A permittivity measurement system for high frequency laboratories

[摘要] The open-ended coaxial probe is revisited as a broadband measurement system for generalhigh frequency permittivity measurements. Three coaxial probes were developedthat are suited for the measurement of both liquids and solids. The components of apermittivity measurement system were investigated and improvements were made tothe coaxial probe where needed. This includes the development of a full wave codewith great calculation time improvements without sacrificing accuracy. This code allowsmeasurements to be performed in a high frequency laboratory and the permittivity extractedwithout any mentionable delay. A capacitance model that better describes theimpedance of an open-ended coaxial line is also suggested that can be used for real-timepermittivity extraction over a limited frequency range.Calibration formed a vital part of the project and great time was spent developing aTRL and a SOLT calibration set for the coaxial probe geometry. The combination of theTRL and SOLT standards also allows measurement of the residual errors after calibrationand is used in an uncertainty analysis of the extracted permittivity.Well known materials such as PTFE, PVC, methanol and water were measured totest the probes. The measured dielectric constants are all within 3% of values quoted inliterature. The loss term of the samples are also in good agreement with the expectedvalues.

[发布机构] Stellenbosch University