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Optical and Electrical Characterization of Pure PMMA for Terahertz Wide-band Metamaterial Absorbers
摘要： The characteristics of relative permittivity and reflectance for poly (methyl methacrylate) (PMMA) films prepared by spin-coating were investigated and an excellent wideband terahertz (THz) metamaterial absorber (MA) had been fabricated by employing PMMA film as the dielectric layer. XRD and AFM indicated that all the PMMA films with thicknesses from 11 to 17 μm were amorphous and extremely smooth with roughness about 0.203 nm. Raman results demonstrated that vibration strength of the same covalent bonds tends to be consistent with an increase in film thickness. The dual beam laser interferometer (DBLI) was employed to study the influence of applied frequency and thickness on the relative permittivity, and the results exhibited dielectric constants increased from 2.88 to 4.04 with the thickness increasing from 9 to 14 μm. And the dielectric constants for PMMA films with a certain thickness (8 μm) gradually declined when the applied frequency increased from 100 to 105 Hz; besides, the dielectric constant in THz band was forecasted approximately 2.5. The terahertz time domain spectrometer (THz-TDS) results revealed that the THz reflectance was of gradual degradation from 80 to 58% at 3.2 THz, as the thickness increased from 11 to 17 μm. In addition, the UV-VIS spectrum showed that thickness had little effect on reflectance and transmittance in visible region, leading to the almost same Eg (energy gap) about 3.7 eV. At last, by employing PMMA film as the dielectric layer, a highly wideband metamaterial absorber with absorption > 80% from 4.1 to 7.4 THz was fabricated.
关键词： Terahertz,Metamaterial absorber,PMMA,Reflectance,Permittivity
更新于2025-09-10 09:29:36
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Wide band fractal-based perfect energy absorber and power harvester
摘要： In this article, a novel wide band polarization and incident angle independent meta-material absorber (MA) and energy harvesting applications which operates at C (4GHz-8 GHz) and X (8GHz-12 GHz) is proposed. The unit-cell of the proposed structure based on fractal circle loop. Four lumped resistors are mounted the structure to obtain a broad band absorption characteristics. Resistors increase the absorption characteristic of proposed MA significantly at mentioned frequency ranges. In addition, under favor of the resistors proposed MA can convert absorbed energy from incident wave to appearing power.
关键词： metamaterial,wide band absorber,energy harvesting,fractal metamaterial absorber
更新于2025-09-09 09:28:46
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Polarization controllable and wide-angle frequency tunable metamaterial absorber
摘要： In this paper, the design, fabrication, and measurement of a high-performance metamaterial absorber (MMA) have been presented. The three major concerns of MMA’s are narrow bandwidth, angle sensitivity, and uncontrollable polarization. By smartly controlling the proposed design, the solutions to these three concerns of MMA are given in this paper. By integrating the design with varactor diodes, we make the MMA tunable to wide frequency ranges. Frequency tunability ranges from 4.2 to 7 GHz. By using circular sectors in the resonator, wide incident angle insensitivity has been achieved. The presented MMA exhibits more than 80% absorptivity up to 70° incident angles. With the proposed design, it is possible to control either TM or TE polarization resonant frequency by ?xing the resonant frequency of other polarization. Also, a biasing technique which is simple and effective to control both TM and TE resonant frequencies simultaneously is given in this paper. Moreover, all these advantages have been achieved by using a single layer low cost FR4 material having thickness 0.6 mm as a substrate. By using a standard parameter retrieval technique, the real and imaginary parts of both permittivity and permeability of the presented MMA are calculated. It is expected that the presented work improves the state-of-the-art in the smart metamaterial absorber domain.
关键词： varactor diodes,metamaterial absorber,polarization controllable,wide-angle frequency tunable,FR4 material
更新于2025-09-09 09:28:46
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A Polarization-Dependent Frequency-Selective Metamaterial Absorber with Multiple Absorption Peaks
摘要： A polarization-dependent, frequency-selective metamaterial (MM) absorber based on a single-layer patterned resonant structure intended for F frequency band is proposed. The design, fabrication, and measurement for the proposed absorber are presented. The absorber’s absorption properties at resonant frequencies have unique characteristics of a single-band, dual-band, or triple-band absorption for different polarization of the incident wave. The calculated surface current distributions and power loss distribution provide further understanding of physical mechanism of resonance absorption. Moreover, a high absorption for a wide range of TE-polarized oblique incidence was achieved. Hence, the MM structure realized on a highly flexible polyimide film, making the absorber suitable for conformal geometry applications. The proposed absorber has great potential in the development of polarization detectors and polarizers.
关键词： metamaterial,absorber,multi-band absorption,polarization-dependent
更新于2025-09-09 09:28:46
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SU-8 based planar metamaterials with fourfold symmetry as selective terahertz absorbers
摘要： We report on the absorption properties of polarization-insensitive transmissive and reflective metamaterial absorbers based on two planar aluminium periodic structures and SU-8 epoxy resist. These absorbers were investigated using numerical simulation and experimental methods in the terahertz range (below 2 THz). SU-8 is a very promising organic material for dielectric layers in planar metamaterials, because its application simplifies the process of fabricating these structures and significantly reduces the fabrication time. The experimental absorption of the metamaterial absorbers has narrowband characteristics that were consistent with the numerical simulations. Power flow analysis in the transmissive metamaterial unit cell shows that the absorption in the terahertz range occurs primarily in the SU-8 layer of the absorber.
关键词： Terahertz spectroscopy,Reflectance,Transmittance,Terahertz metamaterial absorber
更新于2025-09-09 09:28:46
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A NOVEL DUAL-BAND METAMATERIAL ABSORBER AND ITS APPLICATION FOR MICROSTRIP ANTENNA
摘要： In this letter, a novel dual-band metamaterial absorber is presented and analyzed. The absorber is composed of four patches on the top of a thin grounded dielectric substrate which can absorb incident wave at two di?erent frequency bands e?ectively. Then the absorber is loaded on the dual-band microstrip antenna, whose working frequency bands are overlapped with that of the absorber, to reduce the in-band RCS (Radar Cross Section) of antenna. The prototype is simulated, manufactured and measured. Simulated results show that the absorption of the absorber is as high as 98.6% at 4.29 GHz and 99.8% at 6.49 GHz. As to the dual-band antenna loaded with the proposed absorber, its radiation performance is unchanged while the RCS has declined by 8.59 dB at 4.29 GHz and 9.9 dB at 6.49 GHz respectively. There is a good agreement between simulated and measured results, which veri?es that this absorber can be used for in-band RCS reduction of dual-band antenna so as to improve its in-band stealth performance.
关键词： RCS reduction,dual-band metamaterial absorber,microstrip antenna,stealth performance
更新于2025-09-09 09:28:46
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POLARIZATION-INSENSITIVE TRIPLE-BAND MICROWAVE METAMATERIAL ABSORBER BASED ON ROTATED SQUARE RINGS
摘要： An ultra-thin triple-band metamaterial absorber (MA) is proposed in the microwave region, which is composed of a periodic array of three rotated square rings (RSRs) and a continuous metal ?lm separated by only 1 mm dielectric substrate. The fabricated MA exhibits three experimental absorption peaks at 4.88 GHz, 7.88 GHz, and 11.32 GHz with the corresponding absorption rates of 98.8%, 96.5%, and 95.9%, which shows an excellent agreement with the simulated results. The triple-band MA is polarization-insensitive at the normal incidence. Finally, the multi-re?ection interference theory is introduced to interpretate the absorption mechanism. The calculated absorption rates of the improved unit cell for the strongly coupled MA coincide well with the simulated results at wide angles of incidence for both transverse electric (TE) and transverse magnetic (TM) waves.
关键词： polarization-insensitive,microwave,metamaterial absorber,triple-band,rotated square rings
更新于2025-09-09 09:28:46
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - An Ultra-thin Triple-band Metamaterial Absorber with Equivalent Circuit Analysis
摘要： A compact ultra-thin triple-band metamaterial absorber with polarization insensitiveness and wide-angle stability is presented in this paper. The unit cell of the absorber consists of a Jerusalem cross and a concentric circular ring imprinted on a dielectric substrate backed with a metal ground plane. Simulated results exhibit that the proposed absorber has three discrete absorption peaks at 4.4, 6.05, and 13.9 GHz with excellent absorption rates over 0.95. The current distribution and equivalent circuit analysis are investigated to analyze the near-unity absorption mechanism. The structure is then fabricated and experimentally characterized. The measured absorption response shows a good agreement with the simulated and calculated results.
关键词： metamaterial absorber,triple-band,equivalent circuit model
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - A Graphene-Based Tunable THz Metamaterial Absorber
摘要： A graphene-based tunable THz metamaterial absorber is presented in this paper. The proposed absorber is a periodical structure with the unit cell composed of four square gold patches on single-layered graphene, which are placed on a dielectric spacer supported by a gold bottom layer. Simulation results indicate that the absorption frequency can be tuned by varying the chemical potential of graphene through controlling of the electrostatic gating or the geometry size of the gold patch. By introducing more gold patches with different size into the unit cell, we can obviously extend the absorption bandwidth to achieve a broadband absorber.
关键词： broadband,THz,metamaterial absorber,tunable,graphene
更新于2025-09-04 15:30:14