本文選題：Bragg散射頻率 + 高階累積量��； 參考：《哈爾濱工業(yè)大學(xué)》2014年碩士論文

【摘要】：本文針對(duì)高頻雷達(dá)天發(fā)岸收模式下一階海雜波的特性與抑制這一問(wèn)題進(jìn)行了深入分析和仿真研究，其中分別從模型建立和信號(hào)處理兩個(gè)角度，重點(diǎn)研究了新模式下一階海雜波的展寬特性、統(tǒng)計(jì)特性、散射截面積特性以及結(jié)合雜波特性的級(jí)聯(lián)抑制問(wèn)題。 針對(duì)一階海雜波的展寬特性問(wèn)題，首先分析了一階海雜波的空間分布特性，從理論和仿真角度證明了在回波延時(shí)固定的條件下，其分布可以用一個(gè)橢圓來(lái)描述，并據(jù)此進(jìn)一步得到了Bragg散射頻率的計(jì)算公式。此外，考慮到雜波單元內(nèi)雙基地角變化所導(dǎo)致的一階海雜波展寬現(xiàn)象，定量計(jì)算了由雙基地角所引起展寬的空間分布情況。由仿真結(jié)果可以看出，其展寬程度隨著接收波束方位角的增大而減少。而關(guān)于電離層的非線性相徑擾動(dòng)和多徑現(xiàn)象所引起的一階海雜波展寬問(wèn)題，本文結(jié)合了電離層的粗糙面模型對(duì)不同層所引起展寬程度分別進(jìn)行了計(jì)算。結(jié)果表明，電離層引起的展寬主要與積累時(shí)間、發(fā)射波束寬度、電離層相關(guān)距離等參數(shù)有關(guān)。 隨后，對(duì)一階海雜波幅度統(tǒng)計(jì)特性的檢驗(yàn)問(wèn)題，，本文采用計(jì)算高階累計(jì)量的方法，將一個(gè)高斯檢驗(yàn)問(wèn)題轉(zhuǎn)化為一個(gè)二元假設(shè)問(wèn)題。首先，基于最大后驗(yàn)概率準(zhǔn)則對(duì)一階海雜波進(jìn)行了分段，得到了一段近似平穩(wěn)的回波數(shù)據(jù)，并且對(duì)分段后的數(shù)據(jù)進(jìn)行了AR模型參數(shù)估計(jì)，結(jié)合AR模型參數(shù)以及多個(gè)距離門的平穩(wěn)回波數(shù)據(jù)，構(gòu)建三階、四階累積量的協(xié)方差矩陣并計(jì)算檢驗(yàn)統(tǒng)計(jì)量，結(jié)果表明，在置信概率為95%的門限下，多個(gè)距離門回波數(shù)據(jù)的檢驗(yàn)結(jié)果服從高斯分布。 關(guān)于一階海雜波的散射截面積特性，本文首先推導(dǎo)得到了電離層為球面分層、電子濃度服從準(zhǔn)拋物線模型條件下色散系數(shù)的計(jì)算公式，仿真分析了電離層色散效應(yīng)對(duì)高頻窄帶信號(hào)傳播的影響，從匹配濾波角度研究了電離層對(duì)距離分辨率的作用，從而進(jìn)一步得到了其對(duì)實(shí)際雜波分辨單元的影響，隨后以限制雜波單元為參考對(duì)實(shí)際雜波單元進(jìn)行了劃分，結(jié)合Gill提出的雙基地散射截面積計(jì)算公式，仿真分析了在考慮電離層對(duì)雜波分辨單元影響下的一階海雜波散射截面積。 為了對(duì)展寬的一階海雜波進(jìn)行抑制，本文從實(shí)際雜波回波信號(hào)成分入手，提出了一種基于EMD分解以及雜波對(duì)消的級(jí)聯(lián)抑制處理方案。由算法仿真結(jié)果可以看出，EMD分解可以有效提取出展寬的一階海雜波分量，從而為相徑擾動(dòng)函數(shù)的提取提供基礎(chǔ)，考慮到銳化后的回波譜一階海雜波仍然占優(yōu)，本文隨后結(jié)合雜波多維特性，提出了一種基于FBLP的雜波對(duì)消方法，由對(duì)消結(jié)果可以看出，一階海雜波得到了抑制，并且可以有效的檢測(cè)到目標(biāo)信號(hào)。
[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.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN958.93

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