Performance of an interferometer angle-measuring receiver against non line-of-sight transmitters

Experiments have been conducted using a microwave interferometer to measure the direction of arrival of signals when the propagation path is obstructed by bare or wooded ridges. A number of paths with different ranges and scattering angles have been investigated. The receiver and transmitter sites were surveyed to provide accurate position information, relative to terrain features, and calibration of the interferometer over its field of view. An outline of the experimental procedure is given, together with a brief description of the equipment used. Results of mean bearing measurements and corresponding signal strengths are presented as a function of transmitter heading. The distributions of measured parameters are given in histogram form. These are interpreted in terms of a theoretical scattering model which explains the observed differences between propagation over bare and wooded ridges.