Transmission Line Model Analysis of Rectangular Patch Antennas

Abstract

The transmission line model has been utilized to determine the input performance of a rectangular patch antenna excited by a coaxial probe. Approximate expressions have been developed for the resonant propagation constant (or the resonant frequency), quality factor and input resistance of such antennas which clearly indicate the effects of the various antenna parameters including the feed on these quantities under dynamic conditions. The results of computations based on the expressions developed are compared with available measured values. The present work establishes the transmisson line model as a valid representation of rectangular patch antennas, and would facilitate the design of such antennas without elaborate numerical computation. The model has also been applied to determine the resonant parameters for a similar antenna tuned by passive metallic posts. Validity of an approximate expression derived for the resonant frequencies of such tunable antennas has also been established by comparison with available measured results.