volume | PIER Journals

Abstract

Moving target ship imaging in large sea area has always been the focus of military and civilian attention. Due to the limitation of pulse repetition frequency (PRF), there is a contradiction between wide mapping band and azimuth accuracy. The nonlinearity of PRF can also cause discontinuity of mapping band. Therefore, this paper proposes a method of digital beamforming-scan on receiving (DBF-SCORE) beam scanning based on airborne phased array radar to achieve the requirement of scene mapping band with lower PRF. The adaptive Capon spectrum estimation is used to dynamically adjust the beam pointing so that it can always point to the moving target for accurate imaging. Considering the nonuniform sampling of the transmitting pulse period of the antenna, the azimuth nonuniform Fourier transform (NUDFT) algorithm is used to re-sample the nonuniform periodic signal of the multi-channel receiving antenna and obtain the uniform spectrum signal. Finally, fine focusing of moving target is achieved by local phase gradient algorithm (PGA) algorithm, and accurate imaging of moving target in large sea area is realized. The validity of the algorithm can be verified by simulation and real data imaging, which can be used for reference in phased array SAR imaging of moving targets.

1. Heimmer, J., "Multi-mission phased array radar (MPAR) national radar R&D project," Systems, Applications & Technology Conference, 1-2, IEEE Long Island, 2008. Google Scholar

2. Zhang, S. X., M. D. Xing, X. G. Xia, et al. "Multichannel HRWS SAR imaging based on range-variant channel calibration and multi-Doppler-direction restriction ambiguity suppression," IEEE Transactions on Geoscience and Remote Sensing, Vol. 52, No. 7, 4306-4327, 2014.
doi:10.1109/TGRS.2013.2281329 Google Scholar

3. Reigber, A., A. Nottensteiner, M. Limbach, et al. "DBFSAR: An airborne very high-resolution digital beamforming SAR system," Proceedings of the 14th European Radar Conference, 175-178, Nuremberg, Germany, Oct. 2017. Google Scholar

4. Sikaneta, I. and D. Cerutti-Maori, "Demonstrations of HRWS and GMTI with RADARSAT-2," European Conference on Synthetic Aperture Radar, 263-266, Nuremberg, Germany, Apr. 2012. Google Scholar

5. Reigber, A., A. Nottensteiner, M. Limbach, et al. "DBFSAR: An airborne very high-resolution digital beamforming SAR system," European Radar Conference (EuRAD), 175-178, 2017. Google Scholar

6. Cook, C. E. and M. Bernfeld, Radar Signal an Introduction to Theory and Application, Academic Press, 1967.

7. Capon, J., "High-resolution frequency-wavenumber spectral analysis," Proc. IEEE, Vol. 57, 1408-1418, 1969.
doi:10.1109/PROC.1969.7278 Google Scholar

8. Zhang, C., Synthet Icaperture Radar: Theorysystem Analysis and Application, Science Press, 1989.

9. Dutt, A. and V. Rokhlin, "Fast Fourier transforms for nonequispaced data," SIAM Journal on Scientific Computing, Vol. 14, No. 6, 1368-1393, 1993.
doi:10.1137/0914081 Google Scholar

10. Fessler, J. A. and B. P. Sutton, "Nonuniform fast Fourier transforms using min-max interpolation," IEEE Transactions on Signal Processing, Vol. 51, No. 2, 560-574, 2003.
doi:10.1109/TSP.2002.807005 Google Scholar

11. Liu, Q. H. and N. Nguyen, "An accurate algorithm for nonuniform fast Fourier transforms (NUFFT's)," IEEE Microwave and Guided Wave Letters, Vol. 8, No. 1, 18-20, 2002.
doi:10.1109/75.650975 Google Scholar

12. Ren, B. L., S. Y. Li, H. J. Sun, et al. "A fast circular convolution algorithm based on NUFFT for near-field SAR imaging," International Conference on Microwave & Millimeter Wave Technology, 1-4, 2012. Google Scholar

13. Wu, Y., H. Song, X. Shang, et al. "Improved RMA based on Nonuniform Fast Fourier Transforms (NUFFT's)," International Conference on Signal Processing, 2489-2492, 2008. Google Scholar

14. Zhao, X., X. L. Wang, and Z. M. Wang, "Phase gradient autofocus algorithm for SAR images based on optimal contrast criterion," Remote Sensing Technology and Application, Vol. 20, No. 6, 606-610, 2005. Google Scholar

15. Ye, C., X. Ning, J. Yang, et al. "Parallel implementation of a block-wise phase gradient autofocusing method," J. Tsinghua Univ. (Sci. & Tech.), Vol. 52, No. 5, 612-615, 2012. Google Scholar

Dr. Lin Zhang

Dr. Yicheng Jiang