Tomographic synthetic aperture radar (TomoSAR) technology, as an extension of interferometric SAR (InSAR), solves the layover problem and realizes three-dimensional (3-D) imaging. Now, it is an important research direction in the field of radar imaging. However, TomoSAR usually requires the SAR sensor to make enough acquisitions at different spatial locations to achieve high-quality 3-D imaging, which is high time-costly and inefficient. To solve this problem, we extend multi-frequency (MF) InSAR and propose a novel SAR 3-D imaging configuration: MF-TomoSAR. MF-TomoSAR utilizes limited acquisitions with enhanced degrees of freedom (DOF) in frequency to accomplish 3-D imaging. It can achieve a similar imaging quality as the traditional TomoSAR while significantly improving 3-D imaging efficiency. The main contributions are summarized as follows: First, inspired by the idea of extending multi-baseline (MB) InSAR to TomoSAR, the single baseline (SB) MF-TomoSAR signal model is proposed. The SBMF-TomoSAR model utilizes interferometric processing to eliminate the effects of scattering changes due to different working frequencies (WFs). In the extreme case of only one fixed baseline, multiple interferograms with different WFs can be considered as samples at different spatial frequencies (SFs) to achieve 3-D imaging through spectral estimation. Then, in order to solve the sampling limitation caused by a fixed baseline, the MF-TomoSAR configuration is generalized to a general case of multiple baselines, and the MBMF-TomoSAR signal model is proposed. The MBMF-TomoSAR model realizes SF sampling through different WFs with multiple baselines to achieve sampling expansion and ensure the 3-D imaging quality. Finally, the MF-TomoSAR processing framework is proposed with the baseline distribution optimization method. The MF-TomoSAR configuration (either SB or MB) does not change the essence of spectral estimation in tomographic processing, and the classical tomographic processing algorithms can be directly applied to MF-TomoSAR processing. The computer simulation and unmanned aerial vehicle (UAV) SAR 3-D imaging experiment verify the effectiveness of the proposed MF-TomoSAR configuration.

中文翻译：

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多频层析 SAR：一种用于有限采集的新型 3D 成像配置


层析合成孔径雷达 （TomoSAR） 技术作为干涉 SAR （InSAR） 的延伸，解决了停留问题并实现了三维 （3-D） 成像。现已成为雷达成像领域的重要研究方向。然而，TomoSAR 通常需要 SAR 传感器在不同空间位置进行足够的采集才能实现高质量的 3-D 成像，这既费时又低效。为了解决这个问题，我们扩展了多频 （MF） InSAR，并提出了一种新的 SAR 三维成像配置：MF-TomoSAR。MF-TomoSAR 利用频率增强的有限采集来完成 3D 成像。它可以实现与传统 TomoSAR 相似的成像质量，同时显著提高 3D 成像效率。主要贡献总结如下：首先，受将多基线 （MB） InSAR 扩展到 TomoSAR 的思想启发，提出了单基线 （SB） MF-TomoSAR 信号模型。SBMF-TomoSAR 模型利用干涉处理来消除不同工作频率 （WF） 引起的散射变化的影响。在只有一个固定基线的极端情况下，可以将具有不同 WFs 的多个干涉图视为不同空间频率 （SFs） 的样本，通过光谱估计实现三维成像。然后，为了解决固定基线带来的采样限制，将 MF-TomoSAR 配置推广到多基线的一般情况，并提出 MBMF-TomoSAR 信号模型。MBMF-TomoSAR 模型通过具有多个基线的不同 WF 实现 SF 采样，实现采样扩展，保证三维成像质量。 最后，提出了基于基线分布优化方法的MF-TomoSAR处理框架。MF-TomoSAR 配置（SB 或 MB）不会改变层析处理中光谱估计的本质，经典的层析处理算法可以直接应用于 MF-TomoSAR 处理。计算机仿真和无人机 （UAV） SAR 三维成像实验验证了所提 MF-TomoSAR 配置的有效性。