A parasitic grounded stub based dual inverted-l broadband low-coupling MIMO handset antenna

Abstract

This invention belongs to the field of wireless communication technology and discloses a dual inverted "L" broadband low-coupling MIMO mobile phone antenna based on a parasitic grounded stub. This invention proposes a novel antenna structure. This design effectively solves the contradiction between broadband performance and high isolation while maintaining a simple and compact structure. The decoupling and broadband principle of this invention is as follows: an inverted L-shaped parasitic grounded stub with a bent end is introduced below the inner side of the radiating arm. This stub can generate a new coupling path, and the reverse current induced in it exactly cancels the coupling current received by the main radiating arm, achieving decoupling between ports. By slotting on the horizontal arm of the inverted L-shaped radiating stub, a new resonant point is generated in the antenna, effectively widening the antenna's operating bandwidth.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and particularly relates to a dual inverted "L" broadband low-coupling MIMO mobile phone antenna based on parasitic grounding branches. Background Technology

[0002] In the field of modern wireless communication, the popularization and upgrading of smart terminals are accelerating. Faced with the vision of 5G communication for ultra-high speed and multi-functional integration, mobile phone antenna systems must be able to cover a wider frequency band, which directly leads to a significant increase in the complexity of radio frequency systems. Conversely, modern industrial design tends towards extreme portability and full-screen experiences, forcing antenna design to confront extremely stringent space constraints. How to accommodate more radiating elements within increasingly compact structures has become a major technical bottleneck for antenna engineers.

[0003] To overcome bandwidth limitations and address spectrum scarcity, MIMO technology has been widely adopted in 5G systems to achieve a qualitative leap in data transmission rates. However, deploying MIMO systems within the confined environment of mobile terminals easily leads to strong mutual coupling effects between antenna elements. This proximity effect not only manifests as attenuation of radiation performance and deterioration of impedance characteristics, but more seriously, it causes crosstalk between antennas, significantly reducing channel independence and overall system capacity. Therefore, researching and applying advanced decoupling techniques to suppress electromagnetic interference is crucial for maintaining the efficient and stable operation of 5G mobile terminals.

[0004] Based on the above analysis, the problems and shortcomings of the existing technology are as follows: Deploying multiple-input multiple-output (MIMO) systems in confined mobile terminal environments can easily lead to strong mutual coupling effects between antenna elements. This proximity effect not only manifests as attenuation of radiation performance and deterioration of impedance characteristics, but more seriously, it can cause crosstalk between antennas, significantly reducing channel independence and overall system capacity. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a dual inverted "L" broadband low-coupling MIMO mobile phone antenna based on parasitic grounding stubs.

[0006] This invention is implemented as follows: a dual inverted "L" broadband low-coupling MIMO mobile phone antenna based on parasitic grounding stubs includes: A horizontal dielectric substrate, a vertical substrate placed perpendicular to the long sides of both sides of the horizontal dielectric substrate, N dual-port antenna pairs, a metal ground, and a 2N rectangular slot opened at the edge of the metal ground.

[0007] Each dual-port antenna pair consists of two face-to-face slotted inverted L-shaped radiating stubs, face-to-face parasitic grounding stubs with bent ends, two feed stubs, and two ports.

[0008] The antenna units are symmetrically arranged along the two long edges of the mobile phone substrate. The antenna system as a whole includes a horizontal system substrate, two lateral antenna substrates that are vertically fixed to the edge of the horizontal substrate, and a metal ground plane printed on the upper surface of the horizontal substrate. The entire system includes N pairs of dual-port antennas arranged along the side, forming a total of 2N independent antenna ports.

[0009] Furthermore, N depends on the number of deployed antenna pairs, and in this invention, N is 4; each dual-port antenna pair consists of two antenna elements that are distributed in a mirror-symmetric manner.

[0010] Furthermore, the antenna unit mainly includes a slotted inverted L-shaped radiating stub and an inverted L-shaped parasitic grounding stub with its end bent at the lower inner side of the radiating arm.

[0011] Furthermore, the slotted inverted L-shaped radial branch is connected to the power supply branch.

[0012] Furthermore, the inverted L-shaped parasitic grounding stub introduces a new coupling path inside the antenna unit; by adjusting the resonant characteristics of the stub, the reverse current induced by it can just cancel the coupling current received by the main radiating arm, thereby achieving decoupling between ports.

[0013] Furthermore, at the edge of the metal ground plane corresponding to the feed point of each antenna element, a 2N rectangular feed slot is etched; this rectangular slot serves as the ground plane gap of the coplanar waveguide, and together with the feed conductor placed in the center of the slot, it constitutes the coplanar waveguide transmission; between antenna elements and between antenna pairs, the metal ground plane remains intact and continuous, without any additional decoupling gaps, to ensure the integrity of the ground plane; for ease of soldering, solder feet composed of metal patches are added after the feed microstrip line.

[0014] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows: I. This invention proposes a double inverted "L" antenna structure based on parasitic grounding stubs. Its greatest technical advantage is that, without the participation of any lumped components (such as capacitors and inductors), it solves the bottleneck problem of the coexistence of "broadband" and "high isolation" in MIMO antenna systems through pure structural design.

[0015] 1. Innovative decoupling mechanism (using parasitic branches to achieve reverse coupling) To improve isolation, traditional MIMO antennas often require increasing the physical distance between antennas or introducing structures such as neutral lines and defective grounds, but this usually disrupts antenna matching or occupies extra space. This invention creatively constructs a "secondary coupling path" by introducing a parasitic grounding stub (5) with a bent end on the inner side below the inverted L-shaped radiating stub (4).

[0016] Principle and advantages: When the main radiating stub is working, the coupling current generated at adjacent ports will be induced on the parasitic stub. Due to the grounding and special structure of the parasitic stub, the phase of the induced current is opposite to the phase of the original coupling current on the main radiating stub. This phase-opposite current forms a field cancellation in space, thereby reducing the mutual coupling between ports from the physical source without the need for additional circuitry, achieving high isolation.

[0017] 2. Pure structural implementation of broadband technology Claim 3 and the specification mention that the current path is extended by setting a slotted structure on the horizontal arm of the inverted L-shaped radiating branch (4).

[0018] Advantages of the design: The slotting effectively introduces a localized slow-wave effect, exciting new resonant modes without increasing the antenna's physical size. These new resonant frequencies are adjacent to and merge with the original resonant frequencies, thereby expanding the antenna's impedance bandwidth (e.g., 3.12–5.23 GHz as mentioned in the manual). This means that a single antenna can maintain good matching for signals across multiple frequency bands, adapting to the multi-band and wideband development needs of modern communications.

[0019] 3. Compact three-dimensional layout and structural synergy By utilizing the three-dimensional structure of the horizontal dielectric substrate (1) and the vertical substrate (2), combined with the rectangular slot at the edge of the metal ground (3) and the coplanar waveguide feeding structure (claims 5-6), the antenna unit can be tightly integrated into a limited space such as the mobile phone frame, while ensuring radiation performance. The metal ground slot not only serves as part of the feeding structure, but also further guides and constrains the distribution of the electromagnetic field, helping to improve the isolation effect.

[0020] II. Positive Effects of Commercial Value and Engineering Applications From the perspective of industrialization and practical application, this technical solution brings significant economic benefits and improved product performance: 1. Significantly reduce material and manufacturing costs Since no lumped components (capacitors, inductors) are needed for matching or decoupling, the product's BOM (Bill of Materials) is significantly reduced. This not only saves on component procurement costs but also eliminates the surface mount process, reducing the complexity and time required for PCB assembly. For consumer electronics products such as mobile phones, with shipment volumes in the tens of millions, every penny saved translates into substantial profit margins.

[0021] 2. Improve product consistency and long-term reliability Lumped components suffer from tolerance issues, temperature drift, aging, and poor soldering, which can easily lead to performance discrepancies or failures in antennas during production and use. This invention employs a pure structural design, where antenna performance is entirely determined by the etching precision of the PCB or FPC. The manufacturing process is stable, product consistency is excellent, and there is no risk of component detachment, resulting in higher long-term reliability. This makes it particularly suitable for mobile terminals with stringent reliability requirements.

[0022] 3. Expand application scenarios and market adaptability This antenna achieves broadband coverage of 3.12–5.23 GHz, spanning multiple Sub-6 GHz bands. It can be applied not only to mobile phones but also quickly adapted to various platforms such as tablets, CPEs (Customer Premises Equipment), wireless routers, and IoT terminals. This broadband capability allows companies to rapidly develop product lines tailored to the frequency band requirements of different countries and operators based on a single antenna design, shortening the development cycle and enhancing market responsiveness.

[0023] III. Overcoming Technological Bias The technical solution of this invention breaks through the long-standing technical prejudices in this field in its conception: Overcoming Bias: In traditional antenna design, engineers generally believe that achieving broadband impedance matching, especially in miniaturized terminals, often requires complex matching networks (i.e., lumped element tuning) to compensate for the antenna's own capacitive or inductive properties. They also believe that decoupling structures must be designed independently of the main radiator or require the introduction of additional "trap" circuitry.

[0024] This invention breaks with this conventional thinking. It demonstrates that broadband matching and efficient decoupling can be achieved simultaneously through a purely physical structure—a carefully designed parasitic grounding branch and slotted radiating arm—utilizing the "near-field coupling" and "phase control" mechanisms between the structure and the main radiator. This showcases the feasibility and engineering advantages of "purely structured broadband matching" and "integrated decoupling," providing a completely new approach and direction for the design of miniaturized MIMO antennas: replacing expensive and unreliable circuit components by deeply exploring the electromagnetic coupling potential of metallic structures. Attached Figure Description

[0025] Figure 1This is a structural diagram of a double inverted "L" broadband low-coupling MIMO mobile phone antenna based on parasitic grounding branches provided in an embodiment of the present invention.

[0026] Figure 2 This is a top view of a double inverted "L" broadband low-coupling MIMO mobile phone antenna based on parasitic grounding branches provided in an embodiment of the present invention.

[0027] Figure 3 This is a perspective view of the dual-port antenna pair provided in an embodiment of the present invention.

[0028] Figure 4 This is a top view of the dual-port antenna pair provided in an embodiment of the present invention.

[0029] Figure 5 This is the reflection coefficient of the dual-port antenna pair provided in this embodiment of the invention.

[0030] Figure 6 It is the transmission coefficient of the dual-port antenna pair provided in the embodiments of the present invention.

[0031] Figure 7 These are the total efficiency and ECC of the dual-port antenna pair provided in this embodiment of the invention.

[0032] Figure 8 This is the radiation pattern of the dual-port antenna pair provided in the embodiment of the present invention.

[0033] Figure 9 This is a current distribution diagram of a two-port antenna pair without parasitic grounding branches provided in an embodiment of the present invention when excited at port 2 at 4.0 GHz.

[0034] Figure 10 This is a current distribution diagram of a dual-port antenna pair with a parasitic grounding branch provided in an embodiment of the present invention when excited at port 2 at 4.0 GHz.

[0035] Figure 11 This embodiment of the invention provides an antenna with or without parasitic grounding stubs, and an antenna pair transmission coefficient S. 21 The comparison chart.

[0036] In the diagram: 1. Horizontal dielectric substrate; 2. Vertical substrate; 3. Metal ground; 3a. 2N rectangular slots opened at the edge of the metal ground; 4. Inverted L-shaped radiating stub; 5. Face-to-face parasitic grounding stub; 6. Two power supply stubs; 7. Port. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] like Figure 1 As shown, an embodiment of the present invention provides a dual inverted "L" broadband low-coupling MIMO mobile phone antenna based on a parasitic grounding stub, comprising: The system consists of a horizontal dielectric substrate 1, a vertical substrate 2 placed perpendicular to the long sides of both sides of the horizontal dielectric substrate, N dual-port antenna pairs, a metal ground 3, and a 2N rectangular slot opened at the edge of the metal ground.

[0039] Each dual-port antenna pair consists of two face-to-face slotted inverted L-shaped radiating stubs 4, face-to-face parasitic grounding stubs 5 with bent ends, two feed stubs 6, and two ports 7.

[0040] The dual inverted "L" broadband low-coupling MIMO mobile phone antenna based on parasitic grounding branches provided in this invention has the core working principle of achieving wideband response and high isolation in a limited space through three-dimensional layout and multi-path coupling mechanism.

[0041] The antenna adopts a three-dimensional architecture, with the horizontal dielectric substrate 1 and the two vertical substrates 2 on both sides forming a three-dimensional space, effectively utilizing the internal space of the mobile phone. The 2N rectangular slots opened at the edge of the metal ground 3 provide the initial resonance space for the antenna radiator and help guide the radiation path of electromagnetic waves.

[0042] The operating mechanism of each dual-port antenna pair is as follows: two inverted L-shaped radiating stubs 4 are placed face-to-face, serving as the basic radiating elements responsible for generating the main resonant mode. The key lies in the introduction of face-to-face parasitic grounded stubs 5 with bent ends. These parasitic stubs interact with the inverted L-shaped radiating stubs 4 via electromagnetic coupling. The bent design not only lengthens the current path, contributing to resonance at lower frequencies to expand bandwidth, but more importantly, the face-to-face parasitic stubs 5 introduce an additional coupling path between the two radiating elements. This coupling path can generate a coupling signal with opposite phase or canceling amplitude to the direct coupling between the original antenna pairs, effectively canceling or suppressing mutual coupling between the two ports and significantly improving the isolation of the MIMO antenna.

[0043] Two feed stubs 6 connect to two ports 7 respectively, responsible for the excitation signal. The entire antenna, through the combined action of the radiating stub 4, the parasitic grounding stub 5, and the slotted edge of the metal ground 3, excites multiple similar resonant modes. These modes superimpose and merge, ultimately forming a continuous broadband impedance characteristic. Simultaneously, the decoupling effect of the parasitic grounding stub 5 ensures that interference between ports 7 is minimized when multiple antennas operate simultaneously, guaranteeing the channel capacity and communication quality of the MIMO system.

[0044] Figure 2A top view of the MIMO antenna is shown, revealing that face-to-face inverted L-shaped radiating stubs 4 and face-to-face parasitic grounding stubs 5 with bent ends are printed on the inner surface of the vertical substrate 2; "face-to-face" refers to the two inverted "L"-shaped stubs opening opposite each other. This invention introduces a new coupling path by introducing face-to-face parasitic grounding stubs 5. The induced field generated by the face-to-face parasitic grounding stubs 5 is out of phase and has similar amplitude to the coupling field directly received by the main radiating arm at the feed port, causing the two coupled signals to cancel each other out, thus significantly reducing the mutual coupling between ports. Without affecting the decoupling performance, the two face-to-face slotted inverted L-shaped radiating stubs 4 are connected to the two feed stubs 6, and the face-to-face parasitic grounding stubs 5 are connected to the metal ground plane 3, as shown below. Figure 1 The 3D view of the 8×8 MIMO antenna is shown.

[0045] like Figure 3 As shown, to introduce coplanar waveguide feeding, two rectangular slots 3a are formed at the feeding point of each dual-port antenna pair on the edge of the metal ground 3, totaling 2N slots. This invention effectively extends the operating bandwidth of the two ports by creating a rectangular slot on the horizontal arm of the inverted "L"-shaped radiating stub and introducing coplanar waveguide feeding, enabling it to fully cover the N77, N78, and N79 frequency bands of the 5G sub-6 band.

[0046] like Figure 4 As shown, two feed stubs 6 are printed in a rectangular groove 3a of a horizontal dielectric substrate 1. Ports 7, totaling 2N, are soldered to the ends of the two feed stubs 6 to achieve effective signal excitation.

[0047] The MIMO mobile phone antenna system proposed in this embodiment of the invention adopts an 8-element layout and is rectangular in shape. The dielectric substrate of the antenna system is made of FR4 substrate with a dielectric constant of 4.4 and a loss tangent of 0.02. The specific geometric dimensions of the horizontal dielectric substrate are 150mm × 75mm × 0.8mm, and the dimensions of the lateral dielectric substrate assembled perpendicularly to it are 150mm × 7mm × 0.8mm. The dimensions of the metal ground plane are consistent with those of the horizontal substrate (150mm × 75mm). The rectangular slot 3a formed on the metal ground plane has a length and width of 10.8mm and 2.4mm, respectively. To optimize isolation and coverage performance, the center-to-center distance between two dual-port antenna pairs located on the same long side is set to 83mm, and the indentation distance of each antenna pair relative to the edge of the substrate is 10.3mm.

[0048] The antenna system exhibits optimal performance under the aforementioned parameter settings. If the actual parameters deviate significantly from the design values, it will inevitably lead to a severe deterioration in the antenna's radiation characteristics.

[0049] Given the high degree of geometric symmetry of the designed 8-element MIMO array antenna, this simulation verification selects one representative two-port antenna pair as the research object. The simulation results of impedance matching characteristics are as follows: Figure 5 As shown: the -6 dB impedance bandwidths of port 1 and port 2 are 3.04-5.23 GHz and 3.12-5.33 GHz, respectively; combining these characteristics, the effective overlapping operating bandwidth (-6 dB) of this antenna element covers the 3.12-5.23 GHz frequency band. Furthermore, Figure 6 The isolation performance between ports is demonstrated. Observing the transmission coefficient curve, it can be seen that the isolation between ports is greater than 12.9dB across the entire operating frequency band, indicating that the design has excellent port isolation.

[0050] Figure 7 The total radiation efficiency and envelope correlation coefficient (ECC) of the dual-port antenna pair within the operating frequency band are presented. The data show that the antenna exhibits excellent radiation characteristics: within the effective operating frequency band, the total efficiency of port 1 fluctuates between 59% and 80%, while the total efficiency of port 2 remains between 64% and 83%. Furthermore, the calculated ECC values ​​are below 0.04 throughout the entire frequency band, far exceeding the threshold typically required by engineering standards (ECC < 0.5), confirming the excellent independence between MIMO units.

[0051] Figure 8 The figure shows the radiation pattern of the antenna. As can be seen from the figure, Gain-phi and Gain-theta have good complementary characteristics. When Gain-phi is at a small value, Gain-theta is at a large value. This complementary mechanism between components not only greatly improves the omnidirectional radiation performance of the antenna and ensures signal stability in complex environments, but also effectively reduces the envelope correlation coefficient (ECC) between elements from the electromagnetic field dimension, laying the foundation for improving the channel capacity of the MIMO system.

[0052] The 8-port MIMO array proposed in this invention successfully achieves synergistic optimization of wideband coverage and high isolation. Within the effective operating frequency band of 3.12 to 5.23 GHz, the isolation between ports remains consistently above 12.9 dB. This low mutual coupling characteristic achieved over a wide bandwidth makes it an ideal solution for meeting the high-performance requirements of 5G multi-band mobile terminals.

[0053] Example 1 A broadband low-coupling MIMO mobile phone antenna system based on a parasitic grounding stub is disposed in the edge region of the mobile terminal motherboard. The system includes a horizontal system dielectric substrate, two vertical lateral antenna substrates fixed to the long sides of the horizontal substrate, and a metal ground plane printed on the upper surface of the horizontal dielectric substrate. Antenna elements are arranged on the vertical lateral antenna substrates, with four pairs of dual-port antennas arranged on each side edge, thus forming an eight-port MIMO structure. Each antenna element consists of a slotted inverted L-shaped radiating stub and an inverted L-shaped parasitic grounding stub with a bent end. The parasitic grounding stub is located below and inside the radiating stub and connected to the metal ground plane. The parasitic grounding stub is bent to shorten the antenna size. By introducing the parasitic grounding stub, a new coupling path is formed near the radiating stub, causing a redistribution of the original current path, thereby suppressing the coupling between adjacent antennas. Experimental simulations show that the port isolation is significantly improved in the 3.12GHz to 5.23GHz communication band, while maintaining good broadband matching characteristics.

[0054] Example 2 In another structural form, the antenna system still employs a double-inverted-L radiating structure, but with slots added to the radiating stubs. These slots are located in the horizontal portion of the radiating stubs, creating additional resonant modes by altering the current path length, thus further extending the antenna's operating bandwidth. By optimizing the slot length and location, stable coupling is achieved between the radiating stubs and the parasitic grounded stubs, thereby achieving low coupling between multi-port antennas without adding additional decoupling structures. This structure enables broadband communication performance within a relatively small space.

[0055] Example 3 In a further optimized design, rectangular slots are etched along the edges of the metal ground plane at the feed locations of each antenna element. A feed strip is positioned in the center of the rectangular slot, and a coplanar waveguide grounding structure is formed on both sides of the slot. This coplanar waveguide feeding method concentrates the feed current in the radiating stub region, thereby improving radiation efficiency. Simultaneously, since the ground plane maintains a continuous structure, there are no additional decoupling slots between adjacent antenna elements; therefore, the coupling suppression path formed by parasitic grounding stubs becomes the primary decoupling mechanism. Experiments show that this structure achieves high isolation while maintaining system simplicity.

[0056] Example 4 In another layout, the antenna elements are arranged in a mirror-symmetrical manner along the two long sides of the mobile phone substrate. Each dual-port antenna pair consists of two mirror-structured antenna elements, with two radiating stubs positioned face-to-face, and parasitic grounding stubs located inside the respective radiating stubs. This mirror-structure layout allows for a symmetrical current distribution between adjacent antenna elements, thereby reducing coupling caused by unbalanced currents. Simultaneously, the parasitic grounding stubs guide some current back to the ground plane through their bent ends, further weakening the coupling path. This structure maintains stable isolation performance in multi-port arrays.

[0057] Example 5 In another embodiment, the antenna system still employs a multi-port antenna pair structure, but the antenna elements are mounted on a lateral dielectric substrate, allowing the radiating stubs to be arranged vertically with the phone's motherboard. This vertical arrangement increases the radiation space and reduces the impact of the motherboard ground plane on antenna radiation. The parasitic grounding stubs are connected to the motherboard's metal ground, and their bent structure forms an additional coupling path in the vertical direction, allowing current to couple from the radiating stubs to the grounding stubs and redistribute to the ground plane. This method achieves good broadband characteristics and isolation performance within a limited terminal size.

[0058] Example 6 In another optimized scheme, the antenna system comprises four pairs of dual-port antennas, forming a total of eight independent antenna ports. Each antenna element employs a combination structure of inverted L-shaped radiating stubs and parasitic grounding stubs. By adjusting the length and spacing of the bent portions of the parasitic grounding stubs, the coupling strength between them and the radiating stubs can be altered, thereby regulating the antenna isolation performance. Electromagnetic simulation and prototype testing revealed that when the bending length and radiating stub spacing are within a specific range, the inter-port coupling can be significantly reduced without adding additional decoupling components, while maintaining good VSWR and radiation efficiency. This structure demonstrates that the coupling control mechanism formed by parasitic grounding stubs can effectively improve the overall performance of a multi-port mobile phone antenna system.

[0059] like Figure 9 and Figure 10 As shown, the distribution of the antenna surface current is illustrated when port 2 is excited at an operating frequency of 4.0 GHz. Among these, Figure 9 This is a surface current distribution diagram without the inverted L-shaped parasitic branch structure. Figure 10 The surface current distribution diagram is shown when an inverted L-shaped parasitic branch structure is loaded.

[0060] Depend on Figure 9It can be seen that, without the inverted L-shaped parasitic branch, when port 2 is excited, the surface current is not only mainly distributed on the radiating arm corresponding to port 2, but also has a relatively obvious current distribution on the radiating structure corresponding to port 1. This indicates that there is a strong electromagnetic coupling between the two ports, resulting in a low degree of isolation between the ports.

[0061] And by Figure 10 It can be seen that after loading an inverted L-shaped parasitic stub inside the radiating structure, when port 2 is excited, the current is mainly concentrated on the radiating arm corresponding to port 2 and the inverted L-shaped parasitic stub, while the current distribution on the radiating arm corresponding to port 1 is significantly weakened. This is because the inverted L-shaped parasitic stub introduces a new coupling channel in the coupling path and generates an induced current in this channel that is opposite in direction to the original coupling current, thus canceling out the original coupling current and reducing the transmission of coupling energy to port 1.

[0062] like Figure 11 As shown, the port transmission coefficient S of the antenna of the present invention before and after loading the parasitic grounding stub is... 21 The comparison curves show that when the antenna is not loaded with parasitic grounding branches, the transmission coefficient S between ports is... 21 The highest value is approximately -6.9 dB, indicating strong electromagnetic coupling between the two ports and poor port isolation performance. Introducing a parasitic grounding stub into the antenna structure significantly suppresses the inter-port coupling and dramatically improves the antenna's isolation performance. Specifically, after adding the parasitic grounding stub, the overall port isolation increases by approximately 6 dB, and across the entire operating frequency band of the antenna, S... 21 All are less than -12.9dB, meaning the isolation between ports is greater than 12.9dB.

[0063] Therefore, by introducing an inverted L-shaped parasitic stub structure, the coupling effect between ports can be effectively suppressed, and the isolation performance between antenna ports can be improved.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A broadband low-coupling MIMO mobile phone antenna system, characterized in that, include: A dielectric substrate, a metal ground plane disposed on the dielectric substrate, and a plurality of dual-port antenna pairs arranged along the edge of the dielectric substrate; Each dual-port antenna pair includes two antenna elements arranged facing each other, and each antenna element includes an inverted L-shaped radiating stub and a parasitic grounding stub located inside the inverted L-shaped radiating stub. The parasitic grounding stub is electrically connected to the metal floor and forms an electromagnetic coupling path with the inverted L-shaped radiating stub through its end bending structure, so as to establish a coupling suppression effect between adjacent antenna elements. Each antenna element is connected to its corresponding port via a feed stub, enabling the dual-port antenna pair to form a multi-port MIMO radiation array at the edge of the dielectric substrate.

2. The broadband low-coupling MIMO mobile phone antenna system as described in claim 1, characterized in that, The dual-port antenna pair consists of two antenna elements that are distributed in a mirror-symmetric manner.

3. The broadband low-coupling MIMO mobile phone antenna system as described in claim 1, characterized in that, The inverted L-shaped radiating stub is provided with a slotted structure to extend the current path and expand the antenna's operating bandwidth.

4. The broadband low-coupling MIMO mobile phone antenna system as described in claim 1, characterized in that, The parasitic grounding branch is located on the inner side below the inverted L-shaped radiating branch, and forms a coupling area with the radiating branch through an end bending structure.

5. The broadband low-coupling MIMO mobile phone antenna system as described in claim 1, characterized in that, The edges of the metal floor are etched with rectangular slots at the feed positions of each antenna element.

6. The broadband low-coupling MIMO mobile phone antenna system as described in claim 5, characterized in that, The rectangular slot and the feed strip located in the center of the slot together form a coplanar waveguide feed structure.

7. A low-coupling mobile phone MIMO antenna unit structure, characterized in that, include: Inverted L-shaped radial branches, parasitic grounding branches, and power supply branches; The parasitic grounding branch is located on the inner side below the inverted L-shaped radial branch and connected to the metal ground, and the end of the parasitic grounding branch forms a bent structure. The parasitic grounding stub and the inverted L-shaped radiating stub form an additional electromagnetic coupling path to change the antenna current distribution and reduce the coupling between adjacent antennas.

8. The low-coupling mobile phone MIMO antenna unit structure as described in claim 7, characterized in that, The inverted L-shaped radial branches are provided with a slotted structure.

9. The low-coupling mobile phone MIMO antenna unit structure as described in claim 7, characterized in that, The bent portion of the parasitic grounding branch forms a coupling gap with the radiating branch.

10. The low-coupling mobile phone MIMO antenna unit structure as described in claim 7, characterized in that, The feed stub is connected to the antenna port via a coplanar waveguide or microstrip line.

Images