bluuebunny/crossref_metadata_2025 huggingface dataset:
Mutual impedance between two parallel thin linear antennas in chiral medium
Authors: Bhattacharyya Asoke K.
Published: July 2007

The problem of mutual coupling between two parallel thin linear antennas in chiral medium is addressed in this article. Expressions for self‐ and mutual impedances are presented. The effect of chirality of the radiating medium on the mutual resistance and reactance is discussed. It is found that with proper choice of parameters the chirality of the medium may considerably reduce the mutual impedance effect. Also discussed is the role of chirality on the projected values of the self‐ minus mutual resistance of the antenna, which is important in antenna array design. It may be concluded that under certain conditions the self‐ minus mutual resistance is considerably smaller than in the achiral case, so that an array made with chiral antenna elements may produce higher gain.
Computations of the diffraction effect and the nonlinear effect on spatial solitons in nonlinear planar waveguides
Authors: Bian Jie‐Ren , Chan Andrew K.
Published: July 2007

The nonlinear effect and the diffraction effect on a spatial soliton are isolated by rewriting the nonlinear Schrödinger equation into a form of the linear Schrödinger equation with a nonlinear potential. Numerical results on these effects are obtained for a fundamental spatial soliton, a second‐order spatial soliton, and two coupled solitons in a parallel‐plate waveguide. The effects of waveguide loss are also included.
A quasilumped six‐port reflectometer for cellular radio use
Authors: Riddels G. , Fusco V. F.
Published: July 2007

This article describes the design, construction, and performance of a six‐port reflectometer which operates at 925 MHz and is designed for on‐line cellular radio RF component measurement. The effects that reflectometer subcircuit performance have on overall six‐port operation are discussed in terms of the six‐port constants. Due to the conservative bandwidths required by the application, narrow‐band quasilumped hybrid and power splitter circuits are employed throughout. The final design is suitable for ultimate implemenation in MMIC form.
Synthesis of far‐field patterns of circular cylindrical arrays
Authors: Narasimhan M. S. , Rao R. Srihari
Published: July 2007

An analytically simple and numerically efficient procedure to synthesize the far‐field patterns of a cylindrical array of point dipoles with uniform spacing is presented. FFT is employed to determine the excitation currents. A numerical example is presented to validate the synthesis procedure suggested.
Holographic photoelectro‐chemical etching of submicron gratings in n‐InP for DFB/DBR lasers
Authors: Wu Jie , Liu Ruitang , Lin Senmao
Published: July 2007

Second‐order diffraction gratings for 1.55‐μm DFB/DBR lasers have been formed by holographic photoelectrochemical (PEC) etching directly on n‐InP substrates with high uniformity and reproducibility. In particular, the dependence of PEC etching rate on the biasing voltage is investigated. The optimum biasing voltage is also given.
Determination of circuit parameters in a 10‐GHz microstrip RF squid
Authors: Jackson Charles M. , Hu R. , Burch J. F.
Published: July 2007

We have fabricated and tested RF SQUIDS made of Nb and YBa2Cu3O7 (YBCO), a high‐temperature superconductor, at 10 GHz using TE011 mode cavities and HTS microstrip resonators. Devices were screened at 27 MHz, and subsequently evaluated at 10 GHz. The SQUID circuit parameters, k2Q and β, were determined at different temperatures.
Application of the finite element method to Monte Carlo simulations of random rough surface scattering with Neumann boundary conditions
Authors: Krause K. C. , Lou S. H. , Tsang L. , Chan C. H.
Published: July 2007

Scattering from a one‐dimensional random rough surface with Neumann boundary conditions is analyzed using a finite element formulation. Results are in excellent agreement with tapered‐wave integral equation solutions after averaging over realizations. Finite element advantages in CPU time, memory storage, and energy conservation tests are illustrated.
Reduction of the RCS of the leading edge of a conducting wing‐shaped structure by means of lossless dielectric material
Authors: Booysen A. J. , Pistorius C. W. I. , Malherbe J. A. G.
Published: July 2007

The radar cross section of the leading edge of a conducting wing‐shaped structure is reduced by replacing part of the structure with a lossless dielectric material. The structure retains its original external shape, thereby ensuring that the aerodynamic properties are not altered by the structural changes needed to reduce the radar cross section.
Circular coaxial line with a cross of unequal arms as inner conductor
Authors: Lin Weigan
Published: July 2007

Presented here is a circular coaxial line with a cross of unequal arms as the inner conductor to enable us to have two parameters at our disposal to adjust the line characteristics more freely.
Design considerations for high‐TC superconductor microstrip lines based on current distributions
Authors: El‐Ghazaly Samir M. , Itoh Tatsuo , Hammond Robert B.
Published: July 2007

The current distributions on microstrip lines with finite conductor thickness and finite conductivity are investigated in the TM mode. It is found that the lower surface of the conducting strip carries significantly more current than the upper surface. The percentage of the current carried by the lower surface increases with increasing dielectric constant of the substrate. Detailed information on current distributions is useful in design of high‐Tc superconductor lines.
Optimal focusing of gaussian beams
Authors: Brand Faria J. A. ÃO
Published: July 2007

It is well known that a thin focusing lens, placed at the waist of a Gaussian beam with spot size wo, produces a new beam with a smaller waist spot size, given approximately by w'o ⋍ wof/zR, located approximately at the lens focus (where zR is the beam Rayleigh range and f is the lens focal length). We show that the worst situation, corresponding to the maximum waist spot size, occurs when the lens is placed such that the waist of the original beam is at the lens focus. For this case, the focused beam has its new waist at the other lens focus and its spot size is exactly equal to wof/zR. To optimize (minimize) the focused beam waist spot size the lens should be placed as far away as possible from the original beam waist.
On the analysis of microwave MESFET mixers
Authors: Nguyen Cam , Christodoulou Chistos
Published: July 2007

A new and efficient analysis method for microwave MESFET mixers was developed. The analysis incorporates harmonic balance large‐signal analysis, implemented using robust and fast numerical algorithms, into an extended small‐signal analysis originally developed for diode mixers. Simulated performance of a GaAs MESFET mixer circuit using the developed analysis and the commercially available software LIBRA agree very well.
The harmonic gyrotron with a symmetrical double‐ridge structure
Authors: Jianming Gong , Shenggan Liu , Jianhua Xu , Hongbo Cui
Published: July 2007

Analysis of a gyrotron with symmetrically double‐ridge structure shows that the growth rate and efficiency are high only when high‐order mode is combined with high‐order harmonic. The results illustrate that the ridge TE3301 gyrotron is effective at decreasing dc magnetic field B0, and has a growth rate of 10−2 level, a saturation efficiency of 51%, and an output power of QPw = 1800 MW.
Homodyne detection of polarization modulated optical signals
Authors: Betti S. , De Marchis G. , Iannone E. , Lazzaro P.
Published: July 2007

The first homodyne optical receiver for polarization modulated signals is proposed. It is based on the baseband detection of the four quadratures of the electromagnetic field and, from these, the evaluation of the Stokes parameters. The performance is about the same as that of heterodyne ASPSK, so that it seems particularly suitable for high‐bit‐rate systems in FDM environment.
Reciprocal properties of the dyadic Green's function for planar multilayered dielectric/magnetic media
Authors: Barkeshli S. , Pathak P. H.
Published: July 2007

Reciprocal relations are obtained for the electric dyadic Green's function pertaining to planar multilayered dielectric/ magnetic media. These relationships are developed via a utilization of the Green's theorem at the dyadic level.
Accuracy of swept‐frequency measurement of optical modulator frequency response
Authors: Zhu Ning Hua , Zheng Xing Shi , Lin Yi Kun
Published: July 2007

Formulas explaining the principle of the swept‐frequency technique of measuring modulation depth have been derived for square‐wave distortion. Further investigation shows that when the drive voltage is smaller than 1/3 V/pi the measurement is sufficiently accurate for practical application.
A polarimetric optical microrotation sensor employing A birefringent uniaxial crystal
Authors: Faria J. A. Brandão
Published: July 2007

A polarimetric sensor suited for microrotation measurements is described. Its basic component is a uniaxial crystal inside which the extraordinary wave velocity changes with rotation, thus altering the monitored polarization state of the light coming out of the crystal.
Electromagnetic scattering of waves by random rough surface: A finite‐difference time‐domain approach
Authors: Chan C. H. , Lou S. H. , Tsang L. , Kong J. A.
Published: July 2007

Monte Carlo simulation of random rough surface is carried out using the finite‐difference time‐domain (FDTD) method. The solution domain is truncated using a periodic and an absorbing boundary condition. The advantages of using FDTD include (1) matrix inversion is eliminated, (2) time‐domain response is readily available, and (3) scattering intensities for a range of frequencies can be obtained simultaneously.
Concatenated coding for multipulse signaling in noisy optical channels
Authors: Fares Doaa A.
Published: July 2007

Multipulse signaling applied to optical communication channels has become known as a bandwidth efficient signaling format [1]. However, to achieve reliable communication in noisy channels we must resort to some sort of coding. In this article, concatenated coding, recommended by the Consultive Committee for Space Data Systems (CCSDS), is investigated [2] and compared to the standard Reed‐Solomon coding of pulse position modulation signaling.
Rectangular microstrip antenna along a helical direction on a cylindrical substrate
Authors: De Castro Lima Antonio Cesar , Giarola Attilio José
Published: July 2007

A theoretical analysis of a rectangular microstrip antenna along a helical direction on a cylindrical substrate is shown in this article. The cavity model with magnetic side walls approximation is used for the calculation of the resonant frequency and input impedance. The theory of dyadic Green's functions in conjunction with the saddle point method are used for the evaluation of the far fields. Results are shown for the TM01 mode.
Double‐resonance antenna
Authors: Seaux J. P. , Reineix A. , Jecko B.
Published: July 2007

This article describes a new kind of microstrip antenna that uses a double‐resonance phenomenon to radiate as a short dipole. The working wavelength of this antenna is approximately eight times the maximum dimension of the antenna.
Microstrip compact bandpass filters
Authors: Roduit J.‐C. , Skrivervik A. , Zürcher J.‐F.
Published: July 2007

A simple but efficient synthesis method of microstrip bandpass filters using particularly compact resonators is proposed.
Radiation of elementary time‐harmonic current in chiral half‐space
Authors: Cheng Dajun , Xue Liangjin , Xu Reimin
Published: July 2007

The radiation emitted by an elementary time‐harmonic current placed vertically and in parallel in a chiral half‐space bounded by a perfect conductor is studied using an exact formulation. It is found that the coupled image principle holds for both cases.
Laser‐beam diameter measurement using periodic logarithmic grating
Authors: Awwal A. A. S. , Klemer D. R. , Birt T. A. , Vallapareddy M. R. , Kurek C. G. , Kauffman H. G. , Turumella S. R. V. , Flahive S. P.
Published: July 2007

A novel logarithmic grating is proposed for Gaussian laser‐beam diameter measurement. The grating provides accurate measurement of submicron to millimeter diameter laser beams.
Radiation of open‐ended waveguides into stratified media
Authors: Gentili Guido Diffi , Manara G. , Pelosi G. , Tiberio R.
Published: July 2007

A hybrid technique for combining the method of moments and ray methods is applied to analyze a rectangular waveguide‐fed aperture radiating into a semi‐infinite medium through an interposed layer. Numerical and experimental results are compared to test the accuracy and the applicability of this method.
Radiation loss due to step discontinuities in symmetric biaxially anisotropic slab waveguides
Authors: Beker B. , Ho T. Q.
Published: July 2007

This paper is an extension of previous work [1] dealing with guided wave propagation through step discontinuities in anisotropic slab waveguides which focused on the radiated fields only. As opposed to the earlier work, this paper deals with radiation power losses suered by a guided mode incident on the junction, with calculation carried out by an approximate perturbation technique. In addition, the radiation mode solutions to Maxwell's equations in a symmetric biaxially anisotropic slab waveguide are presented for both odd and even symmetries. Characteristics of anisotropic guides are discussed and compared to those of their conventional isotropic counterparts.
Scaled‐down RCS study of a rectangular flat plate coated with lossy material
Authors: Zeng Xuegang , Ruan Chengli , Lin Weigan
Published: July 2007

In terms of an asymptotic high‐frequency estimation of monostatic far‐field radar cross section (RCS) of the rectangular flat plate coated with lossy material, which is derived here from a UTD formula of the impedance wedge, the scaled‐down RCS is studied in this article, while the lossy material used in a scaled‐down model cannot satisfy the physical equivalence conditions.
Predicting openwork shielding efficiency using waveguide aperture discontinuity model
Authors: Yeo T. S. , Leong M. S. , Kool P. S.
Published: July 2007

Openwork shielding efficiency is predicted using a waveguide aperture discontinuity model. Theoretical results are obtained using modal analysis and are found to agree closely with Chen's [1] formulas for prediction of openwork shielding efficiencies.
Equivalence of electric and magnetic sources: A paradox
Authors: Van Bladel J.
Published: July 2007

Formulas exist for replacing an electric current J1 by an equivalent magnetic current K2, and conversely a K2 by an equivalent J3. The latter could therefore be expected to be equivalent to J1. The equivalence, if not handled carefully by “distributional” methods, leads to apparent paradoxes. The resolution of the paradox is based on the use of a formula for the curl of a surface current.
Antenna sheaths in a dusty plasma
Authors: Lonngren Karl E.
Published: July 2007

The region of charge nonneutrality surrounding a metal antenna that is inserted in an infinite homogeneous plasma is called a plasma sheath. Sheaths form in several time scales that are determined by the electron and the ion plasma periods until an eventual steady‐state Langmuir sheath forms. This article describes the sheaths surrounding an antenna in a dusty plasma consisting of electrons, ions, and heavy dust particles to which electrons have attached themselves. Such a plasma is found in active comets and in the rings surrounding several planets in the solar system and in rings around mature stars.
Theory and design of microwave planar electrodes for stochastic cooling of particle beams
Authors: Mcginnis David P.
Published: July 2007

Stochastic cooling is a broadband microwave feedback system used in particle accelerators to reduce beam size growth. Because stochastic cooling is a random process, the performance of the system is directly proportional to the bandwidth of the system. Electrodes that sense and correct the position of particles in the beam must accommodate octave bandwidths in the range from 1 to 16 GHz. This article will outline the theory, design, and measurements of planar electrodes that achieve these wide bandwidths.
Analysis and design of a planar balun
Authors: Nguyen T. , Beyer J. B.
Published: July 2007

The analysis and design of a planar balun is presented. The balun consists of three closely placed parallel metallic strips situated on a dielectric substrate. The effective dielectric constants and characteristic impedances for the three independent propagating modes supported by the structure are obtained using the spectral domain approach. Design information is extracted from a three‐port admittance matrix derived in terms of these modes.
Characteristic impedance of a soliton‐bearing nonlinear transmission line
Authors: Lin‐Liu Y. R. , Chan V. S. , Degrassie J. S. , Ikezi H.
Published: July 2007

The wave reflection and transmission in a nonlinear LC transmission line terminated with a resistive load are studied numerically. It is found that the soliton signals in the strongly nonlinear transmission line are almost perfectly absorbed by the linear resistor terminating the transmission line.
Propagation of profiled optical beams through kerr media
Authors: Banerjee Partha P. , Misra Raj M.
Published: July 2007

The propagation of profiled optical beams through cubically nonlinear Kerr media is investigated, theoretically and numerically. Specifically, propagation through both thin and thick nonlinear media are examined, and the far‐field pattern after exit from the nonlinear medium are studied. The profiles investigated are Gaussian and sinctype, the latter obtained from the Fourier transform of a rectangular slit.
Smooth saddle rf coil for magnetic resonance imaging
Authors: Vaslow Dale F.
Published: July 2007

A new saddle‐shaped radio frequency coil for magnetic resonance imaging is described. Unlike current “saddle‐shaped” coils made from straight‐line segments and circular arcs, this coil is formed from two smoothly continuous loops, each of which is the intersection of an elliptical cylinder and an elliptical cone. Both the Helmholtz and crossed‐ellipse coils are limiting forms of the smooth saddle coil. When compared to the traditional cylindrical saddle and crossed‐ellipse coils, improvements in the homogeneous magnetic field volume are noted. A modest improvement in the signal‐to‐noise ratio is expected.
A superconductive dual‐control active microwave device
Authors: Beyer James B. , Nordman James E. , Hohenwarter Gert K. G. , Martens Jon S.
Published: July 2007

In this article we review the background material necessary for the understanding of the operation of superconducting flux flow transistors. A new microwave flux flow device is then presented which exhibits behavior analogous to that of a dual‐gate FET. Equivalent circuits and experimental results are presented.
Design and properties of fabricated superconducting microstrip delay lines made with nb, nbn and ybco
Authors: Hohenwarter G. K. G. , Track E. K. , Drake R. E. , Patt R. , Radparvar M.
Published: July 2007

We report on design, computer modeling, and experimental evaluation of delay lines fabricated with Nb, NbN, and YBCO superconducting thin films. Constraints resulting from the need to achieve long delays on small substrates and the unavailability of some directly applicable models for simulations will be addressed.
Second harmonic modulation in potassium niobate
Authors: Boothroyd S. A. , Chrostowski J. , Lian H.‐X. , Rawicz A. , Deen J.
Published: July 2007

We consider potassium niobate as a medium for room‐temperature second‐harmonic generation at 430 nm and electro‐optic modulation in a single crystal. Modulation voltages of the order of 60 V are needed to fully switch the second harmonic for an electric field applied along the crystal c axis and modulation frequencies in the megahertz range. Although the electro‐optic coefficient for a field applied along the crystal b axis is 10 times larger than for the c‐axis modulation, the voltage required is three times higher. A laser‐diode‐pumped source of high‐frequency intensity‐modulated blue laser light may find application for undersea communication.
The radiation characteristics of a resonant meander line section as a monopole
Authors: Rashed‐Mohassel J.
Published: July 2007

The characteristics of a meander line section at resonance is studied and the current distribution along the wire is obtained. The far‐field components and the effect of wire radius are studied, and a transition from a simple meander monopole as a compact radiator to a meander line section is investigated.
The effect of laser chirping on optical subcarrier multiplexed system with high‐bit‐rate baseband signal
Authors: Tsao Hen‐Wal , Ho Keang‐Po , Lee Yang‐Han
Published: July 2007

The mixed transmission of digital and analog signals via single‐mode fiber has potential in future fiber‐optic systems. We have studied the effect of chirping of the baseband digital signal on the analog subcarrier channels using computer simulation. If the location of the subcarriers or the bias of the laser is selected properly, the SNR penalty due to chirping and cross talk will be less than 0.5 dB.
A new type of coaxial line of rectangular and oval cylinders with constant electric intensity on the latter cylinder
Authors: Lin Weigan
Published: July 2007

Denoting g(x + iy) = 1/αβ sn2(x + iy, k0) ‐ A/sn2(x + iy, k0) ‐ A/β

A = 1 + α/1 ‐ α/β and k20 = (1 ‐ α/β)/(1 + α)2

we find an equipotential of constant electric intensity to form a new type of TEM transmission line for industrial applications.
Hansen‐woodyard arrays with few elements
Authors: Hansen R. C.
Published: July 2007

Small endfire arrays of isotropes with uniform amplitude and progressive phase are examined. The directivity is maximized, and the increased phase and directivity values are given for N = 2–20.
Vectorial far‐field analysis of the fresnel‐zone plate antenna: A comparison with the parabolic reflector antenna
Authors: Leyten L. , Herben M. H. A. J.
Published: July 2007

An analysis of the radiation properties of the Fresnel‐zone plate antenna (FZPA) and the parabolic reflector antenna (PRA) is presented using the Kirchhoff diffraction theory. Expressions are derived for the vectorial far‐field radiation patterns of both antennas. Some computed co‐ and cross‐polar patterns are shown. The most important differences between the radiation properties of the FZPA and PRA are revealed and discussed. The results of the analysis give good insight into future applications of the FZPA.
Single‐screen triband fss with double‐square‐loop elements
Authors: Wu T. K.
Published: July 2007

A single‐screen double‐square‐loop (DSL) frequency selective surface (FSS) has been developed and tested for triband applications (i.e., to reflect the X‐band and to pass the S‐ and Ku‐band waves). Good agreement between predicted and measured transmission performance is obtained for the DSL FSS on a 0.001‐in.‐thick Kapton with/without a flat Kevlar honeycomb sandwich panel. It is found that this single‐screen DSL FSS with/without the Kevlar honeycomb has a resonant frequency near 8.4 GHz for incident angle steered from normal to 45° and for both TE and TM polarizations.
Plane chiral waveguides with boundary impedance conditions
Authors: Oksanen Markku I. , Koivisto Päivi K. , Tretyakov Sergei A.
Published: July 2007

This article discusses electromagnetic wave propagation in chiral slab waveguides that are characterized by surface impedances of different types. The method applied makes use of the vector circuit theory and the related tangential field requirements on the slab surfaces. The method forms a coherent and solid approach to parallel‐plate waveguide analysis, since all cases considered can be solved from the same general eigenvalue equation. The theory is illustrated by numerical examples.
Comparison of the slope of the field at the reflection boundary of an edge‐induced and surface‐curvature‐induced microwave shadows
Authors: Rahnavard M. H. , Rusch W. V. T.
Published: July 2007

Using diffracted‐field formulas the slope of the field is evaluated at the reflection boundary of an edge‐induced shadow. Retaining high‐frequency terms the wavelength dependency is (λ)−1/2. Using a formula for the field near the turning point of an inflected surface the slope of the field at the reflection boundary is evaluated. Retaining high‐frequency terms, the wavelength dependency is (λ)−5/6 in this case. That is, the shadow for the surface‐curvature‐induced case gets sharper nearly twice as fast as for the edge‐induced case as the frequency increases. This slope is a measure of spillover into the shadow region.
Modeling wire dipoles in an infinite chiral medium and vertically oriented near a chiral half space
Authors: Bhattacharyya Asoke K. , Burke Gerald J. , Miller Edmund K.
Published: July 2007

Extension and application of the NEC (numerical electromagnetics code) thin‐wire model to a wire dipole in an infinite chiral medium and vertically oriented near an interface between a free space and a chiral half space is described. This particular problem was chosen as one in a sequence leading to a capability for modeling wire antennas and scatterers of arbitrary geometry located on either side of, or penetrating such an interface. Results are presented as a function of medium chirality for the dipole in an infinite medium and as a function of chirality and height for the half‐space problem. An approximation for the latter problem which uses the reflection‐coefficient approximation (RCA) is compared with the rigorous treatment and found to produce acceptable results for the cases studied.
On the chiral riccati equation
Authors: Jaggard D. L. , Sun X. , Liu J. C.
Published: July 2007

Chiral media is characterized by a particular handedness and subsequent coupling between electric and magnetic fields as evidenced by the constitutive equations. Wave propagation in stratified chiral media is examined through an initial‐value approach which yields a matrix Riccati equation for the local reflection coefficient, valid for arbitrary angle of incidence. The first reported solution for reflection from an inhomogeneous chiral transition layer is given here.
Novel configuration of transmissive active star couplers using minimum erbiumdoped fibers and pump lasers
Authors: Liaw Jy‐Wang , Chen Yung‐Kuang
Published: July 2007

In this letter we propose a novel configuration by using the basic 4 × 4 active star coupler and the 2 × 2 fiber coupler as building blocks to construct a larger transmissive single‐mode fiber‐optic N × N coupler with gain using minimum erbium‐doped fibers and pump lasers. This configuration provides three main advantages, i.e., high cost effect, pump wavelength independence, and configuration flexibility. The 64 × 64 active star coupler with 4‐dB net gain using moderate pump power is also discussed. It is found that the saving of total cost of the proposed configuration can be more than 55% and 40% of those used previously [1], for 980‐ and 1480‐nm pump lasers, respectively.
Radiation of elementary dipole sources in stratified chiral media
Authors: Cheng Dajun , Cheng Jihua , Xue Liangjin
Published: July 2007

EM radiation of the arbitrarily oriented elementary dipole sources, both electric and magnetic types, embedded in stratified chiral media is investigated using the matrix analysis, in conjunction with the Fourier transformation techniques for the observation points not near the excited sources.
A novel amplifier combining high gain, output power, and efficiency
Authors: Albinsson Björn , Schöön Martin
Published: July 2007

A novel amplifier configuration combining the output power handling capability and efficiency of a balanced amplifier with the gain of a cascaded amplifier is presented. Equations are presented for the gain dependency and the principle is verified by measurements.
Perturbation theory for a cavity resonator with a bi‐isotropic sample: Applications to measurement techniques
Authors: Tretyakov Sergei A. , Viitanen Ari J.
Published: July 2007

Resonator measurement techniques for exploring electromagnetic parameters of bi‐isotropic (nonreciprocal chiral) materials are discussed. The bi‐isotropic materials are the most general linear isotropic materials, and the corresponding constitutive relations are governed by four parameters. A theory of resonator measurement techniques, based on the perturbation analysis, is developed. It is shown that the complex permittivity, permeability, and nonreciprocity (Tellegen) parameter of a small sample can be determined by measuring resonant frequency shifts in a rectangular resonator. To measure the nonreciprocity parameter, a method utilizing a rectangular resonator with two degenerated modes is proposed.
Vernier fiber double‐ring resonator using degenerate two‐wave mixing
Authors: Ja Y. H.
Published: July 2007

We propose the use of degenerate two‐wave mixing in a Vernier optical fiber double‐ring resonator which consists of two single‐coupler fiber rings in series. With the degenerate two‐wave mixing, the Vernier operation can be achieved. In consequence, the effective free spectral range increases significantly and the signal beam is amplified.
A reciprocal phase shifter using novel pseudochiral or ω medium
Authors: Saadoun Mamdouh M. I. , Engheta Nader
Published: July 2007

Here we introduce an idea for a reciprocal phase shifter using a novel class of material, which we name pseudochiral or ω medium. We describe this complex material electromagnetically by a set of bianisotropic constitutive relations, and present the physical insights into the coupling mechanism exhibited in such media. We analyze theoretically the dispersion characteristics of guided modes in a rectangular waveguide loaded partially with a slab of this material. It is shown that the propagation constant β of guided modes can be shifted due to coupling coefficients present in the medium. It is also shown that, unlike the case of magnetically biased ferrite‐loaded waveguide, the dispersion relations here are independent of the direction of propagation, and thus reciprocal phase shifting can be achieved. Potential applications and motivations behind this study are also mentioned.
Microwave imaging for dielectric objects under the born approximation based on projection
Authors: Suh Kyoung‐Whoan , Kim Sang‐Gi , Kim Se‐Yun , Ra Jung‐Woong
Published: July 2007

Microwave imaging for dielectric objects under the Born approximation is suggested by using the computerized tomography based on projection. Limiting factors of degradation in reconstructed images are identified and explored in terms of projection function and necessary condition on the first‐order Born approximation. To illustrate the usefulness of the presented method, simulation and experiment are performed in this article.
Circular microstrip antenna on a spherical surface
Authors: De Castro Lima Antonio Cesar , Descardeci José Ricardo , Giarola Attilio José
Published: July 2007

A theoretical development for the analysis of a circular microstrip antenna on a spherical surface is described here. It consists of using the cavity model with magnetic side walls and the dyadic Green's function formulation. Expressions for calculating the resonant frequency and input impedance are given. A particular example with the antenna operating in its fundamental mode is examined. The characteristics of this antenna, including its radiation pattern, are presented.
Design, analysis, and development of a high power, low‐loss lumped coupler for vhf applications
Authors: Agarwal A. , Kakatkar S. S. , Sarkar B. K.
Published: July 2007

Lumped constant branch line couplers are analyzed and compared with coaxial branch line couplers. The effect of resistances associated with inductors and capacitors on the coupler's performance is studied. Three high‐power lumped couplers of 3 dB, 6 dB, and 10 dB are designed at 53 MHz. Insertion loss of less than 0.1 dB and 40‐kW peak power handling capability is achieved.
Bend loss of step‐index slab waveguides with a trench section
Authors: Yamauchi Junji , Ikegaya Morihiko , Nakano Hisamatsu
Published: July 2007

An optical waveguide bend with a trench section whose refractive index is smaller than that in the cladding is investigated to reduce bend loss. The appropriate location and width of the trench are determined using the beam propagation method. It is found that the attenuation constant shows a minimum value when the trench is made around the radiation point where the field becomes radiative.
Analysis and measurement of mutual coupling between two series‐fed electromagnetically coupled transverse dipoles
Authors: Tessereau S. , Floc'h J. M. , Legay H. , Citerne J.
Published: July 2007

Calculations and measurements of mutual coupling between two series‐fed dipoles electromagnetically coupled transverse dipoles versus element spacing is presented. Calculations are based on an integral equation technique combined with a two‐port model of the coupled elements. An excellent agreement between theoretical and experimental results is observed.
Effect of imperfectly conducting surface of scatter on its radar cross section
Authors: Zhendong Shi , Chunsheng Ding
Published: July 2007

The scale‐down model testing of radar cross section for imperfectly conducting bodies requires physical similarity between models and prototype. Practically, it is often impossible to satisfy all the requirements at the same time; so it is necessary to study the effect of imperfectly conducting surface of scatter on its RCS. Dimensional analysis and theory of the model are used. As a result, relationship between σ/λ2 and λs is obtained, and the comparison between theoretical and experimental values for a cylinder coated with absorbent materials is given.
δmax detection of multipulse signaling in noisy optical channels
Authors: Fares D. A. , Abul‐Shohoud W. H. , Raslan N. A. , Nassef M. A.
Published: July 2007

Optical communication has recently been given a great deal of attention because of its anticipated contribution in increasing our data transmission capability. δmax detection of Reed‐Solomon coded PPM (RSPPM) signaling has been seen as a reliable detection technique [1]. In this article we extend the application of this detection technique to the coded Steiner‐triple pulse format, which has recently proved its outstanding features [2, 3]. It is shown here that an improved performance (with respect to RSPPM), in addition to modest bandwidth expansion and efficient transmission bandwidth, are obtained.
Accurate gaussian laser beam diameter measurement using exponential and rectified sinusoidal rulings
Authors: Cherri A. K. , Awwal A. A. S.
Published: July 2007

Novel exponential and rectified sinusoidal gratings for the measurement of Gaussian laser beam diameter are proposed. It is found that these gratings provide accurate measurement for both small and large Gaussian beam diameters.
Modal analysis of coaxial structures
Authors: O'Clardha T. E. , Lyons B. N.
Published: July 2007

A modal analysis of a coaxial filter is presented. It is shown that a conventional TEM analysis can be inadequate and can lead to poor component performance. Guidelines are included for avoiding this problem.
Temperature dependence of schottky versus backward diodes for radiometry applications
Authors: De Maagt Peter J. , Buss Tom F. , Van Roer Theo G. De
Published: July 2007

In this article the temperature behavior of Schottky and backward diodes operating as square‐law detectors at microwave frequencies is presented. To make a quantitative comparison between both diodes possible, the most important diode parameters are discussed. The criteria for comparison are the voltage sensitivity and the video resistance. © 1992 John Wiley & Sons, Inc.
Optimization of pulse radiation from a simple antenna using resistive loading
Authors: Maloney James G. , Smith Glenn S.
Published: July 2007

The performance of a simple antenna, the open‐ended parallel‐plate waveguide, is optimized for pulse radiation by including a section of waveguide with tapered resistive loading. The novelty of the optimization is that the resistive loading is not only used in the traditional sense to reduce internal reflections, but the frequency dispersion inherent in the loading is also used to compensate for the distortion of the pulse on radiation from the open end. The analysis and optimization are performed using the finite‐difference time‐domain (FDTD) technique. The approach introduced here for optimizing this simple radiator should be applicable to more complex, practical antennas. © 1992 John Wiley & Sons, Inc.
The constitutive parameters of a lossy chiral slab by inversion of plane‐wave scattering coefficients
Authors: Cloete Johannes Hendrik , Smith Anthonie Gronum
Published: July 2007

It is shown how the three complex constitutive parameters of a lossy, homogeneous chiral slab may be obtained from its scattering parameters for illumination by a normally incident, linearly polarized plane wave. The method involves mathematical inversion of the scattering parameters and the result is an explicit, noniterative algorithm which yields the unknown constitutive parameters directly. © 1992 John Wiley & Sons, Inc.
Spectral domain analysis of rectangular microstrip antennas with an air gap
Authors: Fan Zhibo , Lee Kai‐Fong
Published: July 2007

A spectral domain analysis of the rectangular microstrip antenna with an air gap is presented. Numerical results are given on input impedance, resonant frequency, and radiation patterns. It is found that, as the air gap width increases, both the resonant frequency and the impedance bandwidth increase, accompanied by a decrease in beamwidth. © 1992 John Wiley & Sons, Inc.
Scale factors of rcs for lossy targets
Authors: Zhendong Shi
Published: July 2007

In this article the scale factor of RCS for lossy targets is given, by which the RCS of a complex lossy target can be calculated in terms of scale‐model testing, even though the model does not satisfy similarity becausse of coated absorbent materials. © 1992 John Wiley & Sons, Inc.
Low loss electronically tunable bandpass filters on the gaas substrate
Authors: Bahl Inder J. , Griffin Edward L.
Published: July 2007

A new structure for a tunable bandpass filter is described in this letter. The bandwidth or bandpass response of the filter can be varied electronically by using high Q varactors or Schottky diodes. © 1992 John Wiley & Sons, Inc.
H‐scattering of thin‐film modes from periodic gratings of finite extent
Authors: Andrenko Andrey S. , Nosich Alexander I.
Published: July 2007

Dielectric thin‐film guided mode scattering from a finite‐element periodic grating of circular wires or circularly curved metal strips is considered. An accurate solution method is developed and results of computations for the H case are given. © 1992 John Wiley & Sons, Inc.
Complete characterization of MESFET Ids nonlinearities for intermodulation analysis
Authors: Pedro José C. , Perez Jorge
Published: July 2007

This work shows that an accurate characterization of the nonlinear distortion of a GaAs MESFET, does not allow the common approach of splitting the Ids, (Vds, Vds) current in two voltage‐dependent nonlinear current sources, Gm(Vgs) and Gdx(Vds). It is shown that the cross terms of the Ids Taylor series expansion can give an important contribution to the MESFETs intermodulanon distortion behavior. A laboratory procedure for the complete characterization of that element is given. © 1992 John Wiley & Sons, Inc.
Microwave active filter using GaAs monolithic floating active inductor
Authors: Zhang Guang Fei , Villegas M. L. , Ripoll C. S. , Gautier J. L.
Published: July 2007

A broadband tunable microwave floating active inductor is proposed. Its application in the microwave active filter is presented. The design technique is to replace the passive inductor in the conventional LC ladder filter by the proposed floating active inductor. These active filters can, therefore, be implemented in full MMIC form. © 1992 John Wiley & Sons, Inc.
Analysis and development of a broadband interconnect for microstrip lines
Authors: Luong Giam‐Minh , Chang Kai
Published: July 2007

An analysis of an interconnect between two microstrip lines is presented. The interconnect is based on a narrow rectangular slot on the common groud plane of two microstrip lines. A moment method procedure is applied to several integral equations that were formulated by Green's functions of the grounded dielectric slabs and unknown electric and magnetic currents. Low insertion loss over an octave bandwidth was achieved for this interconnect. The theoretical results agree very well with measurements. © 1992 John Wiley & Sons, Inc.
Determination of the transverse delays in the GaAs/AIGaAs modfets
Authors: Goel A. K. , Xu Wei
Published: July 2007

We have developed a computer‐efficient algorithm and the related CAD‐oriented software to calculate the transverse propagation delays in a GaAs/AlGaAs MODFET. The model has been used to study the dependence of these delays on the various MODFET parameters. The results can be utilized for the optimization of high‐speed circuits. © 1992 John Wiley & Sons, Inc.
Design parameters of asymmetric edge‐coupled microstrip open‐end discontinuities
Authors: Martel J. , Boix R. R. , Horno M.
Published: July 2007

A lumped capacitance equivalent circuit is used to characterize the asymmetric edge‐coupled microstrip discontinuity in the case in which the conducting strips are embedded in a multilayered anisotropic medium. The Galerkin method in the spectral domain is employed to determine the excess charge density on the strips of the discontinuity. Original results are provided for the general asymmetric discontinuity in conventional and suspended configurations. © 1992 John Wiley & Sons, Inc.
Triadic cantor target diffraction
Authors: Jaggard D. L. , Spielman T.
Published: July 2007

Electromagnetic wave interactions with a triadic Cantor target are investigated as an example of diffraction by fractal apertures. Of interest is the evolution of diffraction pattern with fractal growth for these self‐similar structures, and the development of efficient methods of calculation. It is found that such structures possess self‐similar diffraction patterns and that simple analytic solutions can be found for these geometries. The solutions also exhibit a sense of self‐similarity in their computation. © 1992 John Wiley & Sons, Inc.
A boundary integral approach to the scattering from periodic gratings
Authors: Moore John , Ling Hao , Graf Urs U. , Jaffe Daniel T.
Published: July 2007

A boundary integral formulation is presented for computing the scattering from infinite periodic gratings. Periodic boundary conditions and expansion of the fields in terms of Floquet harmonics allow the boundary integral formulation to treat just a single period of the infinite grating. Numerical results for a blazed grating designed for use at infrared wavelengths are presented and shown to be in good agreement with a series of measurements. © 1992 John Wiley & Sons, Inc.
Phase grating: Analytical formulas for the near field
Authors: Arrizón Victor , Ojeda‐Castañeda J.
Published: July 2007

We present two simple analytical formulas that describe the irradiance distribution, at certain distances, of any phase grating. Our general results are illustrated with two novel examples: the irradiance distribution at the near field of a low‐frequency blazé grating, and that of a phase grating with a triangular profile. © 1992 John Wiley & Sons, Inc.
A formulation for surface impedance boundary conditions using the finite‐difference time‐domain method
Authors: Kashiwa Tatsuya , Chiba Osamu , Fukai Ichiro
Published: July 2007

In this article, a new formulation for surface impedance boundary conditions is carried out using the finite‐difference time‐domain method. In this formulation, the boundary conditions expressed by the equivalent circuit are only considered in a one‐dimensional space. For simplicity, the validity of the formulation is also shown and discussed. © 1992 John Wiley & Sons, Inc.
Threshold detection of a quadruple pulse signaling in noisy optical channels
Authors: Fares Doaa A. , Rasian Nabil A. , Kaseb Hassan M.
Published: July 2007

In references [1, 2], triple multipulse position modulated (TPPM) signaling has been introduced as a very reliable format for optical communication channels. In this article, such a multipulse model is extended to the Steiner quadruple pulse system (SQS). Considering a threshold demodulation scheme for a fully degraded optical channel, performance of the Reed‐Solomon coded model is evaluated and compared to the standard coded PPM, when similar information efficiency and closest bandwidth expansion are allowed. The gained results are very interesting. © 1992 John Wiley & Sons, Inc.
A technique for the large‐signal characterization of transistors
Authors: Tsang Kim Fung , Yip Peter C. L. , Morgan Gwyn B.
Published: July 2007

A novel method for the characterization of transistors operating in the nonlinear region has been developed. A new measurement method is proposed and the formulation for the characterization has been developed. Calculated results based on the proposed method are promising when compared to measured data. © 1992 John Wiley & Sons, Inc.
Excitation of three‐dimensional solitary waves from a nonlinear slab waveguide
Authors: Liu Shuh‐Fang , Wang Way‐Seen
Published: July 2007

Solitary‐wave excitation in a slab waveguide bounded by two different non‐Kerr‐like media exhibiting saturable self‐focusing nonlinearity is investigated. From numerical calculation it is found that solitary waves are emitted from the nonlinear interfaces. Moreover, mutual interaction between them is observed if the excitation is larger. The simulated results are useful for the study of three‐dimensional solitary waves. © 1992 John Wiley & Sons, Inc.
Grid bandpass filters for quasioptical frequency multiplier array application
Authors: Liu Hong‐Xia L. , Sjogren L. B. , Luhmann N. C.
Published: July 2007

A two‐grid approach for quasioptical bandpass filter design is presented. In this design, an inductive/capacitive grid on one side of a dielectric substrate is transformed to an effective capacitive/inductive reactance at the other grid plate, producing a parallel resonant circuit. Two bandpass filters for use in the millimeter region have been fabricated. Low‐loss power transmission at the design frequencies has been achieved with good quantitative agreement with theory. © 1992 John Wiley & Sons, Inc.
Capacitance of rectangular lines with cross inner conductor, considering angular offset between conductors, side magnetic walls, and off‐centered inner conductor
Authors: Costamagna Eugenio
Published: July 2007

Various coaxial line structures having a cross section in which an equiarmed cross is concentric with an external square are analyzed by means of numerical inversion of the Schwarz‐Christoffel conformal transformation, considering angular offset between conductors and electric or magnetic side walls. Geometries with rectangular outer conductor and off‐centered inner cross conductors are considered. Previous works by Riblet [1] and Lin [2–4] are generalized or completed. © 1992 John Wiley & Sons, Inc.
Backscattering reduction of corner reflectors using scs technique
Authors: Ajaikumar V. , Jose K. A. , Aanandan C. K. , Mohanan P. , Nair K. G.
Published: July 2007

Reduction of radar cross‐section of dihedral corner reflectors using simulated corrugated surface (SCS) is reported. This technique is found to be more effective in the reduction of RCS or corner reflectors for normal incidence. A typical reduction of 40–50 dB is achieved using this method. © 1992 John Wiley & Sons, Inc.
Mutual coupling between rectangular microstrip patch antennas
Authors: Huynh Tan , Lee Kai‐Fong , Chebolu Siva Rao , Lee R. Q.
Published: July 2007

A comprehensive study of the mutual coupling between two rectangular microstrip patch antennas is presented. Using the cavity model, numerical results for both mutual impedance and mutual coupling parameter are given for the E‐plane, H‐plane, diagonal, and perpendicular orientations. The effects of substrate thickness, substrate permittivity, and feed positions are discussed. © 1992 John Wiley & Sons, Inc.