A Modified Physical Optics Approach for Extrapolating Fresnel Region RCS Measurements at High Incidence Angles

The aim of this paper is to extend the application area of the physical optics for RCS measurements at Fresnel region antenna-to-target distances and incidence angles higher than 20° by taking into account the field diffracted by the target edges. The diffracted field is calculated by using an approach based on equivalent currents with diffraction coefficients resulting from the uniform theory of diffraction. The ratio between the analytical expression of the radar cross section at far-field and Fresnel regions results in an extrapolation factor for the diffracted field. The RCS resulting from the scattering parameters measured at Fresnel region distances is then corrected with that extrapolation factor. The experimental validation of the proposed technique demonstrates reasonable agreement with the simulations.