This paper has for objective to explore the study of a sensor based on a rectangular planar resonator (RPR) for applications to Non-destructive Evaluation (NDE). In this context, conception, modeling, simulation and realization have been made on rectangular structures with an anisotropic substrate and an isotropic superstrate. The theoretical model is based on the moment method (MoM) via Galerkin's approach, in which three types of basis and testing functions are used. These functions as well as the spectral dyadic Green function are efficiently implanted on compact structured Fortran 90 codes. The accuracy of the obtained results is assessed using four prototypes of RPRs operating around 6 GHz, taking only into account the Resonant Frequency (RF) of the fundamental dominant mode. The theoretical model is compared to simulation and measurements results and shown very good agreements. The RPR criteria are established theoretically and validated experimentally with two electromagnetic commercial softwares (HFSS and CST); to be used in future prospects as an electromagnetic (EM) sensor for the characterization of superstrates.