超宽带复杂调制雷达信号Nyquist折叠接收及展开可重构理论与方法研究

Nyquist folding receiver (NYFR) is a structure based on the compressive sampling (CS) theory which provides a low-complexity receiving method for sparse signal in ultrawideband environment. This project has preliminarily studied some common radar signal analyzing and processing methods based on NYFR, but the key problems including detection and parameter estimation of ultrawideband complicated modeluated radar signals in low signal-to-noise ratio, the selections of local oscillators and their optimal parameters for the non-overlapping regions, the joint detection and estimation of the multi-channel NYFR structure and the high fidelity recovery of multiple signals have not been studied yet. Based on the analog-to-information converter undersampling CS theory, this project will build a novel Nyquist folding and unfolding reconfigurable structure and method for the ultrawideband complicated modulated radar signals. and based on the structures, do researches on problems inlcuding the mechanism and characteristics of ultrawideband complicated modeluated radar signals, detection and parameter estimation of undersampled sparse signals, information reconstruction based on CS theory and signal structure characters, and high fidelity recovery of multiple signals etc. To solve the above mentioned problems, the theory research and algorithms designment including their performance analysis and related applicationsour group will be mainly concentrated in this project. Building the novel signal processing models, fundamental theories and methods will be a novel work which has both theoretical signifiance and practical value to break through the bottleneck of ultrawideband non-cooperative signal countermeasure techniques.

Nyquist折叠接收结构基于压缩采样理论，提供了超宽频段下的稀疏信号低复杂度接收方法。项目组前期初步开展了基于NYFR的常规雷达信号分析与处理方法研究，但是针对超宽带复杂调制雷达信号低信噪比下的信号检测与参数估计、无混叠Nyquist区域的本振及其参数的优化模型选择、多通道NYFR的联合信号检测与参数估计、多信号高保真恢复等关键问题尚未涉及。项目基于模拟信息转换欠采样压缩感知理论，拟通过构建超宽带复杂调制雷达信号Nyquist折叠展开可重构新型结构，开展超宽带复杂调制雷达信号在Nyquist折叠展开结构中的机理研究、特性分析、欠采样下的稀疏信号检测和参数估计、基于压缩感知和信号结构特征的信息重构、多信号高保真恢复等关键问题的理论研究、算法构建及性能分析和相关应用工作；建立新的信号处理模型、基本理论和方法，对突破超宽带非合作信号对抗技术瓶颈是一项具有重要理论价值和实际意义的创新性工作。

Nyquist折叠接收（NYFR）结构是一种新型可突破当前模数转换器（ADC）采样率限制的超宽频段接收结构。随着电子战和电子对抗的愈加激烈，雷达信号调制方式也变得越来越复杂，使得这些信号难以被有效截获和侦察。NYFR的超宽带接收特性使得该接收结构可以高概率截获分布在超宽频段上的雷达信号，因此，项目组针对被NYFR截获的复杂调制雷达信号，研究了相应的接收和信号处理方法。首先，项目组全面分析了复杂调制雷达信号被NYFR截获后的输出信号在时域、频域、变换域以及噪声特性，为后续信号处理建立了数学模型；然后，针对低信噪比条件下的复杂调制雷达信号重构这一关键问题，基于分数阶自相关、熵权、子空间参数化估计等理论研究了信号被NYFR截获后的检测和参数估计方法；同时，针对NYFR的折叠跨Nyquist区这一关键问题，分析了相应的跨Nyquist区信号特性和时域特征，并提出了相应的参数估计方法；进一步，针对NYFR截获的雷达信号，基于频域分析、数据域变换、信号周期建模、开关阵列模型等理论研究了相应多信号的参数和达到角无模糊估计；最后，针对NYFR结构，研究了相应的接收/发射结构，并基于分数阶自相关、插值方法和稀疏贝叶斯学习理论，提出了非合作信号高保真恢复算法和定位算法。通过本基金的研究，项目组完成了对NYFR结构的机理分析和相应的信号处理理论研究，为新一代非合作超宽频段超宽带接收体制研究的可行思路奠定了理论基础，并通过比例硬件模型验证了该体制的有效性。