Applebaum adaptive array apertures with 2-D IIR space-time circuit-network resonant pre-filters

A modification to the well-known Applebaum adaptive beamformer is proposed employing a low complexity space-time network-resonant IIR beamfiler. The network-resonant filter is a multiple input multiple output (MIMO) linear multidimensional recursive discrete system. It is applied as a pre-filter to an Applebaum adaptive beamformer in order to perform highly directional receive mode beamforming with improved noise and interference rejection. The spatial selectivity (directivity) of the Applebaum beamfomer is enhanced by introducing complex-manifolds from the 2-D IIR beamfilter to the zero-manifold-only transfer function of the adaptive beamformer. This leads to the proposed network-resonant adaptive Applebaum array, which shows angle-dependent levels of additional improvement of output SINR (best case, up to 12 dB improvements, near the end-fire direction). The ability to increase the improvement of the output SINR by 0-12 dB compared the best available adaptive Applebaum beamformer without using additional antenna elements in the array is a useful feature of the scheme. The proposed network-resonant Applebaum adaptive beamformer can be implemented using an upgrade to the digital signal processor without change to the array or RF electronics.