A review of adaptive antennas

Most adaptive receiving arrays permit beam steering in a selected "look" direction while rejecting or nulling strong interferences which arrive at angles other than the look direction. Nulling is accomplished by adjusting parameters of a signal processor connected to the array sensing elements (whether at rf, audio, or seismic frequencies) to minimize total output power. A signal arriving in the look direction would not be nulled because the adaptive process is constrained to maintain a predetermined sensitivity in the look direction. A substantial literature exists in the field. The September 1976 issue of the IEEE Transactions on Antennas and Propagation was dedicated to the subject of adaptive antennas. It is the purpose of this presentation to compare the works of Howells and Applebaum, Widrow, and Frost.