Operating Range Evaluation of RFID Systems

Abstract

Operating range is one of the most significant criteria in evaluating the performance of RFID systems, especially UHF RFID systems. That is because a longer operating range can create more potential application opportunities and ensure a more reliable performance. The operating range is determined by the whole RFID system design rather than just a part of it. Hence, it is worth doing some analysis to find out the methods for evaluating the operating range and which factors, in an overall system design, may play a key role in improving the operating range. In order to achieve this target, this chapter provides in Section 2 an RFID technology background by explaining some relevant terminologies in the antenna performance. The considerations of designing tag antennas in reality are described in Section 3. Then Section 4 and Section 5 analyse two limitations 1) threshold power in exciting a transponder, and 2) sensitivity of a reader, in achieving a successful communication between the transponder and the reader. Section 6 summarises the existing work in the literature on analysing the operating range of UHF RFID systems. The existing work is based on either theoretical analysis according to the Friis equation or totally experimental analysis in real RFID systems. The experimental analysis is a direct solution but may be expensive in cost and time. The limitations of using the Friis equation are given in Section 7. In order to overcome these limitations, Section 8 provides a novel method for evaluating the operating range of RFID systems via a scattering matrix. Lastly the key factors in designing a long operating range RFID systems are identified in Section 9.