Scattering of a Plane Electromagnetic Wave from a Semicircular Crack in a Perfectly Conducting Ground Plane.

摘要

The scattering of TM and TE plane electromagnetic waves from a semicylindrical crack in a perfectly conducting ground plane is determined using a dual-series eigenfunction expansion technique. Orthogonality properties of the sinusoids are used to reduce the solution to the inversion of a truncated infinite matrix. When the radius of the crack is much smaller than the wavelength, small-argument approximations for the spherical radial functions are employed to simplify the results and remove the ka-dependence from the necessary numerical matrix inversion. In this small crack limit, closed-form results are developed for both polarizations, and for the TM polarization, results are found to be different by only a constant factor from those for TM scattering from a narrow slit in an infinitely thin conducting screen. TE scattering from a small crack is found to differ significantly from TE scattering from a narrow slit, which indicates that the slit approximation is not valid for real situations that more closely resemble physically an indentation, or crack. Keywords: Electromagnetics; Scattering; Crack. (jhd)