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A Facile Film-Nanoctahedron Assembly Route to Plasmonic Metamaterial Absorbers at Visible Frequencies
摘要： Plasmonic metamaterial absorbers (MAs) with broadband and near-perfect absorption properties in the visible region were successfully fabricated via a facile film-colloidal nanoparticle (NP) assembly method. In this approach, colloidal octahedral Au NPs were employed as the surface meta-atoms of MAs, while the nanoscale-thick SiO2 and Al films were used as the dielectric spacer and reflector respectively. It is worth noting that the Au nanoctahedron were randomly assembled onto the Al-SiO2 films, and no effort was made to precisely control their spatial arrangements. The optical characterization showed that the as-prepared MAs exhibited broadband high absorption (average absorptivity above 85%) within the whole visible spectrum for a broad range of incident angles (0°–60°). In particular, two polarization-independent near-perfect absorption peaks (absorptance above 99%) were recorded near 540 nm and 727 nm respectively. Moreover, the absorption properties of the MAs can be effectively controlled and tailored by varying the geometry (the thickness of the dielectric spacer and the surface coverages of the Au nanoctahedron). Electromagnetic simulations further demonstrated that enhanced Mie resonances and strong plasmonic coupling effects were critical for the designed MAs. This work here may provide an efficient and alternative route for the design of scalable visible light absorbers for applications such as solar cells, photothermalvoltaics, and biochemical sensors.
关键词： metamaterial absorbers,broadband and near-perfect absorption,aperiodic nanostructures,optical impedance matching,self-assembly
更新于2025-10-22 19:40:53
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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) - Dual Band Antenna For Portable Consumer Devices
摘要： The article proposes the design of a circular shaped patch antenna with a circular slot at its centre and a defected ground plane. The antenna operates in two distinct frequency bands, 2.3 GHz to 5.3 GHz and 7.2 GHz to 20 GHz and hence is suitable for applications in the S-band (2 GHz to 4 GHz), the X-band (8 GHz to 12 GHz) and the Ku-band (12 GHz to 20 GHz). The overall size of the antenna is 30mm*30mm*1.5mm which makes it suitable for applications in compact portable devices such as mobile phones, smart watches, bluetooth headsets, etc. Annealed copper is used as a conductor and the substrate is made up of FR4 which has an electrical permittivity of 4.3 and a loss tangent of 0.025. The simulated re?ection coef?cients, impedance curves and radiation patterns of the proposed antenna are described in detail in this paper.
关键词： antenna,impedance matching,simulations,ultra-wide band
更新于2025-09-23 15:23:52
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Novel Three-Dimensional SiC/Melamine-Derived Carbon Foam-Reinforced SiO <sub/>2</sub> Aerogel Composite with Low Dielectric Loss and High Impedance Matching Ratio
摘要： Novel three-dimensional SiC/melamine-derived carbon foam composite filled by silica aerogel (SiC/MDCF?Aerogel) was first fabricated by the pyrolysis process of commercial melamine foam, chemical vapor deposition of ultrathin SiC films, and the sol?gel method of silica aerogel. The results indicated that the SiC/MDCF?Aerogel composite consisted of the SiC three-dimensional open-celled network structure and the pregnant silica aerogel in the pores. Tiny cracks on the interface of skeletons and clumps were induced during the aging process, which was drastically beneficial to the microwave-absorbing properties. A minimum reflection loss could be obtained as low as ?18.41 dB at the measured frequency of 16.92 GHz when the thickness of the absorber was 3.65 mm, and the reflection loss could drop below ?10 dB when the selected frequencies ranged from 15.80 to 17.52 GHz, along with the thickness ranging from 2.75 to 5.0 mm, which possessed a relatively better microwave absorption performance especially at a higher frequency. Furthermore, the absorption mechanism was also investigated in detail to discuss the influence of the dielectric loss and the impedance matching ratio on the microwave-absorbing performance of SiC/MDCF?Aerogel, which provided certain scientific directions for evaluating the absorbing materials.
关键词： Minimum reflection loss,Tiny cracks,Microwave-absorbing properties,Impedance matching ratio,Dielectric loss,SiC/MDCF?Aerogel
更新于2025-09-23 15:22:29
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Microstrip Line Impedance Matching Using ENZ Metamaterials, Design and Application
摘要： The idea of this paper is to extend the tunneling effect of epsilon-near-zero (ENZ) narrow channel for matching two microstrip lines with different impedance characteristics. The main advantage of this method is the possibility to design a channel with subwavelength electrical size and obtain similar matching condition when compared with a conventional λ/4-transformer. The bandwidth of the structure is directly related to the bandwidth of the ENZ-metamaterials (MTM). The suggested matching circuit is comprised of a metallic wall and an ENZ narrow channel. To realize the ENZ channel, a rectangular waveguide which operates in TE10 mode is designed and implemented using a substrate integrated waveguide (SIW) technology. A set of vias are also needed for emulating the metallic wall to reduce the ENZ channel cross section. The proposed structure for different impedance values of 50?, 100?, and 150? was designed, simulated, fabricated, and tested. Moreover, as an important application of a matching network, a microstrip patch antenna has been matched over the desired frequency band. Simulation results based on CST microwave studio have good agreement with measurements. It is shown that the bandwidth of the circuit is 8%–15%.
关键词： impedance matching,metamaterials (MTM),Epsilon-near-zero (ENZ),microstrip line,tunneling
更新于2025-09-23 15:22:29
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DIAMAGNETO-DIELECTRIC ANISOTROPIC WIDE ANGLE IMPEDANCE MATCHING LAYERS FOR ACTIVE PHASED ARRAYS
摘要： In this paper, we present the full process of designing anisotropic metamaterial (MM) wide angle impedance matching (WAIM) layers. These layers are used to reduce the scan losses that occur in active phased arrays for large scanning angles. Numerical results are provided to show the improvement in performances that such layers can ensure. The proposed anisotropic MM-WAIM layers achieve an improvement of about 1 dB of more radiated power at θ = 70? from broadside, in a 13% of fractional bandwidth on the azimuthal plane φ = 90?. Weaker improvements are obtained in the other azimuthal planes, however keeping the active re?ection coe?cient below ?9 dB for all azimuthal planes up to θ = 60? and up to θ = 70? o?-axis for planes φ = 45?, 90? in the whole operational band.
关键词： scan losses,wide angle impedance matching,anisotropic metamaterial,active phased arrays,impedance matching
更新于2025-09-23 15:21:21
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Magnetoelectric uniaxial metamaterials as wide-angle polarization-insensitive matching layers
摘要： Antire?ection or impedance matching is a topic that has been extensively researched by the optical and microwave communities over the past century and until today. However, due to the diverging wave impedances of TE (s) and TM (p) polarizations with increasing incident angle, it is impossible to achieve perfect matching simultaneously for both polarizations at varying incidence angles with a single conventional isotropic matching layer. To achieve polarization-insensitive matching at an arbitrary incident angle, we propose a magnetoelectric uniaxial metamaterial layer (MEUML) that is inspired by the perfectly matched layer (PML) concept in computational electromagnetics. Similar to the PML, the MEUML requires speci?c uniaxial permittivity and permeability tensors. However, to simultaneously control both the transversal and longitudinal material parameters is not an easy task. To date, a true PML has not been realized with metamaterials. In this paper, we employ a simple and yet special metamaterial unit cell to achieve such control and synthesize a physical MEUML. The unit cell comprises two parallel metallic rings separated by a holey substrate. The transversal electric and magnetic dipole moments, and the longitudinal capacitive and diamagnetic coupling between the rings are judiciously controlled to achieve the required permittivity and permeability tensors. To aid the MEUML synthesis, we also introduce a technique that can extract the material parameter tensors at any incident angle. We ?rst demonstrate this concept by achieving polarization-insensitive matching of a high-index substrate at 45? with a single subwavelength-thick MEUML. We further adapt the concept to the microwave regime by developing a MEUML-based radome. Exceptional matching performance was obtained both in the simulations and measurements. The re?ectance remains below 5% from normal incidence (0?) to near grazing angle (85?) for both polarizations and over a wide bandwidth. With this unprecedented control of the material parameter tensors, the MEUML concept not only can be applied to impedance matching, but also can be utilized in many exotic applications that require extreme control of the material properties.
关键词： wide-angle,impedance matching,polarization-insensitive,radome,magnetoelectric uniaxial metamaterials
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Impedance Matching of Dipole Antennas by Metal Rod and Disk Placing
摘要： It has been researched experimentally and theoretically the impedance-matching possibility of dipole antenna with a coaxial feeder circuit. It has been made in case of a symmetrical dipole antenna placed parallel to a flat perfectly conducting screen by two bracket. It has been chosen a metal pins and discs of small electrical sizes as impedance-matching elements, which actually are placed between the dipole and the screen. Their dimensions and position relative to the dipole can be changed within certain small limits. The configuration and all dimensions of the tuned antenna has been entered into a computer for the calculation of the directivity patterns and dependence of the VSWR antenna on frequency. It is proved that such tuning elements allow to ensure good impedance-matching of the antenna and the feeder circuit, and also that practically does not affect on its directivity pattern.
关键词： near field region,dipole antenna,impedance matching,directivity pattern,flat screen
更新于2025-09-23 15:21:21
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Hierarchically structured metamaterials with simultaneously negative mass density and Young’s modulus by using dynamic homogenization
摘要： We propose one-dimensional hierarchical metamaterials (HMMs) that have simultaneously negative mass density and Young’s modulus in the sense of effective properties. Frequency-dependent effective properties of the HMMs are evaluated by using a dynamic homogenization theory. By considering three necessary conditions for dynamic homogenizability, we verify that our proposed HMMs can have physically meaningful double negativity, whereas the conventional periodic structures cannot. In addition, HMMs yield the broader ranges of the frequency and the effective properties for double negativity due to the large number of geometrical parameters. By exploring all the possible effective properties of HMMs, we discuss whether we can design metamaterials with the opposite sign of material properties in nature, ultimately aiming at perfect impedance matching.
关键词： dynamic homogenization,double negativity,impedance matching,hierarchical metamaterials
更新于2025-09-23 15:21:21
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Graphene disks for frequency control of terahertz waves in broadband applications
摘要： The terahertz (THz) gap lying between the microwave and optical parts of the electromagnetic spectrum has attracted immense attention due to its applications between radiofrequency (RF)/microwave and photonic systems. A structure consisting of a graphene sheet sandwiched between two graphene disks is introduced herein to control the reflection, absorption, and transmission of THz waves. The proposed metamaterial structures are designed analytically using transmission line theory. Also, the dimensions of the structure and the electrical gating of the graphene are optimized utilizing a genetic algorithm. The structure is simulated using two different methods: (1) a circuit model based on transmission line theory and (2) commercial full-wave software based on the finite element method, which are verified by the agreement between their results. Finally, the proposed method is used to design a THz filter and THz wave absorber, which are in great demand for application in modulators, sensors, detectors, and imaging systems.
关键词： Resonator,Circuit method,Coupling effect,Graphene,Genetic algorithm,Absorber design,Impedance matching
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Singapore, Singapore (2019.12.10-2019.12.13)] 2019 IEEE Asia-Pacific Microwave Conference (APMC) - An Ultra Wideband Vivaldi Antenna Array Based on Tightly Coupled Effect
摘要： An ultra wideband Vivaldi antenna array based on tightly coupled effect is proposed. The elements are arranged overlap to get an additional capacitive capacity to achieve impedance matching at low frequency. A sample of a 4×4 Vivaldi array was simulated, fabricated, and tested. The measured farfield waveform is basically agreed with simulated one. The designed antenna gets a bandwidth of 0.4GHz-4.2GHz.
关键词： impedance matching,tightly coupled effect,Ultra wideband,Vivaldi antenna array
更新于2025-09-23 15:21:01