An active interference canceler with reduced harmonic response and synthesizer tuning range

A feedback-based active interference cancellation technique for reducing interference in a broadband LNA is described. The interference is down-converted to baseband, low-pass filtered, then up-converted and subtracted from the input. Harmonic response in the active canceler is eliminated by using harmonic rejection mixers (HRMs). Furthermore, by configuring the HRMs to provide frequency translation while using the LO fundamental or its harmonics, the span required of the frequency synthesizer for driving the HRMs is reduced. Implemented in a 65 nm process, the proposed technique shows 8–13 dB improvement in blocker 1-dB compression.