Vortex electromagnetic wave carries orbital angular momentum. Combined with Doppler information provided by radar platform movement, vortex electromagnetic wave can achieve higher resolution target imaging in SAR Imag...
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Vortex electromagnetic wave carries orbital angular momentum. Combined with Doppler information provided by radar platform movement, vortex electromagnetic wave can achieve higher resolution target imaging in SAR Imaging technology. In this paper, fractional order OAM vortex SAR imaging is studied. Firstly, the side-looking strip SAR imaging model is established. Then, the scattering echo equation of fractional order OAM is derived. Finally, the imaging simulation of multi-point target and single point target under Gaussian SNR is carried out by chirp scaling algorithm. The experimental results show that compared with the integer order OAM Vortex SAR Imaging, the fractional order OAM Vortex SAR Imaging in this paper has stronger robustness in Multi-target and Noise environment, which proves the effectiveness of the fractional order Vortex SAR Imaging.
To improve the imaging quality of conventional imaging algorithms without motion compensation (MOCO) and the efficiency of point-by-point MOCO algorithms for multiple-receiver synthetic aperture sonar (SAS) with azimu...
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To improve the imaging quality of conventional imaging algorithms without motion compensation (MOCO) and the efficiency of point-by-point MOCO algorithms for multiple-receiver synthetic aperture sonar (SAS) with azimuth-invariant six-degree of freedom (DOF) motion errors, an azimuth-invariant MOCO and imaging chirpscaling (CS) algorithm is presented in this paper. Taylor series approximation is used to process the range history in double square root form, while considering the fourth-order and inner terms with respect to the azimuth time. Using the method of series reversion and Fourier transform (FT) properties, the analytical two-dimensional frequency spectrum of the point target response of each receiver is derived. On this basis, the azimuth-invariant MOCO and imaging CS algorithm is proposed for six-DOF motion error compensation and multiple-receiver SAS imaging. Because it considers the azimuth-invariant six-DOF motion errors, the proposed algorithm has better imaging quality than conventional imaging algorithms without MOCO. Additionally, it has a significantly higher efficiency than point-by-point MOCO algorithms because the CS algorithm is a fast FT-based algorithm and does not require interpolation processing. The imaging simulation and experimental results verified the effectiveness and efficiency of the proposed algorithm.
For the problem that the existing chirp scaling algorithm based on the method of series reversion (MSRCSA) needs to approximate the range cell migration (RCM) into a linear term of range and causes a larger range cell...
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For the problem that the existing chirp scaling algorithm based on the method of series reversion (MSRCSA) needs to approximate the range cell migration (RCM) into a linear term of range and causes a larger range cell migration correction (RCMC) error, we propose an improved MSRCSA, which is able to focus azimuth-variation bistatic SAR. Firstly, to avoid the linear approximation for RCM, this paper derives a new curvature factor varying with the azimuth frequency and range, utilizing to describe RCM without any approximation. Secondly, since the new curvature factor is different with the traditional curvature factor varying only with the azimuth frequency, a new scaling function is given to modulate the echo signal so that the required range-variant RCMC shift can be implemented by using phase multiplies. Thirdly, the proposed MSRCSA is implemented by utilizing three phase multiplications and four fast Fourier transforms (FFTs). Finally, the good performance of the proposed MSRCSA is examined by comparing the imaging result of the proposed MSRCSA with that of the existing MSRCSA.
The conventional chirp scaling algorithm is mainly used in side looking or small squint angle mode of synthetic aperture imaging. In application of synthetic sonar, the large squint angle imaging is often required and...
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The conventional chirp scaling algorithm is mainly used in side looking or small squint angle mode of synthetic aperture imaging. In application of synthetic sonar, the large squint angle imaging is often required and the range-azimuth coupling is serious. On the basis of studying the principle of the conventional chirp scaling algorithm, we improved the imaging algorithm in large squint mode. We analysed the structure of the echo frequency spectrum and the compensation of phase factor. The improved imaging algorithm designs a more precision of phase compensation factor, and eliminates the high order degree of range and azimuth coupling in the specific mapping band. Any target point is simulated in imaging region by using the improved algorithm. The simulation conclusion showed that the improved chirp scaling algorithm is able to meet the imaging focus and is more suitable to slant imaging as compared with the traditional algorithm.
A focusing solution for bistatic forward-looking synthetic aperture radar (BFSAR) is presented. Forward-looking imaging is highly desirable in some potential applications, such as self-landing in bad weather, military...
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A focusing solution for bistatic forward-looking synthetic aperture radar (BFSAR) is presented. Forward-looking imaging is highly desirable in some potential applications, such as self-landing in bad weather, military surveillance, and navigation. Unfortunately, monostatic synthetic aperture radar reaches its limit when it is used in a forward-looking configuration. BFSAR can provide a high-resolution image in the forward-looking direction. However, due to the special forward-looking geometry, many proposed methods of deriving a bistatic point target reference spectrum (BPTRS) cannot handle the BFSAR data well. A modified Loffeld's bistatic formula (MLBF) for a forward-looking configuration is proposed first;it can get an accurate BPTRS of BFSAR. Then, a chirp scaling algorithm (CSA) based on MLBF is derived. CSA without interpolation allows high performance. Numerical simulations show that the proposed focusing solution can handle the BFSAR data well and achieve a high-resolution focused image. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
For the problem of the low computational efficiency in the existing CSA based on MSR for the multiple-receiver SAS because it is required to perform image reconstruction for each receiver, an efficiency CSA based on M...
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ISBN:
(纸本)9781665400046
For the problem of the low computational efficiency in the existing CSA based on MSR for the multiple-receiver SAS because it is required to perform image reconstruction for each receiver, an efficiency CSA based on MSR for the multiple-receiver SAS is proposed in this paper. Firstly, to make that the range cell migration, azimuth modulation, and range modulation of different receiver can be represented by that of the reference receiver, the signal of each receiver is shifted to the same shortest range. Secondly, to obtain the imaging result by performing one imaging reconstruction, the multiple receivers signal shifted is transformed into the monostatic signal by azimuth reconstruction. Thirdly, the imaging reconstruction based on MSR's 2D spectrum is derived by utilizing the chirpscaling principle. Finally, the effectiveness of the proposed algorithm is validated by the simulation experiments.
For a synthetic aperture radar (SAR) onboard a geosynchronous-earth-orbit (GEO) satellite, the track can be curvilinear. Thus, the validity of imaging algorithms based on the conventional hyperbolic range equation (CH...
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For a synthetic aperture radar (SAR) onboard a geosynchronous-earth-orbit (GEO) satellite, the track can be curvilinear. Thus, the validity of imaging algorithms based on the conventional hyperbolic range equation (CHRE) becomes questionable. A fourth-order range equation is adopted to improve the accuracy in the approximation of the range history for GEO SAR and a modified chirp scaling algorithm (CSA) is proposed. Simulation results show that the presented algorithm has better performance than the CHRE-based CSA in the GEO case, implying good application prospects.
The area coverage rate is dramatically improved by using the multireceiver technique. However, this configuration leads to the complexity of the synthetic aperture image formation. In order to solve this issue, the ta...
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The area coverage rate is dramatically improved by using the multireceiver technique. However, this configuration leads to the complexity of the synthetic aperture image formation. In order to solve this issue, the target based on the phase centre approximation (PCA) is to be reconstructed. The data related to the multireceiver SAS system is coerced into the data like traditional monostatic synthetic aperture sonar (SAS) system. Then, the data can be processed by traditional imaging methods. In this paper, the chirp scaling algorithm is exploited as an example. Moreover, the influence of some important steps with the monostatic conversion, i.e. pulse compression in the range dimension and the micro range cell migration correction (RCMC), is further discussed in detail. The simulations show that the presented method can focus the target well.
For the chirp scaling algorithm of synthetic aperture radar imaging, an efficient transmission of a large volume of data is indispensable. Prior to imaging, there is a requirement for appropriate pre-processing of the...
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For the chirp scaling algorithm of synthetic aperture radar imaging, an efficient transmission of a large volume of data is indispensable. Prior to imaging, there is a requirement for appropriate pre-processing of the echo signal by digital down conversion (DDC). The DDC module has to remove the carrier, having an appropriate filtering processing and down-sampling processing. No matter what imaging mode is chosen, such as the stripmap mode, spotlight mode, and sliding spotlight, the needs of the whole imaging system are matched by setting a series of configurations about this pre-processing module and this transmission module. The system-on-a-programmable-chip constituted by the Advanced RISC Machine and field programmable gate array (FPGA) is the perfect experimental platform to test the performance of this system. Some of the algorithms, which are more feasible for this specific project for pre-processing in Maltab, were transplanted to FPGA using the VHSIC Hardware Description Language for functional verification. Finally, the processing results in Matlab were compared with this system to find the difference. At the same time, the time that elapsed from the 2 GB original data entering the system to the time the processed results were completely returned to the PC was also counted.
To compensate motion errors of images from the parallel-track bistatic synthetic aperture radar(BiSAR),an improved chirp scaling algorithm(CSA) is *** velocity vector of the moving aircrafts in the parallel-track ...
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To compensate motion errors of images from the parallel-track bistatic synthetic aperture radar(BiSAR),an improved chirp scaling algorithm(CSA) is *** velocity vector of the moving aircrafts in the parallel-track BiSAR system can not remain invariant in an aperture,an actual aperture is divided into subapertures so that it is reasonable to assume that the aircrafts move with constant acceleration vector in a *** on this model,an improved CSA is *** new phase factors incorporate three-dimensional acceleration and *** motion compensation procedure is integrated into the CSA without additional operation *** simulation results show that the presented algorithm can efficiently resolve motion compensation for parallel-track BiSAR.
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