A polarization insensitive metamaterial absorber is proposed consisting of a dielectric layer sandwiched between two tilted parallel metallic strips and a ground plane. First, a new analytical model is introduced to predict the resonance frequency for square, rectangular and wire geometries which shows less relative errors in comparison with previously proposed models. Then, ultra wide bandwidth absorption covering the entire x-band and Ku-band restricting a 10-dB absorption bandwidth is achieved with a relative material thickness λ<sub>0</sub>/10 and a relative FWHM absorption bandwidth of 90% for normal incidence angle. The model also shows good absorption coefficients for oblique incident angles for both s- and p-polarizations. Three different resonance modes are observed, which led to such broadband absorption. Each resonance mode is investigated to determine its dependence on the scatterers and unit cell dimensions, which can help one to design a multiple band absorber. The electromagnetic field distributions of the scatterers are studied to explain the absorber mechanism. The results are compared to previous works showing remarkable improvement.
In this paper, a broadband, ultrathin metamaterial absorber (MA) using randomly distributed scatterers is presented. Each scattering element consists of two parallel strips. These elements can either be isolated or they may overlap with nearby elements. Three different randomly positioned structures are investigated for normal incident angle as well as oblique incident angles showing that these MAs can provide broadband absorption for all cases. The results presented here coincide with some previous works. Each structure obviously has different absorption spectrum and FWHM since the coupling between the randomly positioned scatterers is different in each case. The coupling between neighboring isolated and clustered scatterers form many resonating modes resulting in broadband absorption. The distribution of the electromagnetic fields are analyzed to obtain the physical behavior of the absorber. This shows that promising results can still be obtained for MAs when there is a significant tolerance distance between scatterers due to fabrication errors in micro and nanoscale metadevices.