Abstract: This paper presents an RF CMOS rectifier for a passive UHF RFID tag chip.The rectifier includes an RF-DC converter,a bias,a DC-DC converter,and an oscillator.The operating frequency range of the rectifier is 860～960MHz.The design of the rectifier is based on 0.18μm,1p6m standard digital CMOS process.A switched capacitor circuit technique is used to provide active bias to solve the threshold voltage problem in CMOS transistors.The size of the rectifier is 180μm×140μm.Under -16dBm,900MHz input RF power,the rectifier creates 1.2V Vpp output,and the startup time is 980μs.

Key words: rectifier, RFID, passive transponder, low power.