Q. For a Wilkinson power divider of insertion loss L and the coupler is matched to the external circuitry, and then the gain of the coupler in terms of insertion loss is:

 to evaluate the noise figure of the coupler, third port is terminated with known impedance. then the coupler becomes a two port device. since the coupler is matched, Гs=0 and Гout=s22=0. so the available gain is │s21│2. this is equal to 1/2l from the available data.