Material Characterization using High-Resolution Multiple-Input Multiple-Output Imaging Radars

A comparison between a quasi-optical and a multiple-input multiple-output (MIMO) measurement system for highly accurate over-the-air material characterization is presented. Both setups are described in their principles and the necessary calibration steps are discussed. The ability of finding resonances with sub-percent deviations of the respective reflection and transmission coefficients is shown with an example glass-ceramic plate. Furthermore, a method for estimating the dielectric constant based on nearfield MIMO measurements is introduced. The method is verified based on measurements of different materials and the estimated dielectric constants are compared with reference literature values.