Monopole element at the center of a circular ground plane whose radius is small or comparable to a wavelength

The input impedance and directive gain of a monopole element at the center of a circular ground plane in free space are summarized for arbitrary element length and element radius with ground plane radii of zero to more than two wavelengths. Numerical results are obtained by utilizing various models and are compared with measurements. The models include a ground plane of zero extent, the integral equation method, method of moments, oblate spheroidal wave functions, and the method of moments combined with the geometric theory of diffraction (GTD).