Spherical mm-Wave/THz Antenna Measurement System

This paper presents an automatic characterization system for mm-wave antennas based on a spherical positioning system. It features network-analysis based far-field- and S-parameter measurement of probe- and waveguide-fed antennas between 220 GHz and 330 GHz, expandable down to 75 GHz. In either case, the antenna under test (AUT) is fixed in the center of a spherical coordinate system and fed by an appropriate feeding structure, whereas the receiving antenna is moved along the surface of a hemisphere. Since the movement of the receiving antenna is inherently limited to constant radii, the measurement of amplitude and phase far-field-pattern is possible in principle. Additionally to the measurement results of an open-ended waveguide as AUT, this paper describes two methods for the self-characterization of possible systematic and stochastic measurement uncertainties. On one hand, repetitive measurements along a constant trace are carried out to obtain information about the stochastic uncertainty of far-field measurements. On the other hand, a synthetic aperture radar (SAR)-approach is used to characterize possible unwanted reflections within the measurement setup. Finally, the insight obtained from both antenna measurements and self-characterization is concluded into performance parameters of the presented measurement approach.