I am working with RF front end PCB with the HMC773LC3B used for the upconverter on the Tx chain and downconverter on the Rx chain. The Tx chanin uses the HMC6981 for the power amplifier and is outputing +32dBm at 16GHz. I am observing that the PA is radiating 16GHz from it's package and the HMC773LC3B is absorbing the the 16GHz which is getting downmixed to an IF.
My first prototype used eval boards with the mixers and PA separated by a farther distance than on my PCB design. I can replicate the coupling that I am seeing by moving the HMC773 mixer and eval boards closer together.
Does anyone have recomendations on design guidlines with these components or possible replacements for either the PA or the mixer? Does the new HMC773A have better performance? It seems that I could solve this issue with either a PA that radiates less or a mixer that will absorb less.
I'm not sure how your PCB is laid out so I cannot comment on it. I'm attaching the eval board drawing for the HMC773. I suggest using a similar design for the mixer side. e.g CPWG traces, Rogers substrate, via placement etc. I'd also try to simulate the traces on a 3D EM simulator such as ADS Momentum or Microwave office.
Also a +32dBm signal at your RF port for the mixer is much higher than the absolute maximum power level allowed and this might possibly damage your mixer.
In terms of the HMC773A, it will have similar performance as the HMC773. It is intended as the translation part for the HMC773. It might not have the same performance but will be comparable.