A millimeter-wave multi-polarization common-aperture antenna based on a folded transmission array

Abstract

The present invention discloses a millimeter-wave multi-polarization co-aperture antenna based on a folded transmission array. The antenna is composed of a dual-polarization horn feed, a dual-frequency Huygens metasurface, and a broadband linear circular polarization converter. The co-aperture antenna in the present invention can operate in two frequency bands of 29 and 37 GHz. By adjusting the feeding amplitude of the feeding port, the co-aperture antenna can operate in three polarization states. Compared with other folded transmission array antennas, the proposed antenna has the advantage of being able to achieve three polarization states in two frequency bands, and the aperture efficiency in both frequency bands is greater than 25%. Ultimately, the multi-polarization co-aperture antenna based on the folded transmission array has the characteristics of low profile, multi-polarization, high aperture efficiency, and simple structure. It can realize both frequency division multiplexing and polarization multiplexing, which can greatly improve the channel capacity during satellite communication, reduce the complexity and cost of the system, and can be used in highly integrated and compact modern communication systems.

Description

Technical Field

[0001] The present invention belongs to the field of folded transmission array antennas in microwave device technology, and in particular relates to a millimeter-wave multi-polarization common-aperture antenna based on a folded transmission array. Background Art

[0002] In recent years, co-aperture antennas have undergone a long period of development and achieved remarkable results. However, these achievements still face some challenges. First, some co-aperture antennas are designed based on the transmission array principle. Because the horn is located at the focal length of the array antenna, the overall profile of the array antenna is high, which is not conducive to system integration. Second, although most co-aperture antennas can operate in two frequency bands, the polarization states of these two bands are the same, which only enables frequency reuse and cannot utilize polarization multiplexing. Therefore, the overall capacity and speed improvement of wireless communication systems are limited. Finally, the functional metasurfaces of most folded transmission array antennas are based on a receiver-via-radiator structure design. This structure consists of two dielectric layers and an adhesive layer, as well as metalized vias for connecting the receiving and radiating elements. The co-aperture is achieved by staggering high and low frequency elements. The complex multi-layer structure complicates processing, resulting in high production costs and difficult installation and testing. Finally, the aperture efficiency of most co-aperture antennas is not very high in both frequency bands. Based on this, there is an urgent need to design a common-aperture antenna that has the characteristics of simple structure, low profile, multi-polarization, and high aperture efficiency.

[0003] To address this issue, this paper employed a dual-polarization horn feed, designed a broadband linear circular polarizer, and a dual-band Huygens metasurface. Based on ray tracing theory, the resulting array antenna can operate in right-hand circular polarization, left-hand circular polarization, and linear polarization at frequencies of 29 GHz and 37 GHz, respectively, with aperture efficiencies exceeding 25%. The proposed co-aperture antenna exhibits multi-polarization, a low profile, a simple structure, and high radiation aperture efficiency. Summary of the Invention

[0004] Technical Problem: To address the challenges of existing co-aperture antennas, a millimeter-wave multi-polarization co-aperture antenna based on a folded transmission array was proposed. This antenna aims to achieve multi-polarization and high aperture efficiency while reducing the profile and structural complexity of the co-aperture antenna. The antenna consists of a dual-band Huygens metasurface with an integrated feed antenna and a reflective linear circular polarization converter.

[0005] Technical solution: In order to achieve the above-mentioned purpose of the invention, the millimeter-wave multi-polarization common-aperture antenna based on the folded transmission array of the present invention has a two-layer structure, consisting of a horn feed, a dual-frequency Huygens resonant metasurface, and a reflective linear circularly polarized metasurface; among them, the upper layer is a dual-frequency Huygens resonant metasurface with a horn feed embedded in the middle, and the lower layer is a reflective linear circularly polarized metasurface, and the horn feed is used as the feed source of the folded transmission array.

[0006] The horn feed should enable the antenna's operating frequency to cover a frequency band ranging from 26.5 to 40 GHz, and be able to cover the two operating frequencies of the common aperture antenna, 29 and 37 GHz.

[0007] The overall size of the horn feed is 20.2mm*19.1mm*36mm.

[0008] The dual-frequency Huygens resonant metasurface consists of two square rings with four-corner grooves etched on the upper and lower surfaces of a dielectric substrate. The two square rings include an upper square ring on the upper layer of the dielectric substrate and a lower square ring on the lower layer of the dielectric substrate. The high and low frequency transmission phases are controlled by adjusting the structural parameters in the high and low frequency units.

[0009] The dual-frequency Huygens resonant metasurface is a 2-bit dual-frequency Huygens resonant metasurface unit.

[0010] The reflective linear circularly polarized metasurface is composed of a square ring with a missing corner etched above a grounded dielectric substrate and a circular patch located at the center of the square ring with a missing corner; it converts the linearly polarized wave emitted by the horn feed into a circularly polarized wave.

[0011] The co-aperture antenna undergoes a folding during the beam propagation process, that is, the spherical wave emitted by the horn feed source undergoes a mirror reflection during the final transmission and conversion into a high-gain plane wave, which reduces the height of the antenna to half the focal length and has a lower cross-sectional height compared to the transmission array antenna.

[0012] The dual-frequency Huygens resonant metasurface is a square unit, where the structural size of each unit is determined by the required different transmission phases. The transmission phase corresponding to each unit on the dual-frequency Huygens resonant metasurface needs to satisfy the distribution expressed by the following formula, converting the spherical wave emitted by the feed source into the final high-gain plane wave.

[0013]

[0014] Where Φ(m, n) is the transmission phase corresponding to the m-th row and n-th column unit of the dual-frequency Huygens metasurface, λ is the wavelength in vacuum corresponding to the two operating frequencies of 29 / 37 GHz for the antenna, p is the period length of the Huygens metasurface unit, and f is the focal length of the focusing function of the designed folded transmission array.

[0015] The upper dual-frequency Huygens resonant metasurface consists of 27*27 metasurface units arranged in a circular array, of which the 5*5 metasurface units located in the center are removed to embed the horn feed; the lower reflective linear circularly polarized metasurface consists of 50*50 metasurface units.

[0016] The aperture efficiency of the multi-polarization common aperture antenna is:

[0017] Where G is the simulated achievable gain, λ is the wavelength in vacuum corresponding to the two frequencies 29 / 37 GHz at which the antenna operates, and S is the area of ​​the radiating aperture of the array antenna.

[0018] Beneficial effects: Compared with the prior art, the common-aperture antenna based on the folded transmission array of the present invention has the characteristics of simple structure, low profile, multi-polarization and high aperture efficiency.

[0019] Compared with common co-aperture antennas based on transmission arrays or reflection arrays, the co-aperture antenna based on a folded transmission array provided by the present invention uses mirror reflection in the optical path design, so that the overall cross-section of the antenna is reduced to half of the focal length, and has a low-profile characteristic.

[0020] Compared with other common co-aperture folded transmission array antennas that use a staggered receive-via-transmitter transmission metasurface design, the single-layer Huygens resonant metasurface used in the present invention has a single-layer dielectric and does not require the use of metal vias and adhesive layers, greatly reducing the processing complexity and production costs.

[0021] Most importantly, compared with most other single-polarization or dual-polarization co-aperture antennas, the co-aperture antenna based on the folded transmission array of the present invention has the characteristics of multi-polarization. It can operate in linear polarization state, left-hand circular polarization state, and right-hand circular polarization state. While achieving frequency reuse, it can also achieve polarization reuse. The antenna of the present invention is expected to improve the system capacity and rate in wireless communication systems.

[0022] Furthermore, due to the careful design and optimization of the elements and array during design, the multi-polarized common-aperture antenna of the present invention achieves high aperture efficiency at both operating frequencies. A comparison with other similar works is also presented in the table below.

[0023]

[0024] References:

[0025] [1]J.Yang et al.,“Folded transmitarray Antenna with circularpolarization based onmetasurface,”IEEE Trans.Antennas Propag.,vol.69,no.2,pp.806-814,Feb.2021.

[0026] [2]C.Bian,D.Zhou,Y.Zhang,D.Lv,H.Deng and D.Zhang,“A multi-polarization folded transmitarray antenna based on Huygens’metasurface,”IEEEAntennas Wireless Propag.Lett.,vol.22,no.12,pp.2783-2787,Dec.2023.

[0027] [3]H.Lei,Y.Liu,Y.Jia,Z.Yue,and X.Wang,“A low-profiledual-band dualcircularly polarized folded transmitarray antenna with independent beamcontrol,”IEEE Trans.Antennas Propag.,vol.70,no.5,pp.3852–3857,May 2022.

[0028] [4]M.Wang,M.T.Yim and C.H.Chan,“Dual-polarized folded reflectarrayantenna with active components,”IEEE Trans.Antennas Propag.,doi:10.1109 / TAP.2024.3387842.

[0029] [5]S.Yang, Z.Yan, M.Cai and X.Li, “Low-Profiledual-band circularlypolarized antenna combining transmitarray and reflectarray for satellitecommunications,” IEEE Trans.Antennas Propag., vol.70, no.7, pp.5983-5988, July2022.

[0030] [6]P.P.Zhang et al., “A 20 / 30GHz dualband dual circularly polarizedantenna hybridizing folded reflectarray and folded transmitarray,” in IEEEMTT-S Int.Wireless Symp.(IWS), Harbin, China, Aug.2022, pp.1-3.

[0031] [7]S.Xu, Y.Shen, S.Xue and S.Hu, “26- / 39-GHz low-profiledual-circularly-polarized hybrid antenna with integrated single feed,” IEEE Trans AntennasPropag., vol.71, no.11, pp.8548-8555, Nov.2023.

[0032] [8]R.De Marco, E.Arnieri, F.Greco, A.Bordbar, G.Amendola and L.Boccia, “Low-Profile Dual-Band Dual-Polarized Transmitarray Antenna Based onMultilayer Frequency Selective Surfaces,” IEEE Trans Antennas Propag., vol.71, no.9, pp.7354-7362, Sept.2023. Description of the Drawings

[0033] Figure 1aThis is a schematic diagram of the working principle of the millimeter-wave common-aperture antenna based on the folded transmission array working in the right-hand circular polarization state; Figure 1b This is a schematic diagram of the working principle of the millimeter wave common aperture antenna based on the folded transmission array working in the left-hand circular polarization state; Figure 1c This is a schematic diagram of the working principle of the millimeter-wave common-aperture antenna based on the folded transmission array working in the linear polarization state;

[0034] Figure 2 This is a structural model diagram of a dual-polarized horn feed antenna;

[0035] Figure 3a is the two-dimensional radiation pattern of the feed antenna at 29 GHz; Figure 3b is the two-dimensional radiation pattern of the feed antenna at 37 GHz;

[0036] Figure 4a This is a schematic diagram of the upper structure of the dual-frequency Huygens resonant metasurface; Figure 4b This is a schematic diagram of the underlying structure of the dual-frequency Huygens resonant metasurface;

[0037] Figure 5 is the transmission coefficient amplitude curve of the dual-frequency Huygens resonant metasurface;

[0038] Figure 6 This is a top view of the structure of the reflective linear circular polarization converter;

[0039] Figure 7 is a reflection coefficient amplitude curve of the reflection type linear circular polarization converter;

[0040] Figure 8 is the reflection coefficient phase curve of the reflective linear circular polarization converter;

[0041] Figure 9 This is the axial ratio curve of the reflective linear circular polarization converter at vertical incidence;

[0042] Figure 10 is the axial ratio curve of the reflective linear circular polarization converter at oblique incidence;

[0043] Figure 11 This is a schematic diagram of the structure of a co-aperture antenna based on a folded transmission array;

[0044] Figure 12a It is the XOZ radiation pattern of the co-aperture antenna operating in right-hand circular polarization at 29 GHz; Figure 12b It is the YOZ radiation pattern of the co-aperture antenna operating in right-hand circular polarization at 29 GHz; Figure 12c It is the XOZ radiation pattern of the co-aperture antenna operating in right-hand circular polarization at 37 GHz; Figure 12dThis is the YOZ radiation pattern of the co-aperture antenna operating in right-hand circular polarization at 37 GHz.

[0045] Figure 13a This is a graph showing how the circular polarization gain of a co-aperture antenna changes with low frequency when operating in the right-hand circular polarization state. Figure 13b This is a graph showing how the circular polarization gain of a co-aperture antenna changes with high frequency when operating in the right-hand circular polarization state.

[0046] Figure 14a This is a graph showing the axial ratio of a co-aperture antenna operating in right-hand circular polarization versus low frequency. Figure 14b This is a graph showing the axial ratio of a co-aperture antenna operating in right-hand circular polarization as a function of high frequency.

[0047] Figure 15a It is the XOZ radiation pattern of the co-aperture antenna operating in left-hand circular polarization at 29 GHz; Figure 15b It is the YOZ radiation pattern of the co-aperture antenna operating in left-hand circular polarization at 29 GHz; Figure 15c This is the XOZ radiation pattern of the co-aperture antenna operating in left-hand circular polarization at 37 GHz. Figure 15d is the radiation pattern of the YOZ plane when the co-aperture antenna operates in the left-hand circular polarization state at 37 GHz;

[0048] Figure 16a This is a graph showing how the circular polarization gain of a co-aperture antenna changes with low frequency when operating in the left-hand circular polarization state. Figure 16b This is a graph showing how the circular polarization gain of a co-aperture antenna changes with high frequency when operating in the left-hand circular polarization state.

[0049] Figure 17a This is a graph showing the axial ratio of a co-aperture antenna operating in left-hand circular polarization versus low frequency. Figure 17b This is a graph showing the axial ratio of a common aperture antenna operating in left-hand circular polarization state versus high frequency.

[0050] Figure 18a It is the low-frequency reflection coefficient curve when the common aperture antenna works in the linear polarization state; Figure 18b It is the high-frequency reflection coefficient curve when the common aperture antenna works in the linear polarization state;

[0051] Figure 19a It is the low-frequency two-dimensional radiation pattern of the co-aperture antenna when it works in the linear polarization state; Figure 19b It is the high-frequency two-dimensional radiation pattern of the co-aperture antenna when it works in the linear polarization state;

[0052] Figure 20a This is a graph showing the gain of a common aperture antenna operating in a linear polarization state versus low frequency. Figure 20b This is a graph showing how the gain of a common-aperture antenna working in a linear polarization state changes with high frequency.

[0053] The figure shows: horn feed 1, dual-frequency Huygens resonant metasurface 2, upper square ring 21, lower square ring 22, reflective linear circular polarization metasurface 3, missing-corner square ring 31, and circular patch 32. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings, tables and specific implementation examples.

[0055] The proposed millimeter-wave co-aperture antenna based on a folded transmission array can achieve multiple polarization modes. The operating principle of the co-aperture antenna operating in the right-hand circular polarization state is first described. When a horizontally polarized electromagnetic wave is emitted by the feed source at 29 GHz, it propagates to the bottom surface. The bottom-layer linear circular polarization converter converts the 29 GHz horizontally polarized electromagnetic wave into a right-hand circularly polarized electromagnetic wave. The reflected 29 GHz circularly polarized electromagnetic wave propagates to the top surface. The top-layer dual-band dual-polarization Huygens metasurface transmits the 29 GHz circular polarization. By adjusting the structural dimensions to compensate for the transmission phase, a high-gain right-hand circularly polarized electromagnetic wave is ultimately radiated at 29 GHz. Because a dual-polarization horn feed is used, a dual-band Huygens metasurface operating at 29 / 37 GHz and a broadband linear circular polarization converter are designed, so the operating principle at 37 GHz is the same as above. Finally, a millimeter-wave co-aperture antenna operating in the right-hand circular polarization state is realized. Next, the operating principle of a co-aperture antenna operating in the left-hand circular polarization state is explained. When a vertically polarized electromagnetic wave is emitted by the feed source at 29 GHz and propagates to the bottom surface, the linear circular polarization converter on the bottom surface converts the 29 GHz vertically polarized electromagnetic wave into a left-hand circularly polarized electromagnetic wave. The reflected 29 GHz left-hand circularly polarized electromagnetic wave propagates to the top surface, where the dual-band, dual-polarization Huygens metasurface transmits the 29 GHz left-hand circularly polarized wave. By adjusting the structural dimensions to compensate for the transmission phase, a high-gain left-hand circularly polarized electromagnetic wave is ultimately radiated at 29 GHz. The operating principle at 37 GHz is the same as that at 29 GHz, ultimately realizing a millimeter-wave co-aperture antenna operating in the left-hand circular polarization state. Finally, the operating principle of a co-aperture antenna operating in the linear polarization state is explained. When a 45° polarized electromagnetic wave is emitted by the feed source at 29 GHz and propagates to the bottom surface, the reflective polarization converter at the bottom layer reflects the 29 GHz 45° polarized electromagnetic wave into a linearly polarized electromagnetic wave. The reflected 29 GHz linearly polarized electromagnetic wave then propagates to the top surface, where the dual-frequency, dual-polarization Huygens metasurface transmits the 29 GHz linearly polarized wave. By adjusting the structural dimensions to compensate for the transmission phase, a high-gain linearly polarized electromagnetic wave is ultimately radiated at 29 GHz. The 37 GHz operating principle shares the same propagation path and polarization state as the 29 GHz electromagnetic wave, ultimately achieving a millimeter-wave co-aperture antenna operating under linear polarization.

[0056] To reduce design complexity, a dual-polarized horn antenna is used for feed. Multiple linearly polarized waves can be achieved by simply changing the feed amplitude of the two ports. The overall dimensions of the horn are 20.2mm*19.1mm*36mm.

[0057] The dual-frequency Huygens metasurface structure used is relatively simple, using only one layer of dielectric substrate. The dielectric substrate used is the SJ9036 dielectric substrate produced by Shengyi Technology Group Co., Ltd., with a thickness of 1.27mm, a dielectric constant of 3.5, and a loss tangent value of 0.003. The structure of the designed dual-frequency Huygens metasurface is a double-ring structure with grooves around the upper and lower layers. The outer square ring structure is used to generate a low-frequency 29GHz Huygens resonance frequency point, and the inner square ring structure is used to generate a high-frequency 37GHz Huygens resonance frequency point. Since the designed Huygens resonant metasurface has a centrally symmetrical structure, both x-polarized electromagnetic waves and y-polarized electromagnetic waves can be transmitted, and it has the characteristics of dual polarization. The transmission phase of high and low frequencies can be adjusted by adjusting the high and low frequency structural size parameters of the Huygens metasurface unit.

[0058] The upper structure used includes a Huygens unit structure composed of several metasurface units. In order to convert the spherical wave emitted by the feed source into the final planar high-gain transmitted wave, the transmission phase of each unit in the upper array structure needs to satisfy the following distribution formula:

[0059]

[0060] Here, Φ(m, n) is the transmission phase corresponding to the element in the mth row and nth column of the Huygens metasurface, λ is the wavelength of the electromagnetic wave in free space corresponding to the antenna operating frequency of 29 / 37 GHz, p is the period length of the Huygens metasurface element, and f is the focal length of the designed metasurface's focusing function. However, the transmission phase calculated by this formula is continuous, and the designed Huygens metasurface cannot achieve continuous phase compensation due to the coupling between the two frequency bands. Therefore, the ideal compensation phase needs to be discretely quantized.

[0061] Based on the above formula, we calculated the transmission phase corresponding to each unit on the Huygens metasurface. To simplify the design process and reduce the design workload, the present invention only designed 16 types of Huygens resonant units (0°, 90°, 180°, and 270°) to achieve transmission phase compensation. Then, based on the established database, the structural size distribution of the upper Huygens metasurface array can be determined.

[0062] Furthermore, the reflective linear circular polarization converter used is composed of a three-layer structure. The top layer is a square ring with slots on both sides loaded with a circular patch. The middle layer still uses a SJ9036 dielectric substrate with a thickness of 1.27mm, and the bottom layer is a metal floor.

[0063] Furthermore, the designed polarization-conversion metasurface, with a periodic size of only 2.5 mm, can convert linearly polarized waves into circularly polarized waves in the frequency range of 20 to 40.6 GHz, with an axial ratio of less than 2 dB. Due to its miniaturization, the overall oblique incidence stability is excellent. At an oblique incidence of 35°, the axial ratio remains less than 3 dB in the 20 to 40.6 GHz frequency range.

[0064] The optical path structure of the designed co-aperture antenna includes a single specular reflection, creating a folding effect. This specular reflection occurs when the linearly polarized wave emitted by the feed reaches the reflective polarization converter below. Due to this specular reflection, the overall cross-sectional height of the antenna is half the focal length.

[0065] Reference Figure 1a 、 Figure 1b 、 Figure 1c 、 Figure 2The present invention provides an implementation scheme for a multi-polarized co-aperture antenna based on a folded transmission array and details its operating principle. The co-aperture antenna has a two-layer structure, consisting of a horn feed 1, a dual-frequency Huygens resonant metasurface 2, and a reflective linear circularly polarized metasurface 3. The upper layer is the dual-frequency Huygens resonant metasurface 2 with the horn feed 1 embedded in the center, while the lower layer is the reflective linear circularly polarized metasurface 3. The horn feed 1 serves as the feed for the folded transmission array. The horn feed 1 is designed to enable the antenna's operating frequency to cover the 26.5-40 GHz frequency range, encompassing the co-aperture antenna's two operating frequencies of 29 and 27 GHz. The upper layer, the dual-frequency Huygens metasurface 3, is composed of 27x27 units arranged in a predetermined period to form a circular array surface. The central 5x5 units are removed to accommodate the dual-polarized horn feed 1. The aperture dimensions of the folded transmission array antenna, i.e., the antenna's diameter, are 126.9 mm, and the antenna's cross-sectional height HH = 79 mm. The co-aperture antenna undergoes a folding during beam propagation. This means that the spherical wave emitted by the horn feed 1 undergoes a specular reflection during its final transmission and conversion into a high-gain plane wave, reducing the antenna height to half its focal length and resulting in a lower profile height compared to a transmission array antenna. The antenna's radiation mechanism is as follows: First, by applying different amplitudes to the dual-port feed, the feed can emit x-polarized electromagnetic waves, y-polarized electromagnetic waves, and 45° polarized electromagnetic waves. The electromagnetic waves emitted by the feed propagate through free space onto the underlying metasurface, where they undergo specular reflection. Simultaneously, due to the polarization-converting dual-frequency Huygens metasurface 2, the reflected waves convert the x-polarized waves into right-handed circularly polarized waves, the y-polarized waves into left-handed circularly polarized waves, and the 45° linearly polarized waves into linearly polarized waves. The reflected electromagnetic waves, incident on the upper dual-frequency Huygens metasurface 2, undergo transmission phase modulation under the action of the Huygens metasurface and are converted into uniform plane wave radiation, forming highly directional right-handed circularly polarized beams and left-handed circularly polarized beams in the far field. The multi-polarization folded transmission array antenna, designed through the combined action of a broadband horn feed, a broadband linear-circular polarization conversion metasurface, and a dual-band Huygens metasurface, exhibits dual-band co-aperture characteristics. Based on this radiation mechanism, the spherical electromagnetic wave emitted by the feed undergoes a folding of its optical path before ultimately converting into a planar transmission electromagnetic wave, resulting in a mirror reflection. Therefore, the cross-sectional height of the designed multi-polarization co-aperture antenna is half the preset focal length f of the transmission focusing metasurface, i.e., HH = f / 2. The overall dimensions of the horn feed are 20.2mm*19.1mm*36mm.

[0066] Reference Figure 3a 、 Figure 3bThe gain of the selected dual-polarization feed horn is 15.32 dBi at 29 GHz and 17.26 dBi at 37 GHz. It can be seen that the horn's center angle theta = 0° achieves maximum gain, and the energy in this direction reaches its maximum. At 29 GHz, the half-angle of the -10 dB beam is 26.19°, and at 37 GHz, the half-angle of the -10 dB beam is 20.98°. The polarization state of the electromagnetic wave radiated by the feed can be adjusted by adjusting the amplitude of the dual-port feed.

[0067] Reference Figure 4a 、 Figure 4b The dual-frequency Huygens resonant metasurface 2 is composed of two square rings with four corner grooves etched on the upper and lower surfaces of a dielectric substrate. The square rings include an upper square ring 21 on the upper layer of the dielectric substrate and a lower square ring 22 on the lower layer of the dielectric substrate. The high and low frequency transmission phases are controlled by adjusting the structural parameters of the high and low frequency units. The dual-frequency Huygens resonant metasurface 2 is a 2-bit dual-frequency Huygens resonant metasurface unit.

[0068] The designed Huygens metasurface exhibits a transmission peak with an amplitude of -1.12dB at 29.75GHz and a transmission peak with an amplitude of -0.39dB at 41.45GHz, demonstrating dual-frequency resonance. It is a classic sandwich structure, with the upper and lower layers being double ring structures silk-screened on a dielectric substrate. The dielectric material used is SJ9036, with a thickness of 1.27mm, P1 = 4.7mm, W1 = 0.2mm, W2 = 0.5mm, and L1 = 4.5mm. a1 is the side length of the low-frequency square ring in the upper square ring, a2 is the side length of the high-frequency square ring in the upper square ring, b1 is the length of the low-frequency gap in the lower square ring, b2 is the length of the high-frequency gap in the lower square ring, w1 is the width of the low-frequency square ring in the upper square ring, w2 is the width of the high-frequency square ring in the upper square ring, p1 is the unit period of the Huygens metasurface, L1 is the low-frequency side length of the lower square ring, and L2 is the high-frequency side length of the lower square ring.

[0069] Reference Figure 5The designed Huygens metasurface exhibits a transmission peak with an amplitude of -1.12dB at 29.75GHz and a transmission peak with a transmission amplitude of -0.39dB at 41.45GHz. The Huygens metasurface has the characteristics of dual-frequency resonance. By changing the metal overlapping parts of the upper and lower double-ring structures of the dielectric substrate, the tangential magnetic field is induced to achieve a balance between the electric resonance and magnetic resonance of the metal surface, thereby stimulating the generation of dual-frequency Huygens resonance. The transmission phase and amplitude at the low frequency of 29GHz can be adjusted by adjusting the sizes of a1 and b1, and the transmission phase at the high frequency of 37GHz can be adjusted by adjusting the size parameters of the inner rings a2 and b2. With the help of the variable L2, the amplitude and phase adjustment of high and low frequencies are more flexible. The relationship between the specific unit size of the Huygens metasurface and the electromagnetic performance is shown in Table 1.

[0070] Reference Figure 6 , showing a schematic diagram of the linear-circular conversion metasurface. The reflective linear circular polarization metasurface 3 consists of a square ring 31 etched above a grounded dielectric substrate and a circular patch 32 located at the center of the ring 31. It converts the linearly polarized wave emitted by the horn feed 1 into a circularly polarized wave.

[0071] The polarizer is designed to have a classic sandwich structure. The top layer consists of an open square ring structure loaded with circular patches, the bottom layer is a metal floor, and the middle layer is a dielectric substrate that provides support. After optimization, the polarizer's structural dimensions are: the period length of the polarization conversion metasurface unit (P2) = 2.5 mm, the thickness of the dielectric substrate (H) = 1.27 mm, the distance from the cut corner to the substrate edge (L) = 1.66 mm, the width of the square ring (W) = 0.48 mm, and the radius of the circular patch (R) = 0.3 mm.

[0072] Figure 7 Here are the co-polarization reflection coefficient and cross-polarization reflection coefficient of the line-circle conversion metasurface under vertical irradiation of x-polarized electromagnetic waves. It can be seen that the amplitudes of the two reflection coefficients are equal in the frequency band of 22GHz to 39GHz, and the maximum amplitude difference between the two reflection coefficients is only 1.7dB.

[0073] Figure 8 The phase difference between the co-polarization reflection coefficient and the cross-polarization reflection coefficient of the line-circle conversion metasurface shows that in the range of 20 GHz to 41 GHz, the phase difference is about -90°, and in the range of 44 GHz to 50 GHz, the phase difference is about 90°.

[0074] Figure 9 The curve of the axial ratio of the line-circle conversion metasurface at vertical incidence varies with frequency. It can be seen that the axial ratio is less than 3dB in the frequency range of 20GHz to 41GHz, the 3dB axial ratio bandwidth is 21GHz, and the relative bandwidth reaches 68%.

[0075] Figure 10 The curve of the axial ratio of the line-circle conversion metasurface at oblique incidence shows that the axial ratio gradually increases with the increase of the incident angle. However, even when the oblique incidence angle increases to 30°, the axial ratio is still less than 2dB in the frequency range of 20.2-40.2GHz. When the oblique incidence angle increases to 35°, the axial ratio is still less than 3dB in the frequency range of 20-40GHz, and the oblique incidence stability reaches 35°.

[0076] Figure 11 This is a model diagram of a multi-polarization common-aperture antenna based on a folded transmission array. For clarity, the dual-polarization horn feed 1 has been removed. A 5x5 metasurface slot is created in the center of the upper Huygens metasurface array to accommodate the feed antenna. The upper layer consists of 27x27 dual-band Huygens metasurfaces 2 arranged in a periodic circular array. The lower layer consists of 50x50 line-circle-converted dual-band Huygens metasurface 3 units arranged in a periodic square array. The height between the upper and lower arrays is 79mm.

[0077] Reference Figure 12a 、 Figure 12b 、 Figure 12c 、 Figure 12d When the antenna operates in the right-hand circular polarization state, the provided folded transmission array antenna has an obvious highly directional radiation pattern near the antenna operating frequency of 29GHz and 37GHz. Figure 12a and Figure 12b The radiation pattern of the antenna in the XOZ plane and YOZ plane at 29GHz when operating in the right-hand circular polarization state. The 3dB beamwidth in the XOZ plane and YOZ plane are 5° and 4.7° respectively, the sidelobe levels are -11.5dB and -12.7dB respectively, and the cross-polarization isolation is -19.9dB. Figure 12c and Figure 12d The radiation pattern of the antenna in the XOZ plane and YOZ plane at 29GHz when operating in the right-hand circular polarization state. The 3dB beamwidth in the XOZ plane and YOZ plane are 5° and 4.7° respectively, the sidelobe levels are -11.5dB and -12.7dB respectively, and the cross-polarization isolation is -19.9dB.

[0078] Reference Figure 13a 、 Figure 13b , Figure 14a 、 Figure 14bWe present the frequency-dependent gain and axial ratio results for the co-aperture antenna operating in right-hand circular polarization. The maximum gain is achieved at the low frequency of 29.1 GHz, with a value of 26.02 dBic. The corresponding aperture efficiency is 26.8%. The low-frequency 3dB gain bandwidth is 27 to 29.6 GHz, with a relative bandwidth of 9.2%. The axial ratio is less than 3 dB within the frequency band of 28.5 to 29.1 GHz, demonstrating good circular polarization purity. The maximum gain is achieved at the high frequency of 37 GHz, with a value of 28.01 dBic. The corresponding aperture efficiency is 26.2%. The high-frequency 3dB gain bandwidth is 36.5 to 37.8 GHz, with an axial ratio less than 3 dB within the frequency band of 36.8 to 37.2 GHz.

[0079] Reference Figure 15a 、 Figure 15b When the co-aperture antenna operates in the left-hand circular polarization state, the provided folded transmission array antenna has an obvious highly directional radiation pattern near the antenna operating frequency of 29GHz and 37GHz. Figure 15a and Figure 15b The radiation pattern of the antenna in the XOZ plane and YOZ plane at 29GHz when operating in the left-hand circular polarization state. The 3dB beamwidth in the XOZ plane and YOZ plane are 5° and 4.7° respectively, the sidelobe levels are -11.5dB and -12.7dB respectively, and the cross-polarization isolation is -19.9dB. Figure 15c and 15d The radiation pattern of the antenna in the XOZ plane and YOZ plane at 29GHz when operating in the left-hand circular polarization state. The 3dB beamwidth in the XOZ plane and YOZ plane are 5° and 4.7° respectively, the sidelobe levels are -11.5dB and -12.7dB respectively, and the cross-polarization isolation is -19.9dB.

[0080] Reference Figure 16a 、 Figure 16b 、 Figure 17a 、 Figure 17b , the gain and axial ratio of the co-aperture antenna operating in the left-hand circular polarization state are given as a function of frequency. The maximum gain is obtained at the low frequency of 29.1 GHz, with a value of 26.02 dBic, and the corresponding aperture efficiency is 26.8%. The low-frequency 3dB gain bandwidth is 27-29.6 GHz, with a relative bandwidth of 9.2%. The axial ratio is less than 3 dB in the frequency band of 28.5-29.1 GHz, demonstrating good circular polarization purity. The maximum gain is obtained at the high frequency of 37 GHz, with a value of 28.01 dBic, and the corresponding aperture efficiency is 26.2%. The high-frequency 3dB gain bandwidth is 36.5-37.8 GHz, and the axial ratio is less than 3 dB in the frequency band of 36.8-37.2 GHz.

[0081] Reference Figure 18a 、 Figure 18b , shows the reflection coefficient diagram of the co-aperture antenna operating in the linear polarization state. It can be seen that the overall reflection coefficient is less than -10dB at the low frequency of 27-31GHz, showing a good matching effect. In the high frequency range of 35-39GHz, except for the frequency of 36.2GHz, the reflection coefficient is less than -10dB, showing an overall good impedance matching effect.

[0082] Reference Figure 19a 、 Figure 19b When the co-aperture antenna operates in a linear polarization state, the provided folded transmission array antenna has an obvious highly directional radiation pattern near the antenna operating frequencies of 29 GHz and 37 GHz. Figure 19a and 19b The radiation patterns of the antenna in the XOZ and YOZ planes at 29 GHz and 37 GHz under linear polarization state are as follows: At 29 GHz, the 3 dB beamwidth in the XOZ and YOZ planes is 4.8°, and the sidelobe levels are -13.9 dB; at 37 GHz, the 3 dB beamwidth in the XOZ and YOZ planes is 3.6°, and the sidelobe levels are -14.1 dB and -14.0 dB, respectively.

[0083] Reference Figure 20a 、 Figure 20b The gain variation of the co-aperture antenna in polarization mode with frequency is presented. The maximum gain is achieved at a low frequency of 28.9 GHz, with a value of 26.3 dBi. This corresponds to an aperture efficiency of 28.95% and a low-frequency 3dB gain bandwidth of 28.5 to 29.7 GHz. The maximum gain is achieved at a high frequency of 37 GHz, with a value of 28.01 dBic. This corresponds to an aperture efficiency of 28.91% and a high-frequency 3dB gain bandwidth of 36.7 to 37.5 GHz.

[0084] Different from the existing technology, the present invention provides a millimeter-wave multi-polarization common-aperture antenna based on a folded transmission array. Based on a dual-frequency Huygens metasurface, a broadband linear-circular conversion metasurface, and a dual-polarization feed horn, the present invention, based on the architecture of the folded transmission array, ultimately realizes a multi-polarization common-aperture array antenna. Ultimately, the multi-polarization common-aperture antenna based on the folded transmission array has the characteristics of low profile, multi-polarization (right-hand circular polarization, left-hand circular polarization, linear polarization), high aperture efficiency (right-hand polarization low frequency 26.8%, high frequency 26.2%; left-hand polarization low frequency 26.8%, high frequency 26.2%; linear polarization low frequency 28.95%, high frequency 28.91%), and simple structure (only two layers of dielectric substrate, no metallized through-holes, and no adhesive layer). The proposed antenna can realize both frequency division multiplexing and polarization multiplexing, which can greatly improve the channel capacity during satellite communication, reduce system complexity and reduce system cost, and can be used in highly integrated and compact modern communication systems, radar systems, or satellite communication systems.

[0085] The aperture efficiency of the multi-polarization common aperture antenna is:

[0086] Where G is the simulated achievable gain, λ is the wavelength in vacuum corresponding to the two frequencies 29 / 37 GHz at which the antenna operates, and S is the area of ​​the radiating aperture of the array antenna.

[0087] The above description is merely a preferred embodiment of the present invention. The same operating principles can also be applied to the design of multi-polarization, co-aperture folded transmission array antennas for other frequency bands. This does not limit the scope of the present invention. Simply equivalent variations and modifications made in accordance with the claims and description of the present invention, or direct or indirect applications in other related technical fields, are also within the scope of the present invention.

[0088] Table 1 shows the relationship between the unit size and electromagnetic performance of the 2-bit dual-frequency Huygens resonant metasurface;

[0089] Table 1

[0090]

Claims

1. A millimeter-wave multi-polarization common-aperture antenna based on a folded transmission array, characterized in that: The co-aperture antenna has a two-layer structure, consisting of a horn feed (1), a dual-frequency Huygens resonant metasurface (2), and a reflective linear circular polarization metasurface (3); wherein the upper layer is a dual-frequency Huygens resonant metasurface (2) with the horn feed (1) embedded in the middle, and the lower layer is a reflective linear circular polarization metasurface (3); the horn feed (1) is used as the feed source of the folded transmission array, and the horn feed (1) is fed by a dual-polarization horn antenna; The dual-frequency Huygens resonant metasurface (2) is composed of a plurality of square ring units with four-corner grooves etched on the upper and lower surfaces of a dielectric substrate, wherein the square ring units include an upper square ring (21) on the upper layer of the dielectric substrate and a lower square ring (22) on the lower layer of the dielectric substrate, and the high and low frequency transmission phases are regulated by adjusting the structural parameters of the high and low frequency units; The reflective linear circular polarization metasurface (3) is composed of a plurality of notched square rings (31) etched above a grounded dielectric substrate and a circular patch (32) located at the center of the notched square rings (31); the reflective linear circular polarization metasurface (3) converts the linear polarization wave emitted by the horn feed source (1) into a circular polarization wave; The beam propagation process of the common aperture antenna is folded once, that is, the spherical wave emitted by the horn feed source (1) is mirror-reflected once during the final transmission and conversion into a high-gain plane wave, so that the height of the antenna is reduced to half of the focal length, and the antenna has a lower profile height compared with the transmission array antenna.

2. The millimeter-wave multi-polarization common-aperture antenna based on a folded transmission array according to claim 1, characterized in that: The horn feed (1) is required to enable the antenna's operating frequency to cover a frequency band ranging from 26.5 to 40 GHz, and to cover the two operating frequencies of the common aperture antenna, 29 and 37 GHz.

3. The millimeter-wave multi-polarization common-aperture antenna based on a folded transmission array according to claim 1, characterized in that: The overall size of the horn feed source (1) is 20.2 mm*19.1 mm*36 mm.

4. The millimeter wave multi-polarization common aperture antenna based on the folded transmission array according to claim 1, characterized in that The dual-frequency Huygens resonant metasurface (2) is a 2-bit dual-frequency Huygens resonant metasurface unit.

5. The millimeter wave multi-polarization common aperture antenna based on the folded transmission array according to claim 1, characterized in that The two square ring units in the dual-frequency Huygens resonant metasurface (2) are square units, wherein the structural size of each unit is determined by the required different transmission phases. The transmission phase corresponding to each unit on the dual-frequency Huygens resonant metasurface (2) needs to satisfy the distribution expressed by the following formula, converting the spherical wave emitted by the feed source into the final high-gain plane wave. Where Φ(m,n) is the transmission phase corresponding to the m-th row and n-th column unit of the dual-frequency Huygens metasurface, λ is the wavelength in vacuum corresponding to the two operating frequencies of 29 / 37 GHz, p is the period length of the Huygens metasurface unit, and f is the focal length of the focusing function of the designed folded transmission array.

6. The millimeter-wave multi-polarization common-aperture antenna based on a folded transmission array according to claim 1, characterized in that: The upper dual-frequency Huygens resonant metasurface (2) is composed of 27*27 metasurface units arranged in a circular array, wherein 5*5 metasurface units located at the center are removed to embed the horn feed (1); the lower reflective linear circular polarization metasurface (3) is composed of 50*50 metasurface units.

7. The millimeter wave multi-polarization common aperture antenna based on the folded transmission array according to claim 1, characterized in that The aperture efficiency of the multi-polarization common aperture antenna is: Where G is the simulated achievable gain, λ is the wavelength in vacuum corresponding to the two frequencies 29 / 37 GHz at which the antenna operates, and S is the area of ​​the radiating aperture of the array antenna.

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