Indoor RCS measurement facility ARCHE 3D: RCS multi-calibration under spherical wave

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. 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). The combination of the two rotation capabilities allows full 3D Near-Field monostatic RCS characterization. To correct the gain of instrumentation a calibration method is used; a standard object (like a sphere) is placed at the intersection of the measurement layout axes. But especially in Near-Field, it remains an important error out of the calibration area due to the decrease and sphericity of the electromagnetic waves. This paper compares a new method of calibration based on an experimental correction with the Huygens Lens method. Thanks to many measurements of standard, we are able to perform a multi-calibration method in space domain to reconstruct a RCS measurement in frequency domain.