A low profile broadband dual-polarized metasurface antenna

Abstract

The application belongs to the technical field of wireless communication, and relates to the structural design of a broadband antenna, and specifically provides a low-profile broadband dual-polarized metasurface antenna which is composed of a microstrip feed network 5, a lower layer dielectric substrate 4, a metal floor 3, an upper layer dielectric substrate 2 and a metasurface radiation array 1 which are sequentially stacked from bottom to top. The structure of the metasurface radiation array is creatively designed through eigenmode analysis, so that the strongest current is regulated to the central rectangular patch, thereby enabling the microstrip feed structure to excite vertical and horizontal polarization radiation modes through the cross-shaped slot on the metal floor, realizing the dual-polarization and broadband characteristics of the antenna. Finally, the bandwidths of the two ports of the antenna cover 3.42-6.09 GHz and 3.56-6.24 GHz respectively, the relative bandwidths are 56.15% and 54.69% respectively, the maximum gains of the two ports in the passband can reach 10.4 dBi and 11.0 dBi respectively, and the profile height is only 0.085λ0. Moreover, the application has the advantages of simple structure, wide bandwidth, low profile, low processing and assembling difficulty and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wireless communication, and relates to the structural design of a broadband antenna, and particularly provides a low-profile broadband dual-polarized metasurface antenna. BACKGROUND

[0002] With the continuous development of wireless communication technology, humans have great demands for the quality and rate of communication, which puts forward higher requirements for base station antennas; due to the development and utilization of new frequency bands, the electromagnetic environment is increasingly complex, and wireless devices will face the problem of multipath fading, which requires diversity reception technology to improve the quality of signals, and the polarization diversity of dual-polarized antennas can improve the influence of multipath fading to a certain extent; in addition, the use of dual-polarized antennas can also reduce the number of radiation units, thereby reducing the cost and size of the antenna; considering the aesthetic requirements in commercial applications, low-profile designs are used as much as possible to make the device or antenna look flat.

[0003] Based on this, microstrip antennas have become a research hotspot in recent years due to their low profile, compact structure, ease of processing and installation, and suitability for small and lightweight mobile base station systems; however, the working bandwidth of traditional microstrip antennas is narrow, which is difficult to meet the actual engineering requirements; therefore, metasurface antennas are proposed, which have attracted widespread attention due to their low profile and ease of achieving wideband, and have also expanded new ideas for the implementation of dual-polarized antennas. SUMMARY

[0004] The purpose of the application is to overcome the shortcomings of the prior art and provide a low-profile broadband dual-polarized metasurface antenna, which has the advantages of wide bandwidth, low profile, simple structure and easy implementation, and also has good radiation performance.

[0005] To achieve the above purpose, the technical scheme adopted by the application is:

[0006] A low-profile broadband dual-polarized metasurface antenna is composed of a microstrip feed network 5, a lower layer dielectric substrate 4, a metal ground plate 3, an upper layer dielectric substrate 2 and a metasurface radiation array 1 which are sequentially stacked from bottom to top; characterized in that:

[0007] The super surface radiation array adopts an axisymmetric structure about a line in the upper layer dielectric substrate, comprising: one rectangular patch A, four rectangular patches B, four rectangular patches C, four rectangular patches D and four rectangular patches E; wherein the rectangular patch A is located at the center of the upper surface of the upper layer dielectric substrate 2, the four rectangular patches B and the four rectangular patches C are arranged around the rectangular patch A, the four rectangular patches B are respectively arranged at the four sides of the rectangular patch A, the four rectangular patches C are respectively arranged at the four corners of the rectangular patch A, the four rectangular patches D are respectively arranged parallel to the rectangular patches B, the four rectangular patches E are respectively arranged parallel to the rectangular patches D, and the spacing between any adjacent rectangular patches is the same; the rectangular patches B, the rectangular patches D and the rectangular patches E are all provided with a first gap along the line in the upper layer dielectric substrate, and the rectangular patches D and the rectangular patches E are further provided with two second gaps, and the second gaps are opposite to the gap between the rectangular patches B and the rectangular patches C.

[0008] Further, the size of the rectangular patch A is l1x l1, the size of the rectangular patch B is l1x m1, the size of the rectangular patch C is m1x m1, the size of the rectangular patch D is l2x m2, the size of the rectangular patch E is l2x m3, the spacing between any adjacent rectangular patches is s, and l1> m1, m2> m3, l1< l2< l, l = l1+ 2m1+ 2s; the width of the first gap is g1, and the width of the second gap is g2, and g1< g2, g2 = s.

[0009] Further, a cross-shaped gap 6 is etched at the center of the metal floor 3 and located directly below the rectangular patch A.

[0010] Further, the feed network 5 is composed of two vertically placed Y-shaped microstrip transmission lines 8, which respectively excite the slot mode and the orthogonal mode of the horizontal polarization and the vertical polarization of the super surface array, so as to realize the dual polarization and wideband characteristics of the antenna; the Y-shaped microstrip transmission line 8 is introduced into the fan-shaped structure 10 at the end, so as to realize better impedance matching; the jumper structure 9 arranged on the upper surface of the lower layer dielectric substrate 4 is used at the overlapping place of the two vertically placed Y-shaped microstrip transmission lines 8, and the jumper structure is located in the preset window 7 of the metal floor 3.

[0011] Based on the above technical scheme, the beneficial effects of the present application are as follows:

[0012] This invention provides a low-profile broadband dual-polarized metasurface antenna with multimode resonance. The metasurface radiating array, based on a 3×3 metasurface array, reduces the size of rectangular patches B and C, altering the current distribution of the metasurface array structure and achieving better impedance matching for the main mode. Simultaneously, parasitic rectangular patches D and E are introduced to improve impedance matching for higher-order modes and extend the bandwidth. Furthermore, slots are created on rectangular patches B, D, and E, dividing them into several sub-patterns, further improving the current distribution of the metasurface and allowing the strongest current to be modulated to the rectangular patches. On A, the vertically placed Y-shaped microstrip line feed structure excites both vertical and horizontal polarization radiation modes through the cross-shaped slot 6 on the metal ground plane 3, achieving impedance matching across the entire frequency band and improving bandwidth, thus ultimately realizing the antenna's dual polarization and broadband characteristics. Finally, the bandwidths of the two ports of this invention cover 3.42–6.09 GHz and 3.56–6.24 GHz respectively, with relative bandwidths of 56.15% and 54.69%, respectively. The maximum gain of the two ports within the passband can reach 10.4 dBi and 11.0 dBi, respectively, with a profile height of only 0.085λ0. Furthermore, the antenna of this invention has advantages such as simple structure, wide bandwidth, low profile, and low processing and assembly difficulty. Attached Figure Description

[0013] Figure 1 This is a schematic cross-sectional view of the low-profile broadband dual-polarized metasurface antenna of the present invention.

[0014] Figure 2 This is a schematic diagram of the metasurface radiating array in the low-profile broadband dual-polarized metasurface antenna of the present invention.

[0015] Figure 3 This is a schematic diagram of the metal ground plane in the low-profile broadband dual-polarized metasurface antenna of the present invention.

[0016] Figure 4 This is a schematic diagram of the microstrip feed network in the low-profile broadband dual-polarized metasurface antenna of the present invention.

[0017] Figure 5 This is a schematic diagram illustrating the design principle of the metasurface radiation array in an embodiment of the present invention.

[0018] Figure 6 The S-shaped antenna composed of a metasurface radiating array in the embodiment of the present invention 11 picture.

[0019] Figure 7 This is a diagram showing the mode importance results of the metasurface radiation array in an embodiment of the present invention.

[0020] Figure 8 This is a mode current distribution diagram of the metasurface radiation array in an embodiment of the present invention.

[0021] Figure 9 The S-parameters (SX and SY) of the low-profile broadband dual-polarized metasurface antenna in this embodiment of the invention are... 11 S 22 S 12 Result image.

[0022] Figure 10 This is a gain diagram of the low-profile broadband dual-polarized metasurface antenna in an embodiment of the present invention.

[0023] Figure 11 This is the normalized radiation pattern of the E-plane and H-plane of the low-profile broadband dual-polarized metasurface antenna in an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] This embodiment provides a low-profile broadband dual-polarized metasurface antenna, the cross-sectional schematic of which is shown below. Figure 1 As shown, it consists of a microstrip feed network 5, a lower dielectric substrate 4, a metal ground plane 3, an upper dielectric substrate 2, and a metasurface radiation array 1, stacked sequentially from bottom to top; more specifically:

[0026] The metasurface radiation array 1 consists of 17 metal patches disposed on the upper surface of the upper dielectric substrate 2, and has an axisymmetric structure about the centerline of the upper dielectric substrate, such as... Figure 2As shown in the figure, it includes: 1 rectangular patch A, 4 rectangular patches B, 4 rectangular patches C, 4 rectangular patches D, and 4 rectangular patches E. Among them, the rectangular patch A is located at the center of the upper surface of the upper dielectric substrate 2. The 4 rectangular patches B and the 4 rectangular patches C are arranged around the rectangular patch A. The 4 rectangular patches B are respectively placed on the four sides of the rectangular patch A, and the 4 rectangular patches C are respectively placed at the four corners of the rectangular patch A. The 4 rectangular patches D are respectively arranged parallel to the rectangular patch B, and the 4 rectangular patches E are respectively arranged parallel to the rectangular patch D. And the distance between any adjacent rectangular patches is s. The size of the rectangular patch A is l1×l1, the size of the rectangular patch B is l1×m1, the size of the rectangular patch C is m1×m1, the size of the rectangular patch D is l2×m2, and the size of the rectangular patch E is l2×m3. And l1>m1, m2>m3, l1<l2<l, l = l1 + 2m1 + 2s. The rectangular patches B, D, and E are all provided with a first slit along the center line of the upper dielectric substrate. The rectangular patches D and E are also provided with two second slits. The second slits are facing the gap between the rectangular patches B and C and the width is g2 = s. The width of the first slit is g1 and g1<g2. That is, the rectangular patch B is divided into two equal-sized sub-patches, and the rectangular patches D and E are respectively divided into four sub-patches. The inner two sub-patches have equal sizes, and the outer two sub-patches have equal sizes. The above size annotations are as Figure 5 shown in the figure (c) of this embodiment: l1 = 14mm, m1 = 9mm, l2 = 25mm, m2 = 7mm, m3 = 2mm, s = 0.8mm, g1 = 0.4mm, g2 = s = 0.8mm, and the distance g3 between the first slit and the second slit is 7.8mm;

[0027] The metal floor 3 is arranged on the upper surface of the lower dielectric substrate 4, as Figure 3 shown; a cross-shaped slit 6 is etched at the center position of the metal floor 3 and is located directly below the rectangular patch A. The length of the cross-shaped slit is l3 and the width is w3. In this embodiment: l3 = 25.1mm, w3 = 0.9mm;

[0028] The feeding network 5 is arranged on the lower surface of the lower dielectric substrate 4, as Figure 4 shown, and is composed of two vertically placed Y-shaped (fork-shaped) microstrip transmission lines 8, which respectively excite the slot mode and the orthogonal modes of horizontal polarization and vertical polarization of the metasurface array, so as to achieve the dual-polarization and broadband characteristics of the antenna; a fan-shaped structure 10 is introduced at the end of the Y-shaped microstrip transmission line 8 to achieve better impedance matching; a jumper structure 9 arranged on the upper surface of the lower dielectric substrate 4 is adopted at the overlapping part of the two vertically placed Y-shaped microstrip transmission lines 8. The jumper structure is located within the preset window 7 of the metal floor 3, that is, the jumper structure has no contact with the metal floor;

[0029] The upper dielectric substrate 2 is made of polytetrafluoroethylene with a dielectric constant of 3.5 and a loss tangent of 0.002, and its dimensions are W×W with a height of t1; the lower dielectric substrate 4 is made of Rogers RO4350B with a dielectric constant of 3.66 and a loss tangent of 0.004, and its dimensions are W×W with a height of t2; in this embodiment: t1 = 5mm, t2 = 0.768mm, W = 85mm.

[0030] It should be noted that in the dimension representation "A×B" of all rectangular patches in this invention, "A" represents the length of the longer side and "B" represents the length of the wider side; the parallel arrangement between rectangular patches refers to the parallel arrangement of the longer sides of two rectangular patches.

[0031] In terms of working principle:

[0032] This invention, based on passive characteristic mode analysis, discovers that different modes of a metasurface can guide the broadband design of an antenna. By slotting, shifting, or deleting elements in the metasurface array structure, the distribution of surface currents under different modes can be altered, bringing the different modes of the metasurface closer together, and utilizing multimode resonance to achieve broadband antenna design. The working principle of this invention is explained below by analyzing the evolution process of the metasurface array:

[0033] Based on the fundamental 3×3 metasurface array, the evolution process is as follows: Figure 5 As shown in (a) to (c), reducing the size of rectangular patches B and C alters the current distribution of the metasurface array structure, achieving better impedance matching in the master mode, as... Figure 6 As shown in (a); simultaneously, the introduction of parasitic rectangular patches D and E improves the impedance matching of higher-order modes, as shown in (a). Figure 6 As shown in (b), the bandwidth is expanded; furthermore, slots are opened on rectangular patches B, D, and E, dividing them into several patches, which further improves the current distribution on the metasurface, allowing the strongest current to be modulated to rectangular patch A. This enables the vertically placed Y-shaped microstrip line feeding structure to excite both vertical and horizontal polarization radiation modes through the cross-shaped slot 6 on the metal ground plane 3, achieving impedance matching throughout the entire frequency band and improving bandwidth. Figure 6 As shown in (c).

[0034] Finally, the structure of the metasurface radiation array 1 is as follows: Figure 5 As shown in (c), the pattern importance results are as follows: Figure 7 As shown, modes 1 and 2 are orthogonal modes with their mode importance curves coinciding, as are modes 7 and 8. Both pairs of modes share the same excitation frequency band, making them suitable for dual-polarized antenna designs within the same frequency band. Figure 8The diagram shows the mode current distribution of the metasurface radiation array 1 in four modes. (a) to (d) represent modes 1, 2, 7, and 8, respectively. The current at the rectangular patch A is relatively strong in all four modes. Modes 1 and 7 are horizontal polarization modes, while modes 2 and 8 are vertical polarization modes. This invention uses a slot coupling feeding method. The Y-axis slot of the cross-shaped slot 6 is used to excite modes 1 and 7, and the X-axis slot is used to excite modes 2 and 8. In summary, the feeding network 5 can excite horizontal polarization modes (modes 1 and 7) and vertical polarization modes (modes 2 and 8) through the cross-shaped slot 6.

[0035] The S-parameters (S) of the antenna of this invention 11 S 22 S 12 )like Figure 9 As shown, the 10dB impedance bandwidth of the X-axis port is 56.15% (3.42-6.09GHz), and the 10dB impedance bandwidth of the Y-axis port is 56.15% (3.56-6.24GHz), indicating that the two ports achieve broadband characteristics and can be regarded as dual polarization within the same frequency band; at the same time, the isolation of the two ports is higher than 20dB throughout the entire frequency band.

[0036] The gain curve of the antenna of this invention is as follows: Figure 10 As shown, the maximum gain of the X-axis port and Y-axis port in the passband can reach 10.4dBi and 11.0dBi respectively, and the average gain in the entire frequency band is about 7.5dBi.

[0037] The normalized radiation patterns of the E-plane and H-plane of the antenna of this invention are as follows: Figure 11 As shown, (a) to (c) are the frequency points of 4.2 GHz, 5.3 GHz and 6 GHz respectively. As can be seen from the figure, there is a stable radiation pattern throughout the entire passband, and the cross-polarization is less than -30 dB.

[0038] In summary, this invention proposes a low-profile broadband dual-polarized metasurface antenna. A vertically placed Y-shaped microstrip transmission line 8 excites the slot modes and the horizontally and vertically polarized orthogonal modes of the metasurface array. Through optimization of the metasurface structure, the position with stronger current is positioned directly above the cross-shaped slot 6, ultimately achieving a dual-polarized antenna that excites four modes. The results show that the antenna exhibits broadband and dual-polarization characteristics, and its isolation and cross-polarization meet standards. Furthermore, this invention features a low antenna profile, a simple and compact structure, and ease of fabrication and installation.

[0039] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A low-profile broadband dual-polarized metasurface antenna, which is composed of a microstrip feed network (5), a lower dielectric substrate (4), a metal ground plate (3), an upper dielectric substrate (2) and a metasurface radiation array (1) stacked from bottom to top; characterized in that: the metasurface radiation array adopts an axisymmetric structure about the center line of the upper dielectric substrate, and includes one rectangular patch A, four rectangular patches B, four rectangular patches C, four rectangular patches D and four rectangular patches E; wherein the rectangular patch A is located at the center of the upper surface of the upper dielectric substrate (2), the four rectangular patches B and the four rectangular patches C are arranged around the rectangular patch A, the four rectangular patches B are respectively arranged at the four edges of the rectangular patch A, the four rectangular patches C are respectively arranged at the four corners of the rectangular patch A, the four rectangular patches D are respectively arranged parallel to the rectangular patches B, the four rectangular patches E are respectively arranged parallel to the rectangular patches D, and the spacing between any adjacent rectangular patches is the same; the rectangular patches B, the rectangular patches D and the rectangular patches E are each provided with a first slit along the center line of the upper dielectric substrate, and the rectangular patches D and the rectangular patches E are each provided with two second slits opposite the gap between the rectangular patches B and the rectangular patches C; The size of the rectangular patch A is l 1 x 1 l 1 l 1 x 1 m 1 m 1 x 1 m 1 l 2 x 2 m 2 l 2 x 2 m 3 s 1 l 1 m 1 m 2 m 3 l 1 l 2 l , l = l 1 + 2 m 1 + 2 s .

2. The low-profile wideband dual-polarized metasurface antenna of claim 1, wherein, The width of the first slit is g 1. The width of the second slit is g 2, and g 1 g 2, g 2= s .

3. The low-profile wideband dual-polarized metasurface antenna of claim 1, wherein, a cross-shaped slit (6) is etched at the center of the metal ground plate (3) and located directly below the rectangular patch A.

4. The low-profile wideband dual-polarized metasurface antenna of claim 1, wherein, the feed network (5) is composed of two vertically placed Y-shaped microstrip transmission lines (8), and a jumper structure (9) is arranged on the upper surface of the lower dielectric substrate (4) at the overlapping position of the two vertically placed Y-shaped microstrip transmission lines, the jumper structure is located in a predetermined window (7) of the metal ground plate (3); and a fan-shaped structure (10) is arranged at the end of the Y-shaped microstrip transmission line to achieve impedance matching.

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