Enhancing the survivability of synthetic aperture radar (SAR) in electronic warfare environments is crucial. In this paper, a low-probability-of-intercept (LPI) spotlight SAR imaging method is proposed. It is based on...
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Enhancing the survivability of synthetic aperture radar (SAR) in electronic warfare environments is crucial. In this paper, a low-probability-of-intercept (LPI) spotlight SAR imaging method is proposed. It is based on composite modulation waveform and improved polar format algorithm (PFA). This method addresses the limitation that traditional radar systems with linear frequency modulated (LFM) signals are easy to be intercepted. A hybrid optimization approach combining grey wolf optimizer (GWO) and genetic algorithm (GA) is employed to optimize the composite modulation waveform, achieving both excellent pulse compression and LPI performance. Additionally, PFA is improved to process the optimized signal, addressing the azimuth non-uniform sampling problem in polar interpolation. Simulations of point targets and scenes under PRF agility and encoding sequence agility validate the effectiveness of the proposed algorithm.
Inverse synthetic aperture RADAR (ISAR) imaging produces range-Doppler images by exploiting the motion of the target related to the RADAR. Two cases arise in ISAR imaging: the target motion is known (cooperative targe...
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The polar format algorithm (PFA) is a high-resolution imaging algorithm suitable for earth-based radar imaging of the moon. However, the earth-based radar imaging of moon has the problem of out-of-plane motion, which ...
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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 o...
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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.
polar format algorithm (PFA), which is a classic algorithm for bistatic SAR imaging, has important significance in spotlight bistatic SAR system. In this paper, a fast polar format algorithm based on variable PRF for ...
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ISBN:
(纸本)9781509048281
polar format algorithm (PFA), which is a classic algorithm for bistatic SAR imaging, has important significance in spotlight bistatic SAR system. In this paper, a fast polar format algorithm based on variable PRF for bistatic SAR is proposed. This algorithm can correct range cell migration (RCM) without high-precision interpolation, which can improve the computation efficiency. Point target simulation validates the algorithm.
We present an efficient and computationally simple approach for synthetic aperture radar (SAR) imaging in cases when the radar data have gaps, due to missing pulses and/or notches in the frequency band. Our method is ...
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ISBN:
(纸本)9781628415919
We present an efficient and computationally simple approach for synthetic aperture radar (SAR) imaging in cases when the radar data have gaps, due to missing pulses and/or notches in the frequency band. Our method is a simple variation of gradient projection, in which the search path in each iteration is obtained by projecting the negative-gradient of the L1 norm onto a hyper-plane defining solutions which are consistent with the data. The computations are not complicated since the L1 gradient is simply equal to the sign() of the pixels in the image. Computational efficiency is obtained by incorporating the polar format algorithm, which accomplishes the projection operation using a fast Fourier transform. Sample results are presented using the AFRL Gotcha 2006 radar data set and the Space Dynamics Laboratory FlexSAR system.
In this paper, a new interpretation of the polar format algorithm (PFA) for bistatic spotlight synthetic aperture radar (SAR) imaging is presented. From the viewpoint of two-dimensional decoupling, we examine the comm...
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ISBN:
(纸本)9781479982325
In this paper, a new interpretation of the polar format algorithm (PFA) for bistatic spotlight synthetic aperture radar (SAR) imaging is presented. From the viewpoint of two-dimensional decoupling, we examine the commonly adopted implementation of the PFA, i.e., the separable 1-D range and azimuth resampling procedures for their roles in range cell migration (RCM) correction, respectively. It is shown that the range resampling corrects for the RCM associated with the down-range coordinate of target, while the azimuth resampling compensates for the RCM associated with the cross-range coordinate of target. The presented work provides a new perspective on the mechanism of RCM correction in PFA.
Conventional polar format algorithm (PFA) and its variations normally assume an ideal imaging geometry of a linear flight path, which cannot counteract the non-uniformity of samples existing in the circumstance of a h...
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Conventional polar format algorithm (PFA) and its variations normally assume an ideal imaging geometry of a linear flight path, which cannot counteract the non-uniformity of samples existing in the circumstance of a highly non-linear aperture. This scenario may occur because of various factors such as rugged topography, atmospheric turbulence and intended manoeuvres. To address this challenge, this study develops a novel PFA with aperture accommodation for spotlight synthetic aperture radar (SAR) imaging. The proposed algorithm provides a new adaption of the fast Gaussian grid (FGG) non-uniform fast Fourier transform (NUFFT) scheme to two-dimensional (2D) SAR imaging of 3D scene, whose main idea is to convolve the non-uniform samples onto a uniform grid with a Gaussian kernel and then exploit the efficient 2D FFT for image reconstruction. In virtue of the 2D FGG NUFFT, a favourable tradeoff between reconstruction precision and computational efficiency is gained. Simulations illustrate the superiority of the proposed algorithm over the conventional non-uniform Sinc interpolation method. Also, the public real Gotcha dataset validates the effectiveness of the authors method.
Due to its computational efficiency, the polar format algorithm (PFA) is considered by many to be the workhorse for airborne synthetic aperture radar (SAR) imaging. PFA is implemented in spatial Fourier space, also kn...
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ISBN:
(纸本)9781628410303
Due to its computational efficiency, the polar format algorithm (PFA) is considered by many to be the workhorse for airborne synthetic aperture radar (SAR) imaging. PFA is implemented in spatial Fourier space, also known as "K-space", which is a convenient domain for understanding SAR performance metrics, sampling requirements, etc. In this paper the mathematics behind PFA are explained and computed examples are presented, both using simulated data, and experimental airborne radar data from the Air Force Research Laboratory (AFRL) Gotcha Challenge collect. In addition, a simple graphical method is described that can be used to model and predict wavefront curvature artifacts in PFA imagery, which are due to the limited validity of the underlying far-field approximation. The appendix includes Matlab code for computing SAR images using PFA.
In this paper, we present a detailed analysis on the performance degradation of inverse synthetic aperture radar (ISAR) imagery with the polar format algorithm (PFA) due to the inaccurate rotation center. And a novel ...
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In this paper, we present a detailed analysis on the performance degradation of inverse synthetic aperture radar (ISAR) imagery with the polar format algorithm (PFA) due to the inaccurate rotation center. And a novel algorithm is developed to estimate the rotation center for ISAR targets to overcome the degradation. In real ISAR scenarios, the real rotation center shift is usually not coincided with the gravity center of the high-resolution range profile (HRRP), due to the data-driven translational motion compensation. Because of the imprecise information of rotation center, PFA image yields model errors and severe blurring in the cross-range direction. To tackle this problem, an improved PFA based on integrated cubic phase function (ICPF) is proposed. In the method, the rotation center in the slant range is estimated firstly by ICPF, and the signal is shifted accordingly. Finally, the standard PFA algorithm can be carried out straightforwardly. With the proposed method, wide-angle ISAR imagery of non-cooperative targets can be achieved by PFA with improved focus quality. Simulation and real-data experiments confirm the effectiveness of the proposal.
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