A method for computing scattering by large arrays of narrow strips

The electromagnetic scattering characteristics of an array of narrow, conducting strips can be developed by extending the work of Butler and Wilton (1980) who solved the approximate integral equation for a narrow strip and for a narrow slot by a series of Chebyshev polynomials augmented with the known edge condition. The strips are embedded in a homogeneous medium of infinite extent and are considered narrow relative to wavelength in the medium at the frequency of excitation. The strip currents are expressed as linear combinations of certain basis functions which are exact solutions of the isolated narrow strip integral equation subject to a special excitation. A matrix equation for basis-function coefficients that expresses numerically the coupling among all the strips in an ensemble is obtained and its solution yields the coefficients of all the current expansions. The systems of integral equations for TM and transverse electric plane-wave excitation are solved and data are presented illustrating induced currents and scattered fields. It is shown that for large arrays of narrow strips the method is superior to the traditional moment method.