An RTS-Based Near-Field MIMO Measurement Solution—A Step Toward 5G

Multiple-input and multiple-output (MIMO) over-the-air (OTA) measurements have helped 4G wireless systems significantly for the communication throughput and to enhance the network stability. However, there remains a potential challenge, which may substantially obstruct the OTA test methodologies being adopted in 5G evaluations. According to the MIMO OTA measurement standards, throughput tests should be conducted in the far-field. As a result, a general system covering all the 4G frequency bands should be larger than 3.6 m, and even tens of meters for 5G. In addition to the cost of the chamber hardware, a sizeable footprint of building space is also required for the test system. Consequently, conducting far-field tests directly incurs excessively high costs in 5G. A compact system with dimensions of 1.9 m for 5G MIMO OTA is proposed in this paper, where a near-field to far-field transformation method is adopted into the current standard MIMO OTA test approach (the radiated two-stage approach), and the throughput in the near field is measured. Compared to existing test systems, the compact solution can achieve a cost reduction by at least an order of magnitude and obtain comparable results as a full-scale certification system.