A Reconfigurable Intelligent Surface at mmWave Based on a Binary Phase Tunable Metasurface

Abstract

Originally introduced in the early 2010's, the idea of smart environments through reconfigurable intelligent surfaces (RIS) controlling the reflections of the electromagnetic waves has attracted much attention in recent years in preparation for the future 6G. Since reconfigurable intelligent surfaces are not based on increasing the number of sources, they could indeed pave the way to greener and potentially limitless wireless communications. In this paper, we design, model and demonstrate experimentally a millimeter wave reconfigurable intelligent surface based on an electronically tunable metasurface with binary phase modulation. We first study numerically the unit cell of the metasurface, based on a PIN diode, and obtain a good phase shift and return loss for both polarizations, over a wide frequency range around 28.5 GHz. We then fabricate and characterize the unit cell and verify its properties, before fabricating the whole 10 cm×10 cm reconfigurable intelligent surface. We propose an analytical description of the use that can be done of the binary phase RIS, both in the near field (reflectarray configuration) and in the far field (access point extender). We finally verify experimentally that the designed RIS works as expected, performing laboratory experiments of millimeter wave beamforming both in the near field and far field configuration. Our experimental results demonstrate the high efficiency of our binary phase RIS to control millimeter waves in any kind of scenario and this at the sole cost of the energy dissipated by the PIN diodes used in our design.

Reconfigurable Intelligent Surfaces: Channel Characterization and Modeling

“…In [51], a RIS was fabricated at 28 GHz based on a binaryphase tunable metasurface. Experiments were conducted in near field and far field cases.…”

“…Based on the design described in [51], a RIS was fabricated at 28 GHz in [52]. Four RISs with unit cells of 20×20 were assembled to achieve 40×40 unit cells.…”

A Frequency-Agnostic RIS-based solution to control the Smart Radio Propagation Environment

“…Related Work. RIS design choices in terms of array technology, total number of elements, and inter-element spacing directly affect the achievable performance of RIS-aided wireless networks [7], [8]. In particular, the operating frequency depends on the reflective element geometry and material, whereas the total number of elements N determines the beamforming gain, which in turn may increase the signal-tonoise ratio (SNR) at the receiver up to a factor proportional to N 2 [9].…”

A 2D-programmable and Scalable RIS Remotely Controlled via Digital Infrared Code

“…Despite MSs potentially offer more advanced reflection control such as achieving perfect reflection to angles larger than 70 − 80 • from the normal [10], the features of their unit cells are much finer than of RAs. For that reason, RAs better fit to the relevant technological constraints that are especially important in the millimeter-wave range [11] and, therefore, serve as RISs in most papers.…”

“…A 2-bit version of an RIS controlled with PIN diodes was presented in [25]. While at frequencies below 10 GHz both varactor and PIN diode can be employed, at higher frequencies [26], especially in the 5G FR2 band [11], [27], [28] and above [29], PIN diodes were mostly used due to lower losses. Special DC circuits are to be embedded into the design of the RIS to individually bias the diodes for setting phases of individual patches (or groups of patches).…”