A Stepped-Up Tree Encoder for the 10-ps Wave Union TDC

Abstract

A stepped-up tree encoder (SUTE) has been designed to deal with the issue of non-thermometer-to-binary (NTH2B) encoding for a 10-ps wave union FPGA TDC. The encoder is made up of two pipeline stages: pre-encoding and parallel encoding, and is capable of bubble error correction (BEC) as well. With this encoding algorithm applied in a Xilinx Virtex-4 FPGA, we achieved a NTH2B conversion rate of up to 100 MHz for more than 200-bit non-thermometer codes.