GNGTS 2015 - Atti del 34° Convegno Nazionale

160 GNGTS 2015 S essione 3.3 al. , 2010; Pieraccini et al ., 2006; Piscitelli et al. , 2007). On the other hand, several sources of uncertainty can affect the data, among which clutter (van der Merwe and Gupta, 2000), several kinds of noises (Ouadfeul and Aliouane, 2014), model errors (Pierri et al ., 2001; Persico et al ., 2002) and interferences from other electromagnetic devices (Goodman and Piro, 2013). In this contribution, we propose some results regarding the reconfiguration of the integration time of the harmonic tones radiated and received by a stepped frequency ground penetrating radar (GPR) system in a way programmable vs. the frequency. As will be shown, this can allow an efficient rejection of narrow band electromagnetic interferences on the GPR signal without erasing the disturbed frequencies. In fact, as well known (Noon, 1996), by prolonging the integration time, the spectrum of the real radiated harmonic tone becomes narrower, and by means of a suitable filtering in the receiving chain the signal becomes cleaner with respect to noise and interferences. Moreover, this goal is achieved without increasing the transmitted power (because what is increased is the transmitted energy) On the other hand, this achievement is paid with a prolongation of the time required for the measure, but as far as one can prolong only the disturbed tones, the overall prolongation of the measurement time is customarily not critical. However, this implies that the system satisfies some hardware and software requirements that commercial systems usually do not satisfy. In particular, the availability of the management of the integration time tone by tone is not a standard tool for stepped frequency systems, that in general allow (at most) to prolong in the same way all the radiated tones together, so that the extension of the integration time is performed also at frequencies that do not need it. Moreover, this hardware requirement is not sufficient if one does not set an algorithm able to recognize in the field the most meaningful interferences (if any) so to set the prolongation of the default integration time accordingly in an automatic way. The hardware for having selectively extensible integration times has been made available by the research project AITECH (http://www.aitechnet.com/ibam.html ), thanks to which the Institute for Archaeological and Monumental Heritage IBAM-CNR, together with the University of Florence and the IDS corporation, had the possibility to implement a reconfigurable stepped frequency GPR system. Then, the algorithm has been found thanks to subsequent more recent research activities, also performed within the European Cost Action TU1208. Fig. 1 – Left hand panel, the prototypal reconfigurable stepped frequency system. Right hand panel: diagram of the reconfigurable antennas.