This letter presents a miniaturized conformal dual-band mm-wave frequency selective surface (FSS) for fifth-generation (5G) electromagnetic interference (EMI) shielding applications. Two back-to-back resonators are separated with a 0.254 mm thin dielectric substrate. The proposed FSS exhibits two wide stopbands (S21<-10 dB) in the mm-wave 5G frequency spectrum. The stopband bandwidths (BW) are 42.8% at 28 GHz and 24.2% at 38 GHz. The periodicity of the unit cell is 0.26 λ ₀ , where λ ₀ is the wavelength of the lower stopband. The key features of the proposed FSS include a miniaturized unit cell structure for 28 GHz and 38 GHz frequency bands with a high oblique incident angle (OIA) stable filter behavior up to 60°. The proposed FSS also features polarization insensitivity and conformality. The simulated and measured results show good agreement for EMI shielding applications.

This letter presents a conformal, polarization insensitive high angular incident angle (AIA) stable broadband bandstop mm-wave frequency selective surface (FSS) for 5G (n258, n257 n260, and n261) band electromagnetic interference (EMI) shielding application. Coupled resonators are designed on the back-to-back side of a thin dielectric substrate to achieve broad bandstop features. The top fractal resonator realizes the lower stopband (S21<-10 dB) and makes the FSS unit cell size of 0.24 λₒ, where λₒ is the lower stopband frequency. The FSS geometry offers a -10 dB transmission coefficient (S21) within the range of 23.9645.92 GHz, resulting in a percentage bandwidth (%BW) of 62.85%, effectively covering the desired 5G band. The polarization insensitivity and high AIA stability up to 60° are achieved by symmetric rotational geometry of the resonators and compact unit cell size, respectively. In addition, the thin profile of the FSS makes it suitable for conformal applications. To verify the proposed FSS, a prototype is fabricated and measured considering normal and conformal conditions. The simulated and measured results are found consistent. Therefore, the proposed FSS has the merits of EMI shielding application at 5G mm-wave applications.

The development of metamaterial absorbers has become attractive for various fields of application, such as sensing, detectors, wireless communication, antenna design, emitters, spatial light modulators, etc. Multiband absorbers with polarization insensitivity have drawn significant attention in microwave absorption and sensing research. In this paper, we propose a quad-band polarization-insensitive metamaterial absorber (MMA) for Ku- and K-band applications. The proposed patch comprises two square split-ring resonators (SSRR), four microstrip lines, and an inner Jerusalem cross to generate four corresponding resonances at 12.62 GHz,14.12 GHz, 17.53 GHz, and 19.91 GHz with 97%, 99.51%, 99%, and 99.5% absorption, respectively. The complex values of permittivity, permeability, refractive index, and impedance of MMA were extracted and discussed. The absorption mechanism of the designed MMA was explored by impedance matching, equivalent circuit model, as well as magnetic field and electric field analysis. The overall patch has a rotational-symmetrical structure, which plays a crucial role in acquiring the polarization-insensitive property. The design also shows stable absorption for both transverse electric (TE) and transverse magnetic (TM) modes. Its near-unity absorption and excellent sensing performance make it a potential candidate for sensing applications.

This article presents numerical analysis of an ultrathin concentric hexagonal ring resonator (CHRR) metamaterial absorber (MMA) for ultrawideband visible and infrared optical window applications. The proposed MMA exhibits an absorption of above 90% from 380 to 2500 nm and an average absorbance of 96.64% at entire operational bandwidth with a compact unit cell size of 66 × 66 nm². The designed MMA shows maximum absorption of 99% at 618 nm. The absorption bandwidth of the MMA covers the entire visible and infrared optical windows. The nickel material has been used to design the top and bottom layer of MMA, where aluminium nitride (AlN) has been used as the substrate. The designed hexagonal MMA shows polarization-independent properties due to the symmetry of the design and a stable absorption label is also achieved for oblique incident angles up to 70 °C. The absorption property of hexagonal ring resonator MMA has been analyzed by design evaluation, parametric and various material investigations. The metamaterial property, surface current allocation, magnetic field and electric field have also been analyzed to explore the absorption properties. The proposed MMA has promising prospects in numerous applications like infrared detection, solar cells, gas detection sensors, imaging, etc.

An oblique angle and polarization insensitive metamaterial absorber (MA) are highly desired for the visible and infrared optical applications like, wave energy harvesting, optical filters, and detecting thermal leaks and electrical defects. In this paper, a multi-layered MA consisting of two layers of tungsten resonators on a silicon dioxide substrate, coated with additional SiO₂ materials is investigated. The unit cell size of the MA is 0.5λ × 0.5λ × 0.8λ, at the lowest wavelength. The proposed MA offers an average absorption of 92% from 400 nm to 2400 nm with stable oblique incident angles up to 45°. The structure also achieves polarization insensitivity at the entire visible and near-infrared spectrum. Moreover, the MA is found highly compatible for solar absorber applications with high y A_AM1.5. The structure is also compatible for filter application in optical communication system by modifying the plasmonic nano structure. The modified structure can block the wavelengths of the visible band (450 nm to 800 nm) and transmit optical communication bands (800 to 1675 nm). These versatile absorption and filtering performance make the proposed design highly potential for solar energy harvesting, photodetection, thermal imaging, photo-trapping, and optical communications applications.

This article proposes a square split-ring resonator (SSRR) metamaterial absorber (MMA) for sub-6 GHz application. The unit cell of the MMA was designed and fabricated on commercially available low-cost FR-4 substrate material with a dielectric constant o 4.3. The higher effective medium ratio (EMR) of the designed unit cell shows the compactness of the MMA. The dimension of the unit cell is 9.5 × 9.5 × 1.6 mm³, which consists of two split rings and two arms with outer SSRR. The proposed MMA operates at 2.5 GHz, 4.9 GHz, and 6 GHz frequency bands with a 90% absorption peak and shows a single negative metamaterial property. The E-field, H-field, and surface current are also explored in support of absorption analysis. Moreover, the equivalent circuit model of the proposed MMA is modelled and simulated to validate the resonance behavior of the MMA structure. Finally, the proposed MMA can be used for the specific frequency bands of 5G applications such as signal absorption, crowdsensing, SAR reduction, etc.