Quad-band Metamaterial Absorber Research Articles

Double elliptical resonator based quad-band incident angle and polarization angle insensitive metamaterial absorber for wireless applications

In this article, a double elliptical split ring resonator-based quad band metamaterial absorber (MMA) is demonstrated for applications in the microwave range. The resonator is made up of four squares outside split rings and two elliptical split rings positioned in the middle of the structure. The resonating patch is placed over an FR-4 dielectric layer with a thickness of 1.6 mm. The unit cell has an electrical size of 0.103λ0 × 0.103λ0, where λ0 is the wavelength determined at 2.576 GHz. The MMA shows maximum absorption of 99.83% at 2.576 GHz, 99.98% at 5.648 GHz, 99.56% at 8.32 GHz, and 99.15% at 13.456 GHz with TE mode. For TM mode, at 2.576 GHz, 5.632 GHz, 8.304 GHz, and 13.44 GHz, corresponding absorptions are 99.21%, 99.67%, 99.5%, and 99%, respectively. The MMA is polarisation and incidence angle (0° to 90°) insensitivity for both TM and TE modes. The unit cell provides single negative characteristics including an EMR (effective medium ratio) of 9.71 and a Q factor (quality factor) over 25. The proposed MMA provides high harvesting efficiencies of 92.87%, 76.9%, 94.12%, and 90.97% for frequencies of 2.57 GHz, 5.64 GHz, 8.32 GHz, and 13.45 GHz, correspondingly. The equivalent circuit is modeled to understand the resonance behavior of the MMA and the circuit parameters are determined and validated using Advanced Design Systems (ADS) software. The performance of the MMA is examined using the prototype of the array of the unit cells in an experimental setup. The experimental outcome provides a close similarity with simulation outcomes indicating the good performance of the MMA. The metamaterial absorber's high performance makes it suitable for many applications, such as RF energy harvesting applications, image technologies, stealth technologies, and radar systems as well as minimizing electromagnetic interference in satellites.

An ultra-thin, polarization free wide-angle stable quad-band metamaterial absorber for applications in C, X, and Ku bands

This study proposes and examines an ultrathin, wide-angle stable and polarization-insensitive metamaterial absorber (MMA) with quad-band functionalities. The proposed MMA exhibits four absorption peaks of 95.67%, 99.16%, 95.97%, and 97.02% at 5.026 GHz, 8.582 GHz, 11.73 GHz, and 15.036 GHz, respectively. The corresponding full width at half maximum (FWHM) bandwidth observed from simulations of the proposed MMA is found to be 180 MHz, 360 MHz, 420 MHz, and 580 MHz. It has a thickness of 0.0134 λ0 and the dimension of the unit cell is 0.167 λ0 × 0.167 λ0 at 5.026 GHz. Moreover, it does not display any variations in absorption performance when polarization angle (ϕ) is changed, justifying its polarization insensitive behavior. When changing the incident angle (θ) in case of oblique incidence, the proposed MMA is able to maintain the absorptivity above 90% for transverse electric (TE) mode up to 30° and for transverse magnetic (TM) mode up to 60° at all four frequency, which demonstrates its angular stable characteristics. Analyses of the variation in structural parameter, complex permittivity, complex permeability, surface current density, absolute electric field, and normalized input impedance have also been carried out to authenticate the proposed MMA unit cell structure.

A Quad-Band and Polarization-Insensitive Metamaterial Absorber with a Low Profile Based on Graphene-Assembled Film.

A quad-band metamaterial absorber using a periodically arranged surface structure placed on an ultra-thin substrate is demonstrated in this paper. Its surface structure consists of a rectangular patch and four L-shaped structures distributed symmetrically. The surface structure is able to have strong electromagnetic interactions with incident microwaves, thereby generating four absorption peaks at different frequencies. With the aid of the near-field distributions and impedance matching analysis of the four absorption peaks, the physical mechanism of the quad-band absorption is revealed. The usage of graphene-assembled film (GAF) provides further optimization to increase the four absorption peaks and promotes the low-profile characteristic. In addition, the proposed design has good tolerance to the incident angle in vertical polarization. The proposed absorber in this paper has the potential for filtering, detection, imaging, and other communication applications.

Simple quad-band terahertz metamaterial absorber based on high-order plasmon resonance for sensing applications

We present a simple quad-band terahertz (THz) metamaterial absorber for perfect absorption. Unlike most reported absorbers, the proposed structure achieves perfect absorption based on high-order plasmon resonance, with the absorptivity of the first three peaks all >99.4 % . First, the resonance absorption mechanism of the absorber involving fundamental resonance mode and high-order resonance mode is analyzed in detail. Next, the sensing performance is also studied by changing the ambient refractive index, the numerical results show that the designed multiband metamaterial absorber is very sensitive to small changes in refractive index, and appears highly sensitive in its sensing performance. In particular, figure of merit of the last absorption peak reaches 26.6, which is far superior to most multiband metamaterial absorbers operating in the THz regime. The proposed simple structure not only greatly simplifies the fabrication, but also is insensitive to the polarization of incident waves. The results show that the quad-band metamaterial absorber has potential applications in sensing, imaging, detection, and other fields.

Quad band metamaterial absorber based on asymmetric circular split ring resonator for multiband microwave applications

This article presents a metamaterial based on a modified asymmetric circular split ring resonator for absorber applications in the microwave regime. This metamaterial absorber (MMA) exhibits four absorption peaks to cover C, X, and Ku band applications. The MMA unit cell is formed on a low-cost FR4 substrate with electrical dimensions of 0.106 λ0 × 0.106 λ0, for which wavelength, λ0 is calculated at 4.1 GHz. The resonator of the unit cell is structured with three concentric intercoupled circular split rings with dimensions modified to obtain maximum absorption peaks of 97.9%, 99.1%, 99.5%, and 99.95% at 4.1, 6.86, 11.3, and 13.45 GHz, respectively. Metamaterial and absorber properties are investigated in the analysis of the surface current, electric, and magnetic fields. The unit cell exhibits single negative metamaterial properties with an effective medium ratio (EMR) of 9.15 and quality factor (Q factor) greater than 20. Beyond that, the equivalent circuit of the MMA unit cell is modeled and validated by comparing S11 obtained from Advanced Design System (ADS) and CST software. The MMA array’s absorption properties are also examined in the simulations. Measured results of the unit cell and array correspond well with the result of simulation in terms of absorption at intended frequencies. Given its good EMR, superior quality factor, and high maximum absorption, the MMA can be a good candidate for a multiband absorber in microwave applications like sensing, detecting, notch filtering and to decrease the indirect reverberation and reflections caused by the metallic part of the radar and satellite antennas.

A New Compact Quad-Band Metamaterial Absorber Using Interlaced I/Square Resonators: Design, Fabrication, and Characterization

This paper presents the design and analysis of a new compact quad-band metamaterial absorber (MMA). The proposed structure is constructed as an array of 12 × 13 unit cells, each one is based on a combination of interlaced I/square resonators supporting four distinct resonant frequencies. The proposed metamaterial unit cell is printed on FR-4 substrate with thickness 1.5 mm and size 20 mm × 20 mm. The MMA structure exhibits four distinct absorption peaks at 2.248, 2.878, 4.3 and 5.872 GHz with absorption rates of 96, 93, 93, and 95 %, respectively, under normal incidence. This design achieves a negative permittivity and permeability that is applicable for S-band and C-band operating frequencies. The MMA unit cell structure has a 3-dB bandwidth of 78, 89, 144 and 202.6 MHz. The proposed structure has compactness of 0.15 λ0× 0.15 λ0 with thickness of 0.0112 λο, where λ0 is the free-space wavelength with respect to the lowest resonance frequency (2.248 GHz). The input impedance, surface currents and electric field distributions are shown to illustrate the mechanism of the structure. The design has been fabricated showing a good agreement between simulated and measured results. The proposed absorber structure can be used in different applications such as electro-magnetic protections, as well as military and medical applications. All simulation results are performed using the Computer Simulation Technology (CST), Microwave Studio 2018 software and Mathwork simulation tool MATLAB ver. 2011.

Comment on “Design of a Quad-Band Wide-Angle Microwave Metamaterial Absorber”

In recent days, we read a paper called “Design of a Quad-Band Wide-Angle Microwave Metamaterial Absorber”, which was written by Ren et al. In such report, Ren et al. proposed a quad-band wide-angle absorber based on a metallic hexagonal patch layer. The absorption peaks are located at 6.8 GHz, 8.24 GHz, 11.24 GHz, and 12.7 GHz, whose absorptivity values are 97.2%, 95.2%, 97.7%, and 98.5%, respectively. However, we verified that the results which were given by Ren et al. are wrong because they ignored the polarization conversion. The proposed quad-band metamaterial absorber (QBMA) is not an absorber.

A Compact Design of Multiband Terahertz Metamaterial Absorber with Frequency and Polarization Tunability

A new and simple design of quad-band metamaterial absorber for terahertz frequency has been proposed. The unit cell of the absorber is composed of a top metallic patch having H-shaped slot and a ground metallic plane, both separated by a dielectric layer. The proposed design is capable of providing four distinct absorption peaks over at 0.81, 1.98, 3.25, and 3.50 THz. Our design is a step ahead of the previously proposed terahertz absorbers for its simplistic design approach which removes the fabrication difficulty. Interestingly, rather placing multiple resonators in a single unit cell, we able to accommodate multiple orders of resonances in the proposed design using only a single metallic structure to achieve multiband absorbance. The sensing performance of the absorber in terms of surrounding index is also analyzed. Moreover, we have shown how the proposed structure can be easily converted into a frequency tunable absorber using a simple stub without changing the overall geometry of the absorber. This fast and easy frequency tunability feature is an additional advantage over the simple design of the structure. Also, we lead our work to its upgradation into a polarization tunable absorber where the absorption frequencies are controllable by the polarization of the incident light. The vibrant design of the proposed absorber is expected to find application in detection, imaging, radar cross-section (RCS) reduction, and sensing-related activities.

Quad-Band Terahertz Absorber Based on Dipolar Resonances of Metamaterial Resonator

A novel design of a quad-band metamaterial absorber, which consisted of only a metallic resonator on top of a dielectric spacing layer and a metallic board on the bottom, is presented in this paper. Four near-perfect resonance peaks are observed in this structure. The combination of four dipolar resonances in different sections of the resonator results in the quad-band absorption. The absorption performance, including the operating frequencies and number of the resonance peaks, of the metamaterial can be controlled by changing the parameters of the resonator. The quad-band absorption is very promising for highly integrated absorbing devices.

Wide‐angle quad‐band polarisation‐insensitive metamaterial absorber

Closed ring resonator (CRR)-based quad-band metamaterial absorber is presented. The unit cell of proposed absorber consists of four separate CRRs which are diagonally connected to square patches enclosed within an individual CRR. The structure is fabricated on 0.8 mm-thick FR4 substrate. Simulated peak absorptivities of 98.5, 97.7, 94.8, and 96% are obtained at 4.34, 6.68, 8.58, and 10.64 GHz, respectively. The measured and simulated absorption characteristics of the proposed absorber are in good agreement. The proposed absorber is wide angle and polarisation insensitive and has identical absorption characteristics for both transverse-electric and transverse-magnetic polarised radiations.

A bi-layered quad-band metamaterial absorber at terahertz frequencies

In this work, a quad-band metamaterial absorber is proposed and experimentally demonstrated at terahertz frequency using a bi-layer isotropic structure. The absorber is designed by distributing four metallic square loops with different lengths on two polyimide layers (PI). The backside of PI is covered by an opaque gold film to eliminate the transmission of terahertz waves. The proposed absorber exhibits almost unity absorptions at 0.51, 0.69, 1.05, and 1.34 THz under the normal illuminance. As the incident angle increases from 0° to 50°, the absorption intensities remain above 95%, and the absorption frequencies almost keep stable for both transverse-electric and transverse-magnetic polarizations. The absorption mechanism is interpreted by giving the electromagnetic field distributions at each absorption peak. Experimental results show good agreement with numerical simulations both in the frequency and strength of the four absorption peaks.