自由空间量子密钥分发控制系统的FPGA设计

在量子保密通信蓬勃发展的今天,基于自由空间的量子密钥分发是一个重要的研究方向。它将在未来全球量子通信网络中扮演重要的角色。介绍了自由空间量子密钥分发控制系统中的电子学设计,选用Xilinx公司的VirtexII-Pro系列芯片,使用内部的PowerPC405嵌入式硬核加上功能逻辑模块实现最终量子密钥的提取和外围电路的控制,提高了全系统的集成度和可靠性。该设计成功应用于白天1公里量子密钥分发实验,成码率大于1.5Kbps。     

A fast improved fat tree encoder for wave union TDC in an FPGA

Up to now, the wave union method can achieve the best timing performance in FPGA-based TDC designs. However, it should be guaranteed in such a structure that the non-thermometer code to binary code (NTH2B) encoding process should be finished within just one system clock cycle. So the implementation of the NTH2B encoder is quite challenging considering the high speed requirement. Besides, the high resolution wave union TDC also demands that the encoder convert an ultra-wide input code to a binary code. We present a fast improved fat tree encoder (IFTE) to fulfill such requirements, in which bubble error suppression is also integrated. With this encoder scheme, a wave union TDC with 7.7 ps RMS and 3.8 ps effective bin size was implemented in an FPGA from Xilinx Virtex 5 family. An encoding time of 8.33 ns was achieved for a 276-bit non-thermometer code to a 9-bit binary code conversion. We conducted a series of tests on the oscillating period of the wave union launcher, as well as the overall performance of the TDC; test results indicate that the IFTE works well. In fact, in the implementation of this encoder, no manual routing or special constraints were required; therefore, this IFTE structure could also be further applied in other delay-chain-based FPGA TDCs.