Hello everybody,
please,what is the difference between a capacitor 1n, NP0 and 1n, X7R in terms of e.m.c. quality?
The circuit is LC filter to suppress wide band e.m. emissions.
I know that NP0 is more temperature stable but is there more behind it?
https://en.wikipedia.org/wiki/Ceramic_capacitor

 

There should be little difference between the two for EMI suppression purposes.
NPO's are usually used in frequency determining circuits where a change in capacitance is undesirable.
The important parameters for EMI suppression are its ESR and resonant frequency.