scholarly journals A Novel Ship Imaging Method with Multiple Sinusoidal Functions to Match Rotation Effects in Geosynchronous SAR

2020 ◽  
Vol 12 (14) ◽  
pp. 2249
Author(s):  
Wei Xiong ◽  
Ying Zhang ◽  
Xichao Dong ◽  
Chang Cui ◽  
Zheng Liu ◽  
...  
Keyword(s):  
Rotational Motion ◽  
Numerical Experiments ◽  
Projection Algorithm ◽  
Synthetic Aperture ◽  
Imaging Method ◽  
Back Projection ◽  
Rotation Effect ◽  
Signal Model ◽  
Range Migration ◽  
Sinusoidal Functions

Geosynchronous Synthetic Aperture Radar (GEO SAR) has a very long Coherent Processing Interval (in the order of hundreds of seconds) compared with other SAR platforms. Thus, the current methods of rotation effect matching and ship imaging that operate within a relatively short Coherent Processing Interval (in the order of seconds) are obviously not applicable. To address this problem, a novel ship imaging method with multiple sinusoidal functions matching for rotation effects is proposed for GEO SAR. Firstly, the influence of the rotational motion of a ship on the slant range is analyzed. It can be matched with the sum of multiple sinusoidal functions, and the signal model of a ship with rotational motion is given. Then, multiple sinusoidal functions for the matching-based ship imaging method are proposed, and their procedures are presented as follows: (1) The Generalized Keystone Transform and Generalized Dechirp Process (GKTGDP) is modified to compensate for the range migration and phase caused by the motion of GEO SAR. Then, the signal is focused at the frequencies of sinusoidal functions, and the frequencies can be matched. (2) From the matched frequencies, the other parameters of sinusoidal functions can be matched by parameter searching. (3) Based on the matched results, the Back Projection Algorithm (BPA) is used to take an image of the ship with rotational motion. Finally, the effectiveness of the proposed method is verified by numerical experiments.

scholarly journals A 3-D SAR Imaging Method Based on Back Projection Algorithm

2021 ◽  
Vol 2083 (3) ◽  
pp. 032050
Author(s):  
Qian Han ◽  
Pengbo Wang ◽  
Xinkai Zhou ◽  
Xinchang Hu ◽  
Yanan Guo
Keyword(s):  
3D Imaging ◽  
Bp Algorithm ◽  
Projection Algorithm ◽  
Imaging Method ◽  
Back Projection ◽  
Imaging Processing ◽  
Imaging Algorithm ◽  
Imaging Results ◽  
2D Imaging ◽  
Low Efficiency

Abstract 3D back projection (BP) algorithm is an imaging algorithm based on time domain echo data, which effectively solves the overlapping mask problem existing in 2D SAR. It can complete the imaging processing of echo signal under any geometry configuration, and has the advantages of high target focusing accuracy and high phase preservation. However, the high complexity and low efficiency of 3D BP imaging algorithm limit its application and development. In this paper, a 3d imaging method based on improved back projection algorithm is proposed. Aiming at the problem that existing imaging algorithms need 2D imaging first and then 3D imaging, an improved 3D BP algorithm is proposed to directly 3D imaging, which avoids 2d imaging processing. The proposed method simplifies the steps of the traditional 3D BP algorithm and improves the efficiency of the algorithm. The validity and effectiveness of the proposed method are verified by the 3d imaging results of simulated lattice targets.

scholarly journals A Modified Range Migration Algorithm for FMCW SAR Signal Processing

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Li Yake ◽  
Siu O’ Young
Keyword(s):  
Signal Processing ◽  
Continuous Wave ◽  
Real Data ◽  
Synthetic Aperture ◽  
Signal Spectrum ◽  
Imaging Method ◽  
Memory Size ◽  
Processing Accuracy ◽  
Range Migration ◽  
Accurate Imaging

<p class="AbstractText"><span lang="EN-AU">The range migration algorithm (RMA) is an accurate imaging method for processing synthetic aperture radar (SAR) signals. However, this algorithm requires a big amount of computation when performing Stolt mapping. In high squint and wide beamwidth imaging, this operation also requires big memory size to store the result spectrum after Stolt mapping because the spectrum will be significantly expanded. A modified Stolt mapping that does not expand the signal spectrum while still maintains the processing accuracy is proposed in this paper to improve the efficiency of the RMA when processing frequency modulated continuous wave (FMCW) SAR signals. The modified RMA has roughly the same computational load and required memory size as the range Doppler algorithm (RDA) when processing FMCW SAR data. In extreme cases when the original spectrum is significantly modified by the Stolt mapping, the modified RMA achieves better focusing quality than the traditional RMA. Simulation and real data are used to verify the performance of the proposed RMA.</span></p>

scholarly journals Parameter estimation under non-stationary circumstances using extended signal model

2014 ◽  
Vol 12 ◽  
pp. 43-48
Author(s):  
M. Lechtenberg ◽  
J. Götze ◽  
K. Görner ◽  
C. Rehtanz
Keyword(s):  
Fundamental System ◽  
Estimation Algorithm ◽  
Projection Algorithm ◽  
Back Projection ◽  
Short Term ◽  
Signal Model ◽  
Model Order ◽  
Amplitude Estimation ◽  
Sampled Signal ◽  
Electro Magnetic

Abstract. In the context of transient processes in power system measurements, a sampled signal is analyzed with respect to electro-magnetic influences. These are most likely superposed sinusoids that can be found next to the fundamental system sinusoid. However, such signal is not stationary, i.e. has a varying model order which means that temporary and exponentially damped sinusoids appear eventually. In our previous work, the exponential damping was only considered indirectly but not explicitly incorporated in the signal model used. Regarding the amplitude estimation, this led to inaccuracies since the amplitude was incorrectly assumed constant within a window of samples. In this paper, we use ESPRIT's ability to also estimate a parameter of exponential damping, improve the corresponding signal model, advance the amplitude estimation algorithm and back projection algorithm. Especially short-term signal components can be tracked far more precise.

scholarly journals A New Fast Factorized Back-Projection Algorithm with Reduced Topography Sensibility for Missile-Borne SAR Focusing with Diving Movement

2020 ◽  
Vol 12 (16) ◽  
pp. 2616
Author(s):  
Xinrui Li ◽  
Song Zhou ◽  
Lei Yang
Keyword(s):  
Adverse Effects ◽  
Cross Section ◽  
Time Domain ◽  
Projection Algorithm ◽  
Synthetic Aperture ◽  
Back Projection ◽  
Practical Application ◽  
Echo Signal ◽  
Cylindrical Coordinate ◽  
Significant Performance

Time-domain algorithms have significant performance advantages for missile-borne synthetic aperture radar (SAR) focusing with diving movement. However, due to the diving curve trajectory of the missile platform, the range and angular histories of the target become very sensitive to unknown tomography, which provides difficulties for SAR algorithm development. To address this problem, we have proposed a new fast factorized back-projection (FFBP) algorithm with reduced topography sensibility for missile-borne SAR focusing. The new algorithm was designed based on an orthogonal cylindrical coordinate (OCC) system, in which the cross section of a cylinder in the coordinate system is approximately orthogonal to the diving curve trajectory. Owing to the acquisition symmetry of the OCC system, the range and the angular histories of the grid in the OCC geometry become less dependent of the topography in every recursion of FFBP implementation, which can dramatically reduce the adverse effects of unknown topography and achieve high focusing performance. In the simulation, echo signal based on a set of typical parameters from a missile-borne SAR system is generated with unknown tomography. Promising results with 1 m resolution are finally achieved, which demonstrates the performance of the proposed algorithm. The limitation of the algorithm is also discussed in the final part, which will facilitate the development of raw data processes in practical application.

scholarly journals An Improved Back-Projection Algorithm for GNSS-R BSAR Imaging Based on CPU and GPU Platform

2021 ◽  
Vol 13 (11) ◽  
pp. 2107
Author(s):  
Shiyu Wu ◽  
Zhichao Xu ◽  
Feng Wang ◽  
Dongkai Yang ◽  
Gongjian Guo
Keyword(s):  
Graphics Processing Units ◽  
Low Cost ◽  
Computational Cost ◽  
Satellite System ◽  
Projection Algorithm ◽  
Synthetic Aperture ◽  
Processing Unit ◽  
Back Projection ◽  
Imaging Quality ◽  
Central Processing

Global Navigation Satellite System Reflectometry Bistatic Synthetic Aperture Radar (GNSS-R BSAR) is becoming more and more important in remote sensing because of its low power, low mass, low cost, and real-time global coverage capability. The Back Projection Algorithm (BPA) was usually selected as the GNSS-R BSAR imaging algorithm because it can process echo signals of complex geometric configurations. However, the huge computational cost is a challenge for its application in GNSS-R BSAR. Graphics Processing Units (GPU) provides an efficient computing platform for GNSS-R BSAR processing. In this paper, a solution accelerating the BPA of GNSS-R BSAR using GPU is proposed to improve imaging efficiency, and a matching pre-processing program was proposed to synchronize direct and echo signals to improve imaging quality. To process hundreds of gigabytes of data collected by a long-time synthetic aperture in fixed station mode, a stream processing structure was used to process such a large amount of data to solve the problem of limited GPU memory. In the improvement of the imaging efficiency, the imaging task is divided into pre-processing and BPA, which are performed in the Central Processing Unit (CPU) and GPU, respectively, and a pixel-oriented parallel processing method in back projection is adopted to avoid memory access conflicts caused by excessive data volume. The improved BPA with the long synthetic aperture time is verified through the simulation of and experimenting on the GPS-L5 signal. The results show that the proposed accelerating solution is capable of taking approximately 128.04 s, which is 156 times lower than pure CPU framework for producing a size of 600 m × 600 m image with 1800 s synthetic aperture time; in addition, the same imaging quality with the existing processing solution can be retained.

scholarly journals Small UAV-based SAR system using low-cost radar, position, and attitude sensors with onboard imaging capability

2021 ◽  
pp. 1-12
Author(s):  
Jan Svedin ◽  
Anders Bernland ◽  
Andreas Gustafsson ◽  
Eric Claar ◽  
John Luong
Keyword(s):  
Low Cost ◽  
Projection Algorithm ◽  
Synthetic Aperture ◽  
Back Projection ◽  
Data Link ◽  
Sar Images ◽  
Imaging Capability ◽  
Small Uav ◽  
Aerial Vehicle ◽  
High Resolution Images

Abstract This paper describes a small unmanned aerial vehicle (UAV)-based synthetic aperture radar (SAR) system using low-cost radar (5–6 GHz), position (GNSS/RTK) and attitude (IMU) sensors for the generation of high-resolution images. Measurements using straight as well as highly curved flight trajectories and varying flight speeds are presented, showing range and cross-range lobe-widths close to the theoretical limits. An analysis of the improvements obtained by the use of attitude angles (roll, pitch, and yaw), to correct for the relative offsets in antenna positions as the UAV moves, is included. A capability to generate SAR images onboard with the back-projection algorithm has been implemented using a GPU accelerated single-board computer. Generated images are transmitted to ground using a Wi-Fi data link.

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