Numerical analysis of a coaxial line terminated with a complex gap capacitance

A full wave numerical analysis was performed for a coaxial line terminated by a complex gap capacitance. The scattering parameters, input impedance and the spatial distribution of the electromagnetic field have been obtained in the frequency range of 100 MHz to 20 GHz for specimens 8 μm to 320 μm thick, with a dielectric constant of up to 70. It was found that the impedance characteristic of the network is affected by the LC resonance coupled with the cavity resonance. Embedding in the network an inductive component, such as section of the coaxial transmission line, allows one to decouple these two resonant behaviors. The specimen inductance is linearly dependent on the specimen thickness. At frequencies near the cavity resonance, the specimen section can be treated as a network of a transmission line with capacitance, where the fundamental mode propagates along the diameter of the specimen. The results are useful in improving accuracy of broadband dielectric measurements in extended frequency range of thin films with high dielectric constant that are of interest to bio- and nano-technology.