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Realization of modified Luneburg lens antenna using quasi-conformal transformation optics and additive manufacturing
摘要： We demonstrate a new method for realizing modified Luneburg lens antennas with nearly continuously graded permittivity profiles in three-dimensions. The method used a quasi-conformal transformation optics (QCTO) approach to modify the geometry and permittivity of a spherical Luneburg lens to have a flat surface for convenient integration of antenna feeds. The modified lens was then fabricated using Fused Deposition Modeling (FDM) printing with an effective media approach that employs space-filling curves. The method was validated by designing and fabricating a modified Luneburg lens antenna designed to operate in the Ka-band. The antenna performance of the sample was measured experimentally and shown to compare well to predicted results using full wave simulations. The device was able to achieve a reasonably high degree of beam steering (ie, ?55° to +55°) over the entire Ka-band. We believe this new approach provides a cost-effective and scalable means of realizing practical passive beam steering lenses that operate over a broad range of frequencies.
关键词： additive manufacturing,beamscanning,beamforming,fused deposition modeling,Luneburg lens,transformation optics
更新于2025-09-23 15:22:29
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A non-singular transformation optics invisibility cloak by combining with scattering cancellation.
摘要： A mechanism-based method to suppress the transformation optics cloaking singularities is proposed. Using the invariance nature of the Maxwell’s equations, instead of a point, a scattering cancellation cloaked circle is used as the virtual space for the transformation. The advantages of the proposed method includes non-singular constitutive parameters and significantly reduced variation range. Singularity removal is proved analytically while invisibility is demonstrated numerically using COMSOL Multiphysics.
关键词： Transformation Optics,Non-Singular Invisibility Cloaks,Invisibility Cloaks,Mantle Cloaking
更新于2025-09-23 15:22:29
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A bi-functional illusion device based on transformation optics
摘要： An illusion device based on shifting distance concept has been investigated using linear coordinate transformation method. Distinguishing from the previously designed illusion devices, we construct the shift-illusion device featuring resizing and rotating for both active and passive scatterers, in case; if the shifting-region and physical space share the same origin point. Similarly, when the shifting-region is foreign to the designed device, the proposed illusion design performs as a rotation and relocation-shifting device to change the location of the scatterer. In addition, these proposed devices behave like the stealth effect in the absence of any scatterer as the outer-boundary field distribution is not disturbed. Meanwhile, the proposed concept is further extended for different mapping style to validate the shifting-illusion concept. The constitutive parameters of the proposed devices are homogeneous, which makes it more appreciable for real implementations. It is expected that the proposed design will find potential applications in illusion devices, such as objects protection, and camouflage etc.
关键词： Invisibility cloaks,transformation optics,metamaterials
更新于2025-09-19 17:15:36
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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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DESIGN AND SIMULATION OF ARBITRARILY-SHAPED TRANSFORMATION OPTIC DEVICES USING A SIMPLE FINITE-DIFFERENCE METHOD
摘要： A fast and simple design methodology for transformation optics (TO) is described for devices having completely arbitrary geometries. An intuitive approach to the design of arbitrary devices is presented which enables possibilities not available through analytical coordinate transformations. Laplace’s equation is solved using the ?nite-di?erence method to generate the arbitrary spatial transforms. Simple techniques are presented for enforcing boundary conditions and for isolating the solution of Laplace’s equation to just the device itself. It is then described how to calculate the permittivity and permeability functions via TO from the numerical spatial transforms. Last, a modi?cation is made to the standard anisotropic ?nite-di?erence frequency-domain (AFDFD) method for much faster and more e?cient simulations. Several examples are given at the end to benchmark and to demonstrate the versatility of the approach. This work provides the basis for a complete set of tools to design and simulate TO devices of any shape and size.
关键词： transformation optics,finite-difference method,Laplace’s equation,electromagnetic simulation,anisotropic materials
更新于2025-09-10 09:29:36
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Arbitrarily shaped homogeneous concentrator and its layered realization
摘要： Arbitrary shaped N-sided polygonal electromagnetic concentrators with homogeneous properties are proposed and designed based on coordinate transformation approach. In comparison with the reported concentrators, material parameters of the concentrators developed here are homogeneous and non-negative, which make the devices applicable to practical fabrication. The constitutive parameters equations reported here are effective for concentrators of regular and irregular shape, which provide the flexibility for device design. Furthermore, to remove the anisotropic of material parameters, layered structure concentrator composed of only homogenous, isotropic materials are presented based on effective medium theory. Space compressing ratio and concentrating efficiency are calculated to quantitatively investigate the efficiency of the proposed device. The feasibility of concentrator design with ordinary isotropic materials instead of metamaterials would dramatically reduce the fabrication difficulties and move the device a step further towards the practical use.
关键词： Electromagnetic concentrator,Metamaterials,Transformation optics,Effective medium theory
更新于2025-09-09 09:28:46
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DESIGN OF A PYRAMIDAL HORN ANTENNA WITH LOW E-PLANE SIDELOBES USING TRANSFORMATION OPTICS
摘要： Transformation optics is a convenient way to control the pattern of electromagnetic ?elds. In this paper, using a novel transformation, we propose the design procedure of a horn antenna having low backlobe and sidelobe levels in its E-plane. By applying conformal transformation, the rectangular horn proposed in this paper can be realized with isotropic materials. This proposed antenna can be easily implemented by both ordinary dielectric materials and isotropic graded refractive index (GRIN) materials. In the ?rst proposed design, in addition to the isotropy, homogeneity is furthermore introduced into the horn, and only four kinds of isotropic materials are required throughout. In the second design, it is demonstrated that the designed structure can also be implemented by graded photonic crystals (GPCs) operating in metamaterial regime. They have low loss as well as broad frequency band and are easy to implement. Simulation results are presented to validate the design approach.
关键词： low sidelobes,horn antenna,graded refractive index,graded photonic crystals,Transformation optics,isotropic materials,conformal transformation
更新于2025-09-04 15:30:14
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Implementation of General Dispersive Anisotropic Materials in Lebedev FDTD
摘要： A finite-difference time-domain (FDTD) algorithm—the Lebedev FDTD method—is augmented to allow for the simulation of electromagnetic waves in general dispersive anisotropic materials. Distinct dispersions may be applied to each of the principal axes of the anisotropic medium. The method is based on the auxiliary differential equation and is simple to implement. Because of the collocated nature of the algorithm, multiterm dispersions necessary in previous implementations are avoided. Lebedev grid has previously been studied in detail by different research groups for the simulation of anisotropy. In this paper, we specifically focus on extending frequency-dispersive materials to this method and provide multiple examples to demonstrate the accuracy, validity, and stability of the method.
关键词： dispersive,Anisotropic,invisibility cloak,finite-difference time-domain (FDTD),transformation optics
更新于2025-09-04 15:30:14
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IMPROVEMENT OF RADIATION CHARACTERISTICS OF BALANCED ANTIPODAL VIVALDI ANTENNA USING TRASFORMATION OPTICS
摘要： Transformation optics is a convenient method to control paths of electromagnetic waves and radiation characteristics of antennas. In this paper, we try to increase the gain of Balanced Antipodal Vivaldi Antenna (BAVA) over 8{16 GHz frequency band using an optical conformal transformation. The proposed antenna can be implemented by ordinary dielectric materials and graded photonic crystals (GPCs). In this designed BAVA, better side-lobe level (SLL) and cross-polarization are achieved compared to a conventional BAVA. Simulation results validate the performance of the design approach.
关键词： graded photonic crystals,Transformation optics,Balanced Antipodal Vivaldi Antenna,cross-polarization,side-lobe level,gain improvement
更新于2025-09-04 15:30:14