Abstract
The principal aims of this paper are twofold: (1) to discuss and interrelate the various equivalent circuit representations of a general 2N-terminal waveguide structure that are obtained on different choices of terminal planes; and (2) to describe a precision method for measuring the circuit parameters of such structures. Basic to both of these considerations is a tangent relation introduced by Weissfloch to describe and measure the input-output behavior of a four-terminal waveguide structure.