Miniaturized ultra-wideband 5G MIMO mobile phone antenna for metal frame

Abstract

The invention provides a miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame, and belongs to the technical field of 5G mobile phone terminal antenna structural design, the antenna adopts a hollow rectangular box-shaped dielectric substrate, the outer surface of the hollow rectangular box-shaped dielectric substrate is fully covered with metal to form an all-metal outer frame, an antenna system comprises four antenna pairs arranged along the long sides, and the antenna pairs are arranged along the long sides of the hollow rectangular box-shaped dielectric substrate. Each antenna pair forms a three-dimensional continuous slot structure through a side wall radiation slot etched on the metal frame and a floor coupling slot etched on the metal floor, signal radiation is realized by combining a pair of radiator microstrip lines sharing the slot, decoupling is realized by bridging a lumped capacitor at the middle part of the floor coupling slot, and the antenna pair is used for antenna coupling. According to the invention, a single antenna pair is only 20mm * 7mm in size, 3.29-5.30 GHz in working frequency band coverage, 47% in relative bandwidth, superior to-11dB in port isolation and about 85% in efficiency, and particularly, the problem of compatibility of all-metal materials and signal transmission is solved.

Description

Technical Field

[0001] This invention relates to the field of 5G mobile terminal antenna structure design technology, and more specifically, to a miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame. Background Technology

[0002] With the development of 5G communication technology, the demand for multiple-input multiple-output (MIMO) antenna systems in smartphones is increasing. To meet the aesthetic pursuit of full-screen design, the use of all-metal frame structures in mobile phones is becoming increasingly popular, but this brings huge challenges to antenna design because there are compatibility issues between all-metal materials and signal transmission.

[0003] There are already some MIMO antenna design solutions for mobile phones with metal frames in the existing technology. For example, reference [1] [L. Sun, Y. Li, Z. Zhang and H. Wang, "Self-Decoupled MIMO Antenna Pair With Shared Radiator for 5G Smartphones," in IEEE Transactions on Antennas and Propagation, vol. 68, no. 5, pp. 3423-3432, May 2020.] proposes a self-decoupled MIMO antenna pair with a size of 30mm × 7.5mm, but its operating bandwidth (3.3-4.2 GHz) is relatively narrow and fails to fully cover the 5G N79 frequency band; reference [2] [L. Sun, Y. Li, Z. Zhang and Z. Feng, "Wideband 5G MIMO Antenna WithIntegrated Orthogonal-Mode Dual-Antenna Pairs for Metal-Rimmed Smartphones," in IEEE Transactions on Antennas and Propagation, vol. 68, no. 4, pp.] Although it achieved wideband coverage of 3.3-5.0 GHz, its antenna pair size was as large as 40mm×7.5mm, occupying too much space in the mobile phone; Reference [3] [L. Sun, Y. Li and Z. Zhang, "WidebandIntegrated Quad-Element MIMO Antennas Based on Complementary Antenna Pairsfor 5G Smartphones," in IEEE Transactions on Antennas and Propagation, vol.69, no. 8, pp. 4466-4474, Aug. 2021.] reduced the antenna pair size to 24mm×6mm, but its port isolation (-10dB) and radiation efficiency (75%) both need to be improved.

[0004] How to invent a miniaturized ultra-wideband 5G MIMO mobile phone antenna for metal frames to solve these problems has become an urgent issue for those skilled in the art. Summary of the Invention

[0005] To overcome the above deficiencies, the present invention provides a miniaturized ultra-wideband 5G MIMO mobile phone antenna for metal frames, aiming to solve the problems mentioned in the background.

[0006] This invention is implemented as follows: This invention provides a miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame, comprising: The dielectric substrate is a hollow rectangular box-shaped structure, consisting of a base plate and sidewalls that surround its perimeter. A metal floor covers the lower surface of the dielectric substrate; A metal frame surrounds and is fixed to the periphery of the dielectric substrate, together with the metal floor, forming an all-metal outer frame; Multiple antenna pairs are disposed on the long side of the dielectric substrate; wherein, the antenna pairs include: A pair of sidewall radial grooves formed on the long side of the metal frame; A floor coupling groove formed on the metal floor and connected to the pair of sidewall radiation grooves; A pair of radiating microstrip lines printed on the inner surface of the dielectric substrate are arranged in parallel and symmetrically above the ground plane coupling groove. A decoupling structure is connected across the middle of the floor coupling groove; The feed network, connected to the pair of radiating microstrip lines respectively, is used to provide two independent feed ports for the antenna pair.

[0007] Preferably, the power supply network includes two power supply ports, each connected to a corresponding radiator microstrip line via a microstrip transmission line; A first impedance matching circuit is connected in series on the microstrip transmission line; A second impedance matching circuit is connected between the radiator microstrip line and the metal ground plane.

[0008] Preferably, the first impedance matching circuit includes a first inductor and a first capacitor; the second impedance matching circuit includes a second inductor and a second capacitor, the radiator microstrip line is connected to a metal ground plane through a short-circuit metal post, and the second inductor and the second capacitor are connected in series between the radiator microstrip line and the short-circuit metal post.

[0009] Preferably, the decoupling structure is a third capacitor, with its two ends connected across the two sides of the floor coupling groove, so that the metal floor and the metal frame are electrically connected at the floor coupling groove.

[0010] Preferably, the overall dimensions of the MIMO antenna are 150mm × 75mm × 7mm; the dielectric substrate is a printed circuit board made of FR-4 material; and the height of the metal frame is 6.2mm.

[0011] Preferably, the size of a single antenna pair is 20mm × 7mm.

[0012] Preferably, the antenna operates in a frequency band of 3.29 GHz to 5.30 GHz, with a relative bandwidth of 47%.

[0013] Preferably, the antenna system comprises four antenna pairs, forming an 8-port MIMO antenna system.

[0014] Compared with the prior art, the MIMO antenna provided by the present invention has at least one of the following beneficial effects: 1. Based on shared radiator technology, under the premise of fully covering the 3.29-5.30 GHz (N77 / N78 / N79) 5G core frequency band, the planar projection size of a single antenna pair of the present invention is only 20mm×7mm. This size is significantly smaller than the existing technical solutions that achieve similar or narrower bandwidth, freeing up more clearance area for the internal structure design of mobile phones. In addition, the antenna adopts an all-metal frame design, which caters to consumer preferences.

[0015] 2. This invention achieves a relative bandwidth of 47%, covering a range from 3.29GHz to 5.30GHz. Its bandwidth performance is superior to most existing design schemes, providing a more reliable signal guarantee for 5G communication.

[0016] 3. While achieving the above-mentioned miniaturization and ultra-wideband, the present invention successfully maintains the port isolation below -11dB and the total antenna efficiency as high as about 85%. This shows that the present invention does not sacrifice key performance indicators to reduce size, but achieves a good balance among the three mutually restrictive key indicators of antenna size, operating bandwidth and radiation efficiency, and solves the problem of compatibility between all-metal materials and signal transmission. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is the invention Figure 1 Enlarged structural diagram at point A in the middle; Figure 3 This is the invention Figure 2 Schematic diagram showing the dimensions of each structure; Figure 4 This is a top view of the structure of the present invention; Figure 5 This is a schematic diagram of the impedance matching network structure of the present invention; Figure 6 The MIMO antenna S of the present invention 11 Simulation diagram of equal reflectance coefficient; Figure 7 The MIMO antenna S of the present invention 21 Simulation diagram of equal transmission coefficient; Figure 8 The MIMO antenna S of the present invention 11 Schematic diagram of measured equal reflectance coefficient; Figure 9 The MIMO antenna S of the present invention 21 Schematic diagram of measured transmission coefficient; Figure 10 In the diagram, (a) is the radiation pattern of the XOZ plane of port 1 at 3.4 GHz, and (b) is the radiation pattern of the YOZ plane of port 1 at 3.4 GHz. Figure 11 In the diagram, (c) is the radiation pattern of the XOZ plane of port 1 at 4.9 GHz, and (d) is the radiation pattern of the YOZ plane of port 1 at 4.9 GHz. Figure 12 In the diagram, (e) is the radiation pattern of the XOZ plane of port 2 at 3.4 GHz, and (f) is the radiation pattern of the YOZ plane of port 2 at 3.4 GHz. Figure 13 In the diagram, (g) is the radiation pattern of the XOZ plane of port 2 at 4.9 GHz, and (h) is the radiation pattern of the YOZ plane of port 2 at 4.9 GHz.

[0019] In the figure: 1. Dielectric substrate; 2. Metal ground plane; 3. Metal frame; 4. Radiator microstrip line; 5. Short-circuit metal pillar; 6. Feed port; 7. First inductor; 8. First capacitor; 21. Ground plane coupling groove; 31. Side wall radiating groove; 71. Second inductor; 81. Second capacitor; 82. Third capacitor. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example, refer to Figures 1-13 This embodiment provides a miniaturized ultra-wideband 5G MIMO mobile phone antenna for metal frames, which solves the technical problems of narrow bandwidth, large unit size and poor isolation of traditional metal frame mobile phone antennas while achieving an all-metal appearance.

[0022] The antenna structure includes a FR-4 (ε) r The dielectric substrate 1, made of material with φ = 4.4 and tanδ = 0.02, has a base plate that provides a bearing surface for the radiating elements and the feeding network, while the surrounding sidewalls provide a structural basis for the integration of the metal frame 3. The metal floor 2 fully covers the outer surface of the base plate of the dielectric substrate 1, and the metal frame 3 fully covers the outer surface of the sidewalls of the dielectric substrate 1. Together, they form a complete all-metal frame. This design first satisfies the pursuit of metallic texture in the appearance of mobile phones, but the electromagnetic shielding challenge it brings is precisely what this invention aims to overcome and utilize.

[0023] The MIMO antenna system of the present invention consists of multiple antenna pairs symmetrically arranged along the two long sides of the dielectric substrate 1. Each antenna pair is a basic unit constituting an 8-port MIMO system. Each antenna pair includes a pair of sidewall radiation slots 31 etched on the long side of the metal frame 3, and a ground plane coupling slot 21 etched on the metal ground plane 2 and connected to the sidewall radiation slots 31. This design connects the originally independent frame slots and ground plane slots to form a "π"-shaped three-dimensional slot radiator. Electromagnetic waves are mainly radiated outward through this continuous three-dimensional slot, thus cleverly "bypassing" the shielding effect of the metal. This is the core mechanism for the effective operation of the antenna under an all-metal frame.

[0024] A pair of radiating microstrip lines 4 are printed parallel and symmetrically on the inner surface of the substrate 1, and located directly above the ground plane coupling slot 21. These two radiating microstrip lines 4 are strongly coupled with the shared three-dimensional slot above, and jointly excite a radiation mode, essentially "sharing" the same radiator. This sharing mechanism is one of the key innovations of this invention, which fundamentally reduces the physical size of the antenna pair, because the two ports no longer need their own independent radiators that occupy a large space. The feed network provides an independent feed port 6 for each radiating microstrip line 4, thereby realizing dual-port excitation.

[0025] To achieve excellent impedance matching in the ultra-wideband range and further suppress port coupling caused by the shared radiator, this invention designs a matching circuit: a first impedance matching circuit (including a first inductor 7 and a first capacitor 8) is connected in series on the feed microstrip transmission line, mainly used to adjust the input impedance of the antenna and expand the operating bandwidth; a second impedance matching circuit (including a second inductor 71 and a second capacitor 81) is connected between the radiator microstrip line 4 and the metal ground plane 2 through a short-circuit metal pillar 5. This circuit not only participates in impedance matching, but more importantly, it works in conjunction with the decoupling structure to introduce additional coupling paths to cancel the mutual coupling between ports, thereby significantly improving the isolation.

[0026] The decoupling structure is a third capacitor 82, whose two ends are directly connected across the middle of the ground coupling slot 21. This design is another ingenious feature of the present invention. This lumped capacitor is electrically connected directly between the radiators (ground coupling slot 21) shared by two adjacent ports, forming a highly efficient parallel LC decoupling network. It can generate an anti-phase current in the ultra-wide bandwidth, effectively neutralizing the electromagnetic coupling between ports, thereby improving the port isolation to below -11dB at a very low physical cost, solving the inherent problem of strong interference between MIMO antenna channels under compact spacing.

[0027] Reference Figure 3 The detailed dimensions of the antenna and the parameters of each lumped element mentioned above are shown in Table 1 below: Table 1. Antenna Parameter List

[0028] Based on the antenna structure described in the technical solution provided in this embodiment, further modeling and simulation were performed using HFSS15.0 electromagnetic simulation. The simulation results are referenced. Figure 5 , Figure 6 ,in Figure 6 For MIMO antenna S 11 Simulation diagram of equal reflectance coefficient; Figure 7 For MIMO antenna S 21 Simulation diagram of equal transmission coefficient.

[0029] To verify the performance indicators of the proposed MIMO antenna, a sample of the MIMO antenna was fabricated, and the S-parameters and far-field radiation characteristics of the antenna were measured using a vector network analyzer and a microwave anechoic chamber, respectively.

[0030] The coefficients of the simulation model were compared with the measured coefficients of the MIMO antenna sample in this embodiment. The S-parameters were measured using a Ceyear 3671 vector network analyzer. The measured reflection and transmission coefficients are shown below. Figure 8 and Figure 9As shown, the MIMO antenna described above consists of four identical antenna pairs (part A, part B, part C, and part D). Therefore, only antenna pair A (i.e., part A) was measured during the actual test. Figure 8 It can be seen that antenna A achieves dual resonance at 3.4GHz and 4.9GHz, thus extending the bandwidth. The measured bandwidth is the same as the simulation, and the reflection curves of port 1 and port 2 are similar, which is a result of symmetrical design. Further analysis... Figure 9 It can be seen that, in the range of 3.29-5.30GHz, the transmission coefficient between all ports of the MIMO antenna is better than -11dB, which is consistent with the simulation results. Due to interference and other reasons, the measured curves showed varying degrees of fluctuation, but the overall trend still conforms to the simulation results.

[0031] The far-field radiation performance of the antenna was measured in a microwave anechoic chamber using an NSI2000 Antenna Measurement System. Since the antenna pairs were identical, antenna pair A was randomly selected as the test object. The results are as follows: Figures 10-13 As shown; taking the frequency points of 3.4 GHz and 4.9 GHz as examples, the radiation performance of the antenna is analyzed. Figure 1 The radiation patterns of the MIMO antenna in the XOZ and YOZ planes were obtained by HFSS simulation in the coordinate system. Since the dual ports share the outer rectangular radiating patch, the current in the radiating patch is in the X direction, so it radiates omnidirectionally in the YOZ plane. The main polarization direction is Eφ, as shown in Figures (b), (d), (f), and (h). The Eφ radiation pattern is circular, and the cross polarization is Eθ. The measured results in the YOZ plane are consistent with the simulation. The main polarization direction of the antenna in the Z-axis direction in the XOZ plane is Eθ, which is parallel to the current. Therefore, Eφ in the XOZ plane has two zeros in the positive and negative Z-axis directions. Similarly, the two zeros of Eθ appear in the positive and negative X-axis directions, as shown in Figures (a) and (e). The measured results in the XOZ plane are also consistent with the simulation. The slight fluctuations in the measured data are caused by environmental electromagnetic interference and other factors.

[0032] Simulation and experimental results ( Figures 6-13 The results showed good agreement, verifying the correctness of the above design principles. The antenna's -6dB impedance bandwidth covered 3.29-5.30 GHz, and the isolation between all ports was better than -11dB throughout the entire frequency band. At the two typical frequency points of 3.4 GHz and 4.9 GHz, the antenna's radiation pattern showed stable omnidirectional radiation characteristics, with a total efficiency of approximately 85%.

[0033] In this embodiment, based on shared radiator technology and through the collaborative design of the above structure, an all-metal frame ultra-wideband multiple-input multiple-output (MIMO) mobile phone antenna suitable for fifth-generation (5G) communication technology is proposed. The overall size of the MIMO antenna in this invention is 150mm × 75mm × 7mm, which is compatible with the size of mainstream smartphones. The antenna is an 8-port MIMO antenna composed of 4 antenna pairs. The antenna adopts an all-metal frame design, which caters to consumer preferences. Due to the shared radiator, the size of the antenna pair is only 20mm × 7mm, and the substrate thickness is 0.8mm. Its miniaturization advantage is mainly due to the shared radiator technology and the three-dimensional slot structure. This size can provide enough clearance for the mobile phone.

[0034] To fully cover the 5G N77 / N78 / N79 frequency bands (3.3-5.0 GHz), a matching network was designed using lumped elements to adjust impedance matching. Simulations showed a -6dB bandwidth of 3.29-5.30 GHz, fully covering the 5G N77 / N78 / N79 frequency bands with a relative bandwidth of 47%. A lumped capacitor loading decoupling technique was used at the midpoint of the antenna pair, achieving an isolation of less than -11dB between adjacent ports. The overall efficiency of the antenna across the entire bandwidth reached approximately 85%. Further simulations showed that the antenna's radiation performance did not change significantly when held in hand. Fabrication and testing demonstrated that the antenna's S-parameters and radiation performance met the design requirements, and the measured and simulated results showed good agreement.

[0035] Antenna performance verification To illustrate the superior performance of the proposed antenna, and to verify its performance, a comprehensive comparison was made with various existing MIMO antennas, as shown in Table 2 below. As can be seen from the table, the antenna pair size of the proposed antenna is significantly smaller than that of the reference antenna, and its bandwidth is also superior. Therefore, the antenna proposed in this invention exhibits superior overall performance.

[0036] Table 2. Comparison of Overall Performance of MIMO Antennas

[0037] As shown in Table 2, the comprehensive performance comparison with existing technologies (references [1], [2], [3] in the background technology) shows that the present invention has made breakthroughs in both the contradictory indicators of antenna element size and operating bandwidth. While achieving miniaturization and ultra-wideband, it maintains high isolation and high efficiency, proving that its comprehensive balance in key technical indicators is far superior to existing solutions.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame, characterized in that, include: The dielectric substrate (1) is a hollow rectangular box-shaped material, which is integrally formed by a bottom plate and a side wall surrounding its perimeter; A metal floor (2) covers the lower surface of the dielectric substrate (1); A metal frame (3) surrounds and is fixed around the periphery of the dielectric substrate (1), together with the metal floor (2) forming an all-metal outer frame; Multiple antenna pairs are disposed on the long side of the dielectric substrate (1); wherein, the antenna pairs include: A pair of sidewall radiation grooves (31) formed on the long side of the metal frame (3); A floor coupling groove (21) formed on the metal floor (2) and connected to the pair of sidewall radiation grooves (31); A pair of radiator microstrip lines (4) printed on the inner surface of the dielectric substrate (1) are arranged in parallel and symmetrically above the ground coupling groove (21). A decoupling structure is connected across the middle of the floor coupling groove (21); The feed network is connected to the pair of radiating microstrip lines (4) respectively, and is used to provide two independent feed ports (6) for the antenna pair.

2. The miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame according to claim 1, characterized in that, The power supply network includes: The two feed ports (6) are respectively connected to the corresponding radiator microstrip line (4) via microstrip transmission lines. A first impedance matching circuit is connected in series on the microstrip transmission line; A second impedance matching circuit is connected between the radiator microstrip line (4) and the metal ground plane (2).

3. A miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame according to claim 2, characterized in that, The first impedance matching circuit includes a first inductor (7) and a first capacitor (8); the second impedance matching circuit includes a second inductor (71) and a second capacitor (81). The radiator microstrip line (4) is connected to the metal ground plane (2) through a short-circuit metal post (5). The second inductor (71) and the second capacitor (81) are connected in series between the radiator microstrip line (4) and the short-circuit metal post (5).

4. A miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame according to claim 1, characterized in that, The decoupling structure is a third capacitor (82), with its two ends connected across the two sides of the floor coupling groove (21) to make the metal floor (2) and the metal frame (3) electrically connected at the floor coupling groove (21).

5. A miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame according to claim 1, characterized in that, The overall dimensions of the MIMO antenna are 150mm×75mm×7mm; the dielectric substrate (1) is a printed circuit board made of FR-4 material; the height of the metal frame (3) is 6.2mm.

6. A miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame according to claim 1, characterized in that, The dimensions of a single antenna pair are 20mm × 7mm.

7. A miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame according to claim 1, characterized in that, The antenna operates in the frequency band of 3.29 GHz to 5.30 GHz, with a relative bandwidth of 47%.

8. A miniaturized ultra-wideband 5G MIMO mobile phone antenna for a metal frame according to claim 1, characterized in that, The antenna system comprises four antenna pairs, forming an 8-port MIMO antenna system.

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