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Abstract-In order to meet the approximate plane-wave irradiation condition, adequate large field or compact range system is needed for RCS measurement of large aircraft targets. However, an outside testing field site or a compact range system is very expensive, so some kinds of RCS extrapolation methods based on near-distance testing have been presented. In this overview, two categories of extrapolating technique are summed up, which are based on Huygens Equivalent Reradiating Source (HERS) and Inverse Synthetic Aperture Imaging (ISAI) respectively. Each method is fully elaborated. The comparison and analysis of these extrapolating techniques are discussed in detail.

Abstract-A fast method for electromagnetic imaging from monostatic full rotational near-field scattering is proposed in this paper. It is based on circular spectrum theory which exploits the Fourier decomposition of the targets distribution instead of point by point imaging in earlier works. The novelty of the proposed method is that it simplifies the relationship between the spatial frequency domain and the scattering field. The near-field scattering is analyzed by expanding the distance to Taylor series at the centre of the targets zone. The nearfield focus function is then transformed to spatial frequency domain and evaluated by the method of stationary phase. The imaging result is given by two-dimensional inverse Fourier transformation from spatial frequency domain of targets. The proposed method is validated by comparing the simulation results of distributed targets with the tomographic imaging. The dynamic range of imaging result is derived by distributed targets with different reflection coefficient. Furthermore, the experiment is also conducted in microwave chamber at Ku band with target placed on the turntable.

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