Tensor holographic metasurface antenna array based on liquid crystal

Abstract

The invention discloses a liquid crystal-based tensor holographic metasurface antenna array, which comprises an anisotropic holographic metasurface and a monopole feed source antenna, and is characterized in that the metasurface is composed of rectangular tensor impedance units which are periodically arranged; each tensor unit comprises an upper-layer dielectric substrate, a rectangular metal patch, a liquid crystal layer, an asymmetric cross coupling slot, a lower-layer dielectric substrate and a lower-layer metal floor, the monopole feed source antenna adopts a central coaxial feed mode, and a cylindrical through hole is formed in the dead center of the lower-layer dielectric substrate; a coaxial radio frequency connector penetrates through the through hole to be connected to the upper surface of the lower layer dielectric substrate and is used for generating surface waves, and dynamic switching of left-handed and right-handed circular polarization states and a wave beam scanning function are achieved by utilizing the characteristic of an electric control dielectric constant of a liquid crystal material. According to the tensor holographic metasurface antenna array, the liquid crystal material and the tensor anisotropic unit are fused, so that the beam scanning capability can be realized, and a left-handed circular polarization working state and a right-handed circular polarization working state can be flexibly switched.

Description

Technical Field

[0001] This invention belongs to the field of microwave antenna technology, specifically relating to a liquid crystal-based tensor holographic metasurface antenna array. Background Technology

[0002] Existing phased array antennas achieve beam scanning by controlling the phase of radiating elements using semiconductor phase shifters, but they still suffer from inherent drawbacks such as high power consumption, high cost, and large profile thickness. In recent years, metasurface technology has opened up new avenues for low-profile antenna design by manipulating electromagnetic waves through subwavelength structures. While existing liquid crystal scalar metasurfaces possess dynamic tuning capabilities, they can only control the phase or amplitude of co-polarized channels, meaning they can only convert linearly polarized source fields into linearly polarized target fields. This characteristic makes them unsuitable for the diverse polarization requirements of modern wireless systems. To achieve control over antenna polarization characteristics, such as using linearly polarized surface waves to achieve circularly polarized far-field radiation, more complex tensor impedance modulation surfaces are needed.

[0003] Tensor holographic metasurfaces, by introducing anisotropic units, can simultaneously and independently manipulate the phase and amplitude of orthogonal polarization channels, exhibiting significant advantages in the field of polarization conversion. However, once existing tensor metasurfaces are fabricated, their functions are fixed and they lack dynamic reconfigurability.

[0004] Therefore, there is an urgent need to develop a phased array antenna architecture that integrates liquid crystal dynamic tuning and tensor holographic design in order to break through the bottleneck of existing technology in dynamic reconfigurability. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a liquid crystal-based tensor holographic metasurface antenna array, which achieves flexible and adjustable beam and polarization reconfiguration capabilities, thus solving the problem of limited dynamic reconfigurability of antennas in terms of beam and polarization in the prior art.

[0006] The technical solution adopted in this invention is: a liquid crystal-based tensor holographic metasurface antenna array, comprising: an anisotropic holographic metasurface 1 and a monopole feed antenna 2.

[0007] The anisotropic metasurface 1 is composed of N×N two-dimensional periodically arranged rectangular tensor impedance units, where N≥2 and N is a positive integer.

[0008] Each tensor impedance unit includes: an upper dielectric substrate 5, a rectangular metal patch 6, a liquid crystal layer 7, a metal layer 8, a lower dielectric substrate 9, and a lower metal ground plane 10.

[0009] The monopole feed antenna 2 includes: a coaxial inner conductor 3 and a coaxial outer conductor 4; and the monopole feed antenna 2 adopts a center coaxial feeding method.

[0010] In this design, a coaxial outer conductor 4 is connected to the center of the lower metal ground plane 10 on the lower surface of the lower dielectric substrate 9. A cylindrical through hole is opened at the center of the outer conductor 4, through which the coaxial inner conductor 3 passes and connects to the upper surface metal layer 8 of the lower dielectric substrate 9 to generate surface waves.

[0011] Furthermore, in the tensor holographic metasurface antenna array, each tensor impedance unit has a pair of asymmetrical cross-coupled slots 801 etched on its metal layer 8.

[0012] Furthermore, in the tensor holographic metasurface antenna array, each tensor impedance element has a period of λ / 5, where λ represents the wavelength corresponding to the center frequency of the antenna's operating frequency band.

[0013] Furthermore, in the tensor holographic metasurface antenna array, the coaxial length of the monopole feed antenna 2 is λ / 4, where λ represents the wavelength corresponding to the center frequency of the antenna's operating frequency band.

[0014] Furthermore, in the tensor holographic metasurface antenna array, both the upper dielectric substrate 5 and the lower dielectric substrate 9 are glass substrates, with liquid crystal filling the space between them.

[0015] Furthermore, in the tensor holographic metasurface antenna array, the surface impedance of the anisotropic metasurface 1 is a purely imaginary matrix, and its expression is as follows:

[0016] ;

[0017] in, , , and Tensor surface impedance Components in all directions; superscript Indicates conjugate transpose, symbol Represents the vector outer product; and These represent the target radiation field and the surface current on the impedance surface, respectively. This indicates the operation of taking the imaginary part. Indicates the surface impedance modulation depth. It represents the average equivalent scalar surface impedance.

[0018] Based on the known tensor impedance components , and The equivalent scalar surface impedance expression is as follows:

[0019] ;

[0020] in, This represents the tensor surface impedance. Represents free-space wave impedance. This represents the attenuation constant of the surface wave in the direction normal to the impedance surface. Represents the wavenumber of electromagnetic waves in free space. This indicates the direction of surface wave propagation within the impedance surface. "+" supports propagation of inductive TM-mode surface waves, while "-" supports propagation of capacitive TE-mode surface waves. This represents the equivalent normalized scalar impedance.

[0021] Furthermore, each tensor impedance unit has a rectangular metal patch with 6 impedance components. .

[0022] Furthermore, in the tensor holographic metasurface antenna array, the surface current generated by the monopole feed antenna 2 is expressed as follows:

[0023] ;

[0024] in, This represents the position vector at each tensor impedance unit. express coordinates This represents the surface wave vector.

[0025] Then, define the target wave radiation fields with left-hand circular polarization and right-hand circular polarization. and The expressions are as follows:

[0026] ;

[0027] ;

[0028] in,( , ) indicates the beam direction.

[0029] The beneficial effects of this invention are as follows: The tensor holographic metasurface antenna array of this invention includes an anisotropic holographic metasurface and a monopole feed antenna. The metasurface is composed of periodically arranged rectangular tensor impedance elements. Each tensor element includes an upper dielectric substrate, a rectangular metal patch, a liquid crystal layer, an asymmetric cross-coupled slot, a lower dielectric substrate, and a lower metal ground plane. The monopole feed antenna adopts a central coaxial feeding method. A cylindrical through-hole is opened at the center of the lower dielectric substrate, allowing a coaxial RF connector to pass through the through-hole and connect to the upper surface of the lower dielectric substrate to generate surface waves. Utilizing the electrically controlled dielectric constant of the liquid crystal material, dynamic switching between left-hand and right-hand circular polarization states and beam scanning functionality are achieved. By integrating liquid crystal material and tensor anisotropic elements, the tensor holographic metasurface antenna array of this invention can achieve beam scanning capability and flexibly switch between left-hand and right-hand circular polarization operating states. Attached Figure Description

[0030] Figure 1 This is a three-dimensional structural diagram of a liquid crystal-based tensor holographic metasurface antenna array according to the present invention.

[0031] Figure 2 This is a three-dimensional structural schematic diagram of the tensor impedance unit described in an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the structure of a unit monopole feed antenna in an embodiment of the present invention.

[0033] Figure 4 This is a side view schematic diagram of the tensor holographic metasurface antenna array described in an embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the cross-coupled slot structure of the tensor impedance unit in an embodiment of the present invention.

[0035] Figure 6 This is the scanning pattern of the tensor holographic metasurface antenna array at 30 GHz with a left-hand circularly polarized beam at an embodiment of the present invention.

[0036] Figure 7 This is the scanning pattern of the right-hand circularly polarized beam at 30 GHz for the tensor holographic metasurface antenna array described in this embodiment of the invention. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] like Figure 1 As shown, a liquid crystal-based tensor holographic metasurface antenna array of the present invention includes: an anisotropic holographic metasurface 1 and a monopole feed antenna 2.

[0039] The anisotropic metasurface 1 is composed of N×N two-dimensional periodically arranged rectangular tensor impedance units, where N≥2 and N is a positive integer.

[0040] Among them, such as Figure 2 As shown, each tensor impedance unit includes: an upper dielectric substrate 5, a rectangular metal patch 6, a liquid crystal layer 7, a metal layer 8, a lower dielectric substrate 9, and a lower metal ground plane 10.

[0041] like Figure 3 As shown, the monopole feed antenna 2 includes: a coaxial inner conductor 3 and a coaxial outer conductor 4; and the monopole feed antenna 2 adopts a center coaxial feeding method.

[0042] Among them, such as Figure 4As shown, a coaxial outer conductor 4 is connected to the center of the lower metal ground plane 10 on the lower surface of the lower dielectric substrate 9. A cylindrical through hole is opened at the center of the outer conductor 4, through which the coaxial inner conductor 3 passes and connects to the upper surface metal layer 8 of the lower dielectric substrate 9 to generate surface waves.

[0043] In this embodiment, as Figure 5 As shown, in the tensor holographic metasurface antenna array, each tensor impedance unit has a pair of asymmetrical cross-coupled slots 801 etched on its metal layer 8.

[0044] In this embodiment, in the tensor holographic metasurface antenna array, each tensor impedance element has a period of λ / 5, where λ represents the wavelength corresponding to the center frequency of the antenna's operating frequency band.

[0045] In this embodiment, in the tensor holographic metasurface antenna array, the coaxial length of the monopole feed antenna 2 is λ / 4, where λ represents the wavelength corresponding to the center frequency of the antenna's operating frequency band.

[0046] In this embodiment, in the tensor holographic metasurface antenna array, both the upper dielectric substrate 5 and the lower dielectric substrate 9 are glass substrates, with liquid crystal filling the space between them. In this embodiment, the thickness of the liquid crystal layer 7 is 0.05 mm, and the dielectric constant of the liquid crystal is in the range of 2.6~3.6; the thickness of the upper dielectric substrate 5 and the lower dielectric substrate 9 is 0.7 mm.

[0047] In this embodiment, in the tensor holographic metasurface antenna array, the surface impedance of the anisotropic metasurface 1 is a purely imaginary matrix, and its expression is as follows:

[0048] ;

[0049] in, , , and Tensor surface impedance Components in all directions; superscript Indicates conjugate transpose, symbol Represents the vector outer product; and These represent the target radiation field and the surface current on the impedance surface, respectively. This indicates the operation of taking the imaginary part. Indicates the surface impedance modulation depth. It represents the average equivalent scalar surface impedance.

[0050] Based on the known tensor impedance components , and The equivalent scalar surface impedance expression is as follows:

[0051] ;

[0052] in, This represents the tensor surface impedance. Represents free-space wave impedance. This represents the attenuation constant of the surface wave in the direction normal to the impedance surface. Represents the wavenumber of electromagnetic waves in free space. This indicates the direction of surface wave propagation within the impedance surface. "+" supports propagation of inductive TM-mode surface waves, while "-" supports propagation of capacitive TE-mode surface waves. This represents the equivalent normalized scalar impedance.

[0053] Furthermore, due to the structural symmetry, the rectangular metal patch 6 of each tensor impedance unit has impedance components...

[0054] In this embodiment, the surface current generated by the monopole feed antenna 2 in the tensor holographic metasurface antenna array is expressed as follows:

[0055] ;

[0056] in, This represents the position vector at each tensor impedance unit. express coordinates This represents the surface wave vector.

[0057] Then, define the target wave radiation fields with left-hand circular polarization and right-hand circular polarization. and The expressions are as follows:

[0058] ;

[0059] ;

[0060] in,( , ) indicates the beam direction.

[0061] In this embodiment, electromagnetic simulation software was used to simulate the circular polarization reconfigurability characteristics of the antenna at a frequency of 30 GHz. The simulation results are as follows: Figure 6 and 7 As shown. Figure 6 (a) and (b) are the scanning patterns of the left-hand circularly polarized beam when the azimuth angle φ is 0° and 90°, respectively. Figure 7(a) and (b) show the right-hand circularly polarized beam scanning patterns when the azimuth angle φ is 0° and 90°, respectively. Due to the symmetry of the antenna structure, its left-hand and right-hand circularly polarized beam patterns have the same characteristics. When the azimuth angle φ is 0°, the preset beam scanning angles are -25°, -15°, 0°, and 5°, while the actual simulated angles are -23°, -14°, 3°, and 6°, respectively. When the azimuth angle φ is 90°, the preset scanning angles are -7°, 0°, 15°, and 32°, while the actual simulated angles are -8°, -4°, 14°, and 29°, respectively. The simulation results verify that the liquid crystal tensor holographic metasurface antenna array described in this embodiment has the capability of beam scanning and circular polarization reconfiguration.

[0062] In summary, the tensor holographic metasurface antenna array of the present invention can achieve beam scanning capability by fusing liquid crystal material and tensor anisotropic units, and can flexibly switch between left-hand and right-hand circular polarization operating states.

[0063] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A liquid crystal-based tensor holographic metasurface antenna array, comprising: Anisotropic holographic metasurface (1) and monopole feed antenna (2); Anisotropic metasurface (1) is composed of N×N two-dimensional periodically arranged rectangular tensor impedance units, where N≥2 and N is a positive integer; Each tensor impedance unit includes: an upper dielectric substrate (5), a rectangular metal patch (6), a liquid crystal layer (7), a metal layer (8), a lower dielectric substrate (9), and a lower metal ground plane (10). The monopole-feed antenna (2) includes: a coaxial inner conductor (3) and a coaxial outer conductor (4); and the monopole-feed antenna (2) adopts a center coaxial feeding method; In this case, a coaxial outer conductor (4) is connected to the center of the lower metal floor (10) on the lower surface of the lower dielectric substrate (9). A cylindrical through hole is opened at the center of the outer conductor (4) so ​​that the coaxial inner conductor (3) can pass through the through hole and connect to the upper surface metal layer (8) of the lower dielectric substrate (9) to generate surface waves.

2. The liquid crystal-based tensor holographic metasurface antenna array according to claim 1, characterized in that, Each tensor impedance unit's metal layer (8) is etched with a pair of asymmetrical cross-coupled slots (801).

3. The liquid crystal-based tensor holographic metasurface antenna array according to claim 1, characterized in that, Each tensor impedance element has a period of λ / 5, where λ represents the wavelength corresponding to the center frequency of the antenna's operating frequency band.

4. The liquid crystal-based tensor holographic metasurface antenna array according to claim 1, characterized in that, The coaxial length of the monopole-feed antenna (2) is λ / 4, where λ represents the wavelength corresponding to the center frequency of the antenna's operating frequency band.

5. A liquid crystal-based tensor holographic metasurface antenna array according to claim 1, characterized in that, Both the upper dielectric substrate (5) and the lower dielectric substrate (9) are glass substrates, and liquid crystal is filled between them.

6. The liquid crystal-based tensor holographic metasurface antenna array according to claim 1, characterized in that, The surface impedance of the anisotropic metasurface (1) is a purely imaginary matrix, and its expression is as follows: ； in, , , and Tensor surface impedance Components in all directions; superscript Indicates conjugate transpose, symbol Represents the vector outer product; and These represent the target radiation field and the surface current on the impedance surface, respectively. This indicates the operation of taking the imaginary part. Indicates the surface impedance modulation depth. This represents the average equivalent scalar surface impedance. Based on the known tensor impedance components , and The equivalent scalar surface impedance expression is as follows: ； in, This represents the tensor surface impedance. Represents free-space wave impedance. This represents the attenuation constant of the surface wave in the direction normal to the impedance surface. Represents the wavenumber of electromagnetic waves in free space. Indicates the direction of surface wave propagation within the impedance surface; "+" supports propagating inductive TM mode surface waves, and "-" supports propagating capacitive TE mode surface waves. Represents the equivalent normalized scalar impedance; Furthermore, the impedance components of the rectangular metal patch (6) of each tensor impedance unit .

7. A liquid crystal-based tensor holographic metasurface antenna array according to claim 1, characterized in that, The surface current generated by the monopole-feed antenna (2) is expressed as follows: ； in, This represents the position vector at each tensor impedance unit. express coordinates Represents the surface wave vector; Then, define the target wave radiation fields with left-hand circular polarization and right-hand circular polarization. and The expressions are as follows: ； ； in,( , ) indicates the beam direction.

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