Setup and Characterization of a Volumetric $\boldsymbol{W}$ -Band Near-Field Antenna Measurement System

A volumetric W-band near-field (NF) antenna measurement system is presented and evaluated. The system supports measurements at arbitrary locations within the measurement volume with high positioning accuracy together with corresponding field transformations. The measurement performance of the system is carefully investigated with respect to accuracy and efficiency, e.g., by a comprehensive evaluation of room scattering and by laser scanner measurements. The fast irregular antenna field transformation algorithm (FIAFTA) is utilized to perform the necessary NF to far-field transformations. Due to the flexibility of FIAFTA, so-called nonredundant planar measurements become possible, which overcome the classical half-wavelength sampling requirement entailed by the fast Fourier transform-based transformation approaches. Thus, with a time-factor of about 35, accelerated planar measurement results are achieved by projecting angularly uniform sample grids on the minimum sphere around the antenna under test (AUT) onto the measurement plane, resulting in irregularly thinned planar measurement grids. The error levels between two completely independent measurements employing full and thinned grids are found at a level below -40 dB. Moreover, such measurements allow decreasing mutual interactions between the AUT and the probe by increasing the measurement distance, but without the need to collect more measurement samples.