A high-focusing metasurface lens

Abstract

The invention discloses a high-focusing metasurface lens, comprising a dielectric substrate and a plurality of lens units. The dielectric substrate is in a square shape, and the lens units are arranged on both the front and back sides thereof, and the lens units are arranged in a square array; for the front side of the dielectric substrate: lens units EB are arranged at the four corners of the dielectric substrate; the remaining lens units EB are arranged in the middle of the dielectric substrate, and these lens units EB are located at the grid points on the edge of a grid polygon and on each grid point in the grid polygon; the lens unit EA surrounds the lens unit EB in the middle; the arrangement form of the lens unit on the back side of the dielectric substrate is the same as the arrangement form of the lens unit on the front side of the dielectric substrate, and the lens unit EA on the back side of the dielectric substrate is directly opposite to the lens unit EA on the front side of the dielectric substrate, and the lens unit EB on the back side of the dielectric substrate is directly opposite to the lens unit EB on the front side of the dielectric substrate. The invention has a simple structure, is easy to process, and has a relatively thin thickness.

Description

Technical Field

[0001] The present invention belongs to the field of supersurfaces, and in particular relates to a high-focusing supersurface lens. Background Art

[0002] Antennas, as devices for transmitting and receiving electromagnetic waves, are core equipment in wireless communication and radar systems. In order to meet the communication system's requirements for high gain and low side lobes for antennas, the phase distribution of the surface field at the transmitting antenna port is generally adjusted to achieve focused directional radiation of the radiated wave, thereby reducing the spatial diffusion loss of the radiated wave and further increasing the energy of the radiated wave. This can be achieved by loading a lens in the radiation direction of the antenna. The lens can convert spherical waves into plane waves to achieve high gain and high directivity design of the antenna; the lens can also converge the incident plane waves to a point to achieve the function of electric field focusing. Metasurfaces, a type of two-dimensional structure, are easy to manufacture, small in size, and low in loss, and are now commonly used in microwave lenses. However, in order to achieve arbitrary phase and amplitude, metasurfaces have multi-layer structures with large longitudinal dimensions; or have non-periodic structures and load active devices, which require high processing accuracy and are difficult to process. In order to reduce the thickness of the lens and design an easy-to-process metasurface lens, it is necessary to optimize the design of the lens unit structure to achieve the purpose of using a single-layer metasurface lens to achieve electric field focusing. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a high-focusing metasurface lens, which has a simple structure, is easy to process, and is relatively thin.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A high-focusing metasurface lens comprises a dielectric substrate and a plurality of lens units, wherein the dielectric substrate is in a square shape, the lens units are arranged on both the front and back sides of the dielectric substrate, and the lens units on the front and back sides of the dielectric substrate are arranged in a square array;

[0006] The lens unit includes a lens unit EA and a lens unit EB. For the front side of the dielectric substrate: the lens units EB are arranged at the four corners of the dielectric substrate; the remaining lens units EB are arranged in the middle of the dielectric substrate, and these lens units EB are located at the grid points on the edge of a grid point polygon and at each grid point in the grid point polygon. The grid point polygon is a convex grid point polygon, the number of sides of the grid point polygon is not less than four, and the difference in the length of any adjacent sides in the grid point polygon is not greater than the length between adjacent grid points; the lens unit EA surrounds the lens unit EB in the middle;

[0007] The arrangement form of the lens unit on the back side of the dielectric substrate is the same as that of the lens unit on the front side of the dielectric substrate. The lens unit EA on the back side of the dielectric substrate faces the lens unit EA on the front side of the dielectric substrate one by one, and the lens unit EB on the back side of the dielectric substrate faces the lens unit EB on the front side of the dielectric substrate one by one.

[0008] Preferably, the transmission phases of all lens units EA and the transmission phases of lens units EB are equal and opposite.

[0009] Preferably, the lens unit EA comprises a first solid cross and a hollow cross ring, and the first solid cross is concentrically arranged inside the hollow cross ring and the corresponding sides are parallel.

[0010] Preferably, the lens unit EB comprises a second solid cross.

[0011] Preferably, the lens units are all copper films, and the thickness of the copper films is 0.035 mm.

[0012] Preferably, the dielectric substrate adopts a F4BM antenna board.

[0013] Preferably, the F4BM antenna board has a dielectric constant of 4.3, a loss tangent of 0.0025, and a thickness of 2.8 mm.

[0014] Preferably, the lens units on the front and back sides of the dielectric substrate are arranged in a 11×11 matrix.

[0015] The present invention has the following beneficial effects:

[0016] The high-focusing metasurface lens of the present invention is composed of two single-layer transmission units with similar structures, lens unit EA and lens unit EB. The distribution of the two lens units on the lens is arranged according to the transmission phase, so as to achieve phase control, focus the transmitted plane wave on the focal point, and convert the transmitted spherical wave into a plane wave. This lens is simple to manufacture, compact in structure, and thin in thickness, and solves the problem of large longitudinal size and high processing precision requirements of the focusing metasurface lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of a lens unit EA in an embodiment of the present invention;

[0018] Figure 2 is a schematic structural diagram of a lens unit EB in an embodiment of the present invention;

[0019] Figure 3 is a schematic diagram of the arrangement of lens units in an embodiment of the present invention;

[0020] Figure 4 is a diagram of the simulation result of the electric field energy density on the z-axis of the high-focusing metasurface lens of an embodiment of the present invention under vertical incidence of a plane wave;

[0021] Figure 5 is a diagram showing the simulation results of the electric field intensity at the focus of the high-focusing metasurface lens of an embodiment of the present invention under vertical incidence of a plane wave;

[0022] Figure 6 is a graph of the electric field strength test result at the focus of the antenna far field under the vertical incidence of an approximately plane wave in the embodiment of the present invention;

[0023] Figure 7 is a comparison diagram of S parameter simulation and test results of placing an antenna of the same frequency band at the focus in an embodiment of the present invention;

[0024] Figure 8 is a comparison diagram of gain simulation and test results of placing an antenna of the same frequency band at the focus in an embodiment of the present invention;

[0025] Fig. 9 is a comparison diagram of simulation and test results of the far-field directivity of the YOZ plane with the same frequency band antenna placed at the focus in an embodiment of the present invention;

[0026] Fig.10 It is a comparison diagram of simulation and test results of the XOZ plane far-field directivity of an antenna of the same frequency band placed at the focus in an embodiment of the present invention.

[0027] In the figure, 1-lens unit EA, 1-1-hollow cross ring, 1-2-first solid cross, 2-lens unit EB, 2-1-second solid cross, 3-dielectric substrate. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Reference Figure 1-Figure 3 The high-focusing metasurface lens of the present invention comprises a dielectric substrate 3 and a plurality of lens units, wherein the dielectric substrate 3 is in a square shape, and the lens units are arranged on both the front and back sides of the dielectric substrate 3, and the lens units on the front and back sides of the dielectric substrate 3 are arranged in a square array; the front and back sides of the dielectric substrate 3 are equally divided into grids whose single units are squares, and a lens unit is arranged at the position of each grid point, and the center of the lens unit coincides with the center of the grid point;

[0030] The lens unit includes a lens unit EA1 and a lens unit EB2. Figure 3As shown, for the front side of the dielectric substrate 3: the grid points at the four corners of the dielectric substrate 3 are all provided with lens units EB2; the remaining lens units EB2 are provided in the middle of the dielectric substrate 3, and these lens units EB2 are located at the grid points on the edge of a grid polygon and at the grid points within the grid polygon. The grid polygon is a convex grid polygon, and the number of sides of the grid polygon is not less than four. In the grid polygon, the difference in the length of any adjacent sides is not greater than the length between adjacent grid points; the lens unit EA1 surrounds the lens unit EB2 in the middle; the arrangement of the lens units on the back side of the dielectric substrate 3 is the same as that of the lens units on the front side of the dielectric substrate 3, and the lens units EA1 on the back side of the dielectric substrate 3 are opposite to the lens units EA1 on the front side of the dielectric substrate 3, and the lens units EB2 on the back side of the dielectric substrate 3 are opposite to the lens units EB2 on the front side of the dielectric substrate 3. The transmission phases of all lens units EA1 and the transmission phases of lens units EB2 are equal and opposite. As shown Figure 1 As shown, the lens unit EA1 includes a first solid cross 1-2 and a hollow cross ring 1-1, the first solid cross 1-2 is coaxially arranged inside the hollow cross ring 1-1 and the corresponding sides are parallel, each arm of the hollow cross ring 1-1 has the same length, and each arm of the first solid cross 1-2 has the same length. The lens unit EB2 includes a second solid cross 2-1, and each arm of the second solid cross 2-1 has the same length.

[0031] Example

[0032] The high-focusing metasurface lens of this embodiment is an ultra-thin focusing metasurface lens operating at 10 GHz. The dielectric substrate adopts F4BM, the dielectric constant of F4BM is 4.3, the loss tangent is 0.0025, and the thickness is 2.8 mm. The same cross-shaped metal lines are printed on both sides of the dielectric substrate, and the entire unit is a single-layer structure.

[0033] The lens unit includes two units: lens unit EA1 and lens unit EB2. The side lengths of lens unit EA1 and lens unit EB2 are both p. The same metal pattern of lens unit EA1 is printed on the front and back of the dielectric substrate. The structure of lens unit EA1 includes a hollow cross ring 1-1 and a first solid cross 1-2. The width of the hollow cross ring 1-1 is t, the ring arm length is r, and the arm width is w; the arm length of the solid cross 1-2 inside the hollow cross ring 1-1 is r 1 , arm width is w 1 The front and back sides of the dielectric substrate are printed with the same metal pattern of the lens unit EB2, and the lens unit EB2 includes a second solid cross 2-1. The arm length of the second solid cross 2-1 is r 2 , arm width is w 2 .

[0034] In this embodiment, there are 121 lens units in total, which are arranged in 11 rows and 11 columns, and the side length of the dielectric substrate is 154 mm. There are 56 lens units EA, which are mainly distributed at the edge of the lens, and 65 lens units EB, which are distributed at the center and four corners of the lens. The lens unit EB at the center is shifted to the grid points on the edge of the grid polygon of the dodecagon and the grid points within the grid polygon. The metal patterns of the lens unit EA and the lens unit EB are printed on a complete dielectric substrate of 154 mm × 154 mm.

[0035] The high-focusing metasurface lens of this embodiment adopts a double-sided printed metasurface lens. The same metal pattern is printed on the front and back of the lens. For the lens unit EA, the transmission coefficient amplitude and phase are determined by the arm length r of the hollow cross ring 1-1 and the arm length r of the first solid cross. 1 For lens unit EB, the transmission coefficient amplitude and phase are determined by the arm length r of the second solid cross. 2 The peak frequency of the transmission coefficient amplitude of the transmission unit EA and the transmission unit EB varies with r and r 1 and r 2 The transmission coefficient amplitude of the two units selected in this embodiment has a peak value of 10 GHz, and changes smoothly around 10 GHz, with a wide bandwidth. The transmission coefficient amplitude is greater than 0.85. The unit maintains a high transmission coefficient, ensuring a high transmission capacity of the lens and maintaining a high transmission efficiency of the lens.

[0036] The length r of the solid cross pattern of the transmission unit EA and the transmission unit EB 1 、r 2 , width w 1 、w 2 Determine the value of the 10GHz transmission phase. The transmission phase of the transmission unit EA is +14°, and the transmission phase of the transmission unit EB is -14°. When a plane wave transmits the lens of this embodiment, the deflection direction of the transmitted electromagnetic wave at the center of the lens is opposite to the deflection direction of the transmitted electromagnetic wave at the edge. After superposition, the electromagnetic waves converge at a focus 4λ away from the lens surface in the radial direction.

[0037] The dielectric substrate of the high-focusing metasurface lens of this embodiment is square, with a side length of 154mm and a thickness of 2.8mm. The material selected in the actual processing is F4BM material with a relative dielectric constant of 4.3 and a loss tangent of 0.0025. The metal part is copper-clad, and the top and bottom copper thicknesses are 0.035mm. The specific dimensions of the remaining structures are shown in Table 1:

[0038] Table 1

[0039]

[0040]

[0041] The units of the metasurface lens of this embodiment are arranged in 11 rows and 11 columns. The area of ​​the central region composed of the transmission units EB is as large as possible, so that the electric field intensity at the focus is the strongest.

[0042] An antenna with a center frequency of 10 GHz is placed at the focus of the lens of this embodiment, and the spherical wave emitted by the antenna passes through the lens of the present invention, and the outgoing wave is a plane wave, which simultaneously plays the role of increasing gain and narrowing the main lobe.

[0043] The center frequency of the metasurface lens designed in this embodiment is 10 GHz. Figure 4 The simulation results of the electric field energy density on the z-axis of the lens under vertical plane wave incidence are shown in the figure. Taking the center of the front surface of the lens as the origin, the electric field energy density has a peak at 115.2mm (4λ), and compared with the plane wave excitation without a lens, the energy density at the focus is increased by 11.62dB. This is consistent with the theoretical prediction.

[0044] Figure 5 The simulation result of the electric field intensity at the focus of the lens under vertical incidence of plane wave is shown in the figure. An electric field probe is set at the focus, and the electric field intensity has a peak at 10GHz, which is 11.65dB higher than the electric field intensity when there is no lens plane wave excitation, indicating that the operating frequency of the lens is 10GHz, and the focusing function at 10GHz is achieved.

[0045] Figure 6 For this purpose, the electric field strength test result of the lens at the focus of the antenna far field approximating the vertical incidence of a plane wave is shown in the figure. During the test, the lens was placed in the far field of the antenna (300mm, 10λ), and the radiation wave of the antenna far field was used to approximate the plane wave. The probe was on the z-axis, 420mm away from the antenna. The peak value of the electric field strength at 10GHz on the probe was increased by 16.97dB compared with the electric field strength without the lens, indicating that the lens has a strong focusing effect on the plane wave.

[0046] Figure 7 The S parameter simulation and test results of placing the same frequency band antenna at the focal point of the lens are compared. The simulation results show that the return loss of the lens antenna is less than -10dB at 9.65-10.7GHz, and the test results show that the return loss of the lens antenna is less than -10dB at 9.55-10.4GHz, both covering 10GHz.

[0047] Figure 8The gain simulation and test results of the antenna of the same frequency band placed at the focal point of the lens are compared. The peak gain result of the lens antenna simulation is 17.8dBi at 9.75GHz, which is 8.8dB higher than the gain of a single antenna. The peak gain result of the lens antenna test is 14.4dB at 9.75GHz, which is 5.4dB higher than the gain of a single antenna, and 3.4dB different from the simulation result. After analysis, the reason for the large error is that the actual loss of the lens is large, which leads to a decrease in gain.

[0048] Fig. 9 is the normalized far-field pattern of the YOZ plane (E plane) of an antenna with the same frequency band placed at the focus of this lens. Fig.10 is the normalized far-field radiation pattern of the XOZ plane (H plane). The main lobe width of the simulated radiation pattern of the E plane of the single antenna is 50 degrees, and the main lobe width of the simulated radiation pattern of the H plane is 84 degrees. The main lobe width of the E and H planes of the lens antenna is reduced to 11°. Compared with the simulation results, the main lobe of the test radiation pattern of the single antenna is narrower and has higher side lobes; the main lobe of the test radiation pattern of the lens antenna is pencil-shaped, which is consistent with the simulation results. This shows that this lens has a high convergence effect on spherical waves.

[0049] It can be seen from the above scheme that the high-focusing metasurface lens of the present invention is an ultra-thin focusing metasurface lens working in the X-band, with a thickness of only 2.8mm, and only two units are required. By designing the lens unit and optimizing the distribution of the lens units, the lens can focus the transmitted plane wave at a focal point 4λ away from the lens, and place the antenna of the same frequency band at its focal point. The lens increases the antenna gain by 9dB. It has the advantages of small size, thin thickness, high stability, and easy processing.

Claims

1. A high-focusing metasurface lens, It is characterized in that Comprising a dielectric substrate (3) and a plurality of lens units, wherein the dielectric substrate (3) is in a square shape, the lens units are arranged on both the front and back sides of the dielectric substrate (3), and the lens units on the front and back sides of the dielectric substrate (3) are arranged in a square array; The lens unit comprises a lens unit EA (1) and a lens unit EB (2). For the front side of the dielectric substrate (3), one lens unit EB (2) is arranged at each of the four corners of the dielectric substrate (3); the remaining lens units EB (2) are arranged in the middle of the dielectric substrate (3); these lens units EB (2) are located at grid points on the edge of a grid point polygon and at grid points within the grid point polygon; the grid point polygon is a convex grid point polygon; the number of sides of the grid point polygon is not less than four; in the grid point polygon, the difference in length of any adjacent sides is not greater than the length between adjacent grid points; the lens unit EA (1) surrounds the lens unit EB (2) in the middle; The arrangement form of the lens unit on the back side of the dielectric substrate (3) is the same as the arrangement form of the lens unit on the front side of the dielectric substrate (3); the lens unit EA (1) on the back side of the dielectric substrate (3) is directly opposite to the lens unit EA (1) on the front side of the dielectric substrate (3); and the lens unit EB (2) on the back side of the dielectric substrate (3) is directly opposite to the lens unit EB (2) on the front side of the dielectric substrate (3); The transmission phases of all lens units EA (1) and lens units EB (2) are equal and opposite; The lens unit EA (1) comprises a first solid cross (1-2) and a hollow cross ring (1-1), wherein the first solid cross (1-2) is coaxially arranged inside the hollow cross ring (1-1) and the corresponding sides are parallel; The lens unit EB (2) comprises a second solid cross (2-1); The front and back surfaces of the dielectric substrate (3) are both provided with 121 lens units, the 121 lens units are arranged in 11 rows and 11 columns, there are 56 lens units EA, there are 65 lens units EB, and all lens units have the same size; The length r of the solid cross pattern of the transmission unit EA and the transmission unit EB 1 、r 2 , width w 1 、w 2 Determine the value of the 10GHz transmission phase, the transmission phase of the transmission unit EA is +14°, the transmission phase of the transmission unit EB is -14°, the plane wave transmission lens, the deflection direction of the transmitted electromagnetic wave at the center of the lens is opposite to the deflection direction of the transmitted electromagnetic wave at the edge, and after superposition, the electromagnetic waves converge at a focus 4λ away from the lens surface in the radial direction.

2. A high-focusing metasurface lens according to claim 1, It is characterized in that The lens units are all made of copper film, and the thickness of the copper film is 0.035mm.

3. A high-focusing metasurface lens according to claim 1, It is characterized in that The dielectric substrate (3) adopts an F4BM antenna board.

4. A high-focusing metasurface lens according to claim 1, It is characterized in that The F4BM antenna board has a dielectric constant of 4.3, a loss tangent of 0.0025, and a thickness of 2.8 mm.

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