A high conversion coefficient RF front end of ultra-low power 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 realizes high power convert coefficient and high voltage gain. The boosting clock for CP and the output high voltage in rectifier are multiplexed by custom MTP IP, which minimize the total power consumed by the whole chip. The chip is fabricated in 0.18um standard CMOS process, whose size is 0.7 × 0.75mm². The result shows that the sensitivity of the 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. -15dBm is rather lower than the sensitivity of tag from market (-10dBm). The conversion coefficient of the front end is about 80%.