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2017 International Conference on Radar Systems, Radar 2017

作者： Chen, Shuyuan Liu, Jiaqi Gao, Lu Bai, Jinliang Jiang, Zhiye Xu, Feng Qin, Peng Liu, Hongyan Liu, Xin Li, Hu Gao, Jingpeng National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China

ISBN: (纸本)9781785615153

Sheet beam Extended Interaction Klystron (EIK) is an attractive Millimeter Waves (MMW) amplifier because of its high gain per unit length and compact configuration, which can be used in radar transmission system. In this paper, RF structure and beam wave interaction system of W band sheet beam EIK has been designed. A new and effective method of designing and studying the beam wave interaction system is presented in this *** whole tube consists of one single-gap cavity, six tri-gaps cavities and one five-gaps cavity. By optimizing the position of cavities, the output power can achieve 30 kW and high gain of 50 dB, which is calculated by three dimensional particle in cell (3D-PIC)*** provides a powerful basis for the subsequent study of sheet beam EIK. © 2017 Institution of Engineering and technology. All rights reserved.

关键词： Millimeter waves

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Study of RF structure for W band sheet beam EIK

Study of RF structure for W band sheet beam EIK

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IET International Radar Conference 2015

作者： Chen, Shuyuan Jiang, Zhiye Liu, Jiaqi Gao, Lu Bai, Jingliang Liu, Hongyan Meng, Gang Xu, Feng Li, Hu Liu, Chengguo Zhu, Guangsheng National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China

ISBN: (纸本)9781849199940

Microwave tubes are vacuum electron devices used for the generation and amplification of radio frequencies in the microwave frequency range. Klystron is a kind of microwave tubes which is used in radar. A sheet-beam Extended Interaction Klystron (SBEIK) is an attractive MMW amplifier because of its high gain per unit length and compact configuration. The RF structure is an important part of the whole tube, which is used for beam wave interaction. In this paper, two kinds of barbell cavity has been studied. The difference between the separating multi-gap barbell resonant cavity and the strong coupling multi-gap barbell cavity has been discussed. RF parameters have been calculated by 3D simulations.

关键词： Microwaves

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Experimental Studies of Low-Pressure Plasma Jet by Means of Langmuir Probes and Emission Spectra

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Plasma science and technology 2009年第3期11卷 307-313页

作者：刘磊曹金祥牛田野王亮孟刚刘鑫袁雷邬润辉张生俊任爱民 Key Laboratory of Basic Plasma Physics Chinese Academy of Sciencesand Department of Modern PhysicsUniversity of Science and Technology of China China Academy of Space Technology Test Physics & Numerical Mathematics Laboratory

An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and 50 cm downstream from the nozzle exit were calculated, respectively, by the Boltzmann plot method.

关键词： plasma jet spatial distribution probe array emission spectrum

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Research on dual-polarisation printed dipole antenna for spherical near-field measurements

Research on dual-polarisation printed dipole antenna for sph...

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IET International Radar Conference 2018, IRC 2018

作者： Zheng, Pei Liu, JiaQi Wang, ShangYue Zhang, Ran Fan, Hu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

Here a dual-polarisation printed dipole antenna for spherical near-field measurements is proposed. The printed dipole employs double-layered structure to obtain low cross-polarisation and uses irregular patch to get wide bandwidth. Two such dipoles are cross arranged to form a dual-polarisation dipole antenna. Simulated results show that the bandwidth is over 72% when VSWR is less than 3, the cross-polarisation ratio is better than 30 dB, the port isolation between two dipoles is better than −26 dB, while good radiation performance is also obtained. All the results above prove that the crossed arrangement structure will not affect the performance of the printed dipole, and the strength of mutual coupling between probes can be neglected. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Dipole antennas

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Research on near-field focusing algorithm of reconfigurable reflect-array

Research on near-field focusing algorithm of reconfigurable ...

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IET International Radar Conference 2018, IRC 2018

作者： Liu, Hong Yan Zheng, Pei Wang, Chao Guo, Lei Zhang, Xin Yu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

In this study, the near-field beam focusing algorithm of reconfigurable reflect array for security imaging application is proposed. The proposed near-field focusing algorithm is based on classic array method, which is usually adopted for far-field pattern calculation. In order to satisfy the near-field imaging application, the imaging distance is added to array method, and the improved formula can calculate the shifting phase of every array element precisely. In addition, due to discrete phase characteristic of reconfigurable reflect array, a phase choice method based on trigonometric function is used in authors' design. Based on the proposed algorithm, the shifting phase of every element is calculated and obtained the simulated beam focusing patterns. Meanwhile, the calculated shifting phase is written to whole array by field-programmable gate array, the near-field beam scanning patterns is measured and the measured results are in good agreement with the simulated ones. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Field programmable gate arrays (FPGA)

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Dispersive FDTD scheme with conformal technology for analyzing electromagnetic scattering of inhomogeneous plasma array

Dispersive FDTD scheme with conformal technology for analyzi...

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IET International Radar Conference 2015

作者： Ai, Xia Liu, Shendong Zhang, Shengjun Wang, Mingliang Liu, Jiaqi Meng, Gang Zhou, Hongchao National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical China

ISBN: (纸本)9781849199940

In this paper, a dispersive conformal FDTD method have been proposed to accurate model the interface between two adjacent dispersive mediums. The method is based on the technology of area average between two adjacent dispersive interfaces, which is different from existing dispersive conformal FDTD schemes which involve with the interface between free space and dispersive medium. numerical results show the proposed method would enhance the accurate level compared to the staircasing FDTD scheme involved in the inhomogeneous plasma.

关键词： numerical methods

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Higher order shift operater FDTD scheme for scattering of cloaking structure

Higher order shift operater FDTD scheme for scattering of cl...

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IET International Radar Conference 2015

作者： Ai, Xia Zhang, Shengjun Wang, Mingliang Wang, Weidong Liu, Jiaqi Liu, Chengguo Liu, Xuemei National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical China

ISBN: (纸本)9781849199940

In this paper, a higher-order shift operater (SO) FDTD scheme with second-order accuracy in time and fourth-order in space has been proposed to accurately model scattering of perfect electronic conductor coated with cloaking structures. Several different electromagnetic parameters of the cloaks are taken into account using SO-FDTD method. numerical results indicate that the proposed method is more accuracy than the traditioinal method maintaining the same grid size. Scattering of different kinds of simplified cylindrical cloaks including thickness and loss are presented and could be served as further study on this subject.

关键词： Finite difference time domain method

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The research on the effects of an active FSS with circle element on the characteristics of Radar Absorbing Materials

The research on the effects of an active FSS with circle ele...

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IET International Radar Conference 2015

作者： Wang, Ming-Liang Zhang, Sheng-Jun Liu, Jia-Qi Wang, Wei-Dong Ai, Xia Liu, Shengdong Liang, Wei National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical Beijing China

ISBN: (纸本)9781849199940

An active frequency selective surface (FSS) is designed, and is combined with Radar Absorbing Materials to form a composite absorbing structure. Based on the equivalent theory that the PIN diode can be regarded as resistance, the voltage-loading resistance of active FSS element is researched for RAM containing FSS, and the electromagnetic wave reflectivity performance is analyzed. The influence of active FSS design parameters on the reflectivity of RAM is researched, and the FSS design parameters include the voltage-loading manner, the resistance parameter, and the position in the RAM. The research result shows that the resonance frequency of RAM containing FSS can be dynamically adjusted from 3GHz to 4GHz by changing voltage-loading resistance of active FSS, and the reflectivity can be reduced from -13dB to -35dB.

关键词： Reflection

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Study on reflection selective structure on near infrared

Study on reflection selective structure on near infrared

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International Conference on Electronics and Optoelectronics

作者： Li, Yizhou Wang, Daorong Liu, Jiaqi Li, Hongjie Zhao, Juyan National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical Beijing China

ISBN: (纸本)9781612842738

The paper bring forward a design of multilayer structure which has a high reflectivity for 1.82μm laser beam and a high absorptivity for 1.48μm laser beam. The experiment reveal that the absorptivity of the film reach to 95% at incidence angle from 0 to 40 for 1.48μm laser beam and has a high reflectivity for 1.82μm high power laser at incidence angle of 30o at laser power density above 500w/cm2. © 2011 IEEE.

关键词： Reflection

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Unmanned aerial vehicle infrared detector simulation modelling and performance analysis

Unmanned aerial vehicle infrared detector simulation modelli...

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2017 IASTED International Conference on Modelling, Identification and Control, MIC 2017

作者： Liu, Fang Liu, Xin Liu, Jiaqi National Key Laboratory of Science and Technology On Test Physics and Numerical Mathematics Nandahongmen Road No.1 Beijing China

ISBN: (纸本)9780889869882

An observation model of unmanned aerial vehicle(UAV) infrared detector is developed. The visibility criterion is derived via geometric relationships between the infrared detector, target and earth, the constraint of the detector's frame angle, and the detection range of infrared detector. Because of the infrared sensor can only obtain the angular information of the target, so it is impossible for one detector to locate position of the target. The position of the target is obtained by two or more detectors. The least square method based multi-sensor target tracking method is introduced. It is important to set a filter before using the tracking data as there are observation errors caused by UAV position error, UAV attitude error, sensor pointing error and sensor image plane position error. The extend Kalman Filter (EKF) algorithm is used to smooth the tracking signals. Finally, two UAV infrared detectors observing a low-orbit target is simulated for their observation performance. The result shows that the infrared detectors can observe the target within the scope of the detection range. When the target flies off the top of the UAV, the detectors can't observe it because of the constraint of the frame angle. The observation error is reduced substantially after the EKF is used.

关键词： Infrared detectors

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