A new technique to measure RCS of large target at near distance

In general, RCS measurement must meet the far-field condition, which need a vast measuring area or a costly compact range. To solve the problem, a new technique by extrapolation correction dealing with near-distance RCS measurement of aircraft targets is set up. The RCS of aircraft target under spherical wave illuminating can be adopted to extrapolate far-field RCS of them. The convolution arithmetic utilizing conductive board as a reference target deduces the phase-correction coefficient g(x) between spherical and plane wave, and in fact the convolution calculation of g(x) can be replaced by Fast Fourier Transform, which is related to the scattering field of the reference target measured in near-distance, thus the calculating procedure could be completed simply and quickly. By theoretical simulation for a simple target, the RCS extrapolated can be obtained correctly. Experimental results of complex aircraft target show that this new technique makes experiment agree to theory precisely, moreover, it permits the measurement distance reduced by 15 percent of the minimum distance of far-field. Also, there is no serious limitation of measurement for target in dimension of aperture and depth.