利用收发宽波束实现星机双基地SAR的波束同步

Beam Synchronization Technique for Spaceborne/Airborne Hybrid Bistatic SAR by Wide-beam Illumination and Receiving

由于低轨道雷达卫星的飞行速度远快于飞机,波束同步技术是关系到星机双基地SAR能否具有实用价值的核心技术。已有文献中提出的基于收发波束指向控制的同步方法具有场景长度短、算法复杂等缺点。根据星机双基地SAR"远发近收"的特点,提出一种基于收发宽波束的波束同步方法。从信噪比、系统模糊性等方面对该方法进行量化论证。仿真结果验证了方法的可行性。与已有方法进行比较,结果表明,文中提出的方法能在方位分辨率相等的前提下获得更大的场景长度;而且由于无需进行波束指向控制,成像算法简单。

The beam synchronization of the antenna footprints is a big methodical and technological challenge in spaceborne/airborne hybrid bistatic synthetic aperture radar(SA-BSAR),since there is great difference between the velocities of the platforms.An existing approach based on antenna steering has been presented in the literature.However,it has the demerits of a short scene length and requiring a complex imaging algorithm.Inspired from the fact that the receiving distance in SA-BSAR is much shorter than the one in the spaceborne SAR system,an approach based on wide-beam illumination and receiving is proposed.The feasibility of the proposed approach is quantitatively assessed from the aspects of the SNR(Signal to Noise Ratio) level and the impact on the choice of the PRF(Pulse Repetition Frequency),both theoretically and by simulation.A comparison with the existing approach shows that a longer scene length with the same azimuth resolution can be achieved.Furthermore,the corresponding algorithm is easier to design as the antennas need not be steered.