An adaptive Q factor tuning and input impedance matching method for ultra-low power front end of UHF RFID tag

This paper presents a high conversion coefficient RF front end of an ultra-low power RFID tag, and proposes a new method of more efficient adaptive Q factor tuning and input impedance matching. The Q factor adaptive tuning method makes the front end easier to wake up with limited power, and the adaptive matching method makes the power transmission from antenna to chip more efficient. The conversion block adopts a proposed top structure with a high efficient CMOS differential cross-couple rectifier followed by a high voltage gain charge-pump (CP), which realized high power convert coefficient and high voltage gain. The chip is fabricated in 0.18 um standard CMOS process, whose size is 0.7 × 0.75 mm². The result shows the sensitivity of new top block is about -15 dBm and 5 dBm when with and without Q factor tuning and input impedance matching technology respectively for parallel parasitical capacitance at input interface, which is rather lower than the sensitivity of tag from market(-10 dBm).