Measurement of symmetrical waveguide discontinuities using the eigenvalue approach

The behaviour of symmetrical 2-port networks is usually described in terms of their scattering, impedance or admittance matrices. Since the entries of these matrices are linear combinations of their eigenvalues the latter quantities provide an alternative description of network parameters provided they can be readily measured. In the case of symmetrical 2-port networks the eigenvectors necessary to establish the eigenvalues at any port correspond to either in-phase or out-of-phase signals at each port. One simple eigenvalue test set is a magic tee with the network under test connected between the symmetrical H-plane ports and a single input at either the H-or E-plane ports. The paper includes some experimental results obtained on simple inductive posts, a capacitive iris and inclined resonant slots.