Design of UHF-RFID tags based on the T-match network

Abstract

This paper is focused on the design of global band UHF-RFID tags based on the T-match network. Recently, a systematic method for the design and synthesis of global band UHF-RFID tags using such a matching network has been proposed (G. Zamora et al., IEEE Trans. Microw. Theory Tech., 61, 4090–4098, 2013). The reported design strategy is based on the required equivalent-circuit network for bandwidth maximization in single resonant UHF tags with conjugate matching, obtained in (G. Zamora et al., IET Microwave Antennas and Propagation, 7, 788–794, 2013). Such strategy requires the antenna to be previously designed to exhibit a self-resonance at the intermediate frequency of the UHF-RFID band, f 0 . According to the first abovementioned reference, the value of the antenna resistance at the resonance must be much greater than a certain lower limit that only depends on the elements of the chip equivalent-circuit model. However, the great majority of the commercial UHF-RFID tags, which takes advantage of the T-match network, are based on dipole antennas, which exhibit a resistance value at the half wavelength resonance (typically around 73 Ω) close to the lower limit given by the RFID integrated circuits available on the market today.