Recent progress in angle-insensitive narrowband and broadband metamaterial absorbers

Abstract

Recent progress in angle-insensitive narrowband and broadband metamaterial absorbers is presented herein. Initially, a few narrowband structures are described along with their absorption mechanisms. A bandwidth-enhanced absorber, conceptually derived from the existing narrowband geometry, is also discussed. Finally, several broadband absorbers having wide absorption bandwidths across different microwave frequency ranges are illustrated. The reported structures are primarily designed to exhibit high angularly stable responses suitable for practical applications. Furthermore, their geometries are fourfold symmetric, thereby displaying polarization-independent characteristics. Experimental verifications of the designed absorbers have been confirmed under normal and oblique incidences. The angle insensitivity, polarization independence, flexible absorption bandwidths (from narrowband to broadband), and commercial feasibility of the reported structures might establish them as potential candidates for manifold absorber applications.

Multimode‐Assisted Broadband Impedance‐Gradient Thin Metamaterial Absorber

“…To solve the earlier issues, researchers have developed several strategies to achieve absorbers with multiband, broadband, wide‐angle, polarization‐insensitive, and even tunable characteristics. [ 25–36 ] For example, fractal structure was involved in a triple‐band absorber design, leading to multiple local resonant circuits and thus contributing to near‐unity absorption for a wide range of incident angles under dual‐polarization states. [ 31 ]…”

“…To solve the earlier issues, researchers have developed several strategies to achieve absorbers with multiband, broadband, wide-angle, polarization-insensitive, and even tunable characteristics. [25][26][27][28][29][30][31][32][33][34][35][36] For example, fractal structure was involved in a tripleband absorber design, leading to multiple local resonant circuits and thus contributing to near-unity absorption for a wide range of incident angles under dual-polarization states. [31] To date, several approaches have been proposed to widen the operating bandwidth, including creating multiple resonances by introducing planar/vertical inclusions, [32][33][34][35][36] and lumped elements such as resistances, capacitances, and diodes.…”

Metamaterial Microwave Absorber (MMA) for Electromagnetic Interference (EMI) Shielding in X-Band

“…[17,18] Amongst these, wide angle metamaterial absorbers are most difficult to realize, particularly for the thin structures and they have been generally found to have maximum absorption for orthogonal incidence. [19] Increasing the angle of incidence has been seen to reduce the absorption characteristics considerably in most designs. [20,21,22,23,24,20,25] The flexibility in realizing metamaterial absorbers for various range of frequencies/wavelength, in the microwave region, in which most of the radars operate, make them suitable candidate for designing and fabricating them to provide stealth to military targets against radars or in general as EMI shields.…”

Triple Band Wide Angle Polarization Insensitive Metamaterial Absorber

“…Metamaterial absorbers are preferred because they are superior to other absorbers in angular and polarization stability characteristics. ( Ghosh et al, 2019) First, the metamaterial based microwave absorbers used by Landy and friends were later applied for many microwave bandwidths (Landy et al, 2008). These studies vary according to polarization sensitivity of the transmitted waves (for TE and TM mode), its performance according to the oblique incidence, the band or bands it operates on, and the thickness of the metamaterial absorber according to the wavelength (Huang and Chen, 2011;Tao et al, 2008;Wang et al, 2016;Wang et al, 2020).…”