How to handle the commo-mode LO leakage at the output of mixer?

[polestar707]

I'm simulating a double-balanced mixer in 65nm. I found in the output there is strong even-order LO which is common-mode signal. I think this comes from the nonlinearity of transistor. This large common-mode signal would affect the buffer stage. How to deal with it? Any suggestion would be appreciated. Thank you!

 

[BigBoss]

Do you drive the mixer with square wave ? If you do, square wave has lowest even harmonics.If you don't, make it square wave as much as possible.
If you drive it with a sinusodial signal, the nonlinearity of LO part of your mixer can create IMD.In additional to this, check the OP of the LO and RF/IF part of the mixer.

 

[polestar707]

Do you drive the mixer with square wave ? If you do, square wave has lowest even harmonics.If you don't, make it square wave as much as possible.
If you drive it with a sinusodial signal, the nonlinearity of LO part of your mixer can create IMD.In additional to this, check the OP of the LO and RF/IF part of the mixer.

Thank you.
I drive the mixer with sinusoid LO. It's strange that I didn't notice the strong common-mode even-order harmonics of LO at IF port in order technology, like 0.35um.
Also, can you please tell me what OP is?

 

[BigBoss]

Thank you.
I drive the mixer with sinusoid LO. It's strange that I didn't notice the strong common-mode even-order harmonics of LO at IF port in order technology, like 0.35um.
Also, can you please tell me what OP is?

OP stands for "Operating Point"