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 +24dBm to -14dBm 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 160nA from a 0.9 to 1.25V rectified supply. The RFID chip is fabricated in a 0.13 mu m analog-CMOS technology and the entire chip occupies an area of 0.55 mm(2).