Quadrature upmixer LO leakage power level increases as input IF power level increase.

Dear all,

I have designed a quadrature upmixer. However, I found a strange things about the LO leakage power level. I still could not find out the reason. I hope anyone could give me some suggestions. My case is as follow:
Input IF = 10MHz
LO = 2000MHz
Output up-converted RF = 2010MHz
As I increased the IF power level, the up-converted RF power should increase. This is very normal. However, I found the LO leakage power level also increased too. Originally, I think the up-converted RF power level will change accordingly based on the input IF power level. The LO leakage power level will not change even input IF power level changed. However, this is not. Why will this happen? I simulated in schematic level. So, it would not be caused by the parasitic capacitor in layout.

Thanks,

Ideally the diodes in a mixer function as switches that are controlled solely by the voltage swings of the LO. As the RF/IF increases in power, this will influence the switching action of the diodes which definitely leads to worse spurious performance and worse RF/IF leakage, and I suppose also to worse LO leakage.

A good rule of thumb is to keep the LO 20-30 dB higher than RF/IF.

Can you post your sch?

Just a typical Gilbert cell mixer structure.