A Squint TOPSAR Imaging Algorithm Based on Extend Azimuth Non-linear Chirp Scaling
JIANG Huai① ZHAO Huichang① HAN Min② ZHANG Shuning①
①(School of Electronic & Optical, Nanjing University of Science and Technology, Nanjing 210094, China) ②(State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210094, China)
In the squint Terrain Observation by Progressive scabs (TOPSAR) mode, the different azimuth scatters have different Doppler center frequencies, which causes azimuth under-sampling problem and increase the coupling between range and azimuth. Considering at the characteristics of squint TOPSAR echo, this article proposes a new full aperture imaging algorithm: first, the azimuth signal aliasing is removed by introducing the nonlinear walk correction; second, the nonlinear chirp scaling algorithm for azimuth focusing is applied to compensating the Doppler modulation rate; finally, the image geometric distortion is eliminated by 2-D chirp scaling operation. Compared with the traditional algorithm, the proposed algorithm avoids the interpolation under the case of extending a small amount of data, hence the calculation needed is less. The simulation results prove the effectiveness of the algorithm.
META A, MITTERMAYER J, and SCHEIBER R. Extended chirp scaling algorithm for air and spaceborne SAR data processing in stripmap and ScanSAR imaging modes[J]. IEEE Transactions on Geoscience and Remote Sensing, 1996, 34(5): 1123-1136.
MING Feng, HONG Jun, and WU Yirong. Study on scalloping radiometric error in Scan-SAR[J]. Journal of Electronics & Information Technology, 2006, 28(10): 1806-1808.
[3]
WANG Yan, LI Jingwen, CHEN Jie, et al. A parameter adjusting polar format algori-thm for extremely high squint SAR imaging[J]. IEEE Transactions on Geoscience and Remote Sensing, 2014, 52(1): 640-650. doi: 10.1109/TGRS. 2013.2243156.
[4]
DE ZAN F and GUARNIERI A M. TOPSAR: Terrain observation by progressive scans[J]. IEEE Transactions on Geoscience and Remote Sensing, 2006, 44(9): 2352-2360.
[5]
SUN Guangcai, JIANG Xiuwei, XING Mengdao, et al. Focus improvement of hig-hly squinted data based on azimuth nonlinear scaling[J]. IEEE Transactions on Geoscience and Remote Sensing, 2011, 49(6): 2308-2322. doi: 10.1109/TGRS. 2010.2102040.
[6]
AN Daoxiang, HUANG Xiaotao, JIN Tian, et al. Extended nonlinear chirp scaling algorithm for high-resolution highly squint SAR data focusing[J]. IEEE Transactions on Geoscience and Remote Sensing, 2012, 50(9): 3595-3609. doi: 10.1109/TGRS.2012.2183606.
[7]
META A, MITTERMAYER J, PRATS P, et al. TOPS imaging with TerraSAR-X: Mode design and performance analysis[J]. IEEE Transactions on Geoscience and Remote Sensing, 2010, 48(2): 759-769. doi: 10.1109/TGRS.2009. 2026743.
[8]
PRATS P, SCHEIBER R, MITTERMAYER J, et al. Processing of sliding spotlight and TOPS SAR data using baseband azimuth scaling[J]. IEEE Transactions on Geoscience Remote Sensing, 2010, 48(2): 770-780. doi: 10.1109/TGRS.2009.2027701.
XU Wei and DENG Yunkai. An imaging approach for TOPSAR data based on azimuth preprocessing and processing[J]. Journal of Electronics & Information Technology, 2011, 33(4): 798-804. doi: 10.3724/SP.J.1146. 2010.00668.
[10]
CHEN Qi, HUANG Haifeng, et al. Using TOPSAR for district observation[J]. IEEE Geoscience and Remote Sensing Letters, 2013, 10(2): 406-410. doi: 10.1109/LGRS.2012. 2207086.
[11]
YANG Jun, SUN Guangcai, and XING Mengdao. Squinted TOPS SAR imaging ba-sed on modified range migration algorithm and spectral analysis[J]. IEEE Geoscience and Remote Sensing Letters, 2014, 11(10): 1707-1711. doi: 10.1109/LGRS.2014.2306433.
HUAI Yuanyuan, LIANG Yi, LI Zhenyu, et al. Modified algorithm for subaperture squint SAR imaging based on azimuth resampling[J]. Journal of Electronics & Information Technology Electronics, 2015, 37(7): 1744-1750. doi: 10.11999/JEIT141383.
CHEN Qi, HUANG Haifeng, HE Feng et al. Full aperture imagining algorithm of TOPSAR based on frequency domain extension and SPECAN[J]. Journal of Electronics & Information Technology, 2012, 34(10): 2246-2250. doi: 10.3724/SP.J.1146.2012.00366.
YANG Jun, LI Zhenyu, SUN Guangcai, et al. Novel full aperture imaging algorithm for highly squinted TOPSSAR[J]. Journal of Xidian University, 2015, 42(1): 47-51. doi: 10.3969 /j.issn.1001-2400.2015.01.007.
YANG Jun, WU Yufeng, SUN Guangcai, et al. Squint TOPSSAR imaging method based on azimuth FNCS[J]. Systems Engineering and Electronic, 2012, 34(11): 2237-2243. doi: 10.3969/j.issn.1001-506X.2012.11.09.