Regression analysis of FMCW–LiDAR beat signals for non‐linear chirp mitigation

The performance of a frequency‐modulated continuous wave (FMCW)–light detection and ranging (LiDAR) is severely limited by the inherent non‐linear chirp when laser diodes with direct frequency modulation are used as light sources. To overcome this limitation, optoelectronic feedback techniques were reported for chirp linearisation. The author propose and demonstrate an alternative technique that is based on regression analysis of FMCW–LiDAR beat signals. It is shown that the waveform of the laser frequency modulation accompanied by the non‐linear chirp is analytically expressed in terms of the Fourier series containing both the odd and even harmonics. The analytical expression is utilised in the regression analysis to calculate the unknown distances. A relative accuracy below 1 mm is obtained in the proof‐of‐principle experiment.