Intelligent Reflecting Surface Aided 2D-DOA Estimation for NLOS Target

Direction-of-Arrival (DOA) estimation provides angle information of interesting targets for array radar systems. However, the conventional algorithms are designed for Line-of-Sight (LOS) scenarios and thus cannot be applied in Non-LOS (NLOS) environments. Recently, Intelligent Reflecting Surface (IRS) has been utilized to aid the DOA estimation for NLOS targets. In this work, we formulate the DOA estimation with the aid of IRS in NLOS situations as a novel geometric model. First, we establish an IRS-aided DOA estimation framework, where IRSs are exploited to alter the propagation direction of the probe (echo) signals. Then, we formulate the resultant estimation task as an elliptic parameter calculation problem, where Time of Arrival (TOA) is adopted as the solver. Finally, we derive a closed-form solution for the DOA estimation based on the elliptic equation. Compared with the existing methods, the proposed scheme is able to estimate two-dimensional (2D) DOA for NLOS sources. Numerical simulations have been conducted to verify its effectiveness.