Doubly Tuned RF Resonator for NMR Field Homogeneity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing RF resonators for NMR apparatuses face challenges in maintaining maximum field homogeneity and efficiency when operating at two measurement frequencies, particularly when one frequency is significantly higher than the other, leading to poor field profiles and increased losses due to the need for additional components like bandstop filters which introduce noise and complexity in manufacturing.
Innovation Solution
The introduction of additional electrically conducting ring segments that form current paths with specific capacitive interruptions allows for independent tuning of two frequencies, ensuring maximum efficiency and homogeneity by minimizing interference between the frequencies and avoiding the need for bandstop filters, while maintaining symmetrical configurations to optimize field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bandstop filters are added to block higher frequency signals, then frequency interference is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent removes the bandstop filter component entirely from the system. Instead of adding filters to block unwanted frequencies, the design uses the inherent properties of the birdcage resonator structure and capacitive coupling to achieve frequency separation, thereby eliminating the manufacturing complexity associated with filters while maintaining frequency selectivity
Solution Approach 2:
The patent introduces an intermediate coupling mechanism using capacitive connections between the birdcage resonator and the detection coil. This capacitive coupling acts as a frequency-selective intermediary that naturally attenuates higher frequency signals without requiring active filter components, thus achieving frequency selectivity through passive electrical coupling rather than complex filtering
2Adaptability or versatility
If additional components are added to achieve dual frequency operation, then frequency versatility is improved, but manufacturing precision requirements increase
Solution Approach 1:
The birdcage resonator structure is designed to serve multiple functions simultaneously: it acts as the primary resonating element for both frequencies, provides the coupling mechanism to the detection coil, and establishes the geometric framework for frequency separation. This multi-functionality reduces the need for additional specialized components and their associated precision requirements
Solution Approach 2:
The patent achieves dual frequency operation by modifying geometric parameters of the existing birdcage structure (such as bar positions, ring element configurations, and spacing) rather than adding new components. By adjusting these physical dimensions and electrical parameters within standard manufacturing tolerances, the system achieves versatile frequency operation without imposing stringent precision requirements
3Adaptability or versatility
If symmetry is broken to tune different frequencies, then frequency differentiation is achieved, but field homogeneity deteriorates
Solution Approach 1:
The patent introduces controlled asymmetry in the form of non-uniform capacitive coupling between different bars of the birdcage resonator and the detection coil. Specifically, certain bars are capacitively coupled while others are not, creating an asymmetric current distribution that enables frequency differentiation. This targeted asymmetry achieves frequency separation while maintaining sufficient field homogeneity for NMR detection
Solution Approach 2:
The patent applies different electrical characteristics to different parts of the resonator structure. Specifically, certain bars are equipped with capacitive coupling elements while others remain uncoupled, creating local variations in electrical properties. This local differentiation enables frequency tuning without requiring global asymmetry that would compromise field homogeneity, as each local modification is optimized to minimize its impact on the overall field distribution
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 solution enables maximum field homogeneity and efficiency for both frequencies with identical field profiles, reducing operational losses and simplifying the manufacturing process by eliminating the need for complex bandstop filters and additional components, thus improving the overall performance of the RF resonator.
Implementation Method 1
The bars are capacitively interrupted by sixteen capacitors 13
Implementation Method 2
RF resonator for transmitting and/or receiving signals with a first measurement frequency F1
Implementation Method 3
The inductive couplings between bars 11, the ring elements 12, and between bars and ring elements are not drawn in FIG. 1a
Data Source
AI summary
An RF resonator has a birdcage resonator with two electrically conducting ring elements (12, 33, 47) and N electrically conducting bars (11). At least one pair of electrically conducting ring segments (32a, 32b, 40, 43) forms an additional electrical connection between precisely two bars (11). The pair of ring segments (32a, 32b, 40, 43) define a current path (41, 42) with these two bars (11) which is capacitively interrupted at at least one point. The ring segments (32a, 32b, 40, 43) and the bars (11) electrically connected to the ring segments (32a, 32b, 40, 43) are disposed symmetrically with respect to the yz-plane. The field homogeneity and efficiency are thereby optimized even with frequencies that are far apart.