Microwave signal processing and devices for adaptive beamforming

Adaptive array antennas offer a powerful beamforming functionality, i.e., the main beam is autonomously steered into the desired direction and nulls are steered into the directions from which interference or jamming waves are arriving. The essence of this functionality is complex weighting in each branch of the array and adaptive optimization of these weights. To suppress interference effectively, the weights must be continuously adjusted because deep nulls are likely to appear only in very narrow angles. This paper proposes that adaptive beamforming can be carried our in an analog manner. Three possible architectures are introduced for this purpose, and their topological schemes and electrical features of these architectures are discussed from the viewpoint of adaptive array applications. Key microwave signal processing devices and a blind weight optimization algorithm developed for analog adaptive beamforming are also described.