Elementary Back-scattering Module Suitable for Active RIS Implementation Based on 5.8 GHz Co-Polarized Antenna Pair

This paper describes the development of an active phase and magnitude reconfigurable back-scatterer operating at 5.8 GHz and its over-the-air characterization. The device is suitable for active reflective intelligent surface implementation, where the control of both phase and magnitude of the reflected signal are of concern. The module exploits a pair of 5.8 GHz co-polarized patch antennas laying on the same plane. The reconfigurable section of the module consists of a cascade of an analog phase shifter and a variable gain low noise amplifier.The characterization of the module exploits a time-domain gating technique capable to differentiate between several contributions of module scattered signals, and demonstrated the capability to control the magnitude and the phase of the scattered signal respectively between -7 dB and 12 dB, and 50 degree and 250 degree in a stable and reliable operative state.