Investigation into antenna measurement quality from a large compact range operating at Q-band

The utility of a compact range is based, in part, on an acceptable purity of its collimated plane wave generated in a well-defined spatial volume (a.k.a. quiet zone) over a given frequency spectrum. Improvements that broaden the useable frequency spectrum lead to greater utility. This is especially true for a compact range supporting an R&D environment where RF sensor technology is reaching higher and higher into the frequency spectrum. In this paper we investigate performance of the AFRL OneRY Indoor Range in which the upper frequency of operation has been extended from Ku-band to Q-band. Specifically, we analyze field probe data and antenna pattern data to determine measurement quality. Field probe results derived from uniform linear RF sampling in the quiet zone are assessed in terms of taper and ripple metrics for both amplitude and phase. This data is also processed into beamforming representation and compared against a predicted pattern generated using an ideal plane wave. The quality of antenna pattern data is then assessed through two types of measurements. Firstly, antenna gain calibration accuracy is examined by employing a method we coined the dual reference antenna diagnostic. Similar to a dual cylinder calibration employed as a RCS measurement quality assessment, the dual reference antenna approach measures the gain of two different antennas that each has an associated calibration table. Secondly, azimuth pattern measurements are evaluated in regards to dynamic range and null depths. The paper ends with a discussion on planned follow-on efforts to improve measurement capabilities.