Efficient algorithm for analyzing microstrip antennas using fast-multipole algorithm combined with fixed real-image simulated method

The discrete complex image method (DCIM) is usually used to evaluate the Sommerfeld integrals for the spatial domain Green's function. For solving large scale problems, the far-zone interactions in the method of moments (MoM) can be simplified using a far field approximation with the plane wave expansion. Therefore, the combination of DCIM and Fast Multipole Method (FMM) could not achieve high efficiency due to the poor convergence of the addition theorem. An efficient algorithm combing FMM and fixed real-image simulated method (FRISM) is presented for analyzing microstrip structures in this paper. The fixed images locations lead to fast and convenient computations comparing with complex images such that can be used for wide-band applications. The accuracy and efficiency of the novel method are verified by numerical examples.