Permittivity Determination by Polarimetric MMW Radiometry

Abstract

The characterization of dielectric materials is of great importance for many applications, being for instance quality control during product fabrication, status control of outside constructions over time or determination of ground properties for agricultural purposes. In many outside situations the objects of interest have limited accessibility, the investigation has to be done without destruction of any part of the object, or large areas have to be characterized by automatic operation. The use of microwaves, millimeter-waves or THz waves offers some penetration capability into matter, depending on its chemical and physical decomposition and of course frequency. Many objects of interest consist of a dielectric coating or enclosure, which can electromagnetically be treated as a dielectric layered structure or a dielectric slab surrounded by air. In previous work an approach has been established using polarimetric millimeter-wave radiometry for extracting the real part of the permittivity of surfaces, being the fundamental quantity for many higher level data products. Hereby an imaging radiometer scanner has been used to measure the first three components of the Stokes vector of a scene containing various targets of interest. Those are for instance plane surfaces being tilted such that cold sky radiation is reflected towards the radiometer. Results of various experiments and first error estimation are presented and discussed.