High-isolation wideband mimo magneto-electric dipole antenna based on frequency selective surface

Abstract

The application provides a high-isolation wide-band MIMO magneto-electric dipole antenna based on a frequency selective surface, belongs to the field of radio frequency antennas, and comprises a frequency selective surface, a feed strip, and a metal floor, a first dielectric substrate, a second dielectric substrate and at least two antenna units arranged in sequence from bottom to top. The frequency selective surface is an inwardly bent open resonant ring and is located between adjacent antenna units. The antenna unit comprises four quarter-circle patches which are centrally symmetrical. Each quarter-circle patch extends outwardly with a rectangular patch and is grounded through a first metal column. The four quarter-circle patches are separated to form a transverse gap and a longitudinal gap. A slot is formed in the side edge of the quarter-circle patch facing the transverse gap. The feed strip is located on the upper surface of the second dielectric substrate and is located in the longitudinal gap. The feed strip is grounded through a second metal column. When the distance between adjacent antenna units is small, the frequency selective surface can effectively reduce the coupling coefficient between the antenna units.

Description

Technical Field

[0001] This invention relates to the field of radio frequency antenna technology, and in particular to a high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface. Background Technology

[0002] As a crucial component of RF transceivers, the impedance matching and radiation pattern of RF antennas constantly influence the overall performance of the transceiver. With the rapid development of 5G mobile communication systems, the demands for data transmission rates and system capacity in wireless communication systems are increasing dramatically. In the existing technology, Chinese invention patent application CN119297602A, entitled "A Broadband Dual-Polarized Magnetoelectric Dipole Antenna," addresses the problem of poor impedance bandwidth capability of magnetoelectric dipole antennas, which fails to meet the demands for faster network information transmission, by increasing the operating bandwidth of the magnetoelectric dipole element.

[0003] Multiple-Input Multiple-Output (MIMO) technology has become a crucial pillar of high throughput in 5G technology due to its ability to significantly improve channel capacity and spectrum resources without increasing additional spectrum resources and transmit power. In MIMO antenna arrays, due to space constraints, the spacing between antenna elements becomes increasingly close as the number of elements increases. This close spacing leads to strong surface wave coupling and spatial induced coupling between antennas, thus degrading the bandwidth performance of the MIMO array. Summary of the Invention

[0004] The technical problem to be solved by this invention is: how to reduce the coupling between antenna elements in a MIMO antenna.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution: a high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency selective surface, comprising a frequency selective surface, a feed strip, and a metal ground plane, a first dielectric substrate, a second dielectric substrate, and at least two antenna elements arranged sequentially from bottom to top. The frequency selective surface is an inwardly bent open resonant ring located between adjacent antenna elements. The antenna element includes four centrally symmetrical quarter-circle patches. Each quarter-circle patch extends outward with a rectangular patch and is grounded through a first metal post. The four quarter-circle patches are separated to form a transverse slot and a longitudinal slot. The quarter-circle patches have slots on their sides facing the transverse slots. The feed strip is located on the upper surface of the second dielectric substrate and in the longitudinal slot. The feed strip is grounded through a second metal post.

[0006] This invention utilizes a Frequency Selective Surface (FSS) between adjacent antenna elements. The FSS is an inwardly bent open-circuit resonator, which reduces the operating frequency of the open-circuit resonator. Through resonance within the antenna's operating frequency range, the FSS confines electromagnetic waves at that frequency to the FSS, thereby suppressing coupling of electromagnetic waves to other antenna elements. The FSS exhibits band-stop characteristics in the 3.5GHz-4.5GHz operating frequency range. When the spacing between adjacent antenna elements is small, the FSS effectively reduces the coupling coefficient between them, effectively blocking electromagnetic wave propagation and ultimately achieving decoupling in this frequency band, thus improving the isolation between antenna elements in a MIMO antenna.

[0007] By placing a rectangular patch at the top of each quarter-circle patch, the current path of the antenna can be extended, thereby reducing the antenna's operating frequency. By slotting inside the quarter-circle patch, the current path of the magnetoelectric dipole can be extended, further reducing the antenna's operating frequency, thus effectively reducing the overall size of the antenna.

[0008] Preferably, electromagnetic waves are fed into the second metal pillar, transmitted through the feeding strip, and simultaneously excited four quarter-circular patches to radiate electromagnetic waves outward, thus realizing the transmission of electromagnetic waves; the four quarter-circular patches simultaneously receive electromagnetic waves, which are transmitted through the feeding strip and output from the second metal pillar, thus realizing the reception of electromagnetic waves.

[0009] Preferably, multiple frequency selection surfaces are arranged along the direction of the longitudinal slit and are evenly spaced.

[0010] Preferably, the first end of the open-ended resonant ring and the second end of the open-ended resonant ring form a rectangle, with the opening located between the first end and the second end of the open-ended resonant ring, and the long side and the wide side of the rectangle formed are bent inward at least once.

[0011] Preferably, the operating frequency band of the split-ring resonator is adjusted by adjusting the length of the inward bend of the split-ring resonator.

[0012] Preferably, the rectangular patch is located at the radial end of each quarter-circle patch, with the long side of the rectangular patch parallel to the transverse gap and the wide side of the rectangular patch parallel to the longitudinal gap.

[0013] Preferably, the long side of the groove is parallel to the longitudinal gap, the wide side of the groove is parallel to the transverse gap, and the wide side of the groove near the center of the quarter-circle patch has a notch.

[0014] Preferably, a plurality of first metal pillars are evenly distributed along the transverse and longitudinal gaps and close to the center of the quarter-circle patch, with one end of the first metal pillar connected to the quarter-circle patch and the other end of the first metal pillar connected to the metal floor.

[0015] Preferably, one end of the second metal post is connected to the end of the feed strip, and the other end of the second metal post is connected to the metal ground.

[0016] Preferably, there is at least one first dielectric substrate, and multiple first dielectric substrates are stacked and fixed to the second dielectric substrate with screws. The material of both the first and second dielectric substrates is Rogers 4003C, with a dielectric constant of 3.55 and a loss tangent of 0.0027.

[0017] The advantages provided by this invention are:

[0018] 1. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface of this invention has good impedance matching characteristics in the 3.5-4.5GHz operating range, with a relative bandwidth of 25%, covering the core Sub-6GHz frequency range of 5G communication such as N77 and N78. Furthermore, the coupling between the two antenna elements is low, all below -20dB, and the envelope correlation coefficient is below 0.003, exhibiting good diversity benefits. The antenna also has good radiation characteristics in the operating range, with a peak gain of 7.3dBi in the operating frequency band and an antenna gain of over 6dBi throughout the entire operating frequency band.

[0019] 2. Compared with the existing technology of dual-polarized antennas which improve the operating bandwidth of the magnetoelectric dipole unit, the MIMO magnetoelectric dipole antenna of the present invention can effectively improve channel capacity, thereby increasing the transmission rate of communication. In the MIMO magnetoelectric dipole antenna of the present invention, as the number of antenna elements increases, the spacing between adjacent antenna elements will become smaller and smaller in a limited space. The present invention greatly reduces the operating frequency band affected by the spatial filtering effect of the open resonant ring by placing an inwardly bent open resonant ring in adjacent antenna elements, thereby reducing the coupling of the MIMO antenna.

[0020] 3. In the prior art, the design of broadband dual-polarized magnetoelectric dipole antenna involves etching a semi-elliptical chamfer off a rectangular metal patch. In this invention, the antenna element is initially a circular patch with a gentler curvature, avoiding burrs during processing, ensuring the antenna's processing accuracy, and making it more suitable for large-scale processing. In addition, the antenna of this invention uses a multilayer dielectric substrate and has screw holes for later processing. Compared with the use of adhesive layers, this invention can greatly reduce the antenna's processing cost. Attached Figure Description

[0021] Figure 1A perspective view of a high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface provided in an embodiment of the present invention;

[0022] Figure 2 A top view of the antenna element and frequency selection surface in a high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency selection surface provided in an embodiment of the present invention;

[0023] Figure 3 A top view of the frequency selection surface in a high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency selection surface, provided in an embodiment of the present invention;

[0024] Figure 4 The reflection coefficient and transmission coefficient of the high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface provided in the embodiments of the present invention;

[0025] Figure 5 The radiation patterns of the high-isolation broadband MIMO magnetoelectric dipole antenna based on frequency-selective surface provided in the embodiments of the present invention in the XOZ and YOZ planes at 3.8 GHz;

[0026] Figure 6 The radiation patterns of the high-isolation broadband MIMO magnetoelectric dipole antenna based on frequency-selective surface provided in the embodiments of the present invention in the XOZ and YOZ planes at 4.2 GHz;

[0027] Figure 7 The envelope correlation coefficient of the high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface provided in the embodiments of the present invention;

[0028] Figure 8 Peak gain diagram of a high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface provided in an embodiment of the present invention;

[0029] In the figure: 10 Frequency selection surface, 11 First end, 12 Second end, 13 Long side bend, 14 Wide side bend, 20 Antenna element, 21 Quarter circle patch, 22 Rectangular patch, 23 Horizontal slot, 24 Vertical slot, 25 Slot, 251 Notch, 26 First metal pillar, 30 Feed strip, 31 Second metal pillar, 40 Second dielectric substrate, 50 First dielectric substrate, 60 Metal ground plane. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] like Figure 1 As shown, this embodiment provides a high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface, including a frequency-selective surface 10, an antenna element 20, a feed strip 30, a second dielectric substrate 40, a first dielectric substrate 50, and a metal ground plane 60. Both the second dielectric substrate 40 and the first dielectric substrate 50 are rectangular, forming a... Figure 1 In the coordinate system shown, the X-axis is parallel to the long side of the rectangular dielectric substrate, and the Y-axis is parallel to the wide side of the rectangular dielectric substrate. In this invention, the positive direction of the Z-axis is taken as the top, and the negative direction of the Z-axis is taken as the bottom.

[0032] A metal ground plane 60, a first dielectric substrate 50, a second dielectric substrate 40, and at least two antenna elements 20 are arranged sequentially from bottom to top. There is at least one first dielectric substrate 50. When there are at least two first dielectric substrates 50, multiple first dielectric substrates 50 are stacked and fixed below the second dielectric substrate 40 with screws. Both the first dielectric substrate 50 and the second dielectric substrate 40 are made of Rogers 4003C, with a dielectric constant of 3.55 and a loss tangent of 0.0027. In this invention, the first dielectric substrate 50 has a length of 73mm, a width of 55mm, and a thickness of 2mm. The second dielectric substrate 40 has a length of 73mm, a width of 55mm, and a thickness of 1.52mm. In this embodiment, there are four first dielectric substrates 50, and the total height of the four first dielectric substrates 50 and the second dielectric substrate 40 stacked tightly is 9.52mm.

[0033] See Figure 2 The frequency selective surface 10 is an inwardly bent open resonant ring located between adjacent antenna elements 20. There is at least one frequency selective surface 10; in this embodiment, there are three frequency selective surfaces 10. The three frequency selective surfaces 10 are arranged along the direction of the longitudinal slot 24 and are evenly spaced. See also Figure 3The first end 11 and the second end 12 of the split-ring resonator form a rectangle, with the opening located between the first end 11 and the second end 12. The long and wide sides of the rectangle are each bent inwards at least once. By adjusting the length of the inward bends, the operating frequency of the split-ring resonator can be adjusted, thus reducing its operating frequency. In this embodiment, the long and wide sides of each rectangle are bent inwards four times, with two bends forming a group. The distance between two bends is greater than the distance between two bends within the same group.

[0034] The frequency selective surface of this invention resonates within the antenna's operating frequency range, confining the electromagnetic waves at that frequency within the FSS, thereby suppressing the coupling of electromagnetic waves to another antenna element. By adjusting the length of the inward bend, the operating frequency range can be effectively tuned, thus reducing coupling between broadband MIMO antennas.

[0035] The frequency selective surface 10 of the present invention is placed between antenna elements 20. The frequency selective surface is simulated using the periodic boundary of CST software. Due to the influence of antenna elements 20, by adjusting some dimensions of the frequency selective surface, when the dimensions of the frequency selective surface 10 meet the following conditions: the length FSS_L1 of the enclosed rectangle is 14.5 mm, the width FSS_W1 is 9 mm, the long side of the enclosed rectangle is bent inward to form a long side bend 13, the length FSS_W2 of the long side bend 13 is 3.46 mm, the wide side of the enclosed rectangle is bent inward to form a wide side bend 14, the length FSS_L2 of the wide side bend 14 is 2.42 mm, the frequency selective surface exhibits band-stop characteristics in the operating frequency band range of 3.5 GHz-4.5 GHz. The frequency selective surface can effectively reduce the coupling coefficient between antenna elements, thereby reducing the coupling coefficient between adjacent antenna elements in the MIMO antenna to below 22 dB, thus effectively blocking the propagation of electromagnetic waves, and finally achieving a decoupling effect in this frequency band.

[0036] Antenna element 20 includes four centrally symmetrical quarter-circular patches 21. Each quarter-circular patch 21 extends outward with a rectangular patch 22 and is grounded via a first metal post 26. The four quarter-circular patches 21 are separated to form a transverse slot 23 and a longitudinal slot 24. Multiple first metal posts 26 are evenly distributed along the transverse slot 23 and longitudinal slot 24, close to the center of each quarter-circular patch 21. One end of each first metal post 26 is connected to a quarter-circular patch 21, and the other end is connected to a metal ground plate 60. The first metal posts 26 are used to connect the patch on the upper surface to the ground plate below, realizing the current loop of the magnetic dipole. The rectangular patch 22 is located at the radial end of each quarter-circular patch 21. The long side of the rectangular patch 22 is parallel to the transverse slot 23, and the wide side is parallel to the longitudinal slot 24. By placing the rectangular patch 22 at the top of each quarter-circular patch 21, the rectangular patch can extend the current path of the antenna, thereby reducing the operating frequency of the antenna.

[0037] A slot 25 is formed on the side of the quarter-circular patch 21 facing the transverse slot 23. The long side of the slot 25 is parallel to the longitudinal slot 24, and the wide side of the slot 25 is parallel to the transverse slot 23. A notch 251 is formed on the wide side of the slot near the center of the quarter-circular patch 21. By forming a slot inside the quarter-circular patch 21, the current flow path can be extended, further reducing the operating frequency of the antenna, thereby effectively reducing the overall size of the antenna.

[0038] See also Figure 2 The radius R1 of the quarter-circle patch 21 is 11 mm, the sum of the radius of the quarter-circle patch 21 and the width of the rectangular patch 22, L1, is 12.57 mm, the length L2 of the slot 25 is 5.16 mm, and the length L3 of the feed strip 30 is 13.5 mm. The distance L4 of the transverse gap 23 is 3.18 mm, and the sum W1 of the distance of the longitudinal gap 24 and the lengths of the two rectangular patches 22 is 7.36 mm.

[0039] The feed strip 30 is located on the upper surface of the second dielectric substrate 40 and in the longitudinal slot 24. The feed strip 30 is grounded through the second metal post 31. One end of the second metal post 31 is connected to the end of the feed strip 30, and the other end of the second metal post 31 is connected to the metal ground plane 60. The feed strip 30 and the second metal post 31 together form an L-shaped feed structure.

[0040] Electromagnetic waves are fed in from the second metal pillar 31, transmitted through the feeding strip 30, and simultaneously excited by four quarter-circular patches 21 to radiate electromagnetic waves outward, thus realizing the transmission of electromagnetic waves; the four quarter-circular patches 21 simultaneously receive electromagnetic waves, which are transmitted through the feeding strip 30 and output from the second metal pillar 31, thus realizing the reception of electromagnetic waves.

[0041] This invention utilizes a frequency selective surface (FSS) between adjacent antenna elements. The FSS is an inwardly bent open-circuit resonator, which reduces the operating frequency of the open-circuit resonator. Through resonance within the antenna's operating frequency range, the FSS confines the electromagnetic waves at that frequency to the FSS, thereby suppressing coupling of electromagnetic waves to other antenna elements. The FSS exhibits band-stop characteristics in the 3.5GHz-4.5GHz operating frequency range. This effectively reduces the coupling coefficient between antenna elements, achieving a reduction to below 20dB between adjacent antenna elements in a MIMO antenna. This effectively blocks electromagnetic wave propagation, ultimately achieving decoupling in this frequency band.

[0042] By placing a rectangular patch at the top of each quarter-circle patch, the rectangular patch can extend the current path of the antenna, thereby reducing the antenna's operating frequency; by slotting inside the quarter-circle patch, the current flow path can be extended, further reducing the antenna's operating frequency, thus effectively reducing the overall size of the antenna.

[0043] The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface of the present invention was simulated using the electromagnetic simulation software Ansys Electronics Desktop 2021. The simulation results are as follows: Figures 4 to 8 As shown, Figure 4 The S-parameters represent the scattering parameters, including the reflection coefficient and the transmission coefficient. The results show that the antenna exhibits good impedance matching characteristics within the 3.5-4.5 GHz operating range, with a relative bandwidth of 25%, covering the core Sub-6 GHz frequency range of 5G communication such as N77 and N78. Furthermore, the coupling between the two antenna elements is low, both below -20 dB, and the envelope correlation coefficient is below 0.003, demonstrating good diversity benefits. The antenna also exhibits good radiation characteristics within its operating range, with a peak gain of 7.3 dBi within the operating frequency band, and a gain above 6 dBi throughout the entire operating frequency band.

[0044] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface, characterized in that: Includes a frequency selective surface (10), a feed strip (30), and a metal ground plane (60), a first dielectric substrate (50), a second dielectric substrate (40), and at least two antenna elements (20) arranged from bottom to top. The frequency selective surface (10) is an inwardly bent open resonant ring located between adjacent antenna elements (20). The first end (11) and the second end (12) of the open resonant ring form a rectangle, and the opening is located between the first end (11) and the second end (12) of the open resonant ring. The long side and the wide side of the rectangle formed are bent inward at least once. The antenna unit (20) includes four quarter-circle patches (21) that are centrally symmetrical. Each quarter-circle patch (21) extends outward with a rectangular patch (22) and is grounded through a first metal post (26). The four quarter-circle patches (21) are separated to form a transverse slot (23) and a longitudinal slot (24). The quarter-circle patches (21) have slots (25) on their sides facing the transverse slots (23). The feed strip (30) is located on the upper surface of the second dielectric substrate (40) and in the longitudinal slot (24). The feed strip (30) is grounded through a second metal post (31).

2. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface according to claim 1, characterized in that: Electromagnetic waves are fed in from the second metal pillar (31), transmitted through the feeding strip (30), and simultaneously excited by the four quarter-circle patches (21) to radiate electromagnetic waves outward, thus realizing the transmission of electromagnetic waves; the four quarter-circle patches (21) simultaneously receive electromagnetic waves, which are transmitted through the feeding strip (30) and output from the second metal pillar (31), thus realizing the reception of electromagnetic waves.

3. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface according to claim 1, characterized in that: Multiple frequency selection surfaces (10) are arranged along the direction of the longitudinal slit (24) and are evenly spaced.

4. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface according to claim 1, characterized in that: The operating frequency band of the split-ring resonator can be adjusted by changing the length of the inward bend.

5. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface according to claim 1, characterized in that: A rectangular patch (22) is located at the radial end of each quarter-circle patch (21), with the long side of the rectangular patch (22) parallel to the transverse gap (23) and the wide side of the rectangular patch (22) parallel to the longitudinal gap (24).

6. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface according to claim 1, characterized in that: The long side of the groove (25) is parallel to the longitudinal gap (24), the wide side of the groove (25) is parallel to the transverse gap (23), and the wide side of the groove near the center of the quarter circle patch (21) has a notch (251).

7. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface according to claim 1, characterized in that: Multiple first metal pillars (26) are evenly distributed along the transverse gap (23) and the longitudinal gap (24) and are close to the center of the quarter-circle patch (21). One end of the first metal pillar (26) is connected to the quarter-circle patch (21), and the other end of the first metal pillar (26) is connected to the metal floor (60).

8. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface according to claim 1, characterized in that: One end of the second metal post (31) is connected to the end of the feed strip (30), and the other end of the second metal post (31) is connected to the metal floor (60).

9. The high-isolation broadband MIMO magnetoelectric dipole antenna based on a frequency-selective surface according to claim 1, characterized in that: There is at least one first dielectric substrate (50), and multiple first dielectric substrates (50) are stacked and fixed to the second dielectric substrate (40) by screws. The first dielectric substrate (50) and the second dielectric substrate (40) are both made of Rogers 4003C, with a dielectric constant of 3.55 and a loss tangent of 0.0027.

Images