SLR阵列探测中多通道高精度时间测量方法的研究

The SLR system using array detector can effectively improve echo photons detection efficiency, desired signal recognition rate and signal-to-noise ratio, and it also can realize the closed-loop tracking of weak signals and be conducive to implement of the non-cooperative target ranging and lunar laser ranging. However, the SLR system needs to use multi-channel time measurement technology to measure the arriving time of multi-echo photons, and the performance of multi-channel time measurement technology directly affects laser ranging precision. Using 1m aperture SLR telescope of the Institute of Geodesy and Geophysics, CAS as experiment and application platform, A FPGA-integrated multi-channel time-to-digital converter, which based on delay line loop shrinking method, is proposed in the project, and the designed time measurement method can solve the problem of arrival time measurement of multi-echo photons in the field of SLR system using array detector. The main research contents are: 1) Design and implement of FPGA-integrated multi-channel TDC combining with delay-line-loop shrinking method and multi-phase clock signal extraction. 2) Studying the relationship between redundant latch status information of delay line loop and input delay of measured event, building equivalent segmentation model and implementing multi-measurement for single event. 3) Design online statistics calibration circuit and algorithm, calibrating the measurement error and reducing the impact of temperature and voltage on the measurement accuracy. A multi-channel time measurement method, whose measurement accuracy is better than 5ps, will be realized in this project, and the designed method can be applied directly to 1 meter aperture SLR telescope. The achievement of the project provide the key technology for SLR array detection and make a breakthrough in the field of domestic laser ranging technology about multi-channel time measurement.

基于阵列探测器的SLR系统提高了回波光子探测效率、有效信号识别率和信噪比，可实现弱信号的闭环跟踪，有利于非合作目标测距和激光测月的实现。然而，阵列探测需要多通道高精度时间测量技术测量多回波光子的到达时刻，且测时精度直接影响测距精度。本课题以中科院测地所1米口径SLR望远镜为平台，开展基于延时环缩减法的FPGA多通道高精度时间测量方法的研究，解决SLR阵列探测中多通道时间测量问题，主要研究内容：1）结合延时环缩减法和多时钟脉冲提取法，设计FPGA多通道时间间隔测量方法；2）研究延时环冗余状态信息与输入时延的关系，设计等效细分模型，实现单事件多次测量技术；3）设计在线统计校准电路和算法，标校测量误差，减小温度、电压对测量精度的影响。本课题将实现精度优于5ps的多通道时间测量方法，项目成果直接用于1米口径SLR望远镜，为阵列探测提供关键技术支持，突破国内SLR技术中多通道时间测量的技术瓶颈。

多回波光子达到时刻的多通道时间测量技术可有效提高SLR测距系统的探测效率和有效测距数据数量，为空间碎片测距、月球激光测距等提供关键技术支撑。本项目以解决SLR测距中多通道时间测量问题为目标，开展基于延时环缩减法的多通道TDC技术研究，并在武汉1米口径SLR测距系统开展了测试实验。首先，项目组开展了多通道TDC技术的论证与设计，通过时钟约束和手动布局优化TDC性能，然后研究基于延时环冗余状态信息的锁存电路和细分模型，设计细分算法，最后设计在线测量非线性误差标校电路，并在PolarFire FPGA平台实现了多通道TDC电路，同时利用不同同轴电缆产生的不同固定时间间隔测量结果评估TDC测量精度。目前，研究成果初步应用到了激光测距、时频传递等领域。