Multiband Software Defined Radar for Soil Discontinuities Detection

A multiband Software Defined Radar based on orthogonal frequency-division multiplexing technique is proposed in this work for an accurate soil discontinuities detection, taking into account also the dispersive behavior of media. A multilayer soil structure is assumed as a validation test to demonstrate the effectiveness of the proposed approach, by accurately retrieving the unknown thicknesses and permittivities of the soil layers. 1. Introduction Electromagnetic sensors such as ground penetrating radar (GPR) are largely adopted for the detection of buried land mines, unexploded ordnance, and soil discontinuities. The performance of these sensors strongly depends on the dielectric properties of the soil, which in turn are related to specific parameters, such as texture, bulk density, and water content. The accurate knowledge of soil dielectric constant is of primary importance in this kind of radar application and is particularly difficult to achieve in the presence of dispersive media, where the dielectric properties vary with frequency. The use of a multiband radar technique can be strongly helpful in this case, thus an approach in terms of Software Defined Radar (SDR) system can be adopted to face the problem. As a matter of fact, the use of SDR technology leads to significant advantages in terms of lowcost, compactness, easy implementation of radar functions, and in particular signal processing techniques. The potentialities of SDR systems have been discussed by the authors in [1, 2] for the case of single-band applications. In this work, a multiband SDR technology is proposed to implement a GPR system, in order to perform an accurate soil discontinuities detection. For the considered multiband application, the adoption of SDR concept provides strong advantages with respect to classical radars, due to the easy software implementation of all required hardware modules, such as mixers, filters, modulators/demodulators, and the easier integration into a unique compact system of all necessary signal processing operations. In particular, in the present work, the adoption of an orthogonal frequency-division multiplexing (OFDM) signal processing technique [3–7] is discussed to implement a multiband radar system able to retrieve the frequency variations of soil permittivity. The benefit of multicarrier radar signaling [8] has been well established in various application fields, such as remote sensing of wheatear forecasting [9], detection of buried objects [10], and interpretation of urban scenes [11]. In these works, the strong advantages of OFDM in terms