Permittivity Characterization of Automotive Paint Material at W-Band Frequencies

In this paper, a technique for the characterizing the complex permittivity of a thin layer of automotive paint at millimeter-wave frequencies based on the free-space reflection measurement technique is presented. The retrieval algorithm of the complex permittivity is based on fitting the measured reflection coefficient of a layer of paint backed by a flat metallic plate to the corresponding analytical reflection coefficient of a simple dielectric slab backed by perfect electric conductor. Details of the technique are presented along with validation and permittivity data of different types of paint material. A hybrid low-high frequency technique for measuring the permittivity, devoted for non-uniform paint thickness case, is also introduced.