Xiao-Hua Wang

An Efficient Domain Decomposition Laguerre-FDTD Method for Two-Dimensional Scattering Problems

In this paper, an efficient domain decomposition technique is introduced into the unconditionally stable finite-difference time-domain (FDTD) method based on weighted Laguerre polynomials to solve two-dimensional (2-D) electromagnetic scattering problems. The whole computational space is decomposed into multiple subdomains where there is no direct field coupling between any two different subdomains. For the large sparse matrix equation generated by the implicit scheme, the domain decomposition technique transforms this large scale equation into some independent smaller equations. With the total-field/scattered-field boundary and Murs second-order absorbing boundary condition, the radar cross sections of two 2-D structures are calculated. The numerical examples verify the accuracy and efficiency of the proposed method.

Far-Field Super-Resolution Imaging With Compact and Multifrequency Planar Resonant Lens Based on Time Reversal

Planar resonant lenses (PRLs) consisting of periodically distributed strip resonators with different lengths are proposed for far-field super-resolution electromagnetic imaging. With the help of PRLs, evanescent waves can be converted into propagation waves. So, based on time-reversal (TR) technique, time-reversal mirror in the far-field can receive the electromagnetic signals carrying the subwavelength information. Experiments are performed to validate the proposed method in laboratory environment at microwave band. Far-field super-resolution imaging results with resolutions of λ/20 and λ/10, respectively, are obtained, well beyond the diffraction limit. The compact size and multifrequency property of the proposed PRLs will make them easily be integrated to new super-resolution imaging systems.

Far-Field Super-Resolution Imaging of Scatterers With a Time-Reversal System Aided by a Grating Plate

A time-reversal imaging system for far-field super-resolution imaging of scatterers is proposed. First, a grating plate, similar to the optical far-field super lens, is designed to convert near-field evanescent waves to propagative waves with wavevector modulation. Then, the scattered signals are processed by a time-reversal (TR) technique and retransmitted back. Finally, the images of the targets are reconstructed by doing demodulation operations in the k-domain to the TR field at the refocusing time. Imaging results show that two scatterers separated by 0.1xa0λ can be distinguished clearly.

Near-Field Periodic Subwavelength Holey Metallic Plate for Far-Field Superresolution Focusing

Far-field focusing with superresolution aided by a proposed metallic plate is investigated in this paper. The proposed near-field structure can be employed to distinguish point-like sources with subwavelength distance and enhance the field strength based on the spoof surface plasmon polaritons theory, and by the simulations of near- and far-field spectrums, it can be found that some near-field evanescent waves carried the superresolution information can be converted to propagation waves and propagate to the far-field. Therefore, with the help of time reversal imaging process, the far-field superresolution focusing is validated by the experiments in laboratory environment. A resolution of <inline-formula><tex-math notation=LaTeX>

Time reversal far-field super-resolution electromagnetic imaging aided by the near-field sub-wavelength structures

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Design of a rotated feeding wide-angle scanning phased array with circular polarization

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Multi-frequency electrical resonant lens for far-field sub-wavelength imaging

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Far-field frequency domain electromagnetic time reversal subwavelength imaging of scatterers assisted with grating plate

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Researches on far-field super-resolution imaging based on time-reversed electromagnetics at UESTC

The resolution of traditional far-field imaging systems is restricted by the diffraction limit, because only the propagation waves, emitted by the source or scattered by the object, can be received by the devices of imaging systems. As we know, evanescent waves carry sub-wavelength information. But they cannot propagate to the far-field and exhibit exponential attenuation in the space. Therefore, how to receive the information of these waves in the far-field is a key to realize the super-resolution imaging.

Electromagnetic Scattering From Periodic Array With Object Using a New Efficient Aggregate Basis Function Method

Since the birth of the phased array technology, phased array antennas have been widely used in communication, navigation, electronic warfare and other fields. For the reason that circular polarization antennas have advantages of inhibition of the rainfall depolarization effect and anti-multipath reflection effect, circular polarization antenna chosen as the array elements designed to form a phased array with high performance in this paper. This antenna element, excited through a single feed point, is composed of a square patch in the middle and four circular patches with different radii. Thus, the circular polarization and the wide beam performance of the proposed antenna element are achieved by adjusting the size of the circular patches. To obtain a wide angle scanning function, a 4 × 4 rotated feeding antenna array with this proposed microstrip antenna element is designed. Every four adjacent elements, i.e., 2 × 2 elements, form a subarray in the proposed array. An element in the subarray is regarded as the reference one and the positions of the other three elements deviate from it of 90°, 180° and 270°, respectively. Firstly, the other three elements are fed with the compensation phases of 90°, 180° and 270° to make the cross polarization between the elements to be offset. Secondly, the phase differences are added to control the scan angle in scanning planes. The microstrip antenna array realizes a ±45° wide angle scan in the φ = 0° and φ = 90° planes with the gain more than 15 dB and the axial ratio within the scope of the main lobe width less than 3 dB.