The Research On Magnetodielectric Materials And Their Applications In Integrated Antennas

As an important window of the wireless communication module,the antenna has an extremely important influence on the electronic equipment,and the properties of the antenna substrate material are also an important factor affecting the performance of the antenna.Due to the excellent magnetic properties and dielectric properties of magnetodielectric materials,on the one hand,the problem of too narrow bandwidth caused by high dielectric constant is alleviated,and on the other hand,because the equivalent impedance is close to the free space impedance,ideal matching can be achieved,and greater advantages than higher dielectric materials,so it has been widely studied and applied.NiCuZn materials have good magnetic-dielectric properties and can be used to prepare magnetodielectric materials.In this thesis,the iso-magnetic-dielectric properties are achieved by doping and compounding Ni Cu Zn materials respectively.First,based on the fact that Ti O₂ is a good dielectric material that can adjust the dielectric properties of ferrite,and Bi₂O₃ is a sintering aid that can adjust the magnetic properties and reduce the sintering temperature,this thesis carried out Ni Cu Zn+1wt%Bi₂O₃+6-16wt%Ti O₂ in the experiment,the effects of sintering temperature and TiO₂ doping concentration on the magnetic and dielectric properties of the material were discussed respectively,and the sintering curve was adjusted for the problem that the magnetic loss of the material obtained from the final ideal formula was too large.At 3MHz-30MHz frequency,the permeability is 22.24,the magnetic loss is 0.08;the dielectric constant is 22.16,the dielectric loss is 0.008,and the normalized impedance is about 1.0018.Secondly,since Co₂Z is a ferrite material with high cut-off frequency and higher dielectric constant than magnetic permeability,it can have good compatibility as a composite material.In this thesis,Ni Cu Zn_x/Co₂Z_1-x(x is 0.84-0.94)composite material preparation experiment,the influence of sintering temperature and composite ratio on the magnetic and dielectric properties of the material was discussed.Finally,the main formula of Ni Cu Zn_0.88/Co₂Z_0.12was sintered at 1150?to obtain a material with a performance of 10MHz-200MHz frequency.The lower?'=19.4,?'=18.2,tan?_[is about 0.002,tan?_ì=0.015,the normalized impedance is about 0.967,and the isomagnetic dielectric properties are well realized.Aiming at the materials prepared in the above experiments,the simulation of the microstrip antenna is carried out at the end of this thesis.The Ni Cu Zn_0.88/Co₂Z_0.12composite material sintered at 1150?is used as the main formula,and the microstrip circularly polarized antenna with the center frequency of 200MHz is used.After design and simulation optimization,the antenna performance is finally well optimized by introducing T-shaped slots at both ends of the patch.The final performance is:the center frequency is 200MHz,the S₁₁ is-51d B,and the bandwidth is about 15MHz.