Abstract-In this paper, a full-wave method to efficiently compute the electromagnetic interaction between two devices placed in semi-anechoic conditions is proposed. The aim of this research is the accurate and efficient reproduction of radiated immunity and emission tests in simulation. The employed technique relies on a single simulation (or measurement) of the radiation pattern of each device and allows an arbitrary relative position between the devices. The resulting procedure is practical, has a low computational cost, and shows good agreement with reference solutions.