In this paper, a stepped-frequency spaceborne/airborne bistatic synthetic aperture radar (SFSA-BiSAR) configuration is proposed to show to improve the range resolution of BiSAR. First, the geometry and the signal model of SFSA-BiSAR are formulated, and then an analytical bistatic point target reference spectrum (BPTRS) is derived. Second, based on the developed BPTRS, two imaging algorithms called combination-before-focusing algorithm (CBFA) and combination-after-focusing algorithm (CAFA) are proposed to obtain BiSAR images with improved range resolution. CBFA uses sub-band combination to obtain synthetic BPTRS, and then uses a new bistatic frequency-domain algorithm (BFDA) to obtain the improved BiSAR image, whereas CAFA first uses the BFDA to focus all the sub-pulses, and then uses sub-image combination to obtain the improved BiSAR image. Both of the two algorithms can focus the SFSA-BiSAR signal well and comparison simulations are performed to verify the authors' conclusion. Computation loads are also calculated to compare the two algorithms and show that CAFA uses less floating-point operations than CBFA. Besides, some important parameters of SFSA-BiSAR are analysed both theoretically and numerically to provide a reference for system design.

References

1. 1)
  - 19. Liu, Z., Yang, J., Zhang, X., Pi, Y.: ‘Study on spaceborne/airborne hybrid bistatic SAR image formation in frequency domain’, IEEE Geosci. Remote Sens. Lett., 2008, 5, (4), pp. 578–582 (doi: 10.1109/LGRS.2008.2000622).
2. 2)
  - 11. Wilkinson, A., Lord, R., Inggs, M.: ‘Stepped-frequency processing by reconstruction of target reflectivity spectrum’. Proc. of the 1998 South African Symp. on Communications and Signal Processing, 1998. COMSIG'98, September 1998, pp. 101–104.
3. 3)
  - 29. Walterscheid, I., Espeter, T., Ender, J.H.G.: ‘Performance analysis of a hybrid bistatic SAR system operating in the double sliding spotlight mode’. IEEE Int. Geoscience and Remote Sensing Symp., 2007. IGARSS 2007, July 2007, pp. 2144–2147.
4. 4)
  - 8. Cristallini, D., Pastina, D., Lombardo, P.: ‘Exploiting MIMO SAR potentialities with efficient cross-track constellation configurations for improved range resolution’, IEEE Trans. Geosci. Remote Sens., 2011, 49, (1), pp. 38–52 (doi: 10.1109/TGRS.2010.2053715).
5. 5)
  - 12. Lord, R., Inggs, M.: ‘High resolution SAR processing using stepped-frequencies’. 1997 IEEE Int. Geoscience and Remote Sensing, 1997. IGARSS'97. Remote Sensing – A Scientific Vision for Sustainable Development, August 1997, vol. 1, pp. 490–492.
6. 6)
  - 26. Stolt, R.: ‘Migration by Fourier transform’, Geophysics, 1978, 43, (1), pp. 23–48 (doi: 10.1190/1.1440826).
7. 7)
  - 17. Neo, Y., Wong, F., Cumming, I.: ‘A two-dimensional spectrum for bistatic SAR processing using series reversion’, IEEE Geosci. Remote Sens. Lett., 2007, 4, (1), pp. 93–96 (doi: 10.1109/LGRS.2006.885862).
8. 8)
  - 23. Wang, R., Loffeld, O., Ul-Ann, Q., Nies, H., Ortiz, A., Samarah, A.: ‘A bistatic point target reference spectrum for general bistatic SAR processing’, IEEE Geosci. Remote Sens. Lett., 2008, 5, (3), pp. 517–521 (doi: 10.1109/LGRS.2008.923542).
9. 9)
  - 28. Gebhardt, U., Loffeld, O., Nies, H., Knedlik, S., Ender, J.: ‘Bistatic airborne/spaceborne hybrid experiment: basic considerations’. Remote Sensing, International Society for Optics and Photonics, 2005, pp. 59 781M–59 781M.
10. 10)
  - 14. Nel, W., Tait, J., Lord, R., Wilkinson, A.: ‘The use of a frequency domain stepped frequency technique to obtain high range resolution on the CSIR x-band SAR system’. IEEE Africon Sixth Africon Conf. in Africa, 2002, October 2002, vol. 1, pp. 327–332.
11. 11)
  - 16. Natroshvili, K., Loffeld, O., Nies, H., Ortiz, A., Knedlik, S.: ‘Focusing of general bistatic SAR configuration data with 2-d inverse scaled FFT’, IEEE Trans. Geosci. Remote Sens., 2006, 44, (10), pp. 2718–2727 (doi: 10.1109/TGRS.2006.872725).
12. 12)
  - 9. Xu Hua-ping, Z.Y.-q., Chun-sheng, L.: ‘An algorithm based on spectrum shift estimation for improving range resolution using distributed spaceborne interferometric SAR’, Acta Electron. Sin., 2003, 31, (12), pp. 1790–1794.
13. 13)
  - 10. Hong-hui, Y., Yan-fei, W.: ‘Distributed satellites SAR high range resolution imaging using spectral synthesis’, J. Electron. Inf. Technol., 2005, 27, (6), pp. 928–931.
14. 14)
  - 13. Berens, P.: ‘SAR with ultra-high range resolution using synthetic bandwidth’. IEEE 1999 Int. Geoscience and Remote Sensing Symp., 1999. IGARSS'99 Proc., 1999, vol. 3, pp. 1752–1754.
15. 15)
  - 24. Yang, K., He, F., Liang, D.: ‘A two-dimensional spectrum for general bistatic SAR processing’, IEEE Geosci. Remote Sens. Lett., 2010, 7, (1), pp. 108–112 (doi: 10.1109/LGRS.2009.2028163).
16. 16)
  - 7. Hua, B., Qi, H., Zhang, P., Li, X.: ‘Vector quantization for saturated SAR raw data compression’, Adv. Space Res., 2010, 45, (11), pp. 1330–1337 (doi: 10.1016/j.asr.2010.01.007).
17. 17)
  - 25. Walterscheid, I., Espeter, T., Brenner, A.: ‘Bistatic SAR experiments with PAMIR and TerraSAR-X–setup, processing, and image results’, IEEE Trans. Geosci. Remote Sens., 2010, 48, (8), pp. 3268–3279 (doi: 10.1109/TGRS.2010.2043952).
18. 18)
  - 2. Walterscheid, I., Espeter, T., Gierull, C., Klare, J., Brenner, A., Ender, J.H.G.: ‘Results and analysis of hybrid bistatic SAR experiments with spaceborne, airborne and stationary sensors’. 2009 IEEE Int. Geoscience and Remote Sensing Symp., IGARSS 2009, July 2009, vol. 2, pp. II-238–II-241.
19. 19)
  - 15. Loffeld, O., Nies, H., Peters, V., Knedlik, S.: ‘Models and useful relations for bistatic SAR processing’, IEEE Trans. Geosci. Remote Sens., 2004, 42, (10), pp. 2031–2038 (doi: 10.1109/TGRS.2004.835295).
20. 20)
  - 1. Rodriguez-Cassola, M., Prats, P., Baumgartner, S., et al: ‘New processing approach and results for bistatic TerraSAR-X/f-SAR spaceborne–airborne experiments’. 2009 IEEE Int. Geoscience and Remote Sensing Symp., IGARSS 2009, July 2009, vol. 2, pp. II-242–II-245.
21. 21)
  - 3. Rodriguez-Cassola, M., Baumgartner, S., Krieger, G., Moreira, A.: ‘Bistatic TerraSAR-X/f-SAR spaceborne/airborne SAR experiment: description, data processing, and results’, IEEE Trans. Geosci. Remote Sens., 2010, 48, (2), pp. 781–794 (doi: 10.1109/TGRS.2009.2029984).
22. 22)
  - 27. Loffeld, O., Hein, A., Schneider, F.: ‘SAR focusing: scaled inverse Fourier transformation and chirp scaling’. 1998 IEEE Int. Geoscience and Remote Sensing Symp. Proc., 1998. IGARSS'98, July 1998, vol. 2, pp. 630–632.
23. 23)
  - 20. Wang, R., Loffeld, O., Nies, H., et al: ‘Frequency-domain bistatic SAR processing for spaceborne/airborne configuration’, IEEE Trans. Aerosp. Electron. Syst., 2010, 46, (3), pp. 1329–1345 (doi: 10.1109/TAES.2010.5545192).
24. 24)
  - 18. Bamler, R., Meyer, F., Liebhart, W.: ‘Processing of bistatic SAR data from quasi-stationary configurations’, IEEE Trans. Geosci. Remote Sens., 2007, 45, (11), pp. 3350–3358 (doi: 10.1109/TGRS.2007.895436).
25. 25)
  - 5. Klare, J., Walterscheid, I., Brenner, A., Ender, J.H.G.: ‘Evaluation and optimisation of configurations of a hybrid bistatic SAR experiment between TerraSAR-X and PAMIR’. IEEE Int. Conf. on Geoscience and Remote Sensing Symp., 2006. IGARSS 2006, July 2006, pp. 1208–1211.
26. 26)
  - 21. Clemente, C., Soraghan, J.: ‘Approximation of the bistatic slant range using Chebyshev polynomials’, IEEE Geosci. Remote Sens. Lett., 2012, 9, (4), pp. 682–686 (doi: 10.1109/LGRS.2011.2178812).
27. 27)
  - 4. Hawkins, R., Gibson, J., Saper, R., Hilaire, M.: ‘A tool for bistatic SAR geometry determinations’, Adv. Space Res., 2003, 32, (11), pp. 2311–2318. [Online]. Available at http://www.sciencedirect.com/science/article/pii/S027311770390559X (doi: 10.1016/S0273-1177(03)90559-X).
28. 28)
  - 22. Cumming, I., Wong, F.: ‘Digital processing of synthetic aperture radar data algorithms and implementation’ (Artech House, Norwood, MA, 2005).
29. 29)
  - 6. Espeter, T., Walterscheid, I., Klare, J., Brenner, A., Ender, J.H.G.: ‘Bistatic forward-looking SAR: results of a spaceborne/airborne experiment’, IEEE Geosci. Remote Sens. Lett., 2011, 8, (4), pp. 765–768 (doi: 10.1109/LGRS.2011.2108635).

Range-resolution improvement for spaceborne/airborne bistatic synthetic aperture radar using stepped-frequency chirp trains

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