Radiation Pattern Verification of Active Antenna Systems Using Near-Field Measurements

Abstract

Fifth-generation (5G) new radio and commercial networks are currently deployed by telecommunication service providers around the globe. A 5G active antenna system (AAS) consists of a passive antenna array, a transceiver front end, and a baseband unit-all integrated into a single module. As a consequence, the radio frequency ports of traditional base station antennas can be replaced with an Ethernetbased interface. New methods are needed to verify and optimize the antenna performance under these conditions. In this article, we propose an over-the-air (OTA) near-field method that makes it possible to measure and verify the radiation pattern of an AAS. A vector signal generator is used to provide a single-tone source at 3.5 GHz for a commercial passive base station antenna. To reconstruct both the near-field amplitude and the phase distribution of the near-field region of an antenna, we did the following. Two receiving paths to the vector network analyzer (with a reference antenna located at the back of the base station antenna) were combined with an existing probe antenna of the spherical nearfield measurement system. This way, a far-field radiation pattern can be realized using near-field-tofar-field transformation methods. The radiation patterns, which are measured using the OTA mode near-field method, are consistent with conventional near-field methods for 5G sub-6 GHz radio units.