The PCB has arrived, now the prototype is mostly assembled.
The fist impressions:
- I checked one VCO and seems that it works surprisingly well
- I also checked one 3-3.5GHz amplifier - it's fine
- The wideband 4-7GHz seems to be fail. First of all it's unstable. Also it's quite difficult to make any meaningful measurements, even with a good VNA (I had chance to use it for a few days) - U.FL connectors are quite bad even at their specified 6GHz and currently I can't test the two stages of the amplifier separately because I don't have connector between them. The problems are likely caused by radial stubs which may couple to each other and also diverge from simulation.
I hope to make more measurements soon.
The main challenge will be to fix the 4-7GHz amplifier (at least up to 4-6GHz where I can currently measure it). The worst case will be to replace it with integrated gain blocks but they are noisy, expensive and boring.