Adaptive Nulling Using Photoconductive Attenuators

Traditional adaptive antennas require receivers at each element in the array in order to form the correlation matrix and derive the adaptive weights. This approach is expensive and difficult to implement on many phased array architectures. An alternative is to minimize the total array output power by making only a subset of the elements adaptive. Nulls can be placed in the sidelobes with little effect on the main beam. This paper uses the later approach coupled with new photoconductive attenuators that serve as adaptive amplitude weights. The attenuators on some the elements in a phased array serve as adaptive weights while the remaining elements are uniformly weighted. A genetic algorithm controls the infrared signals to these elements in order to minimize the total output power. Experimental and computer results demonstrate the effectiveness of this approach.