Compact range techniques and measurements

Compact range techniques for measuring the gain patterns of full-size microwave antennas and for making radar reflectivity measurements are described. The basic principle of this technique is the use of a large collimating device to generate a uniform plane wave across the aperture of a target or antenna without requiring the normal far-field separation. Two different collimating devices were used in the investigation, a paraboloid with a point-source feed and a parabolic cylinder with a line-source feed generated by a large hoghorn. Pattern and gain measurements were made on both compact ranges using a 30-inch paraboloidal test antenna, and the measurements were compared with similar ones made on conventional outdoor ranges. Radar cross-section patterns as a function of aspect angle were measured for various size standard targets and compared with theoretically calculable radar cross-section patterns. The results which have been achieved are very encouraging. They demonstrate that the performance of compact ranges at the -band is comparable to that of outdoor ranges.