Gu Chao

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.

A Method of Analyzing Transmission Losses in Left-Handed Metamaterials

A method of analyzing transmission loss in left-handed metamaterials (LHMs) is proposed. As a demonstration of this method, transmission loss of LHMs composed of split-ring resonators (SRR) and conducting wires is studied. By means of retrieving and analyzing the effective constitutive parameters, different transmission losses as well as their origins are studied. The results show that the left-handed bandwidth is narrowed because of high loss caused by the non-zero high imaginary parts of the effective permeability and permittivity. In the effective left-handed band, the radiation loss is very low and can be neglected, and the transmission losses are the sum of the substrate loss and the ohmic loss. Moreover, when the dielectric loss tangent of the substrate is greater than 0.003, the substrate loss is higher than the ohmic loss.

Nonsingularity in two-dimensional cylindrical invisible cloaks

The method of designing electromagnetic invisible cloaks is usually based on the form-invariance of Maxwells equations in coordinate transformation. The exterior boundary of a cylindrical invisible cloak is unchanged and the interior boundary is extended from that of a point to that of a cylindrical region in coordination transformation. This transformation process makes perfect cloaks, but it causes singularity in the constitutive material parameters of cloaks. This singularity makes the cloaks impossible to realize in practice. In order to remove this singularity, this paper sets a small cylindrical region replacing a point in the space transformation. The cylindrical region is so small that it does not affect the invisibility effects, but it can remove the singularity for material parameters. Full wave simulations based on the finite element method were used to verify the designed cloaks.

Multi-window invisible cloaks

This paper reports that a general method of designing invisible cloaks is using variant constitutive material parameters to realize the space transformation. A hollow region can be hidden after this transformation. It was recently shown (Ma H, Qu S B, Xu Z and Wang J F 2009 Appl. Phys. Lett. 94 103501) that when the original point moves to the boundary of a cloak, the cloak can be designed to be open. Based on this theory, we propose multi-window invisible cloaks which can conceal a group of objects. Full wave simulations for invisible cloaks with regular and irregular shapes veried this method.