NQR炸药检测系统中激励脉冲拖尾的抑制

介绍了核四极矩共振（Nuclear Quadrupole Resonance简称NQR）炸药检测系统的基本原理及检测过程中面临的如何消除激励脉冲信号拖尾对NQR检测信号的影响问题. 文中采用了在发射电路中增加消振铃电路来消除激励脉冲拖尾的方法，并给出了电路分析和实验结果. 经实际应用验证，该种方法对消除激励脉冲拖尾具有较好的效果，提高了系统的探测能力.     

基于核四极矩共振原理的炸药探测方法研究与实验

介绍了一种基于核四极矩共振（Nuclear Quadrupole Resonance, NQR）原理的炸药探测方法及其基本原理和其用于炸药探测的依据,提出了一种可行的基于核四极矩共振原理的炸药检测系统,描述了其结构组成、工作原理及实验方法,并给出了对黑索金（RDX）、梯恩梯（TNT）、奥克托今（HMX）、太恩（PETN）和特屈儿（TETRYL）炸药的测试实验结果. 实验表明该方法可行,能实现对以上炸药的探测.     

基于Apollo信号控制台的NQR炸药探测方法

介绍了一种基于Apollo信号控制台的核四极矩共振（NQR）炸药探测方法，描述了系统的结构组成、工作原理和实现方法，并给出了对RDX的测试试验结果. 试验表明该方法可实现对RDX信号的探测.     

相位可控的核四极矩共振激励脉冲发生器设计

在核四极矩共振（NQR）领域，射频激励脉冲信号的优劣对NQR响应信号有重要影响.针对常规方法中射频激励脉冲参数不可控的问题，本文基于32位闪存微型控制器STM32和直接数字频率合成（DDS）芯片AD9910设计了一种相位可控激励脉冲发生器.采用STM32控制AD9910产生波形参数（脉冲宽度、脉冲间隔、脉冲个数和共振频率等）可控的射频激励脉冲，利用LabVIEW软件平台设计脉冲参数设置界面，并建立计算机与微控制器通信，实现波形参数的精确优化控制.实验结果表明，该方法实现了相位可控的NQR激励脉冲序列，可为后续NQR信号检测提供有效激励源.     

一种改进的微弱NQR信号检测算法

核四极矩共振（NQR）是一种固态射频谱分析技术,可用于检测高危险爆炸物. 然而NQR信号本身非常弱,并且易受线圈的热噪声和外部射频干扰的影响,低信噪比限制了NQR的实际应用. 该文提出一种改进的微弱NQR信号检测算法. 首先利用Hankel矩阵方式下奇异值分解的方法,有效地抑制射频干扰和噪声,并将NQR信号分离出来. 然后提出了一种基于MUSIC谱估计的非线性最小二乘检测器,它既保证了高的频率分辨率,又大大降低了运算量. 仿真数据和实测数据结果表明该算法的有效性.     

自制简易核四极共振谱仪

一、前言自1950年德国哥廷根大学的Dehmelt和Kr(?)ger发现~(35)Cl、~(37)Cl的核四极共振信号,到现在已37年.由于核四极共振信号比核磁共振信号弱得多,实验上灵敏度很低,对于生物学上很有意义的~(14)N、~2D、~(17)O等无法检测,使得核四极共振的理论和技术的发展停滞不前.但近年来“核磁——核四极”双     

氮－14远程核四极共振谱仪

为了满足检测与探头有一定距离的含氮化合物的核四极共振信号，本文研制了一台结构简单，造价低廉的核四极共振操测仪．它利用了脉冲付里叶变换技术，可将获得的核自由感应衰减信号或者回波信号进行相干累加．整个系统分硬件和软件两大部分．前者由射频脉冲放大器（约５００Ｗ脉冲输出功率），探头，接收机，ＭＣＳ－９６型单片机和ＰＣ机构成．后者由单片机上的脉冲序列程序与ＰＣ机上的数值信号处理程序组成．利用这台谱仪，可以在几十秒时间内得到距离探头线圈１０ｃｍ内的典型￣（１４）Ｎ样品的核四极共振谱．     

基于软件无线电技术的核四极矩共振谱仪设计

介绍了软件无线电技术的基本原理， 分析了全数字化核四极矩共振谱仪的设计要求，讨论了设计时在软件、硬件方面的一些考虑，给出了基于软件无线电技术的全数字化核四极矩共振谱仪设计一个实例.     

基于小波阀值消噪的硝铵NQR信号处理

针对硝铵（AN）核电四极矩共振（NQR）信号通过傅立叶变换频域分析缺乏信号时域信息的特点,对硝铵NQR信号进行时频分析,达到从强背景噪声下检测出NQR信号的目的. 引入小波分析阀值去噪的方法对硝铵NQR信号进行处理. 对处理后数据与标准信号之间的相关系数进行分析. 实验结果表明小波阀值去噪方法可以成功检测到硝铵的NQR信号.     

氮-14远程核四极共振谱仪

为了满足检测与探头有一定距离的含氮化合物的核四极共振信号,本文研制了一台结构简单,造价低廉的核四极共振操测仪.它利用了脉冲付里叶变换技术,可将获得的核自由感应衰减信号或者回波信号进行相干累加.整个系统分硬件和软件两大部分.前者由射频脉冲放大器(约500W脉冲输出功率),探头,接收机,MCS-96型单片机和PC机构成.后者由单片机上的脉冲序列程序与PC机上的数值信号处理程序组成.利用这台谱仪,可以在几十秒时间内得到距离探头线圈10cm内的典型¹⁴ N样品的核四极共振谱.     

Optimal filtering in multipulse sequences for nuclear quadrupole resonance detection

The application of the multipulse sequences in nuclear quadrupole resonance (NQR) detection of explosive and narcotic substances has been studied. Various approaches to increase the signal to noise ratio (SNR) of signal detection are considered. We discussed two modifications of the phase-alternated multiple-pulse sequence (PAMS): the 180° pulse sequence with a preparatory pulse and the 90° pulse sequence. The advantages of optimal filtering to detect NQR in the case of the coherent steady-state precession have been analyzed. It has been shown that this technique is effective in filtering high-frequency and low-frequency noise and increasing the reliability of NQR detection. Our analysis also shows the PAMS with 180° pulses is more effective than PSL sequence from point of view of the application of optimal filtering procedure to the steady-state NQR signal.     

Feedback optimization of pulse width in the SORC sequence.

A method for increasing the signal-to-noise ratio (SNR) of nuclear quadrupole resonance (NQR) measurements by automatically adjusting a pulse parameter in real-time is presented. This approach is useful in situations where the optimal pulse parameters cannot be chosen beforehand due to lack of knowledge regarding the system. For example, NQR provides a means for detecting explosives by revealing the presence of (14)N. In this particular application, the distance between the search coil and the explosive, as well as the temperature of the explosive, is unknown. As a result, a fixed set of pulse parameters will not yield the largest SNR for all possible search applications. This paper describes a feedback algorithm that uses measurements of the NQR signal to automatically adjust the pulse width in the strong off-resonant comb sequence to maximize the SNR of the NQR measurement. Experimental results obtained using a sample of sodium nitrite are presented.     

PETN炸药NQR信号处理方法

利用核四极共振(Nuclear Quadrupole Resonance, NQR)原理探测隐藏炸药,具有准确率高、误报率低、无放射性沾染和防护问题等优点. 但NQR信号十分微弱,湮没在噪声中,检测困难,这成为制约NQR技术发展的一项瓶颈. 为提升NQR信号信噪比,根据NQR信号的特点,提出了一种基于改进阈值函数小波变换的NQR信号去噪方法. 计算表明该方法可以有效消除外界噪声对信号的干扰,提高探测的准确性.      

Three-Frequency Composite Multipulse Nuclear Quadrupole Resonance Technique for Explosive Detection

New method of multifrequency nuclear quadrupole resonance (NQR) for the explosive detection has been proposed. This technique consists of application of the series of composite excitation circles, each consisting of two or three successive pulses of different frequencies. In this work, we study in detail the multipulse sequence consisting of n excitation sets, each set consists of three pulses. The first pulse is applied with frequency ?? _?, the second pulse with frequency ?? ₀, and the third pulse with frequency ?? _?C, but with a shifted phase. The NQR signal is detected at the frequency ?? ₊. The maximal amplitude of the detected signal is obtained by tuning the pulse parameters at frequencies ?? _? and ?? ₀. We have shown that the phase of the NQR signal at the frequency ?? ₊ second part of the composite pulse with the frequency ?? ₀ the signals with different phases to suppress the spurious signals. The method could be used for increasing the NQR signal, avoiding the spurious signals and improving the reliability of NQR detection. Possible applications of the method for the explosive detection are also discussed.     

爆炸物检测中NQR信号的处理及判识

介绍了基于核四极矩技术的爆炸物检测原理及信号处理方法.系统分析了NQR信号检测中主要误差来源,提出多种方法消除NQR信号处理中检测误差,主要包括相关累加消除随机噪声;单通道自适应消除振铃影响;相关性检测抑制同频干扰.实验表明相关检测可有效提高NQR信号信噪比,提高微弱NQR信号检测的准确性.     

NQR炸药探测系统中射频线圈的设计研究

基于核四极矩共振(Nuclear Quadrupole Resonance, NQR)炸药探测原理,对探测系统中拾取信号的关键部件射频线圈进行了优化设计,并确定了小型螺线管型线圈的直径、长度和匝数. 试验测试表明,此线圈射频场均匀性好、信噪比大、灵敏度高,可以快速准确探测到NQR信号,验证了线圈设计理论的有效性和制作方法的可行性. 该设计方法对提高隐藏炸药探测的准确率以及不同试验条件下射频线圈的设计具有重要意义.     

Polarization enhancement of NQR signals for explosive detection

This paper presents first experiments on using Zeeman polarization-enhanced nuclear quadrupole resonance (NQR) method in detecting explosive substance pentaerythritoltetranitrate (PETN). The NQR signals were detected on nitrogen nuclei at room temperature using a multi-pulse spin-locking sequence after the sample was kept in a very inhomogeneous magnetic field. The dependence of enhancement factor on the time of protons polarization in the magnetic field was studied.     

Emission of nuclear quadrupole resonance from polycrystalline hexamethylenetetramine

The angular dependence of the nuclear quadrupole resonance (NQR) signal intensity emitted from polycrystalline hexamethylenetetramine has been analytically investigated for all directions for non-contact detection of chemicals by nuclear quadrupole resonance. The field pattern of the NQR signal from a column sample was measured. The emitted patterns were the same as that from a united single magnetic dipole, which fitted well to the estimation based on quadrupole principle axis system. This result is helpful to design an antenna for NQR remote detection.