bluuebunny/crossref_metadata_2025_split huggingface dataset:
Helical Antennas
Authors: Adams Arlon T. , Lee Jay K. 
Published: April 2005

AbstractThe 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

Abstract

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

AbstractA “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

AbstractImpedance 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.
Its Radio Service Standards and Wireless Access in Vehicular Environments (ITS‐WAVE) at 5.9 GHZ
Authors: Gerges Ramez L. 
Published: April 2005

AbstractCommunications 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

Abstract
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

AbstractElectromagnetic 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

AbstractThe 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

Abstract
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

AbstractLoop 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

Abstract

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

AbstractTo 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

AbstractThis 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

AbstractWith <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 Lines
Authors: Ma Zhewang , Yamashita Eikichi , Atsuki Kazuhiko 
Published: April 2005

AbstractA 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

AbstractMicrowave 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.
Microwave Heating
Authors: Osepchuk John M. 
Published: April 2005

AbstractMicrowave 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

AbstractThe 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

AbstractMicrowave 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

AbstractSince 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

AbstractThis 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

Abstract
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

AbstractModern 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

Abstract
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

AbstractIn 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).
Mobile Communication
Authors: Wysocki Tadeusz , Zepernick Hans-Jürgen , Weber Ralf 
Published: April 2005

AbstractMobile 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

AbstractThe 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.