Two-dimensional direction estimation of multiple signals using two parallel sparse linear arrays

In this paper, we focus on the problem of estimating the two-dimensional (2-D) direction-of-arrival (DOA) of multiple signals and propose a novel approach for 2-D DOA estimation using two parallel sparse arrays structured by two sparse uniform linear arrays (ULAs) and an auxiliary sensor. Firstly, we obtain automatically paired direction cosine estimates along the x and y axes by using the mutual and internal shift-invariance properties of two sparse ULAs and the propagator method, where the direction cosine estimates along the y-axis are cyclically ambiguous due to the fact that the inter-element spacings of two sparse ULAs exceed a half-wavelength. Then, we extract unambiguous direction cosine estimates by means of the auxiliary sensor and a novel disambiguation procedure. Finally, we use the unambiguous direction cosine estimates to calculate the elevation and azimuth angles. The proposed method does not require extra pair-matching process and can achieve automatic pairing for 2-D DOA estimation. Moreover, it has a low computational complexity without any spectral search. Simulation results demonstrate that the proposed method outperforms the existing methods based on the two-parallel ULA, especially for small number of sensors case.