基于GNSS信号的多孔径无源成像

Multi-aperture passive radar imaging based on GNSS signals

基于全球导航卫星系统(global navigation satellite system,GNSS)信号的无源成像技术具有多种突出优点,但GNSS信号带宽较窄的缺点导致系统距离向分辨率较低。文章以波数域回波与空域目标像之间的傅里叶变换关系为出发点,通过分析回波在波数域的分布特征与信号频率、收发站布站构型之间的内在联系,寻求带宽和孔径对成像分辨率贡献的互补途径,从而建立一种基于GNSS多星照射、少数甚至单个地面站接收的对地成像方案;该方案利用多颗GNSS卫星的轨道互异特征,扩展系统的孔径数量,弥补现有GNSS信号带宽普遍较窄的不足,从而提高成像分辨率;针对GNSS多孔径无源系统波数域数据大、面积缺失的特点,选用鲁棒性和稳健性较强的逐点匹配滤波方法进行图像反演,最后通过数值仿真实验验证成像方案。

Though the passive radar imaging based on global navigation satellite system(GNSS)signal has several advantages,it is badly restricted for application by its low resolution in range dimension due to the narrow bandwidth of GNSS signal.In this paper,the Fourier transform relationship between target scattering function in the space domain and the echoes in the wavenumber domain is proved.It can be seen that the distribution of echoes in the wavenumber domain is inherently linked to both the bandwidth of transmitted signal and the configuration of the illuminators and receivers.Therefore,a multi-aperture passive radar imaging system,which consists of multiple GNSS illuminators and a few stationary ground-based receivers,or even single one,is proposed.It is possible to achieve a high resolution image using narrow-band GNSS illuminators by more apertures constructed from the different satellite orbits.Due to practical limitations,the echoes constitute a non-uniform and discontinuous coverage in wavenumber domain,which directly leads to poor inversion performance,so the scatter-by-scatter matched filtering method is utilized to reconstruct the images for its good robustness.Simulation results are provided to demonstrate the performance improvement by the proposed method.