Calculations on the time domain reflection behaviour of a transmission line partly filled with a polar dielectric

In this paper the reflection behaviour of a transmission line, partly filled with a polar dielectric, is calculated in the time domain, applying an ideal voltage step (zero risetime) to a dielectric sample of infinite length (no multiple reflections).To extend and generalise former work, the polar dielectric is characterised by three relations of the complex permittivity belonging to three current, partly empirical, models. Low frequency conductivity is also included.It turns out to be impossible to determine the dielectric relaxation time immediately because the type of dielectric model involved cannot be recognised from the shape of the response curve. A Fourier transform of this response is then necessary.The high frequency permittivity can be determined directly but not for all dielectrics with the same accuracy.A determination of the low frequency permittivity can be disturbed by a slow approach of the response curve to its large time asymptote and by low frequency conductivity processes.To avoid problems it proves useful to determine the low frequency permittivity and low frequency conductivity seperately with the aid of known standard dielectric measurement techniques.