FPGA-based Circuit Design For High-precision Time Interval Measurement And Timing Control

LiDAR(Light Detection and Ranging,LiDAR)has been one of the most important research topics in national defense scientific research since its inception.As an emerging active remote sensing technology,LiDAR has outstanding speed,accuracy and real-time in the application of capturing three-dimensional spatial information of ground targets.Therefore,it has been developed rapidly after its launch.Among them,the time-of-flight-based pulsed LiDAR has great advantages in detection range and detection accuracy,and the measurement accuracy of the time interval in the system is the bottleneck of the laser ranging accuracy.This subject aims to design and implement a high-precision time interval measurement and timing control circuit system for lidar based on time-of-flight ranging used in the field of surveying and mapping.The system is based on FPGA hardware platform and adopts dedicated timing chip TDC7201,which has the advantages of high measurement accuracy,wide measuring range,good stability,fast processing speed,and individual customization.Aiming at the problem of converting the optical pulse emitted by the laser and the optical signal captured by the detector into a standard LVTTL electrical signal as the front-end input to the TDC7201 chip,an amplifier and shaping circuit based on OPA858 operational amplifier and TLV3501 high-speed comparator is used to realize processing small signal.In order to improve the portability of the time measurement system,the high-precision time interval measurement module and the signal conditioning and anti-jitter module are designed for integrated circuits.At the same time,the delay error introduced by the device is eliminated through the hardware design.This article first analyzes the overall composition structure and work flow of the LiDAR system,and derives system functional requirements and performance standards;and from this,the whole system is designed and divided into four parts:high-precision time interval measurement module,signal conditioning and anti-jitter module,ZYNQ-based timing generation module,and detector peripheral circuit module.For the key issue of achieving accurate measurement of the time interval of the optical pulses emitted by the laser and the optical signals captured by the detector,the dedicated timing chip TDC7201 is used in conjunction with ZYNQ to achieve high-precision and wide-range timing through specific modes.The realization of precise control of the detector opening is based on the development mode of the ZYNQ platform using software and hardware co-design to complete the design and packaging of the controllable delay IP core based on the timer principle.In addition,a bias voltage is provided for the tiny signal of the detector,and the reverse bias output signal is directly connected to the voltage amplifier circuit for amplification.Finally,this article tests and analyzes the performance of the system.The results show that the system can capture pulse signals with a pulse width of 10 ns and an amplitude of 0.26 V and accurately measure the time.The standard deviation of the test is stable at 70ps?86ps,and the upper limit of the measurement range is 8.1ms.The fluctuation error rate of the adjustable delay pulse signal is 1ppm.High-precision time interval measurement and timing control circuit system can achieve the excellent performance of high accuracy,wide range,stability and high capture efficiency.