Dual-frequency eight-unit multiple-input multiple-output (MIMO) antenna for 5G mobile phoneTechnical Field
The invention relates to the technical field of 5G mobile communication, in particular to a double-frequency eight-unit multiple-input multiple-output (MIMO) antenna for 5G.
Background
At present, mobile communication enters the 5G era, and compared with 4G, 5G can provide higher speed, lower time delay, more connection numbers, faster moving speed and higher security. As known from communication system theory, the larger the channel capacity is, the higher the data transmission rate is, and the Multiple Input Multiple Output (MIMO) technology can well improve the channel capacity and the transmission rate. It has been found through research that the channel capacity increases exponentially with the number of transmit and receive antennas in a multipath environment.
A great deal of research is being conducted on MIMO antennas with broadband in 5G communication systems at home and abroad. Most of the research and design 5G antennas can only cover part of the frequency bands, and the single and narrow frequency bands of the antennas cause inconvenient communication, so how to realize the multi-frequency of the antennas is an important problem.
In 11 months 2017, the China industry and informatization department announces that the frequency bands of 3.3GHz-3.6GHz and 4.8GHz-5.0GHz are defined as 5G mobile communication frequency bands. Therefore, in order to meet the 5G communication standard, it is important to design a dual-band MIMO antenna capable of covering 3.5GHz and 4.9 GHz.
The invention aims to provide a 5G dual-frequency eight-unit multiple-input multiple-output (MIMO) antenna, which has the advantages of simple structure, wide frequency band and good isolation compared with the traditional antenna.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
A dual-frequency eight-unit multiple-input multiple-output (MIMO) antenna for a 5G mobile phone comprises a cuboid dielectric substrate and is characterized in that a metal floor is arranged at the bottom of the cuboid dielectric substrate, M similar T-shaped grooves and K convex grooves are symmetrically formed in the surface of the floor, N U-shaped antenna units are uniformly arranged at the top of the dielectric substrate, each antenna unit consists of three microstrip lines, each microstrip line consists of a metal material and is loaded at the top of the dielectric substrate, feed points are arranged on the microstrip line structure, the antenna units at two sides of the top of the dielectric substrate are distributed in a mirror symmetry mode, and the distances among the antenna units at each side are the same.
Preferably, the cuboid is used as a dielectric substrate, the microstrip line is used for feeding the antenna, and the M T-shaped slots and the K convex slots are used for improving the impedance matching performance of the antenna.
Preferably, the cuboid dielectric substrate is made of FR4, has a dielectric constant of 4.4, a length of 150mm, a width of 75mm and a height of 0.4mm, one surface of the printed metal microstrip line is the front surface of the dielectric substrate, and one surface of the printed metal floor is the back surface of the dielectric substrate.
Preferably, the microstrip lines are U-shaped and uniformly and symmetrically distributed along the front surface of the substrate and are loaded above two parallel T-shaped grooves and convex grooves, the first microstrip line has a length of 10mm and a width of 0.75mm and is distributed along the direction parallel to the long side of the medium substrate, the second microstrip line has a length of 3.5mm and a width of 0.6mm and is vertically connected with the first microstrip line and is distributed along the direction parallel to the short side of the medium substrate, and the third microstrip line is vertically connected with the second microstrip line and is distributed along the direction parallel to the long side of the medium substrate and has a length of 2mm and a width of 0.4mm.
Preferably, the T-shaped groove is formed by two grooves, wherein one groove is distributed along the long side of the medium substrate in an I shape, the length is 18mm, the width is 2.4mm, the other groove is square and is connected to the middle left side of the long side of the I-shaped groove, the length and the width are both 0.45mm, and the groove is connected with the edge of the metal floor.
Preferably, the convex grooves and the T-shaped grooves are distributed in parallel and consist of two I-shaped grooves, wherein one I-shaped groove is 18mm in length and 2.3mm in width, the other I-shaped groove is connected to the inner side of the middle of the first groove and is in a convex shape, the length of the other I-shaped groove is 4mm, the width of the other I-shaped groove is 0.8mm, and the T-shaped grooves and the convex grooves are symmetrically distributed along the metal floor.
Preferably, the rightmost side of the T-shaped like groove is spaced from the leftmost side of the adjacent convex groove by 4.5mm.
Preferably, the back surface of the dielectric substrate is tin-coated according to the structure of the floor, and the front surface of the dielectric substrate is tin-coated according to the microstrip line structure.
Compared with the prior art, the invention has the following beneficial effects:
(1) The antenna of the invention is fed from the bottom by a 50 ohm coaxial line and is used for covering the double frequency bands of 3.3GHz-3.6GHz and 4.8GHz-5.0GHz of 5G by an antenna patch.
(2) The antenna can cover a target frequency band, the isolation between ports is better than 13.6dB, the envelope correlation coefficient is smaller than 0.08, and the antenna has good diversity performance.
(3) The antenna has the advantages of simple structure, easy processing, low cost and high channel capacity, and has high practical value in mobile terminal application.
Drawings
Figure 1 is a schematic diagram of the system architecture of the present invention.
Fig. 2 is a block diagram of an antenna element of the present invention.
Fig. 3 is a view showing a structure of the dielectric plate grounding according to the present invention.
Fig. 4 is a graph of simulated and measured S-parameters for antennas Ant1, ant2, ant3 and Ant4 of the present invention.
Fig. 5 is a comparison of simulation and actual measurement of the isolation of the antenna element of the present invention.
Fig. 6 is a simulated and measured radiation pattern contrast plot for the antennas Ant1, ant2, ant3 and Ant4 of the present invention at 3.5 GHz.
Fig. 7 is a simulated and measured radiation pattern contrast plot for the antennas Ant1, ant2, ant3 and Ant4 of the present invention at 4.9 GHz.
Fig. 8 is a graph showing the result of calculating the correlation coefficient between antenna elements according to the present invention.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the invention thereto. It will be appreciated by those skilled in the art that the invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
As shown in fig. 1, a dual-frequency eight-unit multiple-input multiple-output (MIMO) antenna for 5G includes a dielectric substrate 1, a metal floor 3 is disposed at the bottom of the dielectric substrate, and 16 slots with specific shapes are formed on the surface of the floor 3. The length of the whole dielectric substrate is 150mm, the width is 75mm, and the height is 0.4mm. The top of the medium substrate 1 is loaded with 8U-shaped microstrip lines 2, the left 4 and the right 4 are in mirror symmetry, the U-shaped microstrip lines 2 are composed of 3 microstrip lines 4,5 and 6 which are mutually perpendicular and alternately connected, and the microstrip lines are provided with feed points 7 for feeding. At the bottom of the floor 3, T-like grooves 8 and convex grooves 9 are cut for improving the impedance matching performance of the antenna. The invention has simple structure, easy processing, low cost and high channel capacity.
The microstrip line 2 is composed of 4, 5 and 6, wherein the 4 is distributed along the direction parallel to the long side of the dielectric substrate, and the 5 is vertically connected with the 4 and is distributed along the direction parallel to the short side of the dielectric substrate. And 6 and 5 are vertically connected and distributed along the direction parallel to the long side of the dielectric substrate.
Each T-shaped groove 8 is formed by parallel connection of a square groove 10 and an I-shaped groove 11, and is arranged below each microstrip line 2.
The convex groove 9 is formed by connecting an I-shaped groove 12 and an I-shaped groove 13 in parallel and is arranged below each microstrip line 2.
In this embodiment, the microstrip line 4 has a length of 10mm and a width of 0.75mm and is located at the top of the dielectric substrate, the microstrip line 5 has a length of 3.5mm and a width of 0.6mm and is located at the top of the dielectric substrate, and the microstrip line 6 has a length of 2mm and a width of 0.4mm and is located at the top of the dielectric substrate.
The length of the I-shaped groove 11 in the T-shaped groove 8 is 18mm, the width is 2.4mm, and the length and the width of the square groove 10 are 0.45mm;
the length of the I-shaped groove 13 in the convex groove 9 is 18mm, the width is 2.3mm, and the length of the I-shaped groove 12 of the protruding part is 4mm, and the width is 0.8mm.
The spacing between the rightmost side of the T-shaped groove and the leftmost side of the adjacent convex groove is 4.5mm.
The antenna structure described in this example is etched on a dielectric substrate 1, which is made of FR4, has a dielectric constant of 4.4 and a height of 0.4mm, and is tin-plated according to the microstrip line structure on one side and a floor structure on the other side, as an infinite ground plane.
The specific implementation is as follows:
in this embodiment, the circuit board etching technology is adopted to etch the ground plane structure of fig. 3 on one side of a PCB board with a thickness of 0.4mm, the size of the whole dielectric substrate is 150mm×75mm×0.4mm, and the etching technology is also adopted to etch the microstrip line structure of fig. 1 on the other side of an FR4 substrate with a thickness of 0.4 mm.
And simulating the MIMO system by using electromagnetic simulation software ANSYS Electronics Desktop 2018.2, and performing physical manufacturing and testing after simulation debugging is completed. The results of the S parameters are shown in the figure 4, and it can be seen that the two frequency bands of 3.3GHz-3.6GHz and 4.8GHz-5.0GHz of 5G can be covered both in simulation and test results. Because the designed antenna array is mirror symmetry, all units in actual measurement can cover two frequency bands of 3.3GHz-3.6GHz and 4.8GHz-5.0GHz of 5G, thereby meeting the requirement of 5G mobile communication. As can be seen from the figure, the measured antenna resonance point is shifted, because the half-hole process is used between the ground point and the feed point of the antenna, which results in the microstrip line being widened by some width, which results in shifting the resonance point.
As shown in fig. 5, the isolation between the antenna units obtained by simulation and actual measurement is better than 13.6dB, which indicates that the coupling degree between the antenna units is small.
As shown in fig. 6 and 7, simulation and actual measurement two-dimensional radiation direction comparison diagrams of the E-plane and the H-plane of Ant1, ant2, ant3 and Ant4 at resonance points 3.5 GHz and 4.9GHz are shown respectively. As can be seen from the figure, the designed antenna has good radiation characteristics at two frequency points, and can meet the communication requirements. The reason for the difference between actual measurement and simulation may be the problem of errors in the manufacture of the object and the manual measurement operation.
The smaller the envelope correlation coefficient between the antenna elements, the smaller the influence of the antenna elements on each other when independently operated, and the channel capacity will not be affected. As shown in figure 8, the correlation coefficient of the envelope between the antenna units is smaller than 0.08 in the frequency bands of 3.3GHz-3.6GHz and 4.8GHz-5.0GHz, so that the MIMO system has high independence and high practical value.