A Study And Implementation Of High-precision Digital Time Conversion Technology

With the development and progress of electronic technology, time interval control accuracy is increasing rapidly. And its accuracy have already got deeply to picosecond or sub-picosecond levels. Digital-to-Time Converters technology belongs to time interval production technique. It is not only widely used in the field of high energy physics experiments, astronomical measurement and other basic research, but also an indispensable technology in the field of aerospace, remote sensing, radar, electronic measurement and other fields. At present, the high resolution DTC system is realized by using AISC chips, but it has a lack of flexibility, long development cycles and other shortcomings. The DTC system based on FPGA not only has high flexibility and high stability, it can also shorten the development cycle. However, the resolution of DTC system with FPGA chip is not high enough, it is difficult to achieve the same accuracy as the ASIC. Therefore, the design and implement of high precision DTC system using FPGA chip in this paper has important research significance.This paper firstly studied several kinds of traditional methods, further analyzed and compared the advantages and disadvantages of different methods. To realize high precision digital time converter in the FPGA chip, papers improved the direct counting method and the differential delay method, and put forward a new method of time interval generation. The digital time converter with high resolution, wide dynamic range and high stability is realized on Virtex-6 Xilinx FPGA chip. The system selects the Virtex-6 series FPGA internal integrated programmable absolute delay element as the delay unit of differential delay chain, which can not only achieve high accuracy delay, but also make the DTC system accuracy be not affected by temperature and power supply voltage, which greatly enhances the stability of DTC system. In the process of designing the DTC system, it used the modular design method, including coarse time interval production module, fine time interval production module, data processing module, software module and output control module. The paper designs various modules in detail. In addition, the paper also analyzes the critical delay time, and eliminates the influence of the routing delay on the accuracy of the DTC system by manually adjusting the layout and routing, to ensure the design resolution of the DTC system and meet the design requirements.In order to verify the performance of the DTC system, the paper set up a special test platform. A large number of simulation and experimental tests are carried out on the DTC system. The test results show that the resolution of the DTC system is 1ps, and the differential nonlinearity error is-0.17~0.13 LSB, and the integral nonlinearity error is-0.35~0.62 LSB. The linearity of the system can achieve the design requirements of the system. In addition, the stability of the system is tested. And the resolution of the system is not changed with the temperature. Therefore, the paper realizes the DTC system with 1ps resolution, and has good linearity and stability. It has good practical value.