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Showing papers in "Electromagnetics in 1983"


Journal ArticleDOI
TL;DR: The dyadic Green's functions for unbounded and layered anisotropic media have been obtained in this article, where the authors assume that the anisometric medium is assumed to be tilted uniaxial.
Abstract: The dyadic Green's functions (DGF) for unbounded and layered anisotropic media have been obtained. The anisotropic medium is assumed to be tilted uniaxial. With the availability of the DGF's, many problems involving radiation and scattering of electromagnetic waves can readily be solved.

113 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method to use the NAG-1-163 grant between the National Aeronautics and Space Administration, Langley Research Center, Hampton, VA, and the University of Massachusetts, Amherst, HA 01003.
Abstract: This work was supported by Grants NAG-1-163 and NAG-1-279 between the National Aeronautics and Space Administration, Langley Research Center, Hampton, VA, and the University of Massachusetts, Amherst, HA 01003.

94 citations


Journal ArticleDOI
TL;DR: In this paper, a simple theory is developed for the analysis of microstrip patch elements which are loaded at one or more points with lumped linear load impedances, based on a cavity model in which the shape of the field distribution between the patch and ground plane is assumed to be well approximated by that of the resonant modes of a corresponding magnetic-and electric-walled cavity.
Abstract: A simple theory is developed for the analysis of microstrip patch elements which are loaded at one or more points with lumped linear load impedances. The analysis is based on a cavity model in which the shape of the field distribution between the patch and ground plane is assumed to be well approximated by that of the resonant modes of a corresponding magnetic- and electric-walled cavity. The resonant mode of the loaded cavity is represented as an appropriate superposition of the modes of the corresponding unloaded cavity. The characteristic equation for the resonant frequencies of the loaded cavity is obtained in terms of the load impedances and the unloaded cavity multiport open-circuit parameters. An analysis of the input impedance of a rectangular microstrip element shorted at an arbitrary point has been implemented and the results show good agreement with experiment. An ancilliary result showing the equivalence between a thin strip and a circular cylinder model of a feed current distribution...

55 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the variation with feed location of this inductive component both experimentally and by a full modal expansion of the field using the "cavity model".
Abstract: It has been demonstrated that a microstrip antenna excited in a non-degenerate resonant mode has a driving point impedance which can be modeled as a resonant parallel R-L-C circuit in series with the an inductor. The latter is an inductance which can be associated with the feeding probe or microstrip line feed of the antenna. This paper investigates the variation with feed location of this inductive component both experimentally and by a full modal expansion of the field using the “cavity model”. The results demonstrate that the simple, feed position-independent formula for this inductive component is inadequate for certain applications involving loaded microstrip elements. The results also show that the cavity model can predict the variation of feed inductance with feed location reasonably well except near the edge of the patch. The physical mechanism for the variation of this inductive component as well as the physical reason why the cavity model overestimates this parameter with feeds near the...

16 citations


Journal ArticleDOI
TL;DR: In this article, a planar antenna array at 140 GHz using twin-dipole elements was developed using a hybrid approach with beam lead Schottky GaAs diodes mounted on quartz substrates.
Abstract: Planar antenna arrays have been developed at 140 GHz using twin-dipole elements. The initial systems have been fabricated using a hybrid approach with beam lead Schottky GaAs diodes mounted on quartz substrates. Heterodyne measurements of subelement sensitivities have yielded DSB noise temperatures of 12,000 K. Subsequently implementation of completely monolithic systems has been demonstrated using SIS technology.

14 citations


Journal ArticleDOI
TL;DR: In this paper, an approach based on Prony's method is used to find the spatial poles of straight wires of varying length and radius from the far-field patterns, and a correlation is found with radiation from the feed region of an infinite antenna and from the ends of a semi-infinite antenna.
Abstract: An approach based on Prony's method is used to find the spatial poles of straight wires of varying length and radius from the far-field patterns. For the antenna case, poles having the largest residues are found near the feed region and antenna ends; smaller ones are found outside these regions. The poles are attributed to radiation from the exciting source and wire ends, due to charge acceleration, and from a slightly damped traveling wave. In the scattering case, the poles with the largest residues are located at the wire's ends for near-axial incidence and are again due to end radiation. By examination of the residue magnitudes as a function of wire radius, a correlation is found with radiation from the feed region of an infinite antenna and from the ends of a semi-infinite antenna. 19 figures.

9 citations


Journal ArticleDOI
TL;DR: In this article, the effect of substrate lenses, anti-reflection coatings, and adjustable backshorts on the performance of elementary integrated-circuit feed antennas was investigated.
Abstract: Efficiencies of elementary integrated-circuit feed antennas are calculated considering both the substrate and the optics. Calculations are made for dielectric constants of 4, for fused-quartz substrates, and 12, for silicon and gallium-arsenide substrates. The effect of substrate lenses, anti-reflection coatings, and adjustable backshorts is also considered. A feed efficiency of 60% is predicted for a slot on a substrate and substrate lens with dielectric constant 12, and 63% for a dipole on a substrate with dielectric constant 12 and lens of dielectric constant 4.

9 citations


Journal ArticleDOI
TL;DR: Particle Electromagnetic Simulator (PartES) as mentioned in this paper is one of the most popular simulator types in the field of field equivalence principle for the synthesis of the electromagnetic fields.
Abstract: EMP simulation has been developing steadily for almost two decades In the case of large EMP simulators intended for illumination of complete systems with correct spatial dependence, and their sometimes threat-like characteristics including correct frequency spectrum, the state of the art is rather mature Various possibilities have been explored consistent with what Maxwell's equations allow one to do, leading to a somewhat logical list of simulator types Some new thrusts in EMP simulation are pointed toward small EMP simulators which in some cases could be thought of as partial EMP simulators in that they illuminate a part of the system or synthesize part of the relevant sources for an EMP test One of the promising concepts for special applications is the PARTES concept Relying on integral equation descriptions of the electromagnetic interaction processes, and on the field equivalence principle for the synthesis of the electromagnetic fields, one can define a set of electric and magnetic dip

6 citations


Journal ArticleDOI
TL;DR: In this article, an improved theory for the input impedance of a probe-fed microstrip patch antenna has been developed, where the natural modes are established on a transverse resonance condition which incorporates the angularly dependent reflection coefficients and a dynamic wall susceptance associated with the patch boundaries.
Abstract: An improved theory for the input impedance of a probe-fed microstrip patch antenna has been developed. The natural modes are established on a transverse resonance condition which incorporates the angularly dependent reflection coefficients and a dynamic wall susceptance associated with the patch boundaries. The input reactance is shown to be largely associated with the evanescent waves confined to the vicinity of the probe while the input resistance is associated with the excitation of the mode at resonance. Analytical results are presented to describe the input impedance of a rectangular patch antenna as a function of its dimensions, substrate thickness and dielectric constant, probe dimensions and location and the frequency.

4 citations


Journal ArticleDOI
TL;DR: In this article, the authors expand on the concepts of electromagnetic volume/surface topology by including some considerations related to reduction of interference from low-frequency magnetic fields; this may be significant in some applications.
Abstract: This paper expands on the concepts of electromagnetic volume/surface topology by including some considerations related to reduction of interference from low-frequency magnetic fields; this may be significant in some applications. The topology of a subshield can be chosen as a Baumkuget (tree-sphere) to minimize the induced currents on the subshield conductors. Also, grounding networks can be designed on the basis of sublayer grounding subnetworks in the form of trees which do not have grounding conductors penetrating subshields, but connect (ground) the subshields and other equipment.

3 citations


Journal ArticleDOI
TL;DR: In this article, the transient surface current response at a number of locations on the model with various angles of incidence and then fitting each response waveform with a sum, of complex exponentials, was determined.
Abstract: The SEM parameters of a simple swept-wing aircraft model are determined. The technique consists of computing the transient surface current response at a number of locations on the model with various angles of incidence and then fitting each response waveform with a sum, of complex exponentials. The SEM description is derived from the resulting poles and residues.

Journal ArticleDOI
TL;DR: In this article, the singularity expansion method is applied to determine the natural resonances of a perpendicular crossed wire structure oriented parallel to an imperfect ground plane, and three formulations are utilized to account for the finite conductivity of the ground.
Abstract: The singularity expansion method is applied to determine the natural resonances of a perpendicular crossed wire structure oriented parallel to an imperfect ground plane. To account for the finite conductivity of the ground, three formulations are utilized. First, the rigorous Sommerfeld formulation is used; then for structures some distance from the ground an approximate Fresnel reflection coefficient approach is employed. For structures in proximity to the ground a lossy transmission line formulation is presented. Sample results from all three formulations are presented.

Journal ArticleDOI
TL;DR: The radiation of a large amplitude ion-acoustic wave launched from a conical antenna was experimentally measured and contrasted with linear radiation as mentioned in this paper, and significant differences were observed. But the results were not generalized to other types of wave propagation.
Abstract: The radiation of a large amplitude ion-acoustic wave launched from a conical antenna is experimentally measured and contrasted with linear radiation. Significant differences are observed.

Journal ArticleDOI
TL;DR: In this article, a matched asymptotic expansion approach is used to evaluate the resonant frequencies of a coupled two circular disk resonator, together with the translational properties of the cylindrical harmonics.
Abstract: The increasing use of microstrip antenna arrays calls for a rigorous analysis of the coupling between antenna elements. In this paper a full wave analysis is presented to rigorously formulate the resonance of a coupled two circular disk resonator using the Vector Hankel Transform, together with the translational properties of the cylindrical harmonics. The matched asymptotic expansion approach is then used to asymptotically evaluate the resonant frequencies of the structure. The Galerkin moment method and a perturbative approach which can also be used to calculate the resonant frequencies are reviewed. The results obtained using these methods are compared with those of the matched asymptotic expansion approach developed in this paper. It is shown that the asymptotic matching approach provides significant saving in computation time and furthermore supplies simpler expressions for the resonant frequencies as compared to the Galerkin method and the perturbative approach.

Journal ArticleDOI
Juan Rivera1, Tatsuo Itoh1
TL;DR: In this article, a suspended patch antenna excited by an inverted microstrip line is analyzed by a spectral domain technique followed by an equivalent waveguide-to-cavity model.
Abstract: A suspended patch antenna excited by an inverted microstrip line is analyzed by a spectral domain technique followed by an equivalent waveguide-to-cavity model. Accuracy of the results is confirmed by comparison with experimental data.

Journal ArticleDOI
TL;DR: In this paper, various contributions to backscattering from inhomogeneous particles are analyzed rigorously and the dominant contributions included the rainbow and glory, and the front and rear axial rays.
Abstract: The various contributions to backscattering from inhomogeneous particles are analyzed rigorously. These contributions are extracted from the exact solution by employing the Watson transformation. For wavelengths much shorter than the diameter of the inhomogeneous particles (λ < < a), the dominant contributions included in this paper are the rainbow and glory, and the front and rear axial rays. Partial surface waves, creeping waves and whispering gallery modes are small contributors in the geometrical optics limit and will not be treated in this paper.

Journal ArticleDOI
TL;DR: In this paper, the radiation efficiency of printed circuit antennas due to surface wave effects is optimized to 100% for lossless materials with a magnetic superstrate layer on a dielectric substrate.
Abstract: The radiation efficiency of printed circuit antennas due to surface-wave effects is optimized to 100% for lossless materials. This is attained with a magnetic superstrate layer on a dielectric substrate. A combination of substrate-superstrate thickness and material parameters results in the elimination of surface wave modes and, therefore, radiation efficiency optimization. When antennas are printed on a grounded substrate with moderate values of dielectric constant, elimination of surface wave modes and, therefore, 100% radiation efficiency due to material effects can be obtained only with the addition of a magnetic superstrate layer if radiation resistance is to be kept at a useful level.

Journal ArticleDOI
TL;DR: In this paper, the first two terms in the low frequency expansion of the scattered field are determined for a plane wave incident on a perfectly conducting flat plate of infinitesimal thickness, and the next terms can also be expressed in terms of potentials and functions which can be derived from a knowledge of the static fields.
Abstract: For a plane wave incident on a perfectly conducting flat plate of infinitesimal thickness, the first two terms in the low frequency expansion of the scattered field are determined. The zeroth order terms are the static fields and integral equations are developed from which the corresponding potentials can be found. The next terms can also be expressed in terms of potentials and functions which can be derived from a knowledge of the static fields. The far field expansion is obtained and the general method is illustrated in the case of a circular disk.

Journal ArticleDOI
TL;DR: In this article, the fields of an insular guide antenna feeder are computed by a mode matching method to provide accurate data for the guide attenuation and also the launcher radiation loss when the INSULAR guide is connected to a conventional rectangular metal waveguide using a horn launcher transition.
Abstract: The use of printed antenna techniques at millimetre wavelengths to create planar linear travelling wave antennas is commonly considered to be inhibited by the microstrip feeder loss and the alternate use of low loss dielectric feeders is thus attractive. In this investigation an additional source of unwanted loss is considered and a complete assessment, more favourable to microstrip, emerges. The fields of an insular guide antenna feeder are computed by a mode matching method to provide accurate data for the guide attenuation and also the launcher radiation loss when the insular guide is connected to a conventional rectangular metal waveguide using a horn launcher transition. This latter analysis is based both on a chopped surface wave distribution method and an alternative variational method. Similar loss data is computed for microstrip antenna feeders using existing theories and some experimental data presented. A comparison of total unwanted losses for both types of feeders establishes that mi...

Journal ArticleDOI
TL;DR: In this paper, the authors considered the problem of the parallel-plate waveguide with a ferrite substrate, having a semi-infinite upper plate and being excited by a TE mode, and the direction of the static (d.c.) magnetic field was taken to be parallel to the edge of the terminated upper plate.
Abstract: In this paper the problem of the parallel-plate waveguide with a ferrite substrate, having a semi-infinite upper plate and being excited by a TE mode is considered. The direction of the static(d.c.) magnetic field is taken to be parallel to the edge of the terminated upper plate. The problem is formulated on the basis of the Wiener-Hopf technique and ends up in a Wiener-Hopf integral equation with a non-symmetric kernel function, in contrast to the symmetric kernels of all isotropic problems formulated by the same technique. Factorization is now accomplished by a modification of the typical procedure, suitable to the present, non-syrmetric kernel. Expressions for the reflection and coupling coefficients of the modes are given and the far field is computed by application of appropriate asymptotic techniques. The numerical results reveal the definite possibility of controlling most of the operational characteristics of the structure by simply varying the intensity of the magnetizing field.

Journal ArticleDOI
TL;DR: In this article, the authors used a MINC-11 minicomputer to provide fast and efficient automation of the measurement process as well as data analysis capability, and the scattering range was operated using a microwave X-band system.
Abstract: Through the use of an image ground plane, measurements of scattering patterns for objects with at least one plane of symmetry have been made. Until recently, only the magnitude of the patterns were available. Now the system's capability has been expanded to include accurate phase information. The system makes use of bistatic measurements and is interfaced with a MINC-11 minicomputer which provides fast and efficient automation of the measurement process as well as data analysis capability. The scattering range is operated using a microwave X-band system.