低空监视雷达信号处理方法研究

发布时间：2019-05-07 00:58

【摘要】：低空监视雷达在对低空目标进行探测时,由于多径效应的存在,直达信号与多径信号同时进入天线波束主瓣,两者矢量叠加,使回波信号幅度和相位发生改变。同时直达信号与多径信号强烈相干,且难以分辨,严重影响了低空监视雷达对目标的检测与跟踪性能,甚至造成目标丢失。因此,如何抑制多径效应对目标检测与跟踪的影响,对低空监视雷达探测性能的提升非常重要。本文从多径效应这一关键问题出发,通过建立的低空多径回波几何模型,研究了直达信号与多径信号的几何关系。接着分析了影响多径信号的反射系数以及多径阵列信号的回波模型,同时还详细介绍了单脉冲测角原理,并分析了多径下影响目标检测概率与低角跟踪精度的主要因素。然后,以本文建立的理想平面对称镜面反射模型为基础,分析了多径效应对目标检测的影响,还研究了多径下影响低空目标回波信号幅度和功率的主要因素,并推导了低空目标回波信号与多径传播因子的关系。接着对多径下低空监视雷达目标检测方法进行了研究,推导并仿真分析了采用频率分集技术的多频M/N检测器的检测性能曲线,再通过大量实验仿真,得出了使多频M/N检测器具有最佳检测性能时所对应的M值。接下来,为了降低多径对低空监视雷达低角跟踪性能的影响,本文在多径阵列信号模型的基础上,通过对天线方向图进行改进,首先设计了最优对称差波束,进而实现了对称波束单脉冲测角法。接着通过设计双单脉冲的和波束与差波束方向图,实现了双零点单脉冲测角法。再分别仿真并验证了两种算法对解决多径下低角跟踪问题的有效性,同时分析了两种算法的测角性能。由于以上两种改进的单脉冲测角算法均有各自的优缺点及应用场景,所以最后本文通过对两种算法的算法流程、复杂度以及测角精度进行仿真对比分析,给出了不同场景下,对称波束法与双零点法的最小SNR与最小可测仰角表。最后总结并给出了不同的雷达场景与精度要求情况下,如何选择合适的低角跟踪算法,从而达到节省资源,提高低空监视雷达低角跟踪精度的目的,给实际工程提供了理论参考。
[Abstract]:When low altitude surveillance radar is used to detect low altitude target, the direct signal and multipath signal enter the main lobe of antenna beam at the same time because of the multipath effect, the vector superposition of the two signals causes the amplitude and phase of echo signal to change. At the same time, direct signal and multipath signal are strongly coherent and difficult to distinguish, which seriously affects the detection and tracking performance of low altitude surveillance radar, and even results in the loss of target. Therefore, how to suppress the effect of multipath effect on target detection and tracking is very important to improve the detection performance of low altitude surveillance radar. In this paper, based on the key problem of multipath effect, the geometric relationship between direct signal and multipath signal is studied by establishing the geometric model of multipath echo at low altitude. Then the reflection coefficient of the multipath signal and the echo model of the multipath array signal are analyzed. At the same time, the principle of monopulse angle measurement is introduced in detail, and the main factors affecting the target detection probability and the accuracy of low angle tracking under multi-path are also analyzed. Then, based on the ideal plane symmetric mirror reflection model established in this paper, the influence of multipath effect on target detection is analyzed, and the main factors affecting the amplitude and power of echo signal of low altitude target under multi-path are also studied. The relationship between the echo signal of low altitude target and multipath propagation factor is deduced. Then the target detection method of low altitude surveillance radar with multi-path is studied, and the detection performance curve of multi-frequency MN detector using frequency diversity technology is derived and analyzed by simulation, and then a large number of experiments are carried out to simulate the detection performance of the multi-frequency M ~ (N) detector. The M-value corresponding to the optimal detection performance of the multi-frequency M-N detector is obtained. Next, in order to reduce the influence of multipath on the low-angle tracking performance of low-altitude surveillance radar, based on the multipath array signal model, the antenna pattern is improved, and the optimal symmetric difference beam is designed firstly. Then the symmetrical beam monopulse angle measurement method is realized. Then the double-zero monopulse angle measurement method is realized by designing the sum beam and the difference beam pattern of the double monopulse. Then the effectiveness of the two algorithms to solve the problem of low-angle tracking under multi-path is verified and the angle measurement performance of the two algorithms is analyzed. Because the above two improved monopulse angle measurement algorithms have their own advantages and disadvantages and application scenarios, finally, through the simulation and comparison of the algorithm flow, complexity and angle measurement accuracy of the two algorithms, the different scenarios are given. The minimum SNR and minimum measurable elevation table of symmetric beam method and double zero method. Finally, how to select the appropriate low-angle tracking algorithm under different radar scenes and precision requirements is summarized and given, so as to save resources and improve the low-angle tracking accuracy of low-altitude surveillance radar. It provides a theoretical reference for practical engineering.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN957.51

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