低场永磁磁共振系统高稳定匀场电流放大器设计

doi:10.11938/cjmr20263206

摘要/Abstract

摘要：

随着低场永磁磁共振系统在食品检测、材料分析等领域的广泛应用，磁场均匀性对于获取高质量磁共振信号至关重要，而匀场放大器的性能直接决定了磁体的主动匀场效果．本文提出一种专用于低场永磁高分辨磁共振系统的高稳定性、低纹波匀场电流放大器设计方案．该方案采用高集成度的模块化设计，通过控制器局域网总线（Controller Area Network，CAN）通信实现通道扩展，并利用自偏置推挽电路实现了-1 A ~ +1 A的双极性电流输出，显著提高了输出线性度．为确保电流精度和稳定性，电流反馈检测端采用差分方式获取采样电阻两端电压差，有效抑制了共模噪声．该匀场电流放大器的输出电流线性回归系数R²优于0.999 999 9，48 h长期稳定度低至5.3 ppm（1 ppm=10^-6），实现了对匀场线圈电流的精确控制，具有良好的线性度和稳定性，可以满足低场永磁高分辨磁共振系统匀场线圈的驱动需求．

关键词: 低场磁共振, 永磁磁体, 匀场电流放大器, 电流源, 稳定性

Abstract:

The widespread application of low-field permanent magnet NMR systems in areas such as food testing and material analysis places higher demands on the quality of NMR signals. Magnetic field uniformity is crucial for obtaining high-quality signals, and the performance of the shimming current amplifier directly determines the effectiveness of active shimming. This paper presents a specialized high-stability, low-ripple shimming current amplifier design for high-resolution, low-field permanent magnet NMR systems. The design employs a highly integrated modular architecture, supports multi-channel expansion via controller area network (CAN) communication, and utilizes a self-biased push-pull circuit to achieve bipolar current output from -1 A to +1 A, significantly improving output linearity. To ensure accuracy and stability, differential sensing is applied in the current feedback loop to effectively suppress common-mode noise. The amplifier demonstrates a linear regression coefficient R² > 0.999 999 9 and a 48-hour long-term stability of 5.3 ppm (1 ppm=10^-6), enabling precise current control with excellent linearity and stability, thereby meeting the driving requirements of shim coils in high-resolution, low-field NMR systems.

Key words: low-field NMR, permanent magnet, shimming current amplifier, current source, stability

中图分类号:

O482.53

卢星云, 姚守权, 徐俊成, 蒋瑜. 低场永磁磁共振系统高稳定匀场电流放大器设计[J]. 波谱学杂志, 2026, 43(3): 268-278.

LU Xingyun, YAO Shouquan, XU Juncheng, JIANG Yu. A High-stability Shimming Current Amplifier Design for Low-field Permanent Magnet NMR Systems[J]. Chinese Journal of Magnetic Resonance, 2026, 43(3): 268-278.

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参考文献 21

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序号	命令	功能
1	[SWITCHCH0 <value>]	切换通道0输入源（value=0，切换为Z₀输入；value=1，切换为DAC输入）
2	[SETALL <value>]	设定所有通道输出电流值为（value=0~65535）
3	[SETCH0 <value>]	设定通道0输出电流值（value=0~65535）
4	[SETCH1 <value>]	设定通道1输出电流值（value=0~65535）
5	[SETCH2 <value>]	设定通道2输出电流值（value=0~65535）
6	[SETCH3 <value>]	设定通道3输出电流值（value=0~65535）
7	[GETALL]	查询所有通道当前电流设定值
8	[GETCH0]	查询通道0当前电流设定值
9	[GETCH1]	查询通道1当前电流设定值
10	[GETCH2]	查询通道2当前电流设定值
11	[GETCH3]	查询通道3当前电流设定值
12	[RDATACH0 <value>]	返回通道0当前输出电流值（value=0~65535）
13	[RDATACH1 <value>]	返回通道1当前输出电流值（value=0~65535）
14	[RDATACH2 <value>]	返回通道2当前输出电流值（value=0~65535）
15	[RDATACH3 <value>]	返回通道3当前输出电流值（value=0~65535）