MMIC circulators using hexaferrites

MMIC circulators operating at KA-band have been fabricated from single crys tal and polycrystalline hexaferrite platelets integrated into glass-microwa ve integrated circuit wafers. Measurements on circulators utilizing single crystal BaFe11.1Sc0.9O19 showed two-band circulation, below-FMR (at 36 GHz) and above-FMR (at 24 GHz), while those using single crystal BaFe12O19 show ed above-FMR circulation at 32-35 GHz. Self-biased circulators using SrFe12 O19 ceramics showed above-FMR circulation at 32 GHz. All circulators showed reasonable insertion losses and isolation, with the best insertion loss of 1.2 dB at an isolation of 18 dB being found for a BaFe11.1Sc0.9O19 circula tor operating below-FMR.