Disclosed are methods and systems for mitigating unwanted signal components. A received carrier signal is downconverted using a local reference signal that imposes an frequency perturbation or dither. Later, when an intermediate digitized signal is filtered to remove the DC offset that is an artifact of the sampling process, the dither in the carrier signal serves to distinguish the carrier from the unwanted offset. The preferred offset filter is a low pass filter with a passband that is narrow relative to the frequency range of the dither.