Modeling and measurement of path loss in reconfigurable intelligent surface assisted broadcast wireless communication

Reconfigurable intelligent surface (RIS) has proven to be promising for future wireless communication. Due to its ability to manipulate electromagnetic (EM) waves, RIS provides a flexible and programmable way to implement intelligent wireless environments. While path loss modeling has been conducted in some prior research, an issue remaining unknown is the characteristics of multi-beam path loss for RIS. In this paper, we model, simulate and measure the multi-beam path loss in RIS-assisted broadcast communication scenarios. We propose two specific configurations of RIS and derive the path loss models, which reveal that the incident beam can be equally divided into multiple beams without power loss through rational design of the phase coding. The proposed path loss model is validated through simulation subsequently. To further verify our conclusions, we build a millimeter wave (mmWave) measurement system with a 35 GHz fabricated RIS. The measurement result corresponds well with the simulation, which shows a difference of about 3 dB in the received signal power of quad-beam compared with dual-beam, as well as dual-beam compared with single-beam, except for the impact of radiation patterns of the antennas and RIS elements.