Frequency-difference MUSIC: a method for DOA estimation in inhomogeneous media

In this paper, frequency-difference multiple signal classification (FD-MUSIC), a direction of arrival (DOA) method for high frequency signal source in inhomogeneous media, is proposed for an uniform linear array (ULA). In the FD-MUSIC method, the effect of inhomogeneity of media on DOA estimation results of high frequency signals with similar propagation pathes can be effectively suppressed by frequency-difference operation, so as to improve the robustness of DOA estimation. At the same time, combined with the idea of subspace decomposition in the MUSIC method, the DOA estimation azimuth resolution is improved. In order to ensure the DOA estimation performance of the FD-MUSIC method, it is required theoretically that the phase fluctuation of the frequency-difference signals caused by the inhomogeneity of media is far less than 2 π , and the array element spacing of the ULA is less than half of the wavelength corresponding to the frequency-difference Δ f . Two sufficient condition for the FD-MUSIC are given in this paper and the performance of the FD-MUSIC method is analyzed by simulations. When the conditions required by the FD-MUSIC method are satisfied, simulation results show that the DOA estimation performance of the FD-MUSIC method is better than that of the conventional beamforming (CBF) method, the multiple signal classification (MUSIC) method, the frequency-difference beamforming (FDBF) method, and deconvolved frequency-difference beamforming (Dv-FDB) method in the presence of inhomogeneity.