Modeling conductive polymer antennas in the microwave region

The application of conductive polymers, e.g. PEDOT or PPy, for microwave applications has been researched recently due the advantages of these materials in mechanical flexibility, processability and low cost. A crucial aspect of antenna design is to obtain reliable simulation results. This is particularly challenging for materials with moderate conductivity such as conductive polymers, since the conductivity is in the order of thousands to hundreds of thousands S/m - too low to be a “good conductor”. In this study, a comparison of different modeling techniques generally available in commercial field solvers is conducted. The polymers are either modeled as fully discretized lossy dielectrics, as thin conductive sheets or as impedance boundaries. On the example of an ultra-wideband (UWB) antenna built from samples of PEDOT and PPy, the three modeling techniques are compared in terms of accuracy and computational expenditure in commercial finite-difference time-domain and finite-element codes. The influence of the (often unknown) permittivity of the conductor on the simulation results is investigated. It is shown that for thick conductors, i.e. with thicknesses in the range of the skin depth or above, all three models yield very similar results. For much thinner conductive polymers, a fully-discretized lossy dielectric model shows a good agreement with measured data.