Study On Imaging Algorithms And Parameters Estimation Methods For FMCW SAR

In recent years, there is a widespread interest in airborne Synthetic Aperture Radar(SAR) withlow height and near range. The Frequency Modulated Continuous Wave (FMCW) radar system islightweight, compact and low power consuming. So the combination of FMCW techniques and SARtechnology will lead to a cost-effective imaging radar with compact structure and high resolution. Dueto the fact that the “stop-and-go” hypothesis used for the derivation of traditional pulsed SARalgorithms couldn’t be anymore valid, it is necessary to re-examine specific algorithms appropriate forFMCW SAR. Here we start our research from two imaging algorithms which are the most importantnow in FMCW SAR: the Modified Range Doppler Algorithm and the Frequency Scaling Algorithm.Then the parameters estimation methods on the basis of the imaging algorithms in FMCW SAR arealso discussed, the correctness of the aforementioned imaging algorithms and parameters estimationmethods is validated through computer simulation results. The major work of this paper is detailedbelow:Chapter1introduces the history and the development of FMCW SAR at home and abroad. Thenthe main contents and resolved problems of this thesis are outlined.Chapter2establishes the echo signal model of FMCW SAR and makes a thorough analysis inthe broad side and squint mode, identifies the differences of the Dechirp-on-receive technology of theLinear Frequency Modulated (LFM) signal with the matched filtering techniques. The duration timeof FMCW signals is much longer than the pulse signals and that’s why the Doppler frequency shifteffect is induced.Chapter3studies the MRDA which ignores the Residual Video Phase (RVP). The principle ofclassic RDA is simply stated and the point target imaging results of pulsed SAR data using RDA arepresented. After that, the compensation for the Doppler frequency shift effect and the Range CellMigration Correction (RCMC) as well as the Secondary Range Compression (SRC) is analyzed.Finally, the simulation results and analysis of MRDA are provided.Chapter4depicts the FSA algorithm, analyzes how FSA deals with FMCW SAR echo signals.Compared with the MRDA simulation results, both algorithms can effectively process the FMCWSAR data.Chapter5discusses the Doppler parameter estimation problems in FMCW SAR. Two categories of parameters estimation algorithms based on the amplitude and the phase of the images have beentheoretically introduced and analyzed. Here we mainly studies the image amplitude estimation methodincluding the Maximum Contrast、the Minimum Entropy and the Map Drift algorithms, compares theefficiency of the algorithms in pulse SAR and FMCW SAR systems from the perspectives ofcomputation load and parameter accuracy, which moves forward to verify the effectiveness of theparameters estimation methods in this paper.Chapter6summarizes the dissertation and points out the later problems for future work.