The Design And Application Of A Handheld UHF RFID Reader

Radio Frequency Identification(RFID) is an identify technology which uses the space coupling feature of RF signal to transmit information with no contact, and realizes target Identification through the data exchange. Because of its advantages in anti-attrition, speed and security compared with the traditional identify technology, RFID has been widely used, especially the research and development of UHF RFID technology is very quickly in recent years, and China has also launched the UHF RFID policy and technical standard in 2007. UHF RFID reader is the key part of the UHF RFID system, whose performance directly affects the system's identification speed and distance. This paper carries out research and design of a handheld UHF RFID reader used in mobile application environment.After the research and analysis of UHF RFID system's background and development status, this paper analysis the basic theory of RFID from the electromagnetic theory, channel estimation and other aspects, then analysis the key parameters of ISO / IEC 18000-6C (or EPC C1G2) protocol's physical layer and logical layer, including signal modulation parameters, data encoding and decoding methods, logic states of tag and anti-collision algorithm.The key circuits of UHF RFID reader's RF front end of are analyzed then, including the architecture of the transmitter and receiver, signal isolation circuit and power amplifier circuit, from the signal characteristics and hardware cost, considering that the direct quadrature direct up-conversion and down-conversion transceiver architecture is more suitable for UHF RFID reader. With the size of handset, power requirements, handheld UHF RFID hardware circuit design is analyzed, this paper chooses to use AMS AS3992 RFID front-end as the core circuit. Then this paper analyzes the power supply architecture, VCO/PLL configure and work modes of AS3992, designs AS3992 hardware circuit , including timing circuit, VCO/PLL adapt circuit, RF relevant registers, RF frontend, especially performs ADS simulation and optimization for the RF frontend. At last of this chapter, the key parameter of the power supply of the UHF RFID reader module is analyzed, and discussed the RF PCB design considerations.After UHF RFID module hardware design work, this paper designs the functional part of the handheld UHF RFID reader, determines using the STM32 32bit ARM processor as the master control chip; ZG2100 Wi-Fi module is used for wireless communication, analyzes the work modes and communication interface of ZG2100,then designs the driver circuit; the key pad driven by ZLG7290 is used in human-machine interaction circuit and also the QVGA-resolution TFT LCD screen; then designs the Li-ion battery power management circuit, and analyzes the PCB layout of these components.The software design part begins with the analysis of the AS3992 communication protocol, then focus of the EPC C1G2 protocol implementations on AS3992, at last designs the driver code of the peripheral functional components and application based on the RT-thread RTOS.In the test and verification part, the RF parameters of the designed handheld UHF RFID reader were measured and analyzed in accordance with specifications of China's UHF RFID, the reader's reading performance and functions are also tested. Finally, this paper ended with the summary and pointes out the deficiencies and the direction for further research.