New Measurements Concept of Electrically Large Active Antenna Systems in Compact Test Chambers

Basestation antenna systems in 5G new radio present two significant challenges for antenna measurement: Electrically large DUTs (device under test) without traditional RF port interfaces. Therefore, several transceiver performance metrics need to be measured OTA in far-field conditions, including Error Vector Magnitude (EVM), Adjacent Channel Leakage Power (ACLR), and Spectral Emissions Mask (SEM). Due to the basestation size in the 5G sub 6 GHz frequency bands, this requires a far-field chamber with 10 to 50 meters of range length. This paper describes a new measurement concept in compact test chambers using the first commercially available Plane Wave Converter (PWC): The R&S PWC200 is a phased antenna array of 156 elements located in the near-field of the DUT. It uses a variant of a hardware based Fourier transform to create far-field conditions, a quiet zone of a plane wave of e.g. 1m diameter at a distance of 1.5 meters. The measurement system is bidirectional and able to directly measure both traditional antenna metrics of gain as well as transceiver metrics of EVM, ACLR, SEM, and receiver sensitivity. We present sample measurements with the R&S PWC200 of a high gain basestation antenna of dimensions 60 x 60 cm, which are in excellent agreement with measurement results from a third party certified laboratory.