【摘要】：低空監(jiān)視雷達(dá)在對(duì)低空目標(biāo)進(jìn)行探測(cè)時(shí),由于多徑效應(yīng)的存在,直達(dá)信號(hào)與多徑信號(hào)同時(shí)進(jìn)入天線波束主瓣,兩者矢量疊加,使回波信號(hào)幅度和相位發(fā)生改變。同時(shí)直達(dá)信號(hào)與多徑信號(hào)強(qiáng)烈相干,且難以分辨,嚴(yán)重影響了低空監(jiān)視雷達(dá)對(duì)目標(biāo)的檢測(cè)與跟蹤性能,甚至造成目標(biāo)丟失。因此,如何抑制多徑效應(yīng)對(duì)目標(biāo)檢測(cè)與跟蹤的影響,對(duì)低空監(jiān)視雷達(dá)探測(cè)性能的提升非常重要。本文從多徑效應(yīng)這一關(guān)鍵問題出發(fā),通過建立的低空多徑回波幾何模型,研究了直達(dá)信號(hào)與多徑信號(hào)的幾何關(guān)系。接著分析了影響多徑信號(hào)的反射系數(shù)以及多徑陣列信號(hào)的回波模型,同時(shí)還詳細(xì)介紹了單脈沖測(cè)角原理,并分析了多徑下影響目標(biāo)檢測(cè)概率與低角跟蹤精度的主要因素。然后,以本文建立的理想平面對(duì)稱鏡面反射模型為基礎(chǔ),分析了多徑效應(yīng)對(duì)目標(biāo)檢測(cè)的影響,還研究了多徑下影響低空目標(biāo)回波信號(hào)幅度和功率的主要因素,并推導(dǎo)了低空目標(biāo)回波信號(hào)與多徑傳播因子的關(guān)系。接著對(duì)多徑下低空監(jiān)視雷達(dá)目標(biāo)檢測(cè)方法進(jìn)行了研究,推導(dǎo)并仿真分析了采用頻率分集技術(shù)的多頻M/N檢測(cè)器的檢測(cè)性能曲線,再通過大量實(shí)驗(yàn)仿真,得出了使多頻M/N檢測(cè)器具有最佳檢測(cè)性能時(shí)所對(duì)應(yīng)的M值。接下來(lái),為了降低多徑對(duì)低空監(jiān)視雷達(dá)低角跟蹤性能的影響,本文在多徑陣列信號(hào)模型的基礎(chǔ)上,通過對(duì)天線方向圖進(jìn)行改進(jìn),首先設(shè)計(jì)了最優(yōu)對(duì)稱差波束,進(jìn)而實(shí)現(xiàn)了對(duì)稱波束單脈沖測(cè)角法。接著通過設(shè)計(jì)雙單脈沖的和波束與差波束方向圖,實(shí)現(xiàn)了雙零點(diǎn)單脈沖測(cè)角法。再分別仿真并驗(yàn)證了兩種算法對(duì)解決多徑下低角跟蹤問題的有效性,同時(shí)分析了兩種算法的測(cè)角性能。由于以上兩種改進(jìn)的單脈沖測(cè)角算法均有各自的優(yōu)缺點(diǎn)及應(yīng)用場(chǎng)景,所以最后本文通過對(duì)兩種算法的算法流程、復(fù)雜度以及測(cè)角精度進(jìn)行仿真對(duì)比分析,給出了不同場(chǎng)景下,對(duì)稱波束法與雙零點(diǎn)法的最小SNR與最小可測(cè)仰角表。最后總結(jié)并給出了不同的雷達(dá)場(chǎng)景與精度要求情況下,如何選擇合適的低角跟蹤算法,從而達(dá)到節(jié)省資源,提高低空監(jiān)視雷達(dá)低角跟蹤精度的目的,給實(shí)際工程提供了理論參考。
[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.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN957.51

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