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IET International Radar Conference 2018, IRC 2018

作者： Xu, Feng Liu, Xin Liu, Li Wang, Chao Wang, YiFei National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China DFH Satellite Co. Ltd Beijing100094 China

Serious ground clutter is of significant influence for target detection in an airship-borne passive bistatic radar (ABPBR) using frequency modulated broadcasting signals. The authors propose a data segment processing scheme to recover the direct signal from multi-path clutter and suppress the multi-path in the surveillance channel in an ABPBR. Super exponential (SE) equaliser and sample matrix inversion algorithm are exploited to recover the transmitted signal and suppress the serious multi-path interference, respectively. It is shown that the proposed algorithms can accomplish the target detection task effectively by computer simulations. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Airships

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Calculation on External Heat Flux of a Space Camera

Calculation on External Heat Flux of a Space Camera

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第七届计算与信息科学国际学术会议

作者： Lian Xue Jiaqi Liu Lu Gao Zhiqi Liu Luping Zhang China National Key Laboratory of Science and Technology on Test Physics ＆Numerical Mathematics

In order to obtain accurate external heat flux data,the space system thermal simulation module in NX is used to solve the thermal analysis design problem on a camera in space flight *** effects of different time,different seasons and different orbital altitude on the external heat flux of spacecraft surface are *** calculation results show that for different seasons and different orbital altitudes,the variation laws of external heat flux on the same surface are basically the same,and there are only differences in *** differences are small,within 10 %;For the camera launched at different times of the day,the law of external heat flux changes is completely different,and difference in value is also very *** heat flux in the area exposed to the sun is 6.38 times that of the heat flux in the shadow *** results can be used to guide thermal design and calculate the temperature distribution of the *** the other hand,they provide reference for the design of other types of spacecraft with similar orbits.

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A New End-to-end Modulation Recognition Algorithm Based on Deep Learning

A New End-to-end Modulation Recognition Algorithm Based on D...

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International Conference on Signal Processing Proceedings (ICSP)

作者： Jingpeng Gao Fu Wang Lu Gao Xu Wang School of information and Communication Engineering Harbin Engineering University Harbin China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Institute of Space Long March Vehicle Beijing China

ISBN: (数字)9781728144801

ISBN: (纸本)9781728144818

To solve the problem of difficult modulation recognition of emitter signals at low signal-to-noise and low recognition rate caused by improper feature extraction, a new end-to-end modulation recognition algorithm based on deep learning is proposed. The algorithm can effectively recognize LFM, Costas, Frank code, and P1-P4 code. Firstly, an end-to-end modulation recognition network based on bi-directional long-short term memory is proposed to extract the time features of emitter signals for recognition. Then, to extract the space features of emitter signals, it explores a one-dimensional convolutional neural network structure. Finally, one-dimensional convolutional neural network and bi-directional long-short term memory are combined with pre-training and fine-tuning to accelerate the convergence speed and improve the recognition rate. The simulation results show that the recognition rate of the algorithm can reach 75.23% at the -6dB signal-to-noise ratio. It can also be used for modulation recognition in the mechanical field.

关键词： Feature extraction Modulation Training Signal to noise ratio Convolution Speech recognition Frequency modulation

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A method for feature extraction based on SVD and machine learning 2

A method for feature extraction based on SVD and machine lea...

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2019 2nd International Conference on Advanced Materials, Intelligent Manufacturing and Automation, AMIMA 2019

作者： Mao, Wei Huang, Shuxian Liu, Xin Liu, Hongyan Liu, Jiaqi Shu, Yi National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics 100076 China Beijing Institute of Precision Mechatronics and Controls 100076 China Beijing Institute of Long March Vehicle 100076 China

By studying the shortcomings of feature, which extracted from Radar-Cross Section(RCS),using mathematical and statistical method, using the idea of extracting abstract features in image recognition and speech recognition by artificial intelligence for reference[2][3]. This paper explores the possibility of extracting abstract features of target's RCS sequence, and proposes an abstract feature extraction method of RCS sequence based on singular value decomposition(SVD) feature decomposition. Because of the poor interpretability of abstract features, four different machine learning algorithms are used to classify the extracted Abstract features. The experimental results show that the machine learning algorithm can classify different types of spatial objects with high accuracy, which shows that the RCS features of different spatial objects can be characterized by abstract features. © Published under licence by IOP Publishing Ltd.

关键词： Radar cross section

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Study on Polarization em Wave's Transmission Characteristics in Chaff Cloud Based on Oguchi Method 5

Study on Polarization em Wave's Transmission Characteristics...

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5th IEEE International Conference on Computational Electromagnetics, ICCEM 2019

作者： Yang, Kunlong Li, Jianbing Liu, Xin College of Electronic Science National University of Defense Technology Changsha China National Key Laboratory of Science and Technology on Test Physics Numerical Mathematical Beijing Institute of Space Long March Vehicle Beijing China

ISBN: (纸本)9781538671115

The Oguchi method is an important tool for characterizing the transmission characteristics of polarized electromagnetic waves in precipitation. In this paper, the forward scattering matrix of chaff is calculated for the special random medium of chaff cloud. Then the transmission characteristics of polarized electromagnetic wave, including attenuation, (specific) differential phase, are studied by using Oguchi method. The obtained characteristics are consistent with the physical laws, and the feasibility of the Oguchi method in chaff characteristic analysis is preliminarily verified. © 2019 IEEE.

关键词： Forward scattering

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Design of W-band Sheet Beam EIK

Design of W-band Sheet Beam EIK

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Asia-Pacific Conference on Microwave

作者： Shuyuan Chen Jinliang Bai Ran Zhang Pei Zheng Jiaqi Liu Xin Liu Hongyan Liu Lu Gao National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (数字)9781728135175

ISBN: (纸本)9781728135182

Microwave tube is a vacuum electron device which can be used for amplification in the microwave frequency range. Sheet beam Extended Interaction Klystron (EIK) is an attractive Millimeter Waves amplifier because of its compact configuration, small voltage and high gain per unit length. In this paper, RF structure and the whole tube for W-band sheet beam EIK has been designed. A new and effective method of designing and studying W-band sheet beam EIK is presented in this paper. In order to get the same output power, several kinds of W-band sheet beam EIK are designed and compared. By optimizing the position of cavities, the output power can achieve 30 kW, which is calculated by threedimensional particle in cell (3D-PIC) software. It is a powerful basis for the subsequent study of sheet beam EIK.

关键词： Power generation Klystrons Power amplifiers physics mathematics Urban areas

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Modulation recognition of emitter signals based on SDAE-ODCNN

Modulation recognition of emitter signals based on SDAE-ODCN...

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IET International Radar Conference (IET IRC 2020)

作者： X. Wang J. Gao L. Gao F. Wang Harbin Engineering University College of Information and Communication Engineering Harbin China Beijing Institute of Space Long March Vehicle National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

In order to improve the recognition rate of emitter signals modulation under low signal noise ratio (SNR), an end-to-end method based on the stacked denoising autoencoder (SDAE) - one dimensional convolutional neural network (ODCNN) is proposed in this paper. The SADE-ODCNN is designed in this method and trained through a two-step training. In the SDAE-ODCNN model, the encoder of the SDAE can extract the denoised and compressed features of the received emitter signals. Then the ODCNN can further extract features to realize the recognition. The simulation results show that the average recognition rate of the method can reach 0.94 under 0dB. Thus the proposed method has a good application in the field of emitter signals modulation recognition.

关键词： radar computing modulation feature extraction neural nets image denoising learning (artificial intelligence) image classification

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Research on influence of special-shaped honeycomb radar absorbing structure for wide-band absorbing design

Research on influence of special-shaped honeycomb radar abso...

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IET International Radar Conference 2018, IRC 2018

作者： Wang, Ming-Liang Liu, Jia-Qi Xin, Liu Zhao, Xin-Ying Zhang, Sheng-Jun Lei, Mu Xia, Ai Guobin, Wan Wang, Wei-Dong Zhao, Ju-Yan National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical Beijing100076 China Northwestern Polytechnical University Xi'an710072 China

To realise wide-band stealth of radar absorbing material, a special-shaped honeycomb radar absorbing structure within nested cone-shaped scattering configuration is designed. Based on the HS theory and the impedance matching design, the rule about the influence of the geometry parameter and electromagnetic parameter on the absorbing performance is analysed. In addition, the reflectivity performance is analysed on the condition of oblique incidence angles. By optimising the geometry parameters of the special-shaped honeycomb structure and designing the multilayer composite structure based on impedance matching theory, the results indicate that the two absorbing peaks can be formed for the special-shaped honeycomb radar absorbing structure, and the reflectivity is improved for both the vertical and oblique incidence angles. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Reflection

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Complex forward scattering coefficient for signal characterisation

Complex forward scattering coefficient for signal characteri...

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IET International Radar Conference 2018, IRC 2018

作者： Chen, Jing Liu, Xiangrong Liu, Changjiang Dong, Xichao School of Information and Electronics Beijing Institute of Technology Beijing China Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics 100076 China

In this study, modelling and characteristics analysis of forward scattering coefficients and echoes are investigated. Traditional ground-target forward scattering signal model has not considered the impact of scattering phase;thus it is not accurate enough for describing air-target echoes. To solve this problem, a novel echo model was proposed based on the analytical deduction of complex forward scattering coefficient. The novel model separately expresses the target scattering characteristics and Doppler, greatly facilitating the theoretical analyses of echo characteristics. Then, theoretical and simulation investigations on the amplitude and phase characteristics of forward scattering echoes were made based on the complex forward scattering coefficient model. Theoretical explanations for the periodical fluctuation of far-field echo amplitude, periodical saltation of far-field echo phase, shadow blocking of near-field echo amplitude, and slow variation of near-field echo phase were given, respectively. Meanwhile, the boundary between near-field forward scattering and far-field forward scattering was quantitatively defined, which laid the theoretical foundation for the corresponding signal processing algorithms. Finally, with CST simulation results the accuracy of the echo model is verified and impacts of objects' real shapes are analysed. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Forward scattering

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Development of Climate and Earth System Models in China: Past Achievements and New CMIP6 Results

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Journal of Meteorological Research 2020年第1期34卷 1-19页

作者： Tianjun ZHOU Ziming CHEN Liwei ZOU Xiaolong CHEN Yongqiang YU Bin WANG Qing BAO Ying BAO Jian CAO Bian HE Shuai HU Lijuan LI Jian LI Yanluan LIN Libin MA Fangli QIAO Xinyao RONG Zhenya SONG Yanli TANG Bo WU Tongwen WU Xiaoge XIN He ZHANG Minghua ZHANG State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029 College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049 First Institute of Oceanography Ministry of Natural ResourcesQingdao 266061 School of Atmospheric Science Nanjing University of Information Science&TechnologyNanjing 210044 Chinese Academy of Meteorological Sciences China Meteorological AdministrationBeijing 100081 Tsinghua University Beijing 100084 National Climate Center China Meteorological AdministrationBeijing 100081 International Center for Climate and Environment Sciences Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029

The Earth–Climate System Model(ECSM)is an important platform for multi-disciplinary and multi-sphere integration research,and its development is at the frontier of international geosciences,especially in the field of global *** research and development(R&D)of ECSM in China began in the 1980 s and have achieved great *** China,ECSMs are now mainly developed at the Chinese Academy of sciences,ministries,and *** a brief review of the development history of Chinese ECSMs,this paper summarized the technical characteristics of nine Chinese ECSMs participating in the Coupled Model Intercomparison Project Phase 6 and preliminarily assessed the basic performances of four Chinese models in simulating the global climate and the climate in East *** projected changes of global precipitation and surface air temperature and the associated relationship with the equilibrium climate sensitivity under four shared socioeconomic path scenarios were also ***,combined with the international situation,from the perspective of further improvement,eight directions were proposed for the future development of Chinese ECSMs.

关键词： Earth–Climate System Model(ECSM) Chinese models Coupled Model Intercomparison Project Phase 6(CMIP6) model performance climate prediction and projection outlook

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