Impact of Beam Split and IQ Mismatch on BER Performance of IRS-aided THz Communications

Intelligent reflecting surfaces (IRS) and multiple-input and multiple-output (MIMO)-based design are considered for mitigating the effects of molecular absorption in terahertz (THz) systems operating at high-frequency bands. In this THz system, the phenomenon of beam splitting occurs at both the transceiver and IRS. In this paper, time-delay (TD) and delay-phase (DP) based precoding at the transmitter (Tx) and IRS are introduced to overcome the effect of beam splitting. The average bit error rate (BER) of the THz system is analyzed by considering the impact of transmitting antennas, reflecting elements, and in-phase and quadrature (IQ) mismatch for a multi-carrier system. The analysis results show that the beam splitting leads to a reduction in the BER performance by as much as 20 dB.