Tensor dual-beam dual-frequency dual-circular polarization holographic metasurface antenna and implementation method thereof

Abstract

The invention discloses a tensor-based dual-beam dual-frequency dual-circular polarization holographic metasurface antenna and an implementation method thereof. The metasurface adopts a partition and impedance superposition mode, and impedance components of different frequency points and different circular polarizations are averagely superposed to form the tensor holographic metasurface, so that simultaneous radiation of an RHCP and an LHCP can be respectively realized in two frequency bands. When an omnidirectional reference wave generated by a monopole excites the tensor holographic metasurface, different circular polarization beams are generated in the two regions respectively and do not interfere with each other due to the fact that different regions record average impedance components of interference of different circular polarization and reference waves. The monopole added with the metal circular ring is used as a surface wave feed source, so that the overall bandwidth can be widened, and the overall section cannot be increased. The tensor holographic metasurface antenna provided by the invention has the characteristics of low profile, double beams and simple feed structure.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a tensor dual-beam dual-frequency dual-circular polarization holographic metasurface antenna and a realization method thereof. Background Art

[0002] Holographic antenna is an emerging antenna technology that combines holographic technology with the needs of wireless communication and shows broad application prospects. Traditional antennas mainly rely on metal materials and geometric shapes to transmit and receive signals, while holographic antennas achieve more complex and flexible radiation characteristics by designing holographic patterns and using phase control and wavefront modulation. Holographic technology was originally used for image recording. In recent years, with the development of materials science, it has gradually been introduced into antenna design. At the same time, phased array antennas form beams by controlling the phases of each antenna unit, while holographic antennas further improve the flexibility and performance of beams on this basis. The application of new materials such as metamaterials and smart materials enables holographic antennas to exhibit excellent electromagnetic properties at different frequencies, meeting the needs of modern communication systems for high-performance antennas. With the rapid development of 5G and future 6G communication technologies, holographic antennas have shown broad application potential in many fields such as satellite communications, drones, the Internet of Things, and intelligent transportation, becoming an important part of future wireless communications. Summary of the invention

[0003] Based on the tensor holographic impedance metasurface, the present invention proposes a tensor-based dual-beam dual-frequency dual-circularly polarized holographic metasurface antenna and its implementation method. The method can generate specific frequencies, radiation angles and circular polarizations according to the needs of the application scenario, forming electromagnetic waves with arbitrary beam pointing and arbitrary circular polarization.

[0004] To achieve the proposed purpose, the present invention is based on a tensor holographic impedance metasurface, and uses the impedance component superposition and partitioning of tensor units to generate a dual-beam dual-frequency dual circularly polarized holographic metasurface beam. The technical solution adopted is as follows:

[0005] The tensor-based dual-beam dual-frequency dual circularly polarized holographic metasurface antenna includes a dielectric substrate, a circular metal patch with a series of slits printed on the upper surface of the dielectric substrate, a metal ground on the lower surface of the dielectric substrate, and a broadband monopole for feeding the tensor holographic impedance metasurface. The broadband monopole obtains broadband characteristics by loading a metal ring.

[0006] The broadband feeding monopole adopts an SMA connector structure, and the dielectric substrate is a Rogers RO 3010 dielectric board with a dielectric constant of 10.2, a size of 312mm×312mm, and a height of 3.81mm. The radius of the feeding monopole is 0.25mm, the height is 18.3mm, the inner diameter of the loading ring is 3mm, the outer diameter is 3.5mm, and the height is 10mm.

[0007] Specifically, the method for realizing the dual-beam dual-frequency dual-circular polarization holographic metasurface antenna includes the following steps:

[0008] (I) Extract the equivalent scalar surface impedance of the circular slotted tensor impedance unit:

[0009] (1) The present invention adopts a tensor impedance unit, whose specific structure is a tensor circular metal patch structure with a slit in the middle. Its parameter characterization and specific meaning are: circular patch spacing g, gap angle θ s .

[0010] (2) Modeling is performed in HFSS, and master-slave boundary conditions are added to the slotted circular patch unit. Since the magnitude of its surface impedance value changes with the propagation direction of the surface wave, that is, it is anisotropic, the tensor impedance surface cannot be simply represented by the definition of scalar impedance. Therefore, we explore the relationship between its equivalent scalar surface impedance value and the propagation angle of the electromagnetic wave. It can be found that as the propagation direction of the surface wave changes, the equivalent scalar surface impedance curve appears as an ellipse with a major axis and a minor axis that are perpendicular to each other. We use the value of the major axis as the maximum value of the equivalent scalar surface impedance Z max , the short axis corresponds to the minimum impedance Z min Then, by changing the gap angle θ s And the patch spacing g, we can establish the circular metal patch spacing g and the maximum impedance Z corresponding to the long axis max Then, the circular patch spacing g and Z are obtained by fitting the simulation data through MATLAB. max The relational expression is:

[0011] Z max =165.38+360.01g -1 -172.139g -2 +34.83g -3

[0012] Slit rotation angle θ s The electromagnetic wave propagation angle θ when the scalar surface impedance is maximum max The relational expression is:

[0013] θ s =θ max

[0014] (II) Based on different circular polarization expressions, the impedance metasurface components are calculated by performing region superposition on the metasurface;

[0015] (1) The reference beam is generated by using a broadband monopole, and its expression on the metasurface is:

[0016] Among them, x and y represent the coordinates of the center of the tensor unit in the coordinate system, k t is the wave vector of the surface current propagating on the impedance surface, and r is the distance from the center of each unit on the impedance surface to the coordinate origin.

[0017] (2) The target beams are left-hand circularly polarized and right-hand circularly polarized beams, and their expressions are:

[0018]

[0019]

[0020] Among them, E rad|LHCP The left circular polarization beam expression, E rad|RHCP represents the expression of right-hand circularly polarized beam, K0 is the wave number in free space, and θ is the elevation angle of the beam.

[0021] (3) Establish the relationship between the reference wave, target beam and tensor impedance component:

[0022]

[0023] Among them, E x and E y For E rad The electric field components in the x and y directions; Z xx , Z xy , Z yx and Z yy is the component of the tensor impedance surface unit impedance Z in each direction, J x and J y For J surf Current components in the x and y directions.

[0024] (4) In order to satisfy the law of conservation of energy and the reciprocity theorem, the tensor surface impedance matrix Z must be an anti-Hermite pure imaginary matrix. Therefore, in the tensor holographic impedance metasurface impedance modulation process, Z is required to be xy =Z yx .

[0025] (5) According to the principle of holographic antenna, the expression of the holographic surface formed by the interference of the reference wave and the target wave is:

[0026]

[0027] Where X is the average value of the equivalent scalar surface impedance, M is the surface impedance modulation depth, and Z surf is the equivalent scalar impedance value of any point on the impedance metasurface, E rad is the radiation beam expression, J surf is the expression for the surface current, and H is the conjugate transpose.

[0028] (6) By combining the above equations, we can solve the impedance component expression that produces the target angle and target beam. The left-hand circularly polarized impedance component is:

[0029]

[0030]

[0031]

[0032] The expression of right-hand circular polarization impedance component is:

[0033]

[0034]

[0035]

[0036] Where, γ = k0xsinθ-K t r, K t is the surface wave vector generated by the feed source.

[0037] (III) Calculate the maximum equivalent scalar impedance and combine it with the optimal impedance expression to obtain the tensor holographic impedance metasurface structure;

[0038] (1) The equivalent scalar surface impedance formula is:

[0039]

[0040] Among them, K Z and K0 are the radial wave number and total wave number of the surface wave, respectively. Since the surface wave mode excited by the monopole on the impedance surface is the TM mode, the “+” sign is used in the above formula. If the TE mode is used to excite the impedance surface, the “-” sign is used. In the above formula:

[0041] A=-j(η0 2 +Z xx Z xy -Z xy 2 )

[0042] B=-(η0 2 +Z xy Z xy -Z xy 2 ) 2

[0043]

[0044] D=(Z xx cos 2 θk +Z xy sin2θ k +Z yy sin 2 θ k )

[0045] E=-2η0(Z xx sin 2 θ k +Z yy cos 2 θ k -Z xy sin2θ k )

[0046] (2) Substitute the obtained tensor impedance component into the above formula to find the equivalent maximum scalar impedance Z at this time max and the propagation direction of the electromagnetic wave at this time θ max , which is the slit angle of the circular metal patch.

[0047] (IV) Using a monopole with a circular ring for feeding, broadband performance is obtained by adding a circular ring to the monopole antenna, and the expression of the surface wave generated remains unchanged.

[0048] (V) A broadband monopole is used to feed the antenna of the present invention at the center of the holographic surface. The cylindrical wave-like surface current J generated by the feeding monopole surf =e -jktr , through the impedance superposition and partitioning metasurface of the present invention, the target radiation field is obtained.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The present invention utilizes a tensor impedance unit, which has a large degree of design freedom and can accurately control the radiation direction and polarization. By means of impedance superposition and partitioning, an antenna with arbitrary beam pointing, dual circular polarization, and dual beam is formed, and its design flexibility is relatively high.

[0051] (2) The dual-beam dual-frequency dual circularly polarized holographic metasurface beam antenna of the present invention is simple to excite. Adding a circular ring to the monopole will not affect the matching, but can also widen the bandwidth, so that it can excite different tensor units in different areas to achieve circularly polarized beam radiation. The surface current excited by it interacts with the tensor impedance modulation surface to produce the target beam pointing and polarization. Compared with other existing dual-frequency dual circularly polarized antennas, the present invention has a low profile, is easy to conform, and has free and flexible design. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of the working of the holographic antenna used in the present invention

[0053] Figure 2 Schematic diagram of the tensor impedance unit structure used in the present invention

[0054] Figure 3 Schematic diagram of the dual-beam dual-frequency dual-circular polarization holographic metasurface holographic metasurface antenna structure

[0055] Figure 4 The impedance matching of the dual-beam dual-frequency dual-circular polarization holographic metasurface holographic metasurface antenna

[0056] Figure 5 Impedance fitting curve

[0057] Figure 6 Radiation diagram for low frequency

[0058] Figure 7 Schematic diagram of radiation at high frequency

[0059] Figure 8 is the antenna radiation axis ratio

[0060] Fig. 9 Schematic diagram of the 3D radiation of this antenna at low frequency

[0061] Fig.10 Schematic diagram of the 3D radiation of this antenna at high frequency

[0062] Fig.11 Schematic diagram of impedance superposition

[0063] In the above drawings, the component names corresponding to the reference numerals are as follows:

[0064] 1- holographic metal patch, 2- dielectric substrate, 3- holographic complementary ground, 4- feed monopole, 5- monopole loaded ring. DETAILED DESCRIPTION

[0065] The invention is further described below in conjunction with the accompanying drawings and examples. The embodiments of the present invention include but are not limited to the following examples.

[0066] The realization method of the tensor-based dual-beam dual-frequency dual circularly polarized holographic metasurface antenna is to obtain the tensor holographic impedance metasurface structure by extracting the equivalent surface impedance of any tensor impedance unit and combining the modulation formula and the impedance superposition and partitioning method. Finally, the cylindrical electromagnetic beam is obtained by broadband feeding monopole excitation to realize the dual-beam dual-frequency dual circularly polarized holographic metasurface radiation.

[0067] like Figure 1 As shown, this is the working schematic diagram of the tensor holographic antenna. Figure 2The tensor unit used has a specific structure including a dielectric substrate 2, a circular metal patch 1 with a series of slits printed on the upper surface of the dielectric substrate, a metal ground 3 on the lower surface of the dielectric substrate, a broadband monopole 4 for feeding the tensor holographic metasurface, and a metal ring 5 loaded on the monopole.

[0068] A method for realizing a tensor-based dual-beam dual-frequency dual-circularly polarized holographic metasurface antenna. The antenna schematic diagram manufactured by the present invention is shown in FIG. Figure 3 As shown, the feeding monopole 4 adopts an SMA connector structure, with a radius of 0.25 mm and a height of 18.3 mm, and the inner diameter of the loading ring 5 is 3 mm, the outer diameter is 3.5 mm, and the height is 10 mm. The antenna dielectric substrate 2 is a Rogers RO 3010 dielectric board, with a dielectric constant of 10.2, a size of 312 mm×312 mm, and a height of 3.81 mm.

[0069] like Figure 3 As shown, it is a dual-beam dual-frequency dual-circular polarization holographic metasurface tensor holographic impedance metasurface antenna. Forming the metasurface antenna structure includes the following steps:

[0070] (1) Extract the periodic unit p = 6 mm, the relationship between the maximum equivalent scalar surface impedance value and the unit spacing g:

[0071] Z max =165.38+360.01g -1 -172.139g -2 +34.83g -3

[0072] (2) Using broadband monopole feeding, the surface wave expression generated is:

[0073]

[0074] The working frequencies of this antenna are 3.9 GHz and 4.5 GHz, and the target radiation direction is 30°. By combining impedance partitioning and impedance average superposition, combining the target field expression and the tensor holographic impedance metasurface modulation formula, the required impedance components can be calculated.

[0075] (3) Substituting the impedance component into the expression, we can obtain the impedance value when the impedance value changes with the incident angle of the electromagnetic wave, and take the maximum value as the maximum equivalent scalar surface impedance value Z max , at this time, the incident angle of the electromagnetic wave is the slit angle of the metal patch. The impedance superposition is performed on the entire metasurface, and the expression is as follows:

[0076]

[0077] in,

[0078]

[0079]

[0080]

[0081]

[0082] In the above formula, X1 represents the average impedance at low frequency, X2 represents the average impedance at high frequency, M1 represents the modulation depth at low frequency, and M2 represents the modulation depth at high frequency. a is the elevation angle of LHCP radiation, θ b To express the elevation angle of RHCP radiation, Dc = M1cosγ1 + M2cosγ2, Ds = M1sinγ1 + M2sinγ2. L1x represents the component of the LHCP radiation field along the x-axis at 3.9 GHz, E R2x It represents the component of the LHCP radiation field along the x-axis at 3.9 GHz.

[0083] Each tensor unit on the metasurface contains impedance information at two frequencies, 3.9 GHz and 4.5 GHz. At 3.9 GHz, the average impedance is X1 = 247, the modulation depth is M1 = 154, and at 4.5 GHz, the average impedance is X2 = 327, the modulation depth is M2 = 197. The impedance component variation range when 3.9 GHz and 4.5 GHz generate LHCP and RHCP in different regions is calculated and averaged, and then the Z is plotted. surf and θ k The relationship curve of Z max and θ s , and then according to the impedance calculation formula, the g and θ of each tensor unit in the metasurface can be determined s , so that the information of two different frequencies carrying different circular polarizations can be mapped to the same tensor unit.

[0084] For the dual-frequency dual circularly polarized holographic antenna, its overall structure is composed of two single-frequency dual circularly polarized superpositions. The entire holographic metasurface is composed of 52×52 tensor impedance units with a size of 312mm×312mm. A monopole loaded with a metal sleeve is placed in the center to improve impedance matching and increase bandwidth.

[0085] The entire holographic impedance metasurface can be decomposed into two regions, in which the average impedance components of LHCP and RHCP at 3.9 GHz and 4.5 GHz are recorded respectively. A broadband monopole is then used as a feed source to generate a reference wave of an ideal frequency. According to holographic theory, after the average superposition of the impedance components, each tensor impedance unit in the entire metasurface records the impedance information when the reference waves of different frequencies interfere with the target beam. When the reference waves of different frequencies excite the metasurface, radiation beams of different circular polarizations can be generated.

[0086] Since each tensor unit contains information about two frequency points, a fitting formula for one frequency point is used instead of two fitting formulas for dual frequency bands. When the center frequency of the antenna is 3.9 GHz, the surface impedance range is 247-401 jΩ; when the center frequency of the antenna is 4.5 GHz, the surface impedance range is 327-524 jΩ. The impedance range of the two frequency points is averaged to obtain Z surf By scanning the frequency points between 3.9GHz and 4.5GHz, it can be found that at 4.2GHz, the impedance value varies from 283 to 450jΩ, which is consistent with Z surf The fit is basically the same, but it is worth noting that the average impedance X and modulation depth M still use the values ​​of 3.9GHz and 4.5GHz respectively. Therefore, the impedance fitting curve adopts the impedance unit fitting formula at 4.2GHz.

[0087] (4) According to the calculation formula, MATLAB and HFSS are used for joint modeling, and then a broadband monopole is used for feeding to realize dual-beam, dual-frequency, dual-circularly polarized holographic metasurface radiation.

[0088] The above description is only a preferred specific implementation scheme of the present invention and is not intended to limit the present invention. Any adoption of the design principle of the present invention and any modification, replacement, addition, or deletion made thereon shall fall within the protection scope of the present invention.

Claims

1. A tensor-based dual-beam dual-frequency dual-circularly polarized holographic metasurface antenna, characterized in that: The invention comprises a dielectric substrate, a circular metal patch with a series of slits printed on the upper surface of the dielectric substrate, a metal ground on the lower surface of the dielectric substrate, a broadband monopole for feeding the tensor holographic metasurface, and a circular ring loaded on the monopole.

2. The tensor dual-beam dual-frequency dual-circular polarization holographic metasurface antenna according to claim 1, characterized in that: The design steps of the spacing between adjacent circular patches and the rotation angle of the slits are as follows: Based on the target beam expression and the surface wave expression generated by the broadband monopole, the impedance component Z is calculated according to the holographic theory. xx , Z xy , Z yy expression.

3. The tensor dual-beam dual-frequency dual-circularly polarized holographic metasurface antenna according to claim 2, characterized in that: The design steps of the slit angle of the proposed tensor unit are as follows: Based on the equivalent scalar impedance formula, the change curve of the equivalent scalar surface impedance value of the tensor unit at any electromagnetic wave incident angle is obtained, which presents an ellipse. According to different calculation results, when the angle of the major axis of the ellipse curve is consistent with the slit angle of the tensor unit, its impedance value is the maximum value, that is, the maximum equivalent scalar surface impedance.

4. The tensor dual-beam dual-frequency dual-circular polarization holographic metasurface antenna according to claim 3, characterized in that: The size of the proposed circular tensor impedance unit is calculated from the maximum value of the equivalent scalar surface impedance and the spacing g of the circular slotted metal patch, and its formula is: With max =165.38+360.01g -1 -172.139g -2 +34.83g -3 5. The tensor dual-beam dual-frequency dual-circular polarization holographic metasurface antenna according to claim 4, characterized in that: The feeding monopole adopts an SMA connector structure and is used to excite the dual-beam dual-frequency dual-circular polarization holographic metasurface antenna to generate a reference wave required for the target beam.

6. The tensor dual-beam dual-frequency dual-circular polarization holographic metasurface antenna according to claim 5, characterized in that: The dielectric substrate is a Rogers RO 3010 dielectric plate, whose dielectric constant is 10.2, and whose dimensions are a radius of 312mm×312mm and a height of 3.81mm; the radius of the feeding monopole is 0.25mm, the height is 18.3mm, and the inner diameter of the loading ring is 3mm, the outer diameter is 3.5mm, and the height is 10mm.

7. The tensor dual-beam dual-frequency dual-circular polarization holographic metasurface antenna according to claim 6, characterized in that: The size of each tensor impedance unit is 6mm×6mm, and the height of the unit is 3.81mm. The tensor holographic impedance metasurface includes 52×52 tensor impedance units, wherein the gap between the upper patches of adjacent units ranges from 0.5mm to 2.5mm. The broadband monopole generates a reference wave on the upper layer of the metasurface and performs impedance matching with the metasurface at the same time.

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