Li Yinwei, Ding Li, Zheng Qibin, Zhu Yiming, Sheng Jialian
Terahertz Technology Innovation Research Institute, University of Shanghai for Science and Technology, Shanghai 200093, China.
Shanghai Key Laboratory of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China.
Sensors (Basel). 2020 May 7;20(9):2669. doi: 10.3390/s20092669.
Compared with microwave synthetic aperture radar (SAR), terahertz SAR (THz-SAR) is easier to achieve ultrahigh-resolution image due to its higher frequency and shorter wavelength. However, higher carrier frequency makes THz-SAR image quality very sensitive to high-frequency vibration error of motion platform. Therefore, this paper proposes a novel high-frequency vibration error estimation and compensation algorithm for THz-SAR imaging based on local fractional Fourier transform (LFrFT). Firstly, the high-frequency vibration error of the motion platform is modeled as a simple harmonic motion and THz-SAR echo signal received in each range pixel can be considered as a sinusoidal frequency modulation (SFM) signal. A novel algorithm for the parameter estimation of the SFM signal based on LFrFT is proposed. The instantaneous chirp rate of the SFM signal is estimated by determining the matched order of LFrFT in a sliding small-time window and the vibration acceleration is obtained. Hence, the vibration frequency can be estimated by the spectrum analysis of estimated vibration acceleration. With the estimated vibration acceleration and vibration frequency, the SFM signal is reconstructed. Then, the corresponding THz-SAR imaging algorithm is proposed to estimate and compensate the phase error caused by the high-frequency vibration error of the motion platform and realize high-frequency vibration error estimation and compensation for THz-SAR imaging. Finally, the effectiveness of the novel algorithm proposed in this paper is demonstrated by simulation results.
与微波合成孔径雷达（SAR）相比，太赫兹合成孔径雷达（THz - SAR）由于其更高的频率和更短的波长，更容易实现超高分辨率成像。然而，更高的载波频率使得太赫兹合成孔径雷达图像质量对运动平台的高频振动误差非常敏感。因此，本文提出了一种基于局部分数傅里叶变换（LFrFT）的太赫兹合成孔径雷达成像高频振动误差估计与补偿新算法。首先，将运动平台的高频振动误差建模为简谐运动，每个距离像素接收到的太赫兹合成孔径雷达回波信号可视为正弦调频（SFM）信号。提出了一种基于局部分数傅里叶变换的正弦调频信号参数估计算法。通过在滑动的小时间窗口内确定局部分数傅里叶变换的匹配阶数来估计正弦调频信号的瞬时调频率，进而得到振动加速度。因此，通过对估计的振动加速度进行频谱分析可以估计振动频率。利用估计的振动加速度和振动频率，重建正弦调频信号。然后，提出相应的太赫兹合成孔径雷达成像算法，估计并补偿由运动平台高频振动误差引起的相位误差，实现太赫兹合成孔径雷达成像的高频振动误差估计与补偿。最后，仿真结果验证了本文所提新算法的有效性。
