A Magnetic Field Tunable Yttrium Iron Garnet Millimeter-Wave Dielectric Phase Shifter: Theory and Experiment

A magnetically tunable passive narrow-band split-mode mm-wave phase shifter based on dielectric resonance in yttrium iron garnet (YIG) is investigated. The novelty here is the demonstration of a phase shifter in the frequency region between two split dielectric resonances in YIG. It is shown that, under certain conditions, the differential phase shift from the split modes add up, resulting in a larger phase shift than for a single mode phase shifter. Two prototype phase shifters operating in the U- and W-bands at frequencies much higher than ferromagnetic resonance (FMR) in YIG have been designed and characterized. Phase shifts up to 30° with low losses and acceptable standing wave ratio are obtained for moderate bias magnetic fields. Equivalent transmission-line model taking into account coupling between the split resonances is presented and there is reasonable agreement between theory and experiment for both insertion loss and differential phase shift. Suggestions on further improvements of prototype filter characteristics have been outlined.