I've been having difficult matching the LO port of the HMC412B mixer. I need to use it on a variety of different substrates (some low-loss, others low-quality) and I have well-characterized 50 ohm traces for them. Despite this, I'm only getting return loss on the LO port of between -4 and -7 dB, instead of near -11 dB like the datasheet charts show.
I see the eval board is using Rogers 4350 and I got the dimensions of the traces from the gerbers, but do you have the substrate height for it?
Also, is there any other best practices to matching this mixer? I'm following the CPWG design with via-shielding and vias on ground pad.