Showing papers in "Electromagnetics in 1991"
TL;DR: In this paper, a more general and rigorous form of the physical theory of diffraction (PTD) is presented, which is based on the conception of elementary edge waves (EEWs), the waves scattered by the vicinity of an edge infinitesimal element.
Abstract: A more general and rigorous form of the physical theory of diffraction (PTD) is presented. This theory is concerned with the field scattered by perfectly conducting bodies whose surfaces have sharp edges and whose linear dimensions and curvature radii are large in comparison with a wavelength. The PTD proposed here is based on the conception of elementary edge waves (EEWs). These are the waves scattered by the vicinity of an edge infinitesimal element. Their high-frequency asymptotics are given. Various definitions of EEWs (Maggi, Bateman, Rubinowicz, Mitzner, Michaeli) are discussed. Total edge waves (TEWs) scattered by the whole edge are found to be a linear superposition of all EEWs. PTD enables one to determine correctly the first (leading) term in the high-frequency asymptotic expansions for primary and multiple TEWs both in ray regions and diffraction regions such as caustics, shadow boundaries, and focal lines. Some examples of these asymptotics are given. The connection of PTD with other ...
146 citations
TL;DR: In this article, the analysis of a layered planar structure consisting of different bianisotropic materials is performed in the frequency domain, in which reflection and transmission coefficients are determined via a chain-matrix algorithm.
Abstract: The analysis of a layered planar structure consisting of different bianisotropic materials is performed, in the frequency domain. Reflection and transmission coefficients are determined via a chain-matrix algorithm. Numerical results are presented and discussed.
55 citations
TL;DR: In this paper, the authors discuss infinite phased arrays of probe-fed microstrip patches in detail, and give results showing the effect of a cover layer on array performance, as well as the relationship to other approaches.
Abstract: Full-wave solutions for probe–fed microstrip patch antennas and arrays have been receiving a great deal of attention in the literature recently [1–25], In this article, we review previous solutions and their limitations, and describe a very accurate and versatile solution that has been developed by the authors. Applications of our approach to several specific geometries have appeared [20–24] or will appear [25] in the literature. Therefore, this paper focuses on the general features of our technique and its relationship to other approaches. In particular, we discuss infinite phased arrays of probe–fed patches in detail, and give results showing the effect of a cover layer on array performance.
53 citations
TL;DR: In this paper, a plane wave incident on a resistive half plane is considered, where the boundary condition is replaced by a transition condition, and the boundary value problem is solved by the plane wave.
Abstract: Although Maliuzhinets’ method is best suited to the solution of boundary value problems in wedge-shaped, it can also be employed when the boundary condition is replaced by a transition condition, and this is illustrated by considering the problem of a plane wave incident on a resistive half plane
28 citations
TL;DR: A numerical approach based on the method of integral equations is used to solve a very large class of applied electrodynamic problems as discussed by the authors, where many problems of diffraction and excitation for bodies of different nature and form were solved.
Abstract: A numerical approach based on the method of integral equations is used to solve a very large class of applied electrodynamic problems First of all, many problems of diffraction and excitation for bodies of different nature and form were solved Representation of unknown currents as a sum of “uniform” and “nonuniform” components permits the use of integral equations to solve such problems for semi-infinite structures It gives the opportunity to determine the diffraction coefficients used in Keller‘s geometrical theory of diffraction, and nonuniform currents used in Ufimtsev‘s method of edge waves for cases where canonical problems have no analytical solutions It extends the field of application of these asymptotic methods In addition, the method of integral equations can be used to consider objects supporting surface waves
26 citations
TL;DR: In this article, an analysis of infinite arrays of printed antennas on generalized anisotropic substrates is presented, including microstrip dipoles and probe-fed patches, with nine components in both permittivity and permeability tensors.
Abstract: An analysis of infinite arrays of printed antennas on generalized anisotropic substrates is presented. Antenna elements studied include microstrip dipoles and probe-fed patches. In the analysis, the substrate anisotropy is general in form, with nine components in both the permittivity and permeability tensors. This allows the study of uniaxial substrates with tilted optical axis or the biased ferrite substrate. The analysis adopts a rigorous full-wave moment method. Numerical results show that by neglecting substrate anisotropy, the performance of printed antennas may be greatly affected. Results show that it is possible to improve the input impedance match by employing biased ferrite substrates. It is also found that the antenna characteristics may be changed dynamically by varying the bias magnetic fields.
24 citations
TL;DR: In this article, a general Gauss divergence theorem with applications to convolution integrals of the form ∫ f(d) h(d)-vn, where the integration extends over an n-dimensional polyhedral omain, is presented.
Abstract: A general Gauss divergence theorem with applications to convolution integrals of the form ∫ f([xdot]) h([xdot] - ā) dVn, where the integration extends over an n-dimensional polyhedral omain, is presented. The kernel h([xdot] - ā) may be singular, but the given integral must remain integrable. As a result of the Gauss theorem, the given integral is reduced to an integral over the boundary of the n-dimensional polyhedral domain, which can be expressed as a sum of similar integrals over (n-1)-dimensional polyhedral domains. The technique is illustrated with the evaluation of potential integrals for uniform and linear source distributions on polygonal domains, which is known to be of particular importance in the numerical treatment of electromagnetic problems.
20 citations
TL;DR: In this paper, the authors used the four-parameter model in the EH representation for the set of constitutive relations characterizing a biisotropic medium, and studied guided electromagnetic waves in biisotiopic planar structures.
Abstract: Using the four-parameter model in the EH representation for the set of constitutive relations characterizing a biisotropic medium, guided electromagnetic waves in biisotiopic planar structures are studied by means of a new method based on a 2 × 2 coupling matrix eigenvalue-problem. Special attention is paid to the particular case of chiral reciprocal media which is commonly referred to simply as chiral media. Finally, the special problem of hybrid surface mode propagation in a grounded chiroslabguide is analyzed.
19 citations
TL;DR: In this paper, the authors deal with electromagnetic scattering in the presence of nonlinear dielectric objects and describe the electromagnetic field by an integral formalism which takes into account nonlinear effects by solving inhomogeneous wave equations through specific dyadic Green functions.
Abstract: This paper deals with electromagnetic scattering In the presence of nonlinear dielectric objects. The Introduction of equivalent source terms makes it possible to describe the electromagnetic field by an integral formalism which takes into account nonlinear effects by solving inhomogeneous wave equations through specific dyadic Green functions. Examples of application to nonlinear scattering objects, In free space and In a rectangular waveguide, are considered. The related integral problems are reduced to nonlinear systems of algebraic equations. Results of some computer simulations Involving simple scattering objects are also reported.
15 citations
TL;DR: In this article, the effects of nonlinearities on the field components and on the radar cross section at the second and third harmonics were examined, and the effect of non-linearity on radar cross-section at the two different scales was investigated.
Abstract: The general solution of the scattering of harmonic signals, by a medium which has nonlinear constitutive relations, contains higher harmonics. The scattering amplitude consists of the linear component and additional correction terms that depend on the amplitude of the incident wave. In this paper, we examine the effects of nonlinearities on the field components and on the radar cross section at the second and third harmonics.
11 citations
TL;DR: A full wave analysis of infinite arrays of proximity coupled rectangular microstrip antennas of broad band scanning properties is described to demonstrate the substantial effect that a large scanning array environment has upon the bandwidth of a proximity coupled element.
Abstract: This paper describes a full wave analysis of infinite arrays of proximity coupled rectangular microstrip antennas. The broad band scanning properties of these arrays are analyzed numerically in conjunction with experimental results to validate the analysis. A design example is given to demonstrate the substantial effect that a large scanning array environment has upon the bandwidth of a proximity coupled element.
TL;DR: The singular value decomposition (SVD) procedure when applied to the Prony method has proved to be a robust estimator of the poles of an electromagnetic system from its transient response as discussed by the authors.
Abstract: The singular value decomposition (SVD) procedure when applied to the Prony method has proved to be a robust estimator of the poles of an electromagnetic system from its transient response. Two of the major disadvantages of this technique have been eliminated by preprocessing the transient data. Accurate results are obtained for data with low signal-to-noise ratios. Comparisons are made with results that are obtained from other methods of parameter estimation.
TL;DR: In this paper, a simple definition for the "main beam" is suggested for calculating beam efficiency, which is related to the reflector aperture diameter, but is independent of the feed edge taper.
Abstract: This paper presents several topics on the beam efficiency of a reflector antenna. (i) A simple definition for the “main beam” is suggested for calculating beam efficiency. This definition is related to the reflector aperture diameter, but is independent of the feed edge taper. Use of this definition allows a fair comparison of beam efficiencies due to different feeds to be made. (ii) Physical optics theory does not conserve power. Therefore conventional reflector pattern computation methods based on PO can calculate beam efficiency only within 2% to 3% accuracy. A method for calibrating out this PO error is described. (iii) Beam efficiency curves are presented for typical parabolic reflectors fed by open-ended circular cylinder waveguide feeds. While directivity is optimized by a 10 dB edge taper, beam efficiency is optimized for a higher edge taper of over 20 dB. (iv) Beam efficiency curves for cases in which the beam is scanned off-axis are presented. (v) A cluster feed is utilized to improve b...
TL;DR: In this paper, the spectral domain analysis of microstrip arrays and its feed network is considered as a part of the radiating structure and all mutual coupling and surface wave effects are taken into account.
Abstract: The theory is outlined for the spectral domain analysis of microstrip arrays and its feed network which is considered as a part of the radiating structure. All mutual coupling and surface wave effects are taken into account. The surface impedance of the patches and the feedlines may vary with space; the feed network may obtain passive and active lumped loads.
TL;DR: In this paper, an electromagnetic analysis technique for probe-fed patch radiator phased arrays is presented that accurately models their driving point impedances and radiated electric fields, and the use of this analysis methodology to both predict the behavior of and to design patch radiators is discussed.
Abstract: An electromagnetic analysis technique for probe–fed patch radiator phased arrays is presented that accurately models their driving point impedances and radiated electric fields. The use of this analysis methodology to both predict the behavior of and to design patch radiators is discussed. Salient features relevant to radiator synthesis are discussed, including radiator asymmetries due to multiple probe feeds and the realization of matching networks for wideband radiator operation. Key effects relevant to radiator performance, such as feed–network related resonances and surface wave effects, are elucidated and design examples are cited.
TL;DR: The proposed approach is general and systematic and the final results are in analytic form and most of the computational burden can be left to computer algebra.
Abstract: We outline the program of a. functional approach to nonlinear electromagnetic wave propagation and scattering. The proposed approach is general and systematic and the final results are in analytic form. Most of the computational burden can be left to computer algebra. We stress that the proposed approach waits for the next generation of computers to prove practically valuable.
TL;DR: In this article, a generalized nonlinear Schrodinger equation is considered for the decay of the sech-pulses, dynamics of randomly modulated solitons, and evolution of nonsoliton random pulses.
Abstract: We consider a generalized nonlinear Schrodinger equation: iqt + qxx + 2klql 2 q - ikb(lql 2 q)x = 0 at various initial conditions. For the purpose of practical applications in optics, we study the following initial value problems: decay of the sech-pulses; dynamics of randomly modulated solitons, and evolution of nonsoliton random pulses. The first of the above problems is solved exactly. Conditions of the sech-pulse decay are stated. For the solution of the second problem, a perturbation theory is developed. Statistical characteristics of both a soliton under the Gaussian initial fluctuations, and noise generated in the system are obtained. Soliton parameters are distributed according to the Gaussian law. The relationship between correlation characteristics of the noise and those of the linear beam in the problem of the Fraunhofer diffraction on a gap is established. The asymptotic formula describing a nonsoliton solution at sufficiently large times is stated. The Fokker-Plank equation for proba...
TL;DR: In this paper, an integral equation approach is applied to calculate the propagation characteristics of high temperature thin-film superconducting lines at high frequencies, and a parametric study is performed where phase and attenuation constants as well as characteristic impedance are evaluated as functions of frequency, temperature, permittivity and geometry of the structure.
Abstract: An integral equation approach is applied to calculate the propagation characteristics of high temperature thin-film superconducting lines at high frequencies. To evaluate losses in these lines, the superconducting strips are replaced by frequency-dependent surface impedance boundaries. The values of these surface impedances are measured experimentally by a TE01 cavity technique. Using this method, a parametric study is performed where phase and attenuation constants as well as characteristic impedance are evaluated as functions of frequency, temperature, permittivity and geometry of the structure.
TL;DR: In this paper, a quasi-finite element method for calculation of static fields in media with hysteresis is presented, in which the evolution of the electromagnetic system is traced to compute the field history as well as the current value of the field self-consistently.
Abstract: A quasi-finite element method for calculation of static fields in media with hysteresis is presented in this paper. The proposed method utilizes vector Preisach hysteresis model to describe the material behavior. Time-stepping technique is employed in which the evolution of the electromagnetic system is traced to compute the field history as well as the current value of the field self-consistently. At every step in this technique a boundary value problem is solved by using coupled boundary-volume Galerkin's forms. In this formulation, the solution within the material medium is approximated in terms of finite element basis funtions, while the solution outside the material medium is approximated in terms of harmonic functions. An iterative technique for the solution of the resulting set of nonlinear equations is described. The proposed method is demonstrated on two dimensional electrostatic problems.
TL;DR: The multiport network modeling approach provides a detailed equivalent network representation of microstrip patches and has been used successfully for CAD of various microstrip patch configurations and extension of the approach to more general two-dimensional planar arrays is outlined.
Abstract: The multiport network modeling (MNM) approach provides a detailed equivalent network representation of microstrip patches and has been used successfully for CAD of various microstrip patch configurations Combined with the network modeling of the mutual coupling among patches and network models for feed lines in the array, the MNM approach provides a convenient frame work for CAD of microstrip arrays This paper is a review of the state-of-the-art in the use of MNM models in CAD of microstrip arrays The MNM approach for modeling microstrip patches and the mutual coupling among patches is reviewed briefly Application of the MNM approach to the CAD of linear series-fed arrays with a cover layer is discussed The CAD algorithms are described and key advantages of the MNM approach leading to sensitivity, analysis and optimization are highlighted Extension of the approach to more general two-dimensional planar arrays is outlined
TL;DR: In this paper, a Schrodinger-like equation with real eigenvalues is used to describe the dynamical behavior of permanent and induced dipole moments in an external field.
Abstract: Accurate orientational probability distribution functions are derived which describe the dynamical behavior of permanent and induced dipole moments in an external field. The method involves a transformation of the Smoluchowski equation into a Schrodinger–like equation with real eigenvalues. The method is applied here for the first time to the case of suspensions of large noninteracting anisotropic particles which are of interest as artificial Kerr materials for nonlinear electrooptical applications. A matrix presentation is made in which the effects of any combination of permanent and induced dipole moments are described by a single matrix. The eigenfunctions and eigenvalues of this matrix when specific material parameters are substituted provide a Fourier cosine series expansion for the angular distribution function under conditions of cylindrical symmetry which is valid for aligning fields of any magnitude. The only restriction is that larger fields require larger matrices for more accurate res...
TL;DR: In this article, the kinematic problem of one-dimensional space-charge wave propagation on a thin (surface current) electron beam in an axially uniform lossless structure is considered, and the kernel of the integral equation is the Green's function for the waveguiding structure.
Abstract: We consider the kinematic problem of one-dimensional space-charge wave propagation on a thin (surface current) electron beam in an axially uniform lossless structure. A general nonlinear integral equation describing the wave propagation is developed; the kernel of the integral equation is the Green's function for the waveguiding structure. In the small-signal limit, the integral equation becomes linear and homogeneous and yields the linear dispersion relation through the Fourier transform. The general formulation is applied to an annular beam in a perfectly conducting circular waveguide. It is shown that the nonlinear integral equation can be reduced to a nonlinear differential equation through the use of an approximate Green's function. With further approximation, the differential equation yields onoidal wave solutions, including solitary-wave solutions in appropriate limiting cases. Approximate analytical and “exact” numerical results are presented and compared.
TL;DR: In this paper, a model for OPTICAL BISTABILITY in a RIDGE WAVEGUIDE FABRY-PEROT RESONATOR is presented, where the non-linearity is due to a MULTIPLE QUANTUM WELL STRUCTURE INSERTED into the resonator.
Abstract: IN THIS PAPER A MODEL FOR OPTICAL BISTABILITY IN A RIDGE WAVEGUIDE FABRY-PEROT RESONATOR IS PRESENTED. THE NON-LINEARITY IS DUE TO A MULTIPLE QUANTUM WELL STRUCTURE INSERTED INTO THE RESONATOR. NEAR THE EXCITONIC RESONANCE A BISTABLE BEHAVIOUR HAS BEEN FOUND, AS SHOWN BY EXAMPLES OF STEADY-STATE RESPONSE.