Improved Near-field to Far-field Transformation for RCS and Antenna of Large Body

The measurement for radar cross-section (RCS) of electrically large object such as airplane and for radiation pattern of large antenna are demanded strongly. We propose the improved novel near-field to far-field transformation method (NFFFT) in cylindrical scanning, from which RCS can be estimated by pickup near-field data. Our method is featured by the improved focusing factor obtained from the exact transformation integral using small spheres. This factor leads more accurate estimation for strong asymmetrical object, so that RCS measurement is available even in small anechoic chamber. In this paper, applying geometrical theory of diffraction (GTD) to simple shaped models as a target, and it is shown high agreement between them and measured NFFFT results including antenna pattern. Furthermore, we discuss suppression method of unnecessary wave by imaging-area limiting.