Performance Analysis and Optimal Placement for Unambiguous DOA Estimation using Interferometry

Interferometry is considered as a computationally efficient and economically fair method for direction of arrival (DOA) estimation using a limited number of receiving antennas. Moreover, interferometric arrays are capable of providing relatively high-accuracy estimates, with the sacrifice of involving phase ambiguity as a byproduct of large antenna spacing. In this work, we first propose a phase line length matching (PLLM) method for unambiguous DOA estimation. Then, we analyze estimation performance of three-antenna interferometric arrays in both cases of high and low signal-to-noise ratio (SNR). In the case of low SNR, dominant estimation error comes from phase line mismatching, and a metric of line mismatching probability (LMP) is proposed to quantify the performance. In the case of high SNR, a closed-form formula of conditional mean squared error (CMSE) for DOA estimation is derived and compared with Cramer-Rao Bound (CRB). Finally, the influence of interferometric array configuration on estimation performance is discussed and optimal configurations in both cases are suggested as well. Comparative simulation results validate the effectiveness of proposed PLLM method and the superiority of optimal interferometric arrays for unambiguous DOA estimation.