A multi-band MIMO antenna

Abstract

The application discloses a multi-band MIMO antenna; comprising a dielectric substrate, a ground plate, an antenna unit and a coupling unit, the antenna unit and the coupling unit are oppositely arranged on the end surface of the dielectric substrate, the ground plate is located outside the coupling unit, and the coupling unit is used for reducing the coupling between the multiple antenna units; the antenna unit comprises a microstrip line and a radiation patch, the microstrip line is arranged at the edge of the dielectric substrate and connected with the radiation patch, a radiation slot is arranged on the radiation patch, and the radiation slot is used for increasing the frequency band of the antenna unit. The radiation slot arranged on the radiation patch in the application can increase the frequency band of the antenna unit, so that the antenna can work on multiple frequency bands and meet the demand of different communication systems. The arrangement of the coupling unit can reduce the coupling between the multiple antenna units, improve the isolation of the antenna, and enable each antenna unit to work independently, thereby reducing the mutual interference between the antenna units.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antennas, and in particular to a multi-band MIMO antenna. BACKGROUND

[0002] In the era of Internet of Everything, the rapid development of various wireless device terminals greatly facilitates our daily life. In order to meet the actual needs of the current society, the communication rate and channel capacity of the wireless communication system need to be greatly improved. The channel capacity of the traditional single-input single-output (SISO) system is limited. The multi-input multi-output (MIMO) antenna system can achieve the goal of improving the channel capacity. In the MIMO antenna system, multiple antennas are placed in a limited space, which causes the coupling between different units of the antenna, thereby deteriorating the index of the antenna. In the MIMO system, the channel capacity is closely related to the number of antennas at the transmitting and receiving ends. When the channels established between the transmitting antennas and the receiving antennas have small correlation, the more the number of antennas, the larger the signal capacity. However, in the existing MIMO antenna, it is difficult to cover a wide frequency band in a limited antenna design space, and the coupling between the transceiving ends is strong, which affects the performance of the antenna. SUMMARY

[0003] The technical problem solved by the present application is to provide a multi-band MIMO antenna, which solves the problem that it is difficult to cover a wide frequency band in a limited antenna design space, and the coupling between the transceiving ends is strong, which affects the performance of the antenna.

[0004] To solve the above technical problem, one technical solution adopted by the present application is to provide a multi-band MIMO antenna, which comprises a dielectric substrate, a ground plate, an antenna unit and a coupling unit. The antenna unit and the coupling unit are oppositely arranged on the end face of the dielectric substrate. The ground plate is located outside the coupling unit. The antenna unit is provided in a plurality of ways and arranged on the dielectric substrate in a polarization diversity manner. The coupling unit is used to reduce the coupling between the plurality of antenna units. The antenna unit comprises a microstrip line and a radiation patch. The microstrip line is arranged at the edge of the dielectric substrate and connected with the radiation patch. A radiation slot is formed in the radiation patch, which is used to increase the frequency band of the antenna unit.

[0005] In some embodiments, the radiation patch comprises a connecting portion and a radiation portion. The connecting portion is connected between the radiation portion and the microstrip line. The width of the connecting portion is smaller than the width of the microstrip line.

[0006] In some embodiments, the radiation slot comprises a first radiation sub-slot. The first radiation sub-slot is arranged on the radiation portion at one side of the connecting portion.

[0007] In some embodiments, the radiation slot further comprises a second radiation sub-slot, the second radiation sub-slot is disposed on the radiation part on the other side of the connecting part, the connecting part is located between the first radiation sub-slot and the second radiation sub-slot.

[0008] In some embodiments, the first radiation sub-slot is enclosed by the radiation part, one end of the second radiation sub-slot penetrates through the radiation part, so that the radiation part has an opening adjacent to one side of the connecting part.

[0009] In some embodiments, the antenna unit further comprises a resonant ring, the resonant ring is disposed on the inner side of the radiation patch, the resonant ring is used to increase the resonant frequency of the antenna unit.

[0010] In some embodiments, the ground plate comprises a first rectangular part and a second rectangular part, a first right angle of the first rectangular part is aligned with a corner of the dielectric substrate, a second right angle of the first rectangular part is opposite to the first right angle, the second rectangular part extends from the second right angle of the first rectangular part to the center of the dielectric substrate.

[0011] In some embodiments, the size of the first rectangular part is larger than the size of the second rectangular part, the long side of the first rectangular part is parallel to the long side of the second rectangular part.

[0012] In some embodiments, the coupling unit comprises a center part and a branch part, the center part is disposed at the center position of the dielectric substrate, the branch part extends outward from the edge part of the center part.

[0013] In some embodiments, the shape of the center part is circular, the shape of the branch part is rectangular, the branch parts are uniformly distributed outside the center part, and the outer edges of the branch parts are tangent to the center part.

[0014] The beneficial effects of the present application are: in the present application, the plurality of antenna units are arranged on the dielectric substrate in a polarization diversity manner, the polarization diversity technology can effectively reduce the influence of multipath fading on the signal and improve the transmission quality and reliability of the signal; by receiving signals of different polarization directions, the diversity of the signal can be increased. The radiation slot opened on the radiation patch can increase the frequency band of the antenna unit, so that the antenna can work on multiple frequency bands to meet the needs of different communication systems. The antenna unit and the coupling unit are arranged on the end face of the dielectric substrate in a relative manner, which fully utilizes the space of the dielectric substrate, so that the overall structure of the antenna is compact, which is beneficial to realize the function of the multi-band MIMO antenna in a limited space. The arrangement of the coupling unit can reduce the coupling between the plurality of antenna units, improve the isolation of the antenna, so that each antenna unit can work independently and reduce the mutual interference between the antenna units. The ground plate is located outside the coupling unit, which not only helps the electromagnetic shielding of the antenna and reduces the influence of external interference on the performance of the antenna, but also optimizes the radiation pattern of the antenna and improves the radiation efficiency and directivity of the antenna. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a structural schematic diagram according to an embodiment of the present application;

[0016] Figure 2 is a top view structural schematic diagram according to an embodiment of the present application;

[0017] Figure 3 is a bottom view structural schematic diagram according to an embodiment of the present application;

[0018] Figure 4 is a structural schematic diagram after removing the dielectric substrate according to an embodiment of the present application;

[0019] Figure 5 is a top view structural schematic diagram after removing the dielectric substrate according to an embodiment of the present application;

[0020] Figure 6 is a bottom view structural schematic diagram after removing the dielectric substrate according to an embodiment of the present application;

[0021] Figure 7 is a structural schematic diagram of the ground plate according to an embodiment of the present application;

[0022] Figure 8 is a structural schematic diagram of the radiation patch according to an embodiment of the present application;

[0023] Figure 9 is a structural schematic diagram of the resonant ring according to an embodiment of the present application;

[0024] Figure 10 is a structural schematic diagram of the coupling unit according to an embodiment of the present application;

[0025] Figure 11 is a plot of S parameters according to an embodiment of the application;

[0026] Figure 12 is an E-plane pattern at 2.4 GHz according to an embodiment of the application;

[0027] Figure 13 is an H-plane pattern at 2.4 GHz according to an embodiment of the application;

[0028] Figure 14 is an E-plane pattern at 5 GHz according to an embodiment of the application;

[0029] Figure 15 is an H-plane pattern at 5 GHz according to an embodiment of the application;

[0030] Figure 16 is an E-plane pattern at 6 GHz according to an embodiment of the application;

[0031] Figure 17 is an H-plane pattern at 6 GHz according to an embodiment of the application;

[0032] Figure 18 is an E-plane pattern at 7 GHz according to an embodiment of the application;

[0033] Figure 19 is an H-plane pattern at 7 GHz according to an embodiment of the application;

[0034] Figure 20 is a plot of ECC envelope correlation coefficient according to an embodiment of the application;

[0035] Figure 21 is a plot of gain peak according to an embodiment of the application. DETAILED DESCRIPTION

[0036] In order to make the skilled in the art better understand the technical solutions in the application, the technical solutions in the embodiments of the application will be clearly and completely described below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, not all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the application.

[0037] It should be noted that when an element is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or indirectly on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component.

[0038] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or component referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0039] In addition, the terms "first" and "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" and "several" is two or more, unless otherwise specifically limited.

[0040] It should be understood that the structures, proportions, sizes, etc. shown in the drawings of the present application are only used to cooperate with the content disclosed in the description, to be understood and read by those skilled in the art, and do not have technical significance, and any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application.

[0041] Figures 1-21 An embodiment of a multi-band MIMO antenna of the present application is shown, which includes a dielectric substrate 1, a ground plate 2, an antenna unit 3 and a coupling unit 4, the antenna unit 3 and the coupling unit 4 are oppositely arranged on the end surface of the dielectric substrate 1, the ground plate 2 is located outside the coupling unit 4, the antenna unit 3 is provided in multiple and arranged on the dielectric substrate 1 in a polarization diversity manner, and the coupling unit 4 is used to reduce the coupling between the multiple antenna units 3; the antenna unit 3 includes a microstrip line 31 and a radiation patch 32, the microstrip line 31 is arranged at the edge of the dielectric substrate 1 and connected with the radiation patch 32, the radiation patch 32 is provided with a radiation slot 321, and the radiation slot 321 is used to increase the frequency band of the antenna unit 3.

[0042] In this application, multiple antenna elements 3 are arranged on the dielectric substrate 1 in a polarization diversity manner. Polarization diversity technology can effectively reduce the impact of multipath fading on the signal, improve the signal transmission quality and reliability, and increase signal diversity by receiving signals with different polarization directions. The radiating slots 321 formed on the radiating patch 32 can increase the frequency band of the antenna elements 3, enabling the antenna to operate on multiple frequency bands to meet the needs of different communication systems. The antenna elements 3 and the coupling unit 4 are arranged opposite each other on the end face of the dielectric substrate 1. This layout makes full use of the space of the dielectric substrate 1, making the overall antenna structure compact and conducive to realizing the function of a multi-band MIMO antenna in a limited space. The setting of the coupling unit 4 can reduce the coupling between multiple antenna elements 3, improve the isolation of the antenna, enable each antenna element 3 to work independently, and reduce mutual interference between antenna elements 3. The ground plane 2 is located outside the coupling unit 4, which not only helps the electromagnetic shielding of the antenna and reduces the impact of external interference on the antenna performance, but also optimizes the radiation pattern of the antenna and improves the radiation efficiency and directivity of the antenna.

[0043] In some embodiments, such as Figures 1-3 As shown, the dielectric substrate 1 can be square, rectangular, or a regular polygon. This application uses a square substrate as an example. The material of the dielectric substrate 1 can be a ceramic / hydrocarbon composite laminate with a dielectric constant of 3.66. The side length of the dielectric substrate 1 is 50mm to 70mm, and the thickness is 1mm to 3mm. Further, the dielectric substrate 1 has a length of 62mm and a thickness of 1.524mm.

[0044] In some embodiments, such as Figure 3 As shown, four ground planes 2 are provided, located at the four corners of the dielectric substrate 1. Each ground plane 2 includes a first rectangular portion 21 and a second rectangular portion 22. The first right angle Z1 of the first rectangular portion 21 is aligned with the corner of the dielectric substrate 1, and the second right angle Z2 of the first rectangular portion 21 is opposite to the first right angle Z1. The second rectangular portion 22 extends from the second right angle Z2 of the first rectangular portion 21 towards the center of the dielectric substrate 1. This reduces the size of the ground plane 2 and further reduces coupling in the antenna element 3.

[0045] In some embodiments, such as Figure 7 As shown, the size of the first rectangular portion 21 is larger than the size of the second rectangular portion 22, and the long side of the first rectangular portion 21 is parallel to the long side of the second rectangular portion 22.

[0046] In some embodiments, such as Figure 7 As shown, the length L1 of the first rectangular portion 21 is 7mm to 10mm and the width W1 is 5mm to 8mm; the length L2 of the second rectangular portion 22 is 5mm to 8mm and the width W2 is 2mm to 5mm.

[0047] Furthermore, the length L1 of the first rectangular portion 21 is 8.58 mm and the width W1 is 6 mm, and the length L2 of the second rectangular portion 22 is 6.5 mm and the width W2 is 3.99 mm.

[0048] In some embodiments, such as Figures 3-6 As shown, there are four antenna elements 3, which are located at the four corners of the dielectric substrate 1 and arranged orthogonally to each other. That is, they are arranged in a circular array with the center perpendicular line of the dielectric substrate 1 as the center. This reduces the coupling between the four antenna elements 3 and achieves orthogonal polarization between the antenna elements 3, thereby reducing the coupling between the antenna elements 3 while achieving a compact antenna layout.

[0049] In some embodiments, the outer end of the microstrip line 31 is flush with the edge of the dielectric substrate 1, and the inner end of the microstrip line 31 extends into the inner side of the dielectric substrate 1 and connects to the radiating patch 32.

[0050] In some embodiments, such as Figure 8 As shown, the microstrip line 31 has a rectangular structure. The long side of the microstrip line 31 extends into the dielectric substrate 1, one short side of the microstrip line 31 is collinear with the edge line of the dielectric substrate 1, and the other short side of the microstrip line 31 is connected to the radiating patch 32.

[0051] The radiating patch 32 includes a connecting portion 322 and a radiating portion 323, with the connecting portion 322 connecting the radiating portion 323 and the microstrip line 31. The connecting portion 322 is rectangular, and its width is smaller than that of the microstrip line 31.

[0052] In some embodiments, such as Figure 8 As shown, the length L3 of the microstrip line 31 is 4mm to 8mm, and the width W3 of the microstrip line 31 is 2mm to 5mm.

[0053] Furthermore, the length L3 of the microstrip line 31 is 6 mm, and the width W3 of the microstrip line 31 is 3.4 mm.

[0054] The shape of the radiating part 323 can be circular, square, rectangular, or a regular polygon, etc. This increases the current path.

[0055] In some embodiments, the radiating slot 321 can adjust the frequency band and impedance matching. The radiating slot 321 includes a first radiating sub-slot 3211, which is disposed on the radiating portion 323 on one side of the connecting portion 322. The first radiating sub-slot 3211 allows adjustment of the operating frequency band of the antenna element 3, achieving coverage of the 2.36GHz-2.54GHz and 4.69GHz-8.17GHz operating frequency bands. This includes 2.4GHz, 5GHz, 6GHz, and 7GHz in the WIFI 7 band.

[0056] In some embodiments, the radiating slot 321 further includes a second radiating sub-slot 3212, which is disposed on the radiating portion 323 on the other side of the connecting portion 322, i.e., the connecting portion 322 is located between the first radiating sub-slot 3211 and the second radiating sub-slot 3212. The operating frequency band of the antenna element 3 can be further adjusted through the second radiating sub-slot 3212.

[0057] In some embodiments, the first radiating sub-slot 3211 is surrounded by the radiating portion 323, and one end of the second radiating sub-slot 3212 passes through the radiating portion 323, so that the side of the radiating portion 323 adjacent to the connecting portion 322 has an opening.

[0058] In some embodiments, the length of the first radiating sub-slot 3211 is less than the length of the second radiating sub-slot 3212, and the width of the first radiating sub-slot 3211 is greater than the width of the second radiating sub-slot 3212.

[0059] In some embodiments, the radiating portion 323, the first radiating sub-slot 3211, and the second radiating sub-slot 3212 are all rectangular. The radiating portion 323 includes a first included angle J1, a second included angle J2, and a third included angle J3. The first included angle J1 is located between the second included angle J2 and the third included angle J3. The second included angle J2 and the third included angle J3 are arranged opposite to each other. The first included angle J1 is connected to the connecting portion 322. The first radiating sub-slot 3211 is adjacent to the second included angle J2, and the second radiating sub-slot 3212 is adjacent to the third included angle J3.

[0060] In some embodiments, such as Figure 8 As shown, the length L4 of the radiating section 323 is 20mm to 40mm and the width W4 is 4mm to 8mm. The length L5 of the first radiating sub-slot 3211 is 10mm to 20mm and the width W5 is 1mm to 3mm. The length L6 of the second radiating sub-slot 3212 is 10mm to 30mm and the width W6 is 0.5mm to 2mm.

[0061] Furthermore, the length L4 of the radiating section 323 is 29 mm and the width W4 is 6 mm, the length L5 of the first radiating sub-slot 3211 is 16.24 mm and the width W5 is 1.29 mm, and the length L6 of the second radiating sub-slot 3212 is 17.27 mm and the width W6 is 0.78 mm.

[0062] In some embodiments, the antenna unit 3 further includes a resonant ring 33, which is disposed inside the radiating patch 32 and is used to increase the resonant frequency of the antenna unit 3.

[0063] In some embodiments, the resonant ring 33 is in a ring structure of square, rectangle or regular polygon, etc., and the resonant ring 33 has an opening 331 away from one side of the radiation patch 32. By arranging the resonant ring 33, a new resonant frequency can be added to the antenna unit 3, and the frequency range coverage of the antenna unit 3 can be improved.

[0064] In some embodiments, as shown in FIG. 3, the length L7 of the resonant ring 33 is 3mm-8mm, and the size L8 of the opening 331 is 1-3mm. The width W7 of the resonant ring 33 is 0.5mm-2mm. The size W8 of the opening 331 extending out is 0.5mm-2mm. Figure 9

[0065] Further, the length L7 of the resonant ring 33 is 5.5mm, and the size L8 of the opening 331 is 1.5mm. The width W7 of the resonant ring 33 is 1mm. The size W8 of the opening 331 extending out is 1mm.

[0066] In some embodiments, the coupling unit 4 includes a center part 41 and a branch part 42, the center part 41 is arranged at the center position of the dielectric substrate 1, and the branch part 42 extends outward from the edge of the center part 41. In this way, the coupling in the antenna unit 3 can be further reduced, the isolation of the antenna can be improved, and the mutual interference between the antenna units 3 can be reduced.

[0067] In some embodiments, the shape of the center part 41 can be circular, rectangular or polygonal, etc. The shape of the branch part 42 can be elliptical, arc-shaped or rectangular, etc.

[0068] In some embodiments, the shape of the center part 41 is circular, and the shape of the branch part 42 is rectangular. The branch part 42 is uniformly distributed outside the center part 41, and the outer edge of the branch part 42 is tangent to the center part 41. In this way, the current can be guided to the center part 41 without flowing to the antenna unit 3.

[0069] In some embodiments, as shown in FIG. 4, the radius R1 of the center part 41 is 5mm-20mm, the length L9 of the branch part 42 is 15mm-30mm, and the width W9 is 4mm-10mm. Figure 10 Further, the radius R1 of the center part 41 is 12.13mm, the length L9 of the branch part 42 is 23.13mm, and the width W9 is 6.23mm.

[0070] In some embodiments, as shown in FIG. 5, the horizontal coordinate is frequency (Frep), and the vertical coordinate is gain.

[0071] Figure 11 Figure 11 Figure 11 ​​​​The scattering parameters (S parameters) of the antenna are shown in FIG. 6, wherein S11 is the return loss of the antenna 1 port, and S21, S31 and S41 are the coupling coefficients between the antenna 2 port, the antenna 3 port and the antenna 4 port, respectively. Figure 11 It can be seen from the S11 that the antenna has good impedance matching in the working frequency band, and has good isolation coefficients in different port frequency bands.

[0072] In some embodiments, as shown in FIG. 7, the envelope correlation coefficients (ECCs) of the antenna are shown. Figures 12-19 Figures 12-19 In FIG. 8, the E-plane and H-plane patterns at 2.4 GHz, 5 GHz, 6 GHz and 7 GHz are shown, respectively. Figures 12-19 It can be seen from FIG. 8 that the antenna has good radiation patterns at 2.4 GHz, 5 GHz, 6 GHz and 7 GHz.

[0073] In some embodiments, as shown in FIG. 9, the envelope correlation coefficients (ECCs) of the antenna are shown. Figure 20 Figure 20 It can be seen from FIG. 9 that the antenna has good diversity capability.

[0074] In some embodiments, as shown in FIG. 10, the gain of the antenna in the working frequency band is shown. Figure 21 Figure 21 It can be seen from FIG. 10 that the antenna has good gain in the working frequency band.

[0075] Therefore, the application discloses a multi-band MIMO antenna. In the application, a plurality of antenna units are arranged on a dielectric substrate in a polarization diversity manner. The polarization diversity technology can effectively reduce the influence of multipath fading on signals and improve the transmission quality and reliability of signals. By receiving signals of different polarization directions, the diversity of signals can be increased. The radiation slots formed on the radiation patch can increase the frequency band of the antenna unit, so that the antenna can work in multiple frequency bands and meet the needs of different communication systems. The antenna unit and the coupling unit are arranged on the end face of the dielectric substrate in a relative manner. This layout fully utilizes the space of the dielectric substrate, so that the overall structure of the antenna is compact and conducive to realizing the function of the multi-band MIMO antenna in a limited space. The arrangement of the coupling unit can reduce the coupling between the plurality of antenna units, improve the isolation of the antenna, and enable each antenna unit to work independently and reduce mutual interference between the antenna units. The ground plate is located outside the coupling unit, which not only helps electromagnetic shielding of the antenna and reduces the influence of external interference on the performance of the antenna, but also optimizes the radiation pattern of the antenna and improves the radiation efficiency and directivity of the antenna.

[0076] ​​​The above merely illustrates the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation or direct or indirect application in other related technical fields by using the content of the present application specification and drawings are also included in the patent protection scope of the present application.

Claims

1. A multi-band MIMO antenna, characterized in that, The device includes a dielectric substrate, a ground plane, antenna elements, and a coupling unit. The antenna elements and the coupling unit are disposed opposite each other on the end face of the dielectric substrate. The ground plane is located outside the coupling unit. Multiple antenna elements are disposed on the dielectric substrate in a polarization diversity manner. The coupling unit is used to reduce the coupling between the multiple antenna elements. Each antenna element includes a microstrip line and a radiating patch. The microstrip line is disposed on the edge of the dielectric substrate and connected to the radiating patch. The radiating patch has radiating slots, which are used to increase the frequency band of the antenna element. The radiating patch includes a connecting portion and a radiating portion. The connecting portion connects the radiating portion and the microstrip line. The radiating slot includes a first radiating sub-slot and a second radiating sub-slot. The first radiating sub-slot is disposed on the radiating portion on one side of the connecting portion. The second radiating sub-slot is disposed on the radiating portion on the other side of the connecting portion. The connecting portion is located between the first radiating sub-slot and the second radiating sub-slot. The first radiating sub-slot and the second radiating sub-slot extend in the same direction. The length of the first radiating sub-slot is less than the length of the second radiating sub-slot, and the width of the first radiating sub-slot is greater than the width of the second radiating sub-slot. The radiating section, the first radiating sub-slot, and the second radiating sub-slot are all rectangular. The radiating section includes a first included angle, a second included angle, and a third included angle. The first included angle is located between the second included angle and the third included angle. The second included angle and the third included angle are arranged opposite to each other. The first included angle connects to the connecting section. The first radiating sub-slot is adjacent to the second included angle, and the second radiating sub-slot is adjacent to the third included angle. The first radiating sub-slot is surrounded by the radiating portion, and one end of the second radiating sub-slot penetrates the radiating portion, so that the side of the radiating portion adjacent to the connecting portion has an opening.

2. The multi-band MIMO antenna according to claim 1, characterized in that, The width of the connector is smaller than the width of the microstrip line.

3. A multi-band MIMO antenna according to claim 1, characterized in that, The antenna unit further includes a resonant ring disposed inside the radiating patch, and the resonant ring is used to increase the resonant frequency of the antenna unit.

4. A multi-band MIMO antenna according to claim 1, characterized in that, The floor includes a first rectangular portion and a second rectangular portion. The first right angle of the first rectangular portion is aligned with the corner of the dielectric substrate, and the second right angle of the first rectangular portion is opposite to the first right angle. The second rectangular portion extends from the second right angle of the first rectangular portion toward the center of the dielectric substrate.

5. A multi-band MIMO antenna according to claim 4, characterized in that, The size of the first rectangular portion is larger than the size of the second rectangular portion, and the long side of the first rectangular portion is parallel to the long side of the second rectangular portion.

6. A multi-band MIMO antenna according to claim 1, characterized in that, The coupling unit includes a central portion and a branch portion. The central portion is located at the center of the dielectric substrate, and the branch portion extends outward from the edge of the central portion.

7. A multi-band MIMO antenna according to claim 6, characterized in that, The central part is circular in shape, and the branch parts are rectangular in shape. The branch parts are evenly distributed outside the central part, and the outer edge of the branch parts is tangent to the central part.

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