Indoor Channel Characterization Using Transmitting and Reflecting RIS at mmWaves

In this article, we present the results of a measurement campaign conducted in an indoor environment with multiple reconfigurable intelligent surfaces (RISs), including a transmitting and a reflecting one in the Ka-band. On the receiver side, a virtual array of monopole antennas is considered. The reconfiguration capabilities of both binary RISs are validated in various configurations, including different incidence/reflection angles and distances. A multipath components (MPCs) extraction is performed to highlight the impact of RIS within a rich channel. Based on these results, we experimentally validated a general free-space multiple-input multiple-output (MIMO) channel transfer function with an arbitrary number of cascaded RISs, in either transmitting or reflecting modes, as well as a radar-range equation model.