Effects of ground plane truncation on the impedance of a patch antenna

Abstract

The surface-wave admittance of a circular patch antenna with finite ground plane dimensions is formulated. The orthogonal relationship between the space wave and various surface-wave modes is invoked to determine the amplitude of a surface-wave mode produced by the equivalent magnetic current of the patch. The surface wave admittance, and hence the input impedance of a patch is found to vary widely with the ground plane size. Numerical results for the input impedance agree well with the measured data which confirms the validity of the formulation.