Influence of the ground plane geometry on the normalized site attenuation of an OATS

The existence of differences between different open area test sites (OATS) in antenna calibration and electromagnetic compatibility (EMC) compliance measurements is still a real issue. To minimize the differences, it is necessary to analyze the influencing factors. To examine the influence of the ground plane geometry on the site attenuation, a comparison of different open area test site geometries and sizes has been carried out. The investigation has been performed numerically with the method of moments in the frequency range 30-130 MHz for test distances of 3 m and 10 m. The deviation of the site attenuation (with receiving antenna height) in relation to the ideal test site has been calculated. The minimal plane, for example, which is suggested in the standards, shows a high deviation. Furthermore, the significant influence of on and off axis measurements is shown and the reasons are explained.