Multiprobe-Enabled Over-the-Air Calibration of Millimeter-Wave Antenna Arrays: Concepts and experimental validations

Millimeter wave (mm-wave) antenna array systems with high-gain beam-steerable capability play a key role in fulfilling the high data-rate demands of the 5G and beyond wireless technologies. Rigorous array calibration is essential to ensure that their radiation performance fulfills the standard requirements before massive rollout. These tests will exclusively transition to over-the-air (OTA) testing approaches with antennas included due to the lack of antenna connectors and their compact and highly integrated designs in emerging mm-wave radio systems. This has posed huge challenges for measurement and calibration of mm-wave antenna arrays due to the more demanding requirement on system complexity, implementation cost, measurement time, and measurement uncertainty. In this article, a multiprobe framework for phased-array calibration is introduced, aiming to achieve objectives including measurement range reduction, measurement efficiency improvement, and measurement accuracy enhancement compared with the conventional single-probe method. The basic principle, capabilities, limitations, and design of multiprobe configuration are detailed for each measurement objective. Moreover, extensive measurement results were presented to validate the effectiveness and robustness of the proposed multiprobe-based array calibration algorithms for each measurement objective.