The RASCAN holographic subsurface radar [1] has been investigated for the detection of small plastic antipersonnel landmines buried at shallow depth in soil. The investigation consists of the comparison of data obtained by surface scans in an outdoor test bed with two RASCAN systems operating at different discrete frequencies near 2 GHz and 4 GHz, each with receiving antennae both parallel and perpendicular to the polarization of the transmitter. The two systems have different signal penetrations (up to 20 cm in dry soil for the 2 GHz), different antenna radiation patterns and different sensitivities for the parallel and perpendicular polarization images. RASCAN has the capability to record small phase changes in the received signals due to electromagnetic impedance discontinuities. This high sensitivity is an advantage to detect small (5 cm diameter) plastic targets but introduces also clutter signals due to surface irregularities and the other clutter objects commonly found in a battlefield. The choice of the operating frequency, the coupling of the antenna with the soil surface and the scanning spatial sampling is important to get enough information for the efficient detection of small plastic targets. Thanks to the high spatial resolution of the RASCAN images, the detection of targets by direct image interpretation is still possible, but is time consuming, is limited to the sensitivity of the human eye grey scale variations, and may be subjective based on different operators experience and level of expertise. This paper is a comparison of the output of experiments made in Italy, Japan and USA using RASCAN holographic radar to identify the presence of plastic mine simulants buried in soil. Experiments covered the response variability due to surface conditions in Italian experiments, moisture level in Japan experiments and a feature of PMA-2 mines in USA experiments.
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