Stepped Impedance Coupled-Patches Tag Antenna for Platform-Tolerant UHF RFID Applications

We introduce a low-profile platform-tolerant UHF radiofrequency identification (RFID) tag antenna composed of a pair of three-step impedance sections of shorted patches coupled by a slot, which is differentially fed by an RFID chip. Its input impedance is analytically investigated using transmission line (TL) modeling. A further set of parametric studies using electromagnetic simulation shows good flexibility for achieving the required complex input impedance for typical UHF RFID chips. The selected antenna topology has been manufactured and measured, and good agreement with the analytical values has been found.