Figuring out Impaired Reconfigurable Intelligent Surfaces

Reconfigurable intelligent surfaces (RIS) are an array of meta-atoms individually controlled using active components such as p-in diodes to manipulate the reflected or transmitted electromagnetic waves. Such active components are vulnerable to high voltage spikes and environmental factors, and hence the overall RIS performance can be degraded as these individual active components break or become damaged. RISs are an important development in beyond-5G networks, and this paper quantifies the performance degradation of such systems. Here, we use a reflection-type 15 × 15 RIS at 15 GHz and describes the degradation in its performance in terms of realized gain, beam direction and side lobe levels with emulated p-in diodes being damaged. Using simulations and measurements, we conducted two experiments: (i) where the damage occurred randomly, and (ii) where there was concentrated local damage. A drop of approximately 4 dB in gain and a change of 7.7 dB in sidelobe levels (SLL) has been reported when up to 25% of the p-in diodes were randomly not functioning. The beam pointing angle is found to have minimal impact with random distribution of damage showing a shift of ±2°. The effect was more significant when there was concentrated local damage where up to 10° of shift in the beam angles was observed.