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An air cavity method for increasing the underwater acoustic targets strength of corner reflector

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Defence Technology（防务技术） 2020年第2期16卷 493-501页

作者： Yi Luo Xin Chen Da-wei Xiao Wu-di Wen Tao-tao Xie Dept.of Weaponry Eng Naval University of EngineeringWuhan 430033China

In order to improve the underwater acoustic target strength of comer reflectors,according to the principle of acoustic impedance mismatch of the boundary layer,the method of using air cavity to increase the underwater acoustic target strength of corner reflectors is *** acoustic reflection coefficients of underwater air layer and single layer metal sheet are calculated and *** results show that the reflection coefficient of single layer metal sheet is greatly affected by frequency and incidence angle,and the reflection coefficient of air layer in water is large and little affected by frequency and incidence *** this basis,a new kind of airfilled cavity corner reflector is *** acoustic scattering characteristics of underwater airfilled cavity comer reflector are calculated cumulatively,and the results are compared with the monolayer metal sheet corner *** simulation results show that the acoustic reflection effect of the airfilled cavity corner reflector is *** order to verify the correctness of the method,the test was carried out in the silencing *** experimental results show that the simulation results are in good agreement with the experimental results,and the airfilled cavity can improve on acoustic reflection performance of the underwater corner reflector.

关键词： Underwater corner reflector Acoustic target strength Air cavity Acoustic impedance mismatch

The transient scattering mechanism of dipole array with reflector

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Chinese Physics B 2008年第2期17卷 608-617页

作者：张雪芹王均宏李增瑞 Key Laboratory of All Optical Network & Advanced Telecommunication Network Ministry of Education Institute of Lightwave Technology Beijing Jiaotong University

The transient backscattering mechanisms of a dipole array with reflector have been investigated from different aspects： time-domain, frequency-domain, and combined time-frequency domain, using 4 × 8 dipole arrays with reflector as an example. The data of scattering from the arrays under the incidence of Gaussian pulses are obtained by finite differential time domain method. The influences of the array structural parameters, incident wave parameters, and incident angles on the waveforms, spectrum, and time-frequency representations of the backscattered fields of the arrays are analysed and conclusions are drawn. From these characteristics and conclusions, it is possible to deduce the array structure inversely from the backscattered field.

关键词： dipole array reflector scattering time domain

Gradient-based optimization method for producing a contoured beam with single-fed reflector antenna

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Journal of Systems Engineering and Electronics 2019年第1期30卷 22-29页

作者： LIAN Peiyuan WANG Congsi XIANG Binbin SHI Yu XUE Song School of Mechano-Electronic Engineering Xidian University Xinjiang Astronomical Observation Chinese Academy of Sciences Department of Mechanical Engineering Thornton Science Park University of Chester

A gradient-based optimization method for producing a contoured beam by using a single-fed reflector antenna is presented. First, a quick and accurate pattern approximation formula based on physical optics(PO) is adopted to calculate the gradients of the directivity with respect to reflector's nodal displacements. Because the approximation formula is a linear function of nodal displacements, the gradient can be easily derived. Then, the method of the steepest descent is adopted, and an optimization iteration procedure is proposed. The iteration procedure includes two loops: an inner loop and an outer loop. In the inner loop, the gradient and pattern are calculated by matrix operation, which is very fast by using the pre-calculated data in the outer loop. In the outer loop, the ideal terms used in the inner loop to calculate the gradient and pattern are updated, and the real pattern is calculated by the PO method. Due to the high approximation accuracy, when the outer loop is performed once, the inner loop can be performed many times, which will save much time because the integration is replaced by matrix operation. In the end, a contoured beam covering the continental United States(CONUS) is designed, and simulation results show the effectiveness of the proposed algorithm.

关键词： reflector antennas single feed contoured beam gradient-based optimization method.

Research on key technologies for installation and maintenance of reflector of FAST

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Research in Astronomy and Astrophysics 2020年第5期20卷 103-108页

作者： Li-Qiang Song Peng Jiang Qi-Ming Wang Lei Yang National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

The reflector of the Five-hundred-meter Aperture Spherical radio Telescope(FAST)consists of 4450 reflector *** of the reflector faces the challenges of large span,complex terrain,serious interference,complex processes,high position and inability to use conventional *** installation technology for the flexible reflector with a large span was specially studied and *** half-span arc-moving cable cranes and two transfer trucks were jointly operated along a path that follows a circular *** installation of the reflector was completed,two half-span cable cranes were merged into a set of full-span cable cranes for maintenance of the *** of the reflector combines features of unit and site topography of *** installation technology follows scientific and reasonable practices,and is highly efficient and *** represents a breakthrough in many key technologies in construction and maintenance *** has promoted related technical progress in the construction and maintenance of complex *** has also provided an important reference for the construction and maintenance of similar projects,and has strong significance and applicability.

关键词： FAST reflector Installation Maintenance Cable crane

Ultra-thin Bloch-surface-wave-based reflector at telecommunication wavelength

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Photonics Research 2017年第5期5卷 494-499页

作者： R. DUBEY B. VOSOUGHI LAHIJANI M. HAYRINEN M. ROUSSEY M. KUITTINEN H. P. HERZIG Optics & Photonics Technology Laboratory (OPT) ecole Polytechnique Federale de Lausanne (EPFL) rue de la Maladiere 71b Institute of Photonics University of Eastern Finland

We experimentally demonstrate the optical properties of gratings engraved in a single-mode waveguide fabricated on top of a dielectric multilayer platform. The structure can be approached as a reflector for Bloch-surface-wavebased two-dimensional optical systems. The gratings have been fabricated on a thin(～λ∕25) titanium dioxide layer with a thickness of a few tens of nanometers deposited on the top of a multilayer platform. The optical properties of the gratings have been characterized in the near field with the aid of multi-heterodyne scanning nearfield optical microscopy. We investigate the surface wave's interference pattern, produced by incident and reflected light in front of the gratings. The presented gratings behave as an efficient Bloch-surface–wave-basedreflector at telecommunication wavelength.

关键词： reflector Bloch waveguide multilayer behave grating Bragg dielectric titanium fabrication

Theoretical analysis of a parabolic torus reflector antenna with multibeam

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Science China Mathematics 1995年第12期38卷 1520-1531页

作者：杜彪杨可忠钟顺时 Department of Electronics Engineering Shanghai University Shanghai 201800 China The Fifty-fourth Institute Ministry of Electronics Industry Shijiazhuang 050081 China

The parametric equations and the formulas of unit normal vector and surface element for aparabolic torus reflector antenna are derived and the mechanism of producing multibeam is proposed, Based on physical optics, the radiation pattern formulas for the antenna are given, with which the effects of geometric parameters on the antenna are studied. The good agreement between the calculated patterns and the measured ones shows that the theory is helpful for designing parabolic torus antennas.

关键词： multibeam antenna single offset antenna parabolic torus reflector antenna.

Design of Tapered Novel AMC Chessboard reflector for Broadband RCS Reduction

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Journal of Beijing Institute of Technology 2019年第4期28卷 739-743页

作者： Wenbo Zheng Wei Song Xinqing Sheng Center for Electromagnetic Simulation School of Information and ElectronicsBeijing Institute of TechnologyBeijing 100081China

An artificial magnetic conductor(AMC)chessboard reflector is designed which shows low backscattered radar cross sections(RCS)in a broad frequency band in this *** by the phase cancellation principle,a conventional chessboard low RCS metasurface can be formed by polarization-dependent mushroom-shaped *** new features are added to this design based on the conventional chessboard ***,the long edge of the metallic patch on the AMC element is concave to obtain a broader ***,the width of the patch in each AMC block is tapered in one direction to further extend the operating bandwidth for RCS *** backscattered RCS of the tapered AMC reflector is numerically investigated and compared with a non-tapered *** is found that by introducing the above features,an RCS reduction greater than *** can be obtained by the reflectors with relative bandwidth of 46%in the X-band.

关键词： artificial magnetic conductor(AMC) radar cross section(RCS)reduction reflector

SHAPED DUAL-reflector ANTENNA WITH RING FOCUS

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Science China Mathematics 1991年第10期34卷 1243-1255页

作者：章日荣杜树祥王汉礼周康健王涛 Institute No.54 Ministry of Machinery & Electronics Industry Shijiazhuang 050002 PRC

The equations of the reflector contours and the radiation patterns of the shaped dual-reflector antenna have been derived, and the methods of designing the antenna are also intro-duced briefly. The calculated and measured results suggest that this new type of antennahas the advantages of low VSWR (voltage standing-wave ratio), low sidelobe, and high *** it opens a bright prospect for the improvement of mid-and small-aperture anten-na performance, and gives the possibility for the realization of the 1990s new standard spec-ified by CCIR (International Radio Consultative Committee) on mid-and small-aperture an-tenna for satellite-communication earth stations.

关键词： low VSWR (voltage standing-wave ratio) low sidelobe high gain mid- and small-aperture reflector antenna with ring focus.

Properties of metal–insulator–metal waveguide loop reflector

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Chinese Physics B 2019年第9期28卷 249-252页

作者：龙虎曾选科蔡懿陆小微陈红艺徐世祥李景镇 Shenzhen Key Laboratory of Micro-Nano Photonic Information Technology College of Electronic Science and TechnologyShenzhen UniversityShenzhen 518060China Key Laboratory of Optoelectronic Devices and System of Ministry of Education and Guangdong Province College of Optoelectronic EngineeringShenzhen UniversityShenzhen 518060China

A new type and easy-to-fabricate metal-insulator-metal(MIM) waveguide reflector based on Sagnac loop is designed and *** transfer matrix theoretical model for the transmission of electric fields in the reflector is established,and the properties of the reflector are studied and *** simulation results indicate that the reflectivity strongly depends on the coupling splitting ratio determined by the coupling ***, different reflectivities can be realized by varying the coupling *** an optimum coupling length of 750 nm, the 3-dB reflection bandwidth of the MIM waveguide reflector is as wide as 1.5 μm at a wavelength of 1550 nm, and the peak reflectivity and isolation are 78%and 23 dB, respectively.

关键词： surface plasmon polaritons waveguide reflector