Wideband Digital Array DOA Estimation Method Based on SPS-TOPS in the Present of Mutual Coupling

In this paper, a spurious peak suppression direction-of-arrival (DOA) estimation method based on test of orthogonality of projected subspaces (SPS-TOPS) is proposed for wideband digital phased arrays in the present of mutual coupling. In contrast to the frequency focusing approach of coherent signal subspace method (CSSM), SPS-TOPS, based on the original TOPS, estimates DOA by evaluating the orthogenicity between rotated signal subspace and noise subspace at the corresponding frequency subband. In particular, the proposed method considers the impact of mutual coupling among array elements on subspace-based methods, and incorporates auxiliary array elements to avoid changes in the array manifold. Further, a detailed analysis of the spurious peaks in the original TOPS algorithm is conducted, and a spurious peak suppression function is constructed to eliminate spurious peaks in the DOA estimation spectrum. This improvement enhances both accuracy and reliability of the DOA estimation spectrum. Meanwhile, SPS-TOPS optimizes the metric calculation by utilizing Frobenius norm instead of singular value inverse, eliminating the need for SVD operation and significantly enhancing algorithmic efficiency. The comprehensive simulation results demonstrate that the DOA estimation root mean square error of SPS-TOPS is 0.1 $^\circ$ lower than CSSM in the present of mutual coupling while signal noise ratio is 10 dB. Compared with TOPS, the calculation time of SPS-TOPS is reduced from 28.7 s to 7 s when the number of elements is 32 and the spurious peaks are completely eliminated.