分布式卫星调频连续波SAR成像技术研究

Distributed spaceborne FMCW SAR is an innovative spaceborne radar instrument based on a combination of the satellite formation technique and the FMCW SAR technique. It has the advantages of small size and light weight, elasticity and scattering, flexibility and agility, low cost data, and it is expected to improve the quick response ability of spaceborne SAR. However, new challenges in spaceborne imaging are also aroused by the distributed satellite and the FMCW SAR. Firstly, the phase synchronization problem of the received signal caused by the separation of the oscillators, which makes the existing pulsed alternate synchronization method can not be directly applied to FMCW SAR. Secondly, the imaging processing problem of the bistatic FMCW SAR, which makes the existing methods can not solve the imaging problem efficiently and accurately under the conditions of high-speed spaceborne platform, bistatic, large squint angle and FMCW doppler during pulse duration. Therefore, the study is carried out focusing on the phase synchronization and the bistatic imaging problem in the distributed spaceborne FMCW SAR imaging. The signal model of the phase synchronization error, the doppler during pulse duration and the bistatic range history is presented. The phase synchronization method based on alternating bistatic/ping–pong mode and the generalized frequency scaling algorithm is proposed, which is validated by the ground based prototype system. The research results will lay the foundation supports for the new system implementation, promoting the development and practicality of the system.

分布式卫星FMCW SAR是将分布式卫星编队技术与FMCW SAR技术有机结合的新体制天基雷达系统，具有小型轻量化、弹性分散、灵活敏捷、数据产品成本低的优点，能够提高星载SAR快速响应能力。但分布式和FMCW结合也给星载SAR成像带来了新的挑战：（1）收发分置不共频率源引起的信号相位同步问题，现有的基于脉冲交换的相位同步方法不能直接应用于FMCW体制；（2）双基FMCW SAR成像处理问题，现有方法不能解决星载高速平台、双基地、大斜视和FMCW脉内多普勒等相互耦合因素下的高效高精度成像处理。本项目针对分布式卫星FMCW SAR成像中的相位同步和双基成像这两个问题开展研究，在建立相位同步误差、脉内多普勒、双基距离史等模型基础上，研究基于乒乓双站模式的相位同步、通用频率变标等方法，并基于地面原理系统验证方法有效性。项目研究成果将为实现新体制系统提供理论支撑，推动系统的实用化进程。

分布式卫星FMCW SAR是将分布式卫星编队技术与FMCW SAR技术有机结合的新体制天基雷达系统，具有小型轻量化、弹性分散、灵活敏捷、数据产品成本低的优点，能够提高星载SAR快速响应能力。但分布式和FMCW结合也给星载SAR成像带来了新的挑战：（1）收发分置不共频率源引起的信号相位同步问题，现有的基于脉冲交换的相位同步方法不能直接应用于FMCW体制；（2）双基FMCW SAR成像处理问题，现有方法不能解决星载高速平台、双基地、大斜视和FMCW脉内多普勒等相互耦合因素下的高效高精度成像处理。本项目针对分布式卫星FMCW SAR成像中的相位同步和双基成像这两个问题开展研究，在建立相位同步误差、脉内多普勒、双基距离史等模型基础上，研究基于乒乓双站模式的相位同步、通用频率变标等方法，并基于地面原理系统验证方法有效性。项目研究成果将为实现新体制系统提供理论支撑，推动系统的实用化进程。