ISO/IEC15693 Protocol HF-tag Interrogator IF Signal Processing Module Design

Radio Frequency Identification (RFID) is an automatic contactless identification technology utilizing the space-coupling induction principle of alternative magnetic and/or electronic field. In recent years, the adoption and application of RFID system is spreading quickly into many areas of our ordinary life.A typical RFID System consists of tags, an interrogator (reader), an antenna and a controller. The paper focuses on the study of IF Signal Processing which is a pivotal issue in ISO/IEC15693 Protocol HF-tag Interrogator design. In the paper, we develop an IF signal processing module based on digital signal processing(DSP) and acquire more promising base-band signal demodulation and more accurate multi-tag anti-collision operation.The module we designed comprises three parts: A/D converter, Digital Filter, signal synthesis and decision. The A/D converter completes IF original signal sampling and digitization with a dedicated small footprint and low power consumption A/D converter chip. The digital Filter fulfills the selection of our interesting IF sub-carrier signal. We adopt a two parallel filtering scheme considering the IF features of the ISO/IEC 15693 protocol HF tag. The signal synthesis and decision part utilizes the amplitude information of the former filter output and pre-defined thresholds to make the decision of signal validity and the occurrence collision and output desired base-band signal with collision indication. The later two parts are realized on large scale FPGA. In this paper, we discuss a distributed algorithm for digital Filter (FIR) hardware realization and its optimization and a comparator-based scenario of the signal synthesis and decision.In the paper's end, we presented the testing result of the module, conclude the design and discuss the prospect and future research work in this area.