Design and performance of J-band (12.4-18 GHz) ferrite microstrip circulators

A computer program CIRFER is described that facilitates the design of circulators on all-ferrite substrates. With the use of the design approach, J-band circulators have been fabricated using thin-film techniques on ferrite substrates of different 4π₈ values. Good agreement was obtained between theoretical and experimental resonant-disc diameters at the centre frequency of operation of the circulator. The circulators gave isolations of 20-40 dB in mid J-band, with a corresponding loss per pass of the order of 0.5 dB. The microwave performance is sufficiently encouraging to suggest that in certain applications an all-ferrite approach could be considered, which would simplify the circulator design. The computer program CIRFER has been filed with the IEE Computer Program Library.