Abstract: Impedance matching between a waveguide circulator and its input/output ports is achieved by properly dimensioning a gap formed between a ferrite circulator element inside the waveguide circulator and at least a portion of the input/output port aperture itself. Typically, the I/O port aperture has at least a portion which is of lesser height dimension than the internal waveguide circulator cavity. Ridge waveguide or ridge-to-rectangular waveguide adaptor blocks, or the like, may emanate from such input/output circulator apertures.

Abstract: A conductive waveguide structure has a central cavity of full height and input/output ports of a second reduced height emanating therefrom. A smaller ferrite circulator element is centrally disposed within the cavity and has outer extremities spaced from the inner edges of the reduced height input/output ports by a predetermined gap dimension "G" which is chosen to achieve an appropriate impedance match between the impedance of the ferrite element and the higher impedance of the wavguide without the necessity for the usual quarter-wave dielectric impedance matching transformer sections.