A high dynamic range ASK demodulator for passive UHF RFID with automatic over-voltage protection and detection threshold adjustment

This paper presents a passive UHF RFID ASK demodulator that operates over a +24 dBm to -14 dBm RF input power range. The demodulator automatically adjusts between high sensitivity mode for weak RF signal power and over-voltage protection mode for high RF power. The input over-voltage protection circuit is designed to protect the IC from high input power while not impacting the sensitivity at weak input power. The demodulator is comprised of a RF rectifier, a variable gain attenuator with automatic threshold adjustment and a nano-power data slicer. The demodulator handles demodulating signals with a minimum to maximum envelope ratio of 0.8 over the entire input power range, and the data slicer consumes only 160 nA from a 0.9 to 1.25 V rectified supply. The RFID chip is fabricated in a 0.13 mum analog-CMOS technology and the entire chip occupies an area of 0.55 mm².