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

The paper presents analysis of rotationally symmetric monopoles with taldng into account the effect of the finite ground plane. The two 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 paper also presents investigation on the condition number of the MM matrix and on the basis of this calculation the basis functions chosen has smaller extent near to the coaxial excitation and the system of expansion functions are weighted with the distance from the excitation point. Using this method the stability can be hold even at ground planes with greater radius. After comparing the results of MM and MM+GTD can be established that these 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 considerable greater when the radius of ground plane is greater than a wavelength.