Transmission array antenna adopting mixed resonance metasurface unit

Abstract

The invention discloses a transmission array antenna adopting a mixed resonance metasurface unit, and belongs to the field of transmission array antennas in a wireless communication system, the transmission array antenna comprises a y polarization horn antenna and a transmission metasurface, the transmission metasurface comprises a metasurface unit, and the metasurface unit is composed of an upper layer dielectric substrate, a lower layer dielectric substrate and a metal layer; orthogonal metal gratings are etched on the upper layer dielectric substrate and the lower layer dielectric substrate. The metal layer is made of copper and comprises an upper layer horizontal metal grating, a middle metal layer and a lower layer vertical metal grating. The transmission array antenna adopting the mixed resonance metasurface unit not only has flat gain bandwidth under the application of low profile and low cost, but also can realize higher aperture efficiency and low sidelobe level, can meet the requirements of broadband, high aperture efficiency and low sidelobe, and has wide application prospect. Meanwhile, the advantages of low profile, small size and low cost are realized.

Description

Technical Field

[0001] The present invention relates to the field of transmission array antennas in wireless communication systems, and in particular to a transmission array antenna using a hybrid resonant metasurface unit. Background Art

[0002] Transmission array antenna is one of the most attractive research directions in the field of high-gain antenna. It has the advantages of flexible radiation performance, light weight, low profile and no feed shielding, making it very suitable for application in satellite communications, imaging technology and aerospace microwave remote sensing systems.

[0003] Nowadays, all-dielectric transmission array antennas based on 3D printing technology have shown the advantages of low cost and broadband, but there are still problems such as high profile and insufficient aperture efficiency. In order to meet the growing performance requirements of wireless communication systems, more and more work is devoted to improving bandwidth and aperture efficiency. Generally, transmission array antennas can be divided into three categories: the first category is the transmission array antenna based on the receive-transmit (RX-TX) principle. The double-layer structure of this type of transmission unit can meet the advantages of low insertion loss, but its structural design is relatively complex and the phase shift is limited, resulting in limited bandwidth expansion; the second category is the transmission array antenna using a multi-layer frequency selective surface (FSS), which can expand the phase shift range by increasing the number of FSS layers. However, this method will increase the insertion loss and thus reduce the aperture efficiency; the third category is the transmission array antenna based on the polarization conversion principle reported in recent years. The inherent three-layer metal structure and two-layer dielectric substrate can produce the Fabry cavity effect, so that the unit has high transmission efficiency and high polarization conversion rate. Among them, some folded transmission array antennas can not only effectively expand the bandwidth but also greatly reduce the antenna profile height, but this type of antenna often faces the problem of low aperture efficiency and high sidelobe level. Although, a lot of research is being done to design broadband units with high transmittance to improve the overall performance of TA, such transmission array antennas composed of a single type of metasurface units face challenges in the performance balance between bandwidth, aperture efficiency, and low sidelobes.

[0004] Therefore, there is an urgent need for a new structural design that enables the transmission array antenna to simultaneously meet the requirements of broadband, high aperture efficiency and low sidelobe performance. Summary of the invention

[0005] The purpose of the present invention is to provide a transmission array antenna using a hybrid resonant metasurface unit, which not only has a flat gain bandwidth but also can achieve a higher aperture efficiency and a low sidelobe level under low-profile and low-cost applications, and can meet the requirements of broadband, high aperture efficiency and low sidelobe, while having the advantages of low profile, small size and low cost.

[0006] To achieve the above-mentioned purpose, the present invention provides a transmission array antenna using a hybrid resonant metasurface unit, including a horn antenna and a transmission metasurface, wherein the transmission metasurface includes a metasurface unit, and the metasurface unit is composed of an upper dielectric substrate, a lower dielectric substrate and a metal layer.

[0007] Preferably, the horn antenna adopts y-polarization and is located directly above the transmission metasurface as a feed source, and the horn antenna and the metasurface unit are mounted on a fixed bracket.

[0008] Preferably, the upper dielectric substrate and the lower dielectric substrate are both etched with orthogonal metal gratings; the metal layer is made of copper, and the metal layer includes an upper horizontal metal grating, a middle metal layer and a lower vertical metal grating.

[0009] Preferably, the metasurface units are divided into three types according to the structural type, and the metasurface units with three different intermediate metal layer structures constitute a transmission unit group. The three different intermediate metal layer structures are all composed of multiple split circular rings whose opening directions are symmetrical about y=x, and the outermost ring radius and width of the three intermediate metal layers are the same.

[0010] Preferably, the material of the fixing bracket is PLA, the dielectric constant is 2.72, and the tangent loss is 0.015.

[0011] Preferably, the upper dielectric substrate and the lower dielectric substrate are tightly attached to each other, and the material of the upper dielectric substrate and the lower dielectric substrate is F4B substrate, with a dielectric constant of 2.65 and a tangent loss of 0.009.

[0012] Therefore, the present invention adopts the above-mentioned transmission array antenna using a hybrid resonant metasurface unit, which not only has a flat gain bandwidth under low-profile and low-cost applications, but also can achieve higher aperture efficiency and low sidelobe level, which can meet the requirements of broadband, high aperture efficiency and low sidelobe, and at the same time has the advantages of low profile, small size and low cost.

[0013] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of a horn antenna and a transmission metasurface of an embodiment of a transmission array antenna using a hybrid resonant metasurface unit of the present invention;

[0015] Figure 2 is a normalized radiation pattern of an embodiment of a transmission array antenna using a hybrid resonant metasurface unit of the present invention;

[0016] Figure 3It is a schematic diagram of the structure of a metasurface unit of an embodiment of a transmission array antenna using a hybrid resonant metasurface unit of the present invention;

[0017] Figure 4 It is an evolution process and scattering coefficient diagram of a transmission unit group of an embodiment of a transmission array antenna using a hybrid resonant metasurface unit of the present invention;

[0018] Figure 5 It is a phase curve of the transmission phase of the transmission unit group of the transmission array antenna embodiment using the hybrid resonant metasurface unit of the present invention at different frequency points as the structural parameters change;

[0019] Figure 6 It is a transmission phase and transmission amplitude curve diagram of a transmission unit group in a broadband of a transmission array antenna embodiment using a hybrid resonant metasurface unit of the present invention;

[0020] Figure 7 It is a phase distribution diagram of an embodiment of a transmission array antenna using a hybrid resonant metasurface unit of the present invention;

[0021] Figure 8 It is a diagram of the antenna processing object and the measurement environment of an embodiment of a transmission array antenna using a hybrid resonant metasurface unit of the present invention;

[0022] Fig. 9 It is a normalized radiation pattern of a transmission array antenna of an embodiment of a transmission array antenna using a hybrid resonant metasurface unit at 10 GHz, 12 GHz, and 14 GHz of the present invention;

[0023] Fig.10 The present invention discloses a simulated and measured gain and aperture efficiency curve and a maximum sidelobe level diagram of a transmission array antenna embodiment using a hybrid resonant metasurface unit.

[0024] Reference numerals

[0025] 1. Horn antenna; 2. Transmissive metasurface; 21. Upper dielectric substrate; 22. Lower dielectric substrate; 23. Middle metal layer; 24. Upper horizontal metal grating; 25. Lower vertical metal grating. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0027] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0028] Embodiment 1

[0029] The geometric structure diagram of the transmission array antenna designed by the present invention is as follows: Figure 1 and Figure 3 As shown, the antenna consists of a y-polarized feed horn antenna 1 and a planar array of a transmission metasurface 2 with a diameter of D, which can realize the conversion of y-polarized waves to x-polarized waves; the transmission metasurface 2 includes three metasurface units with similar structures, and the metasurface units are composed of two layers of dielectric substrates and three layers of metal layers. The material of the metal layer is copper, and the processing thickness is set to 0.017mm. The processing technology of the metal layer is bare copper process and OSP; the two-layer dielectric substrate includes an upper dielectric substrate 21 and a lower dielectric substrate 22, and the three-layer metal layer includes an upper horizontal metal grating 24, an intermediate metal layer 23 and a lower vertical metal grating 25.

[0030] In order to further explain the working principle of the transmission array antenna, the present invention comprehensively analyzes the working mechanism of the transmission array antenna and explores the laws that affect the performance of the far-field radiation pattern in combination with the array antenna theory.

[0031] According to the design principle of planar space-fed transmission array antenna, multiple radiating elements are arranged in a specific geometric layout, and the feeding amplitude and phase between the elements are controlled to achieve directional radiation of the beam, gain enhancement, and flexible control of the radiation pattern. The array radiation pattern is composed of the superposition of the element radiation pattern and the array factor electric field vector, which determines the directivity and sidelobe distribution of the array radiation. The radiation pattern of a rectangular aperture transmission array with M×N elements can be expressed as:

[0032]

[0033] Among them, θ f (m,n) is the spherical angle in the feed coordinate system, is the position vector of the (m,n)th unit, is the position vector of the feed source. For each unit independent of the azimuth angle, the cosine model can be used for equivalence, thereby simplifying the calculation. Here, qf is the feed mode power factor, qe is the unit mode power factor, M and N represent the number of units, j represents an imaginary number, k = 2π / λ, λ is the wavelength, T mn is the transmission amplitude of the (m,n)th unit, represents the unit vector in the horizontal direction, represents the unit vector in the vertical direction, represents the unit vector perpendicular to the xoy plane, θ is the pitch angle, is the direction angle; ψ is the phase delay required for the (m,n)th unit to set the direction of the main beam, which can be expressed as:

[0034]

[0035] Where F is the focal length, (x i ,y i ) represents the position of the i-th element. For an ideal transmission array, the transmission amplitude is usually set to 1, so once the phase compensation distribution of the transmission array is determined, the element arrangement of the array is determined. For the radiation pattern of a transmission array antenna with a circular aperture, the above formula can still be used after only ignoring the edge elements outside the circular aperture. Let M = N = 31 and the element size be 0.2λ 0 (corresponding to a frequency of 10 GHz), the amplitude-weighted and amplitude-unweighted normalized radiation patterns are obtained through comprehensive theoretical calculations of the antenna array, such as Figure 2 shown.

[0036] in, Figure 2 (a) shows the normalized radiation pattern of the transmission array antenna with transmission amplitude weighted and unweighted at 10 GHz; Figure 2 (b) in FIG. 1 represents the normalized radiation pattern calculated using the array theory algorithm and obtained by CST full-wave simulation; Figure 2 As shown in (a) in the figure, it can be verified that amplitude control can reduce the feasibility of the sidelobe level. Figure 2 As shown in (b), by comparing the normalized radiation patterns obtained by theoretical calculation and CST full-wave simulation, it can be found that the two have good consistency in beam pointing, beam width, sidelobe level, etc.

[0037] In order to verify the design principle, a polarization conversion metasurface unit group was designed to construct a broadband transmission array antenna. The unit geometry is as follows Figure 3As shown, it consists of two dielectric substrates with a thickness of h = 2 mm and three metal layers, and the unit period is p. The upper and lower dielectric substrates are etched with orthogonal metal gratings, and the middle layer of the unit group is composed of multiple split rings, and the outermost ring has the same radius and width. Figure 3 In the structure 3, an additional inner split ring is introduced on the basis of the structure 1. After completing the above initial design, the simulation analysis is performed using CST Microwave Studio software. 1 is the opening size of the inner ring of structure 1, the opening size of the middle ring of structure 3, β 3 is the opening size of the innermost ring of structure 3, r 1 is the radius of the inner ring of structure 1, r 2 is the radius of the outer ring of structure 1, and also the radius of the outermost ring of structures 2 and 3. 3 is the radius of the inner ring of structure 2, r 4 is the radius of the innermost ring of structure 3, t 1 is the width of the metal grating, t 2 is the spacing size of the metal grating, w 1 is the width of the outer ring of structure 1, and also the width of the outermost ring of structures 2 and 3, w 2 is the width of the inner ring of structure 2, w 3 is the width of the middle ring of structure 3, and also the width of the inner ring of structure 1, w 4 is the width of the innermost ring of structure 3, α 2 is the opening size of the outer ring of structure 2. In addition to the opening size α of the outermost split ring of the unit group 1 and α 3 , and the internal split ring opening size β of structure 2 2 In addition, other parameters are shown in Table 1:

[0038] Table 1 Optimal size table of various parameters of the present invention

[0039] parameter size h 2mm p 6mm <![CDATA[β 1 ]]> 70deg <![CDATA[β 3 ]]> 140deg <![CDATA[r 1 ]]> 2.1mm <![CDATA[r 2 ]]> 2.5mm <![CDATA[r 3 ]]> 1.8mm <![CDATA[r 4 ]]> 1mm <![CDATA[t 1 ]]> 1.4mm <![CDATA[t 2 ]]> 1.6mm <![CDATA[w 1 ]]> 0.3mm <![CDATA[w 2 ]]> 0.5mm <![CDATA[w 3 ]]> 0.2mm <![CDATA[w 4 ]]> 0.4mm <![CDATA[α 2 ]]> 170deg

[0040] The designed metasurface unit group middle metal layer is symmetrical about y=x and has the function of polarization conversion. When the y-polarized wave is incident along the negative z-axis, it can be converted into an x-polarized wave. Under the excitation of the x-polarized and y-polarized incident waves, the split ring in the middle layer will decompose the electromagnetic wave into x-polarized and y-polarized components. The x-polarized wave will completely pass through the third metal layer, while the y-polarized wave will be totally reflected.

[0041] In order to better compare the characteristics of each part of the metasurface unit, e.g. Figure 4 As shown, Figure 4The transmission coefficients of co-polarization and cross-polarization are shown. The inherent broadband performance of the "C" structure mainly comes from its symmetric and asymmetric current resonance modes, while the coupling caused by the additional introduction of the split ring structure can enhance the resonance strength. Figure 4 From the simulation results, it can be seen that the coupling effect of the split ring makes the low-frequency resonance points of the three structures move further to the low frequency compared to the "C"-shaped structure, and at the same time enhances the resonance strength of the high-frequency resonance point, thereby improving the transmission efficiency. Among them, structure 3 combines structure 1 and structure 2 to form a three-ring structure, which can introduce a new resonance point and further expand the working bandwidth. Compared with the single "C"-shaped structure, the designed multi-resonance transmission unit not only achieves a wider working bandwidth than the single "C" ring structure, but also provides higher transmission efficiency without increasing the design difficulty. In order to better realize the design of the transmission array antenna, the array theoretical calculation requires that the compensation phase of the transmission array remain consistent at all frequencies. Therefore, the cumulative phase difference of the three different split ring structures designed is 180°. Figure 5 As shown, by changing the parameter α 1 , α 3 and β 2 , thereby changing the transmission phase of the unit to obtain a group of units with 180° phase coverage. The phase and amplitude curves in the broadband are as follows Figure 6 As shown in the figure, it can be calculated that the average cross-polarization transmission coefficient is 0.94 under normal incidence conditions within 8 to 16 GHz, and the relative fractional bandwidth is 66.7%. In addition, by rotating the middle metal layer 90° around the z-axis, a total phase coverage of 360° can be achieved.

[0042] For the array design of transmission array antennas, firstly, the focal ratio of the transmission array can be optimized through the antenna array theory synthesis algorithm to achieve lower sidelobe level and higher aperture efficiency. The final focal ratio F / D is set to 0.645, and the aperture diameter is D = 186mm. Secondly, it is necessary to select and design a suitable feed source. The feed antenna generally uses a microstrip antenna or a horn antenna. Especially for ultra-wideband transmission arrays, the stable gain and phase center of the feed antenna will directly affect the performance of the entire antenna array. Figure 7 As shown, Figure 7 (a) in the figure represents the phase distribution at the transmission aperture of the feed source; Figure 7 (b) in the figure shows the compensation phase distribution of the transmission metasurface; Figure 7 (c) shows the phase distribution of electromagnetic waves after being compensated by the transmission metasurface; Figure 7 (d) in the figure represents the amplitude distribution at the transmission aperture of the feed source; Figure 7(a)-(b) in the figure show the phase distribution of the feed source at the transmission aperture and the compensated phase distribution of the transmission metasurface. Ideally, when the transmission metasurface compensates the spherical wave to a plane wave, the phase difference is 0. However, in actual simulations, due to the coupling and scattering between units, the phase distribution after the transmission array compensation is different from the plane wave, as shown in Figure 2. Figure 7 As shown in (c) in Figure 7 Compared with (a) in the figure, better plane wave compensation has been achieved. Figure 7 As can be seen from (d) in the figure, the illumination amplitude distribution provided by the feed source satisfies the Taylor distribution, which lays a good foundation for the transmission array antenna to achieve low sidelobe performance.

[0043] According to the unit design proposed above, the transmission array antenna was manufactured using PCB technology. Figure 8 As shown, Figure 8 (a) in the figure shows the actual antenna processing diagram, showing the vertical metal grating and intermediate layer structure of the transmission array antenna. The feed source and the fixed bracket of the transmission metasurface are manufactured using 3D printing technology, using PLA as the 3D printing material, and the far-field radiation pattern and achievable gain are measured in a microwave anechoic chamber. The measurement environment is as follows: Figure 8 As shown in (b) in Fig. 9 As shown, Fig. 9 (a)-(c) in the figure represent the normalized radiation patterns of the E-plane of the transmission array antenna measured at 10 GHz, 12 GHz, and 14 GHz; Fig. 9 (d)-(f) in the figure represent the normalized radiation patterns of the H-plane measured by the transmission array antenna at 10 GHz, 12 GHz, and 14 GHz; Fig. 9 The normalized radiation patterns and cross-polarization levels of the E-plane and H-plane measured at three frequency points (10GHz, 12GHz and 14GHz) are described. The measured results are in good agreement with the simulation results, and the peak gains at the three frequency points are measured to be 23.23dBi, 23.1dBi and 22.95dBi, respectively. At 10GHz, the measured SLLs of the E-plane and H-plane are -18.8dB / -23.7dB, respectively, while at 12GHz and 14GHz, the SLLs of the E-plane and H-plane are both lower than -20.8dB. In addition, at the three frequency points, the cross-polarization levels measured on the E-plane and H-plane are all lower than -18.7dB. Fig.10 As shown, Fig.10 (a) shows the gain and aperture efficiency curves of the transmission array antenna simulation and measurement. The peak gain and aperture efficiency obtained by the transmission array antenna simulation and measurement are shown in Fig.10 The formula for calculating the antenna aperture efficiency is as follows:

[0044]

[0045] Where G is the achieved gain, λ is the free space wavelength, S array is the aperture area. The peak aperture efficiency of the antenna is 55.4% at 10GHz, the aperture efficiency exceeds 30% in the range of 8-13.5GHz, and the relative bandwidth is 51%. Compared with the simulation results, the measured results show a loss of less than 1dB at some frequency points. In addition, the 3dB gain bandwidths obtained by antenna simulation and measurement are 9.2-17GHz (59.5%) and 9-16.8GHz (60.5%), respectively, and the measured results have a frequency shift of about 0.2GHz compared with the simulation. These phenomena are mainly caused by factors such as processing loss and measurement errors, which will cause fluctuations in gain and aperture efficiency. The measured maximum gain value reaches 24.35dBi at 13GHz, which is about 0.5dB lower than the simulation result, resulting in a change in the 3dB gain reduction range. Compared with the simulation results, the measurement results show good consistency. Fig.10 (b) in the figure shows that the designed transmission array antenna maintains a low sidelobe level within the 3dB gain bandwidth, with an average sidelobe level of about -22.1dB.

[0046] In summary, the transmission array antenna using multi-resonance hybrid metasurface units proposed in the present invention takes into account the performance of broadband, high aperture efficiency and low sidelobe at the same time under low-cost application. After testing, the results obtained are basically consistent with the simulation, the overall performance of the antenna is good, and it has good practical application potential in millimeter wave wireless communication systems.

[0047] Therefore, the present invention adopts the above-mentioned transmission array antenna using a hybrid resonant metasurface unit, which not only has a flat gain bandwidth under low-profile and low-cost applications, but also can achieve higher aperture efficiency and low sidelobe level, which can meet the requirements of broadband, high aperture efficiency and low sidelobe, and at the same time has the advantages of low profile, small size and low cost.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A transmission array antenna using a hybrid resonant metasurface unit, characterized in that: It comprises a horn antenna and a transmission metasurface, wherein the transmission metasurface comprises a metasurface unit, and the metasurface unit is composed of an upper dielectric substrate, a lower dielectric substrate and a metal layer.

2. The transmission array antenna using a hybrid resonant metasurface unit according to claim 1, characterized in that: The horn antenna adopts y-polarization and is located directly above the transmission metasurface as a feed source. The horn antenna and the metasurface unit are installed on a fixed bracket.

3. The transmission array antenna using a hybrid resonant metasurface unit according to claim 1, characterized in that: The upper dielectric substrate and the lower dielectric substrate are both etched with orthogonal metal gratings; the metal layer is made of copper, and the metal layer includes an upper horizontal metal grating, a middle metal layer and a lower vertical metal grating.

4. The transmission array antenna using a hybrid resonant metasurface unit according to claim 1, characterized in that: The metasurface units are divided into three types according to the structural type. The metasurface units with three different intermediate metal layer structures constitute a transmission unit group. The three different intermediate metal layer structures are all composed of multiple split circular rings with opening directions symmetrical about y=x, and the outermost ring radius and width of the three intermediate metal layers are the same.

5. The transmission array antenna using a hybrid resonant metasurface unit according to claim 2, characterized in that: The material of the fixing bracket is PLA, the dielectric constant is 2.72, and the tangent loss is 0.

015.

6. The transmission array antenna using a hybrid resonant metasurface unit according to claim 3, characterized in that: The upper dielectric substrate and the lower dielectric substrate are tightly attached to each other. The material of the upper dielectric substrate and the lower dielectric substrate is F4B substrate, with a dielectric constant of 2.65 and a tangent loss of 0.009.

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