A Modified Channel Model for the MIMO System Deployed RIS Elements with Imperfect Surface

In this paper, we propose a modified millimeter wave band RIS-assisted end-to-end MIMO channel model, in which the transmission line model is adopted to analyze the RIS element with microdamage. Normally, by independently adjusting the phase shift of RIS elements, incident waves can be reflected in the desired direction by RIS elements working collaboratively. However, the working states of RIS elements are not always ideal. The influence of imperfect elements on channel response and channel capacity is discussed, modeled and simulated in this paper. The simulation results show that, compared with the normal RIS, the anomalous reflection performance will be affected and RIS-assisted channel capacity will decrease.