SIMPLE MODEL FOR APPROXIMATION OF MUTUAL COUPLING IN MICROSTRIP PATCH ARRAY

Abstract

A relatively simple and efficient empirical formulation for the estimation of mutual coupling between two microstrip patch antennas has been proposed in this thesis. The formulation is constructed based on the asymptotic behavior of the electromagnetic wave excited by an electric current on a grounded substrate. It is expressed by a few terms of cylindrical wave functions of two variables, which are center-to-center spacing and azimuthal angular separation between two antennas. The formulation contains coefficients which need to be determined at once, for any given antenna geometry and operating frequency, by matching with few sample values of mutual impedance for several antenna separations using the least square method. The latter are calculated by a rigorous full-wave analysis using a commercial software. The formulation with the obtained coefficients can then be used to estimate the mutual coupling between two similar antennas for any arbitrary separations. The proposed formulation is expected to be far more efficient than the exact solution due to its simple closed form. The proposed approach can be employed to efficiently estimate the mutual coupling between any elements of a microstrip patch array antenna. Some numerical examples are given to illustrate the applicability, validity, and efficiency of the proposed approach. The good agreement of the mutual impedance estimated by the present approach and that obtained by a rigorous full-wave solution has been demonstrated.