ENGINEERING ANSWER
Mixer and oscillator boards bring multiple frequencies and sensitive coupling paths into a small area. Isolation, grounding and power integrity can be as important as nominal transmission-line impedance.
What to decide before release
Map RF, LO and IF routes and their harmonics. Include bias networks, connectors and package parasitics in the review. Separate physical regions where coupling threatens performance and verify with the assembled circuit.
Checks to put in your design brief
- Check LO leakage paths
- Review harmonic terminations
- Measure phase noise or conversion behavior as required
Important distinction
A low-loss substrate does not guarantee oscillator stability or mixer isolation.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.