Exact Green Functions for Microstrip Antenna Analysis

Exact image theory, recently introduced for the analysis of different electromagnetic problems involving planar boundaries between homogeneous media, is applied for the analysis of the microstrip geometry. It is shown that, instead of making direct use of image currents for the problem, two scalar Green functions can be defined in terms of the image currents, to speed up the actual calculation of the integrals in the microstrip problem. With the aid of these Green functions, the analysis of microstrip antennas can be performed with almost the same ease as free-space problems. Only one of the Green functions is seen to be singular with an integrable singularity, roughly the same as for the free-space Green function.