RF and microwave dielectric measurements upon layered materials using reflectometric coaxial sensor

This report describes progress at the National Physical Laboratory on the application of coax-ial reflectometric sensors to the measurement of RF and Microwave dielectric properties of laminated materials. Measurements were performed in the range 300 MHz to 3GHz, but our findings can be applied over the whole of the RF and Microwave range. As a result of the work described both high and low loss materials can be measured by coaxial sensors. Suitable specimens of one, two and three dielectric layers can be characterised. A cell attachment has been constructed for a 14-rnm diameter sensor which allows circular specimens to be mea-sured more accurately. The cell also allows liquid immersion measurements to be performed, which affords greatly improved uncertainties. Three independent computer programs have been written to analyse multilayer laminar specimens. The programs have been intercom-pared and have been shown to agree numerically to well within expected measurement un-certainties. Measurements upon liquid and solid materials of known permittivity have been compared with the program predictions and shown to agree sufficiently well to allow the system to be used for traceable measurements within the National Measurement System.