An application of a hexagonal ferrite to a millimeter-wave Y circulator

Hexagonal ferrite is used for a circulator at mm-wave frequencies. No external magnet is needed. The center frequency is 73.5 GHz, the bandwidth over which the isolation is greater than 20 dB is 2.4 GHz, and the insertion loss is 1.1 dB at the center frequency. The tensor permeability in a strong uniaxial field is determined. The dependence of the circulator bandwidth on an applied field is determined to show that the large uniaxial field of hexagonal ferrite contributes to the wideband performance at mm-wave frequencies.