Comparison of EM solvers on a circularly polarized patch antenna

Today most microwave structures and therefore microstrip antennas are designed and optimized using CAD software packages that can compute all parameters that are of interest to a designer. Different CAD packages use different mathematical methods to calculate currents and electric fields on a structure. Frequently used methods are FDTD (Finite-Difference Time-Domain) and MoM (Method of Moments). Although an algorithm can be written using each method for a specific structure, it is easier to use large program packages that offer possibility to draw and manipulate 3D structures [1]. All those programs can solve almost any kind of structure, but the question is how accurate they predict real, measured values. In this paper we use an almost square single feed circularly polarized patch antenna to compare measured results with the ones that came from simulation of exactly the same structure in three different leading EM solver packages. Our results show that, for this type of antenna, better results are given from solvers that use FDTD calculation method.