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为了应用傅里叶望远镜(FT)技术对同步静止轨道和低轨运动卫星进行高分辨率成像探测,提出了一种基于非均匀采样技术,以低采样频率处理高频返回信息的新方法。对返回的时域信号进行非均匀采样并对数字信号进行离散非均匀傅里叶变换(NUDFT);衰减除高幅值低频信号以外的所有信号后再进行NUDFT即可精确地提取低频分量信息;重复幅值衰减和NUDFT直至提取所有的频率信息;通过相位闭合技术及传统重构方法即可重构目标。该方法降低了采样频率并克服了NUDFT方法的频谱噪声,有效地避免了高频噪声对成像质量的影响,特别是在低轨道多光束傅里叶望远镜成像方面有较大的应用前景。通过数值模拟验证了该方法的可行性,并在不同的信噪比条件下和传统均匀采样重构图像进行了对比研究,证实该方法对噪声的敏感程度与传统方法基本一致。
In order to detect high-resolution imaging of synchrotron orbit and low-orbiting satellites using Fourier Telescope (FT), a new method of processing high-frequency return information with low sampling frequency based on non-uniform sampling technique is proposed. Performing non-uniform sampling on the returned time domain signal and performing discrete non-uniform Fourier transform (NUDFT) on the digital signal; attenuating all signals except the high-amplitude low-frequency signal and then performing NUDFT to accurately extract low-frequency component information; Repeat amplitude attenuation and NUDFT until all frequency information is extracted; targets can be reconstructed by phase closure techniques and traditional reconstruction methods. The method reduces the sampling frequency and overcomes the spectral noise of the NUDFT method, and effectively avoids the influence of high-frequency noise on the imaging quality, and has great application prospect especially in low-orbit multi-beam Fourier telescope imaging. The feasibility of this method is verified by numerical simulation, and compared with the traditional uniformly sampled and reconstructed image under different signal-to-noise ratio conditions. The sensitivity of this method to noise is basically the same as the traditional method.