發(fā)布時(shí)間：2018-04-22 19:15

  本文選題：X波段雷達(dá) + 色散關(guān)系　； 參考：《哈爾濱工程大學(xué)》2014年碩士論文

【摘要】：海浪是一種十分復(fù)雜的自然現(xiàn)象,研究海浪的物理信息對(duì)海洋工程建設(shè)與發(fā)展、海洋能源探索與挖掘、交通運(yùn)輸、海洋捕撈等都具有重大的意義。對(duì)于海浪的監(jiān)測(cè)起源于20世紀(jì)50年代初,而近20年里基于X波段雷達(dá)圖像的海洋參數(shù)反演研究備受矚目。在平臺(tái)處于靜態(tài)環(huán)境下監(jiān)測(cè)海浪已經(jīng)取得顯著成效的同時(shí),如何處理動(dòng)態(tài)環(huán)境帶來的新問題,成為本文的重要研究方向。本文以在研項(xiàng)目為依托,對(duì)由于船速過大導(dǎo)致多普勒頻移、色散關(guān)系濾波器帶通不合適、頻率混疊等問題展開進(jìn)一步分析,并提出解決方案。首先,雷達(dá)平臺(tái)運(yùn)動(dòng)時(shí),增強(qiáng)了多普勒效應(yīng),多普勒效應(yīng)令海浪功率譜發(fā)生頻移。此時(shí)現(xiàn)有的基于色散關(guān)系的帶通濾波器會(huì)保留幾乎全部的圖像譜能量,無法起到濾波效果。本文針對(duì)這一問題,構(gòu)造一種新的帶通濾波器,該濾波器與傳統(tǒng)濾波器具有相同的時(shí)間復(fù)雜度;通過實(shí)驗(yàn)證明該濾波器不僅在動(dòng)態(tài)環(huán)境下可以保留海浪的主要能量,在岸基實(shí)驗(yàn)下同樣可以濾除更多的非海浪噪聲。反演結(jié)果滿足精度要求,且與WAMOS、WAVEX測(cè)量結(jié)果相近。其次,本文實(shí)驗(yàn)中所用雷達(dá)轉(zhuǎn)速不能滿足動(dòng)態(tài)環(huán)境下的反演要求,導(dǎo)致信號(hào)在時(shí)間域欠采樣的產(chǎn)生,從而發(fā)生頻譜混疊現(xiàn)象。本文利用雷達(dá)海上試驗(yàn)參數(shù)分析混疊的產(chǎn)生機(jī)理,并計(jì)算出發(fā)生混疊的海浪參數(shù)與采樣頻率之間的關(guān)系和導(dǎo)致混疊現(xiàn)象發(fā)生的雷達(dá)平臺(tái)相對(duì)于海浪的最小速度。隨后,找到海浪頻率譜的混疊方式,并借助傅里葉變換性質(zhì)重構(gòu)原始色散關(guān)系曲面。導(dǎo)航雷達(dá)反演的海面信噪比與有效波高真值的數(shù)據(jù)量分布不均勻會(huì)導(dǎo)致波高的擬合系數(shù)不準(zhǔn)確,這是一直難以解決的問題。本文最后針對(duì)這一問題設(shè)計(jì)了一個(gè)新的漸近線回歸方法,利用該方法可模擬大海浪下信噪比的開方與有效波高的比值并生成新的擬合系數(shù),通過仿真實(shí)驗(yàn)證明該方法生成的波高在理論范圍內(nèi)。且利用已有數(shù)據(jù)對(duì)該方法進(jìn)行驗(yàn)證,證明該方法對(duì)原數(shù)據(jù)點(diǎn)的模擬度高,仿真結(jié)果符合波高數(shù)據(jù)的分布和變化規(guī)律。
[Abstract]:Ocean wave is a very complicated natural phenomenon. It is of great significance to study the physical information of ocean wave for the construction and development of ocean engineering, exploration and excavation of ocean energy, transportation, marine fishing and so on. The ocean wave monitoring originated in the early 1950s, but in the last 20 years, the ocean parameter inversion based on X-band radar image has attracted much attention. While the platform has achieved remarkable results in monitoring waves under static environment, how to deal with the new problems brought by dynamic environment has become an important research direction in this paper. In this paper, based on the research project, the problems of Doppler frequency shift, inappropriate bandpass of dispersive filter and frequency aliasing due to excessive ship speed are analyzed, and solutions are put forward. Firstly, the Doppler effect is enhanced when the radar platform is moving, and the wave power spectrum is shifted frequently by the Doppler effect. In this case, the existing bandpass filter based on dispersion relation will retain almost all of the spectral energy of the image, and can not play a filtering effect. In this paper, a new bandpass filter is constructed, which has the same time complexity as the traditional filter, and it is proved by experiments that the filter can not only retain the main wave energy in the dynamic environment. More non-wave noise can also be removed in shore-based experiments. The inversion results meet the requirements of accuracy and are close to the WAVEX measurements. Secondly, the radar speed used in the experiments in this paper can not meet the inversion requirements in the dynamic environment, which leads to the generation of under-sampling signals in time domain, thus the phenomenon of spectrum aliasing occurs. In this paper, the mechanism of aliasing is analyzed by using radar sea test parameters, and the relationship between ocean wave parameters and sampling frequency is calculated, and the minimum velocity of radar platform relative to ocean waves which leads to the occurrence of aliasing is calculated. Then, the aliasing mode of wave frequency spectrum is found, and the original dispersion relation surface is reconstructed by Fourier transform. The inhomogeneous distribution of sea surface signal to noise ratio (SNR) and the true value of effective wave height in navigation radar will result in the inaccuracy of the fitting coefficient of wave height, which is always difficult to solve. At last, a new asymptote regression method is designed to solve this problem, which can be used to simulate the ratio of signal-to-noise ratio (SNR) to effective wave height and to generate a new fitting coefficient. The simulation results show that the wave height generated by this method is within the theoretical range. The method is verified by the existing data, and it is proved that the method has a high degree of simulation to the original data points, and the simulation results accord with the distribution and variation law of the wave height data.
【學(xué)位授予單位】：哈爾濱工程大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：P714.1

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本文編號(hào)：1788547