Title :
Periodic Analysis of MR-Safe Transmission Lines
Author :
Syms, Richard R A ; Solymar, Laszlo ; Young, Ian R.
Author_Institution :
Dept. of Electr. & Electron. Eng., Imperial Coll. London, London, UK
Abstract :
In this paper, a theoretical analysis is presented of transmission lines that are periodically interrupted by isolation transformers. Such lines have application as safe interconnects in MRI with internal coils, where the transformers act to block common-mode signals excited by the transmitter while passing differential-mode signals from a detector. The dispersion characteristics are derived, and it is shown that the line is a form of metamaterial supporting magneto-inductive (MI) waves. Propagation can take place in a series of bands, each close to one of the standing wave resonances of an isolated segment. However, it is shown that additional series capacitors are required to implement the protection strategy correctly and the line then operates on a low-frequency lumped-element MI band. Lines operating at 63.8 MHz frequency are constructed using coaxial cables and printed circuit board transformers, and the existence of multiple propagating bands is confirmed.
Keywords :
capacitors; coupled transmission lines; integrated optoelectronics; magnetic resonance imaging; metamaterials; optical interconnections; optical transmitters; transformers; MR-safe transmission lines; MRI; blocked common-mode signals; coaxial cables; detector; differential-mode signals; dispersion characteristics; frequency 63.8 MHz; low-frequency lumped-element MI band; metamaterial supporting magneto-inductive waves; multiple propagating bands; optical transmitter; periodically interrupted transmission lines; printed circuit board isolation transformers; safe interconnects; series capacitor; standing wave resonance; MRI; magneto-inductive (MI) wave; metamaterial; periodic structure;
Journal_Title :
Selected Topics in Quantum Electronics, IEEE Journal of
DOI :
10.1109/JSTQE.2009.2032782
