WorldWideScience
1

Small Signal Loudspeaker Impedance Emulator  

DEFF Research Database (Denmark)

Specifying the performance of audio amplifiers is typically done by playing sine waves into a pure ohmic load. However real loudspeaker impedances are not purely ohmic but characterized by the mechanical resonance between the mass of the diaphragm and the compliance of its suspension which vary from driver to driver. Therefore, a loudspeaker emulator capable of adjusting its impedance to that of a given driver is desired for measurement purposes. This paper proposes a loudspeaker emulator circuit for small signals. Simulations and experimental results are compared and show that it is possible to emulate the loudspeaker impedance with an electric circuit and that its resonance frequency can be changed by tuning two resistors.

Iversen, Niels Elkjær; Knott, Arnold

2014-01-01

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  

OpenAIRE

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

Small signal solutions of the transport equations  

International Nuclear Information System (INIS)

The transport relationships are generally solved by means of simpliying hypotheses or by using numerical analysis. A third method, within the framework of small signal theory, enables solutions to be obtained in closed form. Results are given for two particular cases : (i) minority carrier injection in semiconductors : (ii) Hall effect in a sample of finite length. The consequences of this analysis are believed to be of general importance in connection with the interpretation of electrical measurements on solids involving contacts

5

Small-signal analysis of granular semiconductors  

International Nuclear Information System (INIS)

The small-signal ac response of granular n-type semiconductors is calculated analytically using the drift-diffusion theory when electronic trapping at grain boundaries is present. An electrical equivalent circuit (EEC) model of a granular n-type semiconductor is presented. The analytical model is verified with numerical simulation performed by SILVACO ATLAS. The agreement between the analytical and numerical results is very good in a broad frequency range at low dc bias voltages.

6

Small-signal Loudspeaker Impedance Emulator  

DEFF Research Database (Denmark)

Specifying the performance of audio ampliers is typically done by playing sine waves into a pure ohmic load. However real loudspeaker impedances are not purely ohmic but characterised by the mechanical resonance between the mass of the diaphragm and the compliance of its' suspension which vary from driver to driver. Therefore a loudspeaker emulator capable of adjusting its' impedance to a given driver is in need for measurement purposes. This paper proposes a loudspeaker emulator circuit for small signals. Simulations and experimental results are compared and show that it is possible to emulate the loudspeaker impedance with an electric circuit and that its' resonance frequency can be changed by tuning two resistors.

Knott, Arnold; Iversen, Niels Elkjær

2014-01-01

7

A New Circuit Model of Small-Signal Sziklai Pair Amplifier  

OpenAIRE

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

8

A Novel Circuit Model of Small-Signal Amplifier Developed by Using BJT-JFET-BJT in Triple Darlington Configuration  

OpenAIRE

Two distinct configurations of small-signal amplifiers, consisting hybrid combination of BJT-FET-BJT in Triple Darlington topology, are proposed and qualitatively analyzed perhaps for the first time. The first proposed amplifier crops high voltage with moderate current gain and bandwidth in 1-15mV input signal range at 1 KHz frequency. However, the second amplifier is configured by creating certain modifications in the first circuit. This amplifier produces about double voltage and current ga...

SACHCHIDANAND SHUKLA; SUSMRITA SRIVASTAVA

2013-01-01

9

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 voltage gain (189.846 and high current gain (16.542K with moderate range bandwidth (369.529KHz. These properties offer a flexible application range to the proposed circuit as high voltage gain or high current gain or high power gain amplifier in permissible audio-frequency range. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters, bandwidth and total harmonic distortion of the amplifier are perused to provide a wide spectrum to the qualitative studies. Qualitative performance of the proposed amplifier is also compared with two different circuits which are respectively having BJT-JFET and BJT-MOSFET in Darlington pair configuration. The proposed amplifier may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in audio frequency region.

DR.SACHCHIDANAND SHUKLA

2013-06-01

10

Extending the direct laser modulation bandwidth by exploiting the photon-photon resonance: modeling, simulations and experiments  

Science.gov (United States)

The direct laser modulation bandwidth can be extended substantially by introducing a supplementary photon-photon resonance (PPR) at a higher frequency than the carrier-photon resonance (CPR). The paper presents a modified rate equation model that takes into account the PPR by treating the longitudinal confinement factor as a dynamic variable. The conditions required for obtaining a strong PPR and an enhancement of the small-signal modulation bandwidth are analyzed and experimental results confirming the model are presented. Since the small-signal modulation bandwidth may not be indicative of the large-signal modulation capability, particularly in case of a small-signal modulation response with substantial variations across the bandwidth, we have also analyzed the influence of the PPR-enhanced small-signal modulation response shape on the large-signal modulation capability as well as the methods that can be employed to flatten the small-signal modulation transfer function between the CPR and PPR.

Dumitrescu, M.; Laakso, A.; Viheriala, J.; Kamp, M.; Bardella, P.; Eisenstein, G.

2013-03-01

11

Power system small signal stability analysis and control  

CERN Document Server

Power System Small Signal Stability Analysis and Control presents a detailed analysis of the problem of severe outages due to the sustained growth of small signal oscillations in modern interconnected power systems. The ever-expanding nature of power systems and the rapid upgrade to smart grid technologies call for the implementation of robust and optimal controls. Power systems that are forced to operate close to their stability limit have resulted in the use of control devices by utility companies to improve the performance of the transmission system against commonly occurring power system

Mondal, Debasish; Sengupta, Aparajita

2014-01-01

12

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 maximum voltage gain with different biasing resistances and DC supply voltage and the temperature sensitivity of various performance parameters are elaborately studied and discussed in length. Qualitative performance of the proposed amplifier is also compared with the circuit which is having BJT-MOSFET in Darlington pair configuration. The proposed amplifier can be used to process audio range signal excursions and may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in narrow-band low frequency region.

SUSMRITA SRIVASTAVA

2013-02-01

13

A Novel Circuit Model of Small-Signal Amplifier Developed by Using BJT-JFET-BJT in Triple Darlington Configuration  

Directory of Open Access Journals (Sweden)

Full Text Available Two distinct configurations of small-signal amplifiers, consisting hybrid combination of BJT-FET-BJT in Triple Darlington topology, are proposed and qualitatively analyzed perhaps for the first time. The first proposed amplifier crops high voltage with moderate current gain and bandwidth in 1-15mV input signal range at 1 KHz frequency. However, the second amplifier is configured by creating certain modifications in the first circuit. This amplifier produces about double voltage and current gain than the first amplifier circuit with almost half bandwidth in 1-4mV input-signal-range at 1 KHz frequency. Both the amplifier circuits include two additional biasing resistances. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters, bandwidth and total harmonic distortion of the amplifiers are also perused. The proposed amplifiers can be successfully implemented as high power gain small-signal amplifiers in audio-frequency-range because of the obtained values of the current and voltage gains which are higher than unity.

SACHCHIDANAND SHUKLA

2013-05-01

14

Small signal modulation characteristics of red-emitting (? = 610?nm) III-nitride nanowire array lasers on (001) silicon  

KAUST Repository

The small signal modulation characteristics of an InGaN/GaN nanowire array edge- emitting laser on (001) silicon are reported. The emission wavelength is 610 nm. Lattice matched InAlN cladding layers were incorporated in the laser heterostructure for better mode confinement. The suitability of the nanowire lasers for use in plastic fiber communication systems with direct modulation is demonstrated through their modulation bandwidth of f-3dB,max = 3.1 GHz, very low values of chirp (0.8 Å) and ?-parameter, and large differential gain (3.1 × 10-17 cm2).

Frost, Thomas

2015-02-16

15

Small signal modulation characteristics of red-emitting (? = 610 nm) III-nitride nanowire array lasers on (001) silicon  

Science.gov (United States)

The small signal modulation characteristics of an InGaN/GaN nanowire array edge- emitting laser on (001) silicon are reported. The emission wavelength is 610 nm. Lattice matched InAlN cladding layers were incorporated in the laser heterostructure for better mode confinement. The suitability of the nanowire lasers for use in plastic fiber communication systems with direct modulation is demonstrated through their modulation bandwidth of f-3dB,max = 3.1 GHz, very low values of chirp (0.8 Å) and ?-parameter, and large differential gain (3.1 × 10-17 cm2).

Jahangir, Shafat; Frost, Thomas; Hazari, Arnab; Yan, Lifan; Stark, Ethan; LaMountain, Trevor; Millunchick, Joanna M.; Ooi, Boon S.; Bhattacharya, Pallab

2015-02-01

16

Comparative study of probabilistic methodologies for small signal stability assessment  

Energy Technology Data Exchange (ETDEWEB)

Traditional deterministic approaches for small signal stability assessment (SSSA) are unable to properly reflect the existing uncertainties in real power systems. Hence, the probabilistic analysis of small signal stability (SSS) is attracting more attention by power system engineers. This paper discusses and compares two probabilistic methodologies for SSSA, which are based on the two point estimation method and the so-called Monte Carlo method, respectively. The comparisons are based on the results obtained for several power systems of different sizes and with different SSS performance. It is demonstrated that although with an analytical approach the amount of computation of probabilistic SSSA can be reduced, the different degrees of approximations that are adopted, lead to deceptive results. Conversely, Monte Carlo based probabilistic SSSA can be carried out with reasonable computational effort while holding satisfactory estimation precision. (author)

Rueda, J.L.; Colome, D.G. [Universidad Nacional de San Juan (IEE-UNSJ), San Juan (Argentina). Inst. de Energia Electrica], Emails: joseluisrt@iee.unsj.edu.ar, colome@iee.unsj.edu.ar

2009-07-01

17

Improving Small Signal Stability through Operating Point Adjustment  

Energy Technology Data Exchange (ETDEWEB)

ModeMeter techniques for real-time small signal stability monitoring continue to mature, and more and more phasor measurements are available in power systems. It has come to the stage to bring modal information into real-time power system operation. This paper proposes to establish a procedure for Modal Analysis for Grid Operations (MANGO). Complementary to PSS’s and other traditional modulation-based control, MANGO aims to provide suggestions such as increasing generation or decreasing load for operators to mitigate low-frequency oscillations. Different from modulation-based control, the MANGO procedure proactively maintains adequate damping for all time, instead of reacting to disturbances when they occur. Effect of operating points on small signal stability is presented in this paper. Implementation with existing operating procedures is discussed. Several approaches for modal sensitivity estimation are investigated to associate modal damping and operating parameters. The effectiveness of the MANGO procedure is confirmed through simulation studies of several test systems.

Huang, Zhenyu; Zhou, Ning; Tuffner, Francis K.; Chen, Yousu; Trudnowski, Daniel J.; Mittelstadt, William; Hauer, John F.; Dagle, Jeffery E.

2010-09-30

18

DFIG turbine representation for small signal voltage control studies  

OpenAIRE

This paper addresses the representation of a wind power plant, based on wound rotor asynchronous generators, with a centralized voltage controller, by an equivalent transfer function, valid for small signal voltage control studies. This representation allows to investigate the influence of the centralized plant control gain and short circuit ratio on the system stability, for instance, by analyzing the zero-pole placement. Larger percentages of wind power penetration translate to more demandi...

Garcia, Jorge Martinez; Kjær, Philip Carne; Teodorescu, Remus

2010-01-01

19

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

Directory of Open Access Journals (Sweden)

Full Text Available 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?, is to be essentially used in the proposed circuit to maintain its voltage/current amplification property. With this additional biasing resistance, the proposed amplifier crops considerably wide bandwidth (12.365MHz, significantly high current gain (530.909 and fairly high voltage gain (9.108 in 1-80mV input signal range at 1 KHz frequency. These properties offer a flexible application range to the proposed amplifier as high power gain, wide band, or tuned amplifier in permissible audio-frequency range. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters, bandwidth and total harmonic distortion of the amplifier are also perused to provide a wide spectrum to the qualitative studies

DR. SACHCHIDANAND SHUKLA

2013-04-01

20

Inclusion of small signal stability assessment to electromagnetic transient programs  

Energy Technology Data Exchange (ETDEWEB)

Power system stability refers to the ability of an electrical power system to regain a state of operating equilibrium after being subjected to a physical disturbance. In this study, a small-signal stability (SSS) module was formulated for use with the transient simulation tool called PSCAD. The package was developed in an effort to provide small-signal stability assessment of case studies on PSCAD, and an adaptable simulation background for users to carry out conventional controller design without the need for an outside package. Once fully developed, the SSS module will be capable of incorporating all the system models available on PSCAD. Simulation results for the benchmark 12 bus system showed that it is a powerful and promising tool for carrying out small-signal analysis together with transient analysis, particularly for power system controller design to prevent instabilities. Validation has been carried out by comparison of Eigenvalues with SSAT and time domain responses with PSCAD/EMTDC. It was concluded that SSS could be effectively used to study the stability of a proposed power system before detailed simulation on an EMT type simulation is carried out. 11 refs., 5 tabs., 4 figs.

Lucas, J.R. [Moratuwa Univ. (Sri Lanka); Annakkage, U.D.; Karawita, C. [Manitoba Univ., Winnipeg, MB (Canada); Muthumuni, D.; Jayasinghe, R.P. [Manitoba HVDC Research Centre, Winnipeg, MB (Canada)

2008-07-01

21

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

22

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

23

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

24

DFIG turbine representation for small signal voltage control studies  

DEFF Research Database (Denmark)

This paper addresses the representation of a wind power plant, based on wound rotor asynchronous generators, with a centralized voltage controller, by an equivalent transfer function, valid for small signal voltage control studies. This representation allows to investigate the influence of the centralized plant control gain and short circuit ratio on the system stability, for instance, by analyzing the zero-pole placement. Larger percentages of wind power penetration translate to more demanding requirements coming from the grid codes, for example voltage support at the point of connection has been introduced recently by several grid codes from around the world, making important to analyze this control when applied to wind power plants. The performance of the equivalent transfer function has been evaluated and compared using an equivalent grid with different short circuit ratios and active power injection levels, the cases have been simulated with PSCAD/EMTDC program. Results show that this equivalence can be used for short circuit ratios between 5 and 25 for obtaining an accurate representation of the system voltage dynamics.

Garcia, Jorge Martinez; Kjær, Philip Carne

2010-01-01

25

Analytical theory of a small signal modulation response of a transistor laser with dots-in-well in the base  

International Nuclear Information System (INIS)

We have developed the theory for the threshold base current, light power output and small signal modulation response of a transistor laser, the base of which contains a quantum well (QW) with a layer of quantum dots (QDs) inserted within it. Our theory involves the solution of the continuity equation for an arbitrary location of the QW in the base, and the solution of coupled rate equations for carriers and photons in the QD. The excitonic recombination model is assumed to be valid in the QD. The estimated threshold base current for InAs QDs embedded in the InGaAs QW is found to be smaller than the value for the InGaAs QW in the GaAs base. The values of the modulation bandwidths for different values of the base current however do not reach the high values obtained for the QW system. (paper)

26

Small signal stability program analysis on SVC and HVDC in AC power systems  

Energy Technology Data Exchange (ETDEWEB)

NVdc transmission links and SVCs have controllable characteristics with potential for affecting system stability. To study these effects and to design their controllers for improving system stability, there is a need for their representation in small signal stability programs as well as time simulation programs. In this paper, the authors address the formulation of dc link and SVC models and their controllers for small signal stability. Several examples are studied to show the capability and application of the small signal dc link and SVC models. The small signal results are verified by time domain simulation results of the same study cases.

Arabi, S.; Rogers, G.J.; Wong, D.Y.; Kundur, P. (Ontario Hydro, Toronto, ON (Canada)); Lauby, M.G. (Electric Power Research Inst., Palo Alto, CA (United States))

1991-08-01

27

Impact of random fabrication errors on backward-wave small-signal gain in traveling wave tubes with finite space charge electron beams  

Science.gov (United States)

A one-dimensional small-signal theory for the backward-wave mode in a traveling-wave tube (TWT) is developed, which includes the effects of random fabrication errors. This is of interest since the backward-wave mode is the spatial harmonic typically responsible for instability in a TWT. The described model examines how gain and instantaneous 1-dB bandwidth of the backward-wave mode is affected by random fabrication errors, which are modeled as random perturbations of the phase velocity, interaction impedance, and loss along the TWT's length. Random variation of the phase velocity is found to have the largest effect on both the backward-wave gain and the bandwidth while having only a minor effect on fundamental, forward-wave mode behavior.

Sengele, Sean; Barsanti, Marc L.; Hargreaves, Thomas A.; Armstrong, Carter M.; Booske, John H.; Lau, Y. Y.

2013-02-01

28

Intrinsic stability of an HBT based on a small signal equivalent circuit model  

International Nuclear Information System (INIS)

Intrinsic stability of the heterojunction bipolar transistor (HBT) was analyzed and discussed based on a small signal equivalent circuit model. The stability factor of the HBT device was derived based on a compact T-type small signal equivalent circuit model of the HBT. The effect of the mainly small signal model parameters of the HBT on the stability of the HBT was thoroughly examined. The discipline of parameter optimum to improve the intrinsic stability of the HBT was achieved. The theoretic analysis results of the stability were also used to explain the experimental results of the stability of the HBT and they were verified by the experimental results. (semiconductor devices)

29

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

OpenAIRE

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 ...

Zi Lan Zhao; Wen Ying Liu; Xu Bin Han

2013-01-01

30

Validation of Nonlinear Bipolar Transistor Model by Small-Signal Measurements  

OpenAIRE

A new method for the validity analysis of nonlinear transistor models is presented based on DC-and small-signal S-parameter measurements and realistic consideration of the measurement and de-embedding errors and singularities of the small-signal equivalent circuit. As an example, some analysis results for an extended Gummel Poon model are presented in the case of a UHF bipolar power transistor.

Vidkjær, Jens; Porra, V.; Zhu, J.; Huttunen, T.

2010-01-01

31

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

OpenAIRE

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

32

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

OpenAIRE

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 damp...

Knu?ppel, Thyge; Nielsen, Jørgen Nygaard; Jensen, Kim Høj; Dixon, Andrew; Østergaard, Jacob

2012-01-01

33

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

34

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

35

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

36

Low-bandwidth authentication.  

Energy Technology Data Exchange (ETDEWEB)

Remotely-fielded unattended sensor networks generally must operate at very low power--in the milliwatt or microwatt range--and thus have extremely limited communications bandwidth. Such sensors might be asleep most of the time to conserve power, waking only occasionally to transmit a few bits. RFID tags for tracking or material control have similarly tight bandwidth constraints, and emerging nanotechnology devices will be even more limited. Since transmitted data is subject to spoofing, and since sensors might be located in uncontrolled environments vulnerable to physical tampering, the high-consequence data generated by such systems must be protected by cryptographically sound authentication mechanisms; but such mechanisms are often lacking in current sensor networks. One reason for this undesirable situation is that standard authentication methods become impractical or impossible when bandwidth is severely constrained; if messages are small, a standard digital signature or HMAC will be many times larger than the message itself, yet it might be possible to spare only a few extra bits per message for security. Furthermore, the authentication tags themselves are only one part of cryptographic overhead, as key management functions (distributing, changing, and revoking keys) consume still more bandwidth. To address this problem, we have developed algorithms that provide secure authentication while adding very little communication overhead. Such techniques will make it possible to add strong cryptographic guarantees of data integrity to a much wider range of systems.

Donnelly, Patrick Joseph; McIver, Lauren; Gaines, Brian R.; Anderson, Erik; Collins, Michael Joseph; Thomas,Kurt Adam; McDaniel, Austin

2007-09-01

37

Linearized Modeling of Single Machine Infinite Bus Power System and Controllers for Small Signal Stability Investigation and Enhancement  

OpenAIRE

Small signal stability investigation is vital as thesystem outage due small signal perturbation being unknown tothe system operators. The small signal disturbance may beinitiating event for large system outage. The Single MachineInfinite Bus (SMIB) power system helps in tuning thecontrollers at one machine without considering the effect ofother machines in the power system. The effect of disturbanceseen by the machine being 100%, whereas in interconnectedpower system the effect gets distribut...

Balwinder Singh Surjan

2012-01-01

38

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

39

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

40

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

41

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

International Nuclear Information System (INIS)

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

42

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

Energy Technology Data Exchange (ETDEWEB)

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., E-mail: PJFimognari@XanthoTechnologies.com; Demers, D. R. [Xantho Technologies, LLC, Madison, Wisconsin 53705 (United States); Chen, X. [Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37830 (United States); Schoch, P. M. [Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2014-11-15

43

Appropriate placement of series compensators to improve small signal stability of power system  

OpenAIRE

Series FACTS devices like thyristor controlled series capacitors (TCSC) equipped with appropriate supplementary damping controller can improve the small signal stability of power system if they are located properly. In this paper, trajectory sensitivity analysis (TSA) is used to determine the best locations for installing TCSC to damp out the inter-area mode of oscillation. Based on the modal analysis, an equivalent angle is defined by determining critical and non-critical machines, and then ...

Nasri, Amin

2012-01-01

44

Small signal gain measurements in a small scale HF overtone laser  

Energy Technology Data Exchange (ETDEWEB)

The overtone gain medium of a small-scale HF overtone laser was probed using a sub-Doppler tunable diode laser. Two-dimensional spatially resolved small signal gain and temperature maps were generated for several ro-vibrational transitions in the HF (v=2{yields}v=0) overtone band. Our results compare well with previous measurements of the overtone gain in a similar HF laser device. (orig.)

Wisniewski, C.F.; Hewett, K.B.; Manke, G.C. II; Hager, G.D. [Air Force Research Laboratory, Directed Energy Directorate, 3550 Aberdeen Ave SE, Kirtland AFB, NM 87117-5776 (United States); Crowell, P.G. [Northrup Grumman Information Technology, Science and Technology Operating Unit, Advanced Technology Division, P.O. Box 9377, Albuquerque, NM 87119-9377 (United States); Truman, C.R. [Mechanical Engineering Department, University of New Mexico, Albuquerque, NM 87131 (United States)

2003-07-01

45

A comprehensive computer program package for small signal stability analysis of power systems  

Energy Technology Data Exchange (ETDEWEB)

A powerful package of integrated programs for small signal stability analysis of large interconnected power systems is described. The package has extensive modelling capability and uses alternative eigenvalue calculation techniques, making it suitable for the analysis of a wide range of stability and control problems. Results of eigenvalue calculations for three power systems of differing size and complexity are presented and the accuracy, consistency and convergence of the alternative calculation methods are discussed.

Kunclur, P.; Rogers, G.J.; Wong, D.Y.; Wang, L. (System Planning Div., Ontario Hydro, Ontario (CA)); Lauby, M.G. (Electric Power Research Inst., Palo Alto, CA (USA))

1990-11-01

46

The small signal stability program package: Volume 1, Program package development  

Energy Technology Data Exchange (ETDEWEB)

This report describes the theoretical background of the small signal stability analysis of power systems as embodied in the two programs MASS (multi-area small signal stability) and PEALS (program for eigenvalue analysis of large systems). These programs form, together with a data base program, a Small Signal Stability Package (SSSP) which can be applied to a broad range of stability programs. MASS is a program which forms the state matrix of an interconnected power system and performs an eigenvalue analysis, using the QR technique, on this matrix. PEALS determines, one at a time, those eigenvalues of the power system associated with the rotor angles of the synchronous machines. The basic algorithm used in PEALS was developed under EPRI RP 744-1. However, the modelling and network solution techniques used in PEALS have been newly developed to ensure complete compatibility with MASS and to enable systems having up to 12,000 bus to be studied. In both MASS and PEALS user defined models for excitation systems and dc controls enable the programs to be applied to a wide range of practical power systems. 3 refs., 38 figs.

Kundur, P.; Rogers, G.J.; Wong, D.Y.

1988-05-01

47

Tunable bandwidth optical rotator  

CERN Document Server

We propose and experimentally demonstrate a novel type of polarization rotator which is capable of rotating the polarization plane of a linearly polarized light at any desired angle in either broad or narrow spectral bandwidth. The rotator comprises an array of standard half-wave plates rotated at specific angles with respect to their fast-polarization axes. The performance of the rotator depends on the number of individual half-wave plates and in this paper we experimentally investigate the performance of two composite rotators comprising six and ten half-wave plates.

Dimova, Emiliya; Kyoseva, Elica

2015-01-01

48

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

49

ABB: active bandwidth broker  

Science.gov (United States)

In this paper, we shall discuss a novel design on the policy-based management for the Internet. This design deploys the concept of active networking. As opposed to the traditional network design, active network empowers network node with the ability to manipulate data and program code in packets, and configure the network properties according to the needs of different applications. The policy-based management can control network routers in order to realize end-to-end Quality of Service (QoS), such as differentiated and integrated services, across the Internet. For the moment, the Internet Engineering Task Force (IETF) has defined the framework of the policy-based management. It employs a simple client/server model that uses Common Open Policy Service (COPS) protocol to facilitate policy management and control. Our design of Active Bandwidth Broker (ABB) belongs to an active application. Our goals are to distribute centralized workload of the policy-based management over multiple active nodes in the active networks, introduce mobility of the bandwidth brokers, and allows load sharing to the policy-based management. This results a network-wide intelligent, highly available, and consistent QoS control that allows performance protection for voice, video and Internet business application while reducing costs for growing networks.

Wong, Kason; Law, Eddie

2001-07-01

50

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

OpenAIRE

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

51

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)

52

Linearized Modeling of Single Machine Infinite Bus Power System and Controllers for Small Signal Stability Investigation and Enhancement  

Directory of Open Access Journals (Sweden)

Full Text Available Small signal stability investigation is vital as thesystem outage due small signal perturbation being unknown tothe system operators. The small signal disturbance may beinitiating event for large system outage. The Single MachineInfinite Bus (SMIB power system helps in tuning thecontrollers at one machine without considering the effect ofother machines in the power system. The effect of disturbanceseen by the machine being 100%, whereas in interconnectedpower system the effect gets distributed among differentmachines. Therefore, the controller tuning with SMIB remainsvalid for miltimachine power system as well. In this paper acomparison of PID, PSS, TCDB controllers is presentedthrough small signal stability of power system comprising ofone machine connected to infinite bus and modeled through sixK-constants. The power system components such assynchronous machine, exciter, power system stabilizer, PID,TCDB are also modeled after linearization of governingequations.

Balwinder Singh Surjan

2012-10-01

53

Resolving small signal measurements in experimental plasma environments using calibrated subtraction of noise signals.  

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. PMID:25430262

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

2014-11-01

54

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

55

Small-Signal Capacitance and Current Parameter Modeling in Large-Scale High-Frequency Graphene Field-Effect Transistors  

OpenAIRE

The analytical model of the small-signal current and capacitance characteristics of RF graphene FET is presented. The model is based on explicit distributions of chemical potential in graphene channels (including ambipolar conductivity at high source-drain bias) obtained in the framework of drift-diffusion current continuity equation solution. Small-signal transconductance and output conductance characteristics are modeled taking into account the two modes of drain current s...

Zebrev, Gennady I.; Tselykovskiy, Alexander A.; Batmanova, Daria K.; Melnik, Evgeny V.

2011-01-01

56

PolySac3DB: an annotated data base of 3 dimensional structures of polysaccharides  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Polysaccharides are ubiquitously present in the living world. Their structural versatility makes them important and interesting components in numerous biological and technological processes ranging from structural stabilization to a variety of immunologically important molecular recognition events. The knowledge of polysaccharide three-dimensional (3D structure is important in studying carbohydrate-mediated host-pathogen interactions, interactions with other bio-macromolecules, drug design and vaccine development as well as material science applications or production of bio-ethanol. Description PolySac3DB is an annotated database that contains the 3D structural information of 157 polysaccharide entries that have been collected from an extensive screening of scientific literature. They have been systematically organized using standard names in the field of carbohydrate research into 18 categories representing polysaccharide families. Structure-related information includes the saccharides making up the repeat unit(s and their glycosidic linkages, the expanded 3D representation of the repeat unit, unit cell dimensions and space group, helix type, diffraction diagram(s (when applicable, experimental and/or simulation methods used for structure description, link to the abstract of the publication, reference and the atomic coordinate files for visualization and download. The database is accompanied by a user-friendly graphical user interface (GUI. It features interactive displays of polysaccharide structures and customized search options for beginners and experts, respectively. The site also serves as an information portal for polysaccharide structure determination techniques. The web-interface also references external links where other carbohydrate-related resources are available. Conclusion PolySac3DB is established to maintain information on the detailed 3D structures of polysaccharides. All the data and features are available via the web-interface utilizing the search engine and can be accessed at http://polysac3db.cermav.cnrs.fr.

Sarkar Anita

2012-11-01

57

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

58

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

59

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

Energy Technology Data Exchange (ETDEWEB)

In this work, we fabricate a heterojunction small-signal generator (HSSG) based on a graphene-molybdenum disulfide (MoS{sub 2}) 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). MoS{sub 2} serves as I and G, and graphene works as R in the HSSG. The scale coefficient (??=?I{sub G}/I{sub R}) of the HSSG is 1.14?×?10{sup ?4} (V{sub IG,?IR}?=?0.2?V) to 1.95?×?10{sup ?4} (V{sub IG,?IR}?=?1?V). The current generated from G could be as low as pA scale, which reveals the good performance of the HSSG.

Tan, Zhen; Tian, He; Feng, Tingting; Zhao, Lianfeng; Xie, Dan; Yang, Yi; Xiao, Lei; Wang, Jing; Ren, Tian-Ling, E-mail: RenTL@tsinghua.edu.cn, E-mail: JunXu@tsinghua.edu.cn; Xu, Jun, E-mail: RenTL@tsinghua.edu.cn, E-mail: JunXu@tsinghua.edu.cn [Institute of Microelectronics, Tsinghua University, Beijing 100084, China and Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084 (China)

2013-12-23

60

Small signal modeling of AlGaN/GaN HEMTs with consideration of CPW capacitances  

Science.gov (United States)

Given the coplanar waveguide (CPW) effect on AlGaN/GaN high electron mobility transistors at a high frequency, the traditional equivalent circuit model cannot accurately describe the electrical characteristics of the device. The admittance of CPW capacitances is large when the frequency is higher than 40 GHz; its impact on the device cannot be ignored. In this study, a small-signal equivalent circuit model considering CPW capacitance is provided. To verify the model, S-parameters are obtained from the modeling and measurements. A good agreement is observed between the simulation and measurement results, indicating the reliability of the model. Project supported by the National Natural Science Foundation of China (Nos. 61376078, 61274086) and the Fundamental Research Funds for the Central Universities of China (No. ZYGX2012J041).

Jiangfeng, Du; Peng, Xu; Kang, Wang; Chenggong, Yin; Yang, Liu; Zhihong, Feng; Shaobo, Dun; Qi, Yu

2015-03-01

61

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

62

A New Current-Controlled-Power Technique for Small Signal Applications  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a new current-controlled-power technique for small signal applications is presented. The proposed technique needs no passive devices (a resistor and a capacitor but the well-known SCR technique needs, thus the proposed technique is very suitable for an IC process. An example application as a new current-controlled-power CMOS fullwave rectifier is also given. The example application is simulated by using the SPICE program. Simulation results show that the proposed technique can work well; the controlled-current from 0 µA to 5.5 µA produces the peak area amplitude from 100 mV to 0 mV to the load.

Adisak Monpapassorn

2012-04-01

63

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

64

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 timedomain 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

2014-01-01

65

Small signal stability analysis program package: Version 2. 0 User Manual  

Energy Technology Data Exchange (ETDEWEB)

The Small Signal Stability Package (SSSP) consists of two eigenvalue programs MASS and PEALS along with a data base program. This volume contains two user manuals: one for the programs MASS and PEALS and one for the data base program. The dynamic data and part of the program control data are common to MASS and PEALS and, therefore, a single manual is provided for both programs. Data applicable only to one of the programs is clearly identified in the manual. The MASS-PEALS manual describes the general structure of the dynamic data file for dynamic data supplied in OH, EPRI, IEEE or PECO format. OH dynamic models and their input-data formats are described in detail. The user manual for the data base program, describes the format of the input data required to create a new data base or print data stored in an existing data base. 19 figs., 1 tab.

Rogers, G.J.; Wong, D.Y. (Ontario Hydro, Toronto, ON (Canada))

1990-01-01

66

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

67

On fairness in Bandwidth Allocation  

OpenAIRE

For over a decade, the Nash bargaining solution (NBS) concept from cooperative game theory has been used in networks as a concept that allows one to share resources fairly. Due to its many appealing properties, it has recently been used for assigning bandwidth in a general topology network between applications that have linear utilities. In this paper, we use this concept for the bandwidth allocation between applications with general concave utilities. We study the impact of concavity on the ...

Touati, Corinne; Altman, Eitan; Galtier, Je?ro?me

2001-01-01

68

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

OpenAIRE

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

69

Wide Area Prosumption Control and Sensitivities of Aperiodic Small Signal Stability Indicators  

DEFF Research Database (Denmark)

This paper introduces the concept of prosumption control where intelligent loads and distributed generation are aggregated and controlled to improve power system security. It is expected that intelligent load and generation units can respond to control / market signals and thus present an opportunity of available resources for changing the operating point (OP) of a system to one that is more secure. A prosumption pattern is then a signal to prosumers to shift their demand in time. This makes it possible to temporarily change the distribution of the power demand. A prosumption pattern is balanced, such that frequency can be maintained by other smart grid technologies. To find a prosumption pattern which can improve security, it is necessary to determine sensitivities of stability indicators such that beneficial load permutations can be identified. After introducing prosumption control and patterns, stability indicators for aperiodic small signal angular stability (ASSA) are examined, while the concept of prosumption is described. The methodology presented is shown to be able to assess the margin to instability and to predict how this margin can be affected if a load is changed in the grid. The resulting sensitivities are described and their suitability to be used to search for a prosumption pattern is evaluated.

Wittrock, Martin Lindholm; Jóhannsson, Hjörtur

2014-01-01

70

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

Scientific Electronic Library Online (English)

Full Text Available 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

71

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

72

A Three-Dimensional Model of Small Signal Free-Electron Lasers  

CERN Document Server

Coherent electron cooling is an ultra-high-bandwidth form of stochastic cooling which utilizes the charge perturbation from Debye screening as a seed for a free-electron laser. The amplified and frequency-modulated signal that results from the free-electron laser process is then used to give an energy-dependent kick on the hadrons in a bunch. In this paper, we present a theoretical description of a high-gain free-electron laser with applications to a complete theoretical description of coherent electron cooling.

Webb, Stephen; Litvinenko, Vladimir

2011-01-01

73

A Three-Dimensional Model of Small Signal Free-Electron Lasers  

OpenAIRE

Coherent electron cooling is an ultra-high-bandwidth form of stochastic cooling which utilizes the charge perturbation from Debye screening as a seed for a free-electron laser. The amplified and frequency-modulated signal that results from the free-electron laser process is then used to give an energy-dependent kick on the hadrons in a bunch. In this paper, we present a theoretical description of a high-gain free-electron laser with applications to a complete theoretical des...

Webb, Stephen; Wang, Gang; Litvinenko, Vladimir

2011-01-01

74

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

75

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.

76

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.

Ozimkiewiez, J.; Ruepp, Sarah Renée

2009-01-01

77

Bandwidth-Synthesizing FM Radar  

Science.gov (United States)

Proposed frequency-modulation (FM) radar system uses sawtooth-wave-form linear frequency sweeps and return-signal-processing scheme in which samples of signals from N consecutive sweep periods are combined to multiply range resolution by factor of N. System "synthesizes" bandwith N times that of transmitted signal in sense that to increase resolution of ordinary radar system where consecutive samples are not combined, it is necessary to increase bandwidth of transmitted signal by same factor. Used in FM radar altimeters.

Wu, Chialin

1992-01-01

78

Retaining Bandwidth Efficiency and Efficacy  

OpenAIRE

In this paper we examine how the notion of systemic relevance challenges bandwidth efficiency and efficacy of middle managers of financial service organizations and what managers can do to coop with increasingly complex environments of the firm. As the envisaged merger of The New York Stock Exchange (NYSE Euronext) with Deutsche Börse Group is revitalizing debates concerning institutional configurations of stock markets, we first ask how managers of one of the world’s leading stock exchang...

Timo Meynhardt; Camillo Von Müller

2012-01-01

79

Bandwidth compression of multispectral satellite imagery  

Science.gov (United States)

The results of two studies aimed at developing efficient adaptive and nonadaptive techniques for compressing the bandwidth of multispectral images are summarized. These techniques are evaluated and compared using various optimality criteria including MSE, SNR, and recognition accuracy of the bandwidth compressed images. As an example of future requirements, the bandwidth requirements for the proposed Landsat-D Thematic Mapper are considered.

Habibi, A.

1978-01-01

80

Transient and small signal stability of a two area HVAC power network interconnected with an HVDC link  

Energy Technology Data Exchange (ETDEWEB)

Despite the fact that the conditions necessary for safe and stable operation of power networks are sometimes at variance with economic considerations, power system operators are responsible for supplying safe and economical electric power to customers. Customer demand cannot be met without a stable and reliable power supply. Therefore, power system stability is of crucial importance in this market. This paper presented an analysis of transient and small signal stability of a two-area multi-machine power system. Different aspects were investigated including the responses of generator speed, the terminal voltage, the rotor angle difference and power transmitted, after a transient perturbation of a single phase to ground fault. The study also examined the effect of small signal disturbance of power systems when a direct current (DC) link was interconnected with a weak alternating (AC) link. Using the two-area power system model, the small signal stabilities of three different transmission systems were investigated, notably a high voltage alternating current (HVAC) link; a high voltage direct current (HVDC) link; and the hybrid HVAC/HVDC link. The paper discussed the fundamentals of HVAC and HVDC transmission. Rotor angle stability was also presented. An HVAC/HVDC hybrid network model was described. Simulation results were also provided for power flow; transient stability analysis; and small signal stability analysis. It was concluded that the transient stability test demonstrated that the system is relatively stable and returns to pre-fault condition about 10 seconds after perturbation. The study showed that when a fault occurs in transmission lines, the system responds according to the nature of the fault and the strength of the system.. 9 refs., 3 tabs., 8 figs., 1 appendix.

Azimoh, L.C.; Oyedokun, D.T.; Chowdhury, S.; Chowdhury, S.P.; Folly, K.A. [Cape Town Univ., Cape Town (South Africa). Dept. of Electrical Engineering

2009-07-01

81

Optically-pumped long-wavelength vertical-cavity surface-emitting laser with high modulation bandwidth  

Science.gov (United States)

Optically-pumped long-wavelength vertical-cavity surface-emitting lasers (VCSELs) have been fabricated exhibiting more than 2mW over 20-70°C, and 1.25mW at 85°C. Small-signal modulation measurements on the VCSEL at 20°C indicate a 3dB bandwidth of 14.8GHz at an output power of 2mW. The VCSELs have a narrow spectral width suitable for data transmission over single-mode fiber. The good temperature performance of the VCSEL is maintained in a suspended configuration that would allow monolithic integration.

Ramana Murty, M. V.; Xu, D.; Lin, C.-C.; Shieh, C.-L.; Tsao, J. Y.; Cheng, Julian

2005-02-01

82

On the wide-range bias dependence of transistor d.c. and small-signal current gain factors.  

Science.gov (United States)

Critical reappraisal of the bias dependence of the dc and small-signal ac current gain factors of planar bipolar transistors over a wide range of currents. This is based on a straightforward consideration of the three basic components of the dc base current arising due to emitter-to-base injected minority carrier transport, base-to-emitter carrier injection, and emitter-base surface depletion layer recombination effects. Experimental results on representative n-p-n and p-n-p silicon devices are given which support most of the analytical findings.

Schmidt, P.; Das, M. B.

1972-01-01

83

Bandwidth aspects in second generation current conveyors  

OpenAIRE

This paper discusses bandwidth problems associated with second-generation current conveyors (CCII). In particular, our work is centered in high-capacitance applications, and has been oriented for wireless optical links and applied physics. We discuss techniques for improving bandwidth in these CCIIs, and develop a new CCII structure with larger bandwidth than traditional circuits. These circuits are then compared in terms of their noise and dynamic range characteristics. A test circuit was de...

Alves, L. N.; Aguiar, R. L.; Santos, D. M.

2002-01-01

84

Optimization and small-signal modeling of zero-bias InAs self-switching diode detectors  

Science.gov (United States)

Design optimization of the InAs self-switching diode (SSD) intended for direct zero-bias THz detection is presented. The SSD, which consists of nanometer-sized channels in parallel, was described using an equivalent small-signal circuit. Expressions for voltage responsivity and noise equivalent power (NEP) were derived in terms of geometrical design parameters of the SSD, i.e. the channel length and the number of channels. Modeled design dependencies were confirmed by RF and DC measurements on InAs SSDs. In terms of NEP, an optimum number of channels were found with the detector driven by a 50 ? source. With a matched source, the model predicted a responsivity of 1900 V/W and NEP of 7.7 pW/Hz½ for a single-channel InAs SSD with 35 nm channel width. Monte Carlo device simulations supported observed design dependencies. The proposed small-signal model can be used to optimize SSDs of any material system for low-noise and high-frequency operation as zero-bias detectors. In large signal measurements, the responsivity of the InAs SSDs exhibited a 1 dB deviation from linear responsivity at an input power of -3 dBm from a 50 ? source.

Westlund, A.; Sangaré, P.; Ducournau, G.; Iñiguez-de-la-Torre, I.; Nilsson, P.-Å.; Gaquière, C.; Desplanque, L.; Wallart, X.; Millithaler, J. F.; González, T.; Mateos, J.; Grahn, J.

2015-02-01

85

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

86

Investigating the role of fuel cells in improving the transient and small signal stability of power systems  

Energy Technology Data Exchange (ETDEWEB)

The installation of distributed generation (DG) units has increased in recent years due to technological advances, changing economics and regulatory environments. The use of DG will change the conventional structure of power systems, particularly when high penetration levels will affect the dynamic behaviour of the whole power system. This paper examined the role of fuel cells in improving a power system's transient and dynamic stability. Dynamic modeling and simulations were used to determine the influence of fuel cells on the transient and small signal stability of power systems. The type of the fuel cell was found to play an important role in obtaining an appropriate dynamic model, since the internal chemical reactions change. The study showed that a suitable dynamic model and a proper control scheme of the fuel cell in a DG power system can improve the transient and small signal stability of the overall system in fault situations. Results of several case studies were compared to provide greater insight into the importance of fuel cells and their accurate dynamic modeling and control. 24 refs., 13 figs.

Khatibi, M. [Islamic Azad Univ., Abhar (Iran, Islamic Republic of); Hamidreza Radmand, H. [Iran Univ. of Science and Technology, Tehran (Iran, Islamic Republic of); Shayanfar, H. [Iran Univ. of Science and Technology, Tehran (Iran, Islamic Republic of). Center of Excellence for Power System Automation and Operation

2010-10-15

87

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

88

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

89

Multiple-bandwidth photoacoustic tomography  

International Nuclear Information System (INIS)

Photoacoustic tomography, also referred to as optoacoustic tomography, employs short laser pulses to generate ultrasonic waves in biological tissues. The reconstructed images can be characterized by the convolution of the structure of samples, the laser pulse and the impulse response of the ultrasonic transducer used for detection. Although the laser-induced ultrasonic waves cover a wide spectral range, a single transducer can receive only part of the spectrum because of its limited bandwidth. To systematically analyse this problem, we constructed a photoacoustic tomographic system that uses multiple ultrasonic transducers simultaneously, each at a different central frequency. The photoacoustic images associated with the different transducers were compared and analysed. The system was tested by imaging both mouse brains and phantom samples. The vascular vessels in the brain were revealed by all of the transducers, but the image resolutions differed. The higher frequency detectors provided better image resolution while the lower frequency detectors delineated the major structural traits with a higher signal-noise ratio

90

Small-Signal Analysis of Autonomous Hybrid Distributed Generation Systems in Presence of Ultracapacitor and Tie-Line Operation  

Science.gov (United States)

This paper presents small-signal analysis of isolated as well as interconnected autonomous hybrid distributed generation system for sudden variation in load demand, wind speed and solar radiation. The hybrid systems comprise of different renewable energy resources such as wind, photovoltaic (PV) fuel cell (FC) and diesel engine generator (DEG) along with the energy storage devices such as flywheel energy storage system (FESS) and battery energy storage system (BESS). Further ultracapacitors (UC) as an alternative energy storage element and interconnection of hybrid systems through tie-line is incorporated into the system for improved performance. A comparative assessment of deviation of frequency profile for different hybrid systems in the presence of different storage system combinations is carried out graphically as well as in terms of the performance index (PI), ie integral square error (ISE). Both qualitative and quantitative analysis reflects the improvements of the deviation in frequency profiles in the presence of the ultracapacitors (UC) as compared to other energy storage elements.

Ray, Prakash K.; Mohanty, Soumya R.; Kishor, Nand

2010-07-01

91

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

92

Small-signal model parameter extraction for microwave SiGe HBTs based on Y- and Z-parameter characterization  

International Nuclear Information System (INIS)

High frequency intrinsic small-signal model parameter extraction for microwave SiGe heterojunction bipolar transistors is studied, with a focus on the main feedback elements including the emitter series resistor, internal and external base-collector capacitors as well as the base series resistor, all of which are important in determining the behavior of the device equivalent circuit. In accordance with the respective features of definition of the Y- and Z-parameters, a novel combined use of them succeeds in reasonably simplifying the device equivalent circuit and thus decoupling the extraction of base-collector capacitances from other model parameters. As a result, a very simple direct extraction method is proposed. The proposed method is applied for determining the SiGe HBT small-signal model parameters by taking numerically simulated Y- and Z-parameters as nominal 'measurement data' with the help of a Taurus-device simulator. The validity of the method is preliminarily confirmed by the observation of certain linear relations of device frequency behavior as predicted by the corresponding theoretical analysis. Furthermore, the extraction results can be used to reasonably account for the dependence of the extracted model parameters on device geometry and process parameters, reflecting the explicit physical meanings of parameters, and especially revealing the distributed nature of the base series resistor and its complex interactions with base-collector capacitors. Finations with base-collector capacitors. Finally, the accuracy of our model parameter extraction method is further validated by comparing the modeled and simulated S-parameters as a function of frequency. (semiconductor devices)

93

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

94

Spectral Bandwidth and WEC Performance Assessment  

Energy Technology Data Exchange (ETDEWEB)

This paper investigates the dependency of wave energy conversion on the spectral bandwidth of sea-states. To this aim, the performance of an axisymmetrical Wave Energy Converter is assessed in the frequency domain by using a stochastic model in two far different wave climates (Portugal and North Sea) both represented by more than 23000 energy spectral densities obtained from measurements. The correlation between the performance and various bandwidth parameters found in the literature is observed. Then, refined methods for predicting the long-term converted wave energy based on wave statistics including spectral bandwidth are compared to more common procedures and conclusions are drawn.

Saulnier, J.-B.; Pontes, M.T. [INETI/DER, Lisboa, (Portugal); Ricci, P.; Falcao, Antonio F. de O. [IDMEC/IST, Lisboa, (Portugal)

2007-07-01

95

2008 2nd IEEE International Workshop on Bandwidth on Demand  

OpenAIRE

The following topics were dealt with: provisioning of bandwidth on demand; resource allocation; multi-domain optical networks; network pricing; bandwidth trading; virtual network topology control; bandwidth reservation network and GMPLS signalling.

Hausheer, D.; Antoniadis, P.; Shiomoto, K.; Stiller, B.; Walrand, J.

2008-01-01

96

Bandwidth challenge teams at SC2003 conference  

CERN Multimedia

Results from the fourth annual High-Performance Bandwidth Challenge, held in conjunction with SC2003, the international conference on high-performance computing and networking which occurred last week in Phoenix, AZ (1 page).

2003-01-01

97

Center frequency and bandwidth tunable HTS filter  

Energy Technology Data Exchange (ETDEWEB)

We have developed a bandwidth and a center frequency tuning method for use in high-temperature superconducting microstrip filters. Several {pi}-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.

Harada, H. [Department of Electrical Engineering, Yamanashi University, Kakio-Sekiya Laboratory, 4-3-11 Takeda, Kofu 400-8511 (Japan); 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); 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)

2011-11-15

98

47 CFR 101.109 - Bandwidth.  

Science.gov (United States)

...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES...communications. Frequency band (MHz) Maximum authorized bandwidth...250 25 MHz 17,700 to 18,140 220 MHz 1 18,140 to 18,142 2 MHz...

2010-10-01

99

Tunable-Bandwidth Filter System  

Science.gov (United States)

A tunable-bandwidth filter system (TBFS), now undergoing development, is intended to be part of a remote-sensing multispectral imaging system that will operate in the visible and near infrared spectral region (wavelengths from 400 to 900 nm). Attributes of the TBFS include rapid tunability of the pass band over a wide wavelength range and high transmission efficiency. The TBFS is based on a unique integration of two pairs of broadband Raman reflection holographic filters with two rotating spherical lenses. In experiments, a prototype of the TBFS was shown to be capable of spectral sampling of images in the visible range over a 200-nm spectral range with a spectral resolution of .30 nm. The figure depicts the optical layout of a prototype of the TBFS as part of a laboratory multispectral imaging system for the spectral sampling of color test images in two orthogonal polarizations. Each pair of broadband Raman reflection holographic filters is mounted at an equatorial plane between two halves of a spherical lens. The two filters in each pair are characterized by steep spectral slopes (equivalently, narrow spectral edges), no ripple or side lobes in their pass bands, and a few nanometers of non-overlapping wavelength range between their pass bands. Each spherical lens and thus the filter pair within it is rotated in order to rapidly tune its pass band. The rotations of the lenses are effected by electronically controlled, programmable, high-precision rotation stages. The rotations are coordinated by electronic circuits operating under overall supervision of a personal computer in order to obtain the desired variation of the overall pass bands with time. Embedding the filters inside the spherical lenses increases the range of the hologram incidence angles, making it possible to continuously tune the pass and stop bands of the filters over a wider wavelength range. In addition, each spherical lens also serves as part of the imaging optics: The telephoto lens focuses incoming light to a field stop that is also a focal point of each spherical lens. A correcting lens in front of the field stop compensates for the spherical aberration of the spherical lenses. The front surface of each spherical lens collimates the light coming from the field stop. After the collimated light passes through the filter in the spherical lens, the rear surface of the lens focuses the light onto a charge-coupled-device image detector.

Aye, Tin; Yu, Kevin; Dimov, Fedor; Savant, Gajendra

2006-01-01

100

Sampling of communications systems with bandwidth expansion  

OpenAIRE

Many communication systems are {\\em bandwidth-expanding}: the transmitted signal occupies a bandwidth larger than the {\\em symbol rate}. The sampling theorems of Kotelnikov, Shannon, Nyquist et al. shows that in order to represent a bandlimited signal, it is necessary to sample at what is popularly referred to as the Shannon or Nyquist rate. However, in many systems, the required sampling rate is very high and expensive to implement. In this work we show that it is possible to get suboptimal...

Kusuma, Julius; Ridolfi, Andrea; Vetterli, Martin

2002-01-01

101

Spectral Bandwidth and WEC Performance Assessment  

OpenAIRE

This paper investigates the dependency of wave energy conversion on the spectral bandwidth of sea-states. To this aim, the performance of an axisymmetrical Wave Energy Converter is assessed in the frequency domain by using a stochastic model in two far different wave climates (Portugal and North Sea) both represented by more than 23000 energy spectral densities obtained from measurements. The correlation between the performance and various bandwidth parameters found in the literature is obser...

Saulnier, J. -b; Ricci, P.; Pontes, M. T.; Falca?o, A. F. O.

2007-01-01

102

Sharp Bounds for Bandwidth of Clique Products  

OpenAIRE

The bandwidth of a graph is the labeling of vertices with minimum maximum edge difference. For many graph families this is NP-complete. A classic result computes the bandwidth for the hypercube. We generalize this result to give sharp lower bounds for products of cliques. This problem turns out to be equivalent to one in communication over multiple channels in which channels can fail and the information sent over those channels is lost. The goal is to create an encoding that...

Berger-wolf, Tanya Y.; Harris, Mitchell A.

2003-01-01

103

Thermal noise in a finite bandwidth  

OpenAIRE

In a practical circuit, the output noise due to the thermal noise of a resistor will depend on the actual transfer function of the noise source. The bandwidth will never be infinite because the transfer function of either the noise source or the device measuring the output noise will cause limitations. Consequently, the thermal noise voltage of a resistor in a finite bandwidth is maximum for a given resistor value. That maximum thermal noise voltage depends on the stop frequencies and decreas...

Vargas Drechsler, Manuel; Palla?s Areny, Ramon

2001-01-01

104

Increase Bandwidth for Circular Microstrip Patch Antenna  

OpenAIRE

In this paper a design and performance of acircularly microstrip patch antenna, for the application inWireless Local Area Network (WLAN), are reported here. Theantenna is a proximity coupled microstrip patch antenna wherethe radiating patch is loadedby a V-slot. This miniaturizedmicrostrip antenna has wide bandwidth in the frequency bandof WLAN and exhibits circularly far field with very good axialratio bandwidth. The simulated results using IE3D software areverified by measurement

Sonali Jain; Rajesh Nema ,

2012-01-01

105

Effects of Random Circuit Fabrication Errors on Small Signal Gain and on Output Phase in a Traveling Wave Tube  

Science.gov (United States)

Random fabrication errors may have detrimental effects on the performance of traveling-wave tubes (TWTs) of all types. A new scaling law for the modification in the average small signal gain and in the output phase is derived from the third order ordinary differential equation that governs the forward wave interaction in a TWT in the presence of random error that is distributed along the axis of the tube. These scaling laws extend previous works in that they account for non-synchronous beam velocities and the inclusion of Pierce's ``space charge'' term. Analytical results compare favorably with numerical results in the absence of space charge, in both gain and phase modifications as a result of random error in the phase velocity of the slow wave circuit. Results on the effects of non-synchronous beam velocities and ac space charge are reported. Effects of internal reflections are investigated [1]. [4pt] [1] D. Chernin, et al., IEEE Trans. Electron Devices 59, 1542 (2012).

Rittersdorf, I. M.; Antonsen, T. M., Jr.; Chernin, D.; Lau, Y. Y.

2012-10-01

106

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; Olsen, Rasmus LØvenstein

2014-01-01

107

Optimization model for bandwidth allocation in a network virtualization environment  

OpenAIRE

Bandwidth allocation is one of the main problems in network virtualization. Mechanisms to allocate bandwidth may avoid bottlenecked virtual links. This paper proposes a model based on optimization theory, to distribute the bandwidth among virtual links looking for the minimization of the spare bandwidth in the substrate network.

Botero Vega, Juan Felipe; Hesselbach Serra, Xavier

2009-01-01

108

Adaptable bandwidth planning using reinforcement learning  

Directory of Open Access Journals (Sweden)

Full Text Available In order to improve the bandwidth allocation considering feedback of operational environment, adaptable bandwidth planning based on reinforcement learning is proposed. The approach is based on new constrained scheduling algorithms controlled by reinforcement learning techniques. Different constrained scheduling algorithms,, such as "conflict free scheduling with minimum duration", "partial displacement" and "pattern oriented scheduling" are defined and implemented. The scheduling algorithms are integrated into reinforcement learning strategies. These strategies include: - Q-learning for selection of optimal planning schedule using Q-values; - Informed Q-learning for exploitation and handling of prior-knowledge (patterns of network behaviour; - Relational Q-learning for improving of bandwidth allocation policies dynamically in operational networks considering actual network performance data. Scenarios based on integration of the scheduling algorithms and reinforcement learning techniques in the experimental monitoring and bandwidth planning system called QORE (QoS and resource optimisation are given. The proposed adaptable bandwidth planning is required for more efficient usage of network resources.

Dirk Hetzer

2006-08-01

109

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

110

Hand acceleration impulse bandwidth during target acquisition: Implications for teleoperators bandwidth requirements  

International Nuclear Information System (INIS)

The purpose of this experiment was to provide data about bandwidth requirements for teleoperators. During teleoperation, user inputs are changes in forces applied to the master controller arising from changes in hand acceleration during execution of goal-directed trajectories, so human hand acceleration bandwidth sets an upper bound on teleoperator feedforward bandwidth requirements. Participants completed a set of computerized target acquisition tasks using a mouse, and the computer recorded the cursor trajectory. Movement time, positioning error, the number of acceleration-deceleration impulses, impulse band-width, impulse amplitude, and impulse period were calculated from the trajectory trace. As many as 6 acceleration-deceleration impulses occurred during a single target acquisition, but in most trials (96.8%) there were 4 or fewer. The average acceleration-deceleration impulse bandwidth was 5.63 Hz for the first impulse and 9.20 Hz for subsequent impulses. The average period was 265 ms (3.77 Hz) for the first impulse and 218 ms (4.59 Hz) for succeeding ones. Therefore, to completely capture hand trajectories, master controllers and slave arms must have acceleration bandwidth higher than 9.20 Hz. However, it may be that only the joints closest to the end-effector need to accommodate the highest bandwidths and ''shoulder '' joints may only need to accommodate 5.63 Hz acceleration bandwidth

111

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

112

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 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. PMID:23126892

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

2012-10-01

113

Reconstruction in time-bandwidth compression systems  

Science.gov (United States)

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—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 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, J.; Mahjoubfar, A.; Asghari, M.; Jalali, B.

2014-12-01

114

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

115

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)

116

3 GHz bandwidth rutile Bragg cell  

Science.gov (United States)

We report the development of a 3GHz bandwidth Bragg cell designed for operation at 488nm with a peak optical diffraction efficiency of 2.3%/RF Watt. This device has the highest bandwidth ever reported for an optical polarisation switching Bragg cell. The device is manufactured using an optically rotated cut of single crystal rutile (TiO2). Three prototype devices have been built and each have an acousto-optic response centred on ~5GHz that is flat to better than 3dB. Excellent electrical match to the device transducer has been demonstrated on all three devices. The best device had a VSWR of 2:1 over a bandwidth of 5.55GHz centred on 5.15GHz. These new devices exhibit low acoustic attenuation across the optical aperture and also have low optical scatter. They will permit the development of ultra-wide band acousto-optic spectrometers.

Kent, L. W. J.

2008-09-01

117

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

118

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

119

InGaAs/AlGaInAs/InP Laser with Compressively Strained Multiquantum Well Layers for High Speed Modulation Bandwidth  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The modulation frequency response of compressively strained multiquantum well (MQW) lasers grown with an InGaAs/AlGaInAs/InP heterostructure and emitting at the wavelength of 1.55 mm is presented. The laser devices processed with the mushroom-stripe buried structure presen [...] t a high frequency 3 dB bandwidth above 20 GHz. The frequency response was measured with the small signal modulation technique. The logarithmic subtraction method was employed to extract the intrisic frequency response of the MQW active layer, providing the determination of important laser parameters: the differential gain, the nonlinear gain coefficient and the maximum 3 dB frequency bandwidth.

M.T., Furtado; E.J.T., Manganote; A.C.G., Bordeaux-Rêgo; F., Steinhagen; H., Janning; H., Burkhard.

1997-12-01

120

Novel high-gain, improved-bandwidth, finned-ladder V-band Traveling-Wave Tube slow-wave circuit design  

Science.gov (United States)

The V-band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for inter-satellite communications. As a first effort to develop a high-efficiency V-band Traveling-Wave Tube (TWT), variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite these advantages, however, low bandwidth and high voltage requirements have, until now, prevented its acceptance outside the laboratory. In this paper, the three-dimensional electrodynamic simulation code MAFIA (solution of MAxwell's Equation by the Finite-Integration-Algorithm) is used to investigate methods of increasing the bandwidth and lowering the operating voltage of the ring-plane circuit. Calculations of frequency-phase dispersion, beam on-axis interaction impedance, attenuation and small-signal gain per wavelength were performed for various geometric variations and loading distributions of the ring-plane TWT slow-wave circuit. Based on the results of the variations, a circuit termed the finned-ladder TWT slow-wave circuit was designed and is compared here to the scaled prototype ring-plane and a conventional ferruled coupled-cavity TWT circuit over the V-band frequency range. The simulation results indicate that this circuit has a much higher gain, significantly wider bandwidth, and a much lower voltage requirement than the scaled ring-plane prototype circuit, while retaining its excellent thermal dissipation properties. The finned-ladder circuit has a much larger small-signal gain per wavelength than the ferruled coupled-cavity circuit, but with a moderate sacrifice in bandwidth.

Kory, Carol L.; Wilson, Jeffrey D.

1994-01-01

121

Fast Faraday Cup With High Bandwidth  

Science.gov (United States)

A circuit card stripline Fast Faraday cup quantitatively measures the picosecond time structure of a charged particle beam. The stripline configuration maintains signal integrity, and stitching of the stripline increases the bandwidth. A calibration procedure ensures the measurement of the absolute charge and time structure of the charged particle beam.

Deibele, Craig E [Knoxville, TN

2006-03-14

122

Development and Implementation of the Nordic Grid Model for Power System Small-Signal and Transient Stability Studies in a Free and Open Source Software  

OpenAIRE

This article presents an implementation of a Nordic grid model in Power System Analysis Toolbox (PSAT) -a free and open-source software. A newly developed hydro turbine and hydro governor (HTG) model is implemented with this grid model and compared with the currently available PSAT turbine and governor models. Small-signal and transient stability analyses of the system using the two models are carried out and compared to demonstrate the difference and necessity of accurate hydro turbine and g...

Chompoobutrgool, Yuwa; Li, Wei; Vanfretti, Luigi

2012-01-01

123

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

124

Dynamic MTW: a dynamic bandwidth distribution scheme in EPON  

Science.gov (United States)

An algorithm to improve the bandwidth utilization for EPON by using dynamic bandwidth distribution is put forward. System performance, such as queuing delay under self-similar traffic, is simulated by using OPNET.

Chen, Hong; Ge, Liangwei; Zeng, Lieguang

2002-08-01

125

Measuring Bandwidth for Super Computer Workloads  

CERN Document Server

Parallel computing plays a major role in almost all the fields from research to major concern problem solving purposes. Many researches are till now focusing towards the area of parallel processing. Nowadays it extends its usage towards the end user application such as GPU as well as multi-core processor development. The bandwidth measurement is essential for resource management and for studying the various performance factors of the existing super computer systems which will be helpful for better system utilization since super computers are very few and their resources should be properly utilized. In this paper the real workload trace of one of the super computers LANL is taken and shown how the bandwidth is estimated with the given parameters.

Madheswari, A Neela

2010-01-01

126

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

127

Dynamic Bandwidth Allocation Strategy for Marine VHF Communications  

OpenAIRE

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 st...

Ding Yuan-Ming; Zhang Fang

2013-01-01

128

Wide bandwidth porous silicon coatings for silicon  

Energy Technology Data Exchange (ETDEWEB)

Porous silicon anti-reflection coatings for silicon substrate, with a reflectance of less than 2% in the spectral range of 400-1000 nm, were fabricated. The wide bandwidth operation was realized by introducing a smooth refractive index gradation at the porous silicon-substrate interface to suppress multiple reflection fringes. Low current density anodization was adopted to form the high refractive index layer needed for a smooth refractive index gradation. (orig.)

Uehara, S.; Kurose, K.; Matsubara, T. [Seikei Univ., Tokyo (Japan). Fac. of Eng.

2000-11-16

129

Bandwidth Efficient OFDM Transmitter Diversity Techniques  

OpenAIRE

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 spati...

Lee, King F.; Williams, Douglas B.

2004-01-01

130

DBAS: A Deployable Bandwidth Aggregation System  

OpenAIRE

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 w...

Habak, Karim; Youssef, Moustafa; Harras, Khaled A.

2012-01-01

131

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)

132

Spectral sidebands on a narrow-bandwidth optical probe as a broad-bandwidth THz pulse diagnostic.  

Science.gov (United States)

Broad-bandwidth THz-domain electro-magnetic pulses are typically diagnosed through temporal electro-optic (EO) cross-correlation with an optical probe pulse. Single-shot time-domain measurements of the THz waveform involve complex setups at a bandwidth coverage limited by the probe bandwidth. Here we present an EO-based diagnostic directly in the spectral domain, relying on THz-induced optical sidebands on a narrow-bandwidth optical probe. Experiments are conducted with a 0.11-THz-bandwidth optical probe and a broadband source (0-8 THz detection bandwidth) rich in spectral features. The validity of the sideband diagnostic concept, its spectral resolution, sideband amplitude, and the effects of probe timing are studied. For probe pulses longer than the THz pulse, the sideband technique proves an accurate single-shot spectral diagnostic, with advantages in setup simplicity and bandwidth coverage no longer limited by the laser bandwidth. PMID:22274247

van Tilborg, J; Bakker, D J; Matlis, N H; Leemans, W P

2011-12-19

133

Variable bandwidth broadcasting protocol for video-on-demand  

Science.gov (United States)

We present the first broadcasting protocol that can alter the number of channels allocated to a given video without inconveniencing the viewer and without causing any temporary bandwidth surge. Our variable bandwidth broadcasting (VBB) protocol assigns to each video a minimum number of channels whose bandwidths are all equal to the video consumption rate. Additional channels can be assigned to the video at any time to reduce the customer waiting time or retaken to free server bandwidth. The cost of this additional flexibility is quite reasonable as the bandwidth requirements of our VBB fall between those of the fast broadcasting protocol and the new pagoda broadcasting protocol.

Paris, Jehan-Francois; Long, Darrell D. E.

2003-01-01

134

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

135

Bandwidth Extension of Constant-Q Bandpass Filter using Bandwidth Extension Techniques  

Directory of Open Access Journals (Sweden)

Full Text Available CMOS spiral inductors suffer from a number of drawbacks including a low Q factor, a low self- resonant frequency, and a small and non-tunable inductance and require a large chip area. On the other hand active inductor offers many unique advantages over their spiral counterparts including small chip area, large and tunable inductance and high quality factor. These active inductors have been used successfully in many applications such as in radio frequency (RF front end integrated circuits, filters, and phase shifter and oscillator circuits. The effectiveness of these active inductors is however affected by a number of limitation including small dynamic range, a high noise level and high power consumption. High speed applications such as preamplifier of data transceiver require large bandwidth hence there is a need for technique that achieve larger bandwidth without increased power consumption and design complexity. In this paper, bandwidth extension techniques are used to extend the bandwidth of the bandpass filter. Active inductors are used in the designing of the bandpass filter. A swing independent quality factor, called constant-Q active inductor is used as an active element in the designing of the bandpass filter. Bandpass filter is implemented on both 0.5 µm and 0.35 µm CMOS process. Comparisons are made between resistive compensation technique and inductive series peaking technique. Simulation results shows that the bandwidth is improved by 72%.The operating frequency is also increases from 122.995 MHz to 194.276 MHz at 0.5 µm technology and operating frequency increases from 163.641 MHz to 259.189 MHz at 0.35 µm technology.

Megha Chitranshi

2013-08-01

136

Design of InAlAs/InGaAs PHEMTs and small-signal modeling from 0.5 to 110 GHz  

Science.gov (United States)

90-nm T-shaped gate InP-based In0.52Al0.48As/In0.6Ga0.4As pseudomorphic high electron mobility transistors were designed and fabricated with a gate-width of 2 × 30 ?m, a source—drain space of 2.5 ?m, and a source—gate space of 0.75 ?m. DC, RF and small-signal model characterizations were demonstrated. The maximum saturation current density was measured to be 755 mA/mm biased at Vgs = 0.6 V and Vds = 1.5 V. The maximum extrinsic transconductance was measured to be 1006 mS/mm biased at Vgs = ?0.1 V and Vds = 1.5 V. The extrapolated current gain cutoff frequency and maximum oscillation frequency based on S-parameters measured from 0.5 to 110 GHz were 180 and 264 GHz, respectively. The inflection point (the stability factor k = 1) where the slope from ?10 dB/decade (MSG) to ?20 dB/decade (MAG) was measured to be 83 GHz. The small-signal model of this device was also established, and the S-parameters of the model are consistent with those measured from 0.5–110 GHz.

Zhiming, Wang; Xin, Lü; Xiaobin, Luo; Yuxing, Cui; Xiguo, Sun; Jianghui, Mo; Xingchang, Fu; Liang, Li; Dawei, He

2015-02-01

137

Bandwidth Enhancement in Multilayer Microstrip Proximity Coupled Array  

Directory of Open Access Journals (Sweden)

Full Text Available Now days, there is a huge demand for wireless applications. Antennas which are used in these applications require being low profile, light weight, easily mounted and broad bandwidth. The microstrip antenna has all the features mentioned above except for its narrow bandwidth, typically from less than 1% to several percent. This paper introduces an alternative approach in enhancing the bandwidth of the microstrip antenna. The bandwidth enhancement technique which is studied is the Proximity coupled Microstrip Antenna with Air-Gap. By using this technique, a bandwidth enhancement of 14.77% can be achieved and after that we have designed an array of proximity coupled antenna and achieved a bandwidth of 19% at afrequency of 7GHz.

Shubham Gupta

2012-03-01

138

Variable data driven bandwidth choice in nonparametric quantile regression  

OpenAIRE

The choice of a smoothing parameter or bandwidth is crucial when applying non- parametric regression estimators. In nonparametric mean regression various meth- ods for bandwidth selection exists. But in nonparametric quantile regression band- width choice is still an unsolved problem. In this paper a selection procedure for local varying bandwidths based on the asymptotic mean squared error (MSE) of the local linear quantile estimator is discussed. To estimate the unknown quant...

Abberger, Klaus

2002-01-01

139

Compact antenna arrays with wide bandwidth and low sidelobe levels  

Science.gov (United States)

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

140

Finite bandwidth effects on Raman backscattering in inhomogeneous plasma  

Energy Technology Data Exchange (ETDEWEB)

The effect of bandwidth on Raman backscattering is investigated and an expression for convective amplification is derived, where the effects of collision and phase mismatch were taken into consideration. We found that if we neglect the collision frequency, the dependence of the amplification factor on the bandwidth disappears. The growth rate was also investigated and it was found to decrease with bandwidth. We obtained a formula to estimate the threshold intensity of the pump wave. (author).

Laham, N.M.; Khateeb, A.M.; Ayoub, N.Y.; Abdallah, A.K.; Odeh, I.M.; Dababneh, M.S. [Yarmouk Univ., Irbid (Jordan)

1995-01-01

141

Bandwidth limitation of the Fabry Perot cavity antennas  

International Nuclear Information System (INIS)

The bandwidth behavior of the Fabry Perot cavity antennas are considered on the basis of circuit theory. It is shown that the approaches of regenerative amplifier are applicable to resonator antenna. The equations for bandwidth limitation of the matched resonator antennas are obtained. It is experimentally confirmed that bandwidth of the Fabry Perot cavity antennas can be significantly enlarged by using properly selected partially reflective additional superstates

142

A simple root n bandwidth selector for nonparametric regression  

OpenAIRE

The problem of selecting bandwidth for nonparametric regression is investigated. The methodology used here is a double-smoothing procedure with data-driven pilot bandwidths. After giving an extension of the asymptotic result of Hardle, Hall and Marron (1992) by transfering the ideas of Jones, Marron and Park (1991) into the context of nonparametric regression, some fast data-driven bandwidth selectors for nonparametric regression are proposed. One of them, hpsi, is root n consistent. The perf...

Heiler, Siegfried; Feng, Yuanhua

1995-01-01

143

RECYCLING THE UNUSED BANDWIDTH USING PRIORITY BASED SCHEDULING ALGORITHM  

Directory of Open Access Journals (Sweden)

Full Text Available IEEE802.16 standard was designed to support the bandwidth demanding applications with quality of service (QOS. Bandwidth is reserved for each application to ensure the QOS for variable bit rate (VBR applications, however it is difficult for the subscriber station (SS to predict the amount of incoming data. To ensure the QOS guaranteed services, the SS may reserve more bandwidth than its demand. As a result, the reserved bandwidth may not be fully utilized all the time. In this paper we propose a scheme named bandwidth recycling to recycle the unused bandwidth without changing the existing bandwidth reservation. The idea of the proposed scheme is to allow other SSs to utilize the unused bandwidth when it is available. Thus the system throughput can be improved while maintaining the same QOS guaranteed services. Mathematical analysis and simulation are used to evaluate the proposed scheme. Simulation and analysis results confirm that the proposed scheme can recycle 35% of unused bandwidth on average. By analyzing factors affecting the recycling performance, scheduling algorithms are proposed to improve the overall throughput .the simulation results show that our proposed algorithm improves the over all throughput by 40% in a steady network.

M. Durai Ganesh

2013-10-01

144

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

145

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

146

Effective Bandwidth Utilization in IEEE802.11 for VOIP  

CERN Document Server

Voice over Internet protocol (VoIP) is one of the most important applications for the IEEE 802.11 wireless local area networks (WLANs). For network planners who are deploying VoIP over WLANs, one of the important issues is the VoIP capacity. VoIP bandwidth consumption over a WAN is one of the most important factors to consider when building a VoIP infrastructure. Failure to account for VoIP bandwidth requirements will severely limit the reliability of a VoIP system and place a huge burden on the WAN infrastructure. Less bandwidth utilization is the key reasons for reduced number of channel accesses in VOIP. But in the QoS point of view the free bandwidth of atleast 1-5% will improve the voice quality. This proposal utilizes the maximum bandwidth by leaving 1-5% free bandwidth. A Bandwidth Data rate Moderation (BDM) algorithm has been proposed which correlates the data rate specified in IEEE802.11b with the free bandwidth. At each time BDM will calculate the bandwidth utilization before sending the packet to i...

Bhanu, S Vijay; Balakrishnan, V

2010-01-01

147

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

148

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

149

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

150

Apparent base resistance decomposition by means of small-signal and high-frequency noise analyses of submicron InP/InGaAs HBTs  

International Nuclear Information System (INIS)

We present an original and reliable technique to elucidate the different contributions to the apparent base resistance (RB = RBx + XRBi) of double heterojunction bipolar transistors (HBTs) designed by Alcatel-Thales III–V Lab. The extrinsic base resistance (RBx) is quantified using small-signal measurements. The base-collector junction distribution factor (X) and the intrinsic base resistance (RBi) are extracted from high-frequency noise (HFN) measurements. This method was applied to three InP/InGaAs HBTs having different emitter surfaces (SE). The correct determination of RBx, X and RBi may be a useful tool for compact and/or linear electrical modelling and may give some guidelines to designers to improve operation frequencies. Moreover, this strategy can be applied to any layout and technological variation of HBT; it can be also applied to homojunction bipolar transistors. Our results show that HFN analysis should be included to fully characterize bipolar transistors. (paper)

151

Optical delay control of large-spectral-bandwidth laser pulses  

OpenAIRE

In this letter we report the first experimental observation of temporal delay control of large-spectral-bandwidth multimode laser pulses by means of electromagnetically induced transparency (EIT). We achieved controllable retardation with limited temporal distortion of optical pulses with an input spectral bandwidth of 3.3 GHz. The experimental results compare favorably with theoretical predictions.

Ignesti, Emilio; Cavalieri, Stefano; Fini, Lorenzo; Sali, Emiliano; Tognetti, Marco V.; Eramo, Roberto; Buffa, Roberto

2009-01-01

152

E-Readiness Assessment Model for Low Bandwidth Environment  

Directory of Open Access Journals (Sweden)

Full Text Available This paper reports on assessment of an e-readiness model for low bandwidth environment. The main focus of the model is on technological (bandwidth related critical factors that are barrier to the adoption of technology mediated learning in developing cou ...

Nazir Ahmad Suhail

153

One Method of Cloud Computing Bandwidth Allocation Based on Fairness  

Directory of Open Access Journals (Sweden)

Full Text Available In order to solve the bandwidth allocation unfairness problem in the cloud computing network, one method uses fairness congestion control algorithm, access control list (ACL and traffic policing and traffic shaping in the paper. The method can rationally solve the problem after analyzing the reason of cloud computing bandwidth allocation unfairness. For illustration, one network video conference example was utilized to show the method in solving bandwidth allocation unfairness problem.The experimental results show network bandwidths are fairly allocated, packet loss ratio and latency is obvious improvement. The method deals with non-adaptive UDP and TCP adaptive flow congestion and provides the end-to-end quality of service over the differentiated services networks, and the bandwidth allocation problem based on fairness in the cloud computing network is solved well.

Yiquan Kong

2013-02-01

154

Bandwidth efficient CCSDS coding standard proposals  

Science.gov (United States)

The basic concatenated coding system for the space telemetry channel consists of a Reed-Solomon (RS) outer code, a symbol interleaver/deinterleaver, and a bandwidth efficient trellis inner code. A block diagram of this configuration is shown. The system may operate with or without the outer code and interleaver. In this recommendation, the outer code remains the (255,223) RS code over GF(2 exp 8) with an error correcting capability of t = 16 eight bit symbols. This code's excellent performance and the existence of fast, cost effective, decoders justify its continued use. The purpose of the interleaver/deinterleaver is to distribute burst errors out of the inner decoder over multiple codewords of the outer code. This utilizes the error correcting capability of the outer code more efficiently and reduces the probability of an RS decoder failure. Since the space telemetry channel is not considered bursty, the required interleaving depth is primarily a function of the inner decoding method. A diagram of an interleaver with depth 4 that is compatible with the (255,223) RS code is shown. Specific interleaver requirements are discussed after the inner code recommendations.

Costello, Daniel J., Jr.; Perez, Lance C.; Wang, Fu-Quan

1992-01-01

155

Micromachined piezoelectric ultrasonic transducer with ultra-wide frequency bandwidth  

Science.gov (United States)

An ultrasonic transducer with a wide frequency bandwidth is always preferred for diagnostic ultrasound imaging, because a wide frequency bandwidth can reduce the duration of an ultrasonic pulse and enhance the axial imaging resolution. However, the frequency bandwidth of both conventional ultrasonic transducer and normal piezoelectric micromachined ultrasonic transducer (pMUT) is quite limited. To overcome this limitation, the mode-merging pMUT is presented in this letter. By using the rectangular membrane with large length/width aspect ratio, several resonant modes are excited within a narrow frequency range. When this pMUT works in a largely damped medium, excited modes are merged together and result in an ultra-wide bandwidth. A -6 dB bandwidth of 95% is measured in water for the proposed pMUT without matching layer, which is much broader than that of conventional pMUTs. Benefited from such ultra-wide frequency bandwidth, the pulse duration of 1 ?s is achieved at a central frequency of 1.24 MHz. If this ultra-wide bandwidth pMUT is utilized to replace the conventional transducer for diagnostic ultrasound imaging, the axial resolution can be significantly enhanced without compromising imaging depth.

Wang, Tao; Kobayashi, Takeshi; Lee, Chengkuo

2015-01-01

156

PIN photodiode bandwidth optimization in integrated CMOS process  

Science.gov (United States)

Silicon photodiode integrated with CMOS has been in extensive study for the past ten years due to its wide use in applications such as short-distance communication, VCD players, ambient light sensors and many other intelligent systems. In recent years, high speed blue-ray DVD is replacing conventional DVD due to its larger storage capacity and higher speed. In this work, the photodiode optimized for blue ray is fully integrated with standard 0.35um CMOS process and the bandwidth dependency upon thermal process and epitaxial material is investigated. It was found that the additional substrate thermal process can improve bandwidth for blue and red light but reduce bandwidth for infra-red. It is also found that higher level p-type epi doping does not impact bandwidth for blue light but reduces bandwidth for red and infra-red. The various mechanisms of bandwidth were discussed based on the experimental results. It indicated that the bandwidth of photodiodes depends on photo carriers travel time which can be explained by simple model of drift transport and diffusion transport. The design of photodiode should optimize the depletion region and reduce the carrier travel time.

Fang, Fred; Franke, Matthias; Gaebler, Daniel; Sang Sool, Koo

2011-05-01

157

Bandwidth Enhancement for Microstrip Antenna in Wireless Applications  

Directory of Open Access Journals (Sweden)

Full Text Available Antenna is a vital component in wireless application systems. The microstrip antenna can be used for wireless applications as it has features such as light weight, easily mounted and it is easy to mass produce. Although there are many features that suits well for microstrip antenna to be deployed for wireless applications, there is a very serious limitation where it has a very narrow bandwidth. The typical bandwidth of the microstrip antennas is between 1 - 3%. If this limitation is eliminated, the microstrip antenna can be used to its full potential. An alternative bandwidth enhancement technique is studied and then proposed in order to broaden the bandwidth of the microstrip antenna. The wireless application that is selected to be studied is the Wireless Local Area Network (WLAN based on the IEEE 802.11b standard. In Malaysia, this WLAN band spans from 2.4GHz to 2.48GHz. The bandwidth enhancement technique which is selected is the Identical Dual-Patch Microstrip Antenna with Air-Gap (IDMA. By using this technique, a bandwidth enhancement of about 11% has been achieved. This bandwidth very well covers the required WLAN band with an operating frequency of 2.45GHz.

RSA Raja Abdullah

2009-02-01

158

Effects of driver bandwidth upon resonantly heated electrons  

International Nuclear Information System (INIS)

Experimental data are presented which show that increased bandwidth of an electromagnetic driver can reduce the hot electron temperature due to resonant absorption. This work, done at microwave frequencies, shows that T/sub H/a(Dw/w)/sup -0.25/. It was also observed that the hot electron density increases with increasing bandwidth such that the heat flux (Q/sub H/an/sub H/T/sub H//sup ts3/2/) is nearly constant as a function of bandwidth

159

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

160

Broadening the potential bandwidth of piezoelectric transducers by partial depolarization  

International Nuclear Information System (INIS)

Elastic waves are used more and more in a nondestructive way to probe the physical properties of materials. The resolution of the images or the accuracy of the measurements is directly associated with the ultrasonic signal bandwidth and amplitude a system can generate or detect. The authors propose a technique to broaden the potential bandwidth of piezoelectric generators and sensors, which is based on utilizing a nonuniformly-polarized piezoelectric material. Both simulated and experimental responses are shown. They are in good agreement and exhibit a useful bandwidth over several natural harmonics of the piezoelectric transducer. [copyright] 2001 American Institute of Physics

161

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.

Ozimkiewicz, J.; Ruepp, Sarah Renée

2010-01-01

162

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

163

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

164

Small signal microwave amplifier design  

CERN Document Server

This book explains techniques and examples for designing stable amplifiers for high-frequency applications in which the signal is small and the amplifier circuit is linear. An in-depth discussion of linear network theory provides the foundation needed to develop actual designs. Examples throughout the book will show you how to apply the knowledge gained in each chapter leading to the complex design of low noise amplifiers. Many exercises at the end of each chapter will help students to practice their skills. The solutions to these design problems are available in an accompanying solutions book

Grosch, Theodore

2000-01-01

165

Napter Was Just the Start of the Bandwidth Invasion.  

Science.gov (United States)

Colleges are finding that, regardless of the court rulings against Napster, file-sharing services remain popular with students and problematic to campus networks because of the demand placed on bandwidth by music and video files. (EV)

Carlson, Scott

2001-01-01

166

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

167

Bandwidth allocation and pricing problem for a duopoly market  

Directory of Open Access Journals (Sweden)

Full Text Available This research discusses the Internet service provider (ISP bandwidth allocation and pricing problems for a duopoly bandwidth market with two competitive ISPs. According to the contracts between Internet subscribers and ISPs, Internet subscribers can enjoy their services up to their contracted bandwidth limits. However, in reality, many subscribers may experience the facts that their on-line requests are denied or their connection speeds are far below their contracted speed limits. One of the reasons is that ISPs accept too many subscribers as their subscribers. To avoid this problem, ISPs can set limits for their subscribers to enhance their service qualities. This paper develops constrained nonlinear programming to deal with this problem for two competitive ISPs. The condition for reaching the equilibrium between the two competitive firms is derived. The market equilibrium price and bandwidth resource allocations are derived as closed form solutions.

You Peng-Sheng

2011-01-01

168

On the Security of Bottleneck Bandwidth Estimation Techniques  

Science.gov (United States)

Several wide-area services are increasingly relying on bottleneck bandwidth estimation tools to enhance their network performance. Selfish hosts have, therefore, considerable incentives to fake their bandwidths in order to increase their benefit in the network. In this paper, we address this problem and we investigate the vulnerabilities of current bottleneck bandwidth estimation techniques in adversarial settings. We show that finding “full-fledged” solutions for the multitude of attacks on the end-to-end bandwidth estimation process might not be feasible in the absence of trusted network components; we discuss solutions that make use of such trusted components. Nevertheless, we discuss other possible solutions that alleviate these threats without requiring trusted infrastructure support and we evaluate the effectiveness of our proposals on PlanetLab nodes.

Karame, Ghassan; Gubler, David; ?apkun, Srdjan

169

Broad-bandwidth Brillouin slow light in optical fibers  

OpenAIRE

We experimentally demonstrate that Brillouin slow light with an arbitrary large bandwidth can be readily obtained in conventional optical fibers using a simple and inexpensive pump spectral broadening technique

Gonzalez Herraez, M.; Song, Kwang-yong; The?venaz, Luc

2006-01-01

170

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

171

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

172

Bandwidth-Efficient Cooperative Relaying Schemes with Multiantenna Relay  

Directory of Open Access Journals (Sweden)

Full Text Available We propose coded cooperative relaying schemes in which all successfully decoded signals from multiple sources are forwarded simultaneously by a multiantenna relay to a common multiantenna destination to increase bandwidth efficiency. These schemes facilitate various retransmission strategies at relay and single-user and multiuser iterative decoding techniques at destination, suitable for trade-offs between performance, latency, and complexity. Simulation results show that the proposed schemes significantly outperform direct transmission under the same transmit power and bandwidth efficiency.

Tho Le-Ngoc

2008-05-01

173

A Real-Time Measurement Algorithm for Available Bandwidth  

OpenAIRE

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 full...

Yin, Yi; Wu, Weidong

2009-01-01

174

Review of high bandwidth fiber optics radiation sensors  

Energy Technology Data Exchange (ETDEWEB)

This paper summarizes the use of fiber optics or guided optical systems for radiation sensors. It is limited a passive systems wherein electrical is not required at the sensor location. However, electrically powered light sources, receivers and/or recorders may still be required for detection and data storage in sensor system operation. This paper emphasizes sensor technologies that permit high bandwidth measurements of transient radiation levels, and will also discuss several low bandwidth applications. 60 refs.

Lyons, P.B.

1985-01-01

175

Review of high bandwidth fiber optics radiation sensors  

International Nuclear Information System (INIS)

This paper summarizes the use of fiber optics or guided optical systems for radiation sensors. It is limited a passive systems wherein electrical is not required at the sensor location. However, electrically powered light sources, receivers and/or recorders may still be required for detection and data storage in sensor system operation. This paper emphasizes sensor technologies that permit high bandwidth measurements of transient radiation levels, and will also discuss several low bandwidth applications. 60 refs

176

A Bandwidth Allocation Model Provisioning Framework with Autonomic Characteristics  

OpenAIRE

The Bandwidth Allocation Models (MAM, RDM, G-RDM and AllocTC-Sharing) are managementalternatives currently available which propose different resource (bandwidth) allocation strategies inmultiservice networks. The BAM adoption by a network is typically a management choice andconfiguration task executed by the network operations and management system setup in a static or nearlystatic way. This paper proposes and explores the alternative ofallowing BAM definition and configurationon a more dynam...

Reale, Rafael F.; Bezerra, Romildo M. Da S.; Martins, Joberto S. B.

2013-01-01

177

Image Cipher Technique for Covert and Low Bandwidth Channels  

OpenAIRE

Security of images during the transmission over covert low bandwidth channel has importance in today's image communications for confidential, integrated and secure real time communication. The major security problems during communication over covert and low bandwidth channel is to reduce no of bits, efficient and secure cryptographic techniques such that output gain and performance may lead towards more secure and efficient mechanism. Thus, in this paper, we have purposed a secure, reliable a...

Sangeeta Solanki; Vats, A. K.; Shikha Maan

2011-01-01

178

Collaboration and Document Editing on Bandwidth-Limited Devices  

OpenAIRE

This paper presents the design of CoFi, a novel architecture for supporting document editing and collaborative work over bandwidth-limited clients. CoFi combines the previously disjoint notions of consistency and fidelity in a unified architecture. CoFi enables bandwidth-limited clients to edit documents that are only partially present at the client (because parts of the documents were lossily transcoded, or only a portion of the document was fetched), and to propagate modifications increment...

Lara, Eyal; Kumar, Rajnish; Wallach, Dan S.; Zwaenepoel, Willy

2001-01-01

179

Fluorescence and small-signal gain at 2177 and 2163 Angstrom in CIII by resonant photoexcitation with 310 Angstrom MnVI line radiation  

International Nuclear Information System (INIS)

Line radiation at 310 Angstrom from a laser-produced Mn plasma was used to resonantly photoexcite the 2s 1s - 4p 1p0 transition in CIII ions in a vacuum-arc discharge. Enhanced fluorescence, up to a factor of 180, was observed on the 4p-3d line at 2177 Angstrom. Enhanced fluorescence was also observed on other 4-3 lines in CIII, because the photoexcited 4p population is collisionally redistributed among all the n = 4 levels. A 72-level, collisional-radiative model of CIII was constructed, including the resonant photoexcitation. Measured values of electron density and temperature were used in the model. Theoretical predictions of enhanced fluorescence agree well with the measurements. Small-signal gain coefficients of ? 0.1 cm-1 were theoretically predicted. Single-pass gain measurements show gains as high as 0.4 cm-1 on the 4p-3d, 2177 Angstrom line and the 4f-3d, 2163 Angstrom line. This CIII-MnVI photoexcitation scheme is a prototype for soft x-ray lasers, using higher Z, isoelectronic analogs

180

On the Bandwidth of High-Impedance Frequency Selective Surfaces  

CERN Document Server

In this letter, the bandwidth of high-impedance surfaces (HISs) is discussed by an equivalent circuit approach. Even if these surfaces have been employed for almost 10 years, it is sometimes unclear how to choose the shape of the frequency selective surface (FSS) on the top of the grounded slab in order to achieve the largest possible bandwidth. Here, we will show that the conventional approach describing the HIS as a parallel connection between the inductance given by the grounded dielectric substrate and the capacitance of the FSS may induce inaccurate results in the determination of the operating bandwidth of the structure. Indeed, in order to derive a more complete model and to provide a more accurate estimate of the operating bandwidth, it is also necessary to introduce the series inductance of the FSS.We will present the explicit expression for defining the bandwidth of a HIS, and we will show that the reduction of the FSS inductance results in the best choice for achieving wide operating bandwidth in c...

Costa, Filippo; Monorchio, Agostino; 10.1109/LAWP.2009.2038346

2010-01-01

181

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

182

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

183

Relaxor-PT single crystals for broad bandwidth, high power sonar projectors  

Science.gov (United States)

The high piezoelectric response of the ferroelectric relaxor (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 (PMNT) in single crystal form has generated significant interest in producing broad bandwidth SONAR systems. Both the piezoelectric coefficient (d33 > 2000 pC/N) and coupling coefficient (k33 > 0.90) are superior to those of conventional piezoelectric ceramics. Within the context of a high power acoustic projector, its high losses and low temperature stability have limited its development. Second generation single crystals with compositions modified from the base PMNT have been recently developed to decrease the electromechanical losses and mitigate the thermal property dependence. In this work, the electromechanical properties were measured using single crystals which have been modified in various ways. The modified crystals exhibit electromechanically "hard" behavior with lower losses (tan delta = 0.1--0.2% and QM = 230--950) than unmodified PMNT (tan delta = 0.26% and QM = 190). The measured d33 values of modified single crystals (d33 = 760--1490 pm/V) are also lower than unmodified PMNT (d33 = 1540 pm/V), but the lower piezoelectric response is compensated by the greater stability of the modified single crystals. These modified single crystal properties were also compared to conventional high power piezoelectric ceramics ( d33 = 240 pm/V and QM = 1050) to show similar losses but significantly greater response in the modified PMNT single crystals. Although most piezoelectric materials are measured under small signal conditions (small signal defined by a completely linear relationship between the input and output signals), the high power nature of SONAR projectors demands that these modified single crystals also be evaluated under high power conditions. A test procedure was developed to measure the electromechanical properties of each material as a function of applied electric field over a frequency range which includes the resonance frequency. Modified single crystals showed twice the dynamic strain of unmodified PMNT as a function of electric field, and in many cases also showed greater maximum strain at failure (0.3% compared to 0.15% for unmodified PMNT). When QM was measured as a function of drive level, it was shown to sharply decrease under high dynamic strain. Modified single crystals with greater small signal QM values than unmodified PMNT maintain higher QM values under high drive, with Q M = 50--150 immediately prior to sample failure (Q M = 20 for base PMNT immediately prior to failure). The temperature dependence of modified PMNT single crystal electromechanical properties was also determined, and it was shown that modified crystals possess greater property stability than unmodified PMNT. While the base composition shows a limiting rhombohedral-tetragonal transition at 95 °C, modified single crystals using ternary PIN and PZT components show increased transition temperatures of 125 °C and 144 °C, respectively. The greater phase stability of the PIN ternary crystal was also examined through the coercive field, which was shown to be much greater than that of unmodified PMNT over the temperature range of interest (Ec = 5 kV/cm and 2 kV/cm, respectively, at room temperature). From the combined set of property measurements, the heat generation of each material was predicted for an arbitrary projector device. As a consequence of the lower losses, modified single crystals showed as little as 25% of the heat generation value for unmodified PMNT single crystals. Using this prediction as a performance metric, the crystals with the lowest heat generation were selected for device testing. Transducers with base PMNT and modified single crystals were designed using a finite element modeling approach. This model predicted approximately two octaves of bandwidth for the transducer geometry under investigation. A 5 dB decrease in acoustic output was observed when moving from base PMNT to highly modified crystals, but that result does not account for nonlinear material behavior. Transducers fabricated using mod

Sherlock, Nevin P.

2010-06-01

184

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

185

A novel dynamic bandwidth allocation scheme in EPONs  

Science.gov (United States)

EPONs use a point-to-multipoint topology, in which multiple optical network units (ONUs) share one uplink channel to transmit multimedia traffic to a control element, the optical line terminal (OLT). Hence, to avoid data collision on the shared uplink, ensure a contention-free transmission and so on, medium access control arbitration mechanisms are essential for the successful implementation of EPONs. In this paper, a novel dynamic bandwidth allocation algorithm, the Integrated Two Classes Dynamic Bandwidth Allocation (ITCDBA), is put forward, in which the multipoint control protocol is used defined in the IEEE802.3ah standard. ITCDBA is a hierarchical allocation scheme which dynamically allocates bandwidth according to the instantaneous demands of ONUs, supporting inter-ONU priority scheduling as well as intra-ONU priority scheduling. The simulation result shows that the system throughput of EPON is improved with ITCDBA scheme and the drop rate of the traffic with the highest priority is lower than that with Two-layer bandwidth allocation (TLBA) scheme [11]. In a word, ITCDBA not only can allocate bandwidths between end users effectively and fairly, but also can support differentiated services. Besides, the system performance of EPONs with ITCDBA scheme is improved.

Chen, Hong; Jin, Depeng; Zeng, Lieguang

2005-11-01

186

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

187

Visual bandwidths for face orientation increase during healthy aging.  

Science.gov (United States)

Perception of visual motion declines during healthy aging, and evidence suggests that this reflects decreases in cortical GABA inhibition that increase neural noise and motion bandwidths. This is supported by neurophysiological data on motion perception in senescent monkeys. Much less is known about deficits in higher level form vision. For example, face perception of frontal views remains relatively constant from adolescence through age 70 with a modest decline thereafter. However, we have shown recently that the elderly have a specific deficit in face matching when a transformation must be made between frontal and left or right side views. Here we use face view adaptation to demonstrate that this deficit results from significant broadening of cortical bandwidths for face orientation along with increased internal noise. A neural model shows that these bandwidths increase by a factor of 1.74 between age 26 and age 67 years. This is similar to the increase reported for motion bandwidths in senescent monkeys. Furthermore, the neural model demonstrates that head orientation bandwidth increases can arise from decreased cortical inhibition. Thus, high levels of form vision degrade in parallel with higher levels of motion perception and likely result from similar causes. PMID:21074549

Wilson, Hugh R; Mei, Ming; Habak, Claudine; Wilkinson, Frances

2011-01-01

188

3-DB, 3-D Multigroup Diffusion, X-Y-Z, R-Theta-Z, Triangular-Z Geometry, Fast Reactor Burnup  

International Nuclear Information System (INIS)

1 - Description of problem or function: 3DB is a three-dimensional (x-y-z, r-theta-z, triangular-z) multigroup diffusion code for use in detailed fast-reactor criticality and burnup analysis. The code can be used to - (a) compute keff and perform criticality searches on time absorption, reactor composition, and reactor dimensions by means of either a flux or an adjoint model, (b) compute material burnup using a flexible material shuffling scheme, and (c) compute flux distributions for an arbitrary extraneous source. 2 - Method of solution: Eigenvalues are computed by standard source- iteration techniques. Group re-balancing and successive over-relaxation with line inversion are used to accelerate convergence. Adjoint solutions are obtained by inverting the input data and redefining the source terms. Material burnup is by reactor zone. The burnup rate is determined by the zone and energy-averaged cross sections which are recomputed after each time-step. The isotopic chains, which can contain any number of isotopes are formed by the user. The code does not contain built- in or internal chains. 3 - Restrictions on the complexity of the problem: Since variable dimensioning is employed, no simple bounds can be stated

189

Bandwidth-disorder phase diagram of half doped layered manganites  

CERN Document Server

Phase diagrams in the plane of $r_A$ (the average ionic radius, related to one-electron bandwidth $W$) and $\\sigma^2$ (the ionic radius variance, measuring the quenched disorder), or ``bandwidth-disorder phase diagrams'', have been established for perovskite manganites, with three-dimensional (3$D$) Mn-O network. Here we establish the intrinsic bandwidth-disorder phase diagram of half-doped layered manganites with the two-dimensional (2$D$) Mn-O network, examining in detail the ``mother state'' of the colossal magnetoresistance (CMR) phenomenon in crystals without ferromagnetic instability. The consequences of the reduced dimensionality, from 3$D$ to 2$D$, on the order-disorder phenomena in the charge-orbital sectors are also highlighted.

Mathieu, R; Kaneko, Y; He, J P; Yu, X Z; Kumai, R; Arima, T; Tomioka, Y; Asamitsu, A; Matsui, Y; Tokura, Y

2006-01-01

190

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)

191

Benefits of bandwidth feedback in learning a complex gymnastic skill.  

Science.gov (United States)

The aim of this study was to examine the effects of two different frequencies of feedback during the process of learning a complex gymnastic skill, the round-off salto backward tucked. Thirty male acrobats participated in the study. They were randomly assigned to two groups: B - bandwidth feedback (n=15) or C - 100% feedback (n=15). Group B was provided with error information regarding the key elements of movement techniques only (bandwidth feedback). Our research demonstrates the advantage of augmented feedback information related to errors in the key elements. Information about errors in the key elements during learning a complex gymnastic skill prevents the gymnast from becoming overwhelmed, which promotes better motor control. These results provide support for the generalisation of bandwidth feedback principles to a complex task. Our research shows that the guidance hypothesis can also be tested in practical settings for a complex movement task. PMID:24146719

Sadowski, Jerzy; Mastalerz, Andrzej; Niznikowski, Tomasz

2013-01-01

192

PRIORITY BASED BANDWIDTH ALLOCATION IN WIRELESS SENSOR NETWORKS  

Directory of Open Access Journals (Sweden)

Full Text Available Most of the sensor network applications need real time communication and the need for deadline aware real time communication is becoming eminent in these applications. These applications have different dead line requirements also. The real time applications of wireless sensor networks are bandwidth sensitive and need higher share of bandwidth for higher priority data to meet the dead line requirements. In this paper we focus on the MAC layer modifications to meet the real time requirements of different priority data. Bandwidth partitioning among different priority transmissions is implemented through MAC layer modifications. The MAC layer implements a queuing model that supports lower transfer rate for lower priority packets and higher transfer rate for real time packets with higher priority, minimizing the end to end delay. The performance of the algorithm is evaluated with varying node distribution.

Mary Cherian

2014-12-01

193

Performance Investigation of Virtual Private Networks with Different Bandwidth Allocations  

Directory of Open Access Journals (Sweden)

Full Text Available 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.

Ramaswamy Muthiah

2010-01-01

194

Adaptive broadcasting mechanism for bandwidth allocation in mobile services.  

Science.gov (United States)

This paper proposes a tree-based adaptive broadcasting (TAB) algorithm for data dissemination to improve data access efficiency. The proposed TAB algorithm first constructs a broadcast tree to determine the broadcast frequency of each data and splits the broadcast tree into some broadcast wood to generate the broadcast program. In addition, this paper develops an analytical model to derive the mean access latency of the generated broadcast program. In light of the derived results, both the index channel's bandwidth and the data channel's bandwidth can be optimally allocated to maximize bandwidth utilization. This paper presents experiments to help evaluate the effectiveness of the proposed strategy. From the experimental results, it can be seen that the proposed mechanism is feasible in practice. PMID:25057509

Horng, Gwo-Jiun; Wang, Chi-Hsuan; Chou, Chih-Lun

2014-01-01

195

Analysis of bandwidth measurement methodologies over WLAN systems  

CERN Document Server

WLAN devices have become a fundamental component of nowadays network deployments. However, even though traditional networking applications run mostly unchanged over wireless links, the actual interaction between these applications and the dynamics of wireless transmissions is not yet fully understood. An important example of such applications are bandwidth estimation tools. This area has become a mature research topic with well-developed results. Unfortunately recent studies have shown that the application of these results to WLAN links is not straightforward. The main reasons for this is that the assumptions taken to develop bandwidth measurements tools do not hold any longer in the presence of wireless links (e.g. non-FIFO scheduling). This paper builds from these observations and its main goal is to analyze the interaction between probe packets and WLAN transmissions in bandwidth estimation processes. The paper proposes an analytical model that better accounts for the particularities of WLAN links. The mod...

Portoles-Comeras, Marc; Mangues-Bafalluy, Josep; Domingo-Pascual, Jordi

2009-01-01

196

Bandwidth analysis of all-optical turbo-switch  

Science.gov (United States)

We propose and develop a frequency-domain model to analyze the bandwidth of all-optical turbo-switch. The model has taken the spatial inhomogeneity of semiconductor optical amplifier (SOA) into consideration for the first time. The simulations based on the model show that the 3-dB bandwidth of turbo-switch could reach up to ~270 GHz when the second SOA is oversaturated. However, the overshoot will be higher, which may result in the distortion of the output signal. There is a trade-off between the bandwidth and the flatness of frequency response characteristics for turbo-switch operation. In addition, the optimum position of the delay-interferometer (DI) is investigated, showing that the level of the overshoot is relatively lower if the DI is placed between the two SOAs.

Zhou, Peng; Yang, Xuelin; Hu, Xiaonan; Hu, Weisheng

2015-01-01

197

Gain-switched all-fiber laser with narrow bandwidth  

DEFF Research Database (Denmark)

Gain-switching of a CW fiber laser is a simple and cost-effective approach to generate pulses using an all-fiber system. We report on the construction of a narrow bandwidth (below 0.1 nm) gain-switched fiber laser and optimize the pulse energy and pulse duration under this constraint. The extracted pulse energy is 20 ?J in a duration of 135 ns at 7 kHz. The bandwidth increases for a higher pump pulse energy and repetition rate, and this sets the limit of the output pulse energy. A single power amplifier is added to raise the peak power to the kW-level and the pulse energy to 230 ?J while keeping the bandwidth below 0.1 nm. This allows frequency doubling in a periodically poled lithium tantalate crystal with a reasonable conversion efficiency.

Larsen, Casper; Giesberts, M.

2013-01-01

198

High bandwidth frequency lock of a rigid tunable optical cavity.  

Science.gov (United States)

In this paper, we present a high bandwidth frequency lock of a rigid tunable Fabry Perot cavity based on a set of lead zirconate titanate (PZT) actuators. The cavity spacer was specifically designed such that the frequency of the first resonance of the whole assembly under PZT excitation is above 35 kHz, thus allowing a servo-loop bandwidth of 13 kHz. It is demonstrated that no significant noise is added by the cavity to the output beam with respect to the input beam over the servo-loop bandwidth. This cavity can be used as a pre-mode cleaner in interferometric gravitational wave detectors such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo. PMID:25403002

Millo, Jacques; Merzougui, Mourad; Di Pace, Sibilla; Chaibi, Walid

2014-11-10

199

Ultra Wideband Microstrip Diamond Slotted Patch Antenna with Enhanced Bandwidth  

OpenAIRE

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

200

Exact and Heuristic Solutions to the Bandwidth Minimization Problem  

OpenAIRE

The bandwidth minimization problem is a classical combinatorial optimization problem studied since about 1960. It is formulated as follows. Given a connected graph G=(V,E) with n vertices, the task is to find a permutation l of the vertices (also called a labeling), i.e., a bijection between V and {1,2,...,n}, such that the maximum difference |l(u)-l(v)|, for uv in E, is minimized. This problem is NP-hard, even for binary trees. Applications of the bandwidth problem can be found in many areas...

Vo, Tan Khoa

2011-01-01

201

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)

202

Bandwidth effects in Brillouin scattering from inhomogeneous plasma  

International Nuclear Information System (INIS)

Convective Brillouin amplification in inhomogeneous, drifting plasmas is discussed. The bandwidth of the amplifier is a function of both wave damping and plasma inhomogeneity. For any given plasma model and source spectrum, the final amplified spectrum can be constructed, including the effects of inhomogeneity, drift, damping, and gain narrowing. Conversely, the shape of observed spectra of Brillouin scattering can be used to obtain information about conditions in the underdense plasma corona if it can be assumed that amplification is high enough that the final spectral bandwidth is amplifier dominated

203

Small Bandwidth Asymptotics for Density-Weighted Average Derivatives  

DEFF Research Database (Denmark)

This paper proposes (apparently) novel standard error formulas for the density-weighted average derivative estimator of Powell, Stock, and Stoker (1989). Asymptotic validity of the standard errors developed in this paper does not require the use of higher-order kernels and the standard errors are "robust" in the sense that they accommodate (but do not require) bandwidths that are smaller than those for which conventional standard errors are valid. Moreover, the results of a Monte Carlo experiment suggest that the finite sample coverage rates of con…dence intervals constructed using the standard errors developed in this paper coincide (approximately) with the nominal coverage rates across a nontrivial range of bandwidths.

Cattaneo, Matias D.; Crump, Richard K.

2008-01-01

204

Extending the Bandwidth of Electric Ring Resonator Metamaterial Absorber  

International Nuclear Information System (INIS)

An efficient method is proposed to extend the bandwidth of a metamaterial absorber with multi-resonance structure. The basic unit cell of a metamaterial absorber consists of the electric ring resonator, dielectric substrate (FR-4) and split-wire. By assembling five sandwiched structures with different geometric dimensions into a unit cell, we obtain the superposition of five different absorption peaks. Finally, the bandwidth of metamaterial absorption is extended and the full width at half maximum is up to 1.3 GHz. The simulated and experimental results are consistent. (fundamental areas of phenomenology(including applications))

205

Image Cipher Technique for Covert and Low Bandwidth Channels  

Directory of Open Access Journals (Sweden)

Full Text Available Security of images during the transmission over covert low bandwidth channel has importance in today's image communications for confidential, integrated and secure real time communication. The major security problems during communication over covert and low bandwidth channel is to reduce no of bits, efficient and secure cryptographic techniques such that output gain and performance may lead towards more secure and efficient mechanism. Thus, in this paper, we have purposed a secure, reliable and efficient mechanism using arithmetic coding techniques followed by IMAES (Improved Modified Advanced Encryption standard techniques. The output of encrypted images reveals that proposed technique presents higher performance, quit reliable and robust.

Sangeeta Solanki

2011-05-01

206

Bandwidth Enhancement of Probe Fed Microstrip Patch Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available Microstrip patch antenna becomes verypopular day by day because of its ease of analysis andfabrication, low cost, light weight, easy to feed and theirattractive radiation characteristics. Although patchantenna has numerous advantages, it has also somedrawbacks such as restricted bandwidth, and a potentialdecrease in radiation pattern. Different techniques forbandwidth enhancement of conventional rectangularmicrostrip antenna are proposed in this paper. Byincreasing the height of patch , increasing the substratethickness and decreasing the permittivity of substrate the%bandwidth is increased. HFSS Software is used for thesimulation and design calculation of microstrip patchantenna. The return loss, vswr curve, directivity and gainare evaluated.

Parminder Singh

2013-01-01

207

Distributed Algorithms for Dynamic Bandwidth Provisioning in Communication Networks  

Directory of Open Access Journals (Sweden)

Full Text Available

Efficient dynamic resource provisioning algorithms are necessary to the development and automation of Quality of Service (QoS networks. The main goal of these algorithms is to offer services that satisfy the QoS requirements of individual users while guaranteeing at the same time an efficient utilization of network resources. In this paper we introduce a new service model that provides quantitative per-flow bandwidth guarantees, where users subscribe for a guaranteed rate; moreover, the network periodically individuates unused bandwidth and proposes short-term contracts where extra-bandwidth is allocated and guaranteed exclusively to users who can exploit it to transmit at a rate higher than their subscribed rate. To implement this service model we propose a dynamic provisioning architecture for intra-domain Quality of Service networks. We develop an efficient bandwidth allocation algorithm that takes explicitly into account traffic statistics to increase the users’ benefit and the network revenue simultaneously. We demonstrate through simulation in several realistic network scenarios that the proposed dynamic provisioning model is superior to static provisioning in providing resource allocation both in terms of total accepted load and network revenue.

Antonio Capone

2006-12-01

208

A Practical Approach For Excess Bandwidth Distribution for EPONs  

KAUST Repository

This paper introduces a novel approach called Delayed Excess Scheduling (DES), which practically reuse the excess bandwidth in EPONs system. DES is suitable for the industrial deployment as it requires no timing constraint and achieves better performance compared to the previously reported schemes.

Elrasad, Amr

2014-03-09

209

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

210

A review of single transient oscillographics recorders with gigahertz bandwidth  

International Nuclear Information System (INIS)

Describes research on laser driven inertial confinement in which many phenomena are being diagnosed that occur in a time frame that exceeds the capabilities of even the most advanced, present day oscillographic recording instruments. Many of the by-products of the interaction between laser beam and fuel pellet are monitored to determine the specifics fo the fusion process. By use of appropriate detectors, the information contained in the radiated by-products are converted to electrical signals which are recorded on high bandwidth oscillographic recorders. Range of recording capabilities for one x-ray diagnostic measurement in use at Livermore is shown in graph. Presents block diagram of ideal GHz recording instrument for fusion experiments use. Discusses the GHz bandwidth single transient recording instruments of the USSR and France, who, with the USA, are the only known countries manufacturing it

211

Conical Emission Patterns by Femtosecond Pulses with Different Spectral Bandwidths  

International Nuclear Information System (INIS)

Different conical emission (CE) patterns are obtained experimentally at various incident powers and beam sizes of pump laser pulses with pulse durations of 7 fs, 44 fs and 100 fs. The results show that it is the incident power but not the incident power density that determines a certain CE pattern. In addition, the critical powers for similar CE patterns are nearly the same for the laser pulses with the same spectral bandwidth. Furthermore, as far as a certain CE pattern is concerned, the wider the spectral bandwidth of pump laser pulse is, the higher the critical power is. This will hopefully provide new insights for the generation of CE pattern in optical medium

212

Increasing the effective bandwidth of a laser-fusion driver  

International Nuclear Information System (INIS)

The absorption of narrow-band 1.06 ?m radiation by laser-fusion targets has been less than predicted by classical physics. Thus, early extrapolations of neutron yields and fuel densities that would be achieved as more powerful lasers come on-line have not been fully realized. However, recent experiments at KMS and GILM Ecole Polytechnique are encouraging in that they have shown agreement with theoretical predictions that laser/target interactions should improve at shorter laser wavelengths. More recently theoretical treatments have further suggested that energy absorption may improve if the laser bandwidth can be increased to several percent of the laser frequency. Preliminary experiments at KMS using a plasma filter to broaden the bandwidth tend to support these predictions, but the results are not yet conclusive

213

Input Bandwidth of Hot Electron Bolometer With Spiral Antenna  

Science.gov (United States)

We report the results of our study of the input bandwidth of hot electron bolometers (HEB) embedded into the planar log-spiral antenna. The sensitive element is made of the ultrathin superconducting NbN film patterned as a bridge at the feed of the antenna. The contacts between the antenna and a sensitive element are made from in situ deposited gold (i.e., deposited over NbN film without breaking vacuum), which gives high quality contacts and makes the response of the HEB at higher frequencies less affected by the RF loss. An accurate experimental spectroscopic procedure is demonstrated that leads to the confirmation of the wide (8 THz) bandwidth in this antenna coupled device.

Shurakov, Alexander; Seliverstov, Sergey; Kaurova, Natalia; Finkel, Matvey; Voronov, Boris; Goltsman, Gregory

2012-07-01

214

Two genetic algorithms for the bandwidth multicoloring problem  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper the Bandwidth Multicoloring Problem (BMCP and the Bandwidth Coloring Problem (BCP are considered. The problems are solved by two genetic algorithms (GAs which use the integer encoding and standard genetic operators adapted to the problems. In both proposed implementations, all individuals are feasible by default, so search is directed into the promising regions. The first proposed method named GA1 is a constructive metaheuristic that construct solution, while the second named GA2 is an improving metaheuristic used to improve an existing solution. Genetic algorithms are tested on the publicly-available GEOM instances from the literature. Proposed GA1 has achieved a much better solution than the calculated upper bound for a given problem, and GA2 has significantly improved the solutions obtained by GA1. The obtained results are also compared with the results of the existing methods for solving BCP and BMCP.

Fijuljanin Jasmina

2012-01-01

215

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

216

On Free-Electron Laser Growing Modes and their Bandwidth  

CERN Document Server

Free-electron lasers play an increasing role in science, from generating unique femtosecond X- ray pulses for single short recording of the protein structures to amplifying feeble interactions in advanced cooling systems for high-energy hadron colliders. While modern Free-electron laser codes can describe their amplification mechanism, a deep analytical understanding of the mechanism is of extreme importance for a number of applications. Mode competition, their growth rates and amplification bandwidth are among the most important parameters of a free-electron laser. A dispersion relation, which defines these important characteristics, can be solved analytically only for a very few simple cases. In this letter we show that for a typical bell-shape energy distribution in electron beam there is no more that one growing mode. We also derive an analytical expression which determines the bandwidth of the free-electron laser.

Webb, Stephen; Litvinenko, Vladimir

2011-01-01

217

Bandwidth Improvement of EBG Resonator Antennas Using Double-Layer FSS  

OpenAIRE

A double-layer frequency selective surface (FSS) is proposed as a means to enhance the bandwidth of an electromagnetic band gap (EBG) resonator antenna. Due to its inverted reflection phase variation and its wide selectivity bandwidth, the structure used in the radiating wall of the resonator allows increasing the radiating bandwidth of the last one. The resonator is fed by a patch feeding source placed inside the cavity at the proximity of its metallic ground. The antenna bandwidth is signif...

Bernard Jecko; Lina Moustafa

2008-01-01

218

Gigabit Passive Optical Networks (GPON) the Ultimate Solution for Large Bandwidth  

OpenAIRE

The demand for bandwidth has increased drastically. So optical transmission has got more importance in access networks. The upcoming features like IPTV, High speed internet(HSI), Video on demand(VOD), online gaming are confronting large bandwidth at the customer end.The demand of bandwidth can be satisfied by XDSL, but the distance is restricted by using this type of technique. So we can use optical transmission for achieving large bandwidth by using passive optical networks(PON). One of the ...

Manikantasitaram, A.; K. Mohan Swamy,; Akella.Rama Krishna,

2012-01-01

219

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

220

Extraction of spatial information for low-bandwidth telerehabilitation applications  

OpenAIRE

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 challengi...

Kok Kiong Tan, Phd; Arun Shankar Narayanan; Choon Huat Koh, Phd; Kevin Caves; Helen Hoenig, Md

2014-01-01

221

Forecasting international bandwidth capacity using linear and ANN methods  

OpenAIRE

An artificial neural network (ANN) can improve forecasts through pattern recognition of historical data. This article evaluates the reliability of ANN methods, as opposed to simple extrapolation techniques, to forecast Internet bandwidth index data that is bursty in nature. A simple feedforward ANN model is selected as a nonlinear alternative, as it is flexible enough to model complex linear or nonlinear relationships without any prior assumptions about the data generating process. These d...

Madden, Gary G.; Tan, Joachim

2008-01-01

222

Bandwidth and Energy Efficient Decentralized Sequential Change Detection  

OpenAIRE

The problem of decentralized sequential change detection is considered, where an abrupt change occurs in an area monitored by a number of sensors; the sensors transmit their data to a fusion center, subject to bandwidth and energy constraints, and the fusion center is responsible for detecting the change as soon as possible. A novel sequential detection rule is proposed that requires communication from the sensors at random times and transmission of only low-bit messages, on...

Fellouris, Georgios; Moustakides, George V.

2012-01-01

223

Automated Controllers for Bandwidth Allocation in Network Virtualization  

OpenAIRE

The concept of network virtualization was introduced to facilitate flexible service deployment for the future Internet. This recent technology provides a powerful tool to run multiple logical networks on the same physical substrate defined as virtual networks (VNs). Each physical link is split into virtual links and each VN receives a fraction of the available capacity. Bandwidth allocation for multiple VMs aims at sharing the physical links among multiple VNs. It is a critical challenge for ...

Seddiki, M. Said; Nefzi, Bilel; Song, Ye-qiong; Frikha, Mounir

2013-01-01

224

Estimates of intensity, wavelength, and bandwidth scaling of Brillouin backscatter  

International Nuclear Information System (INIS)

A simple nonlinear, one-dimensional spherical Brillouin model adapted from kinetic simulations and Kruer's theory to a fluid code (LASNEX) is described. Laser absorption and Brillouin reflection are plotted for 0.26501316 W/cm2 on gold disks (pulse length of 1 nsec) and the calculated absorption compared to experiments. Kinetic simulations suggest methods of reducing Brillouin reflection, such as a wide bandwidth and multiline laser

225

Analysis of bandwidth measurement methodologies over WLAN systems  

OpenAIRE

WLAN devices have become a fundamental component of nowadays network deployments. However, even though traditional networking applications run mostly unchanged over wireless links, the actual interaction between these applications and the dynamics of wireless transmissions is not yet fully understood. An important example of such applications are bandwidth estimation tools. This area has become a mature research topic with well-developed results. Unfortunately recent studies...

Portoles-comeras, Marc; Cabellos-aparicio, Albert; Mangues-bafalluy, Josep; Domingo-pascual, Jordi

2009-01-01

226

Latency and Bandwidth Analysis of LTE for a Smart Grid  

OpenAIRE

Smart grid has been proposed as an alternative to the traditional electricity grid recently thanks to its advantages of real time control on consumption demands. The latest wireless network, 3GPP Long Term Evolution (LTE), is considered to be a promising solution to interconnecting the smart objects in a smart grid because LTE provides both low latency and large bandwidth. However, the theories and standards for deploying a smart grid are still under study. Furthermore, the performance of LTE...

Xu, Yuzhe

2011-01-01

227

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

228

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

229

Wide bandwidth transimpedance preamplifier for a scanning tunneling microscope  

Science.gov (United States)

A new two-stage transimpedance preamplifier in feedback picoammeter setup for use in scanning tunneling microscopy is represented. The first stage consisting of a wide band field effect transistor input operational amplifier with resistive feedback has a transimpedance of 20 k? and a 3 dB bandwidth of 35 MHz. This setup is built to investigate sub ?s fluctuations in the tunneling current.

Demming, F.; Dickmann, K.; Jersch, J.

1998-06-01

230

Power-bandwidth-distortion scaling laws for sensor networks  

OpenAIRE

The goal of a class of sensor networks is to monitor an underlying physical reality at the highest possible fidelity. Sensors acquire noisy measurements and have to communicate them over a power- and possibly bandwidth-constrained interference channel to a set of base stations. The goal of this paper is to analyze, as a function of the number of sensors, the trade-offs between the degrees of freedom of the underlying physical reality, the communication resources (power, temporal and spatial b...

Gastpar, Michael; Vetterli, Martin

2004-01-01

231

A comparison of bandwidth selectors for mean shift clustering  

OpenAIRE

We explore the performance of several automatic bandwidth selectors, originally designed for density gradient estimation, as data-based procedures for nonparametric, modal clustering. The key tool to obtain a clustering from density gradient estimators is the mean shift algorithm, which allows to obtain a partition not only of the data sample, but also of the whole space. The results of our simulation study suggest that most of the methods considered here, like cross validat...

Chaco?n, Jose? E.; Monfort, Pablo

2013-01-01

232

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

233

A hybrid ACO approach to the Matrix Bandwidth Minimization Problem  

OpenAIRE

The evolution of the human society raises more and more difficult endeavors. For some of the real-life problems, the computing time-restriction enhances their complexity. The Matrix Bandwidth Minimization Problem (MBMP) seeks for a simultaneous permutation of the rows and the columns of a square matrix in order to keep its nonzero entries close to the main diagonal. The MBMP is a highly investigated P-complete problem, as it has broad applications in industry, logistics, art...

Pintea, Camelia-m; Chira, Camelia; Crisan, Gloria-c

2012-01-01

234

Frequency bandwidth of half-wave impedance repeater  

OpenAIRE

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 functionalit...

Marek Dvorsky; Libor Michalek; Martin Tomis

2012-01-01

235

Large-bandwidth data acquisition network for XFEL facility, SACLA  

International Nuclear Information System (INIS)

The SACLA (SPring-8 Angstrom Compact Free Electron Laser) facility consists of an accelerator building, an undulator building and an experimental facility. SACLA is designed to produce X-ray with a wavelength as short as 0.06 nm and with a repetition rate of 60 Hz. X-ray Free-Electron Laser (XFEL) experiments demands large bandwidth network for data acquisition (DAQ). At SACLA the experimental data rate is to be up to 5.8 Giga bit per second (Gbps). Some of the experiments demands preprocessing and on-line analysis by high-performance computers. In order to fulfill these requirements, a dedicated network system for DAQ and data analysis has been developed. A DAQ network consists of a dedicated 10 Gbps Ethernet (10 GbE) physical layer to secure the data bandwidth and a 1 GbE layer for instrument controls. The DAQ network is connected to a primary storage and indirectly to a PC cluster for data preprocessing. A fire-wall system with virtual private network (VPN) features is also implemented in order to secure remote access from off-site institutes. The use of a large-bandwidth data transfer technique allows the efficient transfer of pre-processed data from SACLA to an off-site supercomputer

236

Bandwidth Enhancement and Radiation Properties of Slotted Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available The design of low-cost, wideband, printed inverted-F antennas (PIFAs that are suitable for portable devices operating at the 2–3 GHz band is described. The design specifications were extracted according to the constraints of high data rate wireless sensor devices. Reactive tuning through slot loading was applied to enforce degeneration of a higher resonance, and thus double the bandwidth in the band of interest. Three slotted antenna configurations are reported plus a baseline configuration; a thorough numerical characterisation of performance is provided. Fractional bandwidth (FBW in the range 22–34% was achieved, which is almost quadruple that of existing implementations. The antennas exhibit total efficiencies around 80% and are elliptically polarised. A suitable figure-of-merit is suggested for performance comparisons; it attempts to capture overall antenna performance in a single quantity. Antenna performance depends heavily on electrical size, which depends on the size of the ground plane, since the RF ground is an integral part of the total radiator. The ground-effect study showed that wrong choice of size can force resonant modes to vanish. Best performance for a slotted PIFA was obtained with a ground plane measuring 0.20l _ 0.28l, significantly smaller than predicted in prior studies. Bandwidth augmentation through slot loading is supported by measurements. Fabricated antennas with sub-optimal ground plane sizes exhibit FBWs in the range 20–23%

Deenanath Sahu,

2013-04-01

237

Improved Radiation and Bandwidth of Triangular and Star Patch Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available This study presents a hexagonal shape Defected Ground Structure (DGS implemented on two element triangular patch microstrip antenna array. The radiation performance of the antenna is characterized by varying the geometry and dimension of the DGS and also by locating the DGS at specific position which were simulated. Simulation and measurement results have verified that the antenna with DGS had improved the antenna without DGS. Measurement results of the hexagonal DGS have axial ratio bandwidth enhancement of 10 MHz, return loss improvement of 35%, mutual coupling reduction of 3 dB and gain enhancement of 1 dB. A new wideband and small size star shaped patch antenna fed capacitively by a small diamond shape patch is proposed. To enhance the impedance bandwidth, posts are incorporated under the patch antenna. HFSS high frequency simulator is employed to analyze the proposed antenna and simulated results on the return loss, the E- and H-plane radiation patterns and Gain of the proposed antenna are presented at various frequencies. The antenna is able to achieve in the range of 4-8.8 GHz an impedance bandwidth of 81% for return loss of less than-10 dB.

M. Ramkumar Prabhu

2012-06-01

238

Bandwidth limitations in current mode and voltage mode integrated feedback amplifiers  

DEFF Research Database (Denmark)

The bandwidth relations of feedback amplifiers have been the subject of intense interest in recent years. Many current mode devices such as current feedback amplifiers have appeared which seem to break what has been considered almost a fundamental law that the product of closed loop gain and closed loop bandwidth remains constant for a feedback amplifier. The constant-bandwidth relations of such amplifier designs are reviewed in this paper and they are combined with the constraints imposed by technology when the feedback amplifier is to be designed in an integrated technology. From this analysis it is concluded that although very high performance designs are indeed feasible with the constant-bandwidth configurations, there are no constant-bandwidth configurations which provide a higher potential loop gain and closed loop bandwidth than the constant gain-bandwidth product configurations

Bruun, Erik

1995-01-01

239

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

240

Bandwidth optimization of individual hop for robust data streaming on emergency medical application  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a new bandwidth estimation method for individual hop for high-speed, non-invasive, and faster convergence transmission in multiple medical data networks. Available Bandwidth Estimation Technique for individual Hops (ABETH has been developed employing parameters like Hop (H, Capacity (C, Bandwidth (B, Available Bandwidth (AB etc. Bandwidth estimation techniques, tools and methods are considered to develop the technique and it represents an effective combination of different other existing techniques aiming to exploit the positive aspects of them. More precisely, the technique which is implied in the method modifies and integrates the one recent tool SPRUCE which estimates available bandwidth and the IP layer capacity estimation formula which measures capacity. This technique provides a linear combination of capacity versus bandwidth which satisfies the link utilization demand.

A. K. M. Fazlul Haque

2009-10-01

241

Study and Analysis of Bandwidth Flow Estimation Techniques for Wired/Wireless Networks  

Directory of Open Access Journals (Sweden)

Full Text Available In this topic, an analysis will be made on bandwidth flow estimation technique which comes under networking domain. Correct bandwidth constrained applications and tools are required for proper bandwidth estimation. A proper monitoring of available bandwidth is required during execution to avoid degradation in performance. A several measurement tools have been proposed in the last few years. After the implementation of 802.11e Wireless Sensor Networks are capable to provide good level of QoS but research works are not much for improving performance of bandwidth constraint applications by checking sufficiency of bandwidth available in transmission route. In this topic we will do the analysis of bandwidth flow estimation technique for wired/wireless networks and we will do comparisons of existing estimation tools.

Pallavi Sharma

2012-01-01

242

A bandwidth efficient coding scheme for the Hubble Space Telescope  

Science.gov (United States)

As a demonstration of the performance capabilities of trellis codes using multidimensional signal sets, a Viterbi decoder was designed. The choice of code was based on two factors. The first factor was its application as a possible replacement for the coding scheme currently used on the Hubble Space Telescope (HST). The HST at present uses the rate 1/3 nu = 6 (with 2 (exp nu) = 64 states) convolutional code with Binary Phase Shift Keying (BPSK) modulation. With the modulator restricted to a 3 Msym/s, this implies a data rate of only 1 Mbit/s, since the bandwidth efficiency K = 1/3 bit/sym. This is a very bandwidth inefficient scheme, although the system has the advantage of simplicity and large coding gain. The basic requirement from NASA was for a scheme that has as large a K as possible. Since a satellite channel was being used, 8PSK modulation was selected. This allows a K of between 2 and 3 bit/sym. The next influencing factor was INTELSAT's intention of transmitting the SONET 155.52 Mbit/s standard data rate over the 72 MHz transponders on its satellites. This requires a bandwidth efficiency of around 2.5 bit/sym. A Reed-Solomon block code is used as an outer code to give very low bit error rates (BER). A 16 state rate 5/6, 2.5 bit/sym, 4D-8PSK trellis code was selected. This code has reasonable complexity and has a coding gain of 4.8 dB compared to uncoded 8PSK (2). This trellis code also has the advantage that it is 45 deg rotationally invariant. This means that the decoder needs only to synchronize to one of the two naturally mapped 8PSK signals in the signal set.

Pietrobon, Steven S.; Costello, Daniel J., Jr.

1991-01-01

243

Reservoir characterization using seismic data after frequency bandwidth enhancement  

Science.gov (United States)

Reservoir characterization is a crucial prerequisite to predict the economic potential of a hydrocarbon reservoir or to examine different production scenarios. Unfortunately, it is impossible to determine the exact reservoir properties at the required scale. The most abundant seismic data have a resolution of around 30 m. Wells resolve the reservoir down to the centimetre scale, but only at some points in the vertical direction. This paper presents a method, referred to as frequency bandwidth enhancement (FBE), for enhancing the frequency bandwidth and restoring high frequencies. The method increases the resolution of seismic data by padding the frequency spectrum of seismic wavelets, thus pushing the notch corresponding to the time limit of resolution to a higher part of the spectrum. This approach (patent pending) results in sharper wavelets capable of identifying thinner beds. A by-product of extending the frequency spectrum is the elimination of the tuning effect of beds thinner than the new limit of resolution. When tuning curves before and after the process are compared, it is observed that although different, the differences are minuscule and insignificant compared to the benefits coming from being able to resolve thinner beds. The procedure enunciated here is robust and helps define trends better, leading to more confident interpretations. Such applications could redefine prospects, which in some cases may have been declared unsuccessful on the basis of interpretation of seismic data with the original bandwidth. The reservoir characterization is realized with the aid of coherence cube processing, which is an extremely powerful tool to efficiently exploit the wealth of structural and stratigraphic information encapsulated in the seismic waveforms of 3D seismic data volumes.

Ma, Yongsheng; Zhu, Xuan; Guo, Tonglou; Rebec, Tony; Azbel, Kostia

2005-09-01

244

Bandwidth-efficient high-speed coded trellis modulation  

Science.gov (United States)

A burst-mode coded trellis modulation system is discussed which is capable of 200-Mbit/s information rate transmission over nonlinear satellite transponders whose center frequencies are separated by 100 MHz. An overall real bandwidth efficiency of 2 bit/s per Hz of the allocated spectrum is projected. Convolutional codec and 8-PSK modulation subsystems together maximize the minimum Euclidean distance between the modulated codeword sequences in the overall coded trellis, resulting in a 4.3-dB asymptotic coding advantage over an uncoded 8-PSK system signalling at the same information rate over the same channel. The system performance has been evaluated by computer simulation.

Fang, R. J. F.; Budinger, J. M.

1988-01-01

245

Bandwidth allocation for video under quality of service constraints  

CERN Document Server

We present queueing-based algorithms to calculate the bandwidth required for a video stream so that the three main Quality of Service constraints, i.e., end-to-end delay, jitter and packet loss, are ensured. Conversational and streaming video-based applications are becoming a major part of the everyday Internet usage. The quality of these applications (QoS), as experienced by the user, depends on three main metrics of the underlying network, namely, end-to-end delay, jitter and packet loss. These metrics are, in turn, directly related to the capacity of the links that the video traffic trave

Anjum, Bushra

2014-01-01

246

Low Bandwidth Vocoding using EM Sensor and Acoustic Signal Processing  

International Nuclear Information System (INIS)

Low-power EM radar-like sensors have made it possible to measure properties of the human speech production system in real-time, without acoustic interference [1]. By combining these data with the corresponding acoustic signal, we've demonstrated an almost 10-fold bandwidth reduction in speech compression, compared to a standard 2.4 kbps LPC10 protocol used in the STU-III (Secure Terminal Unit, third generation) telephone. This paper describes a potential EM sensor/acoustic based vocoder implementation

247

Iterative Available Bandwidth Estimation for Mobile Transport Networks  

DEFF Research Database (Denmark)

Available bandwidth estimation has lately been proposed to be used for end-to-end resource management in existing and emerging mobile communication systems, whose transport networks could end up being the bottleneck rather than the air interface. Algorithms for admission control, handover and adaptive QoS management could take into account such estimations, which may lead to an overall system performance improvement. This paper introduces two new iterative algorithms (Zoom and Adaptive pathChirp) for network load monitoring that can be combined with a linear least squares fitting achieving reliable estimations without causing congestion collapse. Their performance is evaluated in a simulated UTRAN Long Term Evolution backhaul.

Ubeda Castellanos, Carlos; López Villa, Dimas

2007-01-01

248

Bandwidth Extension Method Based on Spectral Envelope Estimation  

Directory of Open Access Journals (Sweden)

Full Text Available In current communication system, high quality audio signal is supposed to be provided with low bit rate and low computational complexity. This paper proposed a novel audio coding bandwidth extension method, which can improve decoded audio quality with increasing only a few coding bits per frame and a little computational complexity. This method calculate high-frequency synthesis filter by using codebook mapping method, and transmit only quantified gain corrections in high-frequency part of multiplexing coding bit stream. The preliminary test show that this method can provide comparable audio quality with lower bit consumption and computational complexity compared to the high frequency regeneration of AMR-WB+.

Bo Hang

2011-06-01

249

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

250

Low Bandwidth Vocoding using EM Sensor and Acoustic Signal Processing  

Energy Technology Data Exchange (ETDEWEB)

Low-power EM radar-like sensors have made it possible to measure properties of the human speech production system in real-time, without acoustic interference [1]. By combining these data with the corresponding acoustic signal, we've demonstrated an almost 10-fold bandwidth reduction in speech compression, compared to a standard 2.4 kbps LPC10 protocol used in the STU-III (Secure Terminal Unit, third generation) telephone. This paper describes a potential EM sensor/acoustic based vocoder implementation.

Ng, L C; Holzrichter, J F; Larson, P E

2001-10-25

251

Gain and bandwidth enhancement for a superconducting electrically small antenna  

Science.gov (United States)

We present a technique that enhances the gain of a superconducting electrically small antenna by manipulating the electromagnetic (EM) near-fields on the antenna aperture to increase the effective aperture area. The antenna has a conducting split ring and three parasitic T-shaped conducting structures to manipulate its EM near-fields. When the distribution of the EM near-fields becomes uniform, the effective aperture area increases, enhancing the antenna gain and bandwidth. The concept proposed in this study is applicable to a single electronically small antenna as well as to an element of an antenna array.

Wang, Ruixia; Wei, Bin; Cao, Bisong; Jiang, Linan

2015-04-01

252

Extending the bandwidth of optical-tweezers interferometry  

International Nuclear Information System (INIS)

High-resolution force and displacement measurements by laser interferometry, combined with optical tweezers in a light microscope, are frequently based on near-infrared lasers. With common silicon PN photodiodes the bandwidth of detection was found to be limited to about 5 kHz at 1064 nm laser wavelength. This is caused by the fact that silicon becomes increasingly transparent for wavelengths approaching the band gap energy, leading to the generation of charge carriers outside the depletion zone of the diode for wavelengths longer than about 850 nm. These charges have to diffuse before they can contribute to the photocurrent. In this technical note we demonstrate experimentally that the detection bandwidth can be extended to at least 100 kHz, either by using wavelengths below 850 nm, or by using different detectors at longer wavelengths: InGaAs PIN photodiodes or special-purpose fully depleted p-type silicon photodiodes. We measured the well-known power spectral density of the Brownian motion of micron-sized beads in optical tweezers and show that the optimized detectors do not cause attenuation within experimental noise. They are indeed linear enough to detect the weak inertial effects of the watery solvent on the power spectral density of the Brownian motion

253

Multi-Modulator for Bandwidth-Efficient Communication  

Science.gov (United States)

A modulator circuit board has recently been developed to be used in conjunction with a vector modulator to generate any of a large number of modulations for bandwidth-efficient radio transmission of digital data signals at rates than can exceed 100 Mb/s. The modulations include quadrature phaseshift keying (QPSK), offset quadrature phase-shift keying (OQPSK), Gaussian minimum-shift keying (GMSK), and octonary phase-shift keying (8PSK) with square-root raised-cosine pulse shaping. The figure is a greatly simplified block diagram showing the relationship between the modulator board and the rest of the transmitter. The role of the modulator board is to encode the incoming data stream and to shape the resulting pulses, which are fed as inputs to the vector modulator. The combination of encoding and pulse shaping in a given application is chosen to maximize the bandwidth efficiency. The modulator board includes gallium arsenide serial-to-parallel converters at its input end. A complementary metal oxide/semiconductor (CMOS) field-programmable gate array (FPGA) performs the coding and modulation computations and utilizes parallel processing in doing so. The results of the parallel computation are combined and converted to pulse waveforms by use of gallium arsenide parallel-to-serial converters integrated with digital-to-analog converters. Without changing the hardware, one can configure the modulator to produce any of the designed combinations of coding and modulation by loading the appropriate bit configuration file into the FPGA.

Gray, Andrew; Lee, Dennis; Lay, Norman; Cheetham, Craig; Fong, Wai; Yeh, Pen-Shu; King, Robin; Ghuman, Parminder; Hoy, Scott; Fisher, Dave

2009-01-01

254

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

255

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

256

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.

257

Bandwidth Optimization in Centralized WLANs for Different Traffic Types  

Directory of Open Access Journals (Sweden)

Full Text Available Allocating bandwidth between different forms of coexisting traffic (such as web-browsing, streaming, and telephony within a wireless LAN is a challenging and interesting problem. Centralized coordination functions in wireless LANs offer several advantages over distributed approaches, having the benefit of a system overview at the controller, but obtaining a stable configuration of bandwidth allocation for the system is nontrivial. We present, review, and compare different mechanisms to achieve this end, and a number of different means of obtaining the configurations themselves. We describe an analytical model of the system under consideration and present two mathematical approaches to derive solutions for any system configuration and deployment, along with an adaptive feedback-based solution. We also describe a comprehensive simulation-based model for the problem, and a prototype that allows comparison of these approaches. Our investigations demonstrate that a self-adaptive dynamic approach far outperforms any static scheme, and that using a mathematical model to produce the configurations themselves confers several advantages.

Haines RJ

2007-01-01

258

Unmanned Aircraft System Control and ATC Communications Bandwidth Requirements  

Science.gov (United States)

There are significant activities taking place to establish the procedures and requirements for safe and routine operation of unmanned aircraft systems (UAS) in the National Airspace System (NAS). Among the barriers to overcome in achieving this goal is the lack of sufficient frequency spectrum necessary for the UAS control and air traffic control (ATC) communications links. This shortcoming is compounded by the fact that the UAS control communications links will likely be required to operate in protected frequency spectrum, just as ATC communications links are, because they relate to "safety and regularity of flight." To support future International Telecommunications Union (ITU) World Radio Conference (WRC) agenda items concerning new frequency allocations for UAS communications links, and to augment the Future Communications Study (FCS) Technology Evaluation Group efforts, NASA Glenn Research Center has sponsored a task to estimate the UAS control and ATC communications bandwidth requirements for safe, reliable, and routine operation of UAS in the NAS. This report describes the process and results of that task. The study focused on long-term bandwidth requirements for UAS approximately through 2030.

Henriksen, Steve

2008-01-01

259

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

260

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

261

A variable bandwidth assignment scheme for the Land Mobile Satellite experiment  

Science.gov (United States)

The Mobile Satellite Experiment is a proposed experimental satellite-based communications network which provides data and voice communications to mobile terminals dispersed in geographically dispersed areas. In this paper, an analytical model is developed to calculate the performance of a Variable Bandwidth Assignment (VBA) Scheme. Under this scheme, the satellite channel bandwidth is dynamically reassigned so that a message may be transmitted in the shortest possible time. To transmit a long message, message channels will be reconfigured to have more bandwidth such that the transmission time is reduced, while to transmit a short message, the channel bandwidth will be shrunk such that the released bandwidth can be used to serve other messages. The model is illustrated with numerical examples. It is shown that a VBA scheme can achieve considerable improvement in transmission delays over a Fixed Bandwidth Assignment Scheme.

Yan, T.-Y.; Li, V. O. K.

262

Dynamic Bandwidth Allocation with Effective Utilization of Polling Interval over WDM/TDM PON  

Science.gov (United States)

WDM/TDM (wavelength-division multiplexing/time-division multiplexing) PON (passive optical network) appears to be an attractive solution for the next generation optical access networks. Dynamic bandwidth allocation (DBA) plays a crucial role in efficiently and fairly allocating the bandwidth among all users in WDM/TDM PON. In this paper, two dynamic bandwidth allocation schemes (DBA1 and DBA2) are proposed to eliminate the idle time of polling cycles (i.e. polling interval), improve bandwidth utilization and make full use of bandwidth resources. The two DBA schemes adjust the time slot of sending request information and make fair scheduling among users to achieve the effective utilization of polling interval in WDM/TDM PON. The simulation and theoretical analyses verify that the proposed schemes outperform the conventional DBA scheme. We also make comparisons between the two schemes in terms of bandwidth utilization and average packet delay to further demonstrate the effectiveness of the scheme of DBA2.

Ni, Cuiping; Gan, Chaoqin; Gao, Ziyue

2014-12-01

263

Bandwidth limitations in current mode and voltage mode integrated feedback amplifiers  

OpenAIRE

The bandwidth relations of feedback amplifiers have been the subject of intense interest in recent years. Many current mode devices such as current feedback amplifiers have appeared which seem to break what has been considered almost a fundamental law that the product of closed loop gain and closed loop bandwidth remains constant for a feedback amplifier. The constant-bandwidth relations of such amplifier designs are reviewed in this paper and they are combined with the constraints imposed by...

Bruun, Erik

2010-01-01

264

Bandwidth selection for kernel estimation in mixed multi-dimensional spaces  

OpenAIRE

Kernel estimation techniques, such as mean shift, suffer from one major drawback: the kernel bandwidth selection. The bandwidth can be fixed for all the data set or can vary at each points. Automatic bandwidth selection becomes a real challenge in case of multidimensional heterogeneous features. This paper presents a solution to this problem. It is an extension of \\cite{Comaniciu03a} which was based on the fundamental property of normal distributions regarding the bias of th...

Bugeau, Aurelie; Pe?rez, Patrick

2007-01-01

265

Multi-Hop Bandwidth Management Protocol for Mobile Ad Hoc Networks  

OpenAIRE

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 nod...

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

2010-01-01

266

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

267

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

OpenAIRE

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.

Maheshwari, D.; Dhanalakshmi, A.

2013-01-01

268

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.

269

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

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.Defence Science Journal, 2012, 62(6, pp.427-430, DOI:http://dx.doi.org/10.14429/dsj.62.2100

Wen-Qin Wang

2012-11-01

270

Bandwidth allocation strategy for traffic systems of scale-free network  

Energy Technology Data Exchange (ETDEWEB)

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 {alpha} 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.

Ling Xiang [School of Engineering Science, University of Science and Technology of China, Hefei 230026 (China); Hu MaobBin, E-mail: humaobin@ustc.edu.c [School of Engineering Science, University of Science and Technology of China, Hefei 230026 (China); Department of Mathematics and Statistics, Curtin University of Technology, Perth WA6845 (Australia); Du Wenbo [School of Computer Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Jiang Rui [School of Engineering Science, University of Science and Technology of China, Hefei 230026 (China); Wu Yonghong [Department of Mathematics and Statistics, Curtin University of Technology, Perth WA6845 (Australia); Wu Qingsong [School of Engineering Science, University of Science and Technology of China, Hefei 230026 (China)

2010-11-01

271

Bandwidth Improvement of EBG Resonator Antennas Using Double-Layer FSS  

Directory of Open Access Journals (Sweden)

Full Text Available A double-layer frequency selective surface (FSS is proposed as a means to enhance the bandwidth of an electromagnetic band gap (EBG resonator antenna. Due to its inverted reflection phase variation and its wide selectivity bandwidth, the structure used in the radiating wall of the resonator allows increasing the radiating bandwidth of the last one. The resonator is fed by a patch feeding source placed inside the cavity at the proximity of its metallic ground. The antenna bandwidth is significantly improved by virtue of employing the double-layer FSS. Modelled results of an antenna working at 5 GHz are shown.

Bernard Jecko

2008-12-01

272

EFFECTIVE BANDWIDTH ALLOCATION APPROACH BASED ON USERS BILLING IN CLOUD ENVIRONMENT?  

Directory of Open Access Journals (Sweden)

Full Text Available Cloud computing is a new development emerging in IT environment with vast requirements of infrastructure and resources. Band width allocation and Load balancing is an important aspect of cloud computing environment. Bandwidth allocation plays a most important part in sharing the resources to the data center networks. In this paper we propose a new bandwidth allocation scheme based on unused bandwidth at passive users, allocation based on user type and also propose an algorithm to allocate bandwidth in a cloud environment.

A.PEDA GOPI?

2014-07-01

273

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

274

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)

275

Graphene metascreen for designing compact infrared absorbers with enhanced bandwidth.  

Science.gov (United States)

We propose a compact, wideband terahertz and infrared absorber, comprising a patterned graphene sheet on a thin metal-backed dielectric slab. This graphene-based nanostructure can achieve a low or negative effective permeability, necessary for realizing the perfect absorption. The dual-reactive property found in both the plasmonic graphene sheet and the grounded high-permittivity slab introduces extra poles into the equivalent circuit model of the system, thereby resulting in a dual-band or broadband magnetic resonance that enhances the absorption bandwidth. More interestingly, the two-dimensional patterned graphene sheet significantly simplifies the design and fabrication processes for achieving resonant magnetic response, and allows the frequency-reconfigurable operation via electrostatic gating. PMID:25824491

Chen, Pai-Yen; Farhat, Mohamed; Ba?c?, Hakan

2015-04-24

276

Delay-bandwidth product of electromagnetically induced transparency media  

International Nuclear Information System (INIS)

The limitations on the delay-bandwidth product (DBP) in an electromagnetically induced transparency medium are investigated analytically by studying the susceptibility of the system, derived through Lindblad's master equation, including dephasing. The effect of inhomogeneous broadening is treated. It is shown that the DBP for a given material is fundamentally limited by the frequency-dependent absorption, while the residual absorption limits the penetration length of a pulse. Simple expression for the optimal choice of parameters to maximize the DBP are derived. Also, the length of a device is presented as a function of DBP and control-field Rabi frequency. Supporting these results, numerical calculations are carried out through the Maxwell-Bloch equations in the slowly varying envelope approximation. The results are scalable, hence they apply to the case of atoms or molecules in a gas as well as quantum dots and wells

277

Auction-based Bandwidth Allocation Mechanisms for Wireless Future Internet  

CERN Document Server

An important aspect of the Future Internet is the efficient utilization of (wireless) network resources. In order for the - demanding in terms of QoS - Future Internet services to be provided, the current trend is evolving towards an "integrated" wireless network access model that enables users to enjoy mobility, seamless access and high quality of service in an all-IP network on an "Anytime, Anywhere" basis. The term "integrated" is used to denote that the Future Internet wireless "last mile" is expected to comprise multiple heterogeneous geographically coexisting wireless networks, each having different capacity and coverage radius. The efficient management of the wireless access network resources is crucial due to their scarcity that renders wireless access a potential bottleneck for the provision of high quality services. In this paper we propose an auction mechanism for allocating the bandwidth of such a network so that efficiency is attained, i.e. social welfare is maximized. In particular, we propose a...

Dramitinos, Emmanouil

2010-01-01

278

High bandwidth synaptic communication and frequency tracking in human neocortex.  

Science.gov (United States)

Neuronal firing, synaptic transmission, and its plasticity form the building blocks for processing and storage of information in the brain. It is unknown whether adult human synapses are more efficient in transferring information between neurons than rodent synapses. To test this, we recorded from connected pairs of pyramidal neurons in acute brain slices of adult human and mouse temporal cortex and probed the dynamical properties of use-dependent plasticity. We found that human synaptic connections were purely depressing and that they recovered three to four times more swiftly from depression than synapses in rodent neocortex. Thereby, during realistic spike trains, the temporal resolution of synaptic information exchange in human synapses substantially surpasses that in mice. Using information theory, we calculate that information transfer between human pyramidal neurons exceeds that of mouse pyramidal neurons by four to nine times, well into the beta and gamma frequency range. In addition, we found that human principal cells tracked fine temporal features, conveyed in received synaptic inputs, at a wider bandwidth than for rodents. Action potential firing probability was reliably phase-locked to input transients up to 1,000 cycles/s because of a steep onset of action potentials in human pyramidal neurons during spike trains, unlike in rodent neurons. Our data show that, in contrast to the widely held views of limited information transfer in rodent depressing synapses, fast recovering synapses of human neurons can actually transfer substantial amounts of information during spike trains. In addition, human pyramidal neurons are equipped to encode high synaptic information content. Thus, adult human cortical microcircuits relay information at a wider bandwidth than rodent microcircuits. PMID:25422947

Testa-Silva, Guilherme; Verhoog, Matthijs B; Linaro, Daniele; de Kock, Christiaan P J; Baayen, Johannes C; Meredith, Rhiannon M; De Zeeuw, Chris I; Giugliano, Michele; Mansvelder, Huibert D

2014-11-01

279

Adaptive data filtering of inertial sensors with variable bandwidth.  

Science.gov (United States)

MEMS (micro-electro-mechanical system)-based inertial sensors, i.e., accelerometers and angular rate sensors, are commonly used as a cost-effective solution for the purposes of navigation in a broad spectrum of terrestrial and aerospace applications. These tri-axial inertial sensors form an inertial measurement unit (IMU), which is a core unit of navigation systems. Even if MEMS sensors have an advantage in their size, cost, weight and power consumption, they suffer from bias instability, noisy output and insufficient resolution. Furthermore, the sensor's behavior can be significantly affected by strong vibration when it operates in harsh environments. All of these constitute conditions require treatment through data processing. As long as the navigation solution is primarily based on using only inertial data, this paper proposes a novel concept in adaptive data pre-processing by using a variable bandwidth filtering. This approach utilizes sinusoidal estimation to continuously adapt the filtering bandwidth of the accelerometer's data in order to reduce the effects of vibration and sensor noise before attitude estimation is processed. Low frequency vibration generally limits the conditions under which the accelerometers can be used to aid the attitude estimation process, which is primarily based on angular rate data and, thus, decreases its accuracy. In contrast, the proposed pre-processing technique enables using accelerometers as an aiding source by effective data smoothing, even when they are affected by low frequency vibration. Verification of the proposed concept is performed on simulation and real-flight data obtained on an ultra-light aircraft. The results of both types of experiments confirm the suitability of the concept for inertial data pre-processing. PMID:25648711

Alam, Mushfiqul; Rohac, Jan

2015-01-01

280

Improvement of the bandwidth of the transient digitizers in the LIDAR Thomson scattering diagnostic on JET  

International Nuclear Information System (INIS)

The main limitation on the spatial resolution of the LIDAR Thomson scattering diagnostic on the JET tokamak is due to the narrow bandwidth of the detection system. The transient digitizers, Tektronik 7912AD, are the main contributors to the narrow bandwidth. It is shown how the digitizers can be modified to improve the response time from approx. 480 to 410 ps. (author)

281

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

282

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)

283

Dynamic Bit Allocation for Object Tracking in Bandwidth Limited Sensor Networks  

CERN Document Server

In this paper, we study the target tracking problem in wireless sensor networks (WSNs) using quantized sensor measurements under limited bandwidth availability. At each time step of tracking, the available bandwidth $R$ needs to be distributed among the $N$ sensors in the WSN for the next time step. The optimal solution for the bandwidth allocation problem can be obtained by using a combinatorial search which may become computationally prohibitive for large $N$ and $R$. Therefore, we develop two new computationally efficient suboptimal bandwidth distribution algorithms which are based on convex relaxation and approximate dynamic programming (A-DP). We compare the mean squared error (MSE) and computational complexity performances of convex relaxation and A-DP with other existing suboptimal bandwidth distribution schemes based on generalized Breiman, Friedman, Olshen, and Stone (GBFOS) algorithm and greedy search. Simulation results show that, A-DP, convex optimization and GBFOS yield similar MSE performance, w...

Masazade, Engin; Varshney, Pramod K

2011-01-01

284

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

285

Design and fabrication of bandwidth tunable HTS transmit filter using ?-shaped waveguides  

International Nuclear Information System (INIS)

We have developed a method for tuning the bandwidth of a high-temperature superconducting (HTS) microstrip filter. Several ?-shaped waveguides are placed between the resonators, and the bandwidth is tuned in discrete steps by changing the switch states of the waveguides, which changes the coupling coefficient between the resonators. The filter contains 3-pole half-wavelength straight-line resonators and two ?-shaped waveguides for bandwidth tuning. It also has several electrical pads distributed around the feed lines for trimming after tuning. The filter was fabricated by depositing YBa2Cu3O7 thin film on an MgO substrate and has a measured center frequency of 5.17 GHz and bandwidth of 220 MHz. Use of the ?-shaped waveguides to adjust the coupling coefficients and the electrical pads to adjust the external quality factors resulted in 80-MHz bandwidth tuning without increased insertion loss.

286

All-optical manipulation of non-degenerate FWM conversion bandwidth by gain-transparent SBS  

Science.gov (United States)

We demonstrate all-optical manipulation of non-degenerate four-wave mixing (FWM) wavelength conversion bandwidth based on phase-matching control through gain-transparent stimulated Brillouin scattering (SBS). A 3-dB bandwidth of 26 nm is achieved when the conversion efficiency is maximized, corresponding to 44% increase from the original value. The bandwidth can also be shrunk to a minimum of 15 nm. The spectral dependence of conversion efficiency can potentially be synthesized randomly, leading to a large tunability in the bandwidth. The performance in bandwidth manipulation is also evaluated in the wavelength conversion of 10 Gbit/s non-return-to-zero (NRZ) on-off-keying (OOK) signal.

Wang, Liang; Shu, Chester

2015-03-01

287

Gigabit Passive Optical Networks (GPON the Ultimate Solution for Large Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available The demand for bandwidth has increased drastically. So optical transmission has got more importance in access networks. The upcoming features like IPTV, High speed internet(HSI, Video on demand(VOD, online gaming are confronting large bandwidth at the customer end.The demand of bandwidth can be satisfied by XDSL, but the distance is restricted by using this type of technique. So we can use optical transmission for achieving large bandwidth by using passive optical networks(PON. One of the most advanced PON solution is Gigabit PON (GPON. This is the most widely used solution where there is a requirement of large bandwidth This paper provides an overview of GPONfeatures, transmission mechanism, optical splitting and power budget.

A.ManikantaSitaram

2012-11-01

288

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

289

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

290

Mechanism of bandwidth improvement in passively cooled SMA position actuators  

International Nuclear Information System (INIS)

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

291

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

292

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

293

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

294

Multispectral image classification focusing on transmission paths with limited bandwidth  

Science.gov (United States)

Technological advances in digital imaging and liquid crystal tunable filters allow for a design of a both compact and cost effective multispectral camera system. Thus an image acquisition system for the visible and near infrared wavelength range can be realised consisting of conventional CCD cameras and tunable filters whose spectral transmittace is controlled electronically. Due to their limited internal payload the use of a lightweight, compact camera system is of particular importance for applications involving mini-unmanned-aerial-vehicles (mini-UAVs). Within the scope of this paper a both compact and economical data acquisition system for multispecral images is described. Despite of their limited functionality (e.g.regarding calibration) in comparison with commercial systems such as AVIRIS the use of these upcoming compact multispectral camera systems can be advantageous in many applications. In order to maintain the systems low weight and price this work proposes to separate data acquisition and processing modules, and transmit pre-processed camera data online to a stationary high performance computer for further processing. Special focus is laid upon transmission paths with limited bandwidth.

Groh, Christine; Rothe, Hendrik

2005-10-01

295

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

296

Automatic Bandwidth Adjustment for Content Distribution in MPLS Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Aggregates of real-time traffic may experience changes in their statistical characteristics often manifesting non stationary behavior. In multi protocol label switching (MPLS networks this type of the traffic is assigned constant amount of resources. This may result in ineffective usage of resources when the load is below than expected or inappropriate performance when the load is higher. In this paper we propose new algorithm for dynamic resource adaptation to temporarily changing traffic conditions. Assuming that network nodes may reallocate resources on-demand using automatic bandwidth adjustment capability of MPLS framework, the proposed algorithm, implemented at ingress MPLS nodes, dynamically decides which amount of resources is currently sufficient to handle arriving traffic with given performance metrics. This decision is then communicated to interior MPLS nodes along the label switched path. As a basic tool of the algorithm we use change-point statistical test that signals time instants at which statistical characteristics of traffic aggregates change. The major advantage of the proposed approach is that it is fully autonomous, that is, network nodes do not need any support from hosts in terms of resource reservation requests. The proposed algorithm is well suited for traffic patterns experiencing high variability, especially, for non stationary type of the traffic.

D. Moltchanov

2008-04-01

297

A scanning SQUID microscope with 200 MHz bandwidth  

Science.gov (United States)

We developed a scanning DC SQUID microscope with novel readout electronics capable of wideband sensing of RF magnetic fields from 50 to 200 MHz and simultaneously providing closed-loop response at kHz frequencies. To overcome the 20 MHz bandwidth limitation of traditional closed-loop SQUIDs, a flux-modulated closed-loop simultaneously locks the SQUID quasi-static flux and flux-biases the SQUID for amplification of the RF flux up to ?0/4 in amplitude. Demodulating the SQUID voltage with a double lock-in technique yields a signal representative of both the amplitude and phase of the RF flux. This provides 80 dB of a linear dynamic range with a flux noise density of 4 ??0 Hz-1/2 at 200 MHz for a Y Ba2Cu3O7 bi-crystal SQUID at 77 K. We describe the electronics’ performance and present images for RF magnetic field of the travelling wave in a coplanar waveguide, the standing wave in an open-circuited microstrip, and a surface mounted device antenna.

Talanov, Vladimir V.; Lettsome, Nesco M., Jr.; Borzenets, Valery; Gagliolo, Nicolas; Cawthorne, Alfred B.; Orozco, Antonio

2014-04-01

298

High Bandwidth Short Stroke Rotary Fast Tool Servo  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the design and performance of a new rotary fast tool servo (FTS) capable of developing the 40 g's tool tip acceleration required to follow a 5 micron PV sinusoidal surface at 2 kHz with a planned accuracy of 50 nm, and having a full stroke of 50 micron PV at lower frequencies. Tests with de-rated power supplies have demonstrated a closed-loop unity-gain bandwidth of 2 kHz with 20 g's tool acceleration, and we expect to achieve 40 g's with supplies providing {+-} 16 Amp to the Lorentz force actuator. The use of a fast tool servo with a diamond turning machine for producing non-axisymmetric or textured surfaces on a workpiece is well known. Our new rotary FTS was designed to specifically accommodate fabricating prescription textured surfaces on 5 mm diameter spherical target components for High Energy Density Physics experiments on the National Ignition Facility Laser (NIF).

Montesanti, R C; Trumper, D L

2003-08-22

299

Analysis of the effect of laser bandwidth on imaging of memory patterns  

Science.gov (United States)

Tighter CD control requirements of the smaller devices in modern semiconductor products demand control of all potential sources of change in imaging characteristics. Bandwidth of ArF lasers is known to be one of the important parameters to be controlled to improve CD control of wafers. CD changes of Device Critical Patterns for memory products, for example spacing of DRAM isolation patterns, due to laser bandwidth changes were investigated through simulations. The purpose of the simulation study was to find out if there are optimum combinations of layout and illumination setting, if variations can be compensated by illumination adjustments and if the bandwidth performance of the laser meets requirements. The simulations were carried out using Cymer proprietary methods for high accuracy using improved laser spectrum sampling techniques[1]. Different CD behavior was observed for different combinations of pattern layout, illumination and bandwidth. Preferred illumination settings were found which suppress CD changes caused by bandwidth variation, especially for diffusion layer of DRAM layouts. Adjustment of illumination settings was demonstrated to cancel out CD shifts due to bandwidth change for the diffusion layer case. For all example cases, which demonstrated typical DRAM product conditions, simulation verified that the amount of CD shift can be controlled within allowed tolerances if Cymer's ABS technology was used for bandwidth control.

Seong, Nakgeuon; Kim, Insung; Kang, Dongwoo; Lee, Sang-Ho; Choi, Jinphil

2008-11-01

300

Bandwidth-tunable band-rejection filter based on helicoidal fiber grating pair of opposite helicities.  

Science.gov (United States)

We have developed a new type of all-fiber band-rejection filter consisting of a helicoidal long-period fiber grating pair of opposite helicities, which provides highly flexible spectral control over the rejection bandwidth. The detailed fabrication method and operation principles of the proposed bandwidth-tunable band-rejection filter are described. The proposed device enables unique rejection bandwidth tuning over more than 14 nm at the rejection level of 15 dB, with low insertion loss and polarization-dependent loss achieved by adjusting torsion stress. PMID:17440538

Shin, Woojin; Yu, Bong-Ahn; Noh, Young-Chul; Lee, Jongmin; Ko, Do-Kyeong; Oh, Kyunghwan

2007-05-15

301

Optimization of Quantum-Dot Molecular Beam Epitaxy for Broad Spectral Bandwidth Devices  

KAUST Repository

The optimization of the key growth parameters for broad spectral bandwidth devices based on quantum dots is reported. A combination of atomic force microscopy, photoluminescence of test samples, and optoelectronic characterization of superluminescent diodes (SLDs) is used to optimize the growth conditions to obtain high-quality devices with large spectral bandwidth, radiative efficiency (due to a reduced defective-dot density), and thus output power. The defective-dot density is highlighted as being responsible for the degradation of device performance. An SLD device with 160 nm of bandwidth centered at 1230 nm is demonstrated.

Hugues, M.

2012-12-01

302

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)

303

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

304

A wide bandwidth analog front-end circuit for 60-GHz wireless communication receiver  

Science.gov (United States)

This paper presents an analog front-end circuit for a 60-GHz wireless communication receiver. The feature of the proposed analog front-end circuit is a bandwidth more than 1-GHz wide. To expand the bandwidth of a low-pass filter and a voltage gain amplifier, a technique to reduce the parasitic capacitance of a transconductance amplifier is proposed. Since the bandwidth is also limited by on-resistance of the ADC sampling switch, a switch separation technique for reduction of the on-resistance is also proposed. In a high-speed ADC, the SNDR is limited by the sampling jitter. The developed high resolution VCO auto tuning effectively reduces the jitter of PLL. The prototype is fabricated in 65nm CMOS. The analog front-end circuit achieves over 1-GHz bandwidth and 27.2-dB SNDR with 224 mW Power consumption.

Furuta, M.; Okuni, H.; Hosoya, M.; Sai, A.; Matsuno, J.; Saigusa, S.; Itakura, T.

2014-03-01

305

Design of a Wide Slot Antenna for Bandwidth Enhancement for Wireless Communication Application  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we are proposing a brief description about Microstrip printed wide slot antenna with a fork like tuning stub for bandwidth enhancement. By applying fork like tuning stub to the microstrip wide slot antenna instead of line feed, it is experimentally found that operating bandwidth can be enhanced. Experimental results indicate that the impedance bandwidth, defined by -10Db return loss, of the proposed wide slot antenna can reach operating bandwidth of 3.1 GHz at operating frequency about 2GHz which is 6 times greater than conventional wide slot antenna. A comprehensive parametric study has been carried out to understand the effects of various dimensional parameters and to optimize the performance of the designed antenna.

Manish Kumar Rajput

2013-03-01

306

Analysis of blocking probability for OFDM-based variable bandwidth optical network  

Science.gov (United States)

Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique. For optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments, optical OFDM is much more flexible compared to traditional WDM systems, enabling elastic bandwidth transmissions, and optical networking is the future trend of development. In OFDM-based optical network the research of blocking rate has very important significance for network assessment. Current research for WDM network is basically based on a fixed bandwidth, in order to accommodate the future business and the fast-changing development of optical network, our study is based on variable bandwidth OFDM-based optical networks. We apply the mathematical analysis and theoretical derivation, based on the existing theory and algorithms, research blocking probability of the variable bandwidth of optical network, and then we will build a model for blocking probability.

Gong, Lei; Zhang, Jie; Zhao, Yongli; Lin, Xuefeng; Wu, Yuyao; Gu, Wanyi

2011-12-01

307

Development of narrow bandwidth SLM dye laser for clean-up  

International Nuclear Information System (INIS)

The development of copper vapor laser (CVL) pumped narrow band SLM dye laser, which offers bandwidth of a few hundred megahertz, an excellent spatial mode (nearly TEM), low divergence and of reasonably good efficiency is discussed

308

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

309

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

310

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

311

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

312

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

313

Continuous-wave non-classical light with GHz squeezing bandwidth  

CERN Document Server

Squeezed states can be employed for entanglement-based continuous-variable quantum key distribution, where the secure key rate is proportional to the bandwidth of the squeezing. We produced a non-classical continuous-wave laser field at the telecommunication wavelength of 1550 nm, which showed squeezing over a bandwidth of more than 2 GHz. The experimental setup used parametric down-conversion via a periodically poled potassium titanyl phosphate crystal (PPKTP). We did not use any resonant enhancement for the funda- mental wavelength, which should in principle allow a production of squeezed light over the full phase-matching bandwidth of several nanometers. We measured the squeezing to be up to 0.3 dB below the vacuum noise from 50 MHz to 2 GHz limited by the measuring bandwidth of the homodyne detector. The squeezing strength was possibly limited by thermal lensing inside the non-linear crystal.

Ast, Stefan; Mehmet, Moritz; Steinlechner, Sebastian; Eberle, Tobias; Schnabel, Roman

2012-01-01

314

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

315

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

316

Stacking resonators to increase the bandwidth of low-profile antennas  

Science.gov (United States)

A method of increasing the bandwidth of low-profile cavity-backed slot and microstrip patch antennas without appreciably adding to the antenna dimensions is presented. This idea incorporates the stacking of structures which have close resonant frequencies. Energy is coupled between cavities via carefully placed slots in the common wall. An approximate two-and-a-half-fold increase in input impedance bandwidth was observed for a certain cavity-backed slot antenna.

Smith, H. K.; Mayes, Paul E.

1987-12-01

317

Bandwidth Enhancement of a Microstrip Line-Fed Rotated Slot Antenna with a Parasitic Center Patch  

OpenAIRE

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 exhibit...

Shilpa Verma, Shalini Shah

2013-01-01

318

A realistic distributed storage system that minimizes data storage and repair bandwidth  

OpenAIRE

In a realistic distributed storage environment, storage nodes are usually placed in racks, a metallic support designed to accommodate electronic equipment. It is known that the communication (bandwidth) cost between nodes within a rack is much lower than the communication (bandwidth) cost between nodes within different racks. In this paper, a new model, where the storage nodes are placed in two racks, is proposed and analyzed. In this model, the storage nodes have differen...

Gasto?n, Bernat; Pujol, Jaume; Villanueva, Merce?

2013-01-01

319

Tuning gain and bandwidth of traveling wave tubes using metamaterial beam-wave interaction structures  

Energy Technology Data Exchange (ETDEWEB)

We employ metamaterial beam-wave interaction structures for tuning the gain and bandwidth of short traveling wave tubes. The interaction structures are made from metal rings of uniform cross section, which are periodically deployed along the length of the traveling wave tube. The aspect ratio of the ring cross sections is adjusted to control both gain and bandwidth. The frequency of operation is controlled by the filling fraction of the ring cross section with respect to the size of the period cell.

Lipton, Robert, E-mail: lipton@math.lsu.edu; Polizzi, Anthony, E-mail: polizzi@math.lsu.edu [Department of Mathematics, Louisiana State University, Baton Rouge, Louisiana 70803-4918 (United States)

2014-10-14

320

Multilevel bandwidth measurements and capacity exploitation in gigabit passive optical networks  

OpenAIRE

The authors report an experimental investigation on the measurement of the available bandwidth for the users in gigabit passive optical networks (GPON) and the limitations caused by the Internet protocols, and transfer control protocol (TCP) in particular. We point out that the huge capacity offered by the GPON highlights the enormous differences that can be showed among the available and actually exploitable bandwidth. In fact, while the physical layer capacity can reach value of 100 Mb/s an...

Mellia, Marco

2014-01-01

321

Tuning gain and bandwidth of traveling wave tubes using metamaterial beam-wave interaction structures  

International Nuclear Information System (INIS)

We employ metamaterial beam-wave interaction structures for tuning the gain and bandwidth of short traveling wave tubes. The interaction structures are made from metal rings of uniform cross section, which are periodically deployed along the length of the traveling wave tube. The aspect ratio of the ring cross sections is adjusted to control both gain and bandwidth. The frequency of operation is controlled by the filling fraction of the ring cross section with respect to the size of the period cell.

322

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

OpenAIRE

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 ...

Gurpreet Singh Bagga; Mritunjay Kumar Rai

2014-01-01

323

Slow-light dynamics of large-bandwidth pulses in warm rubidium vapor  

International Nuclear Information System (INIS)

We study slow-light propagation dynamics in warm Rb vapor. We present data showing significant pulse reshaping when the bandwidth of the pulses is increased and present a model that qualitatively explains the observed behavior. Our data and modeling emphasize how the Doppler broadening in a warm vapor strongly affects the propagation of high-frequency components and leads to unintuitive features on the transmitted pulse shapes. This has important consequences for applications involving the delay of large-bandwidth pulses

324

Log based Pipelined Backoff for Bandwidth Estimation in QoS enabled Multipath Routing for MANETs  

OpenAIRE

QoS enabled routing makes the utilization of resources more efficient by minimizing the unnecessary control messages and should not allow the transmissions that cannot meet the given QoS requirements. Due to the limited bandwidth constraint and dynamic topology of MANETS, supporting QoS is a challenging task. To improve the amount of unconsumed bandwidth and to reduce the overhead associated with the channel contention in MAC (Medium Access Control) layer, log based pipelined concept is appli...

N.SUMATHI,; DR. ANTONY SELVADOSS THANAMANI

2010-01-01

325

Tuning gain and bandwidth of traveling wave tubes using metamaterial beam-wave interaction structures  

CERN Document Server

We employ metamaterial beam-wave interaction structures for tuning the gain and bandwidth of short traveling wave tubes. The interaction structures are made from metal rings of uniform cross section, which are periodically deployed along the length of the traveling wave tube. The aspect ratio of the ring cross sections are adjusted to control both gain and bandwidth. The frequency of operation is controlled by the filling fraction of the ring cross section with respect to the period.

Lipton, Robert

2014-01-01

326

General model for delayed feedback and its application to transimpedance amplifier's bandwidth optimization  

OpenAIRE

Delays in real systems can be of two types: i) intrinsic delays - due to the physical principles of operation of each electronic device; ii) designed delays - due to extra circuits used to add the desired delay. Previous work established the possibility of achieving bandwidth improvements using small delays inside the feedback loop of feedback amplifiers. The modeling approach followed on these contributions used only one designed delay element. The bandwidth reduction effect due to intrinsic...

Alves, L. N.; Barbosa, L.; Macedo, E. A. L.; Aguiar, R. L.

2006-01-01

327

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

OpenAIRE

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, ...

Singh, G.; Kumar, P.

2012-01-01

328

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

OpenAIRE

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 de...

Prof. Jaikaran Singh; Prof. Mukesh Tiwari,; Ms. Neha Patel

2014-01-01

329

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

330

Modeling small-signal response of GaN-based metal-insulator-semiconductor high electron mobility transistor gate stack in spill-over regime: Effect of barrier resistance and interface states  

Science.gov (United States)

We provide theoretical and simulation analysis of the small signal response of SiO2/AlGaN/GaN metal insulator semiconductor (MIS) capacitors from depletion to spill over region, where the AlGaN/SiO2 interface is accumulated with free electrons. A lumped element model of the gate stack, including the response of traps at the III-N/dielectric interface, is proposed and represented in terms of equivalent parallel capacitance, Cp, and conductance, Gp. Cp -voltage and Gp -voltage dependences are modelled taking into account bias dependent AlGaN barrier dynamic resistance Rbr and the effective channel resistance. In particular, in the spill-over region, the drop of Cp with the frequency increase can be explained even without taking into account the response of interface traps, solely by considering the intrinsic response of the gate stack (i.e., no trap effects) and the decrease of Rbr with the applied forward bias. Furthermore, we show the limitations of the conductance method for the evaluation of the density of interface traps, Dit, from the Gp/? vs. angular frequency ? curves. A peak in Gp/? vs. ? occurs even without traps, merely due to the intrinsic frequency response of gate stack. Moreover, the amplitude of the Gp/? vs. ? peak saturates at high Dit, which can lead to underestimation of Dit. Understanding the complex interplay between the intrinsic gate stack response and the effect of interface traps is relevant for the development of normally on and normally off MIS high electron mobility transistors with stable threshold voltage.

Capriotti, M.; Lagger, P.; Fleury, C.; Oposich, M.; Bethge, O.; Ostermaier, C.; Strasser, G.; Pogany, D.

2015-01-01

331

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

332

Statistical results describing the bandwidth and coherence coefficient of whistler mode waves using THEMIS waveform data  

Science.gov (United States)

The bandwidths and coherence coefficients of lower band whistler mode waves are analyzed using Time History of Events and Macroscale Interactions during Substorms (THEMIS) waveform data for rising tones, falling tones, and hiss-like emissions separately. We also evaluate their dependences on the spatial location, electron density, the ratio of plasma frequency to local electron gyrofrequency (fpe/fce), and the wave amplitude. Our results show that the bandwidth normalized by the local electron gyrofrequency (fce) of rising and falling tones is very narrow (~0.01 fce), smaller than that of the hiss-like emissions (~0.025 fce). Meanwhile, the normalized bandwidth of discrete emissions gradually decreases with increasing wave amplitude, whereas that of hiss-like emissions increases slowly. The coherence coefficient of rising and falling tones is extremely large (~1), while the coherence coefficient of hiss-like emissions is smaller but is still larger than 0.5. For all categories of whistler mode waves, the normalized bandwidth increases at larger L shells. Furthermore, the normalized bandwidth is positively correlated with local fpe/fce but is inversely correlated with the electron density. Interactions between radiation belt electrons and whistler mode waves have been widely described by quasi-linear diffusion theory. Our results suggest that although quasi-linear theory is not entirely applicable for modeling electron interactions with rising and falling tones due to their narrow bandwidth and high coherence coefficient, it is suitable to treat wave-particle interactions between electrons and low-amplitude hiss-like emissions. Moreover, the correlations between the normalized bandwidth of chorus waves (especially the discrete emissions) and other parameters may provide insights for the generation mechanism of chorus waves.

Gao, X.; Li, W.; Thorne, R. M.; Bortnik, J.; Angelopoulos, V.; Lu, Q.; Tao, X.; Wang, S.

2014-11-01

333

Wide-bandwidth charge sensitivity with a radio-frequency field-effect transistor:  

OpenAIRE

We demonstrate high-speed charge detection at room temperature with single-electron resolution by using a radio-frequency field-effect transistor (RF-FET). The RF-FET combines a nanometer-scale silicon FET with an impedance-matching circuit composed of an inductor and capacitor. Driving the RF-FET with a carrier signal at its resonance frequency, small signals at the transistor's gate modulate the impedance of the resonant circuit, which is monitored at high speed using the reflected sig...

Nishiguchi, K.; Yamaguchi, H.; Fujiwara, A.; Zant, H. S. J.; Steele, G. A.

2013-01-01

334

Investigation of the bandwidth of multimode optical fibers used with 1550-nm LED and laser sources  

Science.gov (United States)

Multimode optical fibers are not intended to be used with 1550-nm sources; however, it is desirable to utilize 1300/1550-nm wavelength division multiplexing (WDM) on some multimode fibers at Kennedy Space Center (KSC). No information from fiber vendors nor from the literature is available to support this use. Preliminary studies at KSC have suggested that these fibers might be usable at 1550-nm if the fibers possessed enough bandwidth when sourced by LEDs. Detailed bandwidth studies were made on 12 multimode fibers using 1300- and 1550-nm lasers and LEDs. The results showed that the modal bandwidth at 1550-nm was about 50 percent of the 1300-nm value and that the chromatic dispersion could be predicted by extrapolating the vendor's specifications for wavelengths outside the 1550-nm region. Utilizing these data, predictions of the fiber's optical bandwidth were accurately made. Problems with launch conditions and possible differential attenuation at connectors was noted at 1300-nm but was less significant at 1550-nm. It appears that the multimode fibers studied will offer adequate performance in the 1550-nm region for a number of current KSC needs. Studies of additional fibers are encouraged to gain more confidence and better understanding of the 1550-nm bandwidth of KSC's multimode optical fibers before committing to 1300/1550-nm WDM.

White, Preston A., III

1992-01-01

335

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

336

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

337

Preliminary evaluation of a method for fitting hearing aids with extended bandwidth.  

Science.gov (United States)

This paper describes a preliminary laboratory-based evaluation of a method for fitting hearing aids with an extended high-frequency response, called CAMEQ2-HF. Linear filtering was used to implement the CAMEQ2-HF-prescribed gains for speech with an input level of 65 dB SPL. The results obtained using four normal-hearing (NH) and fifteen hearing-impaired (HI) listeners showed: (1) The gains were sufficient to make components above 5 kHz audible when those components were presented alone, and when they were presented together with the lower-frequency components; (2) NH listeners preferred a wider bandwidth (10 or 7.5 kHz versus 5 kHz) for both pleasantness and speech clarity, while HI listeners usually preferred a narrower bandwidth for pleasantness but a wider bandwidth for clarity; (3) HI listeners performed better on the ‘S-test (detection of word-final /s/ or /z/) with a wider than with a narrower bandwidth (7.5 versus 5 kHz); (4) Identification of vowel-consonant-vowel nonsense syllables improved with increasing bandwidth from 5 to 7.5 kHz for the NH but not for the HI listeners. PMID:20672875

Füllgrabe, Christian; Baer, Thomas; Stone, Michael A; Moore, Brian C J

2010-10-01

338

Analysis of memory bandwidth requirements for the H.263 video codec  

Science.gov (United States)

Memory bandwidth is emerging as the fundamental impediment to higher performance and lower power computer and communication systems. In this paper, we present an analysis of memory bandwidth requirements for the H.263 video codec algorithms. We provide data and insight into how the choice of cache parameters affects external bandwidth requirements of video. We make use of memory traces generated as a result of running Telenor's H.263 video encoder and decoder software implementations to simulate a large number of cache configurations. In the area of analysis of video algorithms, this paper focuses on the following issues: we provide a study of how varying cache size, block size, associativity, replacement policy, and organization parameters such a split versus unified cache affects memory bandwidth requirements. A comparative study of encoder and decoder bandwidth requirements is presented. We also study various advanced encoding options provided with the H.263 standard in this light. Based on our study, we provide guidelines for traffic-directed memory system design.

Kapoor, Bhanu

1998-01-01

339

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)

340

Bandwidth-limited laser image projection using a DMD-based beam shaper  

Science.gov (United States)

A digital micromirror device (DMD) laser beam shaper was implemented for projecting spatial bandwidth-limited laser images with precisely controlled intensity. A telescope images the binary DMD pattern with an adjustable pinhole low-pass filter that controls the system bandwidth and converts the binary pixelated image back to grayscale. Images with arbitrary but bandwidth-limited spatial frequency content are formed. System performance was evaluated by examining the spatial frequency response in terms of RMS intensity error by generating sinusoidal-flattop beam profiles with different spatial periods. This system evaluation was used as a reference to predict the error level of arbitrary output beam profiles. In addition, we demonstrated band-limited laser image projection for different spatial bandwidths using a grayscale image superimposed on a flattop laser beam profile. Optimized system bandwidth was simulated by considering the tradeoff between image precision and spatial resolution. Experimental results demonstrated that the RMS error of output beam profiles was consistent with the system evaluation reference. The major residual error in the output beam profile came from the sharp-edged pinhole low-pass filter. Error histograms had a Gaussian distribution with mean value of zero and standard deviation equal to the value of the RMS error. We plan to apply this technique to generate programmable optical trap shapes in ultracold atom experiments.

Liang, Jinyang; Wu, Sih-Ying; Kohn, Rudolph N., Jr.; Becker, Michael F.; Heinzen, Daniel J.

2012-03-01

341

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

342

Optimization of Inter-network Bandwidth Resources for Large-Scale Data Transmission  

Directory of Open Access Journals (Sweden)

Full Text Available In order to solve problems such as low resources utilization of data center backbone bandwidth and expensive daily expenses caused by the tidal effect in the transition of large-scale network data, the new optimization method of bandwidth resource for bulk data transfer is proposed. This method finishes the bulk data transfer by taking full advantage of the idle channel bandwidth. Firstly, the dynamic idle network bandwidth resource was switched into the static flow network; and then the max-min fair multi-commodity flow model is built on the basis of static network; finally, the iterative technique is used to solve the programming model for getting the maximum transport flows and the corresponding transmission path of bulk data transfer. The simulation method was used to test this optimization project. The results show that the optimization method proposed by the paper can significantly improve the utilization of data center backbone bandwidth resource, and the maximum amount of data transmission and the speed of data transfer have been obviously increased

Mu Zhang

2014-03-01

343

Design of high-bandwidth FSM driving circuit of ATP system for laser communications  

Science.gov (United States)

A high-bandwidth driving circuit of FSM (fast-steering mirror) is designed and presented in this paper. The circuit plays an important role in FSM controlling system of the ATP (acquisition, tracking and pointing) system for laser communications. In order to achieve higher bandwidth, smaller size and stability, piezoelectric ceramics and linear power amplifier driving methods are adopted. In the design of the driving circuit, OPA228 and PA93 are selected to constitute bipolar amplification structure to obtain the optimization and balance of magnification and bandwidth. A pre-amplifier is used to achieve a lower input offset voltage and higher bandwidth; a post amplifier to obtain the characteristics of high power and high pressure. In this paper, the working principle and design process of the driving circuit has been described in details and the factors affecting the bandwidth of the circuit are analyzed. Simulations of the driving circuit are validated by using TINA and the experimental results are in agreement with the theoretical analysis.

Lin, Jun-lan

2014-09-01

344

An efficient Bandwidth Demand Estimation for Delay Reduction in IEEE 802.16j MMR WiMAX Networks  

Directory of Open Access Journals (Sweden)

Full Text Available IEEE 802.16j MMR WiMAX networks allow the number of hops between the user andthe MMR-BS to be more than two hops. The standard bandwidth request procedure inWiMAX network introduces much delay to the user data and acknowledgement of theTCP packet that affects the performance and throughput of the network. In this paper,we propose a new scheduling scheme to reduce the bandwidth request delay in MMRnetworks. In this scheme, the MMR-BS allocates bandwidth to its direct subordinate RSswithout bandwidth request using Grey prediction algorithm to estimate the requiredbandwidth of each of its subordinate RS. Using this architecture, the access RS canallocate its subordinate MSs the required bandwidth without notification to the MMR-BS.Our scheduling architecture with efficient bandwidth demand estimation able to reducedelay significantly.

Fath Elrahman Ismael

2010-01-01

345

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

346

Modulation bandwidth of a double tunnelling-injection quantum dot laser  

Science.gov (United States)

The modulation response of a double tunnelling-injection (DTI) quantum dot (QD) laser is studied. Closed-form expressions are obtained for the dynamic characteristics of the laser and the upper limit for the modulation bandwidth is estimated. The optimum cavity length, surface density of QDs, and dc injection current density, maximizing the modulation bandwidth, are shown to exist. The higher the dc injection current density, the smaller should be the optimum values of the cavity length and the surface density of QDs. While the maximum bandwidth is shown to be the same in DTI and conventional QD lasers and unaffected by the differential gain, the optimum dc current density, being inversely proportional to the differential gain, is lower in a DTI laser.

Asryan, Levon V.

2015-03-01

347

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

348

Design and Bandwidth Analysis of Fault-Tolerant Multistage Interconnection Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The design of a suitable interconnection network for inter-processor communication is one of the key issues of the system performance. In this study a new irregular interconnection network IABN (Irregular Augmented Baseline has been proposed. IABN is designed by modifying existing ABN (Augmented Baseline Network. ABN is a regular multi-path network with limited fault tolerance. IABN provides three times more paths between any pair of source-destination in comparison to ABN. The ABN and IABN MINs are analyzed and compared in terms of performance parameters namely Bandwidth, Cost and Bandwidth per unit Cost. The proposed network IABN provides much better fault-tolerance and almost double bandwidth at the expanse of little more cost than ABN.

R. Aggarwal

2008-01-01

349

BECPA : Bandwidth Efficient Cluster Based Packet Aggregation in Wireless Sensor Network  

DEFF Research Database (Denmark)

In recent years, energy consumption and data gathering is a foremost concern in many applications of wireless sensor networks (WSN). The major issue in WSN is effective utilization of the resource as energy and bandwidth with a large gathering of data from the monitoring and control applications. This paper proposes novel bandwidth efficient cluster based packet aggregation algorithm (BECPA) for heterogeneous WSN. It combines the idea of variable packet generation rate of each node with random data. The nodes are randomly distributed with different energy level with equal in numbers. It uses the perfectly compressible aggregation function at cluster head based on the correlation of packets and data generated by nodes. The aggregation functions prevent transmission of redundant packets. Compare to state-of-the-art solutions, the algorithm shows significant energy saving by reducing the number of packets at the sink with better bandwidth utilization in packet aggregation than data aggregation.

Dnyaneshwar, Mantri; Prasad, Neeli R.

2013-01-01

350

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

351

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.

352

Comparison of Available Bandwidth Estimation Techniques in Packet-Switched Mobile Networks  

DEFF Research Database (Denmark)

The relative contribution of the transport network towards the per-user capacity in mobile telecommunication systems is becoming very important due to the ever increasing air-interface data rates. Thus, resource management procedures such as admission, load and handover control can make use of information regarding the available bandwidth in the transport network, as it could end up being the bottleneck rather than the air interface. This paper provides a comparative study of three well known available bandwidth estimation techniques, i.e. TOPP, SLoPS and pathChirp, taking into account the statistical conditions of the available bandwidth and assessing the variability of their estimations. Simulation-based studies on a mobile transport network show that pathChirp outperforms TOPP and SLoPS, both in terms of accuracy and efficiency.

López Villa, Dimas; Ubeda Castellanos, Carlos

2006-01-01

353

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

354

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

355

360/degree/ digital phase detector with 100-kHz bandwidth  

International Nuclear Information System (INIS)

The general availability of digital circuit components with propagation delay times of a few nanoseconds makes a digital phase detector with good bandwidth feasible. Such a circuit has a distinct advantage over its analog counterpart because of its linearity over a wide range of phase shift. A description is given of a phase detector that is being built at Los Alamos National Laboratory for the Fusion Materials Irradiation Test (FMIT) project. The specifications are 100-kHz bandwidth, linearity of /plus or minus/1/degree/ over /plus or minus/180/degree/ of phase shift, and 0.66/degree/ resolution. To date, the circuit has achieved the bandwidth and resolution. The linearity is approximately /plus or minus/3/degree/ over /plus or minus/180/degree/ phase shift. 3 refs

356

On Artificial Magneto-Dielectric Loading for Improving the Impedance Bandwidth Properties of Microstrip Antennas  

CERN Document Server

In the present paper we discuss the effect of artificial magneto-dielectric substrates on the impedance bandwidth properties of microstrip antennas. The results found in the literature for antenna miniaturization using magnetic or magneto-dielectric substrates are revised, and discussion is addressed to the practically realizable artificial magnetic media operating in the microwave regime. Using a transmission-line model we, first, reproduce the known results for antenna miniaturization with non-dispersive material fillings. Next, a realistic dispersive behavior of a practically realizable artificial substrate is embedded into the model, and we show that frequency dispersion of the substrate plays a very important role in the impedance bandwidth characteristics of the loaded antenna. The impedance bandwidths of reduced size patch antennas loaded with dispersive magneto-dielectric substrates and high-permittivity substrates are compared. It is shown that unlike substrates with dispersion-free permeability, pra...

Ikonen, P; Simovski, C; Tretyakov, S A; Ikonen, Pekka; Maslovski, Stanislav; Simovski, Constantin; Tretyakov, Sergei

2005-01-01

357

High Dielectric Low Loss Transparent Glass Material Based Dielectric Resonator Antenna with Wide Bandwidth Operation  

Science.gov (United States)

This paper presents the application of new high permittivity and low loss glass material for antennas. This glass material is transparent. A very simple rectangular dielectric resonator antenna is designed first with a simple microstrip feeding line. In order to widen the bandwidth, the feed of the design is modified by forming a T-shaped feeding. This new design enhanced the bandwidth range to cover the WLAN 5 GHz band completely. The dielectric resonator antenna cut into precise dimensions is placed on the modified microstrip feed line. The design is simple and easy to manufacture and also very compact in size of only 36 × 28 mm. A -10 dB impedance bandwidth of 18% has been achieved, which covers the frequency range from 5.15 GHz to 5.95 GHz. Simulations of the measured return loss and radiation patterns are presented and discussed.

Mehmood, Arshad; Zheng, Yuliang; Braun, Hubertus; Hovhannisyan, Martun; Letz, Martin; Jakoby, Rolf

2015-01-01

358

Joint Bandwidth and Power Allocation with Admission Control in Wireless Multi-User Networks With and Without Relaying  

OpenAIRE

Equal allocation of bandwidth and/or power may not be efficient for wireless multi-user networks with limited bandwidth and power resources. Joint bandwidth and power allocation strategies for wireless multi-user networks with and without relaying are proposed in this paper for (i) the maximization of the sum capacity of all users; (ii) the maximization of the worst user capacity; and (iii) the minimization of the total power consumption of all users. It is shown that the pr...

Gong, Xiaowen; Vorobyov, Sergiy A.; Tellambura, Chintha

2010-01-01

359

Time Slot Groups - A Data Structure for QoS-Constrained Advance Bandwidth Reservation and Admission Control  

OpenAIRE

In this paper we present Time Slot Groups (TSG), a novel, efficient data structure for QoS-constrained advance bandwidth reservation and admission control. The data structure divides the time horizon into T equally sized time slots and can be used for serving efficiently complex bandwidth reservation requests specifying the duration of the reservation, the minimum required bandwidth, the earliest possible starting time and the latest possible finish time. The data structure supports reservati...

Andreica, Mugurel Ionut; Tapus, Nicolae

2008-01-01

360

Roles of Potential Gradient and Electrode Bandwidth on Negative Differential Resistance in One-Dimensional Band Insulator  

Science.gov (United States)

A negative differential resistance (NDR) in a one-dimensional band insulator attached to electrodes is investigated. We systematically examine the effects of an electrode bandwidth and a potential distribution inside the insulator on current–voltage characteristics. We show that, in uncorrelated systems, the NDR is generally caused by a linear potential gradient as well as by a finite electrode bandwidth. In particular, the former reduces the effective bandwidth of the insulator for elastic tunneling by tilting its energy band, so that it brings about the NDR even in the limit of large electrode bandwidth.

Tanaka, Yasuhiro; Yonemitsu, Kenji

2014-12-01

361

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

362

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

363

A bandwidth compressive modulation system using multi-amplitude minimum shift keying /MAMSK/. [for spacecraft communication  

Science.gov (United States)

A bandwidth compressive modem making use of multi-amplitude minimum shift keying (MAMSK) has been designed and implemented in a laboratory environment at microwave frequencies. This system achieves a substantial bandwidth reduction over binary PSK and operates within 0.5 dB of theoretical performance. A number of easily implemented microwave transmitters have been designed to generate the required set of 16 signals. The receiver has been designed to work at 1 Mbit/s and contains the necessary phase tracking, AGC, and symbol synchronization loops as well as a lock detector, SNR estimator and provisions for differential decoding. This paper describes this entire system and presents the experimental results.

Weber, W. J., III; Stanton, P. H.; Sumida, J. T.

1978-01-01

364

Pulse generation without gain-bandwidth limitation in a laser with self-similar evolution  

OpenAIRE

With existing techniques for mode-locking, the bandwidth of ultrashort pulses from a laser is determined primarily by the spectrum of the gain medium. Lasers with self-similar evolution of the pulse in the gain medium can tolerate strong spectral breathing, which is stabilized by nonlinear attraction to the parabolic self-similar pulse. Here we show that this property can be exploited in a fiber laser to eliminate the gain-bandwidth limitation to the pulse duration. Broad (?200 nm) spectra ...

Chong, A.; Liu, H.; Nie, B.; Bale, B. G.; Wabnitz, S.; Renninger, W. H.; Dantus, M.; Wise, F. W.

2012-01-01

365

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

366

Bandwidth Optimization Design of a Multi Degree of Freedom MEMS Gyroscope  

OpenAIRE

A new robust multi-degree of freedom (multi-DOF) MEMS gyroscope is presented in this paper. The designed gyroscope has its bandwidth and amplification factor of the sense mode adjusted more easily than the previous reported multi-DOF MEMS gyroscopes. Besides, a novel spring system with very small coupling stiffness is proposed, which helps achieve a narrow bandwidth and a high amplification factor for a 2-DOF vibration system. A multi-DOF gyroscope with the proposed weak spring system is desi...

Fuhua Yang; Guowei Han; Chaowei Si; Jin Ning

2013-01-01

367

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

368

The large analog bandwidth recorder and digitizer with ordered readout (LABRADOR) ASIC  

International Nuclear Information System (INIS)

Three generations of full-custom analog integrated circuits designed for low-power, high-speed sampling of Radio-Frequency (RF) transients in excess of the Nyquist minimum have been developed. These 0.25?m CMOS devices are denoted the Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR) ASICs and finally consist of nine channels of 260 deep sampling. Continuous sampling is provided with common stop capability. Input analog bandwidth is approximately 1 GHz and sampling speeds are adjustable from 0.02 to 3.7 GSa/s. Completely parallel internal conversion supports 12-bit digitization and readout of all 2340 cells in under 50?s

369

Chrome: Improving the Transmission Reliability by Bandwidth Optimization Using Hybrid Algorithm  

Directory of Open Access Journals (Sweden)

Full Text Available An approach to improve the transmission reliability by network bandwidth optimization using the hybrid algorithm called chrome. The main objective is to design an optimization algorithm to achieve bandwidth optimization in wireless networks using hybrid of Particle Swarm Optimizatio n (PSO and Genetic Algorithm (GA which improves the transmission reliability. In this approach, global search character of PSO and local search character of GA are used. In chrome algorithm, the PSO algorithm is used to search around the environment and where ever necessary the GA’s searching techniques are used for optimization

Ajeeth Kumar J

2013-04-01

370

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

371

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

372

Gain and bandwidth of the gyro-TWT and CARM amplifiers  

International Nuclear Information System (INIS)

Issues concerning the interpretation of gain and bandwidth from the dispersion relation are examined for the gyrotron traveling wave tube (gyro-TWT) and cyclotron autoresonance maser (CARM) amplifiers. A general method for the determination of critical current for oscillation is illustrated. Despite the broad bandwidth predicted for the CARM amplifier by the commonly employed dispersion relation, it is seen in particle simulation that single-particle interaction, rather than collective amplification, prevails over much of the band. Reasons for the discrepancy are analyzed

373

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

OpenAIRE

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 ...

ISHA PURI; ARCHANA AGRAWAL

2011-01-01

374

Pre-emphasis determination for an S-band constant bandwidth FM/FM station  

Science.gov (United States)

Pre-emphasis schedules are given for 11 constant-bandwidth FM subcarriers modulating an S band transmitter at three receiver signal to noise ratios (i.e., 9, 15, and 25 dB). The criterion for establishing these pre-emphasis curves is the achievement, at various receiver intermediate frequency signal to noise ratios, of equal receiver output signal to noise ratios for all channels. It is realized that these curves may not be the optimum pre-emphasis curves based on overall efficiency or maximum utilization of the allotted spectrum, but they are near-optimum for data with channels which require equal output signal to noise ratios, such as spectral densities. The empirically derived results are compared with a simplified, analytically derived schedule and the primary differences are explained. The S band pre-emphasis schedule differs from the lower frequency VHF case. Since most proportional bandwidth and constant bandwidth systems use ground based recorders and some use flight recorders (as the Saturn systems did on VHF proportional bandwidth telemetry), the effects of these recorders are discussed and a modified pre-emphasis schedule is presented showing the results of this study phase.

Wallace, G. R.; Salter, W. E.

1972-01-01

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 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

Bandwidth guaranteed integrated routing and wavelength assignment algorithm in IP over WDM optical networks  

Science.gov (United States)

In this paper, we have developed an integrated online algorithm for dynamically routing bandwidth guaranteed label switched paths (LSPs) in IP over WDM optical networks. Traditionally, routing at upper layer (e.g., IP layer) is independent of wavelength routing at the optical layer. Wavelength routing at the optical layer sets up a quasi-static logical topology which is then used at the IP layer for IP routing. The coarse-grain wavelength channels and the pre-determined virtual topologies with respect to some a priori assumed traffic distribution are barriers to efficient resource use and inflexible to changing traffic. We take into count the combined knowledge of resource and topology information in both IP and optical layers. With this added knowledge, an integrated routing approach can extract better network efficiencies, be more robust to changing traffic patterns at the IP layer than schemes that either use dynamic routing information at the IP layer or use a static wavelength topology only. Our proposed algorithm considers not only the importance of critical links, but also their relative importance to routing possible future LSP set-up requests by characterizing their normalized bandwidth contribution to routing future LSP requests. Moreover, link residual bandwidth information that captures the link's capability of routing future LSPs is also incorporated into our algorithm. Simulation results show that our proposed algorithm performs better than both routing algorithms do in terms of LSP set-up request rejection rate and available bandwidths.

Su, Xu; Wang, Bin; Chen, C. L. P.

2002-07-01

377

Technique for tuning center frequency of HTS microstrip filters without significantly changing bandwidth  

Energy Technology Data Exchange (ETDEWEB)

We have developed a technique for tuning high-temperature superconducting (HTS) microstrip filters in which additional electric pads are placed at the open ends of the resonators for tuning the center frequency. Pads are placed along one side of the open ends of the resonators to enable the effective lengths of the resonators to be adjusted, thereby shifting the center frequency. Pads are also placed around the I/O 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. The pads consist of line-and-space patterns. The former are electrically connected to the resonators, and the latter are electrically connected to the coupled-line elements. Simulated application of this technique to a 3-pole superconducting microstrip combline bandpass filter with half-wavelength resonators, a 5.0-GHz center frequency, and a 120-MHz 3-dB bandwidth shifted the bandwidth 500 MHz. However, the 3-dB bandwidth was reduced about 14 MHz. Use of a modified 3-pole microstrip interdigital bandpass filter mitigated the reduction to 2 MHz. Using this modified filter with additional electric pads is thus an effective way to tune the center frequency of HTS bandpass filters without significantly changing the bandwidth.

Sekiya, N., E-mail: nsekiya@yamanashi.ac.j [University of Yamanashi, 4-3-11 Takeda, Kofu 400-8511 (Japan); Nakagawa, Y. [University of Yamanashi, 4-3-11 Takeda, Kofu 400-8511 (Japan); Saito, A.; Ohshima, S. [Yamagata University, 4-3-16 Johnan, Yonezawa 992-8510 (Japan)

2009-10-15

378

Modulation bandwidth enhancement of white-LED-based visible light communications using electrical equalizations  

Science.gov (United States)

Utilizing the modulation capability of LEDs, there have been many studies about convergence technology to combine illumination and communication. The visible light communication (VLC) system has several advantages such as high security, immunity to RF interference and lower additional cost than comparing to LEDs just for illumination. However, modulation bandwidth of LEDs is not enough for various wireless communication systems. Since the commercial LEDs are designed only for lighting systems; we need an effort to enhance the modulation characteristics of LEDs. When the area of LED is increased, internal junction capacitance of LED is also increased depending on the area of LEDs and then the RC delay time of LED is increased. As a result, the modulation bandwidth of LEDs is limited by large RC delay time. In addition, frequency response of commercial white LED is degraded by the slow response time of the used yellow phosphor. Thus, modulation bandwidth of VLC system is limited to several MHz which is not enough to accommodate high data rate transmission. In this paper, we designed equalization circuit using RLC component for compensating the white LEDs frequency response. Also, we used blue filtering to improve frequency response of white LEDs, which is degraded by yellow phosphorescent component. Power loss by optical filtering and distance is compensated by convex lens. Consequently, we extend the modulation bandwidth of VLC system from 3 MHz to more than 180 MHz, and it allows NRZ-OOK data transmission up to 400 Mbps at 50 cm.

Kwon, D. H.; Yang, S. H.; Han, S. K.

2015-01-01

379

Relative intensity noise transfer of large-bandwidth pump lasers in Raman fiber amplifiers  

Science.gov (United States)

A theoretical analysis of the Raman amplification in optical fibers and the pump-to-signal relative intensity noise (RIN) transfer has been performed in the spectral domain. An efficient Raman amplification of a monochromatic signal beam by a large-bandwidth pump beam has been demonstrated for a pump bandwidth much smaller than the Raman linewidth. Under the same approximation the pump-to-signal RIN transfer has been calculated in both cases of copropagating and counterpropagating beams in the two limiting cases of modulated monochromatic and smooth-profile large-bandwidth pump beams. At low frequencies the excess of noise evidenced in the case of a modulated monochromatic pump beam did not exist in the case of large-bandwidth pseudoincoherent sources. As this noise reduction can be as large as 13 dB for a 40 dB net gain of the amplifier, such incoherent pumping sources must be considered for the purpose of low-noise Raman amplifiers.

Keita, Kafing; Delaye, Philippe; Frey, Robert; Roosen, Gérald

2006-12-01

380

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

381

Bandwidth and power allocation for cooperative relay in cognitive radio networks  

Science.gov (United States)

In this article, we consider a cognitive radio (CR) relay network where one source secondary user (SU) communicates with its corresponding destination SU with the help of relay SUs. Conventionally, equal bandwidth and/or power are allocated to each relay SU, which may not be efficient for the CR with limited bandwidth and power. Therefore, this article presents bandwidth and power allocation with amplify-and-forward (AF) or decode-and-forward (DF) relaying protocol to (1) maximize the sum network throughput; (2) minimize the total transmit power of the CR network with considering the fairness of power drain of relay SUs; (3) maximize the energy efficiency of the CR network. It is shown that DF relaying protocol can achieve better performance when the decoding rate constraint is not considered. In contrast, when considering the decoding rate constraint in DF relaying protocol, we propose the hybrid relaying protocol that combines AF and DF relaying protocols. We formulate the joint bandwidth and power allocation problem with hybrid relaying protocol to maximize the sum network throughput. A greedy algorithm is developed to solve the joint optimization problem, which has much less computational complexity. It is shown that the greedy algorithm has comparable performance to the exhaustive search algorithm. Finally, numerical results are provided to endorse our proposed algorithms.

Yu, Huogen; Tang, Wanbin; Li, Shaoqian

2012-12-01

382

Dynamic and balanced capacity allocation scheme with uniform bandwidth for OFDM-PON systems  

Science.gov (United States)

As the bitrate of orthogonal frequency division multiplexing passive optical network (OFDM-PON) system is continuously increasing, how to effectively allocate the system bandwidth among the huge number of optical network units (ONUs) is one of the key problems before OFDM-PON can be practical deployed. Unlike traditional bandwidth allocation scheme, in this paper, the transmission performance of single ONU is for the first time taken into consideration and optimized. To reduce the manufacturing complexity and fully utilize the processing ability of the receivers, the system bandwidth is equally distributed to the ONUs. Bit loading is used to allocate the total transmission capacity, and power loading is used to guarantee the ONUs have balanced transmission performance even if they operate at different bitrate. In this way, a dynamic and balanced capacity allocation scheme with uniform bandwidth for OFDM-PON systems can be realized. At last, an experimental system is established to verify the feasibility of the proposed scheme, and the influence that the scheme brings to the whole system is also analyzed.

Lei, Cheng; Chen, Hongwei; Chen, Minghua; Yu, Ying; Guo, Qiang; Yang, Sigang; Xie, Shizhong

2015-03-01

383

Log based Pipelined Backoff for Bandwidth Estimation in QoS enabled Multipath Routing for MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available QoS enabled routing makes the utilization of resources more efficient by minimizing the unnecessary control messages and should not allow the transmissions that cannot meet the given QoS requirements. Due to the limited bandwidth constraint and dynamic topology of MANETS, supporting QoS is a challenging task. To improve the amount of unconsumed bandwidth and to reduce the overhead associated with the channel contention in MAC (Medium Access Control layer, log based pipelined concept is applied to backoff procedure. Due to this logarithmic pipelined concept, channel waiting time is reduced. This modified method is integrated with a multipath routing protocol called enhanced link disjoint AOMDV(Adhoc Ondemand Multipath Distance Vector which allows the establishment of multiple paths between a single source and destination node. Multiple paths can be useful in improving the effective bandwidth of communication pairs. This approach is implemented in NS2 simulator. Performance of this method is evaluated in terms of throughput, packet delivery ratio, effective bandwidth utilization, energy consumption.

N.SUMATHI,

2010-11-01

384

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

385

An enhanced dynamic wavelength and bandwidth allocation method in WDM-EPON  

Science.gov (United States)

A kind of dynamic wavelength and bandwidth allocation (DWBA) algorithm of WDM-EPON was studied and then improved to guarantee QoS of multiple-services access. MPCP extension with modified REQUEST message and GRANT message are also proposed.The simulation results based on OPNET indicates the improved algorithm performed well in successful QoS assurance.

Zeng, Zhiwei; Ran, Yang; Huang, Hongbin; Liu, Weiping

2009-11-01

386

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

387

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

388

Effects of frequency and bandwidth on diagnostic information transfer in ultrasonic B-mode imaging.  

Science.gov (United States)

Transmitted pressure pulses in ultrasonic B-mode imaging systems are commonly characterized by their center frequency and bandwidth. Both parameters are associated with tradeoffs in spatial resolution and signal-to-noise in ultrasonic system design, with no general understanding of where they are optimal when applied to specific clinical exams. We use the ideal observer and simple psychophysical studies with human observers to evaluate the efficiency of information transfer in B-mode imaging as a function of the transmitted pulse center frequency and fractional bandwidth. Our approach uses a statistical model of backscatter relevant to breast imaging, and a 2-D model of pulse propagation based on Rayleigh-Sommerfeld diffraction theory. The statistics of the backscattered signal are combined in an ideal observer calculation that quantifies the task-relevant information contained in the radio-frequency (RF) signal after delay-and-sum beamforming. This is followed by a psychophysical evaluation of observer performance on B-mode envelope-detected images in three simple tasks. This experimental design allows us to track the flow of diagnostic information through RF acquisition and subsequent reading of the envelope image. In a low-contrast detection task and a high-contrast boundary discrimination task, optimal efficiency for human observers is observed at the highest center frequencies tested (15 MHz) and at moderate bandwidth (40%). For detection of scattering material in a high-contrast hypoechoic lesion, optimal efficiency was observed at lower center frequencies (5 MHz) and higher bandwidth (80%). The ideal observer analysis shows that this task dependence does not arise in the acquisition stage, where efficiency is maximized at 15 MHz with bandwidths of 60% or greater, but rather in the subsequent processing and reading of the envelope image. In addition, at higher frequencies more information is lost in the processing and reading than in the acquisition of reflected signals. PMID:22711407

Abbey, Craig K; Nguyen, Nghia Q; Insana, Michael F

2012-06-01

389

Joint Bandwidth and Power Allocation with Admission Control in Wireless Multi-User Networks With and Without Relaying  

CERN Document Server

Equal allocation of bandwidth and/or power may not be efficient for wireless multi-user networks with limited bandwidth and power resources. Joint bandwidth and power allocation strategies for wireless multi-user networks with and without relaying are proposed in this paper for (i) the maximization of the sum capacity of all users; (ii) the maximization of the worst user capacity; and (iii) the minimization of the total power consumption of all users. It is shown that the proposed allocation problems are convex and, therefore, can be solved efficiently. Moreover, the admission control based joint bandwidth and power allocation is considered. A suboptimal greedy search algorithm is developed to solve the admission control problem efficiently. The conditions under which the greedy search is optimal are derived and shown to be mild. The performance improvements offered by the proposed joint bandwidth and power allocation are demonstrated by simulations. The advantages of the suboptimal greedy search algorithm fo...

Gong, Xiaowen; Tellambura, Chintha

2010-01-01

390

Digital audio broadcasting: Comparison of coverage at different frequencies and with different bandwidths  

Science.gov (United States)

A Digital Audio Broadcasting (DAB) system capable of reliable reception in vehicles and portables has been developed by the Eureka 147 project. This Report describes a set of experiments performed to investigate the effect on the coverage area by changing the bandwidth of the DAB signal and its transmit frequency band. It is concluded that the choice of a bandwidth for the DAB signal of approximately 1.5 MHz is suitable. This is because it is sufficiently wideband to provide a significant benefit in reducing the location variation of the total received signal power, while being narrow enough to allow suitable channelization within the existing frequency bands. It is also concluded that a frequency allocation below Band IV would be more suitable in order to provide satisfactory coverage for all types of reception from terrestrial DAB transmitters. Above this frequency, the effects of clutter and terrain undulations appear to significantly increase the problems of providing uniform coverage at low antenna heights.

Maddocks, M. C. D.; Pullen, I. R.

391

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

392

Bandwidth Limitations in Characterization of High Intensity Focused Ultrasound Fields in the Presence of Shocks  

Science.gov (United States)

Nonlinear propagation effects result in the formation of weak shocks in high intensity focused ultrasound (HIFU) fields. When shocks are present, the wave spectrum consists of hundreds of harmonics. In practice, shock waves are modeled using a finite number of harmonics and measured with hydrophones that have limited bandwidths. The goal of this work was to determine how many harmonics are necessary to model or measure peak pressures, intensity, and heat deposition rates of the HIFU fields. Numerical solutions of the Khokhlov-Zabolotskaya-Kuznetzov-type (KZK) nonlinear parabolic equation were obtained using two independent algorithms, compared, and analyzed for nonlinear propagation in water, in gel phantom, and in tissue. Measurements were performed in the focus of the HIFU field in the same media using fiber optic probe hydrophones of various bandwidths. Experimental data were compared to the simulation results.

Khokhlova, V. A.; Bessonova, O. V.; Soneson, J. E.; Canney, M. S.; Bailey, M. R.; Crum, L. A.

2010-03-01

393

Transmit Signal and Bandwidth Optimization in Multiple-Antenna Relay Channels  

CERN Document Server

Transmit signal and bandwidth optimization is considered in multiple-antenna relay channels. Assuming all terminals have channel state information, the cut-set capacity upper bound and decode-and-forward rate under full-duplex relaying are evaluated by formulating them as convex optimization problems. For half-duplex relays, bandwidth allocation and transmit signals are optimized jointly. Moreover, achievable rates based on the compress-and-forward transmission strategy are presented using rate-distortion and Wyner-Ziv compression schemes. It is observed that when the relay is close to the source, decode-and-forward is almost optimal, whereas compress-and-forward achieves good performance when the relay is close to the destination.

Ng, Chris T K

2010-01-01

394

Cavity resonance absorption in ultra-high bandwidth CRT deflection structure by a resistive load  

Science.gov (United States)

An improved ultra-high bandwidth helical coil deflection structure for a hode ray tube is described comprising a first metal member having a bore therein, the metal walls of which form a first ground plane; a second metal member coaxially mounted in the bore of the first metal member and forming a second ground plane; a helical deflection coil coaxially mounted within the bore between the two ground planes; and a resistive load disposed in one end of the bore and electrically connected to the first and second ground planes, the resistive load having an impedance substantially equal to the characteristic impedance of the coaxial line formed by the two coaxial ground planes to inhibit cavity resonance in the structure within the ultra-high bandwidth of operation. Preferably, the resistive load comprises a carbon film on a surface of an end plug in one end of the bore.

Dunham, Mark E. (Santa Cruz, NM); Hudson, Charles L. (Santa Barbara, CA)

1993-01-01

395

Advances in broad bandwidth light sources for ultrahigh resolution optical coherence tomography  

Science.gov (United States)

Novel ultra-broad bandwidth light sources enabling unprecedented sub-2 µm axial resolution over the 400 nm-1700 nm wavelength range have been developed and evaluated with respect to their feasibility for clinical ultrahigh resolution optical coherence tomography (UHR OCT) applications. The state-of-the-art light sources described here include a compact Kerr lens mode locked Ti:sapphire laser (lgrc = 785 nm, Dgrlgr = 260 nm, Pout = 50 mW) and different nonlinear fibre-based light sources with spectral bandwidths (at full width at half maximum) up to 350 nm at lgrc = 1130 nm and 470 nm at lgrc = 1375 nm. In vitro UHR OCT imaging is demonstrated at multiple wavelengths in human cancer cells, animal ganglion cells as well as in neuropathologic and ophthalmic biopsies in order to compare and optimize UHR OCT image contrast, resolution and penetration depth.

Unterhuber, A.; Povazay, B.; Bizheva, K.; Hermann, B.; Sattmann, H.; Stingl, A.; Le, T.; Seefeld, M.; Menzel, R.; Preusser, M.; Budka, H.; Schubert, Ch; Reitsamer, H.; Ahnelt, P. K.; Morgan, J. E.; Cowey, A.; Drexler, W.

2004-04-01

396

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

397

Terahertz bandwidth all-optical Hilbert transformers based on long-period gratings.  

Science.gov (United States)

A novel, all-optical design for implementing terahertz (THz) bandwidth real-time Hilbert transformers is proposed and numerically demonstrated. An all-optical Hilbert transformer can be implemented using a uniform-period long-period grating (LPG) with a properly designed amplitude-only grating apodization profile, incorporating a single ?-phase shift in the middle of the grating length. The designed LPG-based Hilbert transformers can be practically implemented using either fiber-optic or integrated-waveguide technologies. As a generalization, photonic fractional Hilbert transformers are also designed based on the same optical platform. In this general case, the resulting LPGs have multiple ?-phase shifts along the grating length. Our numerical simulations confirm that all-optical Hilbert transformers capable of processing arbitrary optical signals with bandwidths well in the THz range can be implemented using feasible fiber/waveguide LPG designs. PMID:22743469

Ashrafi, Reza; Azaña, José

2012-07-01

398

Dispersion management of anisotropic metamirror for super-octave bandwidth polarization conversion  

Science.gov (United States)

Dispersion engineering of metamaterials is critical yet not fully released in applications where broadband and multispectral responses are desirable. Here we propose a strategy to circumvent the bandwidth limitation of metamaterials by implementing two-dimensional dispersion engineering in the meta-atoms. Lorentzian resonances are exploited as building blocks in both dimensions of the dedicatedly designed meta-atoms to construct the expected dispersion. We validated this strategy by designing and fabricating an anisotropic metamirror, which can accomplish achromatic polarization transformation in 4-octave bandwidth (two times of previous broadband converters). This work not only paves the way for broadband metamaterials design but also inspire potential applications of dispersion management in nano-photonics.

Guo, Yinghui; Wang, Yanqin; Pu, Mingbo; Zhao, Zeyu; Wu, Xiaoyu; Ma, Xiaoliang; Wang, Changtao; Yan, Lianshan; Luo, Xiangang

2015-02-01

399

Temperature dependence of the receiver noise temperature and IF bandwidth of superconducting hot electron bolometer mixers  

Science.gov (United States)

In this paper we study the temperature dependence of the receiver noise temperature and IF noise bandwidth of superconducting hot electron bolometer (HEB) mixers. Three superconducting NbN HEB devices of different transition temperatures (Tc) are measured at 0.85 THz and 1.4 THz at different bath temperatures (Tbath) between 4 K and 9 K. Measurement results demonstrate that the receiver noise temperature of superconducting NbN HEB devices is nearly constant for Tbath/Tc, less than 0.8, which is consistent with the simulation based on a distributed hot-spot model. In addition, the IF noise bandwidth appears independent of Tbath/Tc, indicating the dominance of phonon cooling in the investigated HEB devices.

Zhang, W.; Miao, W.; Zhong, J. Q.; Shi, S. C.; Hayton, D. J.; Vercruyssen, N.; Gao, J. R.; Goltsman, G. N.

2014-08-01

400

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

401

Dynamic Bandwidth Allocation Based on Online Traffic Prediction for Real-Time MPEG-4 Video Streams  

Directory of Open Access Journals (Sweden)

Full Text Available The distinct characteristics of variable bit rate (VBR video traffic and its quality of service (QoS constraints have posed a unique challenge on network resource allocation and management for future integrated networks. Dynamic bandwidth allocation attempts to adaptively allocate resources to capture the burstiness of VBR video traffic, and therefore could potentially increase network utilization substantially while still satisfying the desired QoS requirements. We focus on prediction-based dynamic bandwidth allocation. In this context, the multiresolution learning neural-network-based traffic predictor is rigorously examined. A well-known-heuristic based approach RED-VBR scheme is used as a baseline for performance evaluation. Simulations using real-world MPEG-4 VBR video traces are conducted, and a comprehensive performance metrics is presented. In addition, a new concept of renegotiation control is introduced and a novel renegotiation control algorithm based on binary exponential backoff (BEB is proposed to efficiently reduce renegotiation frequency.

Liang Yao

2007-01-01

402

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

403

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

404

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

405

Bandwidth smearing in optical interferometry: Analytic model of the transition to the double fringe packet  

CERN Document Server

Bandwidth smearing is a chromatic aberration due to the finite frequency bandwidth. In long-baseline optical interferometry terms, it is when the angular extension of the source is greater than the coherence length of the interferogram. As a consequence, separated parts of the source will contribute to fringe packets that are not fully overlapping; it is a transition from the classical interferometric regime to a double or multiple fringe packet. While studied in radio interferometry, there has been little work on the matter in the optical, where observables are measured and derived in a different manner, and are more strongly impacted by the turbulent atmosphere. We provide here the formalism and a set of usable equations to model and correct for the impact of smearing on the fringe contrast and phase, with the case of multiple stellar systems in mind. The atmosphere is briefly modeled and discussed.

Lachaume, Régis

2012-01-01

406

Design of a smart material electro-hydraulic actuator with improved frequency bandwidth  

Science.gov (United States)

Smart material electro-hydraulic actuators utilize fluid rectification by one-way valves to convert the small, high-frequency, high-force motions of smart materials such as piezoelectrics and magnetostrictives into useful motions of a hydraulic cylinder. These actuators have potential to replace centralized hydraulic pumps and lines with lightweight, compact, power-by-wire systems. This paper presents the design and testing of an improved actuator system. To increase the frequency bandwidth of operation, a lumped-parameter model is developed and validated based on experimental study of a pump with a performance capacity of 18.4 W. The critical parameters for pump performance are identified and their effect on pump performance assessed. The geometry of the hydraulic manifold that integrates the smart material pump and the output hydraulic cylinder is found to be critical for determining the effective system bandwidth.

Larson, John P.; Dapino, Marcelo J.

2012-04-01

407

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

408

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

409

“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.

410

Steady-state entanglement of cavity arrays in finite-bandwidth squeezed reservoirs  

CERN Document Server

When two chains of quantum systems are driven at their ends by a two-mode squeezed reservoir, they approach a steady state characterized by the formation of many entangled pairs. Each pair is made of one element of the first and one of the second chain. This effect has been already predicted under the assumption of broadband squeezing. Here we investigate the situation of finite-bandwidth reservoirs. This is done by modeling the driving bath as the output field of a non-degenerate parametric oscillator. The resulting non-Markovian dynamics is studied within the theoretical framework of cascade open quantum systems. It is shown that the formation of pair-entangled structures occurs as long as the normal-mode splitting of the arrays does not overcome the squeezing bandwidth of the reservoir.

Zippilli, Stefano

2014-01-01

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

Pickup design for high bandwidth bunch arrival-time monitors in free-electron lasers  

Energy Technology Data Exchange (ETDEWEB)

The increased demands for low bunch charge operation mode in the free-electron lasers (FELs) require an upgrade of the existing synchronization equipment. As a part of the laser-based synchronization system, the bunch arrival-time monitors (BAMs) should have a sub-10 femtosecond precision for high and low bunch charge operation. In order to fulfill the resolution demands for both modes of operation, the bandwidth of such a BAM should be increased up to a cutoff frequency of 40 GHz. In this talk, we present the design and the realization of high bandwidth cone-shaped pickup electrodes as a part of the BAM for the FEL in Hamburg (FLASH) and the European X-ray free-electron laser (European XFEL). The proposed pickup was simulated with CST STUDIO SUITE, and a non-hermetic model was built up for radio frequency (rf) measurements.

Angelovski, Aleksandar; Penirschke, Andreas; Jakoby, Rolf [TU Darmstadt (Germany). Institut fuer Mikrowellentechnik und Photonik; Kuhl, Alexander; Schnepp, Sascha [TU Darmstadt (Germany). Graduate School of Computational Engineering; Bock, Marie Kristin; Bousonville, Michael; Schlarb, Holger [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany); Weiland, Thomas [TU Darmstadt (Germany). Institut fuer Theorie Elektromagnetischer Felder

2012-07-01

413

Pickup design for high bandwidth bunch arrival-time monitors in free-electron lasers  

International Nuclear Information System (INIS)

The increased demands for low bunch charge operation mode in the free-electron lasers (FELs) require an upgrade of the existing synchronization equipment. As a part of the laser-based synchronization system, the bunch arrival-time monitors (BAMs) should have a sub-10 femtosecond precision for high and low bunch charge operation. In order to fulfill the resolution demands for both modes of operation, the bandwidth of such a BAM should be increased up to a cutoff frequency of 40 GHz. In this talk, we present the design and the realization of high bandwidth cone-shaped pickup electrodes as a part of the BAM for the FEL in Hamburg (FLASH) and the European X-ray free-electron laser (European XFEL). The proposed pickup was simulated with CST STUDIO SUITE, and a non-hermetic model was built up for radio frequency (rf) measurements.

414

Generation of narrow-bandwidth, tunable, coherent xuv radiation using high-order harmonic generation  

International Nuclear Information System (INIS)

We theoretically demonstrate the generation of wavelength-tunable, narrow-bandwidth extreme-ultraviolet (xuv) radiation by high-order harmonic generation (HHG) driven by an orthogonally polarized two-color laser field, which is composed of a 10-fs, 1500-nm laser pulse and a 40-fs, 2400-nm laser pulse. By performing classical analysis, we reveal that the rapid change of electron wave-packet dynamics at a subcycle time scale confines high-order harmonic emission to a small spectral region, leading to the generation of narrow-bandwidth xuv radiation. Furthermore, the central wavelength of the xuv radiation can be continuously tuned over a wide range by changing either the peak intensity of the driver laser or the amplitude ratio between the two laser fields at different wavelengths. It is also verified that the use of driver pulses at longer wavelengths leads to a better spectral confinement of the xuv radiation.

415

Bandwidth optimization of compact microstrip antenna for PCS/DCS/bluetooth application  

Science.gov (United States)

A novel compact broadband microstrip patch antenna is presented for various wireless applications. The proposed antenna has been fabricated and the impedance bandwidth and radiation pattern are measured. The simulated and measured antenna characteristics along with radiation pattern and gain are presented. It is stated that the proposed designed antenna can completely cover the required band widths of Digital communication system (DCS 1.71-1.88 GHz), Personal communication system (PCS 1.85-1.88 GHz) and IEEE 802.11b/g (2.4-2.485 GHz) with satisfactory radiation characteristics. The Experimental result shows that the proposed antenna presents a bandwidth 60.25% covering the range of 1.431-2.665 GHz with the maximum radiation efficiency 90%.

Singh, Vinod; Ali, Zakir; Ayub, Shahanaz; Singh, Ashutosh

2014-09-01

416

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

417

Influence of carrier dynamics on the modulation bandwidth of quantum-dot based nanocavity devices  

DEFF Research Database (Denmark)

We theoretically investigate the modulation response of quantum-dot based nanocavity light emitting devices. For high Purcell enhancement factors, our theory predicts the possibility of decreasing the modulation bandwidth with increasing scattering rate into the lasing quantum-dot state. This counterintuitive effect is investigated using a microscopic semiconductor model. The resulting guidelines for possible optimizations of quantum-dot based nanocavity laser devices are given.

Lorke, Michael; Nielsen, Torben Roland

2010-01-01

418

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

419

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

420

Robustness and Actuator Bandwidth of MRP-Based Sliding Mode Control for Spacecraft Attitude Control Problems  

Science.gov (United States)

Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters (MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

Keum, Jung-Hoon; Ra, Sung-Woong

2009-12-01

421

Power-Bandwidth Efficiency and Capacity of Wireless Feedback Communication Systems  

OpenAIRE

The paper is devoted to the analysis of problems appearing in optimisation and improvement of the power-bandwidth efficiency of digital communication feedback systems (FCS). There is shown that unlike digital systems, adaptive FCS with the analogue forward transmission allow full optimisation and derivation of optimal transmission-reception algorithm approaching their efficiency to the Shannon boundary. Differences between the forward channel capacity and capacity of adaptiv...

Platonov, Anatoliy

2011-01-01

422

Earthquake probability at the Kashiwazaki Kariwa nuclear power plant, Japan, assessed using bandwidth optimization  

Science.gov (United States)

On July 16, 2007, a strong 6.8 magnitude earthquake occurred on Japan's west coast, rocking the nearby Kashiwazaki Kariwa nuclear power plant, the largest nuclear power station on Earth. Shaking during this event produced ground accelerations of ~680 gal, exceeding the plant seismic design specification of 273 gal. This occurrence renews concerns regarding seismic hazards at nuclear facilities located in regions with persistent earthquake activity. Seismic hazard assessments depend upon an understanding of the spatial distribution of earthquakes to effectively assess future earthquake hazards. Earthquake spatial density is best estimated using kernel density functions based on the locations of past seismic events. Two longstanding problems encountered when using kernel density estimation are the selection of an optimal smoothing bandwidth and the quantification of the uncertainty inherent in these estimates. Currently, kernel bandwidths are often selected subjectively and the uncertainty in spatial density estimation is not calculated. As a result, hazards with potentially large consequences for society are poorly estimated. We solve these two problems by employing an optimal bandwidth selector algorithm to objectively identify an appropriately sized kernel bandwidth based on earthquake locations from catalog databases and by assessing uncertainty in the spatial density estimate using a modified smoothed bootstrap technique. After applying these methods to the Kashiwazaki Kariwa site, the calculated probability of one or more Mw 6-7 earthquakes within 10 km of the site during a 40 yr facility lifetime is between 0.005 and 0.02 with 95 percent confidence. This result is made more robust by calculating similar probabilities using alternative databases of earthquake locations and magnitudes. The objectivity and quantitative robustness of these techniques make them extremely beneficial for seismic hazard assessment.

Connor, C. B.; Connor, L. J.

2007-12-01

423

Research of QoS on Upward Dynamic Bandwidth Burst Service in GEPON by Numerical Analysis  

Science.gov (United States)

Performances of QoS in Gigabit Ethernet passive optical network (GEPON) upward service is the most critical factor for practical application. This article proposes a novel of dual-clocking algorithm basing on studying in the existing dynamic bandwidth. The improved algorithm both guarantees EF high priority service and supports burst BE data traffic, in the meanwhile conspicuously enhances GEPON network efficiency. The article has confirmed the lgorithm feasibility and the improved properties through the simulation.

Li, Li; Li, Hong-An; Zhang, Tian-Peng

2014-12-01

424

Blended Learning Resources in Constrained Bandwidth Environment: Considerations for Network and Multimedia Optimization  

OpenAIRE

The potential of multimedia teaching and learning approach at higher education is well recognized by researchers, as it is a powerful tool to increase the perceived level of user satisfaction, leading to enhance the blended learning process. However, the learning process can be improved significantly by delivering the content using visual media (video, audio, and graphics). On the other hand, such multimedia contents require larger bandwidth for transmission over the Internet, which is limit...

Jude Lubega; Nazir Ahmad Suhail; Gilbert Maiga

2013-01-01

425

Optical memory bandwidth and multiplexing capacity in the erbium telecommunication window  

Science.gov (United States)

We study the bandwidth and multiplexing capacity of an erbium-doped optical memory for quantum storage purposes. We concentrate on the protocol 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 minimized to achieve optimal performance.

Dajczgewand, J.; Ahlefeldt, R.; Böttger, T.; Louchet-Chauvet, A.; Le Gouët, J.-L.; Chanelière, T.

2015-02-01

426

Efficient routing strategies in scale-free networks with limited bandwidth  

OpenAIRE

We study the traffic dynamics in complex networks where each link is assigned a limited and identical bandwidth. Although the first-in-first-out (FIFO) queuing rule is widely applied in the routing protocol of information packets, here we argue that if we drop this rule, the overall throughput of the network can be remarkably enhanced. We proposed some efficient routing strategies that do not strictly obey the FIFO rule. Comparing with the routine shortest path strategy, the...

Tang, Ming; Zhou, Tao

2011-01-01

427

Investigation of Bandwidth Requirement of Smart Meter Network Using OPNET Modeler  

OpenAIRE

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

428

Bandwidth Optimization in 802.15.4 Networks through Evolutionary Slot Assignment  

OpenAIRE

Traditional Wireless Sensor Networks (WSNs) based on carrier sense methods for channel access suffer from reduced bandwidth utilization, increase energy consumptions and latency problems in networks with high traffic. In this work, a novel Evolutionary Slot Assignment (ESA) algorithm has been developed to in-crease the throughput of large wireless mesh networks with no centralized controller. In the presented scheme, the sensor nodes self-adapt to the traffic patterns of the network by select...

Sazonov, Edward; Krishnamurthy, Vidya

2009-01-01

429

A Literature Study on Dynamic Bandwidth Allocation Mechanisms for Tandem Communication Networks  

OpenAIRE

Modeling and performance prediction are becoming increasingly important issues in the design and operation of computer communications systems. In this paper a review is carried out on how Tandem queuing models with Dynamic Bandwidth Allocation have been applied so far into the performance evaluation of Communication Networks. Queuing network models with finite/infinite capacity buffers and blocking have been applied as more realistic models of systems with finite capac...

Raghavendran, Ch V.; Naga Satish, G.; Rama Sundari, M. V.; Suresh Varma, P.

2014-01-01

430

Banding together for bandwidth: An analysis of survey results from wireless community network participants  

OpenAIRE

Using a resource mobilization framework, this study attempts to better understand the factors motivating people to join wireless community networks that enable members to share bandwidth. In addition, the research illuminates ties between this kind of peer-to-peer networking and civic engagement at a broader level. An in depth survey completed by 43 respondents from throughout Europe and North America found that participants in this movement felt a stronger sense of community, as well as were...

Shaffer, Gwen University Of California

2011-01-01

431

BAC: BANDWIDTH BASED ADMISSION CONTROL SCHEME FOR GATEWAY RELOCATION IN IEEE 802.16e NETWORKS  

OpenAIRE

The next generation wireless communication system aims at supporting multimedia services with different Quality of Services (QoS) and bandwidth requirements. Therefore effective management of limited resources is important to enhance network performance. Access Service Network Gateway (ASN GW) relocation is the process of changing the traffic’s Anchor Point (AP) from one GW to another which is independent of Mobile Station’s (MS’s) Link Layer (LL) handover. The existing standards have d...

Deva Priya, M.; Valarmathi, M. L.; Jaya Bharathi, K.; Deepa, M.

2013-01-01

432

Effects of Bandwidth, Compression Speed, and Gain at High Frequencies on Preferences for Amplified Music  

OpenAIRE

This article reviews a series of studies on the factors influencing sound quality preferences, mostly for jazz and classical music stimuli. The data were obtained using ratings of individual stimuli or using the method of paired comparisons. For normal-hearing participants, the highest ratings of sound quality were obtained when the reproduction bandwidth was wide (55 to 16000 Hz) and ripples in the frequency response were small (less than ± 5 dB). For hearing-impaired participants listening...

Moore, Brian C. J.

2012-01-01

433

Deterministic Formulization of End-to-End Delay and Bandwidth Efficiency for Multicast Systems  

OpenAIRE

End-System multicasting (ESM) is a promising application-layer scheme that has been recently proposed for implementing multicast routing in the application layer as a practical alternative to the IP multicasting. Moreover, ESM is an efficient application layer solution where all the multicast functionality is shifted to the end users. However, the limitation in bandwidth and the fact that the message needs to be forwarded from host-to-host using unicast connection, and consequently incrementi...

Rizvi, Syed S.; Aasia Riasat; Elleithy, Khaled M.

2009-01-01

434

Bandwidth Improvement in Large Reflectarrays by Using True-Time Delay  

OpenAIRE

A significant improvement in the bandwidth of large reflectarrays is demonstrated using elements which allow true-time delay. Two identical, large reflectarrays have been designed using different phase distributions to generate a collimated beam. In the former, the phase distribution is truncated to 360deg as is usual in reflectarray antennas, while in the second, the true phase delay is maintained (three cycles of 360deg). The chosen phase-shifter elements are based on previously measured an...

Carrasco, Eduardo; Encinar Garcinun?o, Jose? Antonio; Barba Gea, Mariano

2008-01-01

435

Battery-Bandwidth Based Handover Framework for 3G/WLAN Using Android Handheld Devices  

OpenAIRE

In a heterogeneous network environment, transparent horizontal and vertical handover is a much desired feature. Effective handover solution would allow mobile device users to stay steadily connected, seamlessly switching between different access networks. If it is consistently connected to networks which offers best Quality of Service (QoS) then that would dramatically improve user experience. Switching of network requires more device energy and also high bandwidth to guarante...

Apoorva Prakash M V; Padma, Dr M. C.

2014-01-01

436

Bandwidth enhancement : correcting magnitude and phase distortion in wideband piezoelectric transducer systems  

OpenAIRE

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

437

Bandwidth Aggregation Techniques in Heterogeneous Multi-homed Devices: A Survey  

OpenAIRE

The widespread deployment of various networking technologies, coupled with the exponential increase in end- user data demand, have led to the proliferation of multi-homed, or multi-interface enabled, devices. These trends drove researchers to investigate a wide spectrum of solutions, at different layers of the protocol stack, that utilize available interfaces in such devices by aggregating their bandwidth. In this survey paper, we provide an overview and examine the evolutio...

Habak, Karim; Harras, Khaled A.; Youssef, Moustafa

2013-01-01

438

Bandwidth Enrichment for Micro-strip Patch Antenna Using Pendant Techniques  

OpenAIRE

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.

D Bhattacharya, R. Prasanna

2013-01-01

439

Sensitivity to temporal modulation rate and spectral bandwidth in the human auditory system: MEG evidence  

Science.gov (United States)

Slow acoustic modulations below 20 Hz, of varying bandwidths, are dominant components of speech and many other natural sounds. The dynamic neural representations of these modulations are difficult to study through noninvasive neural-recording methods, however, because of the omnipresent background of slow neural oscillations throughout the brain. We recorded the auditory steady-state responses (aSSR) to slow amplitude modulations (AM) from 14 human subjects using magnetoencephalography. The responses to five AM rates (1.5, 3.5, 7.5, 15.5, and 31.5 Hz) and four types of carrier (pure tone and 1/3-, 2-, and 5-octave pink noise) were investigated. The phase-locked aSSR was detected reliably in all conditions. The response power generally decreases with increasing modulation rate, and the response latency is between 100 and 150 ms for all but the highest rates. Response properties depend only weakly on the bandwidth. Analysis of the complex-valued aSSR magnetic fields in the Fourier domain reveals several neural sources with different response phases. These neural sources of the aSSR, when approximated by a single equivalent current dipole (ECD), are distinct from and medial to the ECD location of the N1m response. These results demonstrate that the globally synchronized activity in the human auditory cortex is phase locked to slow temporal modulations below 30 Hz, and the neural sensitivity decreases with an increasing AM rate, with relative insensitivity to bandwidth. PMID:21975451

Wang, Yadong; Ding, Nai; Ahmar, Nayef; Xiang, Juanjuan; Poeppel, David

2012-01-01

440

Optimal apparent damping as a function of the bandwidth of an array of vibration absorbers.  

Science.gov (United States)

The transient response of a resonant structure can be altered by the attachment of one or more substantially smaller resonators. Considered here is a coupled array of damped harmonic oscillators whose resonant frequencies are distributed across a frequency band that encompasses the natural frequency of the primary structure. Vibration energy introduced to the primary structure, which has little to no intrinsic damping, is transferred into and trapped by the attached array. It is shown that, when the properties of the array are optimized to reduce the settling time of the primary structure's transient response, the apparent damping is approximately proportional to the bandwidth of the array (the span of resonant frequencies of the attached oscillators). Numerical simulations were conducted using an unconstrained nonlinear minimization algorithm to find system parameters that result in the fastest settling time. This minimization was conducted for a range of system characteristics including the overall bandwidth of the array, the ratio of the total array mass to that of the primary structure, and the distributions of mass, stiffness, and damping among the array elements. This paper reports optimal values of these parameters and demonstrates that the resulting minimum settling time decreases with increasing bandwidth. PMID:23927106

Vignola, Joseph; Glean, Aldo; Judge, John; Ryan, Teresa

2013-08-01

441

Optimal bandwidth-aware VM allocation for Infrastructure-as-a-Service  

CERN Document Server

Infrastructure-as-a-Service (IaaS) providers need to offer richer services to be competitive while optimizing their resource usage to keep costs down. Richer service offerings include new resource request models involving bandwidth guarantees between virtual machines (VMs). Thus we consider the following problem: given a VM request graph (where nodes are VMs and edges represent virtual network connectivity between the VMs) and a real data center topology, find an allocation of VMs to servers that satisfies the bandwidth guarantees for every virtual network edge---which maps to a path in the physical network---and minimizes congestion of the network. Previous work has shown that for arbitrary networks and requests, finding the optimal embedding satisfying bandwidth requests is $\\mathcal{NP}$-hard. However, in most data center architectures, the routing protocols employed are based on a spanning tree of the physical network. In this paper, we prove that the problem remains $\\mathcal{NP}$-hard even when the phys...

Dutta, Debojyoti; Post, Ian; Shinde, Rajendra

2012-01-01

442

A new metasurface reflective structure for simultaneous enhancement of antenna bandwidth and gain  

Science.gov (United States)

A new bi-layered metasurface reflective structure (MRS) on a high-permittivity, low-loss, ceramic-filled, bio-plastic, sandwich-structured, dielectric substrate is proposed for the simultaneous enhancement of the bandwidth and gain of a dual band patch antenna. By incorporating the MRS with a 4 mm air gap between the MRS and the antenna, the bandwidth and gain of the dual band patch antenna are significantly enhanced. The reflection coefficient (S11 < -10 dB) bandwidth of the proposed MRS-loaded antenna increased by 240% (178%), and the average peak gain improved by 595% (128%) compared to the antenna alone in the lower (upper) band. Incremental improvements of the magnitude and directional patterns have been observed from the measured radiation patterns at the three resonant frequencies of 0.9 GHz, 3.7 GHz and 4.5 GHz. The effects of different configurations of the radiating patch and the ground plane on the reflection coefficient have been analyzed. In addition, the voltage standing wave ratio and input impedance have also been validated using a Smith chart.

Ullah, M. Habib; Islam, M. T.

2014-08-01

443

MHBCDA: Mobility and Heterogeneity aware Bandwidth Efficient Cluster based Data Aggregation for Wireless Sensor Network  

DEFF Research Database (Denmark)

Wireless Sensor Network (WSN) offers a variety of novel applications for mobile targets. It generates the large amount of redundant sensing data. The data aggregation techniques are extensively used to reduce the energy consumption and increase the network lifetime, although it has the side effect of reduced reliability. In the mobile environment, it is necessary to consider the techniques which minimize the communication cost with efficient bandwidth utilization by decreasing the packet count reached at the sink. This paper proposes the mobility and heterogeneity aware bandwidth efficient Cluster-based Data Aggregation (MHBCDA) algorithm for the randomly distributed nodes. It considers the mobile sink based packet aggregation for the heterogeneous WSN. It uses predefined region for the aggregation at cluster head to minimize computation and communication cost. The MHBCDA is energy and bandwidth efficient. It exploits correlation of data packets generated by varying the packet generation rate. It prevents transmission of redundant data packets by improving energy consumption by 4.11% and prolongs the network life by 34.45% as compared with state-of-the-art solutions.

Dnyaneshwar, Mantri; Prasad, Neeli R.

2013-01-01

444

Design optimization of the distributed modal filtering rod fiber for increasing single mode bandwidth  

DEFF Research Database (Denmark)

High-power fiber amplifiers for pulsed applications require large mode area (LMA) fibers having high pump absorption and near diffraction limited output. This improves the limiting factor of nonlinear effects, while maintaining good beam quality. Photonic crystal fibers allow realization of short LMA fiber amplifiers having high pump absorption through a pump cladding that is decoupled from the outer fiber. However, achieving ultra low NA for single-mode (SM) guidance is challenging, and thus different design strategies must be applied to filter out higher order modes (HOMs). The novel distributed modal filtering (DMF) design presented here enables SM guidance, and previous results have shown a SM mode field diameter of 60 ?m operating in a 20 nm SM bandwidth. The DMF rod fiber has high index ring-shaped inclusions acting as resonators enabling SM guidance through modal filtering of HOMs. Large preform tolerances are compensated during the fiber draw resulting in ultra low NA fibers with very large cores. In this paper, design optimization of the SM bandwidth of the DMF rod fiber is presented. Analysis of band gap properties results in a fourfold increase of the SM bandwidth compared to previous results, achieved by utilizing the first band of cladding modes. This covers of a large fraction of the Yb emission band, where wavelengths of 1030 nm and 1064 nm can be included.

JØrgensen, Mette Marie; Petersen, Sidsel Rübner

2012-01-01

445

Bandwidth provisioning in infrastructure-based wireless networks employing directional antennas  

Energy Technology Data Exchange (ETDEWEB)

Motivated by the widespread proliferation of wireless networks employing directional antennas, we study the problem of provisioning bandwidth in such networks. Given a set of subscribers and one or more access points possessing directional antennas, we formalize the problem of orienting these antennas in two fundamental settings: (1) subscriber-centric, where the objective is to fairly allocate bandwidth among the subscribers and (2) provider-centric, where the objective is to maximize the revenue generated by satisfying the bandwidth requirements of subscribers. For both the problems, we first design algorithms for a network with only one access point working under the assumption that the number of antennas does not exceed the number of noninterfering channels. Using the well-regarded lexicographic max-min fair allocation as the objective for a subscriber-centric network, we present an optimum dynamic programming algorithm. For a provider-centric network, the allocation problem turns out to be NP-hard. We present a greedy heuristic based algorithm that guarantees almost half of the optimum revenue. We later enhance both these algorithms to operate in more general networks with multiple access points and no restrictions on the relative numbers of antennas and channels. A simulation-based evaluation using OPNET demonstrates the efficacy of our approaches and provides us further in insights into these problems.

Hasiviswanthan, Shiva [Los Alamos National Laboratory; Zhao, Bo [PENN STATE UNIV.; Vasudevan, Sudarshan [UNIV OF MASS AMHERST; Yrgaonkar, Bhuvan [PENN STATE UNIV.

2009-01-01

446

Time Slot Assignment for Maximum Bandwidth in a Mobile Ad Hoc Network  

Directory of Open Access Journals (Sweden)

Full Text Available

Time slot assignment is essential to provide the calculated bandwidth in a TDMA (Time Division Multiple Access-based mobile ad hoc network (MANET, which is a focus of attention of this paper because of its collision-free packet transmission with QoS(Quality of Service support. In this paper, a new time slot assignment algorithm-SAGO (Slot Assignment by Global Overview is proposed, by which more available bandwidth can be obtained than conventional approximate solutions. SAGO assigns time slots from a global overview, that is, time slot assignment is based on the usage of global information such as finding of bottleneck of a route, tentative bandwidth evaluation of a route and assignment of time slot according to the order of their free times in the concerned links. In addition, SAGO’s effectiveness is proved by simulation results.

Yasushi Wakahara

2007-11-01

447

Bandwidth Enhancement of a U-Slot Patch Antenna Using Embedded HIS Structure  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes a new generation of antenna that applies metamaterial as a base construction. With the use of dual band high impedance surface (HIS structures, the bandwidth, return loss, and gain of U-slot patch antenna is improved at resonant frequencies 2.24 GHz and 5.8 GHz. The proposed new modified U-slot antenna has dual band impedance bandwidth from about 2.1886 to 2.27 GHz and 5.6149 to 7.2259 GHz. From the simulation result it was found that the upper frequency band of the proposed antenna lies in the band of $5.725 sim 5.825$ GHz regulated by IEEE 802.11a (upper band and can be used for bluetooth and WLAN applications. We perform this analysis on structures which composed of rectangular lattice patches periodic arrangements. All the dimensions and shapes of the unit cell geometry are optimized in order to get a broad bandwidth and high return loss. The lattice structure comprises of an array of $7 imes 5$ rectangular patches embedded in the substrate.

Pramod Kumar Singhal

2012-10-01

448

A Real-time Data Compression for Massive Data Transmission Over High Delay-bandwidth Network  

Directory of Open Access Journals (Sweden)

Full Text Available Packet dropout and retransmission have become a more and more serious problem in high delay-bandwidth network, it is difficult for traditional streaming compression to deal with reorder packets, people have to use stateless compression, but it can only achieve very low compression ratio. In this study, we introduce a novel Orderless Tolerance Compression Algorithm (OTCA. The algorithm works effectively with orderless packets which is caused by the packet retransmission, through allowing variable delay in the dictionary construction. OTCA performs better compression ratio than stateless compression and low decoding latency than that of streaming compression and excels delay-dictionary compression in both compression ratio and decoding latency especially in high bandwidth network. We conduct extensive experiments to establish the potential improvement for packet compression techniques, using many data files including the Calgary corpus and the Canterbury corpus. Experimental results of the OTCA show that it is a good compromise proposal for transfer massive data over high delay-bandwidth networks.

Zheng Chen

2013-01-01

449

Bandwidth Enhancement and Size Reduction of Microstrip Patch Antenna by Magnetoinductive Waveguide Loading  

Directory of Open Access Journals (Sweden)

Full Text Available A planar magnetoinductive (MI waveguide loaded rectangular microstrip patch antenna is presented and discussed. The MI waveguide consists of two planar metamaterial split squared ring resonators (SSRRs placed in between two microstrip lines. The backward wave propagation takes place through this structure. The rectangular microstrip patch antenna is magnetically coupled to the MI waveguide. The unloaded rectangular microstrip patch antenna resonates at 37.10 GHz. When loaded with planar MI waveguide, its resonant frequency is reduced to 9.38 GHz with the bandwidth and gain of 44% and 4.16 dBi respectively. In loaded condition, the dimension of antenna is 12.50 mm × 3.70 mm (0.390 ? × 0.115 ?. The appreciable bandwidth is achieved in such a small size antenna. The pass band frequency of MI waveguide is predicted by using the theoretical model of dispersion equation. The effective medium theory is used to verify the metamaterial characteristics of SSRR. The simulated results and theoretical calculations are also presented. The results show that the proposed method can be used to design compact and high bandwidth microstrip patch antennas.

Swapna Devi

2011-04-01

450

Ultra-wide bandwidth measurement of partial discharge current pulses in SF6  

International Nuclear Information System (INIS)

This paper presents ultra-wide bandwidth measurements of partial discharge (PD) current pulses. Using a 33 GHz bandwidth oscilloscope together with a direct, matched coaxial connection to the PD source, pulses have been characterized with a greater degree of accuracy than has previously been achieved, with a minimum observed rise time of 24 ps. The PD source consists of a sharp protrusion in pressurized sulfur hexaflouride (SF6) with a tip radius of 25 µm. Both positive and negative corona pulses were recorded, revealing previously indistinguishable frequency content and features such as the appearance of groups of multiple component pulses occurring within a nanosecond time scale. The upper bandwidth limitation of the complete measurement set-up was established. This was calculated by cross-correlating current pulses with corresponding pulses filtered at lower frequencies to determine their similarity. The tendency for multiple consecutive pulses to occur within a short time period was evident. The results provide valuable data for researchers investigating fundamental physical phenomena of SF6 ionization and PD activity. (paper)

451

Ultra-wide bandwidth measurement of partial discharge current pulses in SF6  

Science.gov (United States)

This paper presents ultra-wide bandwidth measurements of partial discharge (PD) current pulses. Using a 33 GHz bandwidth oscilloscope together with a direct, matched coaxial connection to the PD source, pulses have been characterized with a greater degree of accuracy than has previously been achieved, with a minimum observed rise time of 24 ps. The PD source consists of a sharp protrusion in pressurized sulfur hexaflouride (SF6) with a tip radius of 25 µm. Both positive and negative corona pulses were recorded, revealing previously indistinguishable frequency content and features such as the appearance of groups of multiple component pulses occurring within a nanosecond time scale. The upper bandwidth limitation of the complete measurement set-up was established. This was calculated by cross-correlating current pulses with corresponding pulses filtered at lower frequencies to determine their similarity. The tendency for multiple consecutive pulses to occur within a short time period was evident. The results provide valuable data for researchers investigating fundamental physical phenomena of SF6 ionization and PD activity.

Reid, A. J.; Judd, M. D.

2012-04-01

452

A Novel Approach for Gain and Bandwidth Re-Configurability in Helical Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available A Pi-wall shaped partial cavity backed 1½ turn helical antenna has been designed. The helix turns are kept low to provide compact design. The gain and bandwidth re-configurability is achieved by placing the helix in center of the Pi-wall shaped partial cavity which thus can be rotated about its axis providing reflections from the walls at various rotation angle. The rotational angles of the helix are varied with the incremental step size of 45o in anticlockwise direction. The odd number of turns will provide asymmetry of the helix with respect to the cavity walls and will thus excite various resonant bands as the helix is rotated inside the designed cavity. A Computer Simulation Tool is used for the design verification. The antenna is operating in the range of 5-15 GHz and has a peak gain of 7.5 dB and a highest bandwidth of 3.69 GHz. The Pi-shaped partial cavity is fabricated with lightweight aluminum metal and the helix is made of copper. Slight geometrical modification was made during the process of fabrication to improve the bandwidth response of the antenna. The antenna being conformal and robust in design may find its application for personal wireless communication and rough terrain areas.

Rahul Yadav

2013-09-01

453

Metamaterial composite bandpass filter with an ultra-broadband rejection bandwidth of up to 240 terahertz  

DEFF Research Database (Denmark)

We present a metamaterial, consisting of a cross structure and a metal mesh filter, that forms a composite with greater functional bandwidth than any terahertz (THz) metamaterial to date. Metamaterials traditionally have a narrow usable bandwidth that is much smaller than common THz sources, such as photoconductive antennas and difference frequency generation. The composite structure shown here expands the usable bandwidth to exceed that of current THz sources. To highlight the applicability of this combination, we demonstrate a series of bandpass filters with only a single pass band, with a central frequency (f) that is scalable from 0.86–8.51 THz, that highly extinguishes other frequencies up to >240 THz. The performance of these filters is demonstrated in experiment, using both air biased coherent detection and a Fourier transform infrared spectrometer (FTIR), as well as in simulation. We present equations—and discuss their scaling laws—which detail the f and full width at half max (?f) of the pass band, as well as the required geometric dimensions for their fabrication using standard UV photolithography and easily achievable fabrication linewidths. With these equations, the geometric parameters and ?f for a desired frequency can be quickly calculated. Using these bandpass filters as a proof of principle, we believe that this metamaterial composite provides the key for ultra-broadband metamaterial design.

Strikwerda, Andrew; Zalkovskij, Maksim

2014-01-01

454

Extremely large bandwidth and ultralow-dispersion slow light in photonic crystal waveguides with magnetically controllability  

DEFF Research Database (Denmark)

A line-defect waveguide within a two-dimensional magnetic-fluid-based photonic crystal with 45o-rotated square lattice is presented to have excellent slow light properties. The bandwidth centered at $$ \\lambda_{0} $$ = 1,550 nm of our designed W1 waveguide is around 66 nm, which is very large than that of the conventional W1 waveguide as well as the corresponding optimized structures based on photonic crystal with triangular lattice. The obtained group velocity dispersion $$ \\beta_{2} $$ within the bandwidth is ultralow and varies from ?1,191$$ a/(2\\pi c^{2} ) $$ to 855$$ a/(2\\pi c^{2} ) $$ (a and c are the period of the lattice and the light speed in vacuum, respectively). Simultaneously, the normalized delay-bandwidth product is relatively large and almost invariant with magnetic field strength. It is indicated that using magnetic fluid as one of the constitutive materials of the photonic crystal structures can enable the magnetically fine tunability of the slow light in online mode. The concept and resultsof this work may give a guideline for studying and realizing tunable slow light based on the external-stimulus-responsive materials.

Pu, Shengli; Wang, Haotian

2013-01-01

455

Bandwidth-tunable narrowband rectangular optical filter based on stimulated Brillouin scattering in optical fiber.  

Science.gov (United States)

We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in optical fiber with bandwidth tuning from 50 MHz to 4 GHz at less than 15-MHz resolution. The rectangular shape of the filter is precisely achieved utilizing digital feedback control of the comb-like pump spectral lines. The passband ripple is suppressed to ~1 dB by mitigating the nonlinearity influences of the comb-like pump lines generated in electrical and optical components and fibers. Moreover a fiber with a single Brillouin peak is employed to further reduce the in-band ripple and the out-of-band SBS gain at the same time. Finally, we analyze the noise performance of the filter at different bandwidth cases and demonstrate the system performance of the proposed filter with 2.1-GHz bandwidth and 19-dB gain by amplifying a 2-GHz orthogonal frequency-division-multiplexing (OFDM) signal with quadrature-phase-shift-keying (QPSK) and 16-quadrature-amplitude-modulation (16-QAM) on each subscriber. PMID:25321794

Wei, Wei; Yi, Lilin; Jaouën, Yves; Hu, Weisheng

2014-09-22

456

Power-Bandwidth Tradeoff in Multiuser Relay Channels with Opportunistic Scheduling  

CERN Document Server

The goal of this paper is to understand the key merits of multihop relaying techniques jointly in terms of their energy efficiency and spectral efficiency advantages in the presence of multiuser diversity gains from opportunistic (i.e., channel-aware) scheduling and identify the regimes and conditions in which relay-assisted multiuser communication provides a clear advantage over direct multiuser communication. For this purpose, we use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the power-bandwidth tradeoff) over a fading multiuser relay channel with $K$ users in the asymptotic regime of large (but finite) number of users (i.e., dense network). Benefiting from the extreme-value theoretic results of \\cite{Oyman_isit07}, we characterize the power-bandwidth tradeoff and the associated energy and spectral efficiency measures of the bandwidth-limited high signal-to-noise ratio (SNR) and power-limited low SNR regimes, and utilize them in investigating ...

Oyman, Ozgur

2008-01-01

457

The effect of squeeze film constriction on bandwidth improvement in interferometric accelerometers  

International Nuclear Information System (INIS)

This paper studies the effects of a constricted squeeze film on the performance of an optical microelectromechanical system accelerometer. Squeeze films are shown to extend the sensor frequency range (bandwidth) in accelerometers without decreasing the mechanical sensitivity by retarding the resonate response. By restricting the venting of a squeeze film, this preferential behavior is observed at lower frequencies than is expected for ideally vented accelerometers. Due to this effect, constricted squeeze films may be used to improve the bandwidth performance of devices of lower natural frequencies and higher inertial sensitivities. A model, extended from the existing squeeze film theory, is developed for the squeeze film formed between circular plates with generalized mixed boundary pressure conditions to describe the boundary flow resistance. These effects are experimentally observed in a parallel plate Fabry–Pérot interferometric accelerometer through frequency response characterization at mechanical resonance under pressure variation. The analytical results for the constricted squeeze film are used to predict the performance gains due to the frequency-dependent squeeze film parameters. These results are experimentally confirmed by demonstrating improved bandwidth performance due to the constricted squeeze film

458

Signal Processing Algorithm for Controlling Dynamic Bandwidth of Fiber Optic Accelerometer  

International Nuclear Information System (INIS)

This paper presents a signal processing algorithm to control the dynamic bandwidth of a single-degree-of-freedom (SDF) dynamic sensor system. An accelerometer is a representative SDF sensor system. In this paper, a moire-fringe-based fiber optic accelerometer is newly used for the test of the algorithm. The accelerometer is composed of one mass, one damper and one spring as a SDF dynamic system. In order to increase the dynamic bandwidth of the accelerometer, it is needed to increase the spring constant or decrease the mass. However, there are mechanical difficulties of this adjustment. Therefore, the presented signal processing algorithm is very effective to overcome the difficulties because it is just adjustment in the signal processing software. In this paper, the novel fiber optic accelerometer is introduced shortly, and the algorithm is applied to the fiber optic accelerometer to control its natural frequency and damping ratio. Several simulations and experiments are carried out to prove the performance of the algorithm. As a result, it is shown that the presented signal processing algorithm is a good way to broaden the dynamic bandwidth of the fiber optic accelerometer

459

Available Link Bandwidth Based Network Selection in Multi-access Networks  

Directory of Open Access Journals (Sweden)

Full Text Available In a heterogeneous wireless environment, one of the important aspects of seamless communication for ubiquitous computing is the dynamic selection of the best access network. The problem of access network selection has been addressed through various decision methods based on available network information. Available link bandwidth is one of the important information parameters, which can be used as criterion for network selection. In this paper, we consider available bandwidth as a dynamic parameter to select the network in heterogeneous environment. First, we propose a bootstrap approximation based technique to estimate available bandwidth and then utilize it for the selection of the best suitable network in the heterogeneous environment consisting of 2G and 3G standards based wireless networks. The proposed algorithm is implemented in temporal and spatial domains to check its robustness. Estimation time with varying size of files is used as the performance metric. Through numerical results, it is shown that the proposed algorithm gives improved performance as compared to the existing algorithm.

Kiran Ahuja

2014-02-01

460

Terahertz-bandwidth photonic fractional Hilbert transformer based on a phase-shifted waveguide Bragg grating on silicon.  

Science.gov (United States)

We propose and experimentally demonstrate the first THz bandwidth on-chip photonic fractional Hilbert transformer. The reported design uses a novel approach, based on a uniform and nonapodized single phase-shifted integrated waveguide Bragg grating on silicon, where the fractional order P can be engineered by simply varying the effective index modulation ?n. Experimental results for P=1.5 show very low processing error for a broad range of pulse bandwidths between 77 GHz and 2.07 THz, corresponding to a time-bandwidth product as high as 27. PMID:25361324

Burla, Maurizio; Li, Ming; Cortés, Luis Romero; Wang, Xu; Fernández-Ruiz, María Rosario; Chrostowski, Lukas; Azaña, José

2014-11-01

461

Bandwidth Enhancement of A Micro strip Line Fed Hexagonal Wide-Slot Antenna Using Fork-like Tuning Stub  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a printed hexagonal wide slot antenna, fed by a microstrip line with fork like tuning stub for bandwidth enhancement is proposed and experimentally investigated. The impedance, radiation and gain characteristics of this antenna are studied. Simulation and experimental results indicate that a 1.5:1 VSWR bandwidth, of about 1 GHz and 2:1 VSWR bandwidth of 1.34 GHz is achieved at operating frequency around 2.5 GHz, which is about three times larger than a microstrip line fed hexagonal wide slot antenna, with normal tuning stub, considered as reference antenna.

Krishnendu Chattopadhyay

2012-05-01

462

Bandwidth Enhancement of A Micro strip Line Fed Hexagonal Wide-Slot Antenna Using Fork-like Tuning Stub  

OpenAIRE

In this paper, a printed hexagonal wide slot antenna, fed by a microstrip line with fork like tuning stub for bandwidth enhancement is proposed and experimentally investigated. The impedance, radiation and gain characteristics of this antenna are studied. Simulation and experimental results indicate that a 1.5:1 VSWR bandwidth, of about 1 GHz and 2:1 VSWR bandwidth of 1.34 GHz is achieved at operating frequency around 2.5 GHz, which is about three times larger than a microstrip line fed hexag...

Krishnendu Chattopadhyay; Santanu Das; Sekhar Ranjan Bhadra Chaudhuri

2012-01-01

463

Efficient Schottky-like junction GaAs nanowire photodetector with 9?GHz modulation bandwidth with large active area  

Energy Technology Data Exchange (ETDEWEB)

Efficient, low capacitance density GaAs/Indium-Tin-Oxide Schottky-like junction photodetectors with a 50??m square active are fabricated for operation in the gigahertz range. Modulation bandwidth is experimentally measured up to 10?GHz at various applied reverse biases and optical intensities to explore the effects of photo-generated carrier screening on modulation bandwidth. Last, the bandwidth dependence on applied reverse bias and optical intensity is simulated as a means to quantify average carrier velocities in nanowire material systems.

Seyedi, M. A., E-mail: seyedi@usc.edu; Yao, M.; O' Brien, J.; Wang, S. Y.; Dapkus, P. D. [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States)

2014-07-28

464

Characterizing the In-Phase Reflection Bandwidth Theoretical Limit of Artificial Magnetic Conductors With a Transmission Line Model  

Science.gov (United States)

We validate through simulation and experiment that artificial magnetic conductors (AMC s) can be well characterized by a transmission line model. The theoretical bandwidth limit of the in-phase reflection can be expressed in terms of the effective RLC parameters from the surface patch and the properties of the substrate. It is found that the existence of effective inductive components will reduce the in-phase reflection bandwidth of the AMC. Furthermore, we propose design strategies to optimize AMC structures with an in-phase reflection bandwidth closer to the theoretical limit.

Xie, Yunsong; Fan, Xin; Chen, Yunpeng; Wilson, Jeefrey D.; Simons, Rainee N.; Xiao, John Q.

2013-01-01

465

Efficient Schottky-like junction GaAs nanowire photodetector with 9?GHz modulation bandwidth with large active area  

International Nuclear Information System (INIS)

Efficient, low capacitance density GaAs/Indium-Tin-Oxide Schottky-like junction photodetectors with a 50??m square active are fabricated for operation in the gigahertz range. Modulation bandwidth is experimentally measured up to 10?GHz at various applied reverse biases and optical intensities to explore the effects of photo-generated carrier screening on modulation bandwidth. Last, the bandwidth dependence on applied reverse bias and optical intensity is simulated as a means to quantify average carrier velocities in nanowire material systems.

466

Demonstration of an X-Band Multilayer Yagi-Like Microstrip Patch Antenna With High Directivity and Large Bandwidth  

Science.gov (United States)

The feasibility of obtaining large bandwidth and high directivity from a multilayer Yagi-like microstrip patch antenna at 10 GHz is investigated. A measured 10-dB bandwidth of approximately 20 percent and directivity of approximately 11 dBi is demonstrated through the implementation of a vertically-stacked structure with three parasitic directors, above the driven patch, and a single reflector underneath the driven patch. Simulated and measured results are compared and show fairly close agreement. This antenna offers the advantages of large bandwidth, high directivity, and symmetrical broadside patterns, and could be applicable to satellite as well as terrestrial communications.

Nessel, James A.; Zaman, Afroz; Lee, Richard Q.; Lambert, Kevin

2005-01-01

467

Single-Multi-Single Mode Structure Based Band Pass/Stop Fiber Optic Filter With Tunable Bandwidth  

OpenAIRE

We present a simple, efficient and easy to fabricate single-multi-single mode (SMS) fiber-based tunable bandwidth optical bandpass/bandstop filter. The device exploits the transmission characteristics of an SMS structure near its critical wavelength. Using both temperature and strain tuning, we show that the device can be switched between band pass to band stop modes and that the filter bandwidth in each mode can be dynamically tuned. We present a theoretical analysis of the observed behavior...

Tripathi, Saurabh Mani; Kumar, Arun; Marin, Emmanuel; Meunier, Jean-pierre

2010-01-01

468

A Network Selection Indicator Based on Golden Relation between Monetary Cost and Bandwidth in Heterogeneous Wireless Networks  

OpenAIRE

The selection of an optimal access network is an essential aspect of service delivery in heterogeneous wireless networks. Many efficient methods are used in the selection of the best network. The relation between monetary cost and bandwidth affects the network selection process, but this consideration is not accounted for in other selection processes. This study proposes the use of golden ratio to determine the mathematical relation between monetary cost and bandwidth, which can serve as a vi...

Salih, Yass K.; Ong Hang See; Ibrahim, Rabha W.; Salman Yussof; Azlan Iqbal

2014-01-01

469

Bandwidth measurements and capacity exploitation in Gigabit Passive Optical Networks2014 Fotonica AEIT Italian Conference on Photonics Technologies  

OpenAIRE

We report an experimental investigation on the measurement of the available bandwidth for users in Gigabit Passive Optical Networks (GPON) and the limitations caused by the Internet protocols. We point out that the huge capacity offered by the GPON highlights the enormous differences that can be showed among the available and actually exploitable bandwidth in the case of TCP. In this ultrabroadband environment we also investigated on use of the UDP and of the multisession TCP. A correlation i...

Mellia, Marco

2014-01-01

470

Solid immersion lens at the aplanatic condition for enhancing the spectral bandwidth of a waveguide grating coupler  

OpenAIRE

We report a technique to substantially boost the spectral bandwidth of a conventional waveguide grating coupler by using a solid immersion cylindrical lens at the aplanatic condition to create a highly anamorphic beam and reach a much larger numerical aperture, thus enhancing the spectral bandwidth of a free-space propagating optical beam coupled into a single-mode planar integrated optical waveguide (IOW). Our experimental results show that the broadband IOW spectrometer thus created almost ...

Pereira, Marcelo B.; Craven, Jill S.; Mendes, Sergio B.

2010-01-01

471