Fading channel emulation for massive MIMO testing using a conductive phase matrix setup

Functionalities, algorithms, and performances of massive MIMO base stations should be tested in versatile fading radio channel conditions. Base stations of 5G "New radio" that operate on sub 6 GHz frequency bands typically provide antenna connectors enabling RF cable connection of test devices to the device under test (DUT). Furthermore, the number of DUT antennas is high and consequently the need of fading channel emulator (CE) resources becomes high. An approach can be taken to reduce the number of independent fading channels to be emulated. This can be done by using a phase shifting and combining unit (aka phase matrix unit) in between the DUT and CE. The phase matrix concept in fading emulation, together with its capabilities and limitations, is discussed in this paper.