volume | PIER Journals

Abstract

The imaging problem of spotlight synthetic aperture radar (SAR) in the presence of azimuth spectrum folding phenomenon can be resolved by adopting the azimuth deramping-based technique and traditional stripmap SAR imaging algorithm, and this method is the so-called two-step processing approach. However, when the spotlight SAR operates on squinted mode, the echo two-dimensional (2D) spectrum is shifted and skewed due to the squint angle. In such case, the original two-step processing approach is not suitable anymore. This paper presents a novel imaging algorithm using the deramping-based technique and azimuth nonlinear chirp scaling (ANLCS) technique. First, the problem of azimuth spectrum folding phenomenon in squinted spotlight SAR is analyzed. Subsequently, based on the analysis results, the linear range walk correction (LRWC) is applied for removing the squint angle impacts on signal azimuth coarse focusing. At last, a modified azimuth NLCS algorithm is proposed for overcoming the depth of focus (DOF) limitation problem that induced by the LRWC preprocessing. Point targets simulation results are presented to validate the effectiveness of the proposed algorithm to process squinted spotlight SAR data with azimuth spectrum folding phenomenon.

1. Carrara, W. G., R. S. Goodman, and R. M. Majewski, Spotlight Synthetic Aperture Radar: Signal Processing Algorithms, Artech House, 1995.

2. Sun, J., S. Mao, G. Wang, and W. Hong, "Polar format algorithm for spotlight bistatic SAR with arbitrary geometry configuration," Progress In Electromagnetics Research, Vol. 103, 323-338, 2010.
doi:10.2528/PIER10030703 Google Scholar

3. Guo, D., H. Xu, and J. Li, "Extended wavenumber domain algorithm for highly squinted sliding spotlight SAR data processing," Progress In Electromagnetics Research, Vol. 114, 17-32, 2011. Google Scholar

4. Koo, V. C., Y. K. Chan, V. Gobi, M. Y. Chua, C. H. Lim, C.-S. Lim, C. C. Thum, T. S. Lim, Z. Bin Ahmad, K. A. Mahmood, M. H. Bin Shahid, C. Y. Ang, W. Q. Tan, P. N. Tan, K. S. Yee, W. G. Cheaw, H. S. Boey, A. L. Choo, and B. C. Sew, "A new unmanned aerial vehicle synthetic aperture radar for environmental monitoring," Progress In Electromagnetics Research, Vol. 122, 245-268, 2012.
doi:10.2528/PIER11092604 Google Scholar

5. Lanari, R., M. Tesauro, E. Sansosti, and G. Fornaro, "Spotlight SAR data focusing based on a two-step processing approach," IEEE Trans. Geosci. Remote Sens., Vol. 39, No. 9, 1993-2004, 2001.
doi:10.1109/36.951090 Google Scholar

6. Lanari, R., S. Zoffoli, E. Sansosti, G. Fornaro, and S. Serafino, "New approach for hybrid strip-map/spotlight SAR data focusing," IEE Proc. --- Radar Sonar Navig., Vol. 148, No. 6, 363-372, 2001.
doi:10.1049/ip-rsn:20010662 Google Scholar

7. Ding, Z. G., T. Long, T. Zeng, and Y. Zhu, "Deramp range migration processing for space-borne spotlight synthetic aperture radar," Advances in Space Research, Vol. 41, 1822-1826, 2008.
doi:10.1016/j.asr.2008.01.009 Google Scholar

8. Lim, S.-H., J.-H. Han, S.-Y. Kim, and N.-H. Myung, "Azimuth beam pattern synthesis for airborne SAR system optimization," Progress In Electromagnetics Research, Vol. 106, 295-309, 2010.
doi:10.2528/PIER10061901 Google Scholar

9. Wong, F. H. and T. S. Yeo, "New application of nonlinear chirp scaling in SAR data processing," IEEE Trans. Geosci. Remote Sens., Vol. 39, No. 5, 946-953, 2001.
doi:10.1109/36.921412 Google Scholar

10. Wong, F. H. and I. G. Cumming, "Focusing bistatic SAR data using the nonlinear chirp scaling algorithm," IEEE Trans. Geosci. Remote Sens., Vol. 46, No. 9, 2493-2505, 2008.
doi:10.1109/TGRS.2008.917599 Google Scholar

11. Yeo, T. S., N. L. Tan, C. B. Zhang, and Y. H. Lu, "A new subaperture approach to high squint SAR processing," IEEE Trans. Geosci. Remote Sens., Vol. 39, No. 5, 954-968, 2001.
doi:10.1109/36.921413 Google Scholar

12. Chang, Y.-L., C.-Y. Chiang, and K.-S. Chen, "SAR image simulation with application to target recognition," Progress In Electromagnetics Research, Vol. 119, 35-57, 2011.
doi:10.2528/PIER11061507 Google Scholar

13. Cumming, I. G. and F. H. Wong, Digital Processing of Synthetic Aperture Radar Data: Algorithms and Implementation, Artech House, 2005.

14. Mao, X., D.-Y. Zhu, L.Wang, and Z.-D. Zhu, "Comparative study of RMA and PFA on their responses to moving target," Progress In Electromagnetics Research, Vol. 110, 103-124, 2010.
doi:10.2528/PIER10090607 Google Scholar

15. Reigber, A., E. Alivizatos, A. Potsis, and A. Moreira, "Extended wavenumber-domain synthetic aperture radar focusing with integrated motion compensation," IEE Proc. --- Radar Sonar Navig., Vol. 153, No. 3, 301-310, 2006.
doi:10.1049/ip-rsn:20045087 Google Scholar

16. Davidson, G. W., I. G. Cumming, and M. R. Ito, "A chirp scaling approach for processing squint mode SAR," IEEE Trans. Geosci. Remote Sens., Vol. 32, No. 1, 121-133, 1996. Google Scholar

17. Moreira, A., J. Mittermayer, and R. Scheiber, "Extended chirp scaling algorithm for air- and spaceborne SAR data processing in stripmap and scanSAR imaging mode," IEEE Trans. Geosci. Remote Sens., Vol. 34, No. 5, 1123-1135, 1996.
doi:10.1109/36.536528 Google Scholar

Dr. Dao Xiang An

Dr. Z.-M. Zhou

Dr. Xiao-Tao Huang

Dr. Tian Jin