A three-mode self-decoupled eight-port MIMO antenna array for 5G mobile terminals

Abstract

This invention discloses a three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals, belonging to the field of mobile communication antenna technology. The antenna array includes a dielectric substrate, a metal ground layer, and a vertical side plate simulating a mobile phone frame. Four antenna pairs are symmetrically arranged on the inner and outer surfaces of the side plate to form an eight-port MIMO structure. Each antenna pair includes an inner I-shaped main radiating patch, an outer rectangular parasitic patch, and a T-shaped slot in the center of the ground layer. These three elements respectively excite three self-decoupling resonant modes, which are then matched with an L-shaped impedance matching network to achieve impedance matching. This invention requires no external decoupling structure, can cover both the 3.4-3.6GHz and 3.8-5.6GHz dual-band frequencies, has high antenna element isolation, an envelope correlation coefficient below 0.08, excellent radiation efficiency, and a compact, highly integrated overall structure, meeting the requirements of thinner, lighter, and higher-speed communication in 5G mobile terminals.

Description

Technical Field

[0001] This invention relates to the field of mobile communication antenna technology, and in particular to a three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals. Background Technology

[0002] With the commercial deployment of 5G communication technology, smartphones need to support more communication frequency bands (such as n77, n78, and n79 in 5G NR) and have higher data transmission rates and reliability. MIMO technology, by deploying multiple antennas at the transmitter and receiver, and utilizing spatial multiplexing and diversity gain, can significantly improve system capacity and spectral efficiency, and has become one of the key technologies of 5G systems.

[0003] Integrating multiple antenna elements within the extremely limited space of a smartphone introduces strong mutual coupling effects. This mutual coupling leads to reduced antenna efficiency, pattern distortion, and increased channel correlation, thus severely degrading the performance of the MIMO system. Therefore, achieving high isolation (i.e., decoupling) between multiple antennas within a compact space has become a core challenge in 5G mobile phone antenna design.

[0004] Existing decoupling technologies are mainly divided into two categories. External decoupling technologies include introducing neutralization lines, parasitic elements, defective ground structures, or filter networks between antenna elements. While these methods can effectively improve isolation, they usually occupy additional layout space and increase design complexity, which contradicts the trend of high integration and thinness in mobile terminals. Self-decoupling technologies utilize the orthogonality of characteristic modes, polarization orthogonality, or the principle of mode cancellation to enable antenna elements or their shared structures to generate mutually canceling field modes, thereby achieving natural isolation. These methods have greater integration advantages. However, existing self-decoupling designs mostly focus on achieving decoupling within a single narrowband, making it difficult to cover the wide frequency bands or multiple discrete frequency bands required by 5G. Summary of the Invention

[0005] The purpose of this invention is to provide a three-mode self-decoupled eight-port MIMO antenna array for 5G mobile terminals, which can achieve multi-band coverage and high-performance self-decoupling in the compact space of a smartphone, without relying on an external decoupling structure, thus providing a high-performance, highly integrated MIMO antenna solution for 5G smart terminals.

[0006] To achieve the above objectives, the present invention provides a three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals, comprising a dielectric substrate, the back of which is covered with a metal ground layer; vertical side plates of the same material are disposed on both sides of the dielectric substrate, the vertical side plates being used to simulate the structure of a mobile phone frame; four antenna pairs are symmetrically distributed on the inner and outer surfaces of the vertical side plates, and the four antenna pairs together constitute an eight-port MIMO antenna structure. Each of the antenna pairs includes: an I-shaped main radiating patch located inside the vertical side plate, a rectangular parasitic patch located outside the vertical side plate, a T-shaped slot etched in the center of the metal grounding layer, a microstrip feed line, and a coaxial feed interface. Each antenna pair includes two microstrip feed lines, which are respectively connected to the I-shaped main radiating patch and impedance matching is achieved through an L-shaped impedance matching network; the coaxial feed interface is used to connect to external radio frequency circuits. The I-shaped main radiating patch, the rectangular parasitic patch, and the T-shaped slot respectively excite three self-decoupling resonant modes, enabling the antenna array to achieve dual-band self-decoupling operation.

[0007] Preferably, the dielectric substrate is made of Flame Retardant Grade 4 material with a dielectric constant of 4.4 and a loss tangent of 0.02.

[0008] Preferably, the I-shaped main radiating patch includes a long arm, a short arm, two symmetrical short rectangular microstrip lines, and a long rectangular microstrip line connecting the long arm and the short arm; the I-shaped main radiating patch is used to excite the first self-decoupling resonant mode.

[0009] Preferably, the rectangular parasitic patch is composed of a pair of parallel long rectangular microstrip lines and a short rectangular microstrip line of different sizes; the rectangular parasitic patch is used to excite the second self-decoupling resonant mode.

[0010] Preferably, the T-shaped gap consists of a wide gap and a narrow gap; the T-shaped gap is used to excite the third self-decoupling resonant mode.

[0011] Preferably, the L-shaped impedance matching network includes: a first long microstrip line, a second square microstrip line, a third square microstrip line, a parallel inductor, a series capacitor, and a connecting microstrip line connected to the third square microstrip line; the L-shaped impedance matching network is used to optimize the antenna impedance matching characteristics.

[0012] Preferably, the back side of the dielectric substrate is tin-plated with a metal ground layer structure, and the front side and vertical side plate of the dielectric substrate are tin-plated with a microstrip line structure.

[0013] Therefore, the present invention adopts the above-mentioned three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals. The three-mode self-decoupling structure can cover the mainstream 5G communication frequency bands and achieve high isolation between antenna elements without the need for an external decoupling structure. The overall antenna structure is compact and highly integrated, which is suitable for the lightweight design of mobile terminals and meets the eight-port MIMO communication requirements of 5G mobile terminals.

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals according to the present invention. Figure 2 This is a schematic diagram of the antenna pair of the present invention in the vertical side plate; Figure 3 This is a schematic diagram of the L-shaped impedance matching network structure of the present invention; Figure 4 This is a simulation diagram of the antenna array reflection coefficient of the present invention; Figure 5 This is a simulation diagram of the transmission coefficient of the antenna array of the present invention; Figure 6 This is a diagram showing the envelope correlation coefficients of the antenna array of the present invention. Figure 7 This is a diagram showing the radiation efficiency of the antenna array of the present invention; Figure 8 This is a two-dimensional radiation pattern of the antenna array of the present invention.

[0016] Figure Labels 1. Dielectric substrate; 2. Vertical side plate; 3. Metal ground layer; 4. Antenna pair; 5. Long arm; 6. Short arm; 7. Symmetrical short rectangular microstrip line; 8. Long rectangular microstrip line; 9. Long rectangular microstrip line; 10. Short rectangular microstrip line; 11. First long microstrip line; 12. Parallel inductor; 13. Second square microstrip line; 14. Series capacitor; 15. Third square microstrip line; 16. Connecting microstrip line; 17. Wide slot; 18. Narrow slot. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0019] Example 1 This embodiment discloses a three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals, the structure of which is as follows: Figure 1 , Figure 2 , Figure 3 As shown, the core includes a dielectric substrate 1, which is made of Flame Retardant Grade 4 material with a dielectric constant of 4.4, a loss tangent of 0.02, a thickness of 0.8 mm, a length of 150 mm, and a width of 75 mm. A metal ground layer 3 is covered on the back of the dielectric substrate 1, with a length of 150 mm and a width of 74 mm. Vertical side plates 2, made of the same material, are provided on both sides of the dielectric substrate 1. These vertical side plates 2 are used to simulate the structure of a mobile phone frame, with a length of 150 mm, a width of 7 mm, and a height of 0.8 mm.

[0020] Four antenna pairs 4 are symmetrically distributed on the inner and outer surfaces of the vertical side plate 2. The two antenna pairs 4 on the same long side are spaced 38mm apart, together forming an eight-port MIMO antenna structure.

[0021] The back of the dielectric substrate 1 is tin-coated with a metal ground layer 3 structure, and the front and vertical side plates 2 of the dielectric substrate 1 are tin-coated with a microstrip line structure, thus completing the basic fabrication of the conductive structure.

[0022] Each of the antenna pairs 4 includes an I-shaped main radiating patch, a rectangular parasitic patch, a T-shaped slot, a microstrip feed line, and a coaxial feed interface. Each structure excites three self-decoupling resonant modes to achieve dual-band self-decoupling operation. The I-shaped main radiating patch is located inside the vertical side plate 2 and consists of a long arm 5, a short arm 6, two symmetrical short rectangular microstrip lines 7, and a long rectangular microstrip line 8 connecting the long arm and the short arm. It is used to excite the first self-decoupling resonant mode.

[0023] A rectangular parasitic patch is located on the outside of the vertical side plate 2. It consists of a pair of parallel long rectangular microstrip lines 9 and short rectangular microstrip lines 10 of different sizes, and is used to excite the second self-decoupling resonant mode.

[0024] A T-shaped slot is etched at the center of the metal ground layer 3, consisting of a wide slot 17 and a narrow slot 18, and is used to excite the third self-decoupling resonant mode.

[0025] Each antenna pair 4 includes two microstrip feed lines, which are respectively connected to the I-shaped main radiating patch and impedance matched through an L-shaped impedance matching network to optimize the antenna impedance matching characteristics; the coaxial feed interface is used to connect external RF circuits. The L-shaped impedance matching network includes: a first long microstrip line 11, a second square microstrip line 13, a third square microstrip line 15, a parallel inductor 12, a series capacitor 14, and a connecting microstrip line 16 connected to the third square microstrip line 15.

[0026] This embodiment further provides the precise dimensions of each structure, as detailed below: I-shaped main radiating patch: long arm 5 is 28mm long and 2.5mm wide; short arm 6 is 21mm long and 1.5mm wide; symmetrical short rectangular microstrip line 7 is 1.5mm long and 1.2mm wide; long rectangular microstrip line 8 is 2mm long and 1.5mm wide.

[0027] Rectangular parasitic patches: Long rectangular microstrip line 9 is 20mm long and 2.5mm wide; short rectangular microstrip line 10 is 18mm long and 1.5mm wide.

[0028] T-shaped gaps: Wide gap 17 is 18mm long and 2.5mm wide; Narrow gap 18 is 7.5mm long and 1.2mm wide.

[0029] L-shaped impedance matching network: The first long microstrip line 11 is 2.5mm long and 1.5mm wide; the second square microstrip line 13 and the third square microstrip line 15 are both 1.5mm long and 1.5mm wide, and the second square microstrip line 13 is provided with a grounded metal cylinder with a radius of 0.5mm; the parallel inductor 12 is 3nH, 1mm long and 0.5mm wide; the series capacitor 14 is 0.8pF, 1mm long and 0.5mm wide; the connecting microstrip line 16 is 1.5mm long and 1mm wide, and a feed point is provided at the end.

[0030] This embodiment uses PCB etching technology to fabricate the antenna. The metal ground layer 3 is etched on the back of the dielectric substrate 1, and the microstrip line radiation structure is etched on the front and the inner and outer sides of the vertical side plate 2. The feed point is made using a non-tin-covered hole drilling process, and the ground point and feed point are processed using a half-hole process to complete the antenna physical fabrication.

[0031] Based on the above settings, this embodiment was verified using electromagnetic simulation software. The electromagnetic simulation software that can be used is ANSYS Electronics Desktop 2021.R1, and the specific results are as follows.

[0032] The results of the antenna reflection coefficient are attached. Figure 4 As shown, due to the symmetry of the array structure, only port 1 and port 2 are analyzed as examples. It can be seen that the simulation results fully cover the 3.4-3.6 GHz and 3.8-5.6 GHz frequency bands.

[0033] Figure 5 The image shows the antenna transmission coefficient simulation. The antenna array meets the isolation requirements within the operating frequency band.

[0034] Figure 6 Here is a graph showing the envelope correlation coefficient of the antenna element calculated using formula (1): (1); The smaller the envelope correlation coefficient between antenna elements, the less the antenna elements are affected by each other when operating independently, and the channel capacity will not be affected. For example... Figure 6 As shown, the simulated ECC values ​​are all below 0.08 across all operating frequency bands, indicating good spatial diversity performance.

[0035] Figure 7 The antenna radiation efficiency diagram shown indicates that the antenna efficiency of port 1 in the dual-band is better than 71% and 68%, respectively; the antenna efficiency of port 2 in the dual-band is better than 69% and 64%, respectively.

[0036] Figure 8 The figure shows a two-dimensional radiation pattern. As can be seen from the figure, the designed antenna has good radiation characteristics and exhibits pattern diversity. It also verifies the feasibility of self-decoupling of the structure and that it can meet communication requirements.

[0037] Therefore, the present invention adopts the above-mentioned three-mode self-decoupled eight-port MIMO antenna array for 5G mobile terminals to achieve dual-band coverage of 3.4-3.6GHz and 3.8-5.6GHz; it can achieve high isolation without external decoupling structure, and the eight-port MIMO architecture with low envelope correlation coefficient significantly improves communication capacity and efficiency; it has a compact structure and high integration, which is in line with the trend of mobile terminals becoming thinner and lighter, with excellent radiation efficiency and excellent impedance matching, meeting the high-speed communication requirements of 5G mobile terminals.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals, characterized in that, The substrate includes a dielectric substrate (1), the back of which is covered with a metal ground layer (3); vertical side plates (2) of the same material are provided on both sides of the dielectric substrate (1), the vertical side plates (2) are used to simulate the frame structure of a mobile phone; four antenna pairs (4) are symmetrically distributed on the inner and outer surfaces of the vertical side plates (2), and the four antenna pairs (4) together constitute an eight-port MIMO antenna structure. Each of the antenna pairs (4) includes: an I-shaped main radiating patch located inside the vertical side plate (2), a rectangular parasitic patch located outside the vertical side plate (2), a T-shaped slot etched in the center of the metal grounding layer (3), a microstrip feed line, and a coaxial feed interface. Each antenna pair (4) contains two microstrip feed lines, which are respectively connected to the I-shaped main radiating patch and impedance matching is achieved through an L-shaped impedance matching network; the coaxial feed interface is used to connect to external radio frequency circuits; The I-shaped main radiating patch, the rectangular parasitic patch, and the T-shaped slot respectively excite three self-decoupling resonant modes, enabling the antenna array to achieve dual-band self-decoupling operation.

2. The three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals according to claim 1, characterized in that, The dielectric substrate (1) is made of Flame Retardant Grade 4 material with a dielectric constant of 4.4 and a loss tangent of 0.

02.

3. The three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals according to claim 1, characterized in that, The I-shaped main radiating patch includes a long arm (5), a short arm (6), two symmetrical short rectangular microstrip lines (7), and a long rectangular microstrip line (8) connecting the long arm and the short arm; the I-shaped main radiating patch is used to excite the first self-decoupling resonant mode.

4. The three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals according to claim 1, characterized in that, The rectangular parasitic patch consists of a pair of parallel long rectangular microstrip lines (9) and short rectangular microstrip lines (10) of different sizes; the rectangular parasitic patch is used to excite the second self-decoupling resonant mode.

5. The three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals according to claim 1, characterized in that, The T-shaped gap consists of a wide gap (17) and a narrow gap (18); the T-shaped gap is used to excite the third self-decoupling resonant mode.

6. The three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals according to claim 1, characterized in that, The L-shaped impedance matching network includes: a first long microstrip line (11), a second square microstrip line (13), a third square microstrip line (15), a parallel inductor (12), a series capacitor (14), and a connecting microstrip line (16) connected to the third square microstrip line (15); the L-shaped impedance matching network is used to optimize the antenna impedance matching characteristics.

7. The three-mode self-decoupling eight-port MIMO antenna array for 5G mobile terminals according to claim 1, characterized in that, The back of the dielectric substrate (1) is tin-plated with a metal ground layer (3) structure, and the front and vertical side plates (2) of the dielectric substrate (1) are tin-plated with a microstrip line structure.

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