Millimeter Waves Multibands Absorbers Based On Flexible Metamaterial

Electromagnetic metamaterial is not only a new kind of functional materials that based on the artificial composite microstructures,but also means freely control electromagnetic response.The needed response decide the microstructure we designed.Their unique unusual electromagnetic properties which the natural materials do not own,can make metamaterial be widely applied in biochemical detection,energy utilization,electromagnetic devices,stealth and protection,and other potential fields.Reasonable design of metamaterial microstructure and size can make its wave impedance perfectly match with the free space,and then realize the perfect absorption at specific spectrum.The number of existing metamaterials absorber(MA)is not greater than the number of the resonator.The increase of absorption bands must be appropriate to increase the number of resonators,which brings more difficulties in designing and manufacturing MA.The fewer resonators are used for more resonance bands and better absorption performance in this paper.Numerical simulation and theoretical analysis are used to study the multibands absorption mechanism of the proposed metamaterial absorber based on periodic double square ring resonators.Absorptivity curves are calculated under the condition of the TE and TM polarization waves with vertical incidence.The double square ring can realize the perfect absorption with two band,three bands,and four bands by adjusting its size.The surface electric field distributions of the inner and outer square ring are shown to summarize the physical mechanism of multibands absorption.The influences produced by size,material,and incident wave are carefully simulated and discussed.Magnetron sputtering technology and UV-LIGA based on the positive photoresist RZJ-304 are applied to fabricate the periodic "sandwich" microstructure on a FR4 board.Whole manufactured process,main process parameter,and matters needing attention are detailedly discussed.An optical microscope is used to show microstructure of the three fabricated samples and confirm the process effectiveness.Three common measurement methods are introduced in detail.THz – TDS is adopted with overall consideration.The contrastive diagrams show that tested absorption performance at low frequency agrees well with simulation results,while have some deviations at high frequency.The tested absorptivity slightly decreases.The possible sources of these deviations are reasonably analyzedFinally,main work,conclusions,and innovations of this paper are summarized.The inadequacy of the research and development of metamaterial absorber are also summarized and expected.