Preparation Of BaSrTiO₃-based And Y₃Fe₅O₁₂-based Microwave Electromagnetic Materials And Their Microwave Properties

With the continuous development of electronic information technology and communication technology,new requirements have been put forward for related microwave materials.Barium titanate?BaSrTiO₃,BST?,one of the important systems of microwave ferroelectric dielectric materials,has a large dielectric constant,low dielectric loss,good dielectric tuning properties,and is widely used in microwave and tunable devices.The yttrium iron garnet(Y₃Fe₅O₁₂,YIG)is an important species of microwave ferrite.It has a small resonance line width,low saturation magnetization,low dielectric constant and dielectric loss,etc.It has become an important basic material for microwave ferrite devices with a wide range of applications.The purpose of this paper is to prepare a suitable BST/MgO microwave composite material and a pure phase YIG microwave ferrite material,and apply it to mobile phone antenna and UWB?Ultra-Wide-Band,UWB?antennas to improve the performance of the antenna.The main work of this paper is as follows:?1?The pure phase Ba_0.5Sr_0.5TiO₃ was prepared by solid phase synthesis and doped with MgO.The effect of MgO doping with different mass ratio on the performance of the sample was discussed,and the tuning characteristics of the mobile antenna were realized.After the Magnesium Oxide doped with 60 wt%,the relative dielectric constant of the composite ceramics is 96,the dielectric loss is 0.002,and the dielectric tuning rate reaches12.6%under the applied DC voltage of 50 kV/cm.The sample is applied to the design of mobile phone antenna to realize the tunability of antenna bandwidth.The variation of the antenna bandwidth with the position of the ceramic plate on the antenna is obtained by testing.After applying the voltage of 0-4 kV/cm to the ceramic chip,the 698-960 MHz full frequency tuning can be realized,which provides a new design method for the dielectric tuned cell phone antenna.?2?The pure phase Y₃Fe₅O₁₂ was prepared by solid phase synthesis,and the effect of YIG on the non positive distribution ratio of iron and iron deficiency was studied.The band-notched performance of the UWB antenna was realized by the pure phase YIG ceramic chip.With the increase of Fe content,the saturation magnetization increases first and then decreases.The YIG material is applied to the design of UWB antenna to achieve the notch characteristics of the antenna.The UWB antenna is a microstrip slot antenna,and the-10 dB bandwidth measured when the antenna is loaded without ferrite is 2.91-10.98GHz;when the ferrite is loaded on the radiation surface of the antenna,the bandwidth of the antenna changes.In this paper,the bandwidth of the antenna is changed to 2.73-5.12 and 5.87-10.78 GHz,and the bandwidth of WLAN 5GHz?5.15-5.825 GHz?is filtered.The proposed technique has virtue of easy fabrication and keeping antenna miniaturization.