Dual-band platform tolerant antennas for radio-frequency identification

A technique for tuning a single-element planar inverted F-antenna (PIFA) to provide a dual-band operation is introduced. The tuning is possible due to the particular impedance level typical to radio-frequency identification microchips. As the desired impedance level resides near the outer rim of the Smith chart, a single impedance locus may be arranged to pass the input impedance twice resulting in dual-band operation. The tuning of the impedance locus is based on the feed inductance and capacitive coupling at the open end of the patch. In this paper, also a discussion about the principles of platform tolerance of small antennas is provided. A design, circuit model, simulations, and measurement results of dual-band platform tolerant PIFAs are reported and discussed.