Effect of RF/LO frequency on gilbert mixer conversion gain

What is the effect of RF/LO frequency on conversion gain of Gilbert cell mixer. If the RF and LO frequency is increased keeping IF the same, the gain is reduced. what's the reason for this. How it can be compensated.

The gain of any active device is frequency dependant, so Gilbert mixers are in the same category.
There is multiple factors that are limiting the conversion gain vs frequency: Ft of the active device, bias point, SRF of passive components, circuit parasitics, etc.