【作者】 乔勇；

【导师】 蒋瑜；

【作者基本信息】 华东师范大学 ， 无线电物理， 2006， 硕士

【摘要】 核磁共振是研究物质结构的重要技术，核磁共振谱仪是实现这种研究的主要手段。频率源是核磁共振谱仪和磁共振成像系统的重要组成部分，主要用来产生样品激发信号或检波的本振信号。现代核磁共振技术要求频率源在输出频段内的频率具有高稳定度、高谱净度、高分辨率和低相位噪声等特性，并且能够实现频率、相位和幅度的快速调制能力。 本文提出了一种DDS和模拟倍频器相结合的方法，用来产生300MHz核磁共振实验所需要的射频频率。本文围绕着这种方法，研制了应用于300MHz核磁共振谱仪的频率源，并对研制和试验过程进行了讨论。 本论文主要内容如下： 1) 简单介绍谱仪结构和谱仪中频率源的作用，频率源对磁共振的影响。 2) 介绍频率源的各种合成方式及其优缺点。具体介绍了数字化频率源的研制过程，应用何种技术和手段实现了300MHz核磁共振谱仪频率源的指标，以及用这种方法带来的好处和它的特点。 3) 介绍数字化频率源的测试结果和数字化频率源取代了AVANCE 300上的PTS模拟频率源的实验结果。更多还原

【Abstract】 Nuclear Magnetic Resonance (NMR) spectroscopy is the absorption of radio frequency radiation by a nucleus in a strong magnetic field. NMR is one of the most powerful tools in a synthetic or structural chemist’s arsenal. The radio frequency source is an essential part in nuclear magnetic resonance spectroscopy or magnetic resonance imaging instrument. Modern NMR technique such as selective excitation, composite pulses and RF receiver require that the RF source has the characteristic of high stability, high frequency spectrum purity, high frequency resolution and low phase noise.In this paper, a kind of 300MHz frequency source is designed by means of combining DDS with analog frequency doubler. The design details and the experiment results are presented and discussed.The paper begins with a brief outline of the historical development of NMR in chapter 1. Chapter 2 illustrates the NMR basic theory and NMR spectrometer structure including the influence of RF source to the NMR spectrometer. The advantage and disadvantage of all frequency sources are compared in the third section. The fourth section introduced the design process. The design is fit for using in 300MHz NMR spectrometer due mainly to its low phase noise, high stability, high frequency and high purity output. The implementation of this frequency source to NMR is discussed. Finally the test results and 300MHz solid NMR experiment results are shown.更多还原