Biography
Enrollment Date: 2011
Graduation Date：2014
Degree：M.S.
Defense Date：2014.05.27
Advisors：Chun Zhang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design and Implementation of a FPGA-based Time to Digital Converter System in Positioning Technology
Abstract:
Satellite navigation positioning technology and indoor wireless location technology have always been the research hotspots in positioning technology. It’s hard for the satellite navigation positioning technology to meet the demands of complex and diverse situations in the indoor positioning, so research about the indoor positioning is becoming more and more popular. This paper first analyzes and compares some common positioning techniques and the time difference of arrival method (TDOA) is used aimed at the indoor positioning system.The full name of TDC is Time to Digital Converter. It can convert the time difference of two signals into digital signals and obtain the high precision value of the time difference of the tow signals, realizing the positioning of the two signal sources. In this paper, the research status of TDC used in the indoor positioning is introduced, and a device called TDC time interval measuring instrument that can measure the time difference of arrival signals is designed in the project background of indoor positioning technology.The TDC system designed by this paper is divided into rough counters module, fine counters module, logic control module and data display module, which is verified by the FPGA in Xilinx Spartan-6 series. The Gray Code Counter and Binary Counters are used to design the rough counting module. The Gray Code Counter uses cascading five-bit Gray code counters to form high Gray code counters to design the 17-bits Gray code counter and expand the measuring span to millisecond level. The special carry units in FPGA are used in this paper to construct the fine time measurement module, and the delay time of each delay unit is measured by the statistical method. Aimed at the order-change problem, the order-change module is designed to adjust the timing sequence of each delay unit collected by the register to finally achieve test precision of the hundred picoseconds order. The display module based on WinCE system is designed in this paper to display the measuring results. The communication between the FPGA developing board and display board is achieved and the measuring results in FPGA is displayed on the LCD display screen. The simulated and measured results of the TDC time interval measuring instrument are provided in this paper. Each module of the TDC system is correctly simulated. After statistical process, the average delay time of each fine counting delay unit is 31ps. The special carry unit of FPGA delay carry line is acted as the delay unit. On the condition of testing signal inside the FPGA, the measurement error in the range of 100ps-1000ps is no more than 100ps. On the condition of the external input signal, in the range of 10ps to 1000ps, the measurement deviation of time interval is less than 500ps and the corresponding range resolution is at the level of 1 decimeter, which meets the demand of indoor positioning system.