Measuring radar cross section at short distance

Radar cross sections (RCS) must be measured at large distance. We exclude here the special near-field methods. The distance (R) must be so large that different RCS contributions are added in the same way as at infinite distance. This leads to the rule if the target cross range is confined within and a phase error of is tolerated. It is shown, however, that if the RCS is measured as a function of an angle and is low-pass filtered with a cut off period of (radians), the distance requirement could be changed to . All RCS measurements at such distances give approximately the same result after low-pass filtering. We assume that a set of isotropic point scatterers, accurately describes the target.