Matching network capacitor types

[jtf]

We managed to tune PCB antenna as per your instructions. I was wondering if we can use general purpose caps as shunt capacitors or should we use some kind of high frequency capacitors?

[haakonsh]

You need to use high frequency, NP0 rated caps, in the same size as was used during tuning. 

The self-resonant frequency should be equal to or higher than 5GHz.