A compact broadband high-isolation dual-polarized metasurface antenna

Abstract

The application relates to a compact broadband high-isolation dual-polarized metasurface antenna, and belongs to the technical field of antennas. The antenna is composed of a 2*2 metasurface and two L-shaped probe structures with rectangular grooves and U-shaped slots. The antenna adopts L-shaped probe structures and metasurface structures, and does not adopt a complex feeding network, so that a compact antenna size is obtained. Each port can effectively excite two linear polarization radiation modes in the working frequency band, so that a broadband effect is realized. By using a characteristic mode analysis method, rectangular grooves are etched on the L-shaped probe, so that high-order modes are suppressed, and the isolation of the antenna is improved. In addition, U-shaped slots are etched on the L-shaped probe, so that the antenna has high-isolation characteristics. The application has the advantages of broadband, compact size, low profile, high isolation, high front-to-back ratio and low cross-polarization, and has potential application value.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology and relates to a compact broadband high-isolation dual-polarized metasurface antenna. Background Technology

[0002] Dual-polarized antennas can provide a pair of communication channels with the same operating frequency and orthogonal polarization, enabling frequency reuse and polarization diversity. They offer advantages such as large signal transmission capacity and strong resistance to multipath fading, and are widely used in mobile communication systems. With the rapid development of modern RF front-ends, the requirements for the integration of dual-polarized antennas are becoming increasingly stringent, leaving less and less space for antennas. Dual-polarized microstrip antennas have attracted much attention due to their small size, light weight, low cost, and ease of integration with circuits. However, achieving a compact, broadband dual-polarized microstrip antenna while balancing performance characteristics such as impedance bandwidth, isolation, and front-to-back ratio remains challenging.

[0003] To achieve broadband dual-polarized antennas with good port isolation performance, various schemes have been proposed in this field. For example, in the literature "Lin FH, Chen Z N. Resonant metasurface antennas with resonant apertures: Characteristic mode analysis and dual-polarized broadband low-profile design[J].IEEE Transactions on Antennas and Propagation,2020,69(6):3512-3516.", a broadband dual-polarized metasurface antenna with high isolation is realized by using two feed microstrip lines to excite the linear polarization radiation mode of the metasurface as the radiator and the ground gap through slot coupling feeding. However, slot coupling feeding results in a low front-to-back ratio. Furthermore, in the paper "Wong H, Lau KL, Luk KM. Design of dual-polarized L-probe patch antenna arrays with high isolation[J]. IEEE Transactions on Antennas and Propagation, 2004, 52(1):45-52," a broadband dual-polarized microstrip antenna with high isolation and low cross-polarization was achieved by using four L-shaped probe structures combined with a feed network that has 180° phase shift and power division capabilities. However, the feed network not only introduces additional losses but also increases the size of the antenna.

[0004] In the pursuit of compact, high-isolation dual-polarized microstrip antennas, researchers have proposed several solutions. For example, in the paper "Qin X, Li Y. Compact dual-polarized cross-slot antenna with colocated feeding[J].IEEE Transactions on Antennas and Propagation,2019,67(11):7139-7143," a high-isolation dual-polarized cross-slot antenna with a size of only 0.293λ0×0.293λ0×0.008λ0 (λ0 is the free-space wavelength at the center frequency) was proposed. However, the bandwidth of this antenna is only 6.0%, and its directivity is poor. Using two probes to excite the radiation mode of the patch can achieve high isolation, a high front-to-back ratio, and a compact size, but the antenna's operating bandwidth is narrow. In the paper "Gou Y, Yang S, Zhu Q, et al. A compact dual-polarized double E-shaped patch antenna with high isolation[J].IEEE Transactions on Antennas and Propagation, 2013, 61(8):4349-4353," two probes were used to excite two layers of E-shaped patches, thereby achieving a port isolation of over 30dB and stable gain for the antenna, but the operating bandwidth was only 7.7%. In other studies, a structure using two L-shaped probes and a rectangular patch was used, which achieved wide bandwidth, high front-to-back ratio, and compact antenna size, but the antenna isolation and cross-polarization were poor.

[0005] Therefore, in order to meet the requirements of mobile communication systems for miniaturization, broadband, high isolation, low cross-polarization and high front-to-back ratio of dual-polarized antennas, it is of great significance to design a compact broadband high isolation dual-polarized metasurface antenna. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a compact broadband high isolation dual-polarized metasurface antenna, which solves the problems of narrow bandwidth and low front-to-back ratio of existing compact high isolation dual-polarized microstrip antennas.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A compact, broadband, high-isolation, dual-polarized metasurface antenna includes a left feed probe 1, a right feed probe 2, an upper dielectric substrate 4, a middle dielectric substrate 5, and a lower dielectric substrate 6. A metasurface 7 is provided on the upper surface of the upper dielectric substrate 4; a first patch 8 is provided on the upper surface of the middle dielectric substrate; a second patch 9 is provided on the upper surface of the lower dielectric substrate 6, and a metal ground 13 is provided on its lower surface. The left feed probe 1 is connected to the first patch 8 to form a left L-shaped probe; the right feed probe 2 is connected to the second patch 9 to form a right L-shaped probe.

[0009] Optionally, the widths of the first patch 8 and the second patch 9 are different to reduce the difference in horizontal and vertical polarization radiation performance caused by the difference in height.

[0010] Optionally, a U-shaped slit 10 is etched on both the first patch 8 and the second patch 9, and a rectangular groove 12 is etched on both opposite sides of the middle of the two patches. The U-shaped slit 10 and the rectangular groove 12 are the same size.

[0011] Optionally, a large via and a small via are provided at both the left feed probe 1 and the right feed probe 2. The large via is used to prevent air gaps from being left between the upper, middle, and lower dielectric substrates during the soldering of the feed probes and the placement of the chip; the small via is used to place the probe.

[0012] A large via at left feed probe 1 penetrates the upper dielectric substrate 4, and a small via penetrates the middle dielectric substrate 5 and the lower dielectric substrate 6. A large via at right feed probe 2 penetrates the upper dielectric substrate 4 and the middle dielectric substrate 5, and a small via penetrates the lower dielectric substrate 6. The inner walls of all large and small vias are not plated with metal.

[0013] Optionally, the present invention also has two ports, port I and port II. Port I is fed through the left feed probe 1, and port II is fed through the right feed probe 2.

[0014] The beneficial effects of this invention are as follows: It employs a metasurface and two L-shaped probe structures with rectangular slots and U-shaped gaps, eliminating the need for a complex feed network and thus achieving a compact antenna size. Furthermore, each port of the antenna can effectively excite two linearly polarized radiation modes within the operating frequency band, thereby achieving a broadband effect. Simultaneously, the rectangular slots suppress higher-order modes and improve the antenna's isolation; the U-shaped gaps provide high isolation characteristics. Therefore, this invention possesses advantages such as broadband performance, compact size, low profile, high isolation, high front-to-back ratio, and low cross-polarization, and has potential application value.

[0015] 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

[0016] 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:

[0017] Figure 1 This is a schematic diagram of the compact broadband high-isolation dual-polarized metasurface antenna structure of the present invention;

[0018] Figure 2 The structure of the feature mode analysis and the mode importance curves of its 12 modes;

[0019] Figure 3 The six mode currents that can be excited by the probe are: (a) Mode 1 and Mode 2 (at 4.9 GHz), (b) Mode 7 and Mode 8 (at 7.2 GHz), and (c) Mode 11 and Mode 12 (at 8.7 GHz).

[0020] Figure 4 The structure of the characteristic mode analysis and the mode importance curves of its six probe-excited modes;

[0021] Figure 5 The six mode currents that can be excited by the probe are: (a) Mode 1 and Mode 2 (at 4.3 GHz), (b) Mode 7 and Mode 8 (at 6 GHz), and (c) Mode 11 and Mode 12 (at 8.5 GHz).

[0022] Figure 6 For antennas without U-shaped gaps and rectangular slot width L b The impact on S-parameters;

[0023] Figure 7 Comparison of S-parameters for antennas with and without U-shaped slots;

[0024] Figure 8 The surface currents on the left feed probe, the right feed probe, the first patch, and the second patch are shown; (a) without the U-shaped gap, and (b) with the U-shaped gap.

[0025] Figure 9 This is a dimensioned diagram of the antenna according to an embodiment of the present invention;

[0026] Figure 10 The S-parameters and gain curves of the antenna in this embodiment of the invention are shown below;

[0027] Figure 11 This is the front-to-back ratio curve of the antenna in an embodiment of the present invention;

[0028] Figure 12 The antenna radiation pattern in this embodiment of the invention is when the antenna is excited only by port I; (a) at 4.9 GHz, (b) at 5.3 GHz, and (c) at 5.8 GHz.

[0029] Figure 13 The antenna radiation pattern of this embodiment of the invention is when the antenna is excited only by port II; (a) is at 4.9 GHz, (b) is at 5.3 GHz, and (c) is at 5.8 GHz.

[0030] Reference numerals: 1-Left feed probe; 2-Right feed probe; 3-Left large via; 4-Upper dielectric substrate; 5-Middle dielectric substrate; 6-Lower dielectric substrate; 7-Metasurface; 8-First patch; 9-Second patch; 10-U-shaped gap; 11-Right large via; 12-Rectangular groove; 13-Metal ground; 14-Left small via; 15-Right small via. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] 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.

[0034] like Figure 1 The diagram shows a compact, broadband, high-isolation dual-polarized metasurface antenna, comprising a left feed probe 1, a right feed probe 2, an upper dielectric substrate 4, a middle dielectric substrate 5, and a lower dielectric substrate 6. The left feed probe 1 and a first patch 8 form a left L-shaped probe, while the right feed probe 2 and a second patch 9 form a right L-shaped probe. The upper surface of the upper dielectric substrate 4 has a 2×2 arrangement of metasurfaces 7 on its metal portion, while the lower surface is unmetallic and has a large left via 3 and a large right via 11. The upper surface of the middle dielectric substrate 5 has the first patch 8, while the lower surface is unmetallic and has a large right via 11 and a small left via 14. The upper surface of the lower dielectric substrate 6 has the second patch 9, the lower surface has a metal ground plane 13, and a small left via 14 and a small right via 15. Both the first patch 8 and the second patch 9 have a U-shaped slot 10 and two rectangular slots 12 of the same size etched on them.

[0035] The left large via 3 has an unplated inner wall and penetrates the upper dielectric substrate 4. The right large via 11 also has an unplated inner wall and penetrates the upper dielectric substrate 4 and the middle dielectric substrate 5. The left and right large vias 3 and 11 serve to prevent air gaps between the three dielectric substrates after soldering the left feed probe 1 and the first patch 8, and the right feed probe 2 and the second patch 9. The left and right small vias 14 and 15 have unplated inner walls and are used to place the left feed probe 1 and the right feed probe 2, respectively, allowing them to pass through the dielectric substrate. Because the first patch 8 and the second patch 9 have different heights, they are designed with different widths to reduce the difference in horizontal and vertical polarization radiation performance caused by the height difference. The left feed probe 1 passes through the lower dielectric substrate 6 and the middle dielectric substrate 5, connecting to the first patch 8 on the upper surface of the middle dielectric substrate 5. The right feed probe 2 passes through the lower dielectric substrate 6 and connects to the second patch 9 on the upper surface of the lower dielectric substrate 6. Port I is fed through the left feed probe 1, and port II is fed through the right feed probe 2.

[0036] The operating modes of an antenna can be described using the characteristic mode analysis method. In this invention, the characteristic mode analysis method is used to identify the potential radiation modes of the antenna and guide improvements to the antenna structure. In characteristic mode theory, any induced current J can be decomposed into multiple weighted mode currents, expressed as:

[0037]

[0038] Wherein, the mode weighting coefficient α n Represents the mode current J n The contribution of the antenna's total induced current J to the degree of mode excitation is expressed as:

[0039] α n =1 / (1+jλ) n )∫J n ·E i dS (2)

[0040] Where λ n E represents the eigenvalues ​​of pattern n. i Let S represent the external excitation electric field, and S represent the surface area of ​​the conductor. The magnitude of the first part of equation (2) is called the mode importance (MS), expressed as follows:

[0041] MS=1 / |1+jλ n | (3)

[0042] When MS = 1, i.e. λ n When = 0, the corresponding mode n resonates, and the radiation efficiency is the highest. The latter part of equation (2) is called the mode excitation coefficient V. i , means as follows:

[0043] V i =∫J n ·E i dS (4)

[0044] The above formula reflects the relationship between the mode current and the applied excitation. The larger the value, the better the excitation effect of the antenna.

[0045] To illustrate the antenna design process, the mode characteristics of the metasurface 7, the first patch 8 (without etched rectangular slots 12 and U-shaped slots 10), and the second patch 9 (without etched rectangular slots 12 and U-shaped slots 10) are first presented, such as... Figure 2 and Figure 3 As shown, the mode currents for modes 1, 2, 7, 8, 11, and 12 are stronger on the first patch 8 or the second patch 9, and the current directions are consistent. Therefore, these modes are easily excited by the left feed probe 1 or the right feed probe 2. Other modes are not easily excited or are outside the considered frequency band, so their influence can be ignored.

[0046] For modes 1, 2, 7, and 8, the mode current directions on metasurface 7 exhibit consistency, indicating linear polarization modes that meet design requirements. The mode importance curves for modes 1 and 2, and modes 7 and 8 are relatively close, with the mode currents for modes 1 and 7 concentrated on the first patch 8, and the mode currents for modes 2 and 8 concentrated on the second patch 9. Therefore, it is easy to excite modes 1 and 7 at port 1 and modes 2 and 8 at port 2, achieving a broadband dual-linear polarization antenna. For modes 11 and 12, the mode current directions on metasurface 7 are inconsistent, indicating they are unwanted higher-order modes. However, the mode importance curves show that these two modes are easily excited in the same frequency band as modes 7 and 8, causing performance degradation such as cross-polarization. Therefore, they need to be moved out of the operating frequency bands of modes 7 and 8.

[0047] Depend on Figure 3 It can be seen that the mode currents of modes 11 and 12 are mainly concentrated on metasurface 7, while the mode currents of modes 1, 2, 7, and 8 are mainly concentrated on the first patch 8 or the second patch 9. Therefore, changing the structure of the first patch 8 and the second patch 9 has a greater impact on modes 1, 2, 7, and 8, and a smaller impact on modes 11 and 12.

[0048] Since the mode currents of modes 1, 2, 7 and 8 are strongest in the middle of the first patch 8 or the second patch 9, a rectangular groove 12 is etched in the middle of the first patch 8 or the second patch 9. Figure 4 and Figure 5 The paper presents partial mode importance curves and partial mode currents for the structure of metasurface 7, first patch 8 with etched rectangular slots 12, and second patch 9 with etched rectangular slots 12. It can be seen that the mode importance curves of modes 1 and 2 shift to lower frequencies by approximately 0.6 GHz, modes 7 and 8 shift by approximately 1.2 GHz, and modes 11 and 12 shift by approximately 0.2 GHz. The shift in mode importance curves of modes 11 and 12 is relatively small, indicating that modes 11 and 12 are essentially far removed from the operating frequency bands of modes 7 and 8. It can also be seen that the mode current directionality of each mode is not affected by the rectangular slots 12. Therefore, the final result is that port I excites modes 1 and 7, and port II excites modes 2 and 8. It should be noted that the mode analysis here does not consider the influence of the excitation and probe structures; therefore, the actual operating frequency will shift to some extent after adding excitation and probes.

[0049] Figure 6 The S-parameters of the antenna without the U-shaped slot 10 are given as a function of the width L of the rectangular slot 12. b The curve showing the change in |S|. It can be seen that |S|... 11The second resonant point of the curve decreases as the width of the rectangular slot 12 increases, and... Figures 2 to 4 The MS curves showed relatively consistent changes. According to... Figure 3 and Figure 5 The current distribution of target modes 1, 2, 7, and 8 is strongest in the middle of the first patch 8 and the second patch 9. At this location, the two patches are close together and have strong coupling. This means that the rectangular slot 12 can reduce the area of ​​this part, reduce coupling, and thus improve isolation. This can be achieved from |S 21 |With the rectangular groove width L 12 b The increase and decrease can be seen from this.

[0050] To further increase isolation, identical U-shaped slots 10 were etched on the first patch 8 and the second patch 9 based on the rectangular slot 12, such as... Figure 1 As shown. Figure 7 The effect of the etched U-shaped slot 10 on the antenna's S-parameters is shown. It can be seen that the etched U-shaped slot 10 affects the antenna's |S... 11 |and|S 22 The impact is relatively small. It can also be seen that the antenna with the etched U-shaped slot 10 has an in-band |S 21 The maximum value decreased from -25dB to -31dB, indicating a significant increase in isolation. Figure 8 The surface current distribution on the left feed probe 1, right feed probe 2, first patch 8, and second patch 9 is described when port II is fed at 5.5 GHz. It can be seen that the etched U-shaped slot 10 allows the surface current to flow along the edge of the slot, thereby reducing the coupled current on the probe. Therefore, the U-shaped slot 10 can increase the isolation.

[0051] As the preceding analysis shows, the dual-polarized antenna structure proposed in this invention suppresses higher-order modes, and each port can effectively excite two linearly polarized radiation modes within the operating frequency band, achieving broadband performance. Furthermore, the two ports of the antenna also exhibit high isolation. By adjusting the dimensions of the metasurface, patch, rectangular slot, and U-shaped gap, the operating frequency range and mode characteristics of the antenna can be controlled, thereby enabling the antenna to achieve good radiation performance over a wide frequency range.

[0052] This embodiment presents a preferred structure of the present invention. The sample in this embodiment is a compact, broadband, high-isolation, dual-polarized metasurface antenna with an operating frequency of 4.73 GHz to 5.91 GHz. The antenna has dimensions of 30 mm × 30 mm × 3.75 mm, or 0.53λ0 × 0.53λ0 × 0.067λ0 (λ0 represents the free-space wavelength corresponding to the center frequency). The antenna uses a three-layer dielectric substrate, all with a relative permittivity of 2.65 and a loss tangent of 0.01. The thickness of the upper dielectric substrate is 1.5 mm, the thickness of the middle dielectric substrate is 0.25 mm, and the thickness of the lower dielectric substrate is 2 mm.

[0053] The specific dimensions of the sample in this embodiment are as follows: Figure 9 As shown, the specific dimensions of the antenna are shown in Table 1:

[0054] Table 1. Antenna Dimensions

[0055]

[0056] Simulation was performed using the HFSS simulation software. The S-parameters and gain curves of the sample in this embodiment are shown below. Figure 10 As shown. This antenna has two resonant points, |S 11 |and|S 22 The frequency range where all values ​​are less than -10dB is 4.73GHz-5.91GHz, meaning the relative bandwidth of -10dB is 22.2%. 11 |and|S 22 The frequency range where all values ​​are less than -15dB is 4.88GHz-5.77GHz, meaning the relative bandwidth of -15dB is 16.7%. 21 The antenna exhibits high port isolation, with a gain less than -31dB within its operating frequency band. When fed from port I, the antenna gain varies from 6.04dBi to 6.72dBi within its band, and when fed from port II, it varies from 5.77dBi to 6.77dBi, with stable gain. Figure 11 It can be seen that when powered by port I or port II, the front-to-back ratio of the antenna is greater than 22dB within the operating frequency band, and the antenna's rearward radiation is weak. Figure 12 and Figure 13 Radiation patterns are presented for excitation ports I and II, respectively. It can be seen that within the operating frequency band, the antenna exhibits good radiation directivity, with cross-polarization less than -26 dB and low cross-polarization.

[0057] 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 compact, broadband, high-isolation, dual-polarized metasurface antenna, characterized in that: It includes a left-feed probe (1), a right-feed probe (2), an upper dielectric substrate (4), a middle dielectric substrate (5), and a lower dielectric substrate (6); the upper surface of the upper dielectric substrate (4) is provided with a metasurface (7); the upper surface of the middle dielectric substrate is provided with a first patch (8); the upper surface of the lower dielectric substrate (6) is provided with a second patch (9), and the lower surface is provided with a metal ground (13); the left-feed probe (1) is connected to the first patch (8) to form a left L-shaped probe; the right-feed probe (2) is connected to the second patch (9) to form a right L-shaped probe; The widths of the first patch (8) and the second patch (9) are different to reduce the difference in horizontal and vertical polarization radiation performance caused by different heights; A U-shaped slit (10) is etched on both the first patch (8) and the second patch (9); a rectangular groove (12) is etched on both opposite sides of the middle of the first patch (8) and the second patch (9).

2. The compact broadband high-isolation dual-polarized metasurface antenna according to claim 1, characterized in that: The U-shaped slit (10) and rectangular groove (12) of the first patch (8) and the second patch (9) have the same dimensions.

3. The compact broadband high-isolation dual-polarized metasurface antenna according to claim 1, characterized in that: At both the left feed probe (1) and the right feed probe (2), there is a large via and a small via. The large via is used to prevent air gaps from being left between the upper, middle and lower dielectric substrates when soldering the feed probe and mounting the chip. The small via is used to place the probe.

4. A compact, broadband, high-isolation, dual-polarized metasurface antenna according to claim 3, characterized in that: The large via at the left feed probe (1) penetrates the upper dielectric substrate (4), and the small via penetrates the middle dielectric substrate (5) and the lower dielectric substrate (6). Neither the large nor the small vias have metal plating on their inner walls.

5. A compact, broadband, high-isolation, dual-polarized metasurface antenna according to claim 3, characterized in that: The large via at the right feed probe (2) penetrates the upper dielectric substrate (4) and the middle dielectric substrate (5), and the small via penetrates the lower dielectric substrate (6). Neither the large nor the small vias have metal plating on their inner walls.

6. A compact, broadband, high-isolation, dual-polarized metasurface antenna according to claim 1, characterized in that: The antenna is also provided with port I and port II; port I is fed through the left feed probe (1); Port II is fed through the right feed probe (2).

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