Research On Synchronization For Spaceborne/airborne Bistatic Hybrid SAR

Research object of this thesis is Spaceborne/Airborne Bistatic Hybrid SAR( SA-BiSAR) system, which is an asymmetric Bistatic Hybrid SAR system. Spaceborne SAR system has a wide coverage and great concealment, airborne SAR system has a good flexibility, and high resolution, SA-BiSAR system combines their strengths, and has great value whether in the military or civilian areas. Germany, represented by the Western developed countries, have launched a series of SA-BiSAR system test, and achieved encouraging results. However, SA-BiSAR system still faces many challenges when applied in practice, synchronization is one of the conundrum. And due to the asymmetry, synchronization technology of SA-BiSAR has a great difference with symmetric system bistatic SAR system. At present, the synchronization problem has become daunting challenge when SA-BiSAR system is appllied in practice.For synchronization technology of SA-BiSAR system, In this thesis, a systematic study is launched, the main work are as follows:1. It conducts a comprehensive analysis of the main technical parameters of SA-BiSAR system, these technical parameters are: spatial resolution, signal to noise ratio(SNR), imaging time, the length of scene,synthetic aperture time and swath. In combination with these parameters, it gives an analysis of operating modes, which are proposed in existing literature.2. For the deficiencies of the existing space synchronization technology of SA-BiSAR system, it presents a space synchronization scheme, which is based on multi-beam receiving. Meanwhile, it carries out a simulation to SNR, the length of scene, spatial resolution and space synchronization errors in the scheme, demonstrating its performance visually. In this scheme, it broadens receiving beam using “splicing”, and it can get practical length of scene by broadening receiving-beams appropriately. Compared with the "double-wide beam mode", the program has a higher SNR.3. It gives a detailed analysis about origin, effect and model of time synchronization error. Learning from existing theoretical results, a time synchronization scheme of SA-BiSAR system, which is base on direct signal, is designed. And it gives specific implementation steps. In this scenario, in order to extracting the linear drift rate of time synchronization errors, an efficient Doppler centroid estimation algorithmis, which is suitable for real-time processing, is given. Finally, point target imaging simulation is implemented by using RD imaging algorithm which is based on 2D-PSP, the results showed that: after the error compensation, the imaging performance is greatly improved.4. It gives a detailed analysis about origin, effect and model of frequency/phase synchronization error. Learning from existing theoretical results, a frequency/phase synchronization scheme of SA-BiSAR system, which is base on direct signal, is designed. And it gives specific implementation steps. In this scenario, in order to extracting random error term of each pulse, a baseline distance estimation method is given. Finally, point target imaging simulation is implemented by using RD imaging algorithm which is based on 2D-PSP, the results showed that: after the error compensation, the imaging performance is greatly improved.