Hi,
So my passive mixer drives a on chip IF VGA and has a 5p cap at the output for filtering.  Thus, my input impedance  is complex from 1G to 4G .  There is going to be a on chip attenuator before the passive mixer.  My questions are

1.  can the attenuator has a ZL that is not only differernt from Zin but also complex?  If it can, does that make the attenuator design a lot more comlex?
2.  Will my best approach still be trying to make the mixer Zin look like a real resistor?  Is that possible with an capacitive load at the IF port and do this for pretty broad band?

I guess to sum up my questions, what's the best approach in dealing with the attenuator/passive mixer interface?  

Thanks.