發(fā)布時間：2018-04-14 15:37

  本文選題：空時自適應處理 + 降維�。� 參考：《西安電子科技大學》2015年博士論文

【摘要】：具有靈活機動、覆蓋范圍大等優(yōu)點的機載預警雷達在現代化的戰(zhàn)爭中發(fā)揮著重要作用。但是,由于載機快速移動,機載雷達面臨著比地基雷達更加復雜的雜波環(huán)境。在空域和時域聯(lián)合抑制雜波的空時自適應處理方法(Space-time adaptive processing,STAP)能有效抑制機載雷達雜波并檢測到目標。但是,在實際應用中,全維STAP方法會產生計算量大和訓練樣本需求量高的問題。而這些問題進一步促進了一些次優(yōu)的降維或者降秩STAP方法的發(fā)展。由于實際環(huán)境中缺少獨立同分布的訓練樣本,因此到目前為止,還沒有哪一種降維或者降秩STAP方法能夠有效的應用到實際的機載雷達中。因此,考慮到實際環(huán)境中有限的訓練樣本數量以及雷達系統(tǒng)實時處理的需求,本文研究了具有計算量小、訓練樣本數需求量少等優(yōu)點的降維STAP方法。在空時自適應處理之前對雜波進行預濾波處理可以有效的減少雜波自由度(Degrees of freedom,Do Fs),這樣的預處理能提高后續(xù)STAP方法的性能,因為自適應處理器有了更多的自由度來檢測目標。因此,我們根據雜波模型,研究了計算復雜度低、不受訓練樣本影響的機載雷達非自適應雜波預濾波方法。我們的工作主要包括以下幾個方面:1.為了提高后多普勒自適應處理方法在大陣列條件下的雜波抑制和動目標檢測能力,我們提出了一種基于空域分解的后多普勒自適應處理方法。首先將接收到的雜波和目標數據經過多普勒濾波,將濾波后的空域數據分解,然后將FA或者EFA的權系數表示成分離的形式,從而得到一雙二次代價函數,然后利用循環(huán)迭代的思想求解權系數。實驗表明該方法具有快速收斂性,在小樣本、大陣列條件下該方法明顯優(yōu)于因子法和擴展因子法。2.由于機載MIMO雷達采用較小的天線規(guī)模即可形成很大的虛擬陣列孔徑,并且具有高角度分辨率和強雜波抑制能力,近些年來受到了廣大研究者和工程人員的極大關注。但是由于機載MIMO雷達系統(tǒng)自由度過高,相對于傳統(tǒng)機載相控陣雷達STAP方法,MIMO-STAP將會需要更多的訓練樣本數和計算量。因此,我們研究了一種能大幅降低MIMO-STAP所需訓練樣本數和計算量的兩級空域分解方法。該方法首先將接收到的雜波和目標數據經過多普勒濾波,將自適應權系數進行分解,使其變?yōu)閹讉�向量的Kronecker乘積,然后利用循環(huán)迭代的思想求解自適應權。實驗表明該方法具有快速收斂性,在小樣本大陣列條件下該方法明顯優(yōu)于傳統(tǒng)的后多普勒處理方法。3.機載雷達兩維兩脈沖對消器(Two-dimension pulse-to-pulse canceller,TDPC)能有效的沿著雜波跡抑制雜波而對目標信號沒有影響,并且后續(xù)級聯(lián)STAP方法,能有效提高STAP方法的動目標檢測性能,不僅適用于正側視機載雷達,也適用于非正側視機載雷達。而且該方法僅僅利用雷達工作參數和載機速度等先驗知識,濾波器系數可以提前計算好,具有計算量小不受訓練樣本影響的優(yōu)點。但是實際中,受到各種因素的影響,估計的雷達參數有可能會和實際存在較大的誤差。因此,考慮到參數誤差的影響,我們研究了一種穩(wěn)健的TDPC(Robust TDPC,RTDPC)方法。該方法考慮了實際中參數估計的誤差,利用雷達參數、載機平臺速度等信息設計雜波預濾波器以抑制大部分雜波,剩余的少量雜波可由發(fā)展成熟的降維空時自適應處理方法進行抑制。該方法增強了原TDPC方法在參數存在誤差情況下的穩(wěn)健性,進一步提高了TDPC方法的實用性。4.由于接收載機平臺和發(fā)射載機平臺之間復雜的幾何配置,機載雙基地雷達雜波呈現強烈的距離依賴性,空時自適應處理(STAP)所需要的雜波協(xié)方差矩陣的估計誤差變大,這直接會導致STAP算法檢測性能的惡化。針對這一問題,提出了一種機載雙基地雷達雜波預濾波方法。該方法考慮了實際中載機速度的估計與真實速度的誤差,利用雷達系統(tǒng)參數、載機平臺速度等信息設計雜波預濾波器抑制大部分雜波,剩余的少量雜波可由發(fā)展成熟的空時自適應處理算法進行抑制,進而提高STAP算法的動目標檢測能力。計算機仿真實驗表明,該方法能有效的對幾種典型幾何配置下的機載雙基地雷達雜波進行抑制,降低雜波自由度,后續(xù)級聯(lián)能進一步改善STAP算法的動目標檢測性能。5.在空時自適應處理中,相對于處理器自由度,雜波協(xié)方差矩陣是低秩的。根據這一原理,提出了一種利用低秩雜波子空間的雜波對消器(LRCC)以抑制地面強雜波,該方法利用相對較少的線性無關空時導向矢量構造出原雜波,然后再對消相鄰脈沖間的雜波回波。該雜波對消器可以作為預濾波器和傳統(tǒng)空時匹配或者空時自適應算法級聯(lián)以增強后續(xù)動目標檢測算法的性能。仿真結果表明,該方法在正側視和非正側視機載雷達中能有效抑制地雜波而對動目標信號沒有影響。該雜波對消器作為預濾波器,可以提高后續(xù)空時匹配或空時自適應處理算法的動目標檢測性能。
[Abstract]:With flexible, airborne early warning radar coverage range and other advantages play an important role in the modern war. However, because the plane moving fast, facing the airborne radar clutter environment is more complex than the ground-based radar. Adaptive processing method combined clutter suppression of air in space and time when (Space-time adaptive processing. STAP) can effectively inhibit the airborne radar clutter and detect targets. However, in practical application, full dimensional STAP method will have problems of large amount of calculation and training demand. And these problems to further promote the development of some sub optimal dimensionality reduction or reduced rank STAP method. Due to the lack of independent and identical distribution the actual environment of the training samples, so far, there is not any reduction or reduced rank STAP method can be effectively applied to airborne radar in practical. Therefore, considering the actual ring Exit in the limited number of training samples and the real-time processing of radar system, we have investigated the small amount of calculation and dimension reduction STAP method has the advantages of less demand. The number of training samples before the space-time adaptive processing for clutter filter can effectively reduce the clutter degree of freedom (Degrees of, freedom, Do Fs), this pretreatment could improve the performance of the subsequent STAP method, because the adaptive processor has more freedom to detect targets. Therefore, we according to the clutter model of airborne radar with low computational complexity, without training effect of non adaptive clutter filtering method. Our main work includes the following several aspects: 1. in order to improve after Doppler adaptive processing method in array under the condition of clutter suppression and moving target detection, we propose a domain decomposition based on Doppler Adaptive processing method. Firstly, the received clutter and target data through the Doppler filter, spatial data after filtering decomposition, and then the right coefficient of FA or EFA into the form of separation, so as to get a pair of two times the cost function, and then solving the weight coefficient by cyclic iterative method. Experimental results show that the method with fast convergence, in the small sample, a large array under the condition of the method is better than factor method and expansion factor method.2. the antenna airborne MIMO radar using small scale to form a virtual array aperture greatly, and has high angular resolution and strong ability to suppress clutter, in recent years has attracted great attention of many researchers and engineering the airborne MIMO radar system. But because of the degree of freedom is too high, compared with the traditional STAP method for airborne phased array radar, MIMO-STAP will need more training samples and calculation Volume. Therefore, we study a kind of MIMO-STAP can significantly reduce the required number of training samples and the amount of calculation of two spatial decomposition method. Firstly, the received clutter and target data through the Doppler filter, the adaptive weighting coefficients of decomposition, so that it becomes a product of several Kronecker vector, and then use the thought to solve the adaptive weight iteration. The experiments show that this method has fast convergence, in the method of Doppler treatment is obviously superior to the traditional method of small sample of the large array of.3. under the conditions of the airborne radar two dimensional two pulse canceller (Two-dimension pulse-to-pulse, canceller, TDPC) can effectively suppress the clutter clutter along the track and have no effect on the target signal, and the subsequent cascade STAP method, STAP method can effectively improve the target detection performance, not only for the Yu Zheng side looking airborne radar, is also suitable for the non side looking airborne radar Da. And this method only uses radar parameters and aircraft speed prior knowledge, the filter coefficients can be calculated in advance, has the advantages of small calculation amount is not affected by the influence of the training samples. But in practice, the influence of various factors, the radar parameter estimation may and the actual errors. Therefore, considering the influence of parameter errors, we study a robust TDPC (Robust TDPC RTDPC) method. This method considers the error estimation parameters, using radar parameters, aircraft speed and other information platform design clutter pre filter to suppress most clutter, a small amount of residual clutter may be reduced by the development of mature STAP method for suppression. The method enhances the original TDPC method under the condition of error robustness in parameter, further improve the practicability of.4. TDPC method for receiving aircraft platform And the launch vehicle complex geometric configuration platform between airborne bistatic radar clutter has a strong dependence on distance, space-time adaptive processing (STAP) error estimation of the clutter covariance matrix to change, this will directly lead to deterioration of the detection performance of the STAP algorithm. This paper proposes a airborne bistatic radar clutter filtering method. This method considers the error estimation of actual load machine speed and actual speed, the use of radar system parameters, aircraft speed and other information platform design clutter pre filter to suppress most clutter, a small amount of residual clutter may be developed by space-time adaptive processing algorithm inhibition, and improve the target detection ability of STAP algorithm. Simulation results show that this method can be effective for some typical configurations of the airborne bistatic radar clutter suppression, reducing clutter The wave of freedom, will further improve the subsequent level STAP algorithm.5. moving target detection performance in space-time adaptive processing, relative to processor freedom, the clutter covariance matrix is low rank. According to this principle, proposes the use of a low rank clutter subspace clutter canceller (LRCC) to suppression of the strong ground clutter, the method using linear relatively independent space-time steering vector to construct the original clutter cancellation, then adjacent pulses between clutter. The clutter canceller can be used as a pre filter and the traditional space-time matching or space-time adaptive algorithm to enhance the performance of target follow-up cascade detection algorithm. The simulation results show that this method is in the side and non side looking airborne radar can effectively suppress the ground clutter and moving target signal has no effect. The clutter canceller as a pre filter, can increase the space time, or empty The dynamic target detection performance of time adaptive processing algorithm.

【學位授予單位】：西安電子科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TN957.51;TN713

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