A millimeter wave broadband MIMO antenna for 5G mobile communications

Abstract

The present invention relates to a millimeter wave broadband MIMO antenna applied to 5G mobile communication, comprising a dielectric substrate and metal patches printed on the upper and lower surfaces of the dielectric substrate, the metal patches printed on the upper surface of the dielectric substrate comprising four millimeter wave antenna units and a decoupling structure, the metal patches printed on the lower surface of the dielectric substrate are metal ground planes, the four millimeter wave antenna units are the main parts of the MIMO antenna, and are respectively arranged around the dielectric substrate, each millimeter wave antenna unit comprises a main radiation patch, a coplanar waveguide microstrip feeder, a metal structure with a circular groove, and two vertical rectangular gaps and one horizontal rectangular gap on the metal ground plane, and the decoupling structure comprises four planar compact electromagnetic band gap structures arranged between adjacent millimeter wave antenna units and an "X"-shaped metal patch arranged in the middle of the dielectric substrate. The antenna not only has wide bandwidth, high gain and good directional radiation characteristics, but also has a compact structure and maintains high isolation.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to a millimeter wave broadband MIMO antenna applied to 5G mobile communications. Background Art

[0002] The 5G mobile communication era makes the Internet of Everything possible. It is an era of high-speed networks that can carry massive terminal access rates and transmit at ultra-high data rates. However, at this stage, all communication systems use low-frequency bands, and the spectrum resources of the golden communication band below 6GHz are obviously very crowded, which will undoubtedly cause a shortage of bandwidth in the low-frequency band, limiting the demand for future wireless high-speed communications, which is very unfavorable for the further development of the communication system towards the goals people envision.

[0003] However, the millimeter wave band has not been fully developed and utilized. The millimeter wave band has very rich spectrum resources and outstanding advantages such as high bandwidth and low latency. These advantages can fully unleash the full potential of 5G, thereby achieving a revolutionary improvement in consumer service experience and digital transformation of thousands of industries, and truly realizing the vision of 5G to change life and society. Therefore, in order to smoothly enter the 5G era, it is urgent to develop millimeter wave technology.

[0004] In 5G mobile communications, the expected antenna geometry should be compact to facilitate becoming part of mobile terminal devices. Designing antenna units with compact size is a challenge and a promising technology. In addition, MIMO antenna design requires the characteristics of narrow spacing between antenna units, and there should be low mutual coupling and high isolation between antenna units to reduce the impact between adjacent antenna units and improve the performance of the entire antenna.

[0005] With the further development and evolution of 5G mobile communication technology, wide bandwidth and high gain are increasingly required by current communication systems. How to make MIMO antennas maintain low mutual coupling and high isolation in a compact structure while achieving the wide bandwidth, high gain and directional radiation characteristics of MIMO antennas has become the goal and difficulty of current research.

[0006] In recent years, many researchers have designed millimeter-wave MIMO antennas. Although some antennas can achieve wideband, high gain, high isolation and directional radiation characteristics, they cannot maintain the compactness of the structure and cannot meet the requirements of modern wireless communications for terminal equipment; some antennas are small in size, but cannot simultaneously meet the characteristics of wideband, high gain, high isolation and directional radiation, and cannot be well applied to some current mobile terminal devices. Summary of the invention

[0007] The object of the present invention is to provide a millimeter wave broadband MIMO antenna for 5G mobile communications, which not only has a wide bandwidth, high gain and good directional radiation characteristics, but also has a compact structure and maintains high isolation.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a millimeter wave broadband MIMO antenna applied to 5G mobile communications, comprising a dielectric substrate and metal patches printed on the upper and lower surfaces of the dielectric substrate, the metal patches printed on the upper surface of the dielectric substrate comprising four millimeter wave antenna units and a decoupling structure, the metal patches printed on the lower surface of the dielectric substrate are metal ground planes, the four millimeter wave antenna units are the main parts of the MIMO antenna, and are respectively arranged around the dielectric substrate, each millimeter wave antenna unit comprises a main radiation patch, a coplanar waveguide microstrip feeder, a metal structure with a circular groove, and two vertical rectangular gaps and one horizontal rectangular gap on the metal ground plane, the decoupling structure comprises four planar compact electromagnetic band gap structures arranged between adjacent millimeter wave antenna units and an "X"-shaped metal patch arranged in the middle of the dielectric substrate.

[0009] Furthermore, the dielectric substrate is made of a high-frequency plate material with a thickness of 1.575 mm.

[0010] Furthermore, the upper part of the main radiation patch is a semicircular structure for increasing the current path, thereby reducing the size of the antenna; the lower part of the main radiation patch is a conical gradient structure for making a smooth transition of the current at the feeding point to improve the impedance matching of the antenna; the coplanar waveguide microstrip feed line is connected to the lower part of the main radiation patch, and the coplanar waveguide microstrip feed line is a stepped structure to further improve the impedance matching.

[0011] Furthermore, the coplanar waveguide microstrip feed line is connected to the inner core of a 2.92 mm RF connector, and four metal pins of the 2.92 mm RF connector are connected to a metal structure with a circular groove and a metal ground plane.

[0012] Furthermore, the metal structure with the circular groove participates in the radiation of the antenna, generating a new resonance point, thereby expanding the frequency band of the antenna; the metal structure with the circular groove has a rectangular opening at the left and right ends of its upper part, and a rectangular opening connected to the circular groove in the middle of the upper part and the middle of the lower part; the three rectangular openings on the upper part of the metal structure with the circular groove are used to improve the directional radiation characteristics of the millimeter wave antenna unit.

[0013] Furthermore, the four planar compact electromagnetic bandgap structures are mainly used to improve the isolation between adjacent millimeter-wave antenna units. Each planar compact electromagnetic bandgap structure is a rectangular metal patch on which four planar electromagnetic bandgap units are arranged along the length direction. Each planar electromagnetic bandgap unit includes a "cross"-shaped gap and four "L"-shaped gaps arranged around it; the "X"-shaped metal patch is mainly used to improve the isolation between diagonally opposite millimeter-wave antenna units.

[0014] Furthermore, the metal ground plane includes eight vertical rectangular gaps, four horizontal rectangular gaps and sixteen diamond gaps.

[0015] Furthermore, two vertical rectangular slots and one horizontal rectangular slot corresponding to the same millimeter wave antenna unit on the metal ground plane together constitute a defective ground structure, which is used to increase the bandwidth of the millimeter wave antenna unit and further improve the directional radiation characteristics of the millimeter wave antenna unit.

[0016] Furthermore, the diamond-shaped gap is used to further improve the isolation between millimeter-wave antenna units.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the upper part of the main radiation patch is a semicircular structure for increasing the current path, thereby reducing the size of the antenna, and the metal structure with circular grooves participates in the antenna radiation together, generating a new resonance point, thereby expanding the frequency band of the antenna, so that the antenna covers the 5G N258 (24.25-27.5GHz) millimeter wave frequency band; the three rectangular openings on the upper part of the metal structure with circular grooves in the millimeter wave antenna unit and the two vertical rectangular slots and one horizontal rectangular slot on the metal ground plane jointly improve the directional radiation characteristics of the millimeter wave antenna unit; four planar compact electromagnetic band gap structures, an "X"-shaped metal patch and sixteen diamond-shaped slots are set in the millimeter wave MIMO antenna to reduce the mutual coupling between the millimeter wave antenna units, so as to reduce the influence between adjacent antenna units and improve the performance of the entire antenna. The millimeter wave MIMO antenna has a compact structure, wide bandwidth, high gain, high isolation and good directional radiation characteristics, and is suitable for use in future 5G mobile communication terminal equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A top view of an embodiment of the present invention;

[0019] Figure 2 A bottom view of an embodiment of the present invention;

[0020] Figure 3 A side view of an embodiment of the present invention;

[0021] Figure 4 is the reflection coefficient in the embodiment of the present invention |S11 |Simulation result diagram;

[0022] Figure 5 is the reflection coefficient in the embodiment of the present invention |S 21 |Simulation result diagram;

[0023] Figure 6 is the reflection coefficient in the embodiment of the present invention |S 31 |Simulation result diagram;

[0024] Figure 7 is the reflection coefficient in the embodiment of the present invention |S 41 |Simulation result diagram;

[0025] Figure 8 : The simulated radiation patterns of the embodiment of the present invention at Phi=0° and Phi=90° at 24.46GHz;

[0026] Fig. 9 : The simulated radiation patterns of the embodiment of the present invention at Phi=0° and Phi=90° at 27.75GHz;

[0027] Fig.10 FIG. 4 is a peak gain diagram of an embodiment of the present invention within a frequency range.

[0028] In the figure: 1- coplanar waveguide microstrip feed line; 2- main radiation patch; 3- metal structure with circular groove; 4- planar compact electromagnetic bandgap structure; 5- "X" type metal patch; 6- vertical rectangular gap; 7- horizontal rectangular gap; 8- diamond gap; 9- metal ground plane. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] like Figure 1-3As shown, this embodiment provides a millimeter wave broadband MIMO antenna for 5G mobile communications, including a dielectric substrate and metal patches printed on the upper and lower surfaces of the dielectric substrate, the metal patch printed on the upper surface of the dielectric substrate includes four millimeter wave antenna units and a decoupling structure, the metal patch printed on the lower surface of the dielectric substrate is a metal ground plane 9, including eight vertical rectangular slots 6, four horizontal rectangular slots 7 and sixteen diamond slots 8, the four millimeter wave antenna units are the main parts of the MIMO antenna, and are respectively arranged around the dielectric substrate, each millimeter wave antenna unit includes a main radiation patch 2, a coplanar waveguide microstrip feed line 1, a metal structure 3 with a circular groove, and two vertical rectangular slots 6 and a horizontal rectangular slot 7 on the metal ground plane 9, the decoupling structure includes four planar compact electromagnetic band gap structures 4 arranged between adjacent millimeter wave antenna units and an "X"-shaped metal patch 5 arranged in the middle of the dielectric substrate.

[0033] In this embodiment, the dielectric substrate is made of a high-frequency plate material with a size of 32 mm*32 mm*1.575 mm, a dielectric constant of 2.2, and a dielectric loss tangent of 0.0009.

[0034] In this embodiment, the upper part of the main radiation patch 2 is a semicircular structure, which is used to increase the current path, thereby reducing the size of the antenna. The lower part of the main radiation patch 2 is a conical gradient structure, which makes the current at the feeding point transition smoothly to improve the impedance matching of the antenna. The coplanar waveguide microstrip feed line 1 is connected to the lower part of the main radiation patch 2, and its total length is 3.6 mm. It is designed into a stepped structure to further improve the impedance matching.

[0035] In this embodiment, the coplanar waveguide microstrip feed line 1 is connected to the inner core of a 2.92 mm RF connector, and four metal pins of the 2.92 mm RF connector are connected to a metal structure 3 with a circular groove and a metal ground plane 9 .

[0036] In this embodiment, the metal structure 3 with circular grooves of the millimeter wave antenna unit jointly participates in the radiation of the antenna to generate a new resonance point, thereby expanding the frequency band of the antenna; the metal structure 3 with circular grooves has a rectangular opening at the left and right ends of its upper part, and a rectangular opening connected to the circular groove in the middle of the upper part and the middle of the lower part; the three rectangular openings on the upper part of the metal structure 3 with circular grooves can effectively suppress irregular currents and prevent the generation of unbalanced transverse currents, thereby improving the directional radiation characteristics of the millimeter wave antenna unit.

[0037] In this embodiment, the four planar compact electromagnetic bandgap structures 4 in the decoupling structure can form a high-impedance surface structure, which can gradually weaken the surface wave current conducted therein, thereby improving the isolation between adjacent millimeter-wave antenna units. Each planar compact electromagnetic bandgap structure 4 is a rectangular metal patch on which four planar electromagnetic bandgap units are arranged along the length direction, and each planar electromagnetic bandgap unit includes a "cross" shaped gap and four "L" shaped gaps arranged around it; the "X" shaped metal patch 5 in the decoupling structure is mainly used to improve the isolation between diagonally opposite millimeter-wave antenna units.

[0038] In this embodiment, two vertical rectangular slots 6 and one horizontal rectangular slot 7 corresponding to the same millimeter wave antenna unit on the metal ground plane 9 together constitute a defective ground structure, which is used to change the distribution of current, thereby increasing the bandwidth of the millimeter wave antenna unit and further improving the directional radiation characteristics of the millimeter wave antenna unit.

[0039] In this embodiment, the diamond-shaped slot 8 has a blocking effect on the floor current, and the current can be radiated more through the slot, thereby further improving the isolation between the millimeter wave antenna units. The slot is designed to be diamond-shaped, and its gradual structure can radiate the floor current conducted to itself into space within a wider bandwidth.

[0040] The simulation results based on the above structure are as follows Figure 4-10 As shown. Figure 4 As shown in Figure 2, the bandwidth of the millimeter wave MIMO antenna is 23.30-30.83 GHz, and the relative bandwidth reaches 27.82%. Figure 5 As shown, the S 21 Less than -27.70dB in the frequency range, the minimum is -52.94dB; Figure 6 As shown, the S 31 Less than -28.68dB in the frequency range, the minimum is -39.69dB; Figure 7 As shown, the S 41 Less than -18.30dB in the frequency range, the minimum is -22.29dB; Figure 8 and Fig. 9 As shown, the millimeter wave MIMO antenna radiates directionally and has good directional radiation characteristics; Fig.10 As shown, the peak gain of the millimeter wave MIMO antenna is greater than 7.73dBi within the frequency range and can reach a maximum of 10.21dBi.

[0041] In the present invention, the upper part of the main radiation patch is a semicircular structure, which is used to increase the current path, thereby reducing the size of the antenna, and the metal structure with circular grooves participates in the antenna radiation together, generating a new resonance point, thereby expanding the frequency band of the antenna, so that the antenna covers the 5G N258 (24.25-27.5GHz) millimeter wave frequency band. The three rectangular openings on the upper part of the metal structure with circular grooves in the millimeter wave antenna unit and the two vertical rectangular gaps and one horizontal rectangular gap on the metal ground plane jointly improve the directional radiation characteristics of the millimeter wave antenna unit. Four planar compact electromagnetic band gap structures, an "X"-shaped metal patch and sixteen diamond-shaped gaps are set in the millimeter wave MIMO antenna to reduce the mutual coupling between the millimeter wave antenna units, so as to reduce the influence between adjacent antenna units and improve the performance of the entire antenna. The millimeter-wave MIMO antenna operates in the frequency band of 23.30-30.83 GHz, with a relative bandwidth of 27.82%. It has a size of 32mm*32mm*1.575mm, and a peak gain of up to 10.21dBi. It has wide bandwidth, miniaturization, high gain, and good directional radiation characteristics. The isolation within the frequency range is greater than 15dB, making it suitable for use in future 5G mobile communication terminal equipment.

[0042] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A millimeter wave broadband MIMO antenna for 5G mobile communications, characterized in that: It includes a dielectric substrate and metal patches printed on the upper and lower surfaces of the dielectric substrate. The metal patches printed on the upper surface of the dielectric substrate include four millimeter wave antenna units and a decoupling structure. The metal patches printed on the lower surface of the dielectric substrate are metal ground planes. The four millimeter wave antenna units are the main parts of the MIMO antenna and are respectively arranged around the dielectric substrate. Each millimeter wave antenna unit includes a main radiation patch, a coplanar waveguide microstrip feeder, a metal structure with a circular groove, and two vertical rectangular gaps and one horizontal rectangular gap on the metal ground plane. The decoupling structure includes four planar compact electromagnetic band gap structures arranged between adjacent millimeter wave antenna units and an "X"-shaped metal patch arranged in the middle of the dielectric substrate.

2. A millimeter wave broadband MIMO antenna for 5G mobile communications according to claim 1, characterized in that: The upper part of the main radiation patch is a semicircular structure, which is used to increase the current path, thereby reducing the size of the antenna. The lower part of the main radiation patch is a conical gradient structure, which makes the current at the feeding point transition smoothly to improve the impedance matching of the antenna. The coplanar waveguide microstrip feed line is connected to the lower part of the main radiation patch, and the coplanar waveguide microstrip feed line is a stepped structure to further improve the impedance matching.

3. The millimeter wave broadband MIMO antenna for 5G mobile communications according to claim 1, characterized in that: The coplanar waveguide microstrip feed line is connected to the inner core of a 2.92 mm radio frequency connector, and four metal pins of the 2.92 mm radio frequency connector are connected to a metal structure with a circular groove and a metal grounding surface.

4. The millimeter wave broadband MIMO antenna for 5G mobile communications according to claim 1, characterized in that: The metal structure with circular grooves participates in the radiation of the antenna, generates a new resonance point, and thus expands the frequency band of the antenna; the metal structure with circular grooves has a rectangular opening at the left and right ends of its upper part, and a rectangular opening connected to the circular groove in the middle of the upper part and the middle of the lower part; the three rectangular openings on the upper part of the metal structure with circular grooves are used to improve the directional radiation characteristics of the millimeter wave antenna unit.

5. The millimeter wave broadband MIMO antenna for 5G mobile communications according to claim 1, characterized in that: The four planar compact electromagnetic bandgap structures are mainly used to improve the isolation between adjacent millimeter-wave antenna units. Each planar compact electromagnetic bandgap structure is a rectangular metal patch on which four planar electromagnetic bandgap units are arranged along the length direction. Each planar electromagnetic bandgap unit includes a "cross"-shaped gap and four "L"-shaped gaps arranged around it; the "X"-shaped metal patch is mainly used to improve the isolation between diagonally opposite millimeter-wave antenna units.

6. The millimeter wave broadband MIMO antenna for 5G mobile communications according to claim 1, characterized in that: The metal ground plane includes eight vertical rectangular slots, four horizontal rectangular slots and sixteen diamond slots.

7. The millimeter wave broadband MIMO antenna for 5G mobile communications according to claim 6, characterized in that: Two vertical rectangular slots and one horizontal rectangular slot corresponding to the same millimeter wave antenna unit on the metal ground plane together constitute a defective ground structure, which is used to increase the bandwidth of the millimeter wave antenna unit and further improve the directional radiation characteristics of the millimeter wave antenna unit.

8. The millimeter wave broadband MIMO antenna for 5G mobile communications according to claim 6, characterized in that: The diamond-shaped gap is used to further improve the isolation between millimeter wave antenna units.

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