基于直接数字频率合成技术的核磁共振弛豫分析仪场频联锁电路设计

Design of Locking Fields Signal Generating Circuit for Nuclear Magnetic Resonance Instrumentation based on Direct Digital Synthesizer Technology

为了研制一个稳定、高分辨特性的磁共振弛豫分析仪场频联锁系统,利用FPGA作为系统控制核心控制DDS电路,产生快速所需的调制射频信号。然后对锁场系统中发射单元,射频开关以及接收单元进行电路设计。最后,通过实验验证,整个锁场电路在3.268 MHz的频率下,能够激励氘核并产生磁共振信号,并且在接收单元中,能够将u W级的磁共振信号进行前置放大,使其达到330 m W,便于FPGA处理。本系统对将来研制高性能弛豫分析仪有重要的参考意义。

To develop a stable,high resolution field frequency characteristics of nuclear magnetic resonance（ NMR） relaxation analyzer interlocking system,with FPGA to controll DDS chip to generate desired modulated radio frequency（ RF） signal. The system was designed with a launch unit,RF switch and receiving unit. Experiments showed that the system could effectively motivate deuteron produce NMR signal in the frequency of 3. 268 MHz. And in receiving unit,it could carry on the preamplifier for the NMR signal level u W to 330 m W. The design can provide reference for high performance relaxation analyzer.