Terahertz two-dimensional beam scanning antenna regulated and controlled by liquid crystal

Abstract

The invention discloses a liquid crystal regulated terahertz two-dimensional beam scanning antenna. The antenna comprises a first dielectric substrate and a second dielectric substrate which are oppositely arranged; the metal metasurface, the first orientation layer, the nematic phase liquid crystal layer, the second orientation layer and the metal reflecting surface are sequentially arranged between the first dielectric substrate and the second dielectric substrate; the metal metasurface is arranged on the first dielectric substrate, and the metal reflecting surface is arranged on the second dielectric substrate; initial orientation of liquid crystal molecules of the nematic liquid crystal layer is determined by the first orientation layer and the second orientation layer, the scanning antenna is in a first phase at the moment, bias voltage is applied between the metal metasurface and the metal reflection face, then the bias voltage is changed, the liquid crystal molecules of the nematic liquid crystal layer deflect, and the scanning antenna is in a second phase. And controlling the scanning antenna to be in a second phase, a third phase and a fourth phase respectively, wherein the phase difference between adjacent phases is close to 90 degrees. 2-bit coding is realized by changing the resonance characteristic and the phase response of the scanning antenna.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz two-dimensional beam scanning antennas. More specifically, the present invention relates to a liquid crystal-regulated terahertz two-dimensional beam scanning antenna. Background Art

[0002] Electromagnetic metasurface technology has become an important means of freely manipulating electromagnetic waves due to its unique advantages, showing excellent capabilities in electromagnetic wave regulation, such as amplitude-phase adjustment, polarization conversion, beam deflection, and vortex light generation. By encoding and controlling metasurface elements with different phase or amplitude responses using binary digits, the far-field scattered light beam can be flexibly manipulated. For example, under 2-bit encoding, the phase gradient takes 90° as the step, being 0°, 90°, 180°, and 270° respectively, and the corresponding digital encodings are 00, 01, 10, and 11. By introducing semiconductor elements, the phase response of the unit can be regulated, and combined with a field-programmable gate array (FPGA), the implementation manipulation of the encoding sequence can be realized, thereby changing the far-field pattern.

[0003] The terahertz band is between microwave and far-infrared in the electromagnetic spectrum, usually defined as 0.1 - 10 THz. Due to the small size of metasurface units, for terahertz metasurfaces, the unit size is usually only dozens to hundreds of micrometers. For traditional semiconductor devices, such as PIN diodes, it is difficult to be used in terahertz reconfigurable metasurfaces due to size limitations and parasitic effects. The real-time regulation of terahertz beams is mainly achieved through a series of functional materials, such as vanadium dioxide, liquid crystal, graphene, etc.

[0004] The larger the number of bits of the scanning antenna control coding bit, the smaller the phase step of the sub-array is subdivided, thereby improving the accuracy of beam control. Currently, the scanning antenna with 2-bit encoding regulated by liquid crystal in the terahertz band needs to be further explored. Summary of the Invention

[0005] The present invention provides a liquid crystal-regulated terahertz two-dimensional beam scanning antenna, aiming to improve the above problems.

[0006] The present invention is implemented as follows. A liquid crystal-regulated terahertz two-dimensional beam scanning antenna, characterized in that the scanning antenna includes:

[0007] A first dielectric substrate and a second dielectric substrate arranged oppositely;

[0008] A metal metasurface, a first alignment layer, a nematic liquid crystal layer, a second alignment layer, and a metal reflector are sequentially arranged between the first dielectric substrate and the second dielectric substrate;

[0009] The metal metasurface is arranged on the first dielectric substrate, and the metal reflector is arranged on the second dielectric substrate;

[0010] When no bias voltage is applied between the metal metasurface and the metal reflector, the initial orientation of the liquid crystal molecules in the nematic liquid crystal layer is determined by the first alignment layer and the second alignment layer. At this time, the scanning antenna is in the first phase state. After a bias voltage is applied between the metal metasurface and the metal reflector, by changing the bias voltage, the liquid crystal molecules in the nematic liquid crystal layer deflect, controlling the scanning antenna to be in the second phase state, the third phase state, and the fourth phase state respectively. Among them, the phase differences between the first phase state and the second phase state, the second phase state and the third phase state, and the third phase state and the fourth phase state are close to 90°.

[0011] Furthermore, the metal metasurface is composed of a number of metal metasurface linear sub-arrays. The spacing between adjacent metal metasurface linear sub-arrays is 2h. The metal metasurface linear sub-array is formed by sequentially splicing a number of metal metasurface units. The metal metasurface unit is a rectangular metal patch with a square split-ring through slot structure.

[0012] Furthermore, the metal metasurface is composed of 32 metal metasurface linear sub-arrays, and the metal metasurface linear sub-array is formed by splicing every 32 metal metasurface units.

[0013] Furthermore, the metal reflector is composed of a number of metal reflection linear sub-arrays. The spacing between adjacent metal reflection linear sub-arrays is 2h. It is arranged perpendicular to the metal metasurface linear sub-array on the second dielectric substrate. The metal reflection linear sub-array is formed by sequentially splicing a number of metal reflection units. The metal reflection unit is a rectangular metal patch.

[0014] Furthermore, the metal reflector is composed of 32 metal reflection linear sub-arrays, and the metal reflection linear sub-array is formed by splicing 32 metal reflection units.

[0015] Furthermore, the material of the metal patch is gold.

[0016] Furthermore, the materials of the first alignment layer and the second alignment layer are polyimide.

[0017] Furthermore, the first dielectric substrate is made of quartz glass, and the second dielectric substrate is made of quartz glass.

[0018] Furthermore, the operating frequency is in the terahertz band, and the terahertz wave is incident perpendicularly to the plane where the first dielectric substrate is located.

[0019] The terahertz two-dimensional beam scanning antenna regulated by liquid crystal provided by the embodiments of the present invention has the following beneficial effects:

[0020] (1) The metal metasurface unit adopts a slotted resonant structure, which simplifies the structure of the metal metasurface unit while obtaining the required performance, making the manufacturing process simpler. The structure of the metal metasurface unit optimizes the phase shift characteristics of the scanning antenna and improves the phase shift ability.

[0021] (2) Combine the metal metasurface linear subarray and the metal reflection linear subarray. Through the independent control of the metal metasurface linear subarray and the metal reflection linear subarray, two-dimensional control of the metasurface antenna can be achieved. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the terahertz two-dimensional beam scanning antenna regulated by liquid crystal proposed by the present invention;

[0023] Figure 2 It is a schematic structural diagram of the metal metasurface unit provided by an embodiment of the present invention;

[0024] Figure 3 It is a schematic structural diagram of the metal reflection unit provided by an embodiment of the present invention;

[0025] Figure 4 It is a schematic cross-sectional view of the terahertz two-dimensional beam scanning antenna regulated by liquid crystal provided by an embodiment of the present invention;

[0026] Figure 5 It is a curve of the resonant frequency varying with the applied voltage provided by an embodiment of the invention;

[0027] Figure 6 It is the metasurface phase shift curve provided by an embodiment of the invention, where 0 # 、1 # 、2 # 、3 # correspond to the binary codes 00, 01, 10, and 11 respectively;

[0028] Figure 7 It is the metasurface coding sequence diagram and its corresponding three-dimensional far-field scattering pattern provided by Embodiment 1 of the present invention. The working frequency is 345 GHz, where (a) is the coding sequence of the metal reflection linear subarray and (b) is the three-dimensional far-field scattering pattern of the metasurface;

[0029] Figure 8 It is the metasurface coding sequence diagram and its corresponding three-dimensional far-field scattering pattern provided by Embodiment 2 of the present invention. The working frequency is 345 GHz, where (a) is the coding sequence of the metal metasurface linear subarray and (b) is the three-dimensional far-field scattering pattern of the metasurface;

[0030] Figure 9The coding sequence diagram of the metasurface and its corresponding three-dimensional far-field scattering pattern provided in the third embodiment of the present invention, with a working frequency of 345 GHz, where (a) is the coding sequence of the metal reflective linear subarray, and (b) is the three-dimensional far-field scattering pattern of the metasurface;

[0031] Figure 10 The coding sequence diagram of the metasurface and its corresponding three-dimensional far-field scattering pattern provided in the fourth embodiment of the present invention, with a working frequency of 345 GHz, where (a) is the coding sequence of the metal metasurface linear subarray, and (b) is the three-dimensional far-field scattering pattern of the metasurface. Embodiment

[0033] The following further details the specific embodiments of the present invention by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0034] The present invention proposes a liquid crystal-tuned terahertz two-dimensional beam scanning antenna. By dividing the metal metasurface and the reflector into multiple independently fed metal metasurface linear subarrays and metal reflective linear subarrays respectively, filling a liquid crystal material between the metal metasurface and the metal reflector, and using an electric control method to control the orientation of liquid crystal molecules to change the dielectric constant of the liquid crystal layer, thereby changing the resonant characteristics and phase response of the scanning antenna to achieve 2-bit ("00", "01", "10", "11") coding, and this metasurface can achieve dynamic scanning of the beam in a two-dimensional plane.

[0035] Figure 1 The structural schematic diagram of the liquid crystal-tuned terahertz two-dimensional beam scanning antenna provided in the embodiment of the present invention. For the sake of convenience of description, only the parts related to the embodiment of the present invention are shown. The scanning antenna includes:

[0036] The first dielectric substrate 1 and the second dielectric substrate 7 arranged opposite to each other;

[0037] The metal metasurface 2, the first alignment layer 3, the nematic liquid crystal layer 4, the second alignment layer 5, and the metal reflector 6 are sequentially arranged between the first dielectric substrate 1 and the second dielectric substrate 7;

[0038] The metal metasurface 2 is disposed on the first dielectric substrate 1, on the side of the first dielectric substrate 1 close to the second dielectric substrate 7, and the metal reflector 6 is disposed on the second dielectric substrate 7, on the side of the second dielectric substrate 7 close to the first dielectric substrate 1.

[0039] When no bias voltage is applied between the metal metasurface and the metal reflector, the initial orientation of the liquid crystal molecules in the nematic liquid crystal layer 4 is determined by the first alignment layer 3 and the second alignment layer 5. At this time, the scanning antenna is in the first phase state. After applying a bias voltage between the metal metasurface and the metal reflector and changing the bias voltage, the liquid crystal molecules in the nematic liquid crystal layer 4 deflect, controlling the scanning antenna to be in the second phase state, the third phase state, and the fourth phase state respectively. Among them, the phase differences between the first phase state and the second phase state, the second phase state and the third phase state, and the third phase state and the fourth phase state are close to 90°.

[0040] In the embodiment of the present invention, the metal metasurface 2 is composed of a plurality of metal metasurface linear sub-arrays, and the distance between adjacent metal metasurface linear sub-arrays is 2h. The metal metasurface linear sub-array is formed by sequentially splicing a plurality of metal metasurface units. The metal metasurface unit is composed of a rectangular metal patch with a square split-ring through slot structure. The square split-ring through slot is composed of a square through slot and a short-circuit band connecting the inside and outside of the square through slot. The short-circuit band is located in the middle of one of the through slots, as Figure 2 shown. The metal reflector 6 is composed of a plurality of metal reflection linear sub-arrays, and the distance between adjacent metal reflection linear sub-arrays is 2h. It is arranged perpendicular to the metal metasurface linear sub-array on the second dielectric substrate 7. The metal reflection linear sub-array is formed by sequentially splicing a plurality of metal reflection units. The metal reflection unit is a rectangular metal patch, as Figure 3 shown. Since the voltages on the metal metasurface linear sub-arrays on the metal metasurface 2 and the metal reflection linear sub-arrays on the metal reflector 6 can be independently controlled by coding, beam scanning in a specified plane can be achieved.

[0041] In the embodiment of the present invention, the metal metasurface 2 is composed of 32 metal metasurface linear sub-arrays, and the metal metasurface linear sub-array is formed by splicing every 32 metal metasurface units; the metal reflector 6 is composed of 32 metal reflection linear sub-arrays, and the metal reflection linear sub-array is formed by splicing 32 metal reflection units. In addition, the materials of the metal patches in the metal reflection units and the metal metasurface units are both gold.

[0042] In the embodiment of the present invention, the materials of the first alignment layer 3 and the second alignment layer 5 are polyimide (PI).

[0043] In the embodiment of the present invention, the first dielectric substrate 1 is used as the substrate material for supporting the metal metasurface layer 2 and is made of quartz glass; the second dielectric substrate 7 is used as the substrate material for supporting the metal reflector layer 6 and is made of quartz glass.

[0044] In an embodiment of the present invention, the nematic liquid crystal layer 4 is a liquid crystal layer composed of a nematic liquid crystal molecule mixture, and the initial orientation of the liquid crystal molecules is determined by the first alignment layer 3 and the second alignment layer 5 located on both sides of the nematic liquid crystal layer 4.

[0045] In an embodiment of the present invention, the working principle of the liquid crystal-tuned terahertz two-dimensional beam scanning antenna is as follows:

[0046] A bias voltage is applied between the metal metasurface and the metal reflector. When terahertz waves are incident perpendicular to the plane where the first dielectric substrate is located, by designing the size of the scanning antenna, the operating frequency of the scanning antenna is controlled to be in the terahertz band. Under the incident condition of the TE wave mode (the electric field is along the y direction), when no bias voltage is applied, the initial orientation of the liquid crystal molecules is determined by the first alignment layer and the second alignment layer. At this time, the resonant frequency of the scanning antenna is ω 0 , and the corresponding phase state is 0 # , as the bias voltage between the metal metasurface and the metal reflector increases, the liquid crystal molecules will deflect, and the relative dielectric constant of the liquid crystal layer will change accordingly. At this time, the resonant frequency will gradually shift to ω 1 , ω 2 , and ω 3 , and the corresponding phase states are 1 # , 2 # and 3 # ; among them, the phase differences between 0 # , 1 # , 2 # and 3 # are close to 90°. Four phase response states are respectively defined as "00", "01", "10" and "11", and thus a 2-bit encoded metasurface can be obtained.

[0047] The beam scanning antenna proposed by the present invention realizes the two-dimensional flexible control of terahertz beams through the independent voltage control and real-time switching of the coding states of the metal metasurface linear sub-arrays and the metal reflector linear sub-arrays. In the present invention, it is designed that the metal metasurface and the metal reflector are respectively composed of 1×32 metal metasurface linear sub-arrays and metal reflector linear sub-arrays. The metal metasurface linear sub-arrays and the metal reflector linear sub-arrays are arranged in a cross-perpendicular manner. The metal metasurface linear sub-arrays and the metal reflector linear sub-arrays can be independently fed. A field programmable gate array (FPGA) and a signal generator are used to generate multiple bias voltages, which are applied to the multiple metal metasurface linear sub-arrays and the metal reflector linear sub-arrays, and then the phase distribution of the metasurface is changed in real time to realize the real-time flexible control of electromagnetic beams.

[0048] Combined with Figures 2 to 4, where p represents the length of the metal metasurface unit, a represents the length of the square split-ring through slot, g represents the slot width of the square split-ring through slot, w represents the length of the shorting strip, 2h is the spacing between the metal reflection linear subarray and the metal metasurface linear subarray, and h q represents the thickness of the first dielectric substrate 1 and the second dielectric substrate 7, and h g represents the thickness of the metal metasurface 2 and the metal reflection surface 6, and h pi is the thickness of the first alignment layer 3 and the second alignment layer 5, and h lc represents the thickness of the nematic liquid crystal layer 4.

[0049] Example 1: p = 320 μm, a = 236 μm, g = 20 μm, w = 20 μm, h = 5 μm; h q = 400 μm, h g = 300 nm, h pi ≈ 90 nm, h lc = 25 μm. When no bias voltage (0 V) is applied, the phase state is the "00" state. When the bias voltages are 1.5 V, 1.8 V, and 2.7 V respectively, the corresponding phase states are the "01" state, the "10" state, and the "11" state. The measured metasurface parameters are as shown in Figure 5 and 6 . It can be seen from the figure that near 345 GHz, there are four stable states with a phase gradient of 90°, satisfying the 2-bit coding condition.

[0050] When the electromagnetic wave is vertically incident, when the coding sequence is as shown in Figure 7 (a), each coding state represents a metal reflection linear subarray composed of 1 × 32 metal reflection surface units. The far-field beam is analyzed by the full-wave simulation method. In the TE wave mode (the electric field is along the y direction), when the operating frequency is 345 GHz, the three-dimensional far-field scattering pattern of the metasurface is as shown in Figure 7 (b). It can be seen from the figure that the specular reflection beam is significantly suppressed, and it deflects in the yoz plane. The angle formed by the deflected beam and the z-axis is 42.8°.

[0051] Example 2: p = 320 μm, a = 236 μm, g = 20 μm, w = 20 μm, h = 5 μm, h q = 400 μm, h g = 300 nm, h pi ≈ 90 nm, h lc= 25 μm. When no bias voltage (0 V) is applied, the phase state is the "00" state. When the bias voltages are 1.5 V, 1.8 V, and 2.7 V respectively, the corresponding phase states are the "01" state, the "10" state, and the "11" state. Near 345 GHz, there are four stable states with a phase gradient of 90°, satisfying the 2-bit encoding condition.

[0052] When the electromagnetic wave is incident vertically, the coding sequence is as Figure 8 (a) shows. Each coding state represents a metal metasurface linear subarray composed of 1×32 metal metasurface units. The full-wave simulation method is used to analyze its far-field beam. In the TE wave mode (the electric field is along the y direction), when the operating frequency is 345 GHz, the three-dimensional far-field scattering pattern of the metasurface is as Figure 8 (b) shows. It can be seen from the figure that the specular reflection beam is significantly suppressed, and it deflects in the xoz plane. The angle formed by the deflected beam and the z-axis is 42.8°.

[0053] Example 3: p = 320 μm, a = 236 μm, g = 20 μm, w = 20 μm, h = 5 μm, h q = 400 μm, h g = 300 nm, h pi ≈90 nm, h lc = 25 μm. When no bias voltage (0 V) is applied, the phase state is the "00" state. When the bias voltages are 1.5 V, 1.8 V, and 2.7 V respectively, the corresponding phase states are the "01" state, the "10" state, and the "11" state. Near 345 GHz, there are four stable states with a phase gradient of 90°, satisfying the 2-bit encoding condition.

[0054] When the electromagnetic wave is incident vertically, the coding sequence is as Figure 9 (a) shows. Each coding state represents a metal reflector linear subarray composed of 1×32 metal reflector units. The full-wave simulation method is used to analyze its far-field beam. In the TE wave mode (the electric field is along the y direction), when the operating frequency is 345 GHz, the three-dimensional far-field scattering pattern of the metasurface is as Figure 9 (b) shows. It can be seen from the figure that the specular reflection beam is significantly suppressed, and it deflects in the yoz plane. The angle formed by the deflected beam and the z-axis is -19.9°.

[0055] Example 4: p = 320 μm, a = 236 μm, g = 20 μm, w = 20 μm, h = 5 μm. h q = 400 μm, h g = 300 nm, h pi ≈90 nm, h lc= 25 μm. When no bias voltage (0 V) is applied, the phase state is in the "00" state. When the bias voltages are 1.5 V, 1.8 V, and 2.7 V respectively, the corresponding phase states are the "01" state, the "10" state, and the "11" state. Near 345 GHz, there are four stable states with a phase gradient of 90°, satisfying the 2-bit coding condition.

[0056] When the electromagnetic wave is incident vertically, when the coding sequence is as Figure 10 (a) shown, each coding state represents a linear sub-array of a metal metasurface composed of 1×32 metal metasurface units. The full-wave simulation method is used to analyze its far-field beam. In the TE wave mode (the electric field is along the y direction), when the operating frequency is 345 GHz, the three-dimensional far-field scattering pattern of the metasurface is as Figure 10 (b) shown. It can be seen from the figure that the specular reflection beam is significantly suppressed, and it is deflected in the xoz plane. The angle formed by the deflected beam and the z-axis is -19.9°.

[0057] The liquid crystal-regulated terahertz two-dimensional beam scanning antenna provided by the embodiment of the present invention has the following beneficial effects:

[0058] (1) The metal metasurface unit adopts a slotted resonant structure, which simplifies the structure of the metal metasurface unit while obtaining the required performance, making the manufacturing process simpler. The structure of the metal metasurface unit optimizes the phase-shifting characteristics of the scanning antenna and improves the phase-shifting ability;

[0059] (2) By combining the metal metasurface linear sub-array and the metal reflection linear sub-array, two-dimensional control of the metasurface can be achieved through independent control of the metal metasurface linear sub-array and the metal reflection linear sub-array.

[0060] The present invention has been described by way of example. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A liquid crystal controlled terahertz two-dimensional beam scanning antenna, characterized in that: The scanning antenna comprises: A first dielectric substrate and a second dielectric substrate are arranged opposite to each other; A metal super surface, a first alignment layer, a nematic liquid crystal layer, a second alignment layer and a metal reflective surface are sequentially arranged between the first dielectric substrate and the second dielectric substrate; The metal metasurface is arranged on the first dielectric substrate, and the metal reflective surface is arranged on the second dielectric substrate; When no bias voltage is applied between the metal metasurface and the metal reflective surface, the initial orientation of the liquid crystal molecules in the nematic liquid crystal layer is determined by the first orientation layer and the second orientation layer, and the scanning antenna is in a first phase state. After a bias voltage is applied between the metal metasurface and the metal reflective surface, the bias voltage is changed, and the liquid crystal molecules in the nematic liquid crystal layer are deflected, and the scanning antenna is controlled to be in a second phase state, a third phase state, and a fourth phase state, respectively, wherein the phase differences between the first phase state and the second phase state, the second phase state and the third phase state, and the third phase state and the fourth phase state are close to 90°.

2. The liquid crystal controlled terahertz two-dimensional beam scanning antenna according to claim 1, characterized in that: The metal metasurface is composed of several metal metasurface linear subarrays, the spacing between adjacent metal metasurface linear subarrays is 2h, the metal metasurface linear subarrays are composed of several metal metasurface units spliced ​​in sequence, and the metal metasurface unit is a rectangular metal patch with a square split ring slot structure.

3. The liquid crystal controlled terahertz two-dimensional beam scanning antenna as claimed in claim 2, characterized in that: The metal metasurface is composed of 32 metal metasurface linear subarrays, and the metal metasurface linear subarrays are composed of 32 metal metasurface units spliced ​​together.

4. The liquid crystal controlled terahertz two-dimensional beam scanning antenna according to claim 1, characterized in that: The metal reflective surface is composed of a number of metal reflective linear sub-arrays, the spacing between adjacent metal reflective linear sub-arrays is 2h, and is arranged on a second dielectric substrate perpendicular to the metal metasurface linear sub-array. The metal reflective linear sub-array is composed of a number of metal reflective units spliced ​​in sequence, and the metal reflective unit is a rectangular metal patch.

5. The liquid crystal controlled terahertz two-dimensional beam scanning antenna as claimed in claim 4, characterized in that: The metal reflective surface is composed of 32 metal reflective linear sub-arrays, and the metal reflective linear sub-array is composed of 32 metal reflective units spliced ​​together.

6. The liquid crystal controlled terahertz two-dimensional beam scanning antenna according to any one of claims 2 to 5, characterized in that: The material of the metal patch is gold.

7. The liquid crystal controlled terahertz two-dimensional beam scanning antenna according to claim 1, characterized in that: The materials of the first alignment layer and the second alignment layer are polyimide.

8. The liquid crystal controlled terahertz two-dimensional beam scanning antenna according to claim 1, characterized in that: The first dielectric substrate is made of quartz glass, and the second dielectric substrate is made of quartz glass.

9. The liquid crystal controlled terahertz two-dimensional beam scanning antenna according to claim 1, characterized in that: The operating frequency is in the terahertz frequency band, and the terahertz wave is incident perpendicularly to the plane where the first dielectric substrate is located.

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