A Measurement Technique for Verifying the Match Condition of Assembled RFID Tags

In radio frequency identification (RFID) tag design, many measurement methods are available for individually characterizing either the RFID chip or the antenna; however, to the best of the knowledge of the authors, no direct method has been developed for the assembled RFID tag. In this paper, a measurement method for verifying the match condition of the assembled RFID tag is proposed. The proposed method can not only verify the final impedance match condition of the assembled RFID tags but also be used to identify the resistance and reactance mismatch condition between the RFID chip and the antenna. Furthermore, the measurement data obtained from the verification method can be used to estimate the assembly error introduced by different mounting methods. The use of the corrected circuit model of the RFID chip impedance, which includes the assembly error, helps improve the accuracy of the RFID tag design. Five RFID tag antennas, each with a different complex impedance, are used to verify the proposed method. This paper compares the simulated and measured results to illustrate the application of the proposed verification method to the aforementioned RFID tag antennas. It is shown that the experimental tests for the maximum read range agree well with the measured data generated by using the proposed verification method.