Comparison of Three FDTD Modeling Techniques for Coaxial Feed

This paper addresses the difficulties reported in the numerical modeling of coaxial feed probes. A range of finite-difference time-domain (FDTD) modeling techniques (e.g., gap, magnetic frill and transmission line modeling) was successfully applied for specific applications. The same problem was challenged for the case of electromagnetically coupled patch antenna (EMCP). This structure has intricate resonance behavior and operates based on two-mode excitation. These two modes have close values of resonant frequency and can be revealed only with precise probe modeling. The following modeling techniques for the probe feed have been implemented and compared with the measurement results: electric gap modeling, sub-cell modeling of inner conductor and very fine discretization of coaxial probe. The results are discussed in the light of advantages and downsides of each technique and the associated computational parameters to obtain a reliable solution