NMR Probe Head RF Control Loop for Pulse Duration Regulation
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Solution Overview
Problem
NMR spectrometers face challenges with lossy measuring samples, leading to extended pulse durations that reduce spectral width and excitation efficiency, and existing power adjustment methods are inadequate for protecting the measuring head from destruction.
Innovation Solution
A control loop that regulates the duration, phase, and power of RF signals based on measured parameters such as current or voltage over RF components, allowing for precise adjustment of transmission power to maintain minimum pulse duration and correct pulse calculation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If transmission power is increased to compensate for losses in lossy measuring samples, then pulse duration can be maintained, but the measuring head may be destroyed due to excessive power
Solution Approach 1:
The patent implements a control loop that continuously monitors the actual power dissipated in the measuring head and adjusts the transmission power accordingly. This feedback mechanism ensures that the power remains within safe limits while maintaining the minimum pulse duration, preventing destruction of the measuring head even when working with lossy samples.
Solution Approach 2:
The system dynamically adjusts the transmission power parameter based on the measured losses in the measuring head. By changing the power parameter in real-time according to the actual conditions (Q-value, impedance matching), the system maintains optimal pulse duration without exceeding safety thresholds that would cause damage.
2Power
If pulse duration is extended to compensate for losses, then transmission power can be reduced, but spectral width and excitation efficiency are reduced
Solution Approach 1:
The control loop provides real-time feedback on the actual power delivery to the measuring head, enabling dynamic adjustment of transmission parameters. This ensures that the minimum pulse duration is maintained while optimizing transmission power, thereby preserving spectral width and excitation efficiency even when working with lossy samples.
3Ease of operation
If fixed transmission power is used, then system operation is simple, but pulse duration varies with different samples and adjustments
Solution Approach 1:
The control loop automatically monitors and adjusts transmission power based on actual conditions, maintaining consistent minimum pulse duration across different samples and adjustments. This automated feedback mechanism preserves ease of operation while ensuring pulse duration consistency, eliminating the need for manual recalibration.
4Reliability
If transmission power is limited to protect the measuring head, then safety is improved, but pulse duration increases and excitation efficiency decreases
Solution Approach 1:
The control loop provides continuous monitoring of actual power dissipation and adjusts transmission power in real-time to maintain the minimum pulse duration while staying within safety limits. This feedback mechanism ensures both reliability (protection of measuring head) and productivity (maintained excitation efficiency) simultaneously.
Solution Approach 2:
The system dynamically changes the transmission power parameter based on measured conditions (Q-value, impedance matching, sample losses), allowing optimal power delivery that protects the measuring head while maintaining excitation efficiency and minimum pulse duration.
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 consistent minimum pulse duration across various samples and adjustments, preventing destruction and improving spectral width and excitation efficiency without reducing pulse duration, while also allowing for automated pulse determination and correction of non-linearities.
Implementation Method 1
a transmitter which transmits RF signals at measuring frequencies... The NMR probe head comprises at least one RF oscillating circuit which is tuned, by means of RF components, to the resonance frequency of a type of nucleus to be investigated, wherein the RF oscillating circuit comprises at least one RF coil which is disposed around a measuring sample and, by transmitting RF signals, is used to excite nuclear spins
Implementation Method 2
The coil is generally connected to form an oscillating circuit using capacitors and/or a tuning network, and is tuned to the resonance frequency of the nuclear spins... the resonance frequency of an oscillating circuit changes due to the electric field components which penetrate through the measuring sample. It must be readjusted to the transmission frequency after change of a measuring sample
Data Source
AI summary
A method for regulating radio frequency (RF) signals in a nuclear magnetic resonance (NMR) system, comprising a spectrometer, a control loop, and an NMR probe head with RF components (BE, LE, BK), wherein the spectrometer comprises a transmitter that transmits RF signals at measuring frequencies with a transmission power (PS), the NMR probe head contains an RF oscillating circuit, and the RF oscillating circuit comprises an RF coil (LE), is characterized in that the control loop controls the duration and/or the phase and/or the power of the transmitted RF signals. Measurement of a parameter is performed by means of the NMR probe head, via which parameter the current in or the voltage across one of the RF components (BE, LE, BK) can be determined, and the transmission powers (PS) and/or the phases and/or the duration of the RF signals are regulated in dependence on the measured parameter. Any occurring losses can thereby be compensated for without reducing the pulse duration.