Figure 1

Figure 1 An RIS array and unit cell design from Emerald’s visualization tool.

In the rapidly evolving world of wireless communications, improving signal quality and coverage across the electromagnetic (EM) spectrum has become increasingly vital. The ability to steer beams in real-time to concentrate power and conserve bandwidth by controlling exactly where power is directed at a unit cell level has gained significant importance. As a result, metasurfaces and more specifically, reconfigurable intelligent surfaces (RIS), have emerged as a promising solution that can fulfill these new requirements without any required mechanical componentry and thus greatly enhance wireless communication systems.

RIS designs are comprised of an array of unit cells distributed over a surface that is thin relative to the wavelength. These unit cells can be controlled individually and the entire array grants the ability for spatial and/or temporal control of EM radiation. One ability that this type of design creates is reconfigurable beam steering. However, with this ability comes a new challenge of complexity in the simulation since a single far-field simulation is insufficient to characterize the complete behavior of these surfaces.

Emerald by CEMWorks is a comprehensive solution for simulating and analyzing metasurfaces and RIS. This solution has the potential to expedite research and development in this exciting domain. Emerald is well-equipped to handle these challenges due to its powerful set of features:

Customizable Material Properties

Figure 2

Figure 2 (a) Reflected far-field pattern (in dB) with the main lobe 27 degrees off broadside. (b) Reflected far-field pattern (in dB) with the main lobe at 66 degrees off broadside.

Metasurfaces and RIS often rely on specialized materials with precise electromagnetic properties. The solver provides a rich library of material models, enabling users to define custom dielectric and metallic properties. With the ability to tailor these properties, researchers can explore novel metasurface designs and optimize their performance for specific applications, such as beam steering, pattern synthesis and polarization control.

Versatile Geometrical Configurations

Metasurfaces and RIS come in a wide range of geometries, including planar arrays, nanoparticle arrays or surfaces with repeated patterns. Emerald accommodates these diverse configurations, allowing users to model and simulate surfaces of varying complexity. From unit cell arrays to arbitrary structures, researchers can accurately capture the EM response and study the impact of geometrical parameters on RIS functionality.

Broad Frequency Range

Understanding the behavior of metasurfaces and RIS across a wide frequency range is crucial for comprehensive analysis and design optimization. Emerald supports simulations from DC to optical frequencies and it offers a seamless transition between different frequency domains. This capability empowers researchers to investigate metasurfaces spanning from DC to high frequency analysis, unlocking a plethora of applications in telecommunications, sensing, imaging and more.

Advanced Post-processing and Visualization

Analyzing and interpreting simulation results play a vital role in the design and optimization of metasurfaces and RIS. Emerald provides an array of post-processing tools to extract key parameters. Additionally, advanced visualization options, such as 3D models of far-field patterns facilitate an intuitive understanding of RIS behavior.

To demonstrate some of these features, a reflective RIS design consisting of 160 resonant patch unit cells controlled by simulated diodes has been implemented. These diodes control whether current can flow to a parasitic patch, causing the reflected fields to have a relative phase shift of 180 degrees at resonant frequencies. This design is shown in Figure 1.

Since the relative phase for each individual cell that can be reconfigured can be controlled, the total field can be configured by controlling the interference between cells. The cumulative effect opens the possibility to synthesize and reconfigure radiation patterns. As an example, the plots of Figure 2a and Figure 2b display the two resulting far-field reflection patterns of the same surface in two different main lobe configurations.

The arrival of RIS has opened exciting possibilities for controlling and manipulating EM waves. The Emerald EM solver allows researchers to delve into the intricacies of RIS structures, accurately model their behavior and optimize their performance. By combining powerful simulation capabilities with customizable material properties, versatile geometrical configurations and advanced post-processing tools, Emerald paves the way for ground-breaking advancements in metasurface and RIS research and applications.

Winnipeg, Canada