Application Of The Fractional Fourier Transform To ISAR Maneuvering Target Imaging

As a high resolution radar with all-weather, all-time capability, Inverse Synthetic Aperture Radar (ISAR) can obtain the image from a long distance. Now it is used widely used both in astronomy and military. The signal received from the targets of ISAR is normally non-stationary, and Fractional Fourier Transform is a new method to solve this signal. With good cross-terms reduction and high time-frequency resolution, Fractional Fourier Transform (FRFT) is a new linear analysis tool for non-stationary signal processing. It is very suitable for processing the multi-component LFM signal.In this thesis, application of the FRFT to target imaging in ISAR is discussed. Firstly, the definition and the basic characteristics of FRFT and other time frequecy transform are presented, then, the time-frequency properties of LFM signal in FRFT are summed up. Kurtosis detection is the method we used for LFM signal detection and parameters estimation. Further more, we describe the details about ISAR imaging system including related key techniques. FRFT is applied to compensate the phase error caused by target's non-cooperative motion, and simulation is proposed to verify it. Finally, ISAR imaging of maneuvering target based on FRFT is discussed. We present subechoes sepatating algorithm based on FRFT, which can reduce cross-terms. With this algorithm, we simulate the ISAR imaging of two dimesional and three dimensional motion target.The theoretical analysis is validated by presenting and discussing the simulation results.