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Overshoot phenomena:Observation and simulation

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Earth and Planetary Physics 2024年第2期8卷 391-399页

作者： Ting Feng MoRan Liu ShiMin He Xiang Wang Chen Zhou Department of Space Physics School of Electronic InformationWuhan UniversityWuhan 430072China

High-power O-mode radio waves can excite artificial instabilities in the F region,according to experiments conducted at the European Incoherent Scatter Science Association(EISCAT)heating *** main instabilities include the parametric decay instability(PDI),oscillating two-stream instability(OTSI),and thermal parametric instability(TPI).The PDI and OTSI not only compete with each other,but also compete with the TPI,leading to a two-stage overshoot phenomenon:a miniovershoot occurs on a millisecond time scale after pump-on,followed by the main *** gain insight into the miniovershoot via a generalized Zakharov model,whereas the main overshoot can be observed as an enhanced plasma line overshoot phenomenon in incoherent scatter radar *** can also observe that the zero-frequency ion line exists only in the initial heating period after a cold start and that the upshifted and downshifted ion lines behave irregularly in the *** simulation results show that competition between the PDI and OTSI leads to an initial peak,which we named the *** following processes,namely ion density caviton generation,and collapse and cascade in the development of the PDI,contribute to the miniovershoot phenomenon.

关键词： overshoot parametric decay instability oscillating two-stream instability competition

An Efficient radar Detection Method of Maneuvering Small Targets

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Journal of Beijing Institute of Technology 2024年第1期33卷 1-8页

作者： Hongchi Zhang Yuan Feng Shengheng Liu school of Information and Electronics Beijing Institute of Technology and Beijing Key Laboratory of Fractional Signals and SystemsBeijing 100081China school of Information Science and Engineering Southeast UniversityNanjing 210096China

Detection of maneuvering small targets has always been an important yet challenging task for radar signal *** primary reason is that target variable motions within coherent processing interval generate energy migrations across multiple resolution bins,which severely deteriorate the parameter estimation performance.A coarse-to-fine strategy for the detection of maneuvering small targets is *** of small points segmented coherently is performed first,and then an optimal inter-segment integration is utilized to derive the coarse estimation of the chirp *** fractional Fourier transform(FrFT)is then employed to refine the coarse estimation at a significantly reduced computational *** results verify the proposed scheme that achieves an efficient and reliable maneuvering target detection with-16dB input signal-to-noise ratio(SNR),while requires no exact a priori knowledge on the motion parameters.

关键词： small target chirp sparse fractional Fourier transform(FrFT)

Probabilistic modeling of multifunction radars with autoregressive kernel mixture network

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Defence Technology（防务技术） 2024年第5期35卷 275-288页

作者： Hancong Feng Kaili.Jiang Zhixing Zhou Yuxin Zhao Kailun Tian Haixin Yan Bin Tang school of Information and Communication Engineering University of Electronic Science and Technology of ChinaChengdu 611731China

The task of modeling and analyzing intercepted multifunction radars(MFRs)pulse trains is vital for cognitive electronic *** methodologies predominantly rely on prior information or heavily constrained models,posing challenges for non-cooperative *** paper introduces a novel approach to model MFRs using a Bayesian network,where the conditional probability density function is approximated by an autoregressive kernel mixture network(ARKMN).Utilizing the estimated probability density function,a dynamic programming algorithm is proposed for denoising and detecting change points in the intercepted MFRs pulse *** results affirm the proposed method's efficacy in modeling MFRs,outperforming the state-of-the-art in pulse train denoising and change point detection.

关键词： Probabilistic forecasting Multifunction radar Unsupervised learning Change point detection Outlier detection

Multi-Agent Path Planning Method Based on Improved Deep Q-Network in Dynamic Environments

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Journal of Shanghai Jiaotong university(Science) 2024年第4期29卷 601-612页

作者： LI Shuyi LI Minzhe JING Zhongliang school of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai200240China

The multi-agent path planning problem presents significant challenges in dynamic environments,primarily due to the ever-changing positions of obstacles and the complex interactions between agents’*** factors contribute to a tendency for the solution to converge slowly,and in some cases,diverge *** addressing this issue,this paper introduces a novel approach utilizing a double dueling deep Q-network(D3QN),tailored for dynamic multi-agent environments.A novel reward function based on multi-agent positional constraints is designed,and a training strategy based on incremental learning is performed to achieve collaborative path planning of multiple ***,the greedy and Boltzmann probability selection policy is introduced for action selection and avoiding convergence to local *** match radar and image sensors,a convolutional neural network-long short-term memory(CNN-LSTM)architecture is constructed to extract the feature of multi-source measurement as the input of the *** algorithm’s efficacy and reliability are validated in a simulated environment,utilizing robot operating system and *** simulation results show that the proposed algorithm provides a real-time solution for path planning tasks in dynamic *** terms of the average success rate and accuracy,the proposed method is superior to other deep learning algorithms,and the convergence speed is also improved.

关键词： multi-agent path planning deep reinforcement learning deep Q-network

Novel method for extraction of ship target with overlaps in SAR image via EM algorithm

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Journal of Systems Engineering and Electronics 2024年第4期35卷 874-887页

作者： CAO Rui WANG Yong school of Electronics and Information Engineering Harbin Institute of TechnologyHarbin 150001China

The quality of synthetic aperture radar(SAR)image degrades in the case of multiple imaging projection planes(IPPs)and multiple overlapping ship targets,and then the performance of target classification and recognition can be *** addressing this issue,a method for extracting ship targets with overlaps via the expectation maximization(EM)algorithm is ***,the scatterers of ship targets are obtained via the target detection ***,the EM algorithm is applied to extract the scatterers of a single ship target with a single ***,a novel image amplitude estimation approach is pro-posed,with which the radar image of a single target with a sin-gle IPP can be *** proposed method can accom-plish IPP selection and targets separation in the image domain,which can improve the image quality and reserve the target information most *** of simulated and real mea-sured data demonstrate the effectiveness of the proposed method.

关键词： expectation maximization(EM)algorithm image processing imaging projection plane(IPP) overlapping ship tar-get synthetic aperture radar(SAR)

High-resolution, multi-frequency and full-polarization radar database of small and group targets in clutter environment

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Science China(Information Sciences) 2023年第12期66卷 281-282页

作者： Cheng HU Yujia YAN Rui WANG Qi JIANG Jiong CAI Weidong LI radar Research Laboratory School of Information and ElectronicsBeijing Institute of Technology

Detection of small low-altitude targets such as drone swarms, migrating insects and birds is crucial for both military and civilian applications [1]. There exist two main challenges which significantly affect the radar detection and tracking performance. Firstly, weak echo signals of small targets will be buried in strong ground clutter and rain clutter [2].

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Underdetermined direction of arrival estimation with nonuniform linear motion sampling based on a small unmanned aerial vehicle platform

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Defence Technology（防务技术） 2024年第3期33卷 352-363页

作者： Xinwei Wang Xiaopeng Yan Tai An Qile Chen Dingkun Huang Science and Technology on Electromechanical Dynamic Control Laboratory School of Mechatronical EngineeringBeijing Institute of TechnologyBeijing 100081China

Uniform linear array(ULA)radars are widely used in the collision-avoidance radar systems of small unmanned aerial vehicles(UAVs).In practice,a ULA's multi-target direction of arrival(DOA)estimation performance suffers from significant performance degradation owing to the limited number of physical *** improve the underdetermined DOA estimation performance of a ULA radar mounted on a small UAV platform,we propose a nonuniform linear motion sampling underdetermined DOA estimation *** the motion of the UAV platform,the echo signal is sampled at different ***,according to the concept of difference co-array,a virtual ULA with multiple array elements and a large aperture is synthesized to increase the degrees of freedom(DOFs).Through position analysis of the original and motion arrays,we propose a nonuniform linear motion sampling method based on ULA for determining the optimal *** the condition of no increase in the aperture of the physical array,the proposed method obtains a high DOF with fewer sampling runs and greatly improves the underdetermined DOA estimation performance of *** results of numerical simulations conducted herein verify the superior performance of the proposed method.

关键词： Unmanned aerial vehicle(UAV) Uniform linear array(ULA) Direction of arrival(DOA) Difference co-array nonuniform linear motion sampling method

Range-angle-dependent beamforming for FDA-MIMO radar using oblique projection

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Science China(Information Sciences) 2022年第5期65卷 223-241页

作者： Lan LAN Guisheng LIAO Jingwei XU Shengqi ZHU Yuhong ZHANG National Key Laboratory of radar Signal Processing Xidian University school of Electronic Engineering Xidian University

Frequency diverse array(FDA)-multiple-input and multiple-output(MIMO) radar is characterized with a range-angle-dependent transceive beampattern by introducing incremental frequencies among the transmit array elements and separating the transmitted waveforms with matched filtering in the receiver. In this respect, the paper aims to control the range-angle-dependent transceive beampattern for FDA-MIMO radar by designing the weight vector according to the desired response. At the design stage, the weight vectors to control the beampattern responses of different regions are devised by performing the orthogonal decomposition technique. Then, a filtering matrix using the oblique projection operator is constructed to filter the weight vectors for different regions, where two iterative algorithms are developed either considering concurrent or successive control of multiple regions. In such a way, a desired range-angle-dependent transceive beampattern is formed with simultaneously broadened nulls and a flat-top mainlobe. At the analysis stage,the method has been applied to interference mitigation in FDA-MIMO radar, where the mismatch exists both in the sidelobes and mainlobe. Simulated and measured results are provided to corroborate the effectiveness of the proposed methods.

关键词： FDA-MIMO radar range-angle-dependent beamforming weight vector orthogonal decomposition oblique projection interference mitigation

Metasurface-assisted low-frequency performance enhancement of ultra-broadband honeycomb absorber based on carbon nanotubes

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Nano Research 2024年第9期17卷 8542-8551页

作者： Cai-Liang Wang Shuang Bai Pei-Yan Zhao Tao Zhou Hui-Ya Wang Jun-Peng Wang Luo-Xin Wang Guang-Sheng Wang school of Chemistry Beihang UniversityBeijing 100191China Aerospace Science and Industry Corporation of Wuhan Magnetoelectricity Co. Ltd.Wuhan 430070China College of Materials Science and Engineering Key Laboratory for New Textile Materials and Applications of Hubei ProvinceWuhan Textile UniversityWuhan 430200China school of Chemistry and Chemical Engineering Lingnan Normal UniversityZhanjiang 524048China school of Materials Science and Engineering Zhejiang Sci-Tech UniversityHangzhou 310018China

Here,we present a unique method to enhance the low-frequency absorption performance of a honeycomb absorber by integrating a *** geometrical dimensions of the proposed metasurface have been numerically *** introduction of the metasurface allows exploitation of its robust resonance and superior impedance matching in low-frequency bands,thereby improving microwave absorption *** incorporation of the metasurface does not impact the wave transmission performance of the honeycomb core absorber at high-frequency band,thus preserving its high-frequency *** broadens the absorption range,leading to an expanded *** results reveal that the composite absorber(CA)exhibits strong absorption performance with an incident angle stability up to 45°for both transverse electric(TE)and transverse magnetic(TM)*** absorption mechanism of the CA has been investigated by using an equivalent circuit model and electromagnetic field analysis.A prototype was designed,fabricated,and tested to validate the proposed *** simulation and measurement results demonstrate that the prototype can achieve an average absorption rate exceeding 90%across a 1.0-18.0 GHz *** study introduces an innovative technique for creating microwave absorbers for low-frequency wideband applications.

关键词： low frequency metasurface radar absorption impedance matching