Experimental characterisation of a reciprocal microstrip 3-port junction

The first circulation condition in many junction circulators and the condition for the maximum power transfer in a reciprocal 3-port junction are both met when the reflection eigenvalues of the in-phase and degenerate counter-rotating eigen-networks are out of phase. The purpose of the paper is to give some experimental data on the relationship between the aspect ratio of the resonator and the electrical details of the eigen-networks in the case of a junction consisting of a planar disk resonator on an alumina substrate coupled at three places by 50 Omega lines. Aspect ratios between 5 and 16 are suitable for the design of microstrip circulators with modest specifications.