A kind of Ka band electromagnetic super surface unit and low profile Ka band beam scanning antenna loaded with electromagnetic super surface

Abstract

A Ka-band electromagnetic metasurface unit and a low-profile Ka-band beam scanning antenna with the electromagnetic metasurface loaded thereon are disclosed. The Ka-band electromagnetic metasurface unit comprises an upper dielectric substrate, a middle dielectric substrate, and a lower dielectric substrate arranged from top to bottom. Metal layers are printed on the upper surface of the upper dielectric substrate, the upper surface of the middle dielectric substrate, the upper surface of the lower dielectric substrate, and the lower surface of the lower dielectric substrate. The metal patterns, shapes, and sizes of each metal layer are identical. The Ka-band beam scanning antenna comprises an upper Ka-band electromagnetic metasurface, a lower Ka-band electromagnetic metasurface, and a microstrip antenna feed arranged from top to bottom. Using the microstrip antenna as the feed, rotating the two metasurface layers allows for elevation beam scanning within the 30.5 GHz to 32.5 GHz frequency band, achieving a maximum scanning range of ±56°. This invention offers advantages such as low profile, low loss, low cost, high gain, and ease of manufacture.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically relating to a Ka-band electromagnetic metasurface unit and a low-profile Ka-band beam scanning antenna loaded with electromagnetic metasurface. This invention can be used for millimeter-wave antenna communication and high-resolution radar imaging. Background Technology

[0002] With the rapid development of wireless communication technology, broadband, miniaturization, multi-channel communication, and multi-system collaboration of wireless communication devices have become development trends.

[0003] Beam-scanning antennas can be divided into traditional low-complexity mechanical scanning antennas and phased array antennas. A phased array antenna is an antenna array composed of multiple independent, identical or dissimilar antenna elements arranged in a specific configuration. The radiation pattern of the array is adjusted by precisely changing the phase shift of each antenna element using back-end devices. Phased arrays can achieve fast and accurate directionality of wireless signals and have strong target processing capabilities, and have been widely used in satellite communications, radar systems, medical imaging, and other fields. However, phased array systems require a large number of phase shifters and transceiver modules. Under high power conditions, the heat dissipation of the phase shifters or transceiver modules also increases the design difficulty, resulting in high complexity and cost. Therefore, developing low-complexity and low-cost beam-scanning antennas is necessary.

[0004] Compared to phased array antennas, mechanically scanned antennas do not control beam direction through electronic phase shifting as used in phased arrays. Instead, they achieve beam modulation by altering the phase of the electromagnetic wave by loading a beam-modulating electromagnetic metasurface onto the feed antenna. Beam scanning is achieved through the mutual rotation of the two electromagnetic metasurfaces. This design offers the advantage of lower loss and significantly reduced cost, but its most significant drawback is the reduced scanning speed. Therefore, in high-power processing, low-cost, low-complexity, and non-high-speed beam scanning scenarios, mechanically scanned antennas based on electromagnetic metamaterial coatings can provide a good alternative.

[0005] In 2023, Xi'an University of Electronic Science and Technology disclosed a Ka-band metasurface unit based on a low profile in its patent application "Ka-band Metasurface Unit Based on Low Profile and Beam Scanning Antenna Loaded Thereon" (application number 202310202469.2, publication number CN 116031658A). This unit includes an upper dielectric substrate and a lower dielectric substrate. The upper surface of the upper dielectric substrate, the lower surface of the lower dielectric substrate, and either the lower surface of the upper dielectric substrate or the upper surface of the lower dielectric substrate are all printed with metal layers of the same metal pattern with opposite projections. By using different metasurface units at different locations for phase compensation, beam deflection is achieved. Scanning of the main beam on the elevation plane is achieved by changing the relative rotation angle between the two metasurfaces. However, due to the use of a horn antenna as the feed source, this technology suffers from the disadvantage of an excessively high overall profile.

[0006] In 2024, Xi'an University of Electronic Science and Technology disclosed a phase-independently modulated low-sidelobe high-gain metalens antenna and its fabrication method in its patent application "A phase-independently modulated low-sidelobe high-gain metalens antenna and its fabrication method" (application number 202411346960.3, publication number CN 119029560A). The antenna consists of m×m single-layer transmission-type polarization conversion unit structures. Utilizing a single-layer polarization conversion metasurface, only a 180° phase range polarization unit structure needs to be designed and implemented, requiring fewer optimized units. It features easy implementation, low cost, and the ability to integrate and miniaturize devices, facilitating mass production applications. However, because only one layer of metasurface is used, the beam can only be focused in one direction, and beam scanning cannot be achieved. Summary of the Invention

[0007] To overcome the shortcomings of the existing technology, the present invention aims to provide a Ka-band electromagnetic metasurface unit and a low-profile Ka-band beam scanning antenna loaded with electromagnetic metasurface. Based on electromagnetic metamaterials, the present invention utilizes mechanical rotation of a double-layer metasurface to achieve beam scanning of the elevation plane, achieving a maximum scanning effect of ±56° in the frequency band of 30.5–32.5 GHz. It eliminates the need for designing complex feed networks and power divider structures, and has the advantages of low profile, low loss, low cost, high gain, simple structure, and ease of implementation.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A Ka-band electromagnetic metasurface unit includes an upper dielectric substrate 2, a middle dielectric substrate 3, and a lower dielectric substrate 4 arranged from top to bottom. Metal layers 1 are printed on the upper surface of the upper dielectric substrate 2, the upper surface of the middle dielectric substrate 3, the upper surface of the lower dielectric substrate 4, and the lower surface of the lower dielectric substrate 4, respectively. Metal vias 5 are connected between the metal layers 1. Metal patterns of the same shape and size are printed on the metal layers 1. The metal layers 1 have a centrally symmetrical structure.

[0010] The metal pattern printed on the metal layer 1 includes a square patch 101 located at the center of the metal layer 1, a first square annular metal strip 103 and a second square annular metal strip 102 at the edge of the metal layer 1, and the second square annular metal strip 102 is located between the first square annular metal strip 103 and the square patch 101.

[0011] The side length of the square patch (101) is w, and the value of w is 0.5-2.68mm.

[0012] The phase is different if the size of the square patch (101) of the metal layer (1) of the unit is different. Within the range of w value of 0.5-2.68mm, a variety of Ka-band electromagnetic metasurface units are obtained. Each metasurface unit covers 60°, achieving uniform coverage of the entire 360° phase space.

[0013] Within the range of w (0.5-2.68 mm), a custom w value is used to obtain various Ka-band electromagnetic metasurface units. Each metasurface unit covers 60°, achieving uniform coverage of the entire 360° phase space. Specifically:

[0014] The first type of Ka-band electromagnetic metasurface unit, w = 2.68 mm, covers the phase space from 0° to 60°;

[0015] The second type of Ka-band electromagnetic metasurface unit, w = 2.53 mm, covers a phase space of 60° to 120°;

[0016] The third type of Ka-band electromagnetic metasurface unit, w = 2.30 mm, covers a phase space of 120° to 180°;

[0017] The fourth type of Ka-band electromagnetic metasurface unit, w = 2.00 mm, covers a phase space of 180° to 240°;

[0018] The fifth type of Ka-band electromagnetic metasurface unit, w = 1.3 mm, covers a phase space of 240° to 300°;

[0019] The sixth type of Ka-band electromagnetic metasurface unit, w = 0.5 mm, covers a phase space of 300° to 360°.

[0020] A low-profile Ka-band beam-scanning antenna with a Ka-band electromagnetic metasurface includes an upper Ka-band electromagnetic metasurface 6, a lower Ka-band electromagnetic metasurface 7, and a microstrip antenna feed 8 arranged from top to bottom. The geometric centers of the upper Ka-band electromagnetic metasurface 6, the lower Ka-band electromagnetic metasurface 7, and the microstrip antenna feed 8 are all located on the same coordinate axis z. By rotating and changing the angle δ1 between the upper Ka-band electromagnetic metasurface 6 and the central coordinate axis, and the angle δ2 between the lower Ka-band electromagnetic metasurface 7 and the central coordinate axis, beam scanning of the antenna in the elevation plane can be achieved.

[0021] Both the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7 are arranged with M*N arrayed Ka-band electromagnetic metasurface units; by using different Ka-band metasurface units at different positions on the lower Ka-band electromagnetic metasurface 7 to perform phase compensation for spatial phase delay, beam deflection is achieved; where M≥2 and N≥2.

[0022] The specific method for achieving beam scanning of the antenna in the elevation plane by rotating and changing the angle δ1 between the upper Ka-band electromagnetic metasurface 6 and the central coordinate axis, and the angle δ2 between the lower Ka-band electromagnetic metasurface 7 and the central coordinate axis is as follows:

[0023] ψ1 and ψ2 represent the azimuth planes where the linear phase drop direction of the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7 is located, where ψ1 and ψ2 are in the interval [-180°, 180°]; first, the initial azimuth angles of the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface (7) are set. Rotate the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7 in opposite directions along a central axis perpendicular to the two metasurfaces, so that... When α1 = α2, α1 is the angle between the upper Ka-band electromagnetic metasurface 6 and the central axis, and α2 is the angle between the lower Ka-band electromagnetic metasurface 7 and the central coordinate axis. The beam elevation angle θ and azimuth angle can be calculated.

[0024]

[0025] The specific method for achieving beam deflection is as follows:

[0026] 1) The electromagnetic wave radiated by the microstrip antenna feed 8 is approximately a spherical wave. The distances to the lower surfaces of different elements of the lower Ka-band electromagnetic metasurface 7 vary, resulting in a spatial phase delay. Therefore, different Ka-band metasurface elements are used at different locations on the lower Ka-band electromagnetic metasurface 7 to compensate for the spatial phase delay. This is to transform the electromagnetic wave radiated by the microstrip antenna feed 8 into a high-gain beam in a specified direction. The required spatial phase delay compensation is:

[0027]

[0028] Where k0 is the free space wavenumber, and the position coordinates of the (i,j)th metasurface unit are (x... (i,j) ,y (i,j) ), z is the distance from the phase center of the microstrip antenna feed 8 to the lower surface of the lower Ka-band electromagnetic metasurface 7;

[0029] 2) After compensating for the spatial phase delay, a high-gain beam perpendicular to the lower Ka-band electromagnetic metasurface 7 is generated, further changing the focusing direction of the main beam. An additional gradient phase is introduced on the lower Ka-band electromagnetic metasurface 7. The mathematical expression for the introduced gradient phase is:

[0030]

[0031] The sum of the spatial phase delay and the gradient phase is the transmission phase of each metasurface unit on the lower Ka-band electromagnetic metasurface 7. The mathematical expression is:

[0032]

[0033] Where φ0 is the reference phase, indicating that the phase shift distribution across the entire aperture is a relative value, not an absolute value;

[0034] 3) The electromagnetic waves travel the same distance from the lower Ka-band electromagnetic metasurface 7 to the upper Ka-band electromagnetic metasurface 6. Therefore, the upper Ka-band electromagnetic metasurface 6 only needs to change the main beam focusing direction. A gradient phase is introduced into the upper Ka-band electromagnetic metasurface 6, and the specific mathematical expression is as follows:

[0035]

[0036] The operating frequency band of the beam scanning antenna covers 30.5–32.5 GHz.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. This invention utilizes a rotating two-layer electromagnetic metasurface to achieve azimuth and elevation beam scanning in the 30.5GHz to 32.5GHz range. In the elevation plane, it can achieve a maximum scanning effect of ±56°. Compared with traditional phased arrays, this antenna eliminates the need for complex phase shifters and transceiver components, and also eliminates the need to design complex feed phase shift networks. Only a single feed antenna is required to obtain a high-gain, high-directivity beam. It also has the advantages of low profile, low loss, low cost, high gain, and ease of manufacturing. The structure is relatively simple and easy to implement in engineering, making it more suitable for high-power, non-high-speed beam scanning applications.

[0039] 2. In this invention, the metal patches of the metasurface unit are connected through metallized vias located at the geometric center of the dielectric substrate. These vias can improve the transmission phase of the unit, and by changing the size of the metal patches, precise gradient phase division can be achieved, enabling efficient phase control of electromagnetic waves. Traditional Risley prism antennas are relatively heavy and bulky, making them difficult to integrate. Metasurfaces composed of metasurface units achieve the same function as Risley prisms while featuring a low profile, small size, and ease of operation and integration.

[0040] In summary, this invention utilizes a rotating double-layer electromagnetic metasurface to achieve beam scanning in the elevation plane from 30.5 GHz to 32.5 GHz, achieving a maximum scanning range of ±56° within the frequency band. Compared to active phased arrays, this invention offers advantages such as low profile, low loss, low cost, high gain, and ease of manufacturing. Attached Figure Description

[0041] Figure 1 This is a structural diagram of the Ka-band electromagnetic metasurface unit of the present invention.

[0042] Figure 2 This is a side view of the Ka-band electromagnetic metasurface unit structure of the present invention.

[0043] Figure 3 This is a front view of the Ka-band electromagnetic metasurface unit structure of the present invention.

[0044] Figure 4 This is a front view of the structure of the six Ka-band electromagnetic metasurface units with different phases of the present invention.

[0045] Figure 5 This represents the transmission amplitude of the six Ka-band electromagnetic metasurface units with different phases in the frequency band of this invention.

[0046] Figure 6 The transmission phases of the six Ka-band electromagnetic metasurface units with different phases in this invention are within the frequency band.

[0047] Figure 7 This is a diagram of the lower Ka-band electromagnetic metasurface structure of the present invention.

[0048] Figure 8 This is a diagram of the upper Ka-band electromagnetic metasurface structure of the present invention.

[0049] Figure 9 This is a structural diagram of the beam scanning antenna of the present invention.

[0050] Figure 10 This is the radiation pattern of the beam scanning antenna of the present invention when the two metasurfaces are rotated 180° relative to each other, with phi = 0°.

[0051] Figure 11 This is the radiation pattern of the beam scanning antenna of the present invention when the two metasurfaces are rotated 90° relative to each other, and phi = 0°.

[0052] Figure 12 This is the radiation pattern of the beam scanning antenna of the present invention when the two metasurfaces are rotated relative to each other by 60° and phi = 0°.

[0053] Figure 13 This is the radiation pattern of the beam scanning antenna of the present invention when the two metasurfaces are rotated 0° relative to each other, and phi = 0°. Detailed Implementation

[0054] The embodiments and effects of the present invention will be further described below with reference to the accompanying drawings.

[0055] Reference Figure 1 , Figure 2 and Figure 3 A Ka-band electromagnetic metasurface unit includes an upper dielectric substrate 2, a middle dielectric substrate 3, and a lower dielectric substrate 4 arranged from top to bottom, as well as four metal layers 1 printed on the upper surface of the upper dielectric substrate, the upper surface of the middle dielectric substrate, the upper surface of the lower dielectric substrate, and the lower surface of the lower dielectric substrate. The shape and size of the metal patterns in each metal layer 1 are the same, and metal through holes 5 are connected between each metal layer 1.

[0056] The metal layer 1 includes a square patch 101, a square annular metal strip 102, and a square annular metal strip 103 from the inside to the outside. The square patch 101 is located at the center of the unit, and the square annular metal strip 102 and the square annular metal strip 103 are located at the edge of the unit.

[0057] Reference Figure 4 A Ka-band electromagnetic metasurface unit employs a centrosymmetric structure and is insensitive to polarization. Different sizes of the square patches 101 in each metal layer 1 result in different phases. By taking the following values ​​for the side lengths of the square patches 101, six Ka-band electromagnetic metasurface units are obtained, which can essentially cover the entire phase space from 0° to 360°:

[0058] The first type of Ka-band electromagnetic metasurface unit, w = 2.68 mm;

[0059] The second type of Ka-band electromagnetic metasurface unit has a w = 2.53 mm.

[0060] The third type of Ka-band electromagnetic metasurface unit, w = 2.30 mm;

[0061] The fourth type of Ka-band electromagnetic metasurface unit, w = 2.00 mm;

[0062] The fifth type of Ka-band electromagnetic metasurface unit, w = 1.3 mm;

[0063] The sixth type of Ka-band electromagnetic metasurface unit, w = 0.5 mm;

[0064] Reference Figure 7 and Figure 8 Both the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7 are arranged with M*N arrayed Ka-band electromagnetic metasurface units. Different Ka-band metasurface units are used at different positions to compensate for the spatial phase of electromagnetic waves in order to achieve beam deflection; wherein, M≥2 and N≥2.

[0065] Reference Figure 9A low-profile Ka-band beam scanning antenna based on electromagnetic metasurface loading includes an upper Ka-band electromagnetic metasurface 6, a lower Ka-band electromagnetic metasurface 7, and a microstrip antenna feed 8 arranged from top to bottom. The geometric centers of the upper Ka-band electromagnetic metasurface 6, the lower Ka-band electromagnetic metasurface 7, and the microstrip antenna feed 8 are all located on the same coordinate axis z. By rotating and changing the angle α1 between the upper Ka-band electromagnetic metasurface 6 and the central coordinate axis, and the angle α2 between the lower Ka-band electromagnetic metasurface 7 and the central coordinate axis, beam scanning of the antenna in the elevation plane can be achieved.

[0066] The electromagnetic wave radiated by the microstrip antenna feed 8 is approximately a plane wave. The distance to the lower surface of each element of the lower Ka-band electromagnetic metasurface 7 varies, resulting in a spatial phase delay. To convert the electromagnetic wave radiated by the feed into a high-gain beam in a specified direction, different elements are needed at different locations for phase compensation. The required spatial phase delay is:

[0067]

[0068] Where k0 is the free space wavenumber, and the position coordinates of the (i,j)th metasurface unit are (x... (i,j) ,y (i,j) ), z is the distance from the phase center of the feed to the lower surface of the lower Ka-band electromagnetic metasurface 7;

[0069] After compensating for the spatial phase delay, the lower Ka-band electromagnetic metasurface 7 can generate a high-gain beam perpendicular to the aperture. If it is necessary to further change the main beam focusing direction... Therefore, a gradient phase needs to be introduced on the lower Ka-band electromagnetic metasurface 7. The mathematical expression for the gradient phase required for each Ka-band metasurface unit is:

[0070]

[0071] The sum of the spatial phase delay and the gradient phase is the transmission phase of each metasurface unit on the lower Ka-band electromagnetic metasurface 7. The mathematical expression is:

[0072]

[0073] Here, φ0 is the reference phase, which indicates that the phase shift distribution across the entire aperture is a relative value, not an absolute value.

[0074] The transmission phase of each metasurface unit of the upper Ka-band electromagnetic metasurface 6 is The electromagnetic waves are in phase after being transmitted through the lower Ka-band electromagnetic metasurface 7, therefore the upper Ka-band electromagnetic metasurface 6 only needs to change the main beam focusing direction. The specific mathematical expression is:

[0075]

[0076] By coaxially rotating the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7 in opposite directions, the main beam is scanned in a 3-D conical space. ψ1 and ψ2 represent the azimuth planes where the linear phase drop directions of the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7 are located, where ψ1 and ψ2 are within the interval [-180°, 180°]. Specifically:

[0077] First, set the initial azimuth angles of the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7. Rotate the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7 in opposite directions along an axis perpendicular to both metasurfaces, so that... Where δ1 and δ2 are the rotation angles between the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7, respectively. When α1 = α2, the beam elevation angle θ and azimuth angle can be calculated.

[0078]

[0079] The beam scanning antenna operates in the frequency band of 30.5–32.5 GHz. At 31.5 GHz, by rotating the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7, a maximum scanning angle of 56° can be achieved in the elevation plane when δ = δ1 + δ2 = 0°; when δ = δ1 + δ2 = 180°, the scanning angle is 0° and the maximum gain is 20.14 dB.

[0080] Combination Figure 1 and Figure 2 As shown, in this embodiment, the height of the upper dielectric substrate 2, the middle dielectric substrate 3, and the lower dielectric substrate 4 is h = 0.8 mm, the radius of the metal via 5 is r = 0.2 mm, the upper, middle, and lower dielectric substrates are all of model TX220F, with a relative permittivity of 2.2, a loss tangent of 0.001, an overall cross-sectional height of 2.4 mm, and a planar dimension of 4 × 4 mm.

[0081] Combination Figure 3 As shown, in this embodiment, the width w1 of the square annular metal strip 102 in the metal layer 1 is 0.1 mm, and the width w2 of the square annular metal strip 103 is 0.1 mm.

[0082] Combination Figure 9As shown in this embodiment, the beam scanning antenna has an upper Ka-band electromagnetic metasurface 6 composed of 20×20 Ka-band electromagnetic metasurface units, with the units at its four corners removed; and a lower Ka-band electromagnetic metasurface 7 composed of 20×20 Ka-band electromagnetic metasurface units, with the units at its four corners removed.

[0083] The effects of the present invention will be further explained below with reference to simulation experiments.

[0084] Simulation experimental conditions

[0085] The simulation experiments of this invention utilize the Ansys Electronics Desktop software platform installed on computer hardware to simulate Ka-band electromagnetic metasurface units and beam scanning antennas.

[0086] Simulation content and result analysis

[0087] Simulation 1: The transmission coefficient of the metasurface unit in this embodiment of the invention was simulated and calculated in the range of 30.5–32.5 GHz. The results are as follows: Figure 5 and Figure 6 As shown.

[0088] Figure 5 The figure shows the transmission amplitude results of six different Ka-band electromagnetic metasurface units. It can be seen from the figure that the transmission amplitude in the 30.5-32.5 GHz band is above -2 dB, which indicates a high transmission amplitude.

[0089] Figure 6 The figure shows the transmission phase results of six different Ka-band electromagnetic metasurface units. It can be seen from the figure that the transmission phase in the 31.5 GHz band satisfies a 60° phase difference, and the 60° phase difference can be approximately achieved in the 30.5–32.5 GHz band.

[0090] Simulation 2: The beam scanning antenna of this embodiment of the invention was simulated in the range of 30.5–32.5 GHz, where the relative rotation angle between the two Ka-band electromagnetic metasurfaces was 180°. The results are as follows: Figure 10 As shown.

[0091] Figure 10 The figure shows the radiation pattern of the beam scanning antenna in this embodiment in the phi = 0° plane. As can be seen from the figure, the maximum gain at 31.5 GHz points to 0°, which is consistent with the theoretical calculation. The maximum gain is 21.14 dB.

[0092] Simulation 3: The beam scanning antenna of this embodiment of the invention was simulated in the range of 30.5–32.5 GHz, where the relative rotation angle between the two Ka-band electromagnetic metasurfaces was 90°. The results are as follows: Figure 11 As shown.

[0093] Figure 11 The figure shows the radiation pattern of the beam scanning antenna in this embodiment in the phi = 0° plane. As can be seen from the figure, the maximum gain at 31.5 GHz points to 35°, which is consistent with the theoretical calculation, and the maximum gain is 19.80 dB.

[0094] Simulation 4: The beam scanning antenna of this embodiment of the invention was simulated in the range of 30.5–32.5 GHz, where the relative rotation angle between the two Ka-band electromagnetic metasurfaces was 60°. The results are as follows: Figure 12 As shown.

[0095] Figure 12 The figure shows the radiation pattern of the beam scanning antenna in this embodiment in the phi = 0° plane. As can be seen from the figure, the maximum gain at 31.5 GHz points to 43°, which is consistent with the theoretical calculation, and the maximum gain is 18.46 dB.

[0096] Simulation 5: The beam scanning antenna of this embodiment of the invention was simulated in the range of 30.5–32.5 GHz, where the relative rotation angle between the two Ka-band electromagnetic metasurfaces was 0°. The results are as follows: Figure 13 As shown.

[0097] Figure 13 The figure shows the radiation pattern of the beam scanning antenna in this embodiment in the phi = 0° plane. As can be seen from the figure, the maximum gain at 31.5 GHz points to 56°, which is consistent with the theoretical calculation, and the maximum gain is 18.28 dB.

[0098] The metasurface unit in Simulation 1 exhibits good gradient phase characteristics and good transmission coefficient within the desired frequency band of 30.5–32.5 GHz, making it suitable as a gradient phase metasurface unit. As can be seen from Simulation 1, compared to existing technologies, the metasurface unit of this invention shows a smoother variation at different frequency points.

[0099] In simulations 2, 3, 4, and 5, within the operating frequency band of 30.5–32.5 GHz, the beam-scanning antenna can achieve precise beam scanning by rotating the upper Ka-band electromagnetic metasurface 6 and the lower Ka-band electromagnetic metasurface 7. Simultaneously, it can achieve a scanning range of ±56° within the frequency band, with good scanning performance. As can be seen from the above simulation examples, compared with the prior art, the present invention can achieve a larger beam scanning range and lower gain loss.

[0100] The specific embodiments of the present invention do not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the protection scope of the claims of the present invention.

Claims

1. A Ka-band electromagnetic metasurface unit, comprising an upper dielectric substrate (2), a middle dielectric substrate (3), and a lower dielectric substrate (4) arranged from top to bottom, wherein a metal layer (1) is printed on the upper surface of the upper dielectric substrate (2), the upper surface of the middle dielectric substrate (3), the upper surface of the lower dielectric substrate (4), and the lower surface of the lower dielectric substrate (4), characterized in that: Metal through holes (5) are connected between each metal layer (1), and metal patterns of the same shape and size are printed on the metal layer (1); the metal layer (1) has a centrally symmetrical structure. The metal pattern printed on the metal layer (1) includes a square patch (101) located at the center of the metal layer (1), a first square annular metal strip (103) and a second square annular metal strip (102) at the edge of the metal layer (1), and the second square annular metal strip (102) is located between the first square annular metal strip (103) and the square patch (101). Different sizes of the square patch (101) result in different phases; the side length of the square patch (101) is w, which ranges from 0.5 to 2.68 mm. Within this range, custom values ​​of w are used to obtain various Ka-band electromagnetic metasurface units. Each metasurface unit covers 60°, achieving uniform coverage of the entire 360° phase space. Specifically: The first type of Ka-band electromagnetic metasurface unit, w = 2.68 mm, covers the phase space from 0° to 60°; The second type of Ka-band electromagnetic metasurface unit, w = 2.53 mm, covers a phase space of 60° to 120°; The third type of Ka-band electromagnetic metasurface unit, w = 2.30 mm, covers a phase space of 120° to 180°; The fourth type of Ka-band electromagnetic metasurface unit, w = 2.00 mm, covers a phase space of 180° to 240°; The fifth type of Ka-band electromagnetic metasurface unit, w = 1.3 mm, covers a phase space of 240° to 300°; The sixth type of Ka-band electromagnetic metasurface unit, w = 0.5 mm, covers a phase space of 300° to 360°.

2. A low-profile Ka-band beam scanning antenna based on the Ka-band electromagnetic metasurface element of claim 1, characterized in that, The antenna includes an upper Ka-band electromagnetic metasurface (6), a lower Ka-band electromagnetic metasurface (7), and a microstrip antenna feed (8) arranged from top to bottom. The geometric centers of the upper Ka-band electromagnetic metasurface (6), the lower Ka-band electromagnetic metasurface (7), and the microstrip antenna feed (8) are all located on the same coordinate axis z. By rotating and changing the angle δ1 between the upper Ka-band electromagnetic metasurface (6) and the central coordinate axis, and the angle δ2 between the lower Ka-band electromagnetic metasurface (7) and the central coordinate axis, the antenna beam scanning in the elevation plane can be achieved.

3. The low-profile Ka-band beam scanning antenna with a loaded Ka-band electromagnetic metasurface according to claim 2, characterized in that, Both the upper Ka-band electromagnetic metasurface (6) and the lower Ka-band electromagnetic metasurface (7) are arranged with M*N arrayed Ka-band electromagnetic metasurface units; by using different Ka-band metasurface units at different positions on the lower Ka-band electromagnetic metasurface (7) to perform phase compensation for spatial phase delay, beam deflection is achieved; where M≥2 and N≥2.

4. The low-profile Ka-band beam scanning antenna with a loaded Ka-band electromagnetic metasurface according to claim 2, characterized in that, The specific method for achieving beam scanning of the antenna in the elevation plane by rotating and changing the angle δ1 between the upper Ka-band electromagnetic metasurface (6) and the central coordinate axis, and the angle δ2 between the lower Ka-band electromagnetic metasurface (7) and the central coordinate axis is as follows: ψ1 and ψ2 represent the azimuth planes where the linear phase drop direction of the upper Ka-band electromagnetic metasurface (6) and the lower Ka-band electromagnetic metasurface (7) is located, where ψ1 and ψ2 are in the interval [-180°, 180°]; first, the initial azimuth angles of the upper Ka-band electromagnetic metasurface (6) and the lower Ka-band electromagnetic metasurface (7) are set. Rotate the upper Ka-band electromagnetic metasurface (6) and the lower Ka-band electromagnetic metasurface (7) in opposite directions along a central axis perpendicular to the two metasurfaces, so that... When α1 = α2, α1 is the angle between the upper Ka-band electromagnetic metasurface (6) and the central axis, and α2 is the angle between the lower Ka-band electromagnetic metasurface (7) and the central coordinate axis. The beam elevation angle θ and azimuth angle can be obtained by calculation.

5. The low-profile Ka-band beam scanning antenna with a loaded Ka-band electromagnetic metasurface according to claim 3, characterized in that, The specific method for achieving beam deflection is as follows: 1) The electromagnetic wave radiated by the microstrip antenna feed (8) is approximately a spherical wave. The distances to the lower surfaces of the various elements of the lower Ka-band electromagnetic metasurface (7) are different, resulting in a spatial phase delay. Based on this, different Ka-band metasurface elements are used at different positions of the lower Ka-band electromagnetic metasurface (7) to compensate for the spatial phase delay. This is to change the electromagnetic wave radiated by the microstrip antenna feed (8) into a high-gain beam in a specified direction. The required spatial phase delay compensation is: Where k0 is the free space wavenumber, and the position coordinates of the (i,j)th metasurface unit are (x... (i,j) ,y (i,j) ), z is the distance from the phase center of the microstrip antenna feed (8) to the lower surface of the lower Ka-band electromagnetic metasurface (7); 2) After compensating for the spatial phase delay, a high-gain beam perpendicular to the lower Ka-band electromagnetic metasurface (7) is generated, further changing the focusing direction of the main beam. An additional gradient phase is introduced on the lower Ka-band electromagnetic metasurface (7). The mathematical expression for the introduced gradient phase is: The sum of spatial phase delay and gradient phase is the transmission phase of each metasurface unit on the lower Ka-band electromagnetic metasurface (7). The mathematical expression is: Where φ0 is the reference phase, indicating that the phase shift distribution across the entire aperture is a relative value, not an absolute value; 3) The electromagnetic wave travels the same distance from the lower Ka-band electromagnetic metasurface (7) to the upper Ka-band electromagnetic metasurface (6). Therefore, the upper Ka-band electromagnetic metasurface (6) only needs to change the main beam focusing direction. A gradient phase is introduced into the upper Ka-band electromagnetic metasurface (6), and the specific mathematical expression is as follows:

6. The low-profile Ka-band beam scanning antenna with a loaded Ka-band electromagnetic metasurface according to any one of claims 2 to 5, characterized in that, The operating frequency band of the beam scanning antenna covers 30.5–32.5 GHz.

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