Aliased beat frequency recovery in undersampled FMCW LiDAR via cross-channel disambiguation

FMCW LiDAR operating at long range or high sweep rate imposes demanding requirements on ADC sampling rate and data throughput. We demonstrate a six-channel undersampling receiver that recovers aliased beat frequencies using the calibrated responses of parallel low-pass filters (LPFs) with progressively increasing cutoff frequencies. The LPF responses identify the true beat frequency interval, which, together with the observed aliased frequency, resolves the alias ambiguity. A down chirp anchoring strategy further supports reliable recovery near folding boundaries. With the sampling rate reduced from 500 to 50 MS/s, the system achieves a ranging precision of 4.49 mm and a ranging accuracy within 7.46 mm over a maximum tested distance of 18.49 m. The measured resolution is 2.35 cm at 50 MS/s. Simultaneous multi-target ranging and 3D imaging are also demonstrated.