bluuebunny/crossref_metadata_2025_split huggingface dataset:
AlGaAs/GaAs: High electron mobility transistor simulations with PRISM
Authors: Jansen Philippe , Maene N. , Raedt Walter De , Naten S. , Stubbe D. , Schoenmaker Wim , Van Rossum M. , De Meyer K. 
Published: September 2008

AbstractThe two‐dimensional device simulator PRISM (PRogram for Investigating Semiconductor Models) [1], which is a general purpose device simulator, has been adapted to simulate III‐V heterojunction FET's [2]. PRISM can now simulate silicon devices (as MOSFET's, bipolar transistors, SO1 structures, etc.,), GaAs MESFET's, Schottky diodes and AIGaAsl GaAs HEMT's.The program makes use of the finite element method to solve the Poisson equation and the finite boxes method to solve the continuity equations for electrons and holes. There is also an ongoing effort to implement the heat transport equation [3]. The finite element method has rarely been used in HEMT‐simulations. The main advantages of this method are the flexibility in defining sloped device contours and the possibilic to refine the mesh only locally, so that the number of nodes only increases moderately, as opposed to the situation with finite difference simulators. This advantage is very usefull for HEMT's were the thin AlGaAs/GaAs heterojunction region ( 40 nm) has to be simulated accurately compared to the bulk region.Simulations of AlGaAslGaAs HEMT's have been performed, and comparisons with measurements on HEMT's [4] processed in IMEC have been made. The simulated I‐V characteristics and the transconductance curves agree very well. Also sheet concentrations and band diagrams can be extracted from the simulation results.
Monte carlo particle study of transport along the hetero interface in a field‐effect transistor
Authors: Moglestue Canute 
Published: September 2008

AbstractAn inverse heterojunction field‐effect transistor has been simulated by means of the Monte Carlo particle model, which represents a self‐consistent solution of Boltzmann's transport and Poisson's field equation. It was found that a quantum well forms between the source and the drain, which, only at the drain end of gate, gets sufficiently narrow that the lowest subband gets lifted more than the average thermal energy during practical operating conditions of the device. Nowhere is the intersubband separation large enough that multiple subband transport need to be considered. This represents a considerable saving in computer time as the scattering rates can be stored in tables which reside in their entirity in the central memory.The simulated device was found to be a Gunn oscillator with a frequency of 110 GHz. The temporal evolution of the Gunn domains from nucleation to absorption in the drain has been studied.
Physical models for heterostructure FET simulation
Authors: Lugli Paolo , Neviani Andrea , Saraniti Marco 
Published: September 2008

AbstractField effect transistors (FET) based on heterostructures between III‐V binary and ternary compounds have been demonstrated as outstanding semiconductor devices for microwave applications. This paper will present a critical discussion of the physical models that are used to study the prototype of heterostructure devices, that is the High Electron Mobility Transistor (HEMT). The main technological features involved in the fabrication of HEMT are outlined and their incorporation into theoretical models discussed.
Analysis of the effect of irregularities on the electrodes of the calculable cross‐capacitor
Authors: Pogliano Umberto 
Published: September 2008

AbstractA sensitivity function of the cross‐capacitance to the orthogonal displacements is. introduced to analyze the capacitance errors due to surface irregularities on the electrodes of a Lampard‐Thompson calculable cross‐capacitor.A numerical evaluation of the sensitivity function far from the terminal guard electrodes, which defines the active length of the capacitor, has been done.The method allows the evaluation of the errors in real cases, where the surface is not the exactly cylindrical and it can be a possible approach to the study of the two regions near the terminal guard electrodes, where the electrical field is strongly distorted, in order to compute corrective terms or to establish optimum criteria for the shape of these electrodes.
Simplified crosstalk measurements in medium length polarization maintaining fibers
Authors: Galtarossa Andrea , Pavan Antonio , Someda Carlo G. , Zanineilo Ruggiero , Srl. Saifo 
Published: September 2008

AbstractA method has been recently proposed by Sasaoka and Tanaka for rapid crosstalk measurements, and demonstrated for short (10 m) polarization maintaining (PM) fibers. We introduce further simplification and successfully apply the method to medium‐length (100 m) fibers, e.g. for measuring crosstalk vs. fiber length. An accuracy of the order of 0.5 dB is easily achieved when measuring crosstalk around ‐ 30 dB.
A flexible FFT algorithm to process serial data signals using personal computer
Authors: Clemente Fabrizio , Cesarelli Mario , Bracale Marcello 
Published: September 2008

AbstractThe aim of the paper is to demonstrate the possibility of using Personal Computer PC‐DOS (or generally MS‐DOS) for real time (or quasi real time) signal processing of serial data adding a simple A/D conversion card and the mathematical co‐processor XXX87.We have realized an assembly written FFT routine derived from a radix‐4 algorithm by Morris (1979). This algorithm is an autogenerated algorithm. This means that it is modified by another running off‐line algorithm according to the number of FFT points. The program is organized as subroutine to be called by high level language in different procedures.This approach reduces the computational time which is particularly useful when many Fourier transforms on different data array are required.Here reported are two biomedical applications of the routine for the spectral analysis of Doppler ultrasound velocimetry and for the surface electromiography (E.M.G.).
Diffraction of plane waves by a two‐part metal‐backed thin dielectric plane
Authors: Buyukaksoy Alinur , Erdoan Eren , Uzgoren Gökhan 
Published: September 2008

AbstractDiffraction of a H,‐polarized plane wave by the discontinuties occurring in the material properties as well as in the thicknesses of a thin dielectric layer with a perfectly conducting backing is investigated. The effect of the dielectrics are simulated by second order generalized impedance boundary conditions which allow the structure to be treated as an infinitely thin two‐part plane.Then the solution is accomplished by the standard Wiener‐Hopf technique.
From R&D laboratories: Design and realization by MCVD of optical fibres with zero dispersion wavelength around 1550 nm
Authors: Gnazzo Angelantonio , Modone Eros , Cognolato Livio , Cocito Giuseppe 
Published: September 2008

AbstractParameters of optical fibres with zero dispersion at 1550 nm have been designed.In order to realize the critical core radius of 2.16 μm, some adjustments in pressurized MCVD process have been needed. A strict control of the process parameters during deposition, collapse and etching cycles allows to achieve the dispersion‐shifted fibre structure by MCVD as well.
Evolution of wireless information networks
Authors: Goodman David J. 
Published: September 2008

AbstractConsumer and business demands for cellular mobile telephones and residential cordless phones are growing rapidly throughout the world. Both are relatively new and still function with their original, first generation technologies. In response to various pressures second generation systems and services are scheduled for introduction over the next three years. Meanwhile researches are formulating a vision of the third generation, when cordless, cellular, and other wireless networks will merge in a unified means of wireless access to advanced information services.This paper traces the evolution of wireless information networks by examining goals, network architecture, transmission technologies, and control channels. In each instance, we describe, in a general way, first generation systems. We then discuss details of four different second generation systems: Pan‐European Digital Cellular (GSM), North American Digital Cellular (IS‐54), Second Generation Cordless Telecommunications (CT2), and Digital European Cordless Telecommunications (DECT). Finally, we provide a glimpse into the future by presenting work in progress on third generation technology, based on packet transmission and switching.
Access and switching techniques for the broadband network
Authors: Dècina Maurizio , Chiarottino Wolmer , Melen Riccardo , Listanti Marco 
Published: September 2008

AbstractThe objectives and the early technical results of a project for the realization of an ATM local network testbed are described. The aim of the project is to realize a flexible experimentation environment to investigate the critical issues related to the introduction of ATM techniques in the network, including signalling, interworking and service support, in addition to the basic switching technology. After presenting the general structure and the solutions adopted for the testbed, the paper describes the main characteristics of its building blocks currently under development: the switching node with its ATM switching fabric and control units, the access network with the related interfaces and protocols, the customer equipment composed by ATM workstations, ATM terminal adaptors and LAN gateways, the interworking unit connecting the testbed to the telephone network. Finally the resources allocation and policing functions adopted are also discussed.
A fast coefficient computation algorithm for transversal and decision‐feedback equalizers
Authors: Buné Paul A. M. 
Published: September 2008

AbstractDigital transmission is often inflicted by inter‐symbol interference (ISI), which increases the noise sensitivity of the transmission system and eventually causes symbol detection errors on itself. For ISI suppression, a variety of equalizer structures exists, among which transversal and decision‐feedback equalizers are very popular because of their simple primary structure and high degree of flexibility. The paper describes a fast coefficient computation algorithm for these equalizer types starting from a known or estimated channel impulse response, avoiding matrix inversion or iterative coefficient updates by feedback. It has especially been developed for high‐rate TDMA digital mobile radio systems, such as the pan‐European GSM system. Extensive simulations have shown that the performance of the decision‐feedback equalizer (DFE) with this algorithm is fairly comparable with the MLSE/Viterbi equalizer under typical conditions.
Eigenvalue behavior in FH signal rejection in DS spread spectrum systems using complex adaptive filters
Authors: Pajkovié Miodrag Dj. 
Published: September 2008

AbstractEigenvalue behavior of direct sequence (DS) QPSK spread spectrum (SS) receiver using adaptive filters in presence of frequency hopped (FH) interference is analyzed. The analysis is valid both for the adaptive prediction error filters and for transversal filters with two‐sided taps. The improvement factor G depends on filter adaptation rate μ and on transient response of the filter. Thansient responses of the filters using eigenvalue behavior method are analyzed. Presented analysis and results show that slow FH jammer suppression in DS system can be obtained using complex adaptive filters. The adaptation rate dependance on different communication parameters and on discrete time is presented.
A new data structure for variable bit rate broadcast video transmission on ATM network
Authors: Modena Marco , Parladori Giorgio , Vecchietti Giovanna 
Published: September 2008

AbstractThe asynchronous transfer mode (ATM) technique will probably increase the demand for sophisticated video services. The availability of wide bandwidth and fast rerouting at affordable rates will influence the design of new video codecs. Firstly, variable bit rate coding algorithms can efficiently be employed in order to achieve a uniform picture quality at the receiver. Secondly, the impairment due to cell loss that may occur in the ATM environment demands specialized error concealment strategy. In this paper the segmentation and reassembling of the bit stream generated by a hybrid DCT broadcast quality video codec is addressed. A VIDEO PACKET (V.P.), composed of a variable number of ATM cells, is associated to a defined portion of the television signal. Predefined patterns and layered protection included in the V.P. allow the detection of lost cells and consequently the application of a simple error concealment technique.
Throughput analysis of nonpersistent inhibit sense multiple access in multipath fading and shadowing channels
Authors: Prasad Ramjee 
Published: September 2008

AbstractThe capacity of packet radio channels is investigated using the interference model for the coherent and incoherent cumulations in the presence of Rayleigh fading and log‐normal shadowing, assuming a nonpersistent multiple access protocol with inhibit bits to avoid collisions. Expressions for the throughput are derived for uncorrelated packet signals. The combined propagation effects yield higher channel capacity than each individual effect.
Single‐mode optical fibers with geometrical birefringence: Analysis of the propagation by means of finite element method
Authors: Cancellieri Giovanni , Chiaraluce Franco , Checchia Andrea 
Published: September 2008

AbstractThis work presents the results of an analysis regarding propagation in single‐mode fibers conducted by means of finite element method. A particular form of the functional is taken, in order to avoid the presence of nonphysical spurious solutions. Special attention is then given to the choice of the mesh when profile geometry is not circularly simmetric, like in the case of Fibers able to preserve the state of polarization or nominally single‐polarization. This situation has been carefully analysed, showing that particular new kinds of index profiles, such as elliptical azimuthally modulated W profiles, are able to produce extended intervals of single‐polarization operation, to the point where their practical use appears feasible.
A new electronically tunable integrable CCII‐OTA‐based active‐C oscillator
Authors: Abuelma'atti Muhammad Taher 
Published: September 2008

AbstractA new electronically tunable oscillator circuit is proposed. The circuit uses a single current‐conveyor, three operational transconductance amplifiers and two capacitors. The circuit enjoys low sensitivity characteristics and has a high potential for integration in addition to its wide range of electronic tunability.
A methodology for buffer design in ATM switches
Authors: Bernabei Francesco , Ferretti Roberto , Listanti Marco , Zingrillo Giuseppe 
Published: September 2008

AbstractThis paper deals with a general method for buffer design in an ATM system in which the target loss probability should be very low (e.g. less than 10‐9).This method is based on the application of the Generalized Extreme Value Theory (GEVT) on results arising from simulation runs. This theory allows the estimation of very small probabilities which would not be evaluable with traditional Montecarlo approach. An advantage of 4/5 decades with respect to Montecarlo limits can be obtained utilizing the same sample set.The extension of the theory to the case of distribution functions of discrete random variables is here discussed. The applicability of the method is here demonstrated with reference to known probability distribution functions (Exponential, Normal, Weibull, Iperexponential, Geometric, Bernoulli and Poissonian). Moreover, the GEVT is applied in the cases of classical queueing systems, i.e. M/D/l, Geo/D/1 and MMPP/D/1. Finally, the general criteria for the evaluation of the basic GEVT parameters are discussed.
Sinusoidal oscillators with slew‐rate type nonlinearity
Authors: Borys Andrzej 
Published: September 2008

AbstractThis paper is a continuation of [1] and deals with a class of single‐op‐amp sinusoidal oscillators working under the amplitude limiting regime of a slew‐rate nonlinearity. The Wien‐bridge oscillator example is chosen for a detailed analysis. It is shown, using the first‐order determining equation, that the oscillation‐frequency (f0) depends upon the passive elements of the oscillator structure only; it is independent of the op‐amp gain‐bandwidth product (Gfl)! Moreover, the oscillation‐amplitude (A0) is a function of the oscillation‐frequency, of the op‐amp parameters: slew‐rate factor (SR), and GB and finally, of the attenuation of the Wien‐bridge resistive branch (k). Notable is the high sensitivity of the amplitude A0 with respect to the changes in the factor k. Furthermore, an upper bound for the realizable oscillation‐frequency is developed and verified on the experimental data. Finally, the harmonic content (A) is computed for different fo's and compared with those values obtained by means of the describing‐function method.
Performance of heterodyne optical OOK systems with coding
Authors: Majumder Satya Prasad , Gangopadhyay R. 
Published: September 2008

AbstractThe performance degradation of heterodyne optical OOK systems caused by additive receiver noise and phase noise can be substantially overcome by using coding techniques. Using two statistical descriptions of the filtered phase noise process, performance of the coded optical OOK system is evaluated. The results indicate that predictions based on the two phase models closely agree only for sufficiently small ratios of the overall laser linewidth β to the bit rate, namely when βT/M < 2 × 10−2, with T being the bit duration and M the IF bandwidth expansion factor. The analysis further shows that the coded OOK system can attain substantial coding gains; for instance, a coding gain of 10.5 dB is achieved for a rate‐1/2 convolutional code of constraint length K = 7 with βT= 0.64 and M= 10.
Bistatic scattering on a monostatic radar range
Authors: Herdeg Wolfgang F. , Wendel Horst 
Published: September 2008

AbstractSuitable combination of monostatic radar range and reflector plate allows to study bistatic scattering while varying only the aspect angle. We exemplify the scheme by measuring the scattering from an isolated rectangular metal edge. The various scattering contributions are discriminated by high resolution imaging.
Site diversity in land‐mobile cellular telephony network with discontinuous voice transmission
Authors: Linnartz Jean‐Paul M. G. 
Published: September 2008

AbstractCellular radio channels suffer from signal outages due to multipath fading and shadowing. Analytical expressions are given for the probability that the instantaneous C/I‐ratio drops below a required protection ratio. A radio signal from a mobile subscriber exhibits outages at different base station sites with relatively low correlation. The quality of communication over a mobile telephone circuit can be improved by appropriately combining voice segments received at various base stations. The probability of dropping a voice segment for an end‐to‐end «up‐link» circuit (mobile‐to‐PSTN) in an interference‐limited cellular network with discontinuous voice transmission and macro diversity is evaluated mathematically. Asymptotic expressions of the signal outage probability for high average C/I‐ratios are presented in closed form.
Surface acoustic wave resonators
Authors: Avitabile Gianfranco , Roselli Luca , Atzeni Carlo , Manes Gianfranco 
Published: September 2008

AbstractSurface Acoustic Wave (SAW) resonators are implemented by creating a planar resonant cavity, delimited by two distributed, rather than concentrated, mirrors, consisting of arrays of reflecting metal strips. SAW resonators permit to achieve higher frequencies than their bulk‐wave acoustic counterparts with comparable spectral purity and very high Q, while, due to the planar nature, they result of small size and rugged construction.The basic SAW resonator operation, with emphasis on design parameters and device configuration, is presented. A complex simulation package for Computer‐Aided Design of SAW resonators has been developed. Several resonators in the VHF‐UHF frequency band have been designed and tested, exhibiting good agreement with the simulation forecast and state‐of‐the‐art performances.This paper summarizes a three years work conducted under support of the Progetto Finaliz‐zato MADESS, CNR.
Techniques in processing multi‐frequency multi‐polarization spaceborne SAR data
Authors: Curlander John C. , Chang C. Y. 
Published: September 2008

AbstractThis paper presents the algorithm design of the SIR‐C ground data processor, with emphasis on the unique elements involved in the production of registered multi‐frequency polari‐metric data products. A quick‐look processing algorithm used for generation of low‐resolution browse image products and estimation of echo signal parameters is also presented. Specifically, we will discuss the following: 1) Azimuth reference function generation to produce registered polarimetric imagery; 2) Geometric rectification to accommodate cross‐track and along‐track Doppler drifts; 3) Multi‐look filtering designed to generate output imagery with a uniform resolution; and 4): Efficient coding to compress the polarimetric image data for distribution.
Parallel/pipeline multiprocessor architectures for SAR data processing
Authors: Albrizio Rosa , Mazzone Albino , Veneziani Nicola , Aloisio Giovanni 
Published: September 2008

AbstractIn SAR digital data processing, using the range‐Doppler approach, the main computational load occurs in the range and azimuth compressions, for which one‐dimensional circular convolutions in the Fourier domain are used. In the paper it is shown how the intrinsic degrees of parallelism of the process can be efficiently exploited to design a flexible parallel/pipeline multiprocessor architecture, based on advanced components with interconnection capabilities and capable to perform up to the real‐time SAR data focusing. In the proposed architecture, an efficient line compression can be achieved by means of pipelined processors for the range and the azimuth compressions and many of these structures, each performing the compression of a line or its section, can be used to sustain the computational load and the data rate requirements. In the paper, we also show how the data communication between the range and the azimuth processors can be solved when a maximum of eight of these line compressors are used.The performance evaluation of the proposed architecture is made referring to real spaceborne SAR sensors.
On the use of joint time‐frequency representations in SAR signal processing
Authors: Barbarossa Sergio , Gregori Carlo , Nicastro Giuseppe 
Published: September 2008

AbstractThe aim of this paper is to show that some of the open problems in Synthetic Aperture Radar signal processing can be seen in a new and advantageous perspective if the received signals are represented in the time‐frequency domain. The joint time‐frequency representation makes easier the extraction of the information necessary for the formation of the synthetic aperture, responsible for the high cross‐range resolution. The proposed approach is applied to the imaging of moving objects and to the focusing of extended scenes, in presence of instabilities of the radar platform such that the conventional estimation techniques become insufficient. In particular, the time‐frequency analysis allows the estimation of the useful signal parameters even in case of undersampling. This allows the use of relatively low Pulse Repetition Frequencies(PRF), avoiding then the shortcomings due to highPRFs, like the reduction of the sizes of the monitorable areas or the data rate increase.