An active interference cancellation technique with harmonic rejection for a broadband channelizer

A feedback-based active interference suppression technique employing harmonic rejection mixers (HRMs) for enhancing linearity in a broadband channelizer is proposed. In the approach, an interferer is down-converted to baseband, low-pass filtered and then up-converted, where it is subtracted from the input. Using previously reported HRMs capable of LO frequency synthesis in both the down-conversion and up-conversion paths, wideband interference cancellation is achieved without the use of a wide tuning range PLL. Limitation on the maximum achievable interference rejection due to unwanted interaction between inband and out-of-band harmonics is identified. An approach based on a 2-step up-conversion in the feedback path is proposed to remove this limitation. The effectiveness of the proposed technique is verified through simulation.