Non-resonant NMR Transmitter Circuit with Dynamic Capacitor Switching
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Solution Overview
Problem
Narrowband NMR transmitters face challenges such as slow frequency switching, noise introduction, limited discrete frequency settings, and phase coherence issues due to mechanical switches and fixed capacitors, making them inefficient for switching between frequencies.
Innovation Solution
A non-resonant transmitter circuit with a coil coupled to a capacitor and switches, operating in charging and discharging modes, allows for rapid frequency switching by selectively coupling and decoupling the coil with the capacitor, enabling the generation of radio frequency pulses over a wide frequency range while improving power factor and reducing power draw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If mechanical switches and fixed capacitors are used for frequency switching, then frequency can be changed, but switching speed is slow (10-100 ms)
Solution Approach 1:
The patent replaces mechanical switches with electronic switching circuitry including transistors (Q1-Q4), diodes (D1-D4), and capacitors (C1-C4) to achieve frequency switching. This electronic substitution eliminates the mechanical moving parts while enabling rapid switching speeds, directly resolving the contradiction between switching speed and device complexity.
2Adaptability or versatility
If mechanical switches are used for frequency switching, then frequency can be changed, but noise is introduced into the NMR measurement
Solution Approach 1:
The patent replaces mechanical switches with solid-state electronic components including transistors and diodes arranged in an electronic switching network. This substitution eliminates mechanical contact noise while maintaining frequency switching capability, directly resolving the contradiction between adaptability and noise generation.
3Adaptability or versatility
If fixed capacitors are used for frequency tuning, then discrete frequency settings are achieved, but continuous frequency variation is limited
Solution Approach 1:
The patent employs dynamic capacitor switching where capacitors C1-C4 are selectively connected or disconnected through electronic switches controlled by signals from the processor. This dynamic reconfiguration allows continuous frequency variation across a wide range without requiring a large bank of fixed capacitors, resolving the contradiction between adaptability and device complexity.
Solution Approach 2:
The patent changes the effective capacitance value by selectively switching capacitors in and out of the circuit rather than using a fixed capacitor value. This parameter change approach enables continuous frequency adjustment while minimizing the number of physical components needed, directly addressing the contradiction between frequency range and device complexity.
4Adaptability or versatility
If frequency switching is performed with mechanical switches, then different frequencies can be transmitted, but phase coherence of the pulse sequence waveform is not maintained
Solution Approach 1:
The patent replaces mechanical switches with solid-state electronic switches that can be precisely controlled by the processor. This electronic control enables synchronized switching that maintains phase coherence of the pulse sequence waveform while allowing frequency changes, directly resolving the contradiction between adaptability and phase stability.
Solution Approach 2:
The patent incorporates feedback control where the processor monitors and controls the switching timing of the electronic components to maintain phase coherence. This feedback mechanism ensures that frequency switching occurs at appropriate phases of the pulse sequence, preserving waveform integrity while enabling frequency variation.
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
The solution enables efficient and rapid frequency switching with maintained phase coherence, reducing power consumption and noise, and allowing for dynamic frequency variation without the need for hardware modulation, thus improving the performance of NMR systems.
Implementation Method 1
the coil is coupled to a circuit that includes a capacitor, a number of switches, and a power source
Implementation Method 2
The oscillating field is composed of a sequence of radio frequency pulses that tip the magnetization of the atomic nuclei
Implementation Method 3
The transistors selectively couple the coil to the capacitor
Implementation Method 4
The static magnetic field generates an initial magnetization of atomic nuclei within the substance
Data Source
AI summary
A non-resonant transmitter for a magnetic resonance (MR) system, such as a nuclear magnetic resonance (NMR) system, is described herein. The transmitter includes a coil for applying NMR pulse sequences to a substance. The coil is coupled to a circuit that includes a capacitor, a number of switches, and a power source. The transmitter operates in two modes. In a charging mode, the switches decouple the coil from the capacitor and the capacitor is charged by the power source. In a discharging mode, a radio frequency pulse is generated and the switches couple and decouple the coil from the capacitor so that the capacitor provides power to the coil. The addition of the capacitor improves the power factor of the circuit and reduces power draw from the power source.