Indoor 3d Spherical Near Field Rcs Measurement Facility: Innovative Technique For Positioner Error Correction

Indoor RCS measurement facilities are usually dedicated to the characterization of only one azimuth cut and one elevation cut of the full spherical RCS target pattern.In order to perform more complete characterizations, a spherical experimental layout has been developed at CEA for indoor Near-Field monostatic RCS assessment [1].This experimental layout is composed of a 4 meters radius motorized rotating arch (horizontal axis) holding the measurement antennas while the target is located on a mast (polystyrene or Plexiglas) mounted on a rotating positioning system (vertical axis) [2] .The combination of the two rotation capabilities allows full 3D Near-Field monostatic RCS characterization.The major measurement contributors to uncertainty are due to the near field illumination [9], the influence of the mast supporting target under test [8], and the uncertainty due to bearing imperfections of the Roll positioner. This error can create undesired movement along the radial dimension of the test range and corresponding errors in the measurement phase.This paper presents the results obtained after the installation of a hexapod under the roll positioner, allowing correcting the various positioning errors related to the mechanical float, but also to an improper positioning between the positioner roll's center of rotation and the polystyrene mast supporting the target under test.