simulating mixer return losses in ADS

Hello everbody,

I am a novice in mixer design and to begin with i am designing a single diode mixer using ADS. I am slightly confused with the situation on how to simulate the port impedences with LO pumped to diode. I meant the ADS simulation set up..? also how to simulate the return losses..
Please help..its urgent..
Thanx in advance..

hi

from the simulated output s21 and s11 are the insertion and return losses