Analysis of rotationally symmetric broad-band monopoles over circular ground plane

The two analysis methods compared are the method of moments (MM) with surface currents and the method of moments combined with the geometrical theory of diffraction (MM+GTD). The author investigates the condition number of the MM matrix and on the basis of this calculation the basis function chosen has smaller extent near to the coaxial excitation and the expansion functions are weighted with the distance from the excitation point. Using this method the stability can be held even at ground planes with greater radius. The results of MM and MM+GTD are in good agreement when the radius of the ground plane is greater than 2.4 wavelengths depending on the resonance frequency of the monopole but the computational time of MM is considerably greater when the radius of ground plane is greater than a wavelength