Modified approach for high frequency dielectric characterization of thinly metallized soft polymer film using grounded coplanar waveguide

Abstract

In this paper, we introduce the dielectric characterization of soft polymer, polyurethane (PU), between 1 and 31 GHz frequency band using Grounded CoPlanar Waveguide (GCPW) lines with a modified analytical method. The unavoidable thin metallization (1 μm) of GCPW lines on polyurethane yields high conductor losses, which contribute to the extracted global losses up to 58% at 4 GHz. In order to get more precisely the dielectric losses, a modification of an already existing analytical model by coupling it with 3D electromagnetic simulations is proposed, which allows to estimate and subtract quickly the conductor losses. The measurements indicated that polyurethane relative permittivity ranges from 3.49 to 2.65 and the loss tangent was about 0.08, which is in agreement with the state of the art on this grade of PU as well as the Metal-Insulator-Metal capacitors characterizations (from 10−1 to 107 Hz and from 2 × 108 to 5 × 109 Hz). The proposed approach may open a fast and simple way for precisely determining the microwave dielectric properties of (ultra) soft polymers in a large bandwidth.