Characterisation of materials in the millimeter wave frequency region for industrial applications

The millimeter wave region up to the lower THz region offers a good penetration ability for many dielectric materials which are in use today. Especially for the quality control of foods within its package, impurities can be clearly identified as long as the package is free from any metallic material. Another field of interest is the quality of welded-, brazed- and soldered joints. The present paper describes the detection and characterization of different materials under test by two different measurement systems. An vector network analyzer and a ""Stand Alone MilliMeter wave Imager"" called SAMMI developed by Fraunhofer FHR. For the characterization the different materials will be detect with a clustering algorithm in connection with the optimization of the measured data with regard to the problem of ambiguous phase values, called Phase Unwrapping. The permittivity of the different clusters are determined by a reconstruction algorithm.