Permittivity Measurement Techniques at 24 GHz for Automotive Polymer Composites Including Thin Films and Paint Foils

Two different measurement techniques for the determination of complex permittivities of automotive polymer composites used as bumper or car body panels at 24 GHz are presented. The materials in focus of this research are basically plastics for injection molding like polycarbonate and its derivatives. The composites include thin dielectric films and paint foils for coloring and lamination of injection molded panels. The advantages and inconveniences of multi-layer measurements in rectangular waveguides and an open resonator are demonstrated. Additionally, an approach is proposed for further investigations on permittivity and loss tangent of automotive dielectrics in the millimeter-wave region.