Research and Implementation of a Pulsed Laser Ranging Method Based on Digital Mixing

To address the inherent trade-off between measurement accuracy and speed in traditional pulsed laser ranging systems, a novel method based on digital mixing is proposed. The technique proportionally amplifies the time-of-flight interval between the transmitted laser pulse and the received echo signal by employing asynchronous divide-by-two frequency division and digital mixing. This amplified time interval is then precisely quantified using a general-purpose Time-to-Digital Converter (TDC). To facilitate this method, a high-frequency pulsed laser driver and an Avalanche Photodiode (APD) -based receiver circuit were designed and implemented. Furthermore, a Field-Programmable Gate Array (FPGA) was utilized to realize the asynchronous frequency division and digital mixing, simplifying the overall circuit design. A prototype system was constructed and experimentally validated in a laboratory environment. The results demonstrate that the system achieves millimeter-level accuracy over a measurement range of 100-130 cm, effectively resolving the conflict between speed and precision found in conventional approaches and confirming the feasibility of the proposed scheme.