Ground-penetrating radar (GPR) is a wide ranging non-destructive tool used in many fields of application including effective pavement engineering surveys. Despite the high potential and the consolidated results obtained over the past decades, pavement distress manuals based on visual inspections are still widely used, so that only the effects and not the causes of faults are generally considered. In such context, simulation can represent an effective solution for supporting engineers and decision-makers in understanding the deep responses of both revealed and unrevealed damages. In this study, the use of FDTD simulation of the GPR signal is analyzed by simulating three different types of flexible pavement at two different center frequencies of investigation commonly used for road surveys. Comparisons with the undisturbed modelled pavement sections are carried out showing promising agreements with theoretical expectations, and good chances for detecting the shape of damages are demonstrated

Antennas are a critical hardware component of a radar system, dictating its performance in terms of capability to detect targets. In this Chapter, a wide review on Ground-Penetrating Radar (GPR) antennas is given. Firstly, the gen- eral characteristics of GPR antennas are resumed and the requirements they have to satisfy are listed: these are somehow unique and very different than in conventional radar antennas, since GPR antennas operate in a strongly demand- ing environment, in close proximity to or at a limited distance from the natural or manmade investigated area. Subsequently, an overview on the most frequently used GPR antennas, for both pulsed and stepped-frequency radar systems, is pro- vided; recent studies concerning innovative solutions are presented and informa- tion on antenna arrays for GPR applications is included, as well. The Chapter continues with a census of commercial antennas of a number of GPR manufactur- ers, where the centre frequencies and general characteristics of the antennas avail- able on the market are schematically organised in tables. Aided by measurements and powerful computer modelling techniques, GPR antenna designers are increas- ingly able to predict and understand the performance of proposed design in real- istic electromagnetic environments: the Chapter includes two sections reviewing techniques for the experimental characterisation and numerical modelling of GPR antennas. Finally, conclusions are drawn and research perspectives in the field of GPR antennas are discussed