- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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A Hexagonal Pseudo-polar FFT for Formation-Flying Interferometric Radiometry
摘要： A novel mission concept applying satellite formation flight to passive microwave interferometry was recently proposed to significantly improve the interferometer’s spatial resolution. This concept was shown to sample the visibility in a hexagonal tile of polar grids, and to recover the brightness map, this visibility must be inverted via a discrete polar inverse Fourier transform. For a fast and accurate solution, this letter develops a modified hexagonal variant of the pseudo-polar fast Fourier transform (PPFFT) and its inverse and explores its performance when applied to the proposed formation-flight radiometer. Compared to the conventional rectangular PPFFT, we find approximately a fivefold improvement in the recovered radiometric accuracy, where the rms radiometric error is in the order of 10?2 K. The impact of visibility interpolation method is also explored, showing that an FFT-based interpolation technique leads to the most accurate final image recovery.
关键词： mission concept,synthetic aperture imaging,microwave radiometry,Image reconstruction,satellite formation flight
更新于2025-09-11 14:15:04
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[IEEE 2018 International Conference on Optical MEMS and Nanophotonics (OMN) - Lausanne (2018.7.29-2018.8.2)] 2018 International Conference on Optical MEMS and Nanophotonics (OMN) - Stepped-Tuning Optical Diaphragm Fabricated with a Lithography-Less Process
摘要： In this paper, we demonstrate a lithography-less process to fabricate a solid stepped-tuning diaphragm with a decent driving voltage. The device is designed to switch between two aperture sizes, 6 mm and 10 mm.
关键词： lithography-less,PDLC,tunable aperture
更新于2025-09-11 14:15:04
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FAST AND STABLE INTEGRATION METHOD FOR THE APERTURE ADMITTANCE OF AN OPEN-ENDED COAXIAL PROBE TERMINATED INTO LOW-LOSS DIELECTRICS
摘要： The utilization of an open-ended coaxial probe for characterization of dielectric properties or quantitative nondestructive detection of defects in materials ?rstly requires evaluating the aperture admittance. For the case that the probe is terminated into low-loss dielectrics backed by a conducting sheet, however, the admittance expression encounters poles in the vicinity of the path of integration, resulting in low convergence rate or even over?ow in numerical quadrature. In this study, locations and properties of the singularities of the integral formulation for generally lossy, low-loss, and lossless dielectric slabs backed by a perfectly conducting sheet are investigated above all. Subsequently, making use of the contour integral technique, a fast and stable integration method is put forward to calculate the admittance integral formulation. Finally, numerical experiments are conducted to justify the validity and e?ciency of the proposed integration method for low-loss dielectric cases by comparison with the traditional integration method as well as commercial FEM software.
关键词： aperture admittance,numerical quadrature,open-ended coaxial probe,contour integral technique,low-loss dielectrics
更新于2025-09-10 09:29:36
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Joint Sparsity Constraint Interferometric ISAR Imaging for 3-D Geometry of Near-Field Targets with Sub-Apertures
摘要： This paper proposes a new interferometric near-field 3-D imaging approach based on multi-channel joint sparse reconstruction to solve the problems of conventional methods, i.e., the irrespective correlation of different channels in single-channel independent imaging which may lead to deviated positions of scattering points, and the low accuracy of imaging azimuth angle for real anisotropic targets. Firstly, two full-apertures are divided into several sub-apertures by the same standard; secondly, the joint sparse metric function is constructed based on scattering characteristics of the target in multi-channel status, and the improved Orthogonal Matching Pursuit (OMP) method is used for imaging solving, so as to obtain high-precision 3-D image of each sub-aperture; thirdly, comprehensive sub-aperture processing is performed using all sub-aperture 3-D images to obtain the final 3-D images; finally, validity of the proposed approach is verified by using simulation electromagnetic data and data measured in the anechoic chamber. Experimental results show that, compared with traditional interferometric ISAR imaging approaches, the algorithm proposed in this paper is able to provide a higher accuracy in scattering center reconstruction, and can effectively maintain relative phase information of channels.
关键词： interferometric inverse synthetic aperture radar,compressed sensing,joint sparse reconstruction,wide angle,near-field 3-D imaging
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Railway Bridge Monitoring with Sar: A Case Study
摘要： Spaceborne sensors allow large areas of the Earth to be monitored with small revisit times; conversely, use of in situ techniques frequently limits spatial and/or temporal coverage of critical infrastructure observations. In this paper, some of the potentialities of synthetic aperture radar (SAR) for railway bridge monitoring are explored. The study is focused on a case study regarding a bridge near Triflisco, a small city in Campania, Italy. Twenty-six Cosmo-SkyMed stripmap SAR images were acquired over the area, allowing for a permanent-scatterer (PS) analysis of the bridge structure. Thanks to the availability of a detailed ground truth, the physical nature of the bridge PSs, their spatial distribution, and their time behavior are investigated. In particular, the PS behavior is compared to deformation results obtained using thermal loads in a finite-element model of the bridge.
关键词： permanent scatterers,Synthetic aperture radar,F.E.M.,railway bridge
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Smos Instrument Performance After More Than 8 Years in Orbit and Lessons Learnt for Future L-Band Missions
摘要： ESA’s Soil Moisture and Ocean Salinity (SMOS) mission [1] has been in orbit for over 8 years, and its Microwave Imaging Radiometer with Aperture Synthesis (MIRAS) in two dimensions is working well. The data for this whole period has been and is being processed with the operational version of the current Level-1 processor (version v620). Also a representative part of the same data set has been processed with a working version of a new processor (v720) which is now in preparation so that homogenous records of brightness temperatures have been made available. These rich and long data records have allowed learning important lessons from the in-flight experience, and shall eventually lead into the consolidation of the new Level-1 processor version (v720) with its corresponding auxiliary calibration and configuration files. Once the improvements are confirmed the new processor version shall be recommended for the operational chain.
关键词： interferometry,radiometry,aperture synthesis,SMOS
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Small Sample Learning Optimization for Resnet Based Sar Target Recognition
摘要： Deep convolutional neural network (CNN) is an important branch of deep learning. Due to its strong ability of feature extraction, CNN models have been introduced to solve the problems of synthetic aperture radar automatic target recognition (SAR-ATR). However, labeled SAR images are difficult to acquire. Therefore, how to obtain a good recognition result from a small sample dataset is what we mainly focus on. In theory, a deeper network can bring a better training result. But it also brings more difficulties to the training process, especially with limited labeled training data. The residual learning which proposed in recent years can alleviate this problem effectively. In this paper, we use a deep residual network, and introduce the dropout layer into the building block to alleviate overfitting caused by limited SAR data. In order to improve the training effect, the new loss function center loss is adopted and combined with softmax loss as the supervision signal to train the deep CNN. The experimental results show that our method can achieve the classification accuracy of 99.67% with all training data, without data augmentation or pre-training. When data of the training dataset was reduced to 20%, we can still achieve a recognition result higher than 94%.
关键词： center loss,automatic target recognition (ATR),limited labeled data,Convolutional neural network (CNN),synthetic aperture radar (SAR),residual learning
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Salient Seed Extraction Based Target Detection in SAR Images
摘要： A salient seed extraction based target detection method is proposed in this paper, aiming to distinguish target points from background points in SAR images. Different from recent superpixel based method which generates superpixels firstly, and for each superpixel decides whether it belongs to part of a target. The proposed method employs a salient point to region scheme. At first, salient seeds are extracted by mean-shift and region feature based approach. Then, pixels are assigned to the most similar seed and those assigned to the salient seeds are extracted to form the foreground region. Finally, constant false alarm rate (CFAR) operation is employed to detect the target points from the foreground region. The effectiveness of the proposed method is validated by comparing with five state-of-the-art methods on TerraSAR-X images.
关键词： synthetic aperture radar (SAR),Target detection,salient seed extraction
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Research Into Sar Imaging of Moving Ship Target Based on Isar Technology
摘要： The ship targets affected by sea conditions and other environment factors have complex non-cooperation movement, which cause serious defocusing phenomena in high resolution space-borne SAR images. In this paper, a novel ISAR-based imaging algorithm for moving ship target is presented. Firstly, the spatial geometric model of space-borne SAR is given, and the motorial characteristics of moving ship target are analyzed. Then, a novel imaging algorithm is derived, where the range alignment is solved by minimum information entropy criterion, and the accurate focusing is achieved through inverse SAR (ISAR) processing. Experiments based on the simulation and real data of TerraSAR-X are performed to validate the presented algorithm.
关键词： Motion compensation,Inverse Synthetic Aperture Radar(ISAR),Radar imaging,Minimum entropy,Moving Ship Target
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Synthetic aperture radar observations of interannual ocean-atmosphere coupling over the Somali Current
摘要： The covariability of wind stress and sea surface temperature is observed at high resolution over the Western Arabian Sea. Synthetic aperture radar data were acquired over the Somali Current in 2016 and 2017 during the summer monsoon season. The Somali Current, the Southern Gyre and the Great Whirl were all observed at the time of these acquisitions. Wind stress curl derived from the synthetic aperture radar data show the effects of the cold upwelled coastal water and the Somali Current on the wind stress. Significant organized large eddies are also observed east of the Somali Current.
关键词： ocean-atmosphere coupling,wind stress,synthetic aperture radar
更新于2025-09-10 09:29:36