【作者】 姚刚；

【导师】 房旭民；

【作者基本信息】 中国海洋大学 ， 信号与信息处理， 2010， 硕士

【摘要】 爆炸物探测技术在反恐、维护社会安全和战场保障等诸多领域有重要意义,提高爆炸物探测的效率,即提高探测的准确度、降低虚警率、减少探测时间,是爆炸物探测技术研究发展的方向。在诸多爆炸物探测方法中,核电四极矩共振(NQR,Nuclear Quadrupole Resonance)技术依靠探测爆炸物所含元素本质特性而日益受到世人关注。与其他探测方法相比,NQR技术的优势体现在其不但可以判断爆炸物的存在,而且可以确定爆炸物的种类。然而由于NQR信号极其微弱,很易湮灭在噪声和干扰中不易探测,这是制约NQR技术应用的难点。要将NQR技术应用于实际的爆炸物检测中,就必须解决NQR信号的处理问题。为了提取淹没在噪声和干扰背景中的NQR信号,人们采用了多种检测算法,典型算法包括：NQR信号的相干累加、谱分析、自适应滤波、奇异值分解等。然而这些算法对于某些特殊爆炸物探测效率低,实时性不高,限制了NQR技术的应用。所以进一步研究更高效的算法十分必要。小波变换是一种时频分析方法,可以根据信号和噪声的不同特性在不同尺度上进行非线性滤波,在改善信噪比的同时,既有很高的时间(位置)分辨率,而且对信号的形式不敏感。这是传统的滤波方法所无法比拟的,小波变换法特别适用于弱信号的检测和定位。所以可以利用小波阀值去噪的方法对NQR信号进行处理。本文在详细研究了NQR技术原理的基础上,根据NQR信号自身的特性,提出了将小波变换应用于NQR信号处理方法。实验证明,该处理方法有效抑制了振铃拖尾的干扰,缩短了探测时间,提高了探测效率。更多还原

【Abstract】 Explosive detection technology is important in many fields. It can be used to fight against terrorism, protect security of society, protect battlefield, etc.Improving the efficiency of explosive detection means improving the accuracy of detection, reducing false alarm rate and reducing detection time are the development direction of the explosive detection technology.In a number of explosive detection methods, the nuclear quadrupole resonance (NQR, Nuclear Quadrupole Resonance) technique gets more and more attention by the people because it relys on detecting of elements contained in the explosive. Compared with other detection methods, the advantage of NQR technology is that it can not only determine the presence of explosives, but also determine the types of explosive. However, the NQR signal is extremely weak and it is easy to be submerged in the noise and interference.That is the restriction of NQR technology. If we want to make use of NQR technology in the actual project, we must solve the problems in the NQR signal processing.To extract the NQR signal from the context of noise and interference, it has used a variety of detection algorithms, typical algorithms include:NQR signal of coherent accumulation, spectral analysis, adaptive filtering. However, these algorithms are lack of low detection efficiency, and searching more efficient algorithm is very necessary.Wavelet transform is a time-frequency analysis mothod, it can take nonlinear filtering according to the different characteristics of signal and noise in different scales, so that it can improve signal to noise ratio. Wavelet transform mothod have high time(position) resolution, and is not sensitive to the signal form.This is the traditional filtering methods can not achieve, the wavelet transform method is suitable for weak signal detection and signal location particularly. So we can use the threshold method of wavelet transform to processing the NQR signal.In this paper, research the principle of NQR technology, a wavelet transform method is used in NQR signal processing based on the characteristics of NQR signal. Experiments show that the processing algorithm can effectively eliminate background noise, interference suppression of the ring, and increase the detection efficiency.更多还原