300 MHz核磁共振频率源的研制

The Design of A 300 MHz NMR Frequency Source

介绍了基于Analog Device公司AD9954设计的数字化频率源,可以实现宽带高频(5MHz^125 MHz、280 MHz^301 MHz)、高稳定度(1×10-9)、低相位噪声(301 MHz,≤-127 dBc/Hz@250 kHz offset)频率输出以及频率、相位和幅度的高速切换.该数字化频率源可应用于300 MHz核磁共振谱仪和磁共振成像仪,可部分取代昂贵的进口频率源.本文最后给出核磁实验结果.

A digital frequency source designed for a 300 MHz nuclear magnetic resonance spectrometer is described. Controlled by MCU or by PC, the frequency source is capable of generating a frequency-and phase-continuous tunable signal with output frequency ranging from 5 MHz to 125 MHz and 280 MHz to 301 MHz. Practical implementation of the frequency source to a 300 MHz NMR spectrometer is described, and its performance was tested with solid state NMR experiments. It is demonstrated that the frequency source results in radiofrequency output with low phase noise, high stability and high purity.