Standing wave measurements to determine the dielectric properties of liquids and gels for use in microwave phantoms

The aim of this project was to produce microwave phantoms for testing a microwave technique for treating oesophageal malignancies. The microwave phantoms must respond in the same manner as living tissue would when microwaves are applied. The relative permittivity and electrical conductivity must be known in order to match the phantom to the specific tissue being investigated. This paper describes the apparatus developed specifically for this purpose. The apparatus consists of a scalar network analyser with the test material constrained inside the line with a short circuit to reflect the signal back to the analyser. The reflected scalar data gives enough information to allow the relative permittivity and the electrical conductivity to be calculated. Experimental data were compared to standard reference materials. This experimental set-up provides the required dielectric information over a frequency range of 0.8 to 2.5 GHz.