Interference mitigation in radio-frequency (RF) receivers has been studied extensively in various contexts. And although most of the in-band interference mitigation techniques rely on suppressing the interference in the digital domain, strong in-band interference can saturate a receiver's front-end and, thus, prevent it from receiving comparatively weak signals of interest. This is especially so in case of the self-interference (SI) encountered in enclosed full-duplex (FD) radios, but also in case of co- located jammers or radars and signals intelligence receivers. This work presents a digitally assisted method and its implementation for the mitigation of narrowband periodic interference before quantization in order to improve the sensitivity of receivers co- located with strong interference sources. Experimental results are provided and the potential for mitigating more complex waveforms, e.g., pseudorandom jamming, is discussed.