RF Identification (RFID) Reader Front Ends With Active Blocker Rejection

This paper presents a novel active blocker rejecting RF (ABR-RF) front end for RF identification (RFID) applications. The proposed ABR-RF injects the blocker replica within the low-noise amplifier of the RFID receiver chain, through a feed-forward path to actively create an arbitrary narrowband notch filtering for the in-band blockers, while not affecting the gain of the desired signal. The in-band blocker is from the leakage of the RFID self-transmitter because RFID systems use backscattering communication. The notch frequency of the ABR-RF is always locked to the RFID transmitter frequency without any passive element tuning. Fabricated in a 0.18- mum CMOS technology, the prototype improves the ABR-RF's 1-dB compression point by greater than 18 dB, and achieves a 50-dB signal-to-blocker ratio improvement. The receiver path draws 40 mA from a 1.8-V supply voltage. The blocker filtering path adds maximum of 16 mA to reject a maximum in-band blocker of 20 dBm. The die area is 1.8 times 1.2 mm².