Analysis and Optimization of Unilateral Stacked Intelligent Metasurfaces by Using a Multi-Port Network Model

In this paper, we present an analysis and optimization of stacked sntelligent setasurfaces (SIMs) under non-reciprocal conditions. A multi-port network model based on the Z-matrix representation is developed, taking into account the presence of non-reciprocal (unilateral) two-port networks connecting the faced layers of the SIM. A specifically designed optimization algorithm for the global network load of SIM layers in the presence of non-reciprocal two-port networks is proposed. It is found that the optimization algorithm benefits from an iterative procedure that is slightly simplified compared to that used for general SIMs with reciprocal passive network loads.