天地波高频雷达一阶海杂波特性分析与抑制

发布时间：2018-06-24 07:53

本文选题：Bragg散射频率 + 高阶累积量　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：本文针对高频雷达天发岸收模式下一阶海杂波的特性与抑制这一问题进行了深入分析和仿真研究，其中分别从模型建立和信号处理两个角度，重点研究了新模式下一阶海杂波的展宽特性、统计特性、散射截面积特性以及结合杂波特性的级联抑制问题。针对一阶海杂波的展宽特性问题，首先分析了一阶海杂波的空间分布特性，从理论和仿真角度证明了在回波延时固定的条件下，其分布可以用一个椭圆来描述，并据此进一步得到了Bragg散射频率的计算公式。此外，考虑到杂波单元内双基地角变化所导致的一阶海杂波展宽现象，定量计算了由双基地角所引起展宽的空间分布情况。由仿真结果可以看出，其展宽程度随着接收波束方位角的增大而减少。而关于电离层的非线性相径扰动和多径现象所引起的一阶海杂波展宽问题，本文结合了电离层的粗糙面模型对不同层所引起展宽程度分别进行了计算。结果表明，电离层引起的展宽主要与积累时间、发射波束宽度、电离层相关距离等参数有关。随后，对一阶海杂波幅度统计特性的检验问题，本文采用计算高阶累计量的方法，将一个高斯检验问题转化为一个二元假设问题。首先，基于最大后验概率准则对一阶海杂波进行了分段，得到了一段近似平稳的回波数据，并且对分段后的数据进行了AR模型参数估计，结合AR模型参数以及多个距离门的平稳回波数据，构建三阶、四阶累积量的协方差矩阵并计算检验统计量，结果表明，，在置信概率为95%的门限下，多个距离门回波数据的检验结果服从高斯分布。关于一阶海杂波的散射截面积特性，本文首先推导得到了电离层为球面分层、电子浓度服从准抛物线模型条件下色散系数的计算公式，仿真分析了电离层色散效应对高频窄带信号传播的影响，从匹配滤波角度研究了电离层对距离分辨率的作用，从而进一步得到了其对实际杂波分辨单元的影响，随后以限制杂波单元为参考对实际杂波单元进行了划分，结合Gill提出的双基地散射截面积计算公式，仿真分析了在考虑电离层对杂波分辨单元影响下的一阶海杂波散射截面积。为了对展宽的一阶海杂波进行抑制，本文从实际杂波回波信号成分入手，提出了一种基于EMD分解以及杂波对消的级联抑制处理方案。由算法仿真结果可以看出，EMD分解可以有效提取出展宽的一阶海杂波分量，从而为相径扰动函数的提取提供基础，考虑到锐化后的回波谱一阶海杂波仍然占优，本文随后结合杂波多维特性，提出了一种基于FBLP的杂波对消方法，由对消结果可以看出，一阶海杂波得到了抑制，并且可以有效的检测到目标信号。
[Abstract]:In this paper, the characteristics and suppression of the first order sea clutter under the high-frequency radar landing mode are analyzed and simulated, respectively from the point of view of model building and signal processing. In this paper, the broadening characteristics, statistical characteristics, scattering cross-sectional characteristics and cascaded suppression of first-order sea clutter under the new model are studied. Aiming at the broadening characteristics of first-order sea clutter, the spatial distribution characteristics of first-order sea clutter are analyzed, and the theoretical and simulation results show that the distribution of first-order sea clutter can be described by an ellipse under the condition of fixed echo delay. Furthermore, the formula of Bragg scattering frequency is obtained. In addition, considering the first order sea clutter broadening caused by bistatic angle variation in clutter unit, the spatial distribution caused by bistatic angle broadening is calculated quantitatively. The simulation results show that the broadening degree decreases with the increase of the azimuth of the receiving beam. For the first order sea clutter caused by nonlinear phase diameter disturbances and multipath phenomena in the ionosphere, the degree of broadening caused by the ionospheric rough surface model is calculated separately. The results show that the ionospheric broadening is mainly related to the accumulation time, the emission beam width and the ionospheric correlation distance. Then, in order to test the statistical properties of first-order sea clutter amplitude, a Gao Si test problem is transformed into a binary hypothesis problem by using the method of calculating high-order cumulants. Firstly, the first order sea clutter is segmented based on the maximum a posteriori probability criterion, and an approximate stationary echo data is obtained, and the AR model parameters of the segmented data are estimated. Based on AR model parameters and stationary echo data of multiple distance gates, the covariance matrix of third and fourth order cumulants is constructed and the test statistics are calculated. The results show that the confidence probability is 95%. The test results of multiple distance gate echo data are obtained from the Gao Si distribution. With regard to the scattering cross-sectional characteristics of first-order sea clutter, a formula for calculating the dispersion coefficient of ionosphere with spherical stratification and electron concentration under quasi-parabola model is first derived in this paper. The effect of ionospheric dispersion on the propagation of high frequency narrowband signal is simulated and analyzed. The effect of ionosphere on range resolution is studied from the point of view of matched filtering, and the effect of ionospheric dispersion on the real clutter resolution unit is obtained. Then, the actual clutter element is divided with the limited clutter element as the reference. Combined with Gill's bistatic scattering cross section calculation formula, the first order sea clutter cross section area considering the influence of the ionosphere on the clutter resolution unit is simulated and analyzed. In order to suppress the first order sea clutter, a concatenated suppression scheme based on EMD decomposition and clutter cancellation is proposed. The simulation results show that the EMD decomposition can effectively extract the first order sea clutter component, which provides the basis for the extraction of phase path perturbation function, considering that the first order sea clutter is still dominant after sharpening the echo spectrum. In this paper, a new clutter cancellation method based on FBLP is proposed. The results show that the first-order sea clutter is suppressed and the target signal can be detected effectively.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN958.93

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