I've designed in the HMC773LC3B as the mixer in this up-converter. LO is +10dBm at 12GHz, IF is -10dBm at 5GHz, but I'm getting <-40dBm of RF at 17GHz. I've looked at the mixer ports on a curve tracer, LO is AC coupled and IF port has the back/back diodes as would be expected from the data sheet, BUT the RF port is showing a resistive 10ohm, not the AC coupling that the data sheet shows. I've checked mixers insitu and unused parts, all show the 'resistive' Rf port. Is this correct, and the data sheet wrong ??