Self Introduction
A MIM/Coaxial Stub-Line CRLH Zeroth-Order Series-Mode Resonator used as an RF Coil Element for 7-Tesla Magnetic Resonance Imaging
Andreas Rennings1 , Jan Taro Svejda1 , Simon Otto2 , Klaus Solbach2 , and Daniel Erni1
General and Theoretical Electrical Engineering (ATE), 2 High Frequency Engineering (HFT), Faculty of Engineering, University of Duisburg-Essen, and 1 CENIDE – Center for Nanointegration Duisburg Essen, D-47048 Duisburg, Germany
1
Abstract—A novel MIM/coaxial-stub composite right/lefthanded (CRLH) metamaterial transmission-line (TL) structure is proposed. In addition to the common metal-insulator-metal (MIM) series capacitor, a short-circuited coaxial line, which is vertically aligned to the otherwise planar structure, forms the shunt inductor. The zeroth-order (ZO) series mode with its spatially uniform and longitudinally polarized series current of the short-circuited CRLH TL is utilized in the context of RF field excitation in a 7-Tesla magnetic resonance imaging (MRI) scanner. The usage of coaxial stubs instead of sidewise microstrip lines has several advantages, especially for the MRI application, such as a unit cell with smaller width, the unwanted longitudinal magnetic field components excited by the shunt resonantor are shielded by the outer coaxial connector and the upper MIM plate, yielding a high Qsh -to-Qse -ratio (here 250/100), which implies an extremely uniform series current distribution. Here a 40-cm long ZO resonant element for 300 MHz is proposed. FEM eigenmode and FDTD driven-mode full-wave simulation, together with corresponding near-field measurements on fabricated prototypes are presented to comfirm the approach. Index Terms—CRLH metamaterial transmission-line; zerothorder resonator (ZOR); MRI RF coil
Feeding structure in the center
matching VRF network MN 180◦ Balun MN
ZA,1
ZA,2 ZA,1 ground
ZA,2
short
short circuit
MN
Zse /2
Zse /2 =
R 2
1 + jQse
ω ωse ω ωsh
−
ωse ω
Ysh = G 1 +
Andreas Rennings1 , Jan Taro Svejda1 , Simon Otto2 , Klaus Solbach2 , and Daniel Erni1
General and Theoretical Electrical Engineering (ATE), 2 High Frequency Engineering (HFT), Faculty of Engineering, University of Duisburg-Essen, and 1 CENIDE – Center for Nanointegration Duisburg Essen, D-47048 Duisburg, Germany
1
Abstract—A novel MIM/coaxial-stub composite right/lefthanded (CRLH) metamaterial transmission-line (TL) structure is proposed. In addition to the common metal-insulator-metal (MIM) series capacitor, a short-circuited coaxial line, which is vertically aligned to the otherwise planar structure, forms the shunt inductor. The zeroth-order (ZO) series mode with its spatially uniform and longitudinally polarized series current of the short-circuited CRLH TL is utilized in the context of RF field excitation in a 7-Tesla magnetic resonance imaging (MRI) scanner. The usage of coaxial stubs instead of sidewise microstrip lines has several advantages, especially for the MRI application, such as a unit cell with smaller width, the unwanted longitudinal magnetic field components excited by the shunt resonantor are shielded by the outer coaxial connector and the upper MIM plate, yielding a high Qsh -to-Qse -ratio (here 250/100), which implies an extremely uniform series current distribution. Here a 40-cm long ZO resonant element for 300 MHz is proposed. FEM eigenmode and FDTD driven-mode full-wave simulation, together with corresponding near-field measurements on fabricated prototypes are presented to comfirm the approach. Index Terms—CRLH metamaterial transmission-line; zerothorder resonator (ZOR); MRI RF coil
Feeding structure in the center
matching VRF network MN 180◦ Balun MN
ZA,1
ZA,2 ZA,1 ground
ZA,2
short
short circuit
MN
Zse /2
Zse /2 =
R 2
1 + jQse
ω ωse ω ωsh
−
ωse ω
Ysh = G 1 +