Improving Precision of RCS Measurement Based on Spectral Extrapolation Method

This paper proposes a spectral extrapolation method for measuring the RCS at two ends of band more exactly. The measured data are extrapolated to obtain the unknown value out of band with an auto-regressive model (AR model). The parameters in AR model are calculated by using maximum entropy spectral estimation algorithm. Therefore, the span of original band is extended, and the both ends of frequency on original band are inside the range of new band. If a time gating is adding to the new band, the precision at both ends of frequency on original band can be greatly improved. The simulation and experimental results show that about 25% extended data for each ends of original band can be obtained after spectral extrapolation, and even if a time gating reduces the effective frequency domain data, but the maximum error at the ends of band is less than 1dB. Moreover, RCS values near the out of band can be predicted by using spectral extrapolation method. The method can also be applied to broadband RCS measurement.