On the use of antenna weight functions in field strength prediction and interference reduction

In this paper two methods for calculating the received electromagnetic field by a single-parabolic reflector antenna in the shadow region behind a finite-width screen are proposed and analysed. The first one is referred to as the far-field approach and treats the obstacle and reflector antenna diffraction separately. The antenna simply is replaced by a point source having the receiving properties of the reflector antenna considered. The second method is called the near-field approach and considers the combined effect of obstacle and antenna diffraction. It is shown that considerable differences between the results of both methods may exist, even for an obstacle-antenna separation large compared to the Rayleigh distance of the antenna, and both for a CW and broadband analysis of the communications channel. It is concluded that the near-field method gives the best results and can be applied to many practical problems such as interference reduction and searching the optimal position of VSATs in urban environments.