White Noise Array Gain for Minimum Variance Distortionless Response Beamforming With Fractional Lower Order Covariance

In this paper, a special property of the fractional lower order covariance (FLOC)-based minimum variance distortionless response (MVDR) beamformer is found, which is the FLOC MVDR beamformer that has greater white noise array gain (WNAG) than the classic MVDR beamformer in the presence of non-Gaussian stable noise. In order to explain the reason, the analytic WNAG of the FLOC MVDR beamformer is derived with respect to eigenvalues of FLOC matrix. Then, it is theoretically proved and explained through the relation between the WNAG and the eigenvalue separation of the covariance matrix and the reason can be concluded that the eigenvalue separation of the FLOC-based matrix is weaker than that of conventional covariance. Simulation results verify the validity and advantages of the FLOC MVDR beamformer over the MVDR beamformer when the received array noise obeys stable distributions and there exist steering vector mismatches in the beamforming model.