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IEEE International Symposium on Geoscience and Remote Sensing (IGARSS)

作者： Fang Zhou Jun Yang Guangcai Sun Jiajia Zhang School of Computer and Information Hefei University of Technology Hefei China National Key Lab of Radar Signal Processing Xidian University Xi'an China Key Laboratory of Aperture Array and Space Application East China Research Institute of Electronic Engineering Hefei China

ISBN: (数字)9781728163741

ISBN: (纸本)9781728163758

The small satellite SAR has received increasing attention due to its flexibility and low cost. But limited by the data transmission technology, real-time transmission of a large amount of raw data generated by the spaceborne spotlight SAR can hardly be achieved. Meanwhile, the azimuth bandwidth of the spotlight mode is larger than the PRF, resulting in aliasing of the azimuth spectrum. Based on these, this paper proposes a real-time scheme for small satellite SAR with spotlight mode. The method can solve the problem of data transmission and eliminate spectrum overlap in Doppler domain by means of sub-aperture processing. The modified range migration algorithm (RMA) is used to perform range compression and range cell migration compensation (RCMC) on sub-aperture data. Then dechirp in the azimuth time domain is applied to obtain the low-resolution complex image focused in the range time-azimuth frequency domain. Finally, all theected onto a grid image with azimuth interval matching the azimuth full-resolution to complete image fusion.

关键词： Azimuth Spaceborne radar Real-time systems Synthetic aperture radar Doppler effect Imaging Bandwidth

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A fringe suppression terahertz imaging method based on reconstruction from multiple complex-valued images

A fringe suppression terahertz imaging method based on recon...

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International Conference on Infrared and Millimeter Waves

作者： Ying Hunag Feng Qi Key Laboratory of Opto-Electronic Information Processing Chinese Academy of Sciences Shenyang China Shenyang Institute of Automation Chinese Academy of Science Shenyang China Institutes for Robotics and Intelligent Manufacturing Chinese Academy of Sciences Shenyang China University of Chinese Academy of Sciences Beijing China School of Information Engineering Jimei University Xiamen China

Undesired interference fringes are one of the challenges in terahertz amplitude imaging. The paper presents a new fringe suppression complex-field imaging method based on multiple space measurements under the strong clutter environments. A Circle Approximation Method in complex field is proposed here to estimate both the sample signal intensity and the complex clutter component based on the superposition model of the received signal. The advantage of the imaging method is that only a limited number of measurements are needed to achieve high quality restored image. The method is performed on the real metallic sample measurement data taken from continuous THz imaging systems based on the vector network analyzer(VNA) . The results show that the method can effectively restore high contrast images with no obvious fringes under subjective visual evaluation.

关键词： Visualization Imaging Extraterrestrial measurements Reflection Image restoration Approximation methods Clutter

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WaveCNet: Wavelet integrated CNNs to suppress aliasing effect for noise-robust image classification

arXiv

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arXiv 2021年

作者： Li, Qiufu Shen, Linlin Guo, Sheng Lai, Zhihui Computer Vision Institute College of Computer Science and Software Engineering Shenzhen University Shenzhen518060 China Shenzhen Institute of Artificial Intelligence and Robotics for Society Shenzhen518060 China Guangdong Key Laboratory of Intelligent Information Processing Shenzhen University Shenzhen518060 China MyBank Ant Group Hangzhou310012 China

Though widely used in image classification, convolutional neural networks (CNNs) are prone to noise interruptions, i.e. the CNN output can be drastically changed by small image noise. To improve the noise robustness, we try to integrate CNNs with wavelet by replacing the common down-sampling (maxpooling, strided-convolution, and average pooling) with discrete wavelet transform (DWT). We firstly propose general DWT and inverse DWT (IDWT) layers applicable to various orthogonal and biorthogonal discrete wavelets like Haar, Daubechies, and Cohen, etc., and then design wavelet integrated CNNs (WaveCNets) by integrating DWT into the commonly used CNNs (VGG, ResNets, and DenseNet). During the down-sampling, WaveCNets apply DWT to decompose the feature maps into the low-frequency and high-frequency components. Containing the main information including the basic object structures, the low-frequency component is transmitted into the following layers to generate robust high-level features. The high-frequency components are dropped to remove most of the data noises. The experimental results show that WaveCNets achieve higher accuracy on ImageNet than various vanilla CNNs. We have also tested the performance of WaveCNets on the noisy version of ImageNet, ImageNet-C and six adversarial attacks, the results suggest that the proposed DWT/IDWT layers could provide better noise-robustness and adversarial robustness. When applying WaveCNets as backbones, the performance of object detectors (i.e., faster R-CNN and RetinaNet) on COCO detection dataset are consistently improved. We believe that suppression of aliasing effect, i.e. separation of low frequency and high frequency information, is the main advantages of our approach. The code of our DWT/IDWT layer and differentWaveCNets are available at https://***/CVISZU/ WaveCNet. © 2021, CC BY.

关键词： signal sampling

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Hierarchical ship detection method for space-borne SAR image

Hierarchical ship detection method for space-borne SAR image

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IET International radar Conference 2018, IRC 2018

作者： Tang, Wei Zhao, Baojun Tang, Linbo Nan, Jinghong Radar Research Lab School of Information and Electronics Beijing Institute of Technology Beijing China Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing China

Ship detection from space-borne SAR image is a challenging task. The main challenges in this task include the disturbance of sea clutter, island, coastline, and variability in ship sizes. Here, the authors propose a novel hierarchical ship detection framework to overcome the above challenges. Initially, the edge-enhanced maximally stable extremal regions (E-MSER) is employed as ship candidates. Then, through some simple shape analysis, they can eliminate the obvious false alarms which are not conformed to the shape feature of ship. Finally, candidates are represented by an effective multiple features learning framework for discriminating true ship targets. Experimental results on numerous space-borne SAR images demonstrate their proposed scheme that outperforms other traditional methods with higher detection accuracy and lower false alarm. © 2019 Institution of Engineering and Technology. All rights reserved.

关键词： Synthetic aperture radar

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Monopulse SAR angle measurement based on total variation and monotonic iterative algorithm

Monopulse SAR angle measurement based on total variation and...

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IET International radar Conference 2018, IRC 2018

作者： Hu, Bingtao Li, Feng Beijing Key Laboratory of Embedded Real-time information Processing Technology Beijing100081 China Radar Research Laboratory School of Information and Electronics Beijing Institute of Technology Beijing100081 China

Synthetic aperture radar (SAR) monopulse angle measurement is an adequate method of target angle measurement in low signal-to-clutter and noise ratio. However, there is a contradiction between the instantaneous angle measurement and the SAR coherent accumulation. In this study, the authors use the total variation method to solve the above problem, and propose the monotone iterative method to enhance the efficiency of the total variation method, which is verified in the simulation. © 2019 Institution of Engineering and Technology. All rights reserved.

关键词： Angle measurement

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Parameter inversion algorithm of CSAR moving target based on PFA sub-aperture images

Parameter inversion algorithm of CSAR moving target based on...

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IET International radar Conference 2018, IRC 2018

作者： Yao, Di Wang, Zhou Yang, Wengu Li, Feng Radar Research Lab School of Information and Electronics Beijing Institute of Technology Beijing China Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing China

Circular SAR (CSAR) as a new kind of SAR imaging mode has the advantage of long-time observation. For the moving target, the corresponding parameters of the moving target can be calculated by using the position information from the apparent coordinates of the moving target in these CSAR sub-aperture images. The CSAR sub-aperture imaging algorithms include BP and PFA, and the existing parameter estimation model is established on those well-focused and localised images. However, they account for a substantial computation. Here, an improved algorithm for parameter estimation based on CSAR sub-aperture images obtained by PFA is proposed. The wave-front phase error compensation is abandoned, and a new parameter estimation model is established based on PFA images with geometric positioning error. The computational complexity of the whole process of the algorithm is reduced, and the practicability is improved. The point target simulation shows that the method is effective and accurate. © 2019 Institution of Engineering and Technology. All rights reserved.

关键词： Synthetic aperture radar

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Box-particle Bernoulli Filter for Multipath Target Tracking in OTHR 2

Box-particle Bernoulli Filter for Multipath Target Tracking ...

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2nd IEEE International Conference on information Systems and Computer Aided Education, ICISCAE 2019

作者： Qin, Yong Nanchang Institute of Technology Jiangxi Province Key Laboratory of Water Information Cooperative Sensing and Intelligent Processing Nanchang330099 China School of Information Engineering Nanchang Institute of Technology Nanchang330099 China

ISBN: (纸本)9781728130668

This paper proposes a novel box-particle multipath Bernoulli filter (BP-MPBF) for the problem of single target tracking in Over-the-horizon radar (OTHR) under the clutter environment. The proposed algorithm combines the multipath Bernoulli filter (MPBF) with interval analysis to solve the problems of nonlinear measurement models and high computational complexity. First, the OTHR measurement model is established based on interval analysis, and then the box-particle filter is used to derive the BP-MPBF based on the original MPBF. Eventually, simulation results are provided to demonstrate the effectiveness of the BP-MPBF. © 2019 IEEE.

关键词： Target tracking

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Imaging algorithm for multi-channel scan synthetic aperture radar with channel error estimation and compensation

Imaging algorithm for multi-channel scan synthetic aperture ...

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IET International radar Conference 2018, IRC 2018

作者： Xiao, Feng Ding, Zegang Ke, Meng Beijing Key Laboratory of Embedded Real-time Information Processing Technology Radar Research Lab. School of Information and Electronics Beijing Institute of Technology Beijing100081 China

The wide swath synthetic aperture radar (SAR) imaging with a fine resolution is fundamentally a contradiction in conventional SAR imaging. To meet the demand of high-resolution width swath (HRWS) imaging, multi-channel scan mode has received a great deal of attention as a promising concept to realise HRWS observation. In this article, based on extended Chirp Scaling algorithm, an imaging algorithm for multi-channel scan SAR is proposed. Furthermore, channel error estimation and compensation are the key point in multi-channel scan imaging and are integrated into the proposed imaging algorithm. The computer simulation is shown to verify the presented imaging algorithm. © 2019 Institution of Engineering and Technology. All rights reserved.

关键词： Error compensation

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Circular SAR imaging algorithm based on polar format algorithm for moving target

Circular SAR imaging algorithm based on polar format algorit...

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IET International radar Conference 2018, IRC 2018

作者： Wang, Zhou Li, Feng Peng, XiangJun Yao, Di Radar Research Lab School of Information and Electronics Beijing Institute of Technology Beijing China Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing China

For stationary targets, circular synthetic aperture radar (CSAR) imaging has tended to be mature and perfect. However, for moving targets, due to the long synthetic aperture and the variation of slant plane with the observation angle, the motion compensation is more complicated and has no effective approach. Based on the latest moving target trajectory reconstruction method in CSAR (2015), the polar format algorithm can be improved to image the moving targets when the motion parameters have been estimated. First, the authors placed the imaging reference point on the target to track it, and then compensated for the phase error caused by the incident angle changing and the wavefront curvature. The simulation results of point show that the algorithm is effective and accurate. © 2019 Institution of Engineering and Technology. All rights reserved.

关键词： Motion compensation

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Point spread character based low SNR single pixel infrared target detection

Point spread character based low SNR single pixel infrared t...

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IET International radar Conference 2018, IRC 2018

作者： Nan, Jinghong Zhao, Baojun Tang, Linbo Zhang, Zengshuo Tang, Wei Radar Research Lab School of Information and Electronics Beijing Institute of Technology Beijing China Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing China

Robust and efficient low signal-to-noise ratio (SNR) single pixel infrared (IR) target detection has been a key technique in IR searching and tracking system. However, there exist two critical difficulties, i.e. noise disturbance and low contrast between target and background, influencing detection accuracy. A novel IR target detection method is proposed to overcome those difficulties, by utilising the point-spread character. Specifically, a point-spread indicator is advocated to protect the potential target with the median filter to suppress the noise. Afterwards, a two-step enhancement model is built to increase the contrast value between target region and surrounding background effectively. In the first step, a point-spread local contrast method is proposed to enhance targets and suppress background. In the second step, a high boost filter is introduced to further enhance the target. In addition, an adaptive segmentation method is exploited to extract targets from the enhanced image. Experimental results on testing sequences demonstrate that this method outperforms the other state-of-the-art methods in single pixel IR target detection with higher detection rate, lower false alarm rate and less time consuming. © 2019 Institution of Engineering and Technology. All rights reserved.

关键词： Median filters

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