MgFe1.98O4-BaFe12O19 magneto-dielectric composites based ferrite resonator antenna for super-high frequency applications

The structural, morphological, and wideband electromagnetic response of (1-x) MgFe1.98O4 + x BaFe12O19 composites with x = 20, 40, 60, and 80 wt percent (wt%) were investigated. The composites' sintering tem-perature was optimised to be 1250 C for 2 h. The phase purity and independent existence of the end members in the composites were verified using XRD, Raman and FTIR spectroscopy. The microstructures of the sintered composites indicate the effect of grain growth on the density and grain packing efficiency. The relative permittivity of the composites is in the 9-11 range, while the relative permeability is between 1.4 and 2.8. The increase in BaFe12O19 concentration from 20 to 80 wt% resulted in a dilution effect in permeability and enhanced saturation magnetization and coercive field strength. The composites with 20-80 wt% BaFe12O19 possess a characteristic impedance ranging from 0.55 to 0.38 and a miniaturisation factor ranging from 5.16 to 3.82 at 900 MHz. The composites containing 20 and 40 wt% BaFe12O19 exhibited appreciable miniaturisation factors of 5.16 and 5.24, respectively, with characteristic impedances of 0.55 and 0.47. Furthermore, these composites have low magnetic and dielectric losses of the order of 10-1 and 10-3, respectively, making them suitable candidates for resonator antenna applications. A magneto-dielectric resonator antenna using the composite comprising 40 wt% BaFe12O19, with a density greater than 95%, was designed, simulated and fabricated. The fabricated magneto-dielectric resonator antenna resonated at a frequency of 14.7 GHz, with a significantly low return loss of-44 dB and wide impedance bandwidth of 1.44 GHz, suggesting the application potential of the dual-ferrite composite in the Ku-band frequency range.