Ka-band metasurface unit based on low-profile and loaded beam-scanning antenna

Abstract

A low-profile Ka-band metasurface unit comprises an upper dielectric substrate and a lower dielectric substrate, wherein the upper surface of the upper dielectric substrate, the lower surface of the lower dielectric substrate, and the lower surface of the upper dielectric substrate or the upper surface of the lower dielectric substrate are all printed with metal layers with identical patterns and opposite projections; the metal layers comprise K first curved metal wires and K metal wires; K first metallized vias and K second metallized vias are provided through the upper and lower dielectric substrates, wherein the first metallized vias connect the first curved metal wires with opposite projections on each metal layer; and the second metallized vias connect the metal wires with opposite projections on each metal layer. The present invention also provides a corresponding beam antenna, which achieves beam deflection by using different metasurface units at different locations for phase compensation, and achieves scanning of the main beam on the pitch plane by changing the relative rotation angle between the two metasurfaces.

Description

Technical Field

[0001] The present invention belongs to the field of antenna technology and relates to a beam scanning antenna, specifically to a low-profile Ka-band metasurface unit and a loaded beam scanning antenna, which can be used for millimeter-wave antenna communication and high-resolution radar imaging. Background Art

[0002] With the development of modern wireless technology, communication equipment with wide bandwidth, high transmission rate, miniaturization and multi-functional integration has become a development trend. Since high-frequency bands such as millimeter waves can meet the above requirements, they have become a research hotspot in recent years. The Ka-band low-profile electromagnetic metasurface array-loaded beam scanning antenna involved in the present invention has a center frequency of 30.4GHz and is a millimeter-wave antenna. Compared with low-frequency bands, millimeter-wave antenna equipment has the advantages of wide bandwidth, small structure size, good communication security, and high target recognition resolution. At the same time, antennas in the Ka band have important applications in systems such as high-resolution radar, point-to-point data transmission, precision guidance, and high-resolution radar imaging.

[0003] Beam-scanning antennas based on electromagnetic metasurface arrays and phased array antennas with mechanical scanning control the antenna's radiation direction by applying a phase difference to the signal from each element in the metasurface array. As the phase difference changes, the array's radiation pattern also scans in different azimuths. By adjusting the phase difference between adjacent radiating elements by varying the relative rotation angle between the two azimuth disks, the main beam is scanned in the elevation plane. If the two azimuth disks rotate synchronously, scanning in the azimuth plane is also possible. The primary way to reduce the cost of phased arrays is to reduce the cost of T / R units and phase shifters. This significantly reduces the cost of this type of phased array.

[0004] In 2022, P. Wang, W. Ren, and others published a paper titled "Dual-Band Beam-Scanning Antenna at Ka-Bandby Rotation of Two Transmitarrays" in the 9th issue of the IEEE Antennas and Wireless Propagation Letters. The proposed antenna unit achieves dual-frequency beam scanning with a narrow operating band. The paper achieves a 360-degree phase change by varying the size of the unit structure, thereby changing the propagation direction or polarization of the electromagnetic wave. Phase-gradient metasurfaces are achieved by rationally arranging multiple similar unit structures in a periodic arrangement. Phase changes can be achieved by varying the size or orientation of the unit structure.

[0005] For example, patent CN115051157A discloses an electromagnetic metamaterial structure loaded with PIN diodes to achieve phase control and beam steering by changing the state of diodes at different locations. Summary of the Invention

[0006] To overcome the shortcomings of the above-mentioned prior art, the present invention aims to provide a low-profile Ka-band metasurface unit and its loaded beam scanning antenna to solve the technical problems of narrow impedance bandwidth and narrow scanning angle of existing phased array antennas. There is no need to design complex feeding networks and power splitter structures. There is also no high cost of phased array antennas. The overall antenna structure is simpler, the size is smaller, and it is easy to implement and mass-produce.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A low-profile Ka-band metasurface unit comprises an upper dielectric substrate and a lower dielectric substrate, wherein the upper surface of the upper dielectric substrate, the lower surface of the lower dielectric substrate, and the lower surface of the upper dielectric substrate or the upper surface of the lower dielectric substrate are all printed with metal layers with the same pattern and opposite projections;

[0009] The metal layer includes K first curved metal wires and K metal wires; the K first curved metal wires are located on a first circumference and are symmetrically distributed around the center; one end of each metal wire is connected at the center, and the other end of each metal wire is opposite to the midpoint of a first curved metal wire and has a spacing therebetween; wherein K>1;

[0010] K first metallized vias and K second metallized vias are provided through the upper dielectric substrate and the lower dielectric substrate. The first metallized vias connect first arc-shaped metal wires with opposite projections on each metal layer; the second metallized vias connect metal wires with opposite projections on each metal layer.

[0011] In one embodiment, the metal layer also includes K second arc-shaped metal wires, and the K second arc-shaped metal wires are located on the second circumference and are symmetrically distributed around the center; the first circumference and the second circumference are cocentric, and the radius of the first circumference is greater than the radius of the second circumference; the other end of each metal wire is connected to the midpoint of a second arc-shaped metal wire.

[0012] In one embodiment, different phase gradients are achieved by changing the sizes of the first curved metal line, the second curved metal line, and the metal line. The more phase gradient units there are, the more accurate the result is during phase compensation.

[0013] In one embodiment, K=4, and the number of phase gradients is 6, that is, 6 types of Ka-band metasurface units are used to implement gradient division of the phase. By taking the following values for the midpoint distance l1 of the two second curved metal wires connected by the two metal wires located on the same straight line, the angle Theta1 of the second curved metal wire, and the angle Theta2 of the first curved metal wire, full phase coverage is achieved, and the transmission loss is within 1.5 dB, and 6 types of Ka-band metasurface units are obtained:

[0014] The first Ka-band metasurface unit has l1=3.3mm, Theta1=10deg, Theta2=10deg;

[0015] The second Ka-band metasurface unit has l1=2.8mm, Theta1=25deg, Theta2=15deg;

[0016] The third Ka-band metasurface unit has l1=1.87mm, Theta1=20deg, Theta2=45deg;

[0017] The fourth Ka-band metasurface unit has l1 = 3 mm, Theta1 = 8 degrees, and Theta2 = 36 degrees.

[0018] The fifth Ka-band metasurface unit has l1=3.2mm, Theta1=13.2deg, Theta2=35deg;

[0019] The sixth Ka-band metasurface unit, l1 = 3.15 mm, Theta1 = 10 degrees, Theta2 = 10 degrees;

[0020] The transmission amplitude of the six Ka-band metasurface units in the 29.5-31.2 GHz frequency band is above -1.5 dB, and the transmission phase in the 29.5-31.2 GHz frequency band satisfies a 60° phase difference, and satisfies a 60° equal phase difference at the 30.4 GHz frequency point, and an approximate 60° phase difference can be achieved at both ends of the frequency band.

[0021] In one embodiment, the upper dielectric substrate and the lower dielectric substrate are bonded together using a prepreg, and both the upper dielectric substrate and the lower dielectric substrate are penetrated by a first metallized via and a second metallized via.

[0022] The present invention also provides a beam scanning antenna, comprising a horn antenna and a Ka-band metasurface, wherein the Ka-band metasurface is composed of an array of M×N low-profile Ka-band metasurface units, and the Ka-band metasurface is arranged at the aperture position of the horn antenna. Phase compensation is performed by regularly placing Ka-band metasurface units with different phase gradients to achieve beam deflection; wherein M≥2, N≥2; there are two Ka-band metasurfaces, which are coaxially distributed above and below, and beam scanning is achieved by rotating the two Ka-band metasurfaces about an axis orthogonal to the two Ka-band metasurfaces.

[0023] In one embodiment, the spatial phase delay caused by the feed irradiating different positions is calculated by the following formula, that is, the compensation phase required for each position

[0024]

[0025] Then, Ka-band metasurface units with corresponding phase differences are placed at corresponding positions to generate a high-gain beam perpendicular to the aperture surface.

[0026] Among them, D (i,j) is the spatial distance between the phase center of the feed and the (i, j)th Ka-band metasurface unit, k0 is the free space wave number, and the position coordinates of the (i, j)th Ka-band metasurface unit are (x (i,j) ,y (i,j) ), z is the distance between the phase center of the horn antenna and the Ka-band metasurface.

[0027] In one embodiment, for the upper Ka-band metasurface, the phase difference that needs to be compensated for each Ka-band metasurface unit is calculated as follows:

[0028]

[0029] For the lower Ka-band metasurface, the phase difference that needs to be compensated for each Ka-band metasurface unit is the phase shift distribution required by the transmission array aperture. The calculation is as follows:

[0030]

[0031] Where, is the focusing direction of the main beam; φ0 is the reference phase value, and its physical meaning indicates that the phase shift distribution of the entire aperture is a relative value rather than an absolute value.

[0032] In one embodiment, the beam pitch angle θ and azimuth angle are calculated by the following steps:

[0033] First, determine the initial azimuths of the two Ka-band metasurfaces and equal;

[0034] Secondly, the elevation beam scanning is realized and the two Ka-band metasurfaces are rotated in opposite directions along the same rotation axis perpendicular to the two Ka-band metasurfaces. Where ψ1 and ψ2 represent the azimuth planes of the linear phase decrease directions of the lower Ka-band metasurface and the upper Ka-band metasurface, respectively. ψ1 and ψ2 are in the interval [-180°, 180°]. δ1 and δ2 are the rotation angles of the lower Ka-band metasurface and the upper Ka-band metasurface, respectively. When the beam deflection angles α1 and α2 of the two Ka-band metasurfaces are equal, the beam pitch angle θ and azimuth angle can be obtained.

[0035]

[0036]

[0037] In one embodiment, when the deflection angle δ of the two Ka-band metasurfaces is 180°, the deflection angle of the antenna's maximum radiation direction is 0°, the maximum gain is 21.30dB, and the sidelobe level is -16.84dB; when the deflection angle δ of the two Ka-band metasurfaces is 90°, the deflection angle of the antenna's maximum radiation direction is 35.35°, the maximum gain is 19.98dB, and the sidelobe level is -15.97dB; when the deflection angle δ of the two Ka-band metasurfaces is 0°, the deflection angle of the antenna's maximum radiation direction is 50°; wherein δ is the difference between δ1 and δ2.

[0038] In one embodiment, the operating bandwidth of the beam scanning antenna covers 29.5-31.2 GHz.

[0039] Compared to traditional phased array antennas, mechanically beam-steerable antennas do not use any electronic phase-shifting mechanisms. As a result, they benefit from lower losses, reduced cost, and are generally more suitable for high-power applications. However, this comes at the expense of reduced scanning speed. Therefore, in applications where high-power handling, lower cost, and reduced complexity are prioritized over high-speed beam scanning, mechanical beam steering technology can provide a good alternative to traditional active or passive electronically steered arrays.

[0040] The metasurface in this invention utilizes three layers of interconnected conductive metal patches and two dielectric layers bonded together via a prepreg layer. The introduction of metallized vias improves the transmission phase and enables efficient phase control of electromagnetic waves. Multi-layered metasurface structures can result in significant losses, ultimately impacting antenna performance. This invention improves antenna integration and achieves superior performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is the 3D model of the super surface unit of the present invention.

[0042] Figure 2 It is a front view of the super surface unit of the present invention.

[0043] Figure 3 It is a cross-sectional view of the super surface unit of the present invention.

[0044] Figure 4 This is a six-phase gradient unit structure of the present invention.

[0045] Figure 5 It is the transmission amplitude of the six phase gradient units of the present invention.

[0046] Figure 6 It is the transmission phase of the six phase gradient units of the present invention.

[0047] Figure 7 This is the structural diagram of the first-layer metasurface (PSS1) array of the present invention.

[0048] Figure 8 This is the structural diagram of the second-layer metasurface (PSS2) array of the present invention.

[0049] Figure 9 It is the overall structure diagram of the beam scanning antenna of the present invention.

[0050] Figure 10 This is the δ=180° double-layer metasurface loaded antenna pattern of the present invention.

[0051] Figure 11 This is the δ=90° double-layer metasurface loaded antenna pattern of the present invention.

[0052] Figure 12 This is the δ=90° double-layer metasurface loaded antenna pattern of the present invention. DETAILED DESCRIPTION

[0053] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0054] like Figure 1 、 Figure 2 and Figure 3 As shown, the present invention is a low-profile Ka-band metasurface unit comprising an upper dielectric substrate 2 and a lower dielectric substrate 3 stacked one above the other, and three metal layers 1 printed on the two lower dielectric substrates. It is easy to understand that there is a solidified layer between the upper dielectric substrate 2 and the lower dielectric substrate 3. Clearly, the three metal layers 1 can be printed on the upper surface of the upper dielectric substrate 2, the lower surface of the lower dielectric substrate 3, and either the lower surface of the upper dielectric substrate 2 or the upper surface of the lower dielectric substrate 3, respectively. Each metal layer 1 has the same pattern and its projections are opposite to each other.

[0055] refer to Figure 2 , a metal layer 1 of the present invention includes K first curved metal wires 103 and K metal wires 105; the K first curved metal wires 103 are located on the first circumference and are symmetrically distributed around the center; one end of each metal wire 105 is connected at the center, and the other end of each metal wire 105 is opposite to the midpoint of a first curved metal wire 103 and has a spacing therebetween; obviously, K>1.

[0056] To achieve connection at the projected position, the present invention provides first metallized vias 101 and second metallized vias 102 that penetrate the upper dielectric substrate 2 and the lower dielectric substrate 3. The number of first metallized vias 101 and second metallized vias 102 is the same as the number of first curved metal wires 103 and metal wires 105, both K. The first metallized vias 101 connect the first curved metal wires 103 projected opposite to each other on each metal layer 1; the second metallized vias 102 connect the metal wires 105 projected opposite to each other on each metal layer 1.

[0057] The present invention adopts a centrosymmetric structure to make the metasurface unit polarization-insensitive. Existing metasurface units require multiple layers of dielectric plates to achieve full phase gradient coverage. The thickness of the dielectric layer increases the insertion loss of the antenna. The metasurface unit of the present invention achieves full phase coverage by introducing first and second metallized vias 101 and 102. Using three layers of metal and two dielectric substrates, the thickness of the metasurface array is reduced. The operating bandwidth covers 29.5-31.2 GHz, reducing insertion loss and increasing antenna radiation efficiency.

[0058] In some embodiments of the present invention, each metal layer 1 also includes K second arc-shaped metal wires 104, and the K second arc-shaped metal wires 104 are located on the second circumference and are symmetrically distributed around the center; the first circumference and the second circumference are cocentric, and the radius of the first circle is greater than the radius of the second circle; the other end of each metal wire 105 is connected to the midpoint of a second arc-shaped metal wire 104.

[0059] In the present invention, the widths of first curved metal line 103, second curved metal line 104, and metal line 105 are represented as w1, the midpoint distance between two second curved metal lines 104 connected by two metal lines 105 located on the same straight line is represented as l1, the angle of second curved metal line 104 is represented as Theta1, and the angle of first curved metal line 103 is represented as Theta2. By varying some or all of these dimensions, different phase gradients can be obtained to achieve full phase coverage. Obviously, the more phase gradient units, the more accurate the phase compensation results.

[0060] Figure 3Figure 1 is a cross-sectional diagram of a metasurface unit. In some embodiments of the present invention, an upper dielectric substrate 2 and a lower dielectric substrate 3 are bonded together using a prepreg. Both upper and lower dielectric substrates 2 and 3 are penetrated by first and second metallized vias 101 and 102. The heights of the upper and lower dielectric substrates 2 and 3 are denoted as h1, and the height of the prepreg is denoted as h2. Clearly, in the present invention, h1>h2.

[0061] Combine Figure 2 As shown, the upper dielectric substrate 2 and the lower dielectric substrate 3 of the present invention are both square, which is represented by p, and the metal layer 1 is located at its center. In the embodiment of the present invention, p = 5mm, h1 + h2 = 2.075mm, that is, the plane size of the metasurface unit is 5×5mm, and the cross-sectional height is 2.075mm.

[0062] In some embodiments of the present invention, K=4 and the number of phase gradients is 6, that is, 6 types of Ka-band metasurface units are used to implement phase gradient division. Figure 4 As shown, there are 6 types of Ka-band metasurface unit structures corresponding to 6 types of phase gradients. The more phase gradient units there are, the more accurate the result will be during phase compensation, but the workload will also be greater. Therefore, the present invention uses 6 phase gradients to implement beam compensation. Six types of Ka-band metasurface units are used to implement gradient division of the phase, and full phase coverage is achieved by adjusting the structural parameters l1, Theta1, and Theta2 of the metal layer 1, and the transmission loss is within 1.5dB. Table 1 shows the size diagram corresponding to the 6 types of Ka-band metasurface units, where units 1 to 6 are the first to sixth types of Ka-band metasurface units, respectively.

[0063] Table 1 Parameters corresponding to phase gradient metasurface units

[0064]

[0065]

[0066] like Figure 5 Shown is the transmission amplitude diagram of 6 types of Ka-band metasurface units. From the figure, it can be seen that the transmission amplitude of the 6 types of Ka-band metasurface units in the 29.5-31.2GHz frequency band is above -1.5dB, which has a high transmission amplitude and is suitable for use as a transmission metasurface.

[0067] like Figure 6The figure shows the transmission phase diagrams of six Ka-band metasurface units. The diagram shows that the transmission phases of these six Ka-band metasurface units satisfy a 60° phase difference within the 29.5-31.2 GHz frequency band. At 30.4 GHz, they satisfy a 60° phase difference, and a similar 60° phase difference is achieved at both ends of the frequency band, making them suitable for use as transmission metasurfaces.

[0068] Based on the above-mentioned Ka-band metasurface unit, the present invention provides a corresponding beam scanning antenna, including a horn antenna and a Ka-band metasurface, wherein the Ka-band metasurface is composed of an array of M×N Ka-band metasurface units, which is a typical transmission metasurface, with M≥2 and N≥2. The Ka-band metasurface is arranged at the aperture of the horn antenna, and phase compensation is performed by regularly placing Ka-band metasurface units with different phase gradients to achieve beam deflection. There are two Ka-band metasurfaces, which are coaxially distributed above and below. Beam scanning is achieved by rotating the two Ka-band metasurfaces about an axis orthogonal to the two Ka-band metasurfaces.

[0069] The beam-scanning antenna of this invention uses different metasurface units at different locations for phase compensation, achieving beam deflection. By varying the relative rotation angle between two azimuth disks, the phase difference between adjacent radiating units is adjusted, enabling the main beam to be scanned in the elevation plane. This creates a Ka-band beam-scanning antenna with efficient radiation and flexible beam control, suitable for millimeter-wave antenna communications and high-resolution radar imaging.

[0070] In order to change the spherical wave generated by the feed into a high-gain beam propagating in a specific direction, each phase modulation unit of the transmission array antenna must compensate for the spatial phase delay to ensure the same phase.

[0071] In the phase design of the transmission array antenna of the present invention, the first thing that needs to be compensated is the spatial phase delay caused by the feed source irradiating different positions, that is, the compensation phase required at each position. This term can be expressed as:

[0072]

[0073] Where: D (i,j) is the spatial distance between the phase center of the feed and the (i, j)th Ka-band metasurface unit, k0 is the corresponding free space wave number, and the position coordinates of the (i, j)th Ka-band metasurface unit are (x (i,j) ,y (i,j)), z is the distance between the phase center of the horn antenna and the phase-shifted surface (PSS). In the present invention, the phase-shifted surface is a Ka-band metasurface. By placing Ka-band metasurface units with corresponding phase differences at corresponding positions, a transmission array with this phase distribution can generate a high-gain beam perpendicular to the aperture. For example, if a certain position needs to compensate for a 60° phase difference, and the first Ka-band metasurface unit in Table 1 has a 60° phase difference, then the first Ka-band metasurface unit is placed at this position.

[0074] If you need to change the main beam focusing direction It is necessary to introduce an additional gradient phase on the mouth surface, and its mathematical expression is:

[0075]

[0076] That is, the phase difference that needs to be compensated for each Ka-band metasurface unit in the upper Ka-band metasurface.

[0077] Phase shift distribution required for transmission array aperture is the sum of the above two parts, which can be expressed as

[0078]

[0079] This is the phase difference that needs to be compensated for in each Ka-band metasurface unit in the underlying Ka-band metasurface. The last term φ0 is the reference phase value, which physically indicates that the phase shift distribution of the entire aperture is a relative value, not an absolute value.

[0080] The upper and lower phase-shifting surfaces are placed in parallel to facilitate the installation of the antenna. By rotating the two Ka-band metasurfaces around an axis orthogonal to the Ka-band metasurface plane, 3D conical spatial beam scanning is achieved. The present invention defines the lower Ka-band metasurface and the upper Ka-band metasurface with (ψ1, α1) and (ψ2, α2), where ψ1 and ψ2 represent the azimuth planes where the linear phase directions of the lower Ka-band metasurface and the upper Ka-band metasurface are located, and ψ1 and ψ2 are in the interval [-180°, 180°]. α1 and α2 represent the beam deflection angles of the lower Ka-band metasurface and the upper Ka-band metasurface. First, determine the initial azimuth angles of the two phase-shifting surfaces. Secondly, the elevation beam scanning is realized and the two Ka-band metasurfaces are rotated in opposite directions along the same rotation axis perpendicular to the two Ka-band metasurfaces. Where δ1 and δ2 are the rotation angles of the lower Ka-band metasurface and the upper Ka-band metasurface respectively. When α1 and α2 are equal, the beam pitch angle θ and azimuth angle can be accurately calculated.

[0081]

[0082]

[0083] like Figure 7 Figure 1 shows the structure of the Ka-band metasurface, the lower layer, of the first layer, PSS1, of the metamaterial beam-scanning antenna, according to an embodiment of the present invention. The phase values of the horn antenna's spatial position are calculated using Matlab programming, and each phase value of the phase gradient surface is calculated using the above formula (3). The phase gradient values of each unit calculated by Matlab are then arrayed using HFSS, and the metasurface units achieve the corresponding phase values in Matlab.

[0084] like Figure 8 The figure shows the phase gradient value for each element calculated using Matlab. The second-layer PSS1, or the upper Ka-band metasurface, eliminates the spherical wave-to-plane wave conversion step compared to the first-layer PSS1. Therefore, each column of the second-layer PSS1 contains identical elements, with the same deflection angles as the first-layer PSS1 for subsequent beam scanning. Array formation was performed using HFSS, and the metasurface elements achieved the corresponding phase values in Matlab.

[0085] like Figure 9 The figure shows the overall structure of the metamaterial beam scanning antenna. The horn antenna used in the present invention is a standard pyramidal horn produced by Hengda Microwave Company, model HD-320SGAH15K. The horn is 64 mm away from the metasurface array.

[0086] like Figure 10 The figure shows the antenna pattern for a double-layer metasurface loaded with a deflection angle of δ = 180°. The deflection angle for the antenna's maximum radiation direction is 0°, consistent with theoretical calculations. The maximum gain is 21.30 dB, and the sidelobe level is -16.84 dB. δ is the difference between δ1 and δ2.

[0087] like Figure 11 The figure shows the antenna pattern of a double-layer metasurface loaded with a deflection angle of δ = 90°. It can be seen that the antenna's maximum radiation direction deflection angle is 35.35°, consistent with theoretical calculations. The maximum gain is 19.98dB, and the sidelobe level is -15.97dB.

[0088] like Figure 12 The figure shows the radiation pattern of the double-layer metasurface loaded antenna when the deflection angle is δ = 0°. It can be seen that the deflection angle of the antenna's maximum radiation direction is 50°, which is consistent with the theoretical calculation.

[0089] In summary, the Ka-band beam scanning antenna of the present invention can not only realize the beam scanning working state and the wider directional pattern beam, which can achieve large-angle scanning, but also has the characteristics of simple and compact structure, low profile, low cost, high reliability and stable performance.

Claims

1. A low-profile Ka-band metasurface unit, characterized in that: The invention comprises an upper dielectric substrate (2) and a lower dielectric substrate (3), wherein the upper surface of the upper dielectric substrate (2), the lower surface of the lower dielectric substrate (3), and the lower surface of the upper dielectric substrate (2) or the upper surface of the lower dielectric substrate (3) are all printed with metal layers (1) with the same pattern and opposite projections; The metal layer (1) comprises K first curved metal wires (103), K second curved metal wires (104) and K metal wires (105); the K first curved metal wires (103) are located on a first circumference and are symmetrically distributed around the center; one end of each metal wire (105) is connected at the center, and the other end of each metal wire (105) is opposite to the midpoint of a first curved metal wire (103) and has a spacing therebetween; wherein K>1; the K second curved metal wires (104) are located on a second circumference and are symmetrically distributed around the center; the first circumference and the second circumference are cocentric, and the radius of the first circumference is greater than the radius of the second circumference; the other end of each metal wire (105) is connected to the midpoint of a second curved metal wire (104); K first metallized vias (101) and K second metallized vias (102) are provided through the upper dielectric substrate (2) and the lower dielectric substrate (3), wherein the first metallized vias (101) connect first arc-shaped metal wires (103) projected opposite to each other on each metal layer (1); and the second metallized vias (102) connect metal wires (105) projected opposite to each other on each metal layer (1). Different phase gradients are achieved by changing the sizes of the first curved metal wire (103), the second curved metal wire (104) and the metal wire (105); the more phase gradient units there are, the more accurate the result is during phase compensation.

2. The low-profile Ka-band metasurface unit according to claim 1, characterized in that: Taking K=4, taking the number of the phase gradients as 6, that is, using 6 types of Ka-band metasurface units to realize gradient division of the phase, by taking the following values of the midpoint distance l1 of the two second curved metal wires (104) connected by the two metal wires (105) located on the same straight line, the angle Theta1 of the second curved metal wire (104), and the angle Theta2 of the first curved metal wire (103), full phase coverage is achieved, and the transmission loss is within 1.5 dB, and the 6 types of Ka-band metasurface units are obtained: The first Ka-band metasurface unit has l1=3.3mm, Theta1=10deg, Theta2=10deg; The second Ka-band metasurface unit has l1=2.8mm, Theta1=25deg, Theta2=15deg; The third Ka-band metasurface unit has l1=1.87mm, Theta1=20deg, Theta2=45deg; The fourth Ka-band metasurface unit has l1 = 3 mm, Theta1 = 8 degrees, and Theta2 = 36 degrees. The fifth Ka-band metasurface unit has l1=3.2mm, Theta1=13.2deg, Theta2=35deg; The sixth Ka-band metasurface unit, l1 = 3.15 mm, Theta1 = 10 degrees, Theta2 = 10 degrees; The transmission amplitude of the six Ka-band metasurface units in the 29.5-31.2 GHz frequency band is above -1.5 dB, and the transmission phase in the 29.5-31.2 GHz frequency band satisfies a 60° phase difference, and satisfies a 60° equal phase difference at the 30.4 GHz frequency point, and an approximate 60° phase difference can be achieved at both ends of the frequency band.

3. Beam scanning antenna, characterized in that It includes a horn antenna and a Ka-band metasurface, wherein the Ka-band metasurface is composed of an array distribution of M×N Ka-band metasurface units based on a low profile as described in claim 1 or 2, and the Ka-band metasurface is arranged at the aperture position of the horn antenna, and phase compensation is performed by regularly arranging Ka-band metasurface units with different phase gradients to realize beam deflection; wherein M≥2, N≥2; there are two Ka-band metasurfaces, which are coaxially distributed above and below, and beam scanning is realized by rotating the two Ka-band metasurfaces through an axis orthogonal to the two Ka-band metasurfaces.

4. The beam scanning antenna according to claim 3, characterized in that: The spatial phase delay caused by the feed irradiating different positions is calculated by the following formula, that is, the compensation phase required for each position Then, Ka-band metasurface units with corresponding phase differences are placed at corresponding positions to generate a high-gain beam perpendicular to the aperture surface. Among them, D (i,j) is the spatial distance between the phase center of the feed and the (i, j)th Ka-band metasurface unit, k0 is the free space wave number, and the position coordinates of the (i, j)th Ka-band metasurface unit are (x (i,j) ,y (i,j) ), z is the distance between the phase center of the horn antenna and the Ka-band metasurface.

5. The beam scanning antenna according to claim 4, characterized in that: For the upper Ka-band metasurface, the phase difference that needs to be compensated for each Ka-band metasurface unit is calculated as follows: For the lower Ka-band metasurface, the phase difference that needs to be compensated for each Ka-band metasurface unit is the phase shift distribution required by the transmission array aperture. The calculation is as follows: Where, is the focusing direction of the main beam; φ0 is the reference phase value, and its physical meaning indicates that the phase shift distribution of the entire aperture is a relative value rather than an absolute value.

6. The beam scanning antenna according to claim 4, characterized in that: The beam elevation angle θ and azimuth angle are calculated by the following steps: First, determine the initial azimuths of the two Ka-band metasurfaces and equal; Secondly, the elevation beam scanning is realized and the two Ka-band metasurfaces are rotated in opposite directions along the same rotation axis perpendicular to the two Ka-band metasurfaces. Where ψ1 and ψ2 represent the azimuth planes of the linear phase decrease directions of the lower Ka-band metasurface and the upper Ka-band metasurface, respectively. ψ1 and ψ2 are in the interval [-180°, 180°]. δ1 and δ2 are the rotation angles of the lower Ka-band metasurface and the upper Ka-band metasurface, respectively. When the beam deflection angles α1 and α2 of the two Ka-band metasurfaces are equal, the beam pitch angle θ and azimuth angle can be obtained.

7. The beam scanning antenna according to claim 3, characterized in that: When the deflection angle δ of the two Ka-band metasurfaces is 180°, the deflection angle of the antenna's maximum radiation direction is 0°, the maximum gain is 21.30dB, and the sidelobe level is -16.84dB; when the deflection angle δ of the two Ka-band metasurfaces is 90°, the deflection angle of the antenna's maximum radiation direction is 35.35°, the maximum gain is 19.98dB, and the sidelobe level is -15.97dB; when the deflection angle δ of the two Ka-band metasurfaces is 0°, the deflection angle of the antenna's maximum radiation direction is 50°; wherein δ is the difference between δ1 and δ2.

8. The beam scanning antenna according to claim 3, characterized in that: The beam scanning antenna has an operating bandwidth covering 29.5-31.2 GHz.

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