Angle-Dependent Phase Shifter Model for Reconfigurable Intelligent Surfaces: Does the Angle-Reciprocity Hold?

Abstract

The existing phase shifter models adopted for reconfigurable intelligent surfaces (RISs) have ignored the electromagnetic (EM) waves propagation behavior, thus cannot reveal practical effects of RIS on wireless communication systems. Based on the equivalent circuit, this paper introduces an angle-dependent phase shifter model for varactor-based RISs. To the best of our knowledge, this is the first phase shifter model which reveals that the incident angle of EM waves has influence on the reflection coefficient of RIS. In addition, the angle-reciprocity on RIS is investigated and further proved to be tenable when the reflection phase difference of adjacent RIS unit cells is invariant for an impinging EM wave and its reverse incident one. The angle-dependent characteristic of RIS is verified through full-wave simulation. According to our analysis and the simulation results, we find that the angle-reciprocity of varactor-based RIS only holds under small incident angles of both forward and reverse incident EM waves, thus limits the channel reciprocity in RIS-assisted TDD systems.

Accepted by IEEE Communications Letters

References in corpus (5)

• Wireless Communications with Reconfigurable Intelligent Surface: Path Loss Modeling and Experimental Measurement
• Wireless Communications with Programmable Metasurface: New Paradigms, Opportunities, and Challenges on Transceiver Design
• Wireless Communications with Programmable Metasurface: Transceiver Design and Experimental Results
• Programmable Metasurface-based RF Chain-free 8PSK Wireless Transmitter
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Cited by in corpus (7)

• On Channel Reciprocity in Reconfigurable Intelligent Surface Assisted Wireless Network
• Channel Customization for Joint Tx-RISs-Rx Design in Hybrid mmWave Systems
• Channel Customization for Limited Feedback in RIS-assisted FDD Systems
• Blockage-Aware Robust Beamforming in RIS-Aided Mobile Millimeter Wave MIMO Systems
• Reconfigurable Intelligent Sensing Surface aided Wireless Powered Communication Networks: A Sensing-Then-Reflecting Approach
• Electromagnetic Model of Reflective Intelligent Surfaces
• Adaptive Bit Partitioning for Reconfigurable Intelligent Surface Assisted FDD Systems with Limited Feedback