Extrapolation of nearfield RCS measurements to the far zone
Abstract
An algorithmic procedure for extrapolating nearfield radar crosssection (RCS) measurements to the far zone has been derived, coded, and experimentally validated. The deviation of the extrapolation algorithm uses an optical model to estimate the surface currents induced on the scattering body by the incident field, and a specially weighted version of the Fourier transform to calculate the nearfield scattering amplitudes associated with such surface currents. The extrapolation entails three steps. First, nearfield measurements of the scattered electric and/or magnetic field are used to infer the monostatic vector potential. Next, the inverse Fourier transform of the inferred vector potential is multiplied by a special weighting function to estimate an equivalent obliquity factor. Finally, the farfield scattering pattern is estmated by taking the Fourier transform of the reweighted obliquity factor. This extrapolation procedure has been validated using anechoicchamber data taken on a rightcircular aluminum cylinder 25 lambda high and 2.5 lambda in radius at nearfield range of 19 percent of 2Dsquared/lambda where D is the nominal target diameter and lambda the radiation wavelength. The extrapolated RCS pattern for this target was compared with an analytical estimate of its farzone pattern and good amplitude and phase agreement was observed over a 20 deg cone of scattering angles.
 Publication:

IEEE Transactions on Antennas and Propagation
 Pub Date:
 June 1988
 DOI:
 10.1109/8.1184
 Bibcode:
 1988ITAP...36..822F
 Keywords:

 Anechoic Chambers;
 Extrapolation;
 Near Fields;
 Radar Cross Sections;
 Wave Scattering;
 Far Fields;
 Fourier Transformation;
 Green'S Functions;
 Communications and Radar