An Application Design Of Active UHF Tag Based On ARM

RFID is a kind of technology which uses radio to identify the target, and it is the foundation of the Internet of things. In recent years, RFID has a rapid development around the world and many industry standards have been built. Until now passive tags have occupied most of the market shares, while active UHF tags are still in their infancy. Active tags have functions of sensors which passive tags don’t have. Common UHF reader has commands to control the extended functions of active tags.So a design of active UHF electronic tag application system has been proposed in the paper including UHF reader, antenna and active tag. Firstly in the design reader’s analog front end is made by separate components to save cost. Software is realized in ARM9 platform to handle the reader’s base-band signal, and the PWM of ARM9 is used to control RF switch and thus the signal can be encoded, while the return signal of electronic tag is captured by the processor’s external interrupt and then decoded in software state machine. In order to adapt to multitasking application, the reader’s program realized will be transplanted into UCOSII platform, and after that PC software will be developed to control the reader through serial port for reading and writing.Secondly, the performance of antenna directly affects the reader, while the desktop reader mostly use ceramic antenna with high cost. So a new kind of UHF PCB antenna with small shape has been proposed in the paper. The antenna has a dipole antenna structure, and tortuous arms are used on it to reduce its size. Barron is used to match its’ input impedance to 50?. HFSS13 is used to build the antenna module and to optimize the antenna’s shape. After simulation the antenna has been made with PCB.Thirdly, passive electronic tags have no ability to detect the environment around, while the active electronic tags can detect environment by sensors inside. So a kind of active electronic tag using IC SL900 A will be proposed in this paper together with its’ PCB antenna simulated through HFSS13. Extended function commands have been realized for the tag using the software codec solutions on ARM9, and the commands are used for wireless controlling of temperature log.Finally, the designs above need to be tested. The tests include the reader’s RF transmitting circuit, receiving circuit, the reader software, the UHF PCB antenna and the active electronic tag. The test results meet the design requirements.