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Yao J.-J.,Hubei University | He S.-Y.,Hubei University | Zhang Y.-H.,Hubei University | Yin H.-C.,National Electromagnetic Scattering Laboratory | And 2 more authors.
IEEE Transactions on Antennas and Propagation | Year: 2014

This paper presents a novel and original approach for the evaluation of electromagnetic (EM) scattering from electrically large and complex target coated with uniaxial electric anisotropic medium (UEAM) layer. The evaluation includes two indispensable aspects, the geometry modeling of the target and the determination of the surface currents. Once the equivalent surface currents (ESCs) induced on the outer surface of the coated target are determined, the scattered field could be calculated by the corresponding radiation integrals. First, the outer surface of the arbitrarily shaped target is discretized using flat triangle facets. Second, the ESCs on any facet are deduced from the surface fields, which involve a complicated coupling of type I and type II waves existing in the UEAM. Thus, the determination of the surface fields and the ESCs on the surface of the target with large radius of curvature is the crux of the whole evaluation. By making the tangent plane approximation, used in the physical optics (PO) method, any discretized flat facet could be approximated as an infinite PEC plate coated with a homogenous UEAM layer. Thereafter, the scattering from the infinite coated plate is asymptotically calculated by using the proposed spectral domain method combined with saddle point evaluation (SDM-SPE). Ultimately, comparisons of the proposed asymptotic solution with the reference solutions calculated numerically confirm the validity and efficiency of the proposed SDM-SPE. Numerical results of several canonical and complex targets coated with UEAM layer are given by the proposed approach for the first time. © 1963-2012 IEEE.


Li J.,Wuhan University | He S.,Wuhan University | Yu D.,Wuhan University | Deng F.,Wuhan Maritime Communication Research Institute | And 2 more authors.
Optics Express | Year: 2011

A numerical matching method (NMM) based on the framework of the uniform geometrical theory of diffraction (UTD) is proposed to build the spectral functions for computing the diffraction field by anisotropic impedance wedge at an arbitrary skew incidence. The NMM starts from the coupled integral equations before they are converted into the coupled difference equations as the classic Maliuzhinets methods. Then, the spectral function in the Sommerfeld integral representation of the longitudinal components of the EM field is expanded by a series about the spectrum and the skew incident angle with unknown coefficients. With respect to the oblique incident angle based on normal to the edge incidence or grazing to the edge incidence, the spectral function is derived numerically by solving a system of algebraic equations constructed from the coupled integral equations, after choosing the numerical matching regions on the wedge faces and setting a Sommerfeld numerical integration path. On the basis of the sampled incidences, the asymptotic waveform evaluation (AWE) technique is employed to deduce the spectral function at any other skew incidence in the whole angle space (0°-90°) rapidly. Finally, the UTD solutions are provided far beyond the applicability of the perturbation approach and the numerical examples provide a uniform behavior of the field with respect to the observation angle. © 2011 Optical Society of America.


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.


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.


Lu G.,Communication University of China | Yin H.,National Electromagnetic Scattering Laboratory | Li Y.,Communication University of China | Wei X.,National Electromagnetic Scattering Laboratory
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2012

The investigation of multiscale homogenization of metamaterial has important theoretical and application value. Among the existing theories of homogenization of metamaterial, the electromagnetic (EM)characteristics of vector fields are not fully considered. Considering the micro-scale characteristic of the periodic structure and the divergence and curl characteristics of EM field, a new vector correction is proposed to describe the micro-scale EM characteristics, which both the irrotational field and the non-divergence field are considered, so the new micro-scale functions are obtained. By using the multiscale functions and multiscale finite element method(FEM) based on the edge-based vector basis functions, the effective EM parameters and the E-field distributions of periodic composite materials are calculated. Compared with FEM, it is shown that the multiscale FEM can calculate the EM parameters and E-field effectively.


Zhang X.-Z.,National Electromagnetic Scattering Laboratory | Huang P.-K.,National Electromagnetic Scattering Laboratory
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2010

Multi-aspect sythetic aperture radar (SAR) target recognition based on combined time-frequency feature and hidden Markov model (HMM) is investigated. HMM is a powerful tool to analyze and recognize the characteristics of multi-aspect SAR targets as a framework. One of the critical technique is feature extraction from the high resolution range profile (HRRP) of target echoes in the framework. A time-varying frequency factor weighted Fisher discrimination time-frequency spectra feature extraction method is proposed. Recognition experiments are performed by the feature extraction method and HMM, which shows that the performance of this feature extraction method is effective.


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.


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.


Chen H.,Xidian University | Zhang M.,Xidian University | Yin H.-G.,National Electromagnetic Scattering Laboratory
International Journal of Remote Sensing | Year: 2012

This article developed a bistatic facetized sea scattering model, in which the sea surface is envisaged as a profile that is locally approximated by planar facets. The radar return from each local facet is associated to a so-called semi-deterministic scheme, which is established by combining the geometric optics limit of the Kirchhoff approximation with the Bragg components of the Bass-Fuks' two-scale model. In order to evaluate the complex reflective function of the facetized sea surface, a Slope Summation Facet Model is presented by simply associating the facet phase with its relative path delay. Significant computational efficiency and good agreement with experimental data are observed, which make the proposed facet model well suited for application to fast estimation on sea scattering, as well as further simulations on synthetic aperture radar imagery and the composite pattern of ship-sea scattering. © 2012 Taylor & Francis.


Liu Y.,Communication University of China | Liu Y.,City University of Hong Kong | Luk K.M.,City University of Hong Kong | Yin H.,Communication University of China | Yin H.,National Electromagnetic Scattering Laboratory
2010 International Conference on Microwave and Millimeter Wave Technology, ICMMT 2010 | Year: 2010

This paper describes a novel bowtie patch antenna with electric dipole on a HIS substrate with a height of 0.102 λ at the lowest operating frequency. The low profile of the antenna is obtained by using a high impedance surface (HIS). The proposed antenna has a wide impedance bandwidth, which is over 45% ranging from 2GHz to 3.2GHz. And the symmetric radiation pattern with low back radiation is achieved. © 2010 IEEE.

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