This study presents a novel method for time–frequency (TF) signal analysis and chirp rate estimation dedicated for electromagnetic spectrum sensing, electronic warfare, electronic intelligence and/or passive bistatic radar purposes in which frequency modulated signals occur. The approach is based on the double-adaptive chirplet transform, providing optimal analysis window parameters, which is a crucial problem during TF processing. The presented methodology is based on a Gaussian window with two degrees of freedom, which results in a strong concentration of energy on the TF plane around the main component, even if the initial window parameters were mismatched. As an example of the method's usefulness, different types of real-life radar pulses were processed: firstly, two types of non-linear frequency-modulated waveforms were examined as a suitable illustration of the changeability of the analysis window parameters. Secondly, the linear frequency modulated signals were analysed in the presence of strong interference and multipath propagation. The waveforms were processed and compared, creating individual radar signatures, which may allow transmitter classification and signal reconstruction to be carried out in further processing. Moreover, the estimation limitations were compared to the Cramer-Rao lower bound, and an appendix organising mathematical fundamentals for the analysed methods is provided.

中文翻译：

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用于雷达特征提取的双自适应Chirplet变换

这项研究提出了一种用于时频（TF）信号分析和线性调频率估计的新方法，专门用于发生频谱调制信号的电磁频谱感测，电子战，电子情报和/或无源双基地雷达。该方法基于双自适应chirplet变换，可提供最佳分析窗口参数，这是TF处理期间的关键问题。所提出的方法是基于具有两个自由度的高斯窗口，即使初始窗口参数不匹配，这也会导致能量在TF平面上围绕主要成分强烈集中。作为该方法实用性的一个示例，处理了不同类型的现实生活中的雷达脉冲：首先，检查了两种类型的非线性频率调制波形，作为分析窗口参数可变性的合适说明。其次，在存在强干扰和多径传播的情况下分析了线性调频信号。对波形进行处理和比较，以创建单独的雷达信号，从而可以在进一步处理中执行发射机分类和信号重建。此外，将估计限制与Cramer-Rao下界进行了比较，并提供了组织所分析方法的数学基础的附录。对波形进行处理和比较，以创建单独的雷达信号，从而可以在进一步处理中执行发射机分类和信号重建。此外，将估计限制与Cramer-Rao下界进行了比较，并提供了组织所分析方法的数学基础的附录。对波形进行处理和比较，以创建单独的雷达信号，从而可以在进一步处理中执行发射机分类和信号重建。此外，将估计限制与Cramer-Rao下界进行了比较，并提供了组织所分析方法的数学基础的附录。