Performance analysis on synthetic aperture radar-based vibration estimation in clutter

Recently, a time-frequency method based on the discrete fractional Fourier transform (DFrFT) was proposed for estimating target vibrations using synthetic aperture radar (SAR). Later on, a subspace method was incorporated into the DFrFT-based method. It is shown that the subspace method provides better performance than the direct DFrFT-based method in noise. However, the performance of these two methods has not been studied in clutter that cause strong interference with signals from vibrating targets in real-world applications. In this paper, the performance of the two vibration estimation methods in clutter is characterized and compared via simulations. Simulation results demonstrate that the DFrFT-based method, that yielded reliable results when signal-to-clutter ratios (SCR) exceeds 18 dB, now yields reliable results when SCR exceeds 8 dB with the incorporation of the subspace method. Experimental results show that the subspace method correctly estimates the vibration frequency of a 7 Hz vibration from actual SAR data at an estimated SCR of 14 dB.