Application Of Time-Frequency Method In Motion Compensation And Imaging For High-Resolution ISAR

Inverse synthetic aperture radar (ISAR) as all-weather and all-time workingsensor system has found many applications in military, such as strategic defense,anti-satellite weapon, tactical weapon, as well as in science research, such as radarastronomy. A priori knowledge of target motion is generally unknown, therefore, theprincipal challenge in ISAR imaging is the target motion parameter estimation andcompensation. In the thesis, we focus our study on the application of time frequencytechnique in ISAR signal processing including the following aspects:(1) On a close study of many existing motion compensation algorithms, weproposed a new motion compensation approach based on time-frequency analysisand image processing. Because it just focuses on the ISAR image avoiding thecomplicated parameter searching procedure, the computational complexity of thismethod is much less than that of other time-frequency motion compensationalgorithms,meantime it is more effective for maneuvering target imaging than thetraditional translational motion compensation algorithms.(2) Based on the study of ISAR imaging techniques, we analyzed the timefrequency technique for ISAR imaging. Computer simulations show that the timefrequency imaging algorithm has competitive advantage over the R-D imagingapproach.(3) We studied many kinds of time-frequency distributions and applied STFT(Short Time Frequency Transform), WT(Wavelet Transform) and PWVD(PseudoWigner-Ville Distribution) in the ISAR signal processing.In addition, we also analyzed two classical wideband signals: SFCW(steppedfrequency continuous waveforms) and SFCS(stepped frequency chirp signal),moreover, we proposed a new processing method for SFCS based on full-derampingapproach. We applied the new motion compensation algorithm to ISAR imagingwith these two wideband signals. Computer simulations show that the accuracy ofthe estimated motion parameters is satisfied and SFCS has obvious betterperformance than SFCW does for imaging of high speed large target and extendedtarget.