On Antenna Polarization Discrimination, Validating MIMO OTA Test Methodologies

Abstract

The radiated performance of a multiple-input-multiple-output (MIMO) antenna system is commonly evaluated based on a set of antenna-centric figures of merit (FoM). These generally include the antenna's total efficiency, branch imbalance, and magnitude of the complex (or envelope) correlation coefficient. On the other hand, to validate the over-the-air (OTA) performance of the MIMO system, including both antennas and other parts of the real transceivers, test methodologies were created based on a single FoM: the absolute data throughput. While an antenna-centric FoM provides a preliminary overall insights into the radiated performance of the MIMO antenna system, these FoMs are limited in their overall applicability. Each of these FoMs is based on far-field antenna measurements and assuming a uniform distribution of the incoming power, meaning that passive antenna measurements are made in single-input-single-output (SISO) anechoic chambers. Furthermore, without the implementation of channel models with controllable spatial characteristics, it is impossible to isolate the effect of polarization changes on MIMO performance. In this letter, the radiated performance of MIMO antenna systems will be compared in terms of data throughput using different channel models both with and without controllable cross-polarization ratio and other spatial characteristics.