A low power multiple channel receiver mixing architecture for detecting wake-up signals over multiple communication channels in sniff processing performed in an implantable medical device (IMD). The architecture includes a direct conversion real receiver configured to scan a selected center channel and a Weaver receiver configured in parallel to the direct conversion real receiver to simultaneously scan side channels, together simultaneously detecting whether a wake-up signal is being received over the center and side channels with minimal power consumption. The architecture further utilizes a falsing protection algorithm that reduces power consumption during sniff operations by inhibiting the sniffing of channels likely to provide a false indication of a wake-up signal based the presence of unwanted signals on those channels. The falsing protection algorithm restricts those channels from sniff processing likely to provide a false indication of a wake-up signal, such that sniff processing can aborted, prevented, limited or otherwise altered to conserve power consumption.