Comparison of pulsed and stepped frequency continuous wave (SFCW) GPR systems

The use of Ground Penetrating Radar (GPR) in structural investigations is based on the detection of features., embedded objects and flaws that cause a reflection of the transmitted electromagnetic wave. Construction types may vary from concrete to masonry and rock and possible targets include metallic reinforcements., ducts., plastic pipes., air voids., as well as the boundaries of the object itself. While a traditional impulse Ground Penetrating Radar (GPR) system uses time-domain measurements of the reflected waves within the investigated objects., a Stepped-Frequency Continuous-Wave (SFCW) system collects data in the frequency domain and converts the data to time-domain data through computer processing. Until recently., the time-consuming calculations associated with the real-time inverse Fourier transforms in SFCW systems limited its application. Thanks to faster processing capabilities available nowadays., this limitation no longer applies to structural GPR. The experimental work on representative concrete and masonry structures presented in this paper shows a systematic comparison of a new SFCW GPR system with traditional impulse radar systems. The results illustrate that SFCW technology combines the highest resolution in the detection of shallow targets., with a very broad detection range., potentially resolving the resolution/penetration trade-off observed in established structural GPR systems.