Understanding the Coupling Mechanisms in High Frequency EMT

D Goss1, R O Mackin1, E Crescenzo2, H S Tapp3 and A J Peyton1

1 Engineering Department, Lancaster University, Lancaster LA1 4YR, UK, a.peyton@lancaster.ac.uk

2 IXTREM, 9 Rue Edouard Denis Baldus, 71100, Chalon sur Saone, France

3 Institute of Food Research, Norwich Research Park, Colney, Norwich, NR4 7UA, UK

ABSTRACT

This paper discusses the various inductive and capacitive coupling mechanisms associated with high- frequency electromagnetic tomography (EMT), illustrated with their elemental equivalent circuits. Coupling via the target arises from four mechanisms: the desired inductive – inductive (inductive between source and target and inductive between target and detector), and the unwanted capacitive – capacitive, capacitive – inductive and inductive – capacitive. The coupling mechanisms are fundamental to the operation of EMT at high frequencies but have received little attention in the literature to date. This paper describes practical methods of minimising the capacitive contribution to the detected signal, including electrostatic screening, earthing and the use of an outer ground plane.

Keywords Electromagnetic tomography, inductance, capacitive coupling, screening