Liquid crystal metasurface unit

Abstract

A liquid crystal metasurface unit comprises a top dielectric plate layer, an upper metal layer, a liquid crystal layer, a lower metal layer, a lower dielectric plate layer and a bottom floor metal layer which are sequentially stacked from top to bottom. The upper metal layer and the lower metal layer respectively comprise a plurality of metal patches and direct current bias lines, the metal patches comprise liquid crystal control metal patches, and the liquid crystal control metal patches of the upper metal layer and the liquid crystal control metal patches of the lower metal layer are overlapped up and down to form a capacitance effect with the middle liquid crystal layer. The direct current bias lines are electrically connected with the metal patches respectively and used for applying voltage to regulate and control the dielectric constant of the liquid crystal layer through the liquid crystal regulation and control metal patches, and finally the reflection phase of the metasurface unit is changed; the metal patches form a plurality of resonant phase-shifting structures, and the phase regulation and control effects of the resonant phase-shifting structures are mutually superposed, so that the wide reflection phase regulation and control range of the liquid crystal metasurface unit is realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to wireless communication field especially is involved in a liquid crystal hypersurface unit. BACKGROUND

[0002] Reflective array antennas have attracted great interest due to their low cost, ease of construction, and ability to reconfigure beams electronically. Reflective array antennas are also capable of beam scanning, and thus are widely used in satellite communications, radars, and imaging applications. The phase shift function of each unit is a key issue for reflective array antennas, especially for the ability to use control elements or tunable materials to control the beam. The usual control elements are varactor diodes, p-i-n diodes, and micro-electromechanical system switches, the physical structure or resonant frequency of which can be controlled by voltage. However, the parasitic effect of diodes cannot be ignored in the frequency band above 10 GHz. In addition, the reflective phase can also be changed by using tunable materials (such as ferrite and liquid crystal).

[0003] Reflective arrays based on liquid crystal hypersurfaces are an attractive option for microwave and millimeter-wave applications. They have advantages such as cost-effectiveness, ease of integration, or continuous tunability of phase. In addition, compared with arrays that rely on other tunable material systems, liquid crystal materials can work in a wider frequency range, consume less power, and are compatible with modern industrial display manufacturing processes, enabling mass production.

[0004] Most of the liquid crystal-based reflective array units so far have been made with relatively thick liquid crystal layers, such as 50um, 30um, etc. This usually results in greater reflection loss and response time; in addition, the reflection phase control range of most liquid crystal hypersurface units is about 180 degrees, which greatly reduces the practicability of liquid crystal hypersurface arrays.

[0005] It should be noted that the information disclosed in the above background section is only for understanding the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0006] The main purpose of the utility model is to solve the problems in the above background technology, and to provide a liquid crystal hypersurface unit.

[0007] To achieve the above purpose, the utility model adopts the following technical solutions:

[0008] The liquid crystal super surface unit comprises a top layer medium plate layer, an upper layer metal layer, a liquid crystal layer, a lower layer metal layer, a lower layer medium plate layer and a bottom floor metal layer which are sequentially stacked from top to bottom; the upper layer metal layer and the lower layer metal layer respectively comprise a plurality of metal patches and a direct current bias line, wherein the metal patch comprises a liquid crystal control metal patch, the liquid crystal control metal patch of the upper layer metal layer and the liquid crystal control metal patch of the lower layer metal layer overlap each other, and form a capacitive effect with the liquid crystal layer in the middle; the direct current bias line is electrically connected with the metal patch, and is used for applying a voltage to control the dielectric constant of the liquid crystal layer through the liquid crystal control metal patch, so as to change the capacitance value in the capacitive effect; the metal patches form a plurality of resonant phase shift structures, the phase shift effects of the plurality of resonant phase shift structures are superimposed on each other, and a wide reflection phase control range of the liquid crystal super surface unit is realized; the thickness of the liquid crystal layer ranges from 5 to 20 microns; and the top layer medium plate layer and the lower layer medium plate layer are both glass substrates.

[0009] Further, the upper layer metal layer comprises an upper layer direct current bias line, a first upper layer liquid crystal control metal patch and a second upper layer liquid crystal control metal patch; the lower layer metal layer comprises a lower layer direct current bias line, a first lower layer liquid crystal control metal patch and a second lower layer liquid crystal control metal patch; the first upper layer liquid crystal control metal patch and the first lower layer liquid crystal control metal patch overlap each other, and form a first capacitive effect with the liquid crystal layer in the middle; and the second upper layer liquid crystal control metal patch and the second lower layer liquid crystal control metal patch overlap each other, and form a second capacitive effect with the liquid crystal layer in the middle.

[0010] Further, the upper layer metal layer further comprises a first upper layer L-shaped metal patch and a second upper layer L-shaped metal patch; the lower layer metal layer further comprises a first lower layer L-shaped metal patch and a second lower layer L-shaped metal patch; the first upper layer L-shaped metal patch, the first lower layer L-shaped metal patch, the first upper layer liquid crystal control metal patch and the first lower layer liquid crystal control metal patch form a first resonant phase shift structure; the second upper layer L-shaped metal patch, the second lower layer L-shaped metal patch, the second upper layer liquid crystal control metal patch and the second lower layer liquid crystal control metal patch form a second resonant phase shift structure, and the phase shift effects of the first resonant phase shift structure and the second resonant phase shift structure are superimposed on each other, so as to realize a wide reflection phase control range of the liquid crystal super surface unit.

[0011] Further, the side length d of the liquid crystal super surface unit satisfies 0.25λt≤d≤0.5λt, wherein λt=c / ft, ft is a center frequency of a working frequency band, c is the speed of light in vacuum, and λt is a wavelength corresponding to the center frequency of the working frequency band.

[0012] Further, the upper layer DC bias line is connected to the region with the lowest electric field amplitude distribution in the first upper layer L-shaped metal patch and the second upper layer L-shaped metal patch when linearly polarized waves are incident, and the lower layer DC bias line is connected to the region with the lowest electric field amplitude distribution in the first lower layer L-shaped metal patch and the second lower layer L-shaped metal patch when linearly polarized waves are incident.

[0013] Further, two resonance peaks are generated by the first resonance phase shift structure and the second resonance phase shift structure, respectively, the frequencies of the two resonance peaks are close but not equal, and when the relative dielectric constant of the liquid crystal layer changes, the frequencies of the two resonance peaks simultaneously move to low frequencies.

[0014] Further, the reflection phase control range of the liquid crystal metasurface unit is more than 270 degrees, and the reflection loss is less than 2 dB.

[0015] The utility model has the following beneficial effects:

[0016] The utility model provides a liquid crystal metasurface unit, through design multiple resonance phase shift structures in single liquid crystal metasurface unit, utilize the superposition of these structures to realize the reflection phase control range of remarkable broadening, break through the phase control limit of only about 180 degrees of traditional liquid crystal metasurface unit, thereby the practicability of liquid crystal metasurface array is improved significantly, simultaneously, this resonance phase shift structure can utilize the liquid crystal layer of thickness 5-20 microns to control reflection phase, compared with the thicker liquid crystal layer in prior art, the response speed is improved greatly and the reflection loss is reduced, effectively solve the problem of long response time and big loss of traditional thick liquid crystal layer design, in addition, the liquid crystal control metal patch of upper layer metal layer and the liquid crystal control metal patch of lower layer metal layer are overlapped, and form the capacitance effect with the liquid crystal layer in the middle, and the dielectric constant of liquid crystal layer is controlled through the voltage applied by DC bias line through liquid crystal control metal patch, thereby the capacitance value in the capacitance effect is changed, this design realizes the accurate control of reflection phase, and further optimizes the flexibility and precision of phase control, further, by connecting the upper layer and lower layer DC bias line in the region with smaller electric field amplitude distribution when linearly polarized waves are incident, the potential influence of external voltage controller on metasurface reflection phase is eliminated, thereby the stability and precision of phase control are further optimized, these innovative designs not only make the liquid crystal metasurface unit of the utility model have fast response and wide reflection phase control capability, but also maintain the compatibility with modern industrial grade display manufacturing process, realize the advantages such as cost benefit, easy integration and phase continuous adjustable, provide a high-performance, low-power and mass production solution for the application of reflection array antenna of microwave and millimeter wave frequency band, and are especially suitable for satellite communication, radar and imaging fields.

[0017] Other beneficial effects in the embodiments of the utility model will be further described in the following. Attached Figure Description

[0018] Figure 1 This diagram shows the overall structure of a liquid crystal metasurface unit according to an embodiment of the present invention.

[0019] Figure 2 This is a top view of a liquid crystal metasurface unit metal graphic according to an embodiment of the present invention.

[0020] Figure 3 This invention illustrates the reflection amplitude of a fast-response liquid crystal metasurface unit with a wide range of reflection phase modulation according to an embodiment of the present invention.

[0021] Figure 4 This invention illustrates the reflection phase of a fast-response liquid crystal metasurface unit with a wide range of reflection phase modulation according to an embodiment of the present invention.

[0022] Figure 5 This illustration shows the electric field distribution at the resonant frequency of the first resonant phase-shifting structure of a fast-response liquid crystal metasurface unit with a wide range of reflection phase modulation, according to an embodiment of the present invention.

[0023] Figure 6 This illustration shows the electric field distribution at the resonant frequency of the second resonant phase-shifting structure of a fast-response liquid crystal metasurface unit with a wide range of reflection phase modulation, according to an embodiment of the present invention. Detailed Implementation

[0024] The embodiments of this utility model are described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of this utility model.

[0025] See Figures 1 to 2The utility model discloses a liquid crystal super surface unit, including from top to bottom sequentially layering arrangement top layer dielectric plate layer 101, upper layer metal layer, liquid crystal layer 107, lower layer metal layer, lower layer dielectric plate layer 113 and bottom floor metal layer 114, the upper layer metal layer and lower layer metal layer include a plurality of metal patch and direct current bias line respectively, wherein the metal patch includes liquid crystal control metal patch, the liquid crystal control metal patch of upper layer metal layer and the liquid crystal control metal patch of lower layer metal layer overlap, with the liquid crystal layer 107 of intermediate formation capacitance effect, the direct current bias line is electrically connected with the metal patch respectively, for exerting voltage through the liquid crystal control metal patch control the dielectric constant of liquid crystal layer 107, thereby change the capacitance value in the capacitance effect, the metal patch constitutes a plurality of resonant phase shift structures, the phase control effect of a plurality of resonant phase shift structures is mutually superposed, realizes the wide reflection phase control range of liquid crystal super surface unit, wherein the thickness range of liquid crystal layer is 5-20 microns, and the top layer dielectric plate layer 101 and lower layer dielectric plate layer 113 are all glass substrates.

[0026] In the liquid crystal super surface unit of the utility model, the dielectric constant of the liquid crystal layer is controlled by the direct current bias line to change the capacitance value and realize the accurate control of the reflection phase. The utility model designs multiple resonant phase shift structures in a single liquid crystal super surface unit, and the superposition of the structures can realize a wide reflection phase control range of more than 270 degrees, breaking the phase control limit of about 180 degrees of the traditional liquid crystal super surface unit. Thin liquid crystal layers can be used to significantly improve the response speed and reduce the reflection loss. The utility model has the characteristics of fast response, wide phase control range, low loss and easy integration, and is suitable for the application of microwave and millimeter wave frequency bands such as satellite communication, radar and imaging.

[0027] As shown in Figure 1 In some embodiments, the upper layer metal layer includes an upper layer direct current bias line 106, a first upper layer liquid crystal control metal patch 103 and a second upper layer liquid crystal control metal patch 104; the lower layer metal layer includes a lower layer direct current bias line 111, a first lower layer liquid crystal control metal patch 112 and a second lower layer liquid crystal control metal patch 109; the first upper layer liquid crystal control metal patch 103 overlaps the first lower layer liquid crystal control metal patch 112, and forms a first capacitance effect with the liquid crystal layer 107 in the middle; the second upper layer liquid crystal control metal patch 104 overlaps the second lower layer liquid crystal control metal patch 109, and forms a second capacitance effect with the liquid crystal layer 107 in the middle.

[0028] As shown in Figure 1As shown, in some embodiments, the upper metal layer further comprises a first upper L-shaped metal patch 102 and a second upper L-shaped metal patch 105; the lower metal layer further comprises a first lower L-shaped metal patch 108 and a second lower L-shaped metal patch 110; the first upper L-shaped metal patch 102, the first lower L-shaped metal patch 108, the first upper liquid crystal control metal patch 103, and the first lower liquid crystal control metal patch 112 form a first resonant phase shift structure; the second upper L-shaped metal patch 105, the second lower L-shaped metal patch 110, the second upper liquid crystal control metal patch 104, and the second lower liquid crystal control metal patch 109 form a second resonant phase shift structure, the phase shift effects of the first resonant phase shift structure and the second resonant phase shift structure are superimposed on each other, realizing a wide reflection phase control range of the liquid crystal metasurface unit.

[0029] Two resonant phase shift structures are formed in a single liquid crystal metasurface unit, and through the superposition effect of the two resonant phase shift structures, a wider reflection phase adjustment range is realized. Further, this resonant phase shift structure can use a liquid crystal layer with a thickness of 5-20 microns to control the reflection phase, which improves the response speed of the control compared with a thicker liquid crystal layer, and has lower reflection loss.

[0030] In preferred embodiments, the side length d of the liquid crystal metasurface unit satisfies 0.25λt≤d≤0.5λt, where λt=c / ft, ft is the center frequency of the working frequency band, c is the speed of light in vacuum, and λt is the wavelength corresponding to the center frequency of the working frequency band.

[0031] In some embodiments, the top dielectric plate layer 101 and the lower dielectric plate layer 113 are both glass substrates.

[0032] In preferred embodiments, the upper DC bias line 106 is connected to the region with the lowest electric field amplitude distribution in the first upper L-shaped metal patch 102 and the second upper L-shaped metal patch 105; the lower DC bias line 111 is connected to the region with the lowest electric field amplitude distribution in the first lower L-shaped metal patch 108 and the second lower L-shaped metal patch 110.

[0033] The upper DC bias line is connected to the region with smaller electric field amplitude distribution in the first upper L-shaped metal patch and the second upper metal patch when linearly polarized wave is incident; the lower DC bias line is connected to the region with smaller electric field amplitude distribution in the first lower L-shaped metal patch and the second lower metal patch when linearly polarized wave is incident, eliminating the influence of the external voltage controller on the reflection phase of the metasurface.

[0034] In some embodiments, the liquid crystal metasurface unit has two resonant peaks generated by the first resonant phase-shifting structure and the second resonant phase-shifting structure, respectively. The frequencies of the two resonant peaks are close but not equal, and when the relative permittivity of the liquid crystal layer 107 changes, the frequencies of the two resonant peaks shift to lower frequencies simultaneously.

[0035] This invention provides a liquid crystal metasurface unit with a thin liquid crystal layer and a reflection phase modulation range greater than 180 degrees. Preferably, the reflection phase modulation range of the liquid crystal metasurface unit exceeds 270 degrees, and the reflection loss is less than 2 dB.

[0036] The following describes specific embodiments of this utility model.

[0037] A fast-response, wide-phase-tuning liquid crystal metasurface unit includes, from top to bottom, a top dielectric layer 101, an upper metal layer, a liquid crystal layer 107, a lower metal layer, a lower dielectric layer 113, and a bottom ground metal layer 114. The first upper L-shaped metal patch, the first lower L-shaped metal patch, the first upper liquid crystal-tuning metal patch, and the first lower liquid crystal-tuning metal patch constitute a first resonant element; the second upper L-shaped metal patch, the second lower L-shaped metal patch, the second upper liquid crystal-tuning metal patch, and the second lower liquid crystal-tuning metal patch constitute a second resonant element. The phase-tuning effects of the first and second resonant elements are superimposed to achieve a wide reflection phase tuning range for the liquid crystal metasurface unit. The reflection phase of the liquid crystal metasurface is controlled by applying voltage through the upper and lower DC bias lines.

[0038] Specifically, such as Figure 1 As shown, the liquid crystal metasurface unit is preferably a square with a side length of 5.5 mm, and includes, from top to bottom, a top dielectric layer 101, an upper metal layer, a liquid crystal layer 107, a lower metal layer, a lower dielectric layer 113, and a bottom floor metal layer 114. The upper metal layer includes a first upper L-shaped metal patch 102, a second upper L-shaped metal patch 105, an upper DC bias line 106, a first upper liquid crystal control metal patch 103, and a second upper liquid crystal control metal patch 104; the lower metal layer includes a first lower L-shaped metal patch 108, a second lower L-shaped metal patch 110, a lower DC bias line 111, a first lower liquid crystal control metal patch 112, and a second lower liquid crystal control metal patch 109.

[0039] The aforementioned upper DC bias line 106 is electrically connected to the first upper L-shaped metal patch 102, the second upper L-shaped metal patch 105, the first upper liquid crystal control metal patch 103, and the second upper liquid crystal control metal patch 104; the lower DC bias line 111 is electrically connected to the first lower L-shaped metal patch 108, the second lower L-shaped metal patch 110, the first lower liquid crystal control metal patch 112, and the second lower liquid crystal control metal patch 109.

[0040] The thickness of the top dielectric layer 101 and the bottom dielectric layer 113 is preferably 0.5 mm, and the relative permittivity is preferably 3.75; the thickness of the liquid crystal layer 107 is 10 mm, and the relative permittivity of the liquid crystal material varies from 2.55 to 3.75.

[0041] The first upper liquid crystal control metal patch 103 and the first lower liquid crystal control metal patch 112 overlap vertically, forming a capacitive effect with the intermediate liquid crystal layer 107; the second upper liquid crystal control metal patch 104 and the second lower liquid crystal control metal patch 109 overlap vertically, forming a capacitive effect with the intermediate liquid crystal layer 107. A DC voltage, connected via the upper DC bias line 106 to the first upper liquid crystal control metal patch 103 and the second upper liquid crystal control metal patch 104, and connected via the lower DC bias line 111 to the first lower liquid crystal control metal patch 112 and the second lower liquid crystal control metal patch 109, controls the dielectric constant of the liquid crystal layer 107, thereby changing the capacitance value in the capacitive effect, ultimately achieving phase modulation of the metasurface unit's reflection.

[0042] like Figure 3 As shown, the metasurface unit has two resonant peaks, generated by the first and second resonant phase-shifting structures, respectively. The frequencies of the two resonant peaks are close but not equal. When the relative permittivity of the liquid crystal layer changes, both resonant peaks shift to lower frequencies simultaneously.

[0043] like Figure 3 and Figure 4 As shown, when the relative permittivity of the liquid crystal material changes from 2.55 to 3.75, the reflection phase of the liquid crystal metasurface changes continuously and exceeds 270 degrees at its maximum. The reflection loss of the liquid crystal metasurface unit remains below 2dB. This satisfies the design requirements for a 2-bit phase-coded metasurface.

[0044] like Figure 5 As shown, at the resonant frequency corresponding to the first resonant phase-shifting structure of the liquid crystal metasurface unit, the electric field is mainly distributed on the first resonant phase-shifting structure, and the electric field amplitude at the connection between the upper DC bias line 106 and the lower DC bias line 111 and the first resonant phase-shifting structure is relatively low; as Figure 6As shown, at the resonant frequency corresponding to the second resonant phase-shifting structure of the liquid crystal super surface unit, the electric field is mainly distributed on the second resonant phase-shifting structure, and the electric field amplitude at the connection between the upper DC bias line 106 and the lower DC bias line 111 and the second resonant phase-shifting structure is relatively low.

[0045] The above is a further detailed description of the utility model in combination with specific preferred embodiments, and the specific implementation of the utility model cannot be limited to these descriptions. For those skilled in the art to which the utility model belongs, without departing from the concept of the utility model, a number of equivalent substitutions or obvious modifications can be made, and the performance or use is the same, which should be regarded as belonging to the protection scope of the utility model.

Claims

1. A liquid crystal metasurface unit, characterized in that, The liquid crystal super surface unit comprises a top layer dielectric plate layer, an upper layer metal layer, a liquid crystal layer, a lower layer metal layer, a lower layer dielectric plate layer and a bottom floor metal layer which are sequentially stacked from top to bottom; the upper layer metal layer and the lower layer metal layer each comprise a plurality of metal patches and a direct current bias line, wherein the metal patches comprise liquid crystal control metal patches, the liquid crystal control metal patches of the upper layer metal layer and the liquid crystal control metal patches of the lower layer metal layer overlap each other, and form a capacitive effect with the liquid crystal layer in the middle; the direct current bias line is electrically connected with the metal patches respectively, and is used for applying a voltage to control the dielectric constant of the liquid crystal layer through the liquid crystal control metal patches, so as to change the capacitance value in the capacitive effect. The metal patches form a plurality of resonant phase shift structures, the phase control effects of the plurality of resonant phase shift structures are superimposed on each other, and a wide reflection phase control range of the liquid crystal super surface unit is realized; the thickness of the liquid crystal layer ranges from 5 to 20 microns; the top layer dielectric plate layer and the lower layer dielectric plate layer are both glass substrates.

2. The liquid crystal metasurface unit of claim 1, wherein, The upper layer metal layer comprises an upper layer direct current bias line, a first upper layer liquid crystal control metal patch and a second upper layer liquid crystal control metal patch; the lower layer metal layer comprises a lower layer direct current bias line, a first lower layer liquid crystal control metal patch and a second lower layer liquid crystal control metal patch; the first upper layer liquid crystal control metal patch and the first lower layer liquid crystal control metal patch overlap each other, and form a first capacitive effect with the liquid crystal layer in the middle; the second upper layer liquid crystal control metal patch and the second lower layer liquid crystal control metal patch overlap each other, and form a second capacitive effect with the liquid crystal layer in the middle.

3. The liquid crystal metasurface unit of claim 2, wherein, The upper layer metal layer further comprises a first upper layer L-shaped metal patch and a second upper layer L-shaped metal patch; the lower layer metal layer further comprises a first lower layer L-shaped metal patch and a second lower layer L-shaped metal patch; the first upper layer L-shaped metal patch, the first lower layer L-shaped metal patch, the first upper layer liquid crystal control metal patch and the first lower layer liquid crystal control metal patch form a first resonant phase shift structure; the second upper layer L-shaped metal patch, the second lower layer L-shaped metal patch, the second upper layer liquid crystal control metal patch and the second lower layer liquid crystal control metal patch form a second resonant phase shift structure, and the phase shift effects of the first resonant phase shift structure and the second resonant phase shift structure are superimposed on each other, so as to realize a wide reflection phase control range of the liquid crystal super surface unit.

4. The liquid crystal metasurface cell of any one of claims 1 to 3, wherein, The side length d of the liquid crystal super surface unit satisfies 0.25λ t ≤d≤0.5λ t , wherein λ t =c / f t , f t is a center frequency of a working frequency band, c is the speed of light in vacuum, and λ t is a wavelength corresponding to the center frequency of the working frequency band.

5. The liquid crystal metasurface unit of claim 3, wherein, The upper layer direct current bias line is connected with the regions with the lowest electric field amplitude distribution in the first upper layer L-shaped metal patch and the second upper layer L-shaped metal patch when a linearly polarized wave is incident; and the lower layer direct current bias line is connected with the regions with the lowest electric field amplitude distribution in the first lower layer L-shaped metal patch and the second lower layer L-shaped metal patch when a linearly polarized wave is incident.

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