The design of the first version is finished and I'm waiting for PCBs.
I expect that not all the circuits will work as intended and most of them will require some tuning. On the other hand I'm pretty sure I'll be able to make them to work because I did a lot of simulations and also some experiments. I tested some of the used (or similar) circuits, mostly using cheap Arinst SSA-TG spectrum analyzer (up to ~6GHz) and it looks like the simulations really help to roughly estimate how the real world hardware will work. Not all the parts were tested so problems may arise, especially at the highest frequencies.
To be continued...
Design and reports are attached (as zip file) in "Files" section.