基于FPGA与GPS的时间测量电路设计与实现

Design and Realization of Time Measurement Based on FPGA and GPS

摘要: 为宇宙射线缪子（μ子）测量实验设计了基于FPGA的高精度时间-数字转换器（TDC），结合TDC测量值与GPS提供的标准时间(UTC)精确记录了粒子事件的时间信息。TDC采用粗计数+细时间测量相结合的方式，用计数器实现动态范围大于1 s的粗时间测量；使用FPGA加法进位延时链构建时间内插完成了细时间测量，并借助Wave-Union与bin-by-bin方法提高时间分辨并改善非线性。实验室测试双边沿TDC的时间分辨为16.68 ps，时间测量精度（RMS）好于45 ps。测量结果表明，该TDC满足脉冲前沿时间甄别要求。

Abstract: A time-to-digital convertor (TDC) based on field programmable gate array (FPGA) was designed for the cosmic ray μ measurement experiment. The high-precision time provided by TDC and a coordinated universal time (UTC) timestamp from GPS were used to make an accurate record of particle event. The method combining a coarse counter with a dynamic range larger than 1 s and a fine time interpolation based on FPGA carry-in delay chain was adopted in the TDC. The Wave-Union method and bin-by-bin method were used to improve the time resolution and linearity. The measurement results show that the time resolution of a double-edge TDC is 16.68 ps, the time measurement accuracy (RMS) is better than 45 ps, and TDC is sufficient for the pulse leading edge time discrimination.