Microstrip antennas with meshed ground planes are suitable for radiation elements of large satellite phased array antennas. Although they have some mechanical advantages such as the possibility of antenna weight reduction, they also cause electrical problems such as the resonant frequency shift and F/B ratio degradation. The first purpose of this paper is the analytical understanding of the resonant frequency shift, for which two perturbational methods are proposed. One has a closed form expression that provides some useful design data. The other is to solve the integral equations by using the periodicity of the meshed ground plane, which gives more accurate results. The second purpose of this paper is to investigate the backward radiation from the meshed ground plane analytically, for which we derive an analysis method from the calculated results of the resonant frequency shift. The proposed methods are verified with the measured ones.

In this letter, we propose an approximate calculation formula for the resonant frequency of a microstrip antenna with meshed ground plane, which is derived by perturbational technique and is expressed by a simple closed form. The calculated results are in good agreement with FDTD-calculated and measured ones. Therefore, it is confirmed that the proposed formula is valid for approximate evaluation of the resonant frequency of microstrip antenna with meshed ground plane.