Research on Algorithms for Adaptive Array Antennas.

Abstract : Conventional adaptive array processing is accomplished by linearly combining the outputs of tap delay lines attached to each sensor of an array. This type of processing can be interpreted as using an 'all-zero' filter at each sensor to generate a frequency-dependent magnitude and phase shift (weighting) over the operating bandwidth of the array. A new array processing method is presented which uses filters possessing both poles and zeros to perform the frequency-dependent weighting. Adaptation of these filters is based on minimization of the 'equation error' rather than the true output error. Ramifications of the equation error approach to array processing are discussed. The idea of constained array processing is discussed and an optimal array weighting formula is derived. The effects of thermal noise on optimal array weightng and pole and zero filtering is presented. Through computer simulations, the pole nulls while using the same total number ot weights as an 'all zero' filter. The method is expected to be useful in many seismic, acoustic, and electromagnetic array processing applications.