Microwave Reflectometry for the Diagnostic of Cultural Heritage Assets

A non destructive diagnostic method for cultural heritage assets based on microwave reflectometry has been studied and developed. This new method is implemented with a ridged antenna operating in the range 1.5-3 GHz for the detection of reflected wave amplitude and phase variation due to the dielectric properties of the materials under investigation. Particular interest has been devoted to wood structures attacked by fungi and insects and to mural paintings with delaminations due to subsurface humidity. A simplified model of the antenna coupled to the material has been implemented in terms of a cascade of transmission lines in order to investigate the response of the system in presence of dielectric discontinuities. A series of laboratory models have been developed to assess the capability of the method to display in real time images of a calculated parameter which includes both amplitude and phase variation respect to a reference response taken from a homogeneous portion of the investigated item. A novel compact easy to use in-situ optical system mounted on the antenna has been developed to correlate the positions of the antenna on the surface with the optical digital picture, avoiding cumbersome wheel optical encoding which need flat surfaces and raster lines for guiding the manual scan.