Identification of Spurious Modes in Circulators (Correspondence)

The spurious, and sometimes troublesome spikes in circulator characteristics are shown by analysis and experiment to be due to hybrid resonant modes of the ferrite post open-resonator structure. They can be excited by axial nonuniformities such as imperfect contact between the ferrite and the conducting walls, but they cannot exist in axially uniform structures with axially uniform excitation.