The RCS of a microstrip dipole deduced from an expansion of pole singularities

The singularity expansion method (SEM) is applied to the steady-state analysis of plane wave scattering from microstrip dipoles. The current induced on the antenna is expanded in a series of natural modes, where the amplitude of each term in the expansion is expressed as a coupling coefficient weighted by a simple frequency pole. Natural modes occur at pole singularities of the antenna current in the complex frequency plane, and are found by a numerical root search of a homogeneous matrix equation. This formulation results in an accurate and efficient calculation of the radar cross section (RCS) of microstrip dipoles which exhibit some appreciable resonant characteristics, where it is found that the current resonance dominates the response of the antenna. The SEM applied yields good physical insight into the scattering behavior of such antennas. Results obtained with the SEM analysis are compared with a full-wave method-of-moments solution