bluuebunny/crossref_metadata_2025_split huggingface dataset:
E
nsembl and
U
ni
P
rot (
S
wiss‐
P
rot)
Authors: Jackson David , Schneider Reinhard 
Published: April 2005

Abstract
Two of the premier resources for genomic and proteomic information are the Ensembl and UniProt (Swiss‐Prot) database projects. In this chapter, we discuss their principle features and structures and show how they can help biologists separate the data sizzle from the true steaks of knowledge and information.
Acedb genome database
Authors: Durbin Richard , Griffiths Edward 
Published: April 2005

Abstract

Acedb is an integrative database system that has been widely used for management of genome oriented biological data. Since 1990, it has been used to manage and display the results of many of the large genome projects, starting with that for the nematode

C. elegans

from which it derives its name: A C Elegans DataBase. Acedb has many features to manipulate genomic sequence and other high genetic data, but also a flexible design that accommodates novel data types and attributes, and has been used for many other types of information, including those unrelated to biology. It provides an integrated research tool that requires no programming by the user to produce sophisticated representations and displays of genomic data.
Acoustic Microwave Devices
Authors: Smith Peter M. 
Published: April 2005

AbstractAcoustic wave devices are often used in radiofrequency and microwave circuits because of their very small size and the performance that they offer. In this article, we review the basic theory of acoustic wave propagation in crystals. We describe some of the implementations of acoustic wave devices and show how they can be employed in microwave systems. We then present some of the models that are commonly used in the design of acoustic wave devices.
Active Antennas
Authors: Mickelson Alan 
Published: April 2005

AbstractAn antenna is a structure that converts electromagnetic energy propagating in free space into voltage and current in an electrical circuit and vice versa. In a transceiver system, the antenna is used to both receive and transmit free‐space waves. At minimum, a transceiver then must consist of a signal source that serves to drive the antenna as well as a receiver circuit that reads out the signal from the antenna. Until relatively recently, practically all antenna systems operating in the microwave frequency regime (operation frequencies greater than 1 billion cycles per second, or 1 GHz) went to great lengths to isolate the antenna from the circuitsthat is, to find ways to make system operation independent of the antennas electrical characteristics. In contradistinction, an active antenna is one in which the antenna actually serves as a circuit element of either the driver or readout circuit.
Active Filters: Overview of Active Filter Structures
Authors: Billonnet Laurent , Jarry Bernard 
Published: April 2005

AbstractThis article is dedicated to an overview of existing active‐filter structures. We first talk about the different families of filters. We evaluate different ways of classifying microwave active filters (MAFs) and show that two main categories can be finally considered. For the first category, we describe, from a general point of view, various compensation techniques and detail more specifically filters based on the use of gyrators and negative‐impedance converters (NICs). In this step, we emphasize different problems that must be faced by RF and microwave designers in comparison to low‐frequency classical designs. The second category is based on filters resulting from the application, in the microwave domain, of methods and concepts used primarily at low frequency. As an example, this section sums up the different ways of considering and implementing recursive and transversal (R&T) filters for the microwave purpose.
Direction of Arrival Estimation and Adaptive Processing Using a Conformal Phased Array
Authors: Sarkar Tapan K. , Salazar-Palma Magdalena 
Published: April 2005

AbstractThe objective of this article is to present a general methodology for carrying out direction of arrival (DoA) estimation and adaptive processing using conformal arrays. The antenna elements in a conformal array can be unequally spaced, and they need not be situated over a planar surface. In addition, the antenna elements can have a directive gain. The goal is to present a signal processing methodology coupled with electromagnetic physics that can deal with nonuniformly spaced directive antenna elements over a conformal surface.
Anisotropy and Bianisotropy
Authors: Mackay Tom G. , Lakhtakia Akhlesh 
Published: April 2005

AbstractThe electromagnetic properties of an isotropic medium are the same in all directions. Accordingly, isotropic media are characterized simply by scalar constitutive parameters that relate the induction field phasorsandto the primitive field phasorsand. In contrast, anisotropic media exhibit directionally dependent electromagnetic properties, such thatis not aligned withand/oris not aligned with. Furthermore, recent advances have focused attention on bianisotropic media wherein bothandare anisotropically coupled to bothand. Therefore, dyadics (i.e., second‐rank Cartesian tensors) are needed to relate the primitive and the induction field phasors in both anisotropic and bianisotropic media. Correspondingly, these media exhibit a vastly more diverse range of phenomena than do isotropic media. A consequence of this wealth of interesting properties is that electromagnetic analyses are considerably more complicated for anisotropic and bianisotropic media than for isotropic media. In this article, anisotropic and bianisotropic media are discussed in terms of their constitutive dyadics and spacetime symmetries. Planewave propagation, dyadic Green functions, and the conceptualization of anisotropic and bianisotropic media via homogenization are described. A brief account of anisotropic and bianisotropic behavior in nonlinear media concludes this article.
Antenna Anechoic Chambers
Authors: Chung Boon-Kuan 
Published: April 2005

AbstractThe geometric shape of the anechoic chamber can be optimized to achieve better performance. Microwave absorbers to be installed over the entire inner surfaces of the anechoic chamber must be properly selected. The selection criteria may include the reflectivity levels for normal and oblique incident angles, operating frequency, bandwidth, type of bulk materials, size, shape, weight, mechanical stability, mounting method, fire retardant, and lifespan. The anechoic chamber must be sufficiently large to provide the required dimensions of the quiet zone. Shielding enclosure is provided to prevent extraneous energy from masking measurements of the intended signals. Ventilation, access doors, lighting, cabling, and HVAC (heating–ventilation–air conditioning) shall be incorporated in the design according to the operational purpose of the facility. Different construction methods will give rise to varying degrees of imperfection that determine the shielding effectiveness. The performance of the anechoic environment may be evaluated in terms of amplitude ripple and phase change across the quiet zone. There is much interest in trying to reduce the required investment in constructing an anechoic chamber while still maintaining adequate performance. With a suitable computer simulation tool, together with a reasonable absorber model, design of anechoic chamber can be made more economical.
Antenna Arrays for Mobile Communications
Authors: Paulraj Arogyaswami , Gesbert David , Papadias Constantinos 
Published: April 2005

Abstract
Smart antennas constitute a promising but still emerging technology. Spacetime processing algorithms provide powerful tools to enhance the overall performance of wireless cellular networks. Improvements, typically by a factor of 2 in cell coverage or capacity, are shown to be possible according to results from field deployments using simple beamforming. Greater improvements can be obtained from some of the more advanced spacetime processing solutions described in this article.
Antennas for High‐Frequency Broadcasting
Authors: Wilensky Ronald , Sinclair Gordon G. , Greene Richard R. 
Published: April 2005

AbstractThis article describes the antennas, transmission lines, switching systems and baluns used in modern high‐frequency (HF) transmitting stations. Longrange broadcasting uses 10 bands from 5.9 to 26.1 MHz that are defined by internationally established‐ or radio regulations. Short‐range coverage normally uses four international bands from 2.3 to 4.9 MHz. Power levels are typically 50–500 kW. Propagation is via sky waves which are refracted in the ionosphere and return to Earth at a distance depending on the angle of incidence and the height of the reflecting layer. Under ideal conditions HF broadcasts can be received several thousand kilometers from the transmitting station.The principal antenna types used for HF broadcasting are horizontally polarized log‐periodics and dipole arrays. Log‐periodic antennas have a greater frequency range, while dipole arrays are capable of handling more transmitter power. HF broadcast antennas are normally supported by large towers or guyed masts on a fixed bearing; dipole arrays are capable of being steered electrically up to 30° in the azimuthal plane. HF broadcast stations typically have a number of transmitters and antennas and may require complex feeder and swtiching systems. Modern transmitters typically have coaxial outputs, while the antennas have balanced inputs. Standard practice employs coaxial feeder to connect to a matrix of coaxial switches, followed by baluns and balanced feeder to reach the antennas.
Aperture Antennas
Authors: Kozakoff Dennis J. 
Published: April 2005

AbstractAperture antennas include those having large planar areas such as parabolic reflectors. The classic technique used in the calculation of aperture antenna radiation patterns is applying the equivalence principle followed by physical optics approximations. The equivalence principle is based on replacing the physical antenna aperture with a virtual antenna aperture consisting of an ensemble of Huygens sources, each of which is a source of spherical wavelets. The total pattern is taken as a construction of these Huygens secondary waves. It can be further shown that a simple Fourier transform relation exists between the amplitude distribution of these sources and the radiation pattern in angle space. For many aperture antenna problems, the distribution can be assumed from theoretical considerations or determined empirically from near‐field probes of the aperture fields. But there are many other antennas such as horn antennas, where a virtual aperture can also be constructed in front of the physical aperture in order to model and analyze the antenna. Thus, an aperture antenna has more to do with the method used to model the antenna than its actual form.For most aperture antenna problems, these classical techniques are adequate and give reasonably accurate results. However, more modern analysis techniques such as the method of moments (MoM), the finite‐element method (FEM), and the finite‐difference time‐domain (FDTD) method are also discussed. These methods are more robust and accurate, but the complexity and large amount of computer resources required must be traded off with the accuracy desired. Generally, they are infeasible for high‐gain antennas.
Attenuation Measurement
Authors: Hilty Kurt 
Published: April 2005

AbstractWhen a signal is sent along any transmission path, many different mechanisms degrade it. Because of finite conductivity, every cable shows a resistive loss. Scattering loss is dominated by Rayleigh scattering, and below 1600nm absorption losses are caused mainly by OH absorption. Wireless transmission paths, such as microwave links, satellite links, and broadcast or mobile communication, are affected by scattering caused by rain, clouds, and multiple reflections. Many different methods and a variety of systems for measuring attenuation have been developed.
Attenuators
Authors: Sundararajn Raji , Peterson Edward , Nowlin Robert 
Published: April 2005

AbstractAttenuators are linear, passive, or active networks or devices that attenuate electrical or microwave signals, such as voltages or currents, in a system by a predetermined ratio. They may be in the form of transmission‐line, stripline, or wave‐guide components. The most commonly used method in attenuators is to place resistors at the center of an electric field. Due to the electric field, there is current induced, resulting in ohmic loss.
Bandpass Filters
Authors: Ramirez-Angulo Jaime 
Published: April 2005

Abstract
Bandpass filters are common building blocks of many electronic systems. They find applications in diverse fields such as communications, audio, instrumentation, and biomedicine. Bandpass filters are used on the receiver side in order to select or “filter out” only one of the signals transmitted in the channel. A process called demodulation is used to shift the spectrum of the selected signal back to baseband (to a zero center frequency).
Bandstop Filters
Authors: Choi Chiu H. 
Published: April 2005

Abstract

An approach to designing a circuit (a bandstop filter)with a frequency response that satisfies the bandstop requirements is described below. It consists of two steps: the approximation of the requirements by a transfer function and the synthesis of the transfer function. A bandstop filter (also known as
band-reject
,
band-elimination
, or
notch filter
) suppresses a band of frequencies of a signal, leaving intact the low‐ and high‐frequency bands.
BiCMOS Devices and RF Integrated Circuits
Authors: Chen Yupeng , Yang Xiaomin , Thomas X. Wu 
Published: April 2005

AbstractIn this article, BiCMOS technology development focusing on the most recent achievements of SiGe BiCMOS technology is reviewed first. Several important figures of merit of SiGe device for RFIC designers such asfT,fmax, BVCEO(collector–emitter breakdown voltage with an open base), and NFminare studied in detail. We begin with the stringent system requirements of typical modern wireless communication standards. Commercial available technology options for RFIC are compared according to performance, power consumption, level of integration, and cost with special emphasis on GaAs, RF CMOS, and SiGe BiCMOS. Passive devices are also explored with respect to their impacts on RFIC design. The design of key wireless system building blocks is investigated. Recently reported results of SiGe BiCMOS low‐noise amplifiers (LNAs), power amplifiers (PAs) and integrated voltage‐controlled oscillators (VCOs) are reviewed. Finally, future trends of RF integrated system adopting SiGe BiCMOS technology are discussed.
Biological Effects of Radiofrequency Energy as Related to Health and Safety
Authors: Foster Kenneth R. 
Published: April 2005

AbstractThis article reviews biological effects of radiofrequency energy with emphasis on effects with clear implications for to human health and safety. The rationale for two major exposure limits is described. Major areas of controversy about health effects of low‐level radiofrequency energy are described, both as related to uncertainities in the scientific data and in large variations in exposure limits around the world.
Medical Imaging with Microwave: Thermoacoustic Tomography
Authors: Xu Yuan , Wang Lihong V. 
Published: April 2005

AbstractAfter introducing the principles of thermoacoustic tomography and pure microwave imaging, we summarize the mechanisms attributable to the dielectrical properties of biological tissues in the microwave frequency range. Next, we introduce some theoretical results from studies of thermoacoustic tomography, including information about optimal microwave frequencies, effects of acoustical heterogeneity on breast thermoacoustic tomography, limited‐view thermoacoustic tomography, reconstruction algorithms, and spatial resolution. The experimental setups and the results of thermoacoustic tomography in planar and circular geometries are discussed. Finally, in vivo and in vitro results of both thermoacoustic tomography and pure microwave imaging are presented.
Cavity Resonators
Authors: Sharma Arvind K. 
Published: April 2005

AbstractIn this article, a brief description of the cavity resonators most commonly employed in various microwave components is presented. As far as possible, simple expressions have been provided for design applications. Basic parameters of microwave resonators are first presented because they describe a cavity. Then, various coaxial and waveguide resonators are described. Fabrication, coupling, measurements, and applications of cavity resonators are also included.
Chebyshev Filters
Authors: Carlos Antônio , de Queiroz M. 
Published: April 2005

AbstractDirect Chebyshev filters are magnitude filters characterized by uniform ripple in the passband attenuation and monotonically increasing stopband attenuation. A variation are the inverse Chebyshev filters, characterized by maximally flat passband attenuation and uniform ripple in the stopband attenuation. The article discusses the characteristics of these approximations and the derivation of the poles and zeros of their transfer functions in Laplace transform, and presents explicit formulas for the element values of direct Chebyshev lowpassLCladder filters. Useful variations of the approximations are also discussed.
RF Circuit Noise
Authors: Marshall Leach W. 
Published: April 2005

Abstract

The
V
n
−
I
n
noise model of an amplifier is described. The model is used to define signal‐to‐noise ratio and noise factor. The optimum source impedance that minimizes the noise factor is derived. The effect of matching networks on noise factor is described. Two lossless matching network examples illustrate how the source impedance can be transformed to minimize the noise factor. The use of Smith chart noise circles and gain circles to evaluate amplifier performance is described and illustrated by an example. Measurement of noise factor and a method of determining amplifier noise parameters from noise factor measurements are described.
Conformal Antennas
Authors: Sengupta Dipak L. 
Published: April 2005

AbstractSpecifically, this article describes the following:The specific considerations that must be given to the performance of basic slot and microstrip or patch antenna elements when mounted on nonplanar conducting surfacesA selected number of conformal antennas: for example, microstrip conformal antennas and dielectric‐filled edge slot (DFES) antennasA class of wraparound antennas and antenna arraysCylindrical and spherical phased arrays used for omnidirectional and hemispherical coverage, respectively.
Coplanar Waveguide (CPW) Transmission Lines
Authors: Zhu Lei 
Published: April 2005

AbstractThis article gives an overview of various coplanar waveguide (CPW) transmission lines developed to date for promising applications in monolithic microwave integrated circuits (MMICs). The article begins with a detailed description of the geometric schematics, transmission behaviors, and design formulas for the three basic CPW with infinite‐ and finite‐ground widths as well as backed conductor. Several improved CPW structures with metallic enclosure, vertical‐layer reallocation or varied conductor configurations are outlined, aiming at effectively reducing unexpected losses caused by a strip conductor, lossy substrate, or radiation in addition to problematic crosstalk effects. Coupled CPW transmission lines with different coupling architectures are briefly investigated in terms of coupling or interaction extent. Next, a variety of periodic CPW transmission lines with series inductive and/or shunt capacitive loading are presented and their slow‐wave characteristics are primarily applied for size miniaturization of CPW devices. In conclusion, guided‐wave propagation characteristics of periodic CPW are thoroughly studied in terms of dispersive and complex per unit length transmission parameters.
Dielectric Loaded Antennas
Authors: Shafai L. 
Published: April 2005

AbstractDielectric media affect the wave propagation by their reflective index. Their use in antennas can provide a number of diverse benefits. In applications such as high‐gain antennas, they influence the phase of the propagating waves, and thus influence the direction and gain of the transmitted waves. Lens antennas are typical examples that can be used alone, or in conjunction with other antennas, such as horn and microstrip antennas, to enhance their gain. In other applications like dielectric loaded horns and waveguides the use of dielectric inside them controls the excitation of various modes and thus the performance of the horns. Hybrid and multimode horns are examples that can improve the horn performance for reflector feed applications. Similarly, dielectric resonator antennas can control and improve the radiation performance by controlling the excitation and the phase of the wave propagating through them. Dielectrics being non‐conducting can also be used to insulate and, thus, isolate the antennas from living tissues, in medical treatment and studies. Large permittivity of some dielectrics reduces the signal wavelength and in areas of small antennas can be used to reduce the antenna dimensions. Finally, the dielectric permittivity also influences the wave impedance and can be used to match the impedance of antennas to the radiation media and enhance their gain. This article provides a brief review of some of these applications.
Dielectric Resonator Filters
Authors: Bila S. , Baillargeat D. , Verdeyme S. , Guillon P. 
Published: April 2005

AbstractDielectric resonators (DRs) are widely used in microwave circuitry since these components offer a higher integration than do classical empty waveguides and, at particular frequency bands, equivalent electrical performances. This article deals with the design of bandpass microwave filters employing DRs. The electrical characteristic parameters of these circuits are introduced in the first section. In the second section, different topologies of microwave filters using cylindrical DRs are described. The third section is a review of particular applications of DRs in microwave filtering: power handling, out‐of‐band rejection, and high frequency. Finally, the last section proposes an electromagnetic optimisation methodology for the design of DR filters.
Dielectric Resonator Oscillators
Authors: Fusco Vincent F. , Dearn Andrew 
Published: April 2005

AbstractA dielectric resonator (DR) can be used to form the stabilizing element in an oscillator. Dielectric resonator oscillators (DROs) are characterized by the following properties: high‐frequency stability, high efficiency, and low manufacturing cost. They also can be made to provide good temperature stability.Two‐ and three‐terminal active devices exhibit phase noise characteristics at microwave frequencies. Oscillators constructed using these devices can have their phase noise behavior improved by the addition of a DR element.
Directional Couplers
Authors: Rozzi Tullio , Morini Antonio 
Published: April 2005

Abstract
The directional coupler (DC) is the most useful four‐port microwave device. Substantially, it consists of a four‐port device, where a wave entering any port excites two other ports with prescribed amplitudes, whereas the remaining port is isolated. This property makes the DC an essential component when dealing with microwave devices, as it allows to distinguish reflected waves from incident ones. After a definition of the ideal DC, the typical parameters and the electrical characteristics of actual devices are illustrated, then, the main applications are considered and, finally, some common realizations of DC are shown, particularly focusing the attention on different coupling mechanisms and technologies.