Development of a Direction-variable Liquid Crystal Meta-surface Reflector

Matsuno, Hiromi; Ohto, Takuya; Amano, Yoshiharu; Okita, Mitsutaka; Suzuki, Daiichi; Matsunaga, Kazuki; Oka, Shinichiro

doi:10.1109/icc45855.2022.9838358

Cited by 12 publications

(5 citation statements)

References 15 publications

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“…Suppose the incident wave source is in the far‐field. In that case, the required phase addition is expressed as [10]

\begin{equation} \begin{aligned} \Phi _{mn}(\theta _r, \phi _r) &= \dfrac{2\pi}{\lambda _0}D_u{\left\lbrace m{\left(\cos \phi _r\sin \theta _r-\cos \phi _i\sin \theta _i\right)}\right.} \\ &\quad {\left.+n(\sin \phi _r\sin \theta _r-\sin \phi _i\sin \theta _i)\right\rbrace} \end{aligned} \end{equation}

where λ 0 indicates the wavelength in free space, and m and n denote the

mn

‐th indices of the unit cell.…”

Section: Ris Control Methods For Multiple Users Using Stereo Camera I...mentioning

confidence: 99%

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Multi‐user beamforming with a reconfigurable intelligent surface using stereo camera images

Ebihara,

Kumagai,

Kataoka

et al. 2023

Electronics Letters

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This paper proposes and experimentally evaluates, a reconfigurable intelligent surface (RIS) control system for multiple users using stereo camera images. The aim is to enable fast and fair received signal strength (RSS) beamforming for multiple users. In the proposed system, a stereo camera is mounted on top of the RIS. Human bodies are recognized from the obtained images. Subsequently, the beam directions and the phase of the RIS are calculated for the estimated positions. The stereo camera‐based scheme enables fast beamforming because channel state information estimation is omitted. Moreover, identical RSS beamforming is enabled by calculating the weighted sums of the RIS phases for multiple users utilizing distance and angle information of users from the RIS obtained using the stereo camera. Experiments are conducted in an anechoic chamber using RIS operating at 28 GHz. The efficacy of the RIS control system using stereo camera images and its ability to increase the RSS fairly for multiple users is validated via simulations and experiments.

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“…Suppose the incident wave source is in the far‐field. In that case, the required phase addition is expressed as [10]

\begin{equation} \begin{aligned} \Phi _{mn}(\theta _r, \phi _r) &= \dfrac{2\pi}{\lambda _0}D_u{\left\lbrace m{\left(\cos \phi _r\sin \theta _r-\cos \phi _i\sin \theta _i\right)}\right.} \\ &\quad {\left.+n(\sin \phi _r\sin \theta _r-\sin \phi _i\sin \theta _i)\right\rbrace} \end{aligned} \end{equation}

where λ 0 indicates the wavelength in free space, and m and n denote the

mn

‐th indices of the unit cell.…”

Section: Ris Control Methods For Multiple Users Using Stereo Camera I...mentioning

confidence: 99%

“…Suppose the incident wave source is in the far-field. In that case, the required phase addition is expressed as [10] mn (θ r , φ r ) =…”

Section: Ris Control Methods For Multiple Users Using Stereo Camera I...mentioning

confidence: 99%

Multi‐user beamforming with a reconfigurable intelligent surface using stereo camera images

Ebihara,

Kumagai,

Kataoka

et al. 2023

Electronics Letters

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“…To address these problems, we proposed an LC IRS for 28 GHz mobile communication systems [20,21]. The proposed LC IRS was designed with the configuration of an electrode, LC, and ground layers.…”

Section: Contributionmentioning

confidence: 99%

“…To solve these problems, we proposed an LC meta-surface reflector for IRS [20]. In contrast to a conventional IRS, the reflection phase control function is deployed in the substrate between the reflecting element and ground plane.…”

Section: B Design Of the Proposed Lc Irsmentioning

confidence: 99%

Development of a Dual-Polarized Direction-Variable Liquid-Crystal Meta-Surface Reflector for Intelligent Reflecting Surface

et al. 2023

Self Cite

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Intelligent reflecting surfaces (IRSs) have been attracting attention as a solution to coverage hole problems in millimeter-wave communication areas. They are considered to be one of the key technologies of next-generation mobile communication systems. Since polarized multiple-input-multipleoutput (MIMO) is utilized in millimeter-wave communication systems to deliver high-speed data transmission, an IRS is also required to be applied for polarized MIMO and reflect signals in a wide angle range. To realize an IRS for the polarized MIMO, the IRS is required to reflect the signal of each polarization in the same direction with high isolation. In addition, the IRS is required to control the reflection phase over a wide range. In recent research, many proposals related to the development of IRSs have been proposed. However, since the configuration of a conventional IRS with diodes controls the reflection characteristics by controlling the electric length or shape of the reflecting element, it becomes asymmetrical in the direction of each polarization and it is difficult to apply polarized MIMO. To solve this problem, in this paper, we propose a new design of a dual-polarized liquid-crystal-based IRS for 28 GHz mobile communication systems. Since the proposed IRS controls the reflecting phase by controlling the electric thickness of the substrate, the IRS can control the reflecting phase without changing the shape of the reflecting element. By optimizing the design of the reflecting element, the IRS can achieve a wide reflection phase control of 260 degrees for both vertical and horizontal polarizations. The IRS can also control the reflection direction of each polarization in the range of ±60 degrees with a high isolation of more than 20 dB. The main contributions of this paper are 1) a proposal for the design of a liquid crystal IRS for polarized MIMO; 2) a proposal of a design method for the liquid-crystal IRS using unit cell analysis; 3) verification of the proposed IRS through electromagnetic field analysis; 4) development of the proposed liquid-crystal IRS; 5) experimental verification of the proposed IRS in an anechoic chamber, and 6) derivation of the MIMO channel capacity of the proposed dual-polarized IRS.INDEX TERMS Beyond 5G/6G, coverage hole, intelligent reflecting surface, liquid crystal, millimeter wave, polarized MIMO, channel capacity I. INTRODUCTION A. BACKGROUNDIn fifth-generation mobile communication systems (5G), millimeter-wave bands with wide bandwidths are utilized to deliver high data rates and low-latency mobile communication services [1]. These high-frequency bands are also expected to be utilized in beyond 5G/6G mobile networks to satisfy the increasing demand for communication quality. On the other hand, these frequency bands suffer from high blockage loss due to their rectilinear propagation characteristics. This creates coverage holes where a signal from a base station (BS) is insufficient to provide high communication quality in the communication area [2].To overcome the coverage holes, ...

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“…To control the bias voltage individually, we have applied thin-film transistors (TFTs). [13] Further, TFT technology is commonly used in liquid crystal displays and its manufacturing technology is well-established.…”

Section: Introductionmentioning

confidence: 99%

Development of reconfigurable liquid crystal metasurface reflector based on TFT-LCD technology

Okita

Suzuki

Matsunaga

et al. 2023

Emerging Liquid Crystal Technologies XVIII

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For next-generation mobile communications, the application of millimeter wave bands is being explored for high-speed and large-capacity communications. However, coverage holes occur because millimeter waves are found to be blocked by objects. To overcome this problem of coverage holes, we have developed a reconfigurable liquid crystal metasurface reflector by applying thin film transistor liquid crystal display technology. The developed reconfigurable liquid crystal metasurface reflector was designed to operate at 28 GHz, and the measurement findings confirmed that the reflection phase control range was 260° and exhibited equivalent reflection characteristics for both vertical and horizontal polarization. Furthermore, the reflection direction control function was confirmed by varying the reflection direction between 0° and 60° with several phase distributions

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Development of a Direction-variable Liquid Crystal Meta-surface Reflector

Cited by 12 publications

References 15 publications

Multi‐user beamforming with a reconfigurable intelligent surface using stereo camera images

Multi‐user beamforming with a reconfigurable intelligent surface using stereo camera images

Development of a Dual-Polarized Direction-Variable Liquid-Crystal Meta-Surface Reflector for Intelligent Reflecting Surface

Development of reconfigurable liquid crystal metasurface reflector based on TFT-LCD technology

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