A Procedure for Validating Impedance Parameters of HF/UHF RFID Transponder Antennas

The performance of automatic identification in every RFID system is strongly dependent on proper operation of the transponders that are used to mark different kind of objects. The impedance matching between chip and connected antenna is the most significant component determining the design quality of transponder internal circuitry, and hence influencing overall system parameters such as shape and dimensions of interrogation zone, level of identification efficiency, etc. Taking into consideration the various types of RFID systems, the problem has to be considered differently with respect to the operating frequency. Moreover it has to be treated in a different way than it is known from the classical theory of typical radio communication systems. The authors have proposed and developed their own method for validating impedance parameters of RFID transponder antennas operating in the regular HF and UHF bands. It is based on a generalized model of the RFID transponders dedicated to different standards. The developed test procedure consists of four steps involving antenna designing, manufacturing, measuring and validating processes. The practical usefulness of the proposed method is confirmed by experiments conducted with using representative examples designed in research and development projects realized with partners from the industry.