Signal Processing for Small-squinted Multi-rotor UAV-borne FMCW SAR

Multi-rotor unmanned aerial vehicle borne frequency modulated continuous wave Synthetic Aperture Radar is attracting more and more attentions due to its low cost and flexible operation capacity, including radar beam steering away from zero Doppler direction which provides opportunities for capturing squint angle dependent scattering information. However it suffers from large trajectory deviation and severe range azimuth coupling. In this paper, we utilize squint minimization technique to decrease this coupling effect. After which, modified Range Doppler algorithm is derived for imaging, taking into account intra-pulse motions during frequency modulated continuous wave sweep. Raw data based Motion Compensation is carried out with a Doppler tracker, as well as Phase Gradient Autofocus and Minimum Entropy based autofocusing algorithms. Finally, Azimuth Nonlinear Chirp Scaling is used for azimuth compression. Imaging results demonstrate the effectiveness of the above signal processing approach.

[1]  Junfeng Wang,et al.  Minimum-entropy phase adjustment for ISAR , 2004 .

[2]  Mengdao Xing,et al.  Robust Autofocusing Approach for Highly Squinted SAR Imagery Using the Extended Wavenumber Algorithm , 2013, IEEE Transactions on Geoscience and Remote Sensing.

[3]  M. Jin,et al.  Squint Mode Sar Processing Algorithms , 1989, 12th Canadian Symposium on Remote Sensing Geoscience and Remote Sensing Symposium,.

[4]  Giorgio Franceschetti,et al.  On center-beam approximation in SAR motion compensation , 2006, IEEE Geoscience and Remote Sensing Letters.

[5]  Helmut Essen,et al.  Focus FMCW SAR Data Using the Wavenumber Domain Algorithm , 2010, IEEE Transactions on Geoscience and Remote Sensing.

[6]  Mengdao Xing,et al.  Focus Improvement of Highly Squinted Data Based on Azimuth Nonlinear Scaling , 2011, IEEE Transactions on Geoscience and Remote Sensing.

[7]  Yilong Lu,et al.  Design and testing of multi-rotor UAV full-pol SAR system , 2017 .

[8]  Daoxiang An,et al.  Extended Nonlinear Chirp Scaling Algorithm for High-Resolution Highly Squint SAR Data Focusing , 2012, IEEE Transactions on Geoscience and Remote Sensing.

[9]  Zheng Bao,et al.  Weighted least-squares estimation of phase errors for SAR/ISAR autofocus , 1999, IEEE Trans. Geosci. Remote. Sens..

[10]  Tat Soon Yeo,et al.  New applications of nonlinear chirp scaling in SAR data processing , 2001, IEEE Trans. Geosci. Remote. Sens..

[11]  Tat Soon Yeo,et al.  Noniterative quality phase-gradient autofocus (QPGA) algorithm for spotlight SAR imagery , 1998, IEEE Trans. Geosci. Remote. Sens..

[12]  M.R. Ito,et al.  A chirp scaling approach for processing squint mode SAR data , 1996, IEEE Transactions on Aerospace and Electronic Systems.

[13]  Lei Yang,et al.  A Robust Motion Compensation Approach for UAV SAR Imagery , 2012, IEEE Transactions on Geoscience and Remote Sensing.