A 12-Element Wideband Self-Isolated MIMO Antenna for 5G Mobile Terminals

Abstract

The present invention discloses a 12 - element broadband self - isolated MIMO antenna for 5G mobile phone terminals, which includes a substrate, a PIFA antenna pair, a T - shaped monopole antenna and coaxial feeders. The substrate is made of FR - 4 dielectric substrate and includes a large substrate and two small substrates closely arranged on the long - side edges of the large substrate. The PIFA antenna pair is closely arranged on one side of the small substrate and is formed by combining two PIFA units. A "cross" - shaped slot is opened on each PIFA antenna unit to broaden the bandwidth. A T - shaped monopole antenna is introduced into the "cross" - shaped slot and placed orthogonally to the PIFA antenna pair. 12 ports are arranged on the large substrate, and every three ports are in a group, divided into four groups of ports and arranged at the four corners of the large substrate. A slit is opened on the ground between port 1 and port 2 to block the floor - coupled current, and each port is fed by 50Ω coaxial cable.

Description

Technical Field

[0001] The present invention relates to the technical field of antennas, and particularly to a 12-element broadband self-isolated MIMO antenna for 5G mobile phone terminals. Background Art

[0002] With the rapid development of 5G communication technology, multiple-input multiple-output (MIMO) antenna systems have attracted extensive research and attention in recent years. In current mobile phone terminals, the mobile phone antennas have evolved from the original external monopole antennas to internal antennas. People's requirements for the functions and other needs of mobile phones are also getting higher and higher, which leads to the need to arrange a large-capacity battery, multiple cameras, and other electronic components in a narrow mobile phone space. In order to improve the data transmission rate of mobile terminals, the number of MIMO antennas in mobile terminals should be large enough, at least 6 (even more than 8), such as there are 21 antennas arranged inside the Huawei Mate 30 (5G version) mobile phone. Therefore, when arranging so many antennas in such a small space, it is inevitable that the antenna elements will be coupled and affect each other. Such serious coupling will definitely affect the radiation performance of the antenna and make the antenna unable to achieve the expected working effect.

[0003] Although the MIMO antenna system can improve the channel capacity of the system, due to the limited internal space of mobile phone terminals, it is inevitable that there will be serious coupling problems between the antenna elements when arranging so many antennas in such a narrow space. Therefore, how to reduce the mutual coupling between the antenna elements in the MIMO antenna system and design an antenna system with wide bandwidth and good isolation performance on mobile devices with limited space is an urgent problem to be solved at present. Some previous mainstream decoupling technologies, such as adding neutralization lines and decoupling networks; adding electromagnetic bandgap structures for decoupling; adding parasitic resonant units for decoupling, etc. Although they can also achieve high isolation between antenna elements, introducing additional decoupling structures will inevitably reduce the radiation efficiency of the antenna elements, and it should also be avoided in the current compact mobile phone space. The self-decoupling technology is to perform internal decoupling on the MIMO antenna array without introducing lossy external decoupling structures, and without sacrificing other performance indicators of the antenna, achieving a balance between isolation and efficiency. The self-isolated MIMO antenna system proposed by the present invention can achieve broadband self-isolation without introducing additional decoupling structures. Summary of the Invention

[0004] In order to solve the mutual coupling problem existing between the units in the existing MIMO antenna design, the present invention proposes a 12-element broadband self-isolated MIMO antenna for 5G mobile phone terminals, which can keep good isolation performance for each antenna element in a wide frequency band range and good diversity performance of the MIMO antenna without introducing an external decoupling structure.

[0005] The core idea of the present invention is based on the PIFA antenna element and the T-shaped monopole antenna. Two PIFA units are combined to form a PIFA antenna pair, and there is a self-isolation characteristic between the two PIFA units. Furthermore, a slot is opened on the ground plane between port 1 and port 2 to block the coupling current between the ports. The T-shaped monopole antenna is introduced and placed orthogonally to the PIFA antenna pair. It can make each antenna element maintain good isolation performance higher than 10 dB in a wide frequency band range, the envelope correlation coefficients (ECCs) are all less than 0.17, and the radiation efficiency of each antenna element is between 51% and 96%, having good MIMO antenna performance.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A 12-element broadband self-isolation MIMO antenna for 5G mobile phone terminals, characterized by comprising an FR-4 dielectric substrate, a PIFA antenna pair, a T-shaped monopole antenna, a coaxial feeder, and a 50Ω SMA connector;

[0008] The FR-4 dielectric substrate includes a large dielectric substrate and small dielectric substrates I and II closely arranged on the two long edges of the large dielectric substrate;

[0009] The PIFA antenna pair is provided with four, respectively placed at the four corners of the large dielectric substrate and closely arranged on one side of the small substrate;

[0010] The T-shaped monopole antenna is placed orthogonally to the PIFA antenna pair;

[0011] The coaxial feeder is connected to the FR-4 dielectric substrate and is used to feed the microstrip antenna radiation element.

[0012] Further, the size of the large dielectric substrate is 150 mm × 75 mm × 0.8 mm, and the sizes of the small dielectric substrates I and II are 150 mm × 7 mm × 0.8 mm.

[0013] Further, the PIFA antenna pair is composed of two combined PIFA units, there is self-isolation between the two PIFA units, and a "cross" slot is opened on each PIFA unit.

[0014] Further, the "cross" slot includes two mutually perpendicular and through rectangular slot openings, and a T-shaped monopole antenna is arranged therein, and the T-shaped monopole antenna is orthogonally arranged to the PIFA antenna pair.

[0015] Further, the length and width of the horizontally arranged rectangular slot opening in the "cross" slot are 13.5 mm × 1.3 mm, and the width of the vertically arranged rectangular slot opening is 0.4 mm.

[0016] Furthermore, the size of the PIFA antenna pair is 30 mm × 6.2 mm.

[0017] Furthermore, the arm length of the T-shaped monopole antenna is 17 mm and the arm width is 1.75 mm.

[0018] Furthermore, a number of ports are also provided on the large dielectric substrate, and every three ports form a group. Four groups of ports are respectively arranged at the corners of the large dielectric substrate; a slot is opened on the ground plane between the two ports close to the long side of the large dielectric substrate in each group of ports to isolate the ground plane coupling current.

[0019] Furthermore, the number of the ports is 6, 12 or 18.

[0020] Furthermore, all the ports are fed by 50Ω coaxial cables.

[0021] The beneficial effects of the present invention are as follows:

[0022] The present invention provides a 12-element broadband self-isolated MIMO antenna for 5G mobile phone terminals, which has high radiation efficiency, good diversity performance and high isolation degree, can cover the current 5G NR frequency bands N77 / N78 / N79 and the WiFi frequency band (5150 - 5850 MHz), is suitable for being popularized and applied to existing 5G smart phone terminals, and has the following advantages compared with the prior art:

[0023] First, the present invention adopts the monopole antenna and inverted-F antenna which are most widely used in current mobile phone antennas. The structure is simple, can cover a very wide frequency band range, has a high isolation degree between ports, and has good diversity performance;

[0024] Second, in the present invention, the coupling current is guided to the ground plane through the grounding stub between the PIFA antenna pairs to weaken the coupling. The high isolation degree between the antenna elements is realized by using the orthogonal mode to decouple between the T-shaped monopole antenna and the PIFA antenna pairs so that their maximum radiation directions point to different regions, that is, the radiation patterns of the antenna elements do not overlap. Therefore, no additional decoupling elements need to be introduced between the antenna elements;

[0025] Third, the present invention adopts the structure of printed antennas, which are all printed on the dielectric substrate. The structure is simple and compact, the processing is convenient, the cost is low, and it is suitable for popularization. Description of the Drawings

[0026] Figure 1 is the 12×12 MIMO antenna proposed by the present invention;

[0027] Figure 2 is the side view of the 3-element MIMO antenna in the present invention;

[0028] Figure 3A top view of a three-unit MIMO antenna according to the present invention;

[0029] Figure 4 This is a surface current distribution pattern diagram of the planar inverted-F antenna pair of the present invention at 3.6 GHz;

[0030] Figure 5 This is a surface current distribution pattern diagram of the planar inverted-F antenna pair of the present invention at 4.58 GHz;

[0031] Figure 6 This is a surface current distribution pattern diagram of the planar inverted-F antenna pair of the present invention at 5.7 GHz;

[0032] Figure 7 This is a surface current distribution pattern diagram of the T-shaped monopole antenna of the present invention at 3.58 GHz;

[0033] Figure 8 This is a surface current distribution pattern diagram of the T-shaped monopole antenna of the present invention at 5.95 GHz;

[0034] Figure 9 The three-dimensional radiation pattern of the antenna when power is supplied to port 1 of the present invention;

[0035] Figure 10 The three-dimensional radiation pattern of the antenna when power is supplied to port 3 of the present invention;

[0036] Figure 11 is the reflection coefficient of the 12-unit MIMO antenna of the present invention (S11, S22, S33, S44, S55, S66, S 77 , S 88 , S 99 , S 1010 , S 1111 , S 1212 );

[0037] Figure 12 is the reflection coefficient (S) of the 12-unit MIMO antenna of the present invention 21 , S 32 , S 42 , S 82 , S 93 ).

[0038] Figure 13 FIG. 4 is a graph showing the envelope correlation coefficients (ECCs) of the 12-element MIMO antenna of the present invention.

[0039] The numbers in the figure are: 1-PIFA antenna pair, 2-large dielectric substrate, 3-small dielectric substrate I, 4-coaxial feed port, 5-T-shaped monopole antenna, 6-small dielectric substrate II, 7-slot, 8-"cross" slot, 9-ground branch of the PIFA antenna pair. Detailed implementation mode

[0040] In order to enable ordinary technicians in the field to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0041] The present invention proposes a 12-element broadband self-isolated MIMO antenna for a 5G mobile phone terminal, including: an FR-4 dielectric substrate (ε r = 4.4, tanθ = 0.025), where ε r is the dielectric constant of the dielectric substrate, and θ is the dielectric loss angle. The FR-4 dielectric substrate includes a large dielectric substrate 2 with a size of 150mm×75mm×0.8mm, two small dielectric substrates I 3 and small dielectric substrates II 6 with a size of 150mm×7mm×0.8mm. The two small dielectric substrates are orthogonally and closely placed on the two long edges of the large dielectric substrate 2.

[0042] A pair of PIFA antennas 1 is placed closely against the small dielectric substrate I and the small dielectric substrate II 6. On the PIFA antenna unit, a "cross" slot 8 is opened for broadband expansion. And each pair of PIFA antennas 1 is formed by combining two PIFA units, and there is a self-isolation characteristic between the two PIFA units. And there are 8 PIFA units in the present invention. The PIFA units are combined in pairs, and there are 4 pairs of PIFA antennas 1 in total, which are respectively placed at the four corners of the large dielectric substrate 2. The coupling current between the pairs of PIFA antennas 1 is guided to the ground plane through the grounding stub 9 of the PIFA antenna pair to weaken the coupling.

[0043] After parameter simulation and optimization, the present invention sets the height of the small dielectric substrate I 3 and the small dielectric substrate II 6 to 7mm; the size of the pair of PIFA antennas 1 is set to 30mm×6.2mm; the size of the "cross" slot 8 opened on the PIFA unit is 13.5mm×1.3mm, with a width of 0.4mm. It includes two rectangular notches perpendicular to each other. The length and width of the horizontally arranged rectangular notch are 13.5mm×1.3mm, and the width of the vertically arranged rectangular notch is 0.4mm; the arm length of the T-shaped monopole antenna 5 placed orthogonally to the pair of PIFA antennas 1 is 17mm, and the arm width is 1.75mm.

[0044] As shown in the attached Figure 1 and 3 figures, several ports 4 are also provided on the large dielectric substrate 2. As Figure 3 shown, three ports are provided on the large dielectric substrate 2: port 1, port 2, and port ③.

[0045] Preferably, the port 4 includes port 1, port 2, port 3, port 4, port 5, port 6, port 7, port 8, port 9, port 10, port 11 and port 12, and every three ports form a group. The four groups of ports are respectively arranged at the four corners of the large dielectric substrate; gaps 7 are formed on the ground plane (i.e., the back of the large substrate) between port 1 and port 2, port 4 and port 5, port 7 and port 8, and port 10 and port 11 to isolate the floor coupling current, and then the T-shaped monopole antenna 5 and the PIFA antenna pair 1 are orthogonally placed.

[0046] Each of the above ports is fed by a 50Ω coaxial cable. The coaxial cable penetrates through the dielectric substrate from a via hole on the ground plane to the microstrip patch, and then the feeding probe feeds the microstrip antenna radiation unit through the via hole. The feeding probe is connected to the inner conductor of the coaxial cable, and the outer conductor of the coaxial cable is connected to the ground plane.

[0047] From Figures 4 - 10 It can be seen from the surface current distribution pattern and the three-dimensional radiation pattern of the antenna unit at each frequency point that the current modes excited by the PIFA antenna pair 1 and the T-shaped monopole antenna 5 are orthogonal to each other, obtaining a radiation pattern with the maximum radiation direction pointing to different regions, so that the radiation patterns of the MIMO antenna units do not overlap, thereby achieving high isolation between the antenna units without introducing additional decoupling elements.

[0048] From Figure 11 it can be seen that the S parameters (S 11 , S 22 , S33, S 44 , S 55 , S 66 , S 77 , S 88 , S 99 , S 1010 , S 1111 , S 1212 ) are all less than -6dB in the frequency band of 3.1GHz - 6.5GHz. From Figure 12 it can be seen that the isolation degrees (S 21 , S 32 , S 42 , S 82 , S 93 ) between port 1 and port 2, port 3 and port 2, port 4 and port 2, port 8 and port 2, and port 9 and port 3 are all greater than 10dB within 3 - 6.5GHz, having good broadband isolation characteristics. And from Figure 11 it can be seen that the MIMO antenna proposed by the present invention can cover the 5G NR frequency bands N77 / N78 / N79 and the WiFi frequency band (5150 - 5850MHz).

[0049] Figure 13 The envelope correlation coefficients (ECCs) of the 12-element MIMO antenna proposed by the present invention are shown. It can be seen from the figure that the envelope correlation coefficients are all less than 0.17. Therefore, the MIMO antenna system has good diversity performance. Through simulation, it is obtained that the radiation efficiency of each port of the antenna system is also between 51% and 96%. The results are shown in Table 1. It can be seen from Table 1 that it has good radiation characteristics.

[0050] Table 1

[0051]

[0052] The number of ports of the MIMO antenna described in the present invention can be 6, 12 or 18.

[0053] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A 12-unit broadband self-isolated MIMO antenna for 5G mobile phone terminals, characterized in that: It includes an FR-4 dielectric substrate, a PIFA antenna pair (1), a T-shaped monopole antenna (5), a coaxial feed line, and a 50Ω SMA connector; The FR-4 dielectric substrate comprises a large dielectric substrate (2) and a small dielectric substrate I (3) and a small dielectric substrate II (6) closely disposed on two long edges of the large dielectric substrate; Four PIFA antenna pairs (1) are provided, which are respectively placed at the four corners of the large dielectric substrate (2) and closely arranged on one side of the small dielectric substrate I (3) and the small dielectric substrate II (6); A T-shaped monopole antenna (5) is placed orthogonally to the PIFA antenna pair (1); A coaxial feed line (4) connected to the FR-4 dielectric substrate and used to feed the microstrip antenna radiation unit; The large dielectric substrate (2) is further provided with a plurality of ports (4), with three ports forming a group, and the four groups of ports are respectively provided at the corners of the large dielectric substrate (2); a gap (7) is provided on the floor between two ports (4) close to the long side of the large dielectric substrate (2) in each group of ports, for isolating the floor coupling current, thereby introducing the T-shaped monopole antenna (5) and placing it orthogonally with the PIFA antenna pair (1).

2. The 12-element broadband self-isolated MIMO antenna for 5G mobile phone terminals according to claim 1, wherein The size of the large dielectric substrate (2) is 150 mm×75 mm×0.8 mm, and the size of the small dielectric substrate I (3) and the small dielectric substrate II (6) is 150 mm×7 mm×0.8 mm.

3. A 12 - element broadband self - isolated MIMO antenna for 5G mobile terminals according to claim 2, characterized in that, The PIFA antenna pair (1) is composed of two PIFA units combined together, the two PIFA units are self-isolating, and each PIFA unit is provided with a cross-shaped slot (8).

4. A 12 - element broadband self - isolating MIMO antenna for 5G mobile terminals according to claim 3, characterized in that, The "cross"-shaped groove (8) comprises two mutually perpendicular and interpenetrating rectangular notches.

5. The 12-element broadband self-isolated MIMO antenna for a 5G mobile phone terminal according to claim 4, characterized in that, The length and width of the rectangular notch arranged horizontally in the "cross" shaped groove (8) are 13.5 mm × 1.3 mm, and the width of the rectangular notch arranged vertically is 0.4 mm.

6. A 12 - element broadband self - isolated MIMO antenna for 5G mobile terminals according to claim 3, characterized in that, The size of the PIFA antenna pair (1) is 30 mm × 6.2 mm.

7. A 12 - element broadband self - isolating MIMO antenna for 5G mobile terminals according to claim 4, characterized in that, The arm length of the T-shaped monopole antenna (5) is 17 mm, and the arm width is 1.75 mm.

8. A 12 - element broadband self - isolating MIMO antenna for 5G mobile terminals according to claim 1, characterized in that, The number of the ports (4) is 6, 12 or 18.

9. The 12 - element broadband self - isolation MIMO antenna for 5G mobile phone terminals according to claim 8, characterized in that, The ports (4) all adopt 50Ω coaxial feeding.

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