Millimeter wave ferrite devices

Several ferrite control devices have been designed, fabricated and evaluated for 35 GHz dielectric waveguide applications. These devices include phase shifters and circulators utilizing spinel ferrites, and isolators with hexagonal ferrites. These devices were optimized in a magnesium titanate dielectric waveguide type transmission line for operation in the 35 GHz frequency region. The circulator had less than 1 dB insertion loss and greater than 15 dB isolation over a 10% bandwidth. A Reggia-Spencer type phase shifter employing a nickel zinc composition with a saturation magnetization of 5000 Gauss and a remanence of 1950 Gauss produced 125° phase shift per cm with 0.3 dB insertion loss. The resonance isolator had 1 dB insertion loss in the forward direction and more than 20 dB isolation in the reverse direction. Initial material and device evaluation at 94 GHz indicates that problems associated with material losses and the fabrication of small size devices can be overcome with proper material selection, simplified designs and careful device fabrication procedures.