基于雷达波形和压缩感知核联合优化的Sub-Nyquist认知雷达

Cognitive radar and wideband/ultra-wideband radar are two kinds of important radar systems. They have strong capability to reject radar clutter and jamming/electronic counter-measure interferences, and can implement accurate and high-resolution measurements of radar targets. However, current analog-to-digital conversion limits the application of wideband/ultra-wideband radar signals and subsequent signal processing. This proposal incorporates compressive sensing theory into the design of cognitive radars and proposes the concept of sub-Nyquist cognitive radar with digital acquisition of radar echoes by analog-to-information conversion at sub-Nyquist rate. The aim of the study is to develop a framework of the sub-Nyquist cognitive radar and the corresponding intelligent signal processing. Different from traditional cognitive radar, the samples of the proposed sub-Nyquist cognitive radar echoes not only contain the information of radar targets, but also depend closely on the analog-to-information conversion system. To efficiently acquire the information of radar environments and targets, the proposal develops a joint optimization design of radar waveforms and compressive sensing kernels, which is different from the design on radar waveforms only in traditional cognitive radar. The research scopes mainly include the sub-Nyquist sampling-based environment information sensing, the optimization and design of the radar waveform and the sensing kernel, the sub-Nyquist sampling-based target information estimation and so on. Moreover, to evaluate the performance of the proposed sub-Nyquist cognitive radar, the proposal will develop a prototype system with the quadrature compressive sampling system developed in our lab.

认知雷达和宽带/超宽带雷达是雷达研究的两个重要方面，是抑制杂波、电磁干扰/电子对抗信号和实现目标精细化测量的重要途径。然而，模数转换器的发展水平极大地限制了大带宽雷达信号的使用和后续信号处理。本申请提出将压缩感知理论应用于认知雷达，采用模信转换获取Sub-Nyquist率雷达回波信号，发展Sub-Nyquist认知雷达信号处理技术。与传统认知雷达不同，Sub-Nyquist认知雷达采样信号不仅包含雷达回波信息，同时与模信转换结构密切相关。为此，本申请提出雷达发射波形和压缩感知核联合优化的设计思想，以有效获取环境和目标信息。这种设计与传统认知雷达只设计雷达波形有很大的差别。本申请研究内容主要包括Sub-Nyquist率的环境信息感知、雷达波形和压缩感知核联合优化设计、目标信息估计等。除外，本申请还将基于正交压缩采样模信转换，设计和实现Sub-Nyquist认知雷达原理系统，验证其性能。

本项基于压缩感知理论框架，开展面向雷达应用的Sub-Nyquist采样系统设计研究，发展相应的基于Sub-Nyquist采样数据的雷达信号处理方法，建立Sub-Nyquist雷达性能分析理论。项目取得的主要成果如下：.（1）针对雷达回波特点，提出了基于正交压缩采样的sub-Nyquist雷达信号采集系统，并实现了硬件原理电路。针对认知雷达宽带频谱感知的需求，提出了一种多带正交压缩采样系统，实现多带雷达回波信号的sub-Landau率采集。.（2）发展了sub-Nyquist雷达回波快速实时重构技术。针对几种典型的sub-Nyquist采样系统，提出基于分块滑动思想的 sub-Nyquist雷达回波快速实时重构方法，并理论分析了分块重构时的信号重构性能。针对高速运动目标跨距离门的情况，开展了运动目标回波信号快速实时重构技术研究。.（3）发展了sub-Nyquist雷达高分辨目标参数估计方法。针对雷达应用环境无法有效获取目标先验信息的情况，提出了一种基于盲终止条件的雷达目标参数估计算法，理论分析保证了算法的有效性；针对当前离散化稀疏重构算法存在off-gird问题，分别提出了基于内插阵技术的时延-多普勒频率联合估计算法、基于二维原子范数的时延-多普勒频率联合估计算法和基于二维解耦的时延-多普勒频率顺序估计算法。.（4）发展了sub-Nyquist雷达抗干扰技术，分别针对窄带干扰和转发式干扰提出了基于sub-Nyquist采样数据的干扰抑制算法，提高了sub-Nyquist雷达在复杂电磁环境中的生存能力和目标探测性能。.（5）理论分析了sub-Nyquist雷达目标参数估计的克拉美罗界（Cramer-Rao bound, CRB），建立了时延和多普勒估计的CRB与接受回波的信噪比、发射脉冲数、系统采样率、相干处理时间之间的关系，分析了不同sub-Nyquist采样结构对参数估计的影响。.此外，项目开展了sub-Nyquist雷达合成孔径成像、基于时变测量的sub-Nyquist雷达采样系统设计和参数估计以及sub-Nyquist雷达低分辨采样与参数估计等方面的研究。