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On the Time-Domain Airborne SAR Focusing in the Presence of Strong Azimuth Variations of the Squint Angle

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2023年 61卷 1页

作者： Berardino, Paolo Natale, Antonio Esposito, Carmen Lanari, Riccardo Perna, Stefano Inst Elect Sensing Environm Natl Res Council IREA Naples Italy Univ Napoli Parthenope Dipartimento Ingn DI I-80133 Naples Italy

Airborne synthetic aperture radar (SAR) data focusing in the presence of highly variable squint angles is addressed in this work. To do this, a time-domain SAR focusing algorithm has been developed to account for the target-dependent nature of the acquisition squint angle. For comparison purposes, we have considered also a SAR processor based on the use of an azimuth-invariant processing squint angle. Moreover, real data acquired by two different X-band airborne SAR systems have been analyzed. The aims of the work are twofold. First, we show that the adoption of an azimuth-invariant processing squint angle, typically pursued by computationally efficient focusing strategies, may become inappropriate in several airborne missions, which are typically corrupted by motion errors induced by atmospheric turbulence. On the contrary, these problems are circumvented through the developed time-domain focusing strategy, which exploits a target-dependent processing squint angle that is coincident with the acquisition one. Second, we show that the proposed focusing strategy must be properly revised in the case of interferometric processing. In particular, we show that if the (target-dependent) acquisition squint angle is different for the two interferometric channels used, we have to move toward a different focusing paradigm, say, an interferometric focusing solution. This is again based on considering a target-dependent processing squint angle, but for each target, this processing angle should be equal neither to the acquisition squint angle of the "main" acquisition nor to that of the "secondary" one: it must instead lie halfway between them. We prove that this approach is appropriate to obtain high interferometric coherence, and it is suboptimal to separately focus the interferometric channels.

关键词： Airborne synthetic aperture radar (SAR) back-projection algorithm squint

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NON-LINE-OF-SIGHT IMAGING BY MILLIMETER WAVE RADAR

NON-LINE-OF-SIGHT IMAGING BY MILLIMETER WAVE RADAR

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IEEE International Geoscience and Remote Sensing Symposium (IGARSS)

作者： Wei, Jinshan Wei, Shunjun Liu, Xinyuan Wang, Mou Shi, Jun Zhang, Xiaoling Univ Elect Sci & Technol China Sch Informat & Commun Engn Chengdu 611731 Peoples R China

ISBN: (纸本)9781665403696

Non-line-of-sight (NLOS) radar imaging technique aims to reconstruct hidden targets that illuminated wave cannot reach directly, which can greatly expand the range of radar detection. In this paper, inspired by synthetic aperture radar (SAR), an effective two-dimensional (2-D) NLOS imaging technique via multiple input multiple output (MIMO) millimeter-wave (MMW) radar is proposed. In the scheme, a 2-D virtual antenna array is synthesized by MIMO antenna scanning, and the multi-bounces echoes is used to obtain 2D NLOS imaging. Then an algorithm via mirror symmetry back-projection (MSBP) is presented for 2-D high-precision focusing of these NLOS echoes. Moreover, a cost-effective 79GHz MMW NLOS experiment system is developed for technical validation. The effectiveness of MMW NLOS radar imaging is verified by near-field multi-targets experiment, and high-precision 2-D imaging results of hidden knives are obtained by MSBP method.

关键词： Non-Line-of-Sight imaging SAR millimeter wave radar back-projection algorithm

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A planar MIMO UWB array design for high-resolution microwave imaging 56

A planar MIMO UWB array design for high-resolution microwave...

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56th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST)

作者： Ziani, Djamila Meriah, Sidi Mohammed Derraz, Foued Merad, Lotfi Univ Tlemcen Fac Technol Lab Telecommun Tlemcen LTT Tilimsen Algeria Grad Sch Appl Sci Tilimsen Algeria

ISBN: (纸本)9781665428873

In this paper, a planar multiple input multiple output MIMO UWB array is proposed for 3D microwave imaging applications. According to the virtual array concept, the advantage of the MIMO array lies on improving the angular resolution with a reduced number of antennas, and achieve the same resolution as a fully populated conventional arrays. In addition, the UWB systems provide a better range resolution thanks to their large bandwidth. The frequency diversity and its influence on the system's resolution is also studied. For the MIMO array, an optimal UWB antenna element is designed with more than 128% of fractional bandwidth with no considerable distortion of the transmitted impulse. For the imaging algorithm, the back-projection algorithm is implemented and used for the reconstruction of the images. In order to study the performance of the designed system, the full-wave electromagnetic simulator CST MWS is used which allow the modelling in three-dimensions (3D). The resulting images of a different target materials and dielectric properties confirm the reliability of the proposed system and the impact of the spatial and frequency diversity in the resolution improvement while considerably reducing the cost of the MIMO UWB array.

关键词： UWB antenna MIMO arrays Microwave imaging system back-projection algorithm Object detection

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Analysis of a Bistatic Ground-Based Synthetic Aperture Radar System and Indoor Experiments

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REMOTE SENSING 2021年第1期13卷 63-63页

作者： Lee, Hoonyol Moon, Jihyun Kangwon Natl Univ Dept Geophys Chunchon 24341 Kangwon Do South Korea

Recent advancement of satellite synthetic aperture radar (SAR) techniques require more sophisticated system configurations such as the use of bistatic antennas or multi-frequencies. A ground-based experiment is a cost-effective and efficient way to evaluate those new configurations especially in the early stage of the system development. In this paper, a ground-based synthetic aperture radar (GB-SAR) system was constructed and operated in a bistatic mode at Ku-band where a receiving antenna (Rx) follows a transmitting antenna (Tx) separated by a baseline B. A new bistatic GB-SAR focusing algorithm was developed by modifying a conventional range-Doppler algorithm (RDA), and its performance has been evaluated by comparing the results with those from a back-projection algorithm (BPA). The results showed good performance of RDA at far range approaching nominal resolutions of 9.4 cm in range and 4.5 cm in azimuth, but limited quality at near range due to the approximation used in RDA. Signals from three trihedral corner reflectors (CR) reduced with increasing B, showing a typical bidirectional scattering behavior of CR. This GB-SAR system will be a testbed for new SAR imaging configurations with variations in antenna positions and target properties.

关键词： bistatic GB-SAR Ku-band back-projection algorithm range-Doppler algorithm

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Implementing a back-projection Tomographic Reconstruction algorithm Using a Fan-Shaped Beam

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RUSSIAN JOURNAL OF NONDESTRUCTIVE TESTING 2017年第5期53卷 387-392页

作者： Ozdiev, A. Kh. Kryuchkov, Yu. Yu. Tomsk Polytech Univ Phys Tech Inst Tomsk 634050 Russia

A back-projection tomographic reconstruction algorithm using a fan-shaped beam is considered. The freeware that implements the method of back projections is mainly applicable only in the case of parallel radiation. Distinctions in how this approach is applied when using parallel and fan-shaped beams are described in part that is related to the geometry of an experiment. The implementation of the algorithm with allowance for the peculiarities of reconstruction with a divergent beam is presented as a flow chart. The results provided in the paper demonstrate the working capacity of the algorithm.

关键词： X-ray tomography fan-shaped beam reconstruction back-projection algorithm

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3D Absorbed Dose Reconstructed in the Patient from EPID Images for IMRT and VMAT Treatments

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IUPESM World Congress on Medical Physics and Biomedical Engineering

作者： Younan, Fouad Mazurier, Jocelyne Chatrie, Frederic Barbeiro, Ana Rita Berry, Isabelle Franck, Denis Franceries, Xavier Clin Pasteur Serv Radiotherapie Grp Oncorad Garonne 1 Rue Petite Vitesse F-31300 Toulouse France INSERM UMR 1214 TONIC Toulouse NeuroImaging Ctr F-31059 Toulouse France Univ Toulouse III Paul Sabatier UMR 1214 F-31059 Toulouse France INSERM UMR 1037 CRCT F-31000 Toulouse France Univ Toulouse III Paul Sabatier UMR 1037 CRCT F-31000 Toulouse France CNRS LAAS F-31000 Toulouse France CHU Rangueil Dept Nucl Med 1 Ave Prof Jean Poulhes F-31400 Toulouse France

ISBN: (纸本)9789811090233;9789811090226

A back-projection method has been used in this study to reconstruct the 3D absorbed dose matrix in the patient from EPID images for IMRT and VMAT fields. Images were acquired with the Clinac 23iX aS-1000 imager (Varian) and a 6 MV beam. Then a calibration step was performed to transform the grey levels of the pixels into absorbed dose in water via a response function. Correction kernels were also used to correct for the scatter within the EPID. The dose was then back-projected into the patient for all EPID parallel planes for each gantry angle. Finally the total dose was obtained by summing the 3D dose associated for each gantry angulation. First, the 3D dose reconstruction algorithm was tested for 20 IMRT and VMAT prostate and head and neck treatments in a homogeneous cylindrical phantom. Then the algorithm was used for IMRT brain cancer plans on 20 real patients. The EPID reconstructed 3D dose distributions were then compared to the planned dose from TPS (Treatment Planning System, Eclipse Varian) with a 3D global gamma index of 3% and 3 mm criteria. The percentage of points of which the gamma index was larger than unity was greater than 97% for all IMRT treatments both in the phantom and in the patients and over 96% for all VMAT treatments checked in the cylindrical phantom. Our 3D reconstruction algorithm, validated for homogeneous medium, can be used to verify the dose distribution for IMRT and VMAT fields using in vivo EPID images.

关键词： Epid back-projection algorithm 3D absorbed dose Dose verification In vivo dosimetry

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Particle-filter-based human target tracking in image domain for through-wall imaging radar

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JOURNAL OF ENGINEERING-JOE 2019年第20期2019卷 6549-6553页

作者： Chen, Guohao Cui, Guolong Kong, Lingjiang Guo, Shisheng Cao, Lingxiao Univ Elect Sci & Technol China Sch Informat & Commun Engn Dept Elect Engn Chengdu Sichuan Peoples R China

This study deals with a tracking problem for hidden human targets using time-division multiple-input-multiple-output through-wall imaging radar (TWIR). An efficient image-domain tracking algorithm is proposed. Specifically, the authors first utilise back-projection algorithm and the phase coherence factor (PCF) to obtain multi-frame high quality images. Then a tracking algorithm via amplitude-distribution-based particle filter is proposed. Experimental data validates that this algorithm has a commendable effectiveness for hidden target tracking.

关键词： target tracking ultra wideband radar particle filtering (numerical methods) radar imaging particle-filter-based human target tracking image domain through-wall imaging radar tracking problem hidden human targets time-division multiple-input-multiple-output efficient image-domain tracking algorithm back-projection algorithm phase coherence factor multiframe high quality images amplitude-distribution-based particle filter hidden target tracking

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An Improved back-projection algorithm for Magnetic Induction Tomography Image Reconstruction

An Improved Back-projection Algorithm for Magnetic Induction...

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2012 International Conference on Biomaterial and Bioengineering(ICBB 2012)

作者： Li Ke Xiao Lin Qiang Du Institute of Biomedical and Electromagnetic Engineering Shenyang University of Technology

Magnetic induction tomography(MIT) acted as a contactless and non-invasive medical imaging technology has aroused wide concern, while a large amount of calculation and a series of convergence problems in the solution of the inverse problem become technical difficulties for MIT. In order to solve these problems, an improved back-projection image reconstruction algorithm based on the magnetic field lines distribution is presented in this paper. Firstly, the eddy current problem of MIT was solved by the finite element method to obtain the magnetic field distribution. Secondly, the back-projection areas were divided according to the magnetic field lines distribution in the homogeneous field. Finally, image reconstruction was realized by projecting the phase shifts back along the corresponding projection area. The reconstruction results for perturbations with different conductivities appearing at different locations reveal that the improved back-projection algorithm for MIT owning the character of high speed performs well in reflecting location and shape information of the perturbation.

关键词： Magnetic Induction Tomography back-projection algorithm Image Reconstruction

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3D tomography for multistatic GPR subsurface sensing 22

3D tomography for multistatic GPR subsurface sensing

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Conference on Radar Sensor Technology XXII

作者： Pereira, Mauricio Zhang, Yu Orfeo, Dan Burns, Dylan Huston, Dryver Xia, Tian Univ Vermont Sch Engn Burlington VT 05405 USA Aptiv PLC Agoura Hills CA 91301 USA

ISBN: (纸本)9781510617780

Ground penetrating radar (GPR) subsurface sensing is a promising nondestructive evaluation (NDE) technique for inspecting and surveying underground utilities in complex urban environments, as well as for monitoring other key infrastructure such as bridges and railroads. A challenge of such technique lies on image formation from the recorded GPR data. In this work, a fast back projection algorithm (BPA) for three-dimensional GPR image construction is explored. The BPA is a time-domain migration method that has been effectively used in GPR image formation. However, most of the studies in the literature apply a computationally intensive BPA to a two-dimensional dataset under the assumption that an in-plane scattering occurs underneath the GPR antennas. This assumption is not precise for 3D GPR image formation as the GPR radiation scatters in multiple directions as it reaches the ground. In this study, a generalized form for an approximation to determine the scattering point in an air-coupled GPR system is developed which considerably reduces the required computations and can accurately localize the scattering point position. The algorithm is evaluated by applications on GPR data synthesized using GprMax, a finite-difference time domain (FDTD) simulator.

关键词： back-projection algorithm ground penetrating radar migration tomographic reconstruction

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Tomography on Continuous Variable Quantum States

Tomography on Continuous Variable Quantum States

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作者： Ludmila Augusta Soares Botelho UNIVERSIDADE FEDERAL DE MINAS GERAIS - UFMG

学位级别：硕士

In this work we have explored few tools in Quantum State Tomography for Continuous Variable Systems. The concept of quantum states in phase space representation is introduced in a simple manner by using a few statistical concepts. Unlike most texts of Quantum information in which the Wigner function for a single mode is often more used, in this text the multi-modes state Wigner function is also developed. Our numerical investigations indicate that the reconstructed method using back-projection add some error due the choice of cutoff frequency, therefore it is necessary to use data post-processing, like the semi-definite programs, which provides sufficient conditions correctly estimate the state. Once the information about the state is recovered, important features such as entanglement can also be investigated.

关键词： Wigner function quadrature continuous variable Gaussian state coherent state squeezed state Fock state single mode state multi mode state homodyne detection tomography Radon transform inverse Radon back-projection algorithm kernel cutoff characteristic function fidelity semi-definite programs SDP entanglement

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