A numerical analysis of antenna factor of bilog antennas for normalized site attenuation and EMC measurement

The antenna factor (AF) values are typically determined based on the assumption that the antenna is in free space. In practice, the NSA and EMC measurement are often conducted in the presence of a perfectly conducting ground plane. The AF of bilog antenna used for measurement might be seriously affected by a ground plane. In addition, the variation of the active phase center of log periodic element can also induce variations in AF. In this paper, software codes based on method of moments are used to study the AF of a bilog antenna over a ground plane at different heights for both horizontal and vertical polarizations. Meanwhile, the numerical analyses of the mutual coupling between antenna and its image, and the variation of the active phase center are also carried out.