Book Structure and Organization
Up to now, single-antenna airborne SAR is still the most widely-used SAR system in the world. The single-antenna airborne SAR GMTI and GMTIm algorithms are the main topics in this book. Three working modes, including stripmap SAR, WAS mode and FMCW SAR, are studied, and the non-ideal motion error in practical SAR signal processing is analyzed. This book is organized in six chapters, and the main content of each chapter is as follows.
This chapter is the introduction, the development and principle of SAR systems, GMTI algorithms and GMTIm algorithms are introduced in this chapter, and the book structure is given.
Chapter 2 contains two main parts. First, the signal model of a moving target in airborne SAR is established, and impacts of the motions on the echo character are analyzed. Second, the principles of traditional GMTI and GMTIm algorithms are introduced, and the problems and restrains of these algorithms are analyzed.
Chapter 3 studies the GMTI and GMTI of fast moving targets in stripmap SAR. Firstly, the signal model of fast moving targets in stripmap SAR/GMTI mode is established, and the impacts of fast cross-track velocities on the Doppler ambiguity and higher order azimuth phase are analyzed. Then, A classification of targets by the location of their spectra is presented, based on which a Doppler centroid estimation algorithms based on curve fitting, a multiple target indication and echo extraction method, and a fast moving target imaging algorithm based on Hough transform and third-order PFT are presented. Finally, simulations and real data are utilized to prove the effectiveness of these algorithms.
Chapter 4 studies the GMTI algorithms in WAS mode. The signal mode of moving target is established in WAS mode, and a new system design scheme is presented to maintain the sharpening ratio constant without increasing the system and signal processing complexity. Moreover, a real-time DBS algorithm is proposed based on CZT, and a GMTI and motion parameter estimation algorithm based on multiple revisits is presented. Finally, simulations and real data are utilized to prove the effectiveness of these algorithms.
Chapter 5 studies the nonlinearity correction and GMTI algorithms in FMCW SAR. The differences between a FMCW SAR and a pulse SAR are analyzed, and additional phase error of FMCW SAR is calculated. Furthermore, a nonlinearity correction algorithm based on Homomorphic Deconvolution is proposed, and an along-track moving target indication algorithm is presented. By using the additional phase error, the GMTI performance of FMCW SAR is improved.
Chapter 6 researches the non-ideal motion errors in practical SAR signal processing. Pointing at the problem that existing GMTIm algorithms have poor performances in the real SAR data processing, the impact of Doppler centroid is analyzed. The signal model of moving targets with non-ideal motion error is established, and the platform velocity error and cross-track velocity error of the moving target are analyzed. An error estimation and compensation algorithm is presented, and a whole practical SAR data processing scheme with the algorithms in the frontal chapters is proposed. Finally, simulations and real data are utilized to prove the effectiveness of these algorithms.