Wideband Inverse Matrix for Radiated Two-Stage MIMO Measurements

Multiple-input and multiple-output (MIMO) technology is one of the significant components in the growing fifth-generation (5G) communication systems. The 5G system has expanded its frequency range and widened the bandwidth to achieve higher throughput rates and more stable wireless qualities, which brings new challenges to the over-the-air (OTA) MIMO evaluations. The wide bandwidth introduces systematic uncertainties into the MIMO measurement because of the increased amplitude and phase variation issues under different frequencies in the wideband signals, and it could lead to valid MIMO throughput measurement results when severe. The effect on antenna isolation resulting from amplitude and phase variation in wideband MIMO measurements is analyzed based on the radiated two-stage (RTS) MIMO measurement method. A wideband inverse matrix algorithm is introduced to solve this issue and improve the wideband MIMO antenna isolation. The proposed method can be used in both multiple probe anechoic chamber (MPAC) and RTS chambers, which paves the way for decreasing the OTA measurement uncertainties on both 5G sub-6-GHz wideband MIMO and millimeter-wave MIMO evaluations.