波谱学杂志2025，Vol.42Issue(3)：321-333,13.DOI:10.11938/cjmr20253162
用于低场NMR的低噪声前置放大器研制
Development of Low-noise Preamplifier for Low-field NMR
摘要
Abstract
Nuclear magnetic resonance(NMR)technology enables the acquisition of multi-scale molecular dynamics by characterizing the variation of relaxation times under different magnetic field conditions,thereby offering a critical detection methodology for petroleum logging research.To minimize magnetic field gradients induced by susceptibility differences between solid and liquid phases,low-field NMR systems are predominantly employed in petroleum logging applications.However,the inherent limitations of reduced sensitivity in low-field environments present significant challenges for applied studies,necessitating stringent noise performance specifications for receiving circuitry.As the primary stage of the signal reception chain,the preamplifier's noise characteristics fundamentally determine the signal-to-noise ratio(SNR)of NMR measurements.To address the requirements of low-field NMR,this paper adopts a cascade topology combining a common-emitter and common-collector two-stage amplification circuit,and integrates negative feedback to optimize input broadband matching and noise figure.Consequently,a high-gain,low-noise broadband preamplifier has been developed.The implemented preamplifier demonstrates excellent performance parameters:NF≤0.73 dB,gain≥31 dB,gain flatness≤0.35 dB,and equivalent input voltage noise density≤0.45 nV/√Hz across the 10～30 MHz frequency band.Integrated into an NMR spectrometer system,the amplifier demonstrated favorable 1H NMR signal SNR under 0.5 T,0.35 T,and 0.25 T magnetic field conditions.These results indicate that the developed low-noise amplifier provides critical technical support for advancing low-field NMR applications.关键词
低场核磁共振/信噪比/低噪声前置放大器/负反馈/噪声系数Key words
low-field NMR/signal-to-noise ratio/low-noise preamplifier/negative feedback/noise figure分类
数理科学引用本文复制引用
李科言,程鑫,陈俊飞,曹丽,黄臻,刘朝阳..用于低场NMR的低噪声前置放大器研制[J].波谱学杂志,2025,42(3):321-333,13.基金项目
国家重点研发计划(2022YFF0707001) （2022YFF0707001）
国家自然科学基金资助项目(22204168) （22204168）
中国科学院战略性先导科技专项(XDB0540301) （XDB0540301）
国家重大科研仪器研制项目(22327901). （22327901）
