Very high resolution radar imaging with a stepped frequency system

There are many potential applications of the Ground Penetrating Radar waiting for a technology breakthrough in the direction of high resolution. We present some experiments where the requirement of very high resolution is pursued through the effective use of the synthetic aperture technique. The successful application of this technique is subject to the compliance with some essential conditions. First of all, the capacity of the system to illuminate the target with a sufficient aperture. A new non-commercial flexible stepped frequency system has been tested in the frequency range of 2-6GHz- A second factor that is essential for performing a good data focusing is the accuracy of the antenna positioning system: a few millimeters precision should be ensured for the above mentioned applications. A careful design of the processing procedure is the third factor that is essential to exploit all the potential resolution of the data. Of course, the procedure should include a SAR focusing algorithm that improves the resolution and that is quite effective in clutter reduction, especially in the 3D case. Tests indicate that the real footprint of the antenna should be used to calibrate the aperture of the focusing operator because this has a positive impact on the SNR of the final image.