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A high-precision phase-derived range and velocity measurement method based on synthetic wideband pulse Doppler radar

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Science China(information Sciences) 2017年第8期60卷 151-162页

作者： Huayu FAN Lixiang REN Teng LONG Erke MAO Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing Institute of Technology Radar Research Laboratory Beijing Institute of Technology

Development of radar technology needs to address the two-dimensional high resolution of range and velocity simultaneously for high-speed targets. Taking advantage of the superior coherent performance of synthetic wideband pulse Doppler radar, this paper elaborates the principles of phase-derived range and velocity measurements. Moreover, this paper explores the key technologies of unwrapping phase ambiguity, and discusses the phase unwrapping strategy at a low signal-to-noise ratio(SNR). The proposed method can be applied to the conditions of low SNR and has comparatively strong practicality in engineering. Both the ejection ball and civil aircraft experiments have validated the correctness and feasibility of the proposed method. In particular,the experimental results reveal that the accuracy of phase-derived range and velocity measurement has reached a level of submillimeter or millimeter and centimeter/second or submillimeter/second, respectively.

关键词： synthetic wideband PD radar phase-derived range measurement phase-derived velocity measurement unwrapping phase ambiguity track filtering minimum entropy method

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A novel subsidence monitoring technique based on space-surface bistatic differential interferometry using GNSS as transmitters

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Science China(information Sciences) 2015年第6期58卷 68-83页

作者： ZENG Tao ZHANG Tian TIAN WeiMing HU Cheng Beijing Key Laboratory of Embedded Real-time Information Processing Technology Radar Research Laboratory School of Information and ElectronicsBeijing Institute of Technology

Synthetic Aperture radar Differential Interferometry(DIn SAR) technique is an effective tool with large coverage and high spatial accuracy for subsidence monitoring. Nevertheless, the temporal resolution is usually poor so that rapid deformation cannot be measured due to the long revisit time of radar *** SAR Differential Interferometry technique using Global Navigation Satellite System(GNSS) as illuminator has a shorter revisit time, whereas the measurement accuracy is constrained by low signal power, narrow bandwidth and atmospheric delay error. To cope with these problems, in this paper, we propose a novel subsidence monitoring technique based on Space-Surface bistatic Differential Interferometry(SS-DI) with GNSS transmitters, where two stations consist of a reference one and a measurement one that are deployed on the ground. First, we applied a space differential processing between two stations to cancel identical errors such as tropospheric and ionospheric errors etc. Then we used a long time coherent integration to improve the signal noise ratio. Subsequently, we also utilized a time differential processing to construct double differential equations with respect to unknown deformation variables. Finally, we solved the equations to obtain a highly accurate estimation of three dimension deformation. Furthermore, an SS-DI experiment using Beidou-2 as transmitters was carried out to validate the proposed method, where a high accuracy(0.01 mm) device was utilized to simulate subsidence deformation. The experimental results reveal that the proposed method has better performance of spatial measurement accuracy of 0.53 mm compared with differential GPS method.

关键词： differential interferometry subsidence monitoring Beidou-2/Compass-2 space-surface bistatic radar differential GPS

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SAR Tomography with Improved Non-Local Means Filtering Based on Adaptive Window

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Journal of beijing Institute of technology 2023年第6期32卷 670-684页

作者： Shenglei Wang Zhiyang Chen Yuanhao Li Cheng Hu Radar Research Laboratory School of Information and ElectronicsBeijing Institute of TechnologyBeijing 100081China Key Laboratory of Embedded Real-time Information Processing Technology Beijing Institute of TechnologyBeijing 100081China

In order to mitigate speckle noise in synthetic aperture radar(SAR)images and enhance the accuracy of SAR tomography,non-local means(NL-means)filtering has been proven to be an effective method for improving the quality of SAR *** from considerations like noise type and the definition of similarity,the size and shape of filtering windows are critical factors influencing the efficacy of NL-means filtering,yet there has been limited research on this *** paper introduces an enhanced NL-means filtering method based on adaptive windows,allowing for the automatic adjustment of filtering window size according to the amplitude information of the SAR ***,a directional window is incorporated to align SAR interferograms,achieving the dual objective of preserving filtering standards and retaining detailed *** results on interferogram filtering and tomography,based on TerraSAR-X data,demonstrate that the proposed method effectively reduces phase noise while maintaining texture accuracy,thereby improving tomography quality.

关键词： NL-means filter adaptive window SAR interferogram filtering SAR tomography

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Spaceborne Large-Squint Terrain-Matching Synthetic Aperture radar: Concept and technology 6

Spaceborne Large-Squint Terrain-Matching Synthetic Aperture ...

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6th Asia-Pacific Conference on Synthetic Aperture radar, APSAR 2019

作者： Wang, Yan Li, Zhe DIng, Zegang Zeng, Tao Radar Research Lab Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing Institute of Technology Beijing China

ISBN: (纸本)9781728129129

This paper discusses a new spaceborne large-squint terrain-matching synthetic aperture radar (LSTM-SAR) to effectively image the terrains that do not spread along satellite orbit. Different from the traditional spaceborne SAR, the swath of the LSTM-SAR spreads along the target terrain, instead of the satellite orbit, to perform terrain-matched imaging with both high resolution and short data acquisition period. Aiming at giving a sketch of how the LSTM-SAR works, the paper focuses on discussing the following three main aspects: the data acquisition geometry, azimuth sampling manner and raw data focusing algorithm. Specifically, an optimum squint geometry is firstly suggested for two dimensional swath optimization;then two non-uniform azimuth sampling methods are discussed to avoid data loss induced by transmission blockage;lastly, a wide nonlinear chirp scaling based algorithm is discussed to focus the spatially variant spaceborne LSTM-SAR echo. The presented approach is validated via the computer simulations. © 2019 IEEE.

关键词： Synthetic aperture radar

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Modeling and Analysis of the Impacts of Temporal-Spatial Variant Troposphere on Ground-Based SAR Imaging of Asteroids

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Journal of beijing Institute of technology 2023年第6期32卷 727-739页

作者： Tingting Fu Yuanhao Li Zhiyang Chen Zheng Wu Cheng Hu Radar Research Laboratory School of Information and ElectronicsBeijing Institute of TechnologyBeijing 100081China Beijing Key Laboratory of Embedded Real-time Information Processing Technology the Chongqing Institute of Meteorological Sciences Chongqing 401147China

The near-Earth asteroid collisions could cause catastrophic disasters to humanity and the Earth,so it is crucial to monitor ***-based synthetic aperture radar(SAR)is an observation technique for high resolution imaging of *** ground-based SAR requires a long integration time to achieve a large synthetic aperture,and the echo signal will be seriously affected by temporal-spatial variant *** spatiotemporal freezing tropospheric models are *** cope with this,this paper models and analyses the impacts of temporal-spatial variant troposphere on ground-based SAR imaging of *** the background tropo-sphere,a temporal-spatial variant ray tracing method is proposed to trace the 4D(3D spatial+temporal)refractive index network provided by the numerical weather model,and calculate the error of the background *** the tropospheric turbulence,the Andrew power spectral model is used in conjunction with multiphase screen theory,and varying errors are obtained by tracking the changing position of the pierce point on the phase *** simulation,the impact of temporal-spatial variant tropospheric errors on image quality is analyzed,and the simulation results show that the X-band echo signal is seriously affected by the troposphere and the echo signal must be compensated.

关键词： near-Earth asteroids ground-based SAR troposphere ray tracing

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Analysis of micro-motion feature in ISAR imaging via phase-derived velocity measurement technique

Analysis of micro-motion feature in ISAR imaging via phase-d...

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2017 IEEE radar Conference, radarConf 2017

作者： Guo, Liyong Fan, Huayu Liu, Quanhua Hu, Cheng Yang, Xiaopeng Beijing Key Laboratory of Embedded Real-time Information Processing Technology Radar Research Lab Beijing Institute of Technology Beijing100081 China

ISBN: (纸本)9781467388238

A novel ISAR (inverse synthetic aperture radar) motion compensation approach in conjunction with the phase-derived velocity measurement (PDVM) technique to extract micro-motion feature is presented in this paper. In order to obtain high quality ISAR image, the accurate velocity information provided by PDVM is utilized for target motion compensation. By analyzing proper amount of adjacent Doppler cells around the prominent scatterer in the ISAR image, the impact of other scatterers is effectively reduced for micro-motion extraction. Experiments based on radar measured data are performed to show the effectiveness of the proposed method. © 2017 IEEE.

关键词： Inverse synthetic aperture radar

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Repeat-pass space-surface bistatic SAR tomography:accurate imaging and first experiment

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Science China(information Sciences) 2024年第9期67卷 245-262页

作者： Zhiyang CHEN Yuanhao LI Cheng HU Shenglei WANG Xinpeng CHEN Mihai DATCU Andrea Virgilio MONTI-GUARNIERI Radar Technology Research Institute School of Information and Electronics Beijing Institute of Technology Beijing Key Laboratory of Embedded Real-Time Information Processing Technology Beijing Institute of Technology Advanced Technology Research Institute Beijing Institute of Technology CEOSpace Tech University Politehnica of Bucharest Dipartimento di Elettronica Informazione e Bioingegneria Politecnico di Milano

Space-surface bistatic synthetic aperture radar(SS-BiSAR) offers an additional observation angle for monostatic spaceborne SAR, making it a promising technology for high-accuracy deformation retrieval technology in local regions. Repeat-pass SS-BiSAR tomography can accurately estimate the surfaces of buildings and steep areas, effectively removing terrain phases during deformation retrieving. However, inaccuracies in the orbital ephemeris can lead to image geometry distortion, reducing image pair coherence,introducing interferometric phase errors, and consequently deteriorating tomographic precision. This paper precisely models the image geometry distortion and interferometric phase error caused by repeat-pass ephemeris error. We propose an ephemeris correction method based on the chirp-Z transform to address these issues. Furthermore, we introduce an accurate tomography model to improve 3D reconstruction *** first SS-BiSAR tomography experiment, conducted using the Chinese Lutan-1 satellite, demonstrates that the correlation coefficient is improved by 0.16 after ephemeris error correction. Moreover, the density and precision of the tomographic point cloud are improved by 13.7% and 12.1%, respectively.

关键词： space-surface SAR tomography orbit error image distortion Lutan-1

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A tracking filter algorithm for migratory birds based on group situation constraints 2

A tracking filter algorithm for migratory birds based on gro...

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2nd IEEE International Conference on Signal, information and Data processing, ICSIDP 2024

作者： Li, Biao Wang, Rui Cai, Jiong Beijing Key Laboratory of Embedded Real-Time Information Processing Technology The Radar Research Lab School of Information and Electronics Beijing Institute of Technology Beijing China

ISBN: (纸本)9798331515669

Aerial animal migration is closely related to human life, and radar is one of the most effective means of observing it. However, scanning radar has a low data rate, a short integration time, and lacks prior knowledge of target speed, while migratory animals exhibit high mobility. These factors make traditional tracking filter algorithms ineffective at predicting their movement. To address this issue, this paper proposes a tracking filter algorithm based on group dynamics constraints, leveraging the characteristic behavior of migratory animals flying in groups. First, the dynamic state of the group is calculated using the group as the research unit. Then, tracking filtering is performed under the constraint of group dynamics. Simulation and field data have verified the effectiveness of the proposed algorithm. © 2024 IEEE.

关键词： Invertebrates

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High-Squint SAR Imaging for Noncooperative Moving Ship Target Based on High Velocity Motion Platform

High-Squint SAR Imaging for Noncooperative Moving Ship Targe...

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2018 China International SAR Symposium, CISS 2018

作者： Zhou, Zhichao Ding, Zegang Zhang, Tianyi Wang, Yan Radar Research Lab School of Information and Electronics Beijing Institute of Technology Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing China

ISBN: (纸本)9781538671931

For high velocity motion platform, it usually takes a shorter azimuth accumulation time to achieve high-squint synthetic aperture radar (SAR) imaging for noncooperative moving ship target with meter-level resolutions. In this case, three-dimensional relative motion of the ship target can be neglected approximately, mainly the translational motion should be considered. However, the magnitude and direction of the target's translational velocity are unknown. To solve the above problem, a two-step imaging method is proposed in this paper. Firstly, the entire scene is coarsely imaged by using the parameters provided by inertial navigation system. The position of the ship target can be judged by two-dimensional order statistics constant false alarm rate (OS-CFAR) detection and ship target pixel clustering. By constructing the band-pass filter in azimuth frequency domain, the data of the target can be obtained effectively, and to a certain extent, sea clutter and noise are suppressed. Then the motion parameters are estimated. Finally, the target is secondarily imaged with the estimated parameters to achieve precise focus. The results of simulation verify the correctness of the analysis and the validity of the proposed method. © 2018 IEEE.

关键词： Parameter estimation

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Improved SPECAN algorithm based on Doppler rate equalization

Improved SPECAN algorithm based on Doppler rate equalization

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IET International radar Conference 2015

作者： Li, Y. Ding, Z. Long, T. Key Laboratory of Embedded Real-Time Information Processing Technology Radar Research Lab. School of Information and Electronics Beijing Institute of Technology Beijing China

ISBN: (纸本)9781785610387

The spectral analysis (SPECAN) algorithm is efficient and always used for synthetic aperture radar (SAR) data processing. But the azimuth dependence of Doppler rate is neglected in SPECAN algorithm, which results in the defocusing of targets away from the scene center. In order to solve this problem, an improved SPECAN algorithm is proposed. Considering the fact that the region of support in the azimuth frequency domain is different for targets in the same range gate, the algorithm equalizes the Doppler rate by nonlinear chirp scaling (NCS) in the azimuth frequency domain. Moreover, a modified map drift (MD) autofocus method is given to estimate the Doppler rate and its dependence. Finally, the effectiveness of the proposed algorithm is verified by real SAR data.

关键词： Spectrum analysis

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