Study On Synthetic Aperture Radar Echo Simulation

The echo simulation which is very important to the study of the SAR system and the imaging methods is the foundation of the technology of Synthetic Aperture Radar (SAR) simulation. Because the truth of the echo simulated is directly efflunced by the accuraty of the simulation algorithms, the simulation algorithms are thoroughly studied in this paper.In the paper, the echo simulation studies of strip-map SAR, spotlight SAR and multi-polarization SAR are introduced; airborne and spaceborne orbit models are selected; four target models: point target, facet target, extended target and real scenario target are included; the time-domain, frequency-domain, and time-frequency-domain simulation methods are adopted; and the formulae of the echo simulation are gained.In general, the contribution and innovation of this paper can be summerized as follows:(1) The point target simulator of spaceborne SAR is designed and manufactured. In processing of the echo simulation, the ellipse model and the ellipsoid model are used for satellite orbit and target model respectively, and the simulation is very close to the real case. Range direction can generate one point target, and azimuth direction can generate several point targets. So the echo of one point target or several point targets are generated by the simulator. This simulator has been applied in real work to test the SAR system, and to evaluate the characteristics of the system IRF space-domain (the range resolution and the azimuth resolution) and the side-lobe (the peak-peak side-lobe ratio and the integral side-lobe ratio). At the same time, it can be used to evaluate the system BAQ algorithm and study the imaging algorithm.(2) The method of the polarimatric spaceborne SAR raw data simulation is introduced. The ideal target models and the simple SAR imaging geometry aremainly used in the methods of the traditional polarization raw data simulation. Because the elliptical orbit model and the ellipsoidal target model are used in the paper, the target model and the orbit model are very close to the real circumstances. Combined the facet theory and the polarization theory, the formulae of the multi-polarization simulation are educed, and the method of the multi-polarization spaceborne SAR extended target raw data simulation is presented.(3) A novel method of frequency-domain simulation is introduced, based on this method, and the method of the real scenario raw data simulation is presented. On the one hand, the question of the real scenarios simulation velocity is settled. On the other hand, the validity of the frequency-domain real scenario simulation method is shown by the experiment of the real scenario simulation. After the method of the real scenario simulation is used, the simulation study is pushed to a new phase.(4) Taken both the time-domain and the frequency-domain into account, the method of the complex scenario is brought forward. To obtain the raw data of the complex scenarios, the raw data of the extended targets which are generated through the time-domain simulation method are added to those of the scenarios which are generated through the frequency-domain simulation method. With the complex scenario simulation method presented, the separate status of the time-domain simulation and the frequency-domain simulation are broken, and a new path of the abundant data simulation is inaugurated.(5) The new idea of spotlight SAR raw data simulation is created. Based on the theory of spotlight SAR, the method of spotlight SAR raw data simulation is introduced. The validity of this method is validated by the simulation experiment of the extended targets. By means of this method, the useful data for the spotlight SAR system study is offered and the study of the imaging algorithms is accelerated.