I note that active mixers - eg LTC5510 quote increase in NFig with a blocking signal - see fig below. LTC5510 has input P1dBm >10dBm, yet a 0dBm blocker increases the NF from 12dB to 16dB - best case high LO drive. Does this also occur in passive mixers?
It surprises that the NFig starts increasing even though it is 20dB below input 1dB compression point. Is this unique to active mixers, and not to passive? Obviously any mixer close to compression would see NFig change, but I would be surprised if there was any change 10dB below P1dBm
All mixers, passive or active, suffers noise figure degradation in the presence of larger blocking signals. Please take a look at the following Application Note for a quick introduction. You can find more detailed explanations in text books and published articles.
NF degradation with an out-of-band blocker signal present is not unique to mixers. For example, ADI's Programmable Lowpass Filter + VGA products (ADRF6510/16/18/20 & HMC900/1023) all have NF/Noise degradation with a blocker present.