基于GNSS软件定义接收机的被动式雷达成像算法分辨率提升的实现与系统开销研究

The Research for Software Defined Passive GNSS-based Radar Imaging of Resolution Enhancement and Computational Efficiency

被动式GNSS雷达,简称GNSS雷达,是一种利用GNSS信号作为机会式发射源的新体制雷达.其具有载荷低、覆盖范围很广、工作时间全天候的优点.由于GNSS信号是将带宽较窄的导航信号调制在载波信号上,导致距离分辨率很低.通过研究利用GPS信号实现被动式雷达成像的可行性,提出了一种实现成像的流程.提出根据奈韦斯特采样定理可以抽取滤波降低采样率来减少数据量,利用GPS信号中导航码相关性很强的特性实现距离向压缩,通过使用本项目成像场景下适用的匹配滤波函数实现方位向压缩.实现了提高距离分辨率算法,摆脱了物理特性对距离分辨率的限制,也弥补了一些由GPS信号带宽过窄所带来距离分辨率很低的缺陷.通过系统测试验证,表明了利用GPS信号实现雷达成像的可行性,也证实了提高距离分辨率算法能使得成像结果中的距离向分辨单元变得精细,并且通过实验找出了分辨率与采样率的最佳权衡点.

Passive GNSS radar,referred to as GNSS radar,is a new radar system which uses GNSS signal as an opportunistic transmitter.It has the advantages of low load,wide coverage and all-weather working time.However,because GNSS signals modulate narrow bandwidth navigation signals on carrier signals,the range resolution is very low.In this paper,the feasibility of passive radar imaging using GPS signal is studied,and a process of imaging is proposed.According to the Nyquist sampling theorem,the sampling rate can be reduced by filtering.The range compression can be realized by using the strong correlation of navigation codes in GPS signals,and the azimuth compression can be achieved by using the matched filtering function suitable for the imaging scene of this project.On the basis of realizing the imaging,the algorithm of improving the range resolution provided by the teacher is realized,which breaks away from the limitation of the physical characteristics on the range resolution,and makes up for some defects of the low range resolution caused by the narrow bandwidth of GPS signal.The field experimental shows that it is feasible to use GPS signal to realize radar imaging.It also proves that the improved range resolution algorithm can make the range resolution unit in the imaging results more accurate.