Study On The Design And Composite Electromagnetic Property Of Phase Modulation Metamaterials

With the rapid development of electronic technology,military and civilian fields propose higher requirements on the electromagnetic(EM)performance of microwave functional materials.Metamaterials promote the development of EM wave manipulation with their structural design flexibility.Based on EM metamaterials design,this paper explores the relation among phase modulation,polarization conversion and EM scattering,as well as the analysis of the EM properties shown under the combined influence of material intrinsic loss,phase cancellation and other relevant mechanisms,and realizes broadband and high-efficiency design of low-reflection materials.The main research contents and conclusions are as follows:Based on the geometric phase modulation,the polarization conversion and EM scattering properties of metamaterials are studied.Two kinds of unit cells are designed: a 180° phase difference of horizontal-axis and vertical-axis EM waves can be obtained by optimizing the square split-ring unit cell,which can realize circular polarization modulation;a 180° phase difference of diagonal-axis EM waves can be obtained by optimizing the circular split-ring unit cell,which can realize linear polarization conversion and circular polarization modulation.The unit-cell arrays are built,the square and circular split-ring arrays realize reflectivity less than-10 d B at 7.8-14.8 GHz and 6.1-13.8 GHz,respectively.The performance of experimental samples matches well with the simulation results.The EM scattering of arrays originates from the phase cancellation of unit cells.Based on the geometry/transmission phase modulation,a metamaterial with tunable operating bandwidth is designed.The phase-change material vanadium dioxide is introduced into unit-cell design.The geometric phase and transmission phase are controlled by switching between insulating and metallic states,the unit cells with opposite phases in different bandwidth are obtained.At 25 °C and 75 °C,the unit-cell array is designed with reflectivity less than-10 d B at 6.7-10.5 GHz and 14.4-17.2 GHz,respectively.The sample is prepared by magnetron sputtering,the tunability of its operating bandwidth is realized by switching two temperatures.The mechanism is that the unit-cell array has two independent phase modulation modes,which can realize geometry/transmission phase cancellation in different bandwidths.The phase-modulation metamaterials and magnetic absorbing materials are added up to form composites,which show both phase modulation and intrinsic loss properties.Four kinds of unit cells are designed to realize polarization conversion and 90° phase difference.A series of unit-cell arrays are built,the ratio of phase cancellation unit cells determines the reflection properties of array.Metal patterns are applied to the magnetic absorbing material,the tunability of unit-cell ratio to operating bandwidth is verified.The optimal arrays realize reflectivity less than-10 d B at 2.7-18 GHz.The experimental results agree well with the simulation results.This research combines two mechanisms of EM scattering and microwave absorption to realize a broadband and high-efficiency design of low-reflection materials.The phase-modulation metamaterials and dielectric absorbing materials are added up to form composites,which show both phase modulation and intrinsic loss properties in hightemperature environment.A type of dielectric absorbing material is prepared with good temperature stability of dielectric properties.The metallic structure and material are combined into unit cell with 180° phase difference of diagonal-axis EM waves,which can further realize polarization conversion.In 25-700 °C temperature range,the reflectivity of unit-cell array is less than-10 d B at 8.2-12.4 GHz.Experimental sample shows low-reflection properties from normal temperature to high temperature.This research combines two mechanisms of polarization conversion and microwave absorption to realize a broadband,high-efficiency design of low-reflection materials over a wide temperature range.A design method for integrated metamaterial structure of scattering and absorption is proposed,forming a synergistic effect of phase modulation and intrinsic loss.Two kinds of unit cells are built to realize the intrinsic loss performance of material and the phase cancellation properties between unit cells.Combining unit cells into unit-cell array,the absorption properties of unit cells,the scattering properties of unit-cell array,and the summation of absorption and scattering are optimized: with reflectivity below-10 d B at 1-4GHz,reflectivity below-20 d B at 4-8 GHz,reflectivity below-40 d B at 8-18 GHz.The sample is prepared by 3D printing,the performance of experimental sample is basically consistent with the simulation results.This design further broadens the operating bandwidth of material,which reveals the significance for the technology of low-reflection materials.