This dissertation summarizes the research performed towards the development, analysis, and testing of two new sample configurations used for characterizing dielectric materials over a wide band of frequencies. In the two configurations, a cylindrical cavity completely filled with a sample of the dielectric material of interest is used. The two configurations are the following: 1. The cylindrical cavity is adapted to the end of a transmission line and the reflection coefficient is measured. The complex permittivity of the dielectric sample is then derived from the measured reflection coefficient information. 2. The cylindrical cavity is placed between two transmission lines. The complex permittivity of the dielectric material can be computed from either the measured reflection coefficient or the measured transmission coefficient. The full field analysis of these configurations is carried out and the solution is obtained using the method of moments. Computer simulation experiments are performed to test the sensitivity of these techniques and predict their performance. Actual experiments on some dielectric materials with known dielectric properties are performed for verification. The first configuration is also used to characterize two thick film dielectric materials. These configurations proved to provide solutions to the many problems with the conventional configurations found in the literature. / Ph. D.