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Hi,

For a typical double balanced Gilbert cell, how to match the RF input to 100 ohm?

The zero frequency input impedance should be infinity. Even when frequency increases, the input impedance doesn't change significantly at sub-6GHz range.

I understand that inductive degeneration can help with input-matching, but sometimes we need very large value to make the real part 50 or 100 ohm, which might not be realizable.

Since the input impedance is very large, can I directly add a parallel 100 ohm resistor at the input? In my simulation, noise figure doesn't seem to sacrifice a lot. So can I do it?