FPGA-Based Time-to-Digital Converter for Pulsed Laser Ranging

Abstract

This paper implements a Time-to-digital Converter (TDC) in a field-programmable gate array (FPGA), which is made for a single-photon-counting-based pulsed laser ranging system. The fine time is measured by the Tapped Delay Line (TDL) constructed in an internal dedicated carry chain of the FPGA. The length of the TDC is longer than one clock period, and the whole CARRY4 is utilized as a delay unit. The proposed TDC is made up of the fine time measurement module, encoder, coarse time counter, and data transport module, which are achieved in a resource-tensed FPGA Xilinx-ZYNQ. As this paper is done in a shared FPGA, the presented TDC can replace the ASIC-TDC GP22 as the TOF measurement module. By measuring the same time interval and modifying the fixed error in TDC, the results show that the time resolution can reach 53 ps. Compared with the ASIC-TDC GP22, both linearity and measurement range are improved in the proposed TDC, which makes the pulsed laser ranging system more flexible and integrated.