【摘要】 针对高分辨核磁共振波谱仪需要锁场信号锁定磁场的要求,提出采用DDS技术产生稳定、高分辨的锁场信号方案。方案利用FPGA为系统控制核心控制DDS电路,使DDS电路同时输出锁场前端信号和接收机本振前端信号;2个前端信号经过椭圆低通滤波器、功率放大和可变衰减之后,输出频率可变、性能稳定、被调制的锁场信号。实验证明在保证稳定性和高分辨的特性下,采用该方案的波谱仪能够简化系统结构,并对将来研制800 MHz波谱仪有指导意义。更多还原

【Abstract】 A design was proposed by using DDS technology to generate a stable and high-resolution RF signal for locking the static magnetic field of high-resolution NMR(nuclear magnetic resonance) spectrometer.By FPGA,the DDS circuit was controlled to output a front-end locking fields signal and a local oscillator signal of receiver.Then by conditioning circuits that consists of the low-pass elliptic filter circuit,power amplifier circuit,and variable attenuator circuit can be obtained,the stable locking fields signal can be obtained,the signal frequency can be changed and the signal can be modulated.The experimental results indicate that the design can simplify system in which there is no chance of stabilization and high-resolution property,furthermore,the design can be used for reference of researching 800 MHz NMR spectrometer.更多还原