The azimuth multichannel synthetic aperture radar (SAR) technology is capable of overcoming the minimum antenna area constraint and achieving high-resolution and wide-swath (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 ${{\boldsymbol{L}}_{2,{\boldsymbol{q}}}}$ regularization $(0 < {\boldsymbol{q}} \leq 1)$ 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 $2,{\boldsymbol{q}}$-norm, and the ${{\boldsymbol{L}}_{2,{\boldsymbol{q}}}}$ 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.

中文翻译：

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基于$L_{2,q}$正则化的方位多通道SAR模糊抑制及其应用于高分3号超细条带图模式

方位多通道合成孔径雷达（SAR）技术能够克服最小天线面积限制，实现高分辨率和宽幅（HRWS）成像。一般来说，星载多通道SAR系统的脉冲重复频率（PRF）应满足方位角均匀采样条件，但有时由于雷达系统时序条件的限制而无法满足，通常称为“覆盖图”。对于 Gaofen-3 系统，在某些波束位置每个通道的 PRF 略小于双通道模式下均匀采样的 PRF，导致非均匀欠采样，从而导致恢复图像中的方位角模糊。虽然高分三号图像的模糊能量总体上不高，在强目标的弱杂波中，它仍然很明显。在本文中，一种新的基于非均匀欠采样的多通道 SAR 成像方法${{\boldsymbol{L}}_{2,{\boldsymbol{q}}}}$ 正则化 $(0 < {\boldsymbol{q}} \leq 1)$被提议。通过分析多通道SAR系统方位角模糊的原因，建立成像模型，强调与传统单通道SAR的区别。然后，我们将多通道 SAR 数据处理算子与群稀疏性相结合，构建了新的成像方法。组稀疏属性由$2,{\boldsymbol{q}}$- 规范，和 ${{\boldsymbol{L}}_{2,{\boldsymbol{q}}}}$正则化问题可以通过稀疏组阈值函数解决。结果表明，所提出的方法可以有效地抑制非均匀欠采样引起的方位角模糊。仿真和高分3号真实数据实验被用来验证所提出方法的有效性。