SAR-based vibration retrieval using the fractional Fourier transform in slow time

IEEE Trans. Geosci. Remote Sensing

Wright

et al. 2014

Self Cite

Target vibrations introduce nonstationary phase modulation, which is termed the micro-Doppler effect, into returned synthetic aperture radar (SAR) signals. This causes artifacts, or ghost targets, which appear near vibrating targets in reconstructed SAR images. Recently, a vibration estimation method based on the discrete fractional Fourier transform (DFrFT) has been developed. This method is capable of estimating the instantaneous vibration accelerations and vibration frequencies. In this paper, a deghosting method for vibrating targets in SAR images is proposed. For single-component vibrations, this method first exploits the estimation results provided by the DFrFT-based vibration estimation method to reconstruct the instantaneous vibration displacements. A reference signal, whose phase is modulated by the estimated vibration displacements, is then synthesized to compensate for the vibration-induced phase modulation in returned SAR signals before forming the SAR image. The performance of the proposed method with respect to the signal-to-noise and signalto-clutter ratios is analyzed using simulations. Experimental results using the Lynx SAR system show a substantial reduction in ghosting caused by a 1.5-cm 0.8-Hz target vibration in a true SAR image.

“…For completeness, a brief introduction of this method is provided here. The reader may find more details in [18], [20], and [23]- [25].…”

Section: A Review Of the Dfrft-based Vibration Estimation Methodsmentioning

confidence: 98%

mentioning

confidence: 99%

Reduction of Vibration-Induced Artifacts in Synthetic Aperture Radar Imagery

IEEE Trans. Geosci. Remote Sensing

Wright

et al. 2014

Self Cite

“…The autofocus is also performed at this stage. For small vibrations, the vibration-induced phase modulation in range direction is very small [4], [5], [16]; therefore, it is ignored. Range compression is applied to the phase history to separate the scatterers in range.…”

Section: B Signal Modelmentioning

confidence: 99%

SAR-Based Vibration Estimation Using the Discrete Fractional Fourier Transform

IEEE Trans. Geosci. Remote Sensing

Beach

et al. 2012

Self Cite

A vibration estimation method for synthetic aperture radar (SAR) is presented based on a novel application of the discrete fractional Fourier transform (DFRFT). Small vibrations of ground targets introduce phase modulation in the SAR returned signals. With standard preprocessing of the returned signals, followed by the application of the DFRFT, the time-varying accelerations, frequencies, and displacements associated with vibrating objects can be extracted by successively estimating the quasi-instantaneous chirp rate in the phase-modulated signal in each subaperture. The performance of the proposed method is investigated quantitatively, and the measurable vibration frequencies and displacements are determined. Simulation results show that the proposed method can successfully estimate a two-component vibration at practical signal-to-noise levels. Two airborne experiments were also conducted using the Lynx SAR system in conjunction with vibrating ground test targets. The experiments demonstrated the correct estimation of a 1-Hz vibration with an amplitude of 1.5 cm and a 5-Hz vibration with an amplitude of 1.5 mm.

“…However, the performance of the bilinear time-frequency transforms is limited if multiple frequencies are present in the vibration. A new time-frequency method based on the discrete fractional Fourier transform (DFRFT) was proposed for estimating small target vibrations for SAR [5,6]. Simulation results have revealed that the DFRFT method is capable of estimating multi-component vibrations [5].…”

Section: Introductionmentioning

confidence: 96%

Demonstration of target vibration estimation in synthetic aperture radar imagery

2011 IEEE International Geoscience and Remote Sensing Symposium

Beach

et al. 2011

Self Cite

Synthetic-aperture radar (SAR) can be used to remotely estimate ground target vibrations by exploiting the Doppler in the returned signals. Recent studies suggest that timefrequency signal-processing tools can retrieve the vibration signature from the returned SAR signals. A vibration estimation method based on the fractional Fourier transform (FRFT) was reported earlier and it was tested on simulated SAR data. In this paper, a first-time demonstration of the FRFT-based vibration estimation method is reported using real SAR data collected by the Lynx (K u -band) SAR system. The vibrating target is an aluminum triangular trihedral with lateral length of 15 inches. The FRFT-based algorithm is shown to successfully retrieve a 3 mm peak-to-peak amplitude, 5 Hz vibration of the target from real SAR data.