Design of Real Time Location System for UHF RFID

Radio frequency identification (RFID) technology for Real Time Location System (RTLS) is one of the current research focus. This paper applies RFID technology, TDOA location algorithm and CDMA mechanism and designs the location command format and response mode based on the 18000-6C protocol. Based on the above mentioned, we complete a prototype design, including RFID tags and reader. The reader sends customized location command. Then tags will respond to command, generate configurable gold code and send it back to the reader. Because gold codes of different tags are orthogonal or quasi-orthogonal, the reader can receive echoes of multiple tags at the same time, do correlation respectively and locate tags by time difference of arrival (TDOA) simultaneously. Measured results show that the time difference accuracy is within 150ps by using correlation method. Therefore, the prototype has good function and performance, which meets the requirements of design.