Abstract
The downward-looking sparse linear array three-dimensional synthetic aperture radar (DLSLA 3D SAR) has attracted a great deal of attention, due to the ability to obtain three-dimensional (3D) images. However, if the velocity and the yaw rate of the platform are not measured with enough accuracy, the azimuth signal cannot be compressed and then the 3D image of the scene cannot be obtained. In this paper, we propose a method for platform motion parameter estimation, and downward-looking 3D SAR imaging. A DLSLA 3D SAR imaging model including yaw rate was established. We then calculated the Doppler frequency modulation, which is related to the cross-track coordinates rather than the azimuth coordinates. Thus, the cross-track signal reconstruction was realized. Furthermore, based on the minimum entropy criterion (MEC), the velocity and yaw rate of the platform were accurately estimated, and the azimuth signal compression was also realized. Moreover, a deformation correction procedure was designed to improve the quality of the image. Simulation results were given to demonstrate the validity of the proposed method.
Highlights
Three-dimensional synthetic aperture radar (3D SAR) imaging can obtain 3D images of targets, and obtain more abundant target information than traditional SAR imaging, which often suffers from shading and layover effects [1,2,3]
Uniform linear array imaging algorithms are usually based on the beam-forming theory and multiple signal classification (MUSIC) algorithm to realize 3D imaging [13,14]
Sparse array methods exploit the sparsity of the 3D scene, and employ compressed sensing (CS) [15,16] and regularization methods [17] for DLSLA 3D SAR imaging [18,19]
Summary
Three-dimensional synthetic aperture radar (3D SAR) imaging can obtain 3D images of targets, and obtain more abundant target information than traditional SAR imaging, which often suffers from shading and layover effects [1,2,3]. Existing DLSLA 3D SAR researchers have been focusing on three main aspects: Imaging methods, array optimization, and improving the cross-track resolution. A particular issue in DLSLA 3D SAR imaging is that the cross-track resolution is relatively low, because the length of the array is limited by the platform size. In DLSLA 3D SAR, the cross-track resolution depends on the wavelength of the transmitted signal, the length of the array, and the flying height of the platform. The remainder of this paper is organized as follows: The imaging model is established and the Doppler frequency modulation is analyzed in Section 2; in Section 3, cross-track signal reconstruction is discussed; parameter estimation and the azimuth compression based on MEC are described in Remote Sens.
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