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In this article, a textile-based metamaterial with broadband microwave absorption was developed using a screen printing technique. The metamaterial has over 90% absorption from 7.39 GHz to 18 GHz. The metamaterial consists of a to...
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In this article, a textile-based metamaterial with broadband microwave absorption was developed using a screen printing technique. The metamaterial has over 90% absorption from 7.39 GHz to 18 GHz. The metamaterial consists of a top layer of the printed structure of commercial conductive inks on various kinds of clothes, which is separated from a conductive ground plane with flexible dielectric foam of 3.2 mm thickness. The metamaterial absorber was simulated using ANSYS HFSS software for various thicknesses of the printed ink. It was observed that the absorption band varies with variation in printed thickness, and the optimized printed thickness was found to be about 50 mu m. With the increase in printed thickness, the absorption shifts from broadband to narrow band. To achieve the optimum thickness in fabrication, statistically designed experiments were conducted to study the variation of printed thickness and width with different kinds of clothes and substrates (FR4, plain weave cotton cloth, and twill weave cotton cloth), mesh number of the screen (50-110) and the number of passes (1-3). Substrate material and the number of passes were found to be the most significant factors that affect the printed width resolution and thickness. Rigid copper foil and printed cloth could both be used as the ground plane. A complete, flexible absorber was fabricated using printed cloth as the ground plane. The microwave response (absorption) of all the fabricated absorbers was measured and found to be in agreement (more than 90%) with the simulation. Further, the fabricated absorber on the cloth substrate was also made hydrophobic by treating it with polydimethylsiloxane.
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Terahertz (THz) absorber with dynamically tunable bandwidth possesses huge application value in the fields of switches, sensors, and THz detection. However, the perfect absorbers based on photonic crystals and metamaterials are no...
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Terahertz (THz) absorber with dynamically tunable bandwidth possesses huge application value in the fields of switches, sensors, and THz detection. However, the perfect absorbers based on photonic crystals and metamaterials are not intelligent enough to capture the electromagnetic wave in a tunable way. In this paper, we utilized only patterned graphene to tune the absorption positions and the bandwidth in the terahertz regime. More distinguished than some dynamic absorbers proposed before, the performances with peak frequency relative tuning range of 68 % and nearly unity absorbance are obtained by a single cross-shaped graphene layer. Additionally, the working bandwidth can be broadened with stacked structured graphene. The almost perfect absorption shifted from 2.36 similar to 3.2 to 3.26 similar to 3.99 THz continuously via changing the chemical potential of graphene.
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A multilayer, ultra-wideband absorber is proposed in this paper, which consists of a hybrid circuit analog absorber and a metal resonant absorber. The circuit analog absorber is located at the upper part of the absorber to absorb ...
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A multilayer, ultra-wideband absorber is proposed in this paper, which consists of a hybrid circuit analog absorber and a metal resonant absorber. The circuit analog absorber is located at the upper part of the absorber to absorb low-frequency electromagnetic waves, and the metal resonant absorber is located at the bottom of the absorber to absorb high-frequency electromagnetic waves and provide a reflecting plate for the absorber. Through simulation, the absorption rate of the designed absorber can be greater than 90% in the range of 2.33-18.43 GHz, and an equivalent circuit is established for verification. In addition, the absorber has good angular stability and polarization insensitivity. The prototype of the absorber was manufactured and measured, and the test results are basically consistent with the analysis results.
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Abstract Tunable absorbers are promising for reconfigurable metasurface applications. Here a tunable terahertz (THz) perfect absorber is proposed which consists of high resistance silicon (undoped silicon) and can realize the swit...
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Abstract Tunable absorbers are promising for reconfigurable metasurface applications. Here a tunable terahertz (THz) perfect absorber is proposed which consists of high resistance silicon (undoped silicon) and can realize the switch between perfect reflection and perfect absorption (optical pumping, 1064?nm continuous wave). The proposed THz absorber exhibits perfect absorption around 0.74 THz and a 90% absorption bandwidth of 0.5 THz. Additionally, the working frequency range of the device can be easily designed by adjusting the side length and height of the square silicon pillars. Effective medium theory, mode analysis, and impedance matching theory are used to design and explain the proposed THz absorber. The experimental results agree well with the simulations. The proposed scheme allows for more flexible design of THz absorbers, and the device is easier to be fabricated. The proposed tunable THz absorber can find applications in THz sensing, modulator, and optic‐electro switches.
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The design, fabrication, and measurement of a novel and ultrathin metamaterial absorber are presented for X-band. The absorber is constructed of a periodic array of new resonant structure with the thickness of 1/110 of the inciden...
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The design, fabrication, and measurement of a novel and ultrathin metamaterial absorber are presented for X-band. The absorber is constructed of a periodic array of new resonant structure with the thickness of 1/110 of the incidence wavelength. Simulation results show that the absorber can perform with an absorption peak of 100.00% at frequency of 10.116 GHz given a normally incident electromagnetic wave the full width at half maxima bandwidth is 5.057%. This absorber is polarization-independent and wide-angle incidence for both transverse magnetic and transverse electric polarizations. In addition, absorption spectrum curves were studied using the recursive method. To further enhance the absorption bandwidth of the novel design, the scalability property of metamaterials is utilized. Three and nine elements in one unit cell are arranged side by side in different scenarios, which have created double and triple-band with full width at half maxima bandwidth of 10.552 and 17.084%, respectively. In all cases, the proposed structures are fabricated and experimental results show good agreement with the numerical simulation. (C) 2014 Wiley Periodicals, Inc.
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In this study, we have demonstrated the fabrication of perforated absorbers on two substrates, i.e., ITO/PET and Twill weave cloth. Perforation is required to enable the use of absorbers in the application where air breathability,...
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In this study, we have demonstrated the fabrication of perforated absorbers on two substrates, i.e., ITO/PET and Twill weave cloth. Perforation is required to enable the use of absorbers in the application where air breathability, ventilation and thermal equilibrium are necessary. For perforations, holes were machined in all the layers of the absorber. To ascertain the effect of perforations on both the absorbers' performance, simulation, using ANSYS HFSS software, was carried out. In the ITO/PET-based absorber, it was found that there were no significant effects of the variation of hole radius on the absorption. However, for textile-based absorber, the hole radius had a significant impact on the absorption. The proposed ITO/PET-based fabricated MMA can absorb radiation in the frequency band from 7.64 GHz to 16.6 GHz, whereas the textile-based absorber can absorb more than 90% of the frequency band corresponding to 6.61 GHz to 17.91 GHz. The measured absorptions are found to be in good agreement with the simulated results. Furthermore, perforation gives two mechanical advantages to the absorber: first, it reduces the absorber's weight by 25% and 35%, respectively, in the case of ITO/PET- and textile-based absorber, and second, it increases the bendability of the absorber. Through experiments, we found that the perforated sample bends by an extra 22° and 24°, respectively, for ITO/PET- and TWC-based absorber when placed as a cantilever. Theoretically, it was calculated that there would be a four-time increase in the absorber's bendability due to perforations.
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Vanadium nitride (VN)-based metamaterial absorber was investigated for ultra-wideband (UWB) nearly perfect absorber in the visible to infrared regime of the electromagnetic spectrum considering four different VN samples, namely VN...
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Vanadium nitride (VN)-based metamaterial absorber was investigated for ultra-wideband (UWB) nearly perfect absorber in the visible to infrared regime of the electromagnetic spectrum considering four different VN samples, namely VN6, VN8, VN10, and VN12. The absorption properties were extracted for the transverse electric and transverse magnetic incidence waves under different obliquities, and also, considering different parametric conditions of the metamaterial. The constitutive properties of VN samples were initially extracted, followed by the effective constitutive properties of metasurface comprising the nanostrips of VN6 and VN10 mediums as the illustrative examples. The results determine achieving nearly perfect UWB absorption in the stated regime of operating wavelength. Spectral characteristics were also obtained while using other reflectors at the bottom. The results demonstrate using VN at the bottom yields significantly improved spectral features. The absorption related results were also evaluated exploiting the interference theory, and the obtained discrepancies were highlighted. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)
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Most of the recent research on electromagnetic absorbers at terahertz (THz) frequencies is focused on metamaterials based absorber, which provides high absorptivity of electromagnetic (em) radiations in narrow frequency band and t...
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Most of the recent research on electromagnetic absorbers at terahertz (THz) frequencies is focused on metamaterials based absorber, which provides high absorptivity of electromagnetic (em) radiations in narrow frequency band and tailoring of em response of materials. Under this work, we have also attempted the same problem with different approach, i.e., by using combination of different materials in uniform layered configuration system. Result obtained shows em absorption of 10-20 dB in the lower and higher side of measured spectrum and high absorption of 20-30 dB in central part, i.e., from 1 to 2 THz. Materials with such broadband absorptivity find numerous military and civilian applications.
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In this work, a design methodology for robust and effective centrifugal pendulum absorbers is presented with a relative center of mass translation along a given path and angular body rotation. This type of absorber is used in rota...
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In this work, a design methodology for robust and effective centrifugal pendulum absorbers is presented with a relative center of mass translation along a given path and angular body rotation. This type of absorber is used in rotatory machines with rotor angle synchronous excitation, allowing for a reduction of angular rotor fluctuations over the entire speed range. The main areas of application are aircraft drives and automotive drive trains with internal combustion engines. Since the requirements placed on absorbers are increasingly demanding in terms of reducing their mass without sacrificing effectiveness, new design approaches must be pursued. The linear theory used in the past has been replaced by the nonlinear tautochronic design philosophy that provides an increased working range of the pendula. This approach has been extended in recent years with regard to nonlinear detuning in order to obtain effective and robust absorbers. It is known that, in addition to the translation of the pendula, the rotation of the pendulum bodies, contributes to absorber performance, and the nonlinear design tools are extended to this case. The proposed unified design approach allows one to apply existing tuning methodologies of centrifugal pendulum absorbers with their relative rotational movement, referred to as "rocking"absorbers. Maintaining generality, the equations of motion are derived for a system with multiple absorbers and prepared for the application of simulations and continuation algorithms for parameter studies. Additionally, a state transformation is presented, which allows the application of perturbation methods and averaging under the assumption of small parameters. The increased effectiveness of these rocking absorber class when compared to non-rocking absorbers is quantified and demonstrated by numerical case studies.
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In the past decade,new materials have been developed based on the physical and chemical properties of carbon nanotubes.The combination of polyaniline with multiwall carbon nanotubes results in a new functional material with advant...
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In the past decade,new materials have been developed based on the physical and chemical properties of carbon nanotubes.The combination of polyaniline with multiwall carbon nanotubes results in a new functional material with advantageous electromagnetic properties.The objective of this study was to produce a radar absorbing structure consisting of glass fiber woven fabric impregnated with a formulation containing carbon nanotubes,polyurethane resin,with or without polyaniline.A different formulation was used for each woven sheet (multilayer structure).The electromagnetic properties of these nanocomposite materials were characterized by reflectivity measurements using Naval Research Laboratory arch method (frequency range,8 to 12 GHz).The attenuation of both sides of each nanocomposite material was also measured and compared.The attenuation of electromagnetic energy was as high as 70 %,approximately,indicating that these materials can be used as microwave absorbers.
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