Research Of The Microwave Absorption Properties Of Microwave Absorbing Material Enhanced And Tuned By Metamaterials

Both external and domestic experts are keeping highly research enthusiasm as well as attaching importance to microwave absorbing materials (MAMs), no matter it as a kind of most effective invisible material for defense weapons and equipment, or as Anti-EMI materials for different kinds of civilian and military electronic equipment and electronic instrument which with high sensitivity. However, whether traditional MAMs, such as carbon black and ferrite, or novel nanomaterials, they still have some disadvantages such as high density, narrow band, and low absorptivity. Therefore, the demands to develop more economical MAMs with low density, wide and adjustable frequency region for the microwave absorption, and large reflection loss (RL) are ever increasing. We propose and demonstrate a scheme to enhance and tune absorption properties of conventional MAMs by metamaterials. Electromagnetic metamaterials are artificially structured media with unique and distinct properties that are not observed in naturally occurring materials, such as simultaneously negative electrical permittivity (ε) and magnetic permeability (μ). In addition, the resonance frequency can be tuned by adjusting the shape, structure, dimension, or arrangement of the constitutive elements of metamaterials.In this paper, we propose three metamaterials with different structures to enhance and tune absorption properties of conventional MAMs. The first structure composed of split ring resonators (SRRs) and wires, by covering a carbonyl iron powder coating with this metamaterials, we show both by experiments and by simulations that the maximum RL is increased significantly and the frequency region for absorption is shifted to lower frequency. The frequency region in which the maximum RL is less than -10 dB shifts from 5～7 to 4.2～6.2 GHz for perpendicular polarization electromagnetic waves and to 4～9 GHz for parallel polarization waves. Simulation results reveal that the magnetic resonance obtained by SRRs and the electric resonance obtained by copper wires are the main factors in enhancing and tuning microwave absorption properties.The second, the metamaterial composed of SRRs with copper wires was replaced by cut-wire pairs (CWPs) in order to wider the frequency region for microwave absorption. We have prepared a combined absorber by sandwiching the array of subwavelength copper cut wires between two layers of carbonyl iron powder coating. Experimental results and numerical simulations reveal that the frequency region in which the RL is less than -10 dB shifts from 5-7.4 GHz to 3.9-9.4 GHz. The absorption performance can be enhanced and tuned simply by adjusting the dimension of the cut wires, and the arrangement and layer number of the cut wire array.The last structure composed of copper circular patches, by the same combination with the second structure. Simulation results reveal the frequency region in which the RL is less than -10 dB form 5.4 GHz to 11.7 GHz. It's worth noting that the absorption performance is nothing to do with the polarization of incident electromagnetic wave. In addition, The absorption performance can be enhanced and tuned simply by adjusting the dimension of the circular patches,and the arrangement and layer number of the metamaterials.