Liquid crystal-based reflective metasurface

Abstract

This liquid crystal-based reflective metasurface comprises: a first layer comprising a first substrate, a first metal layer formed on a first surface of the first substrate, and a second metal layer formed on a second surface of the first substrate; a second layer comprising a liquid crystal and a second substrate providing a space, in the central portion of a unit cell, in which the liquid crystal can be filled; and a third layer comprising a third substrate and a third metal layer formed on a first surface of the third substrate.

Description

Liquid crystal-based reflective metasurfaces

[0001] The present disclosure relates to a liquid crystal-based reflective metasurface, and more particularly, to a liquid crystal-based reflective metasurface implemented in a multilayer substrate package.

[0002] With the rapid development of 5th and 6th generation mobile communications, communication module design technology to support ultra-high-speed, high-capacity communications is rapidly evolving. In 6G communications, coverage expansion methods are being researched to expand the communication area due to the short radio wave range.

[0003] Reconfigurable Intelligent Surfaces (RIS) can expand communication coverage at a lower cost than repeater installations. Consequently, RIS is being actively developed by domestic and international telecommunications companies. However, the limited availability of phase-variable elements for use in high-frequency bands presents challenges in development and deployment.

[0004] Meanwhile, phased array antennas can adjust beam steering direction by electronically controlling the phase of radio waves on a per-element basis. This element-by-element phase control is typically implemented in phase shifters at the radio frequency (RF) level. These phase shifters increase the weight, size, and cost of the phased array antenna.

[0005] Liquid crystals (LCDs) have the property of variable dielectric properties that vary depending on the applied voltage. Therefore, research is currently underway on using liquid crystals as phase-variable elements for 6G beamforming.

[0006] Meanwhile, RIS modules utilizing phase-variable elements utilizing liquid crystals can be implemented using reflective metasurfaces. However, reflective metasurfaces, which operate as reflectors within a specific frequency band, suffer from the drawback of narrow-band reflection characteristics.

[0007] The present invention aims to improve the reflection performance over a wide frequency band in a liquid crystal-based reflective metasurface.

[0008] The present invention aims to improve phase tunability performance over a wide frequency band in liquid crystal-based reflective metasurfaces.

[0009] The purpose of this specification is to provide a multilayer substrate package having a liquid crystal-based reflective metasurface that can be manufactured in a display process using liquid crystals.

[0010] A liquid crystal-based reflective metasurface according to the present invention comprises a first layer including a first substrate, a first metal layer formed on a first surface of the first substrate, and a second metal layer formed on a second surface of the first substrate; a second layer including a second substrate providing a space in which the liquid crystal can be filled in a central portion of a unit cell; and a third layer including a third substrate and a third metal layer formed on the first surface of the third substrate.

[0011] According to an embodiment, in a structure in which the second metal layer covers the upper part of the liquid crystal and the third metal layer covers the lower part of the liquid crystal, the thickness of the first substrate has a range of 0.025 λ0 to 0.036 λ0, and the size of the first metal layer has a range of 0.262 λ0 to 0.272 λ0.

[0012] According to an embodiment, a wireless signal incident on the first metal layer can be reflected with different phases by a dielectric constant that varies depending on a DC voltage applied to the first metal layer and the liquid crystal.

[0013] According to an embodiment, the first metal layer, the second metal layer, and the liquid crystal having a permittivity that varies depending on a DC voltage form a Reconfigurable Intelligent Surface (RIS) module that causes the reflected signals of the wireless signal reflected at a predetermined ratio or higher to be reflected with different phases. The RIS module can operate in a wide band based on a center frequency due to a dual patch structure of the first metal layer and the second metal layer.

[0014] According to an embodiment of the present disclosure, a liquid crystal-based reflective metasurface implemented in a multilayer substrate package can improve reflectivity over a broad frequency band by more than 2.5 times.

[0015] According to an embodiment of the present disclosure, a phase tunable performance of 135 degrees or more can be obtained by varying the dielectric constant of the liquid crystal over a wide frequency band of 2.5 times or more in a liquid crystal-based reflective metasurface implemented as a multilayer substrate package.

[0016] According to an embodiment of the present disclosure, a double patch structure without a via structure forms two resonant modes and can operate as a reflector throughout the entire operating frequency band.

[0017] According to an embodiment of the present disclosure, it is possible to manufacture a display process using a liquid crystal through a unit cell having a plurality of metal layers that do not include a via structure.

[0018] Further scope of the applicability of this specification will become apparent from the detailed description below. However, since various changes and modifications within the spirit and scope of this specification will be apparent to those skilled in the art, it should be understood that the detailed description and specific examples, such as preferred embodiments, are given by way of example only.

[0019] FIG. 1 illustrates the structure of an array antenna module including a plurality of elements according to the present specification.

[0020] Figure 2 shows a structure implemented with a reflective RIS and a transparent RIS according to the present specification.

[0021] FIGS. 3A and 3B illustrate cross-sectional and perspective views of a first structured liquid crystal-based reflective metasurface having first and second metal layers and a ground layer according to the present disclosure.

[0022] FIGS. 4A and 4B illustrate cross-sectional and perspective views of a second structure liquid crystal-based reflective metasurface having first to third metal layers and a ground layer according to the present disclosure.

[0023] Fig. 5 is a diagram comparing the reflection coefficient characteristics of the liquid crystal-based reflective metasurfaces of the first and second structures.

[0024] Figure 6a shows the phase characteristics according to the change in the permittivity of the liquid crystal in the liquid crystal-based reflective metasurface of the first structure.

[0025] Figure 6b shows the phase characteristics according to the change in the permittivity of the liquid crystal in the liquid crystal-based reflective metasurface of the second structure.

[0026] Figures 7a and 7b show a perspective view and an equivalent circuit model of the liquid crystal-based reflective metasurface of Figures 4a and 4b.

[0027] Figures 8a and 8b show the reflection coefficient and input impedance when the thickness of the first substrate changes to 0.4, 0.6, and 0.8 mm.

[0028] Figure 9a shows the reflection coefficient and input impedance when the thickness of the first substrate changes to 0.8, 1, 1.2, and 1.4 mm.

[0029] Figure 9b shows the reflection coefficient as the dielectric constant changes when the thickness of the first substrate is 1 mm.

[0030] Figure 10a shows the phase of the reflection signal as the dielectric constant changes when the thickness of the first substrate is 0.6 mm.

[0031] Figure 10b shows the phase of the reflection signal as the dielectric constant changes when the thickness of the first substrate is 1 mm.

[0032] Figure 11a shows the reflection coefficient characteristics as the size of the first metal layer changes.

[0033] Figure 11b shows the input impedance value as the size of the first metal layer changes.

[0034] Figures 12a and 12b show the reflection coefficient and the phase of the reflection signal when the first size of the first patch element of the first metal layer is 7.4 mm.

[0035] Figures 13a and 13b show the reflection coefficient and the phase of the reflection signal when the first size of the first patch element of the first metal layer is 8.6 mm.

[0036] Figures 14a and 14b show input impedance characteristics according to changes in the thickness of the first substrate when the dielectric constant of the liquid crystal is 2.5 and 3.5, respectively.

[0037] Figures 15a and 15b show input impedance characteristics according to changes in the first size of the first metal layer when the dielectric constant of the liquid crystal is 2.5 and 3.5, respectively.

[0038] Hereinafter, specific embodiments of the present invention will be described in detail with drawings.

[0039] Hereinafter, embodiments related to this specification will be described in more detail with reference to the drawings. The suffixes "module" and "part" used in the following description for components are assigned or used interchangeably solely for the convenience of writing the specification, and do not have a distinct meaning or role in themselves.

[0040] Hereinafter, an array antenna module having phase-variable characteristics in relation to the present specification will be described.

[0041] In this regard, a module including a plurality of elements according to the present specification may be referred to as a phase delay array antenna module. The antenna module may be configured to include a plurality of radiators and a phase delay element capable of implementing phase delay. The phase delay element may be implemented as a feed structure of a specific structure without separate electronic components such as a phase shifter.

[0042] The array antenna module can be configured to support 6G wireless communication services. In this regard, the array antenna module can be configured to operate in the millimeter wave band or the 10 GHz band. The array antenna module can be applied to mobile communication antennas, vehicle antennas, or satellite communication antennas.

[0043] 6G wireless communication services aren't limited to electronic devices like mobile terminals or video display devices. They can also be applied to fully autonomous vehicles, artificial intelligence (AI) robots, and electronic devices supporting the augmented and virtual reality (AR / VR)-based metaverse.

[0044] FIG. 1 illustrates the structure of an array antenna module, which is a module including a plurality of elements according to the present specification. Referring to FIG. 1, an antenna module (1000) may be configured as an array antenna (1100) including a plurality of elements (1100-1 to 1100-8). The number of the plurality of elements is not limited to eight and may vary depending on the application.

[0045] The antenna module (1000) may be configured as a one-dimensional array antenna in which a plurality of elements are arranged in one axial direction. As another example, the antenna module (1000) may be configured as a two-dimensional array antenna in which a plurality of elements are arranged in one axial direction and another axial direction perpendicular thereto.

[0046] The spacing (G1) between the plurality of elements (1100-1 to 1100-8) can be implemented as a numerical value related to a wavelength corresponding to an operating frequency. Each of the plurality of elements (1100-1 to 1100-8) can be operably coupled to a phase delay element (1150-1 to 1150-8). The phase delay elements (1150-1 to 1150-8) can be formed as a feed structure having a phase delay. The phase delay elements (1150-1 to 1150-8) can be formed as a feed structure connecting adjacent antenna elements.

[0047] A transmission line (1200) connected to a plurality of elements (1100-1 to 1100-8) may be implemented as a waveguide, a microstrip line, a strip line, or a substrate integrated waveguide (SIW). Each of the plurality of elements (1100-1 to 1100-8) may be independently controlled to be turned on / off. Each of the plurality of elements (1100-1 to 1100-8) may be independently controlled to be turned on / off to adjust the beam forming direction of the antenna module (1000).

[0048] As the plurality of elements (1100-1 to 1100-8) are independently turned on / off, the phase of the signal applied to the plurality of elements (1100-1 to 1100-8) can be varied as illustrated in the transmission line (1200) of FIG. 1. As the interval between the on / off operations among the plurality of elements (1100-1 to 1100-8) decreases, the phase difference between adjacent elements increases. Accordingly, as the interval between the on / off operations among the plurality of elements (1100-1 to 1100-8) decreases, the beamforming angle increases.

[0049] Meanwhile, an antenna module comprising a plurality of antenna elements according to the present specification may be capable of phase adjustment when combined with a reconfigurable intelligent surface (RIS). In this regard, FIG. 2 illustrates a structure implemented with a reflective RIS and a transmissive RIS according to the present specification.

[0050] Referring to FIG. 2(a), the antenna module (1000) may be configured to include a reflective RIS (1000a) and at least one external antenna (1300). A wireless signal radiated from the external antenna (1300) may be configured to be reflected by the reflective RIS (1000a). The beamforming angle of the wireless signal may be varied by independently varying the on / off state of each element constituting the reflective RIS (1000a).

[0051] Referring to FIG. 2(b), the antenna module (1000) may be configured to include a transitive RIS (1000a) and at least one external antenna (1300). A wireless signal radiated from the external antenna (1300) may be configured to pass through the transitive RIS (1000b). The beamforming angle of the wireless signal may be varied by independently varying the on / off state of each element constituting the transitive RIS (1000b).

[0052] Hereinafter, a liquid-based reflective meta-surface implemented as a multilayer substrate package according to the present disclosure will be described. In this regard, FIGS. 3A and 3B illustrate a cross-sectional view and a perspective view of a first structured liquid-based reflective meta-surface having first and second metal layers and a ground layer according to the present disclosure. FIGS. 4A and 4B illustrate a cross-sectional view and a perspective view of a second structured liquid-based reflective meta-surface having first to third metal layers and a ground layer according to the present disclosure.

[0053] Referring to FIGS. 3A and 3B, a liquid crystal-based reflective metasurface (1000a) of a first structure will be described. The liquid crystal-based reflective metasurface (1000a) of the first structure may be configured to include a first layer (La1), a second layer (La2), and a ground layer (Lg). The first layer (La1) may include a first substrate (1010), a first metal layer (1110) formed on a first surface of the first substrate (1010), and a second metal layer (1120) formed on a second surface of the first substrate (1010). The first metal layer (1110) and the second metal layer (1120) of the first layer (La1) may be connected by a via (1110v). In this regard, the second metal layer (1120) may also be formed on the first surface of the second substrate (1020).

[0054] The second layer (La2) may include a second substrate (1020) that provides a space in which the liquid crystal (1020a) can be filled in the central portion of the unit cell and a liquid crystal (1020a). The dielectric constant of the liquid crystal (1020a) may vary depending on the bias voltage applied to the second metal layer (1120). For example, as the bias voltage applied to the second metal layer (1120) varies from 0 V to 10 V to 20 V, the dielectric constant of the liquid crystal (1020a) may change to 2.5, 3.0, and 3.5. A ground layer (Lg) may be disposed on the second surface of the second layer (La2). Meanwhile, a third substrate (1030) may be disposed in a lower region of the ground layer (Lg) in the Z-axis direction.

[0055] Referring to FIGS. 4A and 4B, a liquid crystal-based reflective metasurface (1000) of a second structure will be described. The liquid crystal-based reflective metasurface (1000) of the second structure may include a first layer (La1), a second layer (La2), and a third layer (La3). The liquid crystal-based reflective metasurface (1000) of the second structure may be configured to include a ground layer (Lg). The first layer (La1) may include a first substrate (1010), a first metal layer (1110) formed on a first surface of the first substrate (1010), and a second metal layer (1120) formed on a second surface of the first substrate (1010). In this regard, the second metal layer (1120) may also be formed on the first surface of the second substrate (1020).

[0056] The second layer (La2) may include a second substrate (1020) that provides a space in which the liquid crystal (1020a) can be filled in the central portion of the unit cell and a liquid crystal (1020a). The dielectric constant of the liquid crystal (1020a) may vary depending on the bias voltage applied to the second metal layer (1120). For example, as the bias voltage applied to the second metal layer (1120) varies from 0 V to 10 V to 20 V, the dielectric constant of the liquid crystal (1020a) may vary from 2.5 to 3.0 to 3.5. A ground layer (Lg) may be disposed on the second surface of the second layer (La2).

[0057] The third layer (La3) may include a third substrate (1030) and a third metal layer (1130) formed on a first surface of the third substrate (1030). In this regard, the third metal layer (1130) may also be formed on a second surface of the second substrate (1020). Meanwhile, a ground layer (Lg) may further be disposed on the second surface of the third substrate (1030).

[0058] Meanwhile, the wireless signal incident on the first metal layer (1110) can be reflected with different phases by the dielectric constant that varies depending on the DC voltage applied to the first metal layer (1110) and the liquid crystal (1020a). In this regard, the first metal layer (1110), the second metal layer (1120), and the liquid crystal (1020) having the dielectric constant that varies depending on the DC voltage form a reflector-based RIS (Reconfigurable Intelligent Surface) module. The reflector-based RIS module can be configured so that the reflected signals, in which the wireless signal is reflected at a predetermined ratio or more, are reflected with different phases. The reflector-based RIS module can be formed with the liquid crystal-based reflective metasurface (1000a, 1000) of the first or second structure.

[0059] The reflector-based RIS module can operate as a phase-variable reflector in a wideband with respect to a center frequency due to a dual patch structure of a first metal layer (1110) and a second metal layer (1110). In particular, the first metal layer (1110) and the second metal layer (1110) are formed in a floating structure in which they are coupled without being directly connected, thereby operating as a phase-variable reflector in a wideband frequency.

[0060] Meanwhile, Fig. 5 is a diagram comparing the reflection coefficient characteristics of the liquid crystal-based reflective metasurfaces of the first and second structures. Fig. 6a shows the phase characteristics according to the change in the permittivity of the liquid crystal in the liquid crystal-based reflective metasurface of the first structure. Fig. 6b shows the phase characteristics according to the change in the permittivity of the liquid crystal in the liquid crystal-based reflective metasurface of the second structure.

[0061] Referring to FIGS. 3a, 3b, and 5, the liquid crystal-based reflective metasurface (1000a) of the first structure can have a liquid crystal dielectric constant changed to (i) Dk= 2.5, (ii) Dk= 3.0, and (iii) Dk= 3.5. In the second resonance frequency band of the dual resonance, the reflection coefficient (S11) has a value of -5 dB or less, as indicated by the dotted line. Therefore, the liquid crystal-based reflective metasurface (1000a) of the first structure can have a deteriorated reflection performance in the second resonance frequency band.

[0062] Referring to FIGS. 4a, 4b and 5, the liquid crystal-based reflective metasurface (1000) of the second structure can have the dielectric constant of the liquid crystal changed to (i) Dk = 2.5, (ii) Dk = 3.0, (iii) Dk = 3.5. The reflection coefficient (S11) in the second resonance frequency band of the double resonance

[0063] As indicated by the solid line, the reflection loss in both the first and second resonance frequency bands of the dual resonance has a value of -5 dB or higher. Therefore, the liquid crystal-based reflective metasurface (1000) of the second structure can maintain a reflection performance above the threshold in both the first and second resonance frequency bands.

[0064] In the RIS using the liquid crystal (1020a) of FIGS. 3A to 4B, the phase of the reflected signal can be adjusted according to the dielectric constant that varies depending on the DC bias voltage applied to the liquid crystal (1020a). In this regard, a frequency band in which the reflection coefficient of the reflected signal is within -5 dB and the variable phase is 135 degrees or more can be defined as an available frequency band.

[0065] Referring to FIGS. 3A, 3B, and 6A, the liquid crystal-based reflective metasurface (1000a) of the first structure can vary the phase of the reflection signal in the first resonant frequency band as the permittivity (Dk) of the liquid crystal changes to 2.5, 3.0, and 3.5. The phase of the reflection signal in the first resonant frequency band has a first phase value, a second phase value, and a third phase value. The first phase value can be a value greater than the second phase value, and the second phase value can be a value greater than the third phase value. The first difference between the first phase value and the second phase value is greater than or equal to a threshold value. The second difference between the second phase value and the third phase value is greater than or equal to a threshold value.

[0066] Meanwhile, the liquid crystal-based reflective metasurface (1000a) of the first structure can vary the phase of the reflection signal in the second resonant frequency band as the permittivity of the liquid crystal changes to 2.5, 3.0, and 3.5. The first difference between the first phase value and the second phase value of the reflection signal in the second resonant frequency band is less than the threshold value. The second resonant frequency band is a higher frequency band than the first resonant frequency band. In addition, the second difference between the second phase value and the third phase value of the reflection signal in the second resonant frequency band is less than the threshold value. The liquid crystal-based reflective metasurface (1000a) of the first structure can lower the reflection coefficient to -5 dB or less, but the available bandwidth (BW1) is narrow at 1 GHz.

[0067] In this regard, the liquid crystal-based reflective metasurface (1000a) of the first structure satisfies a reflection coefficient of -5 dB or less and a phase-variable characteristic in a first resonant frequency band of 1 GHz from 9.1 to 10.1 GHz. However, the liquid crystal-based reflective metasurface (1000a) of the first structure does not satisfy a reflection coefficient of -5 dB or less and a phase-variable characteristic in a second resonant frequency band higher than the first resonant frequency band. Therefore, in the liquid crystal-based reflective metasurface (1000a) of the first structure, as the permittivity of the liquid crystal changes to 2.5, 3.0, and 3.5, the difference in the phase value of the reflection signal becomes less than a critical value, and thus the phase-variable reflective surface characteristic deteriorates in the second resonant frequency band.

[0068] Referring to FIGS. 4a, 4b, and 6b, the liquid crystal-based reflective metasurface (1000) of the second structure has a first phase value, a second phase value, and a third phase value in the first resonant frequency band as the permittivity (Dk) of the liquid crystal changes to 2.5, 3.0, and 3.5. The first phase value may be a value greater than the second phase value, and the second phase value may be a value greater than the third phase value. The first difference between the first phase value and the second phase value is greater than or equal to a threshold value. The second difference between the second phase value and the third phase value is greater than or equal to a threshold value.

[0069] Meanwhile, in the liquid crystal-based reflective metasurface (1000) of the second structure, as the permittivity of the liquid crystal changes to 2.5, 3.0, and 3.5, the first difference between the first phase value and the second phase value of the reflection signal in the second resonant frequency band is greater than or equal to the threshold value. The second resonant frequency band is a higher frequency band than the first resonant frequency band. In addition, in the second resonant frequency band, the second difference between the second phase value and the third phase value of the reflection signal is greater than or equal to the threshold value. Therefore, in the liquid crystal-based reflective metasurface (1000) of the second structure, as the permittivity of the liquid crystal changes to 2.5, 3.0, and 3.5, the difference between the phase values ​​of the reflection signal becomes less than the threshold value, so that the phase-variable reflective surface characteristics can be maintained in both the first and second resonant frequency bands. Therefore, the usable bandwidth (BW2) of the liquid crystal-based reflective metasurface (1000) of the first structure is a wideband of 2.5 GHz.

[0070] In this regard, in the first state where the DC voltage applied to the liquid crystal (1020a) is 0 V, the dielectric constant of the liquid crystal (1020a) is 2.5, which is the lower limit. In the second state where the DC voltage applied to the liquid crystal (1020a) is 10 V, the dielectric constant of the liquid crystal (1020a) is 3.0. In the third state where the DC voltage applied to the liquid crystal (1020a) is 20 V, the dielectric constant of the liquid crystal (1020a) is 3.5, which is the upper limit.

[0071] In the first state, the reflection signal reflected from the liquid crystal-based reflective meta surface (1000) is reflected at a predetermined ratio or higher with a first phase value. In the second state, the reflection signal reflected from the liquid crystal-based reflective meta surface (1000) is reflected at a predetermined ratio or higher with a second phase value different from the first phase value. In the third state, the reflection signal reflected from the liquid crystal-based reflective meta surface (1000) is reflected at a predetermined ratio or higher with a third phase value different from the second phase value. Here, the predetermined ratio may be set such that the reflection coefficient of the reflection signal is -5 dB or higher compared to an incident wireless signal.

[0072] The liquid crystal-based reflective metasurface (1000) of the second structure can maintain a wideband phase-variable reflection characteristic in two resonance modes by controlling the sizes of the first and second metal layers (1110, 1120) of the non-via structure and the thickness of the first substrate (1010). The liquid crystal-based reflective metasurface (1000) of the second structure satisfies a reflection coefficient and phase-variable characteristic of less than -5 dB in a wideband of 2.5 GHz from 9.5 to 12 GHz. Therefore, the liquid crystal-based reflective metasurface (1000) of the second structure provides a unit cell structure of a liquid crystal-based metasurface capable of securing a reflection coefficient and phase-variable performance.

[0073] In this regard, the second structure liquid crystal-based reflective metasurface (1000) does not include a via structure, so it can utilize glass material as the upper and lower substrates instead of PCB in a multilayer substrate structure. Therefore, there is an advantage in that an LCD (liquid crystal display) process can be used when manufacturing the second structure liquid crystal-based reflective metasurface (1000). In the LCD process, a glass material substrate can be used as the liquid crystal substrate.

[0074] Meanwhile, the liquid crystal-based reflective metasurface according to the present specification can be formed with a coupling structure of the first and second metal layers. In this regard, FIGS. 7A and 7B illustrate a perspective view and an equivalent circuit model of the liquid crystal-based reflective metasurface of FIGS. 4A and 4B. FIG. 7A illustrates a perspective view of the liquid crystal-based reflective metasurface of FIGS. 4A and 4B. FIG. 7B illustrates an equivalent circuit model of the liquid crystal-based reflective metasurface of FIGS. 4A and 4B.

[0075] Referring to FIGS. 4A, 4B, and 7A, the first metal layer (1110) may be formed as a first patch element having a first size (L1p) in the first and second axis directions. The second metal layer (1120) may be formed as a second patch element having a second size (L2p) in the first and second axis directions. In this regard, the first and second axis directions may correspond to the X and Y axes on the XY plane. The second size (L2p) of the second metal layer (1120) may be formed to be the same size as the first size (L1p) of the first metal layer (1110), but is not limited thereto and may be changed depending on the application. As described above, a DC voltage may be applied to the second metal layer (1120) to vary the permittivity of the liquid crystal (1020).

[0076] The third metal layer (1130) may be formed as a third patch element having a third size (L3p) in the first and second axis directions. The third size (L3p) of the third metal layer (1130) may be formed to be larger than the first size (L1p) of the first metal layer (1110). The third size (L3p) of the third metal layer (1130) may be formed to be larger than the first size (L2p) of the second metal layer (1120).

[0077] The third metal layer (1130) may be electrically connected to the ground layer (Lg). In this regard, the third layer (La3) may include a third metal layer (1130) formed on a first surface of the third substrate (1030) and a ground layer (Lg) formed on a second surface of the third substrate (1030).

[0078] Meanwhile, in the liquid crystal-based reflective metasurface according to the present specification, the first and second metal layers may be formed in a floating structure without being connected to each other and separated from the other metal layers. In this regard, the first patch element of the first metal layer (1110) disposed on the first surface of the first substrate (1010) may be configured not to be connected to the ground layer (Lg) and not to be connected to the second patch element of the second metal layer (1120). The second patch element disposed on the first surface of the second substrate (1020) may be configured not to be connected to the ground layer (Lg) and not to be connected to the first patch element of the first metal layer (1110).

[0079] Meanwhile, in the liquid crystal-based reflective metasurface according to the present specification, the thicknesses of the first substrate (1010), the second substrate (1020), and the third substrate (1030) can be designed to optimize the reflective performance. In this regard, the thickness (t1) of the first substrate (1010) can be formed to be thicker than the second thickness (t2) of the second substrate (1020) and the third thickness (t3) of the third substrate (1030). The third thickness (t3) of the third substrate (1030) can be formed to be thicker than the second thickness (t2) of the second substrate (1020).

[0080] The thickness of the liquid crystal region filled with the liquid crystal (1020a) may be formed to be the same as the second thickness (t2) of the second substrate (1020). The size of the liquid crystal region filled with the liquid crystal (1020a) may be formed to be equal to or larger than the second size (L2p) of the second metal layer (1120). The size of the liquid crystal region filled with the liquid crystal (1020a) may be formed to be equal to or smaller than the third size (L3p) of the third metal layer (1130). Therefore, since the dielectric constant has a uniform value in the entire area on the XY plane of the first and second metal layers (1110, 1120) that operate as reflectors of the double patch element structure, the performance of the reflective metasurface is also maintained uniformly. In addition, since the ground is uniformly provided to the entire liquid crystal region filled with the liquid crystal (1020a), the dielectric constant also has a uniform value, so the performance of the reflective metasurface is also maintained uniformly.

[0081] Referring to FIGS. 7A and 7B, a first patch element of a first metal layer (1110) of a first layer (La1) of a liquid crystal-based reflective metasurface (1000) can be equivalent to a first resistor (R1) and a first capacitor (C1). A second patch element of a second metal layer (1120) of a second layer (La2) of a liquid crystal-based reflective metasurface (1000) can be equivalent to a second resistor (R2) and a second capacitor (C2). A first substrate (1010) between the first metal layer (1110) and the second metal layer (1120) can be equivalent to a first inductor (L1). One end of the first inductor (L1) can be equivalent to be connected to the first capacitor (C1) and the other end can be equivalent to be connected to the second capacitor (C2). The liquid crystal (1020a) of the second substrate (1020) can be equivalent to a third resistor (R3) and a second inductor (L2). The third metal layer (1130) of the third layer (La3) can function as a ground (GND).

[0082] The unit cell of the RIS implemented with a liquid crystal-based reflective metasurface can be equivalently expressed as an input impedance of the metal layers and dielectrics constituting the RIS based on the incident surface to which the radio waves are applied. In the present specification, it has three metal layers of the first to third metal layers (1110, 1120, 1130), and each metal layer can be equivalentized as an equivalent circuit having a resistance component and a capacitance component connected in parallel.

[0083] The first substrate (1010), which is the upper substrate, can be implemented as a low-loss dielectric substrate having a loss value below a critical value. The first substrate (1010) does not have a resistance component and can be expressed mainly only by an inductance component. Meanwhile, the second substrate (1020) having a liquid crystal (1020a) can be equivalent to a resistance component and an inductance component. Meanwhile, a reflection coefficient can be derived by using the characteristic impedance of air as a reference for the input impedance in a unit cell of a liquid crystal-based reflective metasurface (1000).

[0084] The reflection coefficient of the liquid crystal-based reflective metasurface (1000) can be expressed by the following mathematical expression 1. In this regard, Zin represents the input impedance of the liquid crystal-based reflective metasurface (1000), and Z0 can be set to 377 ohm as the characteristic impedance of air. Re{Zin} represents the real part of the input impedance (Zin).

[0085]

[0086] Meanwhile, in the liquid crystal-based reflective metasurface according to the present disclosure, the thickness of the upper substrate and the size of the upper metal layer can be adjusted to optimize the reflection performance. In this regard, FIGS. 8A and 8B illustrate the reflection coefficient and input impedance when the thickness of the first substrate changes to 0.4, 0.6, and 0.8 mm. FIG. 8A illustrates the reflection coefficient when the permittivity of the liquid crystal is 3.0 and the thickness of the first substrate changes to 0.4, 0.6, and 0.8 mm. FIG. 8B illustrates the real value of the input impedance when the permittivity of the liquid crystal is 3.0 and the thickness of the first substrate changes to 0.4, 0.6, and 0.8 mm.

[0087] Referring to FIGS. 7a to 8b, the real values ​​of the reflection coefficient and input impedance of RIS are shown according to the change in the thickness of the first substrate (1010), which is the upper substrate disposed in the upper region of the liquid crystal (1020a) in the Z-axis direction. As the thickness (t1) of the first substrate (1010) increases, the reflection coefficient decreases at the first resonant frequency, which can be confirmed by the increase in the size of the real value of the input impedance of RIS.

[0088] In addition, as the thickness (t1) of the first substrate (1010) increases, the second resonant frequency shifts to a lower frequency band. Therefore, as the thickness (t1) of the first substrate (1010) increases, two resonant modes can be used simultaneously to secure broadband characteristics of the reflective meta surface. In addition, it can be seen that as the thickness (t1) of the first substrate (1010) increases, the input impedance value increases at the first and second resonant frequencies, thereby improving the reflection performance at the first and second resonant frequencies.

[0089] Meanwhile, when the thickness of the first substrate in the liquid crystal-based reflective metasurface according to the present specification is increased to 800 μm or more, the reflection performance may deteriorate. In this regard, Fig. 9a shows the reflection coefficient and input impedance when the thickness of the first substrate is changed to 0.8, 1, 1.2, and 1.4 mm. Fig. 9b shows the reflection coefficient according to the change in permittivity when the thickness of the first substrate is 1 mm.

[0090] Referring to FIGS. 7A and 9A, the dielectric constant of the liquid crystal (1020a) can be set to 3.0. When the thickness (t1) of the first substrate (1010) is increased beyond 800 μm, the reflection coefficient decreases somewhat up to 1000 μm. However, when the thickness (t1) of the first substrate (1010) is increased to 1200 μm and 1400 μm, the reflection coefficient increases again.

[0091] Referring to FIGS. 7a and 9b, even when the thickness (t1) of the first substrate (1010) is 1000 um, if the dielectric constant (Dk) of the liquid crystal (1020a) is 2.5, the reflection coefficient performance increases to -5 dB or more. Therefore, the optimal reflection performance is derived when the thickness (t1) of the first substrate (1010) is 800 um (0.8 mm).

[0092] Meanwhile, Fig. 10a shows the phase of the reflection signal as the dielectric constant changes when the thickness of the first substrate is 0.6 mm. Fig. 10b shows the phase of the reflection signal as the dielectric constant changes when the thickness of the first substrate is 1 mm.

[0093] Referring to FIGS. 7A and 10A, the dielectric constant (Dk) of the liquid crystal (1020a) can be varied to 2.5, 3, and 3.5. If the thickness (t1) of the substrate (1010) is 0.6 mm, a frequency band (FB1) in which the phase variation characteristic of the reflection signal due to the change in the dielectric constant is not secured of 135 degrees or more occurs. Therefore, if the thickness (t1) of the first substrate (1010) is 0.6 mm, the operating bandwidth of the liquid crystal-based reflective metasurface narrows.

[0094] Referring to FIGS. 6b, 7a, and 10b, the permittivity (Dk) of the liquid crystal (1020a) can be varied to 2.5, 3, and 3.5. When the thickness (t1) of the first substrate (1010) is 1 mm, the phase variation characteristics of the reflection signal according to the change in permittivity are similar to the phase variation characteristics when the thickness (t1) of the first substrate (1010) is 0.8 mm. However, as shown in FIG. 9b, when the thickness (t1) of the first substrate (1010) is 1 mm and the permittivity is 2.5, the reflection coefficient performance increases to -5 dB or more. Therefore, the optimal reflection performance is derived when the thickness (t1) of the first substrate (1010) is 800 um (0.8 mm).

[0095] In the liquid crystal-based reflective metasurface according to the present disclosure, the size of the upper metal layer upon which the wireless signal is incident has a major impact on the reflection performance. In this regard, Fig. 11a shows the reflection coefficient characteristics as the size of the first metal layer changes. Fig. 11b shows the input impedance values ​​as the size of the first metal layer changes.

[0096] Referring to FIGS. 7A and 11A, the dielectric constant of the liquid crystal (1020a) is 3, and the first size (L1p) of the first patch element of the first metal layer (1110) can be changed to 7.4, 7.8, 8.2, and 8.6 mm. When the first size (L1p) of the first patch element is 7.8, 8.2, and 8.6 mm, the reflection coefficient has a value of -5 dB or higher. However, when the first size (L1p) of the first patch element is 7.4, 8.6 mm, the reflection coefficient has a value of -5 dB or lower, thereby deteriorating the reflection performance.

[0097] Referring to FIGS. 7b and 11b, the dielectric constant of the liquid crystal (1020a) is 3, and the first size (L1p) of the first patch element of the first metal layer (1110) can be changed to 7.4, 7.8, 8.2, and 8.6 mm. As the first size (L1p) of the first patch element decreases, both the first and second resonant frequencies of the input impedance shift to a high frequency band.

[0098] As the first size (L1p) of the first patch element decreases, the input impedance at the second resonant frequency increases, but the input impedance at the first resonant frequency decreases. Therefore, when the first size (L1p) of the first patch element is 7.4 mm, the reflection performance deteriorates at the first resonant frequency. On the other hand, when the first size (L1p) of the first patch element increases, the input impedance at the first resonant frequency increases, but the input impedance at the second resonant frequency decreases. Therefore, when the first size (L1p) of the first patch element is 8.6 mm, the reflection performance deteriorates at the second resonant frequency.

[0099] In this regard, FIGS. 12a and 12b show the reflection coefficient and the phase of the reflection signal when the first size of the first patch element of the first metal layer is 7.4 mm. FIGS. 13a and 13b show the reflection coefficient and the phase of the reflection signal when the first size of the first patch element of the first metal layer is 8.6 mm.

[0100] Referring to FIG. 7a and FIG. 12a, the first size (L1p) of the first patch element of the first metal layer (1110) can be 7.4 mm and the dielectric constant can be changed to 2.5, 3.0, and 3.5. When the first size (L1p) of the first patch element is 7.4 mm and the dielectric constant is 3.0, 3.5, the reflection coefficient has a value of -5 dB or less, thereby deteriorating the reflection performance.

[0101] Referring to FIGS. 7A and 12B, the first size (L1p) of the first patch element of the first metal layer (1110) is 7.4 mm, and the permittivity can be changed to 2.5, 3.0, and 3.5. When the first size (L1p) of the first patch element is 7.4 mm, a frequency band (FB2) in which the phase variation characteristic of the reflection signal according to the change in permittivity is not secured by 135 degrees or more occurs. In this regard, in the second resonant frequency band of 11.2 GHz or more, the phase variation characteristic of 135 degrees or more is not secured according to the change in permittivity. Therefore, when the first size (L1p) of the first patch element is 7.4 mm, the frequency bandwidth performance of the phase variation characteristic is deteriorated.

[0102] Referring to FIG. 7a and FIG. 13a, the first size (L1p) of the first patch element of the first metal layer (1110) can be 8.6 mm and the dielectric constant can be changed to 2.5, 3.0, and 3.5. When the first size (L1p) of the first patch element is 8.6 mm and the dielectric constant is 2.5, 3.0, the reflection coefficient has a value of -5 dB or less, thereby deteriorating the reflection performance.

[0103] Referring to FIGS. 7b and 13b, the first size (L1p) of the first patch element of the first metal layer (1110) is 8.6 mm, and the permittivity can be changed to 2.5, 3.0, and 3.5. When the first size (L1p) of the first patch element is 8.6 mm, a frequency band (FB3) in which the phase variation characteristic of the reflection signal according to the change in permittivity is not secured by 135 degrees or more occurs. In this regard, the phase variation characteristic of 135 degrees or more is not secured according to the change in permittivity in the first resonant frequency band. Therefore, when the first size (L1p) of the first patch element is 8.6 mm, the frequency bandwidth performance of the phase variation characteristic is deteriorated.

[0104] Meanwhile, in the liquid crystal-based reflective metasurface according to the present specification, the input impedance changes depending on the thickness of the first substrate and the size of the first metal layer, thereby changing the reflection characteristics. In this regard, FIGS. 14a and 14b show input impedance characteristics according to changes in the thickness of the first substrate when the permittivity of the liquid crystal is 2.5 and 3.5, respectively. FIG. 14a shows input impedance characteristics according to changes in the thickness of the first substrate when the permittivity of the liquid crystal is 2.5. FIG. 14b shows input impedance characteristics according to changes in the thickness of the first substrate when the permittivity of the liquid crystal is 3.5.

[0105] Meanwhile, FIGS. 15a and 15b show input impedance characteristics according to changes in the first size of the first metal layer when the dielectric constant of the liquid crystal is 2.5 and 3.5, respectively. FIG. 15a shows input impedance characteristics according to changes in the first size of the first metal layer when the dielectric constant of the liquid crystal is 2.5. FIG. 15b shows input impedance characteristics according to changes in the first size of the first metal layer when the dielectric constant of the liquid crystal is 3.5.

[0106] Referring to FIGS. 7a and 14a to 14b, in order to utilize the dual resonance characteristics of the liquid crystal-based reflective metasurface, an input impedance value of 1350 ohm or more must be secured in two resonance modes. The liquid crystal-based reflective metasurface according to the present specification uses a dielectric constant of the liquid crystal (1020a) between 2.5 and 3.5 for phase-variable characteristics. Therefore, a broadband performance of reflectivity is required at both the lower limit of 2.5 and the upper limit of 3.5 of the dielectric constant of the liquid crystal (1020a).

[0107] Referring to FIG. 7a and FIG. 14a, the dielectric constant of the liquid crystal (1020a) is 2.5, and the thickness (t1) of the first substrate (1010) can be changed to 0.92, 1, 1.08, and 1.16 mm. In order to secure an input impedance of 1350 ohm or more in the second resonance mode, the thickness (t1) of the first substrate (1010) needs to be designed to be 1080 um (1.08 mm) or less. If the thickness (t1) of the first substrate (1010) is 1080 um (1.08 mm), it corresponds to a wavelength (λ0) of 0.036 based on the center frequency of 10 GHz of the operating band.

[0108] Referring to FIGS. 7a and 14b, the dielectric constant of the liquid crystal (1020a) is 3.5, and the thickness (t1) of the first substrate (1010) can be changed to 0.7, 0.76, 0.83, and 0.88 mm. In order to secure an input impedance of 1350 ohm or more in the first resonance mode, the thickness (t1) of the first substrate (1010) needs to be designed to be 760 um (0.76 mm) or more. If the thickness (t1) of the first substrate (1010) is 760 um (0.76 mm), it corresponds to a wavelength (λ0) of 0.025 based on the center frequency of 10 GHz of the operating band.

[0109] Referring to FIGS. 7A, 15A, and 15B, the design of the liquid crystal-based reflective metasurface has been described based on 10 GHz. However, the design of the reflective metasurface is not limited to the 10 GHz band, and can be applied to the Sub-6 GHz band or the high-frequency band of 100 GHz or higher by scaling the unit cell of the reflective metasurface. Accordingly, the first substrate (1010) can be designed with a thickness (t1) between 0.025 wavelength (λ0) and 0.036 wavelength (λ0) based on the center frequency (f0) of the operating band. When the thickness (t1) of the first substrate (1010) is between 0.025 wavelength (λ0) and 0.036 wavelength (λ0), the reflective metasurface can secure input impedance and reflection performance through dual resonance.

[0110] Referring to FIG. 7a and FIG. 15a, the dielectric constant of the liquid crystal (1020a) is 2.5, and the first size (L1p) of the first patch element of the first metal layer (1110) can be changed to 8.05, 8.1, 8.15, and 8.2 mm. In order to secure an input impedance of 1350 ohm or more in the second resonance mode, the first size (L1p) of the first patch element of the first metal layer (1110) needs to be designed to be 8.15 mm or less. If the first size (L1p) of the first patch element is 8.15 mm, it corresponds to a wavelength (λ0) of 0.272 based on the center frequency of 10 GHz of the operating band.

[0111] Referring to FIGS. 7a and 15b, the dielectric constant of the liquid crystal (1020a) is 3.5, and the first size (L1p) of the first patch element of the first metal layer (1110) can be changed to 7.8, 7.85, 7.9, and 7.95 mm. In order to secure an input impedance of 1350 ohm or more in the first resonance mode, the first size (L1p) of the first patch element of the first metal layer (1110) needs to be designed to be 7.85 mm or more. If the first size (L1p) of the first patch element is 7.85 mm, it corresponds to a wavelength (λ0) of 0.262 based on the center frequency of 10 GHz of the operating band.

[0112] Referring to FIGS. 7a, 15a, and 15b, the design of the liquid crystal-based reflective metasurface has been described based on 10 GHz. However, the design of the reflective metasurface is not limited to the 10 GHz band, and can be applied to the sub-6 GHz band or the high-frequency band of 100 GHz or higher by scaling the unit cell of the reflective metasurface. Accordingly, the first patch element of the first metal layer (1110) can be designed with a first size (L1p) between 0.262 wavelength (λ0) and 0.272 wavelength (λ0) based on the center frequency (f0) of the operating band. If the first size (L1p) of the first patch element of the first metal layer (1110) is between 0.025 wavelength (λ0) and 0.036 wavelength (λ0), the reflective metasurface can secure input impedance and reflection performance through dual resonance.

[0113] A liquid crystal-based reflective metasurface according to the present specification will be described with reference to FIGS. 4A to 14B. In this regard, the ranges of the thickness (t1) of the first substrate (1010) and the first size (L1p) of the first metal layer (1110) can be summarized as follows. In a structure in which the second metal layer (1120) covers the upper portion of the liquid crystal (1020a) and the third metal layer (1130) covers the lower portion of the liquid crystal (1020a), the thickness (t1) of the first substrate (1010) has a range within 0.025 wavelength (λ0) to 0.036 wavelength (λ0). In a structure in which the second metal layer (1120) covers the upper part of the liquid crystal (1020a) and the third metal layer (1130) covers the lower part of the liquid crystal (1020a), the size (L1p) of the first metal layer (1110) has a range of 0.262 wavelength (λ0) to 0.272 wavelength (λ0).

[0114] The liquid crystal-based reflective metasurface according to the present specification corresponds to an RIS module that operates as a reflector. The RIS module that operates as a reflector can reflect the wireless signal with different phases depending on the variable permittivity of the liquid crystal (1020) at a center frequency of 10 GHz. In this regard, the thickness (t1) of the first substrate (1010) can be formed in a range of 760 μm to 1080 μm. The thickness (t2) of the second substrate (1020) can be formed within a predetermined range based on 250 μm. The thickness (t3) of the third substrate (1030) can be formed within a predetermined range based on 400 μm. Meanwhile, the first size (L1p) of the first patch element of the first metal layer (1110) can be formed in a range of 7.85 mm to 8.15 mm.

[0115] Meanwhile, the first metal layer (1110) and the second metal layer (1120) of the liquid crystal-based reflective metasurface according to the present specification can operate in a dual resonance mode. The first metal layer (1110) coupled with the second metal layer (1120) can operate in a dual resonance mode in the first frequency band and the second frequency band, thereby operating as a wideband phase-tunable reflector. The RIS module implemented with the liquid crystal-based reflective metasurface can be configured to have an input impedance of 1350 ohm or more in the first frequency band and the second frequency band. In this regard, the second frequency band can be set to a higher frequency than the first frequency band.

[0116] Meanwhile, in the liquid crystal-based reflective metasurface according to the present specification, the thickness (t1) of the first substrate (1010) may be formed in a predetermined range in consideration of the permittivity range of the liquid crystal. In this regard, when the permittivity of the liquid crystal (1020a) is a lower limit value, the thickness (t1) of the first substrate (1010) may be set to 1080 um (0.036 wavelength (λ0)) or less so that the input impedance is formed to be 1350 ohm or more in the second frequency band. Meanwhile, when the permittivity of the liquid crystal (1020a) is an upper limit value, the thickness (t1) of the first substrate (1010) may be set to 760 um (0.025 wavelength (λ0)) or more so that the input impedance is formed to be 1350 ohm or more in the first frequency band.

[0117] Meanwhile, in the liquid crystal-based reflective metasurface according to the present specification, the first size (L1p) of the first patch element of the first metal layer (1110) may be formed in a predetermined range in consideration of the permittivity range of the liquid crystal. In this regard, when the permittivity of the liquid crystal (1020a) is a lower limit value, the first size (L1p) of the first patch element of the first metal layer (1110) may be set to 8.15 mm (0.272 wavelength (λ0)) or less so that the input impedance is formed to be 1350 ohm or more in the second frequency band. When the permittivity of the liquid crystal (1020a) is an upper limit value, the first size (L1p) of the first patch element of the first metal layer (1110) may be set to 7.85 mm (0.262 wavelength (λ0)) or more so that the input impedance is formed to be 1350 ohm or more in the first frequency band.

[0118] The liquid-based reflective metasurface according to the present specification has been described above. The technical effects of the liquid-based reflective metasurface according to the present specification are as follows.

[0119] According to an embodiment of the present disclosure, a liquid crystal-based reflective metasurface implemented in a multilayer substrate package can improve reflectivity over a broad frequency band by more than 2.5 times.

[0120] According to an embodiment of the present disclosure, a phase tunable performance of 135 degrees or more can be obtained by varying the dielectric constant of the liquid crystal over a wide frequency band of 2.5 times or more in a liquid crystal-based reflective metasurface implemented as a multilayer substrate package.

[0121] According to an embodiment of the present disclosure, a double patch structure without a via structure forms two resonant modes and can operate as a reflector throughout the entire operating frequency band.

[0122] According to an embodiment of the present disclosure, it is possible to manufacture a display process using a liquid crystal through a unit cell having a plurality of metal layers that do not include a via structure.

[0123] Further scope of the applicability of this disclosure will become apparent from the detailed description below. However, since various changes and modifications within the spirit and scope of this disclosure will become apparent to those skilled in the art, it should be understood that the detailed description and specific embodiments, such as the preferred embodiments of this disclosure, are given by way of example only. The detailed description should not be construed as limiting in any respect but rather as illustrative. The scope of this disclosure should be determined by a reasonable interpretation of the appended claims, and all changes within the scope of equivalents of this disclosure are intended to be embraced therein.

Claims

1. In liquid crystal-based reflective metasurfaces, A first layer comprising a first substrate, a first metal layer formed on a first surface of the first substrate, and a second metal layer formed on a second surface of the first substrate; A second layer comprising a second substrate providing a space in which the liquid crystal can be filled in the central portion of the liquid crystal and the unit cell; and A third substrate, comprising a third layer including a third metal layer formed on a first surface of the third substrate, In a structure in which the second metal layer covers the upper part of the liquid crystal and the third metal layer covers the lower part of the liquid crystal, the thickness of the first substrate has a range of 0.025 λ0 to 0.036 λ0. A liquid crystal-based reflective metasurface, wherein the size of the first metal layer is in the range of 0.262 λ0 to 0.272 λ0.

2. In paragraph 1, A liquid crystal-based reflective metasurface that reflects a wireless signal incident on the first metal layer with different phases by varying the permittivity depending on the DC voltage applied to the first metal layer and the liquid crystal.

3. In paragraph 2, The first metal layer, the second metal layer, and the liquid crystal having a dielectric constant that varies depending on the DC voltage form a RIS (Reconfigurable Intelligent Surface) module that causes the reflected signals of the wireless signal reflected at a predetermined ratio or more to be reflected with different phases, The above RIS module is a liquid crystal-based reflective metasurface that operates in a broadband with respect to a center frequency by a dual patch structure of the first metal layer and the second metal layer.

4. In paragraph 3, The first metal layer is formed as a first patch element having a first size in the first axis and second axis directions, The second metal layer is formed as a second patch element of a second size in the first and second axis directions, A liquid crystal-based reflective metasurface, wherein the second size of the second metal layer is formed to be the same size as the first size of the first metal layer.

5. In paragraph 4, The third metal layer is formed as a third patch element of a third size in the first and second axis directions, A liquid crystal-based reflective metasurface, wherein the third size of the third metal layer is formed to be larger than the first size of the first metal layer.

6. In paragraph 4, The third layer further includes a ground layer formed on the second surface of the third substrate, A DC voltage is applied to the second metal layer to vary the dielectric constant of the liquid crystal, A liquid crystal-based reflective metasurface, wherein the third metal layer is electrically connected to the ground layer.

7. In paragraph 6, The first patch element disposed on the first surface of the first substrate is configured not to be connected to the ground layer and not to be connected to the second patch element, A liquid crystal-based reflective metasurface, wherein the second patch element disposed on the first surface of the second substrate is configured not to be connected to the ground layer and not to be connected to the first patch element.

8. In paragraph 4, The thickness of the first substrate is formed to be thicker than the second thickness of the second substrate and the third thickness of the third substrate, A liquid crystal-based reflective metasurface, wherein the third thickness of the third substrate is formed thicker than the second thickness of the second substrate.

9. In paragraph 8, The thickness of the liquid crystal region filled with the liquid crystal is formed to be the same as the second thickness of the second substrate, A liquid crystal-based reflective metasurface, wherein the size of the liquid crystal region is formed to be greater than or equal to the second size of the second metal layer and less than or equal to the third size of the third metal layer.

10. In paragraph 4, The above RIS module reflects the wireless signal with different phases according to the variable dielectric constant at 10 GHz, The thickness of the first substrate is formed in a range of 760um to 1080um, The second thickness of the second substrate is formed within a predetermined range based on 250 um, A liquid crystal-based reflective metasurface formed within a predetermined range based on a third thickness of the third substrate of 400 um.

11. In paragraph 8, In the first state where the DC voltage applied to the liquid crystal is 0 V, the dielectric constant of the liquid crystal is 2.5, which is the lower limit value. In the second state where the DC voltage applied to the liquid crystal is 10 V, the dielectric constant of the liquid crystal is 3.0, In the third state where the DC voltage applied to the liquid crystal is 20 V, the dielectric constant of the liquid crystal is 3.5, which is the upper limit value. In the above first state, the reflected signal is reflected at a predetermined rate or more with the first phase value, In the second state, the reflected signal is reflected at a predetermined ratio or more with a second phase value different from the first phase value, In the third state, the reflected signal is reflected at a predetermined ratio or more with a third phase value different from the second phase value, The above predetermined ratio is a liquid crystal-based reflective metasurface, wherein the reflection coefficient of the reflected signal is set to -5 dB or more compared to the incident wireless signal.

12. In paragraph 4, The above RIS module reflects the wireless signal with different phases according to the variable dielectric constant at 10 GHz, A liquid crystal-based reflective metasurface, wherein the first size of the first metal layer is formed in a range of 7.85 mm to 8.15 mm.

13. In paragraph 3, The first metal layer coupled to the second metal layer operates in a dual resonance mode in the first frequency band and the second frequency band, The above RIS module has an input impedance of 1350 ohm or more in the first frequency band and the second frequency band, A liquid crystal-based reflective metasurface, wherein the second frequency band is a higher frequency band than the first frequency band.

14. In paragraph 13, When the dielectric constant of the liquid crystal is the lower limit value, the thickness of the first substrate is set to 1080um or less so that the input impedance is formed to be 1350 ohm or more in the second frequency band. A liquid crystal-based reflective metasurface, wherein the thickness of the first substrate is set to 760 um or more so that the input impedance is formed to be 1350 ohm or more in the first frequency band when the dielectric constant of the liquid crystal is an upper limit value.

15. In paragraph 13, When the dielectric constant of the liquid crystal is a lower limit value, the first size of the first metal layer is set to 8.15 mm or less so that the input impedance is formed to be 1350 ohm or more in the second frequency band, A liquid crystal-based reflective metasurface, wherein the first size of the first metal layer is set to be 7.85 mm or more so that the input impedance is formed to be 1350 ohm or more in the first frequency band when the dielectric constant of the liquid crystal is an upper limit value.

Images