A 1-ps Bin Size 4.87-ps Resolution FPGA Time-to-Digital Converter Based on Phase Wrapping Sorting and Selection

Abstract

A field-programmable gate array (FPGA) high-resolution time-to-digital converter (TDC) based on phase-wrapping, sorting, and selection to achieve an extremely fine bin size of 1 ps is proposed in this paper. Based on Nutt interpolation method, a wide measurement range with a high resolution can be realized at the same time. The input signal is fed into tapped delay lines (TDL) with regularized and automated cell placements to generate a multitude of delayed signals with plenty of regularized phase shifts. Due to periodicity, those phase shifts will be equivalently wrapped within a reference clock period and then phase sorting, ROM-based selection are applied to construct a merged TDL with uniform phase division across the reference clock period. The FPGA TDC was implemented successfully on both Altera Stratix IV to achieve a resolution as fine as 1ps with a measurement range of 1s. The short-range integral non-linearity errors (INL) are measured as -1.470 -1.676 LSB for Stratix IV to demonstrate its excellent linearity.INDEX TERMS Field programmable gate array (FPGA), merged TDL, phase selection, phase sorting, phase wrapping, time-to-digital converter.