4557
A Design of 10-100 MHz Broadband NMR Transmission-line Probe
Shouquan Yao1, Juncheng Xu1, Yiqiao Song2, Ming Shen1, Bingwen Hu1, and Yu Jiang1
1Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai, China, 2Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States
1Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai, China, 2Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States
Synopsis
Keywords: New Devices, New Devices, Probe
This work demonstrated a broadband NMR probe with a bandwidth of 10-100 MHz. Based on transmission-line structure, broadband transmission was achieved. As for broadband reception, high-speed active T/R switches and low-noise differential amplifiers were used for high-sensitivity RF reception. The SNR of FID signal detected by broadband probe was 74% of that of conventional resonance probe, which means the feasibility of the broadband NMR transmission-line probe was verified.Purpose
Conventional NMR probes are narrowband circuits based on resonance circuits. When performing multi-core detection, Tuning repeatedly or multi-tuning probes are required, which increases the difficulty of using magnetic resonance probes1,2,3. Broadband magnetic resonance probe can realize RF transmission and NMR signal reception without tuning and matching. Consider the case, which is common in ex-situ NMR, where the excited sample volume is power-limited by large sample size and/or inhomogeneous magnetic field. Broadband probe can easily switch frequencies to move the region of investigation4. In this paper, a broadband NMR probe with a bandwidth of 10-100 MHz was designed. Based on transmission-line structure, broadband transmission was achieved. The transmission-line switching circuit was designed to realize high-sensitivity RF reception.Methods
As shown in Fig. 1 (a) and Fig. 1 (b), the magnetic resonance probe was designed based on transmission-line structure5. The characteristic impedance of the transmission-line probe was designed to be 50 Ω. When the terminal load resistance R1 is matched, a 50 Ω broadband RF power amplifier can be used to achieve broadband RF transmission. In Fig. 1 (b), the PIN diode D5 was used to ground the shielding layer of the transmission-line coil. Switching the coil between transmission-line structure and inductance structure was controlled by the gate signal DRVCoil. The broadband LNA in Fig. 1 (d) was designed with high input impedance. During RF reception, switching the coil to an inductive structure can effectively improve the sensitivity and SNR of the RF reception loop. The broadband T/R switch shown in Fig. 1 (c) was an active switch based on PIN diodes D7-D14. It was controlled by the differential drive of DRV+ and DRV-. The common mode chock T1 and T2 were used to reduce overshoot and oscillation during switching, which achieved fast transceiver switching function.Results
Fig. 2 (a) shows the structure diagram of the broadband NMR probe. A broadband T/R switch and a low-noise preamplifier were integrated into the probe. As shown in Fig. 2 (b), the magnetic resonance coil was designed with a transmission-line probe based on a solenoid structure. By using the broadband probe and resonance probe, FID signals of 1H (21.38 MHz) in H2O sample was detected with a single-pulse sequence on 0.5 T magnet. As shown in Fig. 3, the SNR of FID signal detected by broadband probe was 74% of that of conventional resonance probe, which shows that the broadband probe has a detection sensitivity comparable to that of the conventional resonance probe.Discussion
This paper proposed a novel broadband NMR probe design. The broadband magnetic resonance probe can be used for the detection of NMR signals without tuning. The same probe can be used for the systems with different frequencies, which not only provides the convenience for multi-nuclear detection, but also brings the convenience to the design of magnetic resonance instruments.Acknowledgements
The authors are grateful to Liping Xu for valuable discussions in hardware development.References
1. Tominaga Y, Takeda K. An electro-mechano-optical NMR probe for 1 H–13 C double resonance in a superconducting magnet[J]. Analyst, 2022, 147(9): 1847-1852.
2. Jeong J H, Kim M, Son J, et al. 1H-31P home-built solid-state NMR probe with a scroll coil for 400-MHz NB magnet for biological lossy sample[J]. Journal of Analytical Science and Technology, 2020, 11(1): 1-6.
3. Zalesskiy S S, Danieli E, Blumich B, et al. Miniaturization of NMR systems: Desktop spectrometers, microcoil spectroscopy, and “NMR on a chip” for chemistry, biochemistry, and industry[J]. Chemical reviews, 2014, 114(11): 5641-5694.
4. Mandal S, Utsuzawa S, Cory D G, et al. An ultra-broadband low-frequency magnetic resonance system[J]. Journal of Magnetic Resonance, 2014, 242: 113-125. [5] Scott E, Stettler J, Reimer J A. Utility of a tuneless plug and play transmission line probe[J]. Journal of Magnetic Resonance, 2012, 221: 117-119.
Figures
Fig.1. Schematic diagram of a broadband magnetic
resonance probe. (a) broadband transmission is achieved by the use a 50 Ω
broadband RF power amplifier through (b) transmission-line coils. The reception
with high SNR reception is achieved by the use (c) a broadband balanced T/R
switch and (d) a high input impedance differential amplifier .
Fig. 2. (a)Structure diagram of the broadband magnetic
resonance probe. (b) Shielding and dielectric layers are used to build the coil
into a transmission-line structure.
Fig. 3. The FID signal of 1H in H2O
sample on 0.5 T NMR system: (a) detected by broadband probe, (b) detected by
conventional resonance probe.
DOI: https://doi.org/10.58530/2023/4557