Novel Over-the-Air Test Method for 5G Millimetre Wave Devices, Based on Elliptical Cylinder Reflectors

The goals for 5G New Radio (NR) technology are to deliver wireless communications with higher capacity, performance, and efficiency compared with current mobile technologies. 5G NR will make effective use of the millimetre wave frequency spectrum to achieve these goals. However, these higher frequencies experience greater signal attenuation due to increased path loss and blockages. To overcome these, it is necessary to use high-gain directional active array antenna systems (AAS) at both ends of the communications link, which can steer the radiating beam in multiple directions. The cost-effective and compact implementation of the AAS requires the RF transceiver and antenna array to be highly integrated, making it impossible to independently test the performance of the constituent components due to the lack of inter-stage connectors. Further, the propagation channel is highly dynamic in both temporal and spatial domains. Hence, conformance testing of such systems is most effectively carried out using Over-The-Air (OTA) testing, since traditional conducted non-spatial test methods will not predict the radiated performance in space and the action of the RF transceiver, in particular, the beamformer. This paper presents a highly novel millimetre wave OTA test method facilitating the excitation of a Device Under Test (DUT) from multiple dynamic narrow angles of illumination, thus representing typical operating conditions and avoids the need for physical RF connections. This new method exploits the reflective properties of ellipsoidal surfaces and offers a cost-effective means when compared with other OTA test methods.