I have to translate a VHF (160MHz) receiver schematic into a PCB. After looking here and there, I am a bit confused.
It seems like the main issues with RF are
- to avoid stray inductors and capacitors, by avoiding close tracks (capacity up), wide tracks (capacitor with ground plane underneath), and long tracks (inductance up)
to avoid signal reflections by avoiding sudden changes in "characteristic impedance".
[Please do tell me if I missed others]
I only have a vague idea of what characteristic impedance is (this wonderful video helped a lot though), but it sounds like it's the impedance of the equivalent RLC circuit.
- It should be dependent on the length and the frequency of the signal, how come it isn't?
- Intuitively I should calculate the characteristic impedance of each pad-to-pad trace and make sure it is always 50Ohm. Is that the case?
An online calculator gives (for 18um thick copper, 4.7 of permittivity, 0.5mm thick substrate) me 0.9mm of width to get 50Ohms. Does that mean I should route all traces at this width, keeping them short but without having them too close to eachother, and then I have nothing to worry about?