Calibration procedures for antenna footprint measurement of stepped frequency CW radar

This paper presents the calibration procedures for a stepped frequency continuous wave radar designed for detecting flush buried and surface laid anti personal landmines. To image a subsurface the knowledge of the wave fields radiated by the radar below the surface is necessary. The fields can be calculated in the ground by measuring the antenna footprints on the air/ground interface and then synthetically propagate the wave fields into the subsurface by using the Huygens principle. The acquired measurement data needs to be calibrated because of some imperfections of the measurement system. Firstly, the electrical delay within the spirals, the relative position of the direct signal, and clutter signals are removed by an adaptive software gating. Secondly, the effect of the probe is removed. After the proposed calibrations a considerable improvement observed in the measured footprint patterns.