Research On Low Loss LiZn Gyromagnetic Ferrite And Its Application

As an important component of passive phased array radar,the volume and performance of phase shifter have a very important influence on the miniaturization,high frequency and integration of phased array radar system.The ferrite phase shifter has been widely used in phased array radar due to its advantages of large phase shift and small insertion loss,and the rise of low temperature co-fired ferrite（LTCF）technology also provides an effective solution for the miniaturization of ferrite phase shifter.In order to adapt to the LTCF process,the ferrite material must be sintered at low temperature to reduce the volume of the phase shifter.However,the low-tempuratrue sintered LiZnTi ferrite material has some problems such as low density,poor gyromagnetic properties and poor dielectric properties.Therefore,in this paper,the amount of ion substitution is controlled by means of ion substitution to regulate the ion occupancy in the crystal structure,and the ferrite materials with excellent rotary magnetic properties and loss under low temperature sintering are obtained by means of multi-element assisted firing.Firstly,the main formulation of the ferrite materials was optimized to analyze the correlation between ion substitutions and gyromagnetic properties and microwave loss.The results show that:Zn²⁺could promote the sintering reaction and change the superexchange between the A and B sublattices,thus significantly reducing the ferromagnetic resonance linewidth（ΔH）and coercoerity.Meanwhile,the saturation magnetization could also be improved by increasing the molecular magnetic moment.However,due to the weakening of the superexchange effect,the temperature stability of the material decreases.（2）The use of iron deficiency formula could effectively inhibit the generation of Fe²⁺ions,so that the number of electric dipoles was reduced,and the loss of steering polarization was reduced,thus reducing the dielectric loss.（3）The decrease of Ti⁴⁺content would increase the molecular magnetic moment and thus increase the saturation magnetization,but theΔH would increase slightly.Through the above research,it was obtained that the working line width of ferromagnetism is as low as 96 Oe,the coercivity was as low as 66.64 A/m,and the saturation magnetization was 3531Gs under low temperature sintering,which needs further improvement.In addition,the dielectric loss was slightly higher,which needs further optimization.Secondly,the introduction of low melting point（～600℃）glass Bi₂O₃-ZnO-B₂O₃（BZB）and Bi₂O₃ to form a multiple flux system with a certain melting temperature gradient,through two small grain growth in the sintering process to more fine control the grain growth process to obtain a more uniform and compact microstructure.Research results show that right amount of Bi₂O₃ and BZB glass doped together can obtain the approximate density uniformity,structure good ferrite samples,and the material of various performance with the introduction of multiple doping also has a certain improvement:saturation magnetization ascension to 3918 Gs,the coercive force is 90.2A/m,ferromagnetic resonance linewidth for 94 Oe,dielectric loss tan delta epsilon reduce to 5.32×10^-4,dielectric constant is 15.72.Finally,a microstrip structure ferrite phase shifter applied to the X-band was designed using HFSS 15.0 based on the substrate prepared by the previously obtained ferrite with excellent gyromagnetic properties.The results show that when the frequency was between 9.26GHz and 9.64GHz,S₂₁>-3d B,S₁₁<-10d B,and VSWR<1.9.At the central frequency of 9.3GHz,S₂₁ was-2.41d B,S₁₁ was-11.31d B,VSWR was 1.75,and the phase shift was 131°.