language: en

[Confidential: not for distribution. Submitted to IOP Publishing for peer review]

17 December 2009

Thin-film Magneto-Inductive Cables

by R.R.A.Syms * , L.Solymar, I.R.Young and T.Floume

Abstract Magneto-inductive cables for low (ca 100 MHz) radio frequencies are demonstrated in thin-film form. 20 cm long resonant elements are formed using double-sided patterning of copper-clad polyimide, based on single-turn inductors and parallel plate capacitors that use the substrate as an interlayer dielectric. Continuous cables are formed by overlaying elements, in an arrangement that allows a high, positive coupling coefficient (κ > 0.6) to be achieved despite the use of a planar geometry. Equivalent circuit parameters are extracted from experiments on integrated coupling transducers, and propagation characteristics are compared with simple theory. Low propagation loss (4 dB/m at 55 MHz, falling to 2.3 dB/m at 130 MHz) is demonstrated near the operating frequencies of magnetic resonance imaging, for a potential application as patient-safe cable in internal imaging.

KEYWORDS Metamaterial, periodic structure, magneto-inductive wave PACS numbers 41.20.-q Applied classical electromagnetism 81.05.Zx New materials: theory, design and fabrication 84.30.Bv Circuit theory
Optical and Semiconductor Devices Group, EEE Dept., Imperial College London,
Exhibition Road, London SW7 2AZ, UK

[Corresponding Author:]

TEL +44-207-594-6203 FAX +44-207-594-6308 Email r.syms@imperial.ac.uk 1. Introduction