A 54-58 GHz tunable Ferrite filter

A single-stage ferrite filter has been constructed using the magic-tee design of Grossbach. The ferrite employed was a single-crystal sphere of yttrium iron garnet, the linewidth of which was 2.0 to 2.5 Oe at 56 GHz. The insertion loss of this filter was 1.35 to 1.5 dB over the tuning range of 54 to 58 GHz, and the 3 dB bandwidth was 40 to 69 MHz. Results are also reported of the performance of this filter, using a single-crystal sphere of hexagonal ferrite.