Tunable magneto-dielectric resonator for W-band isolators

Abstract

A magnetic field tunable barium hexaferrite (BaM) dielectric resonator that could potentially function as an isolator operating at 82 -90 GHz has been designed and characterised. A 30 GHz increase in operating frequency was achieved by using dielectric resonances instead of the usual ferromagnetic resonance. The dielectric resonance and the operating frequency of the isolator can be tuned by 0.84 MHz/Oe almost linearly with an applied magnetic field.Introduction: The W-band frequency range (75 -110 GHz) is particularly important for applications such as satellite communication and automobile collision avoidance radars. Therefore, there is a need for tunable resonant devices working at these frequencies. However, devices based on magnetic materials such as garnets, metals, alloys, spinels, and pure hexaferrites would require a very large bias magnetic field for operation in the W-band [1]. Indeed, for hexaferrites with saturation magnetisation M s , anisotropy fields H a , gyromagnetic ratio g, and magnitude field H applied along the easy axis, the ferromagnetic resonance (FMR) frequency in the most favourable case (easy axis lies in the sample plane) is given by [2]

Sub-Terahertz Magnetic and Dielectric Excitations in Hexagonal Ferrites

“…Therefore, such an arrangement ensures selective excitation of only one of the split modes. The nonreciprocal characteristics for the resonator could be utilized for a W-band isolator [31].…”