UHF RFID impedance matching: When is a T-match not a T-match?

Abstract

The T-match is a frequently cited impedance matching technique for UHF RFID tags. However, there appear to be many misconceptions about what the term “T-match” actually implies and when the relevant assumptions no longer apply. This work focuses on creating a clear definition of the T-match design space in order to differentiate it from other impedance matching techniques. A comparison between analytic solutions and numerical simulations shows that the analytic solution is valid only in those cases where very close spacing (s ≤ 0.009λ) between the dipole and T-match arms is maintained, and the length of the T-match is relatively short (l2≤ 0.06λ).