Wide Absorption Bandwidth Research Articles

From intrinsic magnetic-dielectric double loss to circular truncated cone array structural absorber: Dual strategies for ultra-broadband microwave absorption performances

Electromagnetic absorbers with wide effective absorption bandwidth are urgently sought for the cutting-edge electronic application. However, constrained by Kramers-Kronig relationship, expanding effective absorption bandwidth remains a huge challenge for traditional magnetic-dielectric double loss absorbers. In this work, dual strategies are proposed to prepare circular truncated cone array structural absorber for achieving ultra-broadband microwave absorption. Magnetic-dielectric loss components is fabricated with HNO3-oxided FeSiAl flakes/multi-wall carbon nanotubes composites for manipulating permittivity and permeability, which can realize effective absorption bandwidth of 4.0 GHz and optimal reflection loss of −45.49 dB with thickness of 1.3 mm. Sub-wavelength effect and structural design are applied for circular truncated cone array to reach broadband absorption via quarter-wave cancellation, multiple resonance at different thickness and coupling effect of structure and loss composites. The experimental results are in good agreement with the simulation and effective absorption bandwidth of 35 GHz in 5–40 GHz and minimum reflectivity of −38.25 dB at 10.26 GHz are realized, which demonstrates the effectiveness of microscale component and macroscopic structural design. This work proposes a rational route for designing high-efficiency microwave absorbers with both strong and ultra-broadband features.

Ultra-broadband composite terahertz absorber prediction based on K-nearest neighbor

Broadband Terahertz (THz) absorbers with characteristics of thin thickness, wide absorption bandwidth, and tunability can play a significant role in the field of electromagnetic (EM) wave shielding. However, when designing absorbers, it is necessary to analyze a large number of variable structural parameters to obtain the desired broadband absorption spectrum. Therefore, it is difficult to obtain the optimal structure efficiently and accurately by artificially designing the broadband absorbers because a large amount of structural parameter optimization work is required. This study uses the K-nearest neighbor (KNN) algorithm to predict the design of composite multilayer terahertz absorber. The prediction obtained an ultra-large effective absorption bandwidth of 5.493 THz, with an absolute percentage error (APE) of only 0.69%. In addition, the proposed absorber has functions such as polarization insensitivity, stable performance for large incident angles, and absorption intensity tunability. This study will provide a new approach for the structure design of ultra-broadband terahertz absorbers in the future.

Polysilazane hybrid phenolic resin ceramic aerogels with excellent electromagnetic wave absorption performance

AbstractAlthough various aerogels with electromagnetic wave (EMW) absorbing properties have been extensively explored, the development of aerogels with excellent wave absorption performance, low density, and great heat resistance has still met profound challenges. Herein, polysilazane hybrid phenolic resin aerogels (PRVS aerogels) were prepared using the vinyl addition reaction of polysilazane and cross‐linking reaction between polysilazane and phenolic resin. A SiOCN ceramic aerogel with multistage pore structure was prepared via a simple and quick freeze‐drying method and polymer‐derived ceramic (PDC) methods. The SiOCN ceramic aerogels exhibited low density (0.15–0.27 g/cm3), good heat‐shielding (thermal conductivity in the range of 0.03–0.04 W/(m·K)), and excellent wave absorption performance (i.e., RL was about –31.6 dB@16.48 GHz and EAB was 3.85 GHz when the thickness of the ceramic aerogel was 1.2 mm). Hence, the ceramic aerogel absorbing materials could meet the requirements of “wide absorption bandwidth, strong reflection loss, lightweight and thi thickness”. Moreover, the mechanism of low weight, heat insulation, and wave absorption properties of the aerogels were also investigated. We believe this work is of great significance in ceramic aerogels prepared by traditional polymers, which may provide new opportunities for new ceramic aerogels with applications ranging from EMW absorption to aerospace and information technology.

Dually inner-porous composites with Co@C prismatic rods anchored into graphene aerogel toward superior electromagnetic wave absorbing materials

For electromagnetic wave absorbing materials, integration of excellent electromagnetic wave absorbing property in view of strong electromagnetic wave absorbing intensity and wide effective absorption bandwidth with a very low usage, and a ultralight weight into one material is still challenging. Herein, composites of Co@C@GA (CCGA: CCGA-1, CCGA-2, CCGA-3 and CCGA-4) with a dually three-dimensional (3D) and porous structure were obtained through introducing a prismatic rod shaped Co@C prepared by calcining Co-MOF-74–3D graphene aerogel (GA). At a loading of only 12 wt%, all the CCGA with a wide weight ratio of graphene oxide to Co@C (2:1, 4:3, 1:1 and 4:5) exhibit excellent electromagnetic wave absorption properties. A minimum reflection loss (RLmin) of − 70.28 dB at 12.28 GHz with the thickness of 2.913 mm for CCGA-3 and the maximum effective absorption bandwidth (EAB) of 7.12 GHz at a thickness of 2.520 mm for CCGA-4 are achieved. The low filling ratio, the high RLmin intensity, the wide EAB and the compatibility of the two components in a broad compositional range for losing electromagnetic waves are impressive. Co@C with inner-porous and prismatic rod bundles like unique morphology is confirmed to be very important and can endow CCGA with greatly enlarged interface, enhanced conductivity and proper magnetic property, leading to the effective tuning of electromagnetic property and impedance matching condition.

Construction of one-dimensional hierarchical MoS2/Ni3S2 composites with enhanced interfacial polarization and improved wideband microwave absorption

The construction of one-dimensional (1D) sulfides has attracted extensive attention for improving microwave absorption (MA) performance owing to the anisotropic conductive networks. However, the synthesis of conductive 1D hierarchical materials with unique interfacial polarization and excellent MA properties remains challenging. In this study, cable-like MoS2/Ni3S2 was synthesized by a one-step hydrothermal strategy. The complex permittivity of the binary composites could be improved by tuning the thickness of the MoS2 coating. Importantly, the construction of heterogeneous contacts by MoS2 and Ni3S2 contributed to enhanced polarization loss, and the charge distribution was validated by electron holography. The wide efficient absorption bandwidth can reach above 4.8 GHz at a thin thickness. These new discoveries shed light on novel structures for 1D sulfide materials and the design of functional core-shell composites for microwave absorption.

Multifunctional ultralight magnetic CNFs/MXene/Fe3O4 nanodiscs aerogel with superior electromagnetic wave absorption performance

The design of innovative microstructures and the implementation of an appropriate multi-component strategy remain challenging in the development of advanced electromagnetic wave (EMW) absorbing materials. Achieving strong absorption and a wide effective absorption bandwidth while maintaining a thin sample thickness and low filling level is particularly demanding. Herein, a three-dimensional (3D) dielectric cellulose nanofiber (CNF)/Ti3C2Tx MXene carbon aerogel, incorporating magnetic Fe3O4 nanodiscs (NDs), was fabricated using a directional-freezing technique followed by reduction. Surprisingly, the reduction process activates the multifunctional application of aerogel with better elasticity and greatly improved electromagnetic properties, killing two birds with one stone. The structured cellular arrangement and the presence of diverse dielectric/magnetic interfaces contribute to the exceptional absorption capabilities by facilitating optimal impedance matching, enabling multiple polarization modes, and fostering electric/magnetic coupling phenomena. The aerogel exhibits excellent microwave absorption properties, characterized by its ultra-lightweight (3 % of filling ratio and 4.65 mg cm−3 of density), ultra-thin (2.18 mm), ultra-wide frequency band (6.68 GHz) and strong absorption (-56.8 dB). Additionally, the aerogel provides attractive functions such as thermal insulation and great mechanical properties (100 % recovery after 1000 cycles under 50 % strain). This study lays the groundwork for the advancement of microwave-absorbing materials, showcasing their vast potential for multifaceted applications.

Advanced multifunctional IGBT packing materials with enhanced thermal conductivity and electromagnetic wave absorption properties

Insulated-Gate Bipolar Transistors (IGBT) face limitations in high-frequency electronic applications due to heat accumulation and electromagnetic interference issues. To address these challenges, it is crucial to develop packing materials with excellent electromagnetic interference immunity and heat dissipation properties. In this research, a novel epoxy-based packing material (MDCF@C-ZrO2/EP) with high electromagnetic wave absorption and exceptional thermal transport properties was produced by employing a unique three-dimensional carbon structure-induced nanomaterial dispersion strategy. In particular, the three-dimensional MDCF structure effectively prevents packing agglomeration and fosters the formation of an abundant hetero-interface between MDCF and C-ZrO2, leading to improved impedance matching and enhanced electromagnetic wave dissipation capabilities. Remarkably, even at a mere 5 wt% filling level, the material demonstrates an impressive reflection loss value of −58.92 dB and a wide effective absorption bandwidth of 6.68 GHz, effectively covering the entire Ku-band. Additionally, the 3D MDCF@C-ZrO2 significantly enhances the phonon transport path and elevates the thermal conductivity of pure epoxy resin by an impressive ∼ 150%. As a result, this innovative research holds tremendous potential in enabling the application of IGBTs in high-power and high-frequency electronic components, while also contributing to the advancement of next-generation wireless communications and smart devices.

Graphene-like structure of bio-carbon with CoFe Prussian blue derivative composites for enhanced microwave absorption

Traditional carbon materials such as graphene are often applied in the field of electromagnetic wave (EMW) absorption but they have unbalanced impedance matching and high conductivity. Bio-carbon with graphene-like structure derived from apples has many advantages over graphene: it can be prepared in large quantities and the abundant heteroatoms present in the lattice can provide many polarization phenomena. Herein, Prussian blue analogue (PBA) as a source of magnetic component was combined with bio-carbon or reduced graphene oxide (rGO) to study the EMW absorption properties. The fabricated BC/CFC-12-7 displayed performance with a minimum reflection loss (RLmin) of −72.57 dB and a wide effective absorption bandwidth (EAB) of 5.25 GHz with an ultra-thin and nearly equal matching thickness at 1.61 mm. The results show that the good EMW absorption property of bio-carbon composites comes from good conduction loss, large relaxation polarization loss especially from pyridinic-N, and better impedance matching. The optimized radar cross section is found to be –33.55 dB m2 in the far-field condition using CST. This work explored the advantages of bio-carbon as a novel EMW absorbing material compared with graphene and provided ideas for realizing high-performance EMW absorbing materials in the future.

Improvement of the wave-absorbing properties of biomass-derived porous carbon through in-situ growth of SiC nanowires

SiC nanowire-modified biomass porous carbon materials (GF-SiC) have been developed by uniformly encapsulating SiC nanowires on the surface of porous carbon. GF-SiC exhibits remarkable wave absorption properties of a maximum reflection loss of -60.72 dB at a thickness of 1.74 mm and a wide effective absorption bandwidth (RL≤-10 dB) of 5.52 GHz at a thickness of 2.04 mm. The improved wave-absorbing performance of GF-SiC can be attributed to the three-dimensional porous structure, interfacial polarization effects caused by encapsulated SiC nanowires, and improved impedance matching. This work provides a new idea for the development of low-cost environmental electromagnetic wave absorbing materials.

Synthesis of NiCo2O4/CF composites with heterogeneous interfaces as excellent microwave absorbers

The absorbers with strong absorption capacity, wide effective absorption bandwidth (EAB), low filling, lightweight and thin thickness are the future development direction of electromagnetic wave (EMW) absorption field. NiCo2O4/CF composites were synthesized by simple hydrothermal method and calcination method in this study. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and vector network analyzer (VNA) were used to study the crystal structure, microstructure, surface chemical states and microwave absorption properties of the composites, respectively. Carbon fiber (CF) was used as nucleation carrier, and NiCo2O4 formed a dense conductive network on its surface in the shape of nanoneedles. In addition, there are abundant oxygen vacancies and heterogeneous interfaces on the surface of composite materials, which can cause dipole polarization and interface polarization and lead to more dissipation of electromagnetic wave energy. The minimum reflection loss (RLmin) of the NiCo2O4/CF composite is − 59.75 dB at the thickness of 2.01 mm. The maximum effective absorption bandwidth (RL < −10 dB) of the composite is 4.12 GHz (8.84–12.96 GHz) at the thickness of 2.18 mm. In the thickness range of 1.2–5 mm, the effective absorption frequency range of the composite material accounted for 80.78% of the measurement range (3.46–18 GHz), which covered the whole C-band, X-band and Ku-band, as well as a portion of the S-band. NiCo2O4/CF composites have the characteristics of strong absorption and wide absorption bandwidth due to the synergistic effect of dielectric loss and magnetic loss, good impedance matching characteristics and more Debye relaxation processes, which provide new inspiration for the structure and component design of lightweight microwave absorbing materials (MAMs).

A doping strategy to achieve synergistically tuned magnetic and dielectric properties in MoSe2 for broadband electromagnetic wave absorption

Advanced electromagnetic (EM) wave absorbing materials are essential to tackle the even-increasing EM interference and pollution. Conventional methods usually combine magnetic and dielectric components for optimized impedance matching and attenuation. It is, however, challenging to simultaneously tune magnetic and dielectric properties with one wane and the other wax by adjusting the ratio between the corresponding components. Here, simultaneous modulation of both magnetic and dielectric properties has been achieved via a doping strategy in MoSe2. On the one hand, significant room-temperature ferromagnetism could be induced through the generation and coupling of local magnetic moments of Mn2+. On the other hand, Mn doping also enhances the dielectric properties by promoting the formation of amorphous and 1T phase of doped MoSe2. The synergistic magnetic and dielectric effects give rise to optimal absorption performance with a minimum reflection loss (RLmin) of −54.57 dB and a wide effective absorption bandwidth (EAB) of 8.24 GHz at 2.00 mm. Such comprehensive performance surpasses the majority of the transition metal dichalcogenide (TMD)-based composites and is the best among all the single-component TMD absorbers. Consequently, the study sheds light on synergistic modulation of EM properties in single-component materials, providing prospective solutions in the design of magnetic and dielectric devices for EM wave absorption and other fields, such as sensing, information storing, and quantum computing.

Integrated Electromagnetic Device with On‐Off Heterointerface for Intelligent Switching Between Wave‐Absorption and Wave‐Transmission

AbstractIntelligent electromagnetic wave absorbers (IEAs) are in high demand due to their dynamic electromagnetic parameters that can adapt to the complex and volatile application environments of the current 5G era. Despite of this, there is currently a lack of research on the convertible electromagnetic wave (EMW) absorption mode (switching between wave‐absorption and wave‐transmission) and their integrated design with external physical stimulations, so that the electromagnetic device will realize intelligent switching in any conditions. In this work, a V2C‐VO2(M) heterostructure that exhibits a reversible metal–insulator transition at the temperature of 62 °C is fabricated via oxidation of MXene. The heterostructures demonstrate near wave‐transmission characteristics at 25 °C while wave‐absorption behavior with wide effective absorption bandwidth (4.04 GHz) at 70 °C. VO2(M) exhibits stronger intrinsic conductivity after phase transition, and the “on‐off” heterostructure between V2C and VO2 lead to poor/strong local conductive network and interfacial polarization in 25/70 °C, thus creating “quantized” dielectric loss. Furthermore, a multilayered electromagnetic functional device is developed to facilitate the absorber's phase transition temperature at a voltage of 17.5 V. This work presents promising opportunities of the V2C‐VO2(M) heterostructure for various applications, including radar stealth, portable stealth suits, signal regulation, and deicing.

Broadband metamaterial absorber for stealth applications at K-band

This paper focuses on the design and analysis of a polarization-insensitive wide-angle broadband metamaterial absorber for stealth applications at the K band. The unit cell of the metamaterial absorber is comprised of a symmetrically arranged ladder shape geometry made of copper metal, which is imprinted on a metal-backed FR-4 substrate. The structure shows more than 91% absorptivity ranging from 21.2 to 28.2 GHz for both transverse electric (TE) and transverse magnetic (TM) polarized waves under normal incidence. The topology is four-fold symmetric and yields polarization-insensitive responses for different angles of polarization under both TE and TM polarized waves. The structure is also investigated under oblique incidence where the 80% absorptivity holds up to 45° incident angles for both TE and TM waves. The absorption mechanism is explained with the help of top and bottom surface current distribution, induced electric field, and parametric analysis. To verify the resonances in the structure, characteristic mode, and equivalent circuit analysis have been carried out and presented. A prototype of the absorber has been fabricated and simulated results are validated with measured results. The novelty of the proposed absorber lies in its unique metallic pattern on a λ0/8 thin FR-4 substrate while showing the wide absorption bandwidth to normal and oblique incidence. All the above-mentioned attributes in a simple design make it commercially suitable for radar cross-section (RCS) reduction applications at the K band.

Multidimensional nanomaterials synergistic polyimide nanofiber/MXene/NiFe2O4 hybrid aerogel for high-performance microwave absorption

Microwave absorption materials are urgently demanded to control the increasing electromagnetic radiation pollution, but it remains a great challenge to achieve high-performance absorption through ingenious structure design and reasonable multicomponent strategy. Herein, a three-dimensional (3D) hybrid aerogel constructed from multidimensional nanomaterials was fabricated via freeze-drying method followed by heating treatment process. Therein, 2D Ti3C2Tx MXene nanosheets and 0D NiFe2O4 nanoparticles act as the electrical-magnetic skeleton of aerogel, while 1D polyimide nanofibers and polydimethylsiloxane as internal supporting parts and external crosslinker, respectively. The macroscopic interconnected porous structure coupled with the microscopic multiphase heterointerfaces are beneficial to forming the perfect impedance matching and superior dielectric/magnetic synergistic loss effects. Thus, the microwave absorption performance of this hybrid aerogel achieves thin thickness (1.5 mm), light weight (∼9.6 mg/cm3), wide effective absorption bandwidth (−6.24 GHz), and strong absorption (minimum reflection loss of −64.87 dB, 99.99996% microwave absorption) features. Besides, this aerogel also exhibits exceptional structural robustness and mechanical properties, as well as good hydrophobicity and thermal insulation characteristics, which ensure its stable and durable microwave absorption application in complex environments. This study effectively integrates multidimensional nanomaterials into a host–guest aerogel system, providing a valuable strategy for constructing high-performance microwave absorption materials.

Facile fabrication of ultra-light N-doped-rGO/g-C3N4 for broadband microwave absorption

“Thin thickness”, “lightweight”, “wide absorption bandwidth” and “strong absorption” are the new standards of contemporary science and technology for microwave absorption(MA) material. In this study, N-doped-rGO/g-C3N4 MA material was prepared for the first time by simple heat treatment, which the N atoms were doped into rGO and g-C3N4 was dispersed on the surface of N-doped-rGO, and its density is only 0.035 g/cm3. The impedance matching of the N-doped-rGO/g-C3N4 composite was well adjusted by decreasing the dielectric constant and attenuation constant due to the g-C3N4 semiconductor property and the graphite-like structure. Moreover, the distribution of g-C3N4 among N-doped-rGO sheets can produce more polarization effect and relaxation effect by increasing the lamellar spacing. Furthermore, the polarization loss of N-doped-rGO/g-C3N4 could be increased successfully by doping N atoms and g-C3N4. Ultimately, the MA property of N-doped-rGO/g-C3N4 composite was optimized significantly, with a loading of 5 wt%, the N-doped-rGO/g-C3N4 composite exhibited the RLmin of −49.59 dB and the effective absorption bandwidth could reach 4.56 GHz when the thickness was only 1.6 mm. The “thin thickness”, “lightweight”, “wide absorption bandwidth” and “strong absorption” of MA material are actually achieved by the N-doped-rGO/g-C3N4.

Kapok fibers-derived carbon microtubes as efficient electromagnetic wave absorption materials

The superior electromagnetic wave absorption materials have the characteristics of thin matching thickness, low density, wide absorption bandwidth and strong absorption intensity, which can effectively deal with electromagnetic pollution. With the further research, biomass-derived carbon has received great focus due to abundant biological reserves and unique natural structure. Herein, we put forward an excellent electromagnetic wave absorption material, carbon microtubes (CMTs) with a one-dimensional hollow tubular structure, which derived from kapok fibers (KFs) via a facile annealing method. The result shows that the effective absorption bandwidth (EAB) of CMTs is 6.78 GHz under 900 °C annealing conditions. Especially, the filling ratio is just 3 wt% and the matching thickness is 2.06 mm. The superior electromagnetic wave absorption properties of CMTs can be related to its microstructural characteristics. This one-dimensional tubular structure has a large specific surface area increasing the interaction area between the material and electromagnetic waves, while the hollow tube cavity can make the incident electromagnetic waves for multi-ply scattering and reflection strengthening the dissipation capability of the material. This work offers a convenient way to produce effective electromagnetic wave absorption materials with low cost and eco-friendly environment.

Concentration-dependent construction of raspberry-like SiO2 shell on spherical FeNi towards improved electromagnetic performance from kHz to GHz

Constructing resistive layer with novel structure holds great potential in upgrading electromagnetic properties of soft magnetic materials in a wide frequency range. In this work, FeNi@SiO2 composites with controllable core–shell structures, including 2D-type laminar shell and 3D-type raspberry-like shell, were fabricated by modified Stöber method. The structure of SiO2 shell depends highly on the concentration of tetraethyl orthosilicate (TEOS). In detail, a laminar shell can be formed at low TEOS concentration, owing to slow condensation. While at high TEOS concentration, heterogeneous growth on powder surface and homogeneous growth in solution of silica networks are significantly accelerated, resulting in the formation of the raspberry-like shell. Improved electromagnetic performance of FeNi@SiO2 cores at 2 MHz, including high resistivity, low eddy current loss, and low loss factor, should be ascribed to the unique raspberry-like shell structure. Meanwhile, raspberry-like shell also contributes to enhanced attenuation and acceptable impedance matching in GHz range. Consequently, a wide effective absorption bandwidth of 8.92 GHz can be achieved at a thin thickness of 1.85 mm. This work provides deep insights into the growth mechanism of different SiO2 shells and sheds new light on the design of high-performance soft magnetic composites working in different frequency bands.

Homogeneous-heterogeneous interfaces in 2D/2D CoAl/Co9S8/Ni3S4 heterostructures for electromagnetic wave absorption

Exploring electromagnetic wave (EMW) absorbers with ultrathin matching thickness (d ≤ 1.5 mm), strong reflection loss (RL ≤ -50 dB), and wide effective absorption bandwidth (EAB, RL ≤ -10 dB) is urgent and essential for reducing EMW radiation and interference. Herein, a 2D/2D CoAl/Co9S8/Ni3S4 heterostructure was constructured using simple hydrothermal and pyrolysis methods. 2D porous CoAl nanosheets and 2D Co9S8/Ni3S4 ultrathin nanosheets are assembled by small nanoparticle chains. Strikingly, the CoAl/Co9S8/Ni3S4 heterostructure exhibits remarkable EMW absorption performance with a RL value of −61.56 dB, a high EAB of 4 GHz, and an ultrathin matching thickness of 1.25 mm. Mechanism investigations reveal that the CoAl/Co9S8/Ni3S4 heterostructure delivers dual metal sulfides behavior, high specific surface area, strong interactions, rich defects (N doping), and abundant homogeneous and heterogeneous interfaces, which promote good impedance matching, dielectric loss (interface polarization, conductive loss, and dipole polarization), as well as magnetic loss (natural resonance, exchange resonance, and eddy current loss) characteristics. This work can provide insights into the mechanism of dual metal sulfides used as high-performance EMW absorbers and deepen our understanding of the design and application of 2D/2D heterostructures.

Construction of hollow and porous carbon Fiber/CoFe composites derived from strawberry petiole for enhanced microwave absorption

Biomass-derived materials have emerged as lightweight and high-efficiency carbon-based microwave absorber for their huge availability and multifarious microstructure. Herein, we synthesize a strawberry petiole derived carbon fiber (SCF) /magnetic CoFe composites (SCF/CoFe) via solvothermal reaction and calcination treatment. CoFe particles are densely and uniformly distributed on the surface of the uniform hollow and porous SCF. After adjusting the calcination temperature, SCF/CoFe sample with filler content of 15 wt% obtains a minimum reflection loss of −40.4 dB and a wide effective absorption bandwidth of 3.5 GHz at a thin thickness of only 2.0 mm. The hollow and porous structure and synergistic effect between conductive SCF and magnetic CoFe simultaneously contribute to the enhanced impedance matching and attenuation ability, which together result in the remarkable microwave absorption properties.

Design of switchable dual‐band frequency‐selective rasorber/absorber

AbstractThis article presents a novel design of a switchable dual‐band frequency‐selective rasorber/absorber, which is a double‐layered structure. At the top layer, two electric‐field‐coupled resonators with different size are utilized to achieve two transmission bands. At the bottom, to achieve low insertion loss, the frequency‐selective surface based on slots with different lengths resonates at the same frequency as the top layer. By controlling the bias voltage of PIN diodes, the structure can be switched between dual‐band rasorber/absorber mode. The operating principle is analyzed by an equivalent circuit model. When the diodes are in the OFF state, it shows two transmission bands at 2.86 GHz with 0.47 dB insertion loss and 3.61 GHz with 1.04 dB insertion loss. When the diodes are in the ON state, it exhibits a wide fractional absorption bandwidth of 90.1%. Meanwhile, the proposed dual‐band switchable structure is fabricated and measured. There is a good agreement between simulation and measurement.