Abstract
Vibrating targets generally induce sinusoidal micro-Doppler modulation in high resolution synthetic aperture radar (SAR). They could cause defocused and ghost results by conventional imaging algorithms. This paper proposes a method on vibrating target imaging in frequency-modulation continuous-wave (FMCW) SAR systems. The continuous motion of sensor platform during pulse time is considered in the signal model. Based on Bessel series expansion of the signal in the azimuth direction, the influence of platform motion on the azimuth frequency is eliminated after dechirp and deskew. In addition, the range walk is compensated in the two-dimensional frequency domain by Doppler keystone transform. Next, using range cell migration correction, the azimuth quadratic phase compensation and the range curvature correction are made in range-Doppler domain for the focus of paired echoes. The residual video phase of paired echoes is eliminated, and vibration parameters are estimated to compensate in the sinusoidal modulation phase. Then the deghosted image of vibrating targets can be obtained. The proposed method is applicable to multiple targets with various vibrating states due to no need of <italic<a priori</italic< knowledge of targets. Finally, simulations are carried out to validate the effectiveness of the method in FMCW-SAR imaging of vibrating targets.
Highlights
Vibration widely exists in ground targets of interest in radar sensing, such as the engine oscillation of vehicles and tanks, the dynamic response of railway bridges under oncoming trains, and so forth
This paper proposes a method on the frequency-modulation continuous-wave (FMCW)-Synthetic aperture radar (SAR) imaging of vibrating targets
We develop a signal model of vibrating targets in FMCW-SAR and take into account continuous motion of platform during pulse time
Summary
Vibration widely exists in ground targets of interest in radar sensing, such as the engine oscillation of vehicles and tanks, the dynamic response of railway bridges under oncoming trains, and so forth It generally produces nonlinear frequency modulation, named micro-Doppler effect,[1] in radar echoed signals and has attracted much attention in related research.[2,3,4] Synthetic aperture radar (SAR) is a well-established technique for high-resolution imaging of the earth’s surface. The traditional KT algorithm has achieved the compensation of range walk in SAR imaging of moving targets,[24] the range curvature cannot be corrected To solve this defect, the Doppler keystone transform (DKT) algorithm[25] is proposed. The Doppler keystone transform (DKT) algorithm[25] is proposed It corrects range cell migration in the two-dimensional (2-D) frequency domain,[26] indicating the feasibility of DKT for vibrating targets by Bessel series expansion of the vibration signal.
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