Abstract: Power management is an important technique to prolong the lifetime of active RFID tag and wireless sensor. A passive radio-triggered based wake-up circuit is proposed to control the activation and shutting down of the active RFID tag and wireless sensor, and thus eliminates energy wasting wake-up periods. The radio-triggered wake-up circuit is optimized to achieve maximum sensitivity by characterizing both the impedance transformation network and the rectifier circuit. The simulation and measurement results show that the circuit can produce a DC output of 220mV with the received power as low as - 27.7dBm. The wake-up circuit is passive and practice indicates that the lifetime of the active RFID tag and wireless sensor is obviously prolonged.