The Effect of Receiver-side Circular Antenna Arrays on Bit Error Probability in a Wireless Line-of-Sight OAM Communication System

The use of multiple-input multiple-output (MIMO) techniques is one of the proposed methods for detecting message signals multiplexed on a single frequency using multiple wireless orbital angular momentum (OAM) states. In a recent study, the use of a uniform circular array (UCA) of conventional antennas at the receive side was used in an ideal wireless OAM communication system. In this paper, we show that, using non-uniform circular array is also feasible. However, the performance is sub-optimal, compared to the use of UCA. The performance is measured using the condition number of the channel matrix and the bit error probabilities of the zero-forcing (ZF) and minimum mean square error (MMSE) equalizers under the QPSK modulation scheme.