Preparation And Resonator Antenna Design Of MgTiO₃-based Microwave Dielectric Ceramics

Microwave dielectric ceramics are a kind of ceramic materials that can perform electromagnetic wave transmission,reflection,absorption and so on in microwave frequency band circuits.They can be used as various components in microwave communication fields such as filters,antennas,and resonators.MgTiO₃-based microwave dielectric ceramics have a lower dielectric loss?Q·f=160,000 GHz?,which have become one of the most promising systems in recent years.But their low temperature stability??_f=-50 ppm/??and high sintering temperature?1400??limit their further development.This dissertation is to improve the dielectric properties of MgTiO₃ based ceramics by compositing with various additives and reduce the sintering temperature by adding sintering aids,and design the dielectric resonator antenna through using CST simulation software,and testing the radiation performance of the dielectric antenna simulation.?1?Microwave dielectric ceramics with a nominal composition of0.95MgTiO₃-0.05CaTiO₃-xPrAlO₃?x=0-0.015?were prepared by conventional solid-state sintering technique at 1250?.With increasing content of PrAlO₃,the grain size of the obtained ceramics decreased;the dielectric constant and quality factor increased first and then decreased.The temperature coefficient of resonant frequency decreased after PrAlO₃ was doped,but with more PrAlO₃ doped it increased.The obtained 0.95MgTiO₃-0.05CaTiO₃ ceramic doped by PrAlO₃ with x=0.0075 presented the best performance with?_r=19.04,Q·f=42,400 GHz and?_f=-19.40 ppm/?.?2?Microwave dielectric ceramics with a nominal composition of?1-x?MgTiO₃-xCa_0.5Sr_0.5TiO₃?x=0.035-0.045?was prepared by a conventional solid-state sintering technique at 1275?.The composite of Ca_0.5Sr_0.5TiO₃ leads to a decrease in grain size,and the density and density of microwave dielectric ceramics increase first and then decrease.The?_r value of the sample continued to increase,the Q·f value initially increased and then decreased,and the value of?_f continued to increase.The ceramics present the best dielectric properties when x=0.04 with?_r=20.57,Q·f=58,000 GHz and?_f=-1.16 ppm/?.?3?The sintering temperature of 0.9625MgTiO₃-0.0375Ca_0.5Sr_0.5TiO₃ ceramics could be lowered to 1175?by adding 2.0 wt.%B₂O₃ as a sintering aid.When more than 2.0 wt.%B₂O₃was added,a MgTi₂O₅ phase was produced,which lowered the dielectric properties of the ceramics.The results showed that 0.9625MgTiO₃-0.0375Ca_0.5Sr_0.5TiO₃-2 wt.%B₂O₃ could achieve a good combination of dielectric properties:?_r=18.9,Q·f=57,000 GHz and?_f=-1.2ppm/?.?4?Resonator antenna structures were designed by using CST simulation software,and the MgTiO₃-based dielectric ceramics prepared in the above optimization experiments were used as the resonator materials.The radiation performance of the antenna was optimized by changing the structure of the resonator and the dielectric properties of its materials.The antenna simulation test results show that the 0.95MgTiO₃-0.05CaTiO₃-1.5%PrAlO₃ ceramic materials prepared in this work are more suitable for resonators for high bandwidth applications;0.9625MgTiO₃-0.0375Ca_0.5Sr_0.5TiO₃-2 wt.%B₂O₃ ceramic materials are more suitable for resonators of high radiant energy rate and the resonators designed with the0.965MgTiO₃-0.035Ca_0.5Sr_0.5TiO₃ ceramic materials can obtain maximum gain for antenna.The gain can reach the value of 7.865 dB.