Maximum Efficiency of a Two Arm Waveguide Junction (Correspondence)

It is well-known that the efficiency of a two-arm waveguide junction (2-port) depends upon the reflection coefficient Γ_L of the load with which one of the arms is terminated. The efficiency is known to vary between the limits 0 and η_m (maximum efficiency) as Γ_L assumes all possible values within the unit circle. However, there seems to be no published analysis from which one can determine the particular Γ_L giving maximum efficiency if the characteristics of the waveguide junction are known.