Time filter

Source Type

Zang X.F.,Shanghai Key Laboratory of Modern Optical Systems | Li Z.,Shanghai Key Laboratory of Modern Optical Systems | Shi C.,Shanghai Key Laboratory of Modern Optical Systems | Chen L.,Shanghai Key Laboratory of Modern Optical Systems | And 4 more authors.
Optics Express | Year: 2013

Based on composite optical transformation, we propose a rotatable illusion media with positive permittivity and permeability to manipulate terahertz waves, and a new way to realize singular parameterindependent cloaks when the incident wave with a certain width propagates from specific incident directions. The fundamental mechanism of this kind of cloak is that the illusion media can be able to avoid the incident wave interacting with the objects. Comparing with traditional transformationcoordinate-based cloaks such as cylindrical-shaped cloaks, our cloaks are independent of singular material parameters. Furthermore, this type of rotatable illusion media can be applied to design tunable miniaturized highdirectivity antenna (a small antenna array covered with the rotatable illusion media appears like a large one and meanwhile, the radiation directions of the small antenna array is tunable via this rotatable illusion media). Full wave simulations are performed to confirm these points. © 2013 Optical Society of America.


Cheng D.,Communication University of China | Cheng D.,Tianjin University of Technology and Education | Yin H.-C.,Science and Technology on Electromagnetic Scattering Laboratory | Zheng H.-X.,Tianjin University of Technology and Education
Journal of Electromagnetic Waves and Applications | Year: 2012

To investigate a compact dual-band bandstop filter (DBBSF), a defected microstrip structure is proposed in this paper. The filter is composed of a spur-line structure and a rectangle slot. Resonant frequencies and the bandwidths of the filter can be adjusted by changing the length of the slot. The frequencies of designed DBBSF are operated at 2.12 and 2.9 GHz. A fabricated sample has been tested to verify our design. Measured and simulated results are in good agreement. The proposed filter is much more efficient than other similar structures. © 2012 Taylor & Francis.


Cheng D.,Communication University of China | Cheng D.,Tianjin University of Technology and Education | Yin H.-C.,Science and Technology on Electromagnetic Scattering Laboratory | Zheng H.-X.,Tianjin University of Technology and Education
Journal of Electromagnetic Waves and Applications | Year: 2012

A new defected microstrip structure is proposed in this paper. By etching a simple U-shaped slot in the center of microstrip line, a very good bandstop characteristic is exhibited. Its resonant frequency is extracted by transmission line network analysis. At the same time, an accurate method of adjusting the resonant frequency is proposed to match the designed resonant frequency exactly. As advantages of this structure, the lower insertion loss in the passband, higher rejection level, and more simply integrated structure have been mentioned. The applications have been verified in the design of both microstrip dual-band bandstop and bandpass filters by experiment. © 2012 Taylor & Francis.


Zhang M.,Xidian University | Chen H.,Xidian University | Yin H.-C.,Science and Technology on Electromagnetic Scattering Laboratory
IEEE Transactions on Geoscience and Remote Sensing | Year: 2011

This paper is aimed at developing an applicable and feasible facet model, which formulation should be tractable and time saving for personal computers to take charge of the efficient evaluation on the complex reflective function of large-scope 2-D oceans, either in the monostatic or bistatic case. The sea surface is envisaged as a two-scale profile on which the long waves are locally approximated by planar facets. The microscopic profile within a facet is assumed to be represented by a set of sinusoidal ripple patches. The complex reflective function of each modified facet is evaluated by a modified formula of the original Bass and Fuks' two-scale model, in which the phase factor of each facet is with the capillary wave modification. Several examples with application to the frozen or time-evolving case are given to prove the implementation. © 2011 IEEE.


Lin Y.,Science and Technology on Electromagnetic Scattering Laboratory | Guo L.,Science and Technology on Electromagnetic Scattering Laboratory
2015 IEEE 6th International Symposium on Microwave, Antenna, Propagation, and EMC Technologies, MAPE 2015 | Year: 2015

An integral equation domain decomposition method based on discontinuous Galerkin is proposed. The continuity of the induced electrical current at the boundaries between subdomains is enforced by discontinuous Galerkin penalty term. Elemental-wised CN/LT basis functions are used for expanding induced electrical current. Using CN/LT basis functions results in a much smaller linear system than using L2 basis functions, therefore the linear system obtained by using CN/LT basis functions can be solved more efficiently. Furthermore, the local characteristics of CN/LT basis functions provide the flexibility in geometry modeling and efficiency in mesh generation. The numerical results show good accuracy and the induced current satisfy the continuity condition on the artificial interface between subdomains. © 2015 IEEE.


Jiang W.-Q.,Xidian University | Zhang M.,Xidian University | Wei P.-B.,Xidian University | Yuan X.-F.,Science and Technology on Electromagnetic Scattering Laboratory
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2014

The small slop approximation (SSA) is an accurate method to calculate the electromagnetic (EM) scattering properties of rough surfaces. However, its computational complexity restricts its application to smaller domains and there is always the need for speedup in very large cases using pure central processing units (CPUs) hardware. With the development of graphics processing units (GPUs), more processors are dedicated to perform independent calculations. In addition, NVIDIA introduced a parallel computing platform, compute unified device architecture (CUDA), which provides researchers an easy way to use processors on GPU. To calculate EM scattering properties on GPU, we reformulate the SSA method with CUDA to take advantage of GPU threads. Because each thread executes synchronously and deals with a corresponding point data of rough surface, the CUDA-based SSA method calculates faster than the pure-CPU equivalent. To overcome memory limitations, the data of large rough surface are stored on hard disk. Moreover, a subsidiary thread is used to deal with the process of data transmission between the memory and the hard disk and reduce transmitting time further. The factors, block size, data transfers, and register, are also discussed in the optimization of the CUDA application. Test cases running on a NVIDIA GTX 460 GPU indicate that two orders of magnitude speedup, including file input and output, is obtained with our new formulation. © 2008-2012 IEEE.


Li L.-S.,Science and Technology on Electromagnetic Scattering Laboratory | Yin H.-C.,Science and Technology on Electromagnetic Scattering Laboratory
Chinese Physics Letters | Year: 2014

We investigate the optical response of a metallic wire calculated from the classical electromagnetic theory. The Drude (local) approach is compared with the semi-classical hydrodynamical theory calculations that reveal the Fano-like resonances of subsidiary peaks originated from the nonlocality. The bulk plasma resonances containing the nonlocal effects could be depressed by increasing the dissipation, while the blue shift of the surface localized plasma resonances could be enhanced by increasing the Fermi velocity. © 2014 Chinese Physical Society and IOP Publishing Ltd.


Nie D.,Xidian University | Zhang M.,Xidian University | Wang C.,Science and Technology on Electromagnetic Scattering Laboratory | Yin H.-C.,Science and Technology on Electromagnetic Scattering Laboratory
IEEE Transactions on Geoscience and Remote Sensing | Year: 2012

This paper presents a study of the microwave backscattering from 2-D time-evolving nonlinear surfaces of a sea with finite depth by using the second-order small-slope approximation. According to the shallow-water dispersion relation, the revised nonlinear hydrodynamic choppy wave model in connection with an experiment-verified sea spectrum for finite-depth water is employed to construct the wave profiles in the finite-depth sea. The numerical results show that the discrepancy between the choppy surfaces of the infinite-depth sea and their finite-depth counterparts for monostatic normalized radar cross section is much smaller than that between the linear surfaces and the nonlinear choppy surfaces. Furthermore, the comparison of the Doppler spectra of the backscattered echoes from the linear and nonlinear choppy sea surfaces shows that the nonlinear hydrodynamic features significantly impact the Doppler spectrum. In particular, the Doppler spectrum for nonlinear finite-depth sea presents much higher second-order peaks and increased spectral amplitudes in the frequency range around the Doppler peak frequency, which reiterates the importance of the role that the nonlinear hydrodynamic effect of waves played in the interpretation of backscattering from finite-depth nearshore seas from the qualitative point of view. © 2012 IEEE.


Zhu Z.,Nanjing University of Aeronautics and Astronautics | Sun X.,Science and Technology on Electromagnetic Scattering Laboratory | Xue H.,Nanjing University of Aeronautics and Astronautics | Guo H.,Nanjing University of Aeronautics and Astronautics | And 3 more authors.
Journal of Materials Chemistry C | Year: 2014

Graphene is a highly desirable material for efficient electromagnetic wave absorption due to its strong dielectric loss and low density. However, the main drawbacks in pristine graphene, such as high dielectric constant and low permeability, inevitably limit its performance due to the poor impedance matching. In this paper, reduced graphene oxide-spherical carbonyl iron composites (RGO-SCI) have been successfully fabricated through a facile wet chemical method. As expected, an apparent improvement of impedance matching in electromagnetic wave absorption could be found through the combination of RGO and SCI. A carbon-bridge effect was adopted to explain the electromagnetic wave absorbing process, which is closely related to a cross-linked framework structure of as-synthesized composites. Besides, in the range of 7.79-11.98 GHz with the thickness of 3.0 mm, the RGO-SCI composites exhibited efficient electromagnetic wave absorption characteristics (RL < 10 dB) with a minimum reflection loss of -52.46 dB. This journal is © the Partner Organisations 2014.


Chen H.,Xidian University | Zhang M.,Xidian University | Yin H.,Science and Technology on Electromagnetic Scattering Laboratory
Progress in Electromagnetics Research | Year: 2012

A feasible simulator, of which formulation and mechanism should be simple and time saving, is developed in this paper to overcome the diffculties of prediction on the EM scattering from three- dimensional (3-D) electrically very large ship-sea models. The work in this paper is twofold. First, the sea surfaces are supposed to be a combination of many locally-tilted slightly rough facets with two-scale profiles. The radar return from each local facet is associated to a semi- deterministic scheme which is established by combining the geometric optics limit of Kirchho® Approximation (KA-GO) with the Bragg components of Bass-Fuks' two-scale model (BFTSM). Furthermore, we associate the complex reflective function of the respective facet by a so-called Phase-modified Facet Model (PMFM), in which the facet's phase is treated approximately as a combination of inherent part that follows a homogeneous random distribution and coherent part associated with the relative path-delay. Second, in companion with the semi-deterministic treatment of the sea scattering model, a hybrid approximate algorithm is proposed to deal with the composite scattering of electrically large ship-sea model, which is entirely evolved through facets (for the sea surface) and wedges (for the ship target). The method of equivalent currents (MEC) and a hybrid frame which combines the four path model (FPM) with the quasi-image method (QIM) are employed to calculate the scattering characteristics of the ship-like target and ship-sea interactions, respectively. The entire simulator is of comparatively significant computational effciency, and suitable for providing a preliminary prediction on the instantaneous complex reflective functions and normalized radar cross sections (NRCS) mean levels for electrically very large ship-sea model.

Loading Science and Technology on Electromagnetic Scattering Laboratory collaborators
Loading Science and Technology on Electromagnetic Scattering Laboratory collaborators