Adjacent-channel selectivity is defined as the relative attenuation of the adjacent-channel power.
Treating the adjacent-channel signal as noise, the required first adjacent-channel selectivity can be derived.
and the adjacent-channel selectivity requirement at 5 MHz is
Common out-of-channel tests are spurious and intermodulation rejection, and adjacent-channel selectivity.
Adjacent-channel selectivity measures a communications receiver's ability to process a desired signal while rejecting a strong signal in an adjacent channel.
PHASE NOISE REQUIREMENTS FOR ADJACENT-CHANNEL SELECTIVITY