| In recent years,due to the development of communication technology shifting to high freque ncy bands and the rapid breakthrough of high-speed digital integrated circuit technology,existing electronic devices are expected to have higher comprehensive performance.We must study electronic devices with higher operating frequencies and smaller sizes to adapt to the development and changes of electronic communication technology.For transmitting signals and receiving signals,antennas occupy a vital position in communication equipment,which is bound to meet the conditions of high frequency,miniaturization,long aging,and high gain.Therefore,with the continuous development of high-frequency and miniaturization of communication devices,we must develop smaller antennas to meet the needs of engineering and lifeAmong the magnetic materials,carbonyl iron has many advantages such as relatively high saturation magnetization,easy dispersion,and high stability,so it has become a magnetic material with wide application and good prospect in the field of high frequency devices.In this paper.carbonyl iron was used as the research object,and it was studied that how the various experimental parameters of wet ball milling,surface modification and magnetic field orientation have effects on the microstructure,phase structure and electromagnetic properties.According to the double anisotropy theoretical model,the oriented free-face carbonyl iron composite was prepared experimentally and applied to the microstrip patch antenna in three ways.For the anisotropic material as the dielectric substrate,the effect of the high-frequency electromagnetic properties on the application frequency band,working bandwidth and size of the antenna is studied.Covering low-speed wireless personal area network and wireless electronic local area network(902-928 MHz;2.4-2.4835 GHz),the dual-frequency inverted-F antenna coated magnetic material is achieved to miniaturize by adding short-circuit arms,loading magnetic coating and slitting.According to the equivalent electromagnetic parameter theory,the influence of electromagnetic properties for the magnetic super-material on the size and bandwidth of the cladding antenna is discussed.The fabrication process of the magnetic material have been improved to obtain an antenna with excellent emission performance.The main contents and results of the study are as follows:1.Development of easy-face carbonyl iron powder.By adjusting the grinding time,rotating speed,powder ratio,material and protectant,the effects of various parameters on the shape and electromagnetic parameters of the samples were discussed,then the optimum grinding conditions were determined.The sample after ball milling has good sheeting and has high permeability and low loss electromagnetic characteristics.The natural resonance frequency shifts to high frequency after 6 GHz,which can better meet the GHz antenna application.2.Surface modification of easy-face carbonyl iron powder.The conductivity and complex dielectric constant of the easy-surface carbonyl iron powder after wet ball milling are at a high value,resulting in a serious mismatch in material impedance,affecting the radiation efficiency of the antenna.We must ensure the high permeability of the sheet sample while reducing complex dielectric constant.In the experiment,the surface-coated carbonyl iron powder was surface-coated by the hydrolysis reaction of ethyl orthosilicate.The modification results of anhydrous ethanol,ethyl orthosilicate,ammonia and aqueous solution with different volume ratios were studied,and the optimal coating conditions were determined.After surface modification,the carbonyl iron sheet is coated with SiO2 to form a core-shell structure.The insulating layer between the particles result in increasing the contact resistance,lowering the complex permittivity and improving the problem of material impedance mismatch.3.Preparation of oriented easy-to-face carbonyl iron complex.In order to optimize the high frequency magnetic properties of the sample and increase its initial permeability,the magnetic powder/binder is experimentally rotated in a magnetic field.After the composite is oriented,the tabular grains are arranged in parallel along the c-plane,and the easy-magnetized surface is formed on the c-plane,which shows a significantly increased magnetic permeability,which is more advantageous for miniaturization of the antenna(antenna miniaturization factor is 4.The simulation and production.of UHF band miniaturized RFID antenna.The CST software is used to simulate antenna emission characteristics of the compound and the simulating results displays that the size of the magnetic media substrate antenna is 89.2%smaller than that of the dielectric antenna,and the effective emission bandwidth is extended from 35 MHz to 94 MHz.A coaxially fed microstrip patch antenna was fabricated,and the validity of the simulation was verified by test data.5.Loading the magnetic material coating to achieve dual-frequency of the microstrip patch antenna.A magnetic material clad double frequency inverter F antenna is designed and simulated by CST employing the planar inverted F structure,the loading magnetic material coating,the surface of the patch grooves and other technologies.The simulation results show that the antenna's return loss at 0.90 GHz-0.95 GHz and 2.36 GHz-2.52 GHz is lower than-10 dB,completely covering LR-WPAN frequency band(902 MHz-928 MHz)and WBAN/WLAN frequency band(2.4 GHz-2.4835 GHz),indicating that it can be used in both low speed wireless personal area networks and wireless personal area networks6.The simulation and production,of Broadband super-surface antenna.By establishing a magnetic super-surface model,the magnetic super-surface cladding antenna is simulated,and the double-negative electromagnetic parameters of the magnetic material are obtained in the application frequency band of the antenna by using the equivalent electromagnetic parameter theory.The simulation optimization found that after loading the magnetic super-surface,the antenna size was further reduced compared with the magnetic material dielectric substrate antenna,and the bandwidth was significantly broadened.The reliability of the analog data is verified by making an antenna entity and measuring its return loss. |
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