Focusing of Medium-Earth-Orbit SAR With Advanced Nonlinear Chirp Scaling Algorithm

• Published in: IEEE transactions on geoscience and remote sensing Vol. 49; no. 1; pp. 500 - 508
• Main Authors: Huang, Lijia, Qiu, Xiaolan, Hu, Donghui, Ding, Chibiao
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2011; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Altitude; Applied geophysics; Azimuth; Chirp; Earth; Earth sciences; Earth, ocean, space; Exact sciences and technology; Focusing; Geometry; Hyperbolic range equation; Imaging; Internal geophysics; Low earth orbit satellites; Mathematical analysis; medium Earth orbit (MEO); nonlinear chirp scaling (NLCS); Nonlinear equations; Nonlinearity; point target spectrum; Radar signal processing; SAR signal processing; Signal processing algorithms; Spaceborne radar; Studies; Synthetic aperture radar; synthetic aperture radar (SAR); satellites; algorithms; altitude; SAR signal processing; simulation; point target spectrum; frequency; currents; nonlinear chirp scaling (NLCS); medium Earth orbit (MEO); synthetic aperture radar (SAR); Hyperbolic range equation; geometry; Earth orbit; performances; Synthetic aperture radar
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2010.2053211

The signal processing of the medium-Earth-orbit synthetic aperture radar (SAR) is more challenging than that of the current low-Earth-orbit SAR because the imaging geometry is more complicated, and the range and azimuth variances are more severe. This paper deals with these imaging problems in three aspects. First, an advanced hyperbolic range equation (AHRE) is proposed for the first time, which is more precise for a spaceborne SAR than the conventional hyperbolic range equation (CHRE). Second, the point target spectrum based on the AHRE is analytically derived, which is useful for developing efficient SAR processing algorithms. Third, the well-known nonlinear chirp scaling (NLCS) algorithm is modified according to this new spectrum, and the so-called AHRE-based advanced NLCS (A-NLCS) algorithm is established. The simulation results validate the correctness of our method for L-band SAR systems at altitudes from 1000 to 10000 km with an azimuth resolution around 3 m. It is also shown that the A-NLCS algorithm has better performance than the CHRE-based algorithms in longer integration time cases. Therefore, we recommend the A-NLCS algorithm for a spaceborne SAR with a lower frequency, finer resolution, and higher satellite altitude.