Scattering in a section of ferrite-coupled microstrip lines: theory and application in nonreciprocal devices

A section of axially magnetised ferrite coupled microstrip lines (FCL) is analysed using the method of field expansion, which is based on the interaction of the dominant ferrite and isotropic modes in the ferrite-dielectric interfaces of an FCL. The scattering matrix of a four port microstrip FCL junction is obtained from matching of the fields at the ferrite-dielectric interface at both ends of the FCL. The performance of the microstrip FCL section is investigated numerically and the results of simulation are compared with available experimental data to demonstrate the efficiency of the approach. The configurations of the circulator and novel quasicyclic devices comprising the FCL section are reported and their scattering characteristics are calculated and discussed.