# Phase-Modulated Continuous-Wave Coherent Ranging Method and Anti-Interference Evaluation
## 4 Anti-Interference Capability
The \(p\)-values were 0.0589 and 0.6327 with ToF and coherent LiDAR interferences, respectively, demonstrating that the PhMCW system is immune to interference. Additionally, the proposed method can be applied to all types of LiDAR systems, regardless of the ranging method or beam-steering technique used. To the best of our knowledge, this is the first quantitative method for evaluating the anti-interference capability of LiDARs. The PhMCW ranging method is specifically suitable for applications with medium detection ranges such as autonomous vehicles, robotics, and drones. In Table 3, we have outlined the requirements for autonomous vehicle LiDAR and compared the performances of FMCW, commercial ToF, and the PhMCW methods. While the PhMCW has similar performances to commercial ToF LiDARs, it outperforms them with its excellent eye-safe feature and anti-interference ability. While FMCW has the best overall performance, it is limited by low stability, high complexity, and high insertion loss of the frequency-modulated source, as mentioned in references [7; 32; 35; 36; 37; 38]. Thus, the PhMCW is a simple and effective ranging method that satisfies various applications such as autonomous vehicles, robotics, and drones. Finally, it is worth noting that the PhMCW method is especially suitable for detection at 100 m, where the refractive index can be considered constant along the light trajectory. Although factors including temperature, pressure, and humidity inevitably lead to refractive index variation and result in ranging error, they can be calibrated in conjunction with temperature, pressure, and humidity sensors. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Distance** & **Precision** & **Ref** & & **Feature** \\ \hline \multirow{3}{*}{autonomous vehicle requirement} & 50 m (blind zone detection) & & & & \\  & 100–150 m (pedestrian detection) & cm range & [32] & \(\bullet\) & Eye-safe \\  & 100–150 m (pedestrian detection) & & & \(\bullet\) & Anti-interference \\  & & & & \(\bullet\) & Low-cost \\ \hline \multirow{3}{*}{FMCW} & \multirow{3}{*}{75} & \multirow{3}{*}{0.33} & [7] & \(\bullet\) & High performance \\  & & & & \(\bullet\) & Anti-interference \\  & & & & \(\bullet\) & High-cost require complex RF devices and equipment \\ \cline{2-6}  & 100 & 5.09 & [35] & \(\bullet\) & Poor stability: predistortions and IQ modulators are easily affected by thermal and mechanical fluctuations \\ \hline \multirow{3}{*}{Commercial ToF} & \multirow{3}{*}{120} & \multirow{3}{*}{5} & [37] & \(\bullet\) & Mature technology \\  & & & & \(\bullet\) & Potential eye safety issue \\ \cline{1-1} \cline{2-6}  & & 150 & 10 & [38] & \(\bullet\) & Poor anti-interference \\ \hline \multirow{3}{*}{PhMCW} & \multirow{3}{*}{100} & \multirow{3}{*}{8} & \multirow{3}{*}{This work} & \(\bullet\) & Simple system architecture \\  & & & & \(\bullet\) & Eye-safe \\ \cline{1-1} \cline{2-6}  & & & & \(\bullet\) & Anti-interference \\ \cline{1-1} \cline{2-6}  & & & & \(\bullet\) & Low-cost \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison among various LiDAR technologies. **Author Contributions:** Conceptualization, M.Z. and Y.W. ; methodology, Y.W. and Q.H. ; validation,M.Z., Y.W. and S.Z. ; data curation, M.Z., L.L., Y.C.,Y.L., C.Q., P.J. and Y.S. ; writing--original draft preparation, M.Z. ; writing--review and editing, Y.W., L.L., Y.C., Y.L., C.Q., P.J. and Y.S. ; project administration, Y.W., L.Q. and L.W. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was supported by the Science and Technology Development Project of Jilin Province (20230201033 CX, 20200501006 GX, 20200501007 GX, 20200501008 GX) and the National Natural Science Foundation of China (62090054). **Data Availability Statement:** Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request. **Conflicts of Interest:** The authors declare no conflict of interest.