Spatial power spectrum estimation based on a MVDR-MMSE-MUSIC hybrid beamformer

In the computation of the minimum variance distortionless response (MVDR) beamformer, scaling is necessary in order to satisfy the unity gain constraint. When estimating the power in the close vicinity of a source, the MVDR beamformer allocates a at the direction of the source and the scaling factor becomes very large, and substantially increases the gain of the white noise. This situation can cause the non detection of a weaker source located in the vicinity of a higher power source. Comparing the equation of the MVDR beamformer to the Wiener-Hopf MMSE equation we observe that a initial estimate of the power can be used instead of scaling to satisfy the unity gain constraint. As an initial power estimate we propose to estimate the directions and powers of the dominant sources by applying the MUSIC algorithm; and to use this information to estimate the power spectrum using an artificially extended array. We also propose to use the dominant sources´ powers and directions obtained with MUSIC to generate a spectrum composed of triangular windows.