Immunity to Mutual Interference in Coded Phase-Shift LiDAR

Abstract

When the light detection and ranging (LiDAR) scans a space, the echo signal affected by diffuse reflections may be captured by other LiDAR detectors to interfere with their echoes. The ghost points and missed detections are induced by the co-frequency interference in the phase-shift LiDAR. An interference cancellation with a maximum likelihood estimation (ICMLE) signal processing scheme is presented based on the coded phase-shift LiDAR to avoid mutual interference in this paper. The delay time is estimated with maximum likelihood estimation after each component signal is identified from the mixed signal on account of the correlation between the codewords, followed by cancellation of the component signal from the mixed signal step-by-step. The received signal model with mutual interference is developed, and the Cramer-Rao bound (CRB) is theoretically derived to evaluate the performance of the estimators. The Monte-Carlo analysis shows that the component signals can be recognized from the mixed signal with the ICMLE scheme. The mean square error (MSE) of the delay time for the mutual interference of two-channel signals is close to the CRB. The experimental results demonstrate that the ranging is feasible with a range precision of 8.44 × 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{-3}$</tex-math></inline-formula> m using the echo signal estimated by the proposed solution.