A Method for Estimating the Parameters of Spaceborne Synthetic Aperture Radar LFM under a Low Signal-to-Noise Ratio

Due to the complex and harsh electromagnetic environment, the accuracy of the parameter estimation of intercepted low signal-to-noise ratio (SNR) spaceborne synthetic aperture radar (SAR) radiation source linear frequency modulation (LFM) signals is not high; this paper proposes a method for joint parameter estimation of multiple received pulses submerged in Gaussian white noise. This method makes use of the coherence between multiple pulses of the received signal and cooperates with the short-time Fourier transform (STFT) and the robust ordinary least squares (ROLS) to effectively estimate the LFM signal parameters. Finally, the performance of the algorithm is verified by the simulation analysis method. Under the condition of a low SNR (-20 dB), the normalized root mean square error (NRMSE) of the starting frequency can reach 10-3; the NRMSE of the chirp rates of the intrapulse modulation characteristic parameter can reach 2 ×10-3. The comparison with other methods further proves the performance advantage of this method under a low SNR.