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  本文關(guān)鍵詞： 磁共振信號 參考對消算法 能量運算 尖峰噪聲 噪聲相關(guān)性　出處：《地球物理學(xué)報》2016年06期 　論文類型：期刊論文

【摘要】：磁共振探測信號微弱,使用高靈敏度的核磁共振地下水探測儀,極易受到環(huán)境噪聲干擾.其中,工頻諧波噪聲和尖峰噪聲,是影響信號質(zhì)量最嚴(yán)重的兩類噪聲.國內(nèi)外研究表明,通過參考線圈的布設(shè),依據(jù)探測線圈和參考線圈中噪聲相關(guān)性,利用自適應(yīng)參考對消算法,能夠有效抑制工頻諧波噪聲.然而,尖峰噪聲的存在嚴(yán)重影響了主通道與參考道的數(shù)據(jù)相關(guān)性,成為了參考對消算法應(yīng)用的難題與障礙.為解決這一問題,本文提出磁共振信號中尖峰噪聲的抑制方法,推導(dǎo)了能量域磁共振信號表達(dá)式,通過計算信號能量,可有效檢測尖峰噪聲并突出不易識別的小幅度尖峰噪聲,采用基于中位數(shù)的絕對偏差法確定閾值,進(jìn)而剔除尖峰噪聲.為了驗證去噪效果,與應(yīng)用較廣的統(tǒng)計疊加法進(jìn)行對比研究.仿真結(jié)果表明,對于干擾幅度較大、持續(xù)時間較長的尖峰噪聲,能量運算法和統(tǒng)計疊加法均能識別并剔除,且不損失有效的磁共振信號,標(biāo)準(zhǔn)差偏差控制在0.3%以內(nèi),可以滿足實際應(yīng)用的要求;對于小于信號幅度1.5倍的尖峰噪聲,能量運算法可有效識別并剔除,而統(tǒng)計疊加法無法實現(xiàn).針對多通道探測系統(tǒng),使用能量運算法剔除尖峰噪聲后,可明顯提高主通道和參考道的數(shù)據(jù)相關(guān)性,為后續(xù)自適應(yīng)參考對消算法的應(yīng)用奠定了基礎(chǔ).實測數(shù)據(jù)處理結(jié)果進(jìn)一步證明了本文方法的實用性.
[Abstract]:The magnetic resonance detection signal is weak, and the high sensitivity nuclear magnetic resonance groundwater detector is easy to be disturbed by the environmental noise, among which, the power frequency harmonic noise and the peak noise, Domestic and foreign studies show that, according to the noise correlation between the detection coil and the reference coil, the adaptive reference cancellation algorithm is used. However, the existence of peak noise seriously affects the data correlation between the main channel and the reference channel, and becomes a difficult problem and obstacle in the application of the reference cancellation algorithm. In this paper, the suppression method of peak noise in magnetic resonance signal is presented, and the expression of magnetic resonance signal in energy domain is derived. By calculating the signal energy, the peak noise can be effectively detected and the small amplitude peak noise which is not easily recognized can be highlighted. The median based absolute deviation method is used to determine the threshold value, and then the peak noise is eliminated. In order to verify the denoising effect, a comparative study is carried out with the widely used statistical superposition method. The simulation results show that the interference amplitude is large, The long duration peak noise, the energy operation method and the statistical superposition method can be recognized and eliminated, and the effective magnetic resonance signal is not lost, and the standard deviation is controlled within 0.3%, which can meet the requirements of practical application. For the peak noise which is less than 1.5 times the signal amplitude, the energy operation method can effectively identify and eliminate the peak noise, but the statistical superposition method can not be realized. For the multi-channel detection system, the energy operation method is used to eliminate the peak noise. The data correlation between the main channel and the reference channel can be improved obviously, which lays a foundation for the application of the subsequent adaptive reference cancellation algorithm. The experimental data processing results further prove the practicability of the proposed method.
【作者單位】： 吉林大學(xué)儀器科學(xué)與電氣工程學(xué)院/地球信息探測儀器教育部重點實驗室;
【基金】：國家重大科學(xué)儀器設(shè)備開發(fā)和應(yīng)用專項(2011YQ030113) 國家自然科學(xué)基金面上項目(41374075) 吉林省科技重點攻關(guān)項目(20150519008JH,20140204022GX) 中國博士后科學(xué)基金面上項目(2014M561296)聯(lián)合資助
【分類號】：P631.2

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