Interference cancellation matrix beamforming for 3-D beamspace ML/MUSIC bearing estimation

For the case of two closely spaced targets angularly located within the mainlobe of the transmitted beam, 3D-BDML in a computationally simplistic maximum likelihood bearing estimation scheme which operates in a 3-D beamspace generated by three orthogonal, classical beamformers. The presence of strong interferers angularly located outside the mainlobe encompassing the two targets of interest necessitates the use of adaptively formed left, center, and right beams. Let M denote the number of elements comprising the array. Novel procedures are developed for the construction of and M×3 interference cancellation matrix beamformer which retains those properties of the M×3 classical matrix beamformer critical to the computational simplicity of 3D-BDML. The most important of these is commonality of M-3 nulls among the left, center, and right beams. Simulations demonstrating the performance of both single frequency and multifrequency 3D-BDML are presented