Biography
Enrollment Date: 2010
Graduation Date：2013
Degree：M.S.
Defense Date：2013.05.28
Advisors：Chun Zhang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design and Implementation of
a Time Interval Measurement Circuit
in Positioning System
Abstract:
With the rapid development of modern smart transportation system and smart architectures, positioning and distance measurements have been gaining widespread applications in people's everyday life, hence the increased importance of positioning systems. Since the GPS signal cannot penetrate buildings, the positioning scene of indoors and underground cannot use the same positioning techniques as outdoor positioning systems. The RFID technology becomes a hot research topic for its high reliability and low cost. If we integrate positioning module into the RFID reader chip, then positioning information can be obtained through the transmission/reception of signals and time synchronization. Time difference of arrival algorithm, or TDOA, which has higher measurement accuracy and better performance, has been gaining favor among researchers. In TDOA, the accuracy of time interval measurement plays an important role, has great practical significance.Targeting the aforementioned applications, this paper discusses and compares the details in terms of the techniques, algorithms involved and time interval measurement methods. The positioning technology covers the infrared, ultrasonic, ultra wideband (UWB), wireless local area network (WLAN), radio frequency identification (RFID) etc. The positioning algorithm includes received signal strength indicator method (RSSI), angle of arrival method (AOA), time of arrival method (TOA) and time difference of arrival method (TDOA). For underground positioning system, to meet the need of meter distance accuracy, this paper designs common a delay line interpolation implementation of TDC chip. This chip adopts parallel-to-serial shifters to send out 128 levels of voltage output of the delay line, and then the outputs are processed by ecternal logic. The chip uses a symmetric structure and guarantees the accuracy and balance of the clock tree. Finally, the circuit has been tested using 100MHz reference clock. Test results show that the time interval measurement accuracy is 1ns, and the distance accuracy is 0.3m which meets the needs of underground positioning. For indoor positioning system, this paper provides a Venier Ring TDC based on delay line interpolation algorithm. This TDC comprises two delay ring chains, control module, two sets of counters, encoding module and output module. This architecture utilizes coarse counting to expand the range of measurement, shrinks the positioning accuracy to the delay difference of the two types of delay modules through the use of differential ring chains. Analysis, design and simulation of the circuit have been completed.The chip has been fabricated using 0.18µm CMOS process technology.For indoor and underground positioning system, this paper designed two kinds of time interval measurement circuits as followed, both of which are fabricated under 0.18µm CMOS process.