Input impedance of a center-fed circular patch antenna covered by a uniaxial anisotropic superstrate

This Letter presents a waveguide modal analysis for evaluating the input impedance of a circular patch antenna fed by a centered coaxial transmission line. Both the substrate and the superstrate are assumed to be uniaxial anisotropic. The open-region antenna problem is initially transformed into a closed-region coaxial-circular waveguide junction cascading problem by the introduction of a large circular cylindrical magnetic wall to enclose the whole antenna. The resulting waveguide cascading problem is then solved by the conservation of complex power technique (CCPT). Numerical results for the input impedance of a microstrip disk antenna are presented and compared with those obtained by others. Very good agreement is observed Also examined are the effect of the finite thickness of the circular patch and the effect of the superstrate on the antenna's input impedance. (C) 1996 John Wiley & Sons, Inc.