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Zhe Liu , Jianyu Yang, Xiaoling Zhang

Nonlinear Range Cell Migration (RCM) Compensation Method for Spaceborne /Airborne Forward-Looking Bistatic SAR. Zhe Liu , Jianyu Yang, Xiaoling Zhang School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China.

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Zhe Liu , Jianyu Yang, Xiaoling Zhang

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  1. Nonlinear Range Cell Migration (RCM) Compensation Method for Spaceborne/Airborne Forward-Looking Bistatic SAR Zhe Liu , Jianyu Yang, Xiaoling Zhang School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China Presentation byZhe Liu

  2. Outline • Introduction to the SA-FBSAR and its nonlinear RMC • Nonlinear RCM compensation method • Simulation results • Conclusions and further work

  3. transmitter receiver Imaging scene Introduction－What is SA-FBSAR • Spaceborne/Airborne Forward-Looking Bistatic SAR (SA-FBSAR) • Platforms: Transmitter and receiver of SA-FBSAR are low earth orbit (LEO) satelliteand aircraft, respectively. • Working Modes: Transmitter antenna works in side-looking or squint-looking mode; receiver antenna in forward-looking mode. • Target imaging scene: Target scene is along the receiver’s forward-looking direction

  4. Introduction－Emergence of SA-FBSAR Bistatic/ Multistatic SAR(B/M SAR) Monostatic SAR • Diversity of target information • High immunity to attacks • Low cost • Wide coverage, high SNR • Platform flexibility • Power saving S-A B/M SAR Spaceborne B/M SAR Airborne B/M SAR SA-BSAR with radar satellite • wide band • repeated observation Commu. satellite Broadcast satellite Radar satellite SA-FBSAR • attractive potential for aircraft landing and navigation

  5. Introduction－Emergence of SA-FBSAR Fig.1 Imaging result of the first SA-FBSAR feasibility experiment in 2009 In Nov. 2009, FGAN (German Aerospace Center) launched the first experiment to test the feasibility of SA-FBSAR.

  6. Introduction－Challenges of SA-FBSAR imaging Satellite height：500-800km Aircraft height：1 - 5km ·Dramatic geometric difference ·Essential velocity difference Satellite velocity：7.4 -7.6km/s Aircraft velocity：100m/s ·Different working mode Satellite : side-looking Aircraft : forward-looking

  7. Introduction－Challenges of SA-FBSAR imaging • Range cell migration (RCM) features are : • Vary with the target’s range and azimuth location • exhibits significant nonlinearity with target’s range location ·Dramatic geometric difference ·Essential velocity difference ·Different working mode Severe distortion and nonlinear misregistration will occur, if such RCM is not properly compensated

  8. Introduction－effect of nonlinear RCM on imaging results (a) original point scatterers (b) without RCM compensation Fig2. Imaging result of point targets

  9. y x Introduction－effect of nonlinear RCM on imaging results (a) original area target (b) Without RCMC Fig3. Imaging result of area targets

  10. Introduction－Our work • Purpose: find a nonlinear two-dimensional RCM compensation method for SA-FBSAR in frequency domain • Main idea: • Set up SA-FBSAR response spectrum model • Deduce nonlinear RCM analytic formula • Propose SA-FBSAR nonlinear RCM compensation method

  11. Nonlinear RCM Compensation for SA-FBSAR－system geometric model Fig.4 SA-FBSAR system geometry

  12. Origin of nonlinear RCM .

  13. Nonlinear RCM Compensation for SA-FBSAR－system signal spectrum model

  14. Nonlinear RCM Compensation for SA-FBSAR－ nonlinear RCM analytic formula

  15. Nonlinear RCM Compensation for SA-FBSAR－ nonlinear RCM analytical formula

  16. Nonlinear RCM Compensation for SA-FBSAR－ nonlinear RCM compensation method , Fig.5 flow chart of nonlinear RCM compensation method for SA-FBSAR

  17. Simulation － Parameters

  18. Simulation － Point scatterers (a) original point scatterers (b) without RCM compensation (d) with the proposed method (c) with RCMC Method in Ref[1] Fig.6 Imaging results of 15 point scatters Ref[1]: X.Qiu, D. Hu and C. Ding, IEEE Geosci. Remote Sens. Lett., 4, 735-739, 2008.

  19. Simulation － Point scatterers (b) error in azimuth position (a) error in range position

  20. y x Simulation － area target (a) original area target (b) Without RCMC (c) With the proposed RCM compensation Fig. 7 Imaging results of area target

  21. (b) target located at (500,100) (a) Contour of ideal resolution cell’s area (unit: m2) (c) target located at (0,0) Fig.8 two-dimensional resolution performance

  22. Simulation • From the above simulation results, we could find that:Uncompensated RCM could deteriorate imaging result severely, cause nonlinear distortionRCM compensation method designed for other FBSAR system could not compensate the nonlinear RCM, thus could not be applied to SA-FBSAR.The proposed RCM compensation method could effectively compensate the nonlinear RCM in SA-FBSAR, and all targets are arranged in their originally correct positions.

  23. Conclusions & Further work • RCM in SA-FBSAR not only depends on the target’s two-dimensional space location, but also varies with its range location nonlinearly. If not properly corrected, RCM would cause nonlinear distortion in the image and greatly degrade the imaging quality. • We propose a two-dimensional nonlinear RCMC method for SA-FBSAR. The validity of the proposed method is verified. • Further improvement on resolution performance is under research

  24. Thank you

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