Design for the reader of UHF Radio frequency identification

Ultra high frequency radio frequency identification (UHF RFID) system is becoming more wide spread due to its advantages, such as fast read-write speed, large memory, long recognition distance and the capacity of simultaneously reading/writing multi-tags. In this paper, we introduce the characteristics, structure, principle and read/write method of a UHF RFID reader, and present the solution of its interrogator and flow of DSP software program. Received backscatter modulation waves are directly demodulated to basedband signals using zero IF technology. The reader is designed as a quadrature (I/Q) one, which can avoid null points of received signals and enhance the demodulation sensitivity.