Arbitrarily shaped electromagnetic transparent devices with homogeneous, non-negative, anisotropic and generic constitutive parameters are proposed based on linear transformation optics, which provides the flexibility...Arbitrarily shaped electromagnetic transparent devices with homogeneous, non-negative, anisotropic and generic constitutive parameters are proposed based on linear transformation optics, which provides the flexibility for device design that is applicable for the practical fabrication. To remove the anisotropic property, a layered structure is developed based on effective medium theory. Simulation results show that with sufficient layers, the performance of the layered transparent device is nearly as perfect as an ideal device, and it is able to protect an antenna without sacrificing its performance. The feasibility of designing a transparent device by using natural isotropic materials instead of metamaterials would dramatically reduce the difficulty of fabrication and further promote the practicality of the device.展开更多
Electromagnetic field generators based on circular ring resonators,whose perimeters are integer times of equivalent wavelength,are well known to have attractive potential for producing radio vortexes carrying orbital ...Electromagnetic field generators based on circular ring resonators,whose perimeters are integer times of equivalent wavelength,are well known to have attractive potential for producing radio vortexes carrying orbital angular momentum(OAM).We study the radiation characteristics of the generators based on radiation vector and antenna array theory.The behaviors of radiation patterns,field intensity and phase distribution are investigated in detail,and show classical features of OAM beams.The evolution of the generators performance versus the OAM state is also analyzed.The proposed generators can be realized by all kinds of microwave transmission lines,verified by two different prototypes.The discussions and conclusions drawn in this study are useful and meaningful for the radio OAM generator design.展开更多
Transformation thermodynamics as a major extension of transformation optics has recently received considerable attention. In this paper, we present two-dimeusional （2D） and three-dimensional （3D） diamond-shaped tr...Transformation thermodynamics as a major extension of transformation optics has recently received considerable attention. In this paper, we present two-dimeusional （2D） and three-dimensional （3D） diamond-shaped transient thermal cloaks with non-singular homogeneous material parameters. The absence of singularity in the parameters results from the fact that the linear coordinate transformation is performed by expanding a line segment rather than a point into a region, while the mechanism behind the homogeneity is the homogeneous stretching and compression along orthogonal directions during the transformation. Although the derived parameters remain anisotropic, we further show that this can be circumvented by considering a layered structure composed of only four types of isotropic materials based on the effective medium theory. Numerical simulation results confirm the good performance of the proposed cloaks.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61461052 and 11564044)the Key Program of the Natural Science Foundation of Yunnan Province,China(Grant Nos.2013FA006 and 2015FA015)
文摘Arbitrarily shaped electromagnetic transparent devices with homogeneous, non-negative, anisotropic and generic constitutive parameters are proposed based on linear transformation optics, which provides the flexibility for device design that is applicable for the practical fabrication. To remove the anisotropic property, a layered structure is developed based on effective medium theory. Simulation results show that with sufficient layers, the performance of the layered transparent device is nearly as perfect as an ideal device, and it is able to protect an antenna without sacrificing its performance. The feasibility of designing a transparent device by using natural isotropic materials instead of metamaterials would dramatically reduce the difficulty of fabrication and further promote the practicality of the device.
基金Supported by the National Natural Science Foundation of China under Grant No 61461052the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20135301110003+1 种基金the Seventh of Yunnan University Graduate Student Scientific Research Project under Grant No ynuy201443the Doctoral Award for the Academic Newcomers(2014)of Yunnan Province under Grant No C6155501
文摘Electromagnetic field generators based on circular ring resonators,whose perimeters are integer times of equivalent wavelength,are well known to have attractive potential for producing radio vortexes carrying orbital angular momentum(OAM).We study the radiation characteristics of the generators based on radiation vector and antenna array theory.The behaviors of radiation patterns,field intensity and phase distribution are investigated in detail,and show classical features of OAM beams.The evolution of the generators performance versus the OAM state is also analyzed.The proposed generators can be realized by all kinds of microwave transmission lines,verified by two different prototypes.The discussions and conclusions drawn in this study are useful and meaningful for the radio OAM generator design.
基金Acknowledgements This work was supported by the Na- tional Natural Science Foundation of China （Grant Nos. 61161007 and 61261002）, the Specialized Research Fund for the Doctoral Program of Higher Education （Grant No. 20135301110003）, the Key Program of Natural Science of Yunnan Province （Grant No. 2013FA006）, and the Fostering Foundation for the Excellent Ph.D.Dissertation of Yunnan University （Grant No. XT512004）.
文摘Transformation thermodynamics as a major extension of transformation optics has recently received considerable attention. In this paper, we present two-dimeusional （2D） and three-dimensional （3D） diamond-shaped transient thermal cloaks with non-singular homogeneous material parameters. The absence of singularity in the parameters results from the fact that the linear coordinate transformation is performed by expanding a line segment rather than a point into a region, while the mechanism behind the homogeneity is the homogeneous stretching and compression along orthogonal directions during the transformation. Although the derived parameters remain anisotropic, we further show that this can be circumvented by considering a layered structure composed of only four types of isotropic materials based on the effective medium theory. Numerical simulation results confirm the good performance of the proposed cloaks.
