A broadband, high-isolation six-element MIMO slot antenna for 5G mobile terminals

Abstract

The present invention discloses a broadband, high-isolation six-unit MIMO slot antenna for 5G mobile terminals, wherein a metal floor is provided at the bottom of the rectangular dielectric substrate, and M "T"-shaped slots and N "T"-like slots are symmetrically cut on the surface of the floor; N antenna units are evenly provided on the top of the dielectric substrate, and each antenna unit is composed of two microstrip lines and a "T"-like slot corresponding to the floor. The microstrip line is composed of a metal material and loaded on the top of the dielectric substrate. The antenna units on both sides of the top of the dielectric substrate are distributed in mirror symmetry, and the distance between the antenna units on each side is the same. The present invention can cover the 3.3-5.1GHz frequency band, the isolation between antenna units can reach more than 16.2dB, the radiation efficiency exceeds 50%, the correlation coefficient is below 0.02, the antenna structure is simple, the size is small, and it has good practical value in mobile terminal communications.

Description

Technical Field

[0001] The present invention relates to the technical field of 5G mobile communications, and in particular to a broadband, high-isolation six-unit MIMO slot antenna for a 5G mobile terminal. Background Art

[0002] At present, mobile communications have entered the 5G era. Data shows that the transmission rate of 5G is 100 times that of 4G. Research shows that the core of 5G mobile terminal communication technology research and development is to meet the requirements of high-speed data transmission, low latency, broadband, high capacity, and backward compatibility. From the theory of communication systems, it can be known that the larger the channel capacity, the higher the data transmission rate, and the multiple-input multiple-output (MIMO) technology can well improve the channel capacity and transmission rate. Through research, it is found that in a multipath environment, as the number of transmitting and receiving antennas increases, the channel capacity also increases exponentially.

[0003] A lot of research has been done at home and abroad on broadband MIMO antennas in 5G communication systems. Most of the 5G antennas studied and designed can only cover part of the frequency band. The single and narrow frequency band of the antenna will make communication inconvenient, so how to achieve broadband antennas is a key issue.

[0004] In a MIMO system, the coupling between antenna units will increase the signal correlation between units, reduce the channel capacity, and thus affect normal operation. Due to the adverse effects of mutual coupling, it is particularly important to achieve low mutual coupling between antennas. Summary of the invention

[0005] The purpose of the present invention is to provide a broadband, high-isolation six-unit MIMO slot antenna for 5G mobile terminals; the invention has the advantages of wide bandwidth, high isolation, simple structure, high radiation efficiency, etc.

[0006] The present invention achieves the purpose of the invention by adopting the following technical solutions:

[0007] A broadband, high-isolation six-unit MIMO slot antenna for 5G mobile terminals, comprising a dielectric substrate, characterized in that a metal floor is provided at the bottom of the rectangular dielectric substrate, and M "T"-shaped slots and N "T"-shaped slots are symmetrically cut on the surface of the floor; N antenna units are evenly provided on the top of the dielectric substrate, and each antenna unit is composed of two microstrip lines and a "T"-shaped slot corresponding to the floor. The microstrip line is composed of a metal material, loaded on the top of the dielectric substrate, and the microstrip line structure is provided with a feeding point.

[0008] Preferably, the antenna units on both sides of the top of the dielectric substrate are distributed in a mirror-symmetrical manner, and the distance between the antenna units on each side is the same.

[0009] Preferably, the cuboid is used as a dielectric substrate, the microstrip line is used for feeding the antenna, the "T"-shaped slot is used for impedance matching of the antenna, and the "T"-shaped slot is used to reduce coupling between antennas.

[0010] Preferably, the rectangular dielectric substrate is made of FR4, has a dielectric constant of 4.4, is 150 mm long, 75 mm wide and 0.8 mm high; the side with the printed microstrip line is the front side of the dielectric substrate, and the side with the printed metal floor is the back side of the dielectric substrate.

[0011] Preferably, the two microstrip lines are in "I" shape, vertically alternately connected to form an "L"-shaped microstrip line and evenly and symmetrically distributed along the front side of the substrate, loaded above the "T"-shaped groove; the length of the first microstrip line close to the edge of the substrate is 10.9 mm, the length of the other microstrip line is 4 mm, and the width of the microstrip lines is 2.5 mm.

[0012] Preferably, the "T"-like slot consists of two slots: one slot is "U"-shaped, 6mm long and 4.5mm wide, with two protruding smaller slots of 1mm in length and 0.5mm in width; the other is an "I"-shaped open branch embedded in the middle of the "U"-shaped slot, connected to the edge of the metal floor, with a length of 4.4mm and a width of 1mm; the "T"-shaped slot is symmetrically arranged along the antenna units on one side, and it consists of two parts: the slot along the long side of the floor is 11.5mm long and 2mm wide; the slot along the short side of the floor is 7.5mm long and 2mm wide.

[0013] Preferably, the center of the T-slot is spaced 30 mm from the center of the adjacent "T"-shaped slot.

[0014] Preferably, the back side of the dielectric substrate is tin-coated according to the structure of a floor, and the front side of the dielectric substrate is tin-coated according to the structure of a microstrip line.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The antenna of the present invention can cover 3.3GHz-5.1GHz of 5G, with a relative bandwidth of 42.86%. The measured antenna radiation efficiency can reach 50%-63%, and can basically achieve omnidirectional coverage within the frequency band.

[0017] (2) The "T"-shaped isolator introduced in the present invention does not affect the impedance matching of the MIMO antenna, and the isolation degree at the resonant frequencies of 3.9 GHz and 4.3 GHz can reach above 16.2 dB.

[0018] (3) The envelope correlation coefficient between each antenna unit of the present invention is much smaller than 0.3, and has good diversity performance.

[0019] (4) The antenna of the present invention has the advantages of simple structure, easy processing, low cost and high channel capacity, and has high practical value in mobile terminal applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] Figure 2 It is a structural diagram of the slot antenna unit of the present invention.

[0022] Figure 3 It is a diagram of the dielectric plate grounding structure of the present invention.

[0023] Figure 4 It is a comparison diagram of the S11 parameter simulation and actual measurement of the antennas Ant1, Ant2 and Ant3 of the present invention.

[0024] FIG. 5( a ) is a simulation diagram of the antenna unit isolation of the present invention.

[0025] FIG5( b ) is a measured diagram of the antenna unit isolation of the present invention.

[0026] FIG6( a ) is a comparison diagram of the simulated and measured radiation directions of the antenna Ant1 of the present invention.

[0027] FIG6( b ) is a comparison diagram of the simulated and measured radiation directions of the antenna Ant2 of the present invention.

[0028] FIG6( c ) is a comparison diagram of the simulated and measured radiation directions of the antenna Ant3 of the present invention.

[0029] Figure 7 It is a comparison diagram of the simulated and measured radiation efficiencies of the antennas Ant1, Ant2 and Ant3 of the present invention.

[0030] Figure 8 It is a diagram of the calculation results of the correlation coefficient between antenna units of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further explained below by specific examples, but the present invention is not limited to these specific embodiments. Those skilled in the art should appreciate that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0032] like Figure 1As shown, a broadband, high-isolation six-unit MIMO slot antenna for 5G mobile terminals includes a dielectric substrate 1, a floor 3 is provided at the bottom of the dielectric substrate, and 10 grooves of specific shapes are opened on the surface of the floor 3. The length of the entire dielectric substrate is 150mm, the width is 75mm, and the height is 0.8mm. Six "L"-shaped microstrip lines 2 are loaded on the top of the dielectric substrate 1, and the three on the left are mirror-symmetrical with the three on the right. The "L"-shaped microstrip line 2 is composed of two "I"-shaped branches 4 and 5 that are alternately connected to each other vertically. The microstrip line is provided with a feeding point 6 for coupling feeding. At the bottom of the floor 3, a "T"-shaped slot 7 is opened for impedance matching of the antenna. As shown Figure 3 As shown, a "T"-shaped slot 10 is cut in the middle of the antenna units on the same side to reduce the coupling degree between the antennas. The present invention has a simple structure, a small requirement for the antenna clearance area, and a high radiation efficiency.

[0033] The microstrip line 2 is composed of 4 and 5, 4 is distributed along a direction parallel to the short side of the dielectric substrate; 5 is vertically connected to 4 and distributed along a direction perpendicular to the edge of the dielectric substrate.

[0034] Each "T"-shaped slot 7 is composed of a "U"-shaped slot 8 and an "I"-shaped slot 9, and is arranged under each microstrip line 2. The "U"-shaped slot has two protruding parts, and the "I"-shaped slot 9 is embedded in the middle of the "U"-shaped slot 8 and connected to the edge of the floor.

[0035] The “T”-shaped groove 10 consists of a groove 11 and a groove 12. The groove 11 is opened along the long side of the floor, and the groove 12 is vertically embedded in the middle of the groove 11 and connected to the short side edge of the floor.

[0036] In this embodiment, the microstrip line 4 has a length of 4.5 mm and a width of 2.5 mm, and is located on the top of the dielectric substrate; the microstrip line 5 has a length of 10.9 mm and a width of 2.5 mm, and is located on the top of the dielectric substrate.

[0037] The length of the "U"-shaped groove 8 is 6 mm, the width is 4.5 mm, the length of the protruding part is 1 mm, the width is 0.5 mm; the length of the "I"-shaped groove 9 is 4.4 mm, the width is 1 mm.

[0038] The length of the groove 11 is 11.5 mm and the width is 2 mm; the length of the groove 12 is 7.5 mm and the width is 2 mm.

[0039] The distance between the center of the "T"-shaped groove 7 and the center of the "T"-shaped groove 10 opened on the floor is 30 mm.

[0040] The antenna structure described in this embodiment is etched on a dielectric substrate 1. The dielectric substrate is made of FR4, has a dielectric constant of 4.4, and a height of 0.8 mm. One side is tinned according to the structure of a microstrip line; the other side is tinned according to the structure of a floor, serving as an infinite ground plane.

[0041] The specific implementation is as follows:

[0042] This embodiment adopts circuit board etching technology to etch a PCB board with a thickness of 0.8 mm on one side. Figure 3 The ground plane structure of the entire dielectric substrate is 150mm×75mm×0.8mm in size. The feeding point position is based on the non-tin-covered punching process. At the same time, the etching technology is also used to etch out the other side of the 0.8mm thick FR4 substrate. Figure 1 Microstrip line structure.

[0043] The MIMO system was simulated using the electromagnetic simulation software ANSYS Electronics Desktop 2018.2. After the simulation and debugging were completed, the physical object was manufactured and tested. The results of the S parameters are shown in the attached figure. Figure 4 As shown, it can be seen that both the simulation and test results can cover 3.3GHz-5.1GHz. Since the designed antenna array is mirror-symmetrical, all measured units can cover 3.3GHz-5.1GHz, meeting the requirements of 5G mobile communications. As can be seen from the figure, the measured antenna resonance point has shifted. This is because the half-hole process is used between the ground point and the feeding point of the antenna, which causes the microstrip line to be widened, resulting in a shift in the resonance point.

[0044] As shown in Figures 5(a) and (b), the isolation between antenna units obtained by simulation and measurement is both above 16.2 dB, indicating that the degree of coupling between antenna units is very small.

[0045] As shown in Figure 6, there are two-dimensional radiation direction comparison diagrams of the XOZ plane and YOZ plane of Ant1, Ant2 and Ant3 at the resonance points of 3.9GHz and 4.3GHz, respectively. It can be seen from the figure that omnidirectional radiation can be basically achieved at the two frequency points. The reason for the difference between the actual measurement and the simulation may be due to the errors in the physical production and the problems of manual measurement operation.

[0046] Attached Figure 7 The figure shows a comparison of the simulated and measured radiation efficiencies of Ant1, Ant2 and Ant3. As shown in the figure, the measured antenna efficiencies are all above 50% in the 3.3 GHz-5.1 GHz (5G) frequency band.

[0047] Attached Figure 8 The envelope correlation coefficient curve of the antenna unit calculated by formula (1) is:

[0048]

[0049] The smaller the envelope correlation coefficient between antenna units, the less influence the antenna units will have on each other when working independently, and the channel capacity will not be affected. Figure 8 As shown, the envelope correlation coefficient between antenna units is less than 0.02 in the 3.3GHz-5.1GHz (5G) frequency band, so the MIMO system has high independence and high practical value.

Claims

1. A broadband, high-isolation six-element MIMO slot antenna for a 5G mobile terminal, comprising a dielectric substrate, characterized in that: A metal floor is provided at the bottom of the rectangular dielectric substrate, and M "T"-shaped grooves and N "T"-shaped grooves are symmetrically cut on the surface of the floor; N antenna units are evenly arranged on the top of the dielectric substrate, and each antenna unit is composed of two microstrip lines and a "T"-shaped groove corresponding to the floor; the microstrip line is composed of metal material and loaded on the top of the dielectric substrate; The antenna units on both sides of the top of the dielectric substrate are distributed in a mirror-symmetrical manner, and the distance between the antenna units on each side is the same; Microstrip lines are used for antenna feeding, "T"-shaped slots are used for antenna impedance matching, and "T"-shaped slots are used to reduce coupling between antennas; The rectangular dielectric substrate is made of FR4, has a dielectric constant of 4.4, is 150 mm long, 75 mm wide, and 0.8 mm high; the side with the printed microstrip line is the front side of the dielectric substrate, and the side with the printed metal floor is the back side of the dielectric substrate; The "L"-shaped microstrip line is composed of two "I"-shaped branches connected alternately and perpendicularly to each other. The microstrip line is provided with a feeding point for coupling feeding, which is loaded above the "T"-shaped slot; the length of the first microstrip line close to the edge of the substrate is 10.9 mm, distributed in a direction perpendicular to the edge of the dielectric substrate, and the length of the other microstrip line is 4 mm. The width of the microstrip lines is 2.5 mm. The "T"-shaped slot is composed of two slots: one slot is "U"-shaped, 6mm long and 4.5mm wide, and there are two protruding slots with a length of 1mm and a width of 0.5mm; the other is an "I"-shaped open branch embedded in the middle of the "U"-shaped slot, connected to the edge of the metal floor, with a length of 4.4mm and a width of 1mm; the antenna unit along one side of the "T"-shaped slot is symmetrically arranged, and it consists of two parts: the slot along the long side of the floor is 11.5mm long and 2mm wide; The groove along the short side of the floor is 7.5mm long and 2mm wide; The center of the "T"-shaped groove is 30 mm away from the center of the adjacent "T"-shaped groove; The back side of the dielectric substrate is tin-coated according to the structure of a floor, and the front side of the dielectric substrate is tin-coated according to the structure of a microstrip line.

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