A Method with Approximations for Modeling Antennas on Finitely Conductive Grounds

Base on the image theory and the moment of method (MOM), an image method is proposed to analyze the input impedance of the antennas on different grounds media, using the modified reflect coefficients of surface impedance. By comparing the calculated data with the measured data, a conclusion is drew that the radiation efficiency of the vertical antennas at very low frequency (VLF) may be changed obviously by different grounds under them. And the input impedance of the antenna on radial screen on an imperfect ground is varied with the frequency and the causes are analyzed. In fact, the adaptive method reduces the total calculation amount compared to the conventional Sommerfled/Norton method.