Intelligent Metasurfaces with Continuously Tunable Local Surface Impedance for Multiple Reconfigurable Functions

Abstract

Electromagnetic metasurfaces can be characterized as intelligent if they are able to perform multiple tunable functions, with the desired response being controlled by a computer influencing the individual electromagnetic properties of each metasurface inclusion. In this paper, we present an example of an intelligent metasurface which operates in the reflection mode in the microwave frequency range. We numerically show that without changing the main body of the metasurface we can achieve tunable perfect absorption and tunable anomalous reflection. The tunability features can be implemented using mixed-signal integrated circuits (ICs), which can independently vary both the resistance and reactance, offering complete local control over the complex surface impedance. The ICs are embedded in the unit cells by connecting two metal patches over a thin grounded substrate and the reflection property of the intelligent metasurface can be readily controlled by a computer. Our intelligent metasurface can have significant influence on future space-time modulated metasurfaces and a multitude of applications, such as beam steering, energy harvesting, and communications. This paper is published at Phys. Rev. Applied.

Error Analysis of Programmable Metasurfaces for Beam Steering

“…Determining the characteristics of the unit cell that will lead to the desired behavior is typically performed analytically, through methods such as impedance matching [22]. A large subset of designs has been based on the generalization of the Snell's laws of reflection and refraction [6], [50]- [52], which provides fundamental understanding on how to achieve certain functionalities through the drawing of specific phase gradients.…”

“…Beyond that, several authors have proposed to integrate a network of communicating chips within the metasurface containing actuators, control circuits, and even sensors [19], [21], [22], [62]. This concept, referred to as HyperSurface (HSF), opens new opportunities in the design of autonomous self-adaptive programmable metasurfaces but, at the same time, poses further challenges in the implementation, cointegration, and testing of the electronics within and around the metasurface.…”

“…Assuming that our design implements four coding states, it is standard practice in anomalous reflection metasurfaces that the 2π phase range is divided into evenly spaced states with π/2 separation with high reflection amplitude [22].…”

“…Two main approaches have been proposed for the implementation of programmable metasurfaces, namely, (i) by interfacing the tunable elements through an external Field-Programmable Gate Array (FPGA) [17], [18], or (ii) by integrating sensors, control units, and actuators within the metasurface structure [19]- [22].…”

Mobility-Aware Beam Steering in Metasurface-Based Programmable Wireless Environments

“…Software-defined Metasurfaces (SDMs) have received considerable attention, due to their efficiency in exerting control over electromagnetic (EM) waves during their propagation from a transmitter to a receiver [1]. SDMs allow for precise control over the direction, polarization, amplitude and phase of waves impinging over them, in a frequency and encodingselective manner [2]- [4]. Moreover, metasurface hypervisors called HyperSurfaces (HSFs) have been proposed, which allow for chaining and exerting many wave manipulation functionalities at once via well-defined application programming interfaces [5].…”