bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propagation‐loss prediction for numerical terrain model using uniform theory of diffraction
Authors: Legendre J. F. , Chassay G. 
Published: July 2007

AbstractIn this article, the uniform theory of diffraction (UTD) is applied to the problem of predicting propagation loss in the frequency range of UHF‐VHF using a numerical terrain model. A ray optical model with automatic ray‐tracing algorithm for a two‐dimensional piecewise‐linear terrain profile and field computation method are presented in this contribution. The predicted results are compared with measured data and with the results of other propagation prediction models. © 1994 John Wiley & Sons, Inc.
Effects of superstrate loading on the mutual coupling between rectangular microstrip antennas
Authors: Ke Shyh‐Yeong , Wong Kin‐Lu 
Published: July 2007

AbstractThe mutual coupling of rectangular microstrip antennas covered with a lossy or lossless dielectric superstate is analyzed by using a full‐wave approach. Numerical results are obtained by using a moment‐method calculation. Both the E‐ and H‐plane coupling cases are studied. Results indicate that the level of the coupling between microstrip antennas due to the superstate thickness variation is small. However, with the introduction of loss into the superstate layer, a noticeable reduction in the coupling level can be observed. © 1994 John Wiley & Sons, Inc.
Mode characteristics in a lossy parallel‐plate uniaxial chiro‐omega waveguide
Authors: Wenyan Yin , Wei Wan , Xiaowei Sun 
Published: July 2007

AbstractThe dispersion characteristics of propagating modes in a lossy parallel‐plate uniaxial chiro‐omega waveguide are examined, and numerical results are presented to show the influences of bianisotropy, chirality, and omega parameter on the propagation constant and attenuation rate of different hybrid modes. Furthermore, the field distributions of one‐ and three‐order modes are demonstrated, and the lossy effect is taken into consideration. © 1994 John Wiley & Sons, Inc.
Effect of dielectric coatings on parabolic reflector antenna performance
Authors: Lo K. W. , Bird T. S. 
Published: July 2007

AbstractThe effect of a dielectric coating on the gain, co‐polar radiation pattern, and cross‐polarization level of a linearly polarized parabolic reflector antenna is investigated for both dry and wet surface conditions using a physical optics analysis of the equivalent surface currents. By choosing the correct thickness, the effect of a dielectric coating can be minimized, and, at the same time, an equivalent metal‐reflector representation shows that the antenna gain is less sensitive to the coating surface accuracy.
Solving microstrip discontinuities with a combined mode‐matching and method‐of‐lines procedure
Authors: Meyer P. 
Published: July 2007

AbstractA novel technique combining two‐dimensional method‐of‐lines (MOL) analysis with a mode‐matching procedure to analyze microstrip step discontinuties is presented. The MOL is used to calculate the propagation constants and field distributions at discrete points for a number of modes on both sides of a discontinuity. These modes are matched using a modified discrete mode‐matching procedure to produce a generalized S‐parameter description of the discontinuity. The method uses memory sparingly. Results for two microstrip steps are presented.
Analysis of a broadband slot‐coupled dielectric‐coated hemispherical dielectric resonator antenna
Authors: Chen Nan‐Cheng , Su Hsin‐Cheng , Wong Kin‐Lu , Leung Kwok‐Wa 
Published: July 2007

AbstractDielectric‐coated hemispherical dielectric resonator (DR) antennas fed by a microstrip line through a coupling slot are analyzed. The broadside TE111 mode is studied, and the reciprocity theorem is applied in this analysis. In this case the dielectric‐coated DR antenna can be viewed as a series load at the slot position as seen by the microstrip line. The impedance of this series load is calculated by using a Green's‐function formulation, and the input impedance of the slot‐coupled DR antenna can then be obtained using transmission‐line theory. Numerical results for the input impedance are calculated and presented, and the antenna bandwidth is discussed. It is observed that the antenna bandwidth of a dielectric‐coated DR antenna can be as high as two times that of a DR antenna without a coating.
W‐band dual‐frequency circulators
Authors: Dou W. B. , Sun Z. L. 
Published: July 2007

AbstractW‐band dual‐frequency circulators have been develoved. The dual‐frequency circulator resulting from a dual higher‐order mode is used as stated in [3, 4]. The calculated properties of the dual modes, especially the mode‐change frequency point between the dual higher‐order modes, have been verified experimentally.
Influence of the conducting support on the coupling between two microstrip antennas
Authors: Aubreton Th. , Dufrane Ph. , Vaudon P. , Jecko B. 
Published: July 2007

AbstractIn this article we show that, when the direct coupling between antennas is very weak, the limited support, on which two microstrip patches lie, can be the source of an important parasitic coupling. We consider also the influence of the dimensions and the shape of this support. The theoretical results and the measurements are in a very good agreement in the validity domain of the method.
Scattering of electromagnetic waves by vegetation based on the wave approach and the stochastic lindenmayer system
Authors: Chen Zhengxiao , Tsang Leung , Zhang Guifu 
Published: July 2007

AbstractWave scattering from the trees generated by the stochastic Lindenmayer system is studied by Monte Carlo simulations in this article. The scattering coefficients are calculated in three ways: wave approach, tree‐independent scattering, and independent scattering. It shows that the results of tree‐independent scattering agree well with that of wave approach for medium to high frequency. However, independent scattering is not a good approximation except for very high frequency.
Simple closed‐form expressions for microstrip green's functions in a magneto‐dielectric substrate
Authors: Hoorfar Ahmad 
Published: July 2007

AbstractBy invoking a thin substrate approximation, accurate spatial‐domain expressions for the Green's functions, G, and Gm, of microstrip structures in a magneto‐dielectric substrate are derived. The expression for Gm is given in terms of a quasidynamic solution corresponding to a point source and its partial images, while that of Ge is derived in terms of a quasidynamic contribution plus a correction term. It is demonstrated that the addition of the correction term is needed in order to accurately calculate Ge in the near field.
A comparison of two FFT‐based methods for dielectric scattering problems
Authors: Tran T. V. , McCowen A. 
Published: July 2007

AbstractThe performance of two FFT‐based methods for solving dielectric scattering problems is investigated. The first method is associated with van den Berg's integrated‐squared‐error algorithm, where the variational basis function is based on a generalized Neumann series (GNS) expansion of the inverse of the defining integral operator. The second method is the biconjugate‐gradient FFT (Bi‐CGFFT) for symmetric indefinite systems. Both methods are applied to a variety of dielectric problems encompassing both homogeneous and inhomogeneous material compositions in twoand three‐dimensional spaces. Particular emphasis is placed on the identification of the class of problems that yield nonconvergence for the Bi‐CGFFT and the alleviation of this undesirable behavior.
Analytic study of mode locking with a nonlinear mirror
Authors: Bai Yingxin , Zhang Zhuhong , Fan Dianyuan , Wang Zhijiang , Zhang Guoqing 
Published: July 2007

AbstractIn the steady state, a simple mode‐locking equation including the gain saturation is derived for a mode‐locked laser with a nonlinear mirror. Its analytic solution and mode‐locking conditions are obtained. Ignoring the gain saturation, the analytic pulse width is very close to the numerical results.
A microstrip antenna on a conical surface operating in the TM10 mode
Authors: Barbosa Wagner Gomes , Giarola Attílio José 
Published: July 2007

AbstractA theoretical development for the analysis of a microstrip antenna on a conical surface operating in the TM10 mode is described here. It consists of using the cavity model with magnetic side walls for the calculation of the resonant frequency and input impedance. The dyadic Green's‐function formulation is used for the calculation of the radiated far fields. Particular antennas are examined and numerical results are shown for the TM10 mode.
A semiglobal radiation boundary condition for the finite‐difference‐time‐domain method
Authors: De Moerloose Jan , De Zutter Daniel 
Published: July 2007

AbstractIn the analysis of antennas and scattering problems by the finite‐difference‐time‐domain (FDTD) method, the dimensions of the problem space are primarily determined by the quality of the radiation boundary condition (RBC) that is used to truncate the computational grid. The performance of the recently proposed higher‐order boundary conditions in cases of practical importance is often worse than the standard Mur‐second‐order condition. In the present article we will show that the reason for this unexpected result is the inability of this type of one‐way wave equation to deal with the evanescent or inhomogeneous plane‐wave part of the field. On the basis of this consideration we have constructed a new semiglobal operator that does have the required property. By combining this operator with the unusual Mur‐second‐order condition one arrives at an RBC with a much better performance. The novel RBC can also be used to analyze static problems.
Polarization‐optical morphological processor with programmable structure elements
Authors: Peng Haifeng , Liu Liren , Yin Yaozu , Wang Zhijiang 
Published: July 2007

AbstractBased on programmable polarization‐optical neighborhood interconnection, which is a stacked integration of rotatable crystal plates for beam splitting the controllable wave plates for polarization direction controlling, a kind of morphological processor with real‐time programmable structure elements is developed. It is compact in structure and effective as well as stable in performance.
Electromagnetic wave propagation in a chiral‐material‐filled rectangular waveguide
Authors: Samant Abhay R. , Whites Keith W. 
Published: July 2007

AbstractThe analysis of wave propagation in a chiral‐filled rectangular waveguide is presented. The validity of our formulation is established and hence corrects a statement in the literature regarding the longitudinal component of the magnetic field at the four corners of the chiral waveguide. Using this formulation and a finite‐difference numerical method, some of the salient features of this device are described.
Nonlinear performance of a reflective fiber‐optic mode converter
Authors: Shi Chao‐Xiang 
Published: July 2007

AbstractThe optical bistability in a nonlinear fiber‐optic LP01 mode converter by a reflective fiber grating is theoretically investigated. Both the transmissive and reflective properties of the device are analyzed. The output‐versus‐input function of the device exhibits the optical bistability property. The switching power and the bistable hysteresis are also discussed. In addition, a comparison between the nonlinearly reflective mode converter (LP01 ↔ LP02) and the nonlinear fiber Bragg grating reflector (i.e., LP01 and counterpropagating LP01 modes) is also presented. Our results show that the former has much lower switching power than the latter.
Surface‐mode suppression in a thick microstrip antenna by parasitic elements
Authors: Lee Choon Sae , Nalbandian Vahakn , Schwering Felix 
Published: July 2007

AbstractReduction of the surface‐wave excitation is achieved by placing parasitic elements next to the radiating edges of a rectangular microstrip antenna. A new experimental technique is introduced to measure the effect of the parasitic strips in reducing the surface‐wave excitation.
An indium‐phosphide self‐oscillating mixer for a 90‐GHz millimeter‐wave receiver application
Authors: Gund C. F. , Lazarus M. J. 
Published: July 2007

AbstractIndium‐phosphide Gunn diodes are applied as self‐oscillating mixers at frequencies in the region of 90 GHz. Sensitivities for signal equals noise are = ‐80 dBm (10 pW) for 48‐MHz bandwidth of i.f. A mathematical theory using the electron velocity‐field curve provides a good prediction of the conversion efficiency.
Asymptotic methods for the analysis of wave propagation in nonlinear, lossless transmission lines and equivalent circuits
Authors: Ramos J. I. 
Published: July 2007

AbstractPerturbation methods are employed to determine the small‐signal behavior of an LC‐ladder nonlinear, lossless transmission line. It is shown that a straightforward, regular perturbation analysis results in nonuniformly valid expansions, which can be rendered uniformly valid by stretching the time variable. Perturbation methods are also used to show that, when dispersion effects are accounted for, solitons may propagate along the nonlinear, lossless transmission line. The dispersion characteristics of some equivalent circuits derived from a lossless transmission line are also analyzed. © 1995 John Wiley & Sons. Inc.
Analysis of soliton propagation in an optical fiber using a fourier‐series approach
Authors: Ghafouri‐Shiraz H. , Shum P. 
Published: July 2007

AbstractA novel technique that is based on a Fourier‐series approach has been proposed to analyze the propagation behavior of solitons in an optical fiber. In the analysis both the fiber loss and the third‐order dispersion have been considered. The results compare well with the commonly used split‐step Fourier method [1]–[3]. © 1995 John Wiley & Sons. Inc.
2D microwave imaging using TLS‐ESPRIT with matrix enhancement
Authors: van der Merwe A. , Odendaal J. W. , Botha E. C. 
Published: July 2007

AbstractIn this article TLS‐ESPRIT [1] will be used to generate two‐dimensional high‐resolution microwave images. To enable the utilization of the 1D algorithm, a two‐dimensional data matrix is decoupled into two one‐dimensional sequences by forming an enhanced data matrix [2]. Pairing of the two 1D estimates is also addressed. To demonstrate the performance of the 2D algorithm, a microwave image was generated for a target measured in a compact range. © 1995 John Wiley & Sons. Inc.
Bandpass/bandstop filter design in circular waveguide
Authors: Clark P. R. , James G. L. 
Published: July 2007

AbstractWe show that a multiiris bandpass filter used in conjunction with a ring‐loaded slot bandstop filter in circular waveguide exhibits a considerably extended stop band with high localized attenuation. The results of an accurate analysis of the complete filter give exceptionally good agreement with measured data. © 1995 John Wiley & Sons. Inc.
Characteristic impedance of quadruple‐ridged square waveguides
Authors: Garb Khona , Kastner Raphael 
Published: July 2007

AbstractThe characteristic impedance of the fundamental mode in a quadruple‐ridged waveguide is computed using the finite‐element method. The method is validated by comparison with available results for double‐ridged waveguides, and results for quadruple‐ridged waveguides are given for possible use in the design process of quadruple‐ridged waveguides. © 1995 John Wiley & Sons. Inc.
Modal control of a corner reflector to maximize far‐field power
Authors: Washington Gregory , Silverberg Larry 
Published: July 2007

AbstractThe far‐field power transmitted from a corner reflector was maximized by varying its direction angle and corner angle. The optimal direction angle and corner angle are found by the modal autofocus method. The method is shown to converge over a wide range of initial angles. The results are demonstrated in a physical experiment along with complimentary numerical predictions. © 1995 John Wiley & Sons. Inc.
Conditions for the parameter dyadics of lossless bianisotropic media
Authors: Lindell I. V. , Sihvola A. H. , Puska P. , Ruotanen L. H. 
Published: July 2007

AbstractDyadic parameters of lossless bianisotropic media are considered and conditions based on the positive definite energy function are derived. As examples of the conditions, inequalities limiting the magnitude of the magnetoelectric parameters are considered for various nondispersive bianisotropic media treated in the literature. © 1995 John Wiley & Sons. Inc.
Phase‐coherent narrow‐band signal regeneration
Authors: McGinn V. P. , Whitehead M. W. 
Published: July 2007

AbstractA phase‐locked loop is combined with a highly selective bandpass filter in such a way that a steady‐state single‐frequency signal is extracted from a spectrum. The system goal is to maintain the phase of the wave irrespective of the actual signal frequency. © 1995 John Wiley & Sons. Inc.
Modal propagation analysis of a waveguide with a regular pentagonal cross section with conducting and nonconducting boundaries
Authors: Misra Vandana , Choudhury P. K. , Khastgir P. , Ojha S. P. 
Published: July 2007

AbstractUsing the weak guidance approximation and Goell's point‐matching method, a numerical analysis has been made of a guide with a pentagonal cross section, which may find wide applications in integrated optic technology. Two cases have been dealt with, namely, (i) a pentagonal guide cladded with a conducting substance, and (ii) a pentagonal guide loaded with conducting substance on alternate surfaces, the remaining surfaces being made of a dielectric substance. © 1995 John Wiley & Sons. Inc.
A hybrid method for terminating the finite‐element mesh (electrostatic case)
Authors: Roy Tanmoy , Sarkar Tapan K. , Djordjevic Antonije R. , Salazar‐Palma Magdalena 
Published: July 2007

AbstractThe finite‐element or finite‐difference techniques are well known for the solution of Maxwell's equation in differential form. But terminating the mesh accurately at a finite distance from the body in the case of an open problem is a major challenge. Though there have been several techniques presented [1, 2], this new approach allows for the terminating surface to encapsulate the body very tightly. In this proposed method, the finite‐element technique is used for open‐region problems, whereas an integral equation solution approach using the Green's function is applied to enforce the radiation condition. At each iteration cycle, field sources within the domain are evaluated and their potential at the terminating surface is calculated. The proposed method leads to increased computational efficiency of the finite‐element method. It can be generalized for the case of inhomogeneous and nonlinear media, for static and dynamic fields. Typical numerical results are presented for the solution of the Laplace equation to illustrate the accuracy of the technique. © 1995 John Wiley & Sons. Inc.
Wave‐front splitting interferometer for measurement of phase modulation
Authors: Gregory Don A. , McClain John 
Published: July 2007

AbstractA wave‐front splitting interferometer has been constructed and analyzed for measuring the phase modulating properties of popular spatial light modulators (SLM). A modified liquid crystal television (LCTV) was then used in the experiment to verify the technique. It was determined that for this interferometric architecture, one full fringe shift corresponds to a 2π phase modulation. © 1995 John Wiley & Sons. Inc.
Resonant frequencies of a microwave package with vertical diaphragms attached to the top cover
Authors: Chung Shyh‐Jong , Chen Hao‐Hui 
Published: July 2007

AbstractThe resonant frequencies of the modes in a cabineted microwave package are investigated by the mode‐matching method. The upper region of the package is partitioned into several cabinets using vertical diaphragms of a same depth and of negligible thickness. Numerical results are shown to agree with those of the measurement. The change of the resonant frequencies with the diaphragm depth is presented and explained. It is found that the resonance‐free frequency bands can be broadened by suitably designing the positions and the depth of the diaphragms. © 1995 John Wiley & Sons. Inc.
An approach to focused 2D TM near‐field active microwave imaging of dielectric objects
Authors: Caorsi Salvatore , Gragnani Gian Luigi , Pastorino Matteo , Rebagliati Mauro 
Published: July 2007

AbstractA new integral‐equation‐based numerical approach to microwave imaging is presented. It can be applied to focused imaging in the sense that only one part of an inhomogeneous body is viewed as an unknown scatterer to be reconstructed. This approach is of great usefulness in many applications, as it results in a notable computational saving and in high flexibility. Moreover, it allows the range of applicability of the Born approximation to be considerably expanded. © 1995 John Wiley & Sons. Inc.
An exact method for simulating boundary conditions for mesh termination in finite‐difference techniques
Authors: Djordjevic A. R. , Sarkar T. K. , Roy T. , Rao S. M. , Salazar M. 
Published: July 2007

AbstractFinite‐difference methods are standard techniques for solving the differential form of Maxwell's equations. In spite of many advantages, a drawback of the technique is how to implement an absorbing boundary condition in an essentially exact fashion. In this article an absorbing boundary condition is proposed based on the Green's functions arising in integral equations. The radiation condition in this approach is built up iteratively as the solution progresses, utilizing the Green's function. In the proposed method only two layers of meshes outside the boundary may be sufficient. Examples have been presented for the electrostatic case to illustrate the accuracy and convergence of this new technique. © 1995 John Wiley & Sons. Inc.
Rectangular microstrip antenna using manganese ferrite substrate
Authors: Ghosh K. K. , Chaudhuri A. , Biswas S. , Singh S. K. , Sreemany S. , Desai A. , Tewari J. , Majumder A. , Sen B. , Chanda A. , Bhattacharjee A. K. 
Published: July 2007

AbstractA rectangular configuration of the microstrip antenna with manganese ferrite as the substrate has been designed and fabricated and various properties have been studied. From these studies, especially from the radiation characteristics and VSWR plot, it is concluded that this configuration is very useful in the VHF and UHF frequency ranges. © 1995 John Wiley & Sons, Inc.
Impact of spontaneous emission noise of optical amplifiers on the channel capacity of coherent SCM systems
Authors: Wu Jyh‐Horng , Wu Jingshown , Lee Yang‐Han 
Published: July 2007

AbstractAnalysis on the channel capacity of a coherent optical subcarrier multiplexing system using optical amplifiers is presented. The performance criterion, that is, the channel transport capability N, is derived in terms of carrier‐to‐noise ratio, input optical power, and optical amplifier gain. It is found that when the gain of the optical amplifier is large, the spontaneous emission noise limits the number of channels that can be transmitted in this system. As an example, when the gain is well above 20 dB and input optical power is −28 dBm, the maximum value of N is 46. In addition, the optimum phase modulation index is also presented. © 1995 John Wiley & Sons, Inc.
Reduced‐threshold‐current vertical cavity surface‐emitting laser
Authors: Matin M. A. , Benson T. M. , Orton J. W. , Lacklison D. E. , Jezierski A. F. , Foxon C. T. , Roberts J. S. , Sale T. E. 
Published: July 2007

AbstractA simple method for reducing the threshold current of vertical cavity surface‐emitting lasers (VCSELs) is described. The approach modifies the top surface of the laser into a dome shape by chemical etching. This reduces the reflectance of the top mirror over an approximately annular region, thereby reducing the lasing area compared to the contact area in a controlled manner. A sevenfold reduction in threshold current over equivalent conventional VCSELs is demonstrated for a nonoptimized device that maintains a similar threshold current density. © 1995 John Wiley & Sons, Inc.