| In modern warfare, the electromagnetic (EM) environments have been more and more complicated. In order to exploit and utilize the EM information utmost, that is, to let the radar sensing system can adapt adverse battleground environments with intelligent detection and recognition capability; some problems are becoming a groundwork and impendent mission in radar polarization information processing. These problems mainly include studying the polarization phenomena of time-varying EM waves from dynamic and statistical viewpoints, revealing the inherent rules of random EM waves, exploring polarization scattering characteristics of radar targets and environments, and founding effectual descriptive means of polarization statistics of radar targets.The dissertation studies the polarization characteristics of time-varying EM waves and radar target scattering. The methods and conclusions in this thesis can proffer some novel and promising techniques for weakening the influences of adverse EM environments, confronting active jamming, detecting concealed targets and recognizing targets and other applications. The main contributions of the thesis are as follows:Firstly the statistical properties of the normalized Stokes parameters in a Gaussian stochastic plane wave field are described in details. The new dispersion, normalized contrast of fluctuation, skewness and kurtosis are defined to describe the non-Gaussian distribution characteristics. The definitions of the instantaneous coherent polarization function (ICPF) and polarimetric spectrum (ICPS) are presented for the first time, which shows the coherences of the instantaneous Stokes parameters in both time and frequency domain, even in spatial coherence. The new formula of definition can be extended to spatial propagation coherence, both in free space or any linear medium.Secondly Then the statistics of the stochastic plane electromagnetic (EM) wave fields that is Weibull distributed is examined. The polarimetric Weibull distributed wave is characterized by three parameters: the sum of the amplitudes of the two electric vector components, the angle which the major axis makes with the reference coordinate system, and the ratio of the minor to the major axis. The joint and marginal probability densities of these random variables are determined as a function of the covariance matrix. Then the statistical properties of the normalized Stokes parameters are described in details in Weibull distributed stochastic fields. The joint and marginal probability density functions (PDF) of the three components of the normalized Stokes parameters are presented. Results of some numerical calculation can be obtained. The description of the Weibull polarimetric wave filed may be useful to random medium scattering and speckle filtering.Thirdly a new class of distribution, named Extended Weibull distribution, arising from target fluctuation, is presented in this paper, along with their mainly properties and relations. Classical distributions, such as Gamma, Square Root of Gamma and Weibull, are particular cases of this new class. The statistics of Stokes parameters in pol-S AR is given in a new and simple formula. At the same time, the statistics of decomposed parameters for H/A decomposition and SDH decomposition are given for suitable choices of the accurate parameters.Finally the polarization characteristics of radar target in spatial domain are studied. And the statistics of chaff cloud is studied, and the statistics of scattering matrix and radar cross section are presented under different spatial distribution of chaff cloud. At last a new method of 1 -D feature extracting of scattering centers is presented and the precision is analyzed.These conceptions and conclusions proffer theoretical foundations and avail tools for polarization characteristic analyzing of random EM waves or radar target scattering, feature extraction and other applications. And these are possessed of practical significance to engineering applications.
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