PRECISION RADAR CROSS-SECTION MEASUREMENTS FOR COMPUTER CODE VALIDATION

This paper presents precision measurements of the radar cross section (RCS) of simple rod and cylinder targets for all angles of incidence in a plane containing the long axis of the target. The RCS is presented as a contour map as a function of the frequency and the incidence angle. Interference of the scattered fields from the two ends of the rod or cylinder creates a series of sharp minima; these form a characteristic pattern. A wire attached to the rod target scatters strongly at its resonant frequencies, introducing constant-frequency maxima on the RCS contour map. These extensive measured RCS data are used as a reference for validating numerical computations. Wire-grid models of the rod and cylinder targets are constructed using commonly accepted guidelines. It is shown that the resulting RCS is in error by less than 2 dBM2 for segments of length as long as lambda/5, and that the wire grid is capable of precisely determining the resonant frequencies of the wire. A comparison of the RCS of the rod computed using the finite-difference time-domain method with the measured RCS suggests a cell-size correction. Thus, the surface of the conducting object is considered to be 1/4 cell away from the surface of cells designated as perfectly conducting. This ''quarter-cell margin'' guideline greatly improves the agreement between the FDTD RCS of the rod and cylinder targets and the measured RCS.