ISAR Imaging Technology Of Rotating Target With Large Angle

In ISAR imaging, cross range resolution depends on the rotation angle of target, andto get a high resolution ISAR image, people always increase the target rotation angle.Firstly, the research background is introduced, and the development of inverse syn-thesis aperture radar system is reviewed. Then technology development of ISAR imagingis summarized. The development of wavelet and frame theory is introduced and sum-marized behind. Then the issues in ISAR imaging of large rotation angle are proposed.The related knowledge of fundamental theory of ISAR imaging and frame theory are alsointroduced as the spade work for the following work.The Compensation of migration through resolution cell (MTRC) is inevitable intraditional Range Doppler imaging. Compensation for non-uniformly rotation target isstudied. By analysing the character of radar return of uniformly rotation target and non-uniformly rotation target, generalised Keystone transform for the compensation of non-uniformly rotation target is deduced according to the principle of Keystone transformcompensating uniformly rotation target. When target rotation motion can be approxi-mated as2order, the estimation method for parameter γ, which is essential in generalisedKeystonetransform, canbedonebycombiningtime-frequencyanalysisandHoughtrans-form. The fast algorithm for generalised Keystone transform is also deduced by bringingthe matched Fourier transform, and the interpolation can be achieved fast and effective.Frame theory is introduced to ISAR imaing, and the frame based ISAR imagingmethod is proposed. On the premise of scatterer’s isotropy and the motion compensa-tion has been done, the method can image uniformly and non-uniformly rotation targeteffectively and of high quality. The target rotation angle during the imagine processingdetermines the cross range resolution, and the principle of frame based imaging methodmakes the method get rid of the problem of MTRC compensation. The realisation of themethod need the knowledge of target rotation information, and the estimation method isintroduced in the following chapters.The estimation of target rotation rate is not only the necessary step in Frame basedimaging method, but also the only method to scaling the cross range of ISAR image intraditional RD method. And the issue of target rotation rate estimation is studied next.Two classes of methods are introduced, the first one is signal based estimation method and the second one is image based. Frame processing method is utilised in both kinds ofestimation methods, and good results are obtained. The CRLB of rotation rate estimationis deduced according to the Frame model of target return, and the result can also used inother rotation rate estimation method.For the non-uniformly rotation target, adaptive local polynomial Fourier transform(ALPFT) based rotation rate estimation method is proposed. The rotation rate changecurve estimation can be divided into2steps. firstly, the scale factor α(t) is estimated, thenthe basic rotation rate ω0is estimated. As the complexity of the computation of ALPFT,when the target structure is simple, time-frequency analysis is used taking the place ofALPFT. And the second step can be down by means of the method proposed in Chapter5.At last, the dissertation is summarised. And the future work of ISAR imaging oflarge rotation angle target is also discussed.