RF Array Decoupling via Current Source Feed Mode
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Solution Overview
Problem
Conventional magnetic resonance tomography systems face challenges in reducing disturbances caused by signals from neighboring coils or antennas, especially for different geometrical arrangements, which affect the sensitivity and accuracy of examinations, particularly for small objects like limbs or heads.
Innovation Solution
The system employs an RF device with a higher source impedance than the antennas, operating in a current source feed mode to minimize the influence of neighboring antennas, and includes a switch and RF activation matrix to distribute signals with predetermined impedance and phase offsets, reducing crosstalk and enabling circular polarization of electromagnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple antennas are disposed close together to increase receive sensitivity for small objects, then receive sensitivity is improved, but crosstalk between neighboring antennas increases
Solution Approach 1:
The patent introduces a decoupling network as an intermediary component between neighboring antennas. This decoupling network acts as a mediator that blocks or reduces the harmful electromagnetic coupling (crosstalk) between antennas while allowing the antennas to maintain their close proximity for improved receive sensitivity. The decoupling network is specifically designed to suppress the interaction between adjacent antennas without affecting their individual performance.
2Device complexity
If conventional voltage source feed mode is used to simplify the feeding system, then device complexity is reduced, but crosstalk between antennas increases and measurement precision deteriorates
Solution Approach 1:
The patent changes the fundamental feeding parameter from voltage source mode to current source mode. This parameter change transforms the feeding characteristics: current source feed mode inherently provides higher output impedance that naturally suppresses crosstalk between antennas, while maintaining simplified system architecture. The current source feeding ensures that each antenna receives a stable current that is less susceptible to coupling effects from neighboring antennas.
3Adaptability or versatility
If antennas are arranged in different geometrical configurations to adapt to various examination objects, then adaptability is improved, but crosstalk suppression becomes less effective
Solution Approach 1:
The patent segments the electromagnetic coupling path by introducing individual decoupling networks for each antenna connection. This segmentation approach allows each antenna to be independently decoupled from its neighbors, enabling the system to maintain effective crosstalk suppression regardless of the overall geometrical configuration. The segmented decoupling approach works effectively for various arrangements including linear, circular, and three-dimensional configurations.
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 configuration significantly reduces crosstalk between antennas, maintains high sensitivity, and ensures efficient power supply to the sample even with mismatched antennas, minimizing the impact of temperature and geometrical variations, thereby improving the resolution and accuracy of magnetic resonance tomography.
Implementation Method 1
an RF device for generating a radio-frequency signal and a plurality of antennas for emitting the radio-frequency signal
Implementation Method 2
the current through the antenna is thus essentially dependent on an opposing voltage induced in the antenna, which, for example, may emanate from the interaction with a neighboring antenna
Data Source
AI summary
A system for electromagnetic excitation of an object under examination during magnetic resonance tomography includes a radio frequency (RF) device for generating a radio-frequency signal and a plurality of antennas for emitting the radio-frequency signal. A signal connection exists between the output of the RF device and the plurality of antennas. A source impedance of the signal connection to the output of the RF device at a connection point of the plurality of antennas is significantly higher than the impedance of the plurality of antennas at the connection points, so that the plurality of antennas are fed in a current source feed mode if a radio-frequency signal is present.