bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electromagnetic Modeling
Authors: Vahldieck R. , Hoefer Wolfgang J.R. 
Published: April 2005

AbstractNumerical modeling of electromagnetic (EM) fields or computational electromagnetics is a combination of numerical methods and field theory.This article will focus only on some mainstream techniques, most of which employ either the method of weighted residuals or variational principles.We will begin with modeling techniques in the frequency domain, most importantly the method of moments (MoM). This section is followed by time‐domain methods and here in particular the finite‐difference time‐domain method (FDTD) and the transmission‐line matrix (TLM) method. Finally, a brief overview with respect to hybrid methods concludes this article. A comparison between the various modeling approaches as well as their advantages and disadvantages is added where appropriate.
Fast Fourier Transforms and Nufft
Authors: Liu Qing Huo 
Published: April 2005

AbstractThe fast Fourier transform (FFT) algorithm is one of most fundamental and powerful computational tools in computational science and engineering. In this article, the development of the fast Fourier transform algorithm is reviewed, some representative applications in electromagnetics are illustrated, and some recent developments in extending the FFT algorithms to nonuniformly sampled data and to discontinuous functions are summarized.
Feedforward Amplifiers
Authors: Gardner P. 
Published: April 2005

AbstractA feedforward amplifier is a transmitter subsystem in which feedforward linearization is used to correct for the effects of nonlinearities in the gain and phase response of a basic amplifier.Such nonlinearities have the effect of generating intermodulation products in multicarrier systems, and spectral regrowth in systems that use bandlimited, nonconstant envelope modulation. Odd‐order intermodulation is a particular problem in communication systems because it can generate spurious signals very close in frequency to the wanted signals, often in adjacent communication channels. Similarly, spectral regrowth is a problem because it generates unwanted noise or crosstalk in adjacent frequency bands, violating the tough out‐of‐band emissions specifications imposed by modern communication standards. The problems can be reduced, in principle, by the use of separate amplifiers for each channel, and/or linear class A amplifiers backed off well below saturation, but these measures make transmitters highly inefficient.A better compromise between efficiency and linearity can be achieved by using artificial linearization techniques. This article describes one such technique: feedforward linearization. The basic principle of operation is described, the practical limitations are discussed, and comparisons with other linearization techniques are also made. Some advanced techniques are also introduced, including dual‐loop feedforward amplifiers and adaptive feedforward.
Ferrite Loaded Waveguides
Authors: Marqués Ricardo 
Published: April 2005

AbstractThis article describes the main physical effects due to the propagation and guidance of electromagnetic waves in ferrite‐loaded waveguides useful in microwave technology. The linear approach, in which the high‐frequency magnetic susceptibility of the ferrite is a function susceptibility of the ferrite is a function static magnetic field, will be considered valid. This approach includes the analysis of exchange free electromagnetic waves, as well as magnetostatic waves approximations, but not the analysis of spin waves nonlinear effects, magnetoelastic waves, and other complex interactions.
Enhancements of the Finite Difference Time Domain Method
Authors: Mittra Raj , Yu Wenhua , Chen Yinchao 
Published: April 2005

AbstractThere are two major challenging issues encountered in using the conventional finite‐difference time‐domain (FDTD) methods for solving electromagnetic field problems, namely, reducing the errors introduced by the staircasing approximation used to model objects with curved surfaces, and the dispersion effects when the number of cells per wavelength is not sufficiently large. In the first part of this article, we describe a conformal FDTD scheme that mitigates the staircasing error, regardless of whether we are dealing with PEC or dielectric objects. Next, we go on to discuss the multiresolution time‐domain (MRTD) method for the purpose of reducing the dispersive error introduced by large cell sizes in the conventional FDTD scheme. Several representative examples are employed to validate both of the proposed techniques.
Finite‐Difference Time‐Domain Analysis
Authors: Taflove Allen , Hagness Susan C. 
Published: April 2005

AbstractThe finite‐difference time‐domain (FDTD ) solution of Maxwell's equations is a robust and popular computational technique in science and engineering for modeling electromagnetic wave interactions with complex material structures. This article reviews key elements of the foundation of FDTD analysis as well as selected recent and emerging FDTD application areas.
Finlines
Authors: Hoefer Wolfgang J. R. , Vahldieck Ruediger 
Published: April 2005

AbstractFinlines are guiding structures for electromagnetic waves that consist of one or several metallic fins suspended in theEplane of a waveguide enclosure. They are the basic transmission media for the so‐called integratedE‐plane circuit technology.Finlines are applied predominantly in the frequency range between 10 and 100 GHz; but some applications at frequencies up to 170GHz have been realized. Having losses of typically 0.1 dB per wavelength, finlines are not suitable for long‐distance transmission. However, they excel as a circuit medium for millimeter‐wave components and systems due to their low manufacturing cost, wide single‐mode bandwidth, compatibility with discrete active and passive devices, and suitability for integration with other hybrid circuit techniques as well as with standard rectangular waveguides.
Frequency Standards, Characterization
Authors: Ferre-Pikal Eva S. , Walls Fred L. 
Published: April 2005

AbstractWe describe the characterization of frequency standards following the general definitions accepted by the IEEE, the International Telecommunications Union—Radiocommunications (ITU‐R), and the International Radio Consultative Committee (CCIR). We describe what is meant by accuracy and frequency stability of a frequency standard. The variations in frequency (which define the frequency stability) can be classified into two basic types: random and systematic. To characterize random variations in frequency, the systematic effects must be removed from the data. Special statistical techniques other than the standard variance must then be used to quantify random variations in frequency because some of the noise processes are not stationary. As part of the statistical treatment, we describe how to determine confidence intervals for the estimates of the various types of random frequency noise.
Frequency‐Domain Circuit Analysis
Authors: Biey Mario , Maio Ivan A. 
Published: April 2005

AbstractBy using suitable transformationsthat is, Laplace transform or Fourier transform the original integrodifferential equations, which are linear with constant coefficients, are reduced to algebraic equations, where the original time functions are substituted by complex‐valued functions of a complex variable ssjo in the case of Laplace transform, or simply jo in the case of Fourier transform. Then the system of linear algebraic equations is solved for the new transformed functions. Finally, an inverse transformation recovers the requested voltages or currents as functions of time. When following this procedure, the analysis is said to be performed in the frequency domain or, alternatively, in the s domain when an explicit reference to the Laplace transform is preferred.
Gallium Nitride for Electronics
Authors: Lee Jong-Wook , Adesida Ilesanmi 
Published: April 2005

AbstractIn addition to their usefulness in optoelectronic applications, GaN‐based devices also have excellent electronic properties such as high critical breakdown fields, high saturation velocity, and good thermal conductivity. Many laboratories around the world have demonstrated microwave power performance for GaN devices that are far superior to the performance of other solid‐state device technologies. The GaN‐based high‐electron‐mobility transistor (HEMT) is considered an ideal candidate for highpower and high‐temperature RF/microwave applications.
High‐Temperature Superconductors
Authors: Mansour Raafat R. 
Published: April 2005

AbstractThis article provides an overview of the microwave applications of high‐temperature superconductor (HTS) technology. The main characteristics of HTS materials are outlined, highlighting the differences between superconductors and normal conductors. The article also presents the most recent progress in the development of HTS filters, multiplexers, cryogenic receivers, delay lines, and antennas. A brief summary of cryocooler technology and cryopackaging requirements is presented. The benefits of using HTS technology in wireless and satellite systems are also discussed. Newcomers to the field are encouraged to continue reading about the subject to understand more about the potential challenges and limitations of this revolutionary technology.
IMPATT Diodes and Circuits
Authors: Mc Clymonds James W. 
Published: April 2005

AbstractThis article will explain the basic principles for designing IMPATT diode circuits, beginning with the characteristics of the diodes. General circuit principles will be discussed, and calculations of amplifier circuit performance will be illustrated. The general principles then will be applied to several types of single‐diode circuits. Last, an approach for building very high‐power transmitters with hundreds of diodes will be shown.
Integrated Circuits
Authors: Ranganathan N. , Venkataramana Raju D. 
Published: April 2005

AbstractThe field of integrated circuits is broad. The inert substrate processes, further divided as thin and thick film processes, yield devices with good resistive and temperature characteristics. However, they are used mostly in low‐volume circuits and in hybrid ICs. The two most popular active substrate materials are silicon and gallium arsenide (GaAs). The silicon processes can be separated into two classes: MOS (the basic device is a metal oxide semiconductor field effect transistor) and bipolar (the basic device is bipolar junction transistors).The transistor–transistor logic (TTL) family of circuits constitutes the most popular type of bipolar and is still used in many high‐volume applications. The emitter‐coupled logic (ECL) devices are used for high‐speed parts that form the critical path delay of the circuit. The MOS family of processes consists of PMOS, NMOS, CMOS, and BiCMOS.
Magnetrons
Authors: Osepchuk John M. , Ruden Thomas E. 
Published: April 2005

AbstractThe magnetron has survived in an era when most electron tubes have been replaced by solid‐state devices in modern electronic systems.A wide spectrum of related devices are being developed for specialized applications. These include crossed‐field amplifiers, voltage‐tuned magnetrons, beacon magnetrons, and relativistic magnetrons. Applications range from the classical radar through industrial heating to microwave weapons.Future applications remain unpredictable, but many are being explored. Advances in computer modeling will eventually produce success.
Microstrip Transitions
Authors: Holzman Eric L. 
Published: April 2005

AbstractMicrostrip line is a printed microwave transmission line used to interconnect microwave devices on an electronic circuit board. Coaxial and waveguide transmission lines are used to interconnect different electronic circuit boards. Thus, transitions are often required between microstrip and other transmission lines. These transitions must have low loss and be well matched, be easy to fabricate and be mechanically robust. This article surveys many of the most commonly used microstrip transitions.
Low Noise Amplifiers
Authors: Nair Vijay 
Published: April 2005

AbstractThis article discusses the noise theory of silicon and GaAs devices and its application in microwave amplifiers. Discussions of small‐signal equivalent circuits, amplifier gain and stability criteria, gain, and noise figure circles are included. Narrowband and broadband amplifier design procedures and specific considerations are also explained. Low‐noise amplifier (LNA) design techniques and some LNA examples are also presented.
Microwave Circuits
Authors: Gupta K. C. , Cebi Haki , Cho Choonsik , Feng Zhiping 
Published: April 2005

AbstractThe term “microwave circuits” is used to identify the electrical circuits used at microwave frequencies for performing signal processing functions like amplification, frequency conversion, mixing, detection, phase shifting, filtering, and power dividing. By “microwave frequencies,” we refer to electromagnetic signals whose wavelength is in centimeters, roughly from 30 cm to 1 mm with the corresponding frequencies ranging from 1GHz (GHz=109 Hz) to 300 GHz. band. Microwave frequencies present several interesting and unusual features not found in other portions of the electromagnetic frequency spectrum. These features make microwaves uniquely suitable for several useful applications in telecommunications, radar, industrial heating and sensors, and so on. The most common consumer application of microwaves is the domestic microwave oven used for food processing.
Microwave Integrated Circuits
Authors: Das Nirod K. , Bolle Donald M. 
Published: April 2005

AbstractIn this article a general overview and basic principles of operation of a class of highly integrated analog devices and circuits, used for applications in the microwave and millimeter‐wave frequency range, are presented. Although there are subgroups of sister technologies that evolved over the years, having different acronyms such as MIC (microwave integrated circuits in hybrid form), MMIC (monolithic microwave integrated circuits), and MCMs (multichip modules), their basic principles of operation are similar, with their objectives and scopes rapidly overlapping. The discussions in this article may be directed to a broad class of such integrated circuits, referred to in general as microwave and millimeter‐wave integrated circuits, with “MMIC” as a generic acronym.
Microwave Limiters
Authors: Kaul Roger 
Published: April 2005

AbstractA microwave limiter is designed to allow low‐power signals to pass through it, while attenuating high‐power signals. Stated another way, microwave limiters are powerdependent attenuators that prevent intense microwave energy from interfering with susceptible microwave components in the latter stages of a cascade.Many microwave limiter technologies have been investigated since the midtwentieth century. The solid‐state limiter, which was first designed using the varactor diode, today employs the Si pin (or PIN) diode because of the pins lower capacitance per unit area resulting in better thermal characteristics, in addition to the fact that it requires no external power supply. Also a MESFET‐based, MMIC‐compatible microwave limiter is being developed for integration with the low‐noise amplifiers common in MMIC designs. Furthermore, although gaseous limiters are widely used in high‐power radars as receiver protectors, ferrite limiters have not found the same wide use.
Microwave Measurements
Authors: Ferrero Andrea , Teppati Valeria , Pisani Umberto 
Published: April 2005

AbstractThis contribution discusses microwave measurements principles and techniques. The first section describes power, spectral, and noise measurements. Section 2 discusses network analyzer measurements, calibrations, and time‐domain reflectrometry. Finally, some advanced measurement techniques, as load‐pull and time‐domain waveform characterization, are described.
Microwave Solid‐State Devices
Authors: Schreurs Dominique M. M.-P. 
Published: April 2005

AbstractThis article presents an overview of the solid‐state devices that are now being used in telecommunication systems. We discuss several families of microwave and millimeter‐wave diodes and transistors. For each device type, we briefly describe the physical operation, discuss the properties and frequency limitations, and outline the main application areas.
Military Communication
Authors: Wang Charles C. , Nguyen Tien M. , Goo Gary W. 
Published: April 2005

AbstractIn general, military communication systems are different from ordinary systems in various specific security requirements, namely, robustness in hostile environments, shielding from adversaries, and immunity from unfriendly eaves‐dropping. Hostile environments to communications are radiofrequency interference (RFI), spoofing, jamming, and fading, either natural or human‐made. In recent years, synthetic aperture radar (SAR) has been extensively utilized for remote sensing.
Millimeter‐Wave Integrated Circuits
Authors: Wang Huei , Lin Kun-You , Liu Ren-Chieh , Chang Hong-Yeh 
Published: April 2005

AbstractMillimeter‐wave (MMW) components are becoming more available and affordable because of advances in design, processing, testing, and packaging technology. MMW circuits have become smaller, highly integrated, and low‐cost, and are being applied in instrumentation, electronic warfare, satellite communications and other applications. As a result, many MMW systems are being developed and deployed that provide new and unique capabilities such as more information transfer (wider bandwidth), enhanced precision (higher resolution), and all‐weather operation (through fog, dust, and smoke), for both military and commercial applications. Monolithic MMW integrated circuits (MMICs) are crucial to meet the requirements for the MMW systems and play an important role in the MMW components. This article describes the current status of MMW monolithic integrated circuits, including the MMIC technologies, representative designs, and performance for various integrated circuits.
Mixer Circuits
Authors: Kimura Katsuji 
Published: April 2005

AbstractMixers are used to shift the received signal to an intermediate frequency, where it can be amplified with good selectivity, high gain, and low noise, and finally demodulated in a receiver. Mixers have important applications in ordinary low‐frequency and microwave receivers, where they are used to shift signals to frequencies where they can be amplified and demodulated most efficiently. Mixers can also be used as phase detectors and in demodulators, and must perform these functions while adding minimal noise and distortion.
Mobile Radio Channels
Authors: Vaughan Rodney G. 
Published: April 2005

AbstractIn this article we describe the properties of a communications channel when one or both of the radio terminals is moving. Examples of such channels occur with vehicular terminals and cell phones. However, some properties of these channels also occur in links where some form of multipath occurs, such as point‐to‐point links, where there is also a ground bounce path; long‐range point‐to‐point links with atmospheric refractive paths; and non‐line‐of‐sight links, which rely on radiowave scattering for the propagation paths. The changing phase mix of the multipath causes signal fading and propagation paths. The changing phase mix of the multipath causes signal fading and Doppler shifts in the channel, and these conspire to degrade the quality and capacity of both analog and digital communications. The physical link characteristics and their effects on a digital link are described using tractible mathematical and statistical models.
Monolithic Microwave Integrated Circuits (MMICs)
Authors: Bahl Inder J. 
Published: April 2005

AbstractAdvanced military and microwave systems are demanding increased integration, reliability, radiation hardness, compact size, and lower cost when produced in large volume, whereas the microwave commercial market, including wireless communications, mandates low‐cost circuits. Monolithic microwave integrated circuit (MMIC) technology provides an economically viable approach to meeting these needs. This article deals with MMIC fabrication, substrates, matching networks, active devices, and monolithic design of microwave components and circuits, including device modeling and EM simulations. Typical monolithic microwave circuits and their performance, and MMIC packaging are also discussed.
Multibeam Antennas
Authors: Balling Peter 
Published: April 2005

AbstractThe article introduces multibeam antennas by reviewing a number of applications describing their importance for modern radar and communications systems. Simple aperture distributions and antenna sizing formulas for beamwidth and gain rolloff are discussed, and examples are provided on the implementation of both active and passive multibeam antennas using different beamforming technologies.The problem of forming simultaneous multiple beams from a common aperture is investigated considering the Stein limits for passive antennas. The implementation of optimum beamforming networks is discussed. Both array antennas and array‐fed reflector antennas, including dual‐ and multimode antenna systems, are reviewed.The design of multibeam reflector antenna systems is considered in detail. Scan aberrations and cross‐polarization effects of the signal‐offset reflector are quantified, describing means to improve the antenna performance. The potential of compensated dual‐offset reflectors, including front‐fed and side‐fed offset Cassegrain antennas for large scan angles, is demonstrated.
Multiple‐Access Schemes
Authors: Sidi Moshe 
Published: April 2005

AbstractMultiple access schemes are natural not only in communication systems but also in many other systems such as computer systems, storage facilities, or servers of any kind, where resources are shared by a number of nodes. In this article we address mainly shared communication channels.The goal of this article is to survey typical examples of multiple access schemes. These examples include TDMA, FDMA, Aloha, polling, and tree‐based schemes. The allocated space for the topic of multiple access schemes in the encyclopedia (which is yet another shared resource) is just too tiny to include all the ingenious multiple access schemes that have been designed by researchers over the years.
Noise Generators
Authors: Upadhyaya Shambhu J. 
Published: April 2005

AbstractNoise has been studied extensively in the literature because noise reduction is one of the major goals. A more compelling reason for the study of noise is its potential application in real life. These applications encompass biomedical engineering, electronic circuits, communication systems, cryptography, computers, electro‐acoustics, geosciences, instrumentation, and reliability engineering. This article addresses the various noise generation techniques and implementing them in analog and digital circuit technology and concludes with a discussion of typical applications.
Noise, Hot Carrier Effects
Authors: Matulionis Arvydas 
Published: April 2005

AbstractThis article deals with electronic noise caused by electrons and holes in semiconductors. For simplicity, the term electrons will be used, unless mentioning holes is necessary for specific reasons.Measuring noise out of equilibrium provides new information about kinetic processes in electron gas–new as compared with that available from the average values of observables. As a result, investigation of hot electron noise proves to be a powerful tool for diagnosing nonequilibrium states in semiconductors subjected to high electric fields. Moreover, the knowledge obtained of the microscopic origin of hot‐electron noise helps to control it and suggests how to eliminate some sources of excess noise through improvement of material technology and circuit design, thus contributing to development of highly sensitive low‐noise devices.