Generalized network parameters, radiation and scattering by conducting bodies of revolution

Introduces computer programs (FORTRAN IV) designed for field calculation from conducting bodies of revolution. A set of four programs which calculate the generalised impedance matrix and admittance matrix for triangular expansion functions, bistatic radar scattering for an axially incident plane wave, radiation from rotationally symmetric aperture antennas, and radar backscattering for an obliquely incident plane wave, are presented. Results for a number of examples are summarised and discussed. The accuracy of computation depends on the smoothness of the body and of the excitation     

The equivalent circuit of a microstrip crossover in a dielectricsubstrate

A quasi-static analysis is carried out to examine the capacitive coupling between two nonintersecting orthogonal microstrip lines above a ground plane and in a dielectric substrate. The charge density along the width of each strip is described using a prescribed charge distribution. A pair of coupled integral equations is derived and solved by the method of moments to obtain the excess charge densities. The lumped excess capacitances are computed and compared to those obtained using wire lines with radii equal to the equivalent radii of the strips     

Radiation and scattering from electrically small conducting bodies of arbitrary shape

A simple moment solution is given for low frequency electromagnetic scattering and radiation problems. The problem is reduced to the corresponding electrostatic and magnetostatic problems. Each static problem is solved using the Method of Moments. The surface of the perfectly conducting scatterer is modeled by a set of planar triangular patches. Pulse expansion functions and point matching testing are used to compute the charge density in the electrostatic problem. For the magnetostatic current a set of charge-free vector expansion functions is used. The problem is formulated assuming the scatterer to be in an unbounded homogeneous region. Scatterers of various shapes, such as the circular disc, the sphere, and the cube are studied. Special attention is paid to a conducting box with a narrow slot. The computed results are the scattered fields, the induced charge and current distributions, and the induced electric and magnetic dipole moments. These are in close agreement with whatever published data are available.     

Electromagnetic scattering from and transmission through arbitraryapertures in conducting bodies

The general 3-D aperture coupling problem is formulated in terms of an integral equation for the equivalent magnetic current in the aperture, which is numerically solved by the method of moments. The aperture is characterized by two aperture admittance matrices, one for the exterior region and the other for the interior region. These two admittance matrices are determined separately but in a similar manner if the pseudo-image method is used. Numerically workable expressions are developed for the two aperture admittance matrices by decomposing each of them into a half-space admittance matrix and a supplementary admittance matrix. The half-space admittance is relatively easy to compute and has been investigated in the literature. The supplementary admittance matrix is expressed in terms of the generalized impedance combining the existing numerical codes for an arbitrarily shaped scatterer and for an arbitrary aperture in a conducting plane, one can obtain a code which is especially designed for an arbitrary aperture in a conducting surface of arbitrary shape     

Electromagnetic coupling to a conducting wire behind an aperture of arbitrary size and shape

The electromagnetic coupling to a conducting wire behind an aperture in a plane conducting screen is analyzed. The aperture can be of arbitrary size and shape. The wire can be of finite length, with or without terminating loads, or of infinite length. The electric current on the wire and the equivalent magnetic current over the aperture region are calculated by the method of moments. An equivalent circuit for the effect of the aperture on the transmission line mode of the wire is derived.     

The aperture admittance of a circumferential slot in a circularcylinder

A circumferential slot in an infinitely long cylinder when fed with a tangential electric field is considered. Parseval's theorem, in which Fourier integrals appear, is used to express the aperture admittance as the integral from zero to infinity of an infinite series. Recognizing that the first two terms of this infinite series have a nonintegrable singularity when the variable of integration w is equal to the wavenumber k, the authors distort slightly the contour of integration to avoid k. The terms of the infinite series are then approximated when w is close to k. A combination of numerical and analytical schemes employing both large and small argument approximations of Hankel functions is used to perform the integration. It has been found that these integration schemes work very well, and a simple and fast algorithm has resulted     

Control of radar scattering by reactive loading

A method for obtaining a desired radar scattering pattern by reactively loading a conducting body is given. The theory uses the concept of characteristic modes of a loaded body. Any desired real current can be resonated by reactive loads to make it the dominant mode current of that body. If no other mode is near resonance, the radar scattering pattern becomes nearly the same as the radiation pattern of the resonated current. A quality factorQis defined as a measure of the broadband behavior of a scatterer. Procedures for computing the real currents having minimumQand maximum gain-quality ratio are given. A pattern synthesis procedure is developed for obtaining the real current whose radiation field pattern is the least mean-square approximation to a desired field pattern. Numerical examples are given for each procedure discussed.     

The inductance matrix of a multiconductor transmission line inmultiple magnetic media

A simple relationship between the inductance matrix and the auxiliary capacitance matrix is given. For a multiconductor transmission line consisting of N_c conducting cylinders in inhomogeneous media consisting of N_d homogeneous regions with permeabilities μ_i and permittivities ϵ _i, the inductance matrix [L] for the line is obtained by solving the magnetostatic problem of N_c conductors in N_d regions with permeabilities μ _i. The capacitance matrix [C] for the line is obtained by solving the electrostatic problem of N_c conductors in N_d regions with permittivities ϵ _i. It is shown that [L]=μ₀ϵ₀[C^'] ^-1, where [C^'] is the capacitance matrix of an auxiliary electrostatic problem of N_c conductors in N_d regions with relative permittivities set equal to the reciprocals of the relative permeabilities of the magnetostatic problem, i.e. ϵ^' _i/ϵ₀=μ₀/μ_i     

Straight wires with arbitrary excitation and loading

A general analysis of straight wire antennas and scatterers, with arbitrary excitation and loading, is given. The resulting formulas are in matrix notation, in a form suitable for programming on a digital computer. Many numerical results for input admittances, current distributions, radiation patterns, and scattering cross sections of various antennas and scatterers are included.     

Modal analysis of loaded N-port scatterers

AnN-port loaded scatter is one havingNports to which lumped impedance loads or a load network is connected. Methods are given to determine the characteristic modes of a loaded scatterer and for using them in a modal solution for electromagnetic scattering. A procedure is also given for resonating any given real port current, which makes that current the dominant mode of the loaded scatterer. The theory is formulated both in terms of open-circuit and short-circuit network parameters. A number of numerical examples are given for a wire triangle to illustrate the general theory. Computer programs are available for all procedures discussed.