Showing papers in "Electromagnetics in 1982"
TL;DR: In this article, a theory of intensity scattering from a multi-layered random medium with irregular boundaries is developed using the radiative transfer formulation, and explicit forms for the zeroth and first-order solutions are given.
Abstract: A theory of intensity scattering from a multi-layered random medium with irregular boundaries is developed using the radiative transfer formulation. Explicit forms for the zeroth and first-order solutions are given. Special cases are shown and compared with previous results. The similarities and differences between the results of this and previous studies are pointed out. In particular, terms omitted in previous studies are indicated and previous scalar or partially scalar formulations are generalized to permit a complete polarization treatment.
59 citations
TL;DR: In this article, a general reciprocity theorem for two-dimensional fields and scatterers is presented, which is valid for any couple of fields, where the surfaces of the scatterer in the two configurations may be different.
Abstract: The paper presents a general reciprocity theorem which is valid for any couple of fields and scatterers ; especially, the surfaces of the scatterers in the two configurations may be different. The theorem is demonstrated from Maxwell equations in the sense of distributions, which permits one to take automatically into account the boundary conditions. Then, several classical relations are derived from the theorem, for two dimensional as well as three dimensional scatterers : classical reciprocity, optical theorem, relation between far scattered field and near field. Moreover, very simple expressions are found for the functional derivatives of the elements of the scattering matrices, which constitute powerful tools for the numerical solving of inverse scattering problems.
43 citations
TL;DR: In this article, the self and mutual admittances of slot arrays on a conducting cylinder or cone were analyzed under various conditions, and representative numerical results and their comparison with experimental data.
Abstract: This paper begins with an explanation of two approaches for analyzing conformal arrays: the circuit and the scattering approaches. We next review ray techniques for calculating the self and mutual admittances of slot arrays on a conducting cylinder or cone by presenting (i) final formulas for admittance under various conditions, and (ii) representative numerical results and their comparison with experimental data.
23 citations
TL;DR: In this article, a solution for the calculation of mutual coupling between elements in a finite planar rectangular waveguide antenna array is presented, where the aperture dimensions are less than the feeding, waveguide dimensions and the elements are uniformly spaced in each of two directions in either a rectangular or isosceles triangular lattice.
Abstract: A solution is presented for the calculation of mutual coupling between elements in a finite planar rectangular waveguide antenna array. The aperture dimensions can be less than the feeding, waveguide dimensions and the elements are uniformly spaced in each of two directions in either a rectangular or isosceles triangular lattice. The problem is formulated as an integral equation by requiring the transverse electric and magnetic fields to be continuous across the apertures. The integral equation is solved by the method of moments for the equivalent magnetic current in the aperture region. A single expansion function is used to approximate the electric field in each aperture. For apertures that are close together the normal quadruple half-space admittance integral is reduced to single integrals which are evaluated numerically. For apertures father apart, a double numerical integral solution is used. In addition, the symmetry property of the symmetric Toeplitz admittance matrix for the linear array ...
20 citations
TL;DR: In this article, the authors show that the variety of choices available to one in constructing a singularity expansion relates directly to the large-s asymptotic behavior of the resolvent kernel for the integral equation from which the expansion is derived.
Abstract: The issues associated with the choice of.coupling coefficient forms in the singularity expansion and the closely-related subject of whether expansions may be written without an entire function present have persisted as major points of concern and confusion in the development of singularity expansion method theory. In this paper we show that the variety of choices available to one in constructing a singularity expansion relates directly to the large-s asymptotic behavior of the resolvent kernel for the integral equation from which the expansion is derived. The choices range from a cautious extreme in which causality is enforced explicitly to a bold extreme where one depends upon the expansion to sum to a causal result well ahead of the time of arrival of the excitation. By appealing to recently-reported estimates of this asymptotic behavior we define what the acceptable constructions are and discuss them on a comparative basis. A geometrical interpretation of the domain of integration for specific...
19 citations
TL;DR: In this paper, it has been pointed out that the class 1 coupling coefficient form of the SEM expansion for the current density on a scattering object tends to be numerically unstable in the early time, before the leading edge of the incident field clears the object.
Abstract: It has been pointed out by several workers that the class 1 coupling coefficient form of the SEM expansion for the current density on a scattering object tends to be numerically unstable in the early time, before the leading edge of the incident field clears the object. The class 1 form is computationally more attractive than the more reliable class 2 form; it is also the form mandated in some applications as, for example, in the SEM equivalent circuit synthesis. This paper presents a numerical evidence that the class 1 coupling coefficient form yields good results provided the time origin of the problem is placed at the observation point. It is concluded that the assessment of the practical utility of the class 1 coupling coefficient form prevailing in the literature is, perhaps, too pessimistic.
16 citations
TL;DR: In this paper, the small aperture coupling theory was improved by introducing the radiation reaction fields as part of the polarizing field acting on the aperture, and the principles of power conservation and reciproc...
Abstract: The small aperture coupling theory is improved by introducing the radiation reaction fields as part of the polarizing field acting on the aperture. The principles of power conservation and reciproc...
16 citations
TL;DR: In this paper, a numerical solution for electromagnetic coupling to a perfectly conducting body of revolution with a loss-free homogeneous material region is developed, which is exposed by a rotationally symmetric aperture in the conducting body.
Abstract: A numerical solution for electromagnetic coupling to a perfectly conducting body of revolution with a loss-free homogeneous material region is developed here. The material region is exposed by a rotationally symmetric aperture in the conducting body. Application of the equivalence principle introduces an unknown electric current on the surface of the conducting body, and both an unknown equivalent electric current and an unknown equivalent magnetic current in the aperture. These currents satisfy the integral equations obtained by annihilating the tangential components of the electric field on the surface of the conducting body and by enforcing continuity of the tangential components of the electric and magnetic fields across the aperture. These integral equations are solved numerically by means of the method of moments. Numerical results for the above mentioned currents are presented for four different conducting bodies, each of which has a dielectric region and is excited by an axially incident ...
14 citations
TL;DR: In this paper, the authors used the sequential approach to derive the expression for electric field in terms of the electric dyadic Green's function, and determined sufficient conditions for the behavior of the current density that insure that the electric field obeys Maxwell's equations.
Abstract: The sequential approach to distribution theory is used to rigorously derive the expression, which remains valid in the source region, for electric field in terms of the electric dyadic Green's function. Sufficient conditions for the behavior of the current density that insure that the electric field obeys Maxwell's equations are determined explicitly.
12 citations
TL;DR: In this paper, a curve fitting and pole extraction algorithm has been developed and applied to exact frequency domain data for the surface fields on a perfectly conducting sphere, and the data are fitted extremely closely, and for at least a handful of the lowest order SEM poles, the extracted poles and their residues are in good agreement with their known exact values.
Abstract: A curve fitting and pole extraction algorithm has been developed and applied to exact frequency domain data for the surface fields on a perfectly conducting sphere. The data are fitted extremely closely, and for at least a handful of the lowest order SEM poles, the extracted poles and their residues are in good agreement with their known exact values. Unfortunately, this is not true if the frequency response is degraded in accuracy. In particular, noise effects are explored, and it is found that for noise levels typical of the best frequency domain experimental data it is no longer possible to locate more than (at most) the dominant SEM pole to a reasonable degree of accuracy.
9 citations
TL;DR: In this paper, the Fourier spectra of the fields from a uniformly moving harmonic source are investigated and the spectra are found as space integrals of a dyadic Green's function multiplied with the source current density.
Abstract: The Fourier spectra of the fields from a uniformly moving harmonic source are investigated. These spectra are found as space integrals of a dyadic Green's function multiplied with the source current density. The spectra turn out to be bandlimited and to evidence two (infinite) peaks. The analysis is valid for arbitrary velocities and for arbitrary distances between the source volume and the observation point. The spectra of the fields from a moving dipole are treated in some detail.
TL;DR: In this article, the ground effects in the response of a single-wire transmission line illuminated by an E.M.P. was investigated, and the results showed that ground effects were minimal.
Abstract: (1982). GROUND EFFECTS IN THE RESPONSE OF A SINGLE-WIRE TRANSMISSION LINE ILLUMINATED BY AN E.M.P. Electromagnetics: Vol. 2, No. 1, pp. 43-54.
TL;DR: In this paper, a numerical modeling of partially buried vertical wire-antennas and scatterers is presented, where the problem of antenna grounding is formulated in terms of an integro-differential equation over the wire current across the air-ground interface, which is then converted into a numerically solvable form by means of Galerkin's method together with the piecewise linear functions.
Abstract: The purpose of the present work is the numerical modeling of partially buried vertical wire-antennas and scatterers. Our interest is in an efficient computation of their electromagnetic properties. Analytically the problem is formulated in terms of an integro-differential equation over the wire current across the air-ground interface. This equation is then converted into a numerically solvable form by means of Galerkin's method together with the piece-wise linear functions. The inverse Bessel transforms, commonly called Sommerfeld integrals, appearing in the Kernel of the integral equation have been evaluated by numerical integration over the real axis. The resulting computer code“STAKE,” which permits the numerical simulations of partially buried vertical wires, proved to be efficient and accurate in comparison with other computation methods. First the problem of antenna grounding has been investigated for the cases of soil and sea water. The current distributions, input admittances and radiatio...
TL;DR: In this paper, the concept of relative shielding order between pairs of sublayers is introduced and constraints on this non-negative-integer parameter are explored, including that of uniform relative shielding ordering among pairs of a set of primary sub-layers.
Abstract: This paper explores some aspects of qualitative electromagnetic topology for system design. Sublayers are partitioned into sets for separate treatment in the design process. The concept of relative shielding order between pairs of sublayers is introduced and constraints on this non-negative-integer parameter are explored. Special cases are considered, including that of uniform relative shielding order between pairs of a set of sublayers designated primary sublayers.
TL;DR: In this article, a general solution describing electromagnetic wave propagation alone a transmission line periodically loaded with varactor diodes, with arbitrary terminal impedances, was obtained up to 3rd order in the frame of the Volterra functional method.
Abstract: A general solution describing electromagnetic wave propagation alone a transmission line periodically loaded with varactor diodes, with arbitrary terminal impedances, is obtained up to 3rd order in the frame of the Volterra functional method. Forward phase-matched 2nd harmonic generation with matched generator and load impedances is treated in detail. Design curves are given.
TL;DR: In this paper, an integro-differential equation is formulated for the TM illumination of an infinite slot in a conducting screen situated between two dielectric slabs having different electromagnetic properties.
Abstract: An Integro-differential equation is formulated for the problem of TM illumination of an infinite slot in a conducting screen situated between two dielectric slabs having different electromagnetic properties. Numerical results are given for the slot tangential electric field (or equivalent magnetic current) for selected cases where the slab exists only on the shadow side of the screen. Far-zone magnetic fields are computed by a method combining numerical and analytical techniques and are presented for several cases.
TL;DR: In this paper, a criterion is established for the minimum distance of separation between the probe antenna and the test antenna that would result in accurate spherical near-field antenna measurements possible without probe correction.
Abstract: In this paper a criterion is established for the minimum distance of separation between the probe antenna and the test antenna that would result in accurate spherical near-field antenna measurements possible without probe correction. This criterion is arrived at by considering two different types of test antennas and calculating their near-fields with and without directivity of the scanning probe.
TL;DR: In this article, the wire diameter of the loops is approximately equal to the wall thickness of the cylinder, and the measurements are compared with those of a hollow metallic cylinder, one having preferred current flow along the longitude and one having current constraint along the latitude.
Abstract: Scattering from several metallic objects having constrained current flow is measured. These objects consist of a series of loops so arranged as to form an equivalent cylinder. The wire diameter of the loops is approximately equal to the wall thickness of the cylinder. The measurements are compared with those of a hollow metallic cylinder. Additional measurements are presented for spherical objects, one having preferred current flow along the longitude and one having current constraint along the latitude. These are compared with solid sphere measurements.
TL;DR: In this paper, the surface impedance along the sloping beach-sea boundary is calculated using parallel two-layer stratified media theory, and the transition from the land impedance of the land to that of the sea is found to take place over a small fraction of a free space wavelength from the shoreline.
Abstract: SUMMARY Using the compensation theorem integral formulation,the radiation patterns of a verticalel ectric dipolenearal and-sloping beach-sea boundary are investigated numerically.Since the formulation invokes the surface impedance concept,the surface impedance along the sloping beach is calculated using parallel two-layer stratified media theory.The transition of the surface impedance of the land to that of the sea is found to take placeovera small fraction of a free space wavelength from the shoreline,so the sloping beach behaves very much like anabrupt boundary.The additional losses of the sloping beach,compared to an abrupt land-sea boundary,tend to reduce the radiation field slightly at low elevation angles and enhance the field slightly at higher angles.Allowing fora “wet” beach in the immediate foreground of the shoreline has a converse effect. The constitutive parameter so of the land,the distance of the dipole from the shoreline and the height of the dipole have much more pronounced effect son the...