Broadband complex permittivity measurement techniques of materials with thin configuration at microwave frequencies

A test method to evaluate the complex permittivity of materials with thin configuration (thickness of 50-300 mu m) is presented. We evaluate the complex permittivity of materials with various mechanical and electrical characteristics (films, powders, and liquids) at frequencies from 100 MHz to 20 GHz and at temperatures from 293 to 353 K using an experimental method presented in this paper. We have developed a fixture having a circular parallel-plate capacitor which is suitable for the measurement of materials with thin configuration. Our method is based on theoretical consideration of wave propagation in the capacitor, which is associated with multiple reflections along the diameter of the sample. The consideration of time delay in the sample section makes it possible to evaluate the permittivity of high dielectric constant materials in the frequency range up to 20 GHz. In addition, some examples for the measurements show that the resolution with tan delta is as low as 0.001. Our method is powerful to understand the relation between dielectric properties and the microscopic dynamics of dielectric materials, because of the broadband measurement, and finally can be applied for various areas both in fundamental researches and practical applications. (c) 2005 American Institute of Physics.