Abstract
This paper presents a microwave imaging algorithm for high-squint airborne synthetic aperture radar (SAR), which combines back-projection and spectrum fusion together. Two spectrum center functions are proposed for linear and nonlinear trajectories respectively, which are the main contributions of this paper, and not considered in conventional work for high-squint SAR. For linear trajectory, the whole aperture data is first divided into sub-apertures with equal length, and the sub-aperture data is backprojected to a unified polar coordinate to generate multiple low-resolution sub-images. Then, these sub-images are corrected by an accurate spectrum center function, which is caused by the presence of squint angle. After spectrum center correction, spectrums of these sub-images can be coherently connected in cross-range wavenumber domain, generating the whole aperture spectrum. Next, the full-resolution image can be obtained by cross-range Fourier transform. For nonlinear trajectory, the deviations introduce extra spectrum shift, which degrades the focusing performance. Another spectrum center function is proposed according to angular-variant motion-error model, which helps to perform precise spectrum fusion. The proposed imaging algorithm is called high-squint accelerated factorized back-projection (HS-AFBP), and it helps to improve the focusing precision. Both the simulation and real data experiments validate the effectiveness of the proposed HS-AFBP algorithm.
Highlights
Synthetic aperture radar (SAR) plays an important role in remote sensing, surveillance, and reconnaissance tasks, due to its all-weather and all-time working capability [1]
Taking the first sub-image for example, its 2-D spectrum is shown in Figure 12, where subplot (a) is the original spectrum, (b) and (c) are the ones corrected by Accelerated factorized back-projection (AFBP) and high-squint accelerated factorized back-projection (HS-AFBP), respectively
HS-AFBP algorithm is proposed in this paper, which is suitable for high-squint SAR mode, and helps to improve the efficiency and precision of the time-domain imaging algorithms
Summary
Synthetic aperture radar (SAR) plays an important role in remote sensing, surveillance, and reconnaissance tasks, due to its all-weather and all-time working capability [1]. For high-squint SAR imaging, precision and efficiency are two important factors when the imaging algorithm is established. The efficiency is determined by the number of mathematical calculations during the imaging chain for the same dataset, such as multiplication, addition, Fourier transform (FT), and interpolation. Considering both precision and efficiency, various imaging algorithms have been proposed in recent decades with the development of SAR technique. These algorithms in the literature can be divided into two categories: frequency- and time-domain imaging
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