A low-loss dielectric using CaTiO₃-modified Mg_1.8Ti_1.1O₄ ceramics for applications in dielectric resonator antenna

The microwave dielectric properties of (1-x)Mg_1.8Ti_1.1O_4-xCaTiO₃ ceramics prepared by the mixed oxide route have been investigated. Spinel-structured Mg_1.8Ti_1.1O₄, ilmenite-structured MgTiO₃ and perovskite-structured CaTiO₃ were coexisted and the three-phases system was confined by X-ray diffraction patterns, EDX analysis and it also leads to near-zero τ_f. The microstructures of the ceramics were characterized by SEM. The microwave dielectric properties of the ceramics can be effectively controlled by varying the x value. For practical applications, a fine combination of microwave dielectric properties (ε_r~ 19.61, Qxf~ 72,700 GHz at 9.03 GHz, τ_f~ -3.7 ppm/°C) was achieved for 0.91Mg_1.8Ti_1.1O₄-0.09CaTiO₃ ceramics sintered at 1330 °C for 4 h, which makes it is a very promising candidate material for applications in dielectric resonator antenna. A new triple-band dielectric resonator antenna fed by a coplanar waveguide is presented. The proposed antenna, composed of a high permittivity dielectric resonator and printed on FR4 substrate, is fed by a 50 Ω coplanar waveguide transmission line. In order to achieve wideband applications, the antenna with two parasitic inverted-L strip is demonstrated to generate two resonant frequencies covering 3.5 and 5.2 GHz. The measured results show that the antenna covers the frequency bands 2.30-2.72, 3.45-3.61, and 5.05-6.23 GHz with less than -10 dB of S₁₁. The frequency response of the simulation results shows good agreement with the measured data. Good antenna gain, radiation efficiency and radiation patterns of the proposed antenna have also been observed across the operation band. Details of the proposed antenna design and experimental results are presented and discussed.