For imaging systems that rely on approaches using signal correlations, both the magnitude and phase of antenna radiation patterns are critical. Yet the outdoor range (ODR) is not conducive to amplitude measurements, which are impacted by atmospheric attenuation and other factors. Thankfully, both the design and application of a system for measuring the magnitude and phase of antenna radiation patterns from 182 to 194 GHz have been completed by Stephanie L. Smith, John W. Archer, Greg P. Timms, Ken W. Smart, Stephen J. Barker, Stuart G. Hay, and Christophe Granet at Australia’s CSIRO ICT Centre.

That team successfully developed and applied a compact antenna test range (CATR) to accurately measure the magnitude and phase for the radiation patterns of large-aperture, millimeter-wave antennas in a controlled environment. This CATR approach uses shaped-beam horn feeds and a compact paraboloidal reflector to illuminate the antenna under test (AUT) with a field that approximates a plane wave. In addition, the team developed a phase measurement system, with a heterodyne receiver incorporated into a 12-m anechoic chamber.

When idle, the system’s phase variation averages 0.3 deg. over 227 s and 4.5 deg. over 30 min. These measurements translate into amplitude stability beyond ±0.15 dB over a 63-h period. To show this system’s performance and potential applications, the researchers used it to characterize the magnitude and phase radiation patterns of a beam-scanning pillbox antenna for a 186-GHz imaging system. See "A Millimeter-Wave Antenna Amplitude and Phase Measurement System," IEEE Transactions On Antennas And Propagation, April 2012, p. 1744.