Dual-linear polarization metasurface differential filtering antenna

Abstract

The invention relates to a dual-linear polarization metasurface differential filtering antenna, and belongs to the technical field of antennas. The antenna comprises a three-layer dielectric substrate, a metal patch, a through hole, a via hole, a feed column and a metal ground. The first patch of the upper-layer dielectric substrate forms a metasurface to generate two excitation modes to realize a broadband, and a radiation zero point is generated in a high-frequency stop band. The U-shaped patch and the arrow-shaped patch of the middle-layer dielectric substrate form an open-circuit resonator, and a radiation zero point is generated in a low-frequency stop band; the third patch and the second short-circuit column form a second short-circuit patch, and a radiation zero point is generated in a high-frequency stop band; the second patch and the first short-circuit column form a first short-circuit patch, a radiation zero point is generated in the low-frequency stop band, and meanwhile the suppression level of the high-frequency stop band and the low-frequency stop band is further improved. The antenna adopts the differential feed network, so that the isolation degree between antenna ports can be improved. The antenna has the advantages of low profile, wide band, band-pass filtering, high out-of-band rejection, high isolation, low cross polarization and the like, and has potential application value.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology and relates to a dual-linearly polarized metasurface differential filter antenna. Background Technology

[0002] With the continuous advancement of communication technology, the coexistence of multiple frequency wireless networks in the same space has become the norm. This necessitates the effective deployment of antenna systems across different frequency bands to support complex communication environments. However, this frequency band coexistence often leads to mutual interference, thereby degrading antenna performance. To address this challenge, filtered antenna technology has emerged, aiming to reduce interference and improve communication quality through integrated filtering functions.

[0003] Currently, there are three main methods for designing filter antennas: one is to directly integrate the filter into the antenna's feed network to achieve the filtering function; the second is to use the antenna itself to replace the final stage resonator of the multi-stage resonant filter, so that it has the dual functions of filtering output and signal radiation; the third is to modify the existing antenna radiation structure, such as slotting, adding parasitic patches, or introducing short-circuit vias, so that the radiation structure has filtering characteristics.

[0004] Dual-polarized antennas, as a type of antenna capable of simultaneously transmitting and receiving two orthogonally polarized waves, are of great significance for realizing polarization multiplexing and enhancing channel capacity, and have become a core component of next-generation wireless communication networks.

[0005] In recent years, significant achievements have been made in the field of dual-polarized filtering antennas. For example, the paper "BJ Chen, X SYang. Compact dual-polarized filtering antenna based on differential feeding and double-layer metasurface[J].IEEE Transactions on Antennas and Propagation,2022,71(1):1065-1070." proposes a dual-polarized filtering antenna using a double-layer metasurface and a square open-loop resonator. The paper "J Li, J Yin, C Guo, H Zhai, Z Zhao. A miniaturized dual-band dual-polarized base station antenna loaded with duplex baluns[J].IEEE Antennas and Wireless Propagation Letters,2023,22(7):1756-1760." proposes a dual-polarized filtering antenna by combining a duplex balun with low-pass and high-pass filter structures. However, the balun design increases the number of dielectric substrate layers, further increasing the complexity of the antenna structure. Furthermore, the paper "H Yuan, FC Chen, Q XChu. A wideband and high gain dual-polarized filtering antenna based on multiple patches[J]. IEEE Transactions on Antennas and Propagation, 2022, 70(10): 9843-9848" proposes to achieve filtering effect through the magnetic coupling of stacked patches and the electrical coupling of an open-loop resonator, thus realizing a dual-polarized filtering antenna. Although the above-mentioned filtering antennas all have good filtering effect, they all contain an air layer, which not only introduces additional delay but also leads to signal loss.

[0006] Therefore, developing a compact, wide-band dual-polarized filter antenna with excellent out-of-band suppression capability is of paramount importance for improving the overall performance of wireless communication systems. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a dual-linearly polarized metasurface differential filter antenna with advantages such as low profile, wide bandwidth, bandpass filtering, high out-of-band suppression, high isolation, and low cross-polarization.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A dual-polarized metasurface differential filter antenna comprises upper, middle and lower dielectric substrates.

[0010] A first patch is arrayed on the surface of the upper dielectric substrate away from the middle dielectric substrate. The arrayed first patch generates two excitable characteristic modes to achieve broadband and generates a radiation null in the high-frequency stopband. Multiple open-circuit resonators are provided on the surface of the middle dielectric substrate close to the upper dielectric substrate, generating a radiation null in the low-frequency stopband. A metal ground is provided on the surface of the middle dielectric substrate away from the upper dielectric substrate. Multiple fourth patches are distributed on the surface of the lower dielectric substrate away from the middle dielectric substrate. One end of each fourth patch points to the center of the lower dielectric substrate, and the other end is connected to a feed port, forming a differential feed.

[0011] Multiple first short-circuit patches and second short-circuit patches are provided in the middle layer dielectric substrate. The first short-circuit patches generate a radiation null in the low-frequency stopband, and the second short-circuit patches generate a radiation null in the high-frequency stopband. Among them, a portion of the first short-circuit patch is located on a surface of the middle layer dielectric substrate near the upper layer dielectric substrate, and another portion is connected to the metal ground of the middle layer dielectric substrate; a portion of the second short-circuit patch is located on a surface of the middle layer dielectric substrate near the upper layer dielectric substrate, and another portion is connected to the metal ground of the middle layer dielectric substrate.

[0012] Multiple feed pillars are provided between the middle dielectric substrate and the lower dielectric substrate. One end of each feed pillar is connected to each of the open-circuit resonators, and the other end is connected to each of the fourth patches.

[0013] Furthermore, since the feed post needs to pass through the middle dielectric substrate to connect the open-circuit resonator and the fourth patch, a circular gap is provided in the center of the metal ground to prevent the feed post from directly contacting the metal ground when passing through the middle dielectric substrate, which would cause a short circuit.

[0014] Furthermore, the open-circuit resonator includes multiple arrow-shaped patches, with the arrowhead of each patch pointing towards the center of the middle dielectric substrate; a U-shaped patch is provided on both sides of each arrow-shaped patch; and the arrowhead of each arrow-shaped patch is connected to each feed post.

[0015] Furthermore, the first short-circuit patch includes a second patch and a first short-circuit post, wherein the second patches are distributed at the four corners of a surface of the middle layer dielectric substrate near the upper layer dielectric substrate, and each second patch is connected to the metal ground through a first short-circuit post.

[0016] Furthermore, the second short-circuit patch includes a third patch and a second short-circuit post, wherein the third patch is distributed inside each U-shaped patch, and each third patch is connected to the metal ground through a second short-circuit post.

[0017] Furthermore, the diameter of the first short-circuit post is smaller than the diameter of the second short-circuit post.

[0018] The first short-circuit post is placed in the first through-hole, the second short-circuit post is placed in the second through-hole, and the power supply post is placed in the via. The inner walls of the first and second through-holes are not plated with metal, while the inner walls of the via are plated with metal.

[0019] Furthermore, four mutually perpendicular fourth patches are distributed on the surface of the lower dielectric substrate away from the middle dielectric substrate. One end of each fourth patch points towards the center of the lower dielectric substrate, and the other end is connected to a feed port. The four ports constitute a differential feed. Among them, two ports in one direction serve as the first differential ports to excite a linearly polarized wave with the current direction as the x-direction, and two ports in the other direction serve as the second differential ports to excite a linearly polarized wave with the current direction as the y-direction.

[0020] The beneficial effects of this invention are as follows: The dual-polarized metasurface differential filter antenna proposed in this invention is constructed using a three-layer dielectric substrate, metal patches, vias, feed posts, and a metal ground plane. The first patch on the upper dielectric substrate forms a metasurface that generates two excitation modes, achieving broadband bandwidth, and generates a radiation null in the high-frequency stopband. The U-shaped and arrow-shaped patches on the middle dielectric substrate form an open-circuit resonator, generating a radiation null in the low-frequency stopband; the third patch and the second short-circuit post form a second short-circuit patch, forming a band-stop circuit, generating an additional radiation null in the high-frequency stopband; the added second patch and the first short-circuit post form a first short-circuit patch, generating an additional radiation null in the low-frequency stopband, while further improving the suppression levels of the high-frequency and low-frequency stopbands. Furthermore, this invention utilizes characteristic mode analysis to analyze antenna performance and guide antenna structural design. This antenna employs a differential feed network, which can improve the isolation between antenna ports. In summary, the dual-polarized metasurface differential filter antenna proposed in this invention has advantages such as low profile, wide bandwidth, bandpass filtering, high out-of-band suppression, high isolation, and low cross-polarization, and has potential application value.

[0021] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0023] Figure 1 This is a three-dimensional schematic diagram of a dual-polarized metasurface differential filter antenna.

[0024] Figure 2 for Figure 1 The top view, side view, and bottom view of the 3D diagram are shown.

[0025] Figure 3 This is a diagram illustrating the evolution of the dual-polarized metasurface differential filter antenna proposed in this invention.

[0026] Figure 4 Characteristic mode analysis of the upper and middle dielectric substrates of antenna 1. Figure 4 (a) shows the mode significance curves of the excitable modes of antenna 1. Figure 4 (b) represents the mode current of the excitable mode of antenna 1. Figure 4 (c) is the mode pattern of the excitable modes of antenna 1.

[0027] Figure 5 For determining the non-mode null point of mode 9 in antenna 1, Figure 5 (a) is the total near-field amplitude curve. Figure 5 (b) is the curve of the rate of change of the total near-field amplitude E. roc_total .

[0028] Figure 6 Characteristic mode analysis of the upper and middle dielectric substrates of antenna 2. Figure 6 (a) shows the mode significance curves of the excitable modes of antenna 2. Figure 6 (b) represents the mode current of the excitable mode of antenna 2. Figure 6 (c) is the mode pattern of the excitable modes of antenna 2.

[0029] Figure 7 Characteristic mode analysis of the upper and middle dielectric substrates of antenna 3. Figure 7 (a) shows the mode significance curves of the excitable modes of antenna 3. Figure 7 (b) represents the mode current of the excitable modes of antenna 3. Figure 7 (c) is the mode pattern of the excitable modes of antenna 3.

[0030] Figure 8 For determining the non-mode null point of mode 11 in antenna 3, Figure 8 (a) is the total near-field amplitude curve. Figure 8 (b) is the curve of the rate of change of the total near-field amplitude E. roc_total .

[0031] Figure 9 For the final antenna, characteristic mode analysis of the upper and middle dielectric substrates is performed. Figure 9 (a) is the mode significance curve of the final antenna excitable modes. Figure 9 (b) represents the mode currents for the final antenna modes 13 and 14. Figure 9 (c) shows the pattern radiation patterns of the final antenna modes 13 and 14.

[0032] Figure 10 The graph shows a comparison of the S-parameters and gain of antennas 1 through 3. Figure 10 (a) is the S-parameter plot. Figure 10 (b) is the gain diagram.

[0033] Figure 11 The image shows a comparison of the S-parameters and gain of antenna 3 and the final antenna. Figure 11 (a) is the S-parameter plot. Figure 11 (b) is the gain diagram.

[0034] Figure 12 The S-parameters and gain curves of the dual-polarized metasurface differential filter antenna of this invention are shown.

[0035] Figure 13 This is a dimensioned diagram of an embodiment of the dual-polarized metasurface differential filter antenna of the present invention.

[0036] Figure 14 This is the x-polarization radiation pattern of the dual-polarized metasurface differential filter antenna of the present invention. Figure 14 (a) is the E-plane (4.64 GHz). Figure 14 (b) is the H-plane (4.64 GHz). Figure 14 (c) is the E-plane (5.0 GHz). Figure 14 (d) represents the H-plane (5.0 GHz). Figure 14 (e) represents the E-plane (5.38 GHz). Figure 14 (f) represents the H-plane (5.38 GHz).

[0037] Figure 15 This is the y-polarization radiation pattern of the dual-polarized metasurface differential filter antenna of the present invention. Figure 15 (a) is the E-plane (4.64 GHz). Figure 15 (b) is the H-plane (4.64 GHz). Figure 15 (c) is the E-plane (5.0 GHz). Figure 15 (d) represents the H-plane (5.0 GHz). Figure 15 (e) represents the E-plane (5.38 GHz). Figure 15 (f) represents the H-plane (5.38 GHz).

[0038] Reference numerals: 1-Upper dielectric substrate; 2-Middle dielectric substrate; 3-Lower dielectric substrate; 4-First patch; 5-Second patch; 6-Arrow-shaped patch; 7-U-shaped patch; 8-Third patch; 9-First through-hole; 10-Second through-hole; 11-Circular gap; 12-Fourth patch; 13-Via; 14-Power supply post; 15-Second short-circuit post; 16-First short-circuit post; 17-Metallic ground. Detailed Implementation

[0039] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0040] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0041] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0042] like Figure 1 and Figure 2 As shown, a dual-polarized metasurface differential filter antenna is provided in an embodiment of the present invention. The antenna includes an upper dielectric substrate 1, a middle dielectric substrate 2, and a lower dielectric substrate 3.

[0043] The upper dielectric substrate 1 has nine square first patches 4 on its upper surface, and the lower surface of the upper dielectric substrate 1 is free of metal. The middle dielectric substrate 2 has four second patches 5, four arrow-shaped patches 6, eight third patches 8, and eight U-shaped patches 7 on its upper surface. The second patches 5 are square and smaller than the first patches 4. The third patches 8 are rectangular. The lower surface of the middle dielectric substrate 2 is a metal ground 17. The lower dielectric substrate 3 has no metal on its upper surface and four narrow rectangular fourth patches 12 on its lower surface.

[0044] Nine first patches 4 are arrayed on the upper surface of the upper dielectric substrate 1, occupying the center, east, west, south, north, southeast, northeast, southwest, and northwest positions on the upper surface. Four second patches 5 are distributed at the four corners of the upper surface of the middle dielectric substrate 2, occupying the southeast, southwest, northeast, and northwest positions. Four arrow-shaped patches 6 have their arrows pointing to the center of the middle dielectric substrate 2, occupying the east, south, west, and north positions. Four fourth patches 12 are distributed on the lower surface of the lower dielectric substrate 3, and the four fourth patches are perpendicular to each other, occupying the east, south, west, and north positions respectively.

[0045] On the upper surface of the intermediate dielectric substrate 2, U-shaped patches 7 are loaded on both sides of each arrow-shaped patch 6, and a third patch 8 is located inside each U-shaped patch 7. The third patch 8 is rectangular. A circular gap 11 is etched in the center of the metal ground 17 to prevent the power supply post 14 from directly contacting the metal ground 17 and causing a short circuit.

[0046] Four first through-holes 9 are provided in the intermediate dielectric substrate 2, each located at the center of one of the four second patches 5. The inner wall of each first through-hole 9 is not plated with metal, making it a non-metallized through-hole. The first through-holes 9 are used to house first short-circuit posts 16. The first through-holes 9 penetrate the lower surface metal ground 17 of the intermediate dielectric substrate 2 and the four second patches 5 on the upper surface of the intermediate dielectric substrate 2. The first short-circuit posts 16 are metal posts that connect the four second patches 5 on the upper surface of the intermediate dielectric substrate 2 and the lower surface metal ground 17 of the intermediate dielectric substrate 2.

[0047] In addition, eight second through-holes 10 are provided in the intermediate layer dielectric substrate 2, located on the eight third patches 8 respectively. The inner walls of the second through-holes 10 are not plated with metal, making them non-metallized through-holes. The inner diameter of the second through-hole 10 is larger than the inner diameter of the first through-hole 9. The second through-holes 10 are used to house the second short-circuit posts 15, which penetrate the lower surface metal ground 17 of the intermediate layer dielectric substrate 2 and the eight third patches 8 on the upper surface of the intermediate layer dielectric substrate 2. The eight second short-circuit posts 15 are metal posts, connecting the eight third patches 8 on the upper surface of the intermediate layer dielectric substrate 2 and the lower surface metal ground 17 of the intermediate layer dielectric substrate 2. The diameter of the second short-circuit posts 15 is larger than the diameter of the first short-circuit posts 16.

[0048] Four vias 13 are provided in the middle layer dielectric substrate 2 and the lower layer dielectric substrate 3, respectively located near the center of the circuit board for the four arrow-shaped patches 6 and the four fourth patches 12, and penetrating through the arrow-shaped patches 6 and the fourth patches 12. The inner walls of the vias 13 are plated with metal. The vias 13 are used to place the power supply pillars 14. There are four power supply pillars 14, which are metal pillars, and they connect the four arrow-shaped patches 6 on the upper surface of the middle layer dielectric substrate 2 and the four fourth patches 12 on the lower surface of the lower layer dielectric substrate 3.

[0049] The entire antenna is fed through the ports connected by the four fourth patches 12.

[0050] The first patch 4 on the upper surface of the upper dielectric substrate 1 forms a 3×3 uniform metasurface, generating two excitable characteristic modes to achieve broadband operation, while simultaneously generating a radiation null in the high-frequency stopband. The arrow-shaped patch 6 and U-shaped patch 7 on the upper surface of the middle dielectric substrate 2 form an open-circuit impedance resonator, generating a radiation null in the low-frequency stopband. The third patch 8 and the second short-circuit post 15 form a second short-circuit patch, equivalent to a band-stop circuit, generating an additional second radiation null in the high-frequency stopband. The second patch 5 and the first short-circuit post 16 form a first short-circuit patch, generating an additional second radiation null in the low-frequency stopband, while further increasing the suppression level of the upper and lower stopbands.

[0051] The generation of antenna filtering function is analyzed by utilizing characteristic modes, thereby guiding the design of the filtered antenna and enabling the antenna to achieve good out-of-band suppression and bandpass filtering effect. The four arrow-shaped patches 6 on the upper surface of the middle dielectric substrate 2 and the four fourth patches 12 on the lower surface of the lower dielectric substrate 3 form a differential feed network through the feed pillars 14, which can improve the isolation between antenna ports.

[0052] To achieve high port isolation and low cross-polarization in a dual-polarized antenna, differential feeding is used to excite the antenna because it offers high immunity to common-mode noise and ease of integration with balanced circuits. For example... Figure 2 As shown, port 1 + and port 1 - Differential port 1 forms a linearly polarized wave with the excitation current direction in the x-direction, and port 2... + and port 2 - Differential port 2 is formed to generate a linearly polarized wave with the current direction in the y direction.

[0053] To obtain the S-parameters of the differential antenna, it is equivalent to a four-port network, from which we can obtain:

[0054]

[0055] Among them, S 11The reflection coefficient of differential port 1 when differential port 2 is matched; S 12 When differential port 1 is matched, the reverse transmission coefficient transmitted from port 2 to differential port 1; S 21 When matching differential port 2, the forward transmission coefficient from port 1 to differential port 2; S 22 The reflection coefficient of differential port 2 when differential port 1 is matched.

[0056] The operating modes of the antenna described in this embodiment can be explained using the eigenmode analysis method. The eigenmode analysis method is used to identify the modes that may generate radiation nulls outside the antenna band and the operating modes required within the passband, and to guide the improvement of the antenna structure to achieve the required performance.

[0057] Characteristic mode analysis is mainly based on mode significance (MS) and mode current distribution characteristics. MS represents the ability of a specific mode to be effectively excited, and its range is [0,1]. The closer MS is to the maximum value of 1, the stronger the resonant state of the mode and the easier it is to be excited. Conversely, the closer MS is to 0, the more the mode is in a storage state and the more difficult it is to be excited.

[0058] The antenna structure was designed using the method of predicting radiation nulls by combining characteristic mode analysis proposed in the literature "Chen XJ, Lai QX, Pan YM. Characteristic-mode-analysis-aided design of filtering patch antennas[J].IEEE Transactions on Antennas and Propagation,2023,71(3):2224-2234." to achieve the required filtering performance. It divides radiation nulls into two types: mode nulls and non-mode nulls. Mode nulls exist as independent modes, characterized by their MS curve changes resembling sharp pulses. For non-mode nulls, they are hidden in excitable modes, characterized by an inflection point in the total near-field amplitude of the excitable mode, and the rate of change of its total near-field amplitude E roc_total The frequency corresponding to zero is the frequency of the non-mode zero. E roc_total Represented as:

[0059]

[0060] Among them, E total (f i-1 ) and E total (f i ) represents frequency f i-1 and f i The total near-field electric field amplitude at point E. The maximum value among them is expressed as max(E). total (fi-1 E total (f i )).

[0061] Figure 3 This illustrates the structural evolution of the dual-polarized metasurface differential filter antenna provided in this embodiment. Figure 3 The final antenna in the series evolved from antenna 1, antenna 2, and antenna 3.

[0062] The upper surface of the upper dielectric substrate of antenna 1 has nine large square patches arranged in a 3×3 grid. The upper surface of the middle dielectric substrate 2 has four arrow-shaped patches in the east, south, west, and north directions, forming a pair of crossed dipoles. The lower surface of the middle dielectric substrate 2 has a circular gap in the metal ground plane. The lower surface of the lower dielectric substrate 3 has four narrow rectangular patches in the east, south, west, and north directions. The four arrow-shaped patches and the four narrow rectangular patches are connected by feed posts to form a differential feed network.

[0063] Antenna 2, based on antenna 1, has U-shaped patches 7 loaded on both sides of the four arrow-shaped patches 6 on the upper surface of the intermediate dielectric substrate 2. Antenna 3, based on antenna 2, has eight small rectangular patches and eight thick short-circuit posts loaded inside the eight U-shaped patches on the upper surface of the intermediate dielectric substrate 2, forming short-circuited small rectangular patches. Finally, the antenna, based on antenna 3, has four small square patches and four thin short-circuit posts loaded in the southeast, northeast, southwest, and northwest directions on the upper surface of the intermediate dielectric substrate 2, forming short-circuited small square patches.

[0064] By analyzing the evolution of antennas, we can understand how antenna structures gradually achieve broadband and filtering functions. The design goal is a dual-polarized antenna with current directions of x and y. Therefore, without adding a feeding structure, we need to first find the linear polarization modes with current directions of x and y that can be excited in the antenna's radiating structure.

[0065] Figure 4 (a) shows the MS curves of the excitable modes of the upper and middle dielectric substrates of antenna 1, from which the resonant frequencies of each mode can be obtained. Figure 4 (b) shows the current distribution of each mode at its respective resonant frequency. In the y-direction, modes 4, 8, and 9 have stronger mode currents on the cross dipoles on the intermediate dielectric substrate 2, while in the x-direction, modes 5, 7, and 10 have stronger mode currents on the cross dipoles. Since the antenna can only be excited by a pair of differential ports in the corresponding direction to achieve polarization, while the other pair of orthogonal differential ports is connected to a matched load, that is, when differential port 2 is used... + and 2 -At that time, the current in the y-direction is excited, while the differential port 1 + and 1 - Therefore, a matching load is connected, and thus, there is no current in the x-direction. Furthermore, in the mode currents of the cross-dipole, when the current in a particular direction is stronger, that direction is more easily excited. Therefore, during feeding, modes 4 and 8 only have y-direction current on the cross-dipole, while modes 5 and 7 only have x-direction current. In modes 9 and 10, partial current cancellation occurs on the nine large square patches, potentially causing a radiation null point. Meanwhile... Figure 4 (b) shows that modes 4, 5, 7, and 8 exhibit concentrated energy patterns, indicating that they are the desired in-band operating modes. Conversely, modes 9 and 10 exhibit dispersed and attenuated energy patterns, suggesting the possible presence of radiation nulls in these two modes. Therefore, further analysis is needed to confirm the existence of radiation nulls in these two modes and their frequencies.

[0066] Due to Figure 4 (a) It is evident that the MS curves of Mode 9 and Mode 10 are identical, therefore these two modes are degenerate modes. For simplicity, only the existence of non-mode zeros in Mode 9 will be analyzed. From Figure 5 (a) It can be seen that Mode 9 has a distinct inflection point at 7.4 GHz, therefore, a non-mode zero exists in Mode 9. To obtain the accurate frequency of the non-mode zero, such as... Figure 5 As shown in (b), the total near-field amplitude change rate curve E roc_total The frequency at which the non-mode zeros were obtained was 7.41 GHz. This result confirms that non-mode zeros exist in both modes 9 and 10 at this frequency.

[0067] Based on the characteristic mode analysis of antenna 1, it can be seen that antenna 1 only generates a radiation null in the high-frequency stopband. In order to generate a radiation null in the low-frequency stopband, U-shaped patches need to be loaded on both sides of the four arrow-shaped patches on the upper surface of the middle dielectric substrate 2 to form antenna 2. The length of each U-shaped patch with an open terminal corresponds to a quarter wavelength of the target radiation null frequency of 4.1 GHz. At the 4.1 GHz frequency point, the U-shaped patch is equivalent to a short circuit for the arrow-shaped patch, thereby achieving a radiation null in the low-frequency stopband. Figure 6 (a) The MS curves of mode 1 and mode 2 show similar spike pulse changes, indicating that mode 1 and mode 2 are mode zeros. Figure 6 In (b), modes 1 and 2 exhibit current cancellation on the arrow-shaped patch at the resonant frequency of 3.6 GHz, thus preventing effective energy radiation. Therefore, modes 1 and 2 have mode nulls at 3.6 GHz, which, due to the low resonant frequency of 3.6 GHz, should be located within the low-frequency stopband.

[0068] like Figure 6 As shown in (b), mode 4 exhibits linear polarization of the current in the y-direction, while mode 5 exhibits linear polarization of the current in the x-direction. This is because the current in these directions is stronger on the arrow-shaped patches. In mode 8, the current flows in both directions with equal intensity. Since the two arrow-shaped patches in each direction structurally form a dipole, and the current directions of the two arrow-shaped patches in each direction are consistent, matching the actual current distribution direction on the dipole, both directions can be excited. However, since the antenna is only excited by a pair of differential ports in the corresponding direction when achieving polarization in a certain direction, mode 8 is artificially chosen to be dominated by the y-direction current. Similarly, mode 7 is artificially chosen to be dominated by the x-direction current. Modes 9 and 10 can produce radiation nulls due to the cancellation of currents in the overall structure. Figure 6 (c) The mode radiation patterns are shown, confirming that modes 4, 5, 7, and 8 are the desired in-band operating modes due to their concentrated energy patterns. Modes 1 and 2, although exhibiting concentrated energy patterns, cannot effectively radiate energy due to the opposing currents in both directions of the arrow-shaped patch. Meanwhile, modes 9 and 10 show dispersed energy patterns with weaker intensity at the center, indicating the presence of radiation nulls in these modes. Given the high resonant frequency of 6.87 GHz, these radiation nulls should be located within the high-frequency stopband.

[0069] The above characteristic mode analysis shows that antenna 2 generates one radiation null in both the low-frequency and high-frequency stopbands. To enhance the stopband suppression effect, multiple radiation nulls are needed. Based on antenna 2, eight small rectangular patches and eight thick short-circuit pillars are loaded inside the eight U-shaped patches on the upper surface of the intermediate dielectric substrate 2 to form short-circuit small rectangular patches, thus obtaining antenna 3. Figure 7 (a) The antenna newly evokes modes 11 and 12 at 7.03 GHz, although these two modes... Figure 7 (c) shows a concentrated energy pattern, but as Figure 7 As shown in (b), since the arrow-shaped patch surface mode currents have opposite currents that cancel each other out, neither mode can radiate effectively. Therefore, modes 11 and 12 can produce radiation nulls. Since modes 11 and 12 are degenerate modes, only the total near-field amplitude of mode 11 is analyzed here. Figure 8 (a) and (b) show a clear inflection point at 7.03 GHz, where E roc_total The result is zero, proving that both modes can generate non-mode radiation nulls at this frequency. Thus, antenna 3 generates two radiation nulls in the high-frequency stopband, located at 6.87 GHz and 7.03 GHz respectively.

[0070] Simulation of antenna 3 performance, such as Figure 10 (a) and Figure 10As shown in (b), there is only one radiation null point in the low-frequency stopband, and the out-of-band suppression level of the low-frequency stopband is worse than that of the high-frequency stopband. Therefore, based on antenna 3, four small square patches and four thin short-circuit pillars are loaded on the southeast, northeast, southwest and northwest directions of the upper surface of the middle layer dielectric substrate 2 to form short-circuit small square patches, thus obtaining the antenna described in this embodiment.

[0071] Figure 9 (a) shows that, for the final antenna, the new modes 13 and 14 are degenerate modes, both appearing at 2.62 GHz. The MS curves of these modes exhibit spike-like pulse characteristics, which are typical of mode nulls, indicating that modes 13 and 14 are mode nulls. Figure 9 (b) shows the mode currents for modes 13 and 14, concentrated on the U-shaped patch rather than the arrow-shaped patch. Therefore, although... Figure 9 As shown in (c), these two mode patterns have concentrated radiant energy, but they cannot radiate effectively, thus producing a radiation null. Figure 11 As shown in (b), the gain curve of the antenna after feeding reveals that the final antenna generates a radiation null at 3.88 GHz and 4.12 GHz in the low-frequency stopband, respectively, enhancing the out-of-band rejection in the low-frequency stopband. Simultaneously, the out-of-band rejection in the high-frequency stopband increases from 16.4 dB to 20.4 dB. Compared to antenna 3, the final antenna exhibits significantly improved stopband rejection in both the high-frequency and low-frequency stopbands. The final antenna generates two radiation nulls in each stopband, achieving excellent filtering performance.

[0072] Figure 12 The graph shows the final antenna gain and S-parameters. It can be seen that |S 11 The frequency range with a rejection ratio less than -10dB is 4.52GHz to 5.63GHz, meaning the relative bandwidth of -10dB is 21.8%. Within this bandwidth, the isolation is greater than 44dB. The low-frequency stopband rejection level is 21.1dB, and the high-frequency stopband rejection level is 20.4dB. Since the previous characteristic mode analysis did not consider the effects of the probe structure and applied excitation, the actual operating frequency will shift to some extent after adding the probe structure and applied excitation to the antenna.

[0073] Figure 14 The image shows the radiation pattern of the antenna in the x-direction when the antenna is finally excited. At 4.64 GHz, the cross-polarization of the E-plane and H-plane is less than -64 dB in the direction of maximum radiation; at 5 GHz, the cross-polarization of the E-plane and H-plane is less than -52 dB in the direction of maximum radiation; and at 5.63 GHz, the cross-polarization of the E-plane and H-plane is less than -47 dB in the direction of maximum radiation. Figure 15The image shows the y-axis polarization radiation pattern of the antenna when it is finally excited. At 4.64 GHz, the cross-polarization of both the E-plane and H-plane is less than -61 dB in the direction of maximum radiation; at 5 GHz, the cross-polarization of both the E-plane and H-plane is less than -58 dB in the direction of maximum radiation; and at 5.63 GHz, the cross-polarization of both the E-plane and H-plane is less than -48 dB in the direction of maximum radiation. Therefore, it can be seen that adding a feed probe and applying excitation results in good low cross-polarization of the antenna.

[0074] In summary, the dual-linearly polarized metasurface differential filter antenna proposed in this invention can generate two radiation nulls in each of the two stopbands, suppressing radiation in the low-frequency and high-frequency stopbands outside the passband, thus achieving bandpass filtering performance. Simultaneously, it effectively excites two linearly polarized radiation modes within the operating frequency band, achieving broadband performance. The differential feeding method ensures an isolation greater than 44 dB between antenna ports, and within the operating frequency band, the cross-polarization of the E-plane and H-plane in the direction of maximum radiation is less than -47 dB, exhibiting high isolation and low cross-polarization performance. Therefore, the antenna can achieve good radiation performance, filtering effect, high isolation, and low cross-polarization over a wide frequency range.

[0075] like Figure 13 The dimensions of the antenna described in this embodiment are shown. The operating frequency band of this embodiment is 4.52GHz to 5.53GHz, and the antenna dimensions are 50mm × 50mm × 4.3mm, or 0.83λ0 × 0.83λ0 × 0.07λ0 (λ0 represents the free-space wavelength corresponding to the center frequency). The antenna uses a three-layer dielectric substrate, all of which are F4B with a relative permittivity of 2.65 and a loss tangent of 0.0015. The thickness of the upper dielectric substrate is 1.5mm, the middle dielectric substrate is 2mm, and the lower dielectric substrate is 0.8mm.

[0076] The specific dimensions of the antenna are shown in Table 1:

[0077] Table 1

[0078]

[0079] Characteristic mode simulation was performed using CST simulation software, and full-wave electromagnetic simulation was performed using HFSS simulation software. The S-parameters and gain curve of the antenna were obtained as follows: Figure 10 As shown. This antenna has two resonant points, |S 11The frequency range with a gain less than -10dB is 4.52GHz to 5.63GHz, meaning the relative bandwidth of -10dB is 21.8%, and the isolation within this bandwidth is greater than 44dB. The maximum gain within the operating frequency band is 7.97dBi. Gains are -20.2dBi at the low-frequency zero point of 3.88GHz, -26.1dBi at the low-frequency zero point of 4.12GHz, -19.9dBi at the high-frequency zero point of 6.34GHz, and -17.8dBi at the high-frequency zero point of 6.66GHz. The low-frequency stopband rejection level is 21.1dB, and the high-frequency stopband rejection level is 20.4dB. Figure 14 and Figure 15 The radiation patterns of the filtered antenna under excitation are given. It can be seen that within the operating frequency band, the cross-polarization is less than -47dB, exhibiting low cross-polarization performance.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A dual-linearly polarized metasurface differential filter antenna, characterized in that, It includes three dielectric substrates: upper, middle and lower. On one surface of the upper dielectric substrate (1) away from the middle dielectric substrate (2), a first patch (4) is arrayed. Two excitable characteristic modes are generated through the arrayed first patch (4) to achieve broadband and a radiation null point is generated in the high-frequency stopband. Multiple open-circuit resonators are provided on one surface of the middle dielectric substrate (2) near the upper dielectric substrate (1) to generate a radiation null point in the low-frequency stopband; A metal ground (17) is provided on a surface of the middle dielectric substrate (2) away from the upper dielectric substrate (1); a plurality of fourth patches (12) are distributed on a surface of the lower dielectric substrate (3) away from the middle dielectric substrate (2), one end of each fourth patch (12) points to the center of the lower dielectric substrate (3), and the other end is connected to a power supply port, and the power supply ports form a differential power supply. Multiple first short-circuit patches and second short-circuit patches are provided in the middle layer dielectric substrate (2). The first short-circuit patches generate a radiation null in the low-frequency stopband, and the second short-circuit patches generate a radiation null in the high-frequency stopband. Among them, a part of the first short-circuit patch is located on a surface of the middle layer dielectric substrate (2) close to the upper layer dielectric substrate (1), and the other part is connected to the metal ground (17) of the middle layer dielectric substrate (2). A part of the second short-circuit patch is located on a surface of the middle layer dielectric substrate (2) close to the upper layer dielectric substrate (1), and the other part is connected to the metal ground (17) of the middle layer dielectric substrate (2). A plurality of feed posts (14) are provided between the middle dielectric substrate (2) and the lower dielectric substrate (3). One end of each feed post (14) is connected to each of the open-circuit resonators, and the other end is connected to each of the fourth patches (12).

2. The dual-linearly polarized metasurface differential filter antenna according to claim 1, characterized in that, The open-circuit resonator includes multiple arrow-shaped patches (6), with the arrow of each arrow-shaped patch (6) pointing to the center of the middle layer dielectric substrate (2); a U-shaped patch (7) is provided on both sides of each arrow-shaped patch (6); the arrow end of each arrow-shaped patch (6) is connected to each feed post (14).

3. The dual-linearly polarized metasurface differential filter antenna according to claim 2, characterized in that, The first short-circuit patch includes a second patch (5) and a first short-circuit post (16), wherein the second patch (5) is distributed at the four corners of a surface of the middle layer dielectric substrate (2) near the upper layer dielectric substrate (1), and each second patch (5) is connected to the metal ground (17) through a first short-circuit post (16).

4. The dual-linearly polarized metasurface differential filter antenna according to claim 3, characterized in that, The second short-circuit patch includes a third patch (8) and a second short-circuit post (15), wherein the third patch (8) is distributed on the inside of each U-shaped patch (7), and each third patch (8) is connected to the metal ground (17) through a second short-circuit post (15).

5. The dual-linearly polarized metasurface differential filter antenna according to claim 4, characterized in that, The diameter of the first short-circuit post (16) is smaller than the diameter of the second short-circuit post (15).

6. The dual-linearly polarized metasurface differential filter antenna according to claim 5, characterized in that, The first short-circuit post (16) is placed in the first through hole (9), the second short-circuit post (15) is placed in the second through hole (10), and the power supply post (14) is placed in the via (13).

7. The dual-linearly polarized metasurface differential filter antenna according to claim 6, characterized in that, The inner walls of the first through hole (9) and the second through hole (10) are not plated with metal, while the inner wall of the through hole (13) is plated with metal.

8. The dual-linearly polarized metasurface differential filter antenna according to claim 1, characterized in that, Four mutually perpendicular fourth patches (12) are distributed on a surface of the lower dielectric substrate (3) away from the middle dielectric substrate (2). One end of each fourth patch (12) points to the center of the lower dielectric substrate (3), and the other end is connected to a power supply port. The four ports constitute a differential power supply. Among them, two ports in one direction serve as the first differential port to generate a linearly polarized wave with the current direction as x, and two ports in the other direction serve as the second differential port to generate a linearly polarized wave with the current direction as y.

9. The dual-linearly polarized metasurface differential filter antenna according to claim 1, characterized in that, The metal ground (17) has a circular gap (11) in the center to prevent the power supply post (14) from directly contacting the metal ground (17) and causing a short circuit.

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