A time-reversal imaging algorithm for localization and moisture level detection in the polymer foam in an industrial microwave drying system

A microwave tomography (MWT) system has been integrated in an industrial microwave drying system named HEPHAISTOS to obtaining the location and level of the moisture inside a polymer foam. This information is demanded as an input for an intelligent controller. Herein, a time-reversal imaging (TRI) algorithm with a proper Green’s function is proposed for MWT in the X-band frequency range (8 GHz to 12 GHz) to obtain the moisture distribution inside a polymer foam in an industrial microwave drying system. The effective permittivity (which correlates with the moisture level) of the detected moisture level is retrieved by evaluating the largest eigenvalue associated with the multi-static data Matrix and using a minimization problem. Simulation results show the performance of the proposed method.