how to measure input impedance of gilbert mixer in cadence

hi
i m have designed gilbert mixer now i m trying to find its input impedance. i have used single to differential network (not balun) for Rf and LO port. now how input impedance is measured i m working in cadence spectre. anyone have some idea please reply me.

LO Input Impedance has less importance compare to RF/IF Input Impedance because LO port is driven hardly to commutate the mixer pairs.RF/IF Input Impedance can be found easily by
s-parameter simulation or LSSP simulation.Differential impedances are found by termination "port" component to associated inputs.Then you should check Sxx on the Smith Chart or look at ZMx.

If you don't have too much experience doing VNA differential measurements (and simulations), would be better to use a balun because you can choose the right impedance ratio of the balun, as in the list below from TDK:

http://product.tdk.com/en/technicals..._baluns_en.pdf

For using a simulator, TDK provides the S-parameter data for those baluns:

http://product.tdk.com/en/technicals...ral/balun.html