Spectral domain analysis of circularly polarized rectangular patch antennas with a dielectric superstrate

Circularly polarized patch antennas are finding increasing use in far-distance communications such as the satellite broadcasting and communication, and in near-distance communications such as the indoor wireless LAN system and the wireless card system, because of their features of lower cost, less weight and lower profile. Practical patch antennas are often covered with a dielectric superstrate for protection against environmental hazards. It is important to predict the effect of this superstrate on the operating characteristics such as the resonant frequency and input impedance. The spectral domain approach using two entire basis functions, respectively corresponding to electric currents flowing on the patch surface of two degenerate modes, is extended to study the resonant frequencies of two degenerate modes, the circular polarization condition and the input impedance of a circularly polarized rectangular patch antenna with a superstrate, excited by a coaxial probe.