Uncertainty in transmission line microwave measurements

In this paper the author presents revised results of a measurement intercomparison with the National Physical Laboratory showing a significant improvement in the level of agreement. The measurements presented are of complex permittivity and permeability for solid materials at microwave frequencies using a Vector Network Analyser and S-Parameter Test Set. The permittivity and permeability are derived from the measured S-parameters using a transmission line method. The measurement system is designed to meet the requirements of the IS0 9000 and UKAS M10 Accreditation standards to provide internationally recognised measurement traceability to national standards. The current system meets the requirements of UKAS Accreditation. Also included are comparisons with other measurement techniques including a free-space quasi-optic system and a broadband dielectric spectrometer. The materials used in the comparison are polymeric and ceramic in nature, some being purely low loss dielectrics and some having lossy magnetic characteristics. The comparison demonstrates the relevance of using different techniques for different types of materials and/or test sample geometries.