A High Sensitivity and High Dynamic Range ASK Demodulator for Passive UHF RFID with Over-Voltage Protection

A high sensitivity and high dynamic range ultra-high frequency amplitude shift keying (ASK) detector for low-power radio frequency identification (RFID) tag chip is proposed in this paper. The demodulator mainly consists of envelope detector, voltage limiter, reference voltage generator, and a hysteresis comparator. The envelope detector is based on the basic rectification circuit with threshold compensation technology to improve the sensitivity of the RF input for a differential antenna. The voltage limiter reduces the amplitude of the envelope signal when operating in the near field, and controls the magnitude of the discharge current of the voltage-limiting circuit for low power consumption. The proposed demodulator is designed in UMC 110nm CMOS process. The simulation shows that the minimum RF input amplitude of the demodulator is 50 mV when the carrier frequency is 920 MHz and the modulation index is 80% - 100%. The dynamic range of the RF input of the demodulation circuit is 0.05-1.2V, which can reach the power supply voltage. The average power consumption of the demodulator during transient operation is approximately 1.9 $\mu$W with 1. 2V power supply.