The filtering-by-aliasing (FA) receivers have demonstrated sharp analog finite impulse response (FIR) filtering by combining periodically time-varying (PTV) circuit elements with uniform sampling. Seen at the sampled output, the impulse response of an FA receiver can be controlled by the PTV resistor’s resistance that varies over time, which realizes very sharp filtering with 50–70-dB stopband rejection. However, the finite stopband rejection and the inherent sampling in FA result in unwanted in-band residual blocker aliases, which cannot be suppressed further by downstream linear time-invariant (LTI) stages, unlike in a conventional receiver, and the overall blocker rejection may be insufficient in some applications. This paper describes a digital residual alias cancellation technique tailored for the FA receivers. By using a second channel to capture the blocker and equalizing the blocker in the FA and the second channels with digital baseband filters, measurement results, with the cancellation algorithm implemented in MATLAB, show that the residual blocker aliases can be suppressed by another ~15 dB, in addition to the FA analog filtering.
