| Coaxial probes are widely used for in situ measurement of the dielectric properties of materials. Advantages of the coaxial probe include little or no sample preparation along with fast and accurate determination of the complex permittivity. In this work the finite-difference time-domain (FDTD) method is used to numerically model the probe and surrounding region with the objective to investigate and quantify sources of error. Errors investigated include ground plane effects, core deformation, and air inclusion at the termination. Two and three dimensional models have been developed in cylindrical coordinates. An extension to the FDTD method (FD;Results indicted the importance of core and aperture integrity on dielectric measurements. Both core deformities and air inclusions produced discrepancies for small variations that would not be acceptable in dielectric measurements. Ground plane absence produced an error that, while not as significant as termination variations, should be verified before any measurements are performed.;The model and techniques described herein can be used to develop further methods for molding multi-polar and layered materials, coaxial probe design, as well as simulating other physical phenomena suited for cylindrical coordinates. |
