Biography
Enrollment Date: 2012
Graduation Date：2015
Degree：M.S.
Defense Date：2015.06.03
Advisors：Chun Zhang
Department：Institute of Microelectronics，Tsinghua University
Title of Dissertation/Thesis：Design of UHF RFID-Based Location System
Abstract:
With the large-scale emergence of demand for location, a variety of related location technologies appeared on the scene. The UHF RFID-Based location system, due to its high communication speed, high reliability, long distance communication and so on, has become an attractive field at present. This paper presents the design scheme and test method for UHF RFID location system and launches some research on related technologies.
This paper employs the wireless transmission characteristics of 18000-6C protocol, applies the pseudo-random sequence for measuring time difference and TDOA algorithm to RFID system and completes the functional partitioning and modular design.
This paper introduces the customized location command format and response format in detail. So the RFID Reader can locate the RFID tag in an innovative way. The reader sends configuration commands to configure the tag. After successful configuration, the reader sends location command, and the tag will generate pseudo-random sequence according to the command parameters and send it back to the reader. After two receivers of the reader receiving the echoes of tag, the reader does correlation calculation to obtain the arrival time of correlation peak as the arrival time difference. Then, the location of tag can be located by TDOA algorithm.
This paper has completed the design of location tag, which consists of three parts: baseband processor, RF front-end and antenna. The most complex part, baseband processor, consists of clock synchronization module, pseudo-random sequence generator and configuration module, etc. The interaction process between location command and response is verified in FPGA.
This paper has completed the design of location reader which is based on NI Software Defined Radio platform. Onboard FPGA of the location reader can be used to receive and transmit baseband I/Q signal, and combine RF down-conversion and up-conversion module to achieve real-time high throughput. The baseband IQ signal is generated by FPGA and transmitted by antenna after up-conversion. The echo of tag can be received by antenna and sent to FPGA after down-conversion. The data produced by FPGA can be transmitted to the host through DMA channels. In order to measuring the time difference accurately, NI high-speed digitizer is used to achieve the function of triggering acquisition.
Finally, the paper realizes a prototype of location system for time difference measurement and communication, which is integrated by location reader and location tag, and develops the corresponding test program for system verification. Wireless test results show that the prototype can achieve the expected function and performance. Good function includes microsecond level interaction communication, configurable PN sequence, different decoding rate function, etc. The measurement precision is within 150ps by using correlation method, which means the prototype has good performance.