Qu Shao-Bo

Planar Metamaterial Absorber Based on Lumped Elements

We present the design of a planar metamaterial absorber based on lumped elements, which shows a wide-band polarization-insensitive and wide-angle strong absorption. This absorber consists of metal electric resonators, the dielectric substrate, the metal film and lumped elements. The simulated absorbances under two different loss conditions indicate that high absorbance in the absorption band is mainly due to lumped resistances. The simulated absorbances under three different load conditions indicate that the local resonance circuit (lumped resistance and capacitance) could boost up the resonance of the whole RLC circuit. The simulated voltage in lumped elements indicates that the transformation efficiency from electromagnetic energy to electric energy in the absorption band is high, and electric energy is subsequently consumed by lumped resistances. This absorber may have potential applications in many military fields.

A Wide-Band Metamaterial Absorber Based on Loaded Magnetic Resonators

A wide-band polarization-insensitive and wide-angle metamaterial absorber based on loaded magnetic resonators is presented. The unit cell of this absorber consists of a magnetic resonator loaded with lumped resistances, a dielectric substrate and a back metal film. Theoretical and simulated results show that this absorber has a wideband strong absorption for the incident wave from 3.87 GHz to 21.09 GHz. Simulated absorbance values under loading and unloading conditions indicate that electrocircuits resonances are more stable than electromagnetic resonances and thus can be used to realize wide-band absorption. Simulated absorbance values under different polarization angles and different angles of incidence indicate that this absorber is polarization-insensitive and wide-angle. It may have potential applications in military fields.

Mechanical metamaterial with negative Poisson’sratio based on circular honeycomb core

Mechanical metamaterials are artificial structures with mechanical properties defined by their structure rather than their composition. As a new type of metamaterials with unique mechanical properties and promising prospects, mechanical metamaterials have attracted great attention and become a new hot spot in the field of metamaterials. Mechanical metamaterials with negative Poisson’s ratio can exhibit novel mechanical properties such as excellent resistance capability of bending deformation and indentation. This type of materials have good prospects in many applications such as variant flexible wing skin. In this article, we adopt the design method of mechanical metamaterials to improve the structure of traditional honeycomb core and propose a new type of circular honeycomb core unit to obtain negative Poisson’s ratio. The advantage of circular honeycomb core is that this new structure is more stable than traditional concave hexagon honeycomb core. We established the corresponding mechanical model of this structure and adopted energy method to study the dependencies of structure parameters for its effective elastic modulus. The bending strain energy was taken into consideration while the tension and shear strain energy were ignored because they are very small compared with the bending strain energy. Then the expressions of effective elastic modulus in the directions of X and Y axis can be established in the condition of small deformation. In order to verify the validity of theoretical results, finite-element simulation method was employed to our study and we adopted periodic structure as the finite-element simulation model and aluminium alloy as the base material. The results of theory and the simulation have good agreements, and we found that its effective elastic modulus E x is mainly depending on its height h and thickness t while E y is mainly depending on its radius r and thickness t . And the thickness t may bring about deviation between theory and the simulation when it increases. The Poisson’s ratio of this material was also investigated through finite-element simulation method and different values of structure parameters were selected. Among these structure parameters, when h =35 mm, r ³ 21 mm and h =40 mm, r ³ 24 mm or h =45 mm, r ³ 26 mm, negative Poisson’s ratio can be obtained. The results indicate that the composite structure based on circular honeycomb core units can achieve negative Poisson’s ratio, which can be controlled by structure parameters. The excellent mechanical performance of light-weight and its negative Poisson’s ratio make circular honeycomb core a promising candidate as engineering material. And our study may pave a useful path to mechanical metamaterials with negative Poisson’s ratio.

Grating-Coupled Waveguide Cloaking

Based on the concept of a grating-coupled waveguide (GCW), a new strategy for realizing EM cloaking is presented. Using metallic grating, incident waves are firstly coupled into the effective waveguide and then decoupled into free space behind, enabling EM waves to pass around the obstacle. Phase compensation in the waveguide keeps the wave-front shape behind the obstacle unchanged. Circular, rectangular and triangular cloaks are presented to verify the robustness of the GCW cloaking. Electric field animations and radar cross section (RCS) comparisons convincingly demonstrate the cloaking effect.