Free-Space Calibration for a 5G Antenna Array

This paper proposes a photonics-based free-space calibration method for a 5G antenna array. The free-space calibration method uses a highly stabilized planar field imaging system with an electro-optic probe developed by KRISS. This system enables measurements at the reactive near-field region of a 5G antenna array. Then, a complex excitation coefficient of each antenna is determined from the measured magnitude and phase data; based on this, free-space calibration is possible by individually compensating for the magnitude and phase errors of each antenna. The prototype of the 5G antenna array used in the experiment is a 28 GHz 4x1 dual-polarized patch antenna array developed by KRISS. By applying a commercial beamforming IC, the prototype can control the magnitude and phase of individual antennas. To verify the performance of the proposed free-space calibration method, we present the experimental results demonstrating that the electric field of a dual-polarized antenna array is capable of beam steering at 28 GHz.