Low Sidelobe Synthetic Aperture Radar Design for Optimal Output Peak Signal-to-Noise Ratio

Synthetic aperture radar (SAR) fundamentally relies on matched filtering to enhance resolution and peak signal-to-noise ratio (PSNR) in active microwave remote sensing. However, the band-limited nature of echoes introduces significant sidelobes for strong scatterers. Therefore, spectral windowing is required to suppress sidelobes after the echo has been focused with the matched filter. However, the windowing operation destroys the consistency between the magnitude spectrums of the matched filter and the echo, resulting in the PSNR not reaching the optimum and degrading the system performance. In this letter, based on the classical Hamming window, a Hamming frequency modulation (HFM) signal and the optimal azimuth antenna length considering the antenna weighting are proposed so that the amplitude of the 2-D spectrum of the echo is approximately equal to the square root of the Hamming window in both directions. By designing the corresponding matched filter, the spectral weighting is completed during the focusing operation, and the degradation of SAR image quality caused by the traditional windowing operation is solved. Theoretical analysis and experimental results show that the output SNR can be improved by a maximum of 5 dB without increasing the transmit power or reducing the resolution, which significantly improves the system efficiency.