relative permittivity and frequency

Hello

My question is about the substrate FR4 , for 868 MHz and 1.5 GHz , is FR4 has the same relative permitivitty,
I want just to be sure when I calculate the dmemsion of a 50 ohms microstrip line at the thow frequencies

many thanks

Hello

These two files attached to this post can be useful,

good luck

FR4 relative permittivity varies with frequency, but between 868 MHz and 1.5 GHz this don't vary too much.
Anyway would be less variation than other parasitics variation of components on your circuit.

10x for ur answers