bluuebunny/crossref_metadata_2025 huggingface dataset:
Gyrators
Authors: Frey Douglas R.
Published: April 2005

Agyratoris a nonreciprocal electrical network. It is capable of transforming signals or energy represented in terms of one electrical quantity, such as voltage or magnetic field, to another electrical quantity that may be of similar type or of a complementary type, such as current or electric field. Such networks are quite useful in electronic systems, since one often wishes to design systems with a limited set of component types or with restrictions regarding certain physical parameters.
Gyrotrons
Authors: Ives R. Lawrence
Published: April 2005

Gyrotrons and gyroamplifiers produce high levels of RF power between 20 and 200 GHz. Power levels range from a few kilowatts to more than 1 MW of continuous or pulsed power. Because these devices use overmoded RF circuits, they are not subject to size limitation imposed by most linear beam, vacuum, or RF sources. Consequently, high levels of RF power can be produced while avoiding excessive thermal loading from RF losses on the device structures. Gyrotrons are most commonly used to heat plasmas in fusion devices, such as tokamaks and stellerators. Other applications, such as ceramic sintering, microwave chemistry, and RF sources for accelerators and colliders, are also being explored. Gyroamplifiers are being developed for high‐power radar at frequencies above 30 GHz. Research is continuing to increase the output power of both oscillators and amplifiers.
Hankel Transforms
Authors: Rahman M.
Published: April 2005

The object of this article is to introduce integral transform of a particular type, called theHankel transform, and to illustrate theuseof this method by means of examples. The treatment is that of a review article and as such is not meant to be exhaustive; its aim is to give a concatenated account of known results rather than present new ones. The emphasis throughout is on those results that are of frequent occurrence in boundary value problems of mathematical physics, but some indication is also given for possible theoretical investigations.
Harmonics Oscillators, Circuits
Authors: Linares‐Barranco Bernabé , Rodríguez‐Vázquez Ángel
Published: April 2005

In electronics a harmonic oscillator is an electronic circuit that generates a sinusoidal signal. This signal can either be a voltage, a current, or both. Harmonic oscillators are not restricted to electronics. They can be found in many other disciplines. However, they always can be described by similar mathematical equations. A very familiar harmonic oscillator is the harmonic pendulum, which is found in many high‐school physics textbooks.
Helical Antennas
Authors: Adams Arlon T. , Lee Jay K.
Published: April 2005

The helical antenna operates in several different modes. At lower frequencies, thenormalmode predominates, with a beam pattern similar to that of a dipole along the helix axis. As frequency increases and helix circumference approaches one wavelength, two new modes appear. Theaxialmode radiates along the forward direction of the helix axis. It is broadband and circularly polarized. Thebackfiremode radiates along the backward direction of the helix axis, scanning forward in a conical beam as frequency increases.

The quadrifilar helices, along with other multifilar helices, show many of the characteristics of the monofilar helix with some important differences. All three modes are exhibited. The bandwidth of theaxialmode is increased roughly in proportion to the number of wires. Thebackfirequadrifilar helix is useful for mobile communications.

The radiation theory of the helix antennas is outlined. Numerous applications of the different modes are presented. Recent work on human proximity effects is noted.
High‐Frequency Broadcasting
Authors: Elliot Kim Andrew
Published: April 2005

High‐frequency (HF) broadcasting, more commonly known as
shortwave broadcasting
, employs the long‐distance capabilities of skywave propagation for transmissions over long distances. HF is used for international broadcasting. Some international broadcasters additionally use the mediumwave broadcast band (standard AM) to reach audiences in nearer target countries. HF is also used for domestic broadcasting in countries with large remotely populated regions (e.g., Russia, China, Canada, Australia) and in tropical countries, where the effectiveness of mediumwave broadcasting is reduced by poor soil conductivity and static from lightning.
Horn Antennas
Authors: Jull Edward V.
Published: April 2005

A “horn” antenna is a length of conducting tube, flared at one end, and used for the transmission and reception of electromagnetic waves. For an efficient transition between guided and radiated waves, the horn dimensions must be comparable to the wavelength. Consequently horns are used mostly at centimeter and millimeter wavelengths. At lower or higher frequencies they are inconveniently large or small, respectively. They are most popular at microwave frequencies (3–30 GHz), as antennas of moderate directivity or as feeds for reflectors or elements of arrays.
Impedance Transformers and Matching Networks
Authors: Wu Ke , Deslandes Dominic , Cassivi Yves
Published: April 2005

Impedance transformers and matching networks are probably the most widely used building blocks in both passive and active radiofrequency (RF ) and microwave circuits, which can be found everywhere in various systems and applications. The transmission‐line technique is fundamental in the design of impedance transformers and matching networks at microwave frequencies, whatever distributed or lumped element platforms are used. This article presents the basic structures and electrical mechanisms of impedance transformers and matching networks as well as transmission‐line transitions, including typical balun structures. Properties and performances of various circuit elements are summarized, discussed, and compared. Popular examples are shown to highlight application aspects and technical features of practical impedance transformers and matching networks.
Integral Equations
Authors: Rao S. M. , Gothard G. K.
Published: April 2005

Integral equations form a very important branch of mathematics. Unfortunately, very few equations can be solved analytically. In this work, we propose a general numerical method to solve the given integral equation. The method is versatile and has been applied to a variety of problems in the areas of electromagnetics and RF engineering.
Its Radio Service Standards and Wireless Access in Vehicular Environments (ITS‐WAVE) at 5.9 GHZ
Authors: Gerges Ramez L.
Published: April 2005

Communications and information technologies are at the core of Intelligent Transportation Systems (ITS). This article describes ongoing activities to create a new family of standards that supports the emerging intelligent transportation systems (ITS) and telematics wireless markets. The Wireless Access in Vehicular Environments (WAVE) is a radiocommunication system intended to provide seamless, interoperable services to surface transportation systems.
Intermediate‐Frequency Amplifiers
Authors: Walker H. R.
Published: April 2005

Intermediate‐Frequency (IF) amplifiers are used to raise the signal level to a level that can be used by the decisionmaking circuits to properly utilize the received information. While raising the signal level, they must also remove adjacent channel interference and images with filters so that only the desired signal passes. There are many versions of IF amplifiers, most of which are covered here.

The most recent practice is to use integrated circuits and digital signal processing where possible. In many cases, however, this is not possible, and it is necessary to use circuits with the basic component parts in order to accomplish the desired task. The necessary design principles are given.
Electromagnetic Inverse Problems
Authors: Qing Anyong , Gan Yeow Beng
Published: April 2005

Electromagnetic inverse problems are discussed in this article. First, these problems are defined; then the mathematical challenges involved and some future research directions in this topic are discussed. A survey on the state of the art in electromagnetic inverse problems is presented next. The survey includes a brief history of the research on electromagnetic inverse problems, an overview of practical application areas, and a brief summary of the fundamental theories involved in the electromagnetic inverse problems and the inversion algorithms developed. The survey also covers the well‐known real dataset and the tested inversion algorithms. Finally, a standard electromagnetic inverse problem—the reconstruction of multiple perfectly conducting cylinders—is presented to demonstrate clearly the aspects of the electromagnetic inverse problems.
Klystron
Authors: Tallerico Paul J.
Published: April 2005

The klystron is a vacuum electron device for transforming DC energy into RF energy, and it may be either an oscillator or an amplifier. In the past, small reflex klystron oscillators were used as local oscillators in microwave receivers, but these oscillators are not used in modern equipment. Therefore the amplifier klystron is emphasized in this article.
Local Area Networks (LAN)
Authors: Evans Joseph B.
Published: April 2005

Local Area Networks (LANs) are data communications networks within offices, homes, or areas as large as campuses. LANs are based on physical technologies ranging from copper wiring and optical fiber to radio systems. There are a number of commonly used and emerging LAN technologies that offer the opportunity to connect computers and all manner of devices such as sensors and instruments to increasingly pervasive networks.
Loop Antennas
Authors: Siwiak Kazimierz
Published: April 2005

Loop antennas are simple and versatile structures that appear as communication antennas in diverse applications, including pager receivers and massive multielement transmitting arrays. They are analyzed here in electrically small form as nonresonant magnetic field probes, as efficient resonated small antennas, and as large self‐resonant antennas. A rigorous generalized loop analysis in this article reveals details of the current density both along the loop circumference and around the wire circumference. Expressions are given for the loop impedance and loop near fields. The relatively low near‐field wave impedances make loops particularly suitable for body proximate receiving devices, while in the full‐wavelength‐sized structures, where very high transmitter power levels are required, they are suitable because they are not prone to high voltage corona discharge problems.
Magnetic Shielding
Authors: Fugate David W. , Young Frank S.
Published: April 2005

In traditional usage,
magnetic shielding
refers specifically to shields made of
magnetic
materials like iron and nickel. However, this article is more general because it covers not just traditional magnetic shielding but also shielding of alternating magnetic fields with conducting materials, such as copper and aluminum. In typical applications, shielding eliminates magnetic field interference with electron microscopes, computer displays (CRTs), sensitive electronics, or other devices affected by magnetic fields.
Method of Moments
Authors: Kishk Ahmed A.
Published: April 2005

To enable nonexperts in the field to quickly gain some understanding of the method of moments (MoM), the basic principle of the MoM technique is described by an analogy with numerical integration. Then a simple 2D scattering from an infinite conducting cylinder is considered to show the beginner how to formulate a problem and obtain the integral equations to be solved using the method of moments. Formulations for the problem of multihomogeneous dielectric materials are considered. Different possible formulations are presented and discussed. The problems involved in some formulations for conducting objects and how to overcome them are discussed. More detailed reading on different MoM applications is available in the literature listed in the Bibliography at the end of the article.
Microstrip Antennas
Authors: How Hoton
Published: April 2005

This article introduces two calculational methods capable of describing quantitatively the antenna performance. The first method, calledresonant cavity model, is less rigorous but nevertheless has the advantage of being more analytical and, hence, it can be applied with ease. The cavity model is considered inappropriate for a microstrip structure showing a thick substrate, or if the dielectric constant of the substrate is large, because under these conditions excitation of surface waves is significant. The second calculational method concerns the Green function analysis. AGreen functionis defined as the solution of a differential/integral equation under a point source excitation satisfying homogeneous boundary conditions. By using the dyadic Green's functions, the general field solution in a stratified structure excited by external current sources can then be formulated in terms of an integral equation, which is subsequently solved by applying the numerical Galerkin method. This article outlines procedures to calculate the engineering parameters of a microstrip antenna of an arbitrary geometry, and it illustrates calculational results on circular microstrip antennas, showing plots in radiation frequencies, bandwidths, far‐field patterns, input impedances, effects in feeder‐line positions, and interference between antennas. The dyadic Green's functions involving anisotropic/gyromagnetic materials are also introduced, and the transfer matrix technique is explained. A transfer matrix translates the tangential components of the electromagnetic field over one layer of a stratified structure satisfying the boundary conditions therein. Recent developments on printed circuit antennas are reviewed, including the important broadband techniques employing stacked parasitic elements to achieve high gain and low cross‐polarization level. Fractal antennas involving a patch geometry exhibiting a fractional dimension are then introduced.
Microstrip Antennas, Broadband
Authors: Luk K. M. , Mak C. L. , Chair R. , Wong H. , Lee K. F.
Published: April 2005

With <1% in bandwidth, the first microstrip patch antenna has limited applications, mainly for defense purposes. With tremendous effort dedicated to the bandwidth enhancement of microstrip antennas, they are now becoming the most popular antennas selected for modern wireless communications. This article collects different approaches for enhancing the bandwidth of microstrip antennas, including the stacked‐patch, U‐slot patch, and L‐probe coupling techniques. Emphasis is placed on the L‐probe technique, which is demonstrated to be attractive for the development of wideband dual‐polarized patch antennas, and wideband miniature patch antennas for state‐of‐the‐art mobile communications. Throughout the article, design guidelines and principles of operation for most of the designs are highlighted.
Microstrip Circuits
Authors: Edwards Terry C.
Published: April 2005

The general geometry of microstrip materials and techniques for its manufacture are discussed in the article, where the basic advantages are also described in comparison with other types of MIC and MMIC transmission lines.
Microstrip Lines
Authors: Ma Zhewang , Yamashita Eikichi , Atsuki Kazuhiko
Published: April 2005

A microstrip line is a type of open planar transmission line that consists of a dielectric substrate medium with a ground plane on the lower side and a conducting strip on the upper side.

Microstrip line is now one of the most widely used transmission lines for MICs. Active devices (diodes and transistors), lumped circuit elements (capacitors, resistors, inductors), dielectric resonators, and antennas can be easily incorporated into the circuit. Compared with the traditional bulky and heavy metallic waveguides and coaxial lines, the planar microstrip structures are smallsize, lightweight, easy for mass production, and inexpensive.
Microwave Power Amplifiers
Authors: Colantonio Paolo , Giannini Franco , Limiti Ernesto
Published: April 2005

Microwave Power are discussed, focusing mainly on solid‐state implementations. Starting with an introduction on solid‐state and vacuum device power generating capabilities and solid‐state active realization technologies and materials, this article introduces and defines the basic quantities defining and characterizing a microwave power amplifier. The basic concepts of operating class and the relevant expected performances are addressed, including reference cases. Power balance considerations are inferred and high‐efficiency power amplifier design techniques are detailed, including both harmonic tuning approaches and switched‐mode amplifier schemes. Measurement‐based approaches (load pull) and computer‐aided design techniques are also discussed.
Hybrids and Couplers
Authors: Bhartia Prakash , Pramanick Protap
Published: April 2005

Hybrids and couplers are common components used in most microwave integrated circuits. This article deals with the fundamental theory of these devices together with their applications. In addition, design aspects of hybrids and couplers together with characteristics such as losses and improvement in directivity are discussed.
Microwave Heating
Authors: Osepchuk John M.
Published: April 2005

Microwave heating is only part of the noncommunications applications of electromagnetic energy and only part of the range of electromagnetic heating. Themicrowaverange of the spectrum is variously defined. One prefers to think it is characterized by the fact that the dimension of the object to be heated is of the order of the wavelength. In practical terms this means heating at either 915 or 2450 MHz, two of the industrial, scientific, and medical (ISM) frequency assignments (in the United States) power or noncommunication applications.

By far the most dominant heating application is the microwave oven, which today operates at only 2450 MHz.
Microwave Mixers
Authors: Tahim R. S.
Published: April 2005

The frequency conversion function of a mixer plays a critical role in RF and microwave systems in determining their overall performance. For example, the quality of data transmission in the wireless communication systems and the identification of targets using radar and sensor systems are entirely dependent on the mixer performance in the receiver systems. The microwave/millimeter‐wave systems that operate at a number of frequency bands are susceptible to intermodulation frequency products generated in mixers. Spurious signals or distortion in mixers continues to be a problem in virtually all the RF and microwave systems. Therefore, mixers are frequently the dominant components in the receiver in establishing the system's distortion free performance. As a result, microwave and millimeter‐wave mixers have been the subject of continuous research and development for the past several decades and will continue to be the subject of future research in order to make the systems more efficient.
Microwave Oscillators
Authors: Choi Jonghoon , Mortazawi Amir
Published: April 2005

Microwave applications such as communications and radars require stable, efficient, and low‐noise microwave oscillators. For this purpose, microwave oscillators are characterized by their frequency of operation, output power, phase noise, long‐term stability, and DC‐to‐RF efficiency. This article discusses the small‐signal and large‐signal designs of microwave oscillators, based on the negative‐resistance model. Also, the injection‐locking phenomenon is introduced and analyzed employing the equivalent‐circuit model of injection‐locked oscillators. The phase noise of microwave oscillators is explained using Leeson's model. Several practical oscillators are examined. Finally, the state‐of‐the art result for various microwave integrated oscillators is presented.
Microwave Photonics: Technological Evolution and Its Applications
Authors: Daryoush Afshin S.
Published: April 2005

Since the late 1980s, novel microwave photonics techniques have been developed that lead to a performance superior to that obtained with the purely electronic systems. This discipline originated from the concept of light interaction with semiconductor devices and circuits, and has now branched to a number of applications dealing primarily with antenna technology and remote and signal processing. This article reviews the previously established optically controlled devices and circuits, followed by discussions of both directly and externally modulated fiberoptic links. Fiberoptic link performance is discussed in terms of system‐level figures of merit. A multifunction optoelectronic circuit is also discussed. Design innovations are introduced in low‐cost source packaging and system architectures of optically fed large phased‐array antennas. One important advantage of photonics in microwave systems is the optical signal processing based on low‐loss optical fibers. Examples of memory loops, narrowband notch filters, and transversal filters are introduced. All‐optical analog‐to‐digital conversion and diffuse photon near‐IR imaging are two new application areas that are currently under development. The GSPS optical ADC concepts are presented using mode‐locked lasers for optical sampling. Quantization could be achieved in both electrical and optical domains. Finally, an approach based on the diffused photon near‐infrared imaging technique is discussed, leading to medical monitoring and biomedical imaging systems. As the modulation frequency expands to microwave frequencies, a higher spatial resolution is observed.
Microwave Scattering Models for Earth Terrain
Authors: Fung Adrian K.
Published: April 2005

This article treats microwave scattering models for soil surface, leafy vegetation, and snow‐covered terrain. These models are generally useful for understanding the physics of the scattering problem, the design of scatterometers for specific applications, and the inversion of physical or geometric terrain parameters in remote sensing. It begins with introducing basic terms associated with the general scattering problem and terms associated with specific types of terrain. Then, it shows how surface scattering, volume scattering, and surface–volume interaction fit together in terrain scattering through the radiative transfer formulation. Illustrations of theoretical model behaviors are given for each terrain type, while derivations of the scattering models are provided in the references. The applications of these models to data interpretations are discussed.
Microwave Receivers
Authors: Bao-Yen Tsui James
Published: April 2005

In this article, intercept microwave receivers will be the main subject because of their similarities in design goals. Intercept receivers are very useful in military applications. Used in electronic warfare (EW), they are often referred to as EW receivers.

This article includes description of a generic receiver, followed by a discussion of the important terminology and definitions used in receiver design.
Microwave Switches
Authors: Caverly Robert H.
Published: April 2005

Modern microwave systems often require the routing of microwave signals to different locations or subsystems. This signal routing is frequently controlled electronically, and strict system requirements often require rapid signal routing. The system component used to control this flow of microwave energy is the microwave switch. Depending on the application, these devices must be able to rapidly switch applications to hundreds of kilowatts in high power radar applications. A variety of microwave switching systems are presented, including those based on ferrite technology and solid‐state and optoelectronic devices.
Microwave Tubes
Authors: Granatstein Victor L. , Parker Robert K.
Published: April 2005

Microwave tubes are devices that generate or amplify electromagnetic radiation in the frequency range of 0.3–300 GHz (microwave frequencies); they are based on the interaction between the electromagnetic radiation and a stream of electrons inside a vacuum envelope (the tube).

The superior efficiency of microwaves may be understood from the fact that in vacuum the electrons do not pass through a background material that would imped their movement. Thus, the heating of a background material is not a limiting factor of high‐power operation.
Millimeter‐Wave Measurement
Authors: Vernet Guy , Beaudin Gerard , Cros Dominique , Crozat Paul , Dambrine Gilles , Huyart Bernard , Nebus Jean‐Michel
Published: April 2005

In the millimeter‐wave range up to 100 GHz, the equipment and methods of measurement have been extended from the microwave domain. The major problems in the millimeter field are due to the small size of the devices and the transmission line losses. Above 100 GHz, as an alternative, other equipment and methods of measurement, using a quasioptic setup, have been developed or adapted from far‐infrared techniques (dielectric waveguide cavity resonator, free‐space methods).
Missile Guidance
Authors: Rodriguez Armando A.
Published: April 2005

Missile guidance addresses the problem of steering, or guiding, a missile to a target on the basis of a priori known target coordinate information and/or real‐time target measurements obtained from onboard or external sensors.
Mobile Communication
Authors: Wysocki Tadeusz , Zepernick Hans-Jürgen , Weber Ralf
Published: April 2005

Mobile communication has already become an integral part of modern life and is one of the driving forces of telecommunications. Wireless access to global telecommunication can be expected to change the face of telecommunication even further. Apart from traditional voice services and low‐rate data, future mobile communication will provide for multimedia services that are a mixture of voice, data, text, graphic, and video. Land mobile, maritime, aeronautic, and satellite systems will not just coexist but will establish a global mobile system allowing users to communicate at any time and from anywhere in the world.
Mode‐Matching Methods
Authors: Arndt F.
Published: April 2005

The article presents an overview of the state of the art of (mode) matching (MM) methods applied for the rigorous, fast CAD and optimization of waveguide components, and describes some recent advances. The great technical importance of the MM technique is its extremely high computational efficiency achieving complete full‐wave analyses of typical waveguide components several orders of magnitude faster than electromagnetics (EM)‐based methods applying space discretization techniques. Hence, the MM technique allows advantageously the direct EM‐based optimization of waveguide components toward given specifications within shortest response times. Adequate extensions of the MM technique, such as the boundary contour MM (BCMM) method or hybrid combinations with other EM methods such as the finite‐element method, allow extended flexibility. Typical application examples will illustrate the versatility of the MM methods.
Modulation Doped FETs
Authors: Liu Lianghong , Morkoç Hadis
Published: April 2005

Operation 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

Simulation 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

Most 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

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

The 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

The 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

RF 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

The 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

This 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

Dielectric 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

Phase‐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

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

The 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

Despite 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

Three‐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

Quasioptical 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

In 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

Radar 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

Radio 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

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.
Radio Noise
Authors: Dalke Roger
Published: April 2005

In this article, important sources of receiver noise are described and the concept of receiver noise factor is developed. The noise factor concept is then extended to cover the entire radio receiving system, including the receiving antenna and environmental noise. This is followed by a description of important environmental noise sources.