Bandwidth-enhanced and Wide-angle-of-incidence Metamaterial Absorber using a Hybrid Unit Cell

Abstract

In this paper, a bandwidth-enhanced and wide-angle-of-incidence metamaterial absorber is proposed using a hybrid unit cell. Owing to symmetric unit cells, high absorptivity is maintained for all polarization angles. A circular-sector unit cell enables high absorptivity under the oblique incidence of both transverse electric (TE) and transverse magnetic (TM) modes. To enhance the bandwidth, we introduced a hybrid unit cell comprising four circular sectors. Two sectors resonate at 10.38 GHz, and two resonate at 10.55 GHz. Since the two absorption frequencies are near each other, the bandwidth increases. The proposed idea is demonstrated with both full-wave simulations and measurements. The simulated absorptivity exceeds 91% around 10.45 GHz at an angle of incidence up to 70° in both TM and TE polarizations. The measured absorptivity at 10.45 GHz is close to 96.5% for all polarization angles under normal incidence. As the angle of incidence changes from 0° to 70°, the measured absorptivity at 10.45 GHz remains above 90% in the TE mode and higher than 94% in the TM mode. Under an oblique incidence, the measured 90% absorption bandwidth is 1.95% from 10.1–10.2 GHz and 10.4–10.5 GHz up to 70° at the TE mode, and 3.39% from 10.15–10.5 GHz up to 70° at the TM mode.

Recent progress in angle-insensitive narrowband and broadband metamaterial absorbers

“…A few bandwidth-enhanced MM absorbers have been presented based on the technique above; however, most of these structures exhibit poor angular responses under oblique incidence. Because the circular sector-based geometry has resulted in an improved absorption response at higher incident angles, Nguyen and Lim have implemented the concept in achieving a bandwidth-enhanced absorber with angle insensitivity [51]. The proposed geometry comprises a periodic arrangement of four circular sector metallic patches imprinted on a grounded dielectric substrate, as shown in Figure 8a.…”

“…(b) Simulated absorptivity of the proposed structure along with its individual counterparts under normal incidence. Simulated absorptivity of the proposed structure at different incident angles under (c) TE polarization and (d) TM polarization[51].…”

Enhancing Absorption Bandwidth through Vertically Oriented Metamaterials

“…Additionally, the field profile near the point of highest concentration is noticeably altered due to the presence of the other resonator, further demonstrating the intra-cell coupling between them. The performance of metamaterials as a function of the incidence angle of the source, θ, is also of great interest [3,39,[49][50][51]. In Figure 6, spectral absorption is plotted as θ is swept from 0 • to 70 • .…”

Experimental verification of multi-band metamaterial absorber with double structured layers

“…Electromagnetic (EM) metamaterials (MMs) are artificial structures consisting of periodic array, which can demonstrate the unique physical phenomena when EM wave interact with the matters, and these unique physical phenomena is usually not existed in natural materials, For example, EM cloaks [1], perfect lens [2], energy harvesting [3,4], perfect absorbers [5][6][7][8][9][10][11][12][13] et al Since the first perfect MM-based absorber (MMA) was designed and fabricated [5], MMAs have increasingly attract researchers due to their various applications including RCS reduction, sensors and wireless energy transfer [14][15][16]. In the last decades, researchers have introduced various absorbers working on different frequency band, ranging from radio waves to optical light [17][18][19][20][21][22][23][24][25]. In the meantime, the bandwidth of the MMAs has gradually expanded from the single band, multiband to broadband, and even to the ultra-broadband.…”