title: Open-Ended Coaxial Dielectric Probe Effective Penetration Depth Determination.
abstract: We have performed a series of experiments which demonstrate the effect of open-ended coaxial diameter on the depth of penetration. We used a two layer configuration of a liquid and movable cylindrical piece of either Teflon or acrylic. The technique accurately demonstrates the depth in a sample for which a given probe diameter provides a reasonable measure of the bulk dielectric properties for a heterogeneous volume. In addition we have developed a technique for determining the effective depth for a given probe diameter size. Using a set of simulations mimicking four 50 Ω coaxial cable diameters, we demonstrate that the penetration depth in both water and saline has a clear dependence on probe diameter but is remarkably uniform over frequency and with respect to the intervening liquid permittivity. Two different 50 Ω commercial probes were similarly tested and confirm these observations. This result has significant implications to a range of dielectric measurements, most notably in the area of tissue property studies.
authors.affiliation: Thayer School of Engineering at Dartmouth College, Hanover, NH 03755 USA ( paul.meaney@dartmouth.edu ).
authors.forename: Paul M
authors.initials: PM
authors.lastname: Meaney
authors.affiliation: Materials Division of the National Physical Laboratory in Teddington, Middlesex, UK TW11 0LW ( andrew.gregory@npl.co.uk ).
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Gregory
authors.affiliation: Cancer Center at Kuopio University Hospital in Kuopio, Finland 70210 ( jan.seppala@kuh.fi ).
authors.forename: Jan
authors.initials: J
authors.lastname: Seppälä
authors.affiliation: Delfin Technologies, Kuopio, Finland ( tapani.lahtinen@delfintech.com ).
authors.forename: Tapani
authors.initials: T
authors.lastname: Lahtinen
keywords: Dielectric; open-ended coaxial probe; penetration depth; probe diameter; tissue properties