Rotating targets/components often carry beneficial information for identifying high-value targets in video synthetic aperture radar (ViSAR). However, unlike linear motion models, rotating motion models involve more parameters to be estimated, rendering parametric-based methods computationally intensive. Besides, such micro-motion features are relatively insignificant in the microwave band. To conquer the aforementioned problems, this article proposes the nonparametric indication and imaging of rotating targets under terahertz (THz) ViSAR. Taking rotating corner reflectors (RCRs) as the object, the Doppler prior and imaging characteristics (DPIC) are first determined and regarded as the theoretical basis. Combining DPIC and Doppler sensitivity of THz band, RCRs can be easily indicated by the nonparametric time–frequency transform. Thus, range cells of RCRs can be deduced intuitively by the visual saliency, followed by the separation of the residual background and defocused target area. After clutter suppression, two signal of interests (SoIs) of RCRs are extracted from salient points, where unwrapped phases and azimuth spectrums are utilized for fast estimation of phase errors and additional Doppler centroids (DCs), respectively. Finally, the refocused target image is stitched into the residual background. To validate the effectiveness of the proposed method, the airborne field experiment of RCRs is conducted in THz-band for the first time. Moreover, the anti-noise ability, relocation capability, and applicable speed interval of the proposed method are demonstrated, along with its extended application potential in terms of the ground moving target imaging.

中文翻译：

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基于非参数方法的THz-ViSAR旋转目标快速指示与成像


旋转目标/组件通常携带有用的信息，有助于识别视频合成孔径雷达 (ViSAR) 中的高价值目标。然而，与线性运动模型不同，旋转运动模型涉及更多需要估计的参数，使得基于参数的方法计算量大。此外，这种微运动特征在微波波段中相对不显着。为了克服上述问题，本文提出了太赫兹（THz）ViSAR下旋转目标的非参数指示和成像。以旋转角反射器（RCR）为对象，首先确定多普勒先验和成像特性（DPIC）并作为理论基础。结合太赫兹频段的 DPIC 和多普勒灵敏度，RCR 可以通过非参数时频变换轻松表示。因此，可以通过视觉显着性直观地推断出RCR的范围单元，然后分离残留背景和散焦目标区域。杂波抑制后，从显着点提取 RCR 的两个感兴趣信号 (SoI)，其中展开相位和方位频谱分别用于快速估计相位误差和附加多普勒质心 (DC)。最后，将重新聚焦的目标图像拼接到残留背景中。为了验证该方法的有效性，首次在太赫兹频段进行了RCR机载外场实验。此外，还论证了该方法的抗噪声能力、重定位能力和适用的速度区间，以及其在地面运动目标成像方面的扩展应用潜力。