Ferrite tuned millimeter wave bandpass filters with high off resonance isolation

By combining four hexagonal ferrite spheres under the same magnet structure, magnetically tunable bandpass filters were built in waveguide yielding increased off-resonance isolation (ORI), while keeping insertion loss (IL) to a reasonable value. Examples of these filters for the 26.5-40-GHz, 33-50-GHz, 40-60-GHz, and 50-75-GHz ranges are presented with typical ORI above 70 dB and IL less than 13 dB for full band tuning. A performance summary for these four sphere waveguide filters is given showing the similar performance obtained in the different bands.<>