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 ruleR > 2D²/ the target cross range is confined within± D/2and a phase error ofπ /4is 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 ofφc(radians), the distance requirement could be changed toR > 4Dφ⁻¹c(1 - λ/2φcD)). 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.