Arbitrary Waveform Frequency Modulated Continuous Wave LiDAR System

With advantages of high-precision 3-D imaging and simultaneous measurement of target distance and velocity, frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR) has great potential in the fields of autonomous driving, military, and aerospace. However, frequency-modulated (FM) nonlinearity significantly deteriorates its ranging accuracy and has become a problem that cannot be neglected. This article proposes an arbitrary waveform FMCW (AW-FMCW) system, in which the distance of target is extracted precisely irrespective of the FM waveform employed. In proposed AW-FMCW system, the correlation between the phase of coherent signal and the FM waveform of tunable laser is rigorously deduced and analyzed. The distance of target is extracted utilizing minimum mean-square-error (MMSE) estimation. The low-bandwidth short-distance (LBSD) approximation is proposed to simplify the process of the estimation and quadrature coherent detection is employed to acquire the phase signal. The performance in terms of the measured distance and the precision of AW-FMCW system is theorized in detail and validated by Monte Carlo simulations and experiments. In the experiments, three different FM waveforms are utilized for ranging of targets at six different distances, and 0.279 mm ranging precision and $1.35\times 10^{-4}$ relative precision are realized at 2.06 m target detection.