【作者】 曾勇虎；

【导师】 郭桂蓉；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2004， 博士

【摘要】 随着宽带信号理论和技术、极化散射测量技术的发展，具有高分辨成像、全极化测量或极化捷变能力的雷达逐渐成为现代雷达技术发展的主流，从而极大地增强并扩展了雷达的探测功能和应用范围。与现代雷达的宽带、高分辨发展趋势相比，面向窄带、低分辨的经典极化理论越来越显示出其差距和不足。瞬态极化理论体系的建立，为宽带电磁波极化表征、雷达目标宽带极化散射特性刻画提供了有力的理论工具；对于开发目标的极化散射信息、提高宽带极化雷达的探测性能具有重要的意义。 本文以瞬态极化理论为基础，对电磁波的瞬态极化概念加以拓展和完善，建立了电磁波瞬态极化时频分析基本方法，为在时频域上刻画和分析时变电磁波的瞬态极化特性提供了理论基础和数学工具；然后以电磁波瞬态极化时频变换为工具，刻画和分析了宽带极化雷达目标散射回波在时频域上的瞬态极化特性，提出了两种目标识别方法，取得了良好的目标识别效果。 具体内容可分为理论研究和应用研究两个方面： 在理论研究方面，阐释了对时变电磁波作瞬态极化时频分析的必要性及物理涵义，提出了对电磁波瞬态极化时频分布的基本性质要求，然后给出了电磁波瞬态极化短时Fourier变换(简称为瞬态极化STFT)、电磁波瞬态极化Wigner-Ville分布(简称为瞬态极化WVD)、电磁波瞬态极化模糊函数、电磁波一般类瞬态极化时频分布以及电磁波瞬态极化伪Wigner-Ville分布(简称为瞬态极化PWD)的定义，并分别讨论了它们的主要性质，比较了电磁波瞬态极化时频分析方法与常规时频分析方法之间的区别和联系。这些概念和方法构成了电磁波瞬态极化时频分析的基本内容，为随后的目标识别研究提供了理论基础。 在应用研究方面，提出了基于瞬态极化WVD相关的宽带极化雷达目标识别方法，以充分利用目标后向散射回波中的瞬态极化信息，并且揭示了采用瞬态极化WVD相关方法时的性能改善与目标回波极化散度之间的关系；提出了目标回波瞬态极化时频分布奇异值特征提取与识别的方法，由目标回波瞬态极化时频分布各分量的奇异值组成特征矢量，以BP神经网络作为分类器进行了目标识别实验，结果表明其性能优于常规的时频分析方法。 本文对极化雷达时频分析与目标识别的研究表明，采用电磁波瞬态极化时频分析方法，不仅可以刻画时变电磁波在时频域上的能量分布情况，而且可以刻画其在时频域上的极化状态分布情况，因而对于时变电磁波的特性描述和信息开发更加完整和全面；将电磁波瞬态极化时频分析方法应用于宽带极化雷达目标识别，可以获得优于采用常规时国防科技大学研究生院学位论文频分析方法时的识别性能，并且识别算法具有更好的抗噪声能力。 关键词:极化，瞬态极化，时频分析，雷达目标识别，瞬态极化时频分析，瞬态极化短时Fourier变换，瞬态极化Wigner-Ville分布，瞬态极化伪Wigner-Ville分布，瞬态极化模糊函数，一般类瞬态极化时频分布，瞬态极化WVD相关，瞬态极化时频分布奇异值特征第H页更多还原

【Abstract】 With the development of the theory and technology of wide-band signal, and the improvement of polarimetric technology, the radar having ability to get high resolution range profiles and fulfill full polarization measurement or polarization shifting, is becoming the mainstream of modern radars, which improves and extends the detection capability and application domain of radar. Compared with the trend of wide-band and high range resolution in radar technology, the classical polarization theory, which is suitable in narrow-band and low range resolution case, shows its imperfectness and deficiency. The foundation of the theory system of instantaneous polarizaiton(InPol) provides powerful theoretical tools for the representation of electromagnetic(EM) wave’s polarization and description of radar target’s wide-band polarization scattering characteristic. So it is greatly beneficial to the exploitaion of radar target’s polarization scattering imformation and the improvement of wide-band polarimetric radar’s detection performance.In this thesis, with the guidance of InPol theory system, the elementary methods of EM wave’s InPol time-frequency analysis are presented, which are extension and evolution of the concept of EM wave’s instantaneous polarization and provide powerful theoretical tools for the representation and analysis of time-varying EM wave’s InPol properties in time-frequency domain. With these methods, the InPol properties of wide-band polarimetric radar target’s scattering waves are described and analyzed in time-frequency domain, and two effective target recoginition methods are proposed.The work of this thesis includes research both in theory and in application:In theory, it firstly elucidates the necessity and physical meaning of InPol time-frequency analysis(InPol TFA) of time-varying EM waves, and presents the basic property requirements of InPol time-frequency distribution(InPol TFD). Then, some elementary InPol time-frequency transforms, such as InPol short-time Fourier transform(InPol STFT), InPol Wigner-Ville distribution(InPol WVD), InPol ambiguity function, Cohen’s class InPol time-frequency distribution, and InPol pseudo WVD(InPol PWD), are introduced, and their properties are discussed. The difference and relationship between InPol TFA method and conventional TFA method are also compared. These concepts and methods compose the basic framework of EM wave InPol TFA, which lays theoretical foundation for the following target recognition research.In application, two wide-band polarimetric radar target recognition methods are proposed. The one is based on InPol WVD correaltion, which can utilize the InPol information of target’s return well. The relationship between the improvement of this method’s performance and target scattering wave’s polarization divergence are demostrated too. The other is based on features formed by singular values of target return’s InPol TFD, and selects BP network as target classifier. Recognition results show that the method based on InPol TFD has better performance than the method based on conventional TFD.The studies on TFA and target recognition with polarimetric radar in this thesis indicate that with EM wave InPol TFA method, both the energy and the polarization state distribution in time-frequency domain are described for a time-varying EM wave. That is to say, the characteristic description and information exploitaion of a time-varying EM wave are more complete and comprehensive when using this technology. It is proved that wide-band polarimetric target recognition methods based on InPol TFA can achieve higher correct recognition rates and better antmoise performance than the methods based on conventional TFA.更多还原