| Ground moving target indication (GMTI) is a hot topic in the area of Synthetic aperture radar (SAR), it can distinguish moving targets on land from surface clutters. In practice the performance of clutter suppression and moving targets detection is limited by radar platform motion errors and channel errors. Based on displaced phase center antenna (DPCA) technique, the two kinds of errors mentioned above and their correction methods are studied in this paper.Firstly, the principle of SAR imaging is introduced, and the echo model of moving target is built. The effects of moving target Doppler center frequency and Doppler frequency rate on SAR image are discussed. Then, a multi-channel moving target detection algorithm– DPCA is deeply studied. The main performance parameters of DPCA algorithm (such as improvement factor, blind velocity, maximum detectable velocity and minimum detectable velocity) are analyzed theoretically in detail. Simulation experiments validate the detection performance of the algorithm.Then, the platform motion error model is built. The effects of three kinds of motion errors (along-track, yaw, pitch) on SAR imaging and clutter suppression are deeply analyzed. Furthermore, the effect of the channels mismatch is also studied. and verified by simulations.Finally, a method for along-track motion compensation based on cubic spline function is proposed. A kind of mathematics tool called fractional Fourier transform (FrFT), which can estimate the parameters of chirp signal well, is introduced here. Based on FrFT, a method for yaw and pitch directions motion compensation is presented. The validity of these two methods is demonstrated by the simulation results. A method for channel equalization using test signal of point target is proposed. The method is easy to be realized and verified by simulation. |
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