Angle Diversity Reception for LOS Digital Microwave Radio

Digital transmission over line-of-sight (LOS) microwave links is impaired at times by multipath fading in the propagation channel. The multipath can be a result of surface reflections, or induced by atmospheric anomalies such as strong ducting gradients. One principal method of overcoming the effects of multipath is to use a form of diversity transmission and reception. The common forms of diversity in LOS links are frequency and space, or combinations of both in severe cases. This paper describes an alternative form of diversity using angle (of arrival) diversity at the receiving terminal. This form of diversity has the advantages of a) limiting the antenna elevations required for space diversity, and b) spectral efficiency when compared with frequency diversity.