Henrik Forstén writes:
I have been using the OSH Park’s 4 layer process a lot on my own projects. It has FR408 substrate that has better controlled permittivity and lower losses than ordinary FR-4 that other low cost PCB manufacturers use. In my opinion currently it is the best low cost process for making RF PCBs. My previous boards have worked pretty well, but I decided to make a test board that I can use to characterize the process better.
In the above picture is the test board that I made. It has two 50 ohm microstrip lines of different length, one open microstrip line, one microstrip line terminated with 50 ohm resistor and line with 0402 footprint that I populated with a 1 nF capacitor. I’m using this same type of capacitor as a general DC blocking capacitor in my VNA so I’m interested in finding out how it performs at high frequencies.
See the full post on Henrik’s blog.