WorldWideScience
1

Small signal analysis of frequency chirping in injection-locked semiconductor lasers  

Energy Technology Data Exchange (ETDEWEB)

A theoretical and experimental investigation of frequency chirping in injection-locked semiconductor lasers under a condition of small signal modulation is presented. It shows that a substantial reduction of frequency chirping can be obtained which, however, is effective only up to modulation frequencies of the order of the locking bandwidth and is strongly dependent on the frequency detuning between master and slave.

Piazzolla, S.; Spano, P.; Tamburrini, M.

1986-12-01

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 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.

4

T3DB: the toxic exposome database.  

Science.gov (United States)

The exposome is defined as the totality of all human environmental exposures from conception to death. It is often regarded as the complement to the genome, with the interaction between the exposome and the genome ultimately determining one's phenotype. The 'toxic exposome' is the complete collection of chronically or acutely toxic compounds to which humans can be exposed. Considerable interest in defining the toxic exposome has been spurred on by the realization that most human injuries, deaths and diseases are directly or indirectly caused by toxic substances found in the air, water, food, home or workplace. The Toxin-Toxin-Target Database (T3DB - www.t3db.ca) is a resource that was specifically designed to capture information about the toxic exposome. Originally released in 2010, the first version of T3DB contained data on nearly 2900 common toxic substances along with detailed information on their chemical properties, descriptions, targets, toxic effects, toxicity thresholds, sequences (for both targets and toxins), mechanisms and references. To more closely align itself with the needs of epidemiologists, toxicologists and exposome scientists, the latest release of T3DB has been substantially upgraded to include many more compounds (>3600), targets (>2000) and gene expression datasets (>15 000 genes). It now includes extensive data on 'normal' toxic compound concentrations in human biofluids as well as detailed chemical taxonomies, informative chemical ontologies and a large number of referential NMR, MS/MS and GC-MS spectra. This manuscript describes the most recent update to the T3DB, which was previously featured in the 2010 NAR Database Issue. PMID:25378312

Wishart, David; Arndt, David; Pon, Allison; Sajed, Tanvir; Guo, An Chi; Djoumbou, Yannick; Knox, Craig; Wilson, Michael; Liang, Yongjie; Grant, Jason; Liu, Yifeng; Goldansaz, Seyed Ali; Rappaport, Stephen M

2015-01-28

5

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

6

A New Circuit Model of Small-Signal Sziklai Pair Amplifier  

Directory of Open Access Journals (Sweden)

Full Text Available 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 this amplifier circuit suitable to use in Radio and TV receiver stages. The qualitative and tuning performance of the proposed amplifier offers it a flexible application range as high voltage gain, high power gain and tuned amplifier. Tuning performance, variation of voltage gain with frequency and different biasing resistances, input and output noises at operating frequency, temperature dependency of performance parameters and total harmonic distortion of the amplifier are perused for providing wide spectrum to the qualitative studies. The proposed Sziklai pair configuration with NPN driver transistor can be attempted to fabricate a single pack transistor IC version of Sziklai pair. Proposed circuit is also free from poor response problem of small-signal Darlington pair amplifiers at higher frequencies and narrow-band response region for PNP driven small-signal Sziklai pair amplifier.

SachchidaNand Shukla and Susmrita Srivastava

2013-07-01

7

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

8

Small signal suppression in coded aperture imaging in nuclear medicine  

International Nuclear Information System (INIS)

The suppression of small signal information by the quantum noise in an off axis Fresnel zone plate coded aperture system is described. This effect, directly related to the dc gain of the aper- ture and to the spatial variation of the variance in the decoded image, more than outweighs the geometric efficiency and thereby limits the widespread use of this new technique in nuclear medicine. (U.S.)

9

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

10

Estimating small signals by using maximum likelihood and Poisson statistics  

International Nuclear Information System (INIS)

Estimation of small signals from counting experiments with backgrounds larger than signals is solved using maximum likelihood estimation for situations in which both signal and background statistics are Poissonian. Confidence levels are discussed, and Poisson, Gauss and least-squares fitting methods are compared. Efficient algorithms that estimate signal strengths and confidence levels are devised for computer implementation. Examples from simulated data and a low count rate experiment in nuclear physics are given. (author)

11

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

International Nuclear Information System (INIS)

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

12

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-11-18

13

Small signal amplifiers and converters for millimeter wave Satcom systems  

Science.gov (United States)

This paper describes the current state of the art and the various design tradeoffs encompassing the variety of small signal active circuit 'building blocks' deployed in millimeter wave Satcom receivers and transmitters. Included in this catagory are such low noise receiver components as parametric and FET amplifiers and low loss mixer downconverters as well as low level transmitter driver components such as resistive and varactor upconverters. Current and projected state of the art performance data will be presented along with specific examples of operating hardware.

Okean, H. C.

1979-01-01

14

Small-signal theory of gyrotrons and gyroklystrons  

International Nuclear Information System (INIS)

Zhurakovskiy's equation of motion for electrons in a steady magnetic field and a time-varying transverse electric field have been used to derive an interaction impedance for an electron beam passing through a TE cavity with one or more one-half sinusoid axial variations of transverse electric field. In a similar fashion an expression for transconductance of a gyroklystron consisting of TE cavities separated by drift spaces has been derived. The expressions contain relativistic corrections which are important above approximately 50 kV but give results identical with those of Hirshfield et al. at lower voltages. In addition, an analytic small-signal, space-charge theory for gyroklystrons utilizing TE/sub o,n/ cavities and a hollow electron beam has been developed. It predicts exponential growth of the modulation on the beam in a drift space free of all fields other than the space-charge fields and the steady magnetic field. The beam loading, transconductance and space-charge theories have been used to predict the stability and gain of Gyrotrons and gyroklystrons for EBT. The tubes operate at 80 kV and have produced up to 250 kW at 28 GHz

15

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

16

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)

17

Ultrasensitive diagnostics for small signal gain in COIL and AGIL lasers  

Science.gov (United States)

In this paper we describe a novel, ultra-sensitive diode laser based diagnostic for small signal gain in atomic iodine based laser systems. We describe the overall diagnostic design and present initial data on the sensitivity of the device.

Davis, Steven J.; Mulhall, Phillip A.; Polex, Jan; Kessler, William J.

2003-06-01

18

Validation of Nonlinear Bipolar Transistor Model by Small-Signal Measurements  

DEFF Research Database (Denmark)

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.

1992-01-01

19

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

20

SMALL-SIGNAL GAIN MEASUREMENTS AT THE CENTER LINE IN A C.W. DF LASER  

OpenAIRE

Measurements of the small-signal gain of the laser medium produced by a DF combustion-driven continuous wave chemical laser are presented. A low power hydrogen (deuterium) fluoride mixing laser has been developed as probe laser which produces cw radiation on a single line and single TEMooq mode. By applying a saw-tooth voltage to the P.Z.T. crystal modulating the laser cavity length we measured the gain at the center line. The small-signal gain profile along the gas flow direction was observe...

Gastaud, M.; Voignier, F.; Bousselet, P.; Regnier, P.

1980-01-01

21

Dynamic bandwidth reconstruction  

International Nuclear Information System (INIS)

This paper describes a method of dynamically varying the bandwidth of each view in projection reconstruction. It is shown how this versatile function can simultaneously perform four image-processing functions: adaptive noise equalization, correction for missing views, correction for streaking from off-center high-density objects, and acquisition of noncircularly symmetric two-dimensional imaging kernels. A dynamic bandwidth algorithm is described that involves an efficient interpolation operation into a predefined filter look-up table. This is performed during fast Fourier transform convolution of projection data and does not affect reconstruction performance

22

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

23

Bandwidth enhancement and optical performances of multiple quantum well transistor lasers  

CERN Document Server

A detailed rate-equation-based model is developed to study carrier transport effects on optical and electrical characteristics of the Multiple Quantum Well Heterojunction Bipolar Transistor Laser in time-domain. Simulation results extracted using numerical techniques in small-signal regime predict significant enhancement in device optical bandwidth when multiple quantum wells are used. Cavity length and base width are also modified to optimize the optoelectronic performances of the device. An optical bandwidth of \\approx 60GHz is achieved in the case of 5 quantum wells each of 70A widths and a cavity length of 200um.

Taghavi, Iman; Leburton, Jean-Pierre

2012-01-01

24

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

25

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

26

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

DEFF Research Database (Denmark)

Power system stability investigations of wind farms often cover the tasks of low-voltage-fault-ride-through, voltage and reactive power control, and power balancing, but not much attention has yet been paid to the task of small-signal stability. Small-signal stability analysis needs increasing focus since the share of wind power increases substituting power generation from conventional power plants. Here, a study based on modal analysis is presented which investigate the effect of large scale integration of full-load converter interfaced wind turbines on inter-area oscillations in a three generator network. A detailed aggregated wind turbine model is employed which includes all necessary control functions. It is shown that the wind urbines have very low participation in the inter-area power oscillation.

Knüppel, Thyge; Akhmatov, Vladislav

2009-01-01

27

Two neural approaches for small-signal modelling of GaAs HEMTs  

OpenAIRE

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 modellin...

Marinkovi? Zlatica; Crupi Giovanni; Caddemi Alina; Markovi? Vera

2010-01-01

28

Cryogenic small-signal conversion with relaxation oscillations in Josephson junctions  

OpenAIRE

Broadband detection of small electronic signals from cryogenic devices, with the option of simple implementation for multiplexing, is often a highly desired, although non-trivial task. We investigate and demonstrate a small-signal analog-to-frequency conversion system based on relaxation oscillations in a single Josephson junction. Operation and stability conditions are derived, with special emphasis on noise analysis, showing the dominant noise sources to originate from flu...

Furlan, Miha

2005-01-01

29

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

Science.gov (United States)

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

Wei, Chia-Chien

2011-01-15

30

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)

31

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

32

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

33

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

34

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

Directory of Open Access Journals (Sweden)

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

Wenying Liu

2014-11-01

35

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

36

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

37

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

International Nuclear Information System (INIS)

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

38

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

39

Small signal gain and saturation intensity of a Yb:Silica fiber MOPA system  

Science.gov (United States)

In this work, the small signal gain ( ?0) and signal saturation power ( Psat) of a continuous wave (CW) single-frequency ytterbium-doped (YD) double-clad (DC) fiber master oscillator power amplifier (MOPA) array has been determined in the optimum length. At first, we have obtained output versus input signal powers in the amplifier, using the coupled steady-state rate equations for the various end diode pumping such as co/counter propagation and bidirectional modes. On the other hand, the steady-state amplification relation was employed at a presumed ?0 and Psat as initial guess, to generate output signals. Then, using the least square method (LSM), those input/output signal powers were fitted by the best regression curve obtained from the amplification relation to determine the converged ?0 and Psat values. The analytical formulae for ?0 and Psat were derived using the rate equations as well.

Parvin, Parviz; Ilchi-Ghazaani, Maryam; Bananej, Alireza; Lali-Dastjerdi, Zohreh

2009-10-01

40

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

41

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

DEFF Research Database (Denmark)

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

Su, Chi; Chen, Zhe

2012-01-01

42

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

43

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

44

Minimization of intermodulation distortion in GaAs MESFET small-signal amplifiers  

Science.gov (United States)

It is shown how the intermodulation (IM) distortion performance of a small-signal amplifier can be optimized when the amplifier is designed according to available-gain criteria. MESFET output is conjugate-matched, and its input is mismatched to obtain a specified gain. This method generally results in bettter dynamic range than do other options such as matching the input and mismatching the output or simultaneously matching both the input and output (which, in many cases, is impossible). In available-gain design the value of source impedance that provides the desired gain is not unique and can be selected to optimize IM levels. A numerical formulation of the Volterra series allows a complete equivalent circuit of the FET to be used, and the intermodulation calculations include all feedback effects. The sensitivity of the IM intercept point to the source-reflection coefficient is shown to decrease with increasing frequency and is related to the MESFET stability.

Crosmun, Andrea M.; Maas, Stephen A.

1989-09-01

45

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

Science.gov (United States)

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

Tan, Zhen; Tian, He; Feng, Tingting; Zhao, Lianfeng; Xie, Dan; Yang, Yi; Xiao, Lei; Wang, Jing; Ren, Tian-Ling; Xu, Jun

2013-12-01

46

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

47

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

48

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

Scientific Electronic Library Online (English)

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

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

2013-12-01

49

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

50

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

51

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

52

Network Bandwidth Utilization Forecast Model on High Bandwidth Network  

Energy Technology Data Exchange (ETDEWEB)

With the increasing number of geographically distributed scientific collaborations and the scale of the data size growth, it has become more challenging for users to achieve the best possible network performance on a shared network. We have developed a forecast model to predict expected bandwidth utilization for high-bandwidth wide area network. The forecast model can improve the efficiency of resource utilization and scheduling data movements on high-bandwidth network to accommodate ever increasing data volume for large-scale scientific data applications. Univariate model is developed with STL and ARIMA on SNMP path utilization data. Compared with traditional approach such as Box-Jenkins methodology, our forecast model reduces computation time by 83.2percent. It also shows resilience against abrupt network usage change. The accuracy of the forecast model is within the standard deviation of the monitored measurements.

Yoo, Wucherl; Sim, Alex

2014-07-07

53

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

54

Bandwidth reduction in rectalgular grids  

CERN Document Server

We show that the bandwidth of a square two-dimensional grid of arbitrary size can be reduced if two (but not less than two) edges are deleted. The two deleted edges may not be chosen arbitrarily, but they may be chosen to share a common endpoint or to be non-adjacent. We also show that the bandwidth of the rectangular n by m (m greater or equal to n) grid can be reduced by k, for all k that are sufficiently small, if m-n+2k edges are deleted.

Andreescu, T; Sunik, Z; Sunik, Zoran

2003-01-01

55

Improvement of modulation bandwidth in multisection RSOA for colorless WDM-PON.  

Science.gov (United States)

We demonstrated two-section reflective semiconductor optical amplifier (RSOA) with dramatic improvement of small-signal modulation bandwidth above 10 GHz as colorless source for wavelength division multiplexed-passive optical network (WDM-PON). The device provides the fiber-to-fiber gain of 22.8 dB, 3-dB amplified spontaneous emission (ASE) bandwidth of 30 nm, and ripple of 1.5 dB. Good performance at 2.5 Gbps was obtained with an extinction ratio of 8 dB and a power penalty of 2 dB at a 10(-9) bit error rate (BER) up to 20 km transmission. PMID:19770850

Kim, Hyun-Soo; Choi, Byung-Seok; Kim, Ki-Soo; Kim, Dong Churl; Kwon, O-Kyun; Oh, Dae-Kon

2009-09-14

56

On 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. 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 turbine model with all grid relevant control functions is used in the study. Furthermore is the wind power plant (WPP) equipped with a WPP voltage controller and comparisons are presented. The models of wind turbine and WPP voltage controller are kindly provided by Siemens Wind Power A/S for this work. The study is based on modal analysis which are complemented with simulations on the nonlinear system.

Knüppel, Thyge; Akhmatov, Vladislav

2010-01-01

57

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

58

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

OpenAIRE

Up until now, study results on the impact of large-scale wind power integration on small signal stability have often been in conflict. Sometimes, the conclusions are even completely opposite, making people unable to agree on which is right. The reason behind this phenomenon is that most of these studies are based on a certain grid and typical working conditions, so conclusions are reached by comparing changes in oscillation mode, one by one. This study method lacks a broader perspective, and ...

Wenying Liu; Rundong Ge; Huiyong Li; Jiangbei Ge

2014-01-01

59

Broadband Frequency Dispersion Small Signal Modeling of the Output Conductance and Transconductance in AlInN/GaN HEMTs  

OpenAIRE

Frequency dispersion of transconductance and output conductance in AlInN/GaN high electron mobility transistors is investigated in this paper. Broadband dispersion effects in the microwave frequency range are reported for the first time. A small-signal model is developed. Trapping effects are taken into account with parasitic electrical networks including distributed time constants. The model is compared to experimental data for several bias conditions and different types of dispersion.

Seraphin Dieudonne, Nsele; Escotte, Laurent; Tartarin, Jean-guy; Piotrowicz, Ste?phane; Delage, Sylvain L.

2013-01-01

60

Reduction of electromagnetic interference susceptibility in small-signal analog circuits using complementary split-ring resonators  

OpenAIRE

Low-frequency analog and digital electronic circuits are susceptible to electromagnetic interference in the radiofrequency (RF) range. This disturbance is produced when the coupled RF signal is rectified by the nonlinear behavior of the semiconductors used in the small-signal analog input stage of the electronic system. Circuits based on operational amplifiers are usually employed for such input stages. These circuits present an amplitude modulation demodulation produced ...

Pe?rez Robles, Daniel; Gil Gali?, Ignacio; Gago Barrio, Javier; Ferna?ndez Garci?a, Rau?l; Balcells Sendra, Josep; Gonza?lez Di?ez, David; Berbel Artal, Ne?stor; Mon Gonza?lez, Juan

2012-01-01

61

47 CFR 2.202 - Bandwidths.  

Science.gov (United States)

...Signal With Quantized or Digital Information Continuous...desired Speech and music, M=4000, Bandwidth...desired Speech and music, M=4000, Bandwidth...frequency Speech and music, M=4500, lowest...Signal With Quantized or Digital Information...

2010-10-01

62

Fade depth scaling with channel bandwidth  

OpenAIRE

The dependence of small-scale fading on bandwidth is quantified experimentally in the 3.1-10.6GHz band for indoor channels. The fade depth converges to 4dB at 1GHz bandwidth, with little reduction for further increase in bandwidth. A simple yet accurate empirical fade depth model is developed, enabling convenient evaluation of the link budget for a channel with given bandwidth.

Malik, Wq; Allen, B.; Edwards, Dj

2007-01-01

63

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

64

Improving the Bandwidth Selection in Kernel Equating  

Science.gov (United States)

We investigate the current bandwidth selection methods in kernel equating and propose a method based on Silverman's rule of thumb for selecting the bandwidth parameters. In kernel equating, the bandwidth parameters have previously been obtained by minimizing a penalty function. This minimization process has been criticized by practitioners…

Andersson, Björn; von Davier, Alina A.

2014-01-01

65

47 CFR 2.202 - Bandwidths.  

Science.gov (United States)

...Sound carrier relative to video carrier=4.5 MHz 5M75C3F Total vision bandwidth: 5.75 MHz; FM aural bandwidth including guardbands: 250,000 Hz 250KF3E Total bandwidth: 6 MHz 6M25C3F 5. Facsimile Analogue facsimile...

2010-10-01

66

A Method to Simultaneously Extract the Small-Signal Equivalent Circuit and Noise Parameters of Heterojunction Bipolar Transistors  

OpenAIRE

A method to extract the elements of the small-signal equivalent circuit and the noise parameters (NPs) of heterojunction bipolar transistors (HBTs) is presented. The extraction is done by simultaneous fitting of the measured S-parameters, noise figure (for a well-matched impedance), and NPs (estimated using the so-called F50 method). An additional error term, given by the root square sum of the differences between the NPs estimated from the F50 method and the NPs directly computed using the H...

Maya Sa?nchez, Mª Del Carmen; La?zaro Guille?n, Antoni; Pradell I Cara, Llui?s

2006-01-01

67

Advanced bandwidth scheduling algorithms in dedicated networks  

Energy Technology Data Exchange (ETDEWEB)

An increasing number of high performance research network testbeds and production networks have the capability of provisioning dedicated channels for high speed data transfer in support of large scale scientific applications. Each dedicated channel in these networks typically consists of one or more physical links that are shared by multiple applications in both time and bandwidth through in advance reservation. The design of efficient bandwidth scheduling algorithms is critical to maximizing the utilization of dedicated network resources and meeting diverse end-to-end transport performance requirements. The topology of a dedicated network is represented by a graph, where each link maintains a list of residual bandwidths specified as segmented constant functions of time. Given a graph with an aggregated time-bandwidth table combining the reservation information on all links, designated source, and destination vertices, and a specified data size, we formulate and investigate five bandwidth scheduling problems to minimize the data transfer end time under different path and bandwidth constraints. (1) variable path with variable bandwidth (VPVB), which computes the widest (highest bandwidth) path in each time slot; (2) fixed path with variable bandwidth (FPVB), which computes a fixed path with varying bandwidths across different time slots; (3) variable path with fixed bandwidth (VPFB), which computes one path in each time slot with the same bandwidth; (4) fixed path with fixed bandwidth (FPFB), which computes a fixed path with a constant bandwidth; and (5) multiple fixed paths with fixed bandwidths (MFPFB), which computes multiple concurrent fixed paths with constant bandwidths. Among these problems, VPVB represents the most flexible scenario where the network resources are fully utilized and the minimal transfer end time is achieved, while FPFB imposes the most stringent transport conditions by fixing both path and bandwidth. We design an optimal algorithm for each of these scheduling problems. VPVB is solved using an extension of the classical Dijkstra's algorithm, and FPVB is solved using Maximum Permutation Algorithm, which tries all possible permutations of throughputs at different time slots to obtain the minimal transfer end time. The algorithm for VPFB, FPFB, and MFPFB are based on Adjacent Time Slots Search, which finds the minimum transfer end time by examining the possibility of data transfer in any number of contiguous time slots. All these algorithms are of polynomial or pseudo polynomial time complexity with respect to the network size and the total number of time slots in a bandwidth reservation table.

Wu, Qishi [ORNL; Rao, Nageswara S [ORNL; Zhu, Mengxia [ORNL

2009-04-01

68

Measurements of the small-signal gain and saturation intensity for a cw CO2 laser using an intracavity loss element  

International Nuclear Information System (INIS)

A new scheme with an intra-cavity loss element for small-signal gain measurement at two main wavelengths of a tunable gas flow longitudinally excited CO2 laser is presented. By inserting a ZnSe stack polariser into the cavity, the critical condition for the laser is obtained. The small-signal gain and saturation intensity are calculated using the Rigrod formula. The small-signal gain measurement was performed for different gas pressures and different input electric powers. Under the same experimental conditions, the values of the saturation intensities were calculated from the output power and the measured small-signal gains. The advantage of this method is that no probe laser system is required. The results agree with experimental data obtained earlier by the conventional oscillator-amplifier method. (lasers)

69

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

70

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

71

Bandwidth enhancement of circular microstrip antennas  

OpenAIRE

Microstrip Antennas have many advantages such as low profile, light weight, can be easily matched with microwave integrated circuits which leads to use this type of antennas in different applications, on the other side, the great disadvantage of these antennas is the narrow bandwidth which is 2 to 5 %. In this paper a single element circular Microstrip antenna has been designed which had a narrow bandwidth and then two methods of bandwidth enhancement had been designed and compared to the sin...

Ali Hussain Ali Yawer; Abdulkareem Abd Ali Mohammed

2010-01-01

72

Bandwidth enhancement of circular microstrip antennas  

Directory of Open Access Journals (Sweden)

Full Text Available Microstrip Antennas have many advantages such as low profile, light weight, can be easily matched with microwave integrated circuits which leads to use this type of antennas in different applications, on the other side, the great disadvantage of these antennas is the narrow bandwidth which is 2 to 5 %. In this paper a single element circular Microstrip antenna has been designed which had a narrow bandwidth and then two methods of bandwidth enhancement had been designed and compared to the single patch, these two techniques gave a bandwidth of 10% and 38 % respectively. The three designs had been simulated using Microwave Office Package.

Ali Hussain Ali Yawer

2010-01-01

73

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

74

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

75

Bandwidth Allocation Algorithm of Heterogeneous Network  

Directory of Open Access Journals (Sweden)

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

Zhijun Hu

2014-03-01

76

Small signal audio design  

CERN Document Server

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

Self, Douglas

2014-01-01

77

47 CFR 2.202 - Bandwidths.  

Science.gov (United States)

...signal, single-sideband full carrier Bn =M Maximum code frequency is: 2110 Hz, M=2110, Bandwidth: 2110 Hz=2...a telephone channel—a 1020 Hz keyed tone for continual Morse identification. Cmax =9960, M=30, D=480 Hz,...

2010-10-01

78

Bandwidth Selection in Kernel Density Estimation  

OpenAIRE

In kernel density estimation, the most crucial step is to select a proper bandwidth (smoothing parameter). There are two conceptually different approaches to this problem: a subjective and an objective approach. In this report, we only consider the objective approach, which is based upon minimizing an error, defined by an error criterion. The most common objective bandwidth selection method is to minimize some squared error expression, but this method is not without its critics. This a...

Kile, Ha?kon

2010-01-01

79

Bandwidth Selection for Weighted Kernel Density Estimation  

OpenAIRE

In the this paper, the authors propose to estimate the density of a targeted population with a weighted kernel density estimator (wKDE) based on a weighted sample. Bandwidth selection for wKDE is discussed. Three mean integrated squared error based bandwidth estimators are introduced and their performance is illustrated via Monte Carlo simulation. The least-squares cross-validation method and the adaptive weight kernel density estimator are also studied. The authors also con...

Wang, Bin; Wang, Xiaofeng

2007-01-01

80

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

81

A Bandwidth Reconfigurable Antenna for Cognitive Radios  

Science.gov (United States)

Cognitive radios have two operating modes, the searching mode where the system looks for the bandwidth to operate in and the operating mode where users transmit and receive information data through this bandwidth. In the first mode, one may have a very wide bandwidth antenna to be able to scan all the spectrum and in the operating mode one may have a narrow bandwidth antenna to filter out unwanted signals. In this chapter, we present a new antenna capable of operating in both UWB and narrowband modes, which is also tunable in the operating (narrowband) mode. It is composed of a microstrip disc monopole with defect slots in its ground plane. When the slots are deactivated, the antenna exhibits UWB behaviour from 2 to 10 GHz. To narrow the frequency bandwidth, defect slots are activated to act as a band-pass filter that narrows the antenna response. The activation and deactivation of the slots can be achieved by using switches located under the antenna feed line. In this case, the antenna response can be tuned by varying the slots' length. To examine the presented approach, both simulated and measured results are presented and discussed.

Ghanem, F.; Hall, P. S.

82

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

83

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

84

Improving Bandwidth of Yagi-Uda Arrays  

Directory of Open Access Journals (Sweden)

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

Richard A. Formato

2012-01-01

85

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

86

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

87

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)

88

A power efficient bandwidth regulation technique for a low-noise high-gain RF wideband amplifier  

Science.gov (United States)

In this paper, a single-stage deep sub-micron wideband amplifier (LNA) using a reactive resonance tank and passive port-matching techniques is demonstrated operating in the microwave frequency range (K band). A novel power-efficient bandwidth (BW) regulation technique is proposed by incorporating a small impedance in the resonance tank of the amplifier configuration. It manifests a forward gain in the range of 5.9-10.7 dB covering a message bandwidth of 10.6-6.3 GHz. With regulation, input-output reflection parameters ( S 11, S 22) and noise figure can be manipulated by -12.7 dB, -22.7 dB and 0.36 dB, respectively. Symmetric regulation is achieved for bandwidth and small signal gain with respect to moderate tank impedance (36.5% and -26.8%, respectively) but the effect on noise contribution remains relatively low (increase of 7% from a base value of 2.39 dB). The regulated architecture, when analyzed with 90 nm silicon CMOS process, supports low power (9.1 mW) on-chip communication. The circuit is tested with a number of combinations for tank (drain) impedance to verify the efficiency of the proposed technique and achieves better figures of merit when compared with published literature.

Roy, Apratim; Rashid, S. M. S.

2012-09-01

89

Bypassing the bandwidth theorem with PT symmetry  

CERN Document Server

The beat time {\\tau}_{fpt} associated with the energy transfer between two coupled oscillators is dictated by the bandwidth theorem which sets a lower bound {\\tau}_{fpt}\\sim 1/{\\delta}{\\omega}. We show, both experimentally and theoretically, that two coupled active LRC electrical oscillators with parity-time (PT) symmetry, bypass the lower bound imposed by the bandwidth theorem, reducing the beat time to zero while retaining a real valued spectrum and fixed eigenfrequency difference {\\delta}{\\omega}. Our results foster new design strategies which lead to (stable) pseudo-unitary wave evolution, and may allow for ultrafast computation, telecommunication, and signal processing.

Ramezani, Hamidreza; Ellis, F M; Guenther, Uwe; Kottos, Tsampikos

2012-01-01

90

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

91

Bandwidth Enabled Flight Operations: Examining the Possibilities  

Science.gov (United States)

The Bandwidth Enabled Flight Operations project is a research effort at the NASA Ames Research Center to investigate the use of satellite communications to improve aviation safety and capacity. This project is a follow on to the AeroSAPIENT Project, which demonstrated methods for transmitting high bandwidth data in various configurations. For this research, we set a goal to nominally use only 10 percent of the available bandwidth demonstrated by AeroSAPIENT or projected by near-term technology advances. This paper describes the results of our research, including available satellite bandwidth, commercial and research efforts to provide these services, and some of the limiting factors inherent with this communications medium. It also describes our investigation into the needs of the stakeholders (Airlines, Pilots, Cabin Crews, ATC, Maintenance, etc). The paper also describes our development of low-cost networked flight deck and airline operations center simulations that were used to demonstrate two application areas: Providing real time weather information to the commercial flight deck, and enhanced crew monitoring and control for airline operations centers.

Pisanich, Greg; Renema, Fritz; Clancy, Dan (Technical Monitor)

2002-01-01

92

A long range full bandwidth Ethernet bridge  

Energy Technology Data Exchange (ETDEWEB)

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

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

1988-02-01

93

Bandwidth, Broadband, and Planning for Public Access  

Science.gov (United States)

Broadband and bandwidth allocation is an essential technology planning activity that libraries should address on a continual basis. There are five key factors that will impact your network's performance: 1. infrastructure, 2. network load, 3. workstation performance, 4. prioritization of services, and 5. network management. The author thinks it's…

Blowers, Helene

2012-01-01

94

Bandwidth Enhancement Techniques of Dielectric Resonator Antenna  

Directory of Open Access Journals (Sweden)

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

ARCHANA SHARMA

2011-07-01

95

Application of small-signal modeling and measurement techniques to the stability analysis of an integrated switching-mode power system. [onboard Dynamics Explorer Satellite  

Science.gov (United States)

Small-signal modeling techniques are used in a system stability analysis of a breadboard version of a complete functional electrical power system. The system consists of a regulated switching dc-to-dc converter, a solar-cell-array simulator, a solar-array EMI filter, battery chargers and linear shunt regulators. Loss mechanisms in the converter power stage, including switching-time effects in the semiconductor elements, are incorporated into the modeling procedure to provide an accurate representation of the system without requiring frequency-domain measurements to determine the damping factor. The small-signal system model is validated by the use of special measurement techniques which are adapted to the poor signal-to-noise ratio encountered in switching-mode systems. The complete electrical power system with the solar-array EMI filter is shown to be stable over the intended range of operation.

Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.; Rodriguez, G. E.

1980-01-01

96

Trapping effects in a-Si:H investigated by small-signal transient photoconductivity and the steady-state photocarrier-grating technique  

Science.gov (United States)

We report on trapping effects observed in small-signal photoconductivity and steady-state photocarrier-grating (SSPG) experiments. In the former case trapping effects appear since the small-signal photocurrent decays exponentially with time after the excitation is turned off, but with a decay time which depends on the ratio of free to trapped carriers and is determined by the intensity of the cw background illumination. In the case of (steady-state) SSPG measurements, carried out as a function of electric field, an electron drift mobility is obtained which is proportional to the ratio of free to trapped carriers and is therefore again determined by the background illumination. Both experiments show that around 0.4 eV below the electron mobility edge the density of states falls off much more slowly with energy towards midgap than near the mobility edge and may even exhibit a minimum.

Haridim, M.; Zelikson, M.; Weiser, K.

1994-05-01

97

Variable bandwidth Kernel estimator of the mode  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the problem of estimating the mode of a probability density function has been studied.  Parzen (1962 proposed a kernel estimator of the mode depends on a single bandwidth. In this paper, the Parzen estimator has been improved by proposing a kernel estimator with variable bandwidth for the mode of the density function. Proceeding as in Parzen (1962, the consistency and asymptotic normality of the proposed estimator are shown. Moreover, the good  performance of the proposed estimator is tested via simulation study and it is shown that the proposed estimator is more efficient than the Parzen estimator.

Raid B. Salha

2009-09-01

98

High bandwidth concurrent processing on commodity platforms  

CERN Document Server

The I/O bandwidth and real-time processing power required for high- energy physics experiments is increasing rapidly over time. The current requirements can only be met by using large-scale concurrent processing. We are investigating the use of a large PC cluster interconnected by Fast and Gigabit Ethernet to meet the performance requirements of the ATLAS second level trigger. This architecture is attractive because of its performance and competitive pricing. A major problem is obtaining frequent high-bandwidth I/O without sacrificing the CPU's processing power. We present a tight integration of a user-level scheduler and a zero-copy communication layer. This system closely approaches the performance of the underlying hardware in terms of both CPU power and I/O capacity. (0 refs).

Boosten, M; Van der Stok, P D V

1999-01-01

99

Large-bandwidth planar photonic crystal waveguides  

DEFF Research Database (Denmark)

A general design principle is presented for making finite-height photonic crystal waveguides that support leakage-free guidance of light over large frequency intervals. The large bandwidth waveguides are designed by introducing line defects in photonic crystal slabs, where the material in the line defect has appropriate dispersion properties relative to the photonic crystal slab material surrounding the line defect. A three-dimensional theoretical analysis is given for large-bandwidth waveguide designs based on a silicon-air photonic crystal slab suspended in air. In one example, the leakage-free single-mode guidance is found for a large frequency interval covering 60% of the photonic band-gap.

SØndergaard, Thomas; Lavrinenko, Andrei

2002-01-01

100

Bandwidth Enhancement in Multilayer Microstrip Proximity Coupled Array  

OpenAIRE

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 co...

Shubham Gupta; Shilpa Singh

2012-01-01

101

Digital demodulator for wide bandwidth SAR  

DEFF Research Database (Denmark)

A novel approach to the design of efficient digital quadrature demodulators for wide bandwidth SAR systems is described. Efficiency is obtained by setting the intermediate frequency to 1/4 the ADC sampling frequency. One channel is made filter-free by synchronizing the local oscillator with the output decimator. The filter required by the other channel is optimized through global search using the system level performance metrics integrated sidelobe level ratio (ISLR) and peak sidelobe level ratio (PSLR).

JØrgensen, JØrn Hjelm

2000-01-01

102

Soft Computing approaches on the Bandwidth Problem  

OpenAIRE

The Matrix Bandwidth Minimization Problem (MBMP) seeks for a simultaneous reordering of the rows and the columns of a square matrix such that the nonzero entries are collected within a band of small width close to the main diagonal. The MBMP is a NP-complete problem, with applications in many scientific domains, linear systems, artificial intelligence, and real-life situations in industry, logistics, information recovery. The complex problems are hard to solve, that is why a...

Czibula, Gabriela; Crisan, Gloria Cerasela; Pintea, Camelia-m; Czibula, Istvan-gergely

2012-01-01

103

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 exploi...

Lee, King F.; Williams, Douglas B.

2004-01-01

104

Fixed Innovative Bandwidth Utilization in TDM EPON  

Directory of Open Access Journals (Sweden)

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

Muhammad Bilal

2011-03-01

105

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)

106

Recycling of Bandwidth in Metropolitan Area Networks(MAN  

Directory of Open Access Journals (Sweden)

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

Bhargava Devana

2012-01-01

107

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

108

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

109

Optical delay control of large-spectral-bandwidth laser pulses  

International Nuclear Information System (INIS)

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

110

Compact antenna arrays with wide bandwidth and low sidelobe levels  

Energy Technology Data Exchange (ETDEWEB)

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

Strassner, II, Bernd H.

2014-09-09

111

Utility-Based Online Bandwidth Allocation for Bonded Channels  

OpenAIRE

This paper focuses on the bonding group online bandwidth allocation problem in DOCSIS3.0 network. Taking network maximization utility as the goal, an optimal model, which is the Bonding Group based rival service flow Set Utility Maximization (BG-SUM), is built firstly, and then a Bonding Group Online Bandwidth Allocation algorithm (BG-OBA) is proposed to perform fast near-optimal solution. By discretizing the utility functions of requests, the BG-OBA fast allocate bandwidth for service flows ...

Zhongzhen Yang; Jinlin Wang; Jun Lin

2013-01-01

112

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

113

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

114

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

115

Bandwidth-tunable optical spatial filters with nanoparticle arrays.  

Science.gov (United States)

Modeling a nanoparticle array (NPA) inside a thin glass slab as a lumped optical resonator, we propose a systematic approach to design for an efficient optical filter with bandwidth tunability. The quality factor and bandwidth of the resonator are related to the physical, geometrical, and electrical parameters of an NPA and its surrounding medium, whose permittivity is varied to change the bandwidth. We propose a structure amenable to our design approach consisting of an NPA slab surrounded by liquid crystal whose permittivity can be altered. We validate the design procedure with examples of tunable-bandwidth filters at different frequency regimes from NIR to blue. PMID:24921367

Saeidi, Chiya; van der Weide, Daniel

2014-05-19

116

Increase of the grating coupler bandwidth with a graphene overlay  

International Nuclear Information System (INIS)

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

117

Increase of the grating coupler bandwidth with a graphene overlay  

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-03-17

118

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

119

A high-bandwidth spintronic position sensor  

Science.gov (United States)

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

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

2014-09-01

120

Plasmonic photodetector with terahertz electrical bandwidth  

Science.gov (United States)

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

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

2014-04-01

121

Tunable bandwidth of the terahertz metamaterial absorber  

Science.gov (United States)

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

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

2014-08-01

122

A high-bandwidth spintronic position sensor.  

Science.gov (United States)

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

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

2014-09-19

123

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)

124

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

125

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

Science.gov (United States)

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.

Ramirez-Garcia, E.; Aniel, F. P.; Enciso-Aguilar, M. A.; Zerounian, F.

2012-08-01

126

Wavelength conversion bandwidth in fiber based optical parametric amplifiers.  

Science.gov (United States)

We propose a systematic approach to evaluating and optimising the wavelength conversion bandwidth and gain ripple of fourwave mixing based fi ber optical wavelength converters. Truly tunable wavelength conversion in these devices requires a highly tunable pump. For a given fi ber dispersion slope, we fi nd an optimum dispersion curvature that maximises the wavelength conversion bandwidth. PMID:19465963

McKerracher, Ross; Blows, Justin; de Sterke, C

2003-05-01

127

47 CFR 74.535 - Emission and bandwidth.  

Science.gov (United States)

...the displacement frequency (kHz) from the center of the authorized... W = the channel bandwidth (kHz). (2) On any frequency...authorized bandwidth shall be 100 kHz for operating frequencies below...Dec. 14, 1963, as amended at 48 FR 50332, Nov. 1, 1983;...

2010-10-01

128

Bandwidth tunable filter based on silicon microring-MZI structure  

DEFF Research Database (Denmark)

A novel bandwidth tunable bandpass filter based on a silicon microring-MZI structure is proposed and demonstrated. By thermally tuning the resonance offset between the two microring resonators, and adding the two drop transmissions together, the bandwidth of the microring-MZI filter can be easily linearly tuned with low in-band ripples.

Ding, Yunhong; Zhang, Xinliang

2010-01-01

129

Bandwidth Allocation and Reservation - End-to-End Specification  

CERN Document Server

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

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

2006-01-01

130

Method of improving bandwidth efficiency for OTDM transmission systems  

Science.gov (United States)

Spectrum compression based on filters for improving bandwidth efficiency is presented and demonstrated experimentally in 40Gb/s OTDM system. Even after 100km transmission, demultiplexing and clock recovery can be implemented successfully, and the data rate-to-bandwidth ratio has been improved to 4 times.

Chen, Ming; Lv, Bo; Li, Tangjun; Wang, Muguang; Jian, Shuisheng

2009-11-01

131

Optimal Bandwidth Selection in Observed-Score Kernel Equating  

Science.gov (United States)

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

Häggström, Jenny; Wiberg, Marie

2014-01-01

132

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

133

Load Balance Dan Pembagian Bandwidth Pada Jaringan Local Area Network  

OpenAIRE

Pembahasan ini menjelaskan pembangun sebuah jaringan local area network yang menggunakan dua akses ISP (internet services provider). Sistem ini dikembangkan dengan menggunakan PC Mikrotik Router sehingga akses dengan dua ISP yang masuk ke jaringan local menjadi lebih stabil dan juga diterapkan pengaturan bandwidth pada jaringan ini sehingga setiap user mendapat bandwidth yang sama besar.

Sumantri, Tri

2011-01-01

134

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

135

Utility-Based Online Bandwidth Allocation for Bonded Channels  

Directory of Open Access Journals (Sweden)

Full Text Available This paper focuses on the bonding group online bandwidth allocation problem in DOCSIS3.0 network. Taking network maximization utility as the goal, an optimal model, which is the Bonding Group based rival service flow Set Utility Maximization (BG-SUM, is built firstly, and then a Bonding Group Online Bandwidth Allocation algorithm (BG-OBA is proposed to perform fast near-optimal solution. By discretizing the utility functions of requests, the BG-OBA fast allocate bandwidth for service flows and then verifies the feasibility of the bandwidth redistributed to each channel in bonding group. The simulation results show that the convergence speed of BG-OBA is faster than 0-1 integer programming, and the total utility is close to the theoretical optimum, hence it is practical for online bandwidth allocation

Zhongzhen Yang

2013-10-01

136

Schottky Heterodyne Receivers With Full Waveguide Bandwidth  

Science.gov (United States)

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

Hesler, Jeffrey; Crowe, Thomas

2011-01-01

137

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

138

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

139

A Priority Based Bandwidth Reservation Protocol for Wireless Mesh Networks  

Directory of Open Access Journals (Sweden)

Full Text Available In wireless mesh networks, when compared with traditional applications, multimedia application requires the need of inflexible Quality of services (QoS for high speed digital audio and videos. Under such a condition, the need of proper resource allocation is extremely handy. In this paper, we propose to develop a Priority Based Bandwidth Reservation Protocol (PBRP for wireless mesh networks. Our protocol consists of two phases namely Bandwidth Request phase and Bandwidth Reply phase. In the former Phase, a Bandwidth Request (BREQ message is forwarded from the node that requests the admission of a new traffic flow to its destination. In the later Phase, a Bandwidth Reply (BREP message proceeds backwards, hop-by-hop, from the destination node to the node that originated the request along the path laid down by the corresponding (BREQ message. The destination node precedes the reply according to the priority of traffic classes and reserves the bandwidth on the reply path. By simulation results, we show that our proposed protocol achieves high bandwidth utilization and throughput with reduced delay, when compared with existing technique.

K. Valarmathi

2012-01-01

140

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

141

Sonar feature-based bandwidth compression  

Science.gov (United States)

A sonar bandwidth compression (BWC) technique which, unlike conventional methods, adaptively varies the coding resolution in the compression process based on a priori information is described. This novel approach yields a robust compression system whose performance exceeds the conventional methods by factors of 2-to-1 and 1.5-to-1 for display- formatted and time series sonar data, respectively. The data is first analyzed by a feature extraction routine to determine those pixels of the image that collectively comprise intelligence-bearing signal features. The data is then split into a foreground image which contains the extracted source characteristic and a larger background image which is the remainder. Since the background image is highly textured, it suffices to code only the local statistics rather than the actual pixels themselves. This results in a substantial reduction of the bit rate required to code the background image. The feature-based compression algorithm developed for sonar imagery data is also extended to the sonar time series data via a novel approach involving an initial one-dimensional DCT transformation of the time series data before the actual compression process. The unique advantage of this approach is that the coding is done in an alternative two-dimensional image domain where, unlike the original time domain, it is possible to observe, differentiate, and prioritize essential features of data in the compression process. The feature-based BWC developed for sonar data is potentially very useful for applications involving highly textured imagery. Two such applications are synthetic aperture radar and ultrasound medical imaging.

Saghri, John A.; Tescher, Andrew G.

1992-07-01

142

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

143

Bandwidth filtering of CT scans of the spine  

International Nuclear Information System (INIS)

In CT scans of the upper and lower spine, large noise variations are often observed. The oblong profile of the body itself produces nonuniformity in the noise texture. This paper reports on a bandwidth filtering technique developed that can be used to compensate for these nonuniformities during the image reconstruction process. A method of dynamically varying the bandwidth for each view in projection reconstruction is described. By using an efficient table interpolation technique; this function can be performed as part of a standard image reconstruction. The bandwidth variation can be prescribed to compensate for the noise variations seen in upper and lower spine scans

144

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

145

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

146

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

147

Inscription of narrow bandwidth Bragg gratings in polymer optical fibers  

International Nuclear Information System (INIS)

We report on the inscription and characterization of narrow bandwidth fiber Bragg gratings (FBGs) in different spectral regions using polymer optical fibers (POFs). Narrow bandwidth FBGs are increasingly essential for optical filtering in POF transmission systems and photonic applications. Long FBGs with resonance wavelengths of around 600, 850 and 1550 nm were inscribed in several types of polymer optical fibers using a scanning technique with a short optical path. The technique allowed the inscription in relatively short periods of time. The achieved 3 dB bandwidth varied from 0.22 down to 0.045 nm considering FBG lengths of 10 and 25 mm, respectively. (paper)

148

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

149

Large bandwidth RGC transimpedance preamplifier design in SCA  

International Nuclear Information System (INIS)

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

150

Elimination of bandwidth effect in attenuation measurement with picosecond ultrasonics  

Science.gov (United States)

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

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

2014-08-01

151

An octave bandwidth 90-deg coupler topology suitable for MMICs  

Science.gov (United States)

The study addresses the development of MMIC passive 90-deg couplers or hybrids and, in particular, a 90-deg coupler topology consisting of a power divider to establish a coupling ratio, and two phasing networks with 90-deg phase differential. The hybrid can be realized primarily with lumped components, and the required MMIC circuit area is small enough to allow fabrication of two or more hybrids, operating as low as S-band, on a single chip. This hybrid coupler is a three-port device operating in either combiner or divider mode. Emphasis is placed on the design of the phasing networks and the performance of a fabricated hybrid. The insertion performance is 4 db, 3 db coupling, and 1 db loss with the overall insertion loss less than 1 db over the coupling loss are indicated.

Staudinger, Joseph; Seely, Warren

1990-11-01

152

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

153

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

154

An adaptive scheduling scheme for fair bandwidth allocation  

Science.gov (United States)

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

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

2005-02-01

155

Energy efficiency in elastic-bandwidth optical networks  

OpenAIRE

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...

Vizcaino, Jorge Lopez; Ye, Yabin; Tafur Monroy, Idelfonso

2012-01-01

156

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

157

Asymptotics and optimal bandwidth selection for highest density region estimation  

OpenAIRE

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

Samworth, R. J.; Wand, M. P.

2010-01-01

158

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

159

Optical parametric amplification with a bandwidth exceeding an octave  

International Nuclear Information System (INIS)

The possibility of using various schemes of broadband optical parametric amplifiers (OPAs) for amplifying a supercontinuum with the spectral bandwidth exceeding an octave is analysed. Spectral gain profiles are calculated for some specific OPAs employing promising and available nonlinear optical crystals. The realisation of OPAs with spectral bandwidths exceeding an octave in the spectral region from the near-UV to the mid-IR is demonstrated by specific examples. (nonlinear optical phenomena)

160

A spectrally efficient transmission scheme for signals with large bandwidth  

OpenAIRE

In this paper we consider single-carrier with frequency-domain equalization (SC-FDE) schemes where the transmission bandwidth is above the symbol rate. To allow high spectral efficiencies, several channels share the same bandwidth. Since the co-channel interference (CCI) levels can be very high, we propose iterative FDE receivers where we jointly detect all users sharing the same channel. Our performance results show that we can have excellent performances, even with seve...

Silva, Paulo; Dinis, Rui

2012-01-01

161

Heuristics for Bandwidth Reservation in Multihop Wireless Networks  

OpenAIRE

We propose three heuristics to compute QoS routes in a multihop wireless networks considering interferences constraints. It has been proved that reservation under such conditions is an NP-complete problem. Our heuristics are based on Dijkstra's shortest path algorithm in which we integrate the notion of bandwidth capacity in order to satisfy flows requirements.We show with several simulations that these heuristics not only allows computation of routes that save bandwidth of nodes with low cap...

Allard, Ge?raud; Jacquet, Philippe

2004-01-01

162

A new generalized particle approach to parallel bandwidth allocation  

OpenAIRE

This paper presents a new generalized particle (GP) approach to dynamical optimization of network bandwidth allocation, which can also be used to optimize other resource assignments in networks. By using the GP model, the complicated network bandwidth allocation problem is transformed into the kinematics and dynamics of numerous particles in two reciprocal dual force-fields. The proposed model and algorithm are featured by the powerful processing ability under a complex environment that invol...

Feng, X.; Lau, Fcm; Shuai, D.

2006-01-01

163

Large bandwidth, highly efficient optical gratings through high index materials  

OpenAIRE

We analyze the diffraction characteristics of dielectric gratings that feature a high index grating layer, and devise, through rigorous numeri-cal calculations, large bandwidth, highly efficient, high dispersion dielectric gratings in reflection, transmission, and immersed transmission geometry. A dielectric TIR grating is suggested, whose ?1dB spectral bandwidth is doubled as compared to its fused silica equivalent. The short wavelength diffraction efficiency is additionally improved by al...

Rathgen, Helmut; Offerhaus, H. L.

2009-01-01

164

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

165

On the Bandwidth of High-Impedance Frequency Selective Surfaces  

OpenAIRE

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 g...

Costa, Filippo; Genovesi, Simone; Monorchio, Agostino

2010-01-01

166

Improvement of CBQ for bandwidth reclamation of RPR  

Science.gov (United States)

The Resilient Packet Ring (RPR) IEEE 802.17 standard is under development as a new high-speed backbone technology for metropolitan area networks (MAN) [1]. Bandwidth reclamation has been concerned in RPR specifications from draft 0.1 to draft 2.4. According to specifications, allocated bandwidth can be reused, or reclaimed, by a lower priority service class whenever the reclamation does not effect the service guarantees of any equal or higher priority classes on the local station or on any other station on the ring [2]. The class-based queuing (CBQ) algorithm is proposed to implement link-sharing [3]. A hierarchical link-sharing structure can be used to specify guidelines for the distribution of 'excess" bandwidth [4] and it can rate-limit all classes to their allocated bandwidth. There is some sameness between the link-sharing of CBQ and bandwidth reclamation of RPR. The CBQ is a mature technology while RPR is a new technology. Given CBQ improvement and full use so as to make its thought suitable for bandwidth reclamation of RPR is the focus of our work. In this paper, we present the solution that can solve the reclamation problem, which proves to be effective by simulation.

Huang, Benxiong; Wang, Xiaoling; Xu, Ming; Shi, Lili

2004-04-01

167

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

168

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

169

High-power microwave bandwidth broadening by air breakdown  

Science.gov (United States)

Wideband, high-power microwave pulses are expected to have important applications in ultra-wideband radar. The wide bandwidth should generate increased information for target characterization and identification. The high power should result in increased target detection range for conventional targets and targets with reduced signatures. A way to generate wideband, high-power microwave pulses with relatively conventional technology is to tail erode high-power pulses by passage through a low pressure air cell. In this process, the tails of short (3 to 10 ns), high amplitude (greater than 1 MV/m) pulses are removed. This erosion shortens the pulses and generates transmitted pulses with broadened bandwidths. The pressure must be matched to several incident pulse characteristics to create enough electron density to cause strong tail erosion. The important pulse characteristics are amplitude, frequency, pulse length, and pulse shape. We have shown experimentally that tail erosion from air breakdown broadens the 3 dB bandwidths of 2.8608 GHz incident pulses in a rectangular waveguide at 3.5 torr. The incident pulse amplitude varied from 0.67 to 1.16 MV/m. The pulse bandwidth increased from 0.147 GHz by 0.34 to 1.4 pct. relative. The incident bandwidth was 5.12 pct. relative to the incident carrier frequency. This experimental broadening was simulated with a 2D, electromagnetic, electron fluid computer code for avalanche ionization. The simulation predicted bandwidth broadening by 0.029 to 0.13 GHz or 1.0 to 4.4 pct. relative for a peak initial electron density of 10 electrons/cu cm. Although the measured and calculated transmitted electric field envelopes were in close agreement, the calculated bandwidths exceeded those measured by 13 to 47 pct. Because the detectors were not fast enough to resolve individual cycles we presently conclude that the simulation gives better estimates of reality than do the measurements.

Mayhall, D. J.; Yee, J. H.; Alvarez, R. A.

1991-12-01

170

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

171

A Distributed Dynamic Bandwidth Allocation Algorithm in EPON  

Directory of Open Access Journals (Sweden)

Full Text Available EPON (Ethernet Passive Optical Network is a rising bandwidth access technology, and it could realize the comprehensive operation access including data, video, and voice, with good economic characters. IEEE 802.3ah is the industrial standard of EPON, but it doesn’t concretely regulate the uplink bandwidth allocation algorithm of EPON. Therefore, aiming at the uplink channel access of EPON, people have put forward various dynamic bandwidth allocation algorithms, but most of them belong to intensive algorithm, i.e. the distributed bandwidth allocation (DBA algorithm runs in OLT which is the interceder to allocate the uplink transmission time slot for ONU. A new distributed dynamic bandwidth allocation algorithm (DDBA is proposed in this article, in which ONU decides the size of transmission window based on the assistant information transmitted by OLT and self queue length. The simulation result indicates that comparing with IPACT (Interleaved Poling with Adaptive Cycle Time (G. Kramer, 2002, P.89-107, under the high network load, DDBA could obviously improve the average end-to-end time delay and the average queue length.

Feng Cao

2010-06-01

172

Correlation and image compression for limited-bandwidth CCD.  

Energy Technology Data Exchange (ETDEWEB)

As radars move to Unmanned Aerial Vehicles with limited-bandwidth data downlinks, the amount of data stored and transmitted with each image becomes more significant. This document gives the results of a study to determine the effect of lossy compression in the image magnitude and phase on Coherent Change Detection (CCD). We examine 44 lossy compression types, plus lossless zlib compression, and test each compression method with over 600 CCD image pairs. We also derive theoretical predictions for the correlation for most of these compression schemes, which compare favorably with the experimental results. We recommend image transmission formats for limited-bandwidth programs having various requirements for CCD, including programs which cannot allow performance degradation and those which have stricter bandwidth requirements at the expense of CCD performance.

Thompson, Douglas G.

2005-07-01

173

A novel dynamic wavelength bandwidth allocation scheme over OFDMA PONs  

Science.gov (United States)

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

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

2011-12-01

174

Bandwidth selection for smooth backfitting in additive models  

CERN Document Server

The smooth backfitting introduced by Mammen, Linton and Nielsen [Ann. Statist. 27 (1999) 1443-1490] is a promising technique to fit additive regression models and is known to achieve the oracle efficiency bound. In this paper, we propose and discuss three fully automated bandwidth selection methods for smooth backfitting in additive models. The first one is a penalized least squares approach which is based on higher-order stochastic expansions for the residual sums of squares of the smooth backfitting estimates. The other two are plug-in bandwidth selectors which rely on approximations of the average squared errors and whose utility is restricted to local linear fitting. The large sample properties of these bandwidth selection methods are given. Their finite sample properties are also compared through simulation experiments.

Mammen, E; Mammen, Enno; Park, Byeong U.

2005-01-01

175

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

176

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)

177

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

178

Delivery of very high bandwidth with ATM switches and SONET  

Energy Technology Data Exchange (ETDEWEB)

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

Gossage, S.A.

1993-08-01

179

Performance Investigation of Virtual Private Networks with Different Bandwidth Allocations  

CERN Document Server

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

Natarajan, Mahalakshmi Chidambara; Nachiappan, Alamelu

2010-01-01

180

Demonstration of wide bandwidth energy harvesting from vibrations  

International Nuclear Information System (INIS)

We experimentally demonstrate a true wide bandwidth vibration energy harvester based on piezoelectric transduction. Our device is designed to work specifically off-resonance under sinusoidal input vibrations with constant displacement amplitudes. The same device displays wide bandwidth operation under vibrations with constant acceleration amplitudes. We have achieved over 6 nW of wide bandwidth power extraction per active piezoelectric patch between 80–180 Hz for constant 100 µm displacement amplitude, and across 20–90 Hz for constant 3g acceleration amplitude. Simulation of the micro-harvester with optimally fabricated piezoelectric material demonstrates over 1 µW of power across the same frequencies, enabling a fully integrated, self-powered wireless sensor node. (paper)

181

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

182

Wavelength and bandwidth tunable photonic stopband of ferroelectric liquid crystals.  

Science.gov (United States)

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

Ozaki, Ryotaro; Moritake, Hiroshi

2012-03-12

183

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

184

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

185

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

186

Fiber communications using convolutional coding and bandwidth-efficient modulation.  

Science.gov (United States)

In this paper we evaluate numerically the advantage of combining convolutional coding and bandwidth-efficient modulation. We compare different multilevel modulation formats, line codes, and hard/soft decision decoding. Compared with DPSK modulation (with the same bandwidth and information transmission rate), an improvement of almost 5 dB is observed for bit error rates around 10-8. We also study the robustness to intersymbol interference in the form of chromatic dispersion, and find that the improvement of the coded transmission lines improves over the uncoded even in presence of chromatic dispersion. PMID:19503369

Wuth, Torsten; Agrell, Erik; Karlsson, Magnus; Sköld, Mats

2006-01-23

187

Bandwidth Modeling and Estimation in Peer to Peer Networks  

OpenAIRE

Recent studies have shown that the majority of today's internet traffic is related to Peer to Peer (P2P) traffic. The study of bandwidth in P2P networks is very important. Because it helps us in more efficient capacity planning and QoS provisioning when we would like to design a large scale computer networks. In this paper motivated by the behavior of peers (sources or seeds) that is modeled by Ornstein Uhlenbeck (OU) process, we propose a model for bandwidth in P2P networks...

Kiarash Mizanian; Mehdi Vasef; 3.Morteza Analoui

2010-01-01

188

VISA IB Ultra-High Bandwidth, High Gain SASE FEL  

CERN Document Server

The results of a high energy-spread SASE FEL experiment, the intermediary experiment linking the VISA I and VISA II projects, are presented. A highly chirped beam (~1.7%) was transported without correction of longitudinal aberrations in the ATF dogleg, and injected into the VISA undulator. The output FEL radiation displayed an uncharacteristicly large bandwidth (~11%) with extremely stable lasing and measured energy of about 2 microJoules. Start-to-end simulations reproduce key features of the measured results and provide an insight into the mechanisms giving rise to such a high bandwidth. These analyses are described as they relate to important considerations for the VISA II experiment.

Andonian, Gerard; Murokh, Alex; Pellegrini, Claudio; Reiche, Sven; Rosenzweig, J B; Travish, Gil

2004-01-01

189

Water and lipid separation using limited radio frequency pulse bandwidth  

International Nuclear Information System (INIS)

A new method for separating the spatial components of water and lipid in MR imaging is presented. The method entails the use of a limited radiofrequency (RF) pulse bandwidth together with either two-dimensional or three-dimensional scan sequences. The spectral components of water and lipid are separated by 3.5 ppm, e.g., 300 Hz for a 2-T magnet. For any linear magnetic field gradient and selective RF pulse with a bandwidth that is smaller than 3.5 ppm, the excited spins of proton in water and protons in lipid will be located in two separate and parallel sections along the field gradient axis

190

47 CFR 74.462 - Authorized bandwidth and emissions.  

Science.gov (United States)

...frequencies shall not exceed 12.5 kHz. For all remote pickup broadcast...frequencies shall not exceed 12.5 kHz on or after January 1, 2005...authorized bandwidths up to 30 kHz, the emissions shall comply...carrier power. (Sec. 5, 48 Stat. 1068; 47...

2010-10-01

191

The Learning Computer: Low Bandwidth Tool that Bridges Digital Divide  

Science.gov (United States)

This article reports on a project that explores strategies for narrowing the digital divide by providing a practicable e-learning option for the millions living outside the ambit of high performance computing and communication technology. The concept is introduced of a "learning computer," a low bandwidth tool that provides a simplified,…

Johnson, Russell; Kemp, Elizabeth; Kemp, Ray; Blakey, Peter

2007-01-01

192

Bandwidth utilization maximization of scientific RF communication systems  

Energy Technology Data Exchange (ETDEWEB)

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

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

1997-01-01

193

A Bandwidth Characterization Tool For MPEG-2 File  

CERN Document Server

This paper proposes the design and development of MPEG 2 Video Decoder to offer flexible and effective utilization of bandwidth services. The decoder is capable of decoding the MPEG 2 bit stream on a single host machine. The present decoder is designed to be simple, but yet effectively reconstruct the video from MPEG 2 bit stream.

Kugali, Sandeep; Sutagundar, A V

2009-01-01

194

47 CFR 15.35 - Measurement detector functions and bandwidths.  

Science.gov (United States)

...specified, measurements above 1000 MHz shall be performed using a minimum resolution bandwidth of 1 MHz. When average radiated emission...emission measurements below 1000 MHz, there also is a limit on the...specified, e.g. , see §§ 15.250, 15.252, 15.255,...

2010-10-01

195

47 CFR 74.535 - Emission and bandwidth.  

Science.gov (United States)

...above 15 GHz, in any 1 MHz reference bandwidth (BREF...percent up to and including 250 percent of the authorized...frequency by more than 250 percent of the authorized...frequencies below 1 GHz, and 1 MHz for operating frequencies...frequency by less than 250 percent of the...

2010-10-01

196

47 CFR 74.462 - Authorized bandwidth and emissions.  

Science.gov (United States)

...tolerance on frequencies 166.25 MHz or 170.15 MHz shall not exceed 25 kHz...emissions on frequencies above 25 MHz with authorized bandwidths up...than 100 percent up to and including 250 percent of the authorized...

2010-10-01

197

47 CFR 101.809 - Bandwidth and emission limitations.  

Science.gov (United States)

...operation on frequencies below 500 MHz in this service must not exceed the...Maximum Authorized Frequency band (MHz) Bandwidth (MHz) 3,700 to 4,200 1 20...200 1,2 40 13,200 to 13,250 25 21,200 to 23,600 1...

2010-10-01

198

On the Observance of Approximate Invariance of Effective Bandwidth with Finite Number of Sources  

OpenAIRE

The effective bandwidth is a descriptor in the context of stochastic models for statistical sharing of resources. One of the most interesting properties of effective bandwidth is that it does not change when passing a network node under many s...

Kishore Angrishi; Ulrich Killat

2009-01-01

199

Bandwidth efficient block codes for M-ary PSK modulation  

Science.gov (United States)

A class of bandwidth efficient block codes for M-ary PSK modulation is presented. A soft-decision decoding for this class of codes is devised. Some specific short codes for Quad Phase Shift Key (QPSK), 8-PSK and 16-PSK modulations are constructed. These codes have good minimum squared Euclidean distances and provide 2 to 5.8 dB coding gains over uncoded QPSK modulation without (or with little) bandwidth expansion. The complete weight distributions of these specific codes are determined. Based on these weight distributions, their error probabilities are evaluated. Some of these codes have simple trellis structures and hence can be decoded by Viterbi decoding algorithm with relatively simple implementation. Moreover, the codes are very suitable for use as inner codes for various cascaded coding schemes with Reed-Solomon codes as outer codes.

Lin, Shu

1987-01-01

200

Optical tunneling of single-cycle terahertz bandwidth pulses  

Science.gov (United States)

We report time-domain measurements with subpicosecond resolution of optical tunneling of terahertz electromagnetic pulses undergoing frustrated total internal reflection. Measurements of the transmitted electromagnetic pulses over a 3 THz bandwidth permits direct determination of frequency-dependent phase and amplitude changes in both the thin and opaque barrier limits in a single measurement. A complex frequency response function describing propagation through the barrier is developed based upon linear dispersion theory and the Fresnel coefficients at complex angles in the optical barrier. Our measurements are in excellent agreement with this theoretical model across the experimentally determined bandwidth; the model makes no assumptions about the beam path through the barrier and has no adjustable parameters. The theory is shown to satisfy the Kramers-Kronig relations, indicating causal propagation across the barrier.

Reiten, M. T.; Grischkowsky, D.; Cheville, R. A.

2001-09-01

201

Quantitative space-bandwidth product analysis in digital holography.  

Science.gov (United States)

The space-bandwidth product (SBP) is a measure for the information capacity an optical system possesses. The two information processing steps in digital holography, recording, and reconstruction are analyzed with respect to the SBP. The recording setups for a Fresnel hologram, Fourier hologram, and image-plane hologram, which represent the most commonly used setup configurations in digital holography, are investigated. For the recording process, the required SBP to ensure the recording of the entire object information is calculated. This is accomplished by analyzing the recorded interference pattern in the hologram-plane. The paraxial diffraction model is used in order to simulate the light propagation from the object to hologram-plane. The SBP in the reconstruction process is represented by the product of the reconstructed field-of-view and spatial frequency bandwidth. The outcome of this analysis results in the best SBP adapted digital holographic setup. PMID:22192996

Claus, Daniel; Iliescu, Daciana; Bryanston-Cross, Peter

2011-12-01

202

A plasmonic infrared photodetector with narrow bandwidth absorption  

Science.gov (United States)

A plasmonic infrared photodetector with narrow bandwidth infrared absorption was investigated. The structure is constructed by a hydrogenated amorphous silicon (a-Si:H) film covered on a patterned Au layer consisting of the Au disk resonators and Au interdigitated electrodes on an Al2O3/Au substrate. This device exhibited narrow bandwidth infrared absorption corresponded to the localized surface plasmon resonance in the Au-disk/Al2O3/Au tri-layers resonators. The absorption of infrared energy heats up the top hydrogenated amorphous silicon film and reduces the film resistance which can be detected. The optical and electrical characteristics of the photodetector were studied. It was founded that the peak responsivities appeared at the wavelength which coincided with the localized surface plasmon resonance.

Chen, Hung-Hsin; Su, Yan-Chi; Huang, Wei-Lun; Kuo, Chun-Yen; Tian, Wei-Cheng; Chen, Miin-Jang; Lee, Si-Chen

2014-07-01

203

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

204

A wide-bandwidth and high-sensitivity robust microgyroscope  

International Nuclear Information System (INIS)

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

205

Available Network Bandwidth Schema to Improve Performance in TCP Protocols  

Directory of Open Access Journals (Sweden)

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

Marcos Talau

2013-09-01

206

High bandwidth on-chip silicon photonic interleaver.  

Science.gov (United States)

We demonstrate a 120 GHz 3-dB bandwidth on-chip silicon photonic interleaver with a flat passband over a broad spectral range of 70 nm. The structure of the interleaver is based on an asymmetric Mach-Zehnder interferometer (MZI) with 3 ring resonators coupled to the arms of the MZI. The transmission spectra of this device depict a rapid roll-off on the band edges, where the 20-dB bandwidth is measured to be 142 GHz. This device is optimized for operation in the C-band with a channel crosstalk as low as -20 dB. The device also has full reconfiguration capability to compensate for fabrication imperfections. PMID:21164649

Luo, Lian-Wee; Ibrahim, Salah; Nitkowski, Arthur; Ding, Zhi; Poitras, Carl B; Ben Yoo, S J; Lipson, Michal

2010-10-25

207

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

208

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

209

A comparative study of new cross-validated bandwidth selectors for kernel density estimation  

OpenAIRE

Recent contributions to kernel smoothing show that the performance of cross-validated bandwidth selectors improve significantly from indirectness. Indirect crossvalidation first estimates the classical cross-validated bandwidth from a more rough and difficult smoothing problem than the original one and then rescales this indirect bandwidth to become a bandwidth of the original problem. The motivation for this approach comes from the observation that classical crossvalidation...

Mammen, Enno; Miranda, Maria Dolores Martinez; Nielsen, Jens Perch; Sperlich, Stefan

2012-01-01

210

Bandwidth-Unlimited, Dispersion-Free Tunable Optical Delay Using a Prism Pair  

OpenAIRE

We report a nearly perfect bandwidth-unlimited, dispersion-free tunable optical delay system using a prism pair. The observed delay-bandwidth product using a 25-femtosecond light pulse is ~7x104, where the delay time is independent of the signal bandwidth. The present technique breaks from the conventional methods constrained by delay-bandwidth product, nontunability, and delay time dependent optical loss.

Kim, C.; Ham, B. S.

2009-01-01

211

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

OpenAIRE

IEEE 802.16 network protocol is designed to provide a Worldwide Interoperability for Microwave Access (WiMAX). Due to limited bandwidth and an expensive radio spectrum available for communication, it is necessary to use one bandwidth more than one time in a same network when it became unused. For that purpose “Bandwidth Recycling” concept is introduced. The spectrum (bandwidth) is specifically allocated by agency to various users, but many times it is seen that the spectrum is not fully u...

Verulkar, Nilesh M.; Bhadade, Dr Umesh S.

2014-01-01

212

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

213

Bootstrapping techniques to improve the bandwidth of transimpedance amplifiers.  

OpenAIRE

Transimpedance amplifiers using voltage feedback operational amplifiers are widely used for current to voltage conversion in applications when a moderate/high bandwidth and a high sensitivity are required, such as photodiodes, photomultipliers, electron multipliers and capacitive sensors. The conventional circuit presents a virtual earth to the input and at low frequencies, the input capacitance is usually not a significant concern. However, at high frequencies and especially for high sensiti...

Hoyle, C.; Peyton, A. J.

1998-01-01

214

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

215

A Bandwidth Sharing Approach to Improve Licensed Spectrum Utilization  

OpenAIRE

The spectrum of deployed wireless cellular communication systems is found to be underutilized, even though licensed spectrum is at a premium. To efficiently utilize the bandwidth left unused in a cellular system, the primary system (PRI), we propose an overlaid ad hoc secondary network (ASN) architecture, with the ASN operating over the resources left unutilized by the PRI. Our basic design principle is that the ASNoperates in a nonintrusive manner and does not interact with the PRI. In this ...

Papadimitratos, P.; Sankaranarayanan, S.; Mishra, A.

2005-01-01

216

The Discrepancy Principle for Choosing Bandwidths in Kernel Density Estimation  

OpenAIRE

We investigate the discrepancy principle for choosing smoothing parameters for kernel density estimation. The method is based on the distance between the empirical and estimated distribution functions. We prove some new positive and negative results on L_1-consistency of kernel estimators with bandwidths chosen using the discrepancy principle. Consistency crucially depends on a rather weak H\\"older condition on the distribution function. We also unify and extend previous res...

Mildenberger, Thoralf

2011-01-01

217

Optimization of bandwidth in 60^o photonic crystal waveguide bends  

DEFF Research Database (Denmark)

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

Xing, P. F.; Borel, Peter Ingo

2005-01-01

218

Dynamic Bandwidth Provisioning and Malleable Bulk Data Transfer Scheduling  

OpenAIRE

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

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

2008-01-01

219

Transverse flow imaging based on photoacoustic Doppler bandwidth broadening  

OpenAIRE

We propose a new method to measure transverse flow velocity based on photoacoustic Doppler bandwidth broadening, which is determined by the geometry of the probe-beam and the velocity of the transverse flow. By exploiting pulsed laser excitation and raster motor scanning, three-dimensional structure and flow velocity can be imaged simultaneously. In addition, the flow direction can be determined with bidirectional scanning. In a flowing suspension of red-dyed microspheres (diameter: 6 ?m), t...

Yao, Junjie; Wang, Lihong V.

2010-01-01

220

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

221

Designing large-bandwidth planar photonic crystal waveguides  

DEFF Research Database (Denmark)

Our waveguide design is characterized by first of all a large bandwidth, and secondly it is characterized by a relatively high group velocity giving a better modal dispersion match with the modes of standard waveguides used for coupling light into the planar crystal waveguide (PCW). We consider the dispersion properties for a PCW based on introducing a line defect in a photonic crystal with air-holes arranged periodically on a triangular lattice in silicon.

Lavrinenko, Andrei; SØndergaard, Thomas

2002-01-01

222

High-bandwidth polarimeter for a high density, accelerated spheromak.  

Science.gov (United States)

A three-beam heterodyne polarimeter has been built to diagnose the PI-1 plasma injector at General Fusion, Inc. The polarimeter measures plasma density and Faraday rotation, which can provide estimates of magnetic field magnitude and direction. Two important calibration steps are required for the polarimeter to produce reasonable Faraday rotation signals. Beam polarization ellipticity must be measured to ensure there is a linear Faraday rotation response. In addition, the two beams travelling through the plasma must be collinear to reduce error due to differences in plasma density. Once calibrated, the Faraday rotation signals are in much better agreement with other diagnostics. For a null signal, the Faraday rotation measurement noise floor is 0.1° at 0.5 MHz bandwidth. Comparing preliminary spheromak Faraday rotation measurements to a model, the maximum error is about 0.3° at 0.5 MHz bandwidth, which is primarily due to electrical noise during the injector's capacitor discharge and limitations of the model. At a bandwidth of 0.5 MHz, the polarimeter has an axial resolution between 6 cm and 30 cm depending on the speed of the spheromak, which varies between 30 km/s and 150 km/s. The spheromak length ranges from 0.75 m to 2 m. Additional polarimeter chords will be added in future upgrades. PMID:24007066

Carle, Patrick J F; Howard, Stephen; Morelli, Jordan

2013-08-01

223

High-bandwidth polarimeter for a high density, accelerated spheromak  

International Nuclear Information System (INIS)

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

224

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

225

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

226

High-bandwidth polarimeter for a high density, accelerated spheromak  

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-08-15

227

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

228

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

Directory of Open Access Journals (Sweden)

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

Nilesh M. Verulkar

2014-06-01

229

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

Directory of Open Access Journals (Sweden)

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

Norashidah Md Din

2008-05-01

230

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

231

Dynamic Bandwidth Allocation Performance for Dual QoS Classes in Resilient Packet Ring  

Science.gov (United States)

This paper proposes an improved dynamic bandwidth allocation algorithm for dual Quality of Service (QoS) classes to maximize the utilization rate of the Resilient Packet Ring (RPR). To achieve dynamic bandwidth allocation for the two QoS classes in the RPR, each node measures the high priority traffic flow and assigns the appropriate bandwidth; the remaining bandwidth is used for low priority traffic. It passes a control frame containing the measured bandwidth of the high priority traffic to the other nodes. Based on the advertised high priority traffic bandwidth, any node that is congested transmits, to the other nodes, a fairness message to fairly allocate the remaining low priority bandwidth. Simulations demonstrate that the proposed algorithm enhances the utilization rate and reduces the delay of high priority frames.

Okumura, Yasuyuki

232

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

233

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

234

Theoretical and experimental investigation of ac space-charge effect on gain and bandwidth of two- and three-cavity gyroklystrons with TE011 operating mode  

Science.gov (United States)

Both a small signal approach for ac space-charge effects on beam bunching in the gyroklystron drift tube and nonlinear self-consistent field slow-time scale ballistic theory are applied to investigate the wideband gyroklystron gain including the beam velocity spread effects. The analysis of ac space-charge effects on beam bunching, based on the parameters of existing electron guns, results in the possibility of the wideband amplification in the tremendously high gain gyroklystron using the drift tube of the approximately 20 (lambda) length or more. The test results of the IAP two-stage, 16kV, 3A, 20dB gyroklystron operating in TE011 mode are presented and discussed. Also, the test results of the Tory TE011 three-stage, 50kV, 14A gyroklystron are discussed. Having the first drift tube of the approximately 10 (lambda) length, this gyroklystron demonstrates the 40dB gain, the 1.3% bandwidth, and the 230kW output saturated power.

Keyer, Alexander P.; Aksenova, Ludmila A.; Agapova, M. V.; Myasnikov, Vadim E.; Musatov, Vladimir S.; Popov, Leonid G.; Sokolov, Evgeny V.; Zasypkin, Evgeny V.

1995-09-01

235

Wide-bandwidth piezoelectric energy harvester with polymeric structure  

Science.gov (United States)

A polymer based energy harvester with wide bandwidth is designed, fabricated and tested in this work. A polymer based structure has a lower resonance frequency compared to a silicon based structure with the same dimensions due to the much lower stiffness of polymeric materials. Therefore, a polymeric energy harvester is more useful for situations with lower ambient vibration frequencies. Aluminum nitride pads are fabricated on an SU-8 membrane to convert mechanical vibration of the membrane to electrical voltage. A new and scalable microfabrication process flow is proposed to properly fabricate piezoelectric layers on SU-8 structures. The nonlinear stiffness due to the stretching strain in the membrane provides a wider harvestable frequency bandwidth than conventional linear oscillators. Wideband energy harvesters are more useful for practical applications due to uncontrollable ambient vibration frequency. The load-deflection equation of the device is calculated using finite element simulation. This equation is then used in an analytical solution to estimate the nonlinear effect of the structure. A bandwidth of ~146?Hz is obtained for the fabricated device and a maximum open circuit voltage of 1.42?V, maximum power of 1.37?µW, and power density of 3.81?µW?cm?2 were measured at terminal load of 357.4?k? under an excitation acceleration of 4?g. A power output of 10.1?µW and power density of 28.1?µW?cm?2 was estimated using a synchronized switch harvesting on interface (SSHI) electrical interface with electrical quality factor of 5. In addition, the lumped element model has been employed to investigate the scaling effect on a polymeric circular diaphragm.

Rezaeisaray, Mehdi; El Gowini, Mohamed; Sameoto, Dan; Raboud, Don; Moussa, Walied

2015-01-01

236

Optimization of bandwidth of communication channels of corporate networks  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction. This article contains overview of the organization of communication between applications on the corporate network. It is stated that the main digital channel (channel B - 64 kbit/s and the primary digital channel (channel E1 the digital stream - 2048 kbit/s are used as the main channels in corporate networks. Problem areas of the functioning of the corporate network are identified. There are the rent of communication channels, which is growing rapidly with increasing the quality and speed of data transmission, and optimal use of bandwidth of communication channels. Setting of task. Optimal use of transmission channels bandwidth and minimizing the rent cost of channels is possible in two ways - the use of compression techniques of voice and video information and the application of variable structure of channels by using various-speed transmission channels. Differential pulse code modulation, adaptive differential pulse code modulation are the modern methods of speech signals processing. Organization of various-speed channels is performed in the structure of the BCC (for speech signals or PCR (for video. Suggestions for optimizing the structure of the channel signals. Proposed method of various-speed channels formation by using the channel intervals appropriate BCC (octets in the structure of signals E1 as envelopes containing various-speed channels. Channels can be selected for synchronization procedure CRC to simplify recognition of channels in the structure of E1. In this case, the minimal speed in the channel is 4 kbit/s. Conclusions. The proposed structure of envelopes is based on octet channel intervals of standard group signal of the primary group plesiochronous hierarchy E1 when transferring various-speed digital signals maximum allows to use the bandwidth at a fixed structure of channel interval, it makes possible to agree on the structure of the various-speed signals with the existing in communication networks.

G. I. Bondarenko

2014-09-01

237

Space-Bandwidth Capacity-Enhanced Digital Holography  

Science.gov (United States)

We propose a single-shot digital holography in which the space bandwidth available for recording an object wave can be extended in an off-axis configuration. The key points of this technique are utilizing the periodicity of a digital signal and the undersampling, intentionally setting the aliasing to the recorded hologram, and conducting spatial-carrier phase-shifting interferometry and the Fourier transform method. The image quality for both large objects and fine structures can be improved by the keys. The effectiveness of the proposed technique was numerically and experimentally demonstrated. Then, the performance and the optimal angle condition were quantitatively analyzed.

Tahara, Tatsuki; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Matoba, Osamu; Kubota, Toshihiro

2013-02-01

238

Stop bandwidths of nonlinear beam-beam resonances  

International Nuclear Information System (INIS)

A general expression is given for the stop bandwidths, ??/sub N/, of nonlinear beam-beam resonances, which is expanded in powers of Y(s), the vertical beam orbit, and which is valid under certain assumptions regarding the orbits and charge distributions near the interaction regions. This result is applied to obtain results for the rms ??/sub N/ due to random vertical orbit errors, and due to random errors in ?/sub y/ at the crossing points. Numerical results are given for the ISABELLE storage accelerator

239

Frequency Bandwidth of Half-Wave Impedance Repeater  

Directory of Open Access Journals (Sweden)

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

Marek Dvorsky

2012-01-01

240

Efficient and Fair Bandwidth Allocation AQM Scheme for Wireless Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Heterogeneous Wireless Networks are considered nowadays as one of the potential areas in research and development. The traffic management’s schemes that have been used at the fusion points between the different wireless networks are classical and conventional. This paper is focused on developing a novel scheme to overcome the problem of traffic congestion in the fusion point router interconnected the heterogeneous wireless networks. The paper proposed an EF-AQM algorithm which provides an efficient and fair allocation of bandwidth among different established flows. Finally, the proposed scheme developed, tested and validated through a set of experiments to demonstrate the relative merits and capabilities of a proposed scheme

Rafe Alasem

2010-05-01

241

Introducing a Performance Model for Bandwidth-Limited Loop Kernels  

CERN Document Server

We present a performance model for bandwidth limited loop kernels which is founded on the analysis of modern cache based microarchitectures. This model allows an accurate performance prediction and evaluation for existing instruction codes. It provides an in-depth understanding of how performance for different memory hierarchy levels is made up. The performance of raw memory load, store and copy operations and a stream vector triad are analyzed and benchmarked on three modern x86-type quad-core architectures in order to demonstrate the capabilities of the model.

Treibig, Jan

2009-01-01

242

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

243

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

244

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

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

Applying genetic algorithm for the bandwidth allocation of ATM nets  

Science.gov (United States)

In this paper, we develop an improved optimization algorithm based on genetic algorithm (GA) approach for the bandwidth allocation of ATM networks. The ATM switches can be connected with multiples of DS3 trunks via digital cross connect systems (DCS). One of the advantages of DCS is its ability to reconfigure a customer network dynamically. We utilize this advantage in the design and dynamic reconfiguration of ATM networks. The problem is formulated as a network optimization problem where a congestion measure based on the average packet delay is minimized, subject to capacity constraints posed by the underlying facility trunks. We choose the traffic routing on the express pipes and the allocation of the bandwidth on these pipes as the variables in this problem. The previous GA algorithm is not practical because (1) the number of the traffic distribution patterns is huge, and (2) the values of offered traffic are continuous. A new representation of the chromosome, Net- Chro, and the reproduction operator are presented. We show that the previous algorithm cannot guarantee full usage of trunk capacities in the solutions it generates. We also discuss open-loop control to overcome the congestion caused by a trunk failure.

Park, Fransis Y.; Wong, Edward K.

1996-11-01

247

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.

248

Modulator-Based, High Bandwidth Optical Links for HEP Experiments  

CERN Document Server

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

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

2012-01-01

249

A wide bandwidth electrostatic field sensor for lightning research  

Science.gov (United States)

Data obtained from UHF radar observation of direct-lightning strikes to the NASA F-106B aircraft have indicated that most of the 690 strikes acquired during direct-strike lightning tests were triggered by the aircraft. As an aid in understanding the triggered lightning process, a wide bandwidth electric field measuring system was designed for the F-106B by implementing a clamped-detection signal processing concept originated at the Air Force Cambridge Research Lab in 1953. The detection scheme combines the signals from complementary stator pairs clamped to zero bolts at the exact moment when each stator pair is maximally shielded by the rotor, a process that restores the dc level lost by the charge amplifier. The system was implemented with four shutter-type field mills located at strategic points on the aircraft. The bandwidth of the system was determined in the laboratory to be from dc to over 100 Hz, whereas past designs had upper limits of 10 to 100 Hz. To obtain the undisturbed electric field vector and total aircraft charge, the airborne field mill system is calibrated by using techniques involving results from ground and flight calibrations of the F-106B, laboratory tests of a metallized model, and a finite difference time-domain electromagnetic computer code.

Zaepfel, Klaus P.

1989-01-01

250

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

251

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.

R. J. Haines

2007-03-01

252

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

253

A Bandwidth Allocation Model Provisioning Framework with Autonomic Characteristics  

Directory of Open Access Journals (Sweden)

Full Text Available 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 dynamic way. In effect, one of the basic motivations towards BAM dynamic allocation is the factthat multiservice networks characteristics (traffic loadmay change considerably in daily networkoperation and, as such, some dynamics in BAM allocation should be introduced in order to improveperformance. A framework is presented supporting BAM dynamicallocation. The framework adopts anOpenFlow-based software-defined networking (SDN implementation approach in order to supportscalability issues with a centralized controller and managementnetwork view. The framework architecturealso supports the implementation of some autonomic characteristics which, in brief, look for improving andfacilitating the decision-making process involved with BAM provisioning in a multiservice network. Aproof of concept is presented evaluating different BAM performance under different traffic loads in order todemonstrate the framework strategy adopted.

Rafael F. Reale

2013-11-01

254

Punctured Turbo Codes for Bandwidth-efficient Transmission  

Directory of Open Access Journals (Sweden)

Full Text Available Turbo codes are the error-coding schemes applied nowadays in wireless networks. In navalapplications, the information is mostly sent through wireless networks and the data is moreprone to noise. Since very important data has to be communicated, it is necessary to get backthe original data in the receiver. In military applications also, the soldiers wear electronic jacketswhich are connected by wireless networks. In such applications, the data loss is not affordableand there is also a need to utilise the bandwidth efficiently through puncturing by means ofwhich certain bits are deleted before transmission from the output of encoder. By means of thispunctured turbo codes, bandwidth-efficient coding is achieved. Hence, it is necessary to designturbo codes with an efficient puncturing pattern so that the performance of the punctured codeis also improved in spite of deletion of few bits before transmission. This paper deals in choosingthe puncturing patterns that lead to systematic rate-compatible punctured turbo codes (RCPTCswhich also give a reduction in bit-error rate. The design criterion for choosing the best puncturingpatterns is based on the minimum weight of code words and their multiplicities. The best puncturingpattern chosen is tested for its performance by simulating turbo codes for an additive whiteGaussian noise (AWGN channel. Compared with the existing puncturing pattern, the patternproposed is able to achieve a gain of 0.5 dB at a bit-error rate of 10-3.

Shobha Rekh

2006-10-01

255

Explicit Codes Minimizing Repair Bandwidth for Distributed Storage  

CERN Document Server

We consider the problem of data storage across n nodes in a distributed manner. A data collector (DC) should be able to reconstruct the entire data by connecting to any k out of the n nodes and downloading all the data stored in them. When a node fails, it has to be regenerated back using the existing nodes. In a recent paper, Wu et al. have obtained an information theoretic lower bound for the repair bandwidth. Recently, there has been additional interest in storing data in systematic form as no post processing is required when DC connects to k systematic nodes. Because of their preferred status there is a need to regenerate back any systematic node quickly and exactly. Replacement of a failed node by an exact replica is termed Exact Regeneration.In this paper, we consider the problem of minimizing the repair bandwidth for exact regeneration of the systematic nodes. The file to be stored is of size B and each node can store alpha = B/k units of data. A failed systematic node is regenerated by downloading bet...

Shah, Nihar B; Kumar, P Vijay; Ramchandran, Kannan

2009-01-01

256

Bandwidth Enhancement of Antenna Arrays Utilizing Mutual Coupling between Antenna Elements  

OpenAIRE

The mutual coupling effect between antenna elements on an array's bandwidth is investigated using scattering parameters instead of the mutual impedance. First, an approximate expression is derived for matched voltage standing wave ratio (VSWR) bandwidth of a tuned antenna, which reveals that the bandwidth is inversely proportional to the magnitude |?0'(?0)| of the frequency derivative of the reflection coefficient. Next, considering linear antenna arrays with corporat...

Zhongxiang Shen; Wen Wu; Min Wang

2010-01-01

257

Studi Perbandingan Protokol VoIP SIP dan IAX2 : Analisis Bandwidth  

OpenAIRE

VoIP are an networking implementation that should exist in Indonesia. The size of Bandwidth is a must constraint in every networking implementation. SIP and IAX2 are two text-based protocols that were be compared. Using Asteriskguru Online Bandwidth Calculator as comparing tools from both protocol. About 3.13 Kbps per call between SIP and IAX2 is the answer. IAX2 much more greater in bandwidth consumption.

Kalista, Salman

2011-01-01

258

Compensation of Finite Bandwidth Effect by Using an Optimal Filter in Photoacoustic Imaging  

OpenAIRE

Most existing reconstruction algorithms for photoacoustic imaging (PAI) assume that transducers used to receive ultrasound signals have infinite bandwidth. When transducers with finite bandwidth are used, this assumption may result in reduction of the imaging contrast and distortions of reconstructed images. In this paper, we propose a novel method to compensate the finite bandwidth effect in PAI by using an optimal filter in the Fourier domain. Simulation results de...

Chen Zhang; Yan Zhang; Yuanyuan Wang

2013-01-01

259

A Bandwidth-Aware Job Grouping-Based Scheduling on Grid Environment  

OpenAIRE

This study explores the feasibility of job scheduling strategies and extend the job grouping-based approach using the idea of bandwidth-awareness. As today`s best-effort network generally experiences low bandwidth and high delay, we aim to maximize the Grid resource utilization and reduce the delay by considering the bandwidth criterion. A simulation environment using GridSim is developed to model job scheduling process. Exploiting the simulation environment, a job scheduling strategy t...

Ang, T. F.; Ng, W. K.; Ling, T. C.; Por, L. Y.; Liew, C. S.

2009-01-01

260

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

261

Bandwidth Limitations of Nb/AlN/Nb SIS Mixers Around 700 GHz:  

OpenAIRE

We study, using niobium-technology, the bandwidth of SIS mixers operating at frequencies close to the energy-gap frequency. Microstriplines of niobium-silicon dioxide-niobium have different properties for the top and bottom superconductor, which we find to depend on the used fabrication process. Replacing the AlOx tunnel barrier by AlN, the bandwidth increases by 53%. The measurements, using a Fourier Transform Spectrometer (FTS) and performed in ambient air, demonstrate that the bandwidth is...

Lodewijk, C. F. J.; Zijlstra, T.; Zhu, S.; Mena, F. P.; Baryshev, A. M.; Klapwijk, T. M.

2009-01-01

262

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

OpenAIRE

In this paper, we quantitatively analyzed the trade-off between energy per bit for switching and modulation bandwidth of classical electro-optic modulators. A formally simple energy-bandwidth limit (Eq. 10) is derived for electro-optic modulators based on intra-cavity index modulation. To overcome this limit, we propose a dual cavity modulator device which uses a coupling modulation scheme operating at high bandwidth (> 200 GHz) not limited by cavity photon lifetime and simu...

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

2013-01-01

263

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

OpenAIRE

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

Lin, Di; Labeau, Fabrice

2012-01-01

264

The evolution and limits of spectral bandwidth in free electron lasers  

International Nuclear Information System (INIS)

We study the bandwidths in free electron lasers (FELs) under different circumstances; for weakly saturated FELs in storage rings, the bandwidth is given be the formula derived in the super mode theory, while it is given by the Fourier transform of the electron pulse length in the strongly saturated FELs in linacs. The limiting bandwidth for the case of a DC beam is given by a Schawlow-Townes formula, but the approach to the limit is very slow. 14 refs

265

Bandwidth and chirp characterisation of wavelength conversion based on electroabsorption modulators  

DEFF Research Database (Denmark)

It is demonstrated experimentally that the frequency chirp of a data modulated signal can be reduced and the modulation bandwidth increased through wavelength conversion in an electroabsorption modulator.

Xu, Lin; OxenlØwe, Leif Katsuo

2002-01-01

266

Refinements in reduced bandwidth MR imaging of the head at 1.5 T  

International Nuclear Information System (INIS)

Decreasing the sampling bandwidth can be used to reduce scan time at a constant signal-to-noise ratio or to increase the signal-to-noise ratio with a constant scan time. Advantages of the technique can be offset by increased chemical shift misregistration artifact (CSA), which can be problematic along the brain surface and in the orbit. Artifacts associated with reduced (half) bandwidth imaging were identified on intermediate T2-weighted images (2,000/30 [repetition time msec/echo time (TE) msec] from a prospective controlled study of 50 patients referred for magnetic resonance (MR) imaging of the head. These artifacts typically were reduced with greater T2 weighting. In healthy volunteers, the reduced bandwidth-associated CSAs could be minimized by fat suppression (using the Chopper fat suppression technique), for both early and late echoes. Based on these results, two head imaging strategies are proposed: (1) applying the bandwidth reduction only to late echoes in a multiecho study of the head (eg, 2,000/30, default bandwidth; 90-msec TE, half or quarter bandwidth), which results in approximately a 1.4-2 fold increase in signal-to-noise ratio in the late echo without CSA penalty; (2) implementing reduced bandwidth without CSA by a hybrid technique combining fat suppression and reduced bandwidth. This can be used to increase signal-to-noise ratios (all echoes), with CSA below levels observed for default bandwidth studies

267

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

268

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

269

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

270

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.

271

Optical preparation and measurement of atomic coherence at gigahertz bandwidth  

International Nuclear Information System (INIS)

We detail a method for the preparation of atomic coherence in a high-density atomic vapour of 87Rb, utilizing a coherent preparation scheme of off-resonant gigahertz bandwidth pulses. The scheme is found to be faster and more effective than techniques based on resonant interaction, such as coherent population trapping and population inversion. A numerical simulation of the preparation scheme is developed, and its efficiency in preparing coherent states is found to be close to unity at the entrance to the medium. The medium is then probed non-invasively with a laser field, the polarization of which is dependent upon the relative phase of the atomic coherence produced by the preparation fields. (paper)

272

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

273

Development of high frequency and wide bandwidth Johnson noise thermometry  

Science.gov (United States)

We develop a high frequency, wide bandwidth radiometer operating at room temperature, which augments the traditional technique of Johnson noise thermometry for nanoscale thermal transport studies. Employing low noise amplifiers and an analog multiplier operating at 2 GHz, auto- and cross-correlated Johnson noise measurements are performed in the temperature range of 3 to 300 K, achieving a sensitivity of 5.5 mK (110 ppm) in 1 s of integration time. This setup allows us to measure the thermal conductance of a boron nitride encapsulated monolayer graphene device over a wide temperature range. Our data show a high power law (T ˜ 4) deviation from the Wiedemann-Franz law above T ˜ 100 K.

Crossno, Jesse; Liu, Xiaomeng; Ohki, Thomas A.; Kim, Philip; Fong, Kin Chung

2015-01-01

274

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

275

Wide-Bandwidth Capture of Wire-Scanner Signals  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-05-16

276

Impedance Bandwidth and Gain Improvement for Microstrip Antenna Using Metamaterials  

Directory of Open Access Journals (Sweden)

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

H. Xiong

2012-12-01

277

High-bandwidth continuous-flow arc furnace  

Science.gov (United States)

A high-bandwidth continuous-flow arc furnace for stream welding applications includes a metal mass contained in a crucible having an orifice. A power source charges an electrode for generating an arc between the electrode and the mass. The arc heats the metal mass to a molten state. A pressurized gas source propels the molten metal mass through the crucible orifice in a continuous stream. As the metal is ejected, a metal feeder replenishes the molten metal bath. A control system regulates the electrode current, shielding gas pressure, and metal source to provide a continuous flow of molten metal at the crucible orifice. Independent control over the electrode current and shield gas pressure decouples the metal flow temperature and the molten metal flow rate, improving control over resultant weld characteristics.

Hardt, David E. (Concord, MA); Lee, Steven G. (Ann Arbor, MI)

1996-01-01

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

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.

2014-01-01

281

Scaling Mesa Indium Phosphide DHBTs to Record Bandwidths  

Science.gov (United States)

Indium phosphide heterojunction bipolar transistors are able to achieve higher bandwidths at a given feature size than transistors in the Silicon material system for a given feature size. Indium phosphide bipolar transistors demonstrate higher breakdown voltages at a given bandwidth than both Si bipolars and field effect transistors in the InP material system. The high bandwidth of InP HBTs results from both intrinsic material parameters and bandgap engineering through epitaxial growth. The electron mobility in the InGaAs base and saturation velocity in the InP collector are both approximately three times higher than their counterparts in the SiGe material system. Resistance of the base can be made very low due to the large offset in the valence band between the InP emitter and the InGaAs base, which allows the base to be doped on the order of 1020 cm-3 with negligible reduction in emitter injection efficiency. This thesis deals with type-I, NPN dual-heterojunction bipolar transistors. The emitters are InP, and the base is InGaAs. There is a thin (˜ 10 nm) n-type InGaAs "setback" region, followed by a chirped superlattice InGaAs/InAlAs grade to the InP collector. The setback, grade, and collector are all lightly doped n-type. The emitter and collector are contacted through thin (˜ 5 nm) heavily doped n-type InGaAs layers to reduce contact resistivity. The primary focus of this work is increasing the bandwidth of InP HBTs through the proportional scaling of the device dimensions, both layer thicknesses and junction areas, as well as the reduction of the contact resistivities associated with the transistor. Essentially, all RC time constants and transit times must be reduced by a factor of two to double a transistor's bandwidth. Chapter 2 describes in detail the scaling laws and design principles for high frequency bipolar transistor design. A low-stress, blanket sputter deposited composite emitter metal process was developed. Refractory metal base contacts were investigated with UCSB grown epitaxial material and the fabrication of transmission line model structures. Electron beam lithography processes were developed and employed for both emitter and base layers. Epitaxial designs were scaled and revised, and grown by a commercial vendor. These process developments are detailed in Chapter 3. Transistor electrical characteristics were measured using a semiconductor parameter analyzer at DC and network analyzers for RF measurements at frequencies up to 220 GHz. Both on- and off-wafer network analyzer calibration structures were designed and fabricated, and the calibration techniques were compared. New structures for transmission line model measurements of contact resistivity have been designed and used in the measurement of new ohmic contact processes. Measurement techniques are detailed in Chapter 4. Two transistor results are presented in Chapter 5. For each device, epitaxial designs are presented, and band diagrams, both without current flow and under peak bias conditions are shown. The processes used to fabricate each transistor are detailed. For the first result, referred to as DHBT 43, ftau = 360 GHz and fmax > 800 GHz was obtained with 200 nm wide emitter-base junctions and 150 nm thick collectors. For the second result, referred to as DHBT 60, ftau = 530 GHz and fmax = 750 GHz was obtained with 150 nm wide emitter-base junctions and 70 nm thick collectors. Both transistors feature a refractory emitter contact, and the second result uses electron-beam lithography to narrow the emitter-base and base-collector junction widths. DC measurements of common-emitter I-V curves and Gummel plots are used to extract device parameters like breakdown voltage, current gain, and base and collector ideality constants. On-wafer TLM structures are used to extract device base and collector resistance. S-parameter measurements at RF frequencies are used to extract cutoff frequencies ftau and fmax, as well as device parameters necessary to generate hybrid-& equivalent circuit models of the devices. These measurements a

Lobisser, Evan

282

Effects of finite-bandwidth driver pumps on the parametric-decay instability  

International Nuclear Information System (INIS)

The effects of a finite-bandwidth driver pump on the parametric-decay instability are investigated experimentally. The results include the dependence of threshold power, growth rate, and saturation level on the bandwidth of several coherently and randomly modulated pumps

283

Regulating Bandwidth Flow Estimation and Control for Wired/Wireless Networks  

Directory of Open Access Journals (Sweden)

Full Text Available In this topic, an analysis will be made on the problems faced by bandwidth constrained applications which comes under networking domain. For bandwidth constrained applications, a proper monitoring of available bandwidth is an important factor to avoid degradation in performance while execution. Such application example could be video or voice chat on Internet , which consumes more bandwidth and its overall performance is bandwidth constraint. 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. We propose to design and develop a system for 802.11 based ad-hoc networks, which estimate the network traffic bandwidth and control the flow of traffic on given channels. Our research would be capable to work on both wired and wireless ad-hoc network, On top of it, It would be able to show the simulation results on multiple computers.

Pallavi Sharma

2012-01-01

284

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

285

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

286

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.

287

Design and enhancement bandwidth rectangular patch antenna using single trapezoidal slot technique  

Directory of Open Access Journals (Sweden)

Full Text Available 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 microstrip patch Antenna with a trapezoidal slot. Microstrip patch antenna that meets the requirement of operation at 2.4 GHZ, the proposed configurations is simulated and analyzed using (CST- 2010 software package. The VSWR, input impedance‚ radiation patterns and S11 performance are used for the analysis of the different configurations. The simulated results for trapezoidal slot give bandwidth of 287.2 MHZ (11.93% fractional bandwidth. Feed point on the patch that gives a good Match of 50 ohm.

Karim A. Hamad

2012-03-01

288

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)

289

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

Science.gov (United States)

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

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

2014-11-17

290

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

291

Advanced processing for high-bandwidth sensor systems  

Science.gov (United States)

Compute performance and algorithm design are key problems of image processing and scientific computing in general. For example, imaging spectrometers are capable of producing data in hundreds of spectral bands with millions of pixels. These data sets show great promise for remote sensing applications, but require new and computationally intensive processing. The goal of the Deployable Adaptive Processing Systems (DAPS) project at Los Alamos National Laboratory is to develop advanced processing hardware and algorithms for high-bandwidth sensor applications. The project has produced electronics for processing multi- and hyper-spectral sensor data, as well as LIDAR data, while employing processing elements using a variety of technologies. The project team is currently working on reconfigurable computing technology and advanced feature extraction techniques, with an emphasis on their application to image and RF signal processing. This paper presents reconfigurable computing technology and advanced feature extraction algorithm work and their application to multi- and hyperspectral image processing. Related projects on genetic algorithms as applied to image processing will be introduced, as will the collaboration between the DAPS project and the DARPA Adaptive Computing Systems program. Further details are presented in other talks during this conference and in other conferences taking place during this symposium.

Szymanski, John J.; Blain, Phil C.; Bloch, Jeffrey J.; Brislawn, Christopher M.; Brumby, Steven P.; Cafferty, Maureen M.; Dunham, Mark E.; Frigo, Janette R.; Gokhale, Maya; Harvey, Neal R.; Kenyon, Garrett; Kim, Won-Ha; Layne, J.; Lavenier, Dominique D.; McCabe, Kevin P.; Mitchell, Melanie; Moore, Kurt R.; Perkins, Simon J.; Porter, Reid B.; Robinson, S.; Salazar, Alfonso; Theiler, James P.; Young, Aaron C.

2000-11-01

292

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

293

Review of single transient oscillographic recorders with gigahertz bandwidth  

International Nuclear Information System (INIS)

In laser driven inertial confinement fusion research, at Livermore, we are diagnosing many phenomena 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 the laser beam and fuel pellet are monitored to determine the specifics of the fusion process. By the use of appropriate detectors, we convert the information contained in the radiated by-products to electrical signals which are recorded on high bandwidth oscillographic recorders. Our present range of recording capabilities for one x-ray diagnostic measurement in use at Livermore is shown. A commonly used configuration consists of an XRD-31 x-ray detector connected to a direct access Tektronix R7912 transient digitizer using 1/2 in. diameter air dielectric coaxial cable. This configuration gives a system fwhm of approximately 335 ps. Our premier configuration, on the other hand, consists of an improved response detector and a French Thomson-CSF TSN-660 oscilloscope with a shorter length of coaxial cable (typically 20 feet). The system fwhm in this case is less than 120 ps which is our fastest oscillographic recording system at the present time

294

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

295

On the Observance of Approximate Invariance of Effective Bandwidth with Finite Number of Sources  

Directory of Open Access Journals (Sweden)

Full Text Available The effective bandwidth is a descriptor in the context of stochastic models for statistical sharing of resources. One of the most interesting properties of effective bandwidth is that it does not change when passing a network node under many sources limiting regime (infinitely many sources. This is referred as the “invariance property” of effective bandwidth. Numerical simulations have suggested that in some cases, the “invariance property” of effective bandwidths holds already for a surprisingly small number of competing flows even in the presence of aggressive TCP traffic. The real question, though, is: how many input processes are needed for reasonable convergence over the scale of interest? This work addresses this question using recent results from the large deviations theory under many sources limiting regime and the theory of statistical network calculus. We also show that as the number of arrival flows increases, the bound on the departure process’ effective bandwidth converges exponentially fast to that of the effective bandwidth of the arrival. The advantage of identifying the minimum number of independent multiplexing flows at each network node to observe approximate invariance of effective bandwidth is that the task of network resources dimensioning can be greatly simplified.

Kishore Angrishi

2009-11-01

296

Fixed tile rate codec for bandwidth saving in video processors  

Science.gov (United States)

The paper presents an image compression circuit for bandwidth saving in video display processors. This is intra frame tile based compression algorithm offering visually lossless quality for compression rates between 1.5 and 2.5. RGB and YCbCr (4:4:4, 4:2:2 and 4:2:0) video formats are supported for 8/10 bits video signals. The Band Width Compressor (BWC) consists of Lossless Compressor (LC) and Quantization Compressor (QC) that generate output bit streams for tiles of pixels. Size of output bit stream generated for a tile by the LC may be less or greater than a required size of output memory block. The QC generates bit stream that always fits output memory block of the required size. The output bit stream generated by the LC is transmitted if its size is less than the required size of the output memory block. Otherwise, the output bit stream generated by the QC is transmitted. The LC works on pixel basis. A difference between original and predicted pixel's values for each pixel of a tile is encoded as prefix and suffix. The prefix is encoded by means of variable length code, and suffix is encoded as is. The QC divides a tile of pixels on a set of blocks and quantizes pixels of each block independently of the other blocks. The number of quantization bits for all pixels of a block depends on standard deviation calculated over the block. A difference between pixel's value and average value over the block is quantized and transmitted.

Lachine, Vladimir; Dinh, Chon-Tam Le; Le, Dinh Kha; Wong, Jeffrey

2014-02-01

297

Improving precision in resonance ionization mass spectrometry: influence of laser bandwidth in uranium isotope ratio measurements.  

Science.gov (United States)

The use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of (235)U/(238)U ratios by resonance ionization mass spectrometry (RIMS) to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser in a three-color, three-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from 10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation. PMID:21410136

Isselhardt, B H; Savina, M R; Knight, K B; Pellin, M J; Hutcheon, I D; Prussin, S G

2011-04-01

298

Influence of the spectral bandwidth in the entanglement of a nondegenerate parametric amplifier  

CERN Document Server

We propose a simple model for the nondegenerate parametric inter- action that takes into account the finite spectral bandwidth of the pump wave. The Heisenberg equations of motion are solved exactly and we show that the bosonic operators obey to a generalized Bogoliubov transforma- tion, where the degree of squeezing depends on the spectral bandwidth. The average number of photons produced in the interaction, the degree of squeezing as well as the degree of entanglement are computed showing that they decrease with increasing spectral bandwidth.

Martins, Ana M

2012-01-01

299

Gain and noise bandwidth of NbN hot-electron bolometric mixers  

International Nuclear Information System (INIS)

We have measured the noise performance and gain bandwidth of 35 Angstrom thin NbN hot-electron mixers integrated with spiral antennas on silicon substrate lenses at 620 GHz. The best double-sideband receiver noise temperature is less than 1300 K with a 3 dB bandwidth of ?5 GHz. The gain bandwidth is 3.2 GHz. The mixer output noise dominated by thermal fluctuations is 50 K, and the intrinsic conversion gain is about -12 dB. Without mismatch losses and excluding the loss from the beamsplitter, we expect to achieve a receiver noise temperature of less than 700 K. copyright 1997 American Institute of Physics

300

THz-bandwidth photonic Hilbert transformers based on fiber Bragg gratings in transmission.  

Science.gov (United States)

THz-bandwidth photonic Hilbert transformers (PHTs) are implemented for the first time, to the best of our knowledge, based on fiber Bragg grating (FBG) technology. To increase the practical bandwidth limitation of FBGs (typically non-minimum phase response of the PHT into a minimum-phase response by adding an anticipated instantaneous component to the desired system temporal impulse response. Using this methodology, a 3-THz-bandwidth integer PHT and a fractional (order 0.81) PHT are designed, fabricated, and successfully characterized. PMID:25531603

Fernández-Ruiz, María R; Wang, Lixian; Carballar, Alejandro; Burla, Maurizio; Azaña, José; LaRochelle, Sophie

2015-01-01

301

Packet-pair technique for available bandwidth estimation in IPv6 network  

CERN Document Server

This paper presents experimental checking of the model for measuring available bandwidth in IPv6. The experiment was performed using a measuring infrastructure RIPE test box, ensuring precision accuracy. The experimental results showed that to increase the accuracy of available bandwidth, we need to neutralize the effect of the variable part of the delay by increasing the number of measurements. Finally, we made the computer simulation, which allowed us to establish a dependence between the measurement error of the available bandwidth and the number of measurements.

Sultanov, Timur

2011-01-01

302

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

303

A Bandwidth-Aware Job Grouping-Based Scheduling on Grid Environment  

Directory of Open Access Journals (Sweden)

Full Text Available This study explores the feasibility of job scheduling strategies and extend the job grouping-based approach using the idea of bandwidth-awareness. As today`s best-effort network generally experiences low bandwidth and high delay, we aim to maximize the Grid resource utilization and reduce the delay by considering the bandwidth criterion. A simulation environment using GridSim is developed to model job scheduling process. Exploiting the simulation environment, a job scheduling strategy that encompasses the job grouping concept coupled together with bandwidth-aware scheduling is proposed and evaluated. The proposed scheduling strategy focuses on grouping independent jobs with small processing requirements into suitable jobs with larger processing requirements and schedules them in accordance with indeterminist network conditions. The simulation result demonstrates that the proposed strategy succeeds in minimizing the total processing time by at most 82% as compared to its counterpart.

T.F. Ang

2009-01-01

304

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

305

Coherence bandwidth characterization in an urban microcell at 62.4 GHz  

DEFF Research Database (Denmark)

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

Sánchez, M. G.; Hammoudeh, A. M.

2000-01-01

306

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

307

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

308

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

309

High-Density, High-Bandwidth, Multilevel Holographic Memory  

Science.gov (United States)

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

Chao, Tien-Hsin

2008-01-01

310

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

311

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

Scientific Electronic Library Online (English)

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

Carlos David, Zuluaga Ríos; Alfonso, Alzate Gómez.

2011-07-01

312

Bandwidth enhancement for parametric amplifiers operated in chirped multi-beam mode  

OpenAIRE

In this paper we discuss the bandwidth enhancement that can be achieved in multi-Joule optical parametric chirped pulse amplification (OPCPA) systems exploiting the tunability of parametric amplification. In particular, we consider a pair of single pass amplifiers based on potassium dideuterium phosphate (DKDP), pumped by the second harmonic of Nd:glass and tuned to amplify adjacent regions of the signal spectrum. We demonstrate that a bandwidth enhancement up to 50% is poss...

Terranova, F.; Kiriyama, H.; Pegoraro, F.

2008-01-01

313

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.

314

Hop-by-hop routing in wireless mesh networks with bandwidth guarantees  

OpenAIRE

Wireless Mesh Network (WMN) has become an important edge network to provide Internet access to remote areas and wireless connections in a metropolitan scale. In this paper, we study the problem of identifying the maximum available bandwidth path, a fundamental issue in supporting quality-of-service in WMNs. Due to interference among links, bandwidth, a well-known bottleneck metric in wired networks, is neither concave nor additive in wireless networks. We propose a new path weight which captu...

Hou, R.; Lui, Ks; Baker, F.; Li, J.

2012-01-01

315

Transmission Bandwidth Tunability of a Liquid-Filled Photonic Bandgap Fiber  

International Nuclear Information System (INIS)

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

316

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

317

Heuristic for solving cyclic bandwidth sum problem by following the structure of the graph  

OpenAIRE

The cyclic bandwidth sum problem (CBSP) consists of finding a labeling of the vertices of an undirected and unweighted graph with a fixed number of vertices with distinct integers such that the sum of (cyclic) difference of labels of adjacent vertices is minimized. Although theoretical results exist that give optimal value of cyclic bandwidth sum (CBS) for standard graphs, there are neither results in the general case, nor explicit methods to reach this optimal result. In ad...

Hamon, Ronan; Borgnat, Pierre; Flandrin, Patrick; Robardet, Ce?line

2014-01-01

318

A plug-in rule for bandwidth selection in circular density estimation  

OpenAIRE

A new plug-in rule procedure for bandwidth selection in kernel circular density estimation is introduced. The performance of this proposal is checked throughout a simulation study considering a variety of circular distributions exhibiting multimodality, peakedness and/or skewness. The plug-in rule behaviour is also compared with other existing bandwidth selectors. The method is illustrated with two classical datasets of cross-beds layers and animal orientation.

Oliveira, M.; Crujeiras, R. M.; Rodri?guez-casal, A.

2012-01-01

319

The Large Analog Bandwidth Recorder And Digitizer with Ordered Readout (LABRADOR) ASIC  

OpenAIRE

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$\\mu m$ CMOS devices are denoted the Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR) ASICs and finally consist of 9 channels of 260 deep sampling. Continuous sampling is provided with common stop capability. Input analog bandwidth is approximatel...

Varner, G. S.; Ruckman, L. L.; Nam, J. W.; Nichol, R. J.; Cao, J.; Gorham, P. W.; Wilcox, M.

2005-01-01

320

Space Shuffle: A Scalable, Flexible, and High-Bandwidth Data Center Network  

OpenAIRE

Data center applications require the network to be scalable and bandwidth-rich. Current data center network architectures often use rigid topologies to increase network bandwidth. A major limitation is that they can hardly support incremental network growth. Recent work proposes to use random interconnects to provide growth flexibility. However routing on a random topology suffers from control and data plane scalability problems, because routing decisions require global info...

Yu, Ye; Qian, Chen

2014-01-01

321

Bandwidth comparison of photonic crystal fibers and conventional single mode fibers  

DEFF Research Database (Denmark)

We experimentally compare the optical bandwidth of a conventional single-mode fiber (SMF) with 3 different photonic crystal fibers (PCF) all optimized for visible applications. The spectral attenuation, single-turn bend loss, and mode-field diameters (MFD) are measured and the PCF is found to have a significantly larger bandwidth than the SMF for an identical MFD. It is shown how this advantage can be utilized for realizing a larger MFD for the PCF while maintaining a bending resistant fiber.

Nielsen, Martin Dybendal; Folkenberg, Jacob Riis

2004-01-01

322

A Survey of Bandwidth Optimization Techniques and Patterns in VoIP Services and Applications  

OpenAIRE

This article surveys the various techniques adopted for optimising bandwidth for VoIP services over the period 1999-2014. The improvement of bandwidth can be realized through; silence suppression measure of repressing the silent portions (packets) in a voice conversation using Voice Activity Detection algorithm; by so doing, the transmission rate during the inactive periods of speech is reduced, and thus, the mean transmission rate can be reduced. A second measure is packet ...

Daniel, Uchenna Peter; Agbanusi, Nneka Chikazo; Danjuma, Kwetishe Joro

2014-01-01

323

An optimal bandwidth allocation and data droppage scheme for differentiated services in a wireless network  

OpenAIRE

This paper presents an optimal proportional bandwidth allocation and data droppage scheme to provide differentiated services (DiffServ) for downlink pre-orchestrated multimedia data in a single-hop wireless network. The proposed resource allocation scheme finds the optimal bandwidth allocation and data drop rates under minimum quality-of-service (QoS) constraints. It combines the desirable attributes of relative DiffServ and absolute DiffServ approaches. In contrast to relative DiffServ appro...

Sheikh, Waseem; Ghafoor, Arif

2010-01-01

324

Towards a Flow-based Internet Traffic Classification for Bandwidth Optimization  

OpenAIRE

Abstract The evolution of the Internet into a large complex service-based network has posed tremendous challenges for network monitoring and control in terms of how to collect the large amount of data in addition to the accurate classification of new emerging applications such as peer to peer, video streaming and online gaming. These applications consume bandwidth and affect the performance of the network especially in a limited bandwidth networks such as university campuses causing performan...

Abuagla Babiker Mohd; Dr. Sulaiman bin Mohd Nor

2009-01-01

325

HyperTransport 3 Core: A Next Generation Host Interface with Extremely High Bandwidth  

OpenAIRE

As the amount of computing power keeps increasing, host interface bandwidth to memory and input-output devices (I/O) becomes a more and more limiting factor. High speed serial host interface protocols like PCI-Express and HyperTransport (HT) have been introduced to satisfy the applications’ ever increasing demands for more bandwidth. Recent applications in the field of General Purpose Graphic Processing Units (GPGPUs) and Field Programmable Gate Array (FPGA) based coprocessors are an exampl...

Kalisch, Benjamin; Giese, Alexander; Litz, Heiner; Bru?ning, Ulrich

2009-01-01

326

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

327

Energy-bandwidth trade-off in all-optical photonic crystal microcavity switches  

OpenAIRE

The performance of all-optical switches is a compromise between the achievable bandwidth of the switched signal and the energy requirement of the switching operation. In this work we consider a system consisting of a photonic crystal cavity coupled to two input and two output waveguides. As a specific example of a switching application, we investigate the demultiplexing of an optical time division multiplexed signal. To quantify the energy-bandwidth trade-off, we introduce a figure of merit f...

Heuck, Mikkel; Kristensen, Philip Trøst; Mørk, Jesper

2011-01-01

328

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

OpenAIRE

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

Sheikh, Waseem; Ghafoor, Arif

2007-01-01

329

Bandwidth Enhancement of Antenna Arrays Utilizing Mutual Coupling between Antenna Elements  

Directory of Open Access Journals (Sweden)

Full Text Available The mutual coupling effect between antenna elements on an array's bandwidth is investigated using scattering parameters instead of the mutual impedance. First, an approximate expression is derived for matched voltage standing wave ratio (VSWR bandwidth of a tuned antenna, which reveals that the bandwidth is inversely proportional to the magnitude |?0'(?0| of the frequency derivative of the reflection coefficient. Next, considering linear antenna arrays with corporate feed as an example, closed-form expressions of the reflection coefficient are derived at the input port of the feeding network, which shows that the active reflection coefficient of an array is the linear superposition of elements' passive reflection coefficient S11 and the mutual coupling coefficient S12 from adjacent elements. The VSWR bandwidth expressions for an array imply that bandwidth enhancement of the overall array can be achieved when the element passive reflection coefficient S11 and mutual coupling S12 are cancelled, as well as the frequency derivatives S11' and S12' also cancel each other. Slot arrays and a two-element Vivaldi array are investigated to verify the validity of our theoretical analysis. Numerical and experimental results are presented to successfully demonstrate the bandwidth enhancement of antenna arrays utilizing mutual coupling effect.

Zhongxiang Shen

2010-01-01

330

Design of bandwidth tunable HTS filter using H-shaped waveguides  

International Nuclear Information System (INIS)

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

331

Improved data capacity using bandwidth acceleration in HiSeasNet  

Science.gov (United States)

After nearly eight years of operation, the HiSeasNet satellite communications network is providing reliable, continuous Internet connectivity for the UNOLS oceanographic research fleet and it remains a cost-effective solution for oceanographic research needs. Despite adding additional bandwidth and temporary coverage of additional ocean areas in the last few years, users are saturating the shore-to-ship network links with increasing frequency. To improve the long-term capacity and performance of the network in both directions while reducing cost, HiSeasNet is now using network accelerators to improve the efficiency of satellite bandwidth. With a 20% increase in effective shore-to-ship bandwidth and 70% or greater increase in ship-to-shore bandwidth, the one-time cost of the accelerators is lower than the yearly cost of the equivalent increase in bandwidth. With the additional bandwidth, even more data can be sent ashore in near-real-time, voice and video quality may be improved, and even larger volumes of information may be exchanged.

Foley, S.; Berger, J.; Orcutt, J. A.; Vernon, F. L.

2009-12-01

332

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

CERN Document Server

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

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

1999-01-01

333

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

Directory of Open Access Journals (Sweden)

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

Tanski Susanne

2010-07-01

334

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

335

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

336

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

Directory of Open Access Journals (Sweden)

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

Muhammad Yusof Ismail

2009-12-01

337

Improvement on Diversity Gain with Filter Bandwidth Enlargement in Fractional Sampling OFDM Receiver  

Science.gov (United States)

A diversity scheme with Fractional Sampling (FS) in an OFDM receiver has been investigated recently. Through FS, it is possible to separate multipath components and obtain diversity gain in OFDM systems. Enlargement of the bandwidth of the total frequency response between transmit and receive baseband filters allows the FS scheme to achieve path diversity. However, the transmit filter has to be designed according to the spectrum mask of the wireless standards such as IEEE802.11a/g to avoid interference to the other communication systems and the frequency response of the composite channel including the transmit and receive filters has often been set to minimal bandwidth to eliminate adjacent channel signals. In order to achieve the maximum signal-to-noise ratio (SNR), the same filter is commonly used in the transmitter and the receiver. In this paper, the trade-off among the SNR deterioration, adjacent channel interference, and the diversity gain due to the enlargement of the bandwidth of the receive filter is investigated. Numerical results from computer simulations indicate that the BER performance with wider bandwidth in the receiver shows better performance than that with the minimal bandwidth for maximizing the SNR in certain conditions.

Shinkai, Toshiya; Nishimura, Haruki; Sanada, Yukitoshi

338

Exploiting independent filter bandwidth of human factor cepstral coefficients in automatic speech recognition  

Science.gov (United States)

Mel frequency cepstral coefficients (MFCC) are the most widely used speech features in automatic speech recognition systems, primarily because the coefficients fit well with the assumptions used in hidden Markov models and because of the superior noise robustness of MFCC over alternative feature sets such as linear prediction-based coefficients. The authors have recently introduced human factor cepstral coefficients (HFCC), a modification of MFCC that uses the known relationship between center frequency and critical bandwidth from human psychoacoustics to decouple filter bandwidth from filter spacing. In this work, the authors introduce a variation of HFCC called HFCC-E in which filter bandwidth is linearly scaled in order to investigate the effects of wider filter bandwidth on noise robustness. Experimental results show an increase in signal-to-noise ratio of 7 dB over traditional MFCC algorithms when filter bandwidth increases in HFCC-E. An important attribute of both HFCC and HFCC-E is that the algorithms only differ from MFCC in the filter bank coefficients: increased noise robustness using wider filters is achieved with no additional computational cost.

Skowronski, Mark D.; Harris, John G.

2004-09-01

339

Percentage Based Trust Model with Bandwidth Reservation Technique for Privacy Preserving Routing in MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available Routing in Mobile Ad-Hoc Networks are vulnerable to malicious traffic analysis, harmful attackers can mitigate paths and malicious intermediate nodes breaks security, ineffective reserve of available resources ( utilization of bandwidth in node causes losses and as well as anonymity, unobservability of communication is not provided. To detect misbehaviors and effective utilization of resources in trusted nodes the Percentage Based Trust management system, with bandwidth reservation technique is proposed, and for achieving privacy in MANETs the PPRP is proposed. In this paper the scheme called Percentage based Trust management system is defined to allow trustworthy intermediate nodes to participate in path construction with resource reservation technique to allow trusted nodes to select a path which has minimum cost, congestion and bandwidth. In reservation technique, if available bandwidth is greater than traffic jam bandwidth. Using rate monitoring and adjustment methodologies, rate control is performed for the overcrowded flows and then an Privacy Preserving routing Protocol (PPRP is proposed to offer complete anonymity, unlinkability and unobservabilty for all types of packets. PPRP uses novel combination of group signature and Id based encryption techniques for route discovery. The simulation result shows that this paper achieves trustworthy path construction through intermediate nodes with resource allocation technique and stronger privacy protection is achieved than existing scheme like AODV.

Raghu. R , Gopinathan. B

2013-02-01

340

Manipulation of two-dimensional spectra of excitonically coupled molecules by narrow-bandwidth laser pulses  

International Nuclear Information System (INIS)

Graphical abstract: The full broad-bandwidth photon echo signal can be reconstructed using the set of narrow-bandwidth simulations along with the extraction of specific cross-peaks. - Abstract: Complete expressions within the response function theory are derived for a coherent two-dimensional (2D) signal covering the finite-bandwidth and pulse-overlap effects. Ideal time domain, frequency domain as well as mixed regime are considered. Conditions for the strong pulse-overlap effects are also described and analyzed. As demonstrated for the excitonically coupled dimer, certain configurations of central frequencies allow to extract various peaks in the 2D signal, resembling certain physical processes. In the case of weakly overlapping pulses, the scheme for generating both ultra-broad-bandwidth time-domain signal and frequency-domain spectra from a set of narrow-bandwidth multi-color measurements is presented. Possibility of reconstructing microscopic parameters such as inter-molecular couplings and transition dipole orientations from high-resolution crosspeaks is discussed.

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

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)

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

The impacts of bandwidths on the estimation of leaf chlorophyll concentration using normalized difference vegetation indices  

Science.gov (United States)

The aim of this work is to estimate leaf chlorophyll concentration with 6 different normalized difference vegetation indices (NDVIs) under 4 bandwidths (1, 5, 10 and 20 nm). A popular leaf radiative transfer model(i.e. PROSPECT) was used to simulate the leaf reflectance spectra from 400-800nm under varying chlorophyll concentrations. Then 6 combinations of bands sensitive to chlorophyll concentrations were chosen for the calculation of their NDVIs. Simulated spectral response functions were applied to calculate the synthesis reflectance spectra at the intervals of 5, 10 and 20 nm respectively, and then corresponding NDVIs were calculated. The change of correlation coefficients between the NDVIs and the leaf chlorophyll concentrations were examined. Results showed that some NDVIs had a good performance with increasing bandwidth, whereas response of different NDVIs to the 4 bandwidths were different generally. Our results suggested that the improvement of spectral resolution was not necessary for some NDVIs to estimate leaf chlorophyll.

Ma, Mingliang; Shi, Runhe; Liu, Pudong; Wang, Hong; Gao, Wei

2014-10-01

346

Bandwidth and resolution of super-resolution imaging with perforated solids  

Science.gov (United States)

Recent experiments on acoustic superlens and hyperlens found anisotropic metamaterials constructed from periodic perforated solids can be used for super-resolution imaging. Here, we present a theoretical study on the operational bandwidth of these imaging devices using the emerging framework of transformation acoustics. Within the transformation approach, both the microstructural superlens and hyperlens can be discussed using the transfer matrix method on the same footing. We show that the geometrical structure of the periodic metamaterials induces that an acoustics hyperlens has a very wide operational frequency bandwidth with its subwavelength resolution limited by the ratio of image magnification while an acoustics superlens has a very deep subwavelength resolution limited only by the periodicity of the perforations but intrinsically working at a narrow frequency bandwidth. Such investigation will become useful for designing future transformation acoustical imaging devices.

Liang, Zixian; Li, Jensen

2011-12-01

347

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

348

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

Science.gov (United States)

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

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

2014-03-01

349

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

350

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

Directory of Open Access Journals (Sweden)

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

M. Sajid

2014-01-01

351

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

Science.gov (United States)

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

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

2014-07-01

352

RF MEMS suspended band-stop resonator and filter for frequency and bandwidth continuous fine tuning  

Science.gov (United States)

We firstly propose the concept of a frequency and bandwidth fine-tuning method using an RF MEMS-based suspended tunable band-stop resonator. We experimentally show the feasibility of the continuously tuned resonator, including a second-order filter, which consists of cascaded resonators to achieve center frequency and bandwidth fine tuning. The structure consists of a freestanding half-wavelength (?/2) resonator connected to a large displacement comb actuator. The lateral movement of the ?/2 resonator over the main transmission line produces different electromagnetic decoupling values from the main transmission line. The decoupled energy leads to continuous center frequency and bandwidth tuning using the band-stop resonator circuit for fine-tuning applications. The freestanding ?/2 resonator plays the role of a variable capacitor as well as a decoupling resonator in the proposed structure. The fabricated tunable filter shows suitability for Ku-band wireless communication system applications with continuous reconfiguration.

Jang, Yun-Ho; Llamas-Garro, Ignacio; Kim, Yong-Kweon; Kim, Jung-Mu

2012-01-01

353

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

CERN Document Server

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

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

2010-01-01

354

A reflected-wave ruby maser with K-band tuning range and large instantaneous bandwidth  

Science.gov (United States)

A novel maser concept is outlined and a unique design described which permits wide bandwidth and waveguide tuning range by employing four stages cascaded via cryogenically cooled circulators. Theoretical considerations for gain, bandwidth, gain ripple, and noise temperature are included. Operated on a closed-cycle helium refrigerator with a superconducting persistence-mode magnet, the four-stage amplifier is tunable from 18.3 to 26.6 GHz with 30 dB of net gain and achieves 240 MHz of 3-dB bandwidth near the center of this band. The measured noise temperature is 13 + or - 2 K referred to the room-temperature input flange. Applications are foreseen utilizing cooled parametric downconverters and upconverters with this amplifier at IF to extend the low-noise performance up to millimeter frequencies and down to L-band for radio astronomy and planetary spacecraft communications.

Moore, C. R.; Clauss, R. C.

1979-01-01

355

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

Science.gov (United States)

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

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

2014-02-24

356

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

357

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

Science.gov (United States)

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

Lin, Di; Labeau, Fabrice

2012-01-01

358

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

Directory of Open Access Journals (Sweden)

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

Kerpez Kenneth

2008-01-01

359

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

Directory of Open Access Journals (Sweden)

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

Kenneth Kerpez

2008-10-01

360

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

361

Amplifying modeling for broad bandwidth pulse in Nd:glass based on hybrid-broaden mechanism  

Science.gov (United States)

In this paper, the cross relaxation time is proposed to combine the homogeneous and inhomogeneous broaden mechanism for broad bandwidth pulse amplification model. The corresponding velocity equation, which can describe the response of inverse population on upper and low energy level of gain media to different frequency of pulse, is also put forward. The gain saturation and energy relaxation effect are also included in the velocity equation. Code named CPAP has been developed to simulate the amplifying process of broad bandwidth pulse in multi-pass laser system. The amplifying capability of multi-pass laser system is evaluated and gain narrowing and temporal shape distortion are also investigated when bandwidth of pulse and cross relaxation time of gain media are different. Results can benefit the design of high-energy PW laser system in LFRC, CAEP.

Su, J.; Liu, L.; Luo, B.; Wang, W.; Jing, F.; Wei, X.; Zhang, X.

2008-05-01

362

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

Science.gov (United States)

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

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

2009-03-30

363

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

International Nuclear Information System (INIS)

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

364

The first version Buffered Large Analog Bandwidth (BLAB1) ASIC for high luminosity collider and extensive radio neutrino detectors  

OpenAIRE

Future detectors for high luminosity particle identification and ultra high energy neutrino observation would benefit from a digitizer capable of recording sensor elements with high analog bandwidth and large record depth, in a cost-effective, compact and low-power way. A first version of the Buffered Large Analog Bandwidth (BLAB1) ASIC has been designed based upon the lessons learned from the development of the Large Analog Bandwidth Recorder and Digitizer with Ordered Read...

Varner, Gary S.; Ruckman, Larry L.; Wong, Andrew

2008-01-01

365

Estimating individual listeners’ auditory-filter bandwidth in simultaneous and non-simultaneous masking  

DEFF Research Database (Denmark)

Frequency selectivity in the human auditory system is often measured using simultaneous masking of tones presented in notched noise. Based on such masking data, the equivalent rectangular bandwidth (ERB) of the auditory filters can be derived by applying the power spectrum model of masking and assuming a rounded-exponential filter shape. If a forward masking paradigm is used instead of simultaneous masking, filter estimates typically show significantly sharper tuning. This difference in frequency selectivity has commonly been related to spectral suppression mechanisms observed in the cochlea. Considering bandwidth estimates from previous studies based on forward masking, only average data across a number of subjects have been considered. The present study is concerned with bandwidth estimates in simultaneous and forward masking in individual normal-hearing subjects. In order to investigate the reliability of the individual estimates, a statistical resampling method is applied. It is demonstrated that a ratherlarge set of experimental data is required to reliably estimate auditory filter bandwidth, particularly in the case of simultaneous masking. The poor overall reliability of the filter estimates was found to be mainly related to the very short tone duration (i.e., 10 ms) that was chosen. Applying 300-ms long tones in simultaneous masking drastically improved the reliability of the filter estimates. The tone duration in forward masking had to be very short to elicit a sufficient amount of masking. Based on extensive data for three subjects, the difference between forward and simultaneous masking es-timates of auditory filter bandwidth was found to be even larger than previously reported, with a bandwidth decrease by a factor of about 1.8 rather than 1.4. The results of the study can be used to optimize the measures of frequency selectivity which is particularly useful when studying consequences of (individual) hearing impairment.

Buchholz, Jörg; Caminade, Sabine

2010-01-01

366

Power and Efficiency Optimized in Traveling-Wave Tubes Over a Broad Frequency Bandwidth  

Science.gov (United States)

A traveling-wave tube (TWT) is an electron beam device that is used to amplify electromagnetic communication waves at radio and microwave frequencies. TWT's are critical components in deep space probes, communication satellites, and high-power radar systems. Power conversion efficiency is of paramount importance for TWT's employed in deep space probes and communication satellites. A previous effort was very successful in increasing efficiency and power at a single frequency (ref. 1). Such an algorithm is sufficient for narrow bandwidth designs, but for optimal designs in applications that require high radiofrequency power over a wide bandwidth, such as high-density communications or high-resolution radar, the variation of the circuit response with respect to frequency must be considered. This work at the NASA Glenn Research Center is the first to develop techniques for optimizing TWT efficiency and output power over a broad frequency bandwidth (ref. 2). The techniques are based on simulated annealing, which has the advantage over conventional optimization techniques in that it enables the best possible solution to be obtained (ref. 3). Two new broadband simulated annealing algorithms were developed that optimize (1) minimum saturated power efficiency over a frequency bandwidth and (2) simultaneous bandwidth and minimum power efficiency over the frequency band with constant input power. The algorithms were incorporated into the NASA coupled-cavity TWT computer model (ref. 4) and used to design optimal phase velocity tapers using the 59- to 64-GHz Hughes 961HA coupled-cavity TWT as a baseline model. In comparison to the baseline design, the computational results of the first broad-band design algorithm show an improvement of 73.9 percent in minimum saturated efficiency (see the top graph). The second broadband design algorithm (see the bottom graph) improves minimum radiofrequency efficiency with constant input power drive by a factor of 2.7 at the high band edge (64 GHz) and increases simultaneous bandwidth by 500 MHz.

Wilson, Jeffrey D.

2001-01-01

367

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

Science.gov (United States)

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

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

2014-10-20

368

Filter-free nondispersive infrared sensing using narrow-bandwidth mid-infrared thermal emitters  

Science.gov (United States)

We experimentally demonstrate filter-free nondispersive infrared (NDIR) sensing of organic solvents using single-peak narrow-bandwidth mid-infrared thermal emitters. Our emitters are based on multiple quantum wells (MQWs) and two-dimensional (2D) photonic crystal (PC) slabs, and show a single thermal emission peak with a quality factor of over 100 at the fingerprint wavelength (around 9 µm) of the target organic solvents. Using these narrow-bandwidth thermal emitters and commercial pyroelectric sensors without any optical bandpass filters, we successfully distinguish and determine the concentration of the target solvents among other solvents.

Inoue, Takuya; De Zoysa, Menaka; Asano, Takashi; Noda, Susumu

2014-01-01

369

Strain dependence of Brillouin frequency, intensity, and bandwidth in polarization-maintaining fibers.  

Science.gov (United States)

The strain dependence of the Brillouin gain-loss spectrum for PANDA, bow-tie, and tiger polarization-maintaining fibers has been studied in the range 0 to 50 degrees C. We found a linear relationship between the strain and the Brillouin frequency, intensity, and bandwidth for PANDA and bow-tie fibers. For PANDA fiber at 20-cm spatial resolution, Brillouin frequency gives 7-micro epsilon uncertainty, which is the highest accuracy among three parameters, whereas the Brillouin bandwidth gives 19-micro epsilon uncertainty. PMID:15309833

Yu, Qinrong; Bao, Xiaoyi; Chen, Liang

2004-07-15

370

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

371

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

372

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

373

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 wave ratio and input impedance have also been validated using a Smith chart.

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

2014-08-01

374

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

375

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

376

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

OpenAIRE

We report on the inscription and characterization of narrow bandwidth fiber Bragg gratings (FBGs) with 850-nm resonance wavelength in polymer optical fibers (POFs). We use two fibers: an in-house fabricated microstructured POF (mPOF) with relative hole size of 0.5 and a commercial step-index POF, which supports six modes at 850 nm. The gratings have been written with the phase-mask technique and a 325-nm HeCd laser. The mPOF grating has a full-width at half-maximum (FWHM) bandwidth of 0.29 nm...

Stefani, Alessio; Yuan, Wu; Markos, Christos; Bang, Ole

2011-01-01

377

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

DEFF Research Database (Denmark)

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

Bjerregaard, Tobias; SparsØ, Jens

2005-01-01

378

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

Directory of Open Access Journals (Sweden)

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

Stefanie Blain-Moraes

2014-07-01

379

MOS current gain cells with electronically variable gain and constant bandwidth  

OpenAIRE

Two MOS current gain cells are proposed that provide linear amplification of currents supplied by several linear MOS V-I converters. The gain is electronically variable by a voltage or a current and can be made insensitive to temperature and IC processing. The gain cells have a constant (gain-independent) bandwidth

Klumperink, Eric A. M.; Seevinck, Evert

1989-01-01

380

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

CERN Document Server

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

Chacón, José E

2012-01-01

381

Uniform-in-bandwidth consistency for nonparametric estimation of divergence measures  

OpenAIRE

We propose nonparametric estimation of divergence measures between continuous distributions. Our approach is based on a plug-in kernel- type estimators of density functions. We give the uniform in bandwidth consistency for the proposal estimators. As a consequence, their asymp- totic 100% confidence intervals are also provided.

Ngom, Papa; Dhaker, Hamza; Mendy, Pierre; Deme, El Hadji

2014-01-01

382

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

DEFF Research Database (Denmark)

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

Nour, Baqer; Breinbjerg, Olav

2011-01-01

383

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

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

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

386

The research of methods to improve the control bandwidth for liquid crystal beam steering system  

Science.gov (United States)

The liquid crystal beam steering technology with low driving voltage, high diffraction efficiency and without the effect of mechanical inertia?is regard as a potential technology in the field of non-mechanical beam steering. Liquid crystal spatial light modulator (LCSLM) can be applied as a beam steering control device in laser communication, and it can realize the programmable control in real time. And compared with fast steering mirror (FSM), which is widely used at present, LCSLM is smaller, lighter and lower power consumptive in a non-mechanical way, so it's convenient to control. But the system bandwidth is a restricted problem in the research. In this article, the principle of beam steering with LCSLM is introduced firstly. A beam steering bench is set up using reflective pure-phase LCSLM from BNS. The offset of beam spot is detected by the CCD and a classic PI close-loop control experiment is designed to test the system bandwidth. And then the factors which restricted the control bandwidth are analyzed. Considering the effect of the CCD' frame rate, the PSD with higher frame rate is used in the control system and the data model of the liquid crystal is tested. A controller is designed based on the data model and the bandwidth is improved observably.

Hao, Ya-jing; Huang, Yong-mei; Wu, Qiong-yan; Xiao, Wen-ben

2013-08-01

387

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

Science.gov (United States)

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

Gawande, Rohit Sudhir

388

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

Science.gov (United States)

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

Doll, Andrin; Jeschke, Gunnar

2014-09-01

389

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

DEFF Research Database (Denmark)

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

Blaaberg, SØren; Mulvad, Hans Christian Hansen

2009-01-01

390

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

391

Preamplifier design with wide bandwidth using InGaP/GaAs HBT for 10-Gbps photoreceiver module  

International Nuclear Information System (INIS)

We report a preamplifier with wide bandwidth using high-speed and reliable InGaP/GaAs HBT applicable for 10-Gbps photoreceiver modules. The three-stage preamplifier with a negative feedback resistor demonstrates an effective transimpedance gain of 43 dB?, a -3-dB bandwidth of 14 GHz corresponding to a very high transimpedance-bandwidth product of 2.52 THz?, and an output return loss of -18 dB up to -3-dB bandwidth. This compact circuit is fabricated with an area of 800 X 700 ?m2. A photoreceiver module of surface-mountable package type, that is composed of preamplifier and photodiode of surface-illumination type, demonstrates an optical bandwidth of 7.5 GHz at ? = 1.55 ? m and a 45-psec rise/fall time for 10-Gbps. The module shows higher sensitivity for a 10-Gbps optical transmission system.

392

Squeezed light for bandwidth-limited atom optics experiments at the rubidium D1 line  

Energy Technology Data Exchange (ETDEWEB)

We report on the generation of more than 5 dB of vacuum squeezed light at the rubidium D1 line (795 nm) using periodically poled KTiOPO{sub 4} (PPKTP) in an optical parametric oscillator. We demonstrate squeezing at low sideband frequencies, making this source of non-classical light compatible with bandwidth-limited atom optics experiments. When PPKTP is operated as a parametric amplifier, we show a noise reduction of 4 dB stably locked within the 150 kHz-500 kHz frequency range. This matches the bandwidth of electromagnetically induced transparency (EIT) in rubidium hot vapour cells under the condition of large information delay.

Hetet, G; Gloeckl, O; Pilypas, K A; Harb, C C; Buchler, B C; Bachor, H-A; Lam, P K [ARC COE for Quantum-Atom Optics, Australian National University, Canberra, ACT 0200 (Australia)

2007-01-14

393

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

CERN Document Server

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

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

2012-01-01

394

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

International Nuclear Information System (INIS)

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

395

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-10-01

396

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

Science.gov (United States)

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

He, D. F.; Itozaki, H.

2006-10-01

397

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

398

Single-Shot Rotational Raman Thermometry for Turbulent Flames Using a Low-Resolution Bandwidth Technique  

Science.gov (United States)

An alternative optical thermometry technique that utilizes the low-resolution (order 10(exp 1)/cm) pure-rotational spontaneous Raman scattering of air is developed to aid single-shot multiscalar measurements in turbulent combustion studies. Temperature measurements are realized by correlating the measured envelope bandwidth of the pure-rotational manifold of the N2/O2 spectrum with a theoretical prediction of a species-weighted bandwidth. By coupling this thermometry technique with conventional vibrational Raman scattering for species determination, we demonstrate quantitative spatially resolved, single-shot measurements of the temperature and fuel/oxidizer concentrations in a high-pressure turbulent Cf4-air flame. Our technique provides not only an effective means of validating other temperature measurement methods, but also serves as a secondary thermometry technique in cases where the anti-Stokes vibrational N2 Raman signals are too low for a conventional vibrational temperature analysis.

Kojima, Jun; Nguyen, Quang-Viet

2007-01-01

399

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

400

On Impedance Bandwidth of Resonant Patch Antennas Implemented Using Structures with Engineered Dispersion  

CERN Document Server

We consider resonant patch antennas, implemented using loaded transmission-line networks and other exotic structures having engineered dispersion. An analytical expression is derived for the ratio of radiation quality factors of such antennas and conventional patch antennas loaded with (reference) dielectrics. In the ideal case this ratio depends only on the propagation constant and wave impedance of the structure under test, and it can be conveniently used to study what kind of dispersion leads to improved impedance bandwidth. We illustrate the effect of dispersion by implementing a resonant patch antenna using a periodic network of LC elements. The analytical results predicting enhanced impedance bandwidth compared to the reference results are validated using a commercial circuit simulator. Discussion is conducted on the practical limitations for the use of the proposed expression.

Ikonen, P; Tretyakov, S; Alitalo, Pekka; Ikonen, Pekka; Tretyakov, Sergei

2006-01-01

401

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

Directory of Open Access Journals (Sweden)

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

Madsen CK

2005-01-01

402

High-fidelity polarization storage in a gigahertz bandwidth quantum memory  

International Nuclear Information System (INIS)

We demonstrate a dual-rail optical Raman memory inside a polarization interferometer; this enables us to store polarization-encoded information at GHz bandwidths in a room-temperature atomic ensemble. By performing full process tomography on the system, we measure up to 97 ± 1% process fidelity for the storage and retrieval process. At longer storage times, the process fidelity remains high, despite a loss of efficiency. The fidelity is 86 ± 4% for 1.5 ?s storage time, which is 5000 times the pulse duration. Hence, high fidelity is combined with a large time-bandwidth product. This high performance, with an experimentally simple setup, demonstrates the suitability of the Raman memory for integration into large-scale quantum networks. (paper)

403

Improving bandwidth rectangular patch antenna using different thickness of dielectric substrate  

Directory of Open Access Journals (Sweden)

Full Text Available Microstrip patch antenna has some drawbacks of low efficiency, narrow band (<5%, and surface wave losses. In this paper the solution method was used different thickness of dielectric substrate (h= 4, 6 and 8 mm to increase bandwidth, the simulated results for rectangular give bandwidth of (200 MHZ in case (h=6mm.A rectangular micro strip patch antenna that meets the requirement of operation at (2.4 GHZ, the proposed configurations are simulated and analyzed using microwave office 2000 software package. The VSWR, input impedance, radiation patterns and S11 performance are used for the analysis of the different configurations. Feed point on the patch that gives a good match of 50 ohm, input impedance was found by a method of trial and error.

Karim A. Hamad

2011-04-01

404

Triple band polarization-independent metamaterial absorber with bandwidth enhancement at X-band  

Science.gov (United States)

In this paper, we propose a triple band polarization-independent metamaterial absorber using square-shaped closed ring resonators over wide angle of incidence. The unit cell consisting of various square loops is designed by using the parametric analysis so that it exhibits a triple band absorption response with two bands lying in C-band and one in X-band for airborne and surveillance radar signal absorption applications. Furthermore, in X-band, the absorber exhibits a broadband response with full width at half maxima bandwidth of 940 MHz (9.43%). The structure exhibits bandwidth enhanced properties for any angle of polarization under normal incidence. It also shows high absorption for wide angle of incidence up to 60°. The proposed structure is fabricated and experimental results show proper matching with the simulated responses.

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

2013-09-01

405

On the Cell Breathing Technique to Reduce Congestion Applying Bandwidth Limitation  

Directory of Open Access Journals (Sweden)

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

Parminder Kaur

2012-04-01

406

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

407

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

408

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.

409

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

Science.gov (United States)

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

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

2014-02-10

410

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-04-24

411

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

412

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

Directory of Open Access Journals (Sweden)

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

Mohammad Akbari

2014-08-01

413

GHz-bandwidth optical filters based on high-order silicon ring resonators.  

Science.gov (United States)

Previously demonstrated high-order silicon ring filters typically have bandwidths larger than 100 GHz. Here we demonstrate 1-2 GHz-bandwidth filters with very high extinction ratios (~50 dB). The silicon waveguides employed to construct these filters have propagation losses of ~0.5 dB/cm. Each ring of a filter is thermally controlled by metal heaters situated on the top of the ring. With a power dissipation of ~72 mW, the ring resonance can be tuned by one free spectral range, resulting in wavelength-tunable optical filters. Both second-order and fifth-order ring resonators are presented, which can find ready application in microwave/radio frequency signal processing. PMID:21164722

Dong, Po; Feng, Ning-Ning; Feng, Dazeng; Qian, Wei; Liang, Hong; Lee, Daniel C; Luff, B J; Banwell, T; Agarwal, A; Toliver, P; Menendez, R; Woodward, T K; Asghari, Mehdi

2010-11-01

414

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

Science.gov (United States)

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

Ramamoorthy, Raj Kumar; Bhatnagar, Anil K.

2014-04-01

415

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

416

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

International Nuclear Information System (INIS)

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

417

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

Science.gov (United States)

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

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

1998-01-01

418

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.

Mei Han

2007-01-01

419

Methods for full utilization of the bandwidth of fiber optical parametric amplifiers and wavelength converters  

OpenAIRE

In fiber optical parametric amplifiers (OPAs), idlers are generated during the amplification process. For very wide and dense signal input spectra, idlers may overlap with signals, thereby interfering with proper operation as an amplifier. In this paper, filter-based methods to fully utilize the bandwidth of OPAs and wavelength converters in the presence of very broad signal spectra are investigated. In the basic filter setup, two parallel OPAs and two filters are used; alternatively, one can...

Kalogerakis, G.; Marhic, Me; Uesaka, K.; Shimizu, K.; Wong, Kky; Kazovsky, Lg

2006-01-01

420

Bandwidth and dynamic range of a widely tunable Josephson parametric amplifier  

OpenAIRE

The ability to manipulate quantum information encoded in microwave fields has led to a renewed interest in Josephson parametric amplifiers (JPAs). For these applications the ability of JPAs to amplify signals with the least amount of added noise is critical. Unfortunately JPAs are typically narrow band amplifiers with small dynamic range. It is therefore important to understand the bandwidth and dynamic range of any particular JPA in order to determine if it is appropriate f...

Castellanos-beltran, M. A.; Irwin, K. D.; Vale, L. R.; Hilton, G. C.; Lehnert, K. W.

2009-01-01

421

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

422

Power-Bandwidth Tradeoff in Dense Multi-Antenna Relay Networks  

OpenAIRE

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 d...

Oyman, Ozgur; Paulraj, Arogyaswami J.

2007-01-01

423

Laser-induced acoustic point source for accurate impulse response measurements within the audible bandwidth.  

Science.gov (United States)

Laser induced air breakdown is proposed as a sound source for accurate impulse response measurements. Within the audible bandwidth, the source is repeatable, broadband, and omnidirectional. The applicability of the source was evaluated by measuring the impulse response of a room. The proposed source provides a more accurate temporal and spatial representation of room reflections than conventional loudspeakers due to its omnidirectionality, negligible size and short pulse duration. PMID:24907837

Gómez Bolaños, Javier; Delikaris-Manias, Symeon; Pulkki, Ville; Eskelinen, Joona; Hæggström, Edward

2014-06-01

424

Analysis on the space-bandwidth product of digital holography for video hologram recording and reconstruction  

Science.gov (United States)

In this paper, we present an analysis on space bandwidth product of digital hologram. The condition for clear reconstruction of in-axis and off-axis digital hologram case is derived. The correlation efficiency and modulate transfer function (MTF) are then used for quantitative analysis of the reconstruction object. The presented analysis is verified by simulation result and then is applied to record and reconstruct video hologram.

Phan, Anh-Hoang; Piao, Mei-Lan; Park, Jae-Hyeung; Kim, Nam

2012-06-01

425

Bandwidth and resolution of super-resolution imaging with perforated solids  

OpenAIRE

Recent experiments on acoustic superlens and hyperlens found anisotropic metamaterials constructed from periodic perforated solids can be used for super-resolution imaging. Here, we present a theoretical study on the operational bandwidth of these imaging devices using the emerging framework of transformation acoustics. Within the transformation approach, both the microstructural superlens and hyperlens can be discussed using the transfer matrix method on the same footing. We show that the ge...

Zixian Liang; Jensen Li

2011-01-01

426

Bandwidth Analysis of Bootstrap Transimpedance Amplifier for Optical Free Space Receiver  

OpenAIRE

Free Space Optic (FSO) or optical wireless link operates in high noise environments. On the other hand, theperformance is subjected to several atmospheric factors like environmental temperature, fog, smoke, haze and rain. Signalto-noise ratio (SNR) can vary radically with the distance and ambient noise. A good sensitivity and a broad bandwidth willhabitually use a small photodetection area where the aperture is small. However, FSO optical receiver requires a largeaperture and accordingly, to ...

Ramli, A.; Rais, S. S.; Idrus, S. M.

2008-01-01

427

Enhancing Interaction between Smartphones and Web Services on Cloud for Improved Bandwidth and Latency  

OpenAIRE

As cellular network infrastructures are improving day by day; they are becoming the ideal clientsto access the any Web resources, especially Internet Based Services. However, Smartphones have certainlimitations in connecting smartphone based devices to existing Internet based Services. This paper mainlyfocuses on focuses on the following limitations: connection loss, bandwidth, latency, and limited resources.This paper implements a platform independent architecture for connecting smartphones ...

Mandeep Singh; Kanwalvir Singh Dhindsa

2013-01-01

428

Exact risk improvement of bandwidth selectors for kernel density estimation with directional data  

OpenAIRE

New bandwidth selectors for kernel density estimation with directional data are presented in this work. These selectors are based on asymptotic and exact error expressions for the kernel density estimator combined with mixtures of von Mises distributions. The performance of the proposed selectors is investigated in a simulation study and compared with other existing rules for a large variety of directional scenarios, sample sizes and dimensions. The selector based on the exa...

Garci?a-portugue?s, Eduardo

2013-01-01

429

Decrease of the resonance bandwidth of micromechanical oscillators by phase control of the driving force  

OpenAIRE

A method for controlling the amplitude response of micromechanical oscillators is presented. The micromechanical oscillator is driven by two forces acting both in phase, a fixed sinusoidal force and a feedback force whose amplitude depends on the phase shift. This dependence exhibits a pronounced maximum when the phase shift is 90°, i.e., at the resonant frequency. Experiments performed with a microcantilever prove that this class of active control decreases the bandwidth of the amplitude re...

Tamayo, Javier; Lechuga, Laura M.

2003-01-01

430

Compression of Video Tracking and Bandwidth Balancing Routing in Wireless Multimedia Sensor Networks  

OpenAIRE

There has been a tremendous growth in multimedia applications over wireless networks. Wireless Multimedia Sensor Networks(WMSNs) have become the premier choice in many research communities and industry. Many state-of-art applications, such as surveillance, traffic monitoring, and remote heath care are essentially video tracking and transmission in WMSNs. The transmission speed is constrained by big size of video data and fixed bandwidth allocation in constant routing path. I...

Wang, Yin; Yang, Jianjun; Shen, Ju; Guo, Juan; Hua, Kun

2014-01-01

431

Analysis of a PLL Based Frequency Synthesizer using Switched Loop Bandwidth for Mobile WiMAX  

OpenAIRE

This document is focused on design aspects of a fractional-N PLL (Phase Locked Loop) based frequency synthesizer proposed for the Mobile WiMAX (Worldwide Interoperability for Mobile Access) standard. Requirements in terms of phase noise, settling time, frequency resolution and frequency of operation for WiMAX frequency synthesizer are presented. Furthermore, a high-speed CP (Charge Pump) PLL based synthesizer with a switched loop bandwidth is proposed and simulated. It has a 32 MHz reference ...

Valenta, Vaclav; Villegas, Martine; Baudoin, Genevieve

2008-01-01

432

Parallel arithmetic encryption for high-bandwidth communications on multicore/GPGPU platforms.  

OpenAIRE

In this work we study the feasibility of high-bandwidth, secure communications on generic machines equipped with the latest CPUs and General-Purpose Graphical Processing Units (GPGPU). We first analyze the suitability of current Nehalem CPU architectures. We show in particular that high performance CPUs are not sufficient by themselves to reach our performance objectives, and that encryption is the main bottleneck. Therefore we also consider the use of GPGPU, and more particularly we measure ...

Jacquin, Ludovic; Roca, Vincent; Roch, Jean-louis; Alali, Mohamed

2010-01-01

433

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

434

APEnet+: high bandwidth 3D torus direct network for petaflops scale commodity clusters  

OpenAIRE

We describe herein the APElink+ board, a PCIe interconnect adapter featuring the latest advances in wire speed and interface technology plus hardware support for a RDMA programming model and experimental acceleration of GPU networking; this design allows us to build a low latency, high bandwidth PC cluster, the APEnet+ network, the new generation of our cost-effective, tens-of-thousands-scalable cluster network architecture. Some test results and characterization of data tra...

Ammendola, Roberto; Biagioni, Andrea; Frezza, Ottorino; Cicero, Francesca Lo; Lonardo, Alessandro; Paolucci, Pier Stanislao; Rossetti, Davide; Salamon, Andrea; Salina, Gaetano; Simula, Francesco; Tosoratto, Laura; Vicini, Piero

2011-01-01

435

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

436

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

437

Reducing the Disk IO Bandwidth Bottleneck through Fast Floating Point Compression using Accelerators  

Directory of Open Access Journals (Sweden)

Full Text Available Compute-intensive tasks in high-end high performance computing (HPC systems often generate large amounts of data, especially floating-point data that need to be transmitted over the network. Although computation speeds are very high, the overall performance of these applications is affected by the data transfer overhead. Moreover, as data sets are growing in size rapidly, bandwidth limitations pose a serious bottleneck in several scientific applications. Fast floating point compression can ameliorate the bandwidth limitations. If data is compressed well, then the amount of data transfer is reduced. This reduction in data transfer time comes at the expense of the increased computation required by compression and decompression. It is important for compression and decompression rates to be greater than the network bandwidth; otherwise, it will be faster to transmit uncompressed data directly [1]. Accelerators such as Graphics Processing Units (GPU provide much computational power. In this paper, we show that the computational power of GPUs and CellBE processor can be harnessed to provide sufficiently fast compression and decompression for this approach to be effective for data produced by many practical applications. In particularly, we use Holt`s Exponential smoothing algorithm from time series analysis, and encode the difference between its predictions and the actual data. This yields a lossless compression scheme. We show that it can be implemented efficiently on GPUs and CellBE to provide an effective compression scheme for the purpose of saving on data transfer overheads The primary contribution of this work lies in demonstrating the potential of floating point compression in reducing the I/O bandwidth bottleneck on modern hardware for important classes of scientific applications.

Ajith Padyana

2014-03-01

438

Infinite phased arrays of microstrip antennas with parasitic elements: application to bandwidth enhancement  

Science.gov (United States)

Microstrip phased array antennas obtained by the association of two interdigitated biperiodic coplanar subarrays are presented. One of these two subarrays is fed, and the other is parasitic. This type of array is studied for rectangular or triangular patches, using an infinite phased array model for the theoretical approach (1) -(5) . Frequency bandwidth obtained with this geometry is larger than that of conventional monolayer microstrip antennas.

Staraj, Robert; Cambiaggio, Edmond; Papiernik, Albert

1994-05-01

439

A routing and cross-layering approach for energy and bandwidth efficiency in Wireless Sensor Networks  

OpenAIRE

A Wireless Sensor Network (WSN) consists of a large number of small, low-cost and low-power wireless sensing nodes. WSNs can gather information about the environment automatically and unattended and are suitable for many applications. The typical characteristic of WSNs is that they are energy and bandwidth constrained. Hence, routing protocols and algorithms for WSN must aim to conserve these two scarce resources. WSNs are also highly application-specific. This mean, firstly, that there is a ...

Flathagen, Joakim

2013-01-01

440

New Bandwidth Guaranteed QoS Routing Algorithm for MPLS Networks  

OpenAIRE

Internet has become an integrated carrier gradually, which has multi business such as data, voice, video, multimedia and so on. New multimedia applications require the network to guarantee quality of service. MPLS network has the capability of routing with some specific constraints for supporting desired QoS, out of which bandwidth is the most important constraint. The efficient routing algorithm should have low computational complexity, high network utilization and low call blocking percent...

Santosh Kulkarni; Reema Sharma; Ishani Mishra

2012-01-01

441

New methods for more effective use of bandwidth in MPLS networks with fast rerouting  

Science.gov (United States)

Multi-protocol label switching (MPLS) technology is useful for IP Virtual Private Networks (IP-VPNs), guaranteeing bandwidth in IP (Internet Protocol) networks, and carrying out traffic engineering with explicit routing. The advantage of MPLS is its high capability to achieve of reliable networks when used with Fast Rerouting. However, Fast Rerouting requires a lot of network resources. This is because, for the rapid recovery of end-to-end communications after detection of failures, secondary LSPs must already have been reserved as detours in case there are failures on primary node-to-node links. The sharing of bandwidth among secondary LSPs is thus significant as a way of reducing the usage of network resources when Fast Rerouting is applied. In this paper, we propose a new routing algorithm in which bandwidth is shared among the secondary LSPs for multiple primary LSPs. This algorithm produces efficient network-level LSP designs. Three approaches to the dynamical changing of Open Shortest Path First (OSPF) link-cost metrics are applied in the algorithm. Each approach improves efficiency in the sharing of LSPs. The approaches are (1) the broader distribution of primary LSPs to reduce the need for detours in cases of single failures, (2) the concentration of secondary LSPs on links to increase the possibilities for bandwidth sharing, and (3) the distribution of secondary LSPs that cater to a certain failure, thus increasing the numbers of detouring LSPs which are independent of each other on the respective links. The scheme provides a slight improvement over the results of the conventional Dijkstra-algorithm calculation which is used in conventional OSPF. The proposed algorithms are applied with various network models that have been proposed in IETF Internet drafts, e.g.,

Matsuoka, Yasuyuki; Kurimoto, Takashi; Nishikido, Jun; Urushidani, Shigeo

2002-09-01

442

A high-bandwidth, high-voltage divider for neutral injectors  

International Nuclear Information System (INIS)

A description is given of the design, construction, calibration and testing of a voltage divider for which the influence of space potential variation as well as the pick-up of RF- and inductive interference is grossly reduced by its special design. It features voltage capability up to 160 kV, measuring accuracy approaching 10-3 over a bandwidth from d.c. to 100 kHz with negligible phase error, and useful measuring capability to beyond 10 MHz. (author)

443

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

444

High-bandwidth fiber-optic system using laser-diode transmitters  

International Nuclear Information System (INIS)

A system has been developed to transmit analog signals through 1-km-long fiber-optic cables having bandwidths up to 1.5 GHz. Semiconductor injection laser-diode transmitters operating at a wavelength of about 815 nm are directly modulated by electrical signals from radiation detectors. Graded-index optical fibers transmit the optical signals to a remote facility, where they are recorded on a single streak camera

445

Design of bandwidth enhanced and multiband MIMO antennas using characteristic modes  

OpenAIRE

Recent work has shown that, with the help of the Theory of Characteristic Modes (TCM), minor modifications of the terminal chassis can facilitate the design of orthogonal MIMO antennas with viable bandwidth at frequencies below 1 GHz. Herein, a new framework is proposed to further exploit TCM to enhance the performance of the orthogonal MIMO antennas. By correlating the characteristic currents and near fields of modes with high modal significance in a given frequency band, a single feed may b...

Miers, Zachary; Li, Hui; Lau, Buon Kiong

2013-01-01

446

Centralized and distributed routing and spectrum assignment schemes for bandwidth-variable optical networks  

Science.gov (United States)

Flexible bandwidth networking has recently been proposed as a spectrally efficient networking technology that effectively supports dynamically varying traffic demands [1]. This networking technology provides an opportunity to maximize spectral efficiency for each of many arbitrary bandwidth channels generated using one of many possible modulation formats [2]. Path Computation Element (PCE) is first introduced for dynamic routing and spectrum assignment problem in elastic optical network. We proposed three centralized and distributed routing and spectrum assignment solutions. They are Centralized Routing and Distributed Spectrum Assignment (CR+DSA), Centralized Routing and Centralized Spectrum Assignment (CR+CSA) and Distributed Routing and Distributed Spectrum Assignment (DR+DSA). The two centralized proposals both own PCE in its architecture. The performance of three proposed centralized and distributed routing and spectrum assignment solutions have been analyzed and compared. For the experimental evaluation, the performance of Centralized Routing and Centralized Spectrum Assignment is the most adaptable RSA strategy for the whole bandwidth-variable optical networks with dynamic traffic.

Wang, Jingjing; Zhao, Yongli; Zhang, Jie; Wu, Yuyao; Gu, Wanyi; Wang, Dajiang; Cao, Xuping

2011-12-01

447

A Dynamic Bandwidth Assignment Approach Under DDoS Flood Attack  

Directory of Open Access Journals (Sweden)

Full Text Available Distributed denial-of-service (DDoS attacks are a major threat to the Internet. A lot of research is going on to detect, prevent and trace back DDoS attacks. Most of researchers are busy in post attack forensics which comes after the attack has been occurred but nobody is talking about how to design a system which can tolerate such attacks. In this paper we have suggested a approach for dynamic assignment of bandwidth in order to sustain the server. Basic idea is to examine genuine IP user’s traffic flow based on volume. Divide traffic in two categories of genuine traffic and malicious traffic and assign bandwidth as per category. The idea is to design a system which can give services even when the server is under attack. However some performance will degrades but overall Quality of services will be acceptable. A new formula also has been derived for dynamic bandwidth assignment which is based on number of genuine users and traffic volumes of users and attackers.

Raman Singh

2012-05-01

448

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

449

Nonparametric density estimation and optimal bandwidth selection for protein unfolding and unbinding data  

Science.gov (United States)

Dynamic force spectroscopy and steered molecular simulations have become powerful tools for analyzing the mechanical properties of proteins, and the strength of protein-protein complexes and aggregates. Probability density functions of the unfolding forces and unfolding times for proteins, and rupture forces and bond lifetimes for protein-protein complexes allow quantification of the forced unfolding and unbinding transitions, and mapping the biomolecular free energy landscape. The inference of the unknown probability distribution functions from the experimental and simulated forced unfolding and unbinding data, as well as the assessment of analytically tractable models of the protein unfolding and unbinding requires the use of a bandwidth. The choice of this quantity is typically subjective as it draws heavily on the investigator's intuition and past experience. We describe several approaches for selecting the "optimal bandwidth" for nonparametric density estimators, such as the traditionally used histogram and the more advanced kernel density estimators. The performance of these methods is tested on unimodal and multimodal skewed, long-tailed distributed data, as typically observed in force spectroscopy experiments and in molecular pulling simulations. The results of these studies can serve as a guideline for selecting the optimal bandwidth to resolve the underlying distributions from the forced unfolding and unbinding data for proteins.

Bura, E.; Zhmurov, A.; Barsegov, V.

2009-01-01

450

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

451

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

452

Modern Fiber Optic Submarine Cable Telecommunication Systems Planning for Explosive Bandwidth Needs at Different Deployment Depths  

Directory of Open Access Journals (Sweden)

Full Text Available The explosive bandwidth needs, especially in the inter data center market, have pushed transmission data rates to 100 Gbit/sec and beyond. Current terrestrial fibers are inadequate for long haul, high bandwidth deployments. To solve these problems a new fiber is introduced for terrestrial high bandwidth deployments: different polymeric core fibers with enlarged effective area with a significant optical signal to noise ratio improvement over other conventional terrestrial single mode fibers. To ensure the new fiber may be deployed robustly a new coating structure was employed. A rigorous cable structure was then chosen for evaluation. Based on experimental data, both the deep ocean water temperature and pressure are tailored as functions of the water depth. As well as the product of the transmitted bit rate and the repeater spacing is processed over wide ranges of the affecting parameters. It is taken into account the estimation of the total cost of the submarine fiber cable system for transmission technique under considerations. The system capacity as well as the spectral losses, and the dispersion effects are parametrically investigated over wide range ranges of the set of affecting parameters {wavelength, ocean depth (and consequently the ocean pressure and temperature, and the chemical structure}.

Ahmed Nabih Zaki Rashed

2012-10-01

453

Multi-path Probabilistic Available Bandwidth Estimation through Bayesian Active Learning  

CERN Document Server

Knowing the largest rate at which data can be sent on an end-to-end path such that the egress rate is equal to the ingress rate with high probability can be very practical when choosing transmission rates in video streaming or selecting peers in peer-to-peer applications. We introduce probabilistic available bandwidth, which is defined in terms of ingress rates and egress rates of traffic on a path, rather than in terms of capacity and utilization of the constituent links of the path like the standard available bandwidth metric. In this paper, we describe a distributed algorithm, based on a probabilistic graphical model and Bayesian active learning, for simultaneously estimating the probabilistic available bandwidth of multiple paths through a network. Our procedure exploits the fact that each packet train provides information not only about the path it traverses, but also about any path that shares a link with the monitored path. Simulations and PlanetLab experiments indicate that this process can dramatical...

Thouin, Frederic; Rabbat, Michael

2010-01-01

454

Task Mapping and Bandwidth Reservation for Mixed Hard/Soft Fault-Tolerant Embedded Systems  

DEFF Research Database (Denmark)

In this paper we are interested in mixed hard/soft real-time fault-tolerant applications mapped on distributed heterogeneous architectures. We use the Earliest Deadline First (EDF) scheduling for the hard real-time tasks and the Constant Bandwidth Server (CBS) for the soft tasks. The bandwidth reserved for the servers determines the quality of service (QoS) for soft tasks. CBS enforces temporal isolation, such that soft task overruns do not affect the timing guarantees of hard tasks. Transient faults in hard tasks are tolerated using checkpointing with rollback recovery. We have proposed a Tabu Search-based approach for task mapping and CBS bandwidth reservation, such that the deadlines for the hard tasks are satisfied, even in the case of transient faults, and the QoS for the soft tasks is maximized. Researchers have used fixed execution time models, such as the worst-case execution times for hard tasks and average execution times for soft tasks. However, we show that by using stochastic execution times for soft tasks, significant improvements can be obtained. The proposed strategy has been evaluated using an extensive set of benchmarks.

Saraswat, Prabhat Kumar; Pop, Paul

2010-01-01

455

An Improved Fitness Function and Mutation Operator for Metaheuristic Approaches to the Bandwidth Minimization Problem  

Science.gov (United States)

The Bandwidth Minimization Problem (BMP) is a graph layout problem which is known to be NP-complete. Since 1960, a considerable number of algorithms have been developed for addressing the BMP. At present, meta-heuristics (such as evolutionary algorithms and tabu search) are popular and successful approaches to the BMP. In such algorithms, the design of the fitness function (i.e. the metric that attempts to guide the search towards high-quality solutions) plays a key role in performance; the fitness function, along with the operators, induce the `search landscape', and careful attention to these issues may lead to landscapes that are more amenable to successful search. For example, rather than simply use the most obvious quality measure (in this case, the bandwidth itself), it is often helpful to design a more informative measure, indicating not only a solutions quality, but also encapsulating (for example) an indication of how distant this particular solution is from even better solutions. In this paper, a new fitness function and an associated new mutation operator are presented for BMP. These are incorporated within a simple Evolutionary Algorithm (EA), and evaluated on a set of 27 instances of the BMP (from the Harwell-Boeing sparse matrix collection). The results of this EA are compared with results obtained by using the standard fitness function (used in almost all previous researches on metaheuristics applied to the BMP). The results indicate clearly that the new fitness function and operator performed provide significantly superior results in the reduction of bandwidth.

Koohestani, Behrooz; Corne, David W.

2009-04-01

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

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

458

Adaptive Video Streaming Using Bandwidth Estimation for 3.5G Mobile Network  

Science.gov (United States)

Currently deployed mobile networks including High Speed Downlink Packet Access (HSDPA) offer only best-effort Quality of Service (QoS). In wireless best effort networks, the bandwidth variation is a critical problem, especially, for mobile devices with small buffers. This is because the bandwidth variation leads to packet losses caused by buffer overflow as well as picture freezing due to high transmission delay or buffer underflow. In this paper, in order to provide seamless video streaming over HSDPA, we propose an efficient real-time video streaming method that consists of the available bandwidth (AB) estimation for the HSDPA network and the transmission rate control to prevent buffer overflows/underflows. In the proposed method, the client estimates the AB and the estimated AB is fed back to the server through real-time transport control protocol (RTCP) packets. Then, the server adaptively adjusts the transmission rate according to the estimated AB and the buffer state obtained from the RTCP feedback information. Experimental results show that the proposed method achieves seamless video streaming over the HSDPA network providing higher video quality and lower transmission delay.

Nam, Hyeong-Min; Park, Chun-Su; Jung, Seung-Won; Ko, Sung-Jea

459

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

460

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

461

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

462

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

463

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

464

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

465

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)

466

Bandwidths of micro-twisted-pair cables and fusion-spliced SIMM-GRIN fiber  

International Nuclear Information System (INIS)

The SLHC is designed to increase the luminosity of the LHC by a factor of 10. In the present ATLAS pixel detector, electrical signals between the pixel modules and the optical modules (opto-boards) are transmitted in ?1 m of micro-twisted-pair cables. The optical signals between the opto-boards and the off-detector optical modules are transmitted in fiber ribbons. Each fiber link consists of 8 m of rad-hard/low bandwidth SIMM fiber fusion spliced to 70 m of rad-tolerant/medium bandwidth GRIN fiber. We currently transmit optical signals at 80 Mb/s and expect to transmit signals at 1 Gb/s in the SLHC. For the SLHC optical link, we would like to take advantage of some of the design features of the present pixel optical links and the many years of R and D effort and production experience. If the present architecture can transmit signals at the higher speed required by the SLHC, the constraint of requiring no extra service space is automatically satisfied. We have measured the bandwidths of the transmission lines and our preliminary results indicate that the micro-twisted-pair cables can transmit signals up to ?1 Gb/s and the fusion-spliced fiber ribbon can transmit signals up to ?2 Gb/s

467

Development of a wide bandwidth heterodyne detector using a photoconductive element  

International Nuclear Information System (INIS)

Studies on a photoconductive detector such as Ge-Ga detector are described. Successful construction of the detector which works for a heterodyne mode detection with a wide bandwidth and low noise represents a progress in the FIR plasma diagnostics. Video detection in a photoconductor, heterodyne detection by a photoconductor, noise in FIR detection, the noise equivalent power (NEP) in the video mode detection (NEP-V), and NEP in the heterodyne mode (NEP-H) were studied. The minimum signal can be detected by using the photoconductive detector. With the experimental data of signal power, LO power, the voltage responsiveness and the correlation coefficient between the signal and the LO beam, the heterodyne voltage signal at the input should be 147 ?V. By using a 100 voltage gain preamplifier, the heterodyne voltage signal of 14.7 mV can be obtained at the output. The signal power at the input is 21.6 PW. The noise power at the input is 10-13 W by setting the bandwidth of 5 MHz. The signal to noise power ratio at the input by setting the bandwidth of 50 Hz is 2.16 x 107. The characteristics of the Ge-Ga detector to be used were determined. It is possible to get information of the limited capability with the fast response by using 10 ?m radiation, which can be easily modulated. (Kato, T.)

468

A constant loop bandwidth fractional-N frequency synthesizer for GNSS receivers  

International Nuclear Information System (INIS)

A constant loop bandwidth fractional-N frequency synthesizer for portable civilian global navigation satellite system (GNSS) receivers implemented in a 130 nm 1P6M CMOS process is introduced. Via discrete working regions, the LC-VCO obtains a wide tuning range with a simple structure and small VCO gain. Spur suppression technology is proposed to minimize the phase offset introduced by PFD and charge pumps. The optimized bandwidth is maintained by an auto loop calibration module to adjust the charge pump current when the PLL output frequency changes or the temperature varies. Measurement results show that this synthesizer attains an in-band phase noise lower than ?93 dBc at a 10 kHz offset and a spur less than ?70 dBc; the bandwidth varies by ± 3% for all the GNSS signals. The whole synthesizer consumes 4.5 mA current from a 1 V supply, and its area (without the LO tested buffer) is 0.5 mm2. (semiconductor integrated circuits)

469

Dynamic bandwidth allocation policy for multiple QoS multimedia traffic in ATM networks  

Science.gov (United States)

In ATM Networks, real time VBR traffic, which is inherently bursty in nature, requires dynamic bandwidth allocation. There are algorithms proposed in the literature where the bandwidth is allocated in linear proportion to the requirements. But, these algorithms lead to unequal growth in the queue size and reduction in the network performance. Minmax algorithm is one such algorithm which maintains a fair distribution of buffer lengths across the sources of a class, and performs better for homogeneous sources when compared to other dynamic allocation schemes. Nevertheless, this algorithm can be applied only when the sources demand same QoS parameter. To overcome such an inadequacy, we propose a novel method of dynamic bandwidth allocation, viz., Modified Minmax Algorithm (MMA), for multiple QoS sources. Unlike other models, MMA takes cell loss ratio (CLR) also into account besides the buffer occupancies and arrival rates. The performance of MMA has been evaluated using multiple QoS sources simulated for this purpose. The results are encouraging, for it gives better QoS performance (by an order of one) for hetrogeneous sources with different QoS values. Results on the evaluation of the performance of delay and jitter for various buffer sizes are also presented in this paper.

Chandramathi, Soundararajan; Shanmugavel, Subbaiah

2001-11-01

470

A Novel Dynamic Bandwidth Allocation Model for Energy Efficient Multi-beam STICS Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Dynamic bandwidth allocation, keeping in view of energy efficiency is the utmost solutions to achieve flexible and efficient satellite based cellular networks. This would be helpful for communicating with anywhere and with anyone with global coverage. In this research article it is proposed that the assignment of bandwidth must be dynamic for this energy efficient mobile-satellite integrated system since user capacity demand is going to double by 2020. The model for such assignment is chosen in terms of obtaining energy efficiency thereby conducting measurement of interference. For this the quality of service on the basis of link control of threshold for a spectrum must be known. A pattern with frequency reuse ratio of 1 and 3 is selected consecutively keeping the fixed access satellites constant for the evaluation of energy efficient STICS systems. If the quality of link obtained from proposed model is maintained greater than blocking rate the frequency reuse would be unity. But in ideal case we can say that bandwidth requirement for quite large users can be sustained by implementing the model described in this paper

Ramya Ranjan Choudhury

2014-06-01

471

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

472