Diagnosis and Modification of Propagating Electromagnetic Waves Using DoA Systems and EM Skins

Majority of reconfigurable intelligent surfaces (RISs) up to present have been investigated under ideal conditions such as anechoic chambers or experimental sites with predetermined electromagnetic (EM) wave propagation models. For the first time, this article introduces a series of processes to diagnose the EM wave environment using a newly devised real-time diagnosis system and a method to freely customize new EM wave environments using EM skins. First, a diagnosis system that performs direction-of-arrival (DoA) estimation without phase information using the Rotman lens at 28 GHz is designed. A true real-time DoA estimation extracting the DoA data directly from the microcontroller unit (MCU) is implemented. Second, the propagation of EM waves in a miniaturized realistic environment where random reflection and scattering exist is diagnosed, instead of performing under ideal environments such as an anechoic chamber. EM wave control elements are installed using actual DoA information, instead of hypotheses, which relies on the geometry of the space where antennas or EM wave control elements are placed. Finally, the EM field modified by the devised EM wave control elements is reconfirmed using the DoA system. The method is exemplified using two distinct environments in which the aforementioned diagnosis and modification procedures are used to derive the specific EM skin configurations. Each configuration yielded an improvement of received power by 13.2 and 12.1 dB, respectively. This is the first study to demonstrate the possibility of customizing the wireless channel based on empirical characterization of the propagation environment.