- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Planar Directivity of a Dipole Array
摘要： We develop a technique for fast evaluation of superdirective performance of coupled meta-atoms. Traditionally, the directivity of a small antenna is obtained from measurements of the far-field radiated power over a spherical surface. We propose an alternative method of finding the directivity from a faster polar scan over a circular path, by introducing the “planar directivity” (D2D) for dipole arrays. We derive analytical expressions for maximum achievable values of directivity and D2D, establish the correlation between them, and identify the range of parameters (inter-element distance, coupling constant, quality factor) for which the conversion of D2D to D for superdirective dimers is possible.
关键词： dipole arrays,planar directivity,far-field measurements,metamaterials,superdirectivity
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Modular approach to understanding and synthesis of metamaterials and metasurfaces
摘要： The vast majority of previously proposed metamaterials and metasurfaces are anisotropic or bianisotropic (exhibiting magnetoelectric coupling). Nevertheless, their anisotropy was not fully exploited as they were designed only for one or several specific illumination directions. In this talk, we propose a simple analytical approach to characterize properties of general bianisotropic meta-atoms for an arbitrary illumination. The approach is based on the qualitative decomposition of an arbitrary meta-atom into separate basic “modules” with elementary polarization properties. Such decomposition can be used for comprehensive characterization of previously designed structures as well as for synthesizing novel bianisotropic inclusions of arbitrary complexity and with desired response.
关键词： polarization properties,anisotropy,metamaterials,bianisotropic,metasurfaces,magnetoelectric coupling
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Non-linearity Enhances Versatility of Non-Foster Metamaterials and Metasurfaces
摘要： Classical applications of non-Foster elements such as broadband active metamaterials/metasurfaces and broadband matching of small antennas presume their linearity. Here, we show that two well-known types of negative impedance converters - the voltage-conversion type and the current-conversion type, show fundamentally different behavior in non-liner regime. It is followed by different power-dependent properties of generated positive/negative susceptance/reactance. This effect may be used in future self-oscillating and self-mixing metasurfaces as well as in power-tunable metamaterials/metasurfaces.
关键词： negative impedance converters,non-linearity,metamaterials,non-Foster elements,metasurfaces
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Optimization of Meta-atoms for 3D Printed Metamaterial Structures
摘要： Additive manufacturing by fused deposition modelling (FDM) now offers some useful performance for functional materials including conductors. Whilst this technology enables the creation of truly three-dimensional (3D) composite structures its accuracy and resolution are not yet so refined as those of 2D fabrication methods. Moreover, dielectric and metallic filaments used in FDM have complex material properties that depend on print parameters and usually exhibit higher losses than RF substrates and bulk conductors. In this work we investigate by simulations and experiments several magnetic meta-atom variants with a view to developing optimal designs for the successful production of metamaterials at microwaves with FDM techniques. Conductor thickness is shown to be a useful new design parameter to reach the desired degree of miniaturization and resonance quality factor of the meta-atoms at low print resolution.
关键词： 3D printing,Fused deposition modelling,Additive manufacturing,Meta-atoms,Metamaterials
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Acoustic Metamaterials Crystal for Passive Parity-Time-Symmetric Modulation
摘要： The exploration of parity-time (PT) symmetry with classical wave systems has enabled many counter-intuitive ways of wave manipulation and innovative applications, yet is still a great challenge for sound waves as acoustic gain medium is not readily accessible. Here we report the realization of an acoustic metamaterials crystal that respects passive PT symmetry, by interleaving groove- and holey-structured metamaterials to offer intrinsic PT-symmetric potential without any active element. At the exceptional point where a transition from the unbroken to broken PT symmetry phase happens, unidirectional sound reflectionless effect is numerically achieved. Our demonstration provides a feasible path to the investigation of PT symmetry in acoustic wave system with practical structures free of gain medium.
关键词： unidirectional reflectionless effect,passive modulation,acoustic metamaterials,PT symmetry
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Real Sources in Complex Spaces
摘要： We utilize complex transformation optics (CTO) to mimic complex source point (CSP) fields. It is shown that the CSP fields can be exactly reproduced via planar metamaterial slabs associated with the proper complex coordinate transformations. CTO extends the real-valued coordinate transformations to complex-valued coordinate transformations. Of conventional TO, one can also control the amplitude of the fields in addition to their phase paths. In the present paper, we demonstrate that CSP fields can be produced through appropriate material tensors prescribed by the corresponding complex coordinate transformations.
关键词： Complex transformation optics,complex source point,metamaterials,Gaussian beams
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Optical Switching Cell Based On Metamaterials And Ferrite Films
摘要： A principally new switching cell with four inputs and four outputs based on metamaterial and optically transparent ferrite films for processing a large amount of information is proposed in this work. The cell uses the spatial diversity of the information beams under action of the control magnetic field. The principle of the cell's operation is described; calculations of the spatial deviation of the beam and the reflection coefficients of the structure are carried out.
关键词： control magnetic field,optical switching cell,ferrite films,metamaterials,spatial diversity
更新于2025-09-10 09:29:36
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Designing Anisotropic, Inhomogeneous Metamaterial Devices Through Optimization
摘要： A method for designing multi-input, multi-output metamaterial devices is presented. The devices are 2D anisotropic, inhomogeneous media. The design technique consists of a custom FEM solver coupled to a constrained, nonlinear minimization algorithm. The design method has advantages over existing metamaterial design methods such as transformation optics, in that material constraints can be imposed and multi-input, multi-output functionality allowed. Transformation optics devices only achieve multi-input, multi-output functionality through geometrical symmetry. The gradient-based optimization method employed in the metamaterial design process is fast given that an analytic expression for the gradient of the cost function can be written. The proposed technique is demonstrated through the design of two beamforming devices. A commercial full-wave solver is used to validate the design approach. The constitutive parameters of these 2D designs can be implemented using printed-circuit board metamaterials, such as tensor transmission-line metamaterials.
关键词： transformation electromagnetics,optimization,metamaterials,Beamformer,finite-element method
更新于2025-09-10 09:29:36
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Solitons in optical metamaterials with anti-cubic law of nonlinearity by ETEM and IGEM
摘要： This paper studies soliton perturbation in optical metamaterials, with anticubic nonlinearity. Methods: Two integration approaches, namely, the extended trial equation method (ETEM) and the improved G’/G-expansion method (IGEM) are presented. Results: Bright, dark and singular soliton solutions are retrieved. The existence criteria of these solitons in metamaterials are also demonstrated. All solutions have been verified back into its corresponding equation with the aid of maple package program. Conclusions: Finally, we believe that the executed method is robust and efficient than other methods and the obtained solutions in this paper can help us to understand the variation of solitary waves in optical metamaterials.
关键词： Solitons,Extended trial equation method,Anti-cubic nonlinearity,Improved G’/G-expansion method,Optical metamaterials
更新于2025-09-10 09:29:36
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Analytical formulas for complex permittivity of periodic composites. Estimation of gain and loss enhancement in active and passive composites
摘要： The asymptotic homogenization method is applied to complex dielectric periodic composites. An equivalence to coupled dielectric problems with real coefficients is shown. This is similar to a piezoelectric problem: an out-plane mechanical displacement and an in-plane electric potential establishing a correspondence principle. Closed-form formulas for the complex dielectric effective tensor in the case of a square array of circular inclusions embedded in a matrix are given. These formulas are written in terms of a real and symmetric matrix which facilitates the implementation of the computational scheme. We also get similar formulas for multilayered complex dielectric composites. The real closed-form formulas are advantageous for estimating gain and loss enhancement properties of active and passive composites in certain volume fraction intervals. Numerical computations are performed and the results are compared with other approaches showing the usefulness of the obtained formulas. This may be of interest in the context of metamaterials.
关键词： asymptotic homogenization,gain and loss enhancement,complex dielectric composites,effective properties,Metamaterials,closed-form formulas
更新于2025-09-10 09:29:36