高场核磁共振波谱仪频率合成器设计

A Frequency Synthesizer For High-Field NMR Spectrometers

提出了一种基于锁相环(Phase-locked Loop,PLL)与直接数字合成(Direct Digital Synthesis,DSS)等技术相结合的高场核磁共振波谱仪频率合成器设计方案.该系统以单片机为控制器完成算法运行、参数配置和CAN总线通信功能,运用PLL技术和DDS技术相结合的频率合成方案,通过两次混频,使频率粗调和细调灵活可控,实现宽带低噪声频率输出.将该频率合成器用于自主研制开发的核磁共振波谱仪上进行实验验证,测试得到的线形和灵敏度均达到指标要求,结果证明该设计方案具有可行性.

A frequency synthesizer based on PLL and DDS was designed for high-field NMR spectrometers. An MCU controller with CAN interface is used as the center processor for the system, which receives instructions from the NMR console and controls the other components to change the power and frequency of the output. The PLL frequency synthesizer is used to get stable and pure signal for mixing, contributing to low phase noise and wide band spanning from 5 to 645 MHz. Combined with DDS, the resolution of the synthesizer can be as high as μHz. This design has many other benefits, including easy control, high precision and low cost.