A Generalized Method to Extend the Maximum Unambiguous Range of LiDAR With Any Point Acquisition Rate and a Small Sampling Window

In the context of the burgeoning low-altitude economy, light detection and ranging (LiDAR) provides an effective strategy for searching and localizing non-cooperative illegal unmanned aerial vehicles. However, range ambiguity is the main challenge in long-range, high-speed search and localization of aerial targets. In this work, we propose a generalized method to extend the maximum unambiguous range (MUR) of LiDAR. By synthesizing a longer modulated envelope using multiple independent envelopes, the MUR can theoretically be extended to any value without sacrificing the point acquisition rate (PAR). Moreover, through the subdivision of each sub-modulated envelope, the proposed method can compress the signal sampling window to two pulse repetition intervals, significantly reducing data storage and processing requirements. Specifically, we provide a waveform instance based on the proposed generalized method and elaborate on its composition and corresponding data processing method. The signal truncation induced by the randomness of the signal sampling starting position is analyzed, and a corresponding recovery method is developed. Consequently, even a received truncated sub-modulated envelope can still be used for ranging, requiring only that its effective length equals one pulse repetition interval. Furthermore, the parameters selection strategy of this waveform instance is theoretically analyzed to guide the system design. The feasibility and the robustness of the waveform instance are investigated through numerical simulations and a 1 km outdoor experiment.