Abstract
We proposed an ultra-thin polarization-insensitive metamaterial absorber (MMA) for ultra-wideband and wide incident angle operation. The MMA is composed of double-layer symmetric split rings (SSRs) connected with two orthogonally-arranged bars and the ground metallic plane separated by two identical substrates. Multiple metallic layers and scalabilities are employed to provide broadband absorptivity based on the cooperated mechanisms of the Ohmic loss and the Fabry-Perot interference. To further broaden the absorption bandwidth, four lumped resistors are loaded with the SSRs on the top metallic layer. By this means, an ultra-wideband absorbance is achieved nearly in 4~22 GHz, two gentle slope belts with absorptivity over 60% and 80% in 4~12 GHz and 12~22 GHz, respectively. The whole structure is with an ultrathin thickness of 2.4 mm, which is 0.032λlow and 0.176λhigh corresponds to the lowest and highest absorption frequency separately. Meanwhile, the symmetric structure enables the MMA of satisfactory stability for polarization and wide incident angles. Numerical and experimental results prove the capability of the proposed MMA for ultra-wideband absorbance.
Highlights
Electromagnetic (EM) metamaterials (MTMs), consisting of a periodic array of sub-wavelength resonators[1,2,3,4], have been extensively applied for EM compatibility and military applications
The four-fold symmetric structure makes the proposed metamaterial absorber (MMA) insensitive to polarization and incident angles, which provides a good candidate for EM stealth application
The basic unite cell of the proposed MMA consists of two stacked substrates with same metallic patterns imprinted on top surface of them, while the whole structure is backed by a continuous metallic surface
Summary
Electromagnetic (EM) metamaterials (MTMs), consisting of a periodic array of sub-wavelength resonators[1,2,3,4], have been extensively applied for EM compatibility and military applications. A synthesis approach to design an ultra-thin MMA integrated with wide incident angle, polarization insensitivity and broadband application is urgently needed. A double-layered polarization-independent wide-angle incidence MMA capable of ultra-wideband operation is proposed. To further improve the absorption performance, four lumped resistors are added to the gaps between the SSRs on the top metallic surface. In this way, an ultra-wideband absorbance with two gentle slope belts absorptivity over 60% and 80% are respectively achieved in 4~12 GHz and 12~22 GHz through synergetic effects of the Ohmic loss and Fabry-Perot interference. The four-fold symmetric structure makes the proposed MMA insensitive to polarization and incident angles, which provides a good candidate for EM stealth application
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