A 63.3ps TDC Measurement System Based on FPGA for Pulsed Laser Ranging

For pulsed laser ranging systems, the accuracy of the time-to-digital converter (TDC) measurement directly determines the accuracy of the system's ranging. This work uses the internal carry chain of the FPGA to construct the delay chain, together with the encoder, coarse time counter, mean filtering and the trigger modules build up the proposed TDC design. In order to ensure the consistency of the delay chain, this work utilizes the entire CARRY4 carry chain as a single delay unit, and the total delay of the delay chain needs to be more than one clock cycle. Therefore, with careful verifications, 160 delay units are connected in series to form a completed delay chain. In order to reduce the complexity of the design, this work partitions the 160-bit input encoder into five 32-bit input encoders, which is equivalent to divide the delay chain into five segments and then accumulate all the statistical results. The measured results show that the TDC measurement resolution can reach 63.3ps, and the ranging accuracy of the ranging system is 0.95cm, while the measurement error is 0.38cm, and the logic complexity is 3k LUTS and 4k DFFS.