An RF receiver with an integrated adaptive notch filter for multi-standard applications

This paper presents a 2.4GHz current-mode RF direct-conversion receiver implemented in a 90nm CMOS process with a novel adaptive notch filter. The notch filter uses the blocker frequency to up-convert a DC null to the pass-band, attenuating the blocker before entering the receiver. A synthesized inductor on the order of μH realizes the DC null. Blocker attenuation as large as 20dB is observed at a 40MHz offset frequency while the in-band attenuation increases by only 2dB. This proves that this technique is effective in attenuating blockers in broadband multi-standard radios without using any high-Q mechanical filters at their front-ends.