Scattering By Resistive Plates.

The problem of electromagnetic scattering by resistive plates has been solved numerically using two coupled E-field integral equations and the method of moments. The Stratton-Chu representation for the electromagnetic field has been shown to be applicable to this type of problem and integral equations are derived from this representation. The numerical procedure developed guarantees the continuity of the potentials on the plate, a property which is shown to be essential for the convergence of the solution. The same numerical scheme is applicable to other problems involving the E-field integral equations and can be extended to non-planar geometries. The solution was tested by comparison with measured RCS data of resistive and perfectly conducting plates and the agreement for plates of about one square wavelength in area was within 1 to 2 dB for all angles of incidence, including grazing. Other confirmation was provided by the behavior of the currents, in particular, the behavior near the edges. The currents on the resistive plate differ markedly from those on the perfectly conducting one and resemble quite closely (except for attenuation) the physical optics currents. The low frequency behavior of a resistive plate was compared to that of a perfectly conducting one by determining the first two terms of the corresponding Rayleigh series. Analytical expressions have been derived for the quadrupole terms, for both kinds of plates, in terms of the same static potentials required for the computation of the dipole moments. At low frequencies, the transition from resistive to perfectly conducting plates is discontinuous. The electric dipole moments for both kinds of plates are the same, but the magnetic dipole for a resistive plate is zero. The effect of the resistivity appears in the quadrupole term. The dipole moments for plates of several shapes were computed by solving integral equations for the static potentials, employing the same type of numerical technique. This method is more efficient at low frequencies than the general program, and the results of both methods compare well.PhDElectrical engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/158706/1/8204729.pd