Radar cross section (RCS, dimensions velence m~(2)) quantifies the electromagnetic scattering behaviour of a radar target. RCS measurements are made by illuminating the target with a planewave and observing the scattered far-field. If the antennas used for illumination and observation are coincident, the RCS is termed the monostatic RCS. Final evaluation of a target's RCS is often performed by measuring the scattered field from the whole target; however, during the process of target design other RCS assessment techniques become applicable. The scattering sources which contribute to the RCS of a target can often be quasi-2D (two-dimensional). Edges, ducts, gaps, joints and material junctions are structures which contribute to RCS and which have little variation in one dimension. In order to measure the RCS of 2D components (dimensions velence m) measurements are often performed on the isolated component using a conventional RCS range. This approach to characterizing a 2D structure is however limited by the fact that the structure's perimeter is fully illuminated by the incident wave. The complete illumination of the quasi-2D component causes the occurrence of scattering phenomena which are dependent not only upon the 2D structure but also upon the perimeter of the test piece geometry. This effect can cause significant differences between the correct 2D RCS and the 2D RCS derived from measured 3D data. Once a 2D structure has been characterized, the 3D RCS for an arbitrary length of the 2D component is easily obtained through the use of standard transformations; it is for this purpose that 2D RCS data are sought. The geometry of the test piece can be chosen to minimize the effects of scattering from the test piece's perimeter: for the measurement of a material junction, the use of a diamond-shaped test piece has been investigated [1]. Perimeter scattering and other non-2D effects may nonetheless remain in measured data. The use of filtering in the time domain sometimes reduces the error in 2D data taken using a 3D range; however, where perimeter scattering is temporally coincident with test sample scattering, errors will remain in measured data. Errors of between 2-5 dB [m~(2)] are not uncommon [1]. In this contribution, a method is introduced for the direct measurement of 2D RCS at microwave frequencies. The method is outlined in Section 2. Results from preliminary measurements are discussed in Section 3.
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