Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Physically Consistent RIS: From Reradiation Mode Optimization to Practical Realization

Javad Shabanpour, Constantin Simovski, Giovanni Geraci

Abstract

We propose a practical framework for designing a physically consistent reconfigurable intelligent surface (RIS) to overcome the inefficiency of the conventional phase gradient approach. For a section of Cape Town and across three different coverage enhancement scenarios, we optimize the amplitude of the RIS reradiation modes using Sionna ray tracing and a gradient-based learning technique. We then determine the required RIS surface/sheet impedance given the desired amplitudes for the reradiation modes, design the corresponding unitcells, and validate the performance through full-wave numerical simulations using CST Microwave Studio. We further validate our approach by fabricating a RIS using the parallel plate waveguide technique and conducting experimental measurements that align with our theoretical predictions.

Physically Consistent RIS: From Reradiation Mode Optimization to Practical Realization

Abstract

We propose a practical framework for designing a physically consistent reconfigurable intelligent surface (RIS) to overcome the inefficiency of the conventional phase gradient approach. For a section of Cape Town and across three different coverage enhancement scenarios, we optimize the amplitude of the RIS reradiation modes using Sionna ray tracing and a gradient-based learning technique. We then determine the required RIS surface/sheet impedance given the desired amplitudes for the reradiation modes, design the corresponding unitcells, and validate the performance through full-wave numerical simulations using CST Microwave Studio. We further validate our approach by fabricating a RIS using the parallel plate waveguide technique and conducting experimental measurements that align with our theoretical predictions.
Paper Structure (13 sections, 9 equations, 6 figures, 1 table)

This paper contains 13 sections, 9 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. Optimization of Reradiation Modes Amplitude
  3. System Setup and Ray Tracing Simulations
  4. Reradiation Mode Optimization
  5. Physically Consistent RIS Design Framework
  6. Preliminaries: From Impedance to Reradiation Modes
  7. Unitcell Design Framework
  8. Determining the supercell period
  9. Specifying incident and reflected fields
  10. Optimizing the sheet impedance
  11. Numerical Validation
  12. Experimental Validation
  13. Conclusion

Figures (6)

  • Figure 1: Section of Cape Town, showing the location of base station and RIS.
  • Figure 2: (a) Selected geographical area, showing the BS, RIS, and target areas. (b) Coverage map without RIS. (c) Coverage improvement with RIS optimized for equal signal strength. (d--e) Coverage improvement with RIS optimized for minimum guaranteed signal strength.
  • Figure 3: Gradient-based optimization of the RIS reradiation modes amplitude for: (a) equal signal strength on area1 and area2, (b) maximum signal strength on area2, while guaranteeing at least $-100$ dB on area1; (c) maximum signal strength on area2 while guaranteeing at least $-100$ dB on area1.
  • Figure 4: (a) Geometry of the unitcell designed via CST, with values provided in Table I. (b) Fabricated samples of unitcells as detailed in Section V.
  • Figure 5: Full-wave numerical simulation of the reradiation mode power obtained for the discrete sheet reactance values ${Z_{1 \textrm{--} 9}^{\textrm{a}}}$, ${Z_{1 \textrm{--} 9}^{\textrm{b}}}$, and ${Z_{1 \textrm{--} 9}^{\textrm{c}}}$.
  • ...and 1 more figures