【作者】 王军；

【导师】 乔晓林；

【作者基本信息】 哈尔滨工业大学 ， 信号与信息处理， 2006， 硕士

【摘要】 扫描雷达扫过目标时接收的回波脉冲受到天线方向图的调制,造成天线方向图损失。为了充分利用回波能量,提高雷达的检测能力,需要对多个回波脉冲进行加权积累,扫描雷达一般使用检波后的非相参积累(视频积累),最佳积累加权系数与天线方向图成正比。雷达检测器(也称积累器)可以完成对雷达回波信号的加权积累,在反舰导弹末制导雷达上得到广泛应用。本文首先研究了现有几种实用检测器,分析了它们的原理,检测能力,稳定性和对于目标方位估计的精度,并给出了各检测器的实现方法。当仅有噪声输入线性时不变系统时,其输出的概率密度分布难以得到,本文实现了利用离散化的方法得到其输出概率密度分布的近似,从而使某虚警概率下的检测门限值确定变得简单。为了获得更好的积累性能,本文提出了一种新的IIR检测器—三极点滤波器,它是用并联结构来实现的,其运算速度快,积累误差小。遗传算法是一种随机搜索算法,不会陷入局部极值,能够得到全局最优解,在参数优化问题得到广泛应用。三极点滤波器通过遗传算法对其系数进行优化,实现了其单位脉冲响应对最佳积累加权的逼近。在系数优化过程中,使用一种新的时域适应度函数来评价三极点滤波器单位脉冲响应对于最佳积累加权的近似程度,实现了在时域优化设计IIR滤波器。为了对不同检测器的信噪比改善情况进行比较,本文引入了一种输出信噪比的计算方法,并给出了IIR滤波器的输出噪声方差的计算公式。本文在统一的输出信噪比定义下,给出了各检测器输出信噪比的理论分析结果。对于非起伏和脉间瑞利起伏目标两种情形下,通过蒙特卡罗仿真分析了实用检测器的检测性能和对目标方位的估计精度,并给出了分析结果,这些结果可以作为实际工程应用的参考。分析结果表明,三极点滤波器比双极点滤波器在输出信噪比,稳定性上都得到了提高,对目标的方位估计精度略优于双极点滤波器,获得了性能上的整体提高。最后,本文还针对于遗传算法的进化速度进行了研究,引入单纯形交叉策略;发现了传统交叉策略的缺陷,提出一种新的遗传交叉策略—继承交叉策略。仿真结果表明继承交叉策略能够使遗传进化速度加快,本文还给出了继承与单纯形交叉策略的适用范围。更多还原

【Abstract】 During a scan of pulsed scanning radar, the returns are a train of pulses modulated by the antenna beam shape which is normally referred to as antenna beam-shape loss, therefore the radar detection performance is reduced. To use all energy of target returns, non-coherent(video) integration is often implemented after the envelope detector to improve the radar sensitivity. The optimum integration weighting is proportional to antenna gain.Radar detectors (integrators) can accomplish pulsed integration and are commonly employed in terminal guided radar of anti-ship missile. Some detectors which are commonly put into practice are firstly analyzed with their fundamentals, detection capability, stability and angular accuracy and then the realization of these detectors are presented. A new discrete method is provided to get the approximation PDF of system output because the output PDF is difficultly obtained when a linear shift invariant system is excited with noise only. So, the detection threshold can be easily obtained on the basis of the PDF of output system.To improve the performance of radar integration, a novel tri-pole filter is proposed as a video integrator which is implemented using parallel form structure because of its faster running and less integration error than other structures. The genetic algorithm (GA) is a stochastic searching method which provides global search capability and avoids local minima problem. Coefficients optimization of tri-pole filter is accomplished using GA in order that the tri-pole filter’s impulse response can approximate optimum weighting. A new fitness function in time domain is presented which is used to evaluate the similarity between the impulse response of tri-pole filter and optimum integration weighting. Consequently, the design of IIR filter in time domain is realized using this fitness function.For the sake of needs of comparison with output SNR in different radar detectors, a unitized output SNR definition is introduced and a formula through which the output variance of IIR filter can be calculated is presented. Subsequently, the theoretical analysis results of all radar detectors are given更多还原