本文以核磁共振（NMR）射频线圈振铃信号产生原理为对象进行分析研究，提出了一种适用于低场环境下由环状间隙腔线圈与螺线管线圈构成的收发分离式短死时间射频线圈设计方案，采用优化调谐匹配网络提高发射效率；根据射频线圈方案需求设计了快速切换的射频开关及驱动．在此基础上依据仿真结果制作了短死时间射频线圈，并应用于自主研制的低场9.51 MHz便携式NMR谱仪系统，进行NMR实验，结果显示可将收发切换时间缩短至10 μs以内，验证了该设计方案的可行性．
冯涛
,
陈俊飞
,
张震
,
杨春升
,
张志
,
刘朝阳
. 低场核磁共振短死时间射频线圈与射频开关的设计[J]. 波谱学杂志, 2021
, 38(1)
: 1
-11
.
DOI: 10.11938/cjmr20202823
Based on the ring-down signal generation principle of nuclear magnetic resonance (NMR), we presented here a design scheme of transmitting and receiving separated short dead-time radio frequency (RF) coil composed of loop-gap resonator (LGR) coil and solenoid coil in low-field NMR system, to improve transmission efficiency by optimizing tuning and matching network. We also designed a fast RF switch and driver to fulfill the requirement of the RF coil. Based on the simulation results, the short dead-time RF coil was fabricated and applied to a self-developed 9.51 MHz portable low-field NMR spectrometer. The NMR experiments showed that the dead-time was reduced to less than 10 μs, which verified the feasibility of the design scheme.
[1] LIU Z Z, YANG D, SHAO J X, et al. Evolution of pore connectivity in the Fushun oil shale by low-field nuclear magnetic resonance spectroscopy[J]. Chinese J Magn Reson, 2019, 36(3):309-318.刘志军,杨栋,邵继喜,等.基于低场核磁共振的抚顺油页岩孔隙连通性演化研究[J].波谱学杂志, 2019, 36(3):309-318.
[2] CHEN H Y, ZHAO S L, LI X N, et al. B1 mapping on low-field permanent magnet MRI scanner[J]. Chinese J Magn Reson, 2018, 35(4):498-504.陈海燕,赵世龙,李晓南,等.低场永磁体磁共振射频场映像[J].波谱学杂志, 2018, 35(4):498-504.
[3] HONG S X, HU H B, YANG Z T, et al. Effects of tissue coagulative necrosis on longitudinal relaxation time-based magnetic resonance thermometry[J]. Chinese J Magn Reson, 2018, 35(4):440-446.洪声秀,胡红兵,杨增涛,等.组织凝固性坏死对基于纵向弛豫时间的磁共振测温的影响[J].波谱学杂志, 2018, 35(4):440-446.
[4] MITCHELL J, FORDHAM E J. Contributed review:nuclear magnetic resonance core analysis at 0.3 T[J]. Rev Sci Instrum, 2014, 85(11):111502.
[5] BORGIA G C, BROWN R J S, FANTAZZINI P. Different "average" nuclear magnetic resonance relaxation times for correlation with fluid-flow permeability and irreducible water saturation in water-saturated sandstones[J]. J Appl Phys, 1997, 82(9):4197-4204.
[6] WASHBURN K E. Relaxation mechanisms and shales[J]. Concepts Magn Reson A, 2014, 43(3):57-78.
[7] WASHBURN K E, BIRDWELL J E. Updated methodology for nuclear magnetic resonance characterization of shales[J]. J Magn Reson, 2013, 233(Complete):17-28.
[8] YANG Y, SUN Y B, HE X H, et al. The design of a probe used in nuclear quadrupole resonance detection system[J]. Chinese J Magn Reson, 2013, 30(1):113-120.阳燕,孙宜斌,何学辉,等.一种核四极共振探测系统中天线探头的设计方法[J].波谱学杂志, 2013, 30(1):113-120.
[9] DOGANAY O, THIND K, WADE T, et al. Transmit-only/receive-only radiofrequency coil configuration for hyperpolarized 129Xe MRI of rat lungs[J]. Concepts Magn Reson B, 2015, 45(3):115-124.
[10] GOR'KOV P L, CHEKMENEV E Y, LI C, et al. Using low-E resonators to reduce RF heating in biological samples for static solid-state NMR up to 900 MHz[J]. J Magn Reson, 2007, 185(1):77-93.
[11] GOR'KOV P L, WITTER R, CHEKMENEV E Y, et al. Low-E probe for 19F-1H NMR of dilute biological solids[J]. J Magn Reson, 2007, 189(2):182-189.
[12] GAN Z H, GOR'KOV P L, BREY W W, et al. Enhancing MQMAS of low-γ nuclei by using a high B1 field balanced probe circuit[J]. J Magn Reson, 2009, 200(1):2-5.
[13] PAULSON E K, MARTIN R W, ZILM K W. Cross polarization, radio frequency field homogeneity, and circuit balancing in high field solid state NMR probes[J]. J Magn Reson, 2004, 171(2):314-323.
[14] MCNEILL S A, GOR'KOV P L, SHETTY K, et al. A low-E magic angle spinning probe for biological solid state NMR at 750 MHz[J]. J Magn Reson, 2009, 197(2):135-144.
[15] 谯劼.大功率高隔离PIN二极管收发开关电路设计与软件仿真研究[D].成都:电子科技大学, 2012.
[16] DIAO Y J, XIE J Y, XU J C, et al. A high-speed driver for NMR T/R switch[J]. Chinese J Magn Reson, 2016, 33(1):37-43.刁玉剑,谢君尧,徐俊成,等.磁共振快速T/R开关驱动器研制[J].波谱学杂志, 2016, 33(1):37-43.
