WorldWideScience

Sample records for small-signal 3db bandwidth

  1. Analysis of small-signal intensity modulation of semiconductor lasers taking account of gain suppression

    Indian Academy of Sciences (India)

    Moustafa Ahmed; Ali El-Lafi

    2008-07-01

    This paper demonstrates theoretical characterization of intensity modulation of semiconductor lasers (SL’s). The study is based on a small-signal model to solve the laser rate equations taking into account suppression of optical gain. Analytical forms of the small-signal modulation response and modulation bandwidth are derived. Influences of the bias current, modulation index and modulation frequency as well as gain suppression on modulation characteristics are examined. Computer simulation of the model is applied to $1.55-\\mu$m InGaAsP lasers. The results show that when the SL is biased far-above threshold, the increase of gain suppression increases both the modulation response and its peak frequency. The modulation bandwidth also increases but the laser damping rate decreases. Quantitative description of the relationships of both modulation bandwidth vs. relaxation frequency and maximum modulation bandwidth vs. nonlinear gain coefficient are presented.

  2. Small-signal modulation characteristics of a polariton laser.

    Science.gov (United States)

    Baten, Md Zunaid; Frost, Thomas; Iorsh, Ivan; Deshpande, Saniya; Kavokin, Alexey; Bhattacharya, Pallab

    2015-01-01

    Use of large bandgap materials together with electrical injection makes the polariton laser an attractive low-power coherent light source for medical and biomedical applications or short distance plastic fiber communication at short wavelengths (violet and ultra-violet), where a conventional laser is difficult to realize. The dynamic properties of a polariton laser have not been investigated experimentally. We have measured, for the first time, the small signal modulation characteristics of a GaN-based electrically pumped polariton laser operating at room temperature. A maximum -3?dB modulation bandwidth of 1.18?GHz is measured. The experimental results have been analyzed with a theoretical model based on the Boltzmann kinetic equations and the agreement is very good. We have also investigated frequency chirping during such modulation. Gain compression phenomenon in a polariton laser is interpreted and a value is obtained for the gain compression factor. PMID:26154681

  3. 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)

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

    OpenAIRE

    SUSMRITA SRIVASTAVA; NARESH KUMAR CHAUDHARY; SACHCHIDANAND SHUKLA

    2013-01-01

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

  5. Small-signal modeling of graphene barristors

    Science.gov (United States)

    Khayatian, Ahmad; Mohammadi, Saeed; Keshavarzi, Parviz

    2015-08-01

    This paper presents a small-signal model for graphene barristor, a promising device for the future nanoelectronics industry. Because of the functional similarities to the conventional FET transistors, the same configuration and parameters, as those of FETs, are assumed for the model. Transconductance, output resistance, and parasitic capacitances are the main parameters of the small signal equivalent circuit modeled in this work. Recognizing the importance of physical modeling of novel semiconductor devices, we develop physical compact expressions for the device radio-frequency characteristics. Furthermore, we clarify the physics behind the variation of the characteristics as the device parameters change. We also validate our model results with available simulation results. Impact of equilibrium Schottky barrier height of the graphene-silicon junction on the radio frequency performance of barristor is investigated, too.

  6. Small signal solutions of the transport equations

    International Nuclear Information System (INIS)

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

  7. A New Circuit Model of Small-Signal Sziklai Pair Amplifier

    OpenAIRE

    SachchidaNand Shukla and Susmrita Srivastava

    2013-01-01

    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...

  8. A New Circuit Model of Small-Signal Sziklai Pair Amplifier

    Directory of Open Access Journals (Sweden)

    SachchidaNand Shukla and Susmrita Srivastava

    2013-07-01

    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.

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

    OpenAIRE

    SACHCHIDANAND SHUKLA; SUSMRITA SRIVASTAVA

    2013-01-01

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

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

    Directory of Open Access Journals (Sweden)

    DR.SACHCHIDANAND SHUKLA

    2013-06-01

    Full Text Available A new circuit model of a small-signal amplifier is proposed and analyzed on the qualitative scale. Apart from routine biasing components, the proposed amplifier circuit uses two additional biasing resistances and three dissimilar active devices namely MOSFET, JFET and BJT in Triple Darlington configuration. Having a considerably low amount of distortion (0.71%, the proposed circuit successfully amplifies small-signals of 1-5mV range (at 1 KHz frequency and simultaneously provides high voltage gain (189.846 and high current gain (16.542K with moderate range bandwidth (369.529KHz. These properties offer a flexible application range to the proposed circuit as high voltage gain or high current gain or high power gain amplifier in permissible audio-frequency range. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters, bandwidth and total harmonic distortion of the amplifier are perused to provide a wide spectrum to the qualitative studies. Qualitative performance of the proposed amplifier is also compared with two different circuits which are respectively having BJT-JFET and BJT-MOSFET in Darlington pair configuration. The proposed amplifier may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in audio frequency region.

  11. A small - signal stability analysis of DFIG wind generation

    OpenAIRE

    Vittal, Eknath; O'MALLEY, MARK, J.; Keane, Andrew

    2009-01-01

    This paper examines the small-signal stability impacts of high penetrations of doubly-fed induction generator (DFIG) wind turbines on power systems. It provides a basic overview of small-signal stability concepts and then examines the response of DFIG generation to two local contingency event. Using the New England 39 bus test system, this paper will demonstrate the stability implications of DFIG turbines utilizing terminal voltage control and fixed power factor control in response...

  12. Small-signal analysis of a saturated induction motor

    Energy Technology Data Exchange (ETDEWEB)

    Ranta, M.; Hinkkanen, M.; Repo, A.-K.; Luomi, J. (Helsinki University of Technology, Department of Electrical Engineering, Espoo (Finland))

    2008-07-01

    Due to magnetic saturation, the small-signal admittance of an induction motor is dependent on the direction of the excitation signal. The angle-dependence of the admittance can be used in the estimation of the flux angle, and it should be taken into account when identifying motor parameters. In this paper, the small-signal admittance of a 2.2-kW induction motor is measured at different excitation frequencies and operating points. The measured admittances are compared to data obtained by means of finite element analysis (FEA). A small-signal model of the induction motor is fitted to the admittances to analyze the results. The admittances obtained from FEA and laboratory experiments correspond well to each other, particularly at low excitation frequencies. (orig.)

  13. Power system small signal stability analysis and control

    CERN Document Server

    Mondal, Debasish; Sengupta, Aparajita

    2014-01-01

    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

  14. Gain and bandwidth in stagger-tuned gyroklystrons

    International Nuclear Information System (INIS)

    An analytical theory describing the trade-off in the bandwidth and gain in multicavity, stagger-tuned gyroklystrons (GKLs) is developed. The assumption that the cavities are short and therefore the electron ballistic bunching proceeds in long drift sections (point-gap model) allows us to develop analytically both the small-signal and large-signal theories of stagger-tuned GKLs. The results for two-, three-, and four-cavity GKLs are presented which illustrate the bandwidth increase, the gain degradation, and the increase in gain-bandwidth product due to the stagger tuning. copyright 1997 American Institute of Physics

  15. Robustness of Supersensitivity to Small Signals in Nonlinear Dynamical Systems

    OpenAIRE

    Zhou, Changsong; Lai, C.-H.

    2000-01-01

    Nonlinear dynamical systems possessing an invariant subspace can display interesting dynamical behavior, such as on-off intermittency and bubbling. This letter shows that a class of such systems have amazing features of (1) supersensitivity to small input signals and (2) robustness of the supersensitivity in the presence of noise. These features make the systems very promising as small signal detectors.

  16. DFIG turbine representation for small signal voltage control studies

    DEFF Research Database (Denmark)

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

    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 ce...

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

    Directory of Open Access Journals (Sweden)

    SUSMRITA SRIVASTAVA

    2013-02-01

    Full Text Available A new circuit model of a small-signal narrow-band amplifier is proposed and analyzed on the qualitative scale. Proposed amplifier uses two MOSFETs and a BJT in Triple Darlington configuration with two additional biasing resistances in the circuit. With low distortion percentage (1.28%, the proposed circuit successfully amplifies small-signals of 1-10mV range and simultaneously provides high voltage gain (311.593 and current gain (13.971K with narrow bandwidth (9.665KHz. Variations of maximum voltage gain with different biasing resistances and DC supply voltage and the temperature sensitivity of various performance parameters are elaborately studied and discussed in length. Qualitative performance of the proposed amplifier is also compared with the circuit which is having BJT-MOSFET in Darlington pair configuration. The proposed amplifier can be used to process audio range signal excursions and may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in narrow-band low frequency region.

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

    Directory of Open Access Journals (Sweden)

    SACHCHIDANAND SHUKLA

    2013-05-01

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

  19. Comparative study of probabilistic methodologies for small signal stability assessment

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-01

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

  20. Improving Small Signal Stability through Operating Point Adjustment

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-09-30

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

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

    Directory of Open Access Journals (Sweden)

    DR. SACHCHIDANAND SHUKLA

    2013-04-01

    Full Text Available A small-signal amplifier with two identical JFETs in Darlington pair is proposed and qualitatively analyzed perhaps for the first time. Unlike CS-JFET amplifiers, the voltage gain of this amplifier is significantly higher than unity. In addition, this amplifier can also be tuned in the specific range of audible frequency extended from 90Hz to 19KHz. Tuning performance makes this amplifier suitable to use in Radio and TV receivers. An additional biasing resistance RA, ranging in 3K? to 1M?, is to be essentially used in the proposed circuit to maintain its voltage/current amplification property. With this additional biasing resistance, the proposed amplifier crops considerably wide bandwidth (12.365MHz, significantly high current gain (530.909 and fairly high voltage gain (9.108 in 1-80mV input signal range at 1 KHz frequency. These properties offer a flexible application range to the proposed amplifier as high power gain, wide band, or tuned amplifier in permissible audio-frequency range. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters, bandwidth and total harmonic distortion of the amplifier are also perused to provide a wide spectrum to the qualitative studies

  2. Chemical Industry Bandwidth Study

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2006-12-01

    The Chemical Bandwidth Study provides a snapshot of potentially recoverable energy losses during chemical manufacturing. The advantage of this study is the use of "exergy" analysis as a tool for pinpointing inefficiencies.

  3. Glass Industry Bandwidth Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Rue, David M. [Gas Technology Inst., Des Plaines, IL (United States)

    2006-07-01

    This is a study on energy use and potential savings, or "bandwidth" study, for several glassmaking processes. Intended to provide a realistic estimate of the potential amount of energy that can be saved in an industrial process, the "bandwidth" refers to the difference between the amount of energy that would be consumed in a process using commercially available technology versus the minimum amount of energy needed to achieve those same results.

  4. Industrial Glass Bandwidth Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Rue, David M. [Gas Technology Inst., Des Plaines, IL (United States); Servaites, James [Gas Technology Inst., Des Plaines, IL (United States); Wolf, Warren [Gas Technology Inst., Des Plaines, IL (United States)

    2007-08-01

    This is a study on energy use and potential savings, or "bandwidth" study, for several glassmaking processes. Intended to provide a realistic estimate of the potential amount of energy that can be saved in an industrial process, the "bandwidth" refers to the difference between the amount of energy that would be consumed in a process using commercially available technology versus the minimum amount of energy needed to achieve those same results.

  5. Thermal Effects and Small Signal Modulation of 1.3-μm InAs/GaAs Self-Assembled Quantum-Dot Lasers

    Directory of Open Access Journals (Sweden)

    Tong CZ

    2011-01-01

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

  6. The Bandwidth Exchange Architecture

    CERN Document Server

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

    2005-01-01

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

  7. Low-bandwidth authentication.

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-09-01

    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.

  8. Bandwidth in bolometric interferometry

    Science.gov (United States)

    Charlassier, R.; Bunn, E. F.; Hamilton, J.-Ch.; Kaplan, J.; Malu, S.

    2010-05-01

    Context. Bolometric interferometry is a promising new technology with potential applications to the detection of B-mode polarization fluctuations of the cosmic microwave background (CMB). A bolometric interferometer will have to take advantage of the wide spectral detection band of its bolometers to be competitive with imaging experiments. A crucial concern is that interferometers are assumed to be significantly affected by a spoiling effect known as bandwidth smearing. Aims: We investigate how the bandwidth modifies the work principle of a bolometric interferometer and affects its sensitivity to the CMB angular power spectra. Methods: We obtain analytical expressions for the broadband visibilities measured by broadband heterodyne and bolometric interferometers. We investigate how the visibilities must be reconstructed in a broadband bolometric interferometer and show that this critically depends on hardware properties of the modulation phase shifters. If the phase shifters produce shifts that are constant with respect to frequency, the instrument works like its monochromatic version (the modulation matrix is not modified), while if they vary (linearly or otherwise) with respect to frequency, one has to perform a special reconstruction scheme, which allows the visibilities to be reconstructed in frequency subbands. Using an angular power spectrum estimator that accounts for the bandwidth, we finally calculate the sensitivity of a broadband bolometric interferometer. A numerical simulation is performed that confirms the analytical results. Results: We conclude that (i) broadband bolometric interferometers allow broadband visibilities to be reconstructed regardless of the type of phase shifters used and (ii) for dedicated B-mode bolometric interferometers, the sensitivity loss caused by bandwidth smearing is quite acceptable, even for wideband instruments (a factor of 2 loss for a typical 20% bandwidth experiment).

  9. Bandwidth in bolometric interferometry

    CERN Document Server

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

    2009-01-01

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

  10. Forecasting international bandwidth capability

    OpenAIRE

    Madden, Gary G; Coble-Neal, Grant

    2005-01-01

    M-competition studies provide a set of stylized recommendations to enhance forecast reliability. However, no single method dominates across series, leading to consideration of the relationship between selected data characteristics and the reliability of alternative forecast methods. This study conducts an analysis of predictive accuracy in relation to Internet bandwidth loads. Extrapolation techniques that perform best in M-competitions perform relatively poorly in predicting Internet b...

  11. Bandwidth in bolometric interferometry

    OpenAIRE

    Charlassier, R.; Bunn, E.F.; Hamilton, J.-Ch.; Kaplan, J.; Malu, S.

    2009-01-01

    Bolometric Interferometry is a technology currently under development that will be first dedicated to the detection of B-mode polarization fluctuations in the Cosmic Microwave Background. A bolometric interferometer will have to take advantage of the wide spectral detection band of its bolometers in order to be competitive with imaging experiments. A crucial concern is that interferometers are presumed to be importantly affected by a spoiling effect known as bandwidth smeari...

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

    KAUST Repository

    Jahangir, Shafat

    2015-02-16

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

  13. Small-signal theory of subterahertz overmoded surface wave oscillator with distributed wall loss

    Science.gov (United States)

    Wang, Guangqiang; Wang, Jianguo; Li, Shuang; Wang, Xuefeng

    2015-09-01

    A small-signal theory of the overmoded surface wave oscillator (SWO) with distributed wall loss is presented in this letter. The wall loss considered here includes the surface resistance and surface roughness. The cold and hot characteristics of 0.14 THz SWO are studied by the small-signal theory. Numerical results show that as the increase of wall loss, the working frequency decreases slightly, the rise time and startup time of oscillation increase significantly, and the output power decreases dramatically. Particle-in-cell (PIC) simulation confirms the prediction by the small-signal theory.

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

    DEFF Research Database (Denmark)

    Hu, Weihao; Su, Chi; Chen, Zhe; Bak-Jensen, Birgitte

    2011-01-01

    electricity price is proposed. A 17-bus power system with high wind power penetrations, which resembles the Eastern Danish power system, is chosen as the study case. Simulation results show that the optimal load response to electricity prices is an effective measure to improve the small signal stability of...... for demand side management generates different load profiles and may provide an opportunity to improve the small signal stability of power systems with high wind power penetrations. In this paper, the idea of power system small signal stability improvement by using optimal load response to the...... power systems with high wind power penetrations....

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

    OpenAIRE

    DR. SACHCHIDANAND SHUKLA; SUSMRITA SRIVASTAVA

    2013-01-01

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

  16. Small Signal Model for VSC-HVDC Connected DFIG-Based Offshore Wind Farms

    OpenAIRE

    Kai Liao; Zheng-you He; Bin Sun

    2014-01-01

    Large-scale offshore wind farms are integrated with onshore ac grids through the voltage source converter based high voltage direct current (VSC-HVDC) transmission system. The impact on the stability of the ac grids will be significant. The small signal model of a wind farm connected with voltage source converter based dc transmission system is studied in this paper. A suitable model for small signal stability analysis is presented. The control system of wind generator and the HVDC system has...

  17. Estimating Bottleneck Bandwidth using TCP

    Science.gov (United States)

    Allman, Mark

    1998-01-01

    Various issues associated with estimating bottleneck bandwidth using TCP are presented in viewgraph form. Specific topics include: 1) Why TCP is wanted to estimate the bottleneck bandwidth; 2) Setting ssthresh to an appropriate value to reduce loss; 3) Possible packet-pair solutions; and 4) Preliminary results: ACTS and the Internet.

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

    Directory of Open Access Journals (Sweden)

    Zi Lan Zhao

    2013-04-01

    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.

  19. Small-signal modelling and control of photovoltaic based water pumping system.

    Science.gov (United States)

    Ghosh, Arun; Ganesh Malla, Siva; Narayan Bhende, Chandrasekhar

    2015-07-01

    This paper studies small-signal modelling and control design for a photovoltaic (PV) based water pumping system without energy storage. First, the small-signal model is obtained and then, using this model, two proportional-integral (PI) controllers, where one controller is used to control the dc-link voltage and the other one to control the speed of induction motor, are designed to meet control goals such as settling time and peak overshoot of the closed loop responses. The loop robustness of the design is also studied. For a given set of system parameters, simulations are carried out to validate the modelling and the control design. PMID:25707717

  20. Benchmarking of small-signal dynamics of single-phase PLLs

    DEFF Research Database (Denmark)

    Zhang, Chong; Wang, Xiongfei; Blaabjerg, Frede; Wang, Weisheng

    Phase-looked Loop (PLL) is a critical component for the control and grid synchronization of grid-connected power converters. This paper presents a benchmarking study on the small-signal dynamics of three commonly used PLLs for single-phase converters, including enhanced PLL, second......-order generalized integrator based PLL, and the inverse-PLL. First, a unified small-signal model of those PLLs is established for comparing their dynamics. Then, a systematic design guideline for parameters tuning of the PLLs is formulated. To confirm the validity of theoretical analysis, nonlinear time...

  1. T3DB: an integrated database for bacterial type III secretion system

    Directory of Open Access Journals (Sweden)

    Wang Yejun

    2012-04-01

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

  2. Network Bandwidth Utilization Forecast Model on High Bandwidth Network

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Wucherl; Sim, Alex

    2014-07-07

    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.

  3. Black Holes, Bandwidths and Beethoven

    CERN Document Server

    Kempf, A

    2000-01-01

    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.

  4. Steel Industry Energy Bandwidth Study

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2004-10-01

    ITP conducted a study on energy use and potential savings, or "bandwidth" study, in major steelmaking processes. Intended to provide a realistic estimate of the potential amount of energy that can be saved in an industrial process, the "bandwidth" refers to the difference between the amount of energy that would be consumed in a process using commercially available technology versus the minimum amount of energy needed to achieve those same results based on the 2nd law of thermodynamics. The Steel Industry Energy Bandwidth Study (PDF 133 KB) also estimates steel industry energy use in the year 2010, and uses that value as a basis for comparison against the minimum requirements. This energy savings opportunity for 2010 will aid focus on longer term R&D.

  5. Mining Industry Energy Bandwidth Study

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2007-07-01

    The Industrial Technologies Program (ITP) relies on analytical studies to identify large energy reduction opportunities in energy-intensive industries and uses these results to guide its R&D portfolio. The energy bandwidth illustrates the total energy-saving opportunity that exists in the industry if the current processes are improved by implementing more energy-efficient practices and by using advanced technologies. This bandwidth analysis report was conducted to assist the ITP Mining R&D program in identifying energy-saving opportunities in coal, metals, and mineral mining. These opportunities were analyzed in key mining processes of blasting, dewatering, drilling, digging, ventilation, materials handling, crushing, grinding, and separations.

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

    Directory of Open Access Journals (Sweden)

    Sarkar Anita

    2012-11-01

    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.

  7. Design of 3.7 GHz high power 3db power splitter

    International Nuclear Information System (INIS)

    This paper deals with the design of high power 3db power splitter used in 3.7 GHz Lower Hybrid Current Drive (LHCD) system. The initial structure parameters are obtained by analyzing the theory of o-model and e-model and S parameters matrix. Further analysis is performed by High Frequency Structure Simulator (HFSS) program which make sure C=3.03 db, D=35db, I=38.2 db. The thermal generation and cooling means for the large power transmission situation is analyzed too and the final average temperature is 63 degree C. (authors)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-15

    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.

  9. Improvement of Small Signal Stability of SMIB System Using PSO and CSO based Power System Stabilizer

    OpenAIRE

    Y. Raghuvamsi; Raghavendra Rao, M.

    2015-01-01

    In a power system, Low Frequency Oscillations (LFOs) are dangerous and make system unstable. These oscillations are referred to small signal stability and they are mainly due to lack of damping torque. This insufficient damping torque is because of high gain and low time constant of Automatic Voltage Regulator (AVR). AVR is useful for maintaining the terminal voltage of synchronous machine as constant. While doing so, it will make the system damping torque as negative. For providi...

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

    DEFF Research Database (Denmark)

    Su, Chi; Chen, Zhe

    2012-01-01

    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 contr...

  11. Small signal gain measurements in a small scale HF overtone laser

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-07-01

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

  12. Small-Signal Amplification of Period-Doubling Bifurcations in Smooth Iterated Maps

    OpenAIRE

    Zhao, Xiaopeng; Schaeffer, David G.; Berger, Carolyn M.; Gauthier, Daniel J

    2006-01-01

    Various authors have shown that, near the onset of a period-doubling bifurcation, small perturbations in the control parameter may result in much larger disturbances in the response of the dynamical system. Such amplification of small signals can be measured by a gain defined as the magnitude of the disturbance in the response divided by the perturbation amplitude. In this paper, the perturbed response is studied using normal forms based on the most general assumptions of it...

  13. Small signal gain analysis for a wiggler with noncollinear laser wave and electron beam

    OpenAIRE

    Artemiev, A. I.; Klochkov, D. N.; G. Kurizki; N. P. Poluektov; Shubin, N. Yu.

    2004-01-01

    The collective and single-electron amplification regimes of a non-collinear free electron laser are analyzed within the framework of dispersion equations. The small-signal gain and the conditions for self-amplified excitations are found. The collective excitations in a free electron laser are shown to be favored by the non-collinear arrangement of the relativistic electrons and the laser wave. Implications for free-electron lasing without inversion are discussed.

  14. On estimation of instantaneous bandwidth

    OpenAIRE

    Ristic, B.; Boashash, B.

    1996-01-01

    In many applications, the instantaneous frequency of the observed signal describes some physical phenomenon of interest. The instantaneous frequency can be interpreted as the mean frequency at a particular instant of time. Then it is natural to supplement any measure of the instantaneous frequency by the estimate of its instantaneous spread or bandwidth. Assuming a polynomial model of log-envelope of an AM-FM signal, the paper first considers the maximum likelihood (ML) estimation and Cramer-...

  15. Black Holes, Bandwidths and Beethoven

    OpenAIRE

    Kempf, A.

    1999-01-01

    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. It has been claimed that even the recording of an entire Beethoven symphony can occur as part of a signal with 1Hz bandwidth. Bandlimited functions also occur as ultraviolet regularized fields. Their superoscillations...

  16. 47 CFR 2.202 - Bandwidths.

    Science.gov (United States)

    2010-10-01

    ...prove useful. (b) Necessary bandwidth. For a given class of emission, the minimum value of the occupied bandwidth...to the emission and which depends upon the allowable signal distortion. Nc = Number of baseband telephone channels in radio...

  17. Small-signal transient response and turn-on delay of polariton laser diodes

    Science.gov (United States)

    Butté, Raphaël

    2016-03-01

    We present a theoretical description of the small-signal transient response of polariton laser diodes (pol-LDs) based on simplified coupled rate equations describing the exciton reservoir and the ground-state polariton populations. The analytic expressions derived for two pumping geometries, which are valid for all inorganic semiconductors suitable for the realization of pol-LDs, are compared to exact numerical calculations performed for the specific case of GaN-based devices. The two approaches show excellent agreement provided the current step transient remains within the small-signal limit. We report that the temporal attenuation of the envelopes of the oscillations matches half the value of the damping factor ({γ }{{d}}) of the pol-LDs, which is proportional to the square of the oscillation relaxation resonance frequency. An explicit expression for the dependence of {γ }{{d}} on both the exciton-photon detuning and the driving current (equivalently the optical pump power) is also obtained. In a further step, we derive the expression for the turn-on delay (t d) associated with the build-up of the exciton reservoir population up to its threshold value before coherent light emission occurs. We show that t d has the same functional form for the two pumping geometries. It is equal to the effective exciton lifetime ({τ }{x{eff}}) weighted by a logarithmic dependence on the initial and final driving currents. In addition, {τ }{x{eff}} is shown to be approximately equal to the exciton lifetime, which proves to be the main parameter governing the build-up of polariton lasing/condensation. Beyond electrically driven polariton lasers, we highlight that the temporal shape of the transients could also be easily tested by monitoring the time dependence of the output power of optically pumped polariton lasers subjected to a sudden increase in the continuous wave pump power within the small-signal limit.

  18. Rapid Small-Signal Stability Assessment and Enhancement Following Changes in Topology

    Energy Technology Data Exchange (ETDEWEB)

    Saric, AT; Stankovic, AM

    2015-05-01

    The paper proposes a scalable and tractable algorithm for dynamic topology optimization of power systems involving changes in branch on/off status, while respecting small-signal stability (SSS) constraints. A procedure for fast updates of the system matrices (in descriptor form) and without additional full matrix inversions is proposed. To additionally reduce the computation time, only critical eigenvalues (right-most or those in a specified damping ratio and frequency range) are calculated. A quadratic optimization approach is proposed for optimized generation re-dispatch to satisfy SSS constraints. The approach is applied to two (medium- and large-scale) real-world test power systems.

  19. A small signal theory of gyro-devices using the concept of space-charge waves

    Energy Technology Data Exchange (ETDEWEB)

    Oleinik, M.V.; Trubetskov, D.I. [Saratov State Univ. (Russian Federation). Coll. of Applied Science

    1996-06-01

    The linear theory of the interaction between a thin annular beam of gyrating electrons and a traveling electromagnetic wave is developed. This theory is very close in its methodology to the classical small signal theory of O- and M-type devices. Just this fact makes it possible to consider a number of issues in the theory of gyro-devices, namely, space-charge wave propagation in drifting electron beams, noise and parametric phenomena, effects of input signal suppression (Kompfner dip) in gyro-traveling-wave-tubes, and gyro-backward-wave-amplifiers.

  20. A transfer function approach to the small-signal response of saturated semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Nielsen, Mads LØnstrup; Blumenthal, D. J.

    2000-01-01

    A theoretical analysis of the small-signal frequency response (SSFR) of a wavelength converter based on cross-gain modulation in a semiconductor optical amplifier with a finite waveguide loss is presented. We use a transfer function formalism to explain the resonant behavior of the frequency response. The limitations to the magnitude of the spectral overshoot are also accounted for. Operating with the data and CW signals in a co-propagating configuration, we End that the resonance only exists for a finite waveguide loss. In a counter-propagating scheme, a resonance can exist regardless of the presence of loss.

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

    OpenAIRE

    DR. SACHCHIDANAND SHUKLA; SUSMRITA SRIVASTAVA

    2013-01-01

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

  2. Small-signal amplifier based on single-layer MoS2

    OpenAIRE

    Radisavljevic, Branimir; Whitwick, Michael B.; Kis, Andras

    2012-01-01

    In this letter we demonstrate the operation of an analog small-signal amplifier based on single-layer MoS2, a semiconducting analogue of graphene. Our device consists of two transistors integrated on the same piece of single-layer MoS2. The high intrinsic band gap of 1.8 eV allows MoS2-based amplifiers to operate with a room temperature gain of 4. The amplifier operation is demonstrated for the frequencies of input signal up to 2 kHz preserving the gain higher than 1. Our work shows that MoS2...

  3. LMI Based Wide Area TCSC Controller in Mitigating Small Signal Oscillations

    Directory of Open Access Journals (Sweden)

    D. Mondal

    2012-01-01

    Full Text Available This paper proposes a Linear Matrix Inequality(LMI based ?? robust controller design employing WideArea Measurement (WAM based stabilizing signals asgenerator speed. A Three-input, Single-output (TISOcontroller is designed for a Thyristor Controlled Seriescompensator (TCSC in order to mitigate small signaloscillations in a multimachine power system. The controllerdesign has been carried out based on the ?? mixed-sensitivityformulation in a LMI framework with pole-placementconstraint. The small signal performance of the test system hasbeen examined employing eigenvalue analysis as well as timedomain response. The designed controller is found to be robustagainst disturbances like varying generations as well as loadpower demand.

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

    Directory of Open Access Journals (Sweden)

    V. Markovi?

    2010-06-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Balwinder Singh Surjan

    2012-10-01

    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.

  6. Research on a Small Signal Stability Region Boundary Model of the Interconnected Power System with Large-Scale Wind Power

    Directory of Open Access Journals (Sweden)

    Wenying Liu

    2015-03-01

    Full Text Available For the interconnected power system with large-scale wind power, the problem of the small signal stability has become the bottleneck of restricting the sending-out of wind power as well as the security and stability of the whole power system. Around this issue, this paper establishes a small signal stability region boundary model of the interconnected power system with large-scale wind power based on catastrophe theory, providing a new method for analyzing the small signal stability. Firstly, we analyzed the typical characteristics and the mathematic model of the interconnected power system with wind power and pointed out that conventional methods can’t directly identify the topological properties of small signal stability region boundaries. For this problem, adopting catastrophe theory, we established a small signal stability region boundary model of the interconnected power system with large-scale wind power in two-dimensional power injection space and extended it to multiple dimensions to obtain the boundary model in multidimensional power injection space. Thirdly, we analyzed qualitatively the topological property’s changes of the small signal stability region boundary caused by large-scale wind power integration. Finally, we built simulation models by DIgSILENT/PowerFactory software and the final simulation results verified the correctness and effectiveness of the proposed model.

  7. Bandwidth requirements for fine resolution squinted SAR

    Energy Technology Data Exchange (ETDEWEB)

    DOERRY,ARMIN W.

    2000-03-01

    The conventional rule-of-thumb for Synthetic Aperture Radar is that an RF bandwidth of c/(2{rho}{sub r}) is required to image a scene at the desired slant-range resolution {rho}{sub r}, and perhaps a little more to account for window functions and sidelobe control. This formulation is based on the notion that the total bandwidth required is the same bandwidth that is required for a single pulse. What is neglected is that efficient processing of an entire synthetic aperture of pulses will often require different frequency content for each of the different pulses that makeup a synthetic aperture. Consequently, the total RF bandwidth required of a Synthetic Aperture Radar may then be substantially wider than the bandwidth of any single pulse. The actual RF bandwidth required depends strongly on flight geometry, owing to the desire for a radar to maintain a constant projection of the Fourier space collection surface onto the {omega}{sub y} axis. Long apertures required for fine azimuth resolution, and severe squint angles with steep depression angles may require total RF bandwidths well beyond the minimum bandwidth required of any single transmitted pulse, perhaps even by a factor of two or more. Accounting for this is crucial to designing efficient versatile high-performance imaging radars. This paper addresses how a data set conducive to efficient processing might increase the total RF bandwidth, and presents examples of how a fixed RF bandwidth might then limit SAR geometries.

  8. Cryogenic small-signal conversion with relaxation oscillations in Josephson junctions

    CERN Document Server

    Furlan, M

    2006-01-01

    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 fluctuation processes in the junction. At optimum conditions the circuit is found to deliver excellent noise performance over a broad dynamic range. Our simple models successfully apply within the regime of classical Josephson junction and circuit dynamics, which we confirm by experimental results. A discussion on possible applications includes a measurement of the response to a cryogenic radiation detector.

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

    DEFF Research Database (Denmark)

    Su, Chi; Chen, Zhe

    2012-01-01

    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.

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

    DEFF Research Database (Denmark)

    Jóhannsson, Hjörtur; Nielsen, Arne Hejde; Østergaard, Jacob

    2013-01-01

    multiple operating points is derived in the paper. Finally, results from time-domain simulation of instability scenarios in the Nordic32 test system are presented and results used for testing the assessment method. The results illustrate the method’s capability to efficiently identify the location of the......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...

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

    DEFF Research Database (Denmark)

    Jóhannsson, Hjörtur; Nielsen, Arne Hejde; Østergaard, Jacob

    2014-01-01

    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...... 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...... 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...

  12. Real-time remedial action against aperiodic small signal rotor angle instability

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob

    2016-01-01

    This paper presents a method that in real-time determines remedial actions, which restore stable operation with respect to aperiodic small signal rotor angle stability (ASSRAS) when insecure or unstable operation has been detected. An ASSRAS assessment method is used to monitor the stability...... impedance plane to determine an active power redispatch among selected generators to restore stable and secure operation. Since the method is purely based on analytically derived expression, the computation of the remedial actions is fast and well suited for real-time operation. The method was tested on the...... boundary for each generator in real-time. The ASSRAS boundary represents the condition when a generator reaches the maximum steady state active power injection. The proposed control method exploits analytically derived expressions for the ASSRAS boundary and other characteristic curves in the injection...

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

    DEFF Research Database (Denmark)

    Su, Chi; Chen, Zhe

    2012-01-01

    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....

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

    DEFF Research Database (Denmark)

    Su, Chi; Chen, Zhe

    2012-01-01

    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...

  15. Two neural approaches for small-signal modelling of GaAs HEMTs

    Directory of Open Access Journals (Sweden)

    Marinković Zlatica

    2010-01-01

    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.

  16. 3-D effects on small signal gain for undulators with variable parameters

    International Nuclear Information System (INIS)

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

  17. Improvement of Small Signal Stability of SMIB System Using PSO and CSO based Power System Stabilizer

    Directory of Open Access Journals (Sweden)

    Y. Raghuvamsi

    2015-08-01

    Full Text Available In a power system, Low Frequency Oscillations (LFOs are dangerous and make system unstable. These oscillations are referred to small signal stability and they are mainly due to lack of damping torque. This insufficient damping torque is because of high gain and low time constant of Automatic Voltage Regulator (AVR. AVR is useful for maintaining the terminal voltage of synchronous machine as constant. While doing so, it will make the system damping torque as negative. For providing required damping torque thereby minimizing the LFOs, Power System Stabilizer is used in conjunction with AVR. In this paper for SMIB system, the stability is studied with the help of eigen values before and after placement of PSS with optimized PSS parameters using Particle Swarm Optimization (PSO and Cat Swarm Optimization (CSO. The simulation work is performed in the MATLAB/SIMULINK and corresponding results are presented and analyzed.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  19. 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

  20. PLL with MAF-Based Prefiltering Stage: Small-Signal Modeling and Performance Enhancement

    DEFF Research Database (Denmark)

    Darzunaki, Saeed Golestan; Guerrero, Josep M.; Vidal, Ana; Yepes, Alejandro G.; Doval-Gandoy, Jesus

    2016-01-01

    In three-phase applications, the synchronousreference frame phase-locked loop (SRF-PLL) is a standard PLL, which benefits from a simple structure and satisfactory performance under symmetrical and undistorted grid conditions. Under unbalanced and harmonically distorted conditions, however, it...... suffers from a very poor performance in the detection of grid voltage parameters. To deal with this challenge, incorporating different filters inside its control loop or before its input has been proposed. Recently, using the moving average filter (MAF) as the SRF-PLL prefiltering stage has been suggested...... in several works. The MAF is a linear-phase filter that can behave like an ideal lowpass filter under certain conditions. The main aim of this letter is to derive the small-signal model of the SRF-PLL with MAF-based prefiltering stage (briefly called the PMAF-PLL), which has not been presented before...

  1. Small-Signal Amplification of Period-Doubling Bifurcations in Smooth Iterated Maps

    CERN Document Server

    Zhao, X; Berger, C M; Gauthier, D J; Zhao, Xiaopeng; Schaeffer, David G.; Berger, Carolyn M.; Gauthier, Daniel J.

    2006-01-01

    Various authors have shown that, near the onset of a period-doubling bifurcation, small perturbations in the control parameter may result in much larger disturbances in the response of the dynamical system. Such amplification of small signals can be measured by a gain defined as the magnitude of the disturbance in the response divided by the perturbation amplitude. In this paper, the perturbed response is studied using normal forms based on the most general assumptions of iterated maps. Such an analysis provides a theoretical footing for previous experimental and numerical observations, such as the failure of linear analysis and the saturation of the gain. Qualitative as well as quantitative features of the gain are exhibited using selected models of cardiac dynamics.

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

    DEFF Research Database (Denmark)

    Jóhannsson, Hjörtur; Nielsen, Arne Hejde

    2014-01-01

    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.

  3. Electrostatic and Small-Signal Analysis of CMUTs With Circular and Square Anisotropic Plates.

    Science.gov (United States)

    Funding la Cour, Mette; Christiansen, Thomas Lehrmann; Jensen, Jørgen Arendt; Thomsen, Erik Vilain

    2015-08-01

    Traditionally, capacitive micromachined ultrasonic transducers (CMUTs) are modeled using the isotropic plate equation, and this leads to deviations between analytical calculations and finite element modeling (FEM). In this paper, the deflection is calculated for both circular and square plates using the full anisotropic plate equation. It is shown that the anisotropic calculations match excellently with FEM, whereas an isotropic approach causes up to 10% deviations in deflection. For circular plates, an exact solution can be found. For square plates using the Galerkin method, and utilizing the symmetry of the silicon crystal, a compact and accurate expression for the deflection can be obtained. The deviation from FEM in center deflection is element small-signal model for both circular and square anisotropic plates is derived to describe the dynamics of the CMUT. PMID:26492637

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

    OpenAIRE

    Gowri T; Raja K; G.Tholkappia Arasu

    2012-01-01

    The Physical and MAC layers have been specified in IEEE 802.16 networks. The quality of service is ensured by the bandwidth reservation. The subscriber station should reserve the bandwidth more than its demand. But the bandwidth is fully utilized by SS but not all the time. So the bandwidth has recycled by the process of recycling the unused bandwidth. The main objective of the proposed scheme is to utilize the unused bandwidth by recycling and maintain the QOS service. By recycling the throu...

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

    Directory of Open Access Journals (Sweden)

    Gowri T

    2012-03-01

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

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

    OpenAIRE

    Webb, Stephen; Gang WANG; Litvinenko, Vladimir

    2011-01-01

    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...

  7. Bandwidth engineering of photonic crystal waveguide bends

    DEFF Research Database (Denmark)

    Borel, Peter Ingo; Frandsen, Lars Hagedorn; Harpøth, Anders; Leon, Juan Burgos; Liu, H.; Kristensen, Martin; Bogaerts, Wim; Dumon, P.; Baets, Roel; Wiaux, V.; Wouters, J.; Beckx, S.

    2004-01-01

    An effective design principle has been applied to photonic crystal waveguide bends fabricated in silicon-on-insulator material using deep UV lithography resulting in a large increase in the low-loss bandwidth of the bends. Furthermore, it is experimentally demonstrated that the absolute bandwidth...

  8. Directing Traffic: Managing Internet Bandwidth Fairly

    Science.gov (United States)

    Paine, Thomas A.; Griggs, Tyler J.

    2008-01-01

    Educational institutions today face budgetary restraints and scarce resources, complicating the decision of how to allot bandwidth for campus network users. Additionally, campus concerns over peer-to-peer networking (specifically outbound Internet traffic) have increased because of bandwidth and copyright issues. In this article, the authors…

  9. Energy Bandwidth for Petroleum Refining Processes

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2006-10-01

    The petroleum refining energy bandwidth report analyzes the most energy-intensive unit operations used in U.S. refineries: crude oil distillation, fluid catalytic cracking, catalytic hydrotreating, catalytic reforming, and alkylation. The "bandwidth" provides a snapshot of the energy losses that can potentially be recovered through best practices and technology R&D.

  10. Small signal modeling of high electron mobility transistors on silicon and silicon carbide substrate with consideration of substrate loss mechanism

    Science.gov (United States)

    Sahoo, A. K.; Subramani, N. K.; Nallatamby, J. C.; Sylvain, L.; Loyez, C.; Quere, R.; Medjdoub, F.

    2016-01-01

    In this paper, we present a comparative study on small-signal modeling of AlN/GaN/AlGaN double hetero-structure high electron mobility transistors (HEMTs) grown on silicon (Si) and silicon carbide (SiC) substrate. The traditional small signal equivalent circuit model is modified to take into account the transmission loss mechanism of coplanar waveguide (CPW) line which cannot be neglected at high frequencies. CPWs and HEMTs-on-AlN/GaN/AlGaN epitaxial layers are fabricated on both the Si and SiC substrates. S-parameter measurements at room temperature are performed over the frequency range from 0.5 GHz to 40 GHz. Transmission loss of CPW lines are modeled with a distributed transmission line (TL) network and an equivalent circuit model is included in the small-signal transistor model topology. Measurements and simulations are compared and found to be in good agreement.

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

    Directory of Open Access Journals (Sweden)

    Gang Chen

    2013-05-01

    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.

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

    Scientific Electronic Library Online (English)

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

    2013-12-01

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

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

    OpenAIRE

    Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård; Jensen, Kim H.; Dixon, Andrew; Østergaard, Jacob

    2010-01-01

    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...

  14. Controlling the bandwidth of metamaterial properties

    Science.gov (United States)

    Karami, M.; Fiddy, M. A.

    2015-09-01

    Designing metamaterials to possess extreme index values requires near resonant properties which, in turn, leads to these properties over diminishing bandwidths. Recent studies have shown that some bandwidth control might be possible by exploiting metamaterial substrates. We have demonstrated the concept in our design, and investigated the trade-offs between substrate structure, bandwidth extension and increase in losses. Loss management can be controlled by choice of metamaterial elements and replacement of metal by semiconductors. This also has the added advantage of some degree of tunability.

  15. High-Bandwidth Hybrid Sensor (HYSENS) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ATA has demonstrated the primary innovation of combining a precision MEMS gyro (BAE SiRRS01) with a high bandwidth angular rate sensor, ATA's ARS-14 resulting in a...

  16. High bandwidth control of precision motion instrumentation

    Science.gov (United States)

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

    2008-10-01

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

  17. A Deterministic TCP Bandwidth Sharing Model

    OpenAIRE

    Lautenschlaeger, Wolfram

    2014-01-01

    Traditionally TCP bandwidth sharing has been investigated mainly by stochastic approaches due to its seemingly chaotic nature. Even though of great generality, the theories deal mainly with expectation values, which is prone to misinterpretation with respect to the Quality-of-Experience (QoE). We disassemble TCP operating conditions into dominating scenarios and show that bandwidth sharing alone follows mostly deterministic rules. From the analysis we derive significant root...

  18. Sharp Bounds for Bandwidth of Clique Products

    OpenAIRE

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

    2003-01-01

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

  19. Ultrawide Bandwidth RFID: The Next Generation?

    OpenAIRE

    Dardari, Davide; D'Errico, Raffaele; Roblin, Christophe; Sibille, Alain; Win, Moe Z.

    2010-01-01

    Future advanced radio-frequency identification (RFID) systems are expected to provide both identification and high-definition localization of objects with improved reliability and security while maintaining low power consumption and cost. Ultrawide bandwidth (UWB) technology is a promising solution for next generation RFID systems to overcome most of the limitations of the current narrow bandwidth RFID technology such as: reduced area coverage, insufficient ranging resolution for accurate loc...

  20. Polybinary modulation for bandwidth limited optical links

    DEFF Research Database (Denmark)

    Vegas Olmos, Juan José; Jurado-Navas, Antonio

    2015-01-01

    Optical links using traditional modulation formats are reaching a plateau in terms of capacity, mainly due to bandwidth limitations in the devices employed at the transmitter and receivers. Advanced modulation formats, which boost the spectral efficiency, provide a smooth migration path towards...... recent results on poly binary modulation, comprising both binary and multilevel signals as seed signals. The results will show how poly binary modulation effectively reduces the bandwidth requirements on optical links while providing high spectral efficiency....

  1. Adaptable bandwidth planning using reinforcement learning

    Directory of Open Access Journals (Sweden)

    Dirk Hetzer

    2006-08-01

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

  2. Large scale probabilistic available bandwidth estimation

    CERN Document Server

    Thouin, Frederic; Rabbat, Michael

    2010-01-01

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

  3. Improved space bandwidth product in image upconversion

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin; Pedersen, Christian; Tidemand-Lichtenberg, Peter

    2012-01-01

    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 (Δk=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....

  4. High bandwidth differential amplifier for shock experiments.

    Science.gov (United States)

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

    2012-10-01

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

  5. 1 MHz bandwidth true NMR SQUID amplifier

    Science.gov (United States)

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

    1995-10-01

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

  6. 1 MHz bandwidth true NMR SQUID amplifier

    International Nuclear Information System (INIS)

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

  7. Reconfigurable silicon filter with continuous bandwidth tunability.

    Science.gov (United States)

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

    2012-09-01

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

  8. Dealing Bandwidth to Mobile Clients Using Games

    Science.gov (United States)

    Sofokleous, Anastasis A.; Angelides, Marios C.

    This chapter exploits a gaming approach to bandwidth sharing in a network of non-cooperative clients whose aim is to satisfy their selfish objectives and be served in the shortest time and who share limited knowledge of one another. The chapter models this problem as a game in which players consume the bandwidth of a video streaming server. The rest of this chapter is organized in four sections: the proceeding section presents resource allocation taxonomies, following that is a section on game theory, where our approach is sourced from, and its application to resource allocation. The penultimate section presents our gaming approach to resource allocation. The final section concludes.

  9. Large-bandwidth planar photonic crystal waveguides

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Lavrinenko, Andrei

    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...

  10. Optimization model for bandwidth allocation in a network virtualization environment

    OpenAIRE

    Botero Vega, Juan Felipe; Hesselbach Serra, Xavier

    2009-01-01

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

  11. Investigation of spectral bandwidth of optical parametric amplification

    Science.gov (United States)

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

    2004-09-01

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

  12. Big Bandwidth Battle: Universal ADSL Looks Ahead.

    Science.gov (United States)

    Hargadon, Tom

    1998-01-01

    Discusses the new Universal ADSL (Asymmetric Digital Subscriber Line) standard, which promises simple, high-bandwidth access over standard telephone lines. Topics include varieties of DSL; voice and data capacities; adapters and installation for personal computers; Internet backbone capacity; and headend access. (LRW)

  13. Fast Faraday Cup With High Bandwidth

    Science.gov (United States)

    Deibele, Craig E [Knoxville, TN

    2006-03-14

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

  14. Level-1 decision algorithm and bandwidth division

    CERN Document Server

    Jacoby, C

    2003-01-01

    We describe the Level-1 decision algorithm as it is used in the efficiency evaluation for the Trigger System and LHCb Reoptimization TDRs. The available bandwidth is divided between a generic trigger sensitive to all tracks with large impact parameter and high transverse momentum and a few channel-specific enhancements based on signatures involving Level-0 objects.

  15. High bandwidth vapor density diagnostic system

    Science.gov (United States)

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

    1992-01-01

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

  16. OPTIMAL BANDWIDTH ALLOCATION WITH BANDWIDTH RESERVATION AND ADAPTATION IN WIRELESS COMMUNICATION NETWORKS

    Directory of Open Access Journals (Sweden)

    Ali Amiri

    2016-01-01

    Full Text Available Efficient management of bandwidth in wireless networks is a critical factor for a successful communication system. Special features of wireless networks such user mobility and growth of wireless applications and their high bandwidth intensity create a major challenge to utilize bandwidth resources optimally. In this research, we propose a model for an adaptable network bandwidth management method that combines bandwidth reservation and bandwidth adaptation to reduce call blocking and dropping probabilities. The model is an integer program that determines whether or not to accept new calls and decides how to allocate bandwidth optimally in a way to maximize user satisfaction. The results of a simulation study show that the proposed method outperforms an existing method with respect to key performance measures such as call blocking and dropping probabilities and call time survivability. This survivability indicator is a new measure that is introduced for the first time in this paper. We also present a second tradeoff model to allow the network manager to control call dropping probability. The results of a second simulation study show that network users are better off if a zero call dropping policy is adopted as proposed in the first model.

  17. Small-Signal Modeling, Analysis and Testing of Parallel Three-Phase-Inverters with A Novel Autonomous Current Sharing Controller

    DEFF Research Database (Denmark)

    Guan, Yajuan; Quintero, Juan Carlos Vasquez; Guerrero, Josep M.; Coelho, Ernane A. A.

    2015-01-01

    A novel simple and effective autonomous currentsharing controller for parallel three-phase inverters is employed in this paper. The novel controller is able to endow to the system high speed response and precision in contrast to the conventional droop control as it does not require calculating any active or reactive power, instead it uses a virtual impedance loop and a SFR phase-locked loop. The small-signal model of the system was developed for the autonomous operation of inverter-based microgr...

  18. Variable bandwidth Kernel estimator of the mode

    Directory of Open Access Journals (Sweden)

    Raid B. Salha

    2009-09-01

    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.

  19. All-optical bandwidth-tailorable radar

    CERN Document Server

    Zou, Weiwen; Long, Xin; Zhang, Siteng; Cui, Yuanjun; Chen, Jianping

    2015-01-01

    Radar has been widely used in military, security, and rescue. Metamaterial cloak is employed in stealth targets to evade radar detection. Hence modern radar should be reconfigurable at multi-bands for detecting stealth targets, which might be realized based on microwave photonics. Here, we demonstrate an all-optical bandwidth-tailorable radar architecture. It is a coherent system utilizing one mode-locked laser for both signal generation and reception. Heterodyning of two individually filtered optical pulses that are pre-chirped via wavelength-to-time mapping generates wideband linearly-chirped radar signal. The working bands can be flexibly tailored with desired bandwidth at user-preferred carrier frequency. After modulated onto the pre-chirped optical pulse, radar echoes are time-stretched and frequency-compressed by several times. The digitization becomes much easier without loss of detection ability. We believe that the demonstration can innovate the radar's architecture with ultra-high range resolution.

  20. Reconstitution of Low Bandwidth Reaction History

    International Nuclear Information System (INIS)

    The goal of the Test Readiness Program is to transition to a 24 month test readiness posture and if approved move to an 18-month posture. One of the key components of the Test Readiness Program necessary to meet this goal is the reconstitution of the important diagnostics. Since the end of nuclear testing, the ability to field diagnostics on a nuclear test has deteriorated. Reconstitution of diagnostics before those who had experience in nuclear testing either retire or leave is essential to achieving a shorter test readiness posture. Also, the data recording systems have not been used since the end of testing. This report documents the reconstitution of one vital diagnostic: the low bandwidth reaction history diagnostic for FY04. Reaction history is one of the major diagnostics that has been used on all LLNL and LANL tests since the early days of nuclear testing. Reaction history refers to measuring the time history of the gamma and neutron output from a nuclear test. This gives direct information on the nuclear reactions taking place in the device. The reaction history measurements are one of the prime measurements the nuclear weapon scientists use to validate their models of device performance. All tests currently under consideration require the reaction history diagnostic. Thus moving to a shorter test readiness posture requires the reconstitution of the ability to make reaction history measurements. Reconstitution of reaction history was planned to be in two steps. Reaction history measurements that have been used in the past can be broadly placed into two categories. The most common type of reaction history and the one that has been performed on virtually all nuclear tests is termed low bandwidth reaction history. This measurement has a time response that is limited by the bandpass of kilometer length coaxial cables. When higher bandwidth has been required for specific measurements, fiber optic techniques have been used. This is referred to as high-bandwidth reaction history. The first step in the reconstitution of reaction history was thus naturally the reconstitution of the loW--bandwidth capability in FY04. This will be followed in FY06 by the reconstitution of the high bandwidth capability. The reconstitution of the loW--bandwidth reaction history measurement was done in several phases. First the status of legacy equipment has been ascertained. Existing detectors, cables, and recording systems have been inventoried, characterized and, for the most part, satisfied the specifications of the test program and are still useable. The ability to obtain replacement equipment is now available. Modern loW--bandwidth fiber optic recording equipment which was similar to systems used on the old tests, has been evaluated. The ability to characterize and calibrate detectors and other components has been reestablished. New scientists and engineers have been working with designated mentors. These mentors participated on numerous shots during the old test program. Finally as a proof test, two hypothetical test scenarios were proposed: one each from LLNL and LANL. The LANL event was called ALPHA and the LLNL event was called POPOUT. The reaction history diagnostics for these two hypothetical underground tests were completely laid out and analyzed to make sure that the diagnostic could be successfully fielded within a 24 month time frame. In addition as part of a training exercise a reaction history trailer was reconstituted. This system was configured using a combination of new and experienced technical personnel and data analysts in collaboration with LLNL and LANL event physicists

  1. Sharp Bounds for Bandwidth of Clique Products

    CERN Document Server

    Berger-Wolf, T Y; Berger-Wolf, Tanya Y.; Harris, Mitchell A.

    2003-01-01

    The bandwidth of a graph is the labeling of vertices with minimum maximum edge difference. For many graph families this is NP-complete. A classic result computes the bandwidth for the hypercube. We generalize this result to give sharp lower bounds for products of cliques. This problem turns out to be equivalent to one in communication over multiple channels in which channels can fail and the information sent over those channels is lost. The goal is to create an encoding that minimizes the difference between the received and the original information while having as little redundancy as possible. Berger-Wolf and Reingold [2] have considered the problem for the equal size cliques (or equal capacity channels). This paper presents a tight lower bound and an algorithm for constructing the labeling for the product of any number of arbitrary size cliques.

  2. Maximum-Bandwidth Node-Disjoint Paths

    Directory of Open Access Journals (Sweden)

    Mostafa H. Dahshan

    2012-03-01

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

  3. DBAS: A Deployable Bandwidth Aggregation System

    CERN Document Server

    Habak, Karim; Harras, Khaled A

    2012-01-01

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

  4. Feeding Techniques to Improve Bandwidth of MPA

    Directory of Open Access Journals (Sweden)

    Meenu Chinwan

    2013-03-01

    Full Text Available The comprehensive study of MPA shows its important role in the modern wireless communication devices. Detailed literature review of past few decades’ papers on MPA, the MPA has emerged into wide range of communication field. Inherently the patch antenna is narrowband; various techniques were developed to enhancement of bandwidth. Different parameter affect the efficiency of antenna .Specification of MPA has low weight, low profile. This is Omni-directional antenna whose fabrication is easy.

  5. Wide bandwidth porous silicon coatings for silicon

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-11-16

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

  6. Bandwidth allocation in large stochastic networks

    OpenAIRE

    Feuillet, Mathieu

    2012-01-01

    The purpose of this thesis is to tackle three problems inspired by large distributed systems. The tools used for that purpose come from probability and more specifically queueing theory. The studies led during this thesis allowed to understand the behavior of the observed systems and algorithms but also to prove some interesting theoretical results and to emphasize some probabilistic phenomena. In Chapter II, a bandwidth sharing network model is analyzed. Contrary to what has been studied in ...

  7. Combination Exchange Mechanisms for Efficient Bandwidth Allocation

    OpenAIRE

    Jain, Rahul; Varaiya, Pravin P.

    2003-01-01

    The size, scale and multiple ownership of communication network resources makes it important to consider an economic framework wherein we can investigate the efficiency of network operation taking agents' incentives into account. Such a framework has been considered in the design and analysis of pricing mechanisms to regulate congestion and share bandwidth over short time scales. We consider time scales of a few months over which owners of communication links lease bandwi...

  8. Fixed Innovative Bandwidth Utilization in TDM EPON

    Directory of Open Access Journals (Sweden)

    Muhammad Bilal

    2011-03-01

    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.

  9. Sound source localization identification accuracy: bandwidth dependencies.

    Science.gov (United States)

    Yost, William A; Zhong, Xuan

    2014-11-01

    Sound source localization accuracy using a sound source identification task was measured in the front, right quarter of the azimuth plane as rms (root-mean-square) error (degrees) for stimulus conditions in which the bandwidth (1/20 to 2 octaves wide) and center frequency (250, 2000, 4000?Hz) of 200-ms noise bursts were varied. Tones of different frequencies (250, 2000, 4000?Hz) were also used. As stimulus bandwidth increases, there is an increase in sound source localization identification accuracy (i.e., rms error decreases). Wideband stimuli (>1 octave wide) produce best sound source localization accuracy (~6°-7° rms error), and localization accuracy for these wideband noise stimuli does not depend on center frequency. For narrow bandwidths (octave) and tonal stimuli, accuracy does depend on center frequency such that highest accuracy is obtained for low-frequency stimuli (centered on 250?Hz), worse accuracy for mid-frequency stimuli (centered on 2000?Hz), and intermediate accuracy for high-frequency stimuli (centered on 4000?Hz). PMID:25373973

  10. 47 CFR 15.35 - Measurement detector functions and bandwidths.

    Science.gov (United States)

    2010-10-01

    ...bandwidths. The conducted and radiated emission limits shown in this part...frequencies above 1000 MHz, the radiated emission limits are based on the use...bandwidth of 1 MHz. When average radiated emission measurements are specified...

  11. Dynamic Bandwidth Allocation Strategy for Marine VHF Communications

    OpenAIRE

    Ding Yuan-Ming; Zhang Fang

    2013-01-01

    In order to achieve the efficient management of marine VHF communications bandwidth resources under the battlefield environment and to maximize the bandwidth utilization while ensuring high-priority business access channel, the context puts forward a kind of dynamic bandwidth allocation strategy based on business priorities. When the bandwidth resources are sufficient, the system can accommodate more business, otherwise it can call the dynamic allocation st...

  12. Bandwidth Enhancement in Multilayer Microstrip Proximity Coupled Array

    OpenAIRE

    Shubham Gupta; Shilpa Singh

    2012-01-01

    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...

  13. A study of Bandwidth Management in Computer Networks

    OpenAIRE

    Devajit Mahanta,; Majidul Ahmed,; Utpal Jyoti Bora,

    2013-01-01

    Bandwidth management is one of the most widely misunderstood subjects in modern networking. Bandwidth Management is a lot like economics, because the complexities of how it works are beyond simple logic. Internet "bandwidth" is not a spectrum; traffic streams are one bit at a time. Bandwidth on the internet can only be conceptualized over time, and the amount of time that you talk about can greatly change the user experience. For reliable data transmission within computer network and internet...

  14. 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)

  15. Impact of Wind Power Plants with Full Converter Wind Turbines on Power System Small-Signal Stability

    DEFF Research Database (Denmark)

    Knüppel, Thyge; Nygaard Nielsen, Jørgen; Dixon, Andrew

    of the dynamic properties of the WPPs in the power system stability studies become important. The work presented in this report deal with the impact of WPPs based on full converter wind turbines (WTs) on the power system small-signal rotor angle stability. During small disturbances in the power...... actively contribute to the modal damping of weakly damped power oscillations through WPP power oscillation damping control (POD). Emphasis has been put on WPP level PODs due to its simplicity as compared to individual WT PODs, and since this oers a single point of access if the operation of the POD is to......Wind power is being developed in power systems all around the world, and already today wind power covers more than 20 % of the electricity consumption in some countries. As the size of each wind power plant (WPP) increases and as the levels of penetration reaches certain magnitudes, the inclusion...

  16. 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

  17. Study on Small-Signal Impedance of Single-Walled Zigzag Carbon Nanotubes in Terahertz Frequency Regime

    Science.gov (United States)

    Wang, C.; Cao, J. C.

    2013-08-01

    We theoretically study the static and dynamic transport properties of Mott-Gurney diodes based on semiconducting single-walled zigzag carbon nanotubes (CNTs). The electric field and velocity distribution of the diode under dc voltage is obtained by solving the steady-state drift-diffusion equations, which involve the negative differential velocity. The current-voltage characteristic of CNT diode exhibits a distinctive positive differential resistance. The high-frequency impedance is calculated with the small-signal analysis method. A major feature of the proposed CNT diode is that the bias- and tube index-dependent impedance show several negative windows in terahertz frequency range despite the positivity of the dc differential resistance. This property makes the CNT-based Mott-Gurney diode a promising candidate for the generation and amplification of terahertz signals within the desired frequency region.

  18. Small-Signal Modeling, Analysis and Testing of Parallel Three-Phase-Inverters with A Novel Autonomous Current Sharing Controller

    DEFF Research Database (Denmark)

    Guan, Yajuan; Quintero, Juan Carlos Vasquez

    2015-01-01

    A novel simple and effective autonomous currentsharing controller for parallel three-phase inverters is employed in this paper. The novel controller is able to endow to the system high speed response and precision in contrast to the conventional droop control as it does not require calculating any active or reactive power, instead it uses a virtual impedance loop and a SFR phase-locked loop. The small-signal model of the system was developed for the autonomous operation of inverter-based microgrid with the proposed controller. The developed model shows large stability margin and fast transient response of the system. This model can help identifying the origin of each of the modes and possible feedback signals for design of controllers to improve the system stability. Experimental results from two parallel 2.2 kVA inverters verify the effectiveness of the novel control approach.

  19. Self-?eld effects on small-signal gain in two-stage free-electron lasers

    Indian Academy of Sciences (India)

    S Jafari; H Mehdian; A Hasanbeigi

    2011-03-01

    Self-?eld effects, induced by charge and current densities of the electron beam, on gain in two-stage free-electron laser with nonuniform guide magnetic ?eld is presented. The gain equation for small-signal has been derived analytically. The results of numerical calculations show a gain decrement for group I orbits and a gain enhancement for group II orbits, due to the self-?eld effects. The wiggler-induced self-magnetic ?eld has a diamagnetic effect for group I orbits, whereas for group II, it has a paramagnetic effect. It is also found that using a nonuniform guide ?eld, rather than a uniform one, causes the gain to increase.

  20. Bandwidth Efficient OFDM Transmitter Diversity Techniques

    Directory of Open Access Journals (Sweden)

    King F. Lee

    2004-09-01

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

  1. High Quality Geographic Services and Bandwidth Limitations

    Directory of Open Access Journals (Sweden)

    Tumasch Reichenbacher

    2011-12-01

    Full Text Available In this paper we provide a critical overview of the state of the art in human-centric intelligent data management approaches for geographic visualizations when we are faced with bandwidth limitations. These limitations often force us to rethink how we design displays for geographic visualizations. We need ways to reduce the amount of data to be visualized and transmitted. This is partly because modern instruments effortlessly produce large volumes of data and Web 2.0 further allows bottom-up creation of rich and diverse content. Therefore, the amount of information we have today for creating useful and usable cartographic products is higher than ever before. However, how much of it can we really use online? To answer this question, we first calculate the bandwidth needs for geographic data sets in terms of waiting times. The calculations are based on various data volumes estimated by scholars for different scenarios. Documenting the waiting times clearly demonstrates the magnitude of the problem. Following this, we summarize the current hardware and software solutions, then the current human-centric design approaches trying to address the constraints such as various screen sizes and information overload. We also discuss a limited set of social issues touching upon the digital divide and its implications. We hope that our systematic documentation and critical review will help researchers and practitioners in the field to better understand the current state of the art.

  2. Polybinary modulation for bandwidth limited optical links

    DEFF Research Database (Denmark)

    Vegas Olmos, Juan José; Jurado-Navas, Antonio

    2015-01-01

    Optical links using traditional modulation formats are reaching a plateau in terms of capacity, mainly due to bandwidth limitations in the devices employed at the transmitter and receivers. Advanced modulation formats, which boost the spectral efficiency, provide a smooth migration path towards effectively increase the available capacity. Advanced modulation formats however require digitalization of the signals and digital signal processing blocks to both generate and recover the data. There is therefore a trade-off in terms of efficiency gain vs. complexity. Poly binary modulation, a generalized form of partial response modulation, employs simple codification and filtering at the transmitter to drastically increase the spectral efficiency. At the receiver side, poly binary modulation requires low complexity direct detection and very little digital signal processing. This talk will review the recent results on poly binary modulation, comprising both binary and multilevel signals as seed signals. The results will show how poly binary modulation effectively reduces the bandwidth requirements on optical links while providing high spectral efficiency.

  3. Bandwidth Allocation and Session Scheduling using SIP

    Directory of Open Access Journals (Sweden)

    Jean-Marie Garcia

    2006-08-01

    Full Text Available

    Session Initiation Protocol (SIP is a new signaling protocol designed to establish multimedia sessions in telecommunication networks. In this paper, we suggest the extension of SIP functionalities to coordinate QoS mechanisms deployed in IP networks, and especially in DiffServ domain. Indeed, the interaction between small and big TCP sessions may have dramatic consequences on small TCP sessions. Hence, we use SIP to achieve QoS management on a session basis, in which the over all activity of the user during the session is considered. The suggested mechanisms deal with two issues: first, session scheduling based on session duration and/or volume, and second bandwidth allocation on a per-flow basis using equivalent bandwidth estimation techniques. The proposed mechanisms are implemented in the SIP proxy server as QoS management algorithms, and they are validated by simulations.

  4. Bandwidth Estimation For Mobile Ad hoc Network (MANET

    Directory of Open Access Journals (Sweden)

    Rabia Ali

    2011-09-01

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

  5. Small signal audio design

    CERN Document Server

    Self, Douglas

    2014-01-01

    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

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

    Directory of Open Access Journals (Sweden)

    Megha Chitranshi

    2013-08-01

    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.

  7. RAID Disk Arrays for High Bandwidth Applications

    Science.gov (United States)

    Moren, Bill

    1996-01-01

    High bandwidth applications require large amounts of data transferred to/from storage devices at extremely high data rates. Further, these applications often are 'real time' in which access to the storage device must take place on the schedule of the data source, not the storage. A good example is a satellite downlink - the volume of data is quite large and the data rates quite high (dozens of MB/sec). Further, a telemetry downlink must take place while the satellite is overhead. A storage technology which is ideally suited to these types of applications is redundant arrays of independent discs (RAID). Raid storage technology, while offering differing methodologies for a variety of applications, supports the performance and redundancy required in real-time applications. Of the various RAID levels, RAID-3 is the only one which provides high data transfer rates under all operating conditions, including after a drive failure.

  8. A high-bandwidth spintronic position sensor

    International Nuclear Information System (INIS)

    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. (paper)

  9. PEP Deployment and Bandwidth Management Issues

    Science.gov (United States)

    Younghusband, Charles; Slade, Peter; Weaver, Jeff

    This paper will discuss current deployment scenarios for Performance Enhancement Proxies (PEP) technologies in broadband satellite access systems from the perspective of one PEP technology provider. Recent improvements such as DVB-S2 can provide substantial gains at the link layer. In order to achieve further efficiency gains, the satellite industry is now forced to look elsewhere - namely other layers in the data communications network stack. Satellite terminal manufacturers are now moving beyond basic TCP acceleration techniques to more comprehensive optimization techniques that incorporate advances in data compression and flexibility for more deployment scenarios. Some of the advances for PEP technology are in part due to CPU and memory technology advances, resulting in increasingly affordable access to computing power, allowing PEP manufacturers deliver substantial performance and bandwidth savings gains.

  10. Research on the Multi-Period Small-Signal Stability Probability of a Power System with Wind Farms Based on the Markov Chain

    Directory of Open Access Journals (Sweden)

    Rundong Ge

    2015-04-01

    Full Text Available In the traditional studies on small-signal stability probability of a power system with wind farms, the frequency of wind speed was often assumed to obey to some extent a particular probability distribution. The stability probability that is thus obtained, however, actually only reflects the power system stability characteristics on long time scales. In fact, there is a direct correlation between the change of wind speed and the current state of wind speed, resulting in the system stability characteristics in different time periods having a great difference compared with that of long time scales. However, the dispatchers are more concerned about the probability that the power system remains stable in the next period or after several periods, namely the stability characteristics of the power system in a short period or multi-period. Therefore, research on multi-period small-signal stability probability of a power system with wind farms has important theoretical value and practical significance. Based on the Markov chain, this paper conducted in-depth research on this subject. Firstly, the basic principle of the Markov chain was introduced, based on which we studied the uncertainty of wind power by adopting the transition matrix and the wind speed?power output transformation model and established the probability distribution model of multi-period wind power. Then the boundary-based small-signal stability probability evaluation method was used to establish an evaluation model of multi-period small-signal stability probability of power system with wind farms. Finally, taking the power system with two wind farms as an example, we analyzed its small-signal stability probability and studied the influence of the initial states of wind speed and different periods on the probability of stability. This study provides a new method and support for analyzing the small-signal stability probability of a power system with wind farms.

  11. Small-Signal Modeling, Stability Analysis, and Design Optimization of Single-Phase Delay-Based PLLs

    DEFF Research Database (Denmark)

    Golestan, Saeed; Guerrero, Josep M.

    2015-01-01

    Generally speaking, designing single-phase phaselocked loops (PLLs) is more complicated than three-phase ones, as their implementation often involves the generation of a fictitious orthogonal signal for the frame transformation. In recent years, many approaches to generate the orthogonal signal have been proposed, the simplest perhaps being the transfer delay based method. In the transfer delay based PLL (TD-PLL), the orthogonal signal is generated by delaying the original singlephase signal by T=4 (one-quarter of a period). The phase shift caused by the transfer delay block, however, will not be exactly 90 under off-nominal grid frequencies, which results in errors in the estimated quantities by the TD-PLL. To alleviate this issue, an improved version of TD-PLL, called the non-frequency dependent TD-PLL (NTD-PLL), has recently been proposed. The NTD-PLL uses another T=4 delay unit in its feedback path to make the PLL immune to grid frequency variations. To the best of the authors’ knowledge, the accurate small-signal modeling of the TD-PLL and NTD-PLL has not yet been carried out, and no detailed analysis of their performance has been presented. The main aim of this paper is to address these issues and explore new methods to enhance their performance. The stability analysis, control design guidelines and performance comparison with the state-of-the-art PLLs are presented as well.

  12. Flexible Network Bandwidth and Latency Provisioning in the Datacenter

    OpenAIRE

    Jeyakumar, Vimalkumar; Kabbani, Abdul; Mogul, Jeffrey C.; Vahdat, Amin

    2014-01-01

    Predictably sharing the network is critical to achieving high utilization in the datacenter. Past work has focussed on providing bandwidth to endpoints, but often we want to allocate resources among multi-node services. In this paper, we present Parley, which provides service-centric minimum bandwidth guarantees, which can be composed hierarchically. Parley also supports service-centric weighted sharing of bandwidth in excess of these guarantees. Further, we show how to configure these polici...

  13. Compact antenna arrays with wide bandwidth and low sidelobe levels

    Science.gov (United States)

    Strassner, II, Bernd H.

    2014-09-09

    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.

  14. Frequency Bandwidth Optimization of Left-Handed Metamaterial

    Science.gov (United States)

    Chevalier, Christine T.; Wilson, Jeffrey D.

    2004-01-01

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

  15. 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

  16. RECYCLING THE UNUSED BANDWIDTH USING PRIORITY BASED SCHEDULING ALGORITHM

    Directory of Open Access Journals (Sweden)

    M. Durai Ganesh

    2013-10-01

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

  17. Effective Bandwidth Utilization in IEEE802.11 for VOIP

    CERN Document Server

    Bhanu, S Vijay; Balakrishnan, V

    2010-01-01

    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...

  18. Bandwidth efficient CCSDS coding standard proposals

    Science.gov (United States)

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

    1992-01-01

    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.

  19. Bandwidth tunable filter based on silicon microring-MZI structure

    DEFF Research Database (Denmark)

    Ding, Yunhong; Zhang, Xinliang; Huang, Dexiu; Pu, Minhao; Liu, Liu; Xu, Jing; Ou, Haiyan; Peucheret, Christophe

    2010-01-01

    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.

  20. Dynamic Bandwidth Allocation Strategy for Marine VHF Communications

    Directory of Open Access Journals (Sweden)

    Ding Yuan-Ming

    2013-01-01

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

  1. One Method of Cloud Computing Bandwidth Allocation Based on Fairness

    Directory of Open Access Journals (Sweden)

    Yiquan Kong

    2013-02-01

    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.

  2. Small signal analysis of four-wave mixing in InAs/GaAs quantum-dot semiconductor optical amplifiers

    Science.gov (United States)

    Ma, Shaozhen; Chen, Zhe; Dutta, Niloy K.

    2009-02-01

    A model to study four-wave mixing (FWM) wavelength conversion in InAs-GaAs quantum-dot semiconductor optical amplifier is proposed. Rate equations involving two QD states are solved to simulate the carrier density modulation in the system, results show that the existence of QD excited state contributes to the ultra fast recover time for single pulse response by serving as a carrier reservoir for the QD ground state, its speed limitations are also studied. Nondegenerate four-wave mixing process with small intensity modulation probe signal injected is simulated using this model, a set of coupled wave equations describing the evolution of all frequency components in the active region of QD-SOA are derived and solved numerically. Results show that better FWM conversion efficiency can be obtained compared with the regular bulk SOA, and the four-wave mixing bandwidth can exceed 1.5 THz when the detuning between pump and probe lights is 0.5 nm.

  3. PIN photodiode bandwidth optimization in integrated CMOS process

    Science.gov (United States)

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

    2011-05-01

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

  4. A Priority Based Bandwidth Reservation Protocol for Wireless Mesh Networks

    Directory of Open Access Journals (Sweden)

    K. Valarmathi

    2012-01-01

    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.

  5. A NOVEL µ-NEGATIVE METAMATERIAL WITH ENHANCED REJECTION BANDWIDTH

    Directory of Open Access Journals (Sweden)

    Haider Raad

    2013-01-01

    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.

  6. 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

  7. Energy efficiency in elastic-bandwidth optical networks

    DEFF Research Database (Denmark)

    Vizcaino, Jorge Lopez; Ye, Yabin

    2011-01-01

    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.

  8. 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)

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

    1980-01-01

    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.

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

    CERN Document Server

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

    2003-01-01

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

  10. Available Bandwidth Estimation Strategy Based on the Network Allocation Vector

    Directory of Open Access Journals (Sweden)

    Hongtao Liu

    2012-12-01

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

  11. High bandwidth deflection readout for atomic force microscopes

    Science.gov (United States)

    Steininger, Juergen; Bibl, Matthias; Yoo, Han Woong; Schitter, Georg

    2015-10-01

    This contribution presents the systematic design of a high bandwidth deflection readout mechanism for atomic force microscopes. The widely used optical beam deflection method is revised by adding a focusing lens between the cantilever and the quadrant photodetector (QPD). This allows the utilization of QPDs with a small active area resulting in an increased detection bandwidth due to the reduced junction capacitance. Furthermore the additional lens can compensate a cross talk between a compensating z-movement of the cantilever and the deflection readout. Scaling effects are analyzed to get the optimal spot size for the given geometry of the QPD. The laser power is tuned to maximize the signal to noise ratio without limiting the bandwidth by local saturation effects. The systematic approach results in a measured -3 dB detection bandwidth of 64.5 MHz at a deflection noise density of 62 fm / ?{ Hz } .

  12. Napter Was Just the Start of the Bandwidth Invasion.

    Science.gov (United States)

    Carlson, Scott

    2001-01-01

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

  13. Bandwidth allocation and pricing problem for a duopoly market

    Directory of Open Access Journals (Sweden)

    You Peng-Sheng

    2011-01-01

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

  14. MULTILAYER MICROSTRIP ANTENNA QUALITY FACTOR OPTIMIZATION FOR BANDWIDTH ENHANCEMENT

    Directory of Open Access Journals (Sweden)

    M.C. SRIVASTAVA

    2012-12-01

    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.

  15. Modulator-Based, High Bandwidth Optical Links for HEP Experiments

    OpenAIRE

    Underwood, D.G.(Argonne National Laboratory, Argonne, IL, 60439, USA); Drake, G.; Fernando, W. S.; Stanek, R.W.

    2012-01-01

    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, BE...

  16. Variable Neighborhood Search for solving Bandwidth Coloring Problem

    OpenAIRE

    Matic, Dragan; Kratica, Jozef; Filipovic, Vladimir

    2015-01-01

    This paper presents a variable neighborhood search (VNS) algorithm for solving bandwidth coloring problem (BCP) and bandwidth multicoloring problem (BMCP). BCP and BMCP are generalizations of the well known vertex coloring problem and they are of a great interest from both theoretical and practical points of view. Presented VNS combines a shaking procedure which perturbs the colors for an increasing number of vertices and a specific variable neighborhood descent (VND) proced...

  17. Review of high bandwidth fiber optics radiation sensors

    International Nuclear Information System (INIS)

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

  18. Opportunities for Bandwidth Adaptation in Microsoft Office Documents

    OpenAIRE

    Lara, E.; Wallach, D.S.; Zwaenepoel, W.

    2000-01-01

    Microsoft Office, the most popular office productivity suite, produces large documents that can result in long download latencies for platforms with limited bandwidth. To reduce latency and improve the user's experience, these documents need to be adapted for transmission on a limited-bandwidth network. To identify opportunities for adaptation, we characterize documents created by three popular applications from the Microsoft Office suite: Word, PowerPoint, and Excel. Our study encompasses o...

  19. Techniques for bandwidth measurements of optical guided-wave modulators

    OpenAIRE

    Nikles, M.; Thévenaz, Luc; P. Robert

    1992-01-01

    High-speed optical guided-wave switches and modulators are promising components for present and future applications in lightwave communication and measurement systems, or more generally for optical signal processing purposes. Integrated electro-optic modulators with bandwidth extending over a few gigahertz and low drive voltages are now commercially available. Due to their potential applications, bandwidth characterization is an important feature of the metrology of these devices and is often...

  20. Available Bandwidth Estimation Strategy Based on the Network Allocation Vector

    OpenAIRE

    Hongtao Liu; Lianglun Cheng

    2012-01-01

    Available bandwidth is of great importance to network Quality of Service assurance, network load balancing, streaming media rate control, routing, and congestion control, etc.. In this paper, the available bandwidth estimation strategy based on the Network Allocation Vector for Wireless Sensor Networks is proposed. According to the size of the average contention window, network nodes predict the probability of collision in process of frame transmission, and then estimate the number of retrans...

  1. On the Bandwidth of High-Impedance Frequency Selective Surfaces

    CERN Document Server

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

    2010-01-01

    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...

  2. Demand-based bandwidth assignment MAC protocol for wireless LANs

    Science.gov (United States)

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

    2004-04-01

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

  3. Bandwidth-Aware AODV based Routing Protocol in MANETs

    Directory of Open Access Journals (Sweden)

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

    2013-06-01

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

  4. Small-Signal Modeling of the PVR-Based AD Scheme and Controller Design for Three-Phase Standalone DG System

    DEFF Research Database (Denmark)

    Shen, Pan; Han, Yang; Lu, Chang; Guerrero, Josep M.

    2016-01-01

    controllers are based on an enhanced proportional resonant (PR) structure to achieve zero steady-state error, and multi-resonant harmonic compensator (MRHC) plus PR controller to prevent low-order load current harmonics to distort the output voltage. The proposed small-signal model of the islanded DG system...... with multi-loop control strategy in the stationary reference frame is presented. Moreover, an enhanced delay compensation (EDC) scheme based on two integrators of the discrete PR controller is presented to improve stability margins with a higher accuracy compared with the existing methods. Then, a...

  5. [Tumor segmentation of brain MRI with adaptive bandwidth mean shift].

    Science.gov (United States)

    Hou, Xiaowen; Liu, Qi

    2014-10-01

    In order to get the adaptive bandwidth of mean shift to make the tumor segmentation of brain magnetic resonance imaging (MRI) to be more accurate, we in this paper present an advanced mean shift method. Firstly, we made use of the space characteristics of brain image to eliminate the impact on segmentation of skull; and then, based on the characteristics of spatial agglomeration of different tissues of brain (includes tumor), we applied edge points to get the optimal initial mean value and the respectively adaptive bandwidth, in order to improve the accuracy of tumor segmentation. The results of experiment showed that, contrast to the fixed bandwidth mean shift method, the method in this paper could segment the tumor more accurately. PMID:25764711

  6. Performance Investigation of Virtual Private Networks with Different Bandwidth Allocations

    CERN Document Server

    Natarajan, Mahalakshmi Chidambara; Nachiappan, Alamelu

    2010-01-01

    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.

  7. A novel dynamic wavelength bandwidth allocation scheme over OFDMA PONs

    Science.gov (United States)

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

    2011-12-01

    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.

  8. Analysis of bandwidth measurement methodologies over WLAN systems

    CERN Document Server

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

    2009-01-01

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

  9. Enhancement of bandwidth of planar microstrip antenna with meta materials

    Directory of Open Access Journals (Sweden)

    Ahmed Al-Shaheen

    2011-09-01

    Full Text Available In this paper we present a planar left-handed material pattern on the rectangular patch antenna mounted on the substrate is designed to enhance its horizontal radiation as well as to broaden its working bandwidth. The parametric study is done to study the effect of the ground plane slots width of 0.3, 0.4 and 0.5 mm respectively on the return loss and bandwidth enhancement, the best value of g is 0.4 mm. Enhancement in the bandwidth is achieved by introducing the meta material phenomena instead of the single patch antenna is about 19.2 times with g = 0.4 mm.

  10. Bandwidth-Conserving Multicast VoIP Teleconference System

    Directory of Open Access Journals (Sweden)

    Teck-Kuen Chua

    2008-07-01

    Full Text Available Teleconferencing is an essential feature in any business telephone system. A teleconference allows associates to engage in a group discussion by conducting a virtual meeting while remaining at geographically dispersed locations. Teleconferencing increases productivity while reducing travel costs and saving travel time. In a VoIP telephone system, we face the significant challenge of providing a teleconference feature that can support a large-scale teleconference without using excessive bandwidth. This paper presents a new, bandwidth-efficient way of implementing a real-time VoIP teleconference system. This new method provides all of the features that existing teleconference systems provide, but this new approach consumes considerably less data bandwidth than existing systems require. The new system allows a network with a given capacity to accommodate almost double the number of conference participants that an existing system would allow.

  11. Performance Investigation of Virtual Private Networks with Different Bandwidth Allocations

    Directory of Open Access Journals (Sweden)

    Ramaswamy Muthiah

    2010-01-01

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

  12. Arbitrary-bandwidth Brillouin slow light in optical fibers.

    Science.gov (United States)

    González Herráez, Miguel; Song, Kwang Yong; Thévenaz, Luc

    2006-02-20

    Brillouin slow light in optical fibers is a promising technique for the development of all-optical buffers to be used in optical routers. The main drawback of this technique up to now has been its narrow bandwidth, normally restricted to 35 MHz in conventional single-mode optical fibers. In this paper we demonstrate experimentally that Brillouin slow light with an arbitrary large bandwidth can be readily obtained in conventional optical fibers using a simple and inexpensive pump spectral broadening technique. In our experiments, we show the delaying of 2.7 ns pulses over slightly more than one pulse length with only some residual broadening (<25%) of the pulse width. We see no limit to extend this technique to the delaying of GHz-bandwidth signals. PMID:19503463

  13. Gain-switched all-fiber laser with narrow bandwidth

    DEFF Research Database (Denmark)

    Larsen, Casper; Giesberts, M.

    2013-01-01

    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.

  14. PRIORITY BASED BANDWIDTH ALLOCATION IN WIRELESS SENSOR NETWORKS

    Directory of Open Access Journals (Sweden)

    Mary Cherian

    2014-12-01

    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.

  15. Bandwidth of adaptive optics system in atmospheric coherent laser communication

    Science.gov (United States)

    Li, Jiawei; Zhang, Zhen; Gao, Jianqiu; Sun, Jianfeng; Chen, Weibiao

    2016-01-01

    The bit-error-rate performance of free space optical communication systems with binary phase shift keying modulation and coherent homodyne detection is performed. Besides the turbulence-induced wave-front phase error and the amplitude fluctuation, the servo bandwidth of adaptive optics system is investigated. It is shown that Greenwood frequency is large enough for the servo bandwidth of adaptive optics system when the detected photons per bit are more than 100. However, if the photons per bit are less than 70, the Greenwood frequency is only sufficient for weak scintillation. We should increase the servo bandwidth to almost twice the value of Greenwood frequency at least in order to obtain an acceptable BER performance when the scintillation index is larger than 0.7. In addition, we also investigate the aperture averaging effects when the receiving aperture is larger than the coherent length.

  16. CMOS BASED CURRENT FEEDBACK OP-AMP WITH IMPROVED BANDWIDTH

    Directory of Open Access Journals (Sweden)

    Akshay Dubey

    2015-10-01

    Full Text Available A current mode feedback operational amplifier designed using a complimentary MOS circuit technology has been discussed in this paper. A class AB amplifier has been used in the design and the design results in improvement of values of number of parameter when compared to the previously reported architecture. The circuit is designed using 0.35µm technology. Bandwidth of the presented architecture was obtained, that was always greater than 50MHz. On the other hand , bandwidth in case of previously reported circuit was coming out to be always more than 2MHz. Thus in our proposed circuit, there is a considerable improvement in the bandwidth of the circuit. Also the Slew rate, which was improved from 5.2V/µsec to 8.1V/ µsec. Settling time of the proposed circuit has been reduced to 134 nsec which was of order of 212 nsec in case of the previous design.

  17. A Study of Bandwidth Measurement Technique in Wireless Mesh Networks

    Directory of Open Access Journals (Sweden)

    Ajeet Kumar Singh

    2011-09-01

    Full Text Available Wireless mesh networks (WMNs have been proposed as a key technology for next generation wireless networking to provide last-mile broadband access. H ere we have given our observation and study for end to-end bandwidth estimation in WMNs. End-to-end Ban dwidth Estimation is an important metric for network management and monitoring. It can also impr ove the effectiveness of congestion control mechanism, audio/video stream adoration and dynamic overlay. In recent years, many techniques have been developed for bandwidth estimation in the wire d as well as the last-hop wireless networks, but th ey under-perform in WMNs. We investigate attributes th at can affect the bandwidth estimation in WNMs; we found existing techniques do not consider the effec t of attributes like CSMA/CA-based contending traff ic and high interference interference that leads to th e error full estimation.

  18. Effect of backing layer composition on ultrasonic probe bandwidth

    International Nuclear Information System (INIS)

    Backing layer of an ultrasonic probe plays an important role in determining the characteristic of waves that is produced. Previous study has showed that the composition of backing layer determines the sensitivity and signal to noise ratio. In this paper, the relationship between backing layer composition and bandwidth of probes will be discussed. The probes fabricated are 2 MHz and 5 MHz using Lead Zirconate Titanate (PZT) with Alumina as wear plate. Backing layer is a mixture of tungsten powder 100 ?m and slow setting epoxy at a ratio of 4:1 and 8:1 by weight. The bandwidth of fabricated probes is measured using Wayne-Kerr impedance analyser. From the results, it is found that the composition of backing layer effects the bandwidth of ultrasonic probes. (author)

  19. Bandwidth analysis of all-optical turbo-switch

    Science.gov (United States)

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

    2015-01-01

    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.

  20. An octave-bandwidth negligible-loss radiofrequency metamaterial.

    Science.gov (United States)

    Lier, Erik; Werner, Douglas H; Scarborough, Clinton P; Wu, Qi; Bossard, Jeremy A

    2011-03-01

    Metamaterials provide an unprecedented ability to manipulate electromagnetic waves and are an enabling technology for new devices ranging from flat lenses that focus light beyond the diffraction limit to coatings capable of cloaking an object. Nevertheless, narrow bandwidths and high intrinsic losses arising from the resonant properties of metamaterials have raised doubts about their usefulness. New design approaches seek to turn the perceived disadvantages of dispersion into assets that enhance a device's performance. Here we employ dispersion engineering of metamaterial properties to enable specific device performance over usable bandwidths. In particular, we design metamaterials that considerably improve conventional horn antennas over greater than an octave bandwidth with negligible loss and advance the state of the art in the process. Fabrication and measurement of a metahorn confirm its broadband, low-loss performance. This example illustrates the power of clever implementation combined with dispersion engineering to bring metamaterials into their full potential for revolutionizing practical devices. PMID:21278741

  1. An octave-bandwidth negligible-loss radiofrequency metamaterial

    Science.gov (United States)

    Lier, Erik; Werner, Douglas H.; Scarborough, Clinton P.; Wu, Qi; Bossard, Jeremy A.

    2011-03-01

    Metamaterials provide an unprecedented ability to manipulate electromagnetic waves and are an enabling technology for new devices ranging from flat lenses that focus light beyond the diffraction limit to coatings capable of cloaking an object. Nevertheless, narrow bandwidths and high intrinsic losses arising from the resonant properties of metamaterials have raised doubts about their usefulness. New design approaches seek to turn the perceived disadvantages of dispersion into assets that enhance a device’s performance. Here we employ dispersion engineering of metamaterial properties to enable specific device performance over usable bandwidths. In particular, we design metamaterials that considerably improve conventional horn antennas over greater than an octave bandwidth with negligible loss and advance the state of the art in the process. Fabrication and measurement of a metahorn confirm its broadband, low-loss performance. This example illustrates the power of clever implementation combined with dispersion engineering to bring metamaterials into their full potential for revolutionizing practical devices.

  2. Maximizing Communication Quality with Bandwidth Guarantees in Wireless Mesh Networks

    Directory of Open Access Journals (Sweden)

    Mohammed Abdul Majeed

    2013-12-01

    Full Text Available Wireless Mesh Network (WMN helps remote areas to gain access to Internet. There might be number of paths to gain access to Internet. Finding a path with maximum bandwidth is the problem to be addressed. Many solutions towards this came into existence. Recently Hou et al. presented a new path weight approach to capture in order to obtain path bandwidth information. In wireless networks the solution is not easier when compared to its wired counterpart. They used consistency property with respect to path weight to know the best that maximizes bandwidth consistently. In this paper we implement this strategy in WMN. We built a prototype, a simulator, application which demonstrates the proof of concept. The empirical results revealed that our approach is effective and outperforms existing path metrics.

  3. Fabrication of high frequency ultrasonic probe with wide bandwidth

    International Nuclear Information System (INIS)

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

  4. Fiber communications using convolutional coding and bandwidth-efficient modulation

    Science.gov (United States)

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

    2006-01-01

    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.

  5. EFFECTIVE BANDWIDTH FOR SELF-SIMILAR TRAFFIC IN ATM NETWORK

    Directory of Open Access Journals (Sweden)

    Linawati Linawati

    2012-05-01

    Full Text Available This paper proposes a new approach to estimate the effective bandwidth for self-similar traffic in ATM network. In this approach we use the tail distribution of queue length based on FBM model. This approach is derived from the inequalities for Mills’ ratio. Then a comparison with Norros and Trinh&Miki schemes are analysed. The results demonstrate reasonable agreement between numerical and simulation results and between all schemes. Their bandwidth estimation tends closer for CLP improvement.

  6. TDX: A high-bandwidth crossbar-switched communication paradigm

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, P.E.; Eilers, D.L.; Schreiber, A.L.

    1994-08-01

    Digital signal processing systems under development today require scalable and reconfigurable high bandwidth communication resources between processing elements. Shared memory architectures require the ability to transfer data from one processor node to another, as well as maintaining data coherency such as provided by the Scalable Coherent Interface (SCI). Signal processing systems that must move large amounts of data between processor nodes, are best served by a communication system that allows reconfigurable streams of data to flow at deterministic rates with minimal overhead. A Time Domain Crossbar (TDX) communication system providing scalable, programmable, high-bandwidth, streaming communication has been developed and is described in this paper.

  7. 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

  8. Improving Bandwidth Efficiency in E-band Communication Systems

    OpenAIRE

    Mehrpouyan, Hani; Khanzadi, M. Reza; Matthaiou, Michail; Akbar M. Sayeed; Schober, Robert; Hua, Yingbo

    2013-01-01

    The allocation of a large amount of bandwidth by regulating bodies in the 70/80 GHz band, i.e., the E-band, has opened up new potentials and challenges for providing affordable and reliable Gigabit per second wireless point-to-point links. This article first reviews the available bandwidth and licensing regulations in the E-band. Subsequently, different propagation models, e.g., the ITU-R and Cane models, are compared against measurement results and it is concluded that to m...

  9. Bandwidth Enhancement of Probe Fed Microstrip Patch Antenna

    Directory of Open Access Journals (Sweden)

    Parminder Singh

    2013-01-01

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

  10. Bandwidth effects in Brillouin scattering from inhomogeneous plasma

    International Nuclear Information System (INIS)

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

  11. Qualitative properties of ?-fair policies in bandwidth-sharing networks

    OpenAIRE

    Zhong, Y.; Shah, Devavrat; Tsitsiklis, John N.

    2012-01-01

    We consider a flow-level model of a network operating under an ?-fair bandwidth sharing policy (with ? > 0) proposed by Roberts and Massoulié [Telecomunication Systems 15 (2000) 185–201]. This is a probabilistic model that captures the long-term aspects of bandwidth sharing between users or flows in a communication network. We study the transient properties as well as the steady-state distribution of the model. In particular, for ? ? 1, we obtain bounds on the maximum number of flows in th...

  12. Energy and Bandwidth Constrained QoS Enabled Routing for MANETs

    OpenAIRE

    N.Sumathi; C.P. Sumathi

    2013-01-01

    Mobile adhoc networks are rapid deployable self organizing networks. Their key characteristics aredynamic topology, high node mobility, low channel bandwidth and limited battery power. Hence, it isnecessary to minimize bandwidth and energy consumption. To transmit packets, available bandwidth isknown along the route from sender to receiver. Thus, bandwidth estimation is the main metric to supportQuality of Service (QoS). This work focuses on improving the accuracy of available bandwidth andin...

  13. A Practical Approach For Excess Bandwidth Distribution for EPONs

    KAUST Repository

    Elrasad, Amr

    2014-03-09

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

  14. A Preliminary Evaluation of Bandwidth Allocation Model Dynamic Switching

    Directory of Open Access Journals (Sweden)

    Rafael F. Reale

    2014-06-01

    Full Text Available Bandwidth Allocation Models (BAMs are used in order to define Bandwidth Constraints (BCs in a per-class basis for MPLS/DS-TE networks and effectively define how network resources like bandwidth are obtained and shared by applications. The BAMs proposed (MAM – Maximum Allocation Model, RDM – Russian Dolls Model, G-RDM – Generic RDM and AllocTC-Sharing attempt to optimize the use of bandwidth resources on a per-link basis with different allocation and resource sharing characteristics. As such, the adoption of distinct BAMs and/or changes in network resource demands (network traffic profile may result in different network traffic allocation and operational behavior for distinct BAMs. This paper evaluates the resulting network characteristics (li nk utilization, preemption and flows blocking of using BAMs dynamically with different traffic scenarios. In brief, it is investigated the dynamics of BAM switching with distinct traffic scenarios. The paper presents initially the investigated BAMs in relation to their behavior and resource allocation characteristics. Then, distinct BAMs are compared using different traffic scenarios in order to investigate the impact of a dynamic change of the BAM configured in the network. Finally, the paper shows that the adoption of a dynamic BAM allocation strategy may result in benefits for network operation in terms of link utilization, preemption and flows blocking.

  15. Bandwidth utilization maximization of scientific RF communication systems

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  16. Designing large-bandwidth planar photonic crystal waveguides

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Søndergaard, Thomas

    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...

  17. A Bandwidth Characterization Tool For MPEG-2 File

    OpenAIRE

    Kugali, Sandeep.; Manvi, S. S.; Sutagundar, A. V.

    2009-01-01

    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.

  18. Space-bandwidth product of some deblurring filters

    Energy Technology Data Exchange (ETDEWEB)

    Hansche, B.D.

    1977-09-01

    We present an estimate of the space-bandwidth product of a filter of the form W (f) =H (f))/(H/sup 2/(f)+C (f)), which is often encountered in image processing. The estimate applies to blur functions H (f) which are similar to the linear motion blur in that they oscillate smoothly under a decreasing envelope.

  19. Space-bandwidth product of some deblurring filters.

    Science.gov (United States)

    Hansche, B D

    1977-09-01

    We present an estimate of the space-bandwidth product of a filter of the form W(f) = [H(f)]/[H(2)(f) + C(f)], which is often encountered in image processing. The estimate applies to blur functions H(f) which are similar to the linear motion blur in that they oscillate smoothly under a decreasing envelope. PMID:20168966

  20. Gain-switched all-fiber laser with narrow bandwidth

    DEFF Research Database (Denmark)

    Larsen, Casper; Giesberts, M.; Nyga, S.; Fitzau, O.; Jungbluth, B.; Hoffmann, H. D.; Bang, Ole

    2013-01-01

    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...

  1. Graphene electro-optic modulator with 30?GHz bandwidth

    Science.gov (United States)

    Phare, Christopher T.; Daniel Lee, Yoon-Ho; Cardenas, Jaime; Lipson, Michal

    2015-08-01

    Graphene has generated exceptional interest as an optoelectronic material because its high carrier mobility and broadband absorption promise to make extremely fast and broadband electro-optic devices possible. Electro-optic graphene modulators previously reported, however, have been limited in bandwidth to a few gigahertz because of the large capacitance required to achieve reasonable voltage swings. Here, we demonstrate a graphene electro-optic modulator based on resonator loss modulation at critical coupling that shows drastically increased speed and efficiency. Our device operates with a 30?GHz bandwidth and with a state-of-the-art modulation efficiency of 15?dB per 10?V. We also show the first high-speed large-signal operation in a graphene modulator, paving the way for fast digital communications using this platform. The modulator uniquely uses silicon nitride waveguides, an otherwise completely passive material platform, with promising applications for ultra-low-loss broadband structures and nonlinear optics.

  2. Wide-Bandwidth Digital Backend System for VLBI

    Science.gov (United States)

    Whitney, A. R.

    2007-07-01

    Modern digital electronics now allow the replacement of aging VLBI analog backend systems with fully digital systems to provide numerous benefits, including: 1) uniform, repeatable, predictable performance, 2) low cost, 3) increased flexibility, 4) easy expandability, 6) easy transportability, and 5) flexible and rapid implementation through use of modern FPGA devices. A first-generation Digital Backend (DBE) system, based on a polyphase-filter-bank approach that can process four 500 MHz-bandwidth IF signals, has been built (for exercised in real-world VLBI experiments at rates to 4 Gbps/station. Tests at 8 Gbps/station are planned. A second-generation DBE system to process four 1 GHz-bandwidth IFs is now in development in collaboration with UC Berkeley and National Radio Astronomy Observatory; the cost of this system is expected to <10K.

  3. On Free-Electron Laser Growing Modes and their Bandwidth

    CERN Document Server

    Webb, Stephen; Litvinenko, Vladimir

    2011-01-01

    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.

  4. Bandwidth efficient block codes for M-ary PSK modulation

    Science.gov (United States)

    Lin, Shu

    1987-01-01

    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.

  5. Available Network Bandwidth Schema to Improve Performance in TCP Protocols

    Directory of Open Access Journals (Sweden)

    Marcos Talau

    2013-09-01

    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.

  6. 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

  7. BANDWIDTH ENHANCEMENT USING PARASITIC PATCH FOR KU BAND

    Directory of Open Access Journals (Sweden)

    Kalpesh B. Barad

    2014-04-01

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

  8. The Bandwidths of a Matrix. A Survey of Algorithms

    Directory of Open Access Journals (Sweden)

    Mafteiu-Scai Liviu Octavian

    2014-12-01

    Full Text Available The bandwidth, average bandwidth, envelope, profile and antibandwidth of the matrices have been the subjects of study for at least 45 years. These problems have generated considerable interest over the years because of them practical relevance in areas like: solving the system of equations, finite element methods, circuit design, hypertext layout, chemical kinetics, numerical geophysics etc. In this paper a brief description of these problems are made in terms of their definitions, followed by a comparative study of them, using both approaches: matrix geometry and graph theory. Time evolution of the corresponding algorithms as well as a short description of them are made. The work also contains concrete real applications for which a large part of presented algorithms were developed.

  9. Raman scheme for adjustable-bandwidth quantum memory

    International Nuclear Information System (INIS)

    We propose a scenario of quantum memory for light based on Raman scattering. The storage medium is a vapor and the different spectral components of the input pulse are stored in different atomic velocity classes. One uses appropriate pulses to reverse the resulting Doppler phase shift and to regenerate the input pulse, without distortion, in the backward direction. The different stages of the protocol are detailed and the recovery efficiency is calculated in the semiclassical picture. Since the memory bandwidth is determined by the Raman transition Doppler width, it can be adjusted by changing the angle between the input pulse wave vector and the control beams. The optical depth also depends on the beam angle. As a consequence the available optical depth can be optimized depending on the needed bandwidth. The predicted recovery efficiency is close to 100% for large optical depth.

  10. Bandwidth and power efficient satellite TDMA demodulator and decoder

    Science.gov (United States)

    Ames, Stephen A.; Monte, Paul A.; Hoeber, Christopher F.; Chethik, Frank

    1988-01-01

    A proof-of-concept demodulator for TDMA applications requiring high total data rates composed of many low data rate users is proposed. High-spectrum efficiency is obtained via a bandwidth efficient combined modulation and coding system, and low TDMA overhead is obtained via a fast acquiring digital phase lock loop. The system employs a data rate of 200 Mb/s with a bit error rate of better than 5 x 10 to the -7th in the presence of adjacent channel interference 20 dB above the weakest user. The 8-PSK modulation combined with the rate 5/6 forward error correction coding results in a bandwidth efficiency of better than 2 bits/second per Hz.

  11. High bandwidth on-chip silicon photonic interleaver.

    Science.gov (United States)

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

    2010-10-25

    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

  12. Bandwidth and Energy Management in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Ashish Talikoti, Jayashree A

    2012-10-01

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

  13. Bandwidth compression of noisy signals with square-wave subcarrier

    Science.gov (United States)

    Feria, Y.; Statman, J.

    1992-01-01

    This article discusses a method for downconverting the square-wave subcarrier of spacecraft signals, such as the one from Galileo, which results in a compression bandwidth that lowers the sample rate significantly. The study is focused on three issues. The first is the selection of an adequate down-mixing signal for the resulting signal to have a format similar to that of the original signal, except at a lowersub carrier frequency. The second is the control of the noise level so that the signal to noise ratio is not degraded due to the downconversion. The third is to determine the bandwidth of the downconverted signal considering the uncertainty of the residual carrier frequency.

  14. Bandwidth-sharing in LHCONE, an analysis of the problem

    Science.gov (United States)

    Wildish, T.

    2015-12-01

    The LHC experiments have traditionally regarded the network as an unreliable resource, one which was expected to be a major source of errors and inefficiency at the time their original computing models were derived. Now, however, the network is seen as much more capable and reliable. Data are routinely transferred with high efficiency and low latency to wherever computing or storage resources are available to use or manage them. Although there was sufficient network bandwidth for the experiments’ needs during Run-1, they cannot rely on ever-increasing bandwidth as a solution to their data-transfer needs in the future. Sooner or later they need to consider the network as a finite resource that they interact with to manage their traffic, in much the same way as they manage their use of disk and CPU resources. There are several possible ways for the experiments to integrate management of the network in their software stacks, such as the use of virtual circuits with hard bandwidth guarantees or soft real-time flow-control, with somewhat less firm guarantees. Abstractly, these can all be considered as the users (the experiments, or groups of users within the experiment) expressing a request for a given bandwidth between two points for a given duration of time. The network fabric then grants some allocation to each user, dependent on the sum of all requests and the sum of available resources, and attempts to ensure the requirements are met (either deterministically or statistically). An unresolved question at this time is how to convert the users’ requests into an allocation. Simply put, how do we decide what fraction of a network's bandwidth to allocate to each user when the sum of requests exceeds the available bandwidth? The usual problems of any resourcescheduling system arise here, namely how to ensure the resource is used efficiently and fairly, while still satisfying the needs of the users. Simply fixing quotas on network paths for each user is likely to lead to inefficient use of the network. If one user cannot use their quota for some reason, that bandwidth is lost. Likewise, there is no incentive for the user to be efficient within their quota, they have nothing to gain by using less than their allocation. As with CPU farms, some sort of dynamic allocation is more likely to be useful. A promising approach for sharing bandwidth at LHCONE is the ’Progressive Second-Price auction’, where users are given a budget and are required to bid from that budget for the specific resources they want to reserve. The auction allows users to effectively determine among themselves the degree of sharing they are willing to accept based on the priorities of their traffic and their global share, as represented by their total budget. The network then implements those allocations using whatever mix of technologies is appropriate or available. This paper describes how the Progressive Second-Price auction works and how it can be applied to LHCONE. Practical questions are addressed, such as how are budgets set, what strategy should users use to manage their budget, how and how often should the auction be run, and how do we ensure that the goals of fairness and efficiency are met.

  15. Automated Controllers for Bandwidth Allocation in Network Virtualization

    OpenAIRE

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

    2013-01-01

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

  16. Introducing a Performance Model for Bandwidth-Limited Loop Kernels

    OpenAIRE

    Treibig, Jan; Hager, Georg

    2009-01-01

    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 moder...

  17. Optimization of bandwidth in 60^o photonic crystal waveguide bends

    DEFF Research Database (Denmark)

    Xing, P. F.; Borel, Peter Ingo; Frandsen, Lars Hagedorn; Harpøth, Anders; Kristensen, Martin

    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....

  18. Frequency bandwidth of half-wave impedance repeater

    OpenAIRE

    Marek Dvorsky; Libor Michalek; Martin Tomis

    2012-01-01

    This article brings in the second part general information about half-wave impedance repeater. The third part describes the basic functional principles of the half-wave impedance repeater using Smith chart. The main attention is focused in part four on the derivation of repeater frequency bandwidth depending on characteristics and load impedance of unknown feeder line. Derived dependences are based on the elementary features of the feeder lines with specific length. The described functionalit...

  19. Forecasting international bandwidth capacity using linear and ANN methods

    OpenAIRE

    Madden, Gary G; Tan, Joachim

    2008-01-01

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

  20. Bandwidth Efficient Hybrid Synchronization for Wireless Sensor Network

    DEFF Research Database (Denmark)

    Dnyaneshwar, Mantri; Prasad, Neeli R.; Prasad, Ramjee

    2015-01-01

    Data collection and transmission are the fundamental operations of Wireless Sensor Networks (WSNs). A key challenge in effective data collection and transmission is to schedule and synchronize the activities of the nodes with the global clock. This paper proposes the Bandwidth Efficient Hybrid Synchronization Data Aggregation Algorithm (BESDA) using spanning tree mechanism (SPT). It uses static sink and mobile nodes in the network. BESDA considers the synchronization of a local clock of node wit...

  1. Ranging with ultrawide bandwidth signals in multipath environments

    OpenAIRE

    Dardari, Davide; Ferner, Ulric John; Conti, Andrea; Giorgetti, Andrea; Win, Moe Z.

    2008-01-01

    Over the coming decades, high-definition situationally-aware networks have the potential to create revolutionary applications in the social, scientific, commercial, and military sectors. Ultrawide bandwidth (UWB) technology is a viable candidate for enabling accurate localization capabilities through time-of-arrival (TOA)-based ranging techniques. These techniques exploit the fine delay resolution property of UWB signals by estimating the TOA of the first signal path. Exploiting the full capa...

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

    International Nuclear Information System (INIS)

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

  3. Artificial bandwidth extension of spectral envelope along a Viterbi path

    OpenAIRE

    Ya?l?, Can; Turan, M. A. Tu?tekin; Erzin, Engin

    2013-01-01

    In this paper, we propose a hidden Markov model (HMM)-based wideband spectral envelope estimation method for the artificial bandwidth extension problem. The proposed HMM-based estimator decodes an optimal Viterbi path based on the temporal contour of the narrowband spectral envelope and then performs the minimum mean square error (MMSE) estimation of the wideband spectral envelope on this path. Experimental evaluations are performed to compare the proposed estimator to the state-of-the-art HM...

  4. Power--bandwidth limitations of an optical resonance

    CERN Document Server

    Miller, Owen D; Anquillare, Emma; Joannopoulos, John D; Solja?i?, Marin; Johnson, Steven G

    2015-01-01

    We present shape-independent upper limits to the power--bandwidth product for a single resonance in an optical scatterer, with the bound depending only on the material susceptibility. We show that quasistatic metallic scatterers can nearly reach the limits, and we apply our approach to the problem of designing $N$ independent, subwavelength scatterers to achieve flat, broadband response even if they individually exhibit narrow resonant peaks.

  5. Managing high-bandwidth real-time data storage

    Energy Technology Data Exchange (ETDEWEB)

    Bigelow, David D. [Los Alamos National Laboratory; Brandt, Scott A [Los Alamos National Laboratory; Bent, John M [Los Alamos National Laboratory; Chen, Hsing-Bung [Los Alamos National Laboratory

    2009-09-23

    There exist certain systems which generate real-time data at high bandwidth, but do not necessarily require the long-term retention of that data in normal conditions. In some cases, the data may not actually be useful, and in others, there may be too much data to permanently retain in long-term storage whether it is useful or not. However, certain portions of the data may be identified as being vitally important from time to time, and must therefore be retained for further analysis or permanent storage without interrupting the ongoing collection of new data. We have developed a system, Mahanaxar, intended to address this problem. It provides quality of service guarantees for incoming real-time data streams and simultaneous access to already-recorded data on a best-effort basis utilizing any spare bandwidth. It has built in mechanisms for reliability and indexing, can scale upwards to meet increasing bandwidth requirements, and handles both small and large data elements equally well. We will show that a prototype version of this system provides better performance than a flat file (traditional filesystem) based version, particularly with regard to quality of service guarantees and hard real-time requirements.

  6. Improved Radiation and Bandwidth of Triangular and Star Patch Antenna

    Directory of Open Access Journals (Sweden)

    M. Ramkumar Prabhu

    2012-06-01

    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.

  7. Bandwidth Enhancement and Radiation Properties of Slotted Antenna

    Directory of Open Access Journals (Sweden)

    Deenanath Sahu,

    2013-04-01

    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%

  8. Small signal microwave amplifier design

    CERN Document Server

    Grosch, Theodore

    2000-01-01

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

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

    OpenAIRE

    Guruprasad, H S; H D Maheshappa

    2009-01-01

    This paper proposes a dynamic bandwidth management algorithm in which more bandwidth is allocated for higher class users and also higher priority is given to the videos with higher popularity within a class using agent technology. The popularity and weight profile of the videos which is used for efficiently allocating bandwidth is periodically updated by a mobile agent. The proposed approach allocates more bandwidth for higher class users and gives higher priority for higher weight videos [po...

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

    OpenAIRE

    Mu Zhang

    2014-01-01

    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-...

  11. Re-use of Low Bandwidth Equipment for High Bit Rate Transmission Using Signal Slicing Technique

    DEFF Research Database (Denmark)

    Wagner, Christoph; Spolitis, S.; Vegas Olmos, Juan José; Bobrovs, V.; Tafur Monroy, Idelfonso

    : Massive fiber-to-the-home network deployment requires never ending equipment upgrades operating at higher bandwidth. We show effective signal slicing method, which can reuse low bandwidth opto-electronical components for optical communications at higher bit rates.......: Massive fiber-to-the-home network deployment requires never ending equipment upgrades operating at higher bandwidth. We show effective signal slicing method, which can reuse low bandwidth opto-electronical components for optical communications at higher bit rates....

  12. Wide-bandwidth piezoelectric energy harvester with polymeric structure

    Science.gov (United States)

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

    2015-01-01

    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.

  13. Optimization of bandwidth of communication channels of corporate networks

    Directory of Open Access Journals (Sweden)

    G. I. Bondarenko

    2014-09-01

    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.

  14. Optimizing scanning strategies: Selecting scanning bandwidth in adversarial RF environments

    OpenAIRE

    Garnaev, Andrey; Trappe, Wade; Kung, Chun-Ta

    2013-01-01

    In this paper we investigate the problem of designing a spectrum scanning strategy to detect an intelligent Invader who wants to utilize spectrum undetected for his/her unapproved purposes. To deal with this problem we apply game-theoretical tools. We model the situation as a game between a Scanner and an Invader where the Invader faces a dilemma: the more bandwidth the Invader attempts to use leads to a larger payoff if he is not detected, but at the same time also increase...

  15. Introducing a Performance Model for Bandwidth-Limited Loop Kernels

    CERN Document Server

    Treibig, Jan

    2009-01-01

    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.

  16. Iterative Available Bandwidth Estimation for Mobile Transport Networks

    DEFF Research Database (Denmark)

    Ubeda Castellanos, Carlos; López Villa, Dimas; Teyeb, Oumer Mohammed; Elling, Jan

    2007-01-01

    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...

  17. Bandwidth allocation for video under quality of service constraints

    CERN Document Server

    Anjum, Bushra

    2014-01-01

    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

  18. Narrow-Bandwidth Diode-Laser-Based Ultraviolet Light Source

    International Nuclear Information System (INIS)

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

  19. Bandwidth Extension Method Based on Spectral Envelope Estimation

    Directory of Open Access Journals (Sweden)

    Bo Hang

    2011-06-01

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

  20. 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

  1. Broadband metasurfaces enabling arbitrarily large delay-bandwidth products

    Science.gov (United States)

    Ginis, Vincent; Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2016-01-01

    Metasurfaces allow for advanced manipulation of optical signals by imposing phase discontinuities across flat interfaces. Unfortunately, these phase shifts remain restricted to values between 0 and 2 π , limiting the delay-bandwidth product of such sheets. Here, we develop an analytical tool to design metasurfaces that mimic three-dimensional materials of arbitrary thickness. In this way, we demonstrate how large phase discontinuities can be realized by combining several subwavelength Lorentzian resonances in the unit cell of the surface. Our methods open up the temporal response of metasurfaces and may lead to the construction of metasurfaces with a plethora of new optical functions.

  2. Bandwidth Improvement of UWB Microstrip Antenna Using Finite Ground Plane

    Directory of Open Access Journals (Sweden)

    Priyanka Mishra

    2015-06-01

    Full Text Available Microstrip antennas play a vital role in communication system. It is required in high performance wireless applications. But due to its resonant nature microstrip antennas have some considerable drawbacks like narrowband performance. Extensive study has been carried out on microstrip patch antennas in the recent past, but it still have large scope for improvement in the near future. To overcome narrow bandwidth problem, number of methods and techniques have been suggested and investigated, keeping in mind that the basic advantages of microstrip antenna should not be altered such as low profile, light weight, low cost and simple printed circuit structure. The area of investigation includes modification in geometrical shape of the antenna, use of resonators, use of dipole, and many other parameters. This paper presents a comparison between conventional microstrip antenna and microstip antenna with finite ground plane at ultra wideband. HFSS simulation tool is used here for antenna simulation. For feeding purpose microstrip feed line is used (50?. Optimized result provides impedance bandwidth of 7.2GHz with VSWR<2, operating frequency range is from 6.5GHz to 13.7GHz. Proposed antenna is useful for many ultra wideband applications.

  3. Modulator-Based, High Bandwidth Optical Links for HEP Experiments

    CERN Document Server

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

    2012-01-01

    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...

  4. Bandwidth Estimation to Provide QoS Routing in MANET

    Directory of Open Access Journals (Sweden)

    Ms. Swati Kamra,

    2013-04-01

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

  5. Improving microwave antenna gain and bandwidth with phase compensation metasurface

    Directory of Open Access Journals (Sweden)

    Ke Chen

    2015-06-01

    Full Text Available Metasurface, as a planar version of artificial metamaterial, provide an effective way to manipulate electromagnetic wave propagation. Here, we present a transparent metasurface for compensating the out-of-phase radiation from a microstrip patch antenna to improve its radiation gain and bandwidth. Based on the equivalence principle of Huygens’ surface, we propose metasurface composed of both inductive and capacitive resonant elements which could produce high transmission with variable phase characteristics. Such metasurface mounted on a patch antenna can transform the spherical-like phase profile generated from the patch into an in-phase planar one. A prototype antenna has been fabricated and validated the squeezed radiation pattern with suppressed sidelobes as well as enhanced impedance bandwidth due to strong near-field coupling. As operating at around 5.7 GHz, the proposed antenna may have potential application in wireless communication systems especially for point-to-point data transmission. It is believed that the design methodology could also be scaled to other frequency bands such as millimeter or terahertz wave.

  6. The Effect of Pulse Shaping QPSK on Bandwidth Efficiency

    Science.gov (United States)

    Purba, Josua Bisuk Mubyarto; Horan, Shelia

    1997-01-01

    This research investigates the effect of pulse shaping QPSK on bandwidth efficiency over a non-linear channel. This investigation will include software simulations and the hardware implementation. Three kinds of filters: the 5th order Butterworth filter, the 3rd order Bessel filter and the Square Root Raised Cosine filter with a roll off factor (alpha) of 0.25,0.5 and 1, have been investigated as pulse shaping filters. Two different high power amplifiers, one a Traveling Wave Tube Amplifier (TWTA) and the other a Solid State Power Amplifier (SSPA) have been investigated in the hardware implementation. A significant improvement in the bandwidth utilization (rho) for the filtered data compared to unfiltered data through the non-linear channel is shown in the results. This method promises strong performance gains in a bandlimited channel when compared to unfiltered systems. This work was conducted at NMSU in the Center for Space Telemetering, and Telecommunications Systems in the Klipsch School of Electrical and Computer Engineering Department and is supported by a grant from the National Aeronautics and Space Administration (NASA) NAG5-1491.

  7. A Bandwidth Allocation Model Provisioning Framework with Autonomic Characteristics

    Directory of Open Access Journals (Sweden)

    Rafael F. Reale

    2013-11-01

    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.

  8. An exponential time 2-approximation algorithm for bandwidth

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-01-01

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

  9. Improving microwave antenna gain and bandwidth with phase compensation metasurface

    Science.gov (United States)

    Chen, Ke; Yang, Zhongjie; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian

    2015-06-01

    Metasurface, as a planar version of artificial metamaterial, provide an effective way to manipulate electromagnetic wave propagation. Here, we present a transparent metasurface for compensating the out-of-phase radiation from a microstrip patch antenna to improve its radiation gain and bandwidth. Based on the equivalence principle of Huygens' surface, we propose metasurface composed of both inductive and capacitive resonant elements which could produce high transmission with variable phase characteristics. Such metasurface mounted on a patch antenna can transform the spherical-like phase profile generated from the patch into an in-phase planar one. A prototype antenna has been fabricated and validated the squeezed radiation pattern with suppressed sidelobes as well as enhanced impedance bandwidth due to strong near-field coupling. As operating at around 5.7 GHz, the proposed antenna may have potential application in wireless communication systems especially for point-to-point data transmission. It is believed that the design methodology could also be scaled to other frequency bands such as millimeter or terahertz wave.

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

    Directory of Open Access Journals (Sweden)

    Nilesh M. Verulkar

    2014-06-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Pallavi Sharma

    2012-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Norashidah Md Din

    2008-05-01

    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.

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

    Directory of Open Access Journals (Sweden)

    A. K. M. Fazlul Haque

    2009-10-01

    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.

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

    DEFF Research Database (Denmark)

    Knüppel, Thyge

    2012-01-01

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

  15. Development of high frequency and wide bandwidth Johnson noise thermometry

    Energy Technology Data Exchange (ETDEWEB)

    Crossno, Jesse; Liu, Xiaomeng; Kim, Philip [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Ohki, Thomas A.; Fong, Kin Chung, E-mail: kc.fong@bbn.com [Quantum Information Processing Group, Raytheon BBN Technologies, Cambridge, Massachusetts 02138 (United States)

    2015-01-12

    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.

  16. Adaptive slope compensation for high bandwidth digital current mode controller

    DEFF Research Database (Denmark)

    Taeed, Fazel; Nymand, Morten

    An adaptive slope compensation method for digital current mode control of dc-dc converters is proposed in this paper. The compensation slope is used for stabilizing the inner current loop in peak current mode control. In this method, the compensation slope is adapted with the variations in...... converter duty cycle. The adaptive slope compensation provides optimum controller operation in term of bandwidth over wide range of operating points. In this paper operation principle of the controller is discussed. The proposed controller is implemented in an FPGA to control a 100 W buck converter. The...... experimental results of measured loop-gain at different operating points are presented to validate the theoretical performance of the controller....

  17. Graphene metascreen for designing compact infrared absorbers with enhanced bandwidth.

    Science.gov (United States)

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

    2015-04-24

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

  18. Development of high frequency and wide bandwidth Johnson noise thermometry

    International Nuclear Information System (INIS)

    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

  19. Graphene metascreen for designing compact infrared absorbers with enhanced bandwidth

    KAUST Repository

    Chen, Pai-Yen

    2015-03-31

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

  20. Bandwidth Efficient Hybrid Synchronization for Wireless Sensor Network

    DEFF Research Database (Denmark)

    Dnyaneshwar, Mantri; Prasad, Neeli R.; Prasad, Ramjee

    network and then perform the pair-wise synchronization. With the mobility of node, the structure frequently changes causing an increase in energy consumption. To mitigate the problem BESDA aggregate data with the notion of a global timescale throughout the network and schedule based time-division multiple......Data collection and transmission are the fundamental operations of Wireless Sensor Networks (WSNs). A key challenge in effective data collection and transmission is to schedule and synchronize the activities of the nodes with the global clock. This paper proposes the Bandwidth Efficient Hybrid...... Synchronization Data Aggregation Algorithm (BESDA) using spanning tree mechanism (SPT). It uses static sink and mobile nodes in the network. BESDA considers the synchronization of a local clock of node with global clock of the network. In the initial stage algorithm established the hierarchical structure in the...

  1. Ultranarrow-bandwidth excimer lasers for 248-nm DUV lithography

    Science.gov (United States)

    Paetzel, Rainer; Albrecht, Hans Stephen; Berger, Vadim; Bragin, Igor; Kramer, Matthias; Kleinschmidt, Juergen; Serwazi, Marcus

    2000-07-01

    We have developed a KrF excimer laser with ultra narrow linewidth and high repetition rate applicable for optical lithography using DUV wafer scanners with highest numerical aperture (NA) of more than 0.8. A laser bandwidth of less than 0.4 pm, full width half maximum, is achieved by our new design of the laser resonator, which is based on out patented polarization coupled resonator. The new resonator design increase the efficiency of ht laser optics and improves the wavelength stability. The laser tube and solid sate pulser have been adapted to the new laser resonator. As a result, another step in the reduction of the cost of operation is achieved. The laser operates with a repetition rate of 2 kHz and gives a large operation range with respect to wavelength and energy range. The characteristic performance of this new excimer laser is presented.

  2. A Hybrid ACO Approach to the Matrix Bandwidth Minimization Problem

    Science.gov (United States)

    Pintea, Camelia-M.; Cri?an, Gloria-Cerasela; Chira, Camelia

    The evolution of the human society raises more and more difficult endeavors. For some of the real-life problems, the computing time-restriction enhances their complexity. The Matrix Bandwidth Minimization Problem (MBMP) seeks for a simultaneous permutation of the rows and the columns of a square matrix in order to keep its nonzero entries close to the main diagonal. The MBMP is a highly investigated {NP}-complete problem, as it has broad applications in industry, logistics, artificial intelligence or information recovery. This paper describes a new attempt to use the Ant Colony Optimization framework in tackling MBMP. The introduced model is based on the hybridization of the Ant Colony System technique with new local search mechanisms. Computational experiments confirm a good performance of the proposed algorithm for the considered set of MBMP instances.

  3. Ultrawide Bandwidth Receiver Based on a Multivariate Generalized Gaussian Distribution

    KAUST Repository

    Ahmed, Qasim Zeeshan

    2015-04-01

    Multivariate generalized Gaussian density (MGGD) is used to approximate the multiple access interference (MAI) and additive white Gaussian noise in pulse-based ultrawide bandwidth (UWB) system. The MGGD probability density function (pdf) is shown to be a better approximation of a UWB system as compared to multivariate Gaussian, multivariate Laplacian and multivariate Gaussian-Laplacian mixture (GLM). The similarity between the simulated and the approximated pdf is measured with the help of modified Kullback-Leibler distance (KLD). It is also shown that MGGD has the smallest KLD as compared to Gaussian, Laplacian and GLM densities. A receiver based on the principles of minimum bit error rate is designed for the MGGD pdf. As the requirement is stringent, the adaptive implementation of the receiver is also carried out in this paper. Training sequence of the desired user is the only requirement when implementing the detector adaptively. © 2002-2012 IEEE.

  4. Enhanced Gain and Bandwidth of Patch Antenna Using EBG Substrates

    Directory of Open Access Journals (Sweden)

    Mst. Nargis Aktar

    2011-02-01

    Full Text Available Microstrip patch antenna becomes very popular day by day because of its ease of analysis andfabrication, low cost, light weight, easy to feed and their attractive radiation characteristics. Althoughpatch antenna has numerous advantages, it has also some drawbacks such as restricted bandwidth, lowgain and a potential decrease in radiation pattern. In recent years, attention to use Electromagnetic BandGap (EBG substrates to overcome the limitations of patch antenna. In this paper, we propose arectangular microstrip patch antenna with EBG substrates and compare the performance of the proposedantenna with a conventional patch antenna in the same physical dimension. Due to the presence of theEBG structure in the dielectric substrates, the electromagnetic band gap is created that reduces thesurface waves considerably. As a result, the performance of the proposed antenna is better comparing theconventional existing microstrip patch antenna.

  5. Performance evaluation of a high-bandwidth timing module

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Ni, Cuiping; Gan, Chaoqin; Gao, Ziyue

    2014-12-01

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

  7. A Survey of Dynamic-centric Bandwidth Allocation Technique for Wireless Networks

    Directory of Open Access Journals (Sweden)

    Bakkiam David Deebak

    2014-01-01

    Full Text Available Objective of the study is to study and analyze the dynamic-centric metrics of bandwidth allocation and estimation for wireless networks. We also extend the objective to probe Quality of Service (QoS provisioning guarantee for infeasible packet routing networking protocols. This study signifies the bandwidth sharing scheme for real time and non-real time based. So far, the researchers have not examined this signification to have a good impact on throughput rate, packet reception rate, packet dropping rate and packet delay. Nowadays, the network technologies have been focused much on dynamic bandwidth allocation for achieving effective bandwidth utilization, good service rate and improving service satisfaction. Thus, we study a lot of routing strategies to analyze the metrics of bandwidth. In the study, we find the convex optimization technique as suitable to enhance the network throughput performance, providing bandwidth issue is negotiated on network.

  8. A variable bandwidth assignment scheme for the Land Mobile Satellite experiment

    Science.gov (United States)

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

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

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

    OpenAIRE

    Ahmed Nabih Zaki Rashed

    2012-01-01

    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....

  10. Bandwidth Selection in an EM-like algorithm for nonparametric multivariate mixtures

    OpenAIRE

    Benaglia, Tatiana; Chauveau, Didier; Hunter, David

    2011-01-01

    In this paper we describe a method to select the bandwidth used in the nonparametric EM (npEM) algorithm of Benaglia et. al. (2008). This method is a generalization of the Silverman's rule of thumb used to select a bandwidth in kernel density estimation, and it results in one bandwidth for each mixture component and each block of conditionally independent and identically distributed repeated measures.

  11. Orientation bandwidths are invariant across spatiotemporal frequency after isotropic components are removed

    OpenAIRE

    Cass, John; Stuit, Sjoerd; Bex, Peter; Alais, David

    2009-01-01

    It is well established that mammalian visual cortex possesses a large proportion of orientation-selective neurons. Attempts to measure the bandwidth of these mechanisms psychophysically have yielded highly variable results (~6°–180°). Two stimulus factors have been proposed to account for this variability: spatial and temporal frequency; with several studies indicating broader bandwidths at low spatial and high temporal frequencies. We estimated orientation bandwidths using a classic overlay ...

  12. High-Bandwidth Photon-Counting Detectors with Enhanced Near-Infrared Response Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Long-range optical telecommunications (LROT) impose challenging requirements on detector array sensitivity at 1064nm and arrays timing bandwidth. Large photonic...

  13. Locking Bandwidth of an Optically-Injected Multi-Section Tunable Laser

    Science.gov (United States)

    Stolz, C. A.; Labukhin, D.; Zakhleniuk, N.; Loudon, R.; Adams, M. J.

    2010-11-01

    Multi-section tunable lasers with optical injection are simulated using the travelling wave approach. By investigating the trajectory of the system the dynamical state can be obtained. The locking bandwidth for a large injection regime and the dynamics outside the locking bandwidth for small injection strengths are presented. It can be seen that the locking bandwidth becomes symmetric around zero detuning for high injection strengths. The dynamics outside the locking bandwidth for small injection strengths are comparable to a single-section single-mode semiconductor laser and it is shown that the stability map exhibits similar patterns.

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

    Science.gov (United States)

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

    2013-08-01

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

  15. High-Bandwidth Photon-Counting Detectors with Enhanced Near-Infrared Response Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Laser optical communications offer the potential to dramatically increase the link bandwidth and decrease the emitter power in long-range space communications....

  16. Minimum cost maximum flow algorithm for upstream bandwidth allocation in OFDMA passive optical networks

    Science.gov (United States)

    Wu, Yating; Kuang, Bin; Wang, Tao; Zhang, Qianwu; Wang, Min

    2015-12-01

    This paper presents a minimum cost maximum flow (MCMF) based upstream bandwidth allocation algorithm, which supports differentiated QoS for orthogonal frequency division multiple access passive optical networks (OFDMA-PONs). We define a utility function as the metric to characterize the satisfaction degree of an ONU on the obtained bandwidth. The bandwidth allocation problem is then formulated as maximizing the sum of the weighted total utility functions of all ONUs. By constructing a flow network graph, we obtain the optimized bandwidth allocation using the MCMF algorithm. Simulation results show that the proposed scheme improves the performance in terms of mean packet delay, packet loss ratio and throughput.

  17. 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.

  18. 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

  19. Numerical models of broad-bandwidth nanosecond optical parametric oscillators

    International Nuclear Information System (INIS)

    We present three new methods for modeling broad-bandwidth, nanosecond optical parametric oscillators in the plane-wave approximation. Each accounts for the group-velocity differences that determine the operating linewidth of unseeded optical parametric oscillators, and each allows the signal and the idler waves to develop from quantum noise. The first two methods are based on split-step integration methods in which nonlinear mixing and propagation are calculated separately on alternate steps. One method relies on Fourier transforming the fields between t and ω to handle propagation, with mixing integrated over a Δz step; the other transforms between z and kz in the propagation step, with mixing integrated over Δt. The third method is based on expansion of the three optical fields in terms of their respective longitudinal empty cavity modes, taking into account the cavity boundary conditions. Equations describing the time development of the mode amplitudes are solved to yield the time dependence of the three output fields. These models exclude diffraction and group-velocity dispersion but can be readily extended to include them. copyright 1999 Optical Society of America

  20. Social value of high bandwidth networks: creative performance and education.

    Science.gov (United States)

    Mansell, Robin; Foresta, Don

    2016-03-01

    This paper considers limitations of existing network technologies for distributed theatrical performance in the creative arts and for symmetrical real-time interaction in online learning environments. It examines the experience of a multidisciplinary research consortium that aimed to introduce a solution to latency and other network problems experienced by users in these sectors. The solution builds on the Multicast protocol, Access Grid, an environment supported by very high bandwidth networks. The solution is intended to offer high-quality image and sound, interaction with other network platforms, maximum user control of multipoint transmissions, and open programming tools that are flexible and modifiable for specific uses. A case study is presented drawing upon an extended period of participant observation by the authors. This provides a basis for an examination of the challenges of promoting technological innovation in a multidisciplinary project. We highlight the kinds of technical advances and cultural and organizational changes that would be required to meet demanding quality standards, the way a research consortium planned to engage in experimentation and learning, and factors making it difficult to achieve an open platform that is responsive to the needs of users in the creative arts and education sectors. PMID:26809576

  1. Bandwidth Efficient Hybrid Synchronization for Wireless Sensor Network

    DEFF Research Database (Denmark)

    Dnyaneshwar, Mantri; Prasad, Neeli R.

    2015-01-01

    Data collection and transmission are the fundamental operations of Wireless Sensor Networks (WSNs). A key challenge in effective data collection and transmission is to schedule and synchronize the activities of the nodes with the global clock. This paper proposes the Bandwidth Efficient Hybrid Synchronization Data Aggregation Algorithm (BESDA) using spanning tree mechanism (SPT). It uses static sink and mobile nodes in the network. BESDA considers the synchronization of a local clock of node with global clock of the network. In the initial stage algorithm established the hierarchical structure in the network and then perform the pair-wise synchronization. With the mobility of node, the structure frequently changes causing an increase in energy consumption. To mitigate the problem BESDA aggregate data with the notion of a global timescale throughout the network and schedule based time-division multiple accesses (TDMA) techniques as MAC layer protocol. It reduces the collision of packets. Simulation results show that BESDA is energy efficient, with increased throughput, and has less delay as compared with state-of-the-art.

  2. Extraction of spatial information for low-bandwidth telerehabilitation applications

    Directory of Open Access Journals (Sweden)

    Kok Kiong Tan, PhD

    2014-09-01

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

  3. High Bandwidth Short Stroke Rotary Fast Tool Servo

    Energy Technology Data Exchange (ETDEWEB)

    Montesanti, R C; Trumper, D L

    2003-08-22

    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).

  4. Model Based Bandwidth Scavenging for Device Coexistence in Wireless LANs

    Science.gov (United States)

    Plummer, Anthony; Taghizadeh, Mahmoud; Biswas, Subir

    Dynamic Spectrum Access in a Wireless LAN can enable a set of secondary users' devices to access unused spectrum, or whitespace, which is found between the transmissions of a set of primary users' devices. The primary design objectives for an efficient secondary user access strategy are to be able to "scavenge" spatio-temporally fragmented bandwidth while limiting the amount of interference caused to the primary users. In this paper, we propose a secondary user access strategy which is based on measurement and modeling of the whitespace as perceived by the secondary users in a WLAN. A secondary user continually monitors and models its surrounding whitespace, and then attempts to access the available spectrum so that the effective secondary throughput is maximized while the resulting interference to the primary users is limited to a pre-defined bound. We first develop analytical expressions for the secondary throughput and primary interference, and then perform ns2 based simulation experiments to validate the effectiveness of the proposed access strategy, and evaluate its performance numerically using the developed expressions.

  5. 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

  6. QoS routing via multiple paths using bandwidth reservation

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-01-01

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

  7. Automatic Bandwidth Adjustment for Content Distribution in MPLS Networks

    Directory of Open Access Journals (Sweden)

    D. Moltchanov

    2008-04-01

    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.

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

    DEFF Research Database (Denmark)

    Jørgensen, Mette Marie; Petersen, Sidsel Rübner; Laurila, Marko; Lægsgaard, Jesper; Alkeskjold, Thomas T.

    2012-01-01

    . Large preform tolerances are compensated during the fiber draw resulting in ultra low NA fibers with very large cores. In this paper, design optimization of the SM bandwidth of the DMF rod fiber is presented. Analysis of band gap properties results in a fourfold increase of the SM bandwidth compared to...

  9. Bandwidth-length trade-off figures of merit for electro-optic traveling wave modulators

    OpenAIRE

    Ibarra Fusté, Jose Antonio; Santos Blanco, M. Concepción

    2013-01-01

    Closed-form expressions explicitly relating modulation bandwidth and active length in electro-optic traveling wave modulators are presented which fully account for skin-effect electrode loss and optical-electrical wave velocities mismatch. Four operative margins have been identified where the bandwidth–length trade-off figure of merit takes simple forms.

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

    Science.gov (United States)

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

    2013-12-01

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

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

    Science.gov (United States)

    Cevik, Taner

    2013-01-01

    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

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

    International Nuclear Information System (INIS)

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

  13. Energy and Bandwidth Constrained QoS Enabled Routing for MANETs

    Directory of Open Access Journals (Sweden)

    N.Sumathi

    2013-04-01

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

  14. Effects of large laser bandwidth on stimulated Raman scattering instability in underdense plasma

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yao; Yu, Lu-Le; Zheng, Jun; Weng, Su-Ming [Key Laboratory for Laser Plasmas (MoE) and Department of Physics and Astronomy, IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Ren, Chuang [Department of Mechanical Engineering and Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14627 (United States); Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Liu, Chuan-Sheng [East-West Space Science Center, University of Maryland, College Park, Maryland 20742, USA and Chao Kuang Piu College, University of Macau, Macau 999078 (China); Sheng, Zheng-Ming, E-mail: zmsheng@sjtu.edu.cn, E-mail: zhengming.sheng@strath.ac.uk [Key Laboratory for Laser Plasmas (MoE) and Department of Physics and Astronomy, IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2015-05-15

    The effects of laser bandwidth on stimulated Raman scattering (SRS) instability in underdense plasma are studied by particle-in-cell simulations. In the simulations, sinusoidal frequency modulation of the incident laser pulse is used. By changing the size of bandwidth, it is shown that the linear growth of SRS can be suppressed considerably, provided the laser bandwidth is much larger than the SRS linear growth rate. Simulations also show that by choosing the proper frequency modulation parameters or decreasing the linear growth rate of SRS, the inhibitory effects become more obvious. The plasma electron temperature tends to weaken the bandwidth effects especially when it is over a keV level. The laser bandwidth can only increase the time duration for linear growth but cannot diminish the instability completely.

  15. Effects of large laser bandwidth on stimulated Raman scattering instability in underdense plasma

    International Nuclear Information System (INIS)

    The effects of laser bandwidth on stimulated Raman scattering (SRS) instability in underdense plasma are studied by particle-in-cell simulations. In the simulations, sinusoidal frequency modulation of the incident laser pulse is used. By changing the size of bandwidth, it is shown that the linear growth of SRS can be suppressed considerably, provided the laser bandwidth is much larger than the SRS linear growth rate. Simulations also show that by choosing the proper frequency modulation parameters or decreasing the linear growth rate of SRS, the inhibitory effects become more obvious. The plasma electron temperature tends to weaken the bandwidth effects especially when it is over a keV level. The laser bandwidth can only increase the time duration for linear growth but cannot diminish the instability completely

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

    Directory of Open Access Journals (Sweden)

    A.ManikantaSitaram

    2012-11-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Karim A. Hamad

    2012-03-01

    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.

  18. Broad-Bandwidth FPGA-Based Digital Polyphase Spectrometer

    Science.gov (United States)

    Jamot, Robert F.; Monroe, Ryan M.

    2012-01-01

    With present concern for ecological sustainability ever increasing, it is desirable to model the composition of Earth s upper atmosphere accurately with regards to certain helpful and harmful chemicals, such as greenhouse gases and ozone. The microwave limb sounder (MLS) is an instrument designed to map the global day-to-day concentrations of key atmospheric constituents continuously. One important component in MLS is the spectrometer, which processes the raw data provided by the receivers into frequency-domain information that cannot only be transmitted more efficiently, but also processed directly once received. The present-generation spectrometer is fully analog. The goal is to include a fully digital spectrometer in the next-generation sensor. In a digital spectrometer, incoming analog data must be converted into a digital format, processed through a Fourier transform, and finally accumulated to reduce the impact of input noise. While the final design will be placed on an application specific integrated circuit (ASIC), the building of these chips is prohibitively expensive. To that end, this design was constructed on a field-programmable gate array (FPGA). A family of state-of-the-art digital Fourier transform spectrometers has been developed, with a combination of high bandwidth and fine resolution. Analog signals consisting of radiation emitted by constituents in planetary atmospheres or galactic sources are downconverted and subsequently digitized by a pair of interleaved analog-to-digital converters (ADCs). This 6-Gsps (gigasample per second) digital representation of the analog signal is then processed through an FPGA-based streaming fast Fourier transform (FFT). Digital spectrometers have many advantages over previously used analog spectrometers, especially in terms of accuracy and resolution, both of which are particularly important for the type of scientific questions to be addressed with next-generation radiometers.

  19. High-Density, High-Bandwidth, Multilevel Holographic Memory

    Science.gov (United States)

    Chao, Tien-Hsin

    2008-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Biruk Gebre

    2008-06-01

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

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

    Directory of Open Access Journals (Sweden)

    Kishore Angrishi

    2009-11-01

    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.

  2. Error-resilient video communications over CDMA networks with a bandwidth constraint.

    Science.gov (United States)

    Shen, Yushi; Cosman, Pamela C; Milstein, Laurence B

    2006-11-01

    We present an adaptive video transmission scheme for use in a code-division multiple-access network, which incorporates efficient bandwidth allocation among source coding, channel coding, and spreading under a fixed total bandwidth constraint. We derive the statistics of the received signal, as well as a theoretical bound on the packet drop rate at the receiver. Based on these results, a bandwidth allocation algorithm is proposed at the packet level, which incorporates the effects of both the changing channel conditions and the dynamics of the source content. Detailed simulations are done to evaluate the performance of the system, and the sensitivity of the system to estimation error is presented. PMID:17076387

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

    Science.gov (United States)

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

    2007-05-15

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

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

    KAUST Repository

    Majid, M. A.

    2012-12-01

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

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

    CERN Document Server

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

    2013-01-01

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

  6. Effect of bandwidth extension to telephone speech recognition in cochlear implant users

    Science.gov (United States)

    Liu, Chuping; Fu, Qian-Jie; Narayanan, Shrikanth S.

    2009-01-01

    The present study investigated a bandwidth extension method to enhance telephone speech understanding for cochlear implant (CI) users. The acoustic information above telephone speech transmission range (i.e., 3400 Hz) was estimated based on trained models describing the relation between narrow-band and wide-band speech. The effect of the bandwidth extension method was evaluated with IEEE sentence recognition tests in seven CI users. Results showed a relatively modest but significant improvement in the speech recognition with the proposed method. The effect of bandwidth extension method was also observed to be highly dependent on individual CI users. PMID:19206836

  7. High bandwidth based on a tapped delay line equalization in visible light communications

    Science.gov (United States)

    Zhang, Minglun; Guo, Xujing; Zhu, Hetian; Wang, Chao; Bai, Xiaonan; Zhai, Xiangwen

    2015-08-01

    In the visible light communication, the white LED bandwidth severely limits the transmission rate of information. This paper presents an analog pre-equalization technology to compensate for the bandwidth of white LED. The technology not only can debug according to the actual channel changing, but also avoid the high costs of using FPGA technology. The pre-equalization technology is implemented by an analog circuit of tapped-delay-line, in the circuit we select an appropriate delay line and a digital to analog converter. In our LED visible light communication system, we can achieve a bandwidth of 150MHz which was proved theoretically in the paper.

  8. Non-Real-Time Network Traffic in Software-Defined Networking: A Link Bandwidth Prediction-Based Algorithm

    OpenAIRE

    Longfei Dai; Wenguo Yang; Suixiang Gao; Yinben Xia; Mingming Zhu; Zhigang Ji

    2014-01-01

    Network traffic control is the process of managing, prioritizing, controlling or reducing the network traffic by the network scheduler. High utilization of link bandwidth is very significant for network control and maintenance in Software-Defined Networking (SDN). When we get the accurate link bandwidth predictions for T time periods of the future in a specific network topology, the residual link bandwidth could be determined by the link bandwidth capacity and corresponding prediction values....

  9. 77 FR 38210 - Channel Spacing and Bandwidth Limitations for Certain Economic Area (EA)-Based 800 MHz...

    Science.gov (United States)

    2012-06-27

    ... COMMISSION 47 CFR Part 90 Channel Spacing and Bandwidth Limitations for Certain Economic Area (EA)-Based 800... Specialized Mobile Radio (SMR) licensees to exceed a legacy channel spacing requirement and bandwidth... not impacted by EA-based 800 MHz SMR licensees exceeding the channel spacing and bandwidth...

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

    Directory of Open Access Journals (Sweden)

    T.F. Ang

    2009-01-01

    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.

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

    Science.gov (United States)

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

    2011-12-01

    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.

  12. TORQUE RIPPLES MINIMIZATION ON DTC CONTROLLED INDUCTION MOTOR WITH ADAPTIVE BANDWIDTH APPROACH

    Directory of Open Access Journals (Sweden)

    Fatih Korkmaz

    2015-04-01

    Full Text Available Field oriented control (FOC and direct torque control (DTC, also called vector control, are most famous control methods in high-performance motor applications. If we want to specify the basic handicaps of both methods: the FOC has parameter dependence while the DTC has high torque ripples. This paper proposes a new adaptive bandwidth approach to reduce torque ripples in DTC controlled induction motor drives. With the proposed method, instead of fixed bandwidth, adaptive bandwidth approach is investigated in hysteresis controllers on the DTC method. Both the conventional DTC(C-DTC method and adaptive bandwidth DTC (AB-DTC for induction motor are simulated in MATLAB/SIMULINK and the results are presented and discussed to verify the proposed control. The comparisons have shown that, torque ripples have been reduced remarkably with the proposed AB-DTC method.

  13. New scintillators for fiber optics: system sensitivity and bandwidth as a function of fiber length

    International Nuclear Information System (INIS)

    Long-wavelength liquid scintillators have been developed for fiber-optic plasma-diagnostic experiments. Relative system sensitivity and bandwidth data as a function of fiber length for several scintillator systems will be presented

  14. Multi-Hop Bandwidth Management Protocol for Mobile Ad Hoc Networks

    CERN Document Server

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

    2010-01-01

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

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

    International Nuclear Information System (INIS)

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

  16. A Novel Dynamic Bandwidth Allocation Algorithm with Correction-based the Multiple Traffic Prediction in EPON

    Directory of Open Access Journals (Sweden)

    Ziyi Fu

    2012-10-01

    Full Text Available According to the upstream TDM in the system of Ethernet passive optical network (EPON, this paper proposes a novel dynamic bandwidth allocation algorithm which supports the mechanism with correction-based the multiple services estimation. To improve the real-time performance of the bandwidth allocation, this algorithm forecasts the traffic of high priority services, and then pre-allocate bandwidth for various priority services is corrected according to Gaussian distribution characteristics, which will make traffic prediction closer to the real traffic. The simulation results show that proposed algorithm is better than the existing DBA algorithm. Not only can it meet the delay requirement of high priority services, but also control the delay abnormity of low priority services. In addition, with rectification scheme, it obviously improves the bandwidth utilization.

  17. A 750MHz and a 8GHz High Bandwidth Digital FFT Spectrometer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The scope of this project is to to develop a wide bandwidth, low power, and compact single board digital Fast Fourier Transform spectrometer (FFTS) optimized for...

  18. Bandwidth Controllable Tunable Filter for Hyper-/Multi-Spectral Imager Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I proposal introduces a fast speed bandwidth controllable tunable filter for hyper-/multi-spectral (HS/MS) imagers. It dynamically passes a variable...

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

    Science.gov (United States)

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

    2014-03-01

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

  20. Towards Bandwidth Scalable Transceiver Technology for Optical Metro-Access Networks

    DEFF Research Database (Denmark)

    Spolitis, Sandis; Bobrovs, Vjaceslavs

    2015-01-01

    Massive fiber-to-the-home network deployment is creating a challenge for telecommunications network operators: exponential increase of the power consumption at the central offices and a never ending quest for equipment upgrades operating at higher bandwidth. In this paper, we report on flexible signal slicing technique, which allows transmission of high-bandwidth signals via low bandwidth electrical and optoelectrical equipment. The presented signal slicing technique is highly scalable in terms of bandwidth which is determined by the number of slices used. In this paper performance of scalable sliceable transceiver for 1 Gbit/s non-return to zero (NRZ) signal sliced into two slices is presented. Digital signal processing (DSP) power consumption and latency values for proposed sliceable transceiver technique are also discussed. In this research post FEC with 7% overhead error free transmission has been demonstrated over different fiber types and lengths up to 25 km.

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

    DEFF Research Database (Denmark)

    Deng, Lei; Zhao, Ying

    2011-01-01

    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.

  2. Development of narrow bandwidth SLM dye laser for clean-up

    International Nuclear Information System (INIS)

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

  3. Ultra-low Noise, High Bandwidth, 1550nm HgCdTe APD Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To meet the demands of future high-capacity free space optical communications links, a high bandwidth, near infrared (NIR), single photon sensitive optoelectronic...

  4. Effects of dislocations on small signal high frequency hot electron mobility in n-GaN at low and high temperatures under high magnetic fields including hot phonon effect

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, A., E-mail: juimaha@yahoo.co [Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata (India); Sarkar, C.K. [Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata (India)

    2011-04-01

    The small signal high-frequency ac mobility of hot electrons in n-GaN in the extreme quantum limit at low- and high-temperatures has been calculated considering the non-equilibrium phonon distribution as well as the thermal phonon distributions. The energy loss rate has been calculated considering the dominance of the piezo electric coupling scattering and the polar optical phonon scattering while the momentum loss rate has been calculated considering the acoustic phonon scattering via deformation potential and the piezo electric coupling and the dislocation scattering.

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

    OpenAIRE

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

    2006-01-01

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

  6. A novel dynamic bandwidth selection method for thinning noisy point clouds

    OpenAIRE

    Öztürk, Mehmet; HASIRCI, Zeynep

    2012-01-01

    In this paper, we propose a dynamic bandwidth selection method for thinning noisy point clouds into curves. Due to the nonhomogeneous distribution of noise or varying curvature of the data, the thinning procedure requires a dynamically adjusted bandwidth along the curve. On the other hand, the selected local region must be sorted along a suitable direction vector for local curve fitting purposes. The contribution of this paper to the field is 2-folded: first, a normalized eigenvalue ana...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-14

    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.

  8. 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.

  9. Combined Subcarrier Switch Off and Power Loading for 80 MHz Bandwidth WLANs

    OpenAIRE

    Punyal, Oscar; Gross, James

    2011-01-01

    Next generation wireless local area networks, like the upcoming IEEE 802.11ac, strive for large frequency band-widths to cope with the rising traffic demands. Bandwidths of 80 MHz or even 160 MHz are being considered, where a significant frequency diversity among OFDM subcarriers is likely to exist. With a potentially large number of highly attenuated subcarriers it is not clear if the system should better avoid their usage for payload transmission. Such an approach can improve the error perf...

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

    OpenAIRE

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

    2011-01-01

    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...

  11. A Survey of Dynamic-centric Bandwidth Allocation Technique for Wireless Networks

    OpenAIRE

    Bakkiam David Deebak; Rajappa Muthaiah; Thenmozhi, K.; Pitchai Iyer Swaminathan

    2014-01-01

    Objective of the study is to study and analyze the dynamic-centric metrics of bandwidth allocation and estimation for wireless networks. We also extend the objective to probe Quality of Service (QoS) provisioning guarantee for infeasible packet routing networking protocols. This study signifies the bandwidth sharing scheme for real time and non-real time based. So far, the researchers have not examined this signification to have a good impact on throughput ...

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

    Science.gov (United States)

    Lipton, Robert; Polizzi, Anthony

    2014-10-01

    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.

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

    CERN Document Server

    Lipton, Robert

    2014-01-01

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

  14. Effect of bandwidth extension to telephone speech recognition in cochlear implant users

    OpenAIRE

    Liu, Chuping; Fu, Qian-Jie; Narayanan, Shrikanth S.

    2009-01-01

    The present study investigated a bandwidth extension method to enhance telephone speech understanding for cochlear implant (CI) users. The acoustic information above telephone speech transmission range (i.e., 3400 Hz) was estimated based on trained models describing the relation between narrow-band and wide-band speech. The effect of the bandwidth extension method was evaluated with IEEE sentence recognition tests in seven CI users. Results showed a relatively modest but significant improveme...

  15. From advertising profits to bandwidth prices-A quantitative methodology for negotiating premium peering

    OpenAIRE

    Gyarmati, Laszlo; Laoutaris, Nikolaos; Sdrolias, Kostas; Rodriguez, Pablo; Courcoubetis, Costas

    2014-01-01

    We have developed a first of its kind methodology for deriving bandwidth prices for premium direct peering between Access ISPs (A-ISPs) and Content and Service Providers (CSPs) that want to deliver content and services in premium quality. Our methodology establishes a direct link between service profitability, e.g., from advertising, user- and subscriber-loyalty, interconnection costs, and finally bandwidth price for peering. Unlike existing work in both the networking and e...

  16. Correlations between pressure and bandwidth effects in metal-insulator transitions in manganites

    OpenAIRE

    Cui, Congwu; Trevor A. Tyson

    2003-01-01

    The effect of pressure on the metal-insulator transition in manganites with a broad range of bandwidths is investigated. A critical pressure is found at which the metal-insulator transition temperature, T$_{MI}$, reaches a maximum value in every sample studied. The origin of this universal pressure and the relation between the pressure effect and the bandwidth on the metal-insulator transition are discussed.

  17. Investigation of bandwidth utilisation methods to optimise performance in passive bistatic radar

    OpenAIRE

    Olsen, K. E.

    2011-01-01

    This thesis reports on research into the field of multiband Passive Bistatic Radar (PBR). The work is based on the premise that it is possible to improve on the PBR range resolution by exploiting the full broadcasted bandwidth from transmitters of opportunity. This work comprises both Frequency Modulated (FM) radio and Digital Video Broadcast - Terrestrial (DVB-T) waveforms. The work shows how the exploitation of the available frequency scattered bandwidth broadcasted from sing...

  18. Coarse-Grain Bandwidth Estimation Techniques for Large-Scale Space Network

    Science.gov (United States)

    Cheung, Kar-Ming; Jennings, Esther

    2013-01-01

    In this paper, we describe a top-down analysis and simulation approach to size the bandwidths of a store-andforward network for a given network topology, a mission traffic scenario, and a set of data types with different latency requirements. We use these techniques to estimate the wide area network (WAN) bandwidths of the ground links for different architecture options of the proposed Integrated Space Communication and Navigation (SCaN) Network.

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

    OpenAIRE

    N.SUMATHI,; DR. ANTONY SELVADOSS THANAMANI

    2010-01-01

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

  20. BHCDA: Bandwidth Efficient Heterogeneity aware Cluster based Data Aggregation for Wireless Sensor Network

    DEFF Research Database (Denmark)

    Dnyaneshwar, Mantri; Prasad, Neeli R.; Prasad, Ramjee

    2013-01-01

    The fundamental challenge in the design of Wireless sensor Network (WSNs) is proper utilization of resources which are scare. One of the critical challenges is to maximize the bandwidth utilization in data gathering from sensor nodes and forward to sink. The main design objective of this paper is to utilize the available bandwidth efficiently with reduced packet delivery ratio and throughput. BHCDA presents the solution for effective data gathering with in-network aggregation. It considers the n...

  1. High-bandwidth laser frequency stabilization to a fiber-optic delay line.

    Science.gov (United States)

    Sheard, Benjamin S; Gray, Malcolm B; McClelland, David E

    2006-11-20

    Stabilization of laser frequency to interferometers with a large time delay in one arm is of significant interest to space-based gravitational wave detectors such as the Laser Interferometer Space Antenna. A recently proposed technique allows a control bandwidth larger than the inverse delay time to be achieved. We present experimental results demonstrating laser frequency stabilization to an optical fiber delay line. A control bandwidth approximately 50 times the inverse delay time is demonstrated. PMID:17086260

  2. Optimum ArFi laser bandwidth for 10nm node logic imaging performance

    Science.gov (United States)

    Alagna, Paolo; Zurita, Omar; Timoshkov, Vadim; Wong, Patrick; Rechtsteiner, Gregory; Baselmans, Jan; Mailfert, Julien

    2015-03-01

    Lithography process window (PW) and CD uniformity (CDU) requirements are being challenged with scaling across all device types. Aggressive PW and yield specifications put tight requirements on scanner performance, especially on focus budgets resulting in complicated systems for focus control. In this study, an imec N10 Logic-type test vehicle was used to investigate the E95 bandwidth impact on six different Metal 1 Logic features. The imaging metrics that track the impact of light source E95 bandwidth on performance of hot spots are: process window (PW), line width roughness (LWR), and local critical dimension uniformity (LCDU). In the first section of this study, the impact of increasing E95 bandwidth was investigated to observe the lithographic process control response of the specified logic features. In the second section, a preliminary assessment of the impact of lower E95 bandwidth was performed. The impact of lower E95 bandwidth on local intensity variability was monitored through the CDU of line end features and the LWR power spectral density (PSD) of line/space patterns. The investigation found that the imec N10 test vehicle (with OPC optimized for standard E95 bandwidth of300fm) features exposed at 200fm showed pattern specific responses, suggesting areas of potential interest for further investigation.

  3. Accounting for filter bandwidth improves the quantitative accuracy of bioluminescence tomography

    Science.gov (United States)

    Taylor, Shelley L.; Mason, Suzannah K. G.; Glinton, Sophie L.; Cobbold, Mark; Dehghani, Hamid

    2015-09-01

    Bioluminescence imaging is a noninvasive technique whereby surface weighted images of luminescent probes within animals are used to characterize cell count and function. Traditionally, data are collected over the entire emission spectrum of the source using no filters and are used to evaluate cell count/function over the entire spectrum. Alternatively, multispectral data over several wavelengths can be incorporated to perform tomographic reconstruction of source location and intensity. However, bandpass filters used for multispectral data acquisition have a specific bandwidth, which is ignored in the reconstruction. In this work, ignoring the bandwidth is shown to introduce a dependence of the recovered source intensity on the bandwidth of the filters. A method of accounting for the bandwidth of filters used during multispectral data acquisition is presented and its efficacy in increasing the quantitative accuracy of bioluminescence tomography is demonstrated through simulation and experiment. It is demonstrated that while using filters with a large bandwidth can dramatically decrease the data acquisition time, if not accounted for, errors of up to 200% in quantitative accuracy are introduced in two-dimensional planar imaging, even after normalization. For tomographic imaging, the use of this method to account for filter bandwidth dramatically improves the quantitative accuracy.

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

    Directory of Open Access Journals (Sweden)

    Yunfang Ni

    2014-07-01

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

  5. Hybrid Channel Allocation with Priority on Bandwidth Sharing in Wireless Mobile Networks

    Directory of Open Access Journals (Sweden)

    K.Venkatachalam

    2010-10-01

    Full Text Available The main objective of future wireless mobile multimedia networks is to provide services efficiently to the mobile users in all environments. In wireless mobile Communication the channel allocation and bandwidth sharing are the major factors and quality of service is the important issue to decide the system performance. In this work a Hybrid Channel Allocation(HCAstrategy for channel allocation and a novel bandwidth sharing technique applied to Hybrid Channel Allocation strategy for Quality of Service(QoS provisioning are implemented. The proposed HCA strategy considers new calls in Fixed Channel Allocation (FCA method and handoff calls in Dynamic Channel Allocation (DCA method. In the bandwidth sharing of mobile multimedia calls, a multimedia call is considered as a combination of three classes namely voice of CBR, Voice with low rate video of CBR and Voice with high rate video of VBR. Priority of the above classes and a new bandwidth sharing method is implemented. When the required bandwidth is not available for a handoff (HO call, it rejects a low Priority class and postpones bandwidth sharing to the class, that may cause delay, but it is not a major problem for the Quality of Service (QoS. Our method decreases the handoff call dropping probability (CDP when compared with Without Control method (WCM. It also improves the communication quality of handoff calls in mobile multimedia networks.

  6. Wide bandwidth chaotic signal generation in a monolithically integrated semiconductor laser via optical injection

    Science.gov (United States)

    Yin, Xue-Mei; Zhong, Zhu-Qiang; Zhao, Ling-Juan; Lu, Dan; Qiu, Hai-Ying; Xia, Guang-Qiong; Wu, Zheng-Mao

    2015-11-01

    Wide bandwidth chaotic signal generation in a three-section monolithically integrated semiconductor laser (MISL) under external optical injection is investigated experimentally. Through evaluating the effective bandwidth of chaotic signals, the influences of the optical injection on the bandwidth of chaotic signal from the MISL are analyzed. The experimental results indicate that, for the currents of the DFB section (IDFB) and the phase section (IP) are fixed at 70.00 mA and 34.00 mA, respectively, the effective bandwidth of chaos signal generated by the solitary MISL reaches its maximum value of 14.36 GHz when the current of the amplification section (IA) takes 23.22 mA. After an external optical injection is introduced into the MISL, the effective bandwidth of the generated chaotic signal can be beyond 2.5 times of the maximum value. Furthermore, the effects of the injection strength and the frequency detuning on the effective bandwidth of the generated chaotic signal are also discussed.

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

    Science.gov (United States)

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

    2009-11-01

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

  8. Thermal characterization of DC and small-signal parameters of 150 nm and 250 nm gate-length AlGaN/GaN HEMTs grown on a SiC substrate

    Science.gov (United States)

    Alim, Mohammad A.; Rezazadeh, Ali A.; Gaquiere, Christophe

    2015-12-01

    This paper investigated the temperature effects on the performance of the AlGaN/GaN high electron mobility transistor (HEMT) with a 150 nm and 250 nm gate length on a SiC substrate over a temperature range of ?40 to 150 °C including experimental characterization, modelling and analysis by on-wafer measurements up to 50 GHz. All the DC and small signal parameter variations with ambient temperature on the same set of devices have been reported for the first time. The temperature coefficient of all the DC and small signal parameters as well as f t and f max were reported. Some of the extracted equivalent circuit parameters with the theoretical data of the evolution of electrical parameters and the relevant physical equations involved have been compared using the same biasing condition for further accuracy. The theoretical results are shown to be consistent with the extracted data. Some results are also experimentally verified with previous works cited in the paper. The results provide some valuable insights for the underlying physics of the device parameters affected by temperature.

  9. Bandwidth limitation in QPSK optical coherent receiver with DAML carrier phase estimation

    Science.gov (United States)

    Chen, Jian; Feng, Tianping; Fan, Yuanwei; Ma, Zhaohui; You, Xiaodi

    2015-08-01

    We study the limitation of electrical bandwidth in QPSK optical coherent receiver with decision-aided maximum likelihood (DAML) carrier phase estimation. Before signal sampling, a low-pass rectangular filter is utilized to model the bandwidth limitation of electronic devices in the receiver. On one hand the limited bandwidth can reduce the power of additive noise, on the other hand it would distort the signal since inter-symbol interference (ISI) between adjacent symbols occurs. In this paper we discuss the effects on signal amplitude and phase caused by ISI and find original distribution of QPSK constellation points will shift due to ISI. When adjacent symbol interference, that is, the ISI effect of one previous symbol, is taken into account, the distribution changes into the form of 16-QAM, while changing as 4K+1-QAM if K previous symbols are considered. The impact on the subsequent DAML algorithm and the final bit error rate (BER) calculation due to constellation points shifts are analyzed intensively. Monte-Carlo (MC) simulation results show that 0.7 to 0.9 times symbol rate is a reasonable bandwidth range for different optical signal to noise ratios (OSNRs), and optimum bandwidth is often inside this range. Results also reveal that filter-induced ISI would degrade the BER performance of DAML receiver when OSNR is over 10 dB.

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

    Directory of Open Access Journals (Sweden)

    V. Niranjan

    2014-09-01

    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.

  11. Studies of bandwidth dependence of laser plasma instabilities driven by the Nike laser

    Science.gov (United States)

    Weaver, J.; Kehne, D.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Oh, J.; Lehmberg, R. H.; Brown, C. M.; Seely, J.; Feldman, U.

    2012-10-01

    Experiments at the Nike laser facility of the Naval Research Laboratory are exploring the influence of laser bandwidth on laser plasma instabilities (LPI) driven by a deep ultraviolet pump (248 nm) that incorporates beam smoothing by induced spatial incoherence (ISI). In early ISI studies with longer wavelength Nd:glass lasers (1054 nm and 527 nm),footnotetextObenschain, PRL 62(1989);Mostovych, PRL 62(1987);Peyser, Phys. Fluids B 3(1991). stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (??/?˜0.03-0.19%) pulses irradiated targets at moderate to high intensities (10^14-10^15 W/cm^2). The current studies will compare the emission signatures of LPI from planar CH targets during Nike operation at large bandwidth (??˜1THz) to observations for narrower bandwidth operation (??˜0.1-0.3THz). These studies will help clarify the relative importance of the short wavelength and wide bandwidth to the increased LPI intensity thresholds observed at Nike. New pulse shapes are being used to generate plasmas with larger electron density scale-lengths that are closer to conditions during pellet implosions for direct drive inertial confinement fusion.

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

    Directory of Open Access Journals (Sweden)

    Mu Zhang

    2014-03-01

    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

  13. Enhanced Shared-TDD Based Hybrid WDM/TDM-PON with Dynamic Bandwidth Allocation Scheme

    Science.gov (United States)

    Jung, Bokrae; Kim, Min-Gon; Kim, Byong-Whi; Kang, Minho

    Although wavelength division multiplexing-passive optical network (WDM-PON) is known as a high-speed transfer, it creates high channel costs per subscriber and low bandwidth utilization due to the fact that a wavelength is dedicated to each subscriber. Thus, it is imperative to reduce channel costs per subscriber and improve the bandwidth utilization. To achieve these, we first adopt a existing WDM-PON, which uses the bidirectional transmission with a single source for cost-efficiency by employing a gain-saturated reflective semiconductor optical amplifier (RSOA). Secondly, based on the existing WDM-PON, we propose an enhanced hybrid WDM/TDM-PON, which can extend the number of subscribers supported in each wavelength with splitters in the physical layer and a shared-time division duplex (TDD) frame format in the media access control (MAC) layer. Moreover, it can adaptively control the bandwidth through a dynamic bandwidth allocation (DBA) scheme according to the volume of traffic. Compared to the non TDD-based hybrid WDM/TDM-PON, it can reduce channel costs per subscriber from the extended number of subscribers supported in each wavelength. Furthermore, due to the DBA, it can improve the total queueing delay and throughput, and thus increase the bandwidth utilization.

  14. Impact of bandwidth on contrast sensitive structures for low k1 lithography

    Science.gov (United States)

    Conley, Will; Hsieh, Simon; Alagna, Paolo; Hou, Yaching; Martinez, Pedro

    2015-03-01

    Double-patterning ArF immersion lithography continues to advance the patterning resolution and overlay requirements and has enabled the continuation of semiconductor bit-scaling. Over the years Lithography Engineers continue to focus on CD control, overlay and process capability to meet current node requirements for yield and device performance. Reducing or eliminating variability in any process will have significant impact, but the sources of variability in any lithography process are many. The goal from the light source manufacturer is to further enable capability and reduce variation through a number of parameters. Recent improvements in bandwidth control have been realized in the XLR platform with Cymer's DynaPulseTM control technology. This reduction in bandwidth variation could translate in the further reduction of CD variation in device structures. The Authors will discuss the impact that these improvements in bandwidth control have on advanced lithography applications. This can translate to improved CD control and higher wafer yields. A simulation study investigates the impact of bandwidth on contrast sensitive device layers such as contacts and 1x metal layers. Furthermore, the Authors will discuss the impact on process window through pitch and the overlapping process window through pitch that has been investigated. These improvements will be further quantified by the analysis of statistical bandwidth variation and the impact on CD.

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

    CERN Document Server

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

    2010-01-01

    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...

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

    DEFF Research Database (Denmark)

    Dnyaneshwar, Mantri; Prasad, Neeli R.

    2014-01-01

    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.

  17. High bandwidth, high responsivity waveguide-coupled germanium p-i-n photodiode.

    Science.gov (United States)

    Lischke, Stefan; Knoll, Dieter; Mai, Christian; Zimmermann, Lars; Peczek, Anna; Kroh, Marcel; Trusch, Andreas; Krune, Edgar; Voigt, Karsten; Mai, A

    2015-10-19

    A novel waveguide-coupled germanium p-i-n photodiode is demonstrated which combines high responsivity with very high -3 dB bandwidth at a medium dark current. Bandwidth values are 40 GHz at zero bias and more than 70 GHz at -1 V. Responsivity at 1.55 µm wavelength ranges from 0.84 A/W at zero bias to 1 A/W at -1 V. Room temperature dark current density at -1 V is about 1 A/cm2. The high responsivity mainly results from the use of a new, low-loss contact scheme, which moreover also reduces the negative effect of photo carrier diffusion on bandwidth. PMID:26480381

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

    Directory of Open Access Journals (Sweden)

    Krishn Kant Joshi

    2014-05-01

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

  19. Broadband parametric amplification with impedance engineering: Beyond the gain-bandwidth product

    Science.gov (United States)

    Roy, Tanay; Kundu, Suman; Chand, Madhavi; Vadiraj, A. M.; Ranadive, A.; Nehra, N.; Patankar, Meghan P.; Aumentado, J.; Clerk, A. A.; Vijay, R.

    2015-12-01

    We present an impedance engineered Josephson parametric amplifier capable of providing bandwidth beyond the traditional gain-bandwidth product. We achieve this by introducing a positive linear slope in the imaginary component of the input impedance seen by the Josephson oscillator using a ? / 2 transformer. Our theoretical model predicts an extremely flat gain profile with a bandwidth enhancement proportional to the square root of amplitude gain. We experimentally demonstrate a nearly flat 20 dB gain over a 640 MHz band, along with a mean 1-dB compression point of -110 dBm and near quantum-limited noise. The results are in a good agreement with our theoretical model.

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

    Science.gov (United States)

    Kim, Sungwook

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

  1. Narrowing the filter-cavity bandwidth in gravitational-wave detectors via optomechanical interaction.

    Science.gov (United States)

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

    2014-10-10

    We propose using optomechanical interaction to narrow the bandwidth of filter cavities for achieving frequency-dependent squeezing in advanced gravitational-wave detectors, inspired by the idea of optomechanically induced transparency. This can allow us to achieve a cavity bandwidth on the order of 100 Hz using small-scale cavities. Additionally, in contrast to a passive Fabry-Pérot cavity, the resulting cavity bandwidth can be dynamically tuned, which is useful for adaptively optimizing the detector sensitivity when switching amongst different operational modes. The experimental challenge for its implementation is a stringent requirement for very low thermal noise of the mechanical oscillator, which would need a superb mechanical quality factor and a very low temperature. We consider one possible setup to relieve this requirement by using optical dilution to enhance the mechanical quality factor. PMID:25375698

  2. Analysis of blocking rate and bandwidth usage of mobile IPTV services in wireless cellular networks.

    Science.gov (United States)

    Li, Mingfu

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Gurpreet Singh Bagga

    2014-04-01

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

  4. Local intelligent electronic device (IED) rendering templates over limited bandwidth communication link to manage remote IED

    Science.gov (United States)

    Bradetich, Ryan; Dearien, Jason A; Grussling, Barry Jakob; Remaley, Gavin

    2013-11-05

    The present disclosure provides systems and methods for remote device management. According to various embodiments, a local intelligent electronic device (IED) may be in communication with a remote IED via a limited bandwidth communication link, such as a serial link. The limited bandwidth communication link may not support traditional remote management interfaces. According to one embodiment, a local IED may present an operator with a management interface for a remote IED by rendering locally stored templates. The local IED may render the locally stored templates using sparse data obtained from the remote IED. According to various embodiments, the management interface may be a web client interface and/or an HTML interface. The bandwidth required to present a remote management interface may be significantly reduced by rendering locally stored templates rather than requesting an entire management interface from the remote IED. According to various embodiments, an IED may comprise an encryption transceiver.

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

    DEFF Research Database (Denmark)

    Buchholz, Jörg; Caminade, Sabine; Strelcyk, Olaf; Dau, Torsten

    2010-01-01

    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...

  6. Power-Bandwidth Tradeoff in Dense Multi-Antenna Relay Networks

    CERN Document Server

    Oyman, Ozgur

    2007-01-01

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

  7. Design and Bandwidth Analysis of Fault-Tolerant Multistage Interconnection Networks

    Directory of Open Access Journals (Sweden)

    R. Aggarwal

    2008-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-06-01

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

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

    Directory of Open Access Journals (Sweden)

    Kenneth Kerpez

    2008-10-01

    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.

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

    DEFF Research Database (Denmark)

    Saraswat, Prabhat Kumar; Pop, Paul; Madsen, Jan

    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 re...... 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....... 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...

  11. Investigating the influence of chromatic aberration and optical illumination bandwidth on fundus imaging in rats

    Science.gov (United States)

    Li, Hao; Liu, Wenzhong; Zhang, Hao F.

    2015-10-01

    Rodent models are indispensable in studying various retinal diseases. Noninvasive, high-resolution retinal imaging of rodent models is highly desired for longitudinally investigating the pathogenesis and therapeutic strategies. However, due to severe aberrations, the retinal image quality in rodents can be much worse than that in humans. We numerically and experimentally investigated the influence of chromatic aberration and optical illumination bandwidth on retinal imaging. We confirmed that the rat retinal image quality decreased with increasing illumination bandwidth. We achieved the retinal image resolution of 10 μm using a 19 nm illumination bandwidth centered at 580 nm in a home-built fundus camera. Furthermore, we observed higher chromatic aberration in albino rat eyes than in pigmented rat eyes. This study provides a design guide for high-resolution fundus camera for rodents. Our method is also beneficial to dispersion compensation in multiwavelength retinal imaging applications.

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

    Directory of Open Access Journals (Sweden)

    M. Sajid

    2014-01-01

    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.

  13. The biophysical basis of the high-bandwidth information encoding in cortical neurons

    Directory of Open Access Journals (Sweden)

    Andreas Neef

    2015-07-01

    Full Text Available A cortical neuron receives continuously fluctuating input through thousands of synapses. It encodes and relays this input to thousands of downstream neurons using action potentials. Therefore, the dynamics, with which those discrete action potentials are generated, represents a fundamental bottleneck for the flow of information in neural populations. In the last decade it became clear that the bandwidth of information encoding in neural populations in the cerebral cortex is much higher than it had been previously predicted by simulations with conductance based models (Fourcaud-Trocme et al., 2003; Naundorf et al., 2005, 2006; Kondgen et al., 2008; Higgs and Spain, 2009; Tchumatchenko et al., 2011. The biophysical basis of this experimentally observed large bandwidth is not understood, as even basic parameters such as sodium channel surface density and kinetics are still under debate(Kole et al., 2008; Baranauskas et al., 2013. The work presented here uses high resolution electrophysiology and fluorescence microscopy to quantify sodium channel properties and distributions in neurons. In combination with numerical modelling of active and passive neurons, we identify contributions to the ability to encode information with a high bandwidth. A characterization of sodium channels properties in the cell bodies of cortical pyramidal cells allowed us to conclude that each square micrometer contains 20 to 30 sodium channels. By combining current clamp and immunofluorescence in cultured hippocampal neurons we could achieve semi-quantitative fluorescence labeling and obtained estimates for the axonal density of sodium channels. We found the bandwidth of information encoding to be similar between cultured neurons and neurons in slices. Using cultured neurons as a model system, we studied the maturation of neuronal properties in the first weeks in culture. In parallel to the increased bandwidth, other neuronal properties changed: the axonal sodium channel density, the dendritic morphology and the sub-micrometer organization of axon initial segment structure(Xu et al., 2013; Zhong et al.. The presentation details, how those properties influenced the bandwidth of information encoding.

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

    Science.gov (United States)

    Klinger, D. L.

    1974-01-01

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

  15. Efficient Bandwidth Allocation for Integrated Services in Broadband Wireless ATM Networks

    DEFF Research Database (Denmark)

    Liu, Hong; Dittmann, Lars

    1999-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Raju Singh

    2011-03-01

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

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

    DEFF Research Database (Denmark)

    Kolding, Troels E.; Frederiksen, Frank; Pokhariyal, Akhilesh

    2007-01-01

     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 bo...

  18. 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

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

    CERN Document Server

    Singh, Raju

    2011-01-01

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

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

    International Nuclear Information System (INIS)

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

  1. Quantum-mechanical analysis of pulse reconstruction for a narrow bandwidth attosecond x-ray pulse

    International Nuclear Information System (INIS)

    The photoelectron energy spectra (PESs) excited by narrow bandwidth attosecond x-ray pulses in the presence of a few-cycle laser are quantum-mechanically calculated. Transfer equations are used to reconstruct the detailed temporal structure of an attosecond x-ray pulse directly from a measured PES. Theoretical analysis shows that the temporal uncertainties of the pulse reconstruction depend on the x-ray bandwidth. The procedure of pulse reconstruction is direct and simple without making any previous pulse assumption, data fitting analysis and time-resolved measurement of PESs. The temporal measurement range is half of a laser optical cycle. (atomic and molecular physics)

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

    Directory of Open Access Journals (Sweden)

    CH.V. RAGHAVENDRAN

    2014-10-01

    Full Text Available Modeling and performance prediction are becoming increasingly important issues in the design and operation of computer communications systems. In this paper a review is carried out on how Tandem queuing models with Dynamic Bandwidth Allocation have been applied so far into the performance evaluation of Communication Networks. Queuing network models with finite/infinite capacity buffers and blocking have been applied as more realistic models of systems with finite capacity resources. First we review basic properties of exponential queuing systems, and then give an overview of recent progress made in the areas of dynamic bandwidth allocation for tandem queuing network models and performance measures.

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    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 for the detection of the demultiplexed signal. In such investigations it is crucial to consider...

  4. DNA translocation measurements through low-capacitance solid-state nanopore chips at high bandwidths

    Science.gov (United States)

    Chien, Chen-Chi; Niedzwiecki, David; Machielse, Bartholomeus; Balan, Adrian; Lin, Jianxun; Ong, Peijie; Shepard, Kenneth; Drndic, Marija

    2015-03-01

    We perform DNA translocation measurements with low-noise solid state nanopore chips. We obtain higher ion current signal-to-noise ratio and better resolution in ion current signals than previously reported in solid state nanopores at high bandwidths with chip capacitance lowering techniques of applying extra insulation on the chip surface. We show measurements of ion current during translocation of DNA molecules through thin silicon nitride (SiN) nanopores of small diameters at megahertz bandwidths with enhanced ionic signal-to-noise ratios. We further discuss how these results possibly pave the way towards identifying intramolecular DNA sequences with solid-state nanopores.

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

    CERN Document Server

    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

    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.

  6. Slow light in tunable low dispersion wide bandwidth photonic crystal waveguides infiltrated with magnetic fluids

    Science.gov (United States)

    Guillan-Lorenzo, Omar; Diaz-Otero, Francisco J.

    2016-01-01

    We analyze the properties of a photonic crystal waveguide as a device capable of producing slow light along a wide bandwidth. The proposed structure consists of a square lattice of hollow silicon cylinders rotated 45° immersed on a colloidal suspension of magnetic nanoparticles; this arrangement produces "U-type" group index-frequency curves. The cylinder inner radius is carefully chosen to maximize the normalized delay bandwidth product (NDBP) and the concentration of the magnetic fluid is changed in order to make the device tunable in frequency.

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    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...

  8. An FPGA-Based Adaptable 200?MHz Bandwidth Channel Sounder for Wireless Communication Channel Characterisation

    OpenAIRE

    Victor Dunn; Yanyan Yang; Somboon Toautachone; Kenneth Stuart; David L. Ndzi

    2011-01-01

    This paper describes the development of a fast adaptable FPGA-based wideband channel sounder with signal bandwidths of up to 200 MHz and channel sampling rates up to 5.4 kHz. The application of FPGA allows the user to vary the number of real-time channel response averages, channel sampling interval, and duration of measurement. The waveform, bandwidth, and frequency resolution of the sounder can be adapted for any channel under investigation. The design approach and technology used has led to...

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

    Directory of Open Access Journals (Sweden)

    G. Singh

    2012-04-01

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

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    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 an...

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

    DEFF Research Database (Denmark)

    Larsen, Casper; Giesberts, Martin; Nyga, Sebastian; Fitzau, Oliver; Hoffmann, Hans Dieter; Bang, Ole

    2013-01-01

    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.......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....

  12. Complexity and bandwidth enhancement in unidirectionally coupled semiconductor lasers with time-delayed optical feedback

    Science.gov (United States)

    Kanno, Kazutaka; Uchida, Atsushi; Bunsen, Masatoshi

    2016-03-01

    We numerically investigate the frequency bandwidth and the autocorrelation characteristics of chaotic temporal wave forms in unidirectionally coupled semiconductor lasers with time-delayed optical feedback. We evaluate the complexity of the chaotic temporal wave forms by using Lyapunov exponents. We found that larger maximum Lyapunov exponents can be obtained for smaller peak values of the autocorrelation function at the delay time of the optical feedback. On the contrary, the maximum Lyapunov exponent is independent from the frequency bandwidth of the chaotic temporal wave forms.

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

    Directory of Open Access Journals (Sweden)

    Fath Elrahman Ismael

    2010-01-01

    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.

  14. Improving QoS Of WiMAX By On_Demand Bandwidth Allocation Based On PMP Mode

    OpenAIRE

    ZhenTao Sun; Abdullah Gani; XiuYing Sun; Ning Liu

    2011-01-01

    Abstract—The bandwidth allocation in both wired and wireless networks has posed great challenges to network engineers for improving desirable Quality of Service (QoS), Bandwidth allocation is always an important element for improve QoS of network. Despite this, IEEE 802.16e-2005 does not have a bandwidth allocation algorithm or mechanism to support (worldwide interoperability for microwave access) WiMAX network presently. This includes both uplink (UL) and downlink (DL) directions. Thus...

  15. Higher-order effects in bandwidth-limited soliton propagation in optical fibers

    International Nuclear Information System (INIS)

    By means of numerical studies and soliton perturbation theory we examine the effects of higher-order linear and nonlinear terms in bandwidth-limited amplified soliton propagation. We show that these effects are responsible for strong reductions of soliton--soliton interaction in such systems

  16. An Improved QoS Multipath Routing Using Bandwidth Estimation and Rate Adaptation

    Directory of Open Access Journals (Sweden)

    S. Suganya

    2014-06-01

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

  17. BANDWIDTH ENHANCED E- SHAPED MICROSTRIP ANTENNA WITH PAIR OF WIDE SLITS

    Directory of Open Access Journals (Sweden)

    Shushant Kumar Jain

    2012-12-01

    Full Text Available A single-layer single-patch wideband microstrip antenna could be developed, and impedance bandwidth greater than 30% can easily be achieved for a microstrip antenna with a probe feed, A broad-band design of a probe-fed rectangular patch antenna with a pair of wide slits is studied, and the simulated, radiation characteristics are studied. The proposed design is with an air substrate of thickness about 8% of the wavelength of the center operating frequency, the proposed antenna have an impedance bandwidth about 31.32%, with respect to center frequency. For frequencies within the impedance bandwidth, good radiation characteristics are also observed, with a peak antenna gain about 9.3 dBi.  in this paper the wide slits are inserted at one of the radiating edges of the rectangular patch and increasing the length, width of slits and reducing the distance between them upto the specific limit the, proposed design has achieved the wide impedance bandwidth and good radiation characteristics details of the proposed antenna and Some simulation results obtained by IE3D and are given.

  18. Efficient Bandwidth Allocation for Integrated Services in Broadband Wireless ATM Networks

    DEFF Research Database (Denmark)

    Liu, Hong; Dittmann, Lars; Gliese, Ulrik Bo; Danielsen, Per Lander

    1999-01-01

    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...

  19. An overview of high input impedance buffer amplifiers for wide bandwidth signals

    International Nuclear Information System (INIS)

    Recent evaluations of wide bandwidth (150 MHz), high input impedance (>10 k?) amplifiers are shown. Included are discussions of noise performance, dynamic range, phase linearity, cost and other considerations. Accelerator applications for such amplifiers include diagnostic pickups, filters, and signal distribution systems. Operational experiences with pickup preamplifiers in the Fermilab Antiproton Source Damper systems are described. copyright 1995 American Institute of Physics

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

    Science.gov (United States)

    Cardoso, Luis; Figueira, Gonçalo

    2004-07-12

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

  1. Bandwidth Dependence of Laser Plasma Instabilities Driven by the Nike KrF Laser

    Science.gov (United States)

    Weaver, J. L.; Oh, J.; Seely, J.; Kehne, D.; Brown, C. M.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Phillips, L.; Lehmberg, R. H.; McLean, E.; Manka, C.; Feldman, U.

    2011-10-01

    The Nike krypton-fluoride (KrF) laser at the Naval Research Laboratory operates in the deep UV (248 nm) and employs beam smoothing by induced spatial incoherence (ISI). In the first ISI studies at longer wavelengths (1054 nm and 527 nm) [Obenschain, PRL 62, 768(1989);Mostovych, PRL, 59, 1193(1987); Peyser, Phys. Fluids B 3, 1479(1991)], stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (?? / ? ~ 0.03-0.19%) pulses irradiated targets at moderate to high intensities (1014-1015W/cm2) . Recent Nike work showed that the threshold for quarter critical instabilities increased with the expected wavelength scaling, without accounting for the large bandwidth (?? ~ 1-3 THz). New experiments will compare laser plasma instabilities (LPI) driven by narrower bandwidth pulses to those observed with the standard operation. The bandwidth of KrF lasers can be reduced by adding narrow filters (etalons or gratings) in the initial stages of the laser. This talk will discuss the method used to narrow the output spectrum of Nike, the laser performance for this new operating mode, and target observations of LPI in planar CH targets. Work supported by DoE/NNSA.

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

    International Nuclear Information System (INIS)

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

  3. Storing GHz bandwidth heralded single photons in a room-temperature raman memory: Efficiency and noise

    OpenAIRE

    Nunn, J; Michelberger, PS; Champion, TFM; Sprague, MR; Kacmarek, K; Saunders, D; Kolthammer, WS; Jin, X-M; England, DG; Walmsley, IA

    2014-01-01

    We store GHz-bandwidth heralded single photons in a room-temperature Raman memory, which is a crucial primitive for scalable quantum photonics. We discuss methods to suppress four-wave mixing noise, which accompanies the retrieved photons. © 2014 Optical Society of America.

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

    International Nuclear Information System (INIS)

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

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

    DEFF Research Database (Denmark)

    Lorke, Michael; Nielsen, Torben Roland; Mørk, Jesper

    2010-01-01

    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...

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

    Directory of Open Access Journals (Sweden)

    N.SUMATHI,

    2010-11-01

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

  7. The Influence of Reduced Audible Bandwidth on Asynchronous Double-Vowel Identification

    Science.gov (United States)

    Valentine, Susie; Lentz, Jennifer J.

    2012-01-01

    Purpose: In this study, the authors sought to determine whether reduced audible bandwidth associated with hearing loss contributes to difficulty benefiting from an onset asynchrony between sounds. Method: Synthetic double-vowel identification was measured for normal-hearing listeners and listeners with hearing loss. One vowel (Target 2) was 250 ms…

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2013-08-01

    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.

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

    DEFF Research Database (Denmark)

    Kolding, Troels E.; Frederiksen, Frank; Pokhariyal, Akhilesh

     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 inform...

  11. Small-signal Loudspeaker Impedance Emulator

    DEFF Research Database (Denmark)

    Knott, Arnold; Iversen, Niels Elkjær

    2014-01-01

    Specifying the performance of audio ampliers is typically done by playing sine waves into a pure ohmic load. However real loudspeaker impedances are not purely ohmic but characterised by the mechanical resonance between the mass of the diaphragm and the compliance of its' suspension which vary from driver to driver. Therefore a loudspeaker emulator capable of adjusting its' impedance to a given driver is in need for measurement purposes. This paper proposes a loudspeaker emulator circuit for sma...

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

    Directory of Open Access Journals (Sweden)

    Adil Zaidi

    2013-05-01

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

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

    CERN Document Server

    Terranova, F; Pegoraro, F

    2008-01-01

    In this paper we discuss the bandwidth enhancement that can be achieved in multi-Joule OPCPA systems exploiting the tunability of parametric amplification. In particular, we consider a pair of single pass amplifiers based on 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 possible in two configurations; in the first case, one of the two amplifiers is operated near its non-collinear broadband limit; to allow for effective recombination and recompression of the outgoing signals this configuration requires filtering and phase manipulation of the spectral tail of the amplified pulses. In the second case, effective recombination can be achieved simply by spectral filtering: in this configuration, the optimization of the parameters of the amplifiers (pulse, crystal orientation and crystal length) does not follow the recipes of non-collinear OPCPA.

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

    Science.gov (United States)

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

    2014-02-10

    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

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

    Directory of Open Access Journals (Sweden)

    Jude Lubega

    2013-09-01

    Full Text Available The potential of multimedia teaching and learning approach at higher education is well recognized by researchers, as it is a powerful tool to increase the perceived level of user satisfaction, leading to enhance the blended learning process. However, the learning process can be improved significantly by delivering the content using visual media (video, audio, and graphics. On the other hand, such multimedia contents require larger bandwidth for transmission over the Internet, which is limited in developing environments where demand always exceeds the resource. This paper constructs a framework comprising of network optimization and multimedia optimization, as two main components, aimed to improve the multimedia performance in the context of constrained bandwidth environment.

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

    CERN Document Server

    Javaid, Nadeem; Djouani, Karim

    2010-01-01

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

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

    Science.gov (United States)

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

    2014-09-01

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

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

    Directory of Open Access Journals (Sweden)

    Kuda Nageswara Rao

    2010-07-01

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

  19. Enhancing the bandwidth of gravitational-wave detectors with unstable optomechanical filters

    CERN Document Server

    Miao, Haixing; Zhao, Chunnong; Chen, Yanbei

    2015-01-01

    For gravitational-wave interferometric detectors, there is a tradeoff between the detector bandwidth and peak sensitivity when focusing on the shot noise level. This has to do with the frequency-dependent propagation phase lag (positive dispersion) of the signal. We consider embedding an active unstable filter---a cavity-assisted optomechanical device operating in the instability regime---inside the interferometer to compensate the phase, and using feedback control to stabilize the entire system. We show that this scheme in principle can enhance the bandwidth without sacrificing the peak sensitivity. However, there is one practical difficulty for implementing it due to the thermal fluctuation of the mechanical oscillator in the optomechanical filter, which puts a very stringent requirement on the environmental temperature and the mechanical quality factor.

  20. Enhancing the Bandwidth of Gravitational-Wave Detectors with Unstable Optomechanical Filters.

    Science.gov (United States)

    Miao, Haixing; Ma, Yiqiu; Zhao, Chunnong; Chen, Yanbei

    2015-11-20

    Advanced interferometric gravitational-wave detectors use optical cavities to resonantly enhance their shot-noise-limited sensitivity. Because of positive dispersion of these cavities-signals at different frequencies pick up different phases, there is a tradeoff between the detector bandwidth and peak sensitivity, which is a universal feature for quantum measurement devices having resonant cavities. We consider embedding an active unstable filter inside the interferometer to compensate the phase, and using feedback control to stabilize the entire system. We show that this scheme in principle can enhance the bandwidth without sacrificing the peak sensitivity. However, the unstable filter under our current consideration is a cavity-assisted optomechanical device operating in the instability regime, and the thermal fluctuation of the mechanical oscillator puts a very stringent requirement on the environmental temperature and the mechanical quality factor. PMID:26636839

  1. The Mutual Interaction effects between Array Antenna Parameters and Receiving Signals Bandwidth

    Directory of Open Access Journals (Sweden)

    Shahad D. Sateaa

    2014-03-01

    Full Text Available The presence of a single complex adaptive weight in each element channel of an adaptive array antenna is sufficient for processing of narrowband signals. The ability of an adaptive array antenna to null interference deteriorates rapidly as the interference bandwidth increases. The performance of narrowband adaptive array antenna with LMCV Beamforming algorithm is examined. The interaction effects between received signal angle of arrival and array parameters like the interelement spacing and the number of array element and the received signal bandwidth were studied. The output Signal to Interference plus Noise Ratio (SINR and Interference to Noise Ratio (INR are used as performance parameters for evaluation of these effects. It is found that the amount of degradation in the output SINR is increased significantly with the increase of array interelement spacing, number of array elements and when the angle of arrival of received signals are closet to end fire.

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

    Science.gov (United States)

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

    1998-01-01

    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.

  3. Real-Time Multi-path Tracking of Probabilistic Available Bandwidth

    CERN Document Server

    Thouin, Frederic; Rabbat, Michael

    2010-01-01

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

  4. PbS:glass as broad-bandwidth near-infrared light source material.

    Science.gov (United States)

    Yue, Fangyu; Tomm, Jens W; Kruschke, Detlef; Glas, Peter; Bzheumikhov, Kazbek A; Margushev, Zaur Ch

    2013-01-28

    Silicate- and borosilicate-based PbS:glass material and borosilicate-glass-based fibers are fabricated and analyzed. Optical properties including absorption and emission are characterized and related to growth and annealing conditions. In silicate glasses PbS volume fractions of exceeding 0.4 percent and almost octave-spanning emission spectra with a halfwidth of 940 nm are achieved. Fiber bundles with a core being surrounded by three PbS:Glass fibers are pulled. A confinement factor of ? = 0.00406 is determined. Emission properties, in particular emission bandwidth, are subsequently tuned and spectrally widened by annealing fibers in a gradient furnace. The results pave the way towards optically pumped broad-bandwidth light emitters based either on 'bulk' PbS:glass or PbS:glass-based fibers. PMID:23389208

  5. Improving bandwidth rectangular patch antenna using different thickness of dielectric substrate

    Directory of Open Access Journals (Sweden)

    Karim A. Hamad

    2011-04-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  7. Optimization of Connector Position Offset for Bandwidth Enhancement of a Multimode Optical Fiber Link

    Science.gov (United States)

    Rawat, Banmali

    2000-01-01

    The multimode fiber bandwidth enhancement techniques to meet the Gigabit Ethernet standards for local area networks (LAN) of the Kennedy Space Center and other NASA centers have been discussed. Connector with lateral offset coupling between single mode launch fiber cable and the multimode fiber cable has been thoroughly investigated. An optimization of connector position offset for 8 km long optical fiber link at 1300 nm with 9 micrometer diameter single mode fiber (SMF) and 50 micrometer diameter multimode fiber (MMF) coupling has been obtained. The optimization is done in terms of bandwidth, eye-pattern, and bit pattern measurements. It is simpler, is a highly practical approach and is cheaper as no additional cost to manufacture the offset type of connectors is involved.

  8. Tunable bandwidth of pass-band metamaterial filter based on coupling of localized surface plasmon resonance

    Science.gov (United States)

    Han, Bing; Dong, Beibei; Nan, Jingyu; Zhong, Min

    2015-12-01

    A broad pass-band compound structure metamaterial is designed which consists of periodic two metallic particles and hole arrays. The operating bandwidth of the designed structure reaches to ?f ? 33.8 THz. Physical mechanisms are analyzed and validated based on calculated electric field distribution that the interaction and coupled of LSP modes between two metallic particles leads to the bandwidth increased and resonance frequency blue-shifted, while the interaction and coupled between metallic particle and metallic arrays results in the reduced of the pass-band. The pass-band can be expanded through reducing the permittivity of dielectric layer or reducing the width of the metallic particle (a). The effect of the angles of incidence on the pass-band is also analyzed for normal, 15°, 30° and 45°.

  9. Enhancing the Bandwidth of Gravitational-Wave Detectors with Unstable Optomechanical Filters

    Science.gov (United States)

    Miao, Haixing; Ma, Yiqiu; Zhao, Chunnong; Chen, Yanbei

    2015-11-01

    Advanced interferometric gravitational-wave detectors use optical cavities to resonantly enhance their shot-noise-limited sensitivity. Because of positive dispersion of these cavities—signals at different frequencies pick up different phases, there is a tradeoff between the detector bandwidth and peak sensitivity, which is a universal feature for quantum measurement devices having resonant cavities. We consider embedding an active unstable filter inside the interferometer to compensate the phase, and using feedback control to stabilize the entire system. We show that this scheme in principle can enhance the bandwidth without sacrificing the peak sensitivity. However, the unstable filter under our current consideration is a cavity-assisted optomechanical device operating in the instability regime, and the thermal fluctuation of the mechanical oscillator puts a very stringent requirement on the environmental temperature and the mechanical quality factor.

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

    Science.gov (United States)

    Larson, John P.; Dapino, Marcelo J.

    2012-04-01

    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.

  11. Overview of IEPM-BW-Bandwidth Testing of Bulk Data Transfer

    CERN Document Server

    Cottrell, L

    2003-01-01

    Grid Computing capabilities are needed for the High Energy and Nuclear Physics research of today and in the future. Groups such as the Particle Physics Data Grid are developing tools to meet these needs. An additional challenge is the evaluation and fine tuning of these applications, as well as support for long term monitoring, performance analysis, and troubleshooting. In September 2001, SLAC started the development of an infrastructure for measuring the available bandwidth and actual bandwidth utilization that is achievable by the network and various bulk data transfer applications. The purpose of these active and passive measurements is to understand what throughputs are achievable, the constraints, and how to optimize, and to make the data and predictions available for net-workers and application tuning. This paper discusses the measurement methodology and pathologies, analysis, results, and avenues for future development.

  12. Atomic Faraday filter with equivalent noise bandwidth less than 1 GHz

    CERN Document Server

    Zentile, Mark A; Keaveney, James; Adams, Charles S; Hughes, Ifan G

    2015-01-01

    We demonstrate an atomic bandpass optical filter with an equivalent noise bandwidth less than 1 GHz using the D$_1$ line in a cesium vapor. We use the ElecSus computer program to find optimal experimental parameters, and find that for important quantities the cesium D$_1$ line clearly outperforms other alkali metals on either D-lines. The filter simultaneously achieves a peak transmission of 77%, a passband of 310 MHz and an equivalent noise bandwidth of 0.96 GHz, for a magnetic field of 45.3 gauss and a temperature of 68.0$\\,^\\circ$C. Experimentally, the prediction from the model is verified. The experiment and theoretical predictions show excellent agreement.

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

    Directory of Open Access Journals (Sweden)

    Liang Yao

    2007-01-01

    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.

  14. A NEW DATA TRANSFER SCHEME BASED ON BANDWIDTH ALLOCATION FOR VIRTUAL PRIVATE NETWORKS

    Directory of Open Access Journals (Sweden)

    Mahalakshmi C

    2010-05-01

    Full Text Available This paper attempts to develop a data transfer scheme with a view to sufficiently provision the hose model of the Virtual Private Network (VPN and accomplish the desired degree of performance. The basic ideais to extract a service comparable to that of a private dedicated network with leased lines for the endpoints of the VPN. The service providers are expected to guarantee the required bandwidth, in order to address Quality of Service (QoS issues while employing a VPN over a shared network. Thus a tree based mechanism is generated through which well defined resource management procedures are devised to optimize the available bandwidth. The data packets forwarded through such predetermined paths serve to ensure secure communication betweencustomer sites. The NS2 based simulation results are included to demonstrate the merits of the designed approach and highlight the suitability of VPN for real time applications.

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

    Science.gov (United States)

    Kojima, Jun; Nguyen, Quang-Viet

    2007-01-01

    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.

  16. Optimal Resource Allocation and Relay Selection in Bandwidth and Time Exchange Based Cooperative Forwarding

    CERN Document Server

    Islam, Muhammad Nazmul; Kompella, Sastry

    2011-01-01

    In this paper, we investigate joint optimal relay selection and resource allocation that are fundamental to the understanding of bandwidth exchange (BE) and time exchange (TE) enabled incentivized cooperative forwarding in wireless networks. We consider a network where N nodes transmit data in the uplink to an access point (AP) or base station (BS). We first consider the scenario where each node gets an initial amount (equal, optimal or arbitrary) of resource in the form of bandwidth or time, and uses this resource as a flexible incentive for two hop relaying. We focus on ?-fair network utility maximization (NUM) and total power minimization in this environment. For both BE and TE, we show the concavity or convexity of the resource allocation problem for a fixed relay set. Defining the link weights of each relay pair as the utility gain due to cooperation (over noncooperation), we show that the optimal relay selection, often a combinatorially cumbersome problem, reduces to the maximum weighted matching (MWM) ...

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

    DEFF Research Database (Denmark)

    Deng, Lei; Zhao, Ying

    2011-01-01

    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.

  18. 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)

  19. A Study of A Method To Provide Minimized Bandwidth Consumption Using Regenerating Codes In Cloud Storage

    Directory of Open Access Journals (Sweden)

    M.Nithya

    2014-04-01

    Full Text Available Cloud storage systems to protect data from corruptions, redundant data to tolerate failures of storage and lost data should be repaired when storage fails. Regenerating codes provide fault tolerance by striping data across multiple servers, while using less repair traffic than traditional erasure codes during failure recovery. In previous research implemented practical Data Integrity Protection (DIP scheme for regenerating-coding based cloud storage. Functional Minimum-Storage Regenerating (FMSR codes and it construct FMSR-DIP codes, which allow clients to remotely verify the integrity of random subsets of long-term archival data under a multi server setting. The problem is to optimize bandwidth consumption when repairing multiple failures. The cooperative repair of multiple failures can help to further save bandwidth consumption when multiple failures are being repaired.

  20. Wideband Spectroscopy: The Design and Implementation of a 3 GHz Bandwidth, 8192 Channel, Polyphase Digital Spectrometer

    Science.gov (United States)

    Monroe, Ryan M.

    2011-01-01

    A family of state-of-the-art digital Fourier transform spectrometers has been developed, with a combination of high bandwidth and fine resolution unavailable elsewhere. Analog signals consisting of radiation emitted by constituents in planetary atmospheres or galactic sources are downconverted and subsequently digitized by a pair of interleaved Analog-to-Digital Converters, (ADC). This 6 Gsps (giga-sample per second) digital representation of the analog signal is then processed through an FPGA-based streaming Fast Fourier Transform (FFT), the key development described below. Digital spectrometers have many advantages over previously used analog spectrometers, especially in terms of accuracy and resolution, both of which are particularly important for the type of scientific questions to be addressed with next-generation radiometers. the implementation, results and underlying math for this spectrometer, as well as, potential for future extension to even higher bandwidth, resolution and channel orthogonality, needed to support proposed future advanced atmospheric science and radioastronomy, are discussed.

  1. High-Fidelity Polarization Storage in a Gigahertz Bandwidth Quantum Memory

    CERN Document Server

    England, D G; Champion, T F M; Reim, K F; Lee, K C; Sprague, M R; Jin, X -M; Langford, N K; Kolthammer, W S; Nunn, J; Walmsley, I A

    2011-01-01

    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\\pm1% 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\\pm4% for 1.5 \\mu s storage time, which is 5,000 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.

  2. New Bandwidth Guaranteed QoS Routing Algorithm for MPLS Networks

    Directory of Open Access Journals (Sweden)

    Santosh Kulkarni

    2012-03-01

    Full Text Available 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 percentage. This paper proposes a new Bandwidth guaranteed QoS routing algorithm based on MPLS networks. It is based on three objectives: Minimum interference levels with other source destination node pairs, optimizing the network resource utilization using Dijkstra’s algorithm and reducing algorithm complexity. The simulation results show that the proposed algorithm performs better in terms of network utilization, low call blocking percentage, reduced path length and low complexity.

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

    OpenAIRE

    Moore, Brian C.J.

    2012-01-01

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

  4. Scalable Network-layer Defense Against Internet Bandwidth-Flooding Attacks

    OpenAIRE

    Argyraki, Katerina; Cheriton, David R.

    2009-01-01

    In a bandwidth-flooding attack, compromised sources send high-volume traffic to the target with the purpose of causing congestion in its tail circuit and disrupting its legitimate communications. In this paper, we present Active Internet Traffic Filtering (AITF), a network-layer defense mechanism against such attacks. AITF enables a receiver to contact misbehaving sources and ask them to stop sending it traffic; each source that has been asked to stop is policed by its own Internet service pr...

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

    OpenAIRE

    Wetzel, B.; Stefani, A.; Larger, L.; P.A. Lacourt; J.-M. Merolla; T. Sylvestre; A. Kudlinski; Mussot, A.; Genty, G.; Dias, F.(Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, Brazil); Dudley, J. M.

    2012-01-01

    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 co...

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

    DEFF Research Database (Denmark)

    Ding, Yunhong; Pu, Minhao; Liu, Liu; Xu, Jing; Peucheret, Christophe; Zhang, Xinliang; Huang, Dexiu; Ou, Haiyan

    2011-01-01

    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 arm...

  7. Optical memory bandwidth and multiplexing capacity in the erbium telecommunication window

    International Nuclear Information System (INIS)

    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. (paper)

  8. Partial Connection : A New Approach To Improving The Bandwidth Of Banyan Networks

    OpenAIRE

    Nasar, Hamed Nassar, Hamed [???? ???

    1995-01-01

    Banyan networks have been proposed as interconnection networks for large multiprocessors, those containing hundreds or even thousands of processors. Their attractiveness is attributed to two features : low manufacturing cost and self routing. However, these networks have a serious problem, low bandwidth. Unfortuntely, this problem gets worse as the size and/or the load of the network increases. In this paper we introduce a novel approach to solve this problem, partial connection. The idea ...

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

    OpenAIRE

    Jude Lubega; Nazir Ahmad Suhail; Gilbert Maiga

    2013-01-01

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

  10. Optimization of Bandwidth and Energy Consumption in Wireless Local Area Networks

    OpenAIRE

    Conti, Marco; Gregori, Enrico

    2002-01-01

    In the recent years the proliferation of portable computers, handheld digital devices, and PDAs has led to a rapid growth in the use of wireless technologies for the Local Area Network (LAN) environment. Beyond supporting wireless connectivity for fixed, portable and moving stations within a local area, the wireless LAN (WLAN) technologies can provide a mobile and ubiquitous connection to the Internet information services. The design of WLANs has to concentrate on bandwidth consumption becaus...

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

    OpenAIRE

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

    2010-01-01

    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 ...

  12. Analysis in the allocation of bandwidth applied to the concept of flexible optical networks

    Science.gov (United States)

    Puche, William S.; Sierra, Javier E.; Amaya, Ferney O.

    2015-09-01

    The continued increase in the capabilities and performance in fiber optic networks today require more robust network designs to allow high consumption of information and thus enable users to have greater capacity and data content. That's why we in the task of analyzing and implementing the concept of flexible optical networks to optimize the use of bandwidth at high transmission rates and improved spectral efficiency, which represents the industry an effective economy, and energy.

  13. Self-Organization of Balanced Nodes in Random Networks with Transportation Bandwidths

    OpenAIRE

    Yeung, C. H.; Wong, K. Y. Michael

    2009-01-01

    We apply statistical physics to study the task of resource allocation in random networks with limited bandwidths along the transportation links. The mean-field approach is applicable when the connectivity is sufficiently high. It allows us to derive the resource shortage of a node as a well-defined function of its capacity. For networks with uniformly high connectivity, an efficient profile of the allocated resources is obtained, which exhibits features similar to the Maxwel...

  14. Narrow bandwidth red electroluminescence from solution-processed lanthanide-doped polymer thin films

    OpenAIRE

    O'Riordan, Alan; O'Connor, Eamon; Moynihan, Shane; Llinares, Xavier; Van Deun, Rik; Fias, Pascal; Nockemann, Peter; Binnemans, Koen; Redmond, Gareth

    2005-01-01

    Narrow bandwidth red electroluminescence from OLED devices fabricated using a simple solution-based approach is demonstrated. A spin-casting method is employed to fabricate organic light emitting diode (OLED) devices comprising a poly(N-vinylcarbazole) (PVK) host matrix doped with a europium beta-diketonate complex, Eu(dbm)(3)(Phen) (dibenzoylmethanate, dbm; 1,10-phenanthroline, Phen) on glass/ indium tin oxide (ITO)/3,4-polyethylene-dioxythiophene-polystyrene sulfonate (PEDOT) substrates. Sa...

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

    OpenAIRE

    Kuda Nageswara Rao; K.SRINIVASA RAO; P.Srinivasa Rao

    2010-01-01

    This paper deals with the performance evaluation of a two node communication network with dynamic bandwidth allocation and modified phase type transmission having bulk arrivals. The performance of the statistical multiplexing is measured by approximating with the compound Poisson process and the transmission completions with Poisson processes. It is further assumed that the transmission rate at each node are adjusted depending upon the content of the buffer which is connected to it. The packe...

  16. 3-mode detection for widening the bandwidth of resonant gravitational wave detectors

    OpenAIRE

    Baggio, L.; M. Bignotto; Bonaldi, M; Cerdonio, M.; Conti, L.; Falferi, P.; Liguori, N.; Marin, A.; Mezzena, R.; Ortolan, A.; Poggi, S.; Prodi, G. A.; Salemi, F.; Soranzo, G.; Taffarello, L.

    2005-01-01

    We have implemented a novel scheme of signal readout for resonant gravitational wave detectors. For the first time, a capacitive resonant transducer has been matched to the signal amplifier by means of a tuned high Q electrical resonator. The resulting 3-mode detection scheme widens significantly the bandwidth of the detector. We present here the results achieved by this signal readout equipped with a two-stage SQUID amplifier. Once installed on the AURIGA detector, the one-...

  17. Highly Scaled InP/InGaAs DHBTs Beyond 1 THz Bandwidth

    Science.gov (United States)

    Rode, Johann Christian

    This work examines the efforts pursued to extend the bandwidth of InP-based DHBTs above 1 THz. Aggressive lithographic and epitaxial scaling of key device dimensions and simultaneous reduction of contact resistivities have enabled increased RF bandwidths by reduction of device RC and transit delays. A fabrication process for forming base electrodes and base/collector mesas of highly scaled transistors has been developed that exploits superior resolution (10nm) and alignment (metalization technique is presented that removes contaminating lithographic processes from the formation of the base contact, thereby enabling low resistivity contacts (4 ?-microm2) to ultra-thin base layers (20 nm). The composite base metal stack exploits an ultra-thin layer of platinum that controllably reacts with base, yielding low contact resistivity, as well as a thick refractory diffusion barrier which permits stable operation at high current densities and elevated temperatures. Reduction in emitter-base surface leakage and subsequent increase of current gain was achieved by passivating emitter-base semiconductor surfaces with conformally grown ALD Al2O3. RF bandwidth limiting parasitics associated to the perimeter of highly scaled transistors have been identified and significantly reduced, among which are high sheet resistance of base electrodes, excess undercut of emitter stripes and improperly scaled base posts. At 100nm collector thickness, the breakdown voltage of the transistor BVCEO has been increased to more than 4.1V by passivating base/collector surfaces. With the technology improvements discussed, transistors with ftau of 480 GHz and fmax in excess of 1 THz have been demonstrated at 200nm emitter width and 80nm single-sided base contact width. Transistors at the same emitter width, but 30nm base contact width exhibit ftau of 550 GHz and fmax of 850 GHz. Estimations from a finite element model predict higher bandwidth on smaller footprint transistors. However, inadequacies of RF calibration structures prevent f max extraction on these devices.

  18. Potential Upgrade of the CMS Tracker Analog Readout Optical Links using Bandwidth Efficient Digital Modulation

    CERN Document Server

    Dris, Stefanos; Gill, K; Grabit, R; Ricci, D; Troska, J; Vasey, F

    2007-01-01

    The potential application of advanced digital communication schemes in a future upgrade of the CMS Tracker readout optical links is currently being investigated at CERN. We show experimentally that multi-Gbit/s data rates are possible over the current 40 MSamples/s analog optical links by employing techniques similar to those used in ADSL. The concept involves using one or more digitally-modulated sinusoidal carriers in order to make efficient use of the available bandwidth.

  19. Thermal Narrowing of the Electronic Bandwidths in Organic Molecular Semiconductors: Impact of the Crystal Thermal Expansion

    OpenAIRE

    LI, YUAN; Coropceanu, Veaceslav; Brédas, Jean-Luc

    2012-01-01

    We report on electronic-structure calculations for the pentacene and rubrene crystals, based on experimental crystal geometries measured at different temperatures. The results are in very good agreement with angle-resolved photoelectron spectroscopy data that indicate that the widths of the valence and conduction bands in both materials become narrower at higher temperatures. Our findings strongly suggest that the thermal bandwidth narrowing in the pentacene and rubrene crys...

  20. Investigation of Bandwidth Requirement of Smart Meter Network Using OPNET Modeler

    OpenAIRE

    Rahman, M.; Amanullah Mto

    2013-01-01

    Smart meter networks are the backbone for smart electrical distribution grid. Smart meter network requires the bidirectional communications medium and interoperability capability. As thousands of meters are interconnected in the smart meter network, it is vital to select an appropriate communication bandwidth to facilitate real-time two-way information flows and this will also allow further uptake of greenhouse-friendly technology options and enhance energy security. Optimized Network Enginee...

  1. Blast-pressure measurement with a high-bandwidth fibre optic pressure sensor

    Science.gov (United States)

    MacPherson, W. N.; Gander, M. J.; Barton, J. S.; Jones, J. D. C.; Owen, C. L.; Watson, A. J.; Allen, R. M.

    2000-02-01

    A sensor to measure rapidly changing pressures in an explosive air blast requires high bandwidth and high spatial resolution. For such an application a low-cost, electrically isolated sensor is particularly attractive. We describe an optical fibre-based pressure sensor that meets these requirements. The sensor is subjected to an experimental explosive-blast measurement test and the results are discussed with respect to the sensor performance and compared with a simple blast-wave model and conventional pressure transducers.

  2. Relating 2f1-f2 distortion product otoacoustic emission and equivalent rectangular bandwidth

    DEFF Research Database (Denmark)

    Christensen, Anders Tornvig; Ordoñez, Rodrigo; Hammershøi, Dorte

    2015-01-01

    To explore the extent of distortion product otoacoustic emission (DPOAE) toward low frequencies we measured in 21 normal-hearing human subjects its dependence on the ratio between evoking stimulus frequencies, f1 and f2, at 2f1-f2 distortion frequencies 88, 176 and 264 Hz. The "optimal" ratio evoking the largest DPOAE level is frequency dependent but well-guided by 1.52 equivalent rectangular bandwidth (ERB).

  3. 14 GHz bandwidth MSM photodiode AlGaAs/GaAs HEMT monolithic integrated optoelectronic receiver

    OpenAIRE

    Hurm, Volker; Ludwig, Manfred; Rosenzweig, Josef; Benz, Willi; Berroth, Manfred; Bosch, Roland; Bronner, Wolfgang; Hülsmann, Axel; Köhler, Klaus; Raynor, Brian; Schneider, Joachim

    1993-01-01

    A monolithic optoelectronic receiver consisting of an MSM photodiode and a two-stage amplifer has been fabricated using an enhancement/depletion 0.3 ?m recessed-gate AlGaAs/GaAs HEMT process. The band-width of 14.3 GHz implies suitability for transmission rates of up 20 Gbit/s. The transimpendance is 670 ? (into 50 ?) and the projected sensitivity is 16.4 dBm (BER = 10 -9).

  4. Power-Bandwidth Efficiency and Capacity of Wireless Feedback Communication Systems

    OpenAIRE

    Platonov, Anatoliy

    2011-01-01

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

  5. Bandwidth widening in nonlinear electromagnetic vibrational generator by combined effect of bistability and stretching

    International Nuclear Information System (INIS)

    This work reports the novel concept of frequency response widening of vibrational energy harvesters exploiting the combined effects of bistable and monostable nonlinearities in a single device. The bistability is introduced into the system by repulsive arrangement of magnets, while monostable nonlinear force through the stretching is incorporated by large deformation of two-end-fixed cantilevers. The simulation results show wider bandwidth in the bistability and stretching combined configuration compared to the bistable only or the monostable stretching only configuration

  6. Relationship between tinnitus pitch and edge of hearing loss in individuals with a narrow tinnitus bandwidth

    OpenAIRE

    Sereda, Magdalena; Edmondson-Jones, Mark; Hall, Deborah A.

    2014-01-01

    Objective: Psychoacoustic measures of tinnitus, in particular dominant tinnitus pitch and its relationship to the shape of the audiogram, are important in determining and verifying pathophysiological mechanisms of the condition. Our previous study postulated that this relationship might vary between different groups of people with tinnitus. For a small subset of participants with narrow tinnitus bandwidth, pitch was associated with the audiometric edge, consistent with the tonotopic reorganiz...

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

    OpenAIRE

    Mandeep Singh; Kanwalvir Singh Dhindsa

    2013-01-01

    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 ...

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

    OpenAIRE

    Wang, Yadong; Ding, Nai; Ahmar, Nayef; Xiang, Juanjuan; Poeppel, David; Simon, Jonathan Z.

    2011-01-01

    Slow acoustic modulations below 20 Hz, of varying bandwidths, are dominant components of speech and many other natural sounds. The dynamic neural representations of these modulations are difficult to study through noninvasive neural-recording methods, however, because of the omnipresent background of slow neural oscillations throughout the brain. We recorded the auditory steady-state responses (aSSR) to slow amplitude modulations (AM) from 14 human subjects using magnetoencephalography. The r...

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

    OpenAIRE

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

    2013-01-01

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

  10. Widely bandwidth-tunable silicon filter with an unlimited free-spectral range.

    Science.gov (United States)

    St-Yves, Jonathan; Bahrami, Hadi; Jean, Philippe; LaRochelle, Sophie; Shi, Wei

    2015-12-01

    Next-generation high-capacity optical networks require flexible allocation of spectrum resources, for which low-cost optical filters with an ultra-wide bandwidth tunability beyond 100 GHz are desired. We demonstrate an integrated band-pass filter with the bandwidth continuously tuned across 670 GHz (117-788 GHz) which, to the best of our knowledge, is the widest tuning span ever demonstrated on a silicon chip. The filter also features simultaneous wavelength tuning and an unlimited free spectral range. We measured an out-of-band contrast of up to 55 dB, low in-band ripples of less than 0.3 dB, and in-band group delay variation of less than 8 ps. This result was achieved using cascaded Bragg-grating-assisted contra-directional couplers and micro-heaters on the 220 nm silicon-on-insulator platform with a very compact footprint of less than 7000???m2. Another design with the bandwidth continuously tunable from 50 GHz to 1 THz is also presented. PMID:26625028

  11. Bandwidth provisioning in infrastructure-based wireless networks employing directional antennas

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  12. Balancing high gain and bandwidth in multilayer organic photodetectors with tailored carrier blocking layers

    International Nuclear Information System (INIS)

    We present detailed studies of the high photocurrent gain behavior in multilayer organic photodiodes containing tailored carrier blocking layers we reported earlier in a Letter [W. T. Hammond and J. Xue, Appl. Phys. Lett. 97, 073302 (2010)], in which a high photocurrent gain of up to 500 was attributed to the accumulation of photogenerated holes at the anode/organic active layer interface and the subsequent drastic increase in secondary electron injection from the anode. Here, we show that both the hole-blocking layer structure and layer thickness strongly influence the magnitude of the photocurrent gain. Temporal studies revealed that the frequency response of such devices is limited by three different processes with lifetimes of 10??s, 202??s, and 2.72?ms for the removal of confined holes, which limit the 3?dB bandwidth of these devices to 1.4?kHz. Furthermore, the composition in the mixed organic donor-acceptor photoactive layer affects both gain and bandwidth, which is attributed to the varying charge transport characteristics, and the optimal gain-bandwidth product is achieved with approximately 30% donor content. Finally, these devices show a high dynamic range of more than seven orders of magnitude, although the photocurrent shows a sublinear dependence on the incident optical power

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

    Directory of Open Access Journals (Sweden)

    Ahmed Nabih Zaki Rashed

    2012-10-01

    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}.

  14. A frequency and bandwidth tunable metamaterial absorber in x-band

    Science.gov (United States)

    Yuan, H.; Zhu, B. O.; Feng, Y.

    2015-05-01

    Smart control is an attracting and important function for modern electromagnetic wave absorber. This paper presents the design, fabrication, and measurement of a frequency and bandwidth tunable metamaterial absorber (MA) in X-band. The unit cell of the MA consists of a microstrip resonator loaded with the varactors. Simulation and measurement results show that by tuning the bias voltage on the varactors, the peak absorption frequency can be tuned by 0.44 GHz with the peak absorption greater than 95%. Field and circuit model analysis is conducted to reveal the working mode and predict the absorbing frequency. After that, by specially designing the bias circuit so as to adjust the bias voltage on neighboring unit cells separately, dual resonance and absorption peaks occur, and the overall absorption bandwidth can thus be tuned conveniently by controlling the difference of the two resonance frequencies. The center absorbing frequency can also be tuned. Simulation and experiment results show that the 75% absorption (-6 dB reflection) bandwidth can be tuned from 0.40 GHz to 0.74 GHz, which is a two-fold tuning range. This work is believed to improve the state-of-the-art smart metamaterial absorber.

  15. Bandwidth efficient cluster-based data aggregation for Wireless Sensor Network

    DEFF Research Database (Denmark)

    Dnyaneshwar, Mantri; Prasad, Neeli R.

    2015-01-01

    A fundamental challenge in the design of Wireless Sensor Network (WSNs) is the proper utilization of resources that are scarce. The critical challenge is to maximize the bandwidth utilization in data gathering and forwarding from sensor nodes to the sink. The main design objective is to utilize the available bandwidth efficiently. The proposed Bandwidth Efficient Cluster- based Data Aggregation (BECDA) algorithm presents the solution for the effective data gathering with in-network aggregation. It considers the network with heterogeneous nodes in terms of energy and mobile sink to aggregate the data packets. The optimal approach is achieved by intra and inter-cluster aggregation on the randomly distributed nodes with the variable data generation rate. The proposed algorithm uses the correlation of data within the packet for applying the aggregation function on the data generated by nodes. BECDA shows significant improvement in PDR (67.44 & 26.79 %) and throughput (41.25 & 26.16 %) as compared to the state-of-the-art solutions.

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

    DEFF Research Database (Denmark)

    Strikwerda, Andrew; Zalkovskij, Maksim

    2014-01-01

    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.

  17. Estimated Bandwidth Distribution with Admission Control for Enhanced QoS Multicast Routing in MANETs

    Directory of Open Access Journals (Sweden)

    P.Revathi

    2009-09-01

    Full Text Available Wireless networks become more widely used to support advanced services. Traditional approaches to guarantee quality of service (QoS work well only with predictable channel and network access. The Multicast transmission is a more efficient mechanism when compared to uni-casting in supporting group communication applications and hence is an important aspect of future network developments. To enable high QoS for all admitted traffic, the Admission Control monitors the wireless channel and dynamically adapts admission control decisions to enable high network utilization while preventing congestion. Mobile Adhoc networks can provide multimedia users with mobility, if efficient QoS multicast strategies were developed. In load balancing QoS Multicast Routing QMR, constant available bandwidth for the link is assumed. A cross-layer framework to support QoS multicasting is extended for more effective than QMR. The extension reflects good packet delivery ratios associated with lower control overhead and lower packet delivery delay. If minimum real-time requirements are not met, these unusable packets waste scarce bandwidth and hinder other traffic, compounding the problem. Whereas the dynamically adapted mobility with control overhead monitors the high QoS for all admitted traffic, and the bandwidth for each node is enhanced to reflect the good packet delivery ratio associated with lower control overhead and lower packet delivery delay.

  18. Bayesian MCMC Bandwidth Estimation on Kernel Density Estimation for Flood Frequency Analysis

    Science.gov (United States)

    Lee, T.; Ouarda, T. B.; Lee, J.

    2009-05-01

    Recent advances in computational capacity allow the use of more sophisticated approaches that require high computational power, such as the technique of importance sampling and Bayesian Markov Chain Monte Carlo (BMCMC) methods. In flood frequency analysis, the use of BMCMC allows to model the uncertainty associated to quantile estimates obtained through the posterior distributions of model parameters. BMCMC models have been used in association with various parametric distributions in the estimation of flood quantiles. However, they have never been applied with nonparametric distributions for the same objective. In this paper, the BMCMC is used for the selection of a bandwidth of the kernel density estimate (KDE) in order to carry out extreme value frequency analysis. KDE has not gained much acceptance in the field of frequency analysis because of its feature of easily dying off away from the occurrence point (low predictive ability). The use of Gamma kernels allow to solve this problem because of the caracteristics of thicker right tails and variable kernel smoothness. Even if the bandwidth is not changed, the gamma kernel permits alternating its variance according to the estimate point. Furthermore, BMCMC provides the uncertainty induced from the bandwidth selection. The predictive ability of the Gamma KDE is investigated with Monte Carlo simulation. Results show the usefulness of the gamma kernel density estimate in flood freuquency analysis.

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

    Directory of Open Access Journals (Sweden)

    Pramod Kumar Singhal

    2012-10-01

    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.

  20. A Synthetic Bandwidth Method for High-Resolution SAR Based on PGA in the Range Dimension

    Science.gov (United States)

    Li, Jincheng; Chen, Jie; Liu, Wei; Wang, Pengbo; Li, Chunsheng

    2015-01-01

    The synthetic bandwidth technique is an effective method to achieve ultra-high range resolution in an SAR system. There are mainly two challenges in its implementation. The first one is the estimation and compensation of system errors, such as the timing deviation and the amplitude-phase error. Due to precision limitation of the radar instrument, construction of the sub-band signals becomes much more complicated with these errors. The second challenge lies in the combination method, that is how to fit the sub-band signals together into a much wider bandwidth. In this paper, a novel synthetic bandwidth approach is presented. It considers two main errors of the multi-sub-band SAR system and compensates them by a two-order PGA (phase gradient auto-focus)-based method, named TRPGA. Furthermore, an improved cut-paste method is proposed to combine the signals in the frequency domain. It exploits the redundancy of errors and requires only a limited amount of data in the azimuth direction for error estimation. Moreover, the up-sampling operation can be avoided in the combination process. Imaging results based on both simulated and real data are presented to validate the proposed approach. PMID:26131679