I. Introduction
The GPR is a well-established geophysical technique for cavity and pipe detection [1], stratigraphy studies, archaeology and polluted monitoring areas [2], [3], [4]. Moreover, the GPR is particularly suitable when used in the frequency range between 1000 MHz and 2000 MHz, as an effective tool for non destructive testing in order to check rebars and defects in the reinforced concrete [5], [6]. Main difficulties related to the GPR technique are connected to the data processing and interpretation.