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Circulate shifted OFDM chirp waveform diversity design with digital beamforming for MIMO SAR

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Science China(Information Sciences) 2017年第10期60卷 217-228页

作者： Shangwen LIU Zenghui ZHANG wenxian yu Shanghai Key Laboratory of Intelligent Sensing and Recognition Shanghai Jiao Tong University

Waveform diversity design has always been the key to multiple-input multiple-output(MIMO)synthetic aperture radar(SAR) systems, and it is known that synthetic integral side lobe ratio(SISLR) is a more optimal indicator than the integral side lobe ratio(ISLR) to evaluate the orthogonality between different MIMO SAR waveforms. This paper presents proof that it is difficult to obtain the SISLR of an existing waveform such that it is sufficiently low to achieve high SNR for SAR imaging. Thus, it is necessary to find a way to separate these MIMO SAR waveforms in other domains, for example, a spatial domain by digital beamforming(DBF). Learning from Krieger's idea of short-term shift-orthogonal waveforms and using joint time-frequency transforms(Gabor transform) to prove that for most existing SAR waveforms cyclic shift is a good operation with which to generate short-term shift-orthogonal waveforms. This paper presents the designs of four circulate shifted OFDM chirp waveforms, which have a much lower SISLR and retain all the advantages of the classical chirp waveform such as a large time-bandwidth product, constant amplitude, implementation simplicity, and good Doppler tolerance.

关键词： MIMO SAR Gabor transform cyclic shift OFDM chirp waveform synthetic integral side lobe ratio(SISLR)

Aircraft Detection for HR SAR Images in Non-homogeneous Background Using GGMD-Based Modeling

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Chinese Journal of Electronics 2019年第6期28卷 1271-1280页

作者： HU Hao HUANG Lanqing yu wenxian Shanghai Key Laboratory of Intelligent Sensing and Recognition Shanghai Jiao Tong University

In the problem of aircraft detection for High resolution(HR) Synthetic aperture radar(SAR)images, the background areas commonly contain multiple land cover types, such as runways and grassland. The conventional Constant false alarm rate(CFAR) detection in these non-homogeneous backgrounds with homogeneous assumption leads to unreliable detection results. This paper constructs a one-stage detection method based on the Generalized gamma mixture distribution(GGMD),which is regarded as a competitive and applicable model for combining the advantages of the Generalized gamma distribution(GGD) and the Finite mixture model(FMM).In order to evaluate the availability of the proposed algorithm, HR SAR images for aircraft detection from different product types and with various resolutions are examined. Compared with the CFAR algorithms based on the Gamma distribution, the GGD, and the gamma mixture distribution, the proposed algorithm demonstrates its availability and effectiveness for aircraft detection in HR SAR images in non-homogeneous background.

关键词： Constant false alarm rate(CFAR) Generalized gamma mixture distribution(GGMD) Expectation maximization(EM) Synthetic aperture radar(SAR)

A Multicarrier Phase-Coded Waveform Design Scheme for Joint Radar and Communication System

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Chinese Journal of Electronics 2021年第4期30卷 769-780页

作者： DU Zhen ZHANG Zenghui yu wenxian Shanghai Key Laboratory of Intelligent Sensing and Recognition School of Electronic Information and Electrical EngineeringShanghai Jiao Tong University

A Multicarrier phase-coded(MCPC)waveform design scheme with two steps for Joint radar and communication(JRC) system is developed. Firstly, an integrated MCPC waveform design method is addressed by simultaneously maximizing the Signal-to-clutter-to-noise ratio(SCNR) and the Shannon capacity, subject to both the Integrated sidelobe level ratio(ISLR) constraint and the energy constraint. This model is theoretically proved to be a convex optimization problem with respect to the absolute squares of the transmit weights corresponding to different subcarriers, of which the analytical result is also discussed. Subsequently, by further optimizing the phases of the transmit weights, minimizing the Peak to average power ratio(PAPR) for JRC system is recast as a Semidefinite programming(SDP) problem, which can be effectively solved with the Semidefinite relaxation(SDR) technique via Eigenvalue decomposition(EVD)or Complex Gaussian randomization(CGR). Numerical examples are provided to verify the effectiveness of the proposed scheme.

关键词： Waveform design Joint radar and communication system Multicarrier phase-coded waveform Peak to average power ratio

A coupled convolutional neural network for small and densely clustered ship detection in SAR images

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Science China(Information Sciences) 2019年第4期62卷 111-126页

作者： Juanping ZHAO Weiwei GUO Zenghui ZHANG wenxian yu Shanghai Key Laboratory of Intelligent Sensing and Recognition School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University

Ship detection from synthetic aperture radar(SAR) imagery plays a significant role in global marine surveillance. However, a desirable performance is rarely achieved when detecting small and densely clustered ship targets, and this problem is difficult to solve. Recently, convolutional neural networks(CNNs)have shown strong detection power in computer vision and are flexible in complex background conditions,whereas traditional methods have limited ability. However, CNNs struggle to detect small targets and densely clustered ones that exist widely in many SAR images. To address this problem while preserving the good properties for complex background conditions, we develop a coupled CNN for small and densely clustered SAR ship detection. The proposed method mainly consists of two subnetworks: an exhaustive ship proposal network(ESPN) for ship-like region generation from multiple layers with multiple receptive fields, and an accurate ship discrimination network(ASDN) for false alarm elimination by referring to the context information of each proposal generated by ESPN. The motivation in ESPN is to generate as many ship proposals as possible, and in ASDN, the goal is to obtain the final results accurately. Experiments are evaluated on two data sets. One is collected from 60 wide-swath Sentinel-1 images and the other is from20 GaoF en-3(GF-3) images. Both data sets contain many ships that are small and densely clustered. The quantitative comparison results illustrate the clear improvements of the new method in terms of average precision(AP) and F 1 score by 0.4028 and 0.3045 for the Sentinel-1 data set compared with the multi-step constant false alarm rate(CFAR-MS) method. The values are verified as 0.2033 and 0.1522 for the GF-3 data set. In addition, the new method is demonstrated to be more efficient than CFAR-MS.

关键词： SAR image ship detection CNN exhaustive ship proposal network(ESPN) accurate ship discrimination network(ASDN)

Novel cued search strategy based on information gain for phased array radar

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Journal of Systems Engineering and Electronics 2008年第2期19卷 292-297页

作者： Lu Jianbin Hu Weidong Xiao Hui yu wenxian ATR Key Lab National Univ. of Defense Technology Changsha 410073 P. R. China

A search strategy based on the maximal information gain principle is presented for the cued search of phased array radars. First, the method for the determination of the cued search region, arrangement of beam positions, and the calculation of the prior probability distribution of each beam position is discussed. And then, two search algorithms based on information gain are proposed using Shannon entropy and Kullback-Leibler entropy, respectively. With the proposed strategy, the information gain of each beam position is predicted before the radar detection, and the observation is made in the beam position with the maximal information gain. Compared with the conventional method of sequential search and confirm search, simulation results show that the proposed search strategy can distinctly improve the search performance and save radar time resources with the same given detection probability.

关键词： phased array radar search strategy cued search beam position information gain.

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Collaborative visual SLAM for multiple agents:A brief survey

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Virtual Reality & Intelligent Hardware 2019年第5期1卷 461-482页

作者： Danping ZOU Ping TAN wenxian yu Shanghai Key Laboratory of Navigation and Location-Based Services Shanghai Key Laboratory of Intelligent Sensing and RecognitionShanghai Jiao Tong UniversityShanghai 200240China School of Computing Science Simon Fraser UniversityBurnaby V5A 1S6Canada

This article presents a brief survey to visual simultaneous localization and mapping (SLAM) systems applied to multiple independently moving agents, such as a team of ground or aerial vehicles, a group of users holding augmented or virtual reality devices. Such visual SLAM system, name as collaborative visual SLAM, is different from a typical visual SLAM deployed on a single agent in that information is exchanged or shared among different agents to achieve better robustness, efficiency, and accuracy. We review the representative works on this topic proposed in the past ten years and describe the key components involved in designing such a system including collaborative pose estimation and mapping tasks, as well as the emerging topic of decentralized architecture. We believe this brief survey could be helpful to someone who are working on this topic or developing multi-agent applications, particularly micro-aerial vehicle swarm or collaborative augmented/virtual reality.

关键词： Visual SLAM Multiple agent UAV swarm Collaborative AR/VR

A NOVEL MULTILINEAR PREDICTOR FOR FAST VISUAL TRACKING

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Journal of Electronics(China) 2012年第1期29卷 158-165页

作者： Guo Weiwei yu wenxian ATR Laboratory School of Electronic Science and EngineeringNational University of Defense TechnologyChangsha 410073China School of Electronic Information and Electrical Engineering Shanghai Jiaotong UniversityShanghai 200433China

This letter presents a novel prediction scheme employed for fast visual tracking. The proposed multilinear predictor is formulated as a higher order tensor, instead of the existing vector representations. This predictor is based on emploing the Canonical/Parallel factors (CP) decomposition to decompose a tensor as a sum of rank one tensors. In that way, the proposed scheme efficiently retains the underlying structural information of the input data, while reduces at the same time the computational complexity by employing separable filter operations applied at different directions. The efficiency of the proposed scheme is demonstrated in the conducted experiments.

关键词： Regression Tensor Tracking Hough voting

M2C-GVIO:motion manifold constraint aided GNSS-visual-inertial odometry for ground vehicles

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Satellite Navigation 2023年第1期4卷 77-91,I0003页

作者： Tong Hua Ling Pei Tao Li Jie Yin Guoqing Liu wenxian yu Shanghai Key Laboratory of Navigation and Location Based Services Shanghai Jiao Tong UniversityShanghaiChina

Visual-Inertial Odometry(VIO)has been developed from Simultaneous Localization and Mapping(SLAM)as a lowcost and versatile sensor fusion approach and attracted increasing attention in ground vehicle ***,VIOs usually have the degraded performance in challenging environments and degenerated motion *** this paper,we propose a ground vehicle-based VIO algorithm based on the Multi-State Constraint Kalman Filter(MSCKF)*** on a unifed motion manifold assumption,we derive the measurement model of manifold constraints,including velocity,rotation,and translation *** we present a robust flter-based algorithm dedicated to ground vehicles,whose key is the real-time manifold noise estimation and adaptive measurement ***,GNSS position measurements are loosely coupled into our approach,where the transformation between GNSS and VIO frame is optimized ***,we theoretically analyze the system observability matrix and observability *** algorithm is tested on both the simulation test and public datasets including Brno Urban dataset and Kaist Urban *** compare the performance of our algorithm with classical VIO algorithms(MSCKF,VINS-Mono,R-VIO,ORB_SLAM3)and GVIO algorithms(GNSS-MSCKF,VINS-Fusion).The results demonstrate that our algorithm is more robust than other compared algorithms,showing a competitive position accuracy and computational efciency.

关键词： Sensor fusion Visual-inertial odometry Motion manifold constraint

PRECONDITIONED METHODS FOR SPACE-TIME ADAPTIVE PROCESSING

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Journal of Electronics(China) 2008年第4期25卷 465-470页

作者： Zhang Zenghui Hu Weidong yu wenxian College of Electronic Science and Engineering National University of Defense Technology Changsha 410073 China

This paper introduces the preconditioned methods for Space-Time Adaptive Processing(STAP).Using the Block-Toeplitz-Toeplitz-Block(BTTB)structure of the clutter-plus-noise covari-ance matrix,a Block-Circulant-Circulant-Block(BCCB)preconditioner is *** on thepreconditioner,a Preconditioned Multistage Wiener Filter(PMWF)which can be implemented by thePreconditioned Conjugate Gradient(PCG)method is *** results show that thePMWF has faster convergence rate and lower processing rank compared with the MWF.

关键词： Conjugate gradient method Multistage Wiener filter Preconditioner Space-Time Adaptive Processing (STAP)

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