Average power handling capability

hi evveryone
I have a question about this problem.
i sesign radar with the peak power 5.6 KW, pulse width 2 us, frequency 400 Hz. So as I calculated, the average power is 56000*2*e-6*400=4.48 W.
I intend to design using microstrip line with FR4 subtrate. So do you feel that can widstand that kind of power

You didn't mention the operating frequency, but I think a low Er RF substrate would be safer. You should particularly fear partial discharges at the micro strip edges. If you also intend resonant structures (filters) possible sparkovers should be considered.

Thank .
The operating frequency is at 1.5 Ghz (1500 Mhz)

I would use a thick substrate to minimize the chance of discharge. Check the specs of the substrate material thoroughly before doing the design.