Recent Developments in Radiated Two-Stage MIMO OTA Test Method

This paper discusses recent developments with the Radiated Two-Stage (RTS) MIMO OTA test method. It first introduces the concept of the two-stage method which is based on a first stage of antenna pattern measurement followed by a second stage of throughput measurements using a downlink signals from the communication analyzer that incorporate a convolution of the device’s antenna patterns with the desired spatial channel model. The resulting signal is applied to the DUT through the radiated connection, which has the equivalent wireless cable effect. The RTS method was approved by 3GPP in Technical Report 37.977 v12.0.0 and is considered harmonized with the Multi Probe Anechoic Chamber (MPAC) methodology. This paper will review recent RTS advancements in 3GPP and CTIA, including 4x4 MIMO OTA test on LTE devices, analyses of CTIA RTS-MPAC SNR-controlled harmonization test results, and the variable Reference Measurement Channel (RMC) MIMO OTA test for SNR-controlled and UE noise-limited environments.