核磁共振波谱仪锁场数字接收机的设计与实现

Design and Implementation of Digital Receiver for Locking Fields in NMR Spectrometer

针对传统的高分辨核磁共振波谱仪锁场接收机具有系统结构复杂、信号处理难度高等不足,提出采用数字化技术设计锁场接收机的方案。方案采用FPGA为系统控制单元,通过数字中频子系统对经过变频处理的锁场信号进行处理,获得2路正交的数字锁场误差信号;经过D/A变换和信号调理电路,接收机输出相对精度达0.01%的模拟信号到锁场补偿线圈,用于补偿静磁场的漂移。实验证明:采用该方案的核磁共振波谱仪能够简化系统结构,提高系统性能,并对将来研制800 MHz核磁共振波谱仪有指导意义。

A design of digital receiver was proposed to improve the receiver structure and signal processing module for the tra- ditional lock system of high-resolution NMR （Nuclear Magnetic Resonance） spectrometer. By conditioning circuits, The feedback locking signal from the probe of lock system should was processed by down conversion. Then by the IF digitizing Subsystem, the receiver obtained two quadrature digitizing signal for the magnetic field error. Then, by DAC and conditioning circuits, the system output two quadrature analog signal to the compensation solenoid of lock system for which compensate the drift of static magnetic field, and the signal~ relative precision reached O. 01%. The experimental results indicate that the design can simplify system and improve capability, furthermore, the design can be use for reference of researching 800 MHz NMR spectrometer.