bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation Doped FETs
Authors: Liu Lianghong , Morkoç Hadis 
Published: April 2005

AbstractOperation and technology of conventional and pseudomorphic modulation‐doped field‐effect transistors (MODFET s) based on conventional semiconductors, SiGe/Si heterostructures, and recently popularized III–V nitride semiconductors are treated. While conventional AlGaAs/GaAs MODFET represent the genesis of these highly successful devices, pseudomorphic MODFET s (PMODFET s) exhibit additional degrees of freedom in the choice of channel composition. This added degree of freedom has led to device structures that can be tailored to a particular application with significant improvement in performance. Experiments carried out with AlGaAs/InGaAs/GaAs and InAlAs/InGaAs/InP PMODFET s demonstrate that these devices are superior to their counterparts with lattice‐matched channels. MODFET s with unprecedented performance, for instance, with a power gain of 7.3 dB at 140 GHz and a noise level of 1.4 dB in the 90‐GHz range, are described. The advent of high‐quality SiGe layers on Si substrates has paved the way to the exploration and exploitation of heterostructure devices in a Si environment. MODFET s based on the Si/SiGe have been achieved with extraordinary p‐channel performance. With 0.25‐μm gate lengths, the current gain cutoff frequency is about 40 GHz. When the gate length was reduced to 0.1 μm, the current gain cutoff frequency increased to about 70 GHz. Finally, owing to their large bandgaps, large high field electron velocity, large breakdown fields, large thermal conductivity, and robustness, wide‐bandgap nitride semiconductors have paved the way to AlGaN/GaN MODFET s with superior power performance. CW power levels of about 6 W have been achieved at 10 GHz in devices with 1 mm gate periphery that are comparable to power densities extrapolated from smaller devices. When four of these devices were power combined in a single‐stage amplifier, a CW output power of 22.9 W with a power‐added efficiency of 37% was demonstrated at 9 GHz. On the noise figure front, a minimum noise figure for a 1‐mm device of 0.85 dB with an associated gain of 11 dB at 10 GHz was obtained.
Monte Carlo Simulation in Reliability
Authors: Leemis Lawrence M. 
Published: April 2005

AbstractSimulation is presented here as a mathematical and computational technique use to analyze probabilistic models. Monte Carlo simulation, where the passage of time does not play a significant role, is presented here, with an emphasis on reliability applications. Monte Carlo simulation methods are often used when analytic methods become intractable, and they typically give a modeler added insight into the structure of a problem. As reliability and lifetime models become less mathematically tractable, Monte Carlo methods will have increasing importance. The topics addressed in here are basic variate generation techniques, the generation of order statistics, the generation of lifetimes for the accelerated life and proportional hazards lifetime models, and variate generation of a renewal or nonhomogeneous Poisson processes. The generation of order statistics is useful for simulating the lifetime of a series, parallel, ork‐out‐of‐nsystem. The generation of lifetime in the accelerated life and the Cox proportional hazards lifetime models is used to account for the impact of covariates on failure. The generation of a renewal or nonhomogeneous Poisson processes is used to model the failure times of a repairable system.
MOSFET Modeling
Authors: Gupta R. S. , Gupta Mridula , Saxena Manoj 
Published: April 2005

AbstractMost of the material presented in this article is intended to improve the accuracy of the microwave circuit performance prediction of MOSFET and to reduce the computer time required for the design process. The focus of this article is on small‐signal analytical modeling for MOSFET incorporating various physical phenomena such as the bulk substrate resistance effect the fringing field effect, and channel length modulation (CLM) for its incorporation into circuit simulation.Section 1 reviews the small‐signal analytical model for the insulated gate field‐effect transistor (IGFET) with bulk substrate resistance effect. Variation of admittance parameter (Y) and scattering parameter (S) with frequency, with and without substrate resistance has been explained. New expressions forYandSparameters have been derived including the fringing field effect discussed in Section 2. In Section 3, a new physics‐based analytical model is explained in which the relation between AC signal,YandSparameters, and the structural parameters of the MOSFET are established by incorporating CLM effect. An analytical model for parasitic resistance has also been developed for submicrometer fully overlapped lightly doped drain (FOLD) MOSFET in Section 4. The parasitic resistance for FOLD structure is described considering the n−region as a modified buried‐channel MOSFET and the channel region as an intrinsic enhancement‐mode n‐type MOSFET. It is also demonstrated that the FOLD structure shows better results than that of the LDD structure because of reduction in series resistance. Finally, an analytical model has been presented to characterize the 1/fand generation–recombinations (GR) noise in the FOLD MOSFET's operating in the linear region. The 1/fnoise model is developed on the basis of oxide‐trap‐induced carrier number and surface mobility fluctuations.
Neural Networks for Microwave Circuits
Authors: Zhang Qi-Jun , Deo Makarand , Xu Jianjun 
Published: April 2005

Abstract
Neural networks are information processing systems whose design was inspired by the studies of the ability of the human brain to learn from observations, and to generalize by abstraction. In the RF and microwave areas, neural networks are used to model passive and active microwave devices to enhance circuit design. Neural networks can be trained using measured or simulated microwave device data. The trained neural networks become models of microwave devices and can be used in place of CPU‐intensive EM/physics models to significantly speed up circuit design. Here we describe the fundamentals of neural networks from RF and microwave perspective. We describe what neural networks are, how to develop them, and how to use them in RF and microwave CAD.
Nonlinear Circuit Analysis
Authors: Suárez Almudena 
Published: April 2005

AbstractThe aim of this contribution is to give an introductory approach to the state‐of‐the‐art methods for simulation of nonlinear RF circuits. Time‐domain integration, the shooting methods, harmonic balance, and the envelope transient method are presented, showing their principles and general formulation, together with their advantages and shortcomings, when applied to different kinds of circuits and different regimes. Most aspects of practical simulation are covered, at an introductory level, such as the possible instability and coexistence of solutions, the modeling of distributed elements, or the simulation of circuits containing a large number of devices. One of the objectives is to help the designer interpret the simulation results and choose among the different simulation methods and simulation options, even when using commercial analysis tools. The different simulation methods are presented at two levels. A first level applies to forced circuits, such as amplifiers or mixers. A more advanced level shows how the particular method has to be complemented to be applicable to the autonomous and synchronized regimes, in which practical circuits such as oscillators and analog frequency dividers operate. The different simulation methods are compared by means of their application to a common circuit, exhibiting different operation modes.
Oscillator Design
Authors: Mathis Wolfgang , Russer Peter 
Published: April 2005

AbstractThe behavior of electronic oscillators can be studied completely only if nonlinear circuit models are utilized. In this article the main fundamental aspects of analytical as well as numerical methods for analyzing oscillatory circuits are reviewed. First, electronic oscillators are modeled as nonlinear dynamical systems and analytical perturbation methods and bifurcation theory (e.g., Andronov–Hopf bifurcation) are used to analyze sinusoidal as well as relaxation oscillators. Then the theory of noise in oscillatory circuits is discussed. In the second part of the article state‐of‐the‐art methods for the numerical analysis of deterministic and noisy oscillators are presented. In almost all sections original results of the authors are included. The methods are illustrated by means of a few examples.
Packaging RF Devices and Modules
Authors: Lee Y. C. , Zhang Wenge , Su Bingzhi , Feng Zhiping , Gupta K. C. 
Published: April 2005

AbstractRF packaging technologies are advancing rapidly. This article provides basic knowledge to understand the technology advances. Most packaging issues common to those for microelectronics packaging will not be covered here, and they can be found in other articles. The following sections will focus on unique issues for RF packaging. Representative packages and assembly technologies will be reviewed. Critical consideration of RF performance and reliability will be introduced. The reliability section will cover both thermal management and mechanical integrity. A case study will be presented to illustrate a typical design procedure considering various factors. In addition, computer‐aided‐design (CAD) issues and advanced packaging concepts will be introduced, to understand future challenges.
Parallel Algorithms and Computing for Large‐Scale Electromagnetic Simulation
Authors: Lam King Wai , Chan Ka Fai , Chan Chi Hou 
Published: April 2005

AbstractThe rapid growth of technology in computing architecture and networking has resulted in fundamental changes in the way we perform computational analysis in science and engineering. Some problems that are intractable because they are computation‐intensive in memory and/or CPU time can now be solved in an effective manner with the help of parallel computing. The aim of this article is to introduce to readers some examples of parallel computing algorithms that were developed for the computational electromagnetics community but are also applicable to other fields in science and engineering. In this article, the construction components of parallel computing platforms are introduced. A Beowulf cluster, which is a system with distributed memory multiprocessor architecture, will be briefly discussed. Some of the most popular simulation techniques in computational electromagnetics such as the finite‐difference time‐domain (FDTD) method and the method of moments (MoM) are discussed. Several methods of solving a full matrix either directly or iteratively will also be discussed. Illustrative examples are given to demonstrate the use of these algorithms and their implementations on the parallel computing platform for solving large‐scale electromagnetic problems.
Periodic Structures
Authors: Bozzi Maurizio 
Published: April 2005

AbstractThis article gives an overview of periodic structures commonly used in the microwave and millimeter‐wave frequency range. The operation principle of the most significant components, their applications and the classical fabrication technologies are described. The basic theory of the propagation of electromagnetic fields in periodic structures is reported, and includes Floquet's theorem and Brillouin zones. Some numerical methods typically adopted for their analysis are described and discussed.
Permittivity and Measurements
Authors: Komarov V. , Wang S. , Tang J. 
Published: April 2005

AbstractDielectric properties of food, agricultural products, biological tissues, resins, plastics, ceramics, soils, and wood at RF and microwave frequencies are considered. The influence of three main factors—frequency, temperature, and moisture content—on complex dielectric constant behavior of lossy materials is analyzed. The most popular measurement techniques—the open‐ended coaxial probe, transmission‐line, and perturbation methods—are described.
Phase Locked Loops
Authors: Kolumbán Géza 
Published: April 2005

AbstractPhase‐locked loops (PLLs) are frequently used in RF and microwave telecommunication systems and measurement equipment to implement various circuits from carrier recovery to frequency synthesis. The goal of this article is to survey the theory and the most important applications of phase‐locked loops. The main emphasis was placed on the analog PLL theory and frequency synthesis. The former is relatively easy to understand and is the basis of every other PLL analysis. The latter is crucial in RF and microwave engineering since frequency synthesizers are used almost everywhere to generate the signals required in the different applications.The PLL article is organized as follows. Section 1 is devoted to the analog PLL theory. First the baseband model is developed and the linear theory of analog PLL (tracking, modulation, and noise) is discussed. Finally, the most important nonlinear effects (acquisition, cycle slips, hangup) are surveyed.Section 2 discusses the most common PLL applications.Section 3 is devoted to frequency synthesis, where both the sampling (sample‐and‐hold‐type phase detector) and charge‐pump (phase–frequency detector with charge‐pump) PLLs are considered. These phase detectors are edge‐triggered circuits; the discrete‐time operation makes the analysis of these PLLs very complex. The problem of discrete‐time operation arising from the application of edge‐triggered circuits is discussed and design methods are given.
Phase Shifters
Authors: De Flaviis Franco 
Published: April 2005

Abstract
A microwave phase shifter is a two‐port device capable of producing a true delay of a microwave signal flowing through it. The produced time delay can be fixed or adjustable, and the phase shifter is accordingly called fixed phase shifter or tunable phase shifter. The geometry of the phase shifter is intimately related to the guiding structure that is used to design it and is also related to the operational frequency. Most phase shifters are realized in waveguides or in planar structures. Electrically, a phase shifter can be characterized by its scattering parameters matrix.
Power Combiners and Dividers
Authors: Bialkowski Marek E. , Tsai Feng-Chi E. 
Published: April 2005

AbstractThe article provides an extensive review on the topic of microwave and millimeter‐wave power combiners and dividers. Because many power combining and dividing structures can be used interchangeably, the review focuses on power combiners. It commences with an introduction of power combining principles and grouping of power combiners into suitable categories. The main categories considered here include circuit‐level (both resonant and nonresonant type) and space‐level power combiners. Next, operation and fundamental characteristics of circuit and space‐level combiners, which have been presented in the microwave literature, are thoroughly explained. In the subsequent sections, analysis methods for power combiner/divider structures are described. They concern both circuit and electromagnetic field approaches. The use of state‐of‐the art computer software for the analysis of power combining/dividing structures is also covered. The last section of the article is concerned with applications of power combiner/dividers in modern communication and radar systems. Examples of most impressive power combiners of solid‐state devices, in terms of an achieved output power level or highest frequency of operation, are presented. The review concludes with remarks on recent progress in the field of space‐level combiners.
Preamplifiers
Authors: Duque-Carrillo J. F. , Torelli Guido 
Published: April 2005

AbstractDespite the improvements carried out in recent years, all sensors have a common characteristic: a weak signal delivered and a limiting noise level. Therefore, the front end of the sensor‐associated electronic system must be an amplifier, usually called apreamplifier.Some basic concepts useful in analyzing preamplifiers from the noise standpoint, namely, equivalent input noise, noise factor and noise figure, and noise matching, are introduced in this section.
Pulse Compression
Authors: Biegert Jens , Diels Jean-Claude 
Published: April 2005

AbstractThree‐wave interaction in a nonlinear medium can be used to efficiently compress transform‐limited laser pulses with the additional option of shifting the center light frequency.After introducing the general mechanism together with a simple numerical model, we derive a more extensive and complete numerical model to study pulse compression of long (ps) and ultrashort (fs) pulses. A comparison between theory and experiment is given, and limitations of the models are established.
Quasi‐Optical Circuits
Authors: Shiroma Wayne A. , De Lisio Michael P. 
Published: April 2005

AbstractQuasioptical circuits use components typically associated with optics, such as lenses, mirrors, and polarizers, but are targeted toward the millimeter‐ and sub‐millimeter‐wave regimes of the electromagnetic spectrum between 30GHz and a few terahertz. This article focuses on active quasioptical circuits used for generating, amplifying, and processing millimeter‐wave beams.
Radar Equipment
Authors: Ressler Marc , Bennett Matthew , Ton Tuan , Nguyen Lam 
Published: April 2005

AbstractIn recent years, the improvements in solid‐state devices and the explosive growth in the capabilities of digital circuits and digital processors have provided new approaches to radar designs. Analog circuits, which tend to be smaller and have lower power consumption, are being replaced with digital circuits, which are more stable in the presence of varying temperature, vibration, and power supply voltages, while providing flexibility often unavailable in the analog domain.
Radar Target Recognition
Authors: Eom Kie B. 
Published: April 2005

AbstractRadar target recognition technology has advanced remarkably as radar technology advances recently. The resolution and features of modern radar system provide enough information to recognize tactical targets. Different types of radar, such as synthetic aperture radar (SAR ), milimeter‐wave (MMW ) real aperture radar (RAR ), and interferometric synthetic aperture radar (IFSAR ), have been explored for radar target recognition. Target recognition from radar signatures is challenging since the radar signature is very sensitive to changes in look angle. There have been different approaches utilizing unique characteristics of different radar types, and they are reviewed in this article. They are hierarchical modeling of MMW RAR radar signatures for noncoorpertative target recognition, fusion of IFSAR data Earth orbit data for discriminating targets of different heights, the neural network approach, spatial matched filter for SAR , and fusion of multiple sensors.
Radio Direction Finding
Authors: Johnson Richard L. , Hipp Jackie E. , Sherrill William M. 
Published: April 2005

AbstractRadio direction finding (DF) is a technique for estimating radiowave angle of arrival (AoA) and is based on prior knowledge of the antenna responses versus AoA.Traditional DF systems exploit rotating antennas or sampled antenna arrays for which the antenna response patterns are very carefully controlled to provide support for closed‐form DF solutions or for the development of steered beams. Sources contributing to DF errors include local scattering, instrumentation, and propagation. Some more recent DF systems exploit array calibration and digital beamforming techniques to provide reliable AoA estimates while accomodating local scattering. Both of these DF system categories are designed for operation against single component plane waves. More sophisticated DF systems now exploit sampled arrays and DF processing to decompose the complex wavefields created by multiple simultaneous signal components.
Radio Navigation
Authors: Bendixen Gerald 
Published: April 2005

Abstract
A key function of navigation is the estimation of current position of a vessel. The reception of radio signals from transmitters whose location is known is a common means of implementing the position estimation functions. Several different schemes have been developed. A thetatheta system determines the position by the vessels bearing with respect to two transmitters. Rhotheta system use radio signals to determine distance and bearing with respect to the transmitter. Rhorho systems are based on distance measuring equipment (DME) that determines the position of an aircraft using two or more distance values. Hyperbolic systems measure the time delay of signals simultaneously transmitted from three or more stations. The accuracy of each navigation scheme is dependent on the particular implementation. The following sections describe the characteristics of the different equipment.
Radiowave Propagation in Multipath Channels
Authors: Koilpillai R. D. 
Published: April 2005

Abstract
With the rapid growth in wireless communications, there is considerable interest in radiofrequency (RF) propagation and RF channel modeling in the 400 MHz–2 GHz band, where multipath propagation is a characteristic property. This article presents a comprehensive overview of the RF signal variations related to propagation in multipath fading channels. The diverse phenomena that cause signal variations are described via mathematical models. The different types of fading and their salient features are discussed in detail. The goal of this article is to provide a mathematical and an engineering‐oriented treatment of multipath fading, thereby providing the reader with the necessary tools and the information to understand the different RF propagative issues and how they impact wireless communications.
Refraction and Attenuation in Troposphere
Authors: Allnutt Jeremy E. 
Published: April 2005

AbstractWhere two dissimilar media form a common boundary, the different refractive indices of the media will cause the signal direction to diverge from its path if the incident direction is not normal to the boundary. This is called refraction.The average refractive index of a medium is called the bulk refractive index, and it affects the average direction of the electromagnetic energy.In addition to changing the direction of travel of an electromagnetic signal and/or causing scintillations, a medium can both extract energy from a signal passing through it and alter the orientation sense of the electric vector (the polarization) of the signal as it passes through. The loss of energy is called attenuation, and the change in polarization sense is generally referred to as depolarization.
Radar Remote Sensing
Authors: van Zyl Jakob J. , Kim Yunjin 
Published: April 2005

AbstractIn this article, we present the basic principles of how remote sensing radars work. These include SARs (synthetic aperture radar), scatterometers, altimeters, sounders, cloud radars, and rain radars. Radars are active sensors; they provide their own illumination and therefore can be operated during day or night. An additional advantage of particularly lower‐frequency radars is their ability to penetrate clouds, rain, tree canopies, and even dry soil surfaces. We start the discussion by defining the basic concepts of resolution, the radar equation, signal fading, and the geometric distortions associated with the radar imaging geometry. We also include a description of advanced SAR techniques (polarimetry, interferometry, and polarimetric interferometry) and their applications. We complete the chapter by briefly examining nonimaging radars such as scatterometers, altimeters, radar sounders, and meteorological radars. An extensive list of references is provided for each radar for readers who need an in‐depth description of a particular radar.