Y-type hexaferrite materials are candidates for the ferrite substrate in the next generation of planar tunable ferrite phase shifters operating at millimeter-wavelength frequencies. We have designed, fabricated, measured, and modeled such a phase shifter operating at 20 GHz that utilizes a single-crystal Zn{sub}2Y (Zn{sub}2Ba{sub}2Fe{sub}12O{sub}22) substrate. The design and modeling combined the conjugate method of microstripline on magnetic substrate and magnetostatic mode calculation in ferrites. The measured phase shifter figure of merit at 15 GHz (20 GHz) was 47.9°/kOe·dB (105.9°/kOe·dB) for an external applied field of 0.25 kOe (1.8 kOe). This combination of a substantial phase shift and a relatively small external biasing field makes the Y-type hexaferrites promising materials for high-frequency phase shifters.
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