A Power-Efficient Current-Mode ASK Demodulator for Passive RFID Transponders

An ultra-low power fully integrated CMOS current-mode amplitude shift keying (ASK) demodulator for radio frequency identification (RFID) transponders is presented. The proposed ASK demodulator performs signal shaping and amplification in the current domain to achieve higher power efficiency. Owing to a DC elimination technique, the employed current amplifier only amplifies the AC content of the envelope signal resulting in a significant reduction of power consumption. A feedforward correction method is also introduced to match the baseline of the amplified envelope signal with the threshold level of the output buffer, preserving the uniformity of data symbols. The proposed ASK demodulator is implemented in a standard 0.18 µm CMOS process consuming about 5.4 µW. A modulation index of 4% and a data rate of 800 Kbps is supported by the proposed demodulator which fully complies with international standards for passive RF communication.