Projected Iterative MVDR Beamforming for Null Broadening and First Sidelobe Suppression in the Presence of DOA Mismatch
Abstract— Although the minimum variance distortionless response (MVDR) beamformer can keep the desired signal from interfering signals, however, it has notch null and no sidelobe level control which may lead to performance degradation in the case of scattering environment or unexpected interfering signals such as rapidly moving jammer environment. It also has high sidelobe levels for either low number of samples or high input signal to noise ratio (SNR). The projected iterative MVDR (PI-MVDR) beamformer is presented to broaden the width of nulls, suppress the first sidelobe level and support the case of low number of samples no matter of low or high input SNR. The averaged covariance matrix used in the PI-MVDR beamformer can overcome the circumstance of low number of samples over any input SNR value. Projecting the averaged covariance matrix on to the interference space enables the iterative MVDR beamformer to steer a mainbeam toward the desired signal direction and make a broad null in the direction of an unwanted signal. To reduce the first sidelobe level, find the direction corresponding to the strongest sidelobe close to the mainbeam which is considered as a direction of arrival (DOA) of a hypothetical interference signal and employ the PIMVDR beamformer to produce extra wide null. The steering vector of the desired signal is estimated to illustrate the robustness of the PI-MVDR beamformer in the presence of DOA mismatch. Simulation results demonstrated the achievement of the presented approach.
Index Terms— beamformer, covariance matrix, direction of arrival
King Mongkut’s University of Technology Thonburi, THAILAND
Cite: Raungrong Suleesathira, "Projected Iterative MVDR Beamforming for Null Broadening and First Sidelobe Suppression in the Presence of DOA Mismatch, " Proceedings of 2020 the 10th International Workshop on Computer Science and Engineering (WCSE 2020), pp. 90-94, Yangon (Rangoon), Myanmar (Burma), February 26-28, 2020.