NMR Probe Inductive Matching Across a Broad Frequency Range
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Solution Overview
Problem
NMR probes face challenges in matching resonant modes to required impedances across a broad frequency range, particularly in achieving optimal signal-to-noise ratios due to low signal intensity and inefficient coupling constants.
Innovation Solution
The use of a variable inductor in the NMR probe allows for impedance matching to 50 Ohms without varying the coupling constant over a broad frequency range, enhancing the signal-to-noise ratio and improving RF homogeneity by adjusting both the variable capacitor and inductor to match the impedance of the impedance port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional inductive coupling is used in NMR probes, then the circuit can be tuned to specific frequencies, but the signal-to-noise ratio remains low and the frequency range is limited
Solution Approach 1:
The patent applies dynamics by making the inductor variable (tunable) rather than fixed. The variable inductor allows the resonant frequency of the probe circuit to be dynamically adjusted across a broad frequency range while maintaining optimal impedance matching and signal-to-noise ratio at each frequency point
Solution Approach 2:
The patent changes the inductance parameter of the coupling inductor from a fixed value to a variable value. By adjusting the inductance parameter of the variable inductor, the circuit can maintain optimal coupling and impedance matching across different frequencies, thereby improving both signal-to-noise ratio and frequency adaptability
2Reliability
If the coupling constant is varied over a broad frequency range to maintain impedance matching, then impedance matching improves, but the device complexity increases
Solution Approach 1:
The variable inductor serves multiple functions simultaneously: it acts as the coupling element between circuits, provides impedance matching, and enables frequency tuning. This single component performs what would traditionally require multiple separate adjustment mechanisms, thereby maintaining reliability while reducing device complexity
3Object-generated harmful factors
If minimal coupling between coils is used to reduce cross talk, then cross talk is reduced, but the signal intensity decreases
Solution Approach 1:
The patent applies local quality by optimizing the coupling specifically at the impedance matching point. The variable inductor enables strong coupling locally at the resonant frequency where signal intensity is critical, while the frequency selectivity of the resonant circuit naturally suppresses cross-talk at non-resonant frequencies
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables continuous matching of resonant modes across a wide frequency range, achieving improved signal-to-noise ratios and maintaining high circuit fill factors, thereby enhancing the sensitivity and efficiency of NMR experiments.
Implementation Method 1
matching a resonant mode in a circuit to a required impedance (e.g., Z=50 Ohm) using a variable inductor
Implementation Method 2
matching a resonant mode in a circuit
Implementation Method 3
inductively coupling the coupling loop (1012) to the sample coil (1010)
Implementation Method 4
detecting a NMR mode of one or more nuclei of the sample
Data Source
AI summary
In a first aspect, the present invention relates to a Nuclear Magnetic Resonance (NMR) probe and method of use of a NMR probe for matching a resonant mode in a circuit to a required impedance (e.g., Z=50 Ohm) using a variable inductor which allows matching of the resonant mode in the circuit within a broad frequency range. In an additional aspect, the NMR probe and the method of use of a NMR probe allows matching of a resonant mode in a circuit to a required impedance (e.g., Z=50 Ohm) using a variable inductor without requiring the coupling constant K to be varied over a broad frequency range. In a further aspect, the invention relates to a method to detect a Nuclear NMR mode of a nuclei including the steps of introducing a sample into a NMR probe comprising a primary circuit and a secondary circuit, where the primary circuit comprises a sample coil, a first variable capacitor and a RF pulse generator, where the secondary circuit comprises a coupling loop, a variable inductor and an impedance port, introducing the NMR probe into a magnetic field, exciting the sample with the RF pulse generator, inductively coupling the coupling loop to the sample coil, adjusting the first variable capacitor and the variable inductor to match the impedance to the required impedance of the impedance port and detecting a NMR mode of a nuclei of the sample.