Güler Sadri, Zivkovic Irena, Boer Vincent O, Zhurbenko Vitaliy, Thade Petersen Esben
Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark.
Section for Magnetic Resonance, DTU Health Tech, Technical University of Denmark, Kgs. Lyngby, Denmark.
NMR Biomed. 2025 Aug;38(8):e70071. doi: 10.1002/nbm.70071.
High-impedance coils (HICs) and shielded coaxial cable coils (SCCs) are of the same physical structure but with different matching networks and different input impedances (which depend on the mode of operation). This article explores the working and decoupling mechanisms of the HICs and the SCCs and establishes a design principle for highly decoupled elements. Decoupling properties, input impedances, and modes of operation of HICs and SCCs were analyzed and compared through a frequency range from 50 to 500 MHz. The coils were modeled in CST Microwave Studio, and full-wave electromagnetic simulations were performed to analyze coil parameters. Input impedance and S-parameters were examined for individual and two elements with various overlaps. The current distribution is computed along the outer surface of the conductor of the coils. It was shown that HICs have uniform current distribution, although SCCs have a combination of sinusoidal and constant current. Input impedances of SCCs designed for operation at the second resonant mode did not change, while two SCCs overlapped for varying amounts. Contrarily, HICs showed characteristic impedance splitting when various amounts of overlap were examined. maps of the SCC pairs were not affected when the overlap was changed from no overlap to 100% overlap. In contrast, the HICs showed degradation of the field (for the overlap increasing from 20% up to 100%) related to strong inter-element coupling of HIC coils when the amount of overlap increased. The stronger coupling of HICs operating at the first resonance region led to more vital degradation of their observed profile than SCCs. SCCs operating at the second resonance region exhibited stable profiles independent of the overlap amount. When operating in the correct mode, the coaxial cable resonators exhibit favorable decoupling properties in comparison to traditional coil designs.
高阻抗线圈（HIC）和屏蔽同轴电缆线圈（SCC）具有相同的物理结构，但匹配网络和输入阻抗不同（这取决于工作模式）。本文探讨了HIC和SCC的工作和解耦机制，并建立了高度解耦元件的设计原则。通过50至500MHz的频率范围对HIC和SCC的解耦特性、输入阻抗和工作模式进行了分析和比较。这些线圈在CST微波工作室中进行建模，并进行全波电磁仿真以分析线圈参数。检查了单个元件以及具有不同重叠量的两个元件的输入阻抗和S参数。计算了沿线圈导体外表面的电流分布。结果表明，HIC具有均匀的电流分布，而SCC具有正弦电流和恒定电流的组合。设计用于在第二谐振模式下工作的SCC的输入阻抗在两个SCC以不同量重叠时不会改变。相反，当检查不同量的重叠时，HIC显示出特征阻抗分裂。当重叠从无重叠变为100%重叠时，SCC对的场图不受影响。相比之下，当重叠量增加时，HIC显示出场的退化（对于重叠从20%增加到100%），这与HIC线圈的强元件间耦合有关。在第一谐振区域工作的HIC的更强耦合导致其观察到的场分布比SCC更严重的退化。在第二谐振区域工作的SCC表现出与重叠量无关的稳定场分布。与传统线圈设计相比，当以正确模式工作时，同轴电缆谐振器表现出良好的解耦特性。
