Half-massive ceramics for antenna downsizing: improvement of a smart magneto-dielectric material with matching permeability and permittivity, and with enhanced low-loss frequency range

Complex permeability and permittivity of Ni_0.5Zn_0.3Co_0.2Fe_1.98O_4-x half-ceramic ferrites (porosity ~50%), obtained from various annealing temperature T_A (500°C, 800°C, 900°C), are measured and compared. Their characteristic impedance Z, magnetic and dielectric loss tangents are presented. Bandwidth BW and radiation efficiency η values of patch antennas are obtained through numerical simulations and compact formulations. The value of the annealing temperature used for the substrates determines those of BW and η. BW and η are themselves used as criteria to decide which one among the various substrates is proper to be used at given frequency. It is concluded that whereas the sample annealed at 500°C is far to meet the required properties in reason of detrimental magnetic losses, the half massive ceramics got after annealing at T_A=800°C and 900°C show appropriate performances for further applications. The electromagnetic properties of half ceramics materials sound to be very competitive at frequencies up to 0.8GHz.