Preparation And Electromagnetic Properties Of Z-type Hexgonal Ferrites Used For Microwave Antenna Miniaturization

With the development of high-frequency communication and high-speed digital integrated-circuits in recent years, the frequency of various electrical devices becomes higher and the sizes get smaller. So how to enhance the working frequency and achieve reduce miniaturization has become an important research topic for related scientific researchers. As the exports and imports of signals in communication system, antenna is undoubtedly one of the critical components in the system. Therefore, the requirements of developing small antennas for small devices are getting increasingly strong. Co₂Z hexaferrite with high initial permeability, high quality factor and excellent thermal stability is a ferrite material illustrating a good application prospect for microwave patch antennas.In this paper preparation of iron deficiency formulation, Co₂Z hexagonal ferrite preparation technology parameters and Sr-doped Co₂Z hexagonal ferrite have been investigated. The effects of different factors, such as iron formulation, process parameters, on the material phase structure, microstructure and electromagnetic properties are investigated. Studies have shown that under the optimum conditions with a grinding time of 2.5h, calcining temperature of 1240℃/2.5h, the second milling time of 3h, sintering temperature of 1050℃/3.5h, Co₂Z hexagonal ferrite magnetic properties are significantly improved. With the increase of iron deficiency, the relative permeability values of samples firstly increase and then decrease. When the iron content y=10.4, the relative permeability achieves the maximum at 1GHz and is approximately equal to 7. With the amount of iron deficiency increases, the saturation magnetizations decrease and the coercivity forces decrease firstly and then slightly increase. In terms of Sr doping, with the substitution increase the permeabilities of the samples firstly increase and then decrease. For the sample with Sr doping content x = 0.3,μ'r is equal to 7.5 andμ''r is less than 0.4 at 1GHz; the saturation magnetizations increase with the increasing substitution content and the coercive forces firstly decrease slightly and then increase. When x=0.4 and x=0.8, the minimum and the maximum of the coercivity force is 68.11Oe and 176.59Oe, respectively.Then the materials are used as 1GHz microstrip patch antenna substrate material. Through simulation and analysis with simulation software, we have found that the electromagnetic properties of Co₂Z hexagonal ferrite prepared by iron deficient formulation and Sr substitution meet the application requirements of dielectric patch antennas. Magnetic antenna not only has a higher degree of reduction in size but also has better impedance matching characteristics, that is, to achieve greater bandwidth, compareing to conventional dielectric patch antenna. From the simulation results, our previous study of magnetic materials proves that Co₂Z magnetic ferrite material is a good alternative substrate material for microstrip antennas and will have a profound influence on the realization of antennas miniaturization and high frequency.