A Technique for Radar Cross Section Measurements in the Fresnel Region

This letter presents a novel inverse scattering method for estimating the radar cross section of a target placed in the Fresnel region of the radar antennas. By considering a constant current distribution on the transmitting antenna and a uniform illumination of the target and furthermore of the receiving antenna, the electromagnetic field is averaged over the apertures of the antennas. The hypothesis of a constant current distribution stands for ultrawideband antennas, and a quasi-uniform illumination can be assumed for ranges within the Fresnel region and for the particular case where antenna and target sizes are in the same order as the distance to the target. A calibration procedure for the measurement setup is also proposed. A validation of the method through simulations and measurements in an anechoic chamber and in a real, multipath propagation environment is provided by using two different types of antenna systems.