A microstrip bandpass filter with rectangular patch coupled resonator is presented. The filter is designed to be more affected by the dielectric layer above the conductors compared to the same type of parallel-coupled bandpass filter. The filter is designed to operate between 1 GHz to 3 GHz and this can be a sensor base on distributed capacitors. The agreement between the circuit simulator and measured results is excellent and gives a very good prediction for the filter characteristics. The aim of this prototype filter is to show insertion loss (IL) at the bandpass transmission response when a dielectric material is above or near the conductors. A large study around the sensibility and the effect of the dielectric layer is done in order to evaluate its performance in detection and dielectric characterization.