Let me first get the concept of rise time, bandwidth, and firth harmonics in digital signal.
If the signal frequency is 2 GHz then the rise time according to 10%-90% approximation is calculated below.
Time period of 2 GHz signal is 0.5 nsec
Rise time = 0.5/10 nsec = 0.05 nsec
The Bandwidth = 0.35/Rise Time = 0.35/ 0.05 nsec = 7 Ghz
Is the Bandwidth calculated above is 5th harmonics ?
If the stack up is defined correctly, and the trace width is impedance control, then can we use FR4 as dielectric in the PCB having signal as describe above ?