The Study On Novel Low Loss Microwave Dielectric Materials And Their Devices

With the rapid progress in wireless communication, low-loss microwave dielectric materials and their devices become world-wide popular in recent years. Compared with other kinds of microwave devices, microwave dielectric devices have smaller size, lighter weight, being conformal with substrate, being multifunction and suitable for large scale production. Therefore, microwave dielectric devices have a great prospects in the coming information age.In the present thesis, high dielectric constant BaO-Ln2O3-TiO2microwave dielectric ceramic is firstly investigated. Based on investigating the sinter behavior and microwave dielectric properties of BaO-La2O3-Nd2O3-TiO2and BaO-Sm2O3-Nd2O3-TiO2-Al2O3ceramics, the optimal preparation conditions were obtained of the BLT materials. Based on these, a concave structure and stepped impedance structure were employed to design the coaxial mono block microwave dielectric bandpass filters respectively, and their microwave properties were simulated by HFSS software.An ultrahigh Qf value microwave ceramic CaTiO3-MgTiO3(95MCT) with stabile temperature coefficient of resonant frequency was developed by using conventional solid-state reaction method. When doped with ZnO and Nb2O5, the material has an ultrahigh Qf value of around72THz with a low dielectric constant of around20, which can act as antenna substrates and meet the requirements of modern microwave antennas.Then, using95MCT as the substrate, we designed a microstrip patch antenna model based on transmission line theory. We use HFSS software to simulate the radiation properties of the antenna and obtained the central frequency located at2.45GHz. The antenna model was optimized according to the assigned radiation pattern, VSWR and gain properties. The results indicate that the length of the rectangular patch is a critical parameter that can influence the central frequency of the patch antenna and it needs to be optimized during the design process.