Choosing capacitor for RF coupling
At page 7, on the equivalent circuit of the RA08H1317M, the output is already AC coupled. Same thing on page 1 on the block diagram.

If you need to AC couple outside of the component anyway, then you have to find the power dispated by the capacitor due to ESR:

\$P_{cap}=R_{ESR} \cdot I^2=\frac{R_{ESR}}{R_{50Ω}} \cdot P_{RF}&lt;\frac{0.1Ω}{50Ω} \cdot 10W=20mW\$

This is close to the typical power rating for size 0603. Size 0805 and 1206 should have no problem if you asume an ESR below 100mΩ. You should probably use a NPO dielectric.