Focused Test of Orthogonality of Projected Subspaces for Wideband DOA Estimation

The test of orthogonality of projected subspaces (TOPS) utilized the orthogonality of subspace of multiple frequency points of wideband signal to complete the directions of arrival (DOA) estimation. The performance of TOPS was poor at low signal-to-noise ratio, and depended on the choice of reference frequency point. Besides the TOPS often exhibited pseudo-peak. This paper proposed a modification (FTOPS) based on the idea of focus to overcome the shortcomings of TOPS. Firstly, the method of reduced covariance matrix (RCM) was utilized to eliminate the noise. And then the signal subspace at each frequency point was focused on the signal subspace of any reference frequency. Finally, the DOA estimation was completed using the orthogonality between the signal subspace of the reference frequency and the orthogonal projection matrix of the array direction vector. The simulation results show that the FTOPS does not depend on the selection of reference frequency, and can effectively eliminate the pseudo peak, and the performance of FTOPS is superior to the traditional TOPS algorithm at low SNR.