【作者】 娄扬；

【导师】 赵犁丰； 赵振维；

【作者基本信息】 中国海洋大学 ， 通信与信息系统， 2008， 硕士

【摘要】 近年来,由于国际形势的变化,恐怖活动日渐猖獗,为减少恐怖事件的发生,各国纷纷大力提升安全防范设备的技术水平,安全检查中对炸药的检测尤为重要。核四极矩共振技术由于找到了类似人类指纹特征的炸药本质特性而日益成为安全领域专家关注的焦点。利用常见的炸药中均含有N14的特点,将核四极矩共振技术应用于炸药检测,不仅可以准确地判断炸药的存在,而且可以检测出是何种炸药。但是核四极矩共振信号极其微弱,很容易湮没在噪声和干扰当中,因此,要将核四极矩共振技术应用于实际的炸药检测中,就必须解决核四极矩共振信号的处理问题。本文在核四极矩共振技术原理的基础上,深入分析了核四极矩共振信号自身的特性,对NQR信号处理方法进行了研究:1、针对核四极矩共振信号存在严重的振铃拖尾干扰,设计了自适应抵消器,有效抑制了振铃拖尾,提高了NQR信号的信噪比;2、针对传统的离散傅立叶变换应用于频谱分析,存在截断效应,造成主瓣泄漏和频谱间干扰,降低了信号探测准确性的缺点。本文运用经典功率谱估计对NQR信号进行了处理,有效抑制了泄漏和谱间干扰,提高了探测的准确度;3,选取高性能的DSP芯片TMS320C6713将核四极矩共振信号处理算法编程实现,并应用于核四极矩共振炸药探测系统样机中,提高了核四极矩共振信号的提取和识别能力。更多还原

【Abstract】 In recent years, all kinds of terrorisms are gradually prevailing in the world because of the changes of international situation. In order to reduce the occurrence of the terrible events, all countries are promoting their technologies to make sure safety. It is especially important to detect explosives in the field of the security inspection. A new method, Nuclear Quadrupole Resonance (NQR), is able to detect whether there are explosives in a packet, easily and exactly. Many experts in the word are attaching importance to it, and have worked much on it.All kinds of explosives contain a chemical element, 14N. This characteristic can be used for Nuclear Quadrupole Resonance to detect explosives. This method not only tells the existing of explosives, but also the sort. The Nuclear Quadrupole Resonance signal is rather weak, and it is hard to extract it from background interference and noise, which is limiting the application of the technology. Some difficult problems about the processing of Nuclear Quadrupole Resonance signal must be solved before the technology is applied to detect explosives in practice. Based on the principles of Nuclear Quadrupole Resonance, this article puts forward some useful methods about signal processing according to the characteristic of NQR signal.There is very serious interference (so-called ringing), an adaptive filter is designed to kill the ringing effectively. The signal-to-noise ratio of NQR signal is remarkably increased.Leakage of major lobe and interference between consecutive spectrums come into being when a long sequence is cut down in the course of DFT, which reduced the accuracy of signal processing. A method of classic power spectral estimation is applied to eliminate these leakage and interference; as a result, the accuracy of detecting explosives is improved greatly.A high performance DSP chip TMS320C6713 is used as a platform to accomplish the complicated algorithm of signal processing. It has proven that background noise is effectively cut down, and serious interference is killed. The aim of researching a sample machine of detecting explosives is accomplished, which is a good effort to apply NQR theory to practice.更多还原