Moment-method solution of the center-fed microstrip disk antenna invoking feed and edge current singularities

The problem of a microstrip disk antenna excited by a probe at its center is studied using a moment-method approach for the evaluation of the surface current on the disk. The novelty of the work is a careful treatment of the singular effects of the probe and of the disk edge on the surface current on the disk. This is done by including in a proper way an attachment-mode current and an edge current in the surface current on the disk. The inclusion of these two currents accelerates the convergence of the moment-method solution and enables the input impedance to be obtained in a broad frequency range, including the zero-frequency limit. The influence of the probe on the input impedance is taken into account in a correct and accurate way. A comparison between measured and computed results is given, and good agreement is obtained