Study On Fourier Domain Algorithms For SAR Raw Signal Simulation

Synthetic aperture radar(SAR) has the ability to obtain high-resolution microwave images of the observed scene independent of meteorological conditions and sunlight illumination. Hence it has been widely used in military and civilian fields. The SAR raw signal simulation play an vary important role for the SAR imaging algorithm, SAR images processing and SAR system design. In recent years, with the development of the SAR systems, there are more and more problems required to be solved in SAR raw signal simulation. Therefore, there need some new simulation algorithms to make sure SAR raw signal, which we simulated in different mode, is correct.In this thesis, SAR raw signal simulation is deeply studied, and the main contents include SAR raw signal simulation algorithm with variable velocity, raw signal simulation for UWB ground penetrating SAR and raw signal simulation for Bi SAR. The major work and contribution can be summarized as follows.1) It is difficult to obtain its two-dimensional frequency spectrum by a curvilinear trajectory with varying velocity. Based on the geometric model of side-looking SAR and series reversion, the 2-D spectrum is derived precisely. A two-dimensional Fourier domain SAR raw signal simulation algorithm with variable velocity is proposed. Moreover, the complexity and simulation precision are both analyzed. Finally, simulation results show that the efficiency of SAR raw signal simulation can be improved with high phase precision.2) A two-dimensional Fourier domain SAR raw signal simulation algorithm with motion errors is proposed. The curvilinear track caused by aircraft maneuvers and the motion errors caused by atmospheric turbulence can be seen as an ideal track with motion errors. This algorithm gives the instantaneous slant range by vector expression, and analyze that the main motion error should simulate by two steps. We first of all simulate the motion error which caused by same slant range called reference range. And the range-variant problem is effectively solved by introducing a new compensation function. Several simulation and processing results are presented to demonstrate the validity of the proposed algorithms.3) A two-dimensional Fourier domain algorithm of the raw signal simulation for UWB-SAR is proposed. Because of long synthetic aperture and great range migration, the system of UWB-SAR is different from conventional SAR, therefore the efficient simulation approaches for conventional SAR could not directly be applied to UWB-SAR. Based on the analysis of signal characteristics, the new algorithm first of all simulate the main range migration which caused by reference range in azimuth time-domain. Then a new transfer function can be derived. Finally, the range-variant problem is effectively solved by introducing a new compensation function. The simulation results show that this is an effective and accurate method in obtaining the raw signal simulation for UWB-SAR.4) Base on earth, moon and satellite trajectories, a new mode of Bi SAR, which called ground-satellite SAR, is proposed in this chapter. The geometric model of ground-satellite SAR is presented. Then the ambiguity function of ground- satellites bistatic SAR is defined and the ambiguity function formula is derived. Moreover, we analyzed the ambiguity function of ground-satellite SAR through numerical simulation. It is the theory basis of following SAR system design. Furthermore, a two-dimensional Fourier domain SAR raw signal simulation algorithm for ground- satellites bistatic SAR is proposed. According to the geometry and the model of echo signal, two-dimensional spectrum derived by the method of series reversion and realized steps of algorithm are given. Simulated results are utilized to validate the effectiveness of the proposed algorithm.