A high-gain, low-profile metamaterial near-field lens antenna with integrated holographic surface

Abstract

The present invention proposes a high-gain, low-profile metamaterial near-field lens antenna integrated with a holographic surface, comprising a feed source (1), a metamaterial near-field calibration lens (2), and a support structure (3). The feed source is composed of a holographic surface and a monopole composed of periodically arranged tensor impedance units; the metamaterial near-field calibration lens is composed of a plurality of lens units arranged based on the near-field phase distribution of the feed source radiation, and is arranged at a height less than or equal to one wavelength from the upper surface of the holographic surface; and the support structure fixes the relative position of the feed source and the metamaterial near-field lens. The present invention utilizes the compensation capability of the lens units for the electromagnetic wave transmission phase to compensate the feed source composed of the holographic surface and the monopole point by point at each position in the near-field region of its radiation, thereby achieving high-gain radiation of the aperture antenna under a relatively low-profile overall structure, and can be used in the field of wireless communications.

Description

Technical Field

[0001] The present invention belongs to the field of antenna technology and relates to a high-gain, low-profile metamaterial near-field lens antenna with an integrated holographic surface, which can be used in the field of wireless communications. Technical Background

[0002] Metamaterial lenses, with their advantages of low cost, planar structure, and ease of fabrication, are widely used in wireless communication antenna gain enhancement designs. Metamaterial lens antenna design adheres to the Fermat principle, also known as the principle of shortest optical path. This principle states that when light travels through a homogeneous medium, the path it takes is a straight line between its entry and exit points, which is shorter than the optical length of any other path. This principle describes the propagation path of light in any homogeneous medium, and light is also a type of electromagnetic wave. A typical metamaterial lens antenna operates by converting a spherical wave emitted by a feed source into a plane wave after passing through a metamaterial lens. The metamaterial lens, composed of lens units with different phase compensation capabilities, then phase-compensates the spherical wave emitted by the feed source at its focal point and converts it into a plane wave, achieving high-gain radiation. The linear distance between the lens and the feed source's focal point is called the focal length. For a given lens aperture, a larger focal length results in a flatter phase shift across the lens, making phase compensation easier, but also increases the lens antenna system's profile. The parameter that measures the structural characteristics of a lens antenna is the focal ratio, which is the ratio of the focal length to the lens aperture. Currently, the focal ratio of metamaterial lens antennas is generally around 0.5. For example, Chinese patent application number CN108110435B, entitled "Millimeter-wave High-Gain Circularly Polarized Horn Antenna Loaded with a Single Dielectric Planar Lens," discloses an antenna that achieves higher gain for a circularly polarized horn operating in the millimeter-wave band by loading it with a dielectric planar lens. Also based on the Fermat principle, this invention leverages the phase compensation capability of circular through-hole array elements with different through-hole radii to perform phase compensation on the spherical electromagnetic waves emitted by the circularly polarized horn antenna, achieving beam alignment and thereby increasing the original gain of the horn antenna serving as the feed source. The focal ratio is 0.59. Furthermore, by utilizing the design concept of a folded antenna and using reflectors and transmissive mirrors to perform multiple reflections and transmissions of the spherical waves emitted by the feed source for phase alignment, the antenna system's profile can be reduced to one-third of the aperture size. However, for a high-gain lens antenna with 10 times the aperture, the profile height is still relatively high. This type of aperture antenna, which achieves high gain by analyzing the propagation path of spherical waves to obtain the phase distribution on the aperture plane and then performing phase compensation, always has the characteristic of a high cross-section. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and propose a high-gain, low-profile metamaterial near-field lens antenna with an integrated holographic surface, aiming to achieve high-gain radiation of the lens antenna while degrading the antenna profile height.

[0004] To achieve the above objectives, the technical solution adopted by the present invention includes a feed source 1 and a metamaterial near-field calibration lens 2; the metamaterial near-field calibration lens 2 includes m×n lens units 21 arranged periodically in the XOY plane of the three-dimensional coordinate system, and the lens unit 21 includes a square first dielectric substrate 211 with circular through holes 212 of different sizes provided in the center of the plate surface;

[0005] The feed source 1 includes a holographic surface 11 and a monopole 12 arranged at its center; the holographic surface 11 is composed of m×n tensor impedance units 111 arranged periodically in the XOY plane of the three-dimensional coordinate system; the tensor impedance unit 111 includes a square second dielectric substrate 1111, a non-centrosymmetric metal patch 1112 printed on the upper surface of the second dielectric substrate 1111, and a metal floor 1113 on the lower surface;

[0006] The metamaterial near-field calibration lens 2 is arranged above the holographic surface 11, and the distance between the lower surface of the metamaterial near-field calibration lens 2 and the upper surface of the holographic surface 11 is H. The radius R1 of the circular through hole 212 in each lens unit 21 included in the metamaterial near-field calibration lens 2 is the phase value ρ that needs to be compensated according to the position of the lens unit 21. 补偿 (x,y) is determined by:

[0007] ρ 补偿 (x,y)=-4.74R1 3 -8.85R1 2 -37.71R1+201

[0008] ρ 补偿 (x,y)=ρ S -ρ 馈源 (x,y)

[0009] Where, 0.5λ≤H≤λ, λ is the antenna operating wavelength, ρ S The near-field phase of the feed source 1 in the XOY plane at a height H from the upper surface of the holographic surface 11 needs to be compensated to a constant target phase value, ρ 馈源 (x, y) is the near-field phase value of the feed source 1 in the XOY plane at a height H from the upper surface of the holographic surface 11.

[0010] Furthermore, the metamaterial near-field calibration lens 2 and the holographic surface 11 are fixed via a support structure 3 , and a center normal of the metamaterial near-field calibration lens 2 coincides with a center normal of the holographic surface 11 .

[0011] Furthermore, the non-centrosymmetrical metal patch 1112 adopts a circular metal patch structure with two parallel gaps.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] 1. The metamaterial near-field calibration lens of the present invention is arranged above the holographic surface. Each lens unit contained in the metamaterial near-field calibration lens is determined one by one according to the phase value that needs to be compensated at each position of the lens unit. A near-field region of leaky wave radiation is initially formed on the holographic surface, and phase compensation is performed on the entire aperture surface. This abandons the traditional lens antenna construction method of using focus and focal length to design the lens phase distribution, and effectively reduces the cross-sectional height of the metamaterial lens antenna system.

[0014] 2. The metamaterial near-field lens of the present invention includes a plurality of periodically arranged square first dielectric substrates with circular through holes, each comprising a lens unit. A feed source consisting of a holographic surface and a monopole is provided below the lens unit. By adjusting the radius of the circular through hole in each lens unit contained in the metamaterial near-field lens, the phase value of each lens unit is compensated, thereby achieving high-gain radiation. Simulation results show that the aperture efficiency of the present invention can reach 45%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0016] Figure 2 Schematic diagram of the structure of the tensor impedance unit in the present invention;

[0017] Figure 3 Schematic diagram of the structure of the lens unit in the present invention;

[0018] Figure 4 A graph showing the relationship between the radius R1 of the circular through hole on the lens unit and the phase compensation that can be achieved by the lens unit in the present invention;

[0019] Figure 5 The near-field phase distribution diagram of the feed source in the XOY plane at a height of 20 mm from the upper surface of the holographic surface in the present invention;

[0020] Figure 6 S of the embodiment of the present invention 11 Simulation result diagram;

[0021] Figure 7 This is a near-field phase distribution diagram in the XOY plane on the upper surface of the metamaterial near-field lens according to an embodiment of the present invention;

[0022] Figure 8 This is a graph showing the gain simulation results of an embodiment of the present invention when the operating frequency is 15 GHz and the radiation angle is in the direction of θ=0°;

[0023] Figure 9 1 is a diagram of axial ratio simulation results of an embodiment of the present invention when the operating frequency is 15 GHz and the radiation angle ranges from θ=-10° to θ=10°. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Reference Figure 1 The present invention includes a feed source 1, a metamaterial near-field calibration lens 2 and a support structure 3.

[0026] The feed source 1 includes a holographic surface 11 located below and parallel to the metamaterial near-field calibration lens 2, and a monopole 12 arranged at the center of the holographic surface 11. The holographic surface 11 is composed of m×n tensor impedance units 111 periodically arranged in the XOY plane of the three-dimensional coordinate system and placed at the bottom layer of the antenna overall structure. The monopole 12 is composed of the inner conductor of the SMA coaxial cable and is fixed at the center of the holographic surface 11. The length of the SMA coaxial cable inner conductor extending from the holographic surface 1 is T, which is determined by the operating frequency of the antenna overall structure. The metamaterial near-field calibration lens 2 includes m×n lens units 21 periodically arranged in the XOY plane of the three-dimensional coordinate system, and is arranged at a height H from the upper surface of the holographic surface 11, and 0.5λ≤H≤λ, where λ is the antenna operating wavelength. The metamaterial near-field calibration lens 2 is fixed to the holographic surface 11 by a support structure 3, and the center normal of the metamaterial near-field calibration lens 2 coincides with the center normal of the holographic surface 11. In this embodiment, it is assumed but not limited to m=n=71, T=5mm, H=20mm, and the operating frequency of the entire antenna structure is 15GHz.

[0027] Reference Figure 2 Each tensor impedance unit 111 constituting the holographic surface 11 comprises a square second dielectric substrate 1111, a non-centrosymmetric metal patch 1112 printed on the upper surface of the second dielectric substrate 1111, and a metal floor 1113 on the lower surface. The non-centrosymmetric metal patch 1112 is a circular metal patch with two parallel slits. The radius R2 of the non-centrosymmetric metal patch 1112 and the rotation angle θ based on the X-axis are t The metal floor 1113 is printed on the lower surface of the second dielectric substrate 1111 according to the distribution change of the holographic interference pattern. The physical dimensions of the two are the same, and the center normals coincide. The physical dimensions of the second dielectric substrate 1111 are W×W, the thickness is L, and the relative dielectric constant is ε r2 , the relative magnetic permeability is 1, where 2mm≤W≤5mm, 1.5mm≤L≤2mm, 2.2≤ε r2≤6.2, in this example, it is assumed but not limited to W=3mm, L=2mm, ε r2 =3.5.

[0028] The tensor impedance unit 111 is based on the holographic principle interference pattern distribution and is designed as follows:

[0029]

[0030] Where Z represents the impedance distribution of the tensor holographic surface, which is an anti-Hermit pure imaginary second-order matrix, and j is the imaginary unit; Z xx , Z yy represent the impedance distribution of the tensor holographic metasurface in the x and y directions, Z xy and Z yx represent the impedance distribution of the tensor holographic metasurface in the xy and yx directions, Z xy =Z yx ;

[0031]

[0032]

[0033]

[0034] Where B and M represent the magnitude and modulation depth of the average surface impedance, respectively; r is the vector distance between any point on the tensor holographic surface and the monopole feed along the surface. x, y, z are the coordinates of the three-dimensional coordinate system, θ is the deflection direction of the beam relative to the z-axis, k is the right-hand circularly polarized wave vector, is the transverse wave vector of the surface current propagating on the tensor holographic surface; in this example, it is assumed but not limited to θ=0°.

[0035] Furthermore, the radius R2 of the non-centrosymmetric metal patch 1112 is the equivalent scalar impedance Z at its location. max Sure:

[0036] Z max ∈[256, 346]

[0037] Z max =jZ0{-j(Z0 2 -Z xy 2 +Z xx Z yy )

[0038] ±[-(Z0 2 -Z xy 2 +Z xx Zyy ) 2 +4Z0 2

[0039] ×(Z yy cos 2 θ t -Z xy sin2θ t +Z xx sin 2 θ t )

[0040] ×(Z xx cos 2 θ t +Z xy sin2θ t +Z yy sin 2 θ t ) 1 / 2}

[0041] ×[2Z0(Z yy cos 2 θ t -Z xy sin2θ t +Z xx sin 2 θ t )] -1

[0042] Among them, Z0=120π is the wave impedance of free space, θ t is the rotation angle of the non-centrosymmetric metal patch 1112 with the X axis as the reference, Z xx , Z yy and Z xy represent the impedance distribution of the holographic surface in the x direction, y direction, and xy direction, respectively.

[0043] Reference Figure 3 The lens unit 21 constituting the metamaterial near-field calibration lens 2 includes a square first dielectric substrate 211 and a circular through hole 212 arranged at the center of the plate surface. The first dielectric substrate 211 adopts a dielectric constant of ε r1 , a dielectric material with a magnetic permeability of 1, whose physical dimensions are w×w and thickness is l, where 2.2≤ε r1 ≤4.6, 2mm≤w≤5mm, 5mm≤l≤20mm, this example assumes but is not limited to ε r1 =4.4, w=3mm, l=5mm. The radius R1 of the circular through hole 212 in each lens unit 21 included in the metamaterial near-field calibration lens 2 is the phase value ρ that needs to be compensated according to the position of the lens unit 21. 补偿(x,y) is determined, specifically:

[0044] ρ 补偿 (x,y)=-4.74R1 3 -8.85R1 2 -37.71R1+201

[0045] ρ 补偿 (x,y)=ρ S -ρ 馈源 (x,y)

[0046] Among them, ρ S The near-field phase of the feed source 1 in the XOY plane at a height H from the upper surface of the holographic surface 11 needs to be compensated to a constant target phase value, ρ 馈源 (x, y) is the near-field phase value of the feed source 1 in the XOY plane at a height H from the upper surface of the holographic surface 11. Figure 4 In this embodiment, the radius of the circular through hole 212 is 0.5 mm ≤ R1 ≤ 1.4 mm. According to the formula ρ 补偿 (x,y)=-4.74R1 3 -8.85R1 2 -37.71R1+201, at this time the phase compensation value that the lens unit 21 can achieve is between [118°, 180°], and the compensable phase range, that is, the difference between the maximum and minimum values, is Δρ 补偿 =62°. Figure 5 (a) is a near-field phase distribution plane diagram of the feed source in the XOY plane at a height of 20 mm from the upper surface of the holographic surface in this embodiment. Figure 5 (b) is a numerical statistical diagram of the phase values ​​at each position in the plane diagram, and the feed phase ρ in the XOY plane at a height of 20 mm from the upper surface of the holographic surface 馈源 (x, y) The phase range Δρ that can be compensated by the lens unit 21 补偿 = The phase with the largest proportion within the distribution of 62° is between [68°, 130°]. Phase compensation is performed on the position points within this range to compensate them to the same phase value, and the constant target phase value ρ is obtained. S =248°, according to the relationship ρ 补偿 (x,y)=ρ S -ρ 馈源 (x, y), determine the compensation phase required for the point where the phase is between [68°, 130°]; for the feed phase ρ in the XOY plane at a height of 20 mm above the holographic surface 馈源 At the point where (x,y) is less than 68°, the phase value ρ to be compensated 补偿 (x, y) = 180°; for the feed phase ρ in the XOY plane at a height of 20 mm from the holographic surface 馈源At the position where (x,y)>130°, the phase value ρ to be compensated 补偿 (x, y) = 68°; at this point, the corresponding relationship between the position coordinate (x, y) on the metamaterial near-field calibration lens 2 and the radius R1 of the circular through hole 212 is completely established, and the construction of the metamaterial near-field calibration lens 2 is completed.

[0047] The technical effects of the present invention are further described in detail below in conjunction with simulation experiment results.

[0048] 1. Simulation conditions and contents:

[0049] The simulation uses the electromagnetic simulation software CST2017.

[0050] Simulation 1, S of the embodiment of the present invention 11 The simulation results are as follows Figure 6 shown.

[0051] Simulation 2 simulates the near-field phase distribution of the embodiment of the present invention at an operating frequency of 15 GHz. The results are as follows: Figure 7 shown.

[0052] Simulation 3 simulates the far-field radiation pattern of the embodiment of the present invention at an operating frequency of 15 GHz, and the results are as follows: Figure 8 shown.

[0053] Simulation 4, the embodiment of the present invention is simulated for the axial ratio of the radiation angle θ = -10° to θ = +10° when the operating frequency is 15 GHz. The results are as follows: Figure 9 shown.

[0054] 2. Analysis of simulation results:

[0055] Reference Figure 6 S of the embodiment of the present invention 11 Simulation results: The S of the antenna in this example is in the range of 14-16GHz. 11 Both are less than -10dB, indicating that the antenna feed end is well matched.

[0056] Reference Figure 7 A near-field phase distribution diagram in the XOY plane on the upper surface of the metamaterial near-field lens according to an embodiment of the present invention shows that the near-field phase in the XOY plane on the upper surface of the metamaterial near-field lens according to this embodiment is concentrated at 285°, indicating that the metamaterial near-field lens achieves good beam calibration.

[0057] Reference Figure 8 When the operating frequency of the embodiment of the present invention is 15 GHz, the radiation angle is in the direction of θ = 0°. The embodiment realizes right-handed circularly polarized wave radiation in the normal direction, i.e., θ = 0°, with a gain of 28.06 dBi and an aperture efficiency of 45%.

[0058] Reference Figure 9 When the operating frequency of the embodiment of the present invention is 15 GHz, the axial ratio simulation results of the radiation angle from θ = -10° to θ = 10° are shown. The axial ratio of the antenna in this example from θ = -6° to θ = +6° is less than 3 dB, achieving good circularly polarized wave axial ratio characteristics.

[0059] In summary, the present invention completes the beam calibration of the feed antenna composed of the holographic surface and the monopole to a certain extent. Compared with the existing technology, it greatly reduces the cross-sectional height of such aperture lens antennas, and has high-gain radiation while being low-cost and easy to process, giving such aperture lens antennas a wider application space.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the innovative concept of the present invention, but these changes all fall within the scope of protection of the present invention.

Claims

1. A high-gain, low-profile metamaterial near-field lens antenna with an integrated holographic surface, comprising a feed source (1) and a metamaterial near-field calibration lens (2); the metamaterial near-field calibration lens (2) comprises m×n lens units (21) periodically arranged in an XOY plane of a three-dimensional coordinate system, the lens unit (21) comprising a square first dielectric substrate (211) with a circular through hole (212) provided at the center of the plate surface; characterized in that: The feed source (1) comprises a holographic surface (11) and a monopole (12) arranged at the center thereof; the holographic surface (11) is composed of m×n tensor impedance units (111) arranged periodically in an XOY plane of a three-dimensional coordinate system; the tensor impedance unit (111) comprises a square second dielectric substrate (1111), a non-centrosymmetric metal patch (1112) printed on the upper surface of the second dielectric substrate (1111), and a metal floor (1113) on the lower surface; The metamaterial near-field calibration lens (2) is arranged above the holographic surface (11), and the distance between the lower surface of the metamaterial near-field calibration lens (2) and the upper surface of the holographic surface (11) is H. The radius R1 of the circular through hole (212) in each lens unit (21) included in the metamaterial near-field calibration lens (2) is the phase value ρ that needs to be compensated according to the position of the lens unit (21). 补偿 (x,y) is determined by: r 补偿 (x,y)=-4.74R1 3 -8.85R1 2 -37.71R1+201 r 补偿 (x,y)=ρ S -r 馈源 (x,y) Where, 0.5λ≤H≤λ, λ is the antenna operating wavelength, ρ S The near-field phase of the feed source (1) in the XOY plane at a height H from the upper surface of the holographic surface (11) needs to be compensated to a constant target phase value, ρ 馈源 (x, y) is the near-field phase value of the feed source (1) in the XOY plane at a height H from the upper surface of the holographic surface (11).

2. The antenna according to claim 1, wherein The metamaterial near-field calibration lens (2) and the holographic surface (11) are fixed via a support structure (3), and a central normal line of the metamaterial near-field calibration lens (2) coincides with a central normal line of the holographic surface (11).

3. The antenna according to claim 1, wherein: The non-centrosymmetrical metal patch (1112) adopts a circular metal patch structure with two parallel gaps.

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