Automatic probe tuning and matching
Automatic probe tuning and matching
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DOI：
10.1002/mrm.1910390208
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发表时间：
1998-02-01
影响因子：
3.3
通讯作者：
Hoult, DI
中科院分区：
文献类型：
--
作者：
Hwang, F;Hoult, DI
考虑了自动调整和匹配探头的问题，并将注意力集中在困难的主要原因：调整和匹配机制的相互作用。因此，建议使用双谐振、电感耦合探头，因为对于一阶，调谐和匹配对于小扰动是正交的。结果表明，该探头在电桥和核磁共振谱仪的误差信号驱动下，采用调谐匹配元件的负反馈控制，实现了稳定、快速的自动调谐匹配。强调了误差信号近乎正确的相位的重要性，但取消了必须具有特定电缆长度才能实现这一任务的限制。然后，与其他非正交探头类型的情况相比，考虑并显示出对于所选择的探头来说，定相的小误差的影响并不重要。对两种常见的电容耦合探头设计提出了正交化的建议，并给出了一种实用的仪器设计，即在核磁共振接收器不能按下使用的情况下，增加外部元件也可以使用。
The problem of automatically tuning and matching a probe is considered, and attention is drawn to the main cause of difficulty: the interaction of tuning and matching mechanisms. The use of a doubly resonant, inductively coupled probe is therefore advocated, for to first order, tuning, and matching are then orthogonal for small perturbations. It is shown that when such a probe is equipped with negative feedback control of tuning and matching elements, driven by error signals derived from a bridge and the NMR spectrometer, stable and rapid automatic tuning and matching are achieved. The importance of approximately correct phasing of the error signals is emphasized, but the restriction of having to have specific cable lengths to achieve this task is removed. The effects of small errors of phasing are then considered and shown to be unimportant for the chosen probe, in contrast to the situation for other, nonorthogonal probe types. Suggestions for orthogonalization of two common capacitively coupled probe designs are made, and a practical instrument design is then given that, with the addition of external components, can also be used if the NMR receiver cannot be pressed into service.