Advances in the development of step frequency ground penetrating radar

In this paper, we describe the background and developing research in Step Frequency Ground Penetrating Radar (SFGPR), and its potential capability in comparison with the more conventional impulse radar. We also describe our own development of a SFGPR system. Although the SFGPR technique has been investigated since 1972, its potential has not been fully exploited for field applications. The technology needed to implement the technique has, until now, lagged behind that of impulse hardware. However, due to the advances in frequency synthesisers and signal processing, it is now timely that a critical comparison of field performance between the two GPR techniques is made. In Australia, we began a project in 1993 to develop an experimental SFGPR system and to evaluate its performance against impulse radar. The system developed at this stage has been specifically designed for high-resolution, shallow-depth applications to map geological interfaces and to detect buried objects. Early results have demonstrated that a better performance can be more easily realised with the step frequency technique compared with swept-FM or impulse radar for these applications. This paper attempts to convey a fuller understanding of SFGPR by describing how the implementations of the step frequency and impulse techniques are different, although they adhere to the same principles of requiring wide bandwidth for resolution and high energy for penetration depth. We suggest that the controlled transmission of highly coherent signals produces a benefit over impulse radars. Other benefits arise through a more efficient use of transmitter power and received signal power. We present images obtained by our radar on an experimental test pit showing its closerange and high-resolution capability. We also comment on further improvements which the technique allows.