Refocusing vibrating targets in SAR images

Qi Wang; Balu Santhanam; Matthew Pepin; Tom Atwood; Majeed M. Hayat

doi:10.1117/12.919521

3 May 2012 Refocusing vibrating targets in SAR images

Qi Wang, Balu Santhanam, Matthew Pepin, Tom Atwood, Majeed M. Hayat

Proceedings Volume 8361, Radar Sensor Technology XVI; 836106 (2012) https://doi.org/10.1117/12.919521
Event: SPIE Defense, Security, and Sensing, 2012, Baltimore, Maryland, United States

Abstract

In synthetic-aperture radar (SAR) returned signals, ground-target vibrations introduce a phase modulation that is linearly proportional to the vibration displacement. Such modulation, termed the micro-Doppler effect, introduces ghost targets along the azimuth direction in reconstructed SAR images that prevents SAR from forming focused images of the vibrating targets. Recently, a discrete fractional Fourier transform (DFrFT) based method was developed to estimate the vibration frequencies and instantaneous vibration accelerations of the vibrating targets from SAR returned signals. In this paper, a demodulation-based algorithm is proposed to reconstruct focused SAR images of vibrating targets by exploiting the estimation results of the DFrFT-based vibration estimation method. For a single-component harmonic vibration, the history of the vibration displacement is first estimated from the estimated vibration frequency and the instantaneous vibration accelerations. Then a reference signal whose phase is modulated by the estimated vibration displacement with a delay of 180 degree is constructed. After that, the SAR phase history from the vibration target is multiplied by the reference signal and the vibration-induced phase modulation is canceled. Finally, the SAR image containing the re-focused vibration target is obtained by applying the 2-D Fourier transform to the demodulated SAR phase history. This algorithm is applied to simulated SAR data and successfully reconstructs the SAR image containing the re-focused vibrating target.

Citation Download Citation

Qi Wang, Balu Santhanam, Matthew Pepin, Tom Atwood, and Majeed M. Hayat "Refocusing vibrating targets in SAR images", Proc. SPIE 8361, Radar Sensor Technology XVI, 836106 (3 May 2012); https://doi.org/10.1117/12.919521

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