Dual-frequency dual-circularly polarized transmission array antenna based on frequency multiplexing metasurface

Abstract

This invention relates to a dual-band, dual-circularly polarized transmission array antenna based on a frequency-reused metasurface. The frequency-reused metasurface integrates elements of different sizes operating in two different frequency bands onto a single radiating aperture surface through staggered arrangement, achieving dual-band operation with high isolation. Both basic functional units include an upper metal layer constituting a linearly polarized microstrip antenna layer and a lower metal layer constituting a circularly polarized microstrip antenna layer. The basic functional units can independently control the phase of the left-hand and right-hand circularly polarized waves in the transmission field by independently rotating the upper and lower metal layers, ultimately achieving decoupling. This invention enables arbitrary and independent control of the radiated left-hand and right-hand circularly polarized beams in different frequency bands, offering advantages such as low profile, wide bandwidth, high polarization purity, and high aperture efficiency. It holds promise for applications in high-throughput satellite communication systems and next-generation wireless communication systems.

Description

Technical Field

[0001] This invention belongs to the field of artificial electromagnetic metamaterials, specifically relating to a dual-frequency dual-circularly polarized transmission array antenna based on a frequency-reused metasurface. Background Technology

[0002] Circularly polarized high-gain antennas, due to their excellent natural characteristics of avoiding multipath fading and polarization mismatch, can provide stable and reliable signal transmission and reception, and are therefore widely used in many long-distance wireless and satellite communication systems. Reflector array antennas and transmission array antennas are two classic air-fed array antennas. Compared with traditional high-gain phased array antennas and parabolic antennas, they have become more favored by antenna designers in recent years because they simultaneously offer advantages such as low profile, low cost, low loss, and ease of fabrication. With the ever-increasing demand for high capacity in modern communication systems, simple antenna structures that transmit a single circularly polarized electromagnetic wave in a specific frequency band can no longer meet the requirements. Therefore, exploring new design methods for realizing dual-frequency, dual-circularly polarized high-gain antennas remains challenging and is of great significance for future satellite communications.

[0003] Electromagnetic metamaterials, also known as artificial electromagnetic materials, have attracted widespread attention from researchers since their inception due to their unique physical properties not found in nature. Electromagnetic metasurfaces, as a two-dimensional form of electromagnetic metamaterials, are formed by periodically extending and arranging subwavelength unit structures in a two-dimensional plane according to certain rules. They possess advantages such as low profile, light weight, and ease of fabrication. Therefore, combining the concept of electromagnetic metasurfaces with antenna applications will provide a new paradigm for the design of high-performance antennas. In particular, frequency-reused metasurfaces offer greater freedom in the design of electromagnetic functional devices. By realizing arbitrary and independent functional designs within two or more operating frequency bands, the functional integration of devices will be effectively improved, making them more suitable for compact modern wireless communication systems.

[0004] Therefore, designing a frequency-reused metasurface and combining it with a feed antenna to realize a dual-frequency, dual-circularly polarized transmission array antenna can greatly improve the beam freedom of the transmission array antenna, and is expected to play an important role in high-throughput satellite applications. On the other hand, combining the concept of metasurfaces with antenna applications is also of great significance in further exploring the application scope of metasurfaces and enhancing their application value. Summary of the Invention

[0005] Objective of the Invention: The main objective of this invention is to provide a dual-frequency dual-circularly polarized frequency-reusing metasurface and a dual-frequency dual-circularly polarized transmission array antenna based on this frequency-reusing metasurface. A frequency-reusing metasurface is designed using a common-aperture approach. Within each operating frequency band, the metasurface can convert incident circularly polarized electromagnetic waves into two transmitted orthogonal circularly polarized electromagnetic beams, and the direction of each beam can be independently controlled. Combined with the designed planar circularly polarized feed antenna, the dual-frequency dual-circularly polarized transmission array antenna possesses advantages such as low profile, wide bandwidth, and high polarization purity.

[0006] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0007] A dual-frequency circularly polarized frequency-reusing metasurface is disclosed, capable of achieving four beam degrees of freedom in two operating frequency bands. It converts the incident circularly polarized beam of the first frequency band into independently controllable left-hand and right-hand circularly polarized beams, and the incident circularly polarized beam of the second frequency band into independently controllable left-hand and right-hand circularly polarized beams. The metasurface comprises a first and second basic functional unit arranged in an alternating pattern with a common aperture. The two basic functional units have different sizes and correspond to the two frequency bands (e.g., Ku-band and K-band). Each basic functional unit includes an upper metal layer constituting a linearly polarized microstrip antenna layer and a lower metal layer constituting a circularly polarized microstrip antenna layer. These layers are used to convert the received left-hand or right-hand circularly polarized wave into a transmitted linearly polarized wave and achieve decoupling of the left and right circular polarizations, decomposing them into equal-amplitude and independently controllable left-hand and right-hand circularly polarized waves. The decoupling of the left and right circular polarizations is achieved by independently rotating the lower and upper metal layers.

[0008] A dual-frequency dual-circularly polarized transmission array antenna based on a frequency-reused metasurface is composed of the frequency-reused metasurface and a planar circularly polarized feed antenna. The frequency-reused metasurface is formed by periodically extending two basic functional units operating in different frequency bands (such as Ku-band and K-band) through a common-aperture design method. The basic functional units can decompose the transmitted linearly polarized wave into a pair of orthogonal circularly polarized waves and achieve independent modulation. The dual-frequency dual-circularly polarized transmission array antenna can radiate independently adjustable left-hand circularly polarized beams and right-hand circularly polarized beams in the first and second frequency bands, respectively. The circularly polarized feed antenna is divided into a first-band circularly polarized feed antenna and a second-band circularly polarized feed antenna, which are used to excite the operating modes of the two frequency bands respectively.

[0009] Preferably, both basic functional units consist of three metal layers and two dielectric layers, from top to bottom: an upper metal layer, an upper dielectric layer, a middle metal layer, a lower dielectric layer, and a lower metal layer. The lower metal layer is a circularly polarized microstrip antenna layer used to receive circularly polarized electromagnetic waves emitted by the feed source. The upper metal layer is a linearly polarized microstrip antenna layer used to convert the energy radiated from the feed source into linearly polarized transmitted waves and further decompose them into left-hand circularly polarized and right-hand circularly polarized beams for radiation. The basic functional unit is a multilayer laminated structure, with a semi-cured sheet layer fixing the middle metal layer and the lower dielectric layer together.

[0010] Preferably, both basic functional units connect the lower metal layer to the upper metal layer through vertically arranged metallized vias, so that the energy received by the lower metal layer can be coupled to the upper metal layer through the metallized vias and finally radiated out; a circular groove is opened on the middle metal layer to allow the vertically arranged metallized vias to pass through.

[0011] Preferably, both the lower circularly polarized microstrip antenna layer and the upper linearly polarized microstrip antenna layer adopt a circular patch structure; the circular patch constituting the lower circularly polarized microstrip antenna has an asymmetrical U-shaped slot to excite the circular polarization radiation characteristics; the circular patch constituting the upper linearly polarized microstrip antenna has a symmetrical U-shaped slot in the center to excite the linear polarization radiation characteristics.

[0012] Preferably, the phases of the left-hand circularly polarized wave and the right-hand circularly polarized wave in the transmission field are modulated in phase by rotating the lower metal layer, and the phases of the left-hand circularly polarized wave and the right-hand circularly polarized wave in the transmission field are modulated out of phase by rotating the upper metal layer. By combining the two, the phases of the left-hand circularly polarized wave and the right-hand circularly polarized wave in the transmission field can be modulated arbitrarily and independently, and the decoupling of the left and right circularly polarized waves can be achieved.

[0013] Preferably, by independently rotating the lower and upper metal layers, the phase of the left-hand and right-hand circularly polarized waves in the transmission field can be continuously modulated over a range of 360°.

[0014] In practice, the low-frequency feed is designed as a right-hand / left-hand circularly polarized antenna, and the high-frequency feed is designed as a left-hand / right-hand circularly polarized antenna. Correspondingly, the lower metal layer of the basic functional unit in the low-frequency band is designed as a right-hand / left-hand circularly polarized microstrip antenna; the lower metal layer of the basic functional unit in the high-frequency band is designed as a left-hand / right-hand circularly polarized microstrip antenna.

[0015] Preferably, the circularly polarized feed antenna is composed of a 2×2 microstrip antenna array using a rotating feed method, including two radiating patch layers, with the bottom layer serving as the driving layer radiating patch and the top layer serving as the parasitic layer radiating patch. The radiating patch is composed of chamfered square metal patches.

[0016] Beneficial Effects: The dual-frequency dual-circularly polarized transmission array antenna based on a frequency-reused metasurface provided by this invention achieves dual-circularly polarized beam radiation functionality in two operating frequency bands, possessing a total of four beam degrees of freedom, and the pointing of each of the four beams can be arbitrarily and independently designed. Compared with the prior art, this invention has the following advantages:

[0017] 1. This invention combines the design concept of frequency reuse metasurfaces with antenna applications to design a dual-frequency dual-circularly polarized transmission array antenna. Thanks to the flexible and diverse design freedom of metasurfaces, the complexity of traditional antenna design methods is reduced.

[0018] 2. This invention proposes a method for decoupling left and right circular polarization, which enables the designed dual-frequency dual-circular polarization transmission array antenna to independently design the phase of the transmitted left-hand circular polarization and right-hand circular polarization components in both operating frequency bands.

[0019] 3. Compared with existing dual-frequency dual-circular polarization reflective array antennas, the dual-frequency dual-circular polarization transmission array antenna proposed in this invention effectively avoids the influence of feed source obstruction, and the beam pointing design is more flexible and arbitrary.

[0020] 4. Compared with transmission array antennas that use large-volume feed sources such as horn antennas, the dual-frequency dual-circular polarization transmission array antenna proposed in this invention uses a planar microstrip antenna array with a lower profile and lighter weight as the feed source, making the overall volume more compact and more suitable for satellite communication systems with better integration.

[0021] 5. Thanks to the fact that the designed feed antenna operates in different circular polarization modes in two different operating frequency bands, the dual-frequency dual-circular polarization transmission array antenna proposed in this invention has low crosstalk in both frequency bands.

[0022] 6. The dual-frequency dual-circular polarized transmission array antenna designed in this invention uses a high-performance frequency reuse metasurface as the radiating aperture surface. The overall thickness of the metasurface is much lower than the radiating aperture surface thickness used in other reported dual-frequency dual-circular polarized transmission / reflection array antennas. Furthermore, the proposed transmission array antenna has the advantages of wide bandwidth, high polarization purity, and high aperture efficiency. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the structure and function of a dual-frequency dual-circularly polarized transmission array antenna based on a frequency reuse metasurface, according to an embodiment of the present invention.

[0024] Figure 2 Figure 1 shows a three-dimensional decomposition diagram of the basic functional unit of the frequency reuse metasurface according to an embodiment of the present invention (Figure 1), a top view of the upper metal layer (Figure 2), a top view of the lower metal layer (Figure 3), and a top view of the middle metal layer (Figure 4).

[0025] Figure 3 The simulation results of the frequency reuse metasurface basic functional unit's dual-frequency amplitude characteristics as a function of the low-frequency Ku-band unit radius (Figure a) and the K-band unit radius (Figure b) are shown in the figure.

[0026] Figure 4 These are dual-frequency amplitude and phase operating characteristic diagrams of the basic functional unit of the frequency reuse metasurface of the present invention when rotating the upper and lower metal layers of the low-frequency Ku-band unit. Figure a corresponds to the amplitude and phase response of the right-hand and left-hand components in the low-frequency transmission field when rotating the lower metal layer of the Ku-band unit. Figure b corresponds to the amplitude and phase response of the right-hand and left-hand components in the low-frequency transmission field when rotating the upper metal layer of the Ku-band unit. Figure c corresponds to the amplitude and phase response of the right-hand and left-hand components in the high-frequency transmission field when rotating the lower metal layer of the Ku-band unit. Figure d corresponds to the amplitude and phase response of the right-hand and left-hand components in the high-frequency transmission field when rotating the upper metal layer of the Ku-band unit.

[0027] Figure 5 These are dual-frequency amplitude and phase operating characteristic diagrams of the basic functional unit of the frequency reuse metasurface of the present invention when rotating the upper and lower metal layers of the high-frequency K-band unit. Figure a corresponds to the amplitude and phase response of the right-hand and left-hand components in the low-frequency transmission field when rotating the lower metal layer of the K-band unit. Figure b corresponds to the amplitude and phase response of the right-hand and left-hand components in the low-frequency transmission field when rotating the upper metal layer of the K-band unit. Figure c corresponds to the amplitude and phase response of the right-hand and left-hand components in the high-frequency transmission field when rotating the lower metal layer of the K-band unit. Figure d corresponds to the amplitude and phase response of the right-hand and left-hand components in the high-frequency transmission field when rotating the upper metal layer of the K-band unit.

[0028] Figure 6 Figure a shows a three-dimensional structural schematic diagram of the planar microstrip circularly polarized feed antenna used in the dual-frequency dual-circularly polarized transmission array antenna of this invention, a top view of the feeding structure of the K-band left-hand circularly polarized feed antenna (Figure b), and a top view of the feeding structure of the Ku-band right-hand circularly polarized feed antenna (Figure c).

[0029] Figure 7 Figure 1 shows the phase distribution and element rotation angle distribution required for realizing a dual-frequency dual-circularly polarized transmission array antenna using a frequency reuse metasurface according to an embodiment of the present invention. Figure 2a corresponds to the phase distribution required for realizing low-frequency right-hand and left-hand circularly polarized beams, respectively. Figure 3b corresponds to the rotation angle distribution of the upper and lower metal layers of the basic functional unit in the low-frequency Ku-band, respectively. Figure 4c corresponds to the phase distribution required for realizing high-frequency right-hand and left-hand circularly polarized beams, respectively. Figure 5d corresponds to the rotation angle distribution of the upper and lower metal layers of the basic functional unit in the high-frequency K-band.

[0030] Figure 8These are simulation and test results of the gain-axis ratio performance of the dual-frequency dual-circularly polarized transmission array antenna according to an embodiment of the present invention. Figure a corresponds to the low-frequency Ku-band right-hand circular beam, Figure b corresponds to the low-frequency Ku-band left-hand circular beam, Figure c corresponds to the high-frequency K-band right-hand circular beam, and Figure d corresponds to the high-frequency K-band left-hand circular beam.

[0031] Figure 9 These are simulation and test results of the two-dimensional far-field radiation pattern of the dual-frequency dual-circularly polarized transmission array antenna according to an embodiment of the present invention. Figure a corresponds to the E-plane and H-plane radiation pattern of the low-frequency Ku-band right-hand circularly polarized beam, Figure b corresponds to the E-plane and H-plane radiation pattern of the low-frequency Ku-band left-hand circularly polarized beam, Figure c corresponds to the E-plane and H-plane radiation pattern of the high-frequency K-band right-hand circularly polarized beam, and Figure d corresponds to the E-plane and H-plane radiation pattern of the high-frequency K-band left-hand circularly polarized beam. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] Reference Figure 1 This invention discloses a dual-frequency dual-circularly polarized transmission array antenna based on a frequency-reused metasurface. The transmission array antenna includes a frequency-reused metasurface 101 and a planar circularly polarized microstrip feed antenna 102. This dual-frequency dual-circularly polarized transmission array antenna can achieve a total of four beam degrees of freedom in two operating frequency bands. The high and low frequencies of this invention are designed using the K-band and K-band as examples, respectively. When the left-hand circularly polarized wave 103 radiated by the high-frequency K-band feed antenna illuminates the metasurface, the transmission array antenna will radiate independently controllable K-band left-hand circularly polarized beam 105 and right-hand circularly polarized beam 106. When the right-hand circularly polarized wave 104 radiated by the low-frequency Ku-band feed antenna illuminates the metasurface, the transmission array antenna will radiate independently controllable Ku-band left-hand circularly polarized beam 107 and right-hand circularly polarized beam 108. The frequency-reused metasurface 101 employs a common-aperture design method to integrate different sized units operating in two different frequency bands onto the same aperture surface through a staggered arrangement. The high-frequency and low-frequency units operate independently, resulting in low crosstalk between them.

[0034] Specifically, the frequency reuse metasurface is formed by periodically extending two basic functional units operating in the Ku-band and K-band through a common aperture design method. Combined with a left-right circular polarization decoupling method, the basic functional units can decompose the transmitted ray polarized wave into a pair of orthogonal circularly polarized waves and achieve independent modulation. Both basic functional units are composed of three metal layers and two dielectric layers, from top to bottom: upper metal layer, upper dielectric layer, middle metal layer, lower dielectric layer, and lower metal layer. The basic functional units are multilayer laminated structures, with a semi-cured sheet layer fixing the two dielectric structures together. The circularly polarized feed antennas are divided into Ku-band circularly polarized feed antennas and K-band circularly polarized feed antennas, used to excite the operating modes of the two frequency bands respectively.

[0035] The upper metal layer of the two basic functional units constituting the metasurface is a linearly polarized microstrip antenna, and the lower metal layer is a circularly polarized microstrip antenna. The upper linearly polarized microstrip antenna and the lower circularly polarized microstrip antenna are connected through a metallized via placed vertically at the center of the basic functional unit. The circularly polarized electromagnetic wave emitted by the feed can be received by the circularly polarized microstrip antenna below the basic functional unit of the metasurface, and then conducted to the upper metal layer and converted into a linearly polarized wave for radiation. The radiated linearly polarized electromagnetic wave can be further decomposed into a pair of orthogonal circularly polarized electromagnetic waves with equal amplitude, so that the purpose of radiating dual circularly polarized electromagnetic waves can be achieved in each independent operating frequency band.

[0036] The left-hand and right-hand circular polarization decoupling method decomposes the transmitted linearly polarized electromagnetic wave into a pair of equal-amplitude orthogonal circularly polarized electromagnetic waves by independently rotating the upper and lower metal layers of the basic functional unit, and independently modulates the additional phase of the two circularly polarized electromagnetic waves. This allows the final frequency-reusing metasurface to radiate independently controllable dual-circularly polarized beams in each operating frequency band. Specifically, by rotating the metal layer below the basic functional unit, i.e., the circularly polarized microstrip antenna used for receiving, the additional phase of the transmitted left-hand and right-hand circularly polarized waves can be adjusted in phase. Conversely, by rotating the metal layer above the basic functional unit, i.e., the linearly polarized microstrip antenna used for radiating, the additional phase of the transmitted left-hand and right-hand circularly polarized waves can be adjusted in phase out of phase. Based on this, by independently rotating the upper and lower metal layers of the basic functional unit, the transmitted left-hand circularly polarized wave can be decoupled and independently modulated.

[0037] In this embodiment, the metal layer below the basic functional unit, i.e., the circularly polarized microstrip antenna for receiving, is composed of a center-fed metal disc with an asymmetric "U"-shaped slot to excite the circularly polarized radiation mode and broaden the bandwidth. The metal layer above the basic functional unit, i.e., the linearly polarized microstrip antenna for radiating, is composed of a center-fed metal disc with a symmetrical "U"-shaped slot in the center to excite the linearly polarized radiation mode and broaden the bandwidth. It is understood that the implementation methods for the circularly polarized and linearly polarized microstrip antennas are not limited to the design methods used in this embodiment, and can be extended to other circularly polarized and linearly polarized microstrip antenna structures. For example, a square metal patch loaded with an asymmetric "U"-shaped slot, or a square metal patch with a chamfered corner along the diagonal, can all realize the design of a circularly polarized microstrip antenna. A square metal patch loaded with a symmetrical "U"-shaped slot, or a square / circular metal patch without a slot, can all realize the design of a linearly polarized microstrip antenna.

[0038] The circularly polarized feed antenna consists of a 2×2 microstrip antenna array using a rotating feed method, which is used to extend the bandwidth while having low axial ratio characteristics, thereby radiating circularly polarized waves with high polarization purity. The circularly polarized feed antenna consists of two radiating patch layers, with the bottom layer serving as the driving layer radiating patch and the top layer serving as the parasitic layer radiating patch, in order to achieve the purpose of widening the bandwidth. The radiating patch layer is composed of chamfered square metal patches.

[0039] In this embodiment, the low-frequency Ku-band feed is designed as a right-hand circularly polarized antenna, and the high-frequency K-band feed is designed as a left-hand circularly polarized antenna to improve the isolation between the two operating frequency bands, thereby reducing crosstalk. Correspondingly, the metal layer below the low-frequency Ku-band basic functional unit for receiving is designed as a right-hand circularly polarized microstrip antenna, and the metal layer below the high-frequency K-band basic functional unit for receiving is designed as a left-hand circularly polarized microstrip antenna. It is understood that the feed circular polarization allocation scheme used to implement the dual-frequency dual-circularly polarized transmission array using the method described in this invention can be extended to other combinations, i.e., the low-frequency Ku-band uses a left-hand circularly polarized feed, and the high-frequency K-band uses a right-hand circularly polarized feed; correspondingly, the receiving antenna below the low-frequency basic functional unit can be adjusted to a left-hand circularly polarized microstrip antenna, and the receiving antenna below the high-frequency basic functional unit can be adjusted to a right-hand circularly polarized microstrip antenna. For the circularly polarized microstrip antenna with the asymmetric "U" slot, by mirroring and flipping the asymmetric "U" slot, the conversion from one circular polarization mode to another orthogonal circular polarization mode can be achieved during the design process.

[0040] The specific design and effects of the embodiments of the present invention will be explained in detail below with specific simulation and experimental examples. To achieve independent and arbitrary control of the four beams mentioned above, refer to... Figure 2 This invention provides a common-aperture basic functional unit comprising three metal layers, two dielectric layers, and one prepreg layer. For example... Figure 2 As shown in Figure a, the basic functional unit, from top to bottom, consists of an upper low-frequency metal layer 201 and a high-frequency metal layer 202, an upper dielectric layer 205, a middle metal layer 206, a prepreg layer 207, a lower dielectric layer 208, and a lower low-frequency metal layer 203 and a high-frequency metal layer 204. Furthermore, the basic functional unit uses vertically arranged metallized vias 209 to connect the upper and lower metal layers operating in the two frequency bands. Both dielectric layers use F4B dielectric substrate material with a thickness of h1 = 1 mm, a relative permittivity of 3.5, and a loss tangent of 0.001. Both metal layers use copper foil with a thickness of 0.018 mm. The prepreg layer uses Rogers RO4450F with a thickness of h2 = 0.1 mm, a relative permittivity of 3.52, and a loss tangent of 0.004. The top views of the upper and lower metal layers of the basic functional unit are shown below. Figure 2 As shown in b and c, the period length p = 8.5 mm. The specific dimensions of the low-frequency Ku-band unit are: w1 = 1.7 mm, w2 = 2.1 mm, u1 = 0.3 mm, u2 = 0.4 mm, r1 = 2.2 mm, w5 = 1.7 mm, w6 = 2 mm, u5 = 0.24 mm, u6 = 0.44 mm, s1 = 0.55 mm, s2 = 1 mm. The specific dimensions of the high-frequency K-band unit are: r2 = 1.7 mm, w3 = 1.2 mm, w4 = 1.2 mm, u3 = 0.1 mm, u4 = 0.3 mm, w7 = 1.3 mm, w8 = 1.5 mm, u7 = 0.15 mm, u8 = 0.25 mm, s3 = 0.5 mm, s4 = 0.85 mm. The upper metal layer is composed of two different sizes of metal discs for each of the two operating frequency bands. Each disc has a symmetrical "U"-shaped groove at its center to achieve linear polarization radiation characteristics. The lower metal layer is also composed of two different sizes of metal discs for each of the two operating frequency bands. Unlike the upper metal disc, the lower metal disc has an asymmetrical "U"-shaped groove structure to achieve circular polarization radiation characteristics. Figure 2 As shown in Figure d, the basic functional unit has a circular slot in the middle metal layer to allow vertically placed metallized vias to pass through. The diameter of the metallized via connecting the upper and lower metal layers of the low-frequency Ku-band is d1 = 0.3 mm, corresponding to a slot diameter of d2 = 1 mm in the middle metal layer; the diameter of the metallized via connecting the upper and lower metal layers of the high-frequency K-band is d3 = 0.4 mm, corresponding to a slot diameter of d4 = 1 mm in the middle metal layer. The overall thickness of the basic functional unit is 2.154 mm, corresponding to a low-frequency center frequency of approximately 0.12λ. Ku .

[0041] Reference Figure 3The frequency-reusing metasurface can achieve independent control of its respective operating frequency band by adjusting the dimensions of the high-frequency and low-frequency units, without affecting the operating characteristics of the other operating frequency band. For example... Figure 3 As shown in Figure a, when only the diameter r1 of the low-frequency Ku-band metal disc is adjusted, the low-frequency operating frequency band of the frequency-reusing metasurface can be effectively adjusted, while the frequency range of the high-frequency operating band remains largely unaffected. Figure 3 As shown in Figure b, when only the diameter r2 of the high-frequency K-band metal disc is adjusted, the high-frequency operating frequency band of the frequency reuse metasurface can be effectively adjusted, while the frequency range of the low-frequency operating frequency band remains largely unaffected.

[0042] To achieve arbitrarily oriented beams, the basic functional units of the frequency-reused metasurface need to satisfy independent phase modulation of the two circularly polarized components in the two operating frequency bands. This invention provides a decoupling method for left- and right-hand circularly polarized components, enabling independent phase modulation of the left- and right-hand circularly polarized components in the transmission field in both operating frequency bands. For example... Figure 2 As shown in Figure a, the upper and lower metal discs of the designed basic functional unit can be rotated arbitrarily around their connection point during the design process. Let the rotation angle of the upper low-frequency metal disc be α. Ku The rotation angle of the upper high-frequency metal disc is α. K The rotation angle of the lower low-frequency metal disc is β. Ku The rotation angle of the lower high-frequency metal disc is β. K .like Figure 4 As shown in Figure a, when the lower low-frequency metal disc is rotated, the phases of both the right-hand circularly polarized component and the left-hand circularly polarized component in the low-frequency transmission field decrease as the rotation angle increases. Figure 4 As shown in Figure b, when the upper low-frequency metal disc is rotated, the phase of the right-hand circularly polarized component in the low-frequency transmission field increases with the increase of the rotation angle, while the phase of the left-hand circularly polarized component decreases with the increase of the rotation angle. On the other hand, as... Figure 4 As shown in figures c and d, rotating the low-frequency unit has almost no effect on the phase of the left and right circularly polarized components in the transmission field of the high-frequency operating band. Similarly, the above principle also applies to rotating the high-frequency unit to independently modulate the phase of the left and right circularly polarized components in the transmission field of the high-frequency operating band. The relevant simulation results are shown in... Figure 5 As shown. Based on the above analysis, the relationship between the phase response of the left and right circularly polarized components in the two operating frequency bands and the rotation angle parameters in the basic functional unit can be obtained, as shown in the following formula:

[0043]

[0044]

[0045] Where, Φ R (x,y) KuFor the additional phase of the low-frequency right-hand circularly polarized component, Φ L (x,y) Ku For the additional phase of the low-frequency left-hand circularly polarized component, Φ R (x,y) K For the additional phase of the right-hand circularly polarized component in the high-frequency band, Φ L (x,y) K This is the additional phase of the left-hand circularly polarized component in the high-frequency band. Therefore, once the designed directions of the four beams are determined, the required phase distribution for each beam can be calculated, and finally the rotation angle distribution of each metal disc on the frequency reuse metasurface can be obtained.

[0046] like Figure 6 As shown in Figure a, the circularly polarized microstrip feed antenna of this invention comprises four metal layers and three dielectric layers, from top to bottom: parasitic patch metal layer 607, parasitic patch dielectric layer 601, driving patch metal layer 608, driving patch dielectric layer 602, prepreg layer 603, metal ground plane layer 604, feed dielectric layer 605, and feed metal layer 606. The parasitic patch dielectric layer 601 and the driving patch dielectric layer 602 use Rogers RT5880 dielectric substrates with a relative permittivity of 2.2 and a loss tangent of 0.0009. The feed dielectric layer uses Rogers RO4003 dielectric substrates with a relative permittivity of 3.55 and a loss tangent of 0.0027. A certain air layer is provided between the driving patch and the parasitic patch to broaden the antenna's operating bandwidth. The radiating patch is composed of chamfered square elements to excite the circularly polarized operating mode. The feeding structure for a high-frequency left-hand circularly polarized feed antenna and the feeding structure for a low-frequency right-hand circularly polarized feed antenna are respectively as follows: Figure 6 As shown in b and c, the feeding structure employs a rotating differential feeding method to improve the polarization purity of the radiated circularly polarized wave while expanding the antenna's operating bandwidth.

[0047] Reference Figure 7 The required phase distribution of the dual-frequency dual-circularly polarized transmission array antenna in this embodiment of the invention can be calculated using the following formula:

[0048]

[0049]

[0050] Among them, the Ku-band right-hand circularly polarized beam is designed in the xoz plane, with a beam deflection angle θ. R-Ku The angle is 20°; the Ku-band left-hand circularly polarized beam is designed in the yoz plane, with a beam deflection angle θ. L-Ku The K-band right-hand circularly polarized beam is designed in the yoz plane with a beam deflection angle of θ of 20°. R-K-10°; the K-band left-hand circularly polarized beam is designed in the xoz plane, with a beam deflection angle θ. R-Ku The value is -10°. Based on the phase calculation formula above, and considering the relationship between the rotation angle distribution and the phase distribution, the phase distributions of the low-frequency Ku-band right-hand circularly polarized beam and the left-hand circularly polarized beam are finally generated as follows: Figure 7 As shown in Figure a; the rotation angle distribution of the upper and lower metal discs of the Ku-band unit is as follows. Figure 7 As shown in b, the phase distributions of the generated high-frequency K-band right-hand circularly polarized beam and left-hand circularly polarized beam are as follows. Figure 7 As shown in c; the rotation angle distribution of the metal discs above and below the K-band unit is as follows. Figure 7 As shown in d.

[0051] Reference Figure 8 The dual-frequency dual-circularly polarized transmission array antenna in this embodiment of the invention was tested in a microwave anechoic chamber to obtain its far-field radiation performance, including gain-to-axis ratio. The test results are consistent with the simulation results. The results show that the measured beam gains of the transmission array antenna in the Ku band for right-hand circular polarization and left-hand circular polarization are 21.6 dBic and 21.4 dBic, respectively, corresponding to peak aperture efficiencies of 23.6% and 22.6%, respectively, and 3 dB gain bandwidths of 16.4% and 17%, respectively. Within the 3 dB gain bandwidth, the beam-to-axis ratio is less than 3 dB. In the K band, the measured beam gains of the transmission array antenna for right-hand circular polarization and left-hand circular polarization are 21.8 dBic and 22.1 dBic, respectively, corresponding to peak aperture efficiencies of 13% and 13.9%, respectively, and 3 dB gain bandwidths of 9.3% and 9.7%, respectively. Within the 3 dB gain bandwidth, the beam-to-axis ratio is less than 3 dB.

[0052] Figure 9 These are the simulation and test results of the far-field radiation patterns of the four beams radiated by the dual-frequency dual-circularly polarized transmission array antenna in this embodiment of the invention, in the E-plane and H-plane at the center frequency. Figure 9 a and b are the far-field radiation patterns of the right-hand circularly polarized beam and the left-hand circularly polarized beam in the Ku band at 17 GHz, respectively. Figure 9 c and d represent the far-field radiation patterns of the K-band right-hand circularly polarized beam and the left-hand circularly polarized beam at 21.4 GHz, respectively. The simulated and tested beam angles of the four beams radiated by the dual-frequency dual-circularly polarized transmission array antenna are consistent with the theoretical design values, and the axial ratio of the main beam radiation angle is suppressed to within 3 dB, thus each beam has good polarization purity.

[0053] The above description is merely a preferred embodiment of the present invention. The same structure can be used to flexibly design the operating frequency band of the dual-frequency dual-circularly polarized transmission array antenna by proportionally scaling the size of the frequency reuse metasurface-based dual-frequency dual-circularly polarized transmission array antenna. This should not be construed as limiting the scope of the present invention; all simple equivalent changes and modifications made in accordance with the claims and description of the present invention should still fall within the scope of this patent.

Claims

1. A dual-frequency dual-circular polarization frequency multiplexing metasurface, characterized in that, The metasurface achieves four degrees of freedom for beamforming in two operating frequency bands, converting the incident circularly polarized beam in the first frequency band into independently adjustable left-hand and right-hand circularly polarized beams, and the incident circularly polarized beam in the second frequency band into independently adjustable left-hand and right-hand circularly polarized beams. The metasurface includes a first and second basic functional unit arranged in an alternating pattern with a common aperture. These two basic functional units have different sizes and correspond to the two frequency bands respectively. Each includes an upper metal layer constituting the linearly polarized microstrip antenna layer and a lower metal layer constituting the circularly polarized microstrip antenna layer, used to convert the received left-hand or right-hand circularly polarized wave... The wave is converted into a transmitted linearly polarized wave and decoupled into left-hand and right-hand circularly polarized waves with equal amplitude and independent controllability. The decoupling of left-hand and right-hand circularly polarized waves is achieved by independently rotating the lower and upper metal layers. The phases of the left-hand and right-hand circularly polarized waves in the transmission field are modulated in phase by rotating the lower metal layer, and the phases of the left-hand and right-hand circularly polarized waves in the transmission field are modulated out of phase by rotating the upper metal layer. By combining the two, the phases of the left-hand and right-hand circularly polarized waves in the transmission field can be arbitrarily and independently modulated, ultimately achieving the purpose of decoupling left-hand and right-hand circularly polarized waves.

2. The dual-frequency dual-circular polarization frequency multiplexing metasurface according to claim 1, characterized in that, Both basic functional units consist of three metal layers and two dielectric layers, from top to bottom: upper metal layer, upper dielectric layer, middle metal layer, lower dielectric layer, and lower metal layer. The lower metal layer is a circularly polarized microstrip antenna layer used to receive circularly polarized electromagnetic waves emitted by the feed. The upper metal layer is a linearly polarized microstrip antenna layer used to convert the energy radiated from the feed into linearly polarized transmitted waves and further decompose them into left-hand circularly polarized and right-hand circularly polarized beams for radiation. The middle metal layer and the lower dielectric layer are bonded together by a prepreg layer.

3. The dual-frequency dual-circular polarization frequency multiplexing metasurface according to claim 2, characterized in that, Both basic functional units connect the lower metal layer to the upper metal layer through vertically arranged metallized vias, so that the energy received by the lower metal layer can be coupled to the upper metal layer through the metallized vias and finally radiated out. A circular groove is formed on the intermediate metal layer, allowing vertically arranged metallized vias to pass through.

4. The dual-frequency dual-circular polarization frequency multiplexing metasurface according to claim 1, characterized in that, Both the lower circularly polarized microstrip antenna layer and the upper linearly polarized microstrip antenna layer adopt a circular patch structure; the circular patch constituting the lower circularly polarized microstrip antenna has an asymmetrical U-shaped slot to excite the circular polarization radiation characteristics; the circular patch constituting the upper linearly polarized microstrip antenna has a symmetrical U-shaped slot in the center to excite the linear polarization radiation characteristics.

5. The dual-frequency dual-circular polarization frequency multiplexing metasurface according to claim 1, characterized in that, By independently rotating the lower and upper metal layers, continuous modulation of the phase of left-hand and right-hand circularly polarized waves in the transmission field is achieved, covering a range of 360°.

6. The dual-frequency dual-circular polarization frequency multiplexing metasurface according to claim 1, characterized in that, The lower metal layer of the basic functional unit in the low-frequency band is designed as a right-hand circularly polarized microstrip antenna, and the lower metal layer of the basic functional unit in the high-frequency band is designed as a left-hand circularly polarized microstrip antenna; or the lower metal layer of the basic functional unit in the high-frequency band is designed as a right-hand circularly polarized microstrip antenna, and the lower metal layer of the basic functional unit in the low-frequency band is designed as a left-hand circularly polarized microstrip antenna.

7. A dual-frequency dual-circularly polarized transmission array antenna based on a frequency-reused metasurface, characterized in that, The antenna includes a frequency-reused metasurface and a planar circularly polarized microstrip feed antenna according to any one of claims 1-6; the dual-frequency dual-circularly polarized transmission array antenna is capable of radiating independently adjustable left-hand circularly polarized beams and right-hand circularly polarized beams in the first frequency band, and independently adjustable left-hand circularly polarized beams and right-hand circularly polarized beams in the second frequency band.

8. The dual-frequency dual-circularly polarized transmission array antenna based on a frequency-reused metasurface according to claim 7, characterized in that, The low-frequency feed is designed as a right-hand / left-hand circularly polarized antenna, and the high-frequency feed is designed as a left-hand / right-hand circularly polarized antenna. Correspondingly, the metal layer below the basic functional unit of the low-frequency band is designed as a right-hand / left-hand circularly polarized microstrip antenna. The metal layer beneath the basic functional unit in the high-frequency band is designed as a left-hand / right-hand circularly polarized microstrip antenna.

9. The dual-frequency dual-circularly polarized transmission array antenna based on a frequency-reused metasurface according to claim 7, characterized in that, The planar circularly polarized microstrip feed antenna consists of a 2×2 microstrip antenna array using a rotating feed method, including two radiating patch layers. The bottom layer serves as the driving layer radiating patch, and the top layer serves as the parasitic layer radiating patch. The radiating patch is composed of chamfered square metal patches.

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