Computation of the radiation pattern of a microstrip patch antenna in a complex geometry

A hybrid technique for computation of electromagnetic scattering has been developed at the University of Illinois. By utilizing the both high frequency and low frequency methods, the technique can handle large targets with small cracks and cavities on their surfaces. The high-frequency shooting and bouncing ray (SBR) method is used to evaluate the scattering from a large target with the cracks and cavities filled with perfect conductors, and the low frequency finite-element boundary integral (FE-BI) method is employed to analyze the cracks and cavities. The equivalence principle is used to combine the results of the two methods. This hybrid method is extended to compute the radiation pattern of a microstrip patch antenna mounted on a complex geometry. First, the FE-BI method is used to analyze the antenna. The result is an equivalent magnetic current on the surface of the antenna. The SBR method is then used to model the surrounding geometry. Because a microstrip patch antenna is a highly resonant structure, it is assumed that the surrounding geometry has minimal effect the equivalent current. This paper first discusses the theoretical basis of the hybrid FE-BI/SBR method for analyzing the radiation from a microstrip patch antenna. It then presents some numerical results showing the utility and validity of the method.