【作者】 杨志强；

【导师】 郑丰隆；

【作者基本信息】 山东科技大学 ， 测试计量技术及仪器， 2004， 硕士

【摘要】 本文介绍了核磁共振(NMR)的原理及小型核磁共振系统电路部分的设计。核磁共振是原子核的磁矩在恒定磁场和高频磁场同时作用,且满足一定条件时所发生的共振吸收现象,是一种利用原子核在磁场中的能量变化来获得关于核信息的技术。50多年来,由核磁共振转化为探索物质微观结构和性质的高新技术已取得了惊人的进展。从70年代后期起,随着计算机和NMR在理论和技术上的完善,NMR无论在广度、深度上都获得了长足的发展,它已成为物理、化学、生物、医学和地学研究中必不可少的实验手段。在本文介绍的NMR系统中,由信号源产生射频脉冲,经过功率放大器放大后作为激励信号被送至磁共振探头,NMR探头固定在静磁场中,被测样品放在NMR天线的中心,在射频信号发射期间,天线吸收它提供的能量激发样品使样品中的原子核处于高能态,当射频脉冲作用结束后,样品通过弛豫释放能量返回稳定状态,在这个过程中,天线又作为接收装置,接收到的信号是将样品信息调制在射频载波上的调制信号;该信号是十分微弱的,它经前置放大器放大后再进行分析处理,得出样品的相关特性。本文主要介绍小型NMR系统的电路部分,包括: (1) 功率放大器的研制及改进 (2) NMR探头的研制及改进 (3) 弱信号前置放大器的研制 另外,本文还提出了各部分在设计上存在的不足和待改进之处。更多还原

【Abstract】 This text introduce the theory of nuclear magnetic resonance（NMR） and the design of a NMR system. Nuclear magnetic resonance is a subject which studies the phenomenon of resonance absorption when nucleus was placed in the stationary magnetic field and act with applied high frequency fields. It’s a technology that uses the energy change of magnetic field to detect some useful information of the nucleus. During the last 50-year, it makes an incredible progress in the field of studying the microstructure of some matters with nuclear magnetic resonance. From the late 70^th, with the developing of computer science and principle of NMR, it has been an indispensable experimental method which needed by physics chemistry biology medical science and geology. In the NMR system, the RF pulse is generated by the signal source, it is exemplified by power amplifier. And then it is sent to the NMR probe, the NMR probe also is the signal receive apparatus, the received signal is the sample signal which is modulated by the RF signal. The signal which is received by the probe is a small signal, it may be exemplified by the amplifier, and then it may be processed and get the sample signal. The circuit theory which is introduced by the text includes three portions:（ 1 ） The design and modify of the power amplifier.（ 2 ） The design of NMR probe.（ 3 ） The design of pre-amplifier.Moreover, some weak points and the aspects of needing improvements are bring forward.更多还原