Phase unwrapping in DOA estimation via on the least squares of the nearest projection point

The phase interferometer offers a number of advantages, including a simple structure, high direction-finding performance and low computational complexity. As a result, it has become a popular technique for Passive Direction Finding. However, the phase interferometer is significantly affected by phase measurement error, which can easily lead to phase ambiguity when the minimum element spacing exceeds half a wavelength. For this, we propose an enhanced least squares nearest projection point (LS-NPP) phase unwrapping algorithm. By fitting multiple snapshots of phase-difference points using the least squares method, and then utilizing the wrapped phase-difference pattern (WPDP) to identify the nearest phase projection point to the fitted phase point, the ambiguity number is obtained, thereby achieving phase unwrapping. Simulation results demonstrate that the proposed algorithm exhibits a higher probability of correct phase unwrapping under low signal-to-noise ratio (SNR) conditions.