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Department of Energy's ground penetrating radar (GPR): an FM-CW system

The United States Department of Energy's Special Technologies Laboratory (STL) has been actively involved with ground penetrating radar technology since 1968. A ground penetrating radar will utilize the reflective properties of various dielectric interfaces and nonhomogeneous materials in the soil to obtain target information. The production of total site characterization data will require implementation of advanced imaging techniques, data fusion, highly accurate decision, and delineation of subsurface objects. To meet these new technical requirements for high resolution data, STL is moving forward with advances to GPR technology with development of a stepped FM-CW Ground Penetrating Radar. This unit operates over a frequency range of 196 MHz to 708 MHz and produces phase-coherent data. It has a real-time display of data, saves the data to floppy discs and can also produce hard copies in the field. This system has successfully detected targets ranging from 60 mm projectiles to 500 pound bombs up to 15 feet deep. Additional field deployment of the GPR produced successful results on other metallic and nonmetallic targets. This paper outlines the theory of operation of a Stepped Frequency Modulated, Continuous-Wave (FM-CW) Ground Penetrating Radar, provides a technical description of the unit, data display format and presents some sample data sets.