Conventional GPR antennas emit a quasi-monochromatic electromagnetic pulse around a certain frequency. As a consequence, the bandwith (difference between the maximum and minimum radiated frequencies) is very narrow, thus limiting resolution (minimum size of a detectable object).
The Step-Frequency technology is based on emitting a continuous radiation with a time-increasing frequency. This produces a broader frequency spectrum than the one obtained with traditional antennas. Current GPR equipment allow to record data from 100 MHz to 3 GHz. If a similar bandwith dataset was to be achieved using conventional monochromatic antennas, the survey would have to be repeated several times using each time a different antenna, with the associated increase in economical costs.