In this paper, we analyze impedance matching concepts in passive radio frequency identification (RFID) transponders, which are powered by the incoming RF energy and consist of an antenna and an integrated circuit chip, both with complex impedances. The impedance match between the chip and the antenna can be characterized by the power transmission coefficient. We analyze the behavior of the power transmission coefficient and the effect it has on the tag performance. As an example, we consider a specific RFID transponder design, an Intellitag ID card with embedded folded meander antenna operating in 915 MHz band. We present both measurement data and simulation results, which are in good agreement.
K. V. S. Rao, Pavel V. Nikitin, Sander F. Lam