Măsurarea suprafeței echivalente radar într-un mediu real / Radar cross section measurements in a real environment

Radar cross section (RCS) measurements are generally performed in anechoic chambers or in an open area test site, under far-field conditions. Large targets, such as aircrafts, ships, and other large vehicles cannot be placed inside an anechoic chamber, or the cost of such a measuring site would be prohibitive. Moreover, classical near-field to far-field transformations are complex, time-consuming and expensive to be implemented at a large scale, and therefore not suitable for processing data in a real-time scenario. To overcome these drawbacks, we propose a technique to evaluate the RCS in the Fresnel region in a multipath environment. An analytical field-zone extrapolation factor is derived; a computing time saving technique with Fresnel integrals is then developed and experimental results are provided by using three different antenna systems: vivaldi, log-periodic and horn antennas. The RCS measurements are performed over simple and complex targets placed in real environment. The distance averaging technique, coupling subtraction and time gating are proposed in order to reduce the effects of the environment. The RCS is evaluated also at high incidence agles by taking into account the effects of the diffraction.