volume | PIER Journals

Abstract

This paper analyzes the azimuth spectrum folding problem which arises from the dependence of the Doppler centroid on range frequency in squinted spotlight synthetic aperture radar (SAR). Based on the analysis, a novel approach for squinted spotlight SAR is proposed in this paper. In this approach, an azimuth preprocessing step including a deramping operation and an operation of azimuth spectrum replicating and filtering is introduced to eliminate spectrum folding problem. Then, a modified Range Migration Algorithm (RMA) is adopted to process the preprocessed data. This approach extends the focusing capacity of traditional two-step processing approach from broadside spotlight SAR to squinted case. Moreover, this approach is e±cient due to a limited azimuth data extension to resolve the spectrum aliasing problem. Experimental results on simulated raw data validate the proposed approach.

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

2. Chan, Y. K. and V. C. Koo, "An introduction to Synthetic Aperture Radar (SAR)," Progress In Electromagnetics Research B, Vol. 2, 27-60, 2008.
doi:10.2528/PIERB07110101

3. Carrara, W. G., R. S. Goodman, and R. M. Majewski, Spotlight Synthetic Aperture Radar - Signal Processing and Algorithms, Artech House, Boston, MA, 1995.

4. 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

5. Cantalloube, H. and P. Dubois-Fernandez, "Airborne X-band SAR imaging with 10 cm resolution: Technical challenge and preliminary results," IEE Proc Radar Sonar Navig., Vol. 152, 163-176, 2006.
doi:10.1049/ip-rsn:20045097

6. Mittermayer, J., B. Schattler, and M. Younis, "TerraSAR-X commissioning phase execution summary," IEEE Trans. Geosci. Remote Sens., Vol. 48, No. 2, 649-659, 2010.
doi:10.1109/TGRS.2009.2026744

7. Lanari, R., P. Franceschetti, M. Tesauro, and E. Sansosti, "Spotlight SAR image generation based on strip mode focusing techniques," Proc. IGARSS, 1761-1763, Hamburg, Germany, 1999.

8. 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

9. Ren, X.-Z., Y. Qin, and L. H. Qiao, "Interferometric properties and processing for spaceborne spotlight SAR," Progress In Electromagnetics Research B, Vol. 36, 267-281, 2012.
doi:10.2528/PIERB11090609

10. Xu, W., P. P. Huang, and Y.-K. Deng, "Multi-channel SPCMB-TOPS SAR for high-resolution wide-swath imaging," Progress In Electromagnetics Research, Vol. 116, 533-551, 2011.

11. Prati, C., A. M. Guarnieri, and F. Rocca, "Spot mode SAR focusing with the omega-k technique," Proc. IGARSS, 631-634, Helsinki, Finland, 1991.

12. Mittermayer, J., A. Moreira, and O. Loffeld, "Spotlight SAR data processing using the frequency scaling algorithm," IEEE Trans. Geosci. Remote Sens., Vol. 37, No. 5, 2198-2214, 1999.
doi:10.1109/36.789617

13. Davidson, G. W., I. G. Cumming, and M. R. Ito, "A chirp scaling approach for processing squint mode SAR data," IEEE Trans. Aerosp. Electron. Syst., Vol. 32, No. 1, 121-133, 1996.
doi:10.1109/7.481254

14. Moreira, A. and Y. Huan, "Airborne SAR processing of highly squinted data using a chirp scaling approach with integrated motion compensation," IEEE Trans. Geosci. Remote Sens., Vol. 32, No. 5, 1029-1040, 1994.
doi:10.1109/36.312891

15. Davidson, G. W. and I. G. Cumming, "Signal properties of spaceborne squint mode SAR," IEEE Trans. Geosci. Remote Sens., Vol. 35, No. 3, 611-617, 1997.
doi:10.1109/36.581976

16. An, D. X., X. T. Huang, T. Jin, and Z. M. Zhou, "Extended two-step focusing approach for squinted spotlight SAR imaging," IEEE Trans. Geosci. Remote Sens., Vol. 50, No. 7, 2889-2900, 2012.
doi:10.1109/TGRS.2011.2174460

17. An, D. X., Z. M. Zhou, X. T. Huang, and T. Jin, "A novel imaging approach for high resolution squinted spotlight SAR based on the deramping-based technique and azimuth NLCS principle," Progress In Electromagnetics Research, Vol. 123, 485-508, 2012.
doi:10.2528/PIER11112110

18. 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

19. 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.

20. 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

21. Kim, K. T., S. H. Park, and J. I. Park, "Motion compensation for squint mode spotlight SAR imaging using efficient 2D interpolation," Progress In Electromagnetics Research, Vol. 128, 503-518, 2012.

Dr. Yajun Mo

Dr. Yun-Kai Deng

Dr. Yun-Hua Luo

Dr. Bing-Ji Zhao

Dr. He Yan