Near 4π coverage of mono-static radar cross section at 200 GHz using a spherical antenna measurement system

To support antenna applications above 110 GHz, researchers in the Electromagnetics Division at NIST have designed and implemented a high-frequency antenna measurement system. At the heart of the positioning system lies a 6-axis robot capable of performing a multitude of scan geometries around a central point. Our current goals are to provide spherical, planar, and extrapolation antenna measurements on par with other NIST antenna facilities from 50-110 GHz and to extend the range of those measurements to 220 GHz and ultimately to 500 GHz. The robot provides off-the-shelf repeatability of 70 microns. Real-time tracking with a high-speed laser tracker gives the of antenna position to within 20 microns, or λ/20 at 500 GHz, which will be used to with position correction algorithms. We have worked to minimize RF drift and optimize measurement performance from 200-500 GHz with LO stabilization, accurate calibrations, and checks of drift against canonical scatterers.