An improved image-based near-field-to-far-field transformation for cylindrical scanning surfaces

An improved image-based circular near-field-to-far-field transformation (NFFFT) developed recently by the authors for smaller measurement facilities and for targets with pronounced scattering centers offset from the center of the imaging area is extended to a cylindrical scanning surface. Scanning over a surface instead of a circle permits RCS estimations for targets whose size in the direction perpendicular to the measurement plane is comparable to their extension in the measurement plane. The approach consists in near-field imaging of the target, followed by integration of the image. The focusing operator, which is used to generate the image, is built in such a way so that the image of an electrically small PEC sphere is exactly the delta function. The paper describes the effect of various transformation parameters such the sampling rates in the input data and in the image domain on the quality of RCS estimations.