bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiowave Propagation in Multipath Channels
Authors: Koilpillai R. D.
Published: April 2005

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

Where two dissimilar media form a common boundary, the different refractive indices of the media will cause the signal direction to diverge from its path if the incident direction is not normal to the boundary. This is called refraction.

The average refractive index of a medium is called the bulk refractive index, and it affects the average direction of the electromagnetic energy.

In addition to changing the direction of travel of an electromagnetic signal and/or causing scintillations, a medium can both extract energy from a signal passing through it and alter the orientation sense of the electric vector (the polarization) of the signal as it passes through. The loss of energy is called attenuation, and the change in polarization sense is generally referred to as depolarization.
Radar Remote Sensing
Authors: van Zyl Jakob J. , Kim Yunjin
Published: April 2005

In this article, we present the basic principles of how remote sensing radars work. These include SARs (synthetic aperture radar), scatterometers, altimeters, sounders, cloud radars, and rain radars. Radars are active sensors; they provide their own illumination and therefore can be operated during day or night. An additional advantage of particularly lower‐frequency radars is their ability to penetrate clouds, rain, tree canopies, and even dry soil surfaces. We start the discussion by defining the basic concepts of resolution, the radar equation, signal fading, and the geometric distortions associated with the radar imaging geometry. We also include a description of advanced SAR techniques (polarimetry, interferometry, and polarimetric interferometry) and their applications. We complete the chapter by briefly examining nonimaging radars such as scatterometers, altimeters, radar sounders, and meteorological radars. An extensive list of references is provided for each radar for readers who need an in‐depth description of a particular radar.
Ring Resonators and Circuits
Authors: Hsieh Lung-Hwa , Chang Kai
Published: April 2005

Because of their advantages of low cost and easy fabrication, ring resonators are used in many applications such as filters, oscillators, mixers, baluns, hybrids, magic Ts, couplers, and antennas. In addition, they have been successfully used to measure the phase velocity and dispersion of a microstrip line. This article explains the basic field and circuit model analyses that can be used to investigate the characteristics of a ring resonator. On the basis of these analyses, ring resonators can be implemented and designed for different devices. The simple structure and high performance of a ring circuit fulfill the highly desired requirements of many modern wireless systems and other applications.
Schottky Barriers
Authors: Ashok S.
Published: April 2005

The Schottky barrier, one of the earliest and simplest semiconductor interfaces studied, consists of a metal in contact with a semiconductor.

The silicide Schottky barriers are of interest from both fundamental and practical viewpoints, as the MS interface here is buried inside the semiconductor bulk, thus obviating the deleterious influence of surface oxides and other contamination.

We will consider here two basic models, the earlier one due to Schottky and the later one inspired by Bardeen's postulation of the surface states.
Sky Wave Propagation at Low Frequencies
Authors: Johler J. Ralph
Published: April 2005

Although LF sky waves have been used since the earliest days of radio science, vigorous study of these waves occurred mainly between 1950 and 1970. This research was in large measure a consequence of the development of precision pulsed ground‐wave radio navigation and positioning systems. Although the ground wave is very stable with time of day, season, and so on, the ionospheric waves vary with time, and if such waves were not somehow sidestepped, the accuracy and precision of the navigation or positioning system would deteriorate. Thus, from an engineering point of view, LF sky waves were a problem in developing navigation systems such as Loran‐C or Loran‐D. One direct consequence of this research was the development of the wave hop theory of LF sky wave propagation, which will be introduced here.
Slow Wave Structures
Authors: Wu Ke
Published: April 2005

The slow wave is a particular type of wave propagation, usually of the guided‐wave type, and it is described mostly in the frequency‐domain. Slow‐wave structures are wave‐guides or transmission lines in which the wave travels with a phase velocity equal to or less than a certain predesignated velocity of wave propagation. In other words, the slow wave should be interpreted relative to its fast‐wave counterpart compared with a velocity of reference, such as the speed of light in a hollow metallic waveguide. In this description, the slow‐ and fast‐wave‐guiding properties are simply characterized by a popular technical term called the effective permittivity, which may involve the effect of permeability if the relative permeability is not equal to one, even though the concept of a separate effective permeability is valid.
SPICE
Authors: Morong William H.
Published: April 2005

SPICE is a program for component‐level electronic simulation, primarily directed toward analog circuits. SPICE processes a “net list” comprising the unique interconnections of named components with numbered terminals, calculating their interactions in accordance with fundamental electrical laws. Modern SPICE applications include a graphical user interface for schematic entry and for plotting results. SPICE
applications often include provisions for sharing input and output with other programs. SPICE applications are available both by purchase and as “freeware” for download or for Internet use at vendors’ sites. SPICE includes basic components, such as resistors and reactive components, sources, both independent and dependent and the ability to process models of semiconductor devices. Devices cannot be processed as models or including aggregations of models and other components can be processed as subcircuits. Components, models, and subcircuits are usually kept in local SPICE libraries. Although SPICE contain basic components and vendors supply models, parasitic circuit elements must be determined and provided by the SPICE user or other programs. SPICE requires a ground and connected nodes to operate. SPICE assumes, unless otherwise told, ideal components. Many component models do not include such secondary characteristics as thermal rise and breakdown voltage. SPICE sources may provide waveforms. SPICE is capable of performing several types of analysis, and provides an intuitive bridge between time‐ and frequency‐domain. SPICE also includes the ability to set initial conditions to speed the simulation of circuit, including energy‐storing components. SPICE also includes the ability to implement LaPlacian functions. SPICE
has a few faults, but most errors develop from defective models. An understanding of SPICE parameters and of real devices is helpful for correcting erroneous SPICE models.
Superconducting Electromagnets
Authors: Williams John E.C.
Published: April 2005

The design and construction of superconducting magnets has been made possible by the development of technical superconductors. There are three principal materials: the alloy niobiumtitanium (NbTi), the intermetallic compound niobiumtin (Nb3Sn), and the collective high‐temperature superconductors (HTSs) based on copper oxide layers in a perovskite structure.

Technical superconductors are a class having special properties that allow superconductor operation in high magnetic fields and with useful current densities. Superconductors are of two types; both can support the flow of electrical current without resistance only below a combination of maximum temperature, field, and current density, with critical parametersTc,Bc, andJc[1]. For type I superconductors, typical values ofTcandBcare 9 K and 0.1 T, respectively. Flux is excluded from the bulk of a type I superconductor, and current flows only in a surface layer, about 10−4 mm thick.

By contrast, type II superconductors allow flux to penetrate into the bulk of the lattice in the form of an array of flux quanta.
Surface Acoustic Wave Applications
Authors: Malocha Donald C.
Published: April 2005

Since the introduction of the surface acoustic wave (SAW) interdigital transducer in the late 1960s, SAW devices have tremendously affected a broad range of systems. The key to this technology is the ability to sense or tap a traveling electroacoustic wave on a piezoelectric substrate whose velocity is 105 times slower than an electromagnetic wave. The highest cost precision devices are typically used for military and satellite systems, which have the most demanding specifications; the intermediate cost devices are used in modest volume military man packs, military base stations, and commercial base stations; and the lowest cost devices are used in a broad range of commercial and consumer applications. In addition to device technological innovation, research and development on other propagating Rayleigh‐like modes, called pseudo‐SAW, and new substrate materials, such as lithium tetraborate and langasite, have provided lower loss, higher frequency, and wider bandwidth devices.
Surface Acoustic Wave Delay Lines
Authors: Reindl Leonhard M. , Ruppel Clemens C.W.
Published: April 2005

Surface acoustic wave (SAW ) delay lines are special microwave components that have been used for electronic analog signal processing since the early 1970s. A tremendous variety of devices and systems for consumer, commercial, and military applications have been developed, running now at an annual rate of some hundred million U.S. dollars. SAW filters, especially linear and nonlinear delay lines, as well as reflective delay lines play a key role in the radiofrequency (RF ) and intermediate‐frequency (IF ) stages of many electronic systems such as radar systems, spread‐spectrum telecommunication systems, and wireless passive sensor systems. The objective of this article is to provide an overview of the latest developments in SAW delay lines and to identify novel emerging applications, especially in the field of wireless communications and sensing. The pertinent key issues for the successful design and mass fabrication of SAW devices are addressed and the underlying operating principles are discussed.
Surface Acoustic Wave Filters
Authors: Hashimoto Ken-ya , Yamaguchi Masatsune
Published: April 2005

Currently, surface acoustic wave (SAW) filters are widely used in RF stages as well as IF stages of modern telecommunication systems. With successful research and development of SAW devices since the early 1960s, the growth of mobile phone markets has accelerated, with surprising advances in SAW device technologies since the early 1990s. This article discusses how the filtering function of SAW devices is realized using various SAW propagation phenomena, and reviews the performance of current commercial SAW filters. First, SAW transversal filters are discussed. Starting from a brief discussion of their fundamentals, we describe achievable performance, impact of the substrate selection and the most recent advances of this type of filter. Next, filters based on SAW resonators are discussed. After giving basic ideas of SAW resonators, it is shown how SAW resonator filters are composed and designed using SAW resonators.
Synthetic Aperture Radar
Authors: Ozdemir Caner
Published: April 2005

Since its invention in the early 1950s, synthetic aperture radar (SAR) has gathered increasing attention thanks to its attractive capabilities, such as providing good resolutions both in range and cross‐range dimensions. Although primary exercises of airborne and spaceborne SAR systems were for surveillance purposes and for geophysical remote sensing, numerous applications of SAR have been implemented in many areas, from subsurface imaging to crop monitoring. This article begins with the history of SAR and presents the basic principles in SAR signal processing, including range and azimuth compression. Applications and some common problems in SAR imagery are covered as well. Principles of inverse synthetic aperture radar (ISAR) and its applications are demonstrated with examples. Advanced SAR concepts such as motion compensation, interferometric SAR (IFSAR), and polarimetric SAR (POLSAR) imaging are also presented. The article is concluded by discussing some hot topics and emerging technologies in SAR imagery.
Television Broadcast Transmission Standards
Authors: Godber Alan S. , Redford James R.
Published: April 2005

Since the invention of television, images and sound have been captured, processed, transmitted, received, and displayed using analog technology, where the picture and sound elements are represented by signals that are proportional to the image amplitude and sound volume. In more recent years, as solid‐state technology has developed, spurred primarily by the development of computers, digital technology has gradually been introduced into the handling of the television signal, both for image and sound. Many portions of television systems are now hybrid combinations of analog and digital, and it is expected that eventually all television equipment will be fully digital, except for the transducers, cameras, and microphones (whose inputs are analog) and the television displays and loudspeakers (whose outputs are analog).
Transceivers
Authors: Dominique Francis
Published: April 2005

In this article, we will define a radio transceiver and discuss its history, architecture, and the implementation of its most important system blocks. Lastly, we will identify some key obstacles and challenges that face radio designers today.
Transmission Line Matrix (TLM) Method
Authors: Christopoulos Christos
Published: April 2005

This article presents the fundamental ideas behind the transmission‐line modeling or matrix (TLM) method and its applications to complex electromagnetic problems. TLM is considered from different points of view to illustrate its properties and modeling capabilities. A number of more recent enhancements to TLM are presented, especially in the area of materials and multiscale modeling. The article gives a concise introduction to advanced TLM topics and applications.
Transmitters for FM Broadcasting
Authors: Mendenhall Geoffrey N. , Fry P. E. Richard J.
Published: April 2005

The purpose of the FM transmitter is to convert one or more audiofrequency (composite baseband) input signal into a frequency‐modulated, radiofrequency (RF) signal at the desired power output level to feed into the radiating antenna system. In its simplest form, the FM broadcast transmitter can be considered an FM modulator and an RF power amplifier packaged in one unit.
Transmitters for Analog Television
Authors: Collins Gerald W.
Published: April 2005

This article discusses the relevant technology and provides the information needed to understand the operation, design criteria, and some of the future developments of TV transmitters. Although this information is presented from the viewpoint of equipment used in the United States, the principles apply to analog TV broadcasting worldwide. Specific details and numerical constants may differ in other systems, but the fundamental principles are the same.
Transverse Resonance Techniques
Authors: Sorrentino Roberto , Mongiardo Mauro
Published: April 2005

The transverse resonance technique in its various forms is presented and discussed, from the analytical solutions for inhomogeneously filled rectangular waveguides to the conventional approximate solution for transversely discontinuous waveguides (e.g., the ridge waveguide), to the generalized rigorous formulation for waveguide discontinuities and junctions.
Traveling‐Wave Tubes
Authors: Kory Carol L.
Published: April 2005

The traveling‐wave tube (TWT) is a vacuum device invented in the early 1940s [1,2] used for amplification at microwave frequencies. Amplification is attained by surrendering kinetic energy from an electron beam to a radiofrequency (RF) electromagnetic wave. The demand for vacuum devices has been decreasing largely owing to the advent of solid‐state devices. However, although solid state devices have replaced vacuum devices in many areas, there are still many applications such as radar, electronic countermeasures, and satellite communications that require operating characteristics such as high power (watts to megawatts), high frequency (below 1GHz to over 100 GHz), high efficiency (65% efficient, 100 Watt, Kaband TWTs are commonplace), and large bandwidth that only vacuum devices can provide.

The term traveling‐wave tube includes both fast‐wave and slow‐wave devices. This article will concentrate on slow‐wave devices as the vast majority of TWTs in operation around the world fall into thiscategory.
Waveguide Antennas
Authors: Kummer Winifred E.
Published: April 2005

Waveguide antennas are useful for a variety of airborne, ground‐based, space, and missile applications in the microwave frequency band because they offer high radiating efficiency, a high degree of control over the radiation pattern, compact architecture, and low weight.

In waveguide slot arrays the radiating and transmission structures are inexorably intertwined, thus it is appropriate to treat the history of the waveguides together with that of slot radiators.
Waveguide Junctions
Authors: Levy Ralph
Published: April 2005

The properties ofn‐port waveguide junctions are described in fundamental terms, with methods for finding impedance and admittance representations from the scattering matrix, leading to equivalent‐circuit representations. Some of the general properties ofnports are treated, with most examples dealing with three‐ and four‐port junctions. Three‐port networks includeE‐ andH‐plane T junctions andE‐plane bifurcations, and the discussion of four ports includes magic‐Ts and ring hybrids. Emphasis is placed on fundamental properties, the understanding of which is important for future research.
Wavelet Transforms
Authors: Deans Stanley R. , Heine John J. , Gangadharan Deepak , Qian Wei , Kallergi Maria , Clarke Laurence P.
Published: April 2005

Functions that oscillate over time are often called waves. If the function is such that it oscillates only in a localized region and goes to zero outside the region it may be called a wavelet. Thus we say wavelets are localized waves.

The fundamental role of the wavelet transform is to facilitate the analysis of signals or images according to scale. Wavelets are functions with some special mathematical properties that serve as a tool for efficiently dividing data into a sequence of frequency components without losing all information about position.
Wavelets
Authors: Tran Boj N. , Nguyen Tien M. , Shihabi Mazen M.
Published: April 2005

Wavelets have been found to be useful in many scientific and engineering applications, including signal processing, communication, video and image compression, medical imaging, and scientific visualization. The concept of wavelets can be viewed as a synthesis of ideas that originated during the last several decades in engineering, physics, and pure mathematics. The goal of this article is to develop a basic understanding of wavelets, their origin, and their relation to scaling functions, using the theory of multiresolution analysis.
Leaky Modes and High‐Frequency Effects in Microwave Integrated Circuits
Authors: Mesa Francisco , Jackson David R.
Published: April 2005

This article investigates the high‐frequency effects that occur when sources or discontinuities are present on printed‐circuit transmission lines. Although many of the conclusions are general, the analysis and the results will focus on microstrip and stripline types of transmission lines, where there is a single‐strip conductor that is within a layered structure that may contain either one or two ground planes.
Microwave Superconductor Devices
Authors: Sans Carles , Tzuzuki Genichi
Published: April 2005

Several superconductor device applications in the microwave area are very briefly discussed in the introduction. After that, the article focuses mostly on superconducting filters since it seems that the application that can grow first into commercial success is also the application that generates more interest. First, the basic categories of response used for superconductor filters are discussed. One of them, the quasielliptic response, is preferred for real applications because it provides better cutoff performance. However, filter synthesis and realization of this response is not as straightforward as the Chebyshev response. The synthesis of quasielliptic responses can be done by the cross‐coupling technique, one of the cutting‐edge topics in the microwave filter field.

Superconducting technology has opened new horizons in the microwave filter field because superconductors can realize filtering responses that are not realizable with other technologies. Superconductor technology allows very compact planar‐type filter circuits with lumped‐element or distributed structures with very high rejection performance. Many different designs and topologies of superconductor filters have been reported in technical journals and international conferences since the 1990s and to the present, but only several of those can be introduced here in the limited number of pages.

Finally, the application of superconductor filters in cellular networks in a form of cryogenic front‐end receivers is discussed. Various different technologies and their integration procedures are considered, such as low‐noise amplifiers, cryogenics, vacuum mechanics, and electronics. Reliability is one of the most important issues in the real world for these applications. Field test results of superconductor filter front‐end systems for TDMA and CDM a applications are also discussed.
Orthomode Transducers
Authors: Gentili G. G. , Nesti R. , Pelosi G. , Selleri S.
Published: April 2005

In the present work orthomode transducers (OMTs) and polarizers are presented. First, field configurations and propagation properties in common waveguides, which are extensively used in OMTs and polarizers, are analyzed to provide the reader with the necessary background to understand both OMTs and polarizers.

As a second step, some OMT and polarizer devices are described in attempt to highlight their electromagnetic features; this is not intended as a full review of all the known OMT and polarizer configurations, which is beyond the scope of this work, but to provide the reader with a basic knowledge of the principles of their operation. This is done by choosing a small, but representative, set of configurations largely used in practice that analyzed in depth and whose understanding, in the author's opinion, gives the reader a broad knowledge of the argument.

Finally, two example designs are presented, the first related to an OMT and the second to a polarizer.
Retrodirective Systems
Authors: Shiroma Wayne A. , Miyamoto Ryan Y. , Shiroma Grant S. , Ohta Aaron T. , Tamamoto Michael A. , Murakami Blaine T.
Published: April 2005

A retrodirective system reacts to an incoming signal from an unspecified direction by transmitting a response to that same direction, regardless of what that direction is. This automatic beamsteering feature, performed without any prior knowledge of the location of the source, makes retrodirective systems attractive for automatic pointing and tracking systems, microwave‐tracking beacons, radiofrequency identification, solar power satellites, and small‐satellite crosslinks. This article focuses on retrodirective antenna arrays and their applications and characterization. After reviewing the two basic retrodirective array architectures (Van Atta and phase‐conjugating arrays), several two‐dimensional and millimeter‐wave arrays are then discussed, as well as several key applications in wireless communications.
Underground Propagation
Authors: Zhang Y. P.
Published: April 2005

This article presents both natural and guided propagation of radiowaves in underground structures. By natural propagation, we mean that no special‐purpose cables are strung in underground structures to guide radiowaves, whereas by guided propagation we mean that special‐purpose cables such as leaky feeders are strung in underground structures to guide radiowaves. The imperfect waveguide model is developed for the analysis of natural propagation. It predicts that natural propagation is that of waveguide modes. The fundamental mode is important for long‐distance propagation as it suffers the least attenuation, whereas higher order modes are problematic as they cause fluctuation because of addition or subtraction of these modes. The geometrical optical model is also developed for the analysis of natural propagation. It predicts that natural propagation is achieved via a direct ray and many reflected rays. Only the direct ray and those rays with fewer reflections are significant for long‐distance propagation. The diffuse model is developed for the analysis of guided propagation by coupled‐type leaky feeders. It undertakes to calculate the mean power flow per unit solid angle from a coupled‐type leaky feeder according to Lambert's cosine law. The geometrical optical model is developed for the analysis of guided propagation by radiated‐type leaky feeders. It compares a radiated‐type leaky feeder with an array of magnetic diploes, which radiate energy in a certain direction. Furthermore, the statistical characteristics of both natural and guided propagation are also discussed.
UHF receivers
Authors: Bostlan Charles W. , Sweeney Dennis G.
Published: April 2005

An ultra‐high frequency (UHF) receiver receives radio signals with input frequencies between 300 MHz and 3000 MHz. Radio waves in this part of the spectrum usually follow line‐of‐sight paths and penetrate buildings well. The natural radio environment is significantly quieter at UHF than at lower frequencies, making receiver noise performance more important.
Van Atta Array Reflector
Authors: Chung Shyh-Jung , Ho Tan-Hsiung
Published: April 2005

The Van Atta array reflector has the simplest structure for retrodirective arrays, which has found many applications in wireless communications, RF identification (RFID), and intelligent transportation systems (ITSs). The antennas of the Van Atta array are paired and connected by transmission lines with equal length or length differences equal to multiples of a guided wavelength. No active device is required in the basic type; thus this array is much simpler than other kinds of retrodirective arrays. In this literature, the operation principle and a brief development history of the Van Atta array are first described. The theoretical analysis to predict the scattering field pattern in both monostatic and bistatic cases and experimental results of the Van Atta array reflectors is depicted in detail in Section 2. In Section 3, several design examples including one‐dimensional and two‐dimensional Van Atta reflector arrays are introduced. The design concept and operational performance of different kinds of Van Atta arrays are given. Besides passive ones, various active Van Atta reflector arrays are also depicted in this section. Section 4 briefly discusses the applications of the Van Atta arrays, especially in the field of vehicle‐mounting reflectors associated with the ITS. A detailed description of using the Van Atta reflector to enhance the radar cross section (RCS) in vehicle collision warning radar systems and to compose a transponder in the electronic toll collection (ETC) system is conducted. Two examples of transponders using the Van Atta array are introduced in this section. Finally, Section 5 gives a brief summary of the study.
HybridCADTechniques
Authors: Arndt F.
Published: April 2005

Microwave components/systems that meet the tight requirements of advanced applications—in particular concerning reduced mass and size, increased specs and performance, minimized design time, and cost—demandfastEM‐based CAD tools yielding accurate, optimized designs within adequately short response times. This goal makes flexible hybrid solutions desirable, which typically go beyond the efficiency possibilities of single methods. The article presents an overview of the state of the art of hybrid CAD mode‐matching (MM)/finite‐element (FE)/method‐of‐moments (MoM)/finite‐difference (FD) techniques applied for the rigorous, fast CAD and optimization of waveguide components and aperture antennas, and describes some more recent advances. The hybrid techniques presented combine advantageously the efficiency of the MM method with the flexibility of FE, MoM, and FD methods. Typical application examples illustrate the versatility of these techniques; the accuracy is demonstrated by comparisons with available measurements.
Piezoelectric Transducer Controlled Circuits
Authors: Yun Tae-Yeoul
Published: April 2005

This article introduces a new method for tuning microwave circuits of phase shifters, filters, resonators, and oscillators, controlled by a piezoelectric transducer (PET ), with computational and experimental results. An optimized PET ‐controlled phase shifter is demonstrated to operate up to 40 GHz with a maximum total loss of 4 dB and phase shift of 480°. PET controlled tunable bandpass filter, ring resonator, and one‐dimensional (1D) photonic bandgap (PBG ) resonator show a very wide tuning bandwidth of 17.5–28.5% near 10 GHz with little performance degradation. A new PET ‐controlled or voltage‐controlled dielectric resonator oscillator (VCDRO ) is demonstrated with a tuning bandwidth of 3.7% at the center frequency of 11.78 GHz. The tuning bandwidth is slightly less than that of a mechanical tuning using a micrometer‐head‐controlled tunable DRO with a tuning bandwidth of 4.7%. The new tuning method should have many applications in monolithic and hybrid microwave integrated circuits.
Ultra‐Wideband Wireless Systems
Authors: Donlan Brian M. , Buehrer R. Michael , Reed Jeffery H.
Published: April 2005

This article provides an overview of ultra‐wideband (UWB) wireless systems. System issues are discussed including modulation schemes, pulse shapes, interference issues, and channel characterization. Several communications‐ and radar‐specific implementation issues are also addressed. Much of the description is provided in the context of pulse‐based UWB or impulse radio. Furthermore, a section is dedicated to describing the role of the FCC and how current regulations are shaping UWB. The last section extends this discussion and presents several possible applications, providing examples of each.
Coulomb Gauge in Electromagnetics, The
Authors: Nevels Robert D. , Michalski Krzysztof A.
Published: April 2005

High‐frequency electromagnetic wave propagation and scattering problems where the fields are expressed in terms of potentials have been solved almost exclusively with the Lorentz gauge. However, in this article it is shown that any wave guidance or scattering problem that can be analyzed with the Lorentz gauge can as well be found subject to the Coulomb gauge. The Coulomb gauge displays some unique mathematical features that provide insight into the meaning and structure of potentials. The solution method presented here is sometimes referred to as the “hybrid method of moments (MM) Green's function method.” An important consequence of this method is that the Green functions are in their most general dyadic form. A dyadic Green's function formulation provides a compact procedure for handling general three‐dimensional boundary value problems that is uniquely suited to the Coulomb gauge. An interesting aspect of the Coulomb gauge is that is naturally divides the field into static and time‐harmonic components. Comparison between the Lorentz and Coulomb gauges is displayed through the surface current distribution obtained with each of these two gauges for cases where a plane wave illuminates a finite‐length straight wire and a cylinder tipped wedge. Depending on the problem configuration, the numerical solution to problems posed in the Coulomb gauge can have some computational advantage over a Lorentz gauge formulation.
Artificial Magnetic Conductor
Authors: Diaz Rodolfo E. , Clavijo Sergio A.
Published: April 2005

The artificial magnetic conductor (AMC) is a textured ground plane that presents a high impedance to incident waves and nearby horizontal antennas over a prescribed frequency range. In addition, it suppresses the propagation of both transverse electric (TE) and transverse magnetic (TM) surface waves, thus concentrating the radiation from a horizontal antenna into the upper half‐space. The resulting reduced backlobe and reduced mutual coupling to any other antennas on the same surface, combined with the high input impedance, make the AMC an ideal gain‐enhancing ground plane for ultrathin antennas. It is shown that these desirable features of are derived from the AMC's effective anisotropic magnetodielectric constitutive properties. Analysis and design approaches are given that enable the control of these properties according to the desired frequency and bandwidth of operation and the amount of surface‐wave suppression needed. Examples of the latest applications of AMC are given, as well as a brief history of its inception.
Multiresolution Techniques
Authors: Chen Yinchao , Cao Qunsheng , Mittra Raj
Published: April 2005

We begin by reviewing the foundation of the MRTD scheme—the multiresolution analysis (MRA ), and then exploring the properties of the scaling functions and wavelets. Also, we demonstrate the applications of the MRTD technique by analyzing a transverse electromagnetic (TEM ) wave propagation in a dielectric layered stratified space and an integrated microwave circuit, which can be extended to solve electromagnetic engineering problems of a general nature.
Parameter Estimation From Electromagnetic Simulations Using Signal Models
Authors: Naishadham Krishna
Published: April 2005

This article describes two algorithms for estimation of the optimal “system” parameters of time sequences (TSs) and frequency‐domain signatures generated in electromagnetic (EM) simulations. The time‐domain and frequency‐domain signal models are applied to data computed by the finite‐difference time‐domain (FDTD) method, and the method of moments, respectively. The FDTD method requires computation of very long TSs to accurately characterize the slowly decaying transient behavior of resonant structures. Therefore, it becomes critical to investigate methods of reducing the computational time for such objects. Existing methods in EM literature tend to use Prony‐based linear predictor‐type algorithms for modeling and extrapolating time‐domain data. These methods minimize a linearized “equation error” criterion that approximates the true nonlinear fitting‐error criterion posed by the estimation problem. In this article, we describe an efficient iterative method that minimizes the true nonlinear criterion and attains a significantly improved impulse response fitting over Prony's method, using fewer ARMA model parameters. The frequency‐domain state space method (SSM) presented in this article addresses the estimation of rational transfer function models from EM‐simulated data. The data are modeled in terms of complex sinusoids, whose amplitude and phase yield the decay/growth constants and the range, respectively, associated with discrete scattering centers. The model facilitates determination of key geometric and physical parameters of a circuit, antenna, or scatterer, which is an important first step in its design and optimization. Robust state space techniques, borrowed from linear systems theory, are applied to form the system matrix of the underlying microwave problem, whose complex eigenvalues, via signal compression and spectral decomposition, allow for the isolation of specific modal responses suited to calculation of the design parameters.
Submarine Antennas
Authors: Rivera David F. , Bansal Rajeev
Published: April 2005

The design of a submarine antenna differs from its commercial counterpart in two important respects. The antenna must be (1) physically smaller yet able be accommodate numerous electrical functions simultaneously and (2) rugged enough to survive the effects of an unforgiving ocean environment. The successful design of an antenna for such a demanding application is thus an outgrowth of cross‐disciplinary efforts from such diverse fields as materials science, electrochemistry, fluid mechanics, and other allied areas. This article briefly summarizes those aspects of submarine antenna design of importance to the engineer, with an emphasis on its implementation above, beneath or on the sea surface.
Personal Area Networking with Bluetooth
Authors: Zeadally S. , Kumar A.
Published: April 2005

The availability and adoption of a wide range of mobile computing devices (e.g., laptops, personal digital assistants (PDA s), wearable computers) of varying sizes and processing capabilities, along with the emergence of wireless local‐area networks (WLAN s) and wireless personal‐area networks (WPAN s), are enabling the ubiquitous access of information anywhere, anytime. These networks are frequently being used as extensions to the Internet, and end users are increasingly exploiting them to access wireless Internet services. One of the emerging short‐range wireless networking technologies that shows great promise as an enabling technology in the deployment of WPAN s is the recent industry‐standard Bluetooth. In this article, we explore by design, implementation, and experimental performance evaluation, mechanisms and approaches that enable Bluetooth devices to achieve (1) seamless IP connectivity to external IP ‐based networks, (2) high performance even in the presence of IEEE 802.11 interfering traffic, and (3) efficient support for high‐quality audio by exploiting the Audio/Video Distribution Transport Protocol (AVDTP ). We anticipate that our reported experiences and practical results will benefit network designers, developers, and users of Bluetooth technology in WPAN environments.
Adaptive Array Antennas
Authors: Sun Chen , Karmakar Nemai C.
Published: April 2005

Adaptive array antennas play an important role in wireless communications systems. The article begins with a brief introduction to evolution of wireless communications systems. After that, the current and future applications of adaptive array antennas in wireless communications systems are described. The structures and implementations of the adaptive array antennas systems, including switched‐beam antennas, phased‐array antennas, digital beamforming (DBF ) array antennas, parasitic array antennas, and diversity antennas, are described in Section 4. The article concludes with a comparison of different adaptive array antenna architectures.
Molecular Recognition of Sialic Acid End Groups by Phenylboronates
Authors: Djanashvili Kristina , Frullano Luca , Peters Joop A.
Published: April 2005

A multinuclear NMR study of the interaction between phenylboronic acid (PBA) and sialic acid (Neu5 Ac) has been performed. The latter compound is known to be overexpressed on the cell surface of tumor cells. The results of this investigation suggest that the binding of PBA to sialic acid is pH dependent. 17O NMR experiments with glycolic acid as the model compound prove that an interaction at the α‐hydroxycarboxylate occurs at pH < 9, while a study with threonic and erythronic acids shows that the PBA group interacts selectively with the vicinal diol functions at higher pH. Similarly, Neu5 Ac binds PBA through its α‐hydroxycarboxylate at low pH (< 9) and through its glycerol side chain at higher pH values. The conditional stability constant of the phenylboronate ester at pH 7.4 is 11.4. On cell surfaces, sialic acid is connected to the neighboring sugar unit through the 2‐hydroxy group. To mimic this the 2‐α‐O‐methyl derivative of Neu5 Ac was included in this study. The erythro configuration of the hydroxy substituents prevents stable‐complex formation at positions C7 and C8 and, consequently, the strongest interaction is observed at positions C8 and C9, leading to a five‐membered 2‐boron‐1,3‐dioxalate. In addition, a relatively small amount of the C7–C9 six‐membered complex was observed. Molecular modeling studies confirm that the C8–C9 boronate complex has the lowest energy.
The Gallium‐Rich Region of the Ce—Ag—Ga System.
Authors: Gumeniuk R. V. , Akselrud L. G. , Stel'makhovych B. M. , Kuz'ma Yu. B.
Published: April 2005

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New Layered Quaternary Tantalum Thiophosphates Containing Binuclear [Ta2S10] Units: Synthesis and Crystal Structures of the New Compounds K0.42TaPS5 and Rb0.42TaPS5.
Authors: Gutzmann Andreas , Naether Christian , Bensch Wolfgang
Published: April 2005

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GaCl3‐Catalyzed Skeletal Rearrangement of α,α,α‐Trisubstituted Aldehydes.
Authors: Oshita Masayuki , Okazaki Takao , Ohe Kouichi , Chatani Naoto
Published: April 2005

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Remarkable Substituent Effects on the Oxidizing Ability of Triarylbismuth Dichlorides in Alcohol Oxidation.
Authors: Matano Yoshihiro , Hisanaga Teppei , Yamada Hisatsugu , Kusakabe Shingo , Nomura Hazumi , Imahori Hiroshi
Published: April 2005

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Highly Efficient Chemoselective Deprotection of O,O‐Acetals and O,O‐Ketals Catalyzed by Molecular Iodine in Acetone.
Authors: Sun Jianwei , Dong Yanmei , Cao Liya , Wang Xinyan , Wang Shaozhong , Hu Yuefei
Published: April 2005

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Reactions of N‐Quaternary 1‐Phenyl‐3,4‐dihydroisoquinolinium Compounds with Nucleophiles — Products and Their Isomerism — Part 2.
Authors: Moehrle H. , Breves H.
Published: April 2005

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Domino “[3 + 3]‐Cyclization‐Homo‐Michael” Reactions of 1,3‐Bissilyl Enol Ethers with 1,1‐Diacylcyclopropanes.
Authors: Bose Dopal , Nguyen Van Thi Hong Nguyen Van Thi Hong , Ullah Ehsan , Lahiri Sunanda , Goerls Helmar , Langer Peter
Published: April 2005

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One‐Pot Synthesis of N‐Substituted (3‐Oxobutanyl)carbamates from Primary Amines Using Modified Zeolite Hβ at Room Temperature.
Authors: Raje Vivek P. , Bhat Ramakrishna P. , Samant Shriniwas D.
Published: April 2005

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Three‐Component Reaction of Aryl Diazoacetates, Alcohols, and Aldehydes (or Imines): Evidence of Alcoholic Oxonium Ylide Intermediates.
Authors: Lu Chong‐Dao , Liu Hui , Chen Zhi‐Yong , Hu Wen‐Hao , Mi Ai‐Qiao
Published: April 2005

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Selective Cross‐Coupling of 1‐Ethynyl‐4‐iodobenzenes with Activated Arylacetylenes.
Authors: Kovalev A. I. , Takeuchi K. , Asai M. , Ueda M. , Rusanov A. L.
Published: April 2005

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Studies on the Chemistry of 2‐(2‐Oxo‐3‐phenylpropyl)‐benzaldehydes: Novel Total Synthesis of 3‐Phenylnaphthalen‐2‐ols and 2‐Hydroxy‐3‐phenyl‐1,4‐naphthoquinones.
Authors: Martinez Ana , Fernandez Marcos , Estevez Juan C. , Estevez Ramon J. , Castedo Luis
Published: April 2005

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Cycloisomerization of 1,6‐Enynes: Asymmetric Multistep Preparation of a Hydrindan Framework in Water with Polymeric Catalysts.
Authors: Nakai Yasushi , Uozumi Yasuhiro
Published: April 2005

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Combining Two‐Directional Synthesis and Tandem Reactions: Synthesis of Trioxadispiroketals.
Authors: McDermott Paul J. , Stockman Robert A.
Published: April 2005

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Selenium‐Catalyzed Halolactonization: Nucleophilic Activation of Electrophilic Halogenating Reagents.
Authors: Mellegaard Shelli R. , Tunge Jon A.
Published: April 2005

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(S,E)‐N‐[1‐(3‐Heteroarylphenyl)ethyl]‐3‐(2‐fluorophenyl)acrylamides: Synthesis and KCNQ2 Potassium Channel Opener Activity.
Authors: Wu Yong‐Jin , et al. et al.
Published: April 2005

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Pyrroloisoxazoles as a Building Block for 3‐Enoyltetramic Acids.
Authors: Jones Raymond C. F. , Pillainayagam Terence A.
Published: April 2005

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Condensation of Chromone‐3‐carboxaldehyde with Phenylacetic Acids: An Efficient Synthesis of (E)‐3‐Styrylchromones.
Authors: Silva Vera L. M. , Silva Artur M. S. , Pinto Diana C. G. A. , Cavaleiro Jose A. S. , Patonay Tamas
Published: April 2005

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Efficient Synthesis of Functionalized 2‐Carbamoylpyran‐4‐ones by Ring Transformation of 5‐Alkylidene‐2,5‐dihydropyrrol‐2‐ones.
Authors: Anders Joachim T. , Nguyen Van Thi Hong , Langer Peter
Published: April 2005

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IKCa‐Channel Blockers. Part 2. Discovery of Cyclohexadienes.
Authors: Urbahns Klaus , Goldmann Siegfried , Krueger Jochen , Horvath Ervin , Schuhmacher Joachim , Grosser Rolf , Hinz Volker , Mauler Frank
Published: April 2005

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Solvent Dependent Regioselective Hydrogenation of Substituted Quinolines.
Authors: Fache Fabienne
Published: April 2005

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Novel and Convenient Synthesis of 4(1H)Quinolones
Authors: Tois Jan , Vahermo Mikko , Koskinen Ari
Published: April 2005

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A Novel Synthesis of 1‐Substituted 2H‐Isoquinolin‐3‐ones
Authors: Canepa Alicia S. , Bravo Rodolfo D.
Published: April 2005

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New Results on the Reactivity of 5,6‐Diamino‐4‐hydroxy‐2‐mercaptopyrimidine.
Authors: Cosimelli Barbara , Iadanza Manuela , Spisani Raffaella , Novellino Ettore
Published: April 2005

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Cocyclotrimerization of 6‐Alkynylpurines with α,ω‐Diynes as a Novel Approach to Biologically Active 6‐Arylpurines.
Authors: Turek Pavel , Kotora Martin , Tislerova Iva , Hocek Michal , Votruba Ivan , Cisarova Ivana
Published: April 2005

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Synthesis, Physico‐Chemical Properties and Biological Activity of 1‐(4‐Fluorophenyl)‐4‐[3‐(2‐, 3‐ and 4‐alkyloxyphenylcarbamoyloxy)‐2‐hydroxypropyl]piperazinium Chlorides.
Authors: Malik Ivan , Sedlarova Eva , Csoellei Jozef , Racanska Eva , Cizmarik Josef , Kurfuerst Pavel
Published: April 2005

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An Efficient Synthesis of Novel Heterocycle‐Fused Derivatives of 1‐Oxo‐1,2,3,4‐tetrahydropyrazine Using Ugi Condensation.
Authors: Ilyn Alexey P. , Kuzovkova Julia A. , Potapov Victor V. , Shkirando Alexandre M. , Kovrigin Denis I. , Tkachenko Sergey E. , Ivachtchenko Alexandre V.
Published: April 2005

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A Novel Series of Potent γ‐Secretase Inhibitors Based on a Benzobicyclo[4.2.1]nonane Core.
Authors: Lewis Stephen J. , et al. et al.
Published: April 2005

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Samarium Diiodide in the Synthesis of Medium‐Sized Rings — Carbocycles and Heterocycles by Intramolecular Addition of Samarium Ketyls to Alkynes.
Authors: Hoelemann Alexandra , Reissig Hans‐Ulrich
Published: April 2005

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Synthesis of Pinacol Esters of 1‐Alkyl‐1H‐pyrazol‐5‐yl‐ and 1‐Alkyl‐1H‐pyrazol‐4‐ylboronic Acids.
Authors: Ivachtchenko Alexandre V. , Kravchenko Dmitry V. , Zheludeva Valentina I. , Pershin Dmitry G.
Published: April 2005

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