Morelli, Jordan [Department of Physics, Queen' s University, 99 University Ave., Kingston, Ontario K7L 3N6 (Canada); Howard, Stephen [General Fusion, Inc., 108-3680 Bonneville Pl, Burnaby, British Columbia V3N 4T5 (Canada)

2013-08-15

211

High-bandwidth polarimeter for a high density, accelerated spheromak  

International Nuclear Information System (INIS)

A three-beam heterodyne polarimeter has been built to diagnose the PI-1 plasma injector at General Fusion, Inc. The polarimeter measures plasma density and Faraday rotation, which can provide estimates of magnetic field magnitude and direction. Two important calibration steps are required for the polarimeter to produce reasonable Faraday rotation signals. Beam polarization ellipticity must be measured to ensure there is a linear Faraday rotation response. In addition, the two beams travelling through the plasma must be collinear to reduce error due to differences in plasma density. Once calibrated, the Faraday rotation signals are in much better agreement with other diagnostics. For a null signal, the Faraday rotation measurement noise floor is 0.1° at 0.5 MHz bandwidth. Comparing preliminary spheromak Faraday rotation measurements to a model, the maximum error is about 0.3° at 0.5 MHz bandwidth, which is primarily due to electrical noise during the injector's capacitor discharge and limitations of the model. At a bandwidth of 0.5 MHz, the polarimeter has an axial resolution between 6 cm and 30 cm depending on the speed of the spheromak, which varies between 30 km/s and 150 km/s. The spheromak length ranges from 0.75 m to 2 m. Additional polarimeter chords will be added in future upgrades

212

DC SQUID RF magnetometer with 200 MHz bandwidth  

Science.gov (United States)

Because of periodic flux-to-voltage transfer function, Superconducting QUantum Interference Device (SQUID) magnetometers operate in a closed-loop regime [1], which linearizes the response, and increases the dynamic range and sensitivity. However, a transmission line delay between the SQUID and electronics fundamentally limits the closed-loop bandwidth at 20 MHz [1], although the intrinsic bandwidth of SQUIDs is in gigahertz range. We designed a DC SQUID based RF magnetometer capable of wideband sensing coherent magnetic fields up to 200 MHz. To overcome the closed-loop bandwidth limitation, we utilized a low-frequency flux-modulated closed-loop to simultaneously lock the quasi-static magnetic flux and provide AC bias for the RF flux. The SQUID RF voltage is processed by RF electronics based on a double lock-in technique. This yields a signal proportional to the amplitude and phase of the RF magnetic flux, with more than four decades of a linear response. For YBaCuO SQUID on bi-crystal SrTiO substrate at 77 K we achieved a flux noise density of 4 ??0/Hz at 190 MHz, which is similar to that measured at kHz frequencies with conventional flux-locked loop. [1] D. Drung, et al., Supercond. Sci. Technol. 19, S235 (2006).

Talanov, Vladimir; Lettsome, Nesco; Orozco, Antonio; Cawthorne, Alfred; Borzenets, Valery

2012-02-01

213

An Orthogonal Frequency Division Multiplexing Radar Waveform with a Large Time-bandwidth Product  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes a practical orthogonal frequency division multiplexing (OFDM chirp diverse waveform with a large time-bandwidth product for new generation radar systems. Besides large time-bandwidth product and implementation simplicity, the OFDM chirp diverse waveform have good ambiguity function performance in range resolution and doppler resolution. Although the spectra are not uniform across the bandwidth like conventional chirp waveforms, the bandwidth is covered with no visible gaps.

Wen-Qin Wang

2012-11-01

214

Modulator-Based, High Bandwidth Optical Links for HEP Experiments  

Science.gov (United States)

As a concern with the reliability, bandwidth and mass of future optical links in LHC experiments, we are investigating CW lasers and light modulators as an alternative to VCSELs. These links will be particularly useful if they utilize light modulators which are very small, low power, high bandwidth, and are very radiation hard. We have constructed a test system with 3 such links, each operating at 10 Gb/s. We present the quality of these links (jitter, rise and fall time, BER) and eye mask margins (10GbE) for 3 different types of modulators: LiNbO3-based, InP-based, and Si-based. We present the results of radiation hardness measurements with up to ~1012 protons/cm2 and ~65 krad total ionizing dose (TID), confirming no single event effects (SEE) at 10 Gb/s with either of the 3 types of modulators. These optical links will be an integral part of intelligent tracking systems at various scales from coupled sensors through intra-module and off detector communication. We have used a Si-based photonic transceiver to build a complete 40 Gb/s bi-directional link (10 Gb/s in each of four fibers) for a 100m run and have characterized it to compare with standard VCSEL-based optical links. Some future developments of optical modulator-based high bandwidth optical readout systems, and applications based on both fiber and free space data links, such as local triggering and data readout and trigger-clock distribution, are also discussed.

Underwood, David G.; Drake, G.; Fernando, W. S.; Stanek, R. W.

2013-10-01

215

Dual Thresholds Method for Dynamic Bandwidth Allocation in EPON  

Science.gov (United States)

We suggest a dual thresholds method for the dynamic bandwidth allocation in EPON. In the suggested method, a buffer in ONU has two thresholds and ONU generates a normal request and a greedy request based on the two thresholds. Also, OLT estimates the overall traffic load and grants the greedy request when estimated traffic is light. We study upstream channel resource wastage and show the suggested method decreases the upstream channel resource wastage. Using simulation, we validate the dual thresholds method is superior to the existing methods in the mean delay.

Han, Man-Soo

216

Large bandwidth op-amp based white noise current source  

Science.gov (United States)

Electrical noise sources are basic building blocks in many measurement and instrumentation applications and in communication systems. In this paper, we propose a quite simple topology for the realization of a programmable, wide bandwidth, white noise current source that requires only two resistors and one operational amplifier. We validate the proposed approach by means of SPICE simulations and demonstrate, by means of proper measurements, the capability of generating a flat current noise spectrum in a frequency range up to four decades from a few Hz up to 100 kHz.

Giusi, Gino; Scandurra, Graziella; Ciofi, Carmine

2014-02-01

217

Frequency Bandwidth of Half-Wave Impedance Repeater  

Directory of Open Access Journals (Sweden)

Full Text Available This article brings in the second part general information about half-wave impedance repeater. The third part describes the basic functional principles of the half-wave impedance repeater using Smith chart. The main attention is focused in part four on the derivation of repeater frequency bandwidth depending on characteristics and load impedance of unknown feeder line. Derived dependences are based on the elementary features of the feeder lines with specific length. The described functionality is proved in part 4.3 by measurement of transformed impedance using vector several unbalanced feeder lines and network analyzer VNWA3+.

Marek Dvorsky

2012-01-01

218

Modulator reliability and bandwidth improvement: replacing tetrodes with MOSFETs  

International Nuclear Information System (INIS)

Three types of power MOS field effect transistors were studied with the intent of replacing a parallel pair of vacuum tube tetrodes in a linear modulator. The tetrodes have the shortest lifetimes of any other tubes in the system. The FETs offer definite performance advantages when compared to bipolar transistors and definite cost advantages when compared to vacuum tubes. Replacement of the tetrodes does however require careful consideration of voltage, current and to a lesser extent bandwidth capability in order to enhance overall modulator reliability without compromising present performance

219

Study of reducing excimer laser bandwidth by intracavity titling etalons  

International Nuclear Information System (INIS)

The authors studied reducing laser bandwidth by intracavity etalons, and discussed several factors which would affect the experimental result. The experiment research on a discharge pumped, long pulse duration KrF excimer laser was done, in which three etalons provided spectral dispersion. In the experiments, the influence of the apertures and the rate of output coupling was studied. By selecting suitable parameters, output linewidth no more than 3 GHz has been got, this value is 1000 times smaller than the linewidth during free running

220

Narrow-Bandwidth Diode-Laser-Based Ultraviolet Light Source  

Science.gov (United States)

A compact, tunable and narrow-bandwidth laser source for ultraviolet radiation is presented. A grating stabilized diode laser at 1064 nm is frequency-stabilized to below 10 kHz by using a ultra low expansion (ULE) cavity. Injecting light of the diode laser into a tapered amplifier yields a power of 290 mW. In a first frequency-doubling stage, about 47 mW of green light at 532 nm is generated by using a periodically poled KTP crystal. Subsequent second-harmonic generation employing a BBO crystal leads to about 30 ?W of ultraviolet light at 266 nm.

Peng, Yu; Fang, Zhan-Jun; Zang, Er-Jun

2011-10-01

 
 
 
 
221

Narrow-Bandwidth Diode-Laser-Based Ultraviolet Light Source  

International Nuclear Information System (INIS)

A compact, tunable and narrow-bandwidth laser source for ultraviolet radiation is presented. A grating stabilized diode laser at 1064 nm is frequency-stabilized to below 10 kHz by using a ultra low expansion (ULE) cavity. Injecting light of the diode laser into a tapered amplifier yields a power of 290 mW. In a first frequency-doubling stage, about 47 mW of green light at 532 nm is generated by using a periodically poled KTP crystal. Subsequent second-harmonic generation employing a BBO crystal leads to about 30 ?W of ultraviolet light at 266 nm. (fundamental areas of phenomenology (including applications))

222

Analysis of Bandwidth Recycling in IEEE 802.16 Network Using PSA, RB-RFA & HSA  

Directory of Open Access Journals (Sweden)

Full Text Available IEEE 802.16 network protocol is designed to provide a Worldwide Interoperability for Microwave Access (WiMAX. Due to limited bandwidth and an expensive radio spectrum available for communication, it is necessary to use one bandwidth more than one time in a same network when it became unused. For that purpose “Bandwidth Recycling” concept is introduced. The spectrum (bandwidth is specifically allocated by agency to various users, but many times it is seen that the spectrum is not fully utilized by the users in the specific interval. This unused bandwidth can be allocated to other users who demands for more bandwidth for that specific interval without changing existing bandwidth scheme. In this paper we analyse different algorithms which does the recycling of bandwidth as per need is presented. To recycle the unused bandwidth priority based scheduling (PSA algorithm has been developed & to improve the recycling effectiveness rejected bandwidth request first algorithm (RBRFA and history based scheduling algorithm (HSA are outlined. By implementing these all algorithm in Netbean (Version 7.4 Simulator, we have evaluated the performance of our system. Our simulation and analysis result confirmed that the proposed system can recycle unused bandwidth.

Nilesh M. Verulkar

2014-06-01

223

Study of bandwidth effects in monochromator-based spectral responsivity measurements.  

Science.gov (United States)

The errors caused by monochromator bandwidth in spectral responsivity measurements with a monochromator-based apparatus are discussed. Bandwidth effects are not negligible in high-accuracy cryogenic radiometer-based calibrations. A simple numerical method is used to calculate bandwidth effects for different types of detectors, monochromator slit scattering functions, and monochromator output spectral distributions. The method uses low-order Lagrange polynomials fitted segmentwise to measured spectral responsivity and monochromator spectral distribution data in order to make the calculations. It is shown that the shape of the slit function has only a small influence on the bandwidth errors, whereas the output spectral distribution of the monochromator can strongly affect bandwidth errors. It is also shown that in most cases the magnitude of bandwidth effects will vary as the square of the bandwidth. Bandwidth error calculations are presented for various types of detectors (silicon, silicon trap, germanium, InGaAs), for a V(X) detector, and for a typical filter radiometer. A comparison is made between calculated and measured bandwidth effects to validate the method used. In general, calculations of bandwidth effects will be mostly useful for determining uncertainties associated with monochromator bandwidth in spectral responsivity measurements; however, in certain cases the calculations can be used to apply corrections for such effects. PMID:11936792

Boivin, Louis-Philippe

2002-04-01

224

Request-based Dynamic Bandwidth Allocation of Gigabit Passive Optical Network  

Directory of Open Access Journals (Sweden)

Full Text Available We propose request-based dynamic bandwidth allocation (DBA of gigabit passive optical network (GPON. The optical line terminal (OLT in GPON grants bandwidth to optical network units (ONUs. ONUs report request bandwidth which depends on queue lengths of traffic containers (TCONTs to the OLT. In the OLT, DBA of GPON supports a request-based polling order to allocate bandwidth. Our request-based dynamic bandwidth allocation focuses on weight assignments in the request-based polling order. Weight assignments allocate bandwidth in proportion to guaranteed and request bandwidth. We use the C program to simulate results. Simulated results indicate improved performance in queueing delay when total offered loads are or are not shared uniformly to TCONTs.

Chih-Ta Chiu

2013-06-01

225

Fuzzy Logic Bandwidth Prediction and Policing in a DiffServ-Aware Network  

Directory of Open Access Journals (Sweden)

Full Text Available Differentiated Services (DiffServ-aware network potentially can provide the next generation platform for multimedia support in the Internet. In this work we look at improving bandwidth allocation in such a network. We study how to implement bandwidth predicting and policing in a DiffServ aware network using fuzzy logic. A token bucket fuzzy logic bandwidth predictor for real time variable bit rate traffic class is proposed. Here, the AF traffic class is associated with real time variable bit rates traffic. The fuzzy logic bandwidth predictor facilitates bandwidth predicting and dynamic policing based on the class based packet aggregates. This improves the admission control of connections to the network. A simulation study was performed for the fuzzy logic predictor using Network Simulator-2. The simulation results show that the fuzzy logic predictor gave commendable bandwidth prediction value compared to a deterministic bandwidth allocation for the traffic class.

Norashidah Md Din

2008-05-01

226

Bandwidth Estimation to Provide QoS Routing in MANET  

Directory of Open Access Journals (Sweden)

Full Text Available In mobile ad hoc networks (MANETs, the provision of quality of service (QoS guarantees is much more challenging than in wire line networks, mainly due to node mobility, multi-hop communications, contention for channel access, and a lack of central coordination. QoS guarantees are required by most multimedia and other time- or error-sensitive applications. The difficulties in the provision of such guarantees have limited the usefulness of MANETs. However, in the last decade, much research attention has focused on providing QoS assurances in MANET protocols. The QoS routing protocol is an integral part of any QoS solution. We propose a QoS routing protocol is the use of the approximate bandwidth estimation to react to network traffic. Our approach implements Admission control and feedback scheme by using two bandwidth estimation methods (Hello and Listen. We simulate our QoS- routing protocol for nodes running the IEEE 802.11 medium access control. Results of our experiments show those Comparisons among Hello and Listen Methods with the Qos metrics.

Ms. Swati Kamra,

2013-04-01

227

Systems with selective overflow and change of bandwidth  

DEFF Research Database (Denmark)

We consider a loss system with n channels and a finite or infinite overflow group, which is offered N different services, all having Poisson arrival processes. All calls have same bandwidth demand and mean service time, but the mean service time may be different on the primary group and the overflow group, corresponding to data traffic with different bandwidth allocation on primary (micro-cell = femto-cell) and overflow group (macro-cell = LTE-cell). Then using a result of Wallström we can calculate the Binomial moments of the total overflow traffic. Given a certain number of busy channels on the overflow group, we show by balance equations that the number of calls of each service will be Multinomial distributed with probabilities proportional with the arrival rates. Using a recent result of Newcomer & al, we then find moments (done up to fourth order) of individual overflow streams or any combinations of overflow streams. Thus we can find the correlation between services and for example the moments of some traffic streams which may overflow to one system, whereas other traffic streams may be blocked or overflow to another system.

Iversen, Villy Bæk

2012-01-01

228

Series-fed circularly polarized microstrip antennas with broad bandwidth  

Science.gov (United States)

A new series-fed circularly polarized antenna (SFCPA) in microstrip configuration, which consists of a traveling-wave-type crank-line antenna (CLA) and a resonant-type square-ring slot antenna (SRSA), is developed. Unlike the conventional crank-line (CL) antenna array with an open end or a resistive load, the proposed SFCPA uses the SRSA at the termination of the CLA and thus exhibits not only a broad circularly polarized (CP) bandwidth but also a large antenna gain. The characteristics of the SFCPA, including the leaky-wave radiation and the circular polarization, are examined in terms of the dispersion diagram and the current distribution. The SFCPA with the two-cell CLA and the terminated SRSA is fabricated and measured to demonstrate the 10-dB return loss and 3-dB axial ratio (AR) bandwidths of 34.3% and 30.5%, respectively. The frequency-scanning radiation patterns with a 5-7 dBi antenna gain are also presented in the operating band.

Mao, Shau-Gang; Chen, Shiou-Li; Yeh, Jen-Chun; Lin, Tien-Min

2007-08-01

229

A Real-Time Measurement Algorithm for Available Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available Available bandwidth estimation is useful for route selection in overlay networks, QoS, and traffic engineer-ing. Many measurement algorithms, such as Pathload, Pathchar, and Packet Transmission Rate (PTR method, etc. have been proposed. PTR method sends a sequence of packet trains to characterize the interac-tion between probing packets and the competing traffic, and uses the average rate of the packet train as an estimate of the available bandwidth. However, this PTR algorithm does not fully consider the situation that the detection packets lost themselves. This paper improves the original PTR algorithm which considers the specialty of the burst of the network background flow. The improved PTR algorithm uses the method to match the initial gap value and gap step value to solve the problem about the burst of background flow, and the improved PTR algorithm record and control the number of packets with source and destination to solve the lost of some packets. Finally, theory and experiments, verified by the improved algorithm of PTR, can reflect the changes of the network stably and timely under the circumstance of the network fluctuates fre-quently. It improves the accuracy of a network measurement and makes the measurement results, which can reflect the changes of the network more clearly.

Yi YIN

2009-11-01

230

An exponential time 2-approximation algorithm for bandwidth  

Energy Technology Data Exchange (ETDEWEB)

The bandwidth of a graph G on n vertices is the minimum b such that the vertices of G can be labeled from 1 to n such that the labels of every pair of adjacent vertices differ by at most b. In this paper, we present a 2-approximation algorithm for the Bandwidth problem that takes worst-case {Omicron}(1.9797{sup n}) = {Omicron}(3{sup 0.6217n}) time and uses polynomial space. This improves both the previous best 2- and 3-approximation algorithms of Cygan et al. which have an {Omicron}*(3{sup n}) and {Omicron}*(2{sup n}) worst-case time bounds, respectively. Our algorithm is based on constructing bucket decompositions of the input graph. A bucket decomposition partitions the vertex set of a graph into ordered sets (called buckets) of (almost) equal sizes such that all edges are either incident on vertices in the same bucket or on vertices in two consecutive buckets. The idea is to find the smallest bucket size for which there exists a bucket decomposition. The algorithm uses a simple divide-and-conquer strategy along with dynamic programming to achieve this improved time bound.

Kasiviswanathan, Shiva [Los Alamos National Laboratory; Furer, Martin [PENNSYLVANIA STATE U; Gaspers, Serge [U OF MONTPELLIER, FRANCE

2009-01-01

231

Modulator-Based, High Bandwidth Optical Links for HEP Experiments  

CERN Document Server

As a concern with the reliability, bandwidth and mass of future optical links in LHC experiments, we are investigating CW lasers and light modulators as an alternative to VCSELs. These links will be particularly useful if they utilize light modulators which are very small, low power, high bandwidth, and are very radiation hard. We have constructed a test system with 3 such links, each operating at 10 Gb/s. We present the quality of these links (jitter, rise and fall time, BER) and eye mask margins (10GbE) for 3 different types of modulators: LiNbO3-based, InP-based, and Si-based. We present the results of radiation hardness measurements with up to ~1012 protons/cm2 and ~65 krad total ionizing dose (TID), confirming no single event effects (SEE) at 10 Gb/s with either of the 3 types of modulators. These optical links will be an integral part of intelligent tracking systems at various scales from coupled sensors through intra-module and off detector communication. We have used a Si-based photonic transceiver to...

Underwood, D G; Fernando, W S; Stanek, R W

2012-01-01

232

Flexible power and bandwidth allocation in mobile satellites  

Science.gov (United States)

The introduction of L-band mobile communication services by spot beam satellites creates a payload design challenge due to uncertainty in the location and size of the new market to be served. A combination of payload technologies that allow a flexible allocation of power and bandwidth to any portion of the coverage area is described. Power flexibility is achieved by a novel combination of a low-level beam-forming network and a matrix power module which ensures equal sharing of power among individual amplifiers. This eliminates the loss of efficiency and increased mass when an amplifier associated with a beam must be over-designed to meet uncertainties in power distribution between beams. Flexibility in allocation of bandwidth to beams is achieved by intermediate frequency subdivision of the L-band service categories defined by ITU. These spectral subdivisions are assigned to beams by an IF interconnect matrix having beam ports and filter ports as inputs and outputs, respectively. Two such filter switch matrices are required, one for the inbound L-band to feeder link transponder, and one for the outbound feeder link to L-band transponder.

Keyes, L. A.

233

Emergent CSCW systems: the resolution and bandwidth of workplaces.  

Science.gov (United States)

In any collaborative work settings, people naturally develop physical tools and associated work processes that support the management of the interdependencies in information, materials, and social needs. Field studies of management of operating rooms pointed out that collaborative work is supported by an infrastructure that is composed of mostly non-computerized, physical components. The supporting infrastructure is jointly maintained and exploited, with constantly evolving patterns of usage, in response to complexity of coordination needs and the uncertain environment. To represent status and plans, users seem to invent structures based both on idiosyncratic preferences and on negotiated symbols. The fluidity and ease of restructuring workplaces to support collaborative work may be explained in part by the high resolution and bandwidth of workplaces: a large number of ways in which workers could structure their work and a high capacity to convey rich information and meanings quickly to collaborators. We argue that to support health care workers, designers of computer supported cooperative work (CSCW) systems should learn how the physical and perceptual properties of workplaces are exploited, and that CSCW systems should be designed to allow maximum freedom of restructuring and reconfiguring as part of workplaces to enhance bandwidth and resolution of representation and communication. PMID:16822715

Xiao, Yan; Seagull, F Jacob

2007-06-01

234

Ce impurities in superconductors: Zero-bandwidth limit  

International Nuclear Information System (INIS)

The effect of the continuous demagnetization of Ce on the superconductivity of the matrix is studied with a simple, exactly solvable model obtained as a zero-conduction-bandwidth limit of the Mueller-Hartmann and Zittartz and of the Wiecko-Lopez models. Phase diagrams are obtained from the exact free energies. This phase diagrams agree, within the limitations of the model, with those previously calculated by Mueller-Hartmann and Zittartz and by Wiecko and Lopez. The exact calculation of the free energy allows us to extend the Wiecko-Lopez results and to predict a normal phase at low temperatures which has not been observed before. The characteristic features observed in LaCe and (La/sub x/Th/sub 1-x/)Ce are reproduced. The phenomenon of reentrance emerges with a clear physical meaning as a competition for stability between two states with different occupation number of the ''conduction'' electrons which have different degeneracy

235

Hybrid grating reflector with high reflectivity and broad bandwidth  

DEFF Research Database (Denmark)

We suggest a new type of grating reflector denoted hybrid grating (HG) which shows large reflectivity in a broad wavelength range and has a structure suitable for realizing a vertical cavity laser with ultra-small modal volume. The properties of the grating reflector are investigated numerically and explained. The HG consists of an un-patterned III-V layer and a Si grating. The III-V layer has a thickness comparable to the grating layer, introduces more guided mode resonances and significantly increases the bandwidth of the reflector compared to the well-known high-index-contrast grating (HCG). By using an active III-V layer, a laser can be realized where the gain region is integrated into the mirror itself

Taghizadeh, Alireza; Park, Gyeong Cheol

2014-01-01

236

Wide-Bandwidth Capture of Wire-Scanner Signals  

Energy Technology Data Exchange (ETDEWEB)

Integrated charge collected on the sense wires of wire-scanner systems utilized to determine beam profile is generally the parameter of interest. The LANSCE application requires capturing the charge information macropulse-by-macropulse with macropulse lengths as long as 700 {micro}s at a maximum macropulse rate of 120 Hz. Also, for the LANSCE application, it is required that the integration be performed in a manner that does not require integrator reset between macropulses. Due to the long macropulse which must be accommodated and the 8.33 ms minimum pulse period, a simple R-C integrator cannot be utilized since there is insufficient time between macropulses to allow the integrator to adequately recover. The application of wide analog bandwidth to provide accurate pulse-by-pulse capture of the wire signals with digital integration of the wire signals to determine captured charge at each macropulse in applications with comparatively long macropulses and high pulse repetition rates is presented.

Gruchalla, Michael E. [Los Alamos National Laboratory; Gilpatrick, John D. [Los Alamos National Laboratory; Sedillo, James Daniel [Los Alamos National Laboratory; Martinez, Derwin [Los Alamos National Laboratory

2012-05-16

237

Performance evaluation of a high-bandwidth timing module  

International Nuclear Information System (INIS)

The ability to generate highly precise timing signals is essential for the operation of particle accelerators, particularly so in future linear colliders. As a tool to generate precise fixed delays, a module called TD-2.1 has been developed for use at the ATF (Accelerator Test Facility). TD-2.1 is an improved version of a previous module called TD-2, developed for the TRISTAN accelerator. The new version can be used at clock frequencies of up to 1.5 GHz, almost three times the bandwidth of the previous version. Since TD-2.1 is applied in many places to synchronize the ATF accelerator operation, high reliability and stability (low jitter) are essential. The long-term stability and timing jitter of the module were evaluated. The jitter was found to be around 5 ps within the operating range. Stable operation of the module was verified in long-term tests. (author)

238

Impedance Bandwidth and Gain Improvement for Microstrip Antenna Using Metamaterials  

Directory of Open Access Journals (Sweden)

Full Text Available An improved ultra-wideband (UWB and high gain rectangular antenna is specifically designed in this paper using planar-patterned metamaterial concepts. The antenna has isolated triangle gaps and crossed gaps etched on the metal patch and ground plane, respectively. By changing the pattern on the ground, the impedance matching characteristics of the antenna are much better. The -10 dB impedance bandwidth of the proposed antenna is 3.85–15.62 GHz, which is about 267% broader. The proposed antenna has an average gain of 5.42 dB and the peak is 8.36 dB at 13.5 GHz. Compared with the original one, the gain of the proposed antenna improved about 1.4 dB. Moreover, the size is reduced slightly. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range

H. Xiong

2012-12-01

239

Full characterization of the quantum spiral bandwidth of entangled biphotons  

International Nuclear Information System (INIS)

Spontaneous parametric down-conversion has been shown to be a reliable source of entangled photons. Among the wide range of properties shown to be entangled, it is the orbital angular momentum that is the focus of our study. We investigate, in particular, the bi-photon state generated using a Gaussian pump beam. We derive an expression for the simultaneous correlations in the orbital angular momentum, l, and radial momentum, p, of the down-converted Laguerre-Gaussian beams. Our result allows us, for example, to calculate the spiral bandwidth with no restriction on the geometry of the beams: l, p, and the beam widths are all free parameters. Moreover, we show that, with the usual paraxial and collinear approximations, a fully analytic expression for the correlations can be derived.

240

Full characterisation of the quantum spiral bandwidth of entangled biphotons  

CERN Document Server

Spontaneous parametric down conversion has been shown to be a reliable source of entangled photons. Amongst the wide range of properties that have been shown to be entangled, it is the orbital angular momentum that is the focus of our study. We investigate, in particular, the bi-photon state generated using a Gaussian pump beam. We derive an expression for the simultaneous correlations in the orbital angular momentum and radial momentum of the down-converted Laguerre-Gaussian beams. Our result allows us, for example, to calculate the spiral bandwidth with no restriction on the geometry of the beams: $l$, $p$ and the beam widths are all free parameters. Moreover, we show that, with the usual paraxial and collinear approximations, a fully analytic expression for the correlations can be derived.

Miatto, Filippo M; Barnett, Stephen M

2010-01-01

 
 
 
 
241

Full characterization of the quantum spiral bandwidth of entangled biphotons  

Science.gov (United States)

Spontaneous parametric down-conversion has been shown to be a reliable source of entangled photons. Among the wide range of properties shown to be entangled, it is the orbital angular momentum that is the focus of our study. We investigate, in particular, the bi-photon state generated using a Gaussian pump beam. We derive an expression for the simultaneous correlations in the orbital angular momentum, ?, and radial momentum, p, of the down-converted Laguerre-Gaussian beams. Our result allows us, for example, to calculate the spiral bandwidth with no restriction on the geometry of the beams: ?, p, and the beam widths are all free parameters. Moreover, we show that, with the usual paraxial and collinear approximations, a fully analytic expression for the correlations can be derived.

Miatto, Filippo M.; Yao, Alison M.; Barnett, Stephen M.

2011-03-01

242

A Study of Bandwidth-Perception Management Mechanisms in IEEE 802.16 Networks  

CERN Document Server

Bandwidth request-grant mechanisms are used in 802.16 networks to manage the uplink bandwidth needs of subscriber stations (SSs). Requests may be sent by SSs to the base station (BS) by means of several mechanisms defined in the standard. Based on the incoming requests, the BS (which handles most of the bandwidth scheduling in the system) schedules the transmission of uplink traffic, by assigning transmission opportunities to the SSs in an implementation-dependent manner. In this paper we present a study of some bandwidth allocation issues, arising from the management of the perception of subscriber stations' bandwidth needs at the base station. We illustrate how the bandwidth perception varies depending on the policy used to handle requests and grants. By means of ns-2 simulations, we evaluate the potential impact of such policies on the system's aggregate throughput when the traffic is composed of Best-Effort TCP flows.

Arcia-Moret, Andres; Montavont, Nicolas; Ros, David

2010-01-01

243

Dynamic Bandwidth Management in Distributed VoD based on the User Class Using Agents  

CERN Document Server

This paper proposes a dynamic bandwidth management algorithm in which more bandwidth is allocated for higher class users and also higher priority is given to the videos with higher popularity within a class using agent technology. The popularity and weight profile of the videos which is used for efficiently allocating bandwidth is periodically updated by a mobile agent. The proposed approach allocates more bandwidth for higher class users and gives higher priority for higher weight videos [popular videos] so that they can be served with high QoS, reduces the load on the central multimedia server and maximizes the channel utilization between the neighboring proxy servers and the central multimedia server and lower video rejection ratio. The simulation results prove the reduction of load on central multimedia server by load sharing among the neighboring proxy servers, maximum bandwidth utilization, and more bandwidth allocation for higher class users.

Guruprasad, H S

2009-01-01

244

Effects of finite pump bandwidth on the parametric-decay instability  

International Nuclear Information System (INIS)

The feasibility of using finite pump bandwidth to control parametric instability in a plasma is examined experimentally. With two distinctively different experimental arrangements, we study the effects of finite bandwidth pumps on the parametric decay instability. In the first experiment, the parametric decay instability is excited electrostatically by means of grids immersed in a low density plasma. We present experimental results on the effects of finite pump bandwidth on the threshold power, growth, saturation level, and spectral structure of the instability produced plasma waves. We find that as the pump bandwidth approaches and exceeds the instability resonance width, the instability is inhibited. In a second experiment, the instability is excited by high power microwaves launched by a gridded horn into a near critical density plasma. Here we have investigated the effects of finite pump bandwidth on the production of nonthermal hot electrons by parametric instability. We find that with sufficient pump bandwidth, the hot electron production is reduced or eliminated

245

Ultrabroad-bandwidth arbitrary radiofrequency waveform generation with a silicon photonic chip-based spectral shaper  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ultrabroad-bandwidth radiofrequency pulses offer significant applications potential, such as increased data transmission rate and multipath tolerance in wireless communications. Such ultrabroad-bandwidth pulses are inherently difficult to generate with chip-based electronics due to limits in digital-to-analog converter technology and high timing jitter. Photonic means of radiofrequency waveform generation, for example, by spectral shaping and frequency-time mapping, can overcome the bandwidth...

Khan, Maroof H.; Shen, Hao; Xuan, Yi; Zhao, Lin; Xiao, Shijun; Leaird, Daniel E.; Weiner, Andrew M.; Qi, Minghao

2010-01-01

246

An Algorithm That Predicts CSI to Allocate Bandwidth for Healthcare Monitoring in Hospital's Waiting Rooms  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In wireless healthcare monitoring systems, bandwidth allocation is an efficient solution to the problem of scarce wireless bandwidth for the monitoring of patients. However, when the central unit cannot access the exact channel state information (CSI), the efficiency of bandwidth allocation decreases, and the system performance also decreases. In this paper, we propose an algorithm to reduce the negative effects of imperfect CSI on system performance. In this algorithm, the central unit can p...

Lin, Di; Labeau, Fabrice

2012-01-01

247

ENERGY AND BANDWIDTH INFLUENCE ON EFFICIENCY IN WIRELESS NETWORKS: A REVIEW  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we review the efficiency of wireless ad hoc networks. The wireless networks efficiency deals with the bandwidth and the energy efficiency of the networks that depends upon the energy supply of the nodes. This energy and the bandwidth related to it are the major constraints to be considered in this paper. The network comprises of the nodes that consist of different channels for transmission purpose and these are the major areas for bandwidth efficiency. The energy concerned is t...

PROF. R.K SINGH,; TANU PREET SINGH

2010-01-01

248

Quality of Service in Mobile Ad Hoc Networks using Bandwidth Estimation Method in AODV and AOMDV  

Directory of Open Access Journals (Sweden)

Full Text Available Bandwidth Estimation is an important issue in MANETs, because the path of the nodes in the network can change dynamically. Due to predefined infrastructure and bandwidth constraint the Quality of Service (QOS is challenging assignment in Mobile Ad hoc network. In this paper we propose bandwidth estimation mechanisms using AODV and AOMDV protocol. The performance shows that increase packet delivery ratio and throughput and also reduce end - to - end delay.

Mrs.D.Maheshwari

2013-06-01

249

Dynamic Bandwidth Allocation for QoS in IEEE 802.16 Broadband Wireless Networks  

Science.gov (United States)

IEEE 802.16 broadband wireless access (BWA) technology is suitable for providing multimedia applications without accessing the wired networks directly. Although IEEE 802.16 standard well defines the quality of service (QoS) framework, it makes no specific recommendation with regard to the bandwidth allocation. In this paper, we propose an algorithm for allocating bandwidth in response to dynamic changes in the arrival rate such that the total bandwidth is efficiently utilized.

Jeon, Jae-Han; Lim, Jong-Tae

250

Expanding the bandwidth of planar MNG materials with co-directional split-ring resonators  

Science.gov (United States)

An effective approach to expand the bandwidth of negative permeability of small-sized planar materials is proposed. Based on qualitative analysis of equivalent circuit models, the fractional bandwidth of an ?-negative (MNG) material is expanded from 3.53% up to 12.87% by adding split-ring resonators (SRRs) and arranging them by proposed steps. Moreover, the experimental results validate the effectiveness of bandwidth-expanding methods, which is promising for the extensive application of metamaterials in the microwave field.

Tang, Ming-Chun; Xiao, Shao-Qiu; Wang, Duo; Ge, Guang-Ding; Bai, Yan-Ying; Zhang, Jun-Rui; Wang, Bing-Zhong

2011-06-01

251

Bandwidth allocation strategy for traffic systems of scale-free network  

International Nuclear Information System (INIS)

In this Letter, the bandwidth resource allocation strategy is considered for traffic systems of complex networks. With a finite resource of bandwidth, an allocation strategy with preference parameter ? is proposed considering the links importance. The performance of bandwidth allocation strategy is studied for the local routing protocol and the shortest path protocol. When important links are slightly favored in the bandwidth allocation, the system can achieve the optimal traffic performance for the two routing protocols. For the shortest path protocol, we also give a method to estimate the network traffic capacity theoretically.

252

Comb-based radio-frequency photonic filtering with 20 ns bandwidth reconfiguration.  

Science.gov (United States)

We present a scheme to generate a 10 GHz optical frequency comb that is bandwidth reconfigurable on a time scale of tens of nanoseconds via electronic control of the drive signal to a phase modulator. When such a comb is used as the source for a radio-frequency (RF) photonic filter employing dispersive propagation, the RF filter bandwidth varies in inverse proportion to the optical bandwidth. As a result we are able to demonstrate, for the first time to our knowledge, bandwidth-reconfigurable RF filtering with transition times under 20 ns. The reconfiguration speed is determined by the response time of a programmable RF variable attenuator. PMID:23903127

Wu, Rui; Song, Minhyup; Leaird, Daniel E; Weiner, Andrew M

2013-08-01

253

Analysis and improvement of dynamic bandwidth allocation in EPON  

Science.gov (United States)

Ethernet Passive Optical Network (EPON) has been considered as the best candidate of the next generation access network, because of it"s particular advantages, such as inexpensive, simple, scalable, and capable of delivering bundled voice, data and video services. However, the standard isn"t approved, many questions are still discussing. Dynamic Bandwidth Allocation (DBA) is one of the hop topics. If we use static bandwidth allocation in EPON system, slots may not be filled to capacity in the case when the OLT grants to an ONU a slot smaller than the ONU requested based on its queue size. Then the packet will have to wait for the next slot, so there is an unused remainder at the end of the slot. As a result variable-length packets don"t fill the static slot completely. Conventional E-PON uses a slot-size based DBA algorithm. Packets of all priorities are put in the same slot. Due to the burstness of traffic and packet length variation, the starting point of each slot is push-pulled from frame to frame, as a result delay variation of packet is not under control. We can not support appropriate Qos to real-time traffic. In our design, we divide Ethernet data into three parts, one is the steady part that has N time slots for voice traffic, corresponding to N ONUs. In this case, there are M ONUs those has video traffic for transmit, the second part having M time slots will be established named Quasi-dynamic. And the other is the dynamic part that is basically one giant slot for data traffic, shared by all ONUs. Since the steady part of the frame can be approximated by constant flows, it will make influence upon voice. Establish or remove Quasi-dynamic channels will take less than 50ms delay variation. So this arithmetic can match the video"s character of less than 100-ms maximum jitter. Usually, for the low priority class traffic, there is no requirement on any QoS parameters; therefore, optimizing throughput is the goal. So we use IPACT algorithm in the third part, making utilization almost 100%.

Wang, Qing; He, Yan

2005-02-01

254

Mechanism of bandwidth improvement in passively cooled SMA position actuators  

Science.gov (United States)

The heating of shape memory alloy (SMA) materials leads to a thermally driven phase change which can be used to do work. An SMA wire can be thermally cycled by controlling electric current through the wire, creating an electro-mechanical actuator. Such actuators are typically heated electrically and cooled through convection. The thermal time constants and lack of active cooling limit the operating frequencies. In this work, the bandwidth of a still-air-cooled SMA wire controlled with a PID controller is improved through optimization of the controller gains. Results confirm that optimization can improve the ability of the actuator to operate at a given frequency. Overshoot is observed in the optimal controllers at low frequencies. This is a result of hysteresis in the wire's contraction-temperature characteristic, since different input temperatures can achieve the same output value. The optimal controllers generate overshoot during heating, in order to cause the system to operate at a point on the hysteresis curve where faster cooling can be achieved. The optimization results in a controller which effectively takes advantage of the multi-valued nature of the hysteresis to improve performance.

Gorbet, R. B.; Morris, K. A.; Chau, R. C. C.

2009-09-01

255

Extraction of spatial information for low-bandwidth telerehabilitation applications  

Directory of Open Access Journals (Sweden)

Full Text Available Telemedicine applications, based on two-dimensional (2D video conferencing technology, have been around for the past 15 to 20 yr. They have been demonstrated to be acceptable for face-to-face consultations and useful for visual examination of wounds and abrasions. However, certain telerehabilitation assessments need the use of spatial information in order to accurately assess the patient’s condition and sending three-dimensional video data over low-bandwidth networks is extremely challenging. This article proposes an innovative way of extracting the key spatial information from the patient’s movement during telerehabilitation assessment based on 2D video and then presenting the extracted data by using graph plots alongside the video to help physicians in assessments with minimum burden on existing video data transfer. Some common rehabilitation scenarios are chosen for illustrations, and experiments are conducted based on skeletal tracking and color detection algorithms using the Microsoft Kinect sensor. Extracted data are analyzed in detail and their usability discussed.

Kok Kiong Tan, PhD

2014-09-01

256

A 5-MHz bandwidth SQUID magnetometer with additional positive feedback  

Science.gov (United States)

A fast SQUID (superconducting quantum interference device) magnetometer system using the latest multiloop magnetometer W7A with additional positive feedback has been built. A 3-dB bandwidth of 5 MHz has been achieved in a simple direct-coupled flux-locked loop. The feedback range is ±620 ?0 or ±290 nT, the white-noise level 3.4×10-6 ?0/?Hz or 1.6 fT/?Hz, and the 1/ f corner frequency ?7 Hz. Above 1 MHz the noise level increases slightly, approximately with ?S? ?f1/6. At high signal frequencies a slew rate of about 8×105 ?0/s has been measured. Below the pole frequency of the second integrator (480 kHz) the slew rate increases with decreasing frequency, having a maximum of 3×107 ?0/s at 7.6 kHz. The total harmonic distortion (THD) decreases strongly with the signal amplitude below the slew rate limit. For a sinusoidal signal with half the maximum amplitude, the THD is ?4% at 1 MHz, ?0.04% at 100 kHz, and ?2.7 ppm (1 ppm=10-6) at 10 kHz. Below about 2 kHz the THD becomes almost frequency independent and lies between 0.4 and 7 ppm for signal amplitudes between 2.5 and 620 ?0.

Drung, D.; Matz, H.; Koch, H.

1995-04-01

257

Bandwidth of a Nonlinear Harvester with Optimized Electrical Load  

Science.gov (United States)

Many researchers have investigated the possibility of amplifying ambient vibrations and converting the associated kinetic energy into usable electric energy. The vast majority of vibration harvesting devices use mechanical oscillators to boost the amplitude of vibration; however, this can result in a rather narrow band of excitation over which the harvesting device is effective. One approach proposed to overcome this limitation is to substitute the conventional linear oscillator with an oscillator featuring a non-linear compliance characteristic: these mechanisms produce broader frequency responses. The design and optimization of nonlinear energy harvesting devices is however not trivial and there is no consensus among the publish works that the benefits of non-linear oscillators can be realized in the energy harvesting context. This work attempts to further develop understanding of nonlinear energy harvesters by investigating the optimum resistive load. The definition of an optimal load for the nonlinear device is first considered, given due consideration to bandwidth and stability of the operating point, and comparisons with linear devices is shown. Finally, the issue of multiple solutions in the frequency response is addressed.

Cammarano, A.; Gonzalez-Buelga, A.; Neild, S. A.; Burrow, S. G.; Inman, D. J.

2013-12-01

258

Wide bandwidth nanowire electromechanics on insulating substrates at room temperature  

Science.gov (United States)

We present a simple fabrication scheme for nano-scale devices on insulating substrates. Doubly clamped InAs nanowire resonators with local gate configuration are fabricated on sapphire substrates. Parasitic capacitance is reduced on insulating substrates thus enabling measurements at all temperatures and particularly above room temperature, an essential requirement for NEMS sensors. Mechanical motion of the nanowire is capacitively actuated and detected using a network analyser. This technique provides wide bandwidth radio frequency transduction and allows the nanowire oscillations to be probed at a much faster rate compared to mixing techniques. Both in-plane and out-of-plane vibrational modes of the nanowire are observed and the non-linear response of the resonators is studied. Quality factor of the resonator increases at low temperatures. We also study the relation between mechanical motion and thermal strains in the nanowire. This opens up a new approach in studying thermal properties of nanostructures. Our method of fabrication can be extended to NEMS devices on flexible substrates and other nanostructures.

Sebastian, Abhilash; Mathew, John; Sengupta, Shamashis; Gokhale, Maheshwar; Bhattacharya, Arnab; Deshmukh, Mandar

2013-03-01

259

High bandwidth piezoresistive force probes with integrated thermal actuation.  

Science.gov (United States)

We present high-speed force probes with on-chip actuation and sensing for the measurement of pN-scale forces at the microsecond time scale. We achieve a high resonant frequency in water (1-100 kHz) with requisite low spring constants (0.3-40 pN/nm) and low integrated force noise (1-100 pN) by targeting probe dimensions on the order of 300 nm thick, 1-2 ?m wide and 30-200 ?m long. Forces are measured using silicon piezoresistors while the probes are actuated thermally with an aluminum unimorph and silicon heater. The piezoresistive sensors are designed using open source numerical optimization code that incorporates constraints on operating temperature. Parylene passivation enables operation in ionic media and we demonstrate simultaneous actuation and sensing. The improved design and fabrication techniques that we describe enable a 10-20 fold improvement in force resolution or measurement bandwidth over prior piezoresistive cantilevers of comparable thickness. PMID:23175616

Doll, Joseph C; Pruitt, Beth L

2012-09-01

260

High-bandwidth piezoresistive force probes with integrated thermal actuation  

Science.gov (United States)

We present high-speed force probes with on-chip actuation and sensing for the measurement of pN-scale forces at the microsecond timescale. We achieve a high resonant frequency in water (1-100 kHz) with requisite low spring constants (0.3-40 pN nm-1) and low integrated force noise (1-100 pN) by targeting probe dimensions on the order of 300 nm thick, 1-2 ?m wide and 30-200 ?m long. Forces are measured using silicon piezoresistors, while the probes are actuated thermally with an aluminum unimorph and silicon heater. The piezoresistive sensors are designed using the open-source numerical optimization code that incorporates constraints on operating temperature. Parylene passivation enables operation in ionic media and we demonstrate simultaneous actuation and sensing. The improved design and fabrication techniques that we describe enable a 10-20-fold improvement in force resolution or measurement bandwidth over prior piezoresistive cantilevers of comparable thickness.

Doll, Joseph C.; Pruitt, Beth L.

2012-09-01

 
 
 
 
261

Numerical Models of Broad-Bandwidth Nanosecond Optical Parametric Oscillators  

Energy Technology Data Exchange (ETDEWEB)

We present three new methods for modeling broad-bandwidth, nanosecond optitcal parametric oscillators in the plane-wave approximation. Each accounts for the group-velocity differences that determine the operating linewidth of unseeded optical parametric oscillators, and each allows the signal and idler waves to develop from quantum noise. The first two methods are based on split-step integration methods in which nonlinear mixing and propagation are calculated separately on alternate steps. One method relies on Fourier transforming handle propagation, wiih mixing integrated over a the fields between t and u to Az step: the other transforms between z and k= in the propagation step, with mixing integrated over At. The third method is based on expansion of the three optical fields in terms of their respective longitudinal empty cavity modes, taking into account the cavity boundary condi- tions. Equations describing the time development of the mode amplitudes are solved to yield the time dependence of the three output fields. These plane-wave models exclude diffractive effects, but can be readily extended to include them.

Bowers, M.S.; Gehr. R.J.; Smith, A.V.

1998-10-22

262

High-bandwidth protein analysis using solid-state nanopores.  

Science.gov (United States)

High-bandwidth measurements of the ion current through hafnium oxide and silicon nitride nanopores allow the analysis of sub-30 kD protein molecules with unprecedented time resolution and detection efficiency. Measured capture rates suggest that at moderate transmembrane bias values, a substantial fraction of protein translocation events are detected. Our dwell-time resolution of 2.5 ?s enables translocation time distributions to be fit to a first-passage time distribution derived from a 1D diffusion-drift model. The fits yield drift velocities that scale linearly with voltage, consistent with an electrophoretic process. Further, protein diffusion constants (D) are lower than the bulk diffusion constants (D0) by a factor of ~50, and are voltage-independent in the regime tested. We reason that deviations of D from D0 are a result of confinement-driven pore/protein interactions, previously observed in porous systems. A straightforward Kramers model for this inhibited diffusion points to 9- to 12-kJ/mol interactions of the proteins with the nanopore. Reduction of ? and D are found to be material-dependent. Comparison of current-blockage levels of each protein yields volumetric information for the two proteins that is in good agreement with dynamic light scattering measurements. Finally, detection of a protein-protein complex is achieved. PMID:24507610

Larkin, Joseph; Henley, Robert Y; Muthukumar, Murugappan; Rosenstein, Jacob K; Wanunu, Meni

2014-02-01

263

High resolution, high bandwidth global shutter CMOS area scan sensors  

Science.gov (United States)

Global shuttering, sometimes also known as electronic shuttering, enables the use of CMOS sensors in a vast range of applications. Teledyne DALSA Global shutter sensors are able to integrate light synchronously across millions of pixels with microsecond accuracy. Teledyne DALSA offers 5 transistor global shutter pixels in variety of resolutions, pitches and noise and full-well combinations. One of the recent generations of these pixels is implemented in 12 mega pixel area scan device at 6 um pitch and that images up to 70 frames per second with 58 dB dynamic range. These square pixels include microlens and optional color filters. These sensors also offer exposure control, anti-blooming and high dynamic range operation by introduction of a drain and a PPD reset gate to the pixel. The state of the art sense node design of Teledyne DALSA's 5T pixel offers exceptional shutter rejection ratio. The architecture is consistent with the requirements to use stitching to achieve very large area scan devices. Parallel or serial digital output is provided on these sensors using on-chip, column-wise analog to digital converters. Flexible ADC bit depth combined with windowing (adjustable region of interest, ROI) allows these sensors to run with variety of resolution/bandwidth combinations. The low power, state of the art LVDS I/O technology allows for overall power consumptions of less than 2W at full performance conditions.

Faramarzpour, Naser; Sonder, Matthias; Li, Binqiao

2013-10-01

264

QoS routing via multiple paths using bandwidth reservation  

Energy Technology Data Exchange (ETDEWEB)

The authors address the problem of computing a multipath, consisting of possibly overlapping paths, to transmit data from the source node s to the destination node d over a computer network while ensuring deterministic bounds on end-to-end delay or delivery rate. They consider two generic routing problems within the framework wherein bandwidth can be reserved, and guaranteed, once reserved, on various links of the communication network. The first problem requires that a message of finite length be transmitted from s to d within {tau} units of time. The second problem requires that a sequential message of r units be transmitted at a rate of {eta} such that maximum time difference between two units that are received out of order is no more than q. They propose a polynomial-time algorithm to the first problem based on an adaptation of the classical Ford-Fulkerson`s method. They present simulation results to illustrate the applicability of the proposed algorithm. They show the second problem to be NP-complete and propose a polynomial-time approximate solution.

Rao, N.S.V.; Batsell, S.G.

1997-11-01

265

QoS routing via multiple paths using bandwidth reservation  

Energy Technology Data Exchange (ETDEWEB)

The authors address the problem of computing a multipath, consisting of possibly overlapping paths, to transmit data from the source node s to the destination node d over a computer network while ensuring deterministic bounds on end-to-end delay or delivery rate.They consider two generic routing problems within the framework wherein bandwidth can be reserved, and guaranteed, once reserved, on various links of the communication network. The first problem requires that a message of finite length be transmitted from s to d within {tau} units of time. The second problem requires that a sequential message of r units be transmitted at a rate of {eta} such that maximum time difference between two units that are received out of order is no more than q. They propose a polynomial-time algorithm to the first problem based on an adaptation of the classical Ford-Fulkerson`s method. They present simulation results to illustrate the applicability of the proposed algorithm. They show the second problem to be NP-complete, and propose a polynomial-time approximately solution.

Rao, N.S.V.; Batsell, S.G.

1998-01-01

266

A Survey of Bandwidth Utilization: Case Study of Federal University of Technology Minna  

Science.gov (United States)

The effective utilization of the limited scarce bandwidth resources allocated by a spectrum regulator usually the Nigerian Communications Commissions (NCC) in Nigeria universities is paramount in maximizing the usage of the expensive scarce bandwidth resources. A significant bandwidth allocation is needed in order to meet up with the challenges of the day and the task of networking, communicating and reaching the word in our universities. Therefore, bandwidth management becomes necessary and essential. This paper contributes in that direction by surveying the bandwidth utilization at Federal University of Technology Minna campus with the hope of proffering a general solution that can be adopted in Nigerian universities for effective bandwidth management. Also, factors that hindered the development of most Nigeria universities are also examined. The federal university of technology minna which is structured like all other universities in the country in terms of the bandwidth requirement was choosing as a case study for this research work. Furthermore, some policies which can be adopted in order to effectively manage the scarce bandwidth resources in Nigerian universities are also proposed.

Haq, A.; Bello Salau, H.; Aibinu, A. M.; Onwuka, E. N.

2013-12-01

267

A Hybrid OFDM-TDM Architecture with Decentralized Dynamic Bandwidth Allocation for PONs  

Science.gov (United States)

One of the major challenges of passive optical networks is to achieve a fair arbitration mechanism that will prevent possible collisions from occurring at the upstream channel when multiple users attempt to access the common fiber at the same time. Therefore, in this study we mainly focus on fair bandwidth allocation among users, and present a hybrid Orthogonal Frequency Division Multiplexed/Time Division Multiplexed architecture with a dynamic bandwidth allocation scheme that provides satisfying service qualities to the users depending on their varying bandwidth requirements. Unnecessary delays in centralized schemes occurring during bandwidth assignment stage are eliminated by utilizing a decentralized approach. Instead of sending bandwidth demands to the optical line terminal (OLT) which is the only competent authority, each optical network unit (ONU) runs the same bandwidth demand determination algorithm. ONUs inform each other via signaling channel about the status of their queues. This information is fed to the bandwidth determination algorithm which is run by each ONU in a distributed manner. Furthermore, Light Load Penalty, which is a phenomenon in optical communications, is mitigated by limiting the amount of bandwidth that an ONU can demand. PMID:24194684

Cevik, Taner

2013-01-01

268

Enhanced spectral efficiency using bandwidth switchable SAW filtering for mobile satellite communications systems  

Science.gov (United States)

Currently proposed mobile satellite communications systems require a high degree of flexibility in assignment of spectral capacity to different geographic locations. Conventionally this results in poor spectral efficiency which may be overcome by the use of bandwidth switchable filtering. Surface acoustic wave (SAW) technology makes it possible to provide banks of filters whose responses may be contiguously combined to form variable bandwidth filters with constant amplitude and phase responses across the entire band. The high selectivity possible with SAW filters, combined with the variable bandwidth capability, makes it possible to achieve spectral efficiencies over the allocated bandwidths of greater than 90 percent, while retaining full system flexibility. Bandwidth switchable SAW filtering (BSSF) achieves these gains with a negligible increase in hardware complexity.

Peach, Robert; Malarky, Alastair

1990-01-01

269

Energy and Bandwidth Constrained QoS Enabled Routing for MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available Mobile adhoc networks are rapid deployable self organizing networks. Their key characteristics aredynamic topology, high node mobility, low channel bandwidth and limited battery power. Hence, it isnecessary to minimize bandwidth and energy consumption. To transmit packets, available bandwidth isknown along the route from sender to receiver. Thus, bandwidth estimation is the main metric to supportQuality of Service (QoS. This work focuses on improving the accuracy of available bandwidth andincorporating a QoS-aware scheme into the route discovery procedure. It is also important to limit theenergy consumed by nodes. Probability based overhearing method is proposed to reduce energy spent onoverhearing nodes. This experiment is implemented in NS2 simulator and the performance of the network isanalyzed in terms of QoS parameters.

N.Sumathi

2013-04-01

270

Revealing statistical properties of quasi-CW fibre lasers in bandwidth-limited measurements.  

Science.gov (United States)

We introduce a general technique how to reveal in experiments of limited electrical bandwidth which is lower than the optical bandwidth of the optical signal under study, whether the statistical properties of the light source obey Gaussian distribution or mode correlations do exist. To do that one needs to perform measurements by decreasing the measurement bandwidth. We develop a simple model of bandwidth-limited measurements and predict universal laws how intensity probability density function and intensity auto-correlation function of ideal completely stochastic source of Gaussian statistics depend on limited measurement bandwidth and measurement noise level. Results of experimental investigation are in good agreement with model predictions. In particular, we reveal partial mode correlations in the radiation of quasi-CW Raman fibre laser. PMID:25402047

Gorbunov, O A; Sugavanam, S; Churkin, D V

2014-11-17

271

Maximum operable speed of WDM PON employing bandwidth-limited RSOAs  

Science.gov (United States)

There have been numerous efforts to develop a practical wavelength-division-multiplexed passive optical network (WDM PON) by utilizing the reflective semiconductor optical amplifier (RSOA). However, the ultimate operating speed of this WDM PON is primarily limited by the narrow modulation bandwidth of the RSOA. We estimate the maximum operable speed of such a bandwidth-limited RSOA by using the Shannon's capacity theorem. The results show that the operating speed of the RSOA can be increased to ~60 Gb/s when its modulation bandwidth is ~3 GHz. We also find that, if the modulation bandwidth of the RSOA is less than ~3 GHz, the use of the high-level (i.e., >4 levels per symbol) modulation formats is not very effective for increasing its operating speed due to their requirements of the high signal-to-noise ratio (SNR). To operate the RSOA at 100 Gb/s, its modulation bandwidth should be >5.8 GHz.

Cho, Keun Yeong; Hong, Ui Hyun; Choi, Hyeokgyu; Chung, Yun C.

2014-02-01

272

Analysis of restriction factors of widening diffraction bandwidth of multilayer dielectric grating  

International Nuclear Information System (INIS)

In order to design a multilayer dielectric grating with wide-bandwidth diffraction spectrum, the restriction factors of both the reflection bandwidth of multilayer dielectric high-reflectivity mirror and the guided-mode resonance phenomenon are studied in detail. The reflection characteristics of high-reflectivity mirror in zeroth and — 1st transmitted diffraction orders are quantitatively evaluated. It is found that the reflection bandwidth of high-reflectivity mirror in — 1st transmitted diffraction order, which determines the final diffraction bandwidth of multilayer dielectric grating, is evidently compressed. Furthermore, it is demonstrated that the reducing of grating period is an effective approach to the elimination of guided mode resonance over a required broad band range both spectrally and angularly. In addition, the expressions for calculating the maximum period ensuring no guided mode resonance in the required bandwidth are derived. Finally, two high-efficiency pulse-compression gratings with broad-band are presented. (classical areas of phenomenology)

273

Real-Time Virtual Instruments for Remote Sensor Monitoring Using Low Bandwidth Wireless Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The development of a peer-to-peer virtual instrumentation system for remote acquisition, analysis and transmission of data on low bandwidth networks is described. The objective of this system is to collect high frequency/high bandwidth data from multiple sensors placed at remote locations and adaptively adjust the resolution of this data so that it can be transmitted on bandwidth limited networks to a central monitoring and command center. This is achieved by adaptively re-sampling (decimating the data from the sensors at the remote location before transmission. The decimation is adjusted to the available bandwidth of the communications network which is characterized in real-time. As a result, the system allows users at the remote command center to view high bandwidth data (at a lower resolution with user-aware and minimized latency. This technique is applied to an eight hydrophone data acquisition system that requires a 25.6 Mbps connection for the transmission of the full data set using a wireless connection with 1 – 3.5 Mbps variable bandwidth. This technique can be used for applications that require monitoring of high bandwidth data from remote sensors in research and education fields such as remote scientific instruments and visually driven control applications.

Biruk Gebre

2008-06-01

274

High-Density, High-Bandwidth, Multilevel Holographic Memory  

Science.gov (United States)

A proposed holographic memory system would be capable of storing data at unprecedentedly high density, and its data transfer performance in both reading and writing would be characterized by exceptionally high bandwidth. The capabilities of the proposed system would greatly exceed even those of a state-of-the art memory system, based on binary holograms (in which each pixel value represents 0 or 1), that can hold .1 terabyte of data and can support a reading or writing rate as high as 1 Gb/s. The storage capacity of the state-of-theart system cannot be increased without also increasing the volume and mass of the system. However, in principle, the storage capacity could be increased greatly, without significantly increasing the volume and mass, if multilevel holograms were used instead of binary holograms. For example, a 3-bit (8-level) hologram could store 8 terabytes, or an 8-bit (256-level) hologram could store 256 terabytes, in a system having little or no more size and mass than does the state-of-the-art 1-terabyte binary holographic memory. The proposed system would utilize multilevel holograms. The system would include lasers, imaging lenses and other beam-forming optics, a block photorefractive crystal wherein the holograms would be formed, and two multilevel spatial light modulators in the form of commercially available deformable-mirror-device spatial light modulators (DMDSLMs) made for use in high speed input conversion of data up to 12 bits. For readout, the system would also include two arrays of complementary metal oxide/semiconductor (CMOS) photodetectors matching the spatial light modulators. The system would further include a reference-beam sterring device (equivalent of a scanning mirror), containing no sliding parts, that could be either a liquid-crystal phased-array device or a microscopic mirror actuated by a high-speed microelectromechanical system. Time-multiplexing and the multilevel nature of the DMDSLM would be exploited to enable writing and reading of multilevel holograms. The DMDSLM would also enable transfer of data at a rate of 7.6 Gb/s or perhaps somewhat higher.

Chao, Tien-Hsin

2008-01-01

275

Narrow bandwidth Bragg gratings imprinted in polymer optical fibers for different spectral windows  

Science.gov (United States)

The production and characterization of narrow bandwidth fiber Bragg gratings (FBGs) in different spectral regions using polymer optical fibers (POFs) is reported. Narrow bandwidth FBGs are increasingly important for POF transmission systems, WDM technology and sensing applications. Long FBGs with resonance wavelength around 600-nm, 850-nm and 1550-nm in several types of polymer optical fibers were inscribed using a scanning technique with a short optical path. The technique allowed the inscription in relative short periods of time. The obtained 3-dB bandwidth varies from 0.22 down to 0.045 nm considering a Bragg grating length between 10 and 25-mm, respectively.

Marques, Carlos A. F.; Bilro, Lúcia B.; Alberto, Nélia J.; Webb, David J.; Nogueira, Rogério N.

2013-10-01

276

Suitability of Data Intensive Application in a Bandwidth Constrained Global Grid Network  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: To check the suitability of real time data intensive applications in a global grid network. Approach: With improved bandwidth availability, taking the grid to the internet is becoming a reality. However issues regarding the security and bandwidth utilization needs to be understood as these factors become crucial to the success of the grid as a commercial model. Results: Here in this research work we investigate the effect of data intensive applications running in a grid with different number of nodes under constrained bandwidth. Conclusion/Recommendations: Our simulation shows that increasing node count does not guarantee improved quality of service.

T. R. Srinivasan

2011-01-01

277

Bandwidth and unpredictability properties of semiconductor ring lasers with chaotic optical injection  

Science.gov (United States)

The bandwidth and unpredictability properties of chaotic semiconductor ring lasers (SRLs) are numerically investigated. The SRL is brought to chaotic behaviors by utilizing chaotic optical injection from a master laser with optical feedback. The bandwidth and unpredictability degree of chaotic signal are examined for parameter regions of injection strength and frequency detuning. The chaos unpredictability degree is evaluated quantitatively by permutation entropy (PE). It is shown that, chaos can be obtained in large parameter regions, and simultaneous enhancement of bandwidth and unpredictability degree could be achieved for proper injection parameters. Such results are important for carrying out chaos-based communications and fast random number generations (RNGs).

Li, Nianqiang; Pan, Wei; Xiang, Shuiying; Yan, Lianshan; Luo, Bin; Zou, Xihua; Zhang, Liyue

2013-12-01

278

Bandwidth studies of an injection-seeded ?-barium borate optical parametric oscillator  

Science.gov (United States)

Spectral and temporal properties of a scanning injection-seeded beta -barium borate optical parametric oscillator pumped by the third harmonic of a 10-Hz Nd:YAG laser have been studied. The seed source was a cw diode laser with a wavelength of 830 nm tunable over a range of 50 GHz. We measured the bandwidth of the seeded optical parameter oscillator, using a two-photon resonance in barium and a Fabry-Perot etalon, to be approximately 400 MHz for pump power levels more than two times above threshold. This is \\similar 2 times the Fourier-transform-limited bandwidth. At lower pump powers the bandwidth was smaller.

Boon-Engering, J. M.; van der Veer, W. E.; Gerritsen, J. W.; Hogervorst, W.

1995-02-01

279

Bandwidth optical parametric amplifier by using photonic crystal fiber with pump depletion  

Science.gov (United States)

Bandwidth gain characteristics of two-pump fiber optical parametric amplifier (FOPA) with photonic crystal fiber (PCF) are discussed. The pump depletion is considered in. Broader 62dB gain can be obtained in the range from 1370nm to 1790nm.The effects of dispersion characteristics of the PCF on the gain bandwidth are analyzed. And the influences of signal and pump powers are also taken into account. From the analysis that by properly selecting the PCF and setting the pump and signal powers, wider gain bandwidth can be achieved, which is useful for the dense wavelength diversion multiplexing (DWDM)system.

Zhu, Hongna; Wang, Li; Luo, Bin; Gao, Xiaorong; Wang, Zeyong

2012-10-01

280

Expanding the bandwidth of planar MNG materials with co-directional split-ring resonators  

International Nuclear Information System (INIS)

An effective approach to expand the bandwidth of negative permeability of small-sized planar materials is proposed. Based on qualitative analysis of equivalent circuit models, the fractional bandwidth of an ?-negative (MNG) material is expanded from 3.53% up to 12.87% by adding split-ring resonators (SRRs) and arranging them by proposed steps. Moreover, the experimental results validate the effectiveness of bandwidth-expanding methods, which is promising for the extensive application of metamaterials in the microwave field. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

 
 
 
 
281

Breaking the energy-bandwidth limit of electro-optic modulators: theory and a device proposal  

CERN Document Server

In this paper, we quantitatively analyzed the trade-off between energy per bit for switching and modulation bandwidth of classical electro-optic modulators. A formally simple energy-bandwidth limit (Eq. 10) is derived for electro-optic modulators based on intra-cavity index modulation. To overcome this limit, we propose a dual cavity modulator device which uses a coupling modulation scheme operating at high bandwidth (> 200 GHz) not limited by cavity photon lifetime and simultaneously features an ultra-low switching energy of 0.26 aJ, representing over three orders of magnitude energy consumption reduction compared to state-of-the-art electro-optic modulators.

Lin, Hongtao; Liu, Jifeng; Zhang, Lin; Michel, Jurgen; Hu, Juejun

2013-01-01

282

Increased spectral bandwidths in nonlinear conversion processes by use of multicrystal designs.  

Science.gov (United States)

The fourth-harmonic generation of broadband 243-nm radiation is reported. The broadband radiation is achieved by implementation of a multicrystal design to overcome spectral bandwidth limitations, and a plane-wave analysis is developed that shows increased spectral bandwidths for these designs. The fourth harmonic of a Cr:LiSAF laser operating at 972 nm is generated in beta-barium borate (BBO). The results demonstrate a spectral bandwidth at 243 nm more than five times broader than that which is expected from a single BBO crystal of equivalent length. PMID:18091854

Brown, M

1998-10-15

283

Error modeling of precision orientation sensors in a fixed base simulation. Ph.D. Thesis; [models of noise and dynamic characteristics of a gyro and autocollimator for very small signals  

Science.gov (United States)

Models of noise and dynamic characteristics of gyro and autocollimator for very small signal levels are presented. Measurements were evaluated using spectral techniques for identifying noise from base motion. The experiment was constructed to measure the precession, due to relativistic effects, of an extremely precise earth-orbiting gyroscope. The design goal for nonrelativistic gyro drift is 0.001 arcsec per year. An analogous fixed base simulator was used in developing methods of instrument error modeling and performance evaluation applicable to the relativity experiment sensors and other precision pointing instruments. Analysis of autocollimator spectra uncovered the presence of a platform gimbal resonance. The source of resonance was isolated to gimbal bearing elastic restraint properties most apparent at very small levels of motion. A model of these properties which include both elastic and coulomb friction characteristics is discussed, and a describing function developed.

Klinger, D. L.

1974-01-01

284

A fair and bandwidth-guaranteed scheduling algorithm for buffered crossbar switches  

Science.gov (United States)

Buffered crossbar switch is becoming attractive due to its feature of distributed scheduling, which makes the scheduler more scalable than that in an un-buffered crossbar switch. However, previous researches on buffered crossbar switches mainly aimed at improving the throughput and cell delay performance, scarcely at the fairness and bandwidth guarantee. In this paper, we discuss the necessities of providing bandwidth guarantee in buffered crossbar switches, and propose a novel RR_MCF algorithm. RR_MCF uses a simple round robin policy at input scheduling, and a most credit first policy at output scheduling. By given a predetermined reserved bandwidth matrix, simulations show RR_MCF could provide good bandwidth guarantee for each flow, even with the presence of ill-behaved flows.

Xu, Yang; Wu, Beibei; Li, Wei; Li, Wenjie; Liu, Bin

2005-10-01

285

Coherence bandwidth characterization in an urban microcell at 62.4 GHz  

DEFF Research Database (Denmark)

Results of experiments made at 62.4 GHz in an urban mobile radio environment to characterize the coherence bandwidth are presented. The correlation coefficients between signal envelopes separated in frequency are measured and expressed as functions of distance from the base station. Due to the high variation of this coefficient with distance and in order to provide accurate estimates of the coherence bandwidth in the microcell, the correlation coefficient has to be measured over large sections. Two methods to calculate the coherence bandwidth are presented and compared. It is shown that estimating this parameter from the frequency correlation function obtained at each position may yield incorrect results. The coherence bandwidths for correlation levels of 0.5, 0.7, and 0.9 are given. A ray-tracing tool has been used to assist in interpreting experimental results.

Sánchez, M. G.; Hammoudeh, A. M.

2000-01-01

286

High bandwidth data recording systems for pulsed power and laser produced plasma experiments  

International Nuclear Information System (INIS)

We present two high bandwidth data transmission and recording systems for the measurement of transient signals during pulsed power and laser produced plasmas. These systems use fiber optic cables to transmit analog data over long distances to high bandwidth digitizing oscilloscopes. One system is based on the direct modulation of a laser diode and has a bandwidth of 1.5 GHz. The other system is based upon a Mach-Zehnder modulator and has a bandwidth of 12 GHz, and is limited by the photoreceiver. The signals are recorded on commercial digitizing oscilloscopes that have approximately six effective bits. The transmission systems use many off-the-shelf components from the telecommunications industry and thus have a high reliability and a moderate cost. Investigation of the reduction in optical transmission of the fibers during exposure to high dose radiation will also be discussed

287

High Bandwidth Data Recording Systems for Pulsed Power and Laser Produced Plasma Experiments.  

Energy Technology Data Exchange (ETDEWEB)

We present two high bandwidth data transmission and recording systems for the measurement of transient signals during pulsed power and laser produced plasmas. These systems use fiber optic cables to transmit analog data over long distances to high bandwidth digitizing oscilloscopes. One system is based on the direct modulation of a laser diode and has a bandwidth of 1.5 GHz. The other system is based upon a fiber-optic Mach-Zehnder modulator and has a bandwidth of 12 GHz, and is limited by the photo receiver. The signals are recorded on commercial digitizing oscilloscopes that have approximately 6 effective bits. The transmission systems use many off-the-shelf components from the telecommunications industry and thus have a high reliability and a moderate cost. Results from recent measurements will be presented. Investigation of the reduction in optical transmission by the fibers during exposure to high dose radiation will also be discussed.

May, M J; Clancy, T; Fittinghoff, D; Halvorson, C; MIlls, T; Nikitin, A; Perry, T; Roberson, P; Smith, D; Teruya, A; Miller, K; Trainham, C

2006-05-02

288

A Novel Framework for Distributed Dynamic Bandwidth Allocation in EPONWiMAX Networks  

Directory of Open Access Journals (Sweden)

Full Text Available In Ethernet Passive Optical Networks (EPON, allocation of bandwidth to the Optical Network Units (ONU is a critical issue in determining the performance of the network. The resource allocation process in EPON is carried out by the Dynamic Bandwidth Allocation (DBA algorithm. The onus of resource allocation or DBA estimation is bore solely by Optical Line Terminal (OLT which results in more idle time at the OLT, thereby resulting in wastage of bandwidth and increased delay in data transmission. In this paper, a new framework for EPON is proposed, wherein, the DBA estimation is shared by the OLT and ONU, thereby reducing the idle time in OLT and improving the bandwidth utilization. The proposed framework is evaluated under heavy load conditions with the help of OPNET simulations and it has been demonstrated that the proposed framework outperforms the conventional scheme in terms of throughput, percentage of utilization and other QoS services.

S.Ramya

2014-01-01

289

Multi-Hop Bandwidth Management Protocol for Mobile Ad Hoc Networks  

CERN Document Server

An admission control scheme should play the role of a coordinator for flows in a data communication network, to provide the guarantees as the medium is shared. The nodes of a wired network can monitor the medium to know the available bandwidth at any point of time. But, in wireless ad hoc networks, a node must consume the bandwidth of neighboring nodes, during a communication. Hence, the consumption of bandwidth by a flow and the availability of resources to any wireless node strictly depend upon the neighboring nodes within its transmission range. We present a scalable and efficient admission control scheme, Multi-hop Bandwidth Management Protocol (MBMP), to support the QoS requirements in multi-hop ad hoc networks. We simulate several options to design MBMP and compare the performances of these options through mathematical analysis and simulation results, and compare its effectiveness with the existing admission control schemes through extensive simulations. KEYWORDS

Pattanayak, Binod Kumar; Jagadev, Alok Kumar; Nayak, Manojranjan

2010-01-01

290

THz Tube Waveguides With Low Loss, Low Dispersion, and High Bandwidth  

DEFF Research Database (Denmark)

We propose, model and experimentally characterize a novel class of terahertz hollow-core tube waveguides with high-loss cladding material, resulting in propagation with low loss, low dispersion, and high useful bandwidth.

Bao, Hualong; Nielsen, Kristian

2014-01-01

291

Bandwidth Estimation Problem & Solutions in IEEE 802.11 based Ad Hoc Networks  

Directory of Open Access Journals (Sweden)

Full Text Available With the rise in multimedia applications in ad hoc networks it is necessary to ensure the quality of service support from network. The routers which may be mobile nodes in ad hoc networks should be able to evaluate the resources available in the network, prior to offering guarantees on delay, bandwidth or any other metric. Estimating the available bandwidth is often required before performing admission control, flows management, congestion control or routing based on bandwidth constraints so that before any new flow is admitted the existing flow does not degrade. Lot of work in terms of various tools and techniques has been proposed to evaluate the available bandwidth in last decade; no consensus has yet been arrived. We present a comprehensive review on the various state of art work proposed carried out in this area

Neeraj Gupta

2012-11-01

292

Finite-Bandwidth Resonances of High-Order Axial Modes (HOAM) in a Gyrotron Cavity  

CERN Document Server

Finite-bandwidth resonances of high-order axial modes (HOAM) in an open gyrotron cavity are studied numerically using the GYROSIM problem-oriented software package for modelling, simulation and computer-aided design (CAD) of gyrotron tubes.

Sabchevski, Svilen

2014-01-01

293

Experimental Demonstration of a Bandwidth Scalable LAN Emulation over EPON Employing OFDMA  

DEFF Research Database (Denmark)

We propose a novel EPON system supporting bandwidth scalable local area network emulation by using orthogonal frequency division multiplexing access technology. Added to the EPON traffic, 250Mbps and 500Mbps OFDM LAN traffics are experimentally emulated.

Deng, Lei; Zhao, Ying

2011-01-01

294

Transmission Bandwidth Tunability of a Liquid-Filled Photonic Bandgap Fiber  

International Nuclear Information System (INIS)

A temperature tunable photonic bandgap fiber (PBGF) is demonstrated by an index-guiding photonic crystal fiber filled with high-index liquid. The temperature tunable characteristics of the fiber are experimentally and numerically investigated. Compression of transmission bandwidth of the PBGF is demonstrated by changing the temperature of part of the fiber. The tunable transmission bandwidth with a range of 250 nm is achieved by changing the temperature from 30°C to 90°C

295

Measurements of higher order noise correlations in a quantum dot with a finite bandwidth detector  

CERN Document Server

We present measurements of the fourth and fifth cumulants of the distribution of transmitted charge in a tunable quantum dot. We investigate how the measured statistics is influenced by the finite bandwidth of the detector and by the finite measurement time. By including the detector when modeling the system, we use the theory of full counting statistics to calculate the noise levels for the combined system. The predictions of the finite-bandwidth model are in good agreement with measured data.

Gustavsson, S; Ihn, T; Ensslin, K; Reinwald, M; Wegscheider, W

2006-01-01

296

Quality-of-Service Routing in Heterogeneous Networks with Optimal Buffer and Bandwidth Allocation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present an interdomain routing protocol for heterogeneous networks employing different queuing service disciplines. Our routing protocol finds optimal interdomain paths with maximum reliability while satisfying the end-to-end jitter and bandwidth constraints in networks employing heterogeneous queuing service disciplines. The quality-of-service (QoS) metrics are represented as functions of link bandwidth, node buffers and the queuing service disciplines employed in the routers along the pa...

Sheikh, Waseem; Ghafoor, Arif

2007-01-01

297

Bandwidth statistics from the eigenvalue moments for the Harper-Hofstadter problem  

CERN Document Server

I propose a method for studying the product of bandwidths for the Harper-Hofstader model. This method requires knowledge of the moments of the midband energies. I conjectured a general formula for these moments. I computed the asymptotic representation for the product of bandwidths in the limit of a weak magnetic flux using Szego's theorem for Hankel matrices. I then give a first approximation for the edge of the butterfly spectrum and discuss its connection with P. Levy's formula for Brownian motion .

Lipan, O

2000-01-01

298

Ultranarrow bandwidth moiré reflecting Bragg gratings recorded in photo-thermo-refractive glass.  

Science.gov (United States)

An experimental demonstration of a moiré reflecting Bragg grating in photo-thermo-refractive glass is carried out. This narrowband filter is obtained by the recording of two reflecting Bragg gratings with different periods. Filters with central wavelength at 1550 nm, bandwidth of 50 pm, and transmission higher than 95% are demonstrated. The methods to decrease bandwidth to 1 pm are finally investigated. PMID:20160828

Smirnov, Vadim; Lumeau, Julien; Mokhov, Sergiy; Zeldovich, Boris Ya; Glebov, Leonid B

2010-02-15

299

Auction-based bandwidth allocation and scheduling in noncooperative wireless networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate bandwidth allocation and scheduling in non-cooperative wireless networks as a mixed integer programming problem. Fast Vickrey-Clarke-Groves (VCG) auction-based bandwidth allocation (FABA), incorporating relaxation-based greedy algorithm (RGA) and split-flow-based algorithm (SFA), is proposed by modifying the traditional VCG auction to make it computationally feasible. With incentives provided by FABA, the dominant strategy of any selfish node in the network is to be cooperative...

Zhou, H.; Leung, Kc; Li, Vok

2014-01-01

300

On Bandwidth Characteristics of Tuning Fork Micro-Gyroscope with Mechanically Coupled Sense Mode  

Directory of Open Access Journals (Sweden)

Full Text Available The bandwidth characteristics of a tuning fork micro-gyroscope with mechanically coupled sense mode were investigated in this paper to provide some references for mechanical bandwidth design. The concept of sense mode mechanical coupling is introduced first. Theoretical frequency response analyses were then carried out on the mechanical part of the gyroscope. Equations representing the relationships between the differential output signal and the frequency of the input angular rate were deduced in full frequency range and further simplified in low frequency range. Based on these equations, bandwidth characteristics under ideal and non-ideal conditions are discussed. Analytical results show that under ideal conditions, the bandwidth characteristics of a tuning fork micro-gyroscope are similar to those of a single mass micro-gyroscope, but under non-ideal conditions, especially when sense mass and/or stiffness are asymmetric, the bandwidth characteristics would be quite different because the in-phase mode would participate in the anti-phase vibration response. Experimental verifications were carried out on two micro-gyroscope prototypes designed in our laboratory. The deduced equations and analytical results can be used in guiding the mechanical bandwidth design of tuning fork micro-gyroscopes with mechanically coupled sense mode.

Yunfang Ni

2014-07-01

 
 
 
 
301

On bandwidth characteristics of tuning fork micro-gyroscope with mechanically coupled sense mode.  

Science.gov (United States)

The bandwidth characteristics of a tuning fork micro-gyroscope with mechanically coupled sense mode were investigated in this paper to provide some references for mechanical bandwidth design. The concept of sense mode mechanical coupling is introduced first. Theoretical frequency response analyses were then carried out on the mechanical part of the gyroscope. Equations representing the relationships between the differential output signal and the frequency of the input angular rate were deduced in full frequency range and further simplified in low frequency range. Based on these equations, bandwidth characteristics under ideal and non-ideal conditions are discussed. Analytical results show that under ideal conditions, the bandwidth characteristics of a tuning fork micro-gyroscope are similar to those of a single mass micro-gyroscope, but under non-ideal conditions, especially when sense mass and/or stiffness are asymmetric, the bandwidth characteristics would be quite different because the in-phase mode would participate in the anti-phase vibration response. Experimental verifications were carried out on two micro-gyroscope prototypes designed in our laboratory. The deduced equations and analytical results can be used in guiding the mechanical bandwidth design of tuning fork micro-gyroscopes with mechanically coupled sense mode. PMID:25051030

Ni, Yunfang; Li, Hongsheng; Huang, Libin; Ding, Xukai; Wang, Haipeng

2014-01-01

302

Design of bandwidth tunable HTS filter using H-shaped waveguides  

International Nuclear Information System (INIS)

We have developed a bandwidth tuning method for use in high-temperature superconducting (HTS) microstrip filters. Several H-shaped waveguides are placed between the resonators, and the bandwidth is adjusted by changing the switch states of the waveguides. The coupling coefficients between the resonators are controlled by switching the connection or isolation of the center gaps of the waveguides so as to tune the bandwidth. The effects of using this method were evaluated by simulation using a filter composed of 3-pole half-wavelength straight-line resonators with an H-shaped waveguide between each pair and additional electric pads for post-tuning trimming. The filter was designed to have a center frequency of 5 GHz and a bandwidth of 100 MHz by using an electromagnetic simulator based on the moment method. The simulation showed that bandwidth tuning of 150 MHz can be obtained by using H-shaped waveguides to adjust the coupling coefficients. It also showed that using additional electric pads around the feed lines, which was previously shown to be useful for trimming to improve insertion loss after center-frequency tuning, is also useful for bandwidth tuning.

303

The Minimum Bandwidth of Narrowband Spikes in Solar Flare Decimetric Radio Waves  

CERN Document Server

The minimum and the mean bandwidth of individual narrowband spikes in two events in decimetric radio waves is determined by means of multi-resolution analysis. Spikes of a few tens of millisecond duration occur at decimetric/microwave wavelength in the particle acceleration phase of solar flares. A first method determines the dominant spike bandwidth scale based on their scalegram, the mean squared wavelet coefficient at each frequency scale. This allows to measure the scale bandwidth independently of heuristic spike selection criteria, e.g. manual selection. The major drawback is a low resolution in the bandwidth. To overcome this uncertainty, a feature detection algorithm and a criterion for spike shape in the time-frequency plane is applied to locate the spikes. In that case, the bandwidth is measured by fitting an assumed spike profile into the denoised data. The smallest FWHM bandwidth of spikes was found at 0.17 % and 0.41 % of the center frequency in the two events. Knowing the shortest relevant bandwi...

Messmer, P; Messmer, Peter; Benz, Arnold O.

1999-01-01

304

Improved scheme for estimating T-CONT bandwidth demand in status reporting DBA for NG-PON  

Science.gov (United States)

A scheme for estimating T-CONT bandwidth demand within dynamic bandwidth allocation (DBA) for next-generation passive optical network (NG-PON) is proposed and evaluated. Estimating T-CONT bandwidth demand is considered as a main challenge in gigabit-capable passive optical network (GPON) DBA. The proposed minimum guaranteed T-CONT content (MGTC) scheme allows for a more conservative estimate of bandwidth demand. It is shown that at high load significant improvements in delay, jitter and bandwidth utilization can be achieved with the proposed scheme. For light loads the conventional scheme shows better delay performance. However, this may be overcome by controlled overgranting in the MGTC scheme.

Skubic, Björn; Chen, Biao; Chen, Jiajia; Ahmed, Jawwad; Wosinska, Lena

2009-11-01

305

Density estimation and adaptive bandwidths: A primer for public health practitioners  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Geographic information systems have advanced the ability to both visualize and analyze point data. While point-based maps can be aggregated to differing areal units and examined at varying resolutions, two problems arise 1 the modifiable areal unit problem and 2 any corresponding data must be available both at the scale of analysis and in the same geographic units. Kernel density estimation (KDE produces a smooth, continuous surface where each location in the study area is assigned a density value irrespective of arbitrary administrative boundaries. We review KDE, and introduce the technique of utilizing an adaptive bandwidth to address the underlying heterogeneous population distributions common in public health research. Results The density of occurrences should not be interpreted without knowledge of the underlying population distribution. When the effect of the background population is successfully accounted for, differences in point patterns in similar population areas are more discernible; it is generally these variations that are of most interest. A static bandwidth KDE does not distinguish the spatial extents of interesting areas, nor does it expose patterns above and beyond those due to geographic variations in the density of the underlying population. An adaptive bandwidth method uses background population data to calculate a kernel of varying size for each individual case. This limits the influence of a single case to a small spatial extent where the population density is high as the bandwidth is small. If the primary concern is distance, a static bandwidth is preferable because it may be better to define the "neighborhood" or exposure risk based on distance. If the primary concern is differences in exposure across the population, a bandwidth adapting to the population is preferred. Conclusions Kernel density estimation is a useful way to consider exposure at any point within a spatial frame, irrespective of administrative boundaries. Utilization of an adaptive bandwidth may be particularly useful in comparing two similarly populated areas when studying health disparities or other issues comparing populations in public health.

Tanski Susanne

2010-07-01

306

An impact excitation system for repeatable, high-bandwidth modal testing of miniature structures  

Science.gov (United States)

Miniature components and devices are increasingly seen in a myriad of applications. In general, the dynamic behavior of miniature devices is critical to their functionality and performance. However, modal testing of miniature structures poses many challenges. This paper presents a design and evaluation of an impact excitation system (IES) for repeatable, high-bandwidth, controlled-force modal testing of miniature structures. Furthermore, a dynamic model of the system is derived and experimentally validated to enable the identification of the system parameters that yield single-hit impacts with desired bandwidth and force magnitude. The system includes a small instrumented impact tip attached to a custom designed flexure-based body, an automated electromagnetic release mechanism, and various precision positioners. The excitation bandwidth and the impact force magnitude can be controlled by selecting the system parameters. The dynamic model of the system includes the structural dynamics of the flexure-based body, the electromagnetic force and the associated eddy-current damping, and the impact event. A validation study showed an excellent match between the model simulations and experiments in terms of impact force and bandwidth. The model is then used to create process maps that relate the system parameters to the number of hits (single vs. multiple), the impact force magnitudes and the excitation bandwidths. These process maps can be used to select system parameters or predict system response for a given set of parameters. A set of experiments is conducted to compare the performances of the IES and a (manual) miniature impact hammer. It is concluded that the IES significantly improves repeatability in terms of the impact bandwidth, location, and force magnitude, while providing a high excitation-bandwidth and excellent coherence values. The application of the IES is demonstrated through modal testing of a miniature contact-probe system.

Bediz, Bekir; Korkmaz, Emrullah; Burak Ozdoganlar, O.

2014-06-01

307

Maximum Bandwidth Enhancement of Current Mirror using Series-Resistor and Dynamic Body Bias Technique  

Directory of Open Access Journals (Sweden)

Full Text Available This paper introduces a new approach for enhancing the bandwidth of a low voltage CMOS current mirror. The proposed approach is based on utilizing body effect in a MOS transistor by connecting its gate and bulk terminals together for signal input. This results in boosting the effective transconductance of MOS transistor along with reduction of the threshold voltage. The proposed approach does not affect the DC gain of the current mirror. We demonstrate that the proposed approach features compatibility with widely used series-resistor technique for enhancing the current mirror bandwidth and both techniques have been employed simultaneously for maximum bandwidth enhancement. An important consequence of using both techniques simultaneously is the reduction of the series-resistor value for achieving the same bandwidth. This reduction in value is very attractive because a smaller resistor results in smaller chip area and less noise. PSpice simulation results using 180 nm CMOS technology from TSMC are included to prove the unique results. The proposed current mirror operates at 1Volt consuming only 102 µW and maximum bandwidth extension ratio of 1.85 has been obtained using the proposed approach. Simulation results are in good agreement with analytical predictions.

V. Niranjan

2014-09-01

308

ENERGY AND BANDWIDTH INFLUENCE ON EFFICIENCY IN WIRELESS NETWORKS: A REVIEW  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we review the efficiency of wireless ad hoc networks. The wireless networks efficiency deals with the bandwidth and the energy efficiency of the networks that depends upon the energy supply of the nodes. This energy and the bandwidth related to it are the major constraints to be considered in this paper. The network comprises of the nodes that consist of different channels for transmission purpose and these are the major areas for bandwidth efficiency. The energy concerned is the receivers processing energy, transmitter’s energy requirement for transmission, loses in the form of heat from the transmitter devices. All nodes in the network are mobile but for measuring the efficiency at particular instant, the nodes are considered to be static and communicating in half duplexmode. The review about the tradeoff between the bandwidth and the energy efficiency of the wireless networks is studied. The transmission in the paper is studied at the common rate and common power supply to the transmitter. The energy efficiency of the network depends upon the signal to noise ration of the transmission and the bandwidth efficiency of the network is relatively higher at the transmission at common power than the common rate for the non equidistant relaying nodes.

PROF. R.K SINGH,

2010-11-01

309

H.264/SVC parameter optimization based on quantization parameter, MGS fragmentation, and user bandwidth distribution  

Science.gov (United States)

In the situation of limited bandwidth, how to improve the performance of scalable video coding plays an important role in video coding. The previously proposed scalable video coding optimization schemes concentrate on reducing coding computation or trying to achieve consistent video quality; however, the connections between coding scheme, transmission environments, and users' accesses manner were not jointly considered. This article proposes a H.264/SVC (scalable video codec) parameter optimization scheme, which attempt to make full use of limited bandwidth, to achieve better peak signal-to-noise ratio, based on the joint measure of user bandwidth range and probability density distribution. This algorithm constructs a relationship map which consists of the bandwidth range of multiple users and the quantified quality increments measure, QP e , in order to make effective use of the video coding bit-stream. A medium grain scalability fragmentation optimization algorithm is also presented with respect to user bandwidth probability density distribution, encoding bit rate, and scalability. Experiments on a public dataset show that this method provides significant average quality improvement for streaming video applications.

Chen, Xu; Zhang, Ji-Hong; Liu, Wei; Liang, Yong-Sheng; Feng, Ji-Qiang

2013-12-01

310

Design and fabrication of center frequency and bandwidth tunable HTS filter  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? We have developed a bandwidth and a center frequency tunable HTS filter. ? A tunable passband ratio of 1.8:1 was achieved. ? An 8% of center frequency tuning at 5 GHz was achieved. ? Adjustment of external quality factors improves the filter response after tuning. -- Abstract: We have developed a bandwidth and a center frequency tuning method for use in high-temperature superconducting microstrip filters. A pair of waveguide is placed between the resonators, and the bandwidth is adjusted by changing the switch states of the waveguides. Additional electrical pads are placed open ends of the resonators for tuning the center frequency. Pads are also placed around the input/output coupled-line elements to enable the external quality factors to be adjusted, thereby reducing the insertion loss caused by tuning. A prototype three-pole tunable bandpass filter was fabricated by depositing YBa{sub 2}Cu{sub 3}O{sub 7} thin film on an MgO substrate and has a measured center frequency of 4.83 GHz and bandwidth of 121 MHz. Use of the waveguides to adjust the coupling coefficients, the electrical pads to adjust the effective lengths of the resonators and the pads to adjust the external quality factors resulted in 120-MHz bandwidth tuning and 400-MHz center frequency tuning without increased insertion loss.

Sekiya, N., E-mail: nsekiya@yamanashi.ac.jp [Department of Electrical Engineering, Yamanashi University, Kakio-Sekiya Laboratory, 4-3-11 Takeda, Kofu 400-8511 (Japan); Harada, H.; Kakio, S. [Department of Electrical Engineering, Yamanashi University, Kakio-Sekiya Laboratory, 4-3-11 Takeda, Kofu 400-8511 (Japan); Ohshima, S. [Yamagata University, 4-3-16 Johnan, Yonezawa 992-8510 (Japan)

2013-01-15

311

Movie approximation technique for the implementation of fast bandwidth-smoothing algorithms  

Science.gov (United States)

Bandwidth smoothing algorithms can effectively reduce the network resource requirements for the delivery of compressed video streams. For stored video, a large number of bandwidth smoothing algorithms have been introduced that are optimal under certain constraints but require access to all the frame size data in order to achieve their optimal properties. This constraint, however, can be both resource and computationally expensive, especially for moderately priced set-top-boxes. In this paper, we introduce a movie approximation technique for the representation of the frame sizes of a video, reducing the complexity of the bandwidth smoothing algorithms and the amount of frame data that must be transmitted prior to the start of playback. Our results show that the proposed approximation technique can accurately approximate the frame data with a small number of piece-wise linear segments without affecting the performance measures that the bandwidth soothing algorithms are attempting to achieve by more than 1%. In addition, we show that implementations of this technique can speed up execution times by 100 to 400 times, allowing the bandwidth plan calculation times to be reduced to tens of milliseconds. Evaluation using a compressed full-length motion-JPEG video is provided.

Feng, Wu-chi; Lam, Chi C.; Liu, Ming

1997-12-01

312

Design and fabrication of center frequency and bandwidth tunable HTS filter  

International Nuclear Information System (INIS)

Highlights: ? We have developed a bandwidth and a center frequency tunable HTS filter. ? A tunable passband ratio of 1.8:1 was achieved. ? An 8% of center frequency tuning at 5 GHz was achieved. ? Adjustment of external quality factors improves the filter response after tuning. -- Abstract: We have developed a bandwidth and a center frequency tuning method for use in high-temperature superconducting microstrip filters. A pair of waveguide is placed between the resonators, and the bandwidth is adjusted by changing the switch states of the waveguides. Additional electrical pads are placed open ends of the resonators for tuning the center frequency. Pads are also placed around the input/output coupled-line elements to enable the external quality factors to be adjusted, thereby reducing the insertion loss caused by tuning. A prototype three-pole tunable bandpass filter was fabricated by depositing YBa2Cu3O7 thin film on an MgO substrate and has a measured center frequency of 4.83 GHz and bandwidth of 121 MHz. Use of the waveguides to adjust the coupling coefficients, the electrical pads to adjust the effective lengths of the resonators and the pads to adjust the external quality factors resulted in 120-MHz bandwidth tuning and 400-MHz center frequency tuning without increased insertion loss

313

High-bandwidth quantum memory protocol for storing single photons in rare-earth doped crystals  

International Nuclear Information System (INIS)

We present a detailed analysis of a high-bandwidth quantum memory protocol for storing single photons in a rare-earth-ion doped crystal. The basic idea is to benefit from a coherent free-induced decay type re-emission which occurs naturally when a photon with a broadband spectrum is absorbed by a narrow atomic transition in an optically dense ensemble. This allows for a high-bandwidth memory for realistic material parameters. Long storage time and on-demand readout are obtained by means of spin states in a lambda-type configuration, through the transfer of the optical coherence to a spin coherence (so-called spin-wave storage). We give explicit formulae and show numerical results which make it possible to gain insight into the dependence of the memory efficiency on the optical depth and on the width and the shape of stored photons. We present a feasibility study in rare-earth doped crystals and show that high efficiencies and high bandwidth can be obtained with realistic parameters. High-bandwidth memories using spin-wave storage offers the possibility of very high time-bandwidth products, which is important for experiments where high repetition rates are needed. (paper)

314

ENHANCEMENT OF BANDWIDTH OF RECTANGULAR PATCH ANTENNA USING TWO SQUARE SLOTS TECHNIQUES  

Directory of Open Access Journals (Sweden)

Full Text Available The research in wireless communication has spurred the development of extra ordinary range of antennas, each with its own advantage and limitations. There are many applications where space is at premium, and where there is an urgent need for an antenna with the flexibility to efficiently combine the capabilities of multiple antennas. In fact rapidly developing market in personal communication systems (PCS, mobile satellite communications, direct broadband television (DBS wireless local area networks (WLANs suggest that demand for Microstrip antennas and array will increase even further. Conventional Microstrip patch antennas has some drawbacks of low efficiency, narrow bandwidth (3-6% of the central frequency, its bandwidth is limited to a few percent which is not enough for most of the wireless communication systems nowadays. In this paper one of the efficient methods used for the enhancement of patch antenna bandwidth is the loading of rectangular microstrip patch antenna with two square slots across its side surface. This type of Microstrip patch antenna meets the requirement of operation for wireless applications. The proposed configuration is simulated and analyzed using GENESYS software package. The VSWR, input impedance‚ and S11 performance are used for the analysis of the different configurations. The simulated results for square slots antenna structure give bandwidth of 311 MHZ. Feed point on the patch that gives a good match of 50 ohm. The results of the fabricated microstrip antenna give the bandwidth of 286 MHz.

Patil V. P.

2012-10-01

315

Analysis of Design Optimization of Bandwidth and Loss Performance of Reflectarray Antennas Based on Material Properties  

Directory of Open Access Journals (Sweden)

Full Text Available An investigation for the enhancement strategy of bandwidth performance and analysis of different types of losses associated with reflectarray antennas is presented in this paper. Studies are carried out using different commercially available dielectric materials with dielectric permittivity (?r values ranging from 2.08 to 13 and loss tangent (tan? ranging from 0.0003 to 0.025. The performance of different dielectric materials for the design of infinite reflectarray is analyzed in terms of bandwidth, reflection loss and Figure of Merit (FOM. Bandwidths at different levels are observed and it has been noticed that 10% bandwidth varies from 84 MHz to 360MHz and 20% bandwidth varies from 126 MHz to 540MHz based on the selection of dielectric substrate for reflectarray antenna design. Moreover it has been demonstrated that the reflection loss of the reflectarray antenna can be factorized into dielectric loss and conductor loss which depends on the material properties used for the design. Detailed numerical analysis is carried out in order to verify the acquired results.

Muhammad Yusof Ismail

2009-12-01

316

Hexagonal Nonradiating Edge-Coupled Patch Configuration for Bandwidth Enhancement of Patch Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available For increasing the impedance bandwidth of patch antenna two novel configurations are described for the ISM band applications. A hexagonal patch structure is used in both of the configurations. First structure uses six additional patches which are gap-coupled to the each nonradiating edge of the original hexagonal patch whereas in the second configuration fractals are used in each of the hexagonal of first order. HFSS is used for the simulation. The simulation result shows that with a regular hexagonal patch which gives 6% of impedance bandwidth, a slight improvement in bandwidth with respect to square patch can be achieved. Further with the two novel configurations up to 15.5% of the impedance is achieved. The result shows that the fractal configuration is suitable for the circularly polarized radiation. The simulated gain over the operating band is found to be more than 9-dB.

Krishn Kant Joshi

2014-05-01

317

Further discussion on bandwidth-enhanced chaos synchronization communication based on mutually coupled VCSELs  

Science.gov (United States)

A bandwidth-enhanced chaos synchronization communication system is proposed and its communication performance is investigated numerically. The results show that, using a bandwidth-enhanced chaotic signal from a driving vertical cavity surface-emitting laser (D-VCSEL) to drive two mutually coupled VCSELs (MC-VCSELs), the high-quality isochronal chaos synchronization with over 30GHz bandwidth between two corresponding LP modes in the two MCVCSELs can be obtained. Taking two LP modes as two different communication channels and adopting chaos masking (CMS) encryption scheme, this system can realize the bidirectional dual-channel high-speed chaos communication at 10Gbits/s transmission rate. Moreover, the parameters mismatches tolerance of this communication system and the influence of message transmission rate on the communication performance also are discussed.

Zhang, Zi-Yang; Xu, Yi-Na; Luo, Jie; He, Xiu; He, Yang; Lin, Xiao-Dong; Deng, Tao

2014-07-01

318

Dynamic Online Bandwidth Adjustment Scheme Based on Kalai-Smorodinsky Bargaining Solution  

Science.gov (United States)

Virtual Private Network (VPN) is a cost effective method to provide integrated multimedia services. Usually heterogeneous multimedia data can be categorized into different types according to the required Quality of Service (QoS). Therefore, VPN should support the prioritization among different services. In order to support multiple types of services with different QoS requirements, efficient bandwidth management algorithms are important issues. In this paper, I employ the Kalai-Smorodinsky Bargaining Solution (KSBS) for the development of an adaptive bandwidth adjustment algorithm. In addition, to effectively manage the bandwidth in VPNs, the proposed control paradigm is realized in a dynamic online approach, which is practical for real network operations. The simulations show that the proposed scheme can significantly improve the system performances.

Kim, Sungwook

319

Narrowing the Filter-Cavity Bandwidth in Gravitational-Wave Detectors via Optomechanical Interaction  

Science.gov (United States)

We propose using optomechanical interaction to narrow the bandwidth of filter cavities for achieving frequency-dependent squeezing in advanced gravitational-wave detectors, inspired by the idea of optomechanically induced transparency. This can allow us to achieve a cavity bandwidth on the order of 100 Hz using small-scale cavities. Additionally, in contrast to a passive Fabry-Pérot cavity, the resulting cavity bandwidth can be dynamically tuned, which is useful for adaptively optimizing the detector sensitivity when switching amongst different operational modes. The experimental challenge for its implementation is a stringent requirement for very low thermal noise of the mechanical oscillator, which would need a superb mechanical quality factor and a very low temperature. We consider one possible setup to relieve this requirement by using optical dilution to enhance the mechanical quality factor.

Ma, Yiqiu; Danilishin, Shtefan L.; Zhao, Chunnong; Miao, Haixing; Korth, W. Zach; Chen, Yanbei; Ward, Robert L.; Blair, D. G.

2014-10-01

320

Optimal Bandwidth and Power Allocation for Sum Ergodic Capacity under Fading Channels in Cognitive Radio Networks  

CERN Document Server

This paper studies optimal bandwidth and power allocation in a cognitive radio network where multiple secondary users (SUs) share the licensed spectrum of a primary user (PU) under fading channels using the frequency division multiple access scheme. The sum ergodic capacity of all the SUs is taken as the performance metric of the network. Besides all combinations of the peak/average transmit power constraints at the SUs and the peak/average interference power constraint imposed by the PU, total bandwidth constraint of the licensed spectrum is also taken into account. Optimal bandwidth allocation is derived in closed-form for any given power allocation. The structures of optimal power allocations are also derived under all possible combinations of the aforementioned power constraints. These structures indicate the possible numbers of users that transmit at nonzero power but below their corresponding peak powers, and show that other users do not transmit or transmit at their corresponding peak power. Based on t...

Gong, Xiaowen; Tellambura, Chintha

2010-01-01

 
 
 
 
321

Power-Bandwidth Tradeoff in Dense Multi-Antenna Relay Networks  

CERN Document Server

We consider a dense fading multi-user network with multiple active multi-antenna source-destination pair terminals communicating simultaneously through a large common set of $K$ multi-antenna relay terminals in the full spatial multiplexing mode. We use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the power- bandwidth tradeoff) in meaningful asymptotic regimes of signal-to-noise ratio (SNR) and network size. We design linear distributed multi-antenna relay beamforming (LDMRB) schemes that exploit the spatial signature of multi-user interference and characterize their power-bandwidth tradeoff under a system wide power constraint on source and relay transmissions. The impact of multiple users, multiple relays and multiple antennas on the key performance measures of the high and low SNR regimes is investigated in order to shed new light on the possible reduction in power and bandwidth requirements through the usage of such practical relay cooperation...

Oyman, Ozgur

2007-01-01

322

Narrow Bandwidth 850-nm Fiber Bragg Gratings in Few-Mode Polymer Optical Fibers  

DEFF Research Database (Denmark)

We report on the inscription and characterization of narrow bandwidth fiber Bragg gratings (FBGs) with 850-nm resonance wavelength in polymer optical fibers (POFs). We use two fibers: an in-house fabricated microstructured POF (mPOF) with relative hole size of 0.5 and a commercial step-index POF, which supports six modes at 850 nm. The gratings have been written with the phase-mask technique and a 325-nm HeCd laser. The mPOF grating has a full-width at half-maximum (FWHM) bandwidth of 0.29 nm and the step-index POF has a bandwidth of 0.17 nm. For both fibers, the static tensile strain sensitivity is measured to be 0.71 pm/$muvarepsilon$ at 850 nm and 1.3 pm/$muvarepsilon$ at 1550 nm.

Stefani, Alessio; Yuan, Wu

2011-01-01

323

Bandwidth-enhanced polarization-insensitive microwave metamaterial absorber and its equivalent circuit model  

Science.gov (United States)

In this paper, a bandwidth-enhanced polarization-insensitive ultra-thin metamaterial absorber has been presented. A simple equivalent circuit model has been proposed describing the absorption phenomenon to estimate the frequency of absorption of the proposed microwave absorber. The basic structure consists of concentric rings embedded one inside another to enhance bandwidth by incorporating the scalability property of the metamaterials. Simulation results show that the structure has enhanced bandwidth response with full width at half maxima (FWHM) of 1.15 GHz (9.40-10.55 GHz) with two absorption peaks at 9.66 and 10.26 GHz (96% and 92.5% absorptivity, respectively). The structure is symmetric in design giving rise to polarization-insensitivity and can achieve high absorption for oblique incidence up to 40°. The proposed absorber has been fabricated and measured in anechoic chamber, showing that experimental results agree well with the simulated responses.

Ghosh, Saptarshi; Bhattacharyya, Somak; Kaiprath, Yadunath; Vaibhav Srivastava, Kumar

2014-03-01

324

Bandwidth Enhancement of UWB Microstrip Antenna with a Modified Ground Plane  

Directory of Open Access Journals (Sweden)

Full Text Available This article presents a bandwidth enhancing technique using a modified ground plane with diagonal edges, rectangular slot, and T-shape cut for the design of compact antennas. The proposed low-cost, compact-size circular patch antenna on 3?cm × 5.1?cm printed circuit board (FR-4 is designed and validated through simulations and experiments. Results show that the T-shaped ground plane with the presence of the diagonal cuts at the top corners and the rectangular slots can increase the bandwidth. Return losses of ?19 and ?26?dB for the first and second resonant frequencies, respectively, can be achieved when the depth of the diagonal cut is 5?mm, the dimension of each rectangular slot is 5×3?mm, and the T-shaped size is 8×4?mm, providing a 28.67% wider bandwidth than FCC standard.

N. Prombutr

2009-01-01

325

Performance Analysis of Spatial Reused Bandwidth Reservation in Ad Hoc Networks  

Directory of Open Access Journals (Sweden)

Full Text Available in this paper, an approach for spatial reused bandwidth reservation in ad hoc networks is proposed. Resource reservation in wireless networks is an essential component that is needed to support multimedia and real-time applications, such as audio/video conferencing. On the other hand, directional antenna technology provides the capability for considerable increase in spatial reuse, which increases the efficiency of communication. In our approach for spatial reused bandwidth reservation, the source node tries to discover multiple node-disjoint paths that are capable of satisfing the desired Quality of Service (QoS requirement in ad hoc networks using directional antennas. The simulation result shows the performance of this spatial reused bandwidth reservation approach. There is a significant gain in the performance with a decrease in the number of paths, as well as an increase in the percentage of successfully received data packets and reservation success rate.

Yuan Li

2010-11-01

326

A Distributed Cluster Scheme For Bandwidth Management In Multi-hop MANETs  

CERN Document Server

Electronic collaboration among devices in a geographically localized environment is made possible with the implementation of IEEE 802.11 based wireless ad hoc networks. Dynamic nature of mobile ad hoc networks(MANETs) may lead to unpredictable intervention of attacks or fault occurrence, which consequently may partition the network, degrade its performance, violate the QoS requirements and most importantly, affect bandwidth allocation to mobile nodes in the network. In this paper, we propose a new distributed cluster scheme for MANETs, especially in harsh environments, based on the concept of survivability to support QoS requirements and to protect bandwidth efficiently. With the incorporation of clustering algorithms in survivability technology, we employ a simple network configuration and expect to reduce occurrences of faults in MANETs. At the same time, we address the scalability problem, which represents a great challenge to network configuration. We do expect a simplification of accessing bandwidth allo...

Pattanayak, Binod Kumar; Mishra, Manoj Kumar; Nayak, Manoj Ranjan

2010-01-01

327

Speech Enhancement Using an Artificial Bandwidth Extension Algorithm in Multicast Conferencing Through Cloud Services  

Directory of Open Access Journals (Sweden)

Full Text Available In the emerging scenario, Multicast conferencing plays an important role in e-education and e-business The multi conferencing systems have several shortcomings such as the conventional select-and-forward conference bridges gives inconsistent speech quality, due to full mesh and multicast architectures needs a large bandwidth at the endpoints. For a large scale voice conferencing through IP, now-a-days a tandem free architecture is coming up to reduce the bandwidth since it uses the compressed Low bit rate (Narrow Band speech. The speech quality is to be increased by employing Artificial Bandwidth Extension (BWE algorithm provided by Application Software Provider (ASP at the endpoints. In this study, a new approach, the SaaS (Software as a Service of cloud computing service is introduced to import Artificial BWE algorithm in to the cloud and the performance of SaaS over ASP is analyzed.

G. Gandhimathi

2014-01-01

328

Influences of finite gain bandwidth on pulse propagation in parabolic fiber amplifiers with distributed gain profiles  

International Nuclear Information System (INIS)

The evolutions of the pulses propagating in decreasing and increasing gain distributed fiber amplifiers with finite gain bandwidths are investigated by simulations with the nonlinear Schrödinger equation. The results show that the parabolic pulse propagations in both the decreasing and the increasing gain amplifiers are restricted by the finite gain bandwidth. For a given input pulse, by choosing a small initial gain coefficient and gain variation rate, the whole gain for the pulse amplification limited by the gain bandwidth may be higher, which is helpful for the enhancement of the output linearly chirped pulse energy. Compared to the decreasing gain distributed fiber amplifier, the increasing gain distributed amplifier may be more conducive to suppress the pulse spectral broadening and increase the critical amplifier length for achieving a larger output linearly chirped pulse energy

329

An Algorithm That Predicts CSI to Allocate Bandwidth for Healthcare Monitoring in Hospital's Waiting Rooms.  

Science.gov (United States)

In wireless healthcare monitoring systems, bandwidth allocation is an efficient solution to the problem of scarce wireless bandwidth for the monitoring of patients. However, when the central unit cannot access the exact channel state information (CSI), the efficiency of bandwidth allocation decreases, and the system performance also decreases. In this paper, we propose an algorithm to reduce the negative effects of imperfect CSI on system performance. In this algorithm, the central unit can predict the current CSI by previous CSI when the current CSI is not available. We analyze the reliability of the proposed algorithm by deducing the standard error of estimated CSI with this algorithm. In addition, we analyze the efficiency of the proposed algorithm by discussing the system performance with this algorithm. PMID:22536228

Lin, Di; Labeau, Fabrice

2012-01-01

330

Analysis of Blocking Rate and Bandwidth Usage of Mobile IPTV Services in Wireless Cellular Networks.  

Science.gov (United States)

Mobile IPTV services over wireless cellular networks become more and more popular, owing to the significant growth in access bandwidth of wireless cellular networks such as 3G/4G and WiMAX. However, the spectrum resources of wireless cellular networks is rare. How to enhance the spectral efficiency of mobile networks becomes an important issue. Unicast, broadcast, and multicast are the most important transport schemes for offering mobile IPTV services over wireless cellular networks. Therefore, bandwidth usages and blocking rates of unicast, broadcast, and multicast IPTV services were analyzed and compared in this paper. Simulations were also conducted to validate the analytical results. Numerical results demonstrate that the presented analysis is correct, and multicast scheme achieves the best bandwidth usage and blocking rate performance, relative to the other two schemes. PMID:25379521

Li, Mingfu

2014-01-01

331

A high-bandwidth amplitude estimation technique for dynamic mode atomic force microscopy  

International Nuclear Information System (INIS)

While often overlooked, one of the prerequisites for high-speed amplitude modulation atomic force microscopy is a high-bandwidth amplitude estimation technique. Conventional techniques, such as RMS to DC conversion and the lock-in amplifier, have proven useful, but offer limited measurement bandwidth and are not suitable for high-speed imaging. Several groups have developed techniques, but many of these are either difficult to implement or lack robustness. In this contribution, we briefly outline existing amplitude estimation methods and propose a new high-bandwidth estimation technique, inspired by techniques employed in microwave and RF circuit design, which utilizes phase cancellation to significantly improve the performance of the lock-in amplifier. We conclude with the design and implementation of a custom circuit to experimentally demonstrate the improvements and discuss its application in high-speed and multifrequency atomic force microscopy

332

Optical Sideband Generation: a Longitudinal Electron Beam Diagnostic Beyond the Laser Bandwidth Resolution Limit  

Energy Technology Data Exchange (ETDEWEB)

Electro-optic sampling (EOS) is widely used as a technique to measure THz-domain electric field pulses such asthe self-fields of femtosecond electron beams. We present an EOS-based approach for single-shot spectral measurement that excels in simplicity (compatible with fiber integration) and bandwidth coverage (overcomes the laser bandwidth limitation), allowing few-fs electron beams or single-cycle THz pulses to be characterized with conventional picosecond probes. It is shown that the EOS-induced optical sidebands on the narrow-bandwidth optical probe are spectrally-shifted replicas of the THz pulse. An experimental demonstration on a 0-3 THz source is presented.

Lawrence Berkeley National Laboratory; Tilborg, J. van; Matlis, N. H.; Plateau, G. R.; Leemans, W. P.

2010-06-01

333

Non-stationary 1D Thin Bed Model for Non-stationary Frequency Bandwidth Expansion Algorithms  

Directory of Open Access Journals (Sweden)

Full Text Available Seismic resolution has always been a quest of a geophysicist to obtain detailed structural and stratigraphic information from the seismic data. New algorithm developed for frequency bandwidth expansion are usually tested on stationary thin bed models before their implementation on real seismic data. These models are created by using the Ricker or Rayleigh criterion. But seismic wavelet is non-stationary, which changes its shape, amplitude and frequency contents as the wave propagates subsurface. A new technique is presented in this paper to create non-stationary thin bed model where the frequency bandwidth of the seismic wavelet decreases smoothly. The study describes the comprehensive mathematical formulation of new technique and testing of new bandwidth expansion algorithms like Differential Resolution and Short Time Fourier Transform Half Cepstrum for their effectiveness for non-stationary and stationary thin bed models.

M. Sajid

2014-01-01

334

Silicon waveguide infrared photodiodes with >35 GHz bandwidth and phototransistors with 50 AW-1 response.  

Science.gov (United States)

SOI CMOS compatible Si waveguide photodetectors are made responsive from 1100 to 1750 nm by Si+ implantation and annealing. Photodiodes have a bandwidth of >35 GHz, an internal quantum efficiency of 0.5 to 10 AW-1, and leakage currents of 0.5 nA to 0.5 microA. Phototransistors have an optical response of 50 AW-1 with a bandwidth of 0.2 GHz. These properties are related to carrier mobilities in the implanted Si waveguide. These detectors exhibit low optical absorption requiring lengths from <0.3 mm to 3 mm to absorb 50% of the incoming light. However, the high bandwidth, high quantum efficiency, low leakage current, and potentially high fabrication yields, make these devices very competitive when compared to other detector technologies. PMID:19333283

Geis, M W; Spector, S J; Grein, M E; Yoon, J U; Lennon, D M; Lyszczarz, T M

2009-03-30

335

Bandwidth Efficient Multicasting Operation in AODV Protocol for Mobile Ad-Hoc Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Multicasting technique provides an important service for improving throughput, bandwidth and delay of distributed systems and applications. In unicast and broadcast transmissions there is wastage of bandwidth, so multicasting transmission approach is used to deliver the data from sender to group of destinations. Reactive routing protocol is used for the route establishment from source to destination only when it is required. AODV and DSR are the reactive routing protocols which uses flooding approach for establishing the route from source to destination. In this approach network resource like bandwidth, node energy has been wasted. To overcome this problem, flooding approach will be replaced with the multicasting approach and outcomes are efficient in reducing delay, improving throughput.

Gurpreet Singh Bagga

2014-04-01

336

Optical Sideband Generation: a Longitudinal Electron Beam Diagnostic Beyond the Laser Bandwidth Resolution Limit  

International Nuclear Information System (INIS)

Electro-optic sampling (EOS) is widely used as a technique to measure THz-domain electric field pulses such asthe self-fields of femtosecond electron beams. We present an EOS-based approach for single-shot spectral measurement that excels in simplicity (compatible with fiber integration) and bandwidth coverage (overcomes the laser bandwidth limitation), allowing few-fs electron beams or single-cycle THz pulses to be characterized with conventional picosecond probes. It is shown that the EOS-induced optical sidebands on the narrow-bandwidth optical probe are spectrally-shifted replicas of the THz pulse. An experimental demonstration on a 0-3 THz source is presented.

337

Analysis of Blocking Rate and Bandwidth Usage of Mobile IPTV Services in Wireless Cellular Networks  

Science.gov (United States)

Mobile IPTV services over wireless cellular networks become more and more popular, owing to the significant growth in access bandwidth of wireless cellular networks such as 3G/4G and WiMAX. However, the spectrum resources of wireless cellular networks is rare. How to enhance the spectral efficiency of mobile networks becomes an important issue. Unicast, broadcast, and multicast are the most important transport schemes for offering mobile IPTV services over wireless cellular networks. Therefore, bandwidth usages and blocking rates of unicast, broadcast, and multicast IPTV services were analyzed and compared in this paper. Simulations were also conducted to validate the analytical results. Numerical results demonstrate that the presented analysis is correct, and multicast scheme achieves the best bandwidth usage and blocking rate performance, relative to the other two schemes. PMID:25379521

Li, Mingfu

2014-01-01

338

Multichannel optical filters with an ultranarrow bandwidth based on sampled Brillouin dynamic gratings.  

Science.gov (United States)

We first propose a multichannel optical filter with an ultra-narrow 3-dB bandwidth based on sampled Brillouin dynamic gratings (SBDGs). The multichannel optical filter is generated when an optical pulse interfaces with an optical pulse train based on an ordinary stimulated Brillouin scattering (SBS) process in a birefringent optical fiber. Multichannel optical filter based on SBDG is generated with a 3-dB bandwidth from 12.5 MHz to 1 GHz. In addition, a linearly chirped SBDG is proposed to generate multichannel dispersion compensator with a 3-dB bandwidth of 300 MHz and an extremely high dispersion value of 432 ns/nm. The proposed multichannel optical filters have important potential applications in the optical filtering, multichannel dispersion compensation and optical signal processing. PMID:24663752

Guo, Jin-Jin; Li, Ming; Deng, Ye; Huang, Ningbo; Liu, Jianguo; Zhu, Ninghua

2014-02-24

339

An optimized bandwidth efficient demand assigned protocol for integrated Mobile Satellite Services  

Science.gov (United States)

This paper describes the design of a demand assigned protocol based on bandwidth efficiency for integrated services of a Mobile Satellite System (MSS). An MSS provides data (closed-ended) and voice (open-ended) communications services for a large number of mobile users dispersed over a wide geographical area. Each mobile requests its desired service through a designated set of channels to a network management center. Either pure or slotted ALOHA random access scheme can be used to make connection requests, while data and voice communications are demand assigned. All channels have equal bandwidth and can be adaptively used for reservation requests, data connections or voice connections to maximize the bandwidth utilization. In this paper, perfect communications channels are assumed. It has been shown that, for the case considered, using the slotted ALOHA scheme for making connection requests can save about 30 percent on the total number of channels over using the pure ALHOA scheme.

Yan, T.-Y.; Wang, C. C.

1985-01-01

340

Bandwidth Impacts of Localizing Peer-to-Peer IP Video Traffic in Access and Aggregation Networks  

Directory of Open Access Journals (Sweden)

Full Text Available This paper examines the burgeoning impact of peer-to-peer (P2P traffic IP video traffic. High-quality IPTV or Internet TV has high-bandwidth requirements, and P2P IP video could severely strain broadband networks. A model for the popularity of video titles is given, showing that some titles are very popular and will often be available locally; making localized P2P attractive for video titles. The bandwidth impacts of localizing P2P video to try and keep traffic within a broadband access network area or within a broadband access aggregation network area are examined. Results indicate that such highly localized P2P video can greatly lower core bandwidth usage.

Kenneth Kerpez

2008-10-01

 
 
 
 
341

Bandwidth Impacts of Localizing Peer-to-Peer IP Video Traffic in Access and Aggregation Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract This paper examines the burgeoning impact of peer-to-peer (P2P traffic IP video traffic. High-quality IPTV or Internet TV has high-bandwidth requirements, and P2P IP video could severely strain broadband networks. A model for the popularity of video titles is given, showing that some titles are very popular and will often be available locally; making localized P2P attractive for video titles. The bandwidth impacts of localizing P2P video to try and keep traffic within a broadband access network area or within a broadband access aggregation network area are examined. Results indicate that such highly localized P2P video can greatly lower core bandwidth usage.

Kerpez Kenneth

2008-01-01

342

Low-Bandwidth Channel Quality Indication for OFDMA Frequency Domain Packet Scheduling  

DEFF Research Database (Denmark)

 In this paper, we study methods for lowering the bandwidth needed for the UE to transmit channel quality indication (CQI) for time and frequency domain scheduling (FDPS) in OFDMA. We consider smart compression methods, such as threshold based indication, to only include scheduler-relevant information in the CQI. We find that a 60-70% CQI bandwidth reduction is possible with less than 5-10% impact on scheduling performance. Further, we consider the impact of lowering the CQI reporting rate on both mobility performance and increased measuring accuracy due to longer averaging interval. We find that FDPS can provide around 30-45% gain for the UTRAN long-term evolution (aka 3.9G) with a CQI reporting bandwidth as low as 10 kbit/s in a 20MHz system (3-10 km/h).

Kolding, Troels E.; Frederiksen, Frank

2007-01-01

343

Design and Simulation of Microstrip E-shaped Patch Antenna for Improved Bandwidth and Directive Gain  

Directory of Open Access Journals (Sweden)

Full Text Available Despite the many advantages of microstrip patch antennas, they do have some considerable drawbacks. One of the main limitations with patch antennas is their inherently narrowband performance due to its resonant nature. With bandwidth as low as a few percent; broadband applications using conventional patch designs are limited. So for the antenna miniaturization and bandwidth improvement E-shaped microstrip patch antenna used. In this paper, authors cover two aspects of microstrip antenna designs. The first is the analysis of single element narrowband rectangular microstrip antenna which operates at the central frequency of 6.5GHz. The second aspect is the analysis and design of slot cut E-shaped microstrip antenna. The simulation process has been done through high frequency structure simulator (HFSS. The properties of antenna such as bandwidth, return loss, VSWR has been investigated and compared between a single element rectangular and E-shaped microstrip antenna.

Prof. Jaikaran Singh

2014-03-01

344

Increased-bandwidth in ultrashort-pulse measurement using an angle-dithered nonlinear-optical crystal.  

Science.gov (United States)

We show that the usual phase-matching-bandwidth constraint in ultrashort-laser-pulse measurement techniques is overly restrictive. Specifically, the phase-matching bandwidth need not exceed the pulse bandwidth on every pulse. Instead, only the phase-matching bandwidth integrated over the measurement period need exceed the pulse bandwidth. We show that angle-dithering a second-harmonic-generation crystal that is otherwise too narrowband (that is, too thick) can yield sufficient phase-matching bandwidth and an accurate pulse measurement. We apply this technique to frequency-resolved optical gating (FROG) and show that accurate pulse measurements can be made using a comparatively very thick and hence narrowband crystal. An additional advantage of using a thick crystal is increased signal strength. PMID:19407885

O'Shea, P; Kimmel, M; Gu, X; Trebino, R

2000-11-01

345

High efficiency and broad bandwidth grating coupler between nanophotonic waveguide and fibre  

International Nuclear Information System (INIS)

A high efficiency and broad bandwidth grating coupler between a silicon-on-insulator (SOI) nanophotonic waveguide and fibre is designed and fabricated. Coupling efficiencies of 46% and 25% at a wavelength of 1.55 ?m are achieved by simulation and experiment, respectively. An optical 3 dB bandwidth of 45 nm from 1530 nm to 1575 nm is also obtained in experiment. Numerical calculation shows that a tolerance to fabrication error of 10 nm in etch depth is achievable. The measurement results indicate that the alignment error of ±2 ?m results in less than 1 dB additional coupling loss. (classical areas of phenomenology)

346

Efficient Bandwidth Allocation for Integrated Services in Broadband Wireless ATM Networks  

DEFF Research Database (Denmark)

An efficient bandwidth allocation scheme is proposed for supporting intergrated services in wireless ATM networks. These include CBR, VBR amd ABR types of traffic. The proposed scheme is based om A-PRMA for carrying ATM traffic in a dynamic TDMA type access system. It allows mobile users to adjust the reserved bandwidth according to their current demands and the wireless channel status. Extensive simulation results show that the proposed scheme can provide QoS guarantees with low cell transfer delay, high channel utilization (more than 70 %) and short buffer length requirements.

Liu, Hong; Dittmann, Lars

1999-01-01

347

A BitTorrent-Based Dynamic Bandwidth Adaptation Algorithm for Video Streaming  

Science.gov (United States)

In this paper, we propose a BitTorrent-based dynamic bandwidth adaptation algorithm for video streaming. Two mechanisms to improve the original BitTorrent protocol are proposed: (1) the decoding order frame first (DOFF) frame selection algorithm and (2) the rarest I frame first (RIFF) frame selection algorithm. With the proposed algorithms, a peer can periodically check the number of downloaded frames in the buffer and then allocate the available bandwidth adaptively for video streaming. As a result, users can have smooth video playout experience with the proposed algorithms.

Hsu, Tz-Heng; Liang, You-Sheng; Chiang, Meng-Shu

348

Ionospheric effects on a wide-bandwidth, polarimetric, space-based, synthetic-aperture radar  

Energy Technology Data Exchange (ETDEWEB)

The earth's ionosphere consists of an ionized plasma which will interact with any electromagnetic wave propagating through it. The interaction is particularly strong at vhf and uhf frequencies but decreases for higher microwave frequencies. These interaction effects and their relationship to the operation of a wide-bandwidth, synthetic-aperture, space-based radar are examined. Emphasis is placed on the dispersion effects and the polarimetric effects. Results show that high-resolution (wide-bandwidth) and high-quality coherent polarimetrics will be very difficult to achieve below 1 GHz.

Brock, B.C.

1993-01-01

349

Ionospheric effects on a wide-bandwidth, polarimetric, space-based, synthetic-aperture radar  

Energy Technology Data Exchange (ETDEWEB)

The earth`s ionosphere consists of an ionized plasma which will interact with any electromagnetic wave propagating through it. The interaction is particularly strong at vhf and uhf frequencies but decreases for higher microwave frequencies. These interaction effects and their relationship to the operation of a wide-bandwidth, synthetic-aperture, space-based radar are examined. Emphasis is placed on the dispersion effects and the polarimetric effects. Results show that high-resolution (wide-bandwidth) and high-quality coherent polarimetrics will be very difficult to achieve below 1 GHz.

Brock, B.C.

1993-01-01

350

Why is the bandwidth of sodium observed to be narrower in photoemission experiments?  

CERN Document Server

The experimentally predicted narrowing in the bandwidth of sodium is interpreted in terms of the non-local self-energy effect on quasi-particle energies of the electron liquid. The calculated self-energy correction is a monotonically increasing function of the wavenumber variable. The usual analysis of photo-emission experiments assumes the final state energies on the nearly-free-electron-like model and hence it incorrectly ascribes the non-local self-energy correction to the final state energies to the occupied state energies, thus leading to a seeming narrowing in the bandwidth.

Yasuhara, H; Higuchi, M

1999-01-01

351

20 µm long slow-light Bragg reflector waveguide modulator with over 20 GHz modulation bandwidth  

Science.gov (United States)

A slow-light Bragg reflector waveguide optical modulator is designed and optimized for operations with a large modulation bandwidth and ultra-low power consumption. Devices with various modulator lengths are fabricated and characterized. Extinction ratios over 15 and 30 dB are obtained with reverse bias voltages below 1 and 1.5 V, respectively. In a 20 µm long modulator, a 3 dB modulation bandwidth exceeds 20 GHz with a bias voltage of only ?600 mV. The total energy consumption of the modulator is estimated to be lower than 100 fJ/bit, including both the load and dynamic power dissipations.

Gu, Xiaodong; Suzuki, Ayako; Matsutani, Akihiro; Koyama, Fumio

2014-11-01

352

Simple piezoelectric-actuated mirror with 180 kHz servo bandwidth  

CERN Document Server

We present a high bandwidth piezoelectric-actuated mirror for length stabilization of an optical cavity. The actuator displays a transfer function with a flat amplitude response and greater than 135$^\\circ$ phase margin up to 200 kHz, allowing a 180 kHz unity gain frequency to be achieved in a closed servo loop. To the best of our knowledge, this actuator has achieved the largest servo bandwidth for a piezoelectric transducer (PZT). The actuator should be very useful in a wide variety of applications requiring precision control of optical lengths, including laser frequency stabilization, optical interferometers, and optical communications.

Briles, Travis C; Cingoz, Arman; Schibli, Thomas; Ye, Jun

2010-01-01

353

Simple piezoelectric-actuated mirror with 180 kHz servo bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a high bandwidth piezoelectric-actuated mirror for length stabilization of an optical cavity. The actuator displays a transfer function with a flat amplitude response and greater than 135$^\\circ$ phase margin up to 200 kHz, allowing a 180 kHz unity gain frequency to be achieved in a closed servo loop. To the best of our knowledge, this actuator has achieved the largest servo bandwidth for a piezoelectric transducer (PZT). The actuator should be very useful in a wi...

Briles, Travis C.; Yost, Dylan C.; Cingoz, Arman; Schibli, Thomas; Ye, Jun

2010-01-01

354

A Novel Compact Microstrip Elliptical Patch Resonator Filter with Tunable Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available A novel elliptical patch resonator for a compact bandpass filter with tunable bandwidth is presented. This bandpass filter has the advantage of great flexibility in which the center frequency can be changed easily. The bandwidth of this filter can be modified by simply changing one variable, and this makes the proposed design unique. The order of the elliptical patch resonator can be increased, and three types of different orders of the same design are compared. The proposed filter can be used for future compact advanced wireless communication systems.

Ruwaybih Alsulami

2013-02-01

355

Frequency response and bandwidth in low-numerical-aperture step-index plastic optical fibers.  

Science.gov (United States)

By experimental measurement and from a numerical solution to the time-dependent power flow equation, the frequency response, bandwidth, mode coupling, and mode-dependent attenuation are determined for a low-numerical-aperture (NA) plastic optical fiber. Frequency response and bandwidth are specified as a function of fiber length. Numerical results are verified against experimental measurements. Mode coupling and modal attenuation are found to differ substantially between two fiber varieties of the same type (both low-NA, step-index, and plastic), implying their preferential suitability that is application-specific. PMID:25402786

Savovi?, Svetislav; Drlja?a, Branko; Kova?evi?, Milan S; Djordjevich, Alexandar; Baji?, Jovan S; Stupar, Dragan Z; Stepniak, Grzegorz

2014-10-20

356

Confidentiality & Authentication Mechanism for Biometric Information Transmitted over Low Bandwidth & Unreliable channel  

Directory of Open Access Journals (Sweden)

Full Text Available The security of bio-metric information – finger print, retina mapping, DNA mapping and some otherchemical and biological modified genes related information - transfer through low bandwidth andunreliable or covert channel is challenging task. Therefore, Security of biometric information is essentialrequirement in this fast developing communication world. Thus, in this paper, we propose efficient andeffective mechanism for confidentiality and authentication for biometric information transmitted by usingarithmetic encoding representation over low bandwidth and unreliable channel. It enhances the speed ofencryption, decryption and authentication process. It uses arithmetic encoding scheme and public keycryptography e.g. modified version of RSA algorithm called RSA-2 algorithm.

Raju Singh

2011-03-01

357

Optimal Streaming Protocol for VoD Using Clients' Residual Bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A true VoD system has tremendous demand in the market. The existing VoD system does not cater the needs and demands of the market. The major problem in the VoD system is serving of clients with expected QoS is difficult. In this paper, we proposed a protocol and algorithm that chains the proxy servers and subscribed clients. Our objective is to send one server stream and this stream should be served to N asynchronous clients. The server bandwidth is scarcity and on the client uplink bandwidth...

Ashok Kumar, R.; Hareesh, K.; Ganesan, K.; Manjaiah, D. H.

2010-01-01

358

Bandwidth and wavelength-tunable optical bandpass filter based on silicon microring-MZI structure  

DEFF Research Database (Denmark)

A novel and simple bandwidth and wavelength-tunable optical bandpass filter based on silicon microrings in a Mach-Zehnder interferometer (MZI) structure is proposed and demonstrated. In this filter design, the drop transmissions of two microring resonators are combined to provide the desired tunability. A detailed analysis and the design of the device are presented. The shape factor and extinction ratio of the filter are optimized by thermally controlling the phase difference between the two arms of the MZI. Simultaneous bandwidth and wavelength tunability with in-band ripple control is demonstrated by thermally tuning the resonance offset between the two microring resonators.

Ding, Yunhong; Pu, Minhao

2011-01-01

359

Low Voltage CMOS Fully Differential Current Feedback Amplifier with Controllable 3-dB Bandwidth  

International Nuclear Information System (INIS)

This paper presents a new CMOS fully differential current feedback operational amplifier with controllable 3-dB bandwidth suitable for analog data processing and acquisition applications. The FDCFOA has the advantage of a wide range controllable 3-dB bandwidth (?57 MHz to 500 MHz) without changing the feedback resistance this guarantee the stability of the circuit. The FDCFOA has a standby current of 320?A. PSpice simulations of the FDCFOA block were given using 0.25?m CMOS technology from AMI MOSIS and dual supply voltages ±0.75 V

360

A Scheduling Discipline for Latency and Bandwidth Guarantees in Asynchronous Network-on-Chip  

DEFF Research Database (Denmark)

Guaranteed services (GS) are important in that they provide predictability in the complex dynamics of shared communication structures. This paper discusses the implementation of GS in asynchronous Network-on-Chip. We present a novel scheduling discipline called Asynchronous Latency Guarantee (ALG) scheduling, which provides latency and bandwidth guarantees in accessing a shared media, e.g. a physical link shared between a number of virtual channels. ALG overcomes the drawbacks of existing scheduling disciplines, in particular the coupling between latency and bandwidth guarantees. A 0.12 &956;m CMOS standard cell implementation of an ALG link has been simulated. The operation speed of the design was 702 MDI/s.

Bjerregaard, Tobias; SparsØ, Jens

2005-01-01

 
 
 
 
361

Absorption line shape recovery beyond the detection bandwidth limit: application to the Boltzmann constant determination  

CERN Document Server

A theoretical model of the influence of detection bandwidth properties on observed line shapes in laser absorption spectroscopy is described. The model predicts artificial frequency shifts, extra broadenings and line asymmetries which must be taken into account in order to obtain accurate line parameters. The theoretical model is validated by experiments performed on H2O and NH3 molecular lines recorded by precision laser spectroscopy. Particular emphasis is put on the detection bandwidth adjustments required to perform a spectroscopic determination of the Boltzmann constant at the 1 ppm level of accuracy.

Rohart, François; Sow, Papa Lat Tabara; Tokunaga, Sean K; Chardonnet, Christian; Darquié, Benoît; Dinesan, H; Fasci, E; Castrillo, A; Gianfrani, L; Daussy, Christophe

2014-01-01

362

Tunable Bandwidth Third Order Switched-Capacitor with Multiple Feedbacks Filter for Different Center Frequencies  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes third order tunable bandwidth active Switched-Capacitor filter. The circuit consists of only op-amps and switched capacitors. The circuit is designed for circuit merit factor Q = 10. The proposed circuit implements three filter functions low pass, band pass and high pass simultaneously in single circuit. The filter circuit can be used for both narrow as well as for wide bandwidth. For various values of cut-off frequencies the behaviour of circuit is studied. The circuit works properly only for higher central frequencies, when f0 > 10 kHz.

Sanjay R. Bhagat

2010-04-01

363

Gap-Coupling: A Potential Method for Enhancing the Bandwidth of Microstrip Antennas  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a technical review on gap-coupled microstrip antennas is presented. The gap-coupled microstrip antennas give a large bandwidth as compared to the conventional microstrip antennas. The method of bandwidth enhancement using gap-coupled microstrip antennas has been elaborated. The gap-coupled microstrip antennas also produce two resonances. The dual frequency operation of the gap-coupled microstrip antenna is also described. A research overview of gap-coupled microstrip antennas, challenges, types of gap-coupled microstrip antennas as well as numerical methods of calculating various parameters of the gap-coupled microstrip antennas are discussed in this paper.

G. Singh

2012-04-01

364

Wide-bandwidth, meandering vibration energy harvester with distributed circuit board inertial mass  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A wide-bandwidth, meandering piezoelectric vibration energy harvester is presented for the first time utilizing the sensor node electronics as a distributed inertial mass. The energy harvester achieves an experimental maximum power output of 198 mu W when excited with a peak acceleration of 0.2 g (where 1 g is 9.8 m/s(2)) at 35 Hz. The output power remains higher than half of the maximum power (99 mu W) for the frequency band from 34.4 to 42 Hz, achieving a half-power fractional bandwidth of ...

Berdy, David F.; Jung, Byunghoo; Rhoads, Jeff F.; Peroulis, Dimitrios

2012-01-01

365

System identification requirements for high-bandwidth rotorcraft flight control system design  

Science.gov (United States)

The application of system identification methods to high-bandwidth rotorcraft flight control system design is examined. Flight test and modeling requirements are illustrated using flight test data from a BO-105 hingeless rotor helicopter. The proposed approach involves the identification of nonparametric (transfer function and state space) model identification. Results for the BO-105 show the need for including coupled body/rotor flapping and lead-lag dynamics in the identification model structure to allow the accurate prediction of control ssytem bandwidth limitations.

Tischler, Mark B.

1991-01-01

366

Confidentiality & Authentication Mechanism for Biometric Information Transmitted over Low Bandwidth & Unreliable channel  

CERN Document Server

The security of bio-metric information - finger print, retina mapping, DNA mapping and some other chemical and biological modified genes related information - transfer through low bandwidth and unreliable or covert channel is challenging task. Therefore, Security of biometric information is essential requirement in this fast developing communication world. Thus, in this paper, we propose efficient and effective mechanism for confidentiality and authentication for biometric information transmitted by using arithmetic encoding representation over low bandwidth and unreliable channel. It enhances the speed of encryption, decryption and authentication process. It uses arithmetic encoding scheme and public key cryptography e.g. modified version of RSA algorithm called RSA-2 algorithm.

Singh, Raju

2011-01-01

367

New methods for bandwidth enhancement of integrated high-sensitivity optical receivers  

Science.gov (United States)

Optoelectronic integrated circuits (OEICs) offering high bandwidth and high sensitivity as well are needed for the pickups of optical storage systems of the next generation, such as Blu-Ray or HDDVD. High bandwidth is necessary to enable high data transfer rates between the disk and the processing device, and high sensitivity allows to operate at low optical power and to deal with the lower efficiency of the photodiodes for blue light. Two methods will be presented to increase the bandwidth of the OEIC while maintaining high sensitivity. The first approach reduces the parasitic capacitance by placing the feedback resistor in a low-doped region. By this way the parasitic capacitance of the resistor is combined in series with the small depletion-layer capacitance of the low-doped region, which results in a drastically reduced effective capacitance. Using this method the 3dB-frequency of a standard one-stage transimpedance amplifier is increased by 55% from 67MHz to 104MHz. In the second approach the feedback resistor is replaced by a network that consists of two resistive voltage dividers that are coupled via a capacitor. Using such a capacitive-coupled voltage divider (CCVD) the feedback path is split into a low- and a high-frequency path and the effective band-limiting RC-constant is reduced. A bandwidth of 378MHz could be achieved. With a measured transimpedance of 212k? this results in a GBW of 80.3THz?.

Seidl, C.; Dietrich, H.; Nemecek, A.; Knorr, J.; Swoboda, R.; Zimmermann, H.

2005-07-01

368

An Improved QoS Multipath Routing Using Bandwidth Estimation and Rate Adaptation  

Directory of Open Access Journals (Sweden)

Full Text Available Mobile Adhoc Networks (MANETs are composed of nodes which communicate with one another without network infrastructure. Their advantage being that they can be used in isolation or along with wired infrastructure, usually via a gateway node to ensure traffic relay for both networks. Quality of Service (QoS is harder to ensure in ad hoc networks than in other network types, as wireless bandwidth is shared by adjacent nodes with network topology changing as nodes move. Most QoS protocols are implemented for specific scenarios and consider parameters such as network topologies, bandwidth, mobility, security and so on. This work proposes a novel multipath routing protocol which is an extension of AOMDV by discovering routes based on available bandwidth and rate adaptation. The method with Hello message box is used to calculate available bandwidth for a route. Relative Fairness and Optimized Throughput is an approach for rate adaptation in this paper which is to ensure fairness and allow nodes to adapt transmission rates and contention windows to channel quality. In sequence this is determined by calculating the access probability of a channel for each node in a distributed manner approximating successful and failed transmissions.

S. Suganya

2014-06-01

369

Final Report on LDRD Project: High-Bandwidth Optical Data Interconnects for Satellite Applications  

Energy Technology Data Exchange (ETDEWEB)

This report describes the research accomplishments achieved under the LDRD Project ''High-Bandwidth Optical Data Interconnects for Satellite Applications.'' The goal of this LDRD has been to address the future needs of focal-plane-array (FPA) sensors by exploring the use of high-bandwidth fiber-optic interconnects to transmit FPA signals within a satellite. We have focused primarily on vertical-cavity surface-emitting laser (VCSEL) based transmitters, due to the previously demonstrated immunity of VCSELs to total radiation doses up to 1 Mrad. In addition, VCSELs offer high modulation bandwidth (roughly 10 GHz), low power consumption (roughly 5 mW), and high coupling efficiency (greater than -3dB) to optical fibers. In the first year of this LDRD, we concentrated on the task of transmitting analog signals from a cryogenic FPA to a remote analog-to-digital converter. In the second year, we considered the transmission of digital signals produced by the analog-to-digital converter to a remote computer on the satellite. Specifically, we considered the situation in which the FPA, analog-to-digital converter, and VCSEL-based transmitter were all cooled to cryogenic temperatures. This situation requires VCSELs that operate at cryogenic temperature, dissipate minimal heat, and meet the electrical drive requirements in terms of voltage, current, and bandwidth.

SERKLAND, DARWIN K.; GEIB, KENT M.; BLANSETT, ETHAN L.; KARPEN, GARY D.; PEAKE, GREGORY M.; HARGETT, TERRY; MONTANO, VICTORIA; SULLIVAN, CHARLES T.; ALLERMAN, ANDREW A.; RIENSTRA, JEFFREY L.

2003-04-01

370

Effects of Stimulus Bandwidth on the Imitation of English Fricatives by Normal-Hearing Children  

Science.gov (United States)

Purpose: Recent studies from the authors' laboratory have suggested that reduced audibility in the high frequencies (because of the bandwidth of hearing instruments) may play a role in the delays in phonological development often exhibited by children with hearing impairment. The goal of the current study was to extend previous findings on the…

Stelmachowicz, Patricia G.; Nishi, Kanae; Choi, Sangsook; Lewis, Dawna E.; Hoover, Brenda M.; Dierking, Darcia; Lotto, Andrew

2008-01-01

371

Performance of a High-Concentration Erbium-Doped Fiber Amplifier with 100 nm Amplification Bandwidth  

International Nuclear Information System (INIS)

Increasing demand for higher bandwidth has driven the need for higher Wavelength Division Multiplexing (WDM) channels. One of the requirements to achieve this is a broadband amplifier. This paper reports the performance of a broadband, compact, high-concentration and silica-based erbium-doped fiber amplifier. The amplifier optimized to a 2.15 m long erbium-doped fiber with erbium ion concentration of 2000 ppm. The gain spectrum of the amplifier has a measured amplification bandwidth of 100 nm using a 980 nm laser diode with power of 150 mW. This silica-based EDFA shows lower noise figure, higher gain and wider bandwidth in shorter wavelengths compared to Bismuth-based EDFA with higher erbium ion concentration of 3250 ppm at equivalent EDF length. The silica-based EDF shows peak gain at 22 dB and amplification bandwidth between 1520 nm and 1620 nm. The lowest noise figure is 5 dB. The gain is further improved with the implementation of enhanced EDFA configurations.

372

Investigation of bandwidth, efficiency, and quality factor for circular patch antennas with magneto-dielectric substrate  

DEFF Research Database (Denmark)

This article documents an investigation of the effect of a magneto-dielectric substrate on the performance of a circular patch antenna; in particular, the radiation efficiency, the quality factor, and the bandwidth. Both analytical and numerical methods have been used to model the patch antenna. The numerical method is used for lossy substrates, while the analytical method is used for lossless substrates.

Nour, Baqer; Breinbjerg, Olav

2011-01-01

373

Understanding the Theory and Practice of Molecular Spectroscopy: The Effects of Spectral Bandwidth  

Science.gov (United States)

The near-UV spectrum of benzene is used to illustrate the effects of variations in instrument spectral bandwidth on absorbance and molar absorptivity measurements and on the independence of values of quantities such as the oscillator strength that are based on integrated absorptivity. Excel-based computer simulations are provided that help develop…

Hirayama, Satoshi; Steer, Ronald P.

2010-01-01

374

Bandwidth selection for multivariate density derivative estimation, with applications to clustering and bump hunting  

CERN Document Server

In a recent paper, Chac\\'on, Duong and Wand (2011) provided an asymptotic analysis for kernel estimation of multivariate density derivatives of arbitrary order. However, that paper did not address in detail the most important topic for any kernel estimator in practice, that is, the choice of the bandwidth. In the multivariate context there are different levels of sophistication on the bandwidth matrix to be used in the estimator. The simplest parameterization of such a bandwidth, consisting of a positive scalar multiple of the identity matrix, is easier to analyze from a mathematical point of view, but its lack of flexibility can lead to a substantial loss in terms of efficiency, which worsens as the order of the derivative increases, as compared to the most general parameterization, using a symmetric positive definite matrix. Here we present three new methods which allow for an automatic (data-dependent) selection of the bandwidth matrix within the most general class of matrices. We study their theoretical a...

Chacón, José E

2012-01-01

375

Efficient "Pure" Blue OLEDs Employing Tetradentate Pt Complexes with a Narrow Spectral Bandwidth.  

Science.gov (United States)

Efficient deep-blue-emitting tetradentate platinum complexes with a narrow spectral bandwidth are presented, which demonstrate CIEx ? 0.15 and CIEy organic light-emitting diode (OLED) with 24.8% peak external quantum efficiency and CIE coordinates of (0.147, 0.079) is fabricated using PtON7-dtb. PMID:25207726

Fleetham, Tyler; Li, Guijie; Wen, Lele; Li, Jian

2014-11-01

376

A low-noise PLL design achieved by optimizing the loop bandwidth  

International Nuclear Information System (INIS)

This paper describes a low-noise phase-locked loop (PLL) design method to achieve minimum jitter. Based on the phase noise properties extracted from the transistor, and the low-pass or high-pass transfer characteristics of different noise sources to the output, an optimal loop bandwidth design method, derived from a continuous-time PLL model, further improves the jitter characteristics of the PLL. The described method not only finds the optimal loop-bandwidth to minimize the overall PLL jitter, but also achieves optimal loop-bandwidth by changing the value of the resistor or charge pump current. In addition, a phase-domain behavioral model in ADS is presented for accurately predicting improved jitter performance of a PLL at system level. A prototype PLL designed in a 0.18?m CMOS technology is used to investigate the accuracy of the theoretical predictions. The simulation shows significant performance improvement by using the proposed method. The simulated RMS and peak-to-peak jitter of the PLL at the optimal loop-bandwidth are 10.262 ps and 46.851 ps, respectively. (semiconductor integrated circuits)

377

A dynamic bandwidth and phase linearity measurement technique for 4-channel MSK VLF antenna systems  

Science.gov (United States)

This paper presents a method for performing dynamic measurements of antenna bandwidth and phase linearity parameters for VLF transmitter systems. These measurements were undertaken in support of both National and NATO VLF MSK upgrade programs and relate to VLF transmitting antenna characteristics required in order to comply with STANAG 5030.

Harrington, M. D.

1993-05-01

378

On the selection of a sampling filter bandwidth for a digital data detector.  

Science.gov (United States)

Consideration of the problem of selecting a low-pass sampling bandwidth for the digital mechanization of a matched-filter bit-synchronizer combination. An attempt is made to determine how large a data rate can be provided for a fixed sampling rate (limited by hardware considerations on the sampling device) without paying an excessive penalty in SNR performance.

Simon, M. K.

1972-01-01

379

Gain-switched, Yb-doped, all-fiber laser with narrow bandwidth  

DEFF Research Database (Denmark)

We demonstrate that an all-fiber, narrow bandwidth, high pulse energy pulsed laser can be constructed from commercially available components by applying gain-switching. After single-stage amplification the pulses are frequency doubled in ppSLT with high efficiency.

Larsen, Casper; Giesberts, Martin

2013-01-01

380

4Bs or Not 4Bs: Bricks, Bytes, Brains, and Bandwidth  

Science.gov (United States)

The effective integration of planning to include bricks, bytes, brains, and bandwidth (the 4Bs) represents an opportunity for community colleges to extend their capacity as knowledge-intensive organizations, coupling knowledge, technology, and learning. Integration is important to ensure that the interplay among organizations, agents within them,…

Treat, Tod

2011-01-01

 
 
 
 
381

Effect of transmitter positions on channel bandwidth in diffuse indoor multi-transmitter optical wireless systems.  

Science.gov (United States)

We describe an accurate method to estimate the channel impulse response in diffuse indoor multi-transmitter optical wireless systems. We compare our method with the ceiling bounce method extended for multiple transmitters. Our results show that the channel bandwidth depends not only on the horizontal separation between the transmitter and the receiver, but also on their actual positions.

Arumugam, Sivabalan; John, Joseph

2005-11-01

382

Electroencephalographic effects of ketamine on power, cross-frequency coupling and connectivity in the alpha bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available Recent studies of propofol-induced unconsciousness have identified characteristic properties of electroencephalographic alpha rhythms that may be mediated by drug activity at ?-aminobutyric acid (GABA receptors in the thalamus. However, the effect of ketamine, a non-GABAergic anesthetic drug, on alpha oscillations has not been systematically evaluated. We analyzed the electroencephalogram of 28 surgical patients during consciousness and ketamine-induced unconsciousness with a focus on frontal power, frontal cross-frequency coupling, frontal-parietal functional connectivity (measured by coherence and phase lag index, and frontal-to-parietal directional connectivity (measured by directed phase lag index in the alpha bandwidth. Unlike past studies of propofol, ketamine-induced unconsciousness was not associated with increases in the power of frontal alpha rhythms, characteristic cross-frequency coupling patterns of frontal alpha power and slow-oscillation phase, or decreases in coherence in the alpha bandwidth. Like past studies of propofol using undirected and directed phase lag index, ketamine reduced frontal-parietal (functional and frontal-to-parietal (directional connectivity in the alpha bandwidth. These results suggest that directional connectivity changes in the alpha bandwidth may be state-related markers of unconsciousness induced by both GABAergic and non-GABAergic anesthetics.

Stefanie Blain-Moraes

2014-07-01

383

Bandwidth increase by controlled angular dispersion of signal beam in optical parametric amplification.  

Science.gov (United States)

Angular dispersion of the signal beam inside the nonlinear media is introduced to improve the non-collinear phase-matching range. Simulations run for BBO crystals predict that bandwidth increase is possible for most of the application spectral range and that it can surpass one order of magnitude in some particular configurations. PMID:19483830

Cardoso, Luis; Figueira, Gonçalo

2004-07-12

384

Modelamiento y análisis de pequeña señal de un generador de inducción y un STATCOM conectados a un sistema de potencia / Modeling and analysis of a small signal of an induction generator and a STATCOM connected to a power system  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish En este documento se presenta el modelamiento y análisis de pequeña señal de un generador de inducción (IG) y un compensador síncrono estático (STATCOM), conectados a un barraje infinito, que representa un sistema de potencia; el IG es modelado como un sistema de quinto orden y se le acopla un STATC [...] OM que es estudiado como un modelo de primer orden. El comportamiento dinámico fue simulado y comparado usando MATLAB/Simulink, bajo dos condiciones de perturbación: una variación en el torque de la máquina y una variación en la tensión del barraje infinito debido a un fallo en este punto. Las respuestas obtenidas por el software reflejan que el compensador actúa de forma adecuada, contrarrestando variaciones en potencia y tensión. Cabe resaltar que se debe agregar una etapa de sintonización de parámetros para mejorar las respuestas obtenidas. Abstract in english This paper presents the modeling and small-signal analysis of an induction generator (IG) and a static synchronous compensator (STATCOM) connected to an infinite bus bar, representing a power system, the IG is modeled as ffith-order system and is coupled to a STATCOM is studied as a model of first o [...] rder. The dynamic behavior was simulated and compared using MATLAB/ Simulink, two conditions of disturbance: a variation in the torque of the machine and a variation in the infinite bus bar voltage because of a failure at this point. The responses obtained by the software show that the compensator acts appropriately counteracting power and voltage variations. Significantly, it must add a stage of tuning parameters to improve the responses.

Carlos David, Zuluaga Ríos; Alfonso, Alzate Gómez.

2011-07-01

385

Ambient and Cryogenic, Decade Bandwidth, Low Noise Receiving System for Radio Astronomy Using Sinuous Antenna  

Science.gov (United States)

Traditionally, radio astronomy receivers have been limited to bandwidths less than an octave, and as a result multiple feeds and receivers are necessary to observe over a wide bandwidth. Next generation of instruments for radio astronomy will benefit greatly from reflector antenna feeds that demonstrate very wide instantaneous bandwidth, and exhibit low noise behavior. There is an increasing interest in wideband systems from both the cost and science point of view. A wideband feed will allow simultaneous observations or sweeps over a decade or more bandwidth. Instantaneous wide bandwidth is necessary for detection of short duration pulses. Future telescopes like square kilometer array (SKA), consisting of 2000 to 3000 coherently connected antennas and covering a frequency range of 70 MHz to 30 GHz, will need decade bandwidth single pixel feeds (SPFs) along with integrated LNAs to achieve the scientific objectives in a cost effective way. This dissertation focuses on the design and measurement of a novel decade bandwidth sinuous-type, dual linear polarized, fixed phase center, low loss feed with an integrated LNA. A decade bandwidth, low noise amplifier is specially designed for noise match to the higher terminal impedance encountered by this antenna yielding an improved sensitivity over what is possible with conventional 50 O amplifiers. The self-complementary, frequency independent nature of the planar sinuous geometry results in a nearly constant beam pattern and fixed phase center over more than a 10:1 operating frequency range. In order to eliminate the back-lobe response over such a wide frequency range, we have projected the sinuous pattern onto a cone, and a ground plane is placed directly behind the cone's apex. This inverted, conical geometry assures wide bandwidth operation by locating each sinuous resonator a quarter wavelength above the ground plane. The presence of a ground plane near a self complementary antenna destroys the self complementary nature of the composite structure resulting in frequency dependent impedance variations. We demonstrate, using simulations and measurements, how the return loss can be improved by modifying the sinuous geometry. The feed-LNA combination is characterized for important properties such as return loss, system noise, far field beam patterns including cross-polarization over a wide frequency range. The system is developed as a feed for a parabolic reflector. The overall system performance is calculated in terms of the A/Tsys ratio. A cryogenic version would have a direct impact on specialized observing applications requiring large instantaneous bandwidths with high sensitivity. A novel cryogenic implementation of this system is demonstrated using a Stirling cycle, one-stage refrigerator. The cryocooler offers advantages like low cost, light weight, small size, low power consumption, and does not require routine maintenance. The higher antenna input impedance and a balanced feeding method for the sinuous antenna offers a unique set of challenges when developing a cryogenic system.

Gawande, Rohit Sudhir

386

Fourier-transform electron spin resonance with bandwidth-compensated chirp pulses  

Science.gov (United States)

Electron spin echo experiments using chirp pulses at X-band around 9 GHz have been performed with a home-built spectrometer based on an arbitrary waveform generator. Primary echoes without phase dispersion were obtained by employing the Böhlen-Bodenhausen scheme with the refocusing pulse being half as long as the coherence-generating pulse. To account for physical bandwidth limitation by the resonator, the instantaneous sweep rate of the chirps was adapted to the spectrometer’s frequency response function, which can be recorded from the sample under study within a few minutes. Such bandwidth-compensated chirp pulses are experimentally shown to achieve an almost uniform excitation bandwidth that exceeds the resonator bandwidth. This uniform excitation allows for computing frequency-domain spectra by Fourier-transformation (FT) of the echo signal. For a nitroxide in dilute solid solution with a spectral width of 200 MHz, the FT EPR spectrum agrees remarkably well with a field-swept echo-detected EPR spectrum. The overall spectral perturbation for operation far beyond the resonator bandwidth was characterized by acquiring a 700 MHz wide spectral range of a copper (II) EPR spectrum with nearly uniform amplitude with excitation and refocusing pulses of 200 and 100 ns, respectively. Furthermore, peculiarities were observed in solid-state FT EPR spectra of disordered systems. To understand these peculiarities two-dimensional data sets were acquired that correlate the FT EPR spectrum to inversion recovery or nuclear modulation. The echo envelope modulation experiments reveal echo decay rates increased by enhanced instantaneous diffusion and passage-specific effects in the nuclear modulations. The latter effect can be suppressed by nuclear modulation averaging. Apparent longitudinal relaxation times for a given subset of orientations are influenced by nuclear modulation effects. Proper extraction of orientation-dependent relaxation times thus requires an experimental setup that minimizes the modulations.

Doll, Andrin; Jeschke, Gunnar

2014-09-01

387

The effect of stimulus bandwidth on the nonlinear-derived tone-burst-evoked otoacoustic emission.  

Science.gov (United States)

Intermodulation distortion has been hypothesized as a mechanism contributing to the generation of short-latency (SL) components in the transient-evoked otoacoustic emission (TEOAE). Presumably, nonlinear interactions between the frequency components within the evoking stimulus induce cochlear distortion products, which mix in the cochlea and ear canal with reflected energy from each stimulus-frequency's tonotopic place. The mixing of these different components is evidenced in the bandpass-filtered emission waveform as a series of different latency peaks. The current study tested the hypothesis that intermodulation distortion, induced within the spectral bandwidth of the evoking stimulus, is the primary mechanism through which the SL components are generated. The nonlinear-derived tone-burst-evoked OAE (TBOAEnl) was evoked using 2-kHz tone bursts with durations of 3, 6, 12, and 24 cycles. As tone burst duration doubled, the spectral bandwidth was halved. It was hypothesized that contributions to the TBOAEnl from SL components would decrease as tone burst duration increased and spectral bandwidth decreased, if the SL components were generated through intermodulation distortion. Despite differences in spectral bandwidth between the evoking stimuli, the latencies and magnitudes of the different latency components between the 3- and 6-cycle TBOAEnl were comparable. The 12- and 24-cycle TBOAEnl envelopes were characteristic of destructive phase interactions between different latency components overlapping in time. The different latency components in the 3- and 6-cycle TBOAEnl introduced a characteristic level dependency to TBOAEnl magnitude and latency when analyzed across a broad time window spanning the different components. A similar dependency described the 12- and 24-cycle TBOAEnl input/output and latency-intensity functions, suggesting that the SL components evident in the shorter-duration TBOAEnl equally contributed to the longer-duration TBOAEnl, despite reductions in spectral bandwidth. The similarity between the different TBOAEnl suggests that they share a common generation mechanism and casts doubt on intermodulation distortion as the generation mechanism of SL TEOAE components in humans. PMID:25245497

Lewis, James D; Goodman, Shawn S

2014-12-01

388

Low Voltage, High Bandwidth & Input Impedance CMOS Differential Amplifier at NANO Scale  

Directory of Open Access Journals (Sweden)

Full Text Available Since analog circuits have proved primarily essential in many of today’s high complex performance systems. This paper demonstrate designing and simulation of low power CMOS technology based differential amplifier at nano scale of different channel length(45nm,32nm,22nm via applying various supply voltages i.e. 1.1V, 0.95V , 0.9V respectively. Here the high input impedance, low power dissipation circuit is mainly characterized in terms of common mode rejection ratio (CMRR, voltage gain and gain band width product .The input impedance calculated are in the range of 190 G? (giga ohm, cut off frequency (-3db approximately greater than 50 MHz (mega hertz and average power dissipation in the order of less than 130 ?w (micro watt. The simulation result shows that all transistors are operated in saturation region, with this unique behavior of MOSFET transistor operating in this region not only allows a designer to work at a low voltage but also at a high frequency. Finally, the analog design consists of low operating voltages via very deep sub micron (nano scale technology.. The simulation is carried out using PTM Low Power 45nm, 32nm, & 22nm Metal Gate / High-K / Strained-Si technology with H-spice. A Matlab tool is also used to plot the graph of various parameters at different channel length in two dimensions (2-D.

Adil Zaidi

2013-05-01

389

Design of zone-based bandwidth management scheme in IEEE 802.16 multi-hop relay networks  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract IEEE 802.16 Wireless Network technology is a hot research issue in recent years. It provides wider coverage of radio and higher speed wireless access, and Quality-of-Service plays an important part in the standard. For mobile multi-hop wireless network, IEEE 802.16j/MR network not only can supply large area wireless deployment, but also can provide high quality network service to mobile users. Although Mobile QoS supporting has been extensively investigated, Mobile QoS supporting in the IEEE 802.16-MR network is relatively unexplored. In this article, the probability of a mobile user who visits a Relay Station (RS is known beforehand. With the visiting probability at each RS and the system specified size of the range for bandwidth allocation, Base Station (BS can calculate the required bandwidth to meet the mobile user's demand and allocate appropriate bandwidth for a mobile user roaming in the range of the bandwidth allocation. The range of bandwidth allocation for mobile users is called the Zone in this article, which includes the user's current RS and the nearby RSs. The proposed scheme is therefore called Zone-based bandwidth management scheme. The simulation results demonstrate that Zone-based bandwidth management scheme can reduce QoS degradation and bandwidth re-allocation overhead.

Chen Kuo-Yang

2011-01-01

390

All-optical characterization of large-signal modulation bandwidth of a monolithically integrated DFB-EA  

DEFF Research Database (Denmark)

We use an all-optical method to characterize the modulation bandwidth of a DFB-EA designed for 100 Gb/s Ethernet. In a large-signal wavelength conversion set-up, we show the device has an all-optical bandwidth of 83 GHz.

Blaaberg, SØren; Mulvad, Hans Christian Hansen

2009-01-01

391

A Novel Optical Vector Spectral Analysis Technique Employing a Limited-Bandwidth Detector  

Directory of Open Access Journals (Sweden)

Full Text Available A new technique for obtaining frequency-dependent magnitude and phase information across an optical channel is presented using tunable allpass optical filters and a detector with a small bandwidth relative to the full channel width. This technique has application to optical monitoring of intersymbol interference distortions, including chromatic and polarization-mode dispersion effects, and thus can provide vector information for input to the control of adaptive optical filters. A method for generating a test signal spanning the spectrum of a modulated data signal without introducing intersymbol interference is discussed. This technique can also be used to characterize an optical pulse source and does not scale in complexity or cost as the bandwidth of the source increases.

Madsen CK

2005-01-01

392

Mott insulating state in a quarter-filled two-orbital Hubbard chain with different bandwidths  

International Nuclear Information System (INIS)

We investigate the ground-state properties of the one-dimensional two-band Hubbard model with different bandwidths. The density-matrix renormalization group method is applied to calculate the averaged electron occupancies n as a function of the chemical potential ?. Both at quarter and half fillings, 'charge plateaux' appear in the n-? plot, where d?/dn diverges and the Mott insulating states are realized. To see how the orbital polarization in the one-quarter charge plateau develops, we apply the second-order perturbation theory from the strong-coupling limit at quarter filling. The resultant Kugel-Khomskii spin-orbital model includes a magnetic field coupled to orbital pseudo-spins. This field originates from the discrepancy between the two bandwidths and leads to a finite orbital pseudo-spin magnetization.

393

A Tandem Communication Network with Dynamic Bandwidth Allocation and Modified Phase Type Transmission having Bulk Arrivals  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with the performance evaluation of a two node communication network with dynamic bandwidth allocation and modified phase type transmission having bulk arrivals. The performance of the statistical multiplexing is measured by approximating with the compound Poisson process and the transmission completions with Poisson processes. It is further assumed that the transmission rate at each node are adjusted depending upon the content of the buffer which is connected to it. The packets transmitted through the first node may be forwarded to the buffer connected to the second node or get terminated with certain probabilities. The performance measures of the network like, mean content of the buffers, mean delays, throughput, transmitter utilization etc. are derived explicitly under transient conditions. Sensitivity analysis with respect to the parameters is also carried through numerical illustration. It is observed that the dynamic bandwidth allocation and batch size distribution of arrivals has a tremendous influence on the performance measures.

Kuda Nageswara Rao

2010-07-01

394

Anamorphic Spectrum Transform and its Application to Time-Bandwidth Compression  

CERN Document Server

A mathematical transform for compressing the time-bandwidth product of analog signals is introduced. As one of its applications, this physics-based signal grooming allows a conventional digitizer to sample and digitize the analog signal with variable resolution. The net result is that frequency components that were beyond the digitizer bandwidth can now be captured and, at the same time, the total digital data volume is reduced. This analog compression is loss-less and is made possible because the proposed transformation, performed prior to sampling, causes more samples to be allocated to higher frequencies, where they are needed, and less to lower frequencies, where they are redundant. Our method is inspired by operation of Fovea centralis in human eye and by anamorphic transformation in visual arts. The proposed transform can also be performed in digital domain as a data compression algorithm to alleviate the storage and transmission bottlenecks of big data.

Asghari, Mohammad H

2013-01-01

395

Linearized SQUID Array (LISA) for High Bandwidth Frequency-Domain Readout Multiplexing  

CERN Document Server

We have designed and demonstrated a Superconducting Quantum Interference Device (SQUID) array linearized with cryogenic feedback. To achieve the necessary loop gain a 300 element series array SQUID is constructed from three monolithic 100-element series arrays. A feedback resistor completes the loop from the SQUID output to the input coil. The short feedback path of this Linearized SQUID Array (LISA) allows for a substantially larger flux-locked loop bandwidth as compared to a SQUID flux-locked loop that includes a room temperature amplifier. The bandwidth, linearity, noise performance, and dynamic range of the LISA are sufficient for its use in our target application: the multiplexed readout of transition-edge sensor bolometers.

Lanting, T; Spieler, H; Lee, A T; Yamamoto, Y

2009-01-01

396

Linearized superconducting quantum interference device array for high bandwidth frequency-domain readout multiplexing  

Science.gov (United States)

We have designed and demonstrated a superconducting quantum interference device (SQUID) array linearized with cryogenic feedback. To achieve the necessary loop gain, a 300-element series array SQUID is constructed from three monolithic 100-element series arrays. A feedback resistor completes the loop from the SQUID output to the input coil. The short feedback path of this linearized SQUID array (LISA) allows for a substantially larger flux-locked loop bandwidth as compared to a SQUID flux-locked loop that includes a room temperature amplifier. The bandwidth, linearity, noise performance, and 3 ?0 dynamic range of the LISA are sufficient for its use in our target application: the multiplexed readout of transition-edge sensor bolometers.

Lanting, T.; Dobbs, M.; Spieler, H.; Lee, A. T.; Yamamoto, Y.

2009-09-01

397

“Water window” sources: Selection based on the interplay of spectral properties and multilayer reflection bandwidth  

International Nuclear Information System (INIS)

Development of laser-produced plasma “water window” sources poses a major challenge in x-ray research and most effort has focused on line sources for use with zone plate optics. Here, a comparison of carbon and nitrogen line emission with that from both 3d – 4f and 4d – 4f unresolved transition arrays shows that, at power densities available from “table-top” solid-state lasers, 3d – 4f emission from zirconium plasmas is most intense, and calculations show that in an imaging system based on multilayer mirrors, for reflectance bandwidths >1% has superior performance than either line or broader-band sources. For bandwidths <1%, line sources are preferable.

398

Invariant bandwidth of erbium in ZnO-PbO-tellurite glasses: Local probe/model  

Energy Technology Data Exchange (ETDEWEB)

A series of [(70TeO{sub 2}?(30?x)ZnO?xPbO){sub 0.99}?(Er{sub 2}O{sub 3}){sub 0.01}; where x = 5, 10, 15 and 20] tellurite glasses, were prepared using the melt quenching technique. Crucial emission bandwidth of erbium at 1.5 ?m has been derived and found to be the same for all the glasses, irrespective of PbO content. This identical bandwidth in all tellurite glasses is attributed to the presence of erbium in tellurium rich disordered environments. This result has been complemented through XANES spectra and the obtained invariant first shell of 6.5 oxygen atoms, confirm the unchanged environment in these glasses for all PbO content.

Ramamoorthy, Raj Kumar [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad-500046 (India); Bhatnagar, Anil K., E-mail: anilb42@gmail.com [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad-500046, India and School of Physics, University of Hyderabad, Hyderabd-500046 (India)

2014-04-24

399

On Determining the Fair Bandwidth Share for ABR Connections in ATM Networks  

CERN Document Server

The ABR service is designed to fairly allocate the bandwidth unused by higher priority services. The network indicates to the ABR sources the rates at which they should transmit to minimize their cell loss. Switches must constantly measure the demand and available capacity, and divide the capacity fairly among the contending connections. In order to compute the fair and efficient allocation for each connection, a switch needs to determine the effective number of active connections. In this paper, we propose a method for determining the number of active connections and the fair bandwidth share for each. We prove the efficiency and fairness of the proposed method analytically, and simulate it by incorporating it into the ERICA switch algorithm.

Fahmy, S; Kalyanaraman, S; Goyal, R K; Vandalore, B R; Fahmy, Sonia; Jain, Raj; Kalyanaraman, Shivkumar; Goyal, Rohit; Vandalore, Bobby

1998-01-01

400

Terabit bandwidth-adaptive transmission using low-complexity format-transparent digital signal processing.  

Science.gov (United States)

In this paper, we propose a low-complexity format-transparent digital signal processing (DSP) scheme for next generation flexible and energy-efficient transceiver. It employs QPSK symbols as the training and pilot symbols for the initialization and tracking stage of the receiver-side DSP, respectively, for various modulation formats. The performance is numerically and experimentally evaluated in a dual polarization (DP) 11 Gbaud 64QAM system. Employing the proposed DSP scheme, we conduct a system-level study of Tb/s bandwidth-adaptive superchannel transmissions with flexible modulation formats including QPSK, 8QAM and 16QAM. The spectrum bandwidth allocation is realized in the digital domain instead of turning on/off sub-channels, which improves the performance of higher order QAM. Various transmission distances ranging from 240 km to 6240 km are demonstrated with a colorless detection for hardware complexity reduction. PMID:24663520

Zhuge, Qunbi; Morsy-Osman, Mohamed; Chagnon, Mathieu; Xu, Xian; Qiu, Meng; Plant, David V

2014-02-10

 
 
 
 
401

Fast random bit generation with bandwidth-enhanced chaos in semiconductor lasers.  

Science.gov (United States)

We experimentally demonstrate random bit generation using multi-bit samples of bandwidth-enhanced chaos in semiconductor lasers. Chaotic fluctuation of laser output is generated in a semiconductor laser with optical feedback and the chaotic output is injected into a second semiconductor laser to obtain a chaotic intensity signal with bandwidth enhanced up to 16 GHz. The chaotic signal is converted to an 8-bit digital signal by sampling with a digital oscilloscope at 12.5 Giga samples per second (GS/s). Random bits are generated by bitwise exclusive-OR operation on corresponding bits in samples of the chaotic signal and its time-delayed signal. Statistical tests verify the randomness of bit sequences obtained using 1 to 6 bits per sample, corresponding to fast random bit generation rates from 12.5 to 75 Gigabit per second (Gb/s) ( = 6 bit x 12.5 GS/s). PMID:20389568

Hirano, Kunihito; Yamazaki, Taiki; Morikatsu, Shinichiro; Okumura, Haruka; Aida, Hiroki; Uchida, Atsushi; Yoshimori, Shigeru; Yoshimura, Kazuyuki; Harayama, Takahisa; Davis, Peter

2010-03-15

402

Real-Time Multi-path Tracking of Probabilistic Available Bandwidth  

CERN Document Server

Applications such as traffic engineering and network provisioning can greatly benefit from knowing, in real time, what is the largest input rate at which it is possible to transmit on a given path without causing congestion. We consider a probabilistic formulation for available bandwidth where the user specifies the probability of achieving an output rate almost as large as the input rate. We are interested in estimating and tracking the network-wide probabilistic available bandwidth (PAB) on multiple paths simultaneously with minimal overhead on the network. We propose a novel framework based on chirps, Bayesian inference, belief propagation and active sampling to estimate the PAB. We also consider the time evolution of the PAB by forming a dynamic model and designing a tracking algorithm based on particle filters. We implement our method in a lightweight and practical tool that has been deployed on the PlanetLab network to do online experiments. We show through these experiments and simulations that our app...

Thouin, Frederic; Rabbat, Michael

2010-01-01

403

Invariant bandwidth of erbium in ZnO-PbO-tellurite glasses: Local probe/model  

International Nuclear Information System (INIS)

A series of [(70TeO2?(30?x)ZnO?xPbO)0.99?(Er2O3)0.01; where x = 5, 10, 15 and 20] tellurite glasses, were prepared using the melt quenching technique. Crucial emission bandwidth of erbium at 1.5 ?m has been derived and found to be the same for all the glasses, irrespective of PbO content. This identical bandwidth in all tellurite glasses is attributed to the presence of erbium in tellurium rich disordered environments. This result has been complemented through XANES spectra and the obtained invariant first shell of 6.5 oxygen atoms, confirm the unchanged environment in these glasses for all PbO content

404

Dual band-notched monopole antenna with enhanced bandwidth for ultra-wideband wireless communications  

Directory of Open Access Journals (Sweden)

Full Text Available A new configuration of an ultra-wideband (UWB dual band-notched antenna is presented. The designed geometry consists of octagonal radiating patch, a 50 ? microstrip feed-line on the front and an asymmetric partial ground on the back. For impedance bandwidth enhancement, a unilateral stepped structure is utilised on the ground. By etching two E-shaped slots connected to each other on the radiating patch and applying E-shaped defected ground structure on the back, dual notched bands are achieved. The antenna is printed on a low profile FR4 substrate with a compact size of 25 × 18 × 1 mm^3. The experimental results indicate that the antenna has an impedance bandwidth from 2.55 to 21.65 GHz for voltage standing wave ratio ?2, except the notched bands on worldwide interoperability for microwave access and wireless local area network bands. Moreover, stable radiation patterns and gains within the operating band are shown.

Mohammad Akbari

2014-08-01

405

High-Tc dc SQUID readout electronics with low noise and high bandwidth  

International Nuclear Information System (INIS)

Using AD797 low noise op amps and 2SA1048 low noise transistors, we have developed a composite preamplifier for use in dc SQUID readout electronics. This preamplifier has a small dc drift and super low noise at high frequencies. The equivalent input voltage noise of the preamplifier is about 0.35 nV/?Hz from 100 kHz to 10 MHz. Using this preamplifier, we developed dc SQUID readout electronics having low noise and high bandwidth. Used with a 3 mm2 high-Tc dc SQUID, the white flux noise was about 18 ??0/?Hz above 100 kHz and the FLL bandwidth was about 2 MHz. This readout electronics can be used for the applications of SQUID-based NDE and SQUID-based NQR

406

High-T{sub c} dc SQUID readout electronics with low noise and high bandwidth  

Energy Technology Data Exchange (ETDEWEB)

Using AD797 low noise op amps and 2SA1048 low noise transistors, we have developed a composite preamplifier for use in dc SQUID readout electronics. This preamplifier has a small dc drift and super low noise at high frequencies. The equivalent input voltage noise of the preamplifier is about 0.35 nV/{radical}Hz from 100 kHz to 10 MHz. Using this preamplifier, we developed dc SQUID readout electronics having low noise and high bandwidth. Used with a 3 mm{sup 2} high-T{sub c} dc SQUID, the white flux noise was about 18 {mu}{phi}{sub 0}/{radical}Hz above 100 kHz and the FLL bandwidth was about 2 MHz. This readout electronics can be used for the applications of SQUID-based NDE and SQUID-based NQR.

He, D.F. [Superconducting Materials Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)]. E-mail: he.dongfeng@nims.go.jp; Itozaki, H. [Superconducting Materials Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Graduate School of Science Engineering, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

2006-10-01

407

High- Tc dc SQUID readout electronics with low noise and high bandwidth  

Science.gov (United States)

Using AD797 low noise op amps and 2SA1048 low noise transistors, we have developed a composite preamplifier for use in dc SQUID readout electronics. This preamplifier has a small dc drift and super low noise at high frequencies. The equivalent input voltage noise of the preamplifier is about 0.35 nV/?Hz from 100 kHz to 10 MHz. Using this preamplifier, we developed dc SQUID readout electronics having low noise and high bandwidth. Used with a 3 mm 2 high- Tc dc SQUID, the white flux noise was about 18 ?? 0/?Hz above 100 kHz and the FLL bandwidth was about 2 MHz. This readout electronics can be used for the applications of SQUID-based NDE and SQUID-based NQR.

He, D. F.; Itozaki, H.

2006-10-01

408

Low Latency Wireless Ad-Hoc Networking: Power and Bandwidth Challenges and a Hierarchical Solution  

CERN Document Server

This paper is concerned with the scaling of the number of hops in a large scale wireless ad-hoc network (WANET), a quantity we call network latency. A large network latency affects all aspects of data communication in a WANET, including an increase in delay, packet loss, required processing power and memory. We consider network management and data routing challenges in WANETs with scalable network latency. On the physical side, reducing network latency imposes a significantly higher power and bandwidth demand on nodes, as is reflected in a set of new bounds. On the protocol front, designing distributed routing protocols that can guarantee the delivery of data packets within scalable number of hops is a challenging task. To solve this, we introduce multi-resolution randomized hierarchy (MRRH), a novel power and bandwidth efficient WANET protocol with scalable network latency. MRRH uses a randomized algorithm for building and maintaining a random hierarchical network topology, which together with the proposed r...

Sarshar, N; Roychowdhury, V P; Sarshar, Nima; Rezaei, Behnam A.; Roychowdhury, Vwani P.

2006-01-01

409

Real-time full bandwidth measurement of spectral noise in supercontinuum generation  

CERN Document Server

The ability to measure real-time fluctuations of ultrashort pulses propagating in optical fiber has provided significant insights into fundamental dynamical effects such as modulation instability and the formation of frequency-shifting rogue wave solitons. We report here a detailed study of real-time fluctuations across the full bandwidth of a fiber supercontinuum which directly reveals the significant variation in measured noise statistics across the spectrum, and which allows us to study correlations between widely separated spectral components. For two different propagation distances corresponding to the onset phase of spectral broadening and the fully-developed supercontinuum, we measure real time noise across the supercontinuum bandwidth, and we quantify the supercontinuum noise using statistical higher-order moments and a frequency-dependent intensity correlation map. We identify correlated spectral regions within the supercontinuum associated with simultaneous sideband generation, as well as signatures...

Wetzel, B; Larger, L; Lacourt, P A; Merolla, J M; Sylvestre, T; Kudlinski, A; Mussot, A; Genty, G; Dias, F; Dudley, J M; 10.1038/srep00882

2012-01-01

410

Tunable single Stokes extraction from 20??GHz Brillouin fiber laser using ultranarrow bandwidth optical filter.  

Science.gov (United States)

The individual extraction of a Brillouin Stokes line from a 20 GHz comb generated from the compact configuration of a multiwavelength Brillouin fiber ring laser configuration has been achieved using an ultranarrow bandwidth (UNB) optical filter. The narrowest bandwidth transmission of a UNB optical filter that is 50 pm is used in order to get particular Stokes. The Stokes filtered is in the wavelength range of 1549.768-1551.016 nm. High SNR within the range of 54.97-11.73 dB with almost nil peak power loss being obtained was monitored by a 0.16 pm optical spectrum analyzer, giving convincing results. Relatively, the proposed configuration could provide wide tunability and narrow selection of the Brillouin Stokes. PMID:25322403

Ahmad, H; Razak, N F; Zulkifli, M Z; Ismail, M F; Munajat, Y; Harun, S W

2014-10-10

411

An experimental study on the bandwidth and tunability of MSP-based one-way transmission  

Science.gov (United States)

We studied how the constitution parameters and applied bias magnetic field influence the bandwidth and frequency tunability of the one-way transmission (OWT) caused by magnetic surface plasmon resonance of the magnetic photonic crystals (MPC). We found that wide-band OWT could be obtained using ferrite rods with larger normalized radius and suppressing the bulk modes of MPC in the frequencies where the edge and bulk modes coexist. We verified that bias magnetic field tunes the frequencies of OWT but has little effects on its bandwidth by experiments, and a simple way is proposed to suppress the bulk modes by introducing air defect near the edge of the MPC and experimentally demonstrated its effectiveness. This work provides a way toward practical applications for wide-band tunable one-way devices.

Li, Zhen; Wu, Rui-xin; Poo, Yin; Li, Qing-bo; Liu, Rong-juan; Li, Zhi-yuan

2014-08-01

412

A novel microstrip patch antenna with large impedance bandwidth in VHF/UHF range  

Energy Technology Data Exchange (ETDEWEB)

In this paper a novel antenna is presented. This antenna, employing microstrip circular disc as radiator is seen to perform over a large impedance bandwidth ( 130MHz to 876 MHz). The disk resonator is loaded with L-C-R circuit across a selective location in the disk via a thin shorting pin. The theoretical modeling predicts TM01 mode of operation. Therefore the beam pattern shows a null in the broadside direction. The said antenna is proposed to be developed for end use in coal mine where the antenna can be flush mounted on coal strata. Thus it will be able to measure the angle of arrival of any reflective component due to presence of waterbed at a distance. The measured as well as simulated results regarding impedance bandwidth and beam pattern agrees well. The simulated efficiency using IE3D is 48% whereas measured efficiency is nearly 45%. 7 refs., 5 figs., 1 tab.

Chakravarty, T.; Roy, S.M.; Sanyal, S.K.; De, A. [Durgapur Institute for Advanced Technology & Management, Rajbandh (India)

2005-07-01

413

Linear and Nonlinear Analysis of Magnetic Bearing Bandwidth Due to Eddy Current Limitations  

Science.gov (United States)

Finite element analysis was used to study the bandwidth of alloy hyperco50a and silicon iron laminated rotors and stators in magnetic bearings. A three dimensional model was made of a heteropolar bearing in which all the flux circulated in the plane of the rotor and stator laminate. A three dimensional model of a plate similar to the region of a pole near the gap was also studied with a very fine mesh. Nonlinear time transient solutions for the net flux carried by the plate were compared to steady state time harmonic solutions. Both linear and quasi-nonlinear steady state time harmonic solutions were calculated and compared. The finite element solutions for power loss and flux bandwidth were compared to those determined from classical analytical solutions to Maxwell's equations.

Kenny, Andrew; Palazzolo, Alan

2000-01-01

414

Experimental demonstration of an improved EPON architecture using OFDMA for bandwidth scalable LAN emulation  

DEFF Research Database (Denmark)

We propose and demonstrate an improved Ethernet passive optical network (EPON) architecture supporting bandwidth-scalable physical layer local area network (LAN) emulation. Due to the use of orthogonal frequency division multiple access (OFDMA) technology for the LAN traffic transmission, there is no need to change the existing EPON architecture. Only one receiver at each optical network unit (ONU) is required to detect both LAN traffic and EPON downstream traffic, which makes the proposed system simple and cost-effective. Moreover, flexible assignment of LAN traffic bandwidth is realized by allocating different number of subcarriers or using different modulation formats. The 250Mb/s 4-quadrature amplitude modulation (4-QAM) and 500Mb/s 16-QAM OFDM LAN traffic are successfully emulated with the EPON traffic in our experiment.

Deng, Lei; Zhao, Ying

2011-01-01

415

Three-Pole Tunable Bandpass Filters With Constant Fractional Bandwidth Using Mixed Comb-line Resonators  

Science.gov (United States)

A novel three-pole tunable bandpass filter using mixed combline resonators with a center frequency band of 0.9-1.8 GHz is proposed in this paper. The varactor-tuned filter is designed on a Rogers substrate with ?r = 2.2 and h = 1 mm, with 1-dB fractional bandwidth of 11% ± 0.6% (absolute bandwidth 97 MHz to 187.2 MHz). Its insertion loss is varying from 4.58 dB to 2.86 dB and return loss is better than 10 dB within the tuning frequency range. The measured third-order inter-modulation intercept point and 1-dB power compression point at midband (1.35 GHz) are higher than 17 and 8 dBm, respectively. The measured results show good agreement with the simulated ones.

Zhao, Zhiyuan; Chen, Jiang; Yang, Lin; Chen, Kunhe

2014-09-01

416

Interference and Bandwidth Adjusted (ETX) in Wireless Multi-hop Networks  

CERN Document Server

In this paper, we propose a new quality link metric, interference and bandwidth adjusted ETX (IBETX) for wireless multi-hop networks. As MAC layer affects the link performance and consequently the route quality, the metric therefore, tackles the issue by achieving twofold MAC-awareness. Firstly, interference is calculated using cross-layered approach by sending probes to MAC layer. Secondly, the nominal bit rate information is provided to all nodes in the same contention domain by considering the bandwidth sharing mechanism of 802.11. Like ETX, our metric also calculates link delivery ratios that directly affect throughput and selects those routes that bypass dense regions in the network. Simulation results by NS-2 show that IBETX gives 19% higher throughput than ETX and 10% higher than Expected Throughput (ETP). Our metric also succeeds to reduce average end-to-end delay up to 16% less than Expected Link Performance (ELP) and 24% less than ETX.

Javaid, Nadeem; Djouani, Karim

2010-01-01

417

Solid-State Laser Source of Tunable Narrow-Bandwidth Ultraviolet Radiation  

Science.gov (United States)

A solid-state laser source of tunable and narrow-bandwidth UV light is disclosed. The system relies on light from a diode laser that preferably generates light at infrared frequencies. The light from the seed diode laser is pulse amplified in a light amplifier, and converted into the ultraviolet by frequency tripling, quadrupling, or quintupling the infrared light. The narrow bandwidth, or relatively pure light, of the seed laser is preserved, and the pulse amplifier generates high peak light powers to increase the efficiency of the nonlinear crystals in the frequency conversion stage. Higher output powers may be obtained by adding a fiber amplifier to power amplify the pulsed laser light prior to conversion.

Goldberg, Lew; Kliner, Dahv A.; Koplow, Jeffrey P.

1998-01-01

418

Terahertz bandwidth RF spectrum analysis of femtosecond pulses using a chalcogenide chip.  

Science.gov (United States)

We report the first demonstration of the use of an RF spectrum analyser with multi-terahertz bandwidth to measure the properties of femtosecond optical pulses. A low distortion and broad measurement bandwidth of 2.78 THz (nearly two orders of magnitude greater than conventional opto-electronic analyzers) was achieved by using a 6 cm long As(2)S(3) chalcogenide waveguide designed for high Kerr nonlinearity and near zero dispersion. Measurements of pulses as short as 260 fs produced from a soliton-effect compressor reveal features not evident from the pulse's optical spectrum. We also applied an inverse Fourier transform numerically to the captured data to re-construct a time-domain waveform that resembled pulse measurement obtained from intensity autocorrelation. PMID:19466183

Pelusi, M D; Vo, T D; Luan, F; Madden, S J; Choi, D-Y; Bulla, D A P; Luther-Davies, B; Eggleton, B J

2009-05-25

419

Experimental demonstration of an improved EPON architecture using OFDMA for bandwidth scalable LAN emulation  

Science.gov (United States)

We propose and demonstrate an improved Ethernet passive optical network (EPON) architecture supporting bandwidth-scalable physical layer local area network (LAN) emulation. Due to the use of orthogonal frequency division multiple access (OFDMA) technology for the LAN traffic transmission, there is no need to change the existing EPON architecture. Only one receiver at each optical network unit (ONU) is required to detect both LAN traffic and EPON downstream traffic, which makes the proposed system simple and cost-effective. Moreover, flexible assignment of LAN traffic bandwidth is realized by allocating different number of subcarriers or using different modulation formats. The 250 Mb/s 4-quadrature amplitude modulation (4-QAM) and 500 Mb/s 16-QAM OFDM LAN traffic are successfully emulated with the EPON traffic in our experiment.

Deng, Lei; Zhao, Ying; Yu, Xianbin; Arlunno, Valeria; Borkowski, Robert; Liu, Deming; Monroy, Idelfonso Tafur

2011-12-01

420

BANDWIDTH AND GAIN INCREMENT OF MICROSTRIP PATCH ANTENNA WITH SHIFTED ELLIPTICAL SLOT  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes the increment in Bandwidth and Gain of Rectangular Microstrip Patch antenna with Shifted Elliptical slot. First we have designed a Rectangular microstrip patch antenna. After that an elliptical slot is cut inside a rectangular patch which is shifted towards right. The results of both the designs are compared and it was found that an increase in the bandwidth of 21% and gain of 7.21 dBi is being achieved as that of a simple Rectangular microstrip patch antenna. Microstrip patch antenna is designed on a Duroid 5880 substrate with a dielectric constant of 2.2. The antenna is fed by a Coaxial probe feed. The antenna designs and performances are analyzed using Zealand IE3D software. The antenna can be used for many modern communication systems.

ISHA PURI

2011-07-01

 
 
 
 
421

0.77-V drive voltage electro-optic modulator with bandwidth exceeding 67??GHz.  

Science.gov (United States)

A 0.77-V drive voltage (V?) electro-optic modulator with bandwidth exceeding 67 GHz is described. Modulator is a compound semiconductor device fabricated using substrate removal technology. This allows placement of metal electrodes on both sides of an optical waveguide containing a p-i-n diode. Hence ohmic losses are reduced significantly. Electrode gap is essentially the same as i layer thickness, which can be kept very uniform and small. Waveguide core also contains a MQW, which improves electro-optic efficiency. Lack of p doping in the waveguide and large detuning between MQW absorption peak and operating wavelength keep the propagation loss low. Large size of the waveguide also helps to keep coupling loss low. Modulator is designed as a traveling wave device using the loaded line approach, which is used for velocity matching. Combination of these approaches yields a device with the lowest V? and widest bandwidth. PMID:25361159

Dogru, Selim; Dagli, Nadir

2014-10-15

422

On the Cell Breathing Technique to Reduce Congestion Applying Bandwidth Limitation  

Directory of Open Access Journals (Sweden)

Full Text Available In order to effectively analyze or evaluate the performance of Wireless Local Area Networks (WLANs, it is important to identify what types of network settings can cause bad performance in the network when analyzing poor network performance, there is an important factor which is responsible for poor performance is when a number of users may obtain a much larger share of the available bandwidth in access point in a limited boundary as provided in the concept of cell breathing technique. In this paper, we proposed a new concept in which we can set bandwidth limitation so that no user can access data more than the specified limit for a particular access point. In this way the different users will get an efficient access over the network.

Parminder Kaur

2012-04-01

423

Narrow-bandwidth solar upconversion: design principles, efficiency limits, and case studies  

CERN Document Server

We employ a detailed balance approach to model a single-junction solar cell with a realistic narrow-band, non-unity-quantum-yield upconverter. As upconverter bandwidths are increased from 0 to 0.5 eV, maximum cell efficiencies increase from the Shockley-Queisser limit of 30.58% to over 43%. Such efficiency enhancements are calculated for upconverters with near-infrared spectral absorption bands, readily accessible with existing upconverters. While our model shows that current bimolecular and lanthanide-based upconverting materials will improve cell efficiencies by <1%, cell efficiencies can increase by several absolute percent with increased upconverter quantum yield - even without an increased absorption bandwidth. By examining the efficiency limits of a highly realistic solar cell-upconverter system, our model provides a platform for optimizing future solar upconverter designs.

Briggs, Justin A; Dionne, Jennifer A

2013-01-01

424

Multiuser Joint Energy-Bandwidth Allocation with Energy Harvesting - Part II: Multiple Broadcast Channels & Proportional Fairness  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we consider the energy-bandwidth allocation for a network with multiple broadcast channels, where the transmitters access the network orthogonally on the assigned frequency band and each transmitter communicates with multiple receivers orthogonally or non-orthogonally. We assume that the energy harvesting state and channel gain of each transmitter can be predicted for $K$ slots {\\em a priori}. To maximize the weighted throughput, we formulate an optimization p...

Wang, Zhe; Aggarwal, Vaneet; Wang, Xiaodong

2014-01-01

425

Human performance decrements associated with the bandwidth of laser protective eyewear concepts  

Science.gov (United States)

Protecting the eye from coherent light sources is of critical concern to both military and civilian laser users. Laser protective eyewear degrades visual performance. Common and emerging applications use lasers emitting at numerous wavelengths or single lasers emitting at multiple wavelengths. Protection against multiple wavelengths increases the difficulty in selecting or building protective eyewear and concomitantly usually increases the performance penalty. Pursuit tracking performance decrements were measured as a function of bandwidth and peak wavelength transmission for 12 bandpass filters. Eight volunteers tracked a target subtending 34 milliradians (mrad) at a constant velocity of 5 mrad/sec for 15 sec. The target traversed an arc located 5 m from the tracker. Each volunteer received two training days and two test days. Twelve bandpass filters, with bandwidths of 10, 25, 40, and 70 nm, and peak wavelengths of 450, 550, and 650 nm were randomly inserted into the optics of the tracker. No volunteer received all 4 bandwidths of one peak wavelength on either test day, thereby reducing any adaptational effect. Luminance was equated across filters using Neutral Density (ND) filters. An ND filter of equal Optical Density served as the control. The total luminance at the eye was 0.8 cd/m2. Trials were collected at a rate of 4 per filter. The 10 nm blue filter elicited the poorest performance, followed by the 25, 40, and 70 nm blue filters. The red filters enhanced performance across all but the narrowest bandwidth. It can be assumed that the blue end of the visible spectrum with it's `forward of the retina' focusing properties and the low number of blue photoreceptors are responsible for the large decrements. Current philosophy in laser eye protection is to allow as much of the blue end of the spectrum through a filter to preserve scotopic transmission. The shortwave transmission may inadvertently increase error rates for visual tasks.

Molchany, Jerome W.; Lund, David J.

1996-04-01

426

A controllable bandwidth filter using varactor-loaded metamaterial-inspired transmission lines  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This letter presents a tunable bandwidth bandpass filter based on varactor-loaded metamaterial coplanar waveguide (CPW) lines. The CPW lines are based on series gaps and split-ring resonators. The varactors are reverse-biased semiconductor diodes connected between both sides of each series gap. This configuration, directly inspired from the so-called metamaterial technology, takes advantage of the high dispersion of the loaded transmission line. Therefore, strong permitti...

Lucas Borja, Alejandro; Carbonell Olivares, Jorge; Marti?nez Pe?rez, Jorge Daniel; Boria Esbert, Vicente Enrique; Lippens, Didier

2011-01-01

427

Why is the bandwidth of sodium observed to be narrower in photoemission experiments?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The experimentally predicted narrowing in the bandwidth of sodium is interpreted in terms of the non-local self-energy effect on quasi-particle energies of the electron liquid. The calculated self-energy correction is a monotonically increasing function of the wavenumber variable. The usual analysis of photo-emission experiments assumes the final state energies on the nearly-free-electron-like model and hence it incorrectly ascribes the non-local self-energy correction to th...

Yasuhara, H.; Yoshinaga, S.; Higuchi, M.

1999-01-01

428

A millimeter unilateral finline SIS mixer with a wide IF bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Superconductor-Insulator-Superconductor (SIS) tunnel junction mixers are now commonly used in as- tronomical receivers at (sub)millimeter wavelengths because of their superb sensitivity, high dynamic range and stability of operation. Niobium SIS mixers operating at frequencies well below the super- conducting gap (?680 GHz) have already achieved quantum limited sensitivity. Therefore to further enhance the receiver sensitivity, increasing the Intermediate Frequency (IF) bandwidth of SIS ...

Zhou, Yangjun; Yassin, Ghassan

2013-01-01

429

Magnetic Field Enhancement of Dielectronic Recombination from a Continuum of Finite Bandwidth  

Energy Technology Data Exchange (ETDEWEB)

We have examined dielectronic recombination of Ba{sup +} and e{sup {minus}} from a continuum of finite bandwidth. Applying magnetic fields of up to 240thinspthinspG perpendicular to small electric fields from 0.1 to 5thinspthinspV/cm increases the recombination rate, while applying the magnetic field parallel to the electric field does not change the rate. The largest magnetic field enhancement observed was approximately 50{percent} . {copyright} {ital 1999} {ital The American Physical Society }

Klimenko, V.; Ko, L.; Gallagher, T.F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22901 (United States)

1999-11-01

430

Human Medial Olivocochlear Reflex: Effects as Functions of Contralateral, Ipsilateral, and Bilateral Elicitor Bandwidths  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Animal studies have led to the view that the acoustic medial olivocochlear (MOC) efferent reflex provides sharply tuned frequency-specific feedback that inhibits cochlear amplification. To determine if MOC activation is indeed narrow band, we measured the MOC effects in humans elicited by 60-dB sound pressure level (SPL) contralateral, ipsilateral, and bilateral noise bands as a function of noise bandwidth from 1/2 to 6.7 octaves. MOC effects were quantified by the change in stimulus frequenc...

Lilaonitkul, Watjana; Guinan, John J.

2009-01-01

431

Bandwidth Enhancement of a Microstrip Line-Fed Rotated Slot Antenna with a Parasitic Center Patch  

Directory of Open Access Journals (Sweden)

Full Text Available With day to day advancement wireless and communication industry, a single device needs to operate at multi frequency and enormous high bandwidth. Microstrip antenna is only to fit in this. A small rotated square slot antenna with a parasitic patch for bandwidth enhancement is proposed and investigated. A simple 50- microstrip line is used to excite the slot. A rotated square slot resonator with center parasitic patch is considered as reference geometry. The rotated square slot antenna exhibits two resonances .By embedding a parasitic patch into the center of the rotated square slot, the lower resonant frequency is decreased and the higher resonant frequency is increased. Thus, broadband characteristic of the wide-slot antenna is achieved. The measured results demonstrate that this structure exhibits a wide impedance bandwidth, which is over 85% for dB ranging from 2.19 to 5.95 GHz. Also, a stable and Omni directional radiation pattern is observed within the operating bandwidth. In this design, a smaller ground plane is considered compared to the reference antenna (rotated square slot antenna with the parasitic center patch. The proposed antenna has a strong application in UWB and WiMax devices. The IEEE 802.16 working group has been established a new operating band name as Worldwide Interoperability for Microwave access (WiMax. WiMax has three allocated frequency bands. The low band (2.5-2.69 GHz, the middle band (3.2-3.8 GHz and the upper band (5.2-5.8 GHz.

SHILPA VERMA, SHALINI SHAH, PAURUSH BHULANIA

2013-06-01

432

High-bandwidth fiber-optic system using laser-diode transmitters  

International Nuclear Information System (INIS)

A system has been developed to transmit analog signals through 1-km-long fiber-optic cables having bandwidths up to 1.5 GHz. Semiconductor injection laser-diode transmitters operating at a wavelength of about 815 nm are directly modulated by electrical signals from radiation detectors. Graded-index optical fibers transmit the optical signals to a remote facility, where they are recorded on a single streak camera

433

Maximizing Utilization and Performance of Guaranteed-Bandwidth Long Fat Networks and Virtual Circuits  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Like many big science projects, the Large Synoptic Survey Telescope (LSST) has multiple geographic locations among which large amounts of data must be transferred. One particular type of data, crosstalk-corrected images, must be moved from South America to North America under stringent deadline requirements. LSST is provisioning an international network with bandwidth guarantees to handle this traffic. In prior work, we re-examined TCP congestion control for this use case an...

Freemon, D. Michael

2014-01-01

434

Bandwidth enhancement : correcting magnitude and phase distortion in wideband piezoelectric transducer systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Acoustic ultrasonic measurements are widespread and commonly use transducers exhibiting resonant behaviour due to the piezoelectric nature of their active elements, being designed to give maximum sensitivity in the bandwidth of interest. We present a characterisation of such transducers that provides both magnitude and phase information describing the way in which the receiver responds to a surface displacement over its frequency range. Consequently, these devices work efficien...

Assous, Said; Rees, John; Lovell, Mike; Linnett, Laurie; Gunn, David

2011-01-01

435

Investigation of Bandwidth Requirement of Smart Meter Network Using OPNET Modeler  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Smart meter networks are the backbone for smart electrical distribution grid. Smart meter network requires the bidirectional communications medium and interoperability capability. As thousands of meters are interconnected in the smart meter network, it is vital to select an appropriate communication bandwidth to facilitate real-time two-way information flows and this will also allow further uptake of greenhouse-friendly technology options and enhance energy security. Optimized Network Enginee...

Rahman, M.; Amanullah Mto

2013-01-01

436

Bandwidth Enrichment for Micro-strip Patch Antenna Using Pendant Techniques  

Directory of Open Access Journals (Sweden)

Full Text Available A probe feed, slotted hexagonal patch antenna has been proposed. Bandwidth enhancement has been improved by suitably cutting slots into hexagonal patch.Proposed antenna is suitable for various telecoms, LAN, WiFi applications in ISM-band. It is demonstrated that the proposed antenna exhibits resonance in ISM-Band and a peak gain of 6dBi.The antenna structure is described and simulated results are presented.

Dr. D. Bhattacharya, R. Prasanna

2013-08-01

437

Controlling the nuclear polarization in quantum dots using optical pulses with a modest bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We show that detuned optical pulse trains with a modest spectral width can polarize nuclear spins in InAs quantum dots. The pulse bandwidth is large enough to excite a coherent superposition of both electron spin eigenstates in these negatively charged dots but narrow enough to give partial spectral selectivity between the eigenstates. The coherent precession of electron spin states and periodic excitation focuses the nuclear spin distribution, producing a discrete set of pr...

Carter, S. G.; Economou, Sophia E.; Shabaev, A.; Bracker, A. S.

2011-01-01

438

Optical memory bandwidth and multiplexing capacity in the erbium telecommunication window  

CERN Document Server

We study the bandwidth and multiplexing capacity of an erbium-doped optical memory for quantum storage purposes. We concentrate on the protocol ROSE (Revival of a Silenced Echo) because it has the largest potential multiplexing capacity. Our analysis is applicable to other protocols that involve strong optical excitation. We show that the memory performance is limited by instantaneous spectral diffusion and we describe how this effect can be minimised to achieve optimal performance.

Dajczgewand, Julian; Böttger, Thomas; Louchet-Chauvet, Anne; Gouët, Jean-Louis Le; Chanelière, Thierry

2014-01-01

439

Endfire microstrip log periodic patch antenna having 3-1 bandwidth capability  

Science.gov (United States)

A novel wideband microstrip antenna using a series fed linear array of patch resonators in a log periodic arrangement is described. The antenna produces an endfire beam and can be designed to operate over any 3 to 1 bandwidth in the frequency range 1 to 18 GHz (VSWR less than 2.2). The radiation characteristics are similar to those of a log periodic array of half wave dipoles in free space. The antenna can be easily fabricated using printed circuit techniques.

Jairam, H.; Gilman, D.

440

High-efficiency, wide-bandwidth optical fanout elements in dichromated gelatin.  

Science.gov (United States)

We have combined the flexibility of computer-generated binary holograms with the high optical quality of dichromated gelatin holography to fabricate a range of efficient, wide-bandwidth, and compact space-invariant fanout elements. Our approach is based on a certain novel coherent spatial filtering technique, termed the inverse central dark ground method, which permits the use of a binary-amplitude hologram corresponding to the desired binaryphase profile in the object arm of the interferometric recording setup. PMID:19768050

Robertson, B; Taghizadeh, M R; Turunen, J; Vasara, A

1990-06-15

 
 
 
 
441

Beam Tilt and Angular Dispersion in Broad-Bandwidth, Nanosecond Optical Parametric Oscillators  

Energy Technology Data Exchange (ETDEWEB)

We show that the signal and idler beams generated by certain types of unseeded, nanosecond optical parametric oscillators are tilted and angularly dispersed and have anomalously large bandwidths. This effect is demonstrated in both laboratory measurements and a numerical model. We show how the optical cavity design influences the tilts and how they can be eliminated or minimized. We also determine the conditions necessary to injection seed these parametric oscillators.