the questions about the rf MOSFET and the Coupler design

1.Can the 100M rf MOSFET Power Transistor be used for the 40.68M?
2.the output power is 30W,how to design the output power coupler,which is use to check the output impedance is 50Ohm or not.if it is 50Ohm,then the output is on,if not,off. the coupler is to sense the it and send the signal to control circuits to work

thanks a lot