一种基于短时傅里叶变换的机载SAR自聚焦算法

摘要

The Short-Time Fourier Transform (STFT) is an important method widely used in the study of the nonstationary signals. After discussing the filtering and the estimation of chirp rate for Linear Frequency Modulation (LFM) signal by using the STFT, this paper proposes a novel autofocus method based on the STFT. The proposed autofocus method firstly utilizes the STFT to estimate and compensate the Quadratic Phase Error (QPE), which is the main part of phase error influencing the quality of the SAR image. And when estimating the residual phase error, the STFT filtering is used for filtering the noise and interference of the time-variant signals to raise the Signal-to-Clutter Ratio (SCR). The experiment results using both simulated data and real data demonstrate the validation of the proposed autofocus method.%短时傅里叶变换(Short-Time Fourier Transform, STFT)是研究非平稳信号最为广泛使用的重要方法。该文在讨论了利用STFT对线性调频信号(LFM)进行滤波以及调频率估计后，提出一种基于STFT的机载SAR自聚焦算法。该算法首先利用STFT对影响SAR图像质量的主要相位误差二次相位误差(QPE)进行估计和补偿，然后在残余相位误差估计时利用STFT对时变信号进行滤波以提高信杂比(SCR)。仿真和实测数据的处理结果验证了该文算法的有效性。