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Chen X.,Wuhan University | He S.-Y.,Wuhan University | Yu D.-F.,Wuhan University | Yin H.-C.,National Electromagnetic Scattering Laboratory | And 2 more authors.
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2013

An accurate creeping ray-tracing algorithm is presented in this paper to determine the tracks of creeping waves (or creeping rays) on arbitrarily shaped free-form parametric surfaces [nonuniform rational B-splines (NURBS) surfaces]. The main challenge in calculating the surface diffracted fields on NURBS surfaces is due to the difficulty in determining the geodesic paths along which the creeping rays propagate. On one single parametric surface patch, the geodesic paths need to be computed by solving the geodesic equations numerically. Furthermore, realistic objects are generally modeled as the union of several connected NURBS patches. Due to the discontinuity of the parameter between the patches, it is more complicated to compute geodesic paths on several connected patches than on one single patch. Thus, a creeping ray-tracing algorithm is presented in this paper to compute the geodesic paths of creeping rays on the complex objects that are modeled as the combination of several NURBS surface patches. In the algorithm, the creeping ray tracing on each surface patch is performed by solving the geodesic equations with a Runge-Kutta method. When the creeping ray propagates from one patch to another, a transition method is developed to handle the transition of the creeping ray tracing across the border between the patches. This creeping ray-tracing algorithm can meet practical requirements because it can be applied to the objects with complex shapes. The algorithm can also extend the applicability of NURBS for electromagnetic and optical applications. The validity and usefulness of the algorithm can be verified from the numerical results. © 2013 Optical Society of America. Source


Chen X.,Wuhan University | He S.-Y.,Wuhan University | Yu D.-F.,Wuhan University | Yin H.-C.,National Electromagnetic Scattering Laboratory | And 2 more authors.
IEEE Antennas and Wireless Propagation Letters | Year: 2013

One of the great challenges in calculating the uniform geometrical theory of diffraction (UTD) surface diffracted fields on NURBS surfaces is due to the difficulty in determining the geodesic paths along which the creeping waves propagate. On one single parametric surface patch, the geodesic computation needs to be performed by solving the geodesic equations numerically. Furthermore, realistic objects are generally modeled as the union of several connected NURBS patches. Due to the discontinuity of parameter between patches, it is more complicated to compute geodesic paths on several connected patches than on one single patch. Therefore, this letter develops an adjustable modeling scheme that can adjust the parameterizations of several connected patches to support the geodesic computation throughout these patches. Based on the geodesic computation, the UTD diffractions by NURBS models can be analyzed. © 2013 IEEE. Source


Liu Y.,Communication University of China | Liu Y.,City University of Hong Kong | Luk K.M.,City University of Hong Kong | Yin H.C.,Communication University of China | Yin H.C.,National Electromagnetic Scattering Laboratory
Progress In Electromagnetics Research Letters | Year: 2010

Utilizing the special physical characteristic of a high impedance surface, a radio frequency identification tag antenna working at 920 MHz for metallic ground is proposed. The antenna not only overcomes the problem of impedance mismatching when placing on a metallic object, but also exhibits a low-profile antenna structure. Source


Zhang M.,Xidian University | Nie D.,Xidian University | Yin H.-C.,National Electromagnetic Scattering Laboratory
Waves in Random and Complex Media | Year: 2011

A versatile composite surface model (VCSM) is presented for estimation of the electromagnetic backscattering coefficient of the sea. Taking into account the statistical characteristics of the sea surface and the validity conditions of component models for the small-scale and large-scale surfaces in the composite surface model (CSM), a method for the two-scale decomposition of sea surfaces is introduced. On this basis, the cutoff wavenumber with wind speed dependence and incident wave frequency dependence is applied to separate the sea spectrum into large- and small-scale components at different sea states with increased accuracy. Then, numerical results of the backscattering coefficient are evaluated and discussed in the case of different wind speeds, polarizations as well as incident frequencies. Finally, the VCSM is verified through the comparisons with the available experimental data, and the comparisons of the VCSM results and the classical CSM results also show that the VCSM behaves better. © 2011 Taylor & Francis. Source


Zhang M.,Xidian University | Luo W.,Xidian University | Liu J.T.,Xidian University | Bai L.,Xidian University | Zhou P.,National Electromagnetic Scattering Laboratory
Chinese Physics Letters | Year: 2010

Numerical modeling on the composite electromagnetic (EM) scattering from a two-dimensional (2-D) object located on a rough surface is presented by using the efficient method of fundamental solution (MFS). The proposed special choice of the MFS is an interesting alternative to the onerous mesh generation in the traditional numerical methods, particularly for the method of moment (MoM). There is no mesh scheme and singularity analysis, the field to be solved can be obtained directly in terms of the fundamental solutions of the appropriate wave equations. The numerical results are obtained and compared with the traditional MoM results, to demonstrate the accuracy and effectiveness of this technique. © 2010 Chinese Physical Society and IOP Publishing Ltd. Source

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