Self-biased millimeter wave notch filter based on single crystal hexaferrite resonator with regular domain structure for 45–57 GHz region

Self-biased millimeter wave (mm-wave) notch filter consists of a resonator based on single crystal barium hexaferrite (BaFe₁₂O₁₉), which is operated in the multidomain region has been realized and investigated. The filter is designed using the length of dielectric waveguide. Depending on the type of preliminary created regular domain structure in hexaferrite the filter resonance frequency f_r can vary in the range of 47-51 GHz, with a maximum rejection at the frequency f_r of about 22-24 dB and 3dB-bandwidth of about Δf = 50 MHz. Also, it is shown that the resonance frequency f_r of such a filter is tunable in the range of 45-57 GHz by applying a low external DC magnetic biasing fields H₀ <; 4πM_s to the hexaferrite resonator.