Validation of diffraction theory by means of extensive measurements, part 1

In the FEL computer model the radar cross section of arbitrary objects is calculated by applying geometrical optics and physical optics. In order to perform the computations more accurately, the model also accounts for diffraction phenomena. A large number of measurements and simulations carried out to validate the diffraction theory implemented is presented. During the analysis of the results, it turned out that there was a large difference between measurements using horizontal polarization and those using vertical polarization. At vertical polarization the measurements and simulations generally showed good agreements. At horizontal polarization, however, large differences between the measurements and the simulations occurred. Further analysis showed that these differences were most likely due to the fact that the implemented diffraction theory does not account for multiple diffraction. Apart from that, the anechoic chamber caused problems because of its relatively high clutter level, which was in the same order of magnitude as the measured signals. For further validation efforts, it is therefore recommended to include multiple diffraction in the computer model and to perform new measurements under more controlled conditions.