Off-grid DOA Estimation with Arbitrary-Spaced Linear Array using Single Snapshot

Most of the single-snapshot direction-of-arrival (DOA) estimation algorithms fail to estimate off-grid sources due to finite discretized sampling grid points, such as conventional beamforming and compressive sensing based methods. Meanwhile, existing effective off-grid DOA estimation algorithms based on Fourier coefficients interpolation are only applicable to uniform linear arrays (ULAs). In order to overcome these two shortcomings, we propose an off-grid DOA estimation technique for arbitrary-spaced linear arrays using single snapshot in this work. The initial DOA estimates are obtained using conventional beamforming in the first step. Subsequently, a fine estimation is deployed to correct the angle bias of single off-grid source based on a closed-form formula of the angle offset. In the case of multiple sources, an estimate-subtract strategy is adopted, where remaining sources other than the estimated one are removed from the received data utilizing the estimated information and each source is sequentially corrected in one iteration based on the method of single source case. Simulation results demonstrate the effectiveness and efficiency of the proposed method for off-grid DOA estimation with arbitrary-spaced linear arrays.