gilbert cell mixer

Excuse me, for bias of Gilbert-cell mixer, what is optimum Vbe of LO transistors? How could I bias them to realize switches?

Thanks in advance!

the LO pairs in ideal case they should work as swtiches so u need to bias the BJT near the turn on , so the LO can make the transistor work properly

Khouly

does it mean that Vbe is almost 0.7V?

Yes, it should be work as a switch.
So I bias it to make the Vce≈Vbe.
And you should simulation the IP3 of it to select the best point.

no,Vce cannot equal to Vbe ,Vbe shoud be 0.7v