Abstract
The azimuth multichannel synthetic aperture radar (SAR) technology is capable of overcoming the minimum antenna area constraint and achieving high-resolution and wideswath (HRWS) imaging. Generally speaking, the pulse repetition frequency (PRF) of the spaceborne multichannel SAR systems should satisfy the azimuthal uniform sampling condition, but it is sometimes impossible due to the limitation of radar system timing conditions, which is often referred as “coverage diagram.” For the Gaofen-3 system, the PRF of each channel at some beam positions is slightly less than that of uniform sampling in the dual-channel mode, leading to the nonuniform undersampling, hence, resulting the azimuth ambiguities in the recovered images. Although the ambiguous energy in Gaofen-3 images is not high in general, it is still noticeable amid surrounding weak clutters of strong targets. In this article, a novel multichannel SAR imaging method for nonuniform undersampling based on L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2,q</sub> regularization (0 <; q ≤ 1) is proposed. By analyzing the reasons of azimuth ambiguities in the multichannel SAR system, the imaging model is established with emphasizing the difference from conventional single-channel SAR. Then, we combine the multichannel SAR data processing operators with the group sparsity property to construct the novel imaging method. The group sparsity property is modeled by the 2, q-norm, and the L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2,q</sub> regularization problem can be solved via sparse group thresholding function. It is shown that the proposed method can efficiently suppress the azimuth ambiguities caused by nonuniform undersampling. Simulations and Gaofen-3 real data experiments are exploited to verify the effectiveness of the proposed method.
Highlights
S YNTHETIC aperture radar (SAR) is an important remote sensing technology that can work in all-weather and all-time, and has been widely applied into many fields such as marine surveillance, agricultural production monitoring, and target detection [1]–[4]
We propose a novel multichannel synthetic aperture radar (SAR) imaging method for nonuniform undersampling condition inspired by L2,q regularization
Limited by the beam position design of the spaceborne multichannel SAR systems, sometimes the pulse repetition frequency (PRF) of each channel is less than that of uniform sampling, which will result in nonuniform undersampling
Summary
S YNTHETIC aperture radar (SAR) is an important remote sensing technology that can work in all-weather and all-time, and has been widely applied into many fields such as marine surveillance, agricultural production monitoring, and target detection [1]–[4]. In [19], Quan et al introduced Lq regularization into multichannel SAR signal reconstruction to solve the azimuth ambiguities caused by nonuniform sampling. 2) Compared with the Lq-regularization-based method in [19], the proposed method considers both the main imaging area and ambiguous areas when deriving the sparse SAR imaging model, and introduces the group sparsity property into multichannel SAR data processing. We adopt the proposed method in the scene of sparse sea surface, achieving the azimuth ambiguities suppression of ship targets and improving the imaging quality. Lq-REGULARIZATION-BASED MULTICHANNEL SAR IMAGING METHOD FOR NONUNIFORM SAMPLING
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