“…There are three commonly used approaches to implement high-performance FPGA-TDC: (1) multiphase method, which uses phase differences between multiple clocks as the interpolation mechanism to achieve high resolution [ 10 , 11 ]; (2) Vernier method, in which the resolution is given by the difference between two delay lines [ 12 ]; and (3) the tapped delay line (TDL) method, which uses FPGA’s cells as the interpolator to improve the resolution. In the past few years, TDL has become the main implementation method of FPGA-TDC [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. In 2006, Song et al used dedicated carry chain as TDL for time interpolation, achieving a TDC with 69.5 ps resolution and 65.8 ps precision in the Virtex-II FPGA [ 18 ].…”