5G high-isolation MIMO mobile phone antenna

Abstract

The invention discloses a 5G high-isolation MIMO mobile phone antenna for fifth generation mobile communication, and belongs to the technical field of mobile communication. The MIMO mobile phone antenna comprises eight annular slot antenna units which have the same structure and are symmetrically distributed on two sides; the annular slot antenna unit comprises a dielectric substrate, a radiation microstrip line, a hexagonal parasitic slotted structure, a grounding plate and a coaxial connector. According to the MIMO antenna, the decoupling structure design is introduced, so that the isolation degree is improved under the condition that the size of the antenna is not obviously increased; an optimized antenna unit structure and overall layout are adopted, so that extra loss caused by complex circuit design is effectively reduced; the 5G mobile communication frequency band is covered, and excellent signal independence performance is ensured; the antenna is compact in structure and small in overall size, the compact layout requirement of ultra-thin equipment is well met, space occupation and key frequency band performance are remarkably improved, and an ideal solution is provided for high-density integration of a 5G terminal.

Description

Technical Field

[0001] The present invention belongs to the technical field of mobile communications, and particularly relates to a 5G high-isolation multiple-input multiple-output (MIMO) mobile phone antenna. Background Art

[0002] With the full commercialization of 5G technology, multiple-input multiple-output (MIMO) antennas have become a core technology for modern communication terminals due to their characteristic of significantly improving channel capacity and data rate through spatial diversity. However, as terminal devices continue to develop towards being thinner, lighter, and more multifunctional, the antenna design space has been drastically compressed. Antenna units arranged in high density will cause a strong mutual coupling effect, resulting in a decrease in isolation, a reduction in radiation efficiency, and deterioration of the envelope correlation coefficient (ECC), seriously restricting the actual performance of MIMO systems.

[0003] The prior art "Design of a 5G High-Isolation 4-Element MIMO Mobile Phone Antenna" discloses a MIMO antenna with a working frequency band of 3.45 - 3.64 GHz. The four units of this antenna are respectively placed at the four corners of a dielectric substrate with a thickness of 1.5 mm, and a parasitic circular slotted structure is introduced to reduce the coupling between units. The isolation of the designed MIMO mobile phone antenna is higher than 18 dB, but its diversity performance still needs to be improved.

[0004] The prior art "An 8-Element MIMO Mobile Phone Antenna with T-Type Ground Slot Decoupling for 5G" discloses a MIMO mobile phone antenna with an overall size of 150 mm × 75 mm × 7 mm and operating in the Sub-6G frequency band (5G NR N78). This antenna uses an inverted L-shaped stub to feed and couple to an F-shaped radiation stub, and by making the resonant frequencies of the two branched stubs of the F-shaped radiation stub close to each other, the working bandwidth is broadened. In addition, a ground slot structure is used to achieve high isolation of the antenna. The designed MIMO mobile phone antenna achieves an isolation higher than 16.8 dB in the range of 3.3 - 3.8 GHz, but its radiation gain is low, and the isolation performance and diversity performance can be further optimized.

[0005] In summary, although the prior art has partially alleviated the mutual coupling effect between units through technical means such as parasitic unit loading and defected ground structure, there are still technical problems such as poor diversity performance and low radiation gain. Therefore, there is an urgent need for a MIMO antenna design scheme with a compact structure, excellent radiation performance, and high isolation to meet the requirements of 5G terminal devices. Summary of the Invention

[0006] The object of the present invention is to overcome the defects of the above prior art and provide a 5G high-isolation MIMO mobile phone antenna.

[0007] The technical problems proposed by the present invention are solved as follows:

[0008] A 5G high isolation MIMO mobile phone antenna includes eight circular slot antenna units with the same structure; the eight circular slot antenna units are symmetrically distributed on both sides, and adjacent circular slot antenna units are closely arranged;

[0009] The circular slot antenna unit includes a dielectric substrate, a radiation microstrip line, a hexagonal parasitic slot structure, a ground plane, and a coaxial connector; the radiation microstrip line and the hexagonal parasitic slot structure are located on the upper surface of the dielectric substrate, and the ground plane is located on the lower surface of the dielectric substrate; the radiation microstrip line extends inward from the edge of the dielectric substrate and is perpendicular to the edge of the dielectric substrate; the hexagonal parasitic slot structure is located on the axis where the radiation microstrip line is located, and a set of opposite sides is parallel to the edge of the dielectric substrate; the ground plane is provided with a circular slot, and the center of the circular slot is located on the axis where the radiation microstrip line is located; the outer conductor of the coaxial connector is connected to the ground plane, and the inner core is connected to the radiation microstrip line;

[0010] For the entire ground plane formed by connecting the ground planes of the eight circular slot antenna units, between adjacent circular slot antenna units on the same side, a T-shaped slot is opened on the ground plane; a fence-shaped slot is opened at the horizontal axis of the entire ground plane.

[0011] Further, the hexagonal parasitic slot structure is provided with two groups of symmetrically distributed slots; the first group of slots extends from the corner of the hexagon towards the center and is perpendicular to the radiation microstrip line; the second group of slots extends from the middle position of the side not adjacent to the first group of slots towards the center.

[0012] Further, the long branch of the T-shaped slot is parallel to the radiation microstrip line, and the short branch is perpendicular to the radiation microstrip line.

[0013] Further, the end of the radiation microstrip line and the hexagonal parasitic slot structure are located directly above the internal space of the circular slot.

[0014] Further, the fence-shaped slot is symmetric about the vertical axis of the entire ground plane, and several fences are unevenly distributed.

[0015] The beneficial effects of the present invention are:

[0016] The MIMO antenna of the present invention, through the introduction of a decoupling structure design, can increase the isolation to more than 20 dB without significantly increasing the antenna size; at the same time, the present invention adopts an optimized antenna unit structure and overall layout, effectively reducing the additional loss caused by complex circuit design;

[0017] The MIMO antenna of the present invention covers the N77 and N78 frequency bands of 5G mobile communication, with an ECC value less than 0.001, far lower than the 0.45 required for 5G communication, ensuring excellent signal independence performance; the overall size is 150mm×75mm, and the thickness is only 0.8mm, which can well meet the compact layout requirements of ultra-thin devices; compared with the prior art, the present invention has achieved significant improvements in terms of space occupation and key frequency band performance, providing an ideal solution for the high-density integration of 5G terminals. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a three-dimensional overall structure schematic diagram of the MIMO mobile phone antenna of the present invention;

[0019] Figure 2 is a schematic diagram of the upper surface structure of the MIMO mobile phone antenna of the present invention;

[0020] Figure 3 is a schematic diagram of the lower surface structure of the MIMO mobile phone antenna of the present invention;

[0021] Figure 4 is a schematic diagram of the hexagonal parasitic slot structure in the MIMO mobile phone antenna of the present invention;

[0022] Figure 5 is an S-parameter curve graph of the MIMO mobile phone antenna in the embodiment;

[0023] Figure 6 is a low envelope correlation coefficient curve graph of the antenna unit in the MIMO mobile phone antenna in the embodiment;

[0024] Figure 7 is the E-plane radiation pattern of the antenna unit in the MIMO mobile phone antenna in the embodiment;

[0025] Figure 8 is the H-plane radiation pattern of the antenna unit in the MIMO mobile phone antenna in the embodiment;

[0026] Figure 9 is the gain curve graph of the antenna unit in the MIMO mobile phone antenna in the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention will be further described below in conjunction with the drawings and embodiments.

[0028] This embodiment provides a 5G high-isolation MIMO mobile phone antenna, and its three-dimensional overall structure schematic diagram is as Figure 1 shown, and the schematic diagram of the upper surface structure is as Figure 2 shown, and the schematic diagram of the lower surface structure is as Figure 3As shown, it includes eight circular slot antenna units with the same structure; the eight circular slot antenna units are symmetrically distributed on both sides, and adjacent circular slot antenna units are closely arranged;

[0029] The circular slot antenna unit includes a dielectric substrate 1, a radiating microstrip line 2, a hexagonal parasitic slot structure 3, a ground plane 4, and a coaxial connector; the radiating microstrip line 2 and the hexagonal parasitic slot structure 3 are located on the upper surface of the dielectric substrate 1, and the ground plane 4 is located on the lower surface of the dielectric substrate 1; the radiating microstrip line 2 extends inward from the edge of the dielectric substrate 1 and is perpendicular to the edge of the dielectric substrate 1; the hexagonal parasitic slot structure 3 is located on the axis where the radiating microstrip line 2 is located, and a set of opposite sides is parallel to the edge of the dielectric substrate 1, and two sets of symmetrically distributed slots are opened; as Figure 4 shown, the first set of slots extends from the corner of the hexagon towards the center and is perpendicular to the radiating microstrip line 2; the second set of slots extends from the middle position of the side not adjacent to the first set of slots towards the center; the ground plane 4 is provided with a circular slot 5, and the center of the circular slot 5 is located on the axis where the radiating microstrip line 2 is located, so that the end of the radiating microstrip line 2 and the hexagonal parasitic slot structure 3 are located directly above the internal space of the circular slot 5; the outer conductor of the coaxial connector is connected to the ground plane 4, and the inner core is connected to the radiating microstrip line 2.

[0030] For the entire ground plane formed by connecting the ground planes 4 of the eight circular slot antenna units, between adjacent circular slot antenna units on the same side, a T-shaped slot 6 is opened on the ground plane 4, the long branch is parallel to the radiating microstrip line 2, and the short branch is perpendicular to the radiating microstrip line 2; a fence-shaped slot 7 is opened at the horizontal axis of the entire ground plane, and several fences on the fence-shaped slot 7 are not completely evenly distributed and are symmetric about the vertical axis.

[0031] The circular slot antenna unit feeds the radiating microstrip line through a coaxial connector; the radiating microstrip line serves as the main radiation structure and effectively radiates the fed RF signal. Due to the electromagnetic coupling effect, the current on the radiating microstrip line will generate an induced current at the edge of the circular slot. Specifically, the high-frequency current on the radiating microstrip line generates an alternating electromagnetic field around it, and this electromagnetic field will strongly couple with the circular slot below. The current coupled to the circular slot flows along the edge of the slot, forming a circular current path. Since the shape of the slot is circular, the flowing direction of the current at the edge of the slot is tangential. This tangential current distribution enables the circular slot antenna unit to have an omnidirectional radiation characteristic, that is, the radiation intensity is relatively uniform on the plane where the circular slot antenna unit is located.

[0032] During the radiation process of the radiating microstrip line, the signal encounters a hexagonal parasitic slot structure. The main function of the hexagonal parasitic slot structure is to reduce the coupling degree between the radiating microstrip line and the integrated components. When the signal passes through the radiating microstrip line, the hexagonal parasitic slot structure guides the current to flow around it. Compared with the antenna without this structure, after introducing the hexagonal parasitic slot structure, the current density in the area near the feeding port decreases significantly. This design method not only reduces the coupling between the radiating microstrip line and the components, but also inhibits the current density coupling between the radiating microstrip lines of adjacent circular ring slot antenna elements, improving the isolation of the antenna.

[0033] Between the adjacent circular ring slot antenna elements on the same side, a T-shaped slot is introduced. By cutting the T-shaped slot on the ground plane, the current distribution on the ground plane is changed. If the T-shaped slot is not loaded, when a certain circular ring slot antenna element is excited, obvious coupled current will be induced on the adjacent circular ring slot antenna element, that is, there is a strong mutual coupling phenomenon between the adjacent circular ring slot antenna elements on the same side. After loading the T-shaped slot, when a certain circular ring slot antenna element is excited, the surface current of the ground plane is confined to the periphery of the T-shaped slot, and the coupled current on the adjacent circular ring slot antenna elements on the same side is significantly reduced. This shows that the T-shaped slot significantly reduces the mutual coupling between the adjacent circular ring slot antenna elements on the same side and improves the isolation. Between the circular ring slot antenna elements distributed on both sides, a fence-shaped slot is further introduced. The design method of the fence-shaped slot can be regarded as superimposing multiple T-shaped slots on the ground plane, further optimizing the current distribution and enhancing the decoupling effect.

[0034] In this embodiment, the length of the radiating microstrip line 2 in the circular ring slot antenna element is 8 mm and the width is 3 mm; the outer radius of the circular ring slot is 9.4 mm, the inner radius is 7.6 mm, and the distance between the center of the circle and the edge of the dielectric substrate 1 is 12.7 mm; the distance between the center of the hexagonal parasitic slot structure 3 and the edge of the dielectric substrate 1 is 13.5 mm, the side length of each side is 3 mm, the length of the first group of slots is 0.5 mm and the width is 0.2 mm, the length of the second group of slots is 0.2 mm and the width is 1.6 mm; the length of the short branch of the T-shaped slot 6 is 9.7 mm and the width is 1 mm, the length of the long branch is 0.4 mm and the width is 4 mm; the total width of the fence-shaped slot 7 is 150 mm, the length is 1 mm, the length of a single fence is 4 mm and the width is 0.5 mm, the distance between the fence closest to the side and the left edge of the dielectric substrate 1 is 20 mm, the distance between the second closest fence and the third closest fence is 20 mm, and the distance between the third closest fence and the third closest fence is 42 mm. The dielectric substrate 1 is made of FR4 substrate with a thickness of 0.8 mm. The overall size of the MIMO mobile phone antenna in this embodiment is 150 mm × 75 mm, meeting the requirements of the internal space of the mobile phone.

[0035] The antenna described in this embodiment is simulated, and its S-parameter curve is as follows Figure 5 shown. The port numbers of the eight circular-ring slot antenna elements are sequentially 1 to 8, and S11 to S18 respectively represent the transmission coefficients between port 1 to port 8 and port 1. It can be seen from Figure 5 this that the operating frequency band of the antenna described in this embodiment is from 3.25 GHz to 3.86 GHz, covering the test frequency bands N77 and N78 of 5G mobile communication; the isolation is improved to more than 20 dB.

[0036] The low envelope correlation coefficient curve of the circular-ring slot antenna element is as follows Figure 6 shown. It can be seen that the low envelope correlation coefficient ECC value is less than 0.001, meeting the requirements of 5G communication (ECC < 0.45).

[0037] The E-plane pattern, H-plane pattern and gain curve of the circular-ring slot antenna element are respectively as follows Figure 7 , Figure 8 and Figure 9 shown. It can be seen that its radiation pattern is symmetric and stable, and the peak gain reaches 8.4 - 8.9 dBi.

[0038] In summary, the antenna described in this embodiment has a simple structure, a low profile, and a small occupied space, and is suitable for the application of 5G full-screen mobile phones. It effectively solves the problems of large space occupation and insufficient performance in the prior art, and provides an efficient and compact antenna solution for 5G terminal devices. This antenna adopts a symmetric layout, with a circular-ring slot structure designed at the bottom, a radiation microstrip line and a hexagonal parasitic slotted structure configured on the front. In addition, T-shaped slots and fence-shaped slots are respectively introduced between adjacent circular-ring slot antenna elements distributed on the same side and on both sides, so that the isolation of the MIMO antenna is improved to more than 20 dB, and the envelope correlation coefficient ECC is less than 0.001, ensuring excellent signal independence performance. The peak gain of the circular-ring slot antenna reaches 8.4 - 8.9 dBi, and the radiation pattern is basically symmetric, having good radiation characteristics.

Claims

1. A 5G high isolation MIMO mobile phone antenna, characterized in that, It includes eight ring-shaped slot antenna units with the same structure; the eight ring-shaped slot antenna units are symmetrically distributed on both sides, and the adjacent ring-shaped slot antenna units are closely arranged. The ring-shaped slot antenna unit includes a dielectric substrate (1), a radiating microstrip line (2), a hexagonal parasitic slot structure (3), a ground plane (4) and a coaxial connector; the radiating microstrip line (2) and the hexagonal parasitic slot structure (3) are located on the upper surface of the dielectric substrate (1), and the ground plane (4) is located on the lower surface of the dielectric substrate (1); the radiating microstrip line (2) extends from the edge of the dielectric substrate (1) inward and is perpendicular to the edge of the dielectric substrate (1); the hexagonal parasitic slot structure (3) is located on the axis where the radiating microstrip line (2) is located, and a set of opposite sides is parallel to the edge of the dielectric substrate (1); the ground plane (4) is provided with a ring-shaped slot (5), and the center of the ring-shaped slot (5) is located on the axis where the radiating microstrip line (2) is located; the outer conductor of the coaxial connector is connected to the ground plane (4), and the inner core is connected to the radiating microstrip line (2). For the whole ground plane formed by connecting the ground planes (4) of the eight ring-shaped slot antenna units, between the adjacent ring-shaped slot antenna units on the same side, a T-shaped slot (6) is opened on the ground plane (4); a fence-shaped slot (7) is opened at the horizontal axis of the whole ground plane.

2. The 5G high isolation MIMO mobile phone antenna according to claim 1, wherein The hexagonal parasitic slot structure (3) is provided with two groups of symmetrically distributed slots; the first group of slots extends from the corner of the hexagon to the center and is perpendicular to the radiating microstrip line (2); the second group of slots extends from the middle position of the side not adjacent to the first group of slots to the center.

3. The 5G high isolation MIMO mobile phone antenna according to claim 1, characterized in that, The long branch of the T-shaped slot (6) is parallel to the radiating microstrip line (2), and the short branch is perpendicular to the radiating microstrip line (2).

4. The 5G high isolation MIMO mobile phone antenna according to claim 1, characterized in that, The end of the radiating microstrip line (2) and the hexagonal parasitic slot structure (3) are located directly above the internal space of the ring-shaped slot (5).

5. The 5G high isolation MIMO mobile phone antenna according to claim 1, characterized in that, The fence-shaped slot (7) is symmetric about the vertical axis of the whole ground plane, and several fences are unevenly distributed.

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