Moment matching compact models of multiport lossless junctions from terminal frequency response

A novel multipoint moment matching technique is presented to derive compact models of lossless n-port junctions. The model is deduced directly from the scattering parameters of the junction, evaluated at a limited set of frequency samples together with their frequency derivative, in a numerically well-conditioned way. The model itself is lossless by construction and can be synthesized by a lumped circuit composed of ideal transformers, positive capacitors and inductors, all with frequency independent parameters. The performance of the proposed model has been successfully tested on both transmission line and waveguide junctions, including multimode ports.