Simple, Fast, and Effective Identification of an Equivalent Circuit of a Waveguide Junction With $N$ Ports

A simple, drawable, and efficient equivalent circuit is proposed to represent a discontinuity/junction with N ports. The circuit is based on N transmission lines connected to the sides of a polygon with N side. N( N-1)/2 susceptances are placed on the sides and on the inner diagonals of the polygon. The circuit modularity permits to identify the N( N+1)/2 electrical parameters in a simple way. In fact, the lengths of the N transmission lines are obtained solving a system of N polynomial equations and the N( N-1)/2 susceptances are obtained solving a simple linear equation system. The proposed circuit is used to evaluate the equivalent circuit of some directional couplers in the horizontal plane and of a 3-D six-port coupler acting on the horizontal and vertical planes.