Antenna structure and terminal device

Abstract

The application provides an antenna structure and a terminal device. The antenna structure comprises a first antenna unit, a second antenna unit and an inductive decoupling element. The first antenna unit comprises a first radiation branch and a feed point arranged at a first end of the first radiation branch. The second antenna unit comprises a second radiation branch and a feed point arranged at a second end of the second radiation branch. A gap is formed between a first end of the second radiation branch and a second end of the first radiation branch, so as to form an equivalent capacitor through the gap. The inductive decoupling element is electrically connected between the second end of the first radiation branch and the first end of the second radiation branch, so as to form an equivalent inductor. The equivalent capacitor and the equivalent inductor form an LC resonant structure, so as to realize decoupling between the first antenna unit and the second antenna unit. The gap has a finger shape, which can be used to reduce the size of the inductive decoupling element, so as to facilitate miniaturization of the antenna structure, and further facilitate application of the antenna structure to a miniaturized terminal device with a small clearance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antennas, and in particular to an antenna structure and a terminal device. BACKGROUND

[0002] With the development of modern wireless communication technology, antennas play an increasingly important role as front-end devices of wireless communication systems, and higher requirements are put forward for antenna design. At present, the number of antennas required by terminal devices is increasing, and MIMO (Muti-input Muti-output) technology improves channel capacity by increasing spectral efficiency without increasing spectral bandwidth, which requires multiple antennas of the base station and the terminal device to be independent of each other. However, with the development of miniaturization of terminal devices, for example, the trend of full-screen, narrow frame, and extreme clearance in mobile phone design, the screen ratio is getting larger and larger, and the space available for antenna design inside the small terminal device is getting smaller and smaller. It is quite challenging to integrate multiple low-coupling antennas inside the terminal device. In order to layout multiple antennas in limited space, in one possible case, at least two feeding points can be provided on the same radiator, and multiple antenna units can be formed by combining different feeding points with the radiator. However, due to the reuse of the same radiator, the isolation between the ports is poor, which affects the performance of the antenna. Therefore, how to improve the isolation between antennas in limited space is one of the main problems faced by terminal antennas, and is also an important research direction at present and in the future. SUMMARY

[0003] The present application provides an antenna structure and a terminal device, which can achieve good port isolation and have the characteristics of high efficiency and miniaturization, and can meet the performance requirements of antennas in the field of intelligent terminal communication, and are also suitable for application to miniaturized terminal devices.

[0004] In a first aspect, the present application provides an antenna structure, which comprises a first antenna unit, a second antenna unit and an inductive decoupling element. The first antenna unit comprises a first radiating branch and a first feeding point arranged at a first end of the first radiating branch. The second antenna unit comprises a second radiating branch and a second feeding point, a first end of the second radiating branch and a second end of the first radiating branch form a slot, and a second end of the second radiating branch is arranged with the second feeding point. Wherein the slot is in a interdigital shape, and the slot forms an equivalent capacitance between the second end of the first radiating branch and the first end of the second radiating branch. The inductive decoupling element is electrically connected between the second end of the first radiating branch and the first end of the second radiating branch, wherein the inductive decoupling element forms an equivalent inductance between the second end of the first radiating branch and the first end of the second radiating branch. Wherein the equivalent capacitance and the equivalent inductance form an LC resonant structure, and the LC resonant structure is used to realize decoupling between the first antenna unit and the second antenna unit.

[0005] The antenna structure provided by the present application realizes decoupling between the first antenna unit and the second antenna unit through the slot and the inductive decoupling element, and at the same time, the interdigital slot is used to reduce the size of the inductive decoupling element, thereby facilitating the miniaturization of the antenna structure, reducing the space occupied by the antenna structure, and facilitating the application of the antenna structure to miniaturized terminal devices with small clearance, and improving the communication performance of the terminal device.

[0006] In an embodiment, the antenna structure further comprises a third antenna unit, the third antenna unit comprises a third radiating branch, a first end of the third radiating branch is arranged with a third feeding point, and a second end of the third radiating branch is suspended. Wherein the second radiating branch and the third radiating branch are formed on the same radiator, the second end of the second radiating branch is adjacent to the first end of the third radiating branch, and the second feeding point and the third feeding point are close to each other to realize self-decoupling between the second antenna unit and the third antenna unit.

[0007] In the antenna structure provided in the application, since the second antenna unit and the third antenna unit share the radiator, self-decoupling can be achieved between the two without introducing additional decoupling structures, without the need to increase the size of the antenna, and good port isolation can still be maintained in the case of extremely close port distance, thereby facilitating the miniaturization of the antenna structure, reducing the space occupied by the antenna structure, effectively reducing the complexity of design and processing of the antenna structure, facilitating the application of the antenna structure to miniaturized terminal devices with small clearances, and improving the communication performance of the terminal device.

[0008] In an embodiment, the antenna structure further comprises a first decoupling branch, which is arranged between the second end of the first radiating branch and the first end of the second radiating branch, wherein a first sub-slot in the shape of a finger is formed between the first end of the first decoupling branch and the second end of the first radiating branch, and a second sub-slot in the shape of a finger is formed between the second end of the first decoupling branch and the first end of the second radiating branch, and the slot comprises the first sub-slot and the second sub-slot.

[0009] The first sub-slot forms a first equivalent sub-capacitance between the second end of the first radiating branch and the first end of the first decoupling branch, and the second sub-slot forms a second equivalent sub-capacitance between the second end of the first decoupling branch and the first end of the second radiating branch, and the first equivalent sub-capacitance and the second equivalent sub-capacitance are connected in series between the second end of the first radiating branch and the first end of the second radiating branch, and the equivalent capacitance comprises the first equivalent sub-capacitance and the second equivalent sub-capacitance connected in series. That is, the first sub-slot, the second sub-slot, and the first decoupling branch can constitute a capacitive decoupling element, which together with the inductive decoupling element forms an LC resonant structure to achieve decoupling between the first antenna unit and the second antenna unit.

[0010] In an embodiment, the inductive decoupling element comprises a second decoupling branch, an inductive element, and a third decoupling branch, wherein the second decoupling branch extends from the second end of the first radiating branch, and the free end of the second decoupling branch is electrically connected to the first end of the inductive element. The third decoupling branch extends from the first end of the second radiating branch, and the free end of the third decoupling branch is electrically connected to the second end of the inductive element.

[0011] Thus, when the first antenna unit is excited, the second decoupling branch can participate in electromagnetic wave radiation of the first antenna unit, and meanwhile can participate in decoupling between the first antenna unit and the second antenna unit. Similarly, when the second antenna unit is excited, the third decoupling branch can participate in electromagnetic wave radiation of the second antenna unit, and meanwhile can participate in decoupling between the first antenna unit and the second antenna unit. That is, the antenna structure provided by the present application can realize decoupling between the first antenna unit and the second antenna unit by arranging the inductive decoupling element to include the second decoupling branch and the third decoupling branch, and meanwhile can enhance the radiation capability of the first antenna unit and the second antenna unit respectively.

[0012] In an embodiment, the gap and the inductive decoupling element are used to adjust the CM impedance between the first antenna unit and the second antenna unit to be close to or equal to the DM impedance between the first antenna unit and the second antenna unit, so as to adjust the resonant frequency of the LC resonant structure to be the same as the decoupling frequency between the first antenna unit and the second antenna unit, thereby realizing decoupling between the first antenna unit and the second antenna unit, improving the isolation between the first antenna unit and the second antenna unit, and making the antenna structure have better radiation performance, thereby improving the communication performance of the terminal device.

[0013] In an embodiment, the first antenna unit and the second antenna unit are same-frequency antenna units, or the operating frequency bands of the first antenna unit and the second antenna unit at least partially overlap. The first radiation branch and the second radiation branch are arranged approximately symmetrically on both sides of the gap.

[0014] In an embodiment, the second antenna unit and the third antenna unit are same-frequency antenna units, or the operating frequency bands of the second antenna unit and the third antenna unit at least partially overlap. The second radiation branch and the third radiation branch are arranged approximately symmetrically on both sides of the center of the radiator.

[0015] In one embodiment, the electrical length of the second radiating branch is equal to one quarter of the electromagnetic wave length of the resonant frequency of the second antenna unit. The electrical length of the third radiating branch is equal to one quarter of the electromagnetic wave length of the resonant frequency of the third antenna unit. The second feeding point and the third feeding point are spaced apart by a preset distance, and the preset distance is less than the length of the second radiating branch and the length of the third radiating branch. For the second antenna unit and the third antenna unit of the common radiator, the spacing between the feeding points of the two affects the isolation effect between the two. The closer the distance between the feeding points of the two, the better the decoupling effect between the two, and accordingly, the higher the isolation between the two.

[0016] In one embodiment, the first antenna unit, the second antenna unit, and the third antenna unit are formed on the same radiator, which is any one of a flexible circuit board antenna, a printed circuit board antenna, or a microstrip antenna.

[0017] In a second aspect, the present application provides a terminal device, which comprises a housing and the antenna structure of the first aspect. The terminal device comprises the antenna structure, which can achieve good isolation between the ports of a MIMO antenna system, has high efficiency, small size, simple structure, and the like, can meet the performance requirements of antennas in the field of intelligent terminal communication, is conducive to the miniaturization of the terminal device, and can improve the communication performance of the terminal device. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0019] Figure 1 A back structure schematic diagram of a terminal device provided by the embodiments of the present application.

[0020] Figure 2 A schematic diagram of an antenna structure provided by the first embodiment of the present application when arranged at a first position.

[0021] FIG. 3(a) is a first perspective schematic diagram of the antenna structure provided by the first embodiment of the present application when arranged at a second position.

[0022] FIG. 3(b) is a second perspective schematic diagram of the antenna structure provided by the first embodiment of the present application when arranged at the second position.

[0023] Figure 4FIG. 1(a) is a schematic diagram of an antenna structure according to a first embodiment of the present application.

[0024] FIG. 5(a) is a schematic diagram of a reflection coefficient curve of a CM resonant mode of the antenna structure shown in FIG. 5(a), and simulation diagrams of current and electric field distribution. Figure 2

[0025] FIG. 5(b) is a schematic diagram of a reflection coefficient curve of a DM resonant mode of the antenna structure shown in FIG. 5(b), and simulation diagrams of current and electric field distribution. Figure 2

[0026] FIG. 6(a) is a simulation diagram of current distribution when the first feed point of the antenna structure shown in FIG. 6(a) is in an excited state. Figure 4

[0027] FIG. 6(b) is a simulation diagram of current distribution when the second feed point of the antenna structure shown in FIG. 6(b) is in an excited state. Figure 4

[0028] FIG. 7(a) is a schematic diagram of S parameter curves of the antenna structure shown in FIG. 7(a) when the inductive decoupling element is not loaded. Figure 4

[0029] FIG. 7(b) is a schematic diagram of S parameter curves of the antenna structure shown in FIG. 7(b) when the inductive decoupling element is loaded. Figure 4

[0030] FIG. 7(c) is a schematic diagram of S parameter and antenna efficiency curves of the antenna structure shown in FIG. 7(c) when the inductive decoupling element is loaded. Figure 4

[0031] FIG. 8(a) is a 3D pattern at a frequency point of 3.5 GHz when the first feed point of the antenna structure shown in FIG. 8(a) is in an excited state. Figure 4

[0032] FIG. 8(b) is a 3D pattern at a frequency point of 3.5 GHz when the second feed point of the antenna structure shown in FIG. 8(b) is in an excited state. Figure 4

[0033] Figure 9 FIG. 10 is a schematic diagram of envelope correlation coefficient of the antenna structure shown in FIG. 10. Figure 4

[0034] FIG. 11(a) is a schematic diagram of the antenna structure according to a third embodiment of the present application in a first position. Figure 10 FIG. 11(b) is a schematic diagram of the antenna structure according to the third embodiment of the present application in a second position.

[0035]

[0036] ​​​​​​​​​​Fig. 11(b) is a second perspective view of the antenna structure of the third embodiment of the present application when the antenna structure is arranged in a second position.

[0037] Figure 12 Fig. 12 is a schematic view of an antenna structure of the fourth embodiment of the present application.

[0038] Fig. 13(a) is a simulation of the current distribution of the antenna structure of the single port when the antenna structure is in an excited state.

[0039] Fig. 13(b) is a simulation of the electric field distribution of the antenna structure of the single port when the antenna structure is in an excited state.

[0040] Fig. 14(a) is a simulation of the current distribution of one of the feed points of the dual port antenna structure of the shared radiator when the feed point is in an excited state.

[0041] Fig. 14(b) is a simulation of the current distribution of the other feed point of the dual port antenna structure of the shared radiator when the feed point is in an excited state.

[0042] Fig. 15(a) is a schematic view of the S parameter curve of the antenna structure shown in Fig. 15. Figure 10 Fig. 15(b) is a schematic view of the S parameter and antenna efficiency curve of the antenna structure shown in Fig. 15.

[0043] Figure 10 Fig. 16(a) is a 3D pattern at a frequency of 3.5 GHz of the first feed point of the antenna structure shown in Fig. 16 when the feed point is in an excited state.

[0044] Fig. 16(b) is a 3D pattern at a frequency of 3.5 GHz of the second feed point of the antenna structure shown in Fig. 16 when the feed point is in an excited state. Figure 10 Fig. 16(c) is a 3D pattern at a frequency of 3.5 GHz of the third feed point of the antenna structure shown in Fig. 16 when the feed point is in an excited state.

[0045] Figure 10 Fig. 17 is a schematic view of the envelope correlation coefficient of the antenna structure shown in Fig. 16.

[0046] Fig. 18 is a schematic view of the envelope correlation coefficient of the antenna structure shown in Fig. 17. Figure 10

[0047] Figure 17 Figure 10

[0048] The following detailed description will further describe the present application with reference to the above-mentioned figures. DETAILED DESCRIPTION

[0049]

[0050]

[0051] The following detailed description will further describe the present application with reference to the above-mentioned figures. DETAILED DESCRIPTION ​​​​

[0052] The technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. The drawings are only used for illustrative description and are schematic diagrams and cannot be understood as limitation of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0053] Unless otherwise defined, all technical and scientific terms used in the present application have the same meanings as commonly understood by one of ordinary skill in the art. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application. For example, in the embodiments of the present application, "first", "second", and "third" are used to distinguish different objects, not to limit a specific order. In addition, the words such as "exemplarily" or "for example" are used to represent an example, illustration or description. Any embodiment or design scheme described as "exemplarily" or "for example" in the embodiments of the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the words such as "exemplarily" or "for example" are intended to present the related concept in a specific way.

[0054] Please refer to Figure 1 , Figure 1 A schematic diagram of the back structure of a terminal device 100 is provided in the embodiments of the present application. The terminal device 100 includes a shell 11 and a display screen (not shown in the figure), and the shell 11 and the display screen together enclose a receiving cavity to accommodate the internal structure of the terminal device 100, such as a battery 12, a circuit board 13, etc. In the embodiments of the present application, the terminal device 100 takes a mobile phone as an example. The shell 11 includes a back cover 111 and a frame 112, and a rear camera 14 can be provided on the back cover 111. The terminal device 100 is also provided with an antenna to realize the wireless communication function of the terminal device 100. In the embodiments of the present application, the terminal device 100 includes an antenna structure 20 arranged in the receiving cavity.

[0055] It should be noted that Figure 1 only some structural components included in the terminal device 100 are schematically shown, and the actual structure and position of these structural components are not limited by Figure 1 , and the terminal device 100 can actually have more structural components relative to the structural components shown in Figure 1 , for example, the terminal device 100 can also include a processor, a memory, a front camera, a fingerprint module, etc.

[0056] Please refer to Figure 2The first embodiment of the present application provides a dual-port antenna structure 201, wherein the antenna structure 201 includes a first antenna unit 21 and a second antenna unit 22, wherein the first antenna unit 21 includes a first radiating branch 211 and a first feeding point 212, wherein the first end of the first radiating branch 211 is provided with the first feeding point 212, and the second end of the first radiating branch 211 is suspended, that is, the second end of the first radiating branch 211 is an open end. The second antenna unit 22 includes a second radiating branch 221 and a second feeding point 222, wherein the first end of the second radiating branch 221 is suspended, that is, the first end of the second radiating branch 221 is an open end, and the second end of the second radiating branch 221 is provided with the second feeding point 222.

[0057] In the first embodiment, a gap 24 is formed between the first end of the second radiation branch 221 and the second end of the first radiation branch 211. In one embodiment, the first radiation branch 211 and the second radiation branch 221 may be two branches formed by slits on the same radiator A1.

[0058] The antenna form of the radiator A1 can be any one of the following: flexible circuit board antenna, printed circuit board antenna, microstrip antenna. In one embodiment, Figure 2 As shown, the radiator A1 can be attached to the surface of the circuit board 13 inside the terminal device 100, for example, on the surface of the circuit board 13 facing the back cover 111. In a specific implementation, an insulating medium can be provided between the surface of the circuit board 13 and the radiator A1 to electrically isolate the circuit board 13 and the radiator A1 from each other. For example, the routing layer of the circuit board 13 can be printed on the front side of a dielectric substrate, and the first radiation branch 211 and the second radiation branch 221 can be printed on the back side of the dielectric substrate. In another embodiment, as shown in Figures 3(a) and 3(b), the radiator A1 can be attached to the side of the circuit board 13 facing the frame 112. In a specific implementation, a layer of insulating dielectric layer can be first provided on the side of the circuit board 13, and then the radiator A1 can be attached to the surface of the dielectric layer away from the circuit board 13. It should be noted that the arrangement of the radiator A1 on the circuit board 13 shown in the embodiment of the present application is only a schematic illustration. In a specific implementation, the arrangement of the radiator A1 can be adjusted accordingly according to actual needs.

[0059] The circuit board 13 can be used as a metal ground plate of the first antenna unit 21 and the second antenna unit 22. A first feeding port (not shown in the figure) and a second feeding port (not shown in the figure) can be arranged on the circuit board 13, the first feeding port is electrically connected with the first feed source 31, and the second feeding port is electrically connected with the second feed source 32. The first feeding point 212 can be electrically connected with the first feeding port through a connection structure such as a feeding spring, so as to realize the excitation of the first antenna unit 21 by the first feed source 31. Similarly, the second feeding point 222 can be electrically connected with the second feeding port through a connection structure such as a feeding spring, so as to realize the excitation of the second antenna unit 22 by the second feed source 32.

[0060] In the first embodiment, the first antenna unit 21 and the second antenna unit 22 are same-frequency antenna units, or the operating frequency bands of the first antenna unit 21 and the second antenna unit 22 at least partially overlap. In the embodiment of the present application, the antenna structure 201 covers the N78 frequency band (3.4 GHz-3.6 GHz) of 5G as an example. In other embodiments, the antenna structure 201 can also be designed to cover the N77 frequency band (3.3 GHz-4.2 GHz) or the N79 frequency band (4.4 GHz-5.0 GHz), etc., to meet the communication needs of 5G terminal devices.

[0061] In order to realize the decoupling between the first antenna unit 21 and the second antenna unit 22, please refer to Figure 2 or Figure 3(a)-Figure 3(b) In the first embodiment, the gap 24 forms an equivalent capacitance between the second end of the first radiating branch 211 and the first end of the second radiating branch 221. That is, the gap 24 is equivalent to a capacitive decoupling element.

[0062] The antenna structure 201 further comprises an inductive decoupling element 25 electrically connected between the second end of the first radiating branch 211 and the first end of the second radiating branch 221, the inductive decoupling element 25 forms an equivalent inductance between the second end of the first radiating branch 211 and the first end of the second radiating branch 221. Wherein, the equivalent capacitance and the equivalent inductance form an LC resonance structure, and the LC resonance structure is used to realize the decoupling between the first antenna unit 21 and the second antenna unit 22.

[0063] That is, the antenna structure 201 forms a capacitive decoupling element by forming a gap 24 (for example, the gap 24 is opened on the radiator A1) between the first radiation branch 211 and the second radiation branch 221, and sets the inductive decoupling element 25 between the first radiation branch 211 and the second radiation branch 221, and forms an LC resonance structure through the capacitive decoupling element and the inductive decoupling element 25 to achieve decoupling between the first antenna unit 21 and the second antenna unit 22. Wherein, the parameters corresponding to the LC resonance structure meet the decoupling requirement of the decoupling frequency band between the first antenna unit 21 and the second antenna unit 22, so as to achieve decoupling between the first antenna unit 21 and the second antenna unit 22 within the radiation bandwidth of the first antenna unit 21 and the second antenna unit 22.

[0064] In the first embodiment, the gap 24 is in a finger shape, and the gap 24 can also be used to reduce the inductance value of the equivalent inductance corresponding to the inductive decoupling element 25, so as to achieve the purpose of reducing the size of the inductive decoupling element 25 to reduce the space occupied by the inductive decoupling element 25 in the accommodating cavity of the terminal device 100.

[0065] Specifically, since the larger the inductance value is, the larger the volume of the inductance is generally, the purpose of reducing the volume of the inductance can be achieved by reducing the inductance value. According to the resonance frequency formula of the LC resonance structure: f = 1 / (2*π*√LC), under the condition that the resonance frequency f is unchanged, the inductance value of the equivalent inductance is inversely proportional to the capacitance value of the equivalent capacitance. According to the calculation formula of the capacitance: C = εrS / (4πkd), under the condition that the relative dielectric constant εr of the medium, the electrostatic force constant K, and the distance d of the capacitance plate are unchanged, the capacitance value C of the capacitance is proportional to the facing area S of the capacitance plate.

[0066] The antenna structure 201 provided in the present application can increase the length of the gap 24 by designing the gap 24 between the first radiation branch 211 and the second radiation branch 221 to be in a finger shape, under the condition that the thickness and width of the first radiation branch 211 and the second radiation branch 221, and the spacing between the two radiation branches are unchanged, so as to increase the facing area of the capacitance plate of the equivalent capacitance, increase the capacitance value of the equivalent capacitance, and then reduce the inductance value of the equivalent inductance, so as to achieve the purpose of reducing the size of the inductive decoupling element 25.

[0067] In the first embodiment, as Figure 2Or as shown in FIG. 3(b), the gap 24 is a continuous gap. That is, a gap 24 is formed on the radiator Al in a direction through the width and thickness of the radiator Al to form the first radiating branch 211 and the second radiating branch 221.

[0068] In a second embodiment, as shown in FIG. 3(c), two gaps are formed on the radiator Al in a direction through the width and thickness of the radiator Al to form the first radiating branch 211 and the second radiating branch 221. That is, in the second embodiment, the dual-port antenna structure 202 further comprises a first decoupling branch 241 disposed between the second end of the first radiating branch 211 and the first end of the second radiating branch 221, wherein a first sub-gap G1 in the shape of a cross is formed between the first end of the first radiating branch 211 and the second end of the first decoupling branch 241, a second sub-gap G2 in the shape of a cross is formed between the second end of the first decoupling branch 241 and the first end of the second radiating branch 221, and the gap 24 comprises the first sub-gap G1 and the second sub-gap G2. Figure 4

[0069] The first sub-gap G1 forms a first equivalent sub-capacitance between the second end of the first radiating branch 211 and the first end of the first decoupling branch 241, the second sub-gap G2 forms a second equivalent sub-capacitance between the second end of the first decoupling branch 241 and the first end of the second radiating branch 221, the first equivalent sub-capacitance and the second equivalent sub-capacitance are connected in series between the second end of the first radiating branch 211 and the first end of the second radiating branch 221, and the equivalent capacitance comprises the first equivalent sub-capacitance and the second equivalent sub-capacitance connected in series. That is, the first sub-gap G1, the second sub-gap G2, and the first decoupling branch 241 can constitute a capacitive decoupling element, which, together with the inductive decoupling element 25, forms an LC resonant structure to achieve decoupling between the first antenna unit 21 and the second antenna unit 22.

[0070] In other embodiments, the gap 24 can also comprise three or more sub-gaps. The number of gaps formed on the radiator Al is not limited in the present application.

[0071] Please refer again to Figure 2 , FIG. 3(a) or Figure 4 , the inductive decoupling element 25 is connected across the outside of the gap 24. In an implementation, the inductive decoupling element 25 can be disposed on the surface or side of the circuit board 13, for example Figure 2 and Figure 4 ​As shown, the inductive decoupling element 25 and the first and second radiating stubs 211 and 221 can be arranged on the same surface of the circuit board 13. Alternatively, in another embodiment, as shown in FIG. 3(a) and FIG. 3(b), the inductive decoupling element 25 can be arranged on the side of the circuit board 13 away from the first and second radiating stubs 211 and 221 and across the gap 24. Alternatively, in other embodiments, the inductive decoupling element 25 can be arranged on the surface of the circuit board 13 while the first and second radiating stubs 211 and 221 are arranged on the side of the circuit board 13; or the inductive decoupling element 25 can be arranged on the side of the circuit board 13 while the first and second radiating stubs 211 and 221 are arranged on the surface of the circuit board 13.

[0072] The first end of the inductive decoupling element 25 is electrically connected to the second end of the first radiating stub 211, and the second end of the inductive decoupling element 25 is electrically connected to the first end of the second radiating stub 221. Specifically, the inductive decoupling element 25 includes a second decoupling stub 251, a third decoupling stub 252, and an inductive element 253, wherein the second decoupling stub 251 extends from the second end of the first radiating stub 211, and the free end of the second decoupling stub 251 is electrically connected to the first end of the inductive element 253. The third decoupling stub 252 extends from the first end of the second radiating stub 221, and the free end of the third decoupling stub 252 is electrically connected to the second end of the inductive element 253. In this way, when the first antenna unit 21 is excited, the second decoupling stub 251 can participate in the electromagnetic wave radiation of the first antenna unit 21, and at the same time, participate in the decoupling between the first and second antenna units 21 and 22. Similarly, when the second antenna unit 22 is excited, the third decoupling stub 252 can participate in the electromagnetic wave radiation of the second antenna unit 22, and at the same time, participate in the decoupling between the first and second antenna units 21 and 22. That is, the antenna structure 201 or 202 provided by the present application can realize the decoupling between the first and second antenna units 21 and 22 by arranging the inductive decoupling element 25 to include the second and third decoupling stubs 251 and 252, and at the same time, enhance the radiation capability of the first and second antenna units 21 and 22, respectively.

[0073] In an embodiment, the first antenna unit 21 and the second antenna unit 22 can each be a monopole antenna, the electrical length of the first radiating branch 211 is equal to one quarter of the electromagnetic wave length of the resonant frequency of the first antenna unit 21, and the electrical length of the second radiating branch 221 is equal to one quarter of the electromagnetic wave length of the resonant frequency of the second antenna unit 22. In other embodiments, the first antenna unit 21 and the second antenna unit 22 can also be designed as other forms of antennas, such as IFA antennas, etc.

[0074] In the first embodiment or the second embodiment, the first radiating branch 211 and the second radiating branch 221 are arranged approximately symmetrically on both sides of the gap 24. The gap 24 and the inductive decoupling element 25 are used to adjust the CM impedance between the first antenna unit 21 and the second antenna unit 22 to be equal or approximately equal to the DM impedance between the first antenna unit 21 and the second antenna unit 22, so as to adjust the resonant frequency of the LC resonant structure to be the same as the decoupling frequency between the first antenna unit 21 and the second antenna unit 22, thereby achieving decoupling between the first antenna unit 21 and the second antenna unit 22 and improving the isolation between the first antenna unit 21 and the second antenna unit 22. It should be noted that the "decoupling frequency" referred to in the present application refers to a resonant frequency at which the coupling between the first antenna unit 21 and the second antenna unit 22 can be eliminated. For example, in an embodiment, if the first antenna unit 21 and the second antenna unit 22 are co-frequency antenna units, the "decoupling frequency" can be defined as a frequency that is the same as the resonant frequency of the first antenna unit 21 and the resonant frequency of the second antenna unit 22. If the operating frequency bands of the first antenna unit 21 and the second antenna unit 22 at least partially overlap, the "decoupling frequency" can be defined as a frequency that overlaps with the resonant frequency of the first antenna unit 21 and the resonant frequency of the second antenna unit 22.

[0075] The isolation of the antenna structure 201 is further described below in connection with simulation tests.

[0076] Please refer to FIG. 5(a), which is a simulation test result of the isolation of the antenna structure 201. Figure 2The following diagrams illustrate a reflection coefficient curve obtained from a simulation test of the common-mode (CM) resonant mode of the dual-port antenna structure 201, as well as simulated current and electric field distribution diagrams. In the reflection coefficient curve diagram shown in FIG5(a), the curves labeled 1, 2, and 3 represent the corresponding reflection coefficient curves when the structure of the slot 24 remains unchanged and the equivalent inductance of the inductive decoupling element 25 is set to 3 nh, 5 nh, and 8 nh, respectively. As can be seen from the reflection coefficient curve diagram shown in FIG5(a), while the structure of the slot 24 remains unchanged, the resonant frequency and antenna efficiency of the antenna structure 201 change with the change in the equivalent inductance of the inductive decoupling element 25.

[0077] Please refer to Figure 5(b). Figure 5(b) is a diagram of Figure 2 The following diagrams illustrate a reflection coefficient curve obtained from simulation testing of the differential mode (DM) resonant mode of the dual-port antenna structure 201, as well as simulated current and electric field distribution diagrams. In the reflection coefficient curve diagram shown in FIG5(b), the curves labeled 1, 2, and 3 represent the corresponding reflection coefficient curves when the structure of the slot 24 remains unchanged and the equivalent inductance of the inductive decoupling element 25 is set to 3 nh, 5 nh, and 8 nh, respectively. As can be seen from the reflection coefficient curve diagram shown in FIG5(b), when the structure of the slot 24 remains unchanged, the resonant frequency and antenna efficiency of the antenna structure 201 do not change with changes in the equivalent inductance of the inductive decoupling element 25.

[0078] As can be seen from the reflection coefficient curves shown in Figures 5(a) and 5(b), adding an inductor at a suitable location on the antenna structure 201 has little effect on the DM resonance of the antenna structure 201, but primarily affects the resonant frequency of the CM resonance of the antenna structure 201. Therefore, by adjusting the matching, that is, the inductance of the inductive element 253, the CM resonance of the antenna structure 201 can be individually adjusted, thereby achieving high isolation between the two ports of the antenna structure 201.

[0079] For the first antenna unit 21 and the second antenna unit 22 of the same frequency, due to the reflection coefficient S 11 =S 22 , transmission coefficient S 12 =S 21 , according to the corresponding relationship between the reflection coefficient and transmission coefficient of the CM resonance mode and the DM resonance mode: S cc11 =(S 11 +S 12 +S 21 +S 22 ) / 2,S dd11 =(S 11 -S12 - S 21 + S 22 ) / 2, we can get: S cc11 - S dd11 = 2S 21 That is, when single-port excitation, if the CM resonant mode and the DM resonant mode have the same impedance matching, the CM resonant frequency is equal to or approximately equal to the DM resonant frequency, and the excitation current amplitude of the CM resonant mode and the DM resonant mode is the same, then the current in the passive port can be completely cancelled, at this time, the transmission coefficient S 21 between the two antenna units is 0, and the two antenna units have the best isolation.

[0080] As can be seen from the current and electric field distribution simulation diagrams shown in FIG. 5(a) and FIG. 5(b), when the amplitude and phase of the CM signal and the DM signal fed in one of the ports (for example, the first feeding point 212) are the same, and the amplitude of the CM signal and the DM signal fed in the other port (for example, the second feeding point 222) is the same but the phase is opposite, the CM mode and the DM mode on the first radiating branch 211 have the same direction of the radiating current, and the CM mode and the DM mode near the first radiating branch 211 also have the same direction of the radiating electric field, which can realize the same direction superposition of the radiating currents of the two modes and the same direction superposition of the radiating electric fields of the two modes, thereby enhancing the radiation capability. The CM mode and the DM mode on the second radiating branch 221 have opposite directions of the radiating current, and the CM mode and the DM mode near the second radiating branch 221 also have opposite directions of the radiating electric field, that is, the opposite direction radiating currents of the two modes cancel each other, and the opposite direction radiating electric fields of the two modes also cancel each other, which is equivalent to that no radiating current and radiating electric field are generated on the second radiating branch 221. Therefore, when excitation signals are fed in one of the ports, and no excitation signal is fed in the other port, it is equivalent to that the sum of the CM signal and the DM signal with the same amplitude and phase is fed in the one port, and the CM signal and the DM signal with the same amplitude but opposite phase are fed in the other port, and the excitation current fed in the one port does not couple into the other port.

[0081] It can be seen that the antenna structure 201 provided by the present application adjusts the CM impedance of the antenna structure 201 to be close to or equal to the DM impedance of the antenna structure 201 by using the gap 24 and the inductive decoupling element 25, so that the CM resonant frequency is equal to or approximately equal to the DM resonant frequency, which can not only improve the isolation between the first antenna unit 21 and the second antenna unit 22, but also enable the antenna structure 201 to have better radiation performance, thereby improving the communication performance of the terminal device 100.

[0082] In the following, the first antenna unit 21 and the second antenna unit 22 of the antenna structure 202 are both operated in the N78 frequency band and the resonant frequency is 3.5 GHz. Figure 4 The performance of the antenna structure 202 is analyzed.

[0083] Figure 6(a) shows Figure 4 The current distribution simulation diagram of the dual-port antenna structure 202 when the first feed point 212 is in an excited state is shown in Figure 6(a). As can be seen from the current distribution simulation diagram shown in Figure 6(a), when the first feed point 212 of the first antenna element 21 is in an excited state, the radiation current is mainly concentrated in the first radiation branch 211 of the first antenna element 21, and only a weak radiation current is generated in the second radiation branch 221 and the second feed point 222 of the second antenna element 22. In other words, when the first feed point 212 is in an excited state, the radiation current generated in the first radiation branch 211 has little impact on the second feed point 222.

[0084] Figure 6(b) shows Figure 4 The current distribution simulation diagram of the second feed point 222 of the dual-port antenna structure 202 when it is in an excited state is shown in Figure 6(b). As can be seen from the current distribution simulation diagram shown in Figure 6(b), when the second feed point 222 of the second antenna element 22 is in an excited state, the radiation current is mainly concentrated in the second radiating branch 221 of the second antenna element 22, and only weak radiation current is generated in the first radiating branch 211 and the first feed point 212 of the first antenna element 21. In other words, when the second feed point 222 is in an excited state, the radiation current generated in the second radiating branch 221 has little impact on the first feed point 212.

[0085] As can be seen from the current distribution simulation diagrams shown in FIG. 6( a ) and FIG. 6 ( b ), there is a high degree of isolation between the first feeding point 212 and the second feeding point 222 .

[0086] Figure 7(a) shows Figure 4 The figure shows a schematic diagram of the S-parameter curve of the dual-port antenna structure 202 when the inductive decoupling element 25 is not loaded. Reference numeral S11 indicates the reflection coefficient curve of the first antenna unit 21, reference numeral S22 indicates the reflection coefficient curve of the second antenna unit 22, and reference numeral S21 indicates the transmission coefficient curve between the first antenna unit 21 and the second antenna unit 22. As can be seen from the S-parameter curve shown in FIG7(a), within the operating frequency band (3.4-3.6 GHz), the isolation between the two ports (i.e., the first feeding point 212 and the second feeding point 222) is very poor, at only 2.7 dB to 3.2 dB.

[0087] Figure 7(b) showsFigure 4 The figure shows a schematic diagram of the S-parameter curve of the dual-port antenna structure 202 when the inductive decoupling element 25 is loaded. Reference numeral S11 indicates the reflection coefficient curve of the first antenna unit 21, reference numeral S22 indicates the reflection coefficient curve of the second antenna unit 22, and reference numeral S21 indicates the transmission coefficient curve between the first antenna unit 21 and the second antenna unit 22. As can be seen from the S-parameter curve shown in FIG7(b), within the operating frequency band (3.4-3.6 GHz), the reflection coefficient S11 of the first antenna unit 21 and the reflection coefficient S22 of the second antenna unit 22 are both less than -6 dB, and the isolation between the two ports (i.e., the first feeding point 212 and the second feeding point 222) is higher than 13 dB, and can reach up to 37 dB, indicating very good isolation.

[0088] Figure 7(c) shows Figure 4 The figure shows the S-parameters and antenna efficiency curves of the dual-port antenna structure 202 when loaded with the inductive decoupling element 25. Reference numeral S11 indicates the reflection coefficient curve of the first antenna unit 21, reference numeral S22 indicates the reflection coefficient curve of the second antenna unit 22, reference numeral Rad_P1 indicates the radiation efficiency curve of the first antenna unit 21, reference numeral Rad_P2 indicates the radiation efficiency curve of the second antenna unit 22, reference numeral Tot_P1 indicates the system efficiency curve of the first antenna unit 21, and reference numeral Tot_P2 indicates the system efficiency curve of the second antenna unit 22. As can be seen from FIG7(c), within the operating frequency band (3.4-3.6 GHz), the antenna efficiency (radiation efficiency and system efficiency) of the first antenna unit 21 and the antenna efficiency of the second antenna unit 22 are both high, with no efficiency pits. It can be seen that the antenna structure 202 provided in the embodiment of the present application not only improves the isolation between the first antenna unit 21 and the second antenna unit 22, but also improves the antenna efficiency of the first antenna unit 21 and the second antenna unit 22.

[0089] Figure 8(a) shows Figure 4 The 3D directional pattern at 3.5 GHz frequency when the first feeding point 212 of the dual-port antenna structure 202 is in the excited state is shown in FIG8(b). Figure 4 The 3D radiation pattern of the dual-port antenna structure 202 at 3.5 GHz when the second feed point 222 is in an excited state is shown. As can be seen from the 3D radiation patterns shown in Figures 8(a) and 8(b), the antenna structure 202 provided in this embodiment of the application improves the isolation between the two ports while maintaining stable radiation patterns and polarization patterns.

[0090] Figure 9 forFigure 4 The envelope correlation coefficient (ECC) of the dual-port antenna structure 202 is shown in the diagram. The ECC is a coefficient used to represent the MIMO performance of multiple antennas. The smaller the ECC, the better the throughput performance of the antenna. Generally, the ECC is required to be less than 0.2. From the diagram, it can be seen that the ECC between the two ports of the antenna structure 202 in the working frequency band of 3.4-3.6 GHz is less than 0.12, and the antenna structure 202 has good diversity performance. Figure 9

[0091] In summary, the dual-port antenna structure 202 provided by the embodiments of the present application forms a gap structure between the first antenna unit 21 and the second antenna unit 22, and forms inductive lines on the first radiation branch 211 and the second radiation branch 221 without increasing the spacing between the antenna units, so that the CM impedance and the DM impedance of the antenna structure 202 are equal, thereby adjusting the resonant frequency of the antenna structure 202 in the common mode state to be equal to the resonant frequency of the antenna structure 202 in the differential mode state, effectively improving the isolation between the first antenna unit 21 and the second antenna unit 22, and achieving the purpose of improving the antenna efficiency of the antenna structure 202.

[0092] In addition, the gap 24 between the first antenna unit 21 and the second antenna unit 22 is designed as a cross-shaped opening structure, which can effectively reduce the size of the inductive decoupling element 25, thereby facilitating the further miniaturization of the antenna structure 202, further reducing the space occupied by the antenna structure 202, and facilitating the application of the antenna structure 202 to a miniaturized terminal device 100 with a small clearance.

[0093] Please refer to Figure 10 The third embodiment of the present application further provides a three-port antenna structure 203, wherein, with respect to Figure 4 the dual-port antenna structure 202, Figure 10 The three-port antenna structure 203 shown in the diagram adds a third antenna unit 23, and the third antenna unit 23 includes a third radiation branch 231. The first end of the third radiation branch 231 is provided with a third feeding point 232, and the second end of the third radiation branch 231 is suspended, i.e., the second end of the third radiation branch 231 is an open end.

[0094] ​In the third embodiment, the first radiation branch 211, the second radiation branch 221, and the third radiation branch 231 may be three branches formed on the same radiator A2. The antenna form of the radiator A2 may be any one of the following: a flexible circuit board antenna, a printed circuit board antenna, or a microstrip antenna. The arrangement of the radiator A2 in the housing 11 of the terminal device 100 may be similar to the arrangement of the radiator A1 in the first embodiment, for example Figure 10 As shown, the radiator A2 can be attached to the surface of the circuit board 13 facing the back cover 111. Optionally, as shown in Figures 11(a) and 11(b), the radiator A2 can be attached to the side of the circuit board 13 facing the frame 112. It should be noted that the arrangement of the radiator A2 on the circuit board 13 shown in the embodiment of the present application is only a schematic illustration. In a specific implementation, the arrangement of the radiator A2 can be adjusted accordingly according to actual needs. In some embodiments, the double-slit structure (first sub-slit G1 and second sub-slit G2) included in the antenna structure 203 can also be designed as follows Figure 12 The antenna structure 204 shown includes a single slot structure.

[0095] The circuit board 13 can also serve as a metal floor for the third antenna unit 23. A third feed port (not shown) can also be provided on the circuit board 13. The third feed port is electrically connected to the third feed source 33. The third feed point 232 can be electrically connected to the third feed port, for example, via a connection structure such as a feed spring, to enable the third feed source 33 to excite the third antenna unit 23.

[0096] In the third embodiment, the antenna structure 203 is a three-port MIMO antenna structure 203. The first antenna unit 21, the second antenna unit 22, and the third antenna unit 23 are co-frequency antenna units, or the operating frequency bands of the first antenna unit 21, the second antenna unit 22, and the third antenna unit 23 at least partially overlap. In the embodiment of the present application, the antenna structure 203 covering the 5G N78 frequency band is taken as an example. In other embodiments, the antenna structure 203 can also be designed to cover the N77 frequency band, or the N79 frequency band, etc., to meet the communication requirements of 5G terminal devices.

[0097] Among them, in the antenna structure 203 provided in the third embodiment, the structures of the first antenna unit 21 and the second antenna unit 22 and the decoupling principle therebetween can be referred to the previous detailed description of the structures of the first antenna unit 21 and the second antenna unit 22 included in the antenna structure 201 or 202 and the decoupling principle therebetween, which will not be repeated here.

[0098] In the third embodiment, the second radiating branch 221 and the third radiating branch 231 are formed on the same radiator A2, the second end of the second radiating branch 221 is adjacent to the first end of the third radiating branch 231, and the second feeding point 222 and the third feeding point 232 are close to each other to realize self-decoupling between the second antenna unit 22 and the third antenna unit 23. That is, the second radiating branch 221 and the third radiating branch 231 are a self-decoupling antenna design, and the same radiator A2 is excited through two feeding ports.

[0099] The antenna structure 203 can also be understood as that the slot 24 is formed on the radiator A2, and the first feeding point 212, the second feeding point 222 and the third feeding point 232 are arranged on the radiator A2, so as to construct the first antenna unit 21, the second antenna unit 22 and the third antenna unit 23.

[0100] In an embodiment, the first antenna unit 21, the second antenna unit 22 and the third antenna unit 23 can all be monopole antennas, the electrical length of the first radiating branch 211 is equal to one fourth of the electromagnetic wave wavelength of the resonant frequency of the first antenna unit 21, the electrical length of the second radiating branch 221 is equal to one fourth of the electromagnetic wave wavelength of the resonant frequency of the second antenna unit 22, and the electrical length of the third radiating branch 231 is equal to one fourth of the electromagnetic wave wavelength of the resonant frequency of the third antenna unit 23. In other embodiments, the first antenna unit 21, the second antenna unit 22 and the third antenna unit 23 can also be designed as other forms of antennas, such as IFA antennas and the like.

[0101] In the third embodiment, the second feeding point 222 and the third feeding point 232 are spaced apart by a preset distance, and the preset distance is less than the length of the second radiating branch 221 and the length of the third radiating branch 231.

[0102] In the third embodiment, the second radiating branch 221 and the third radiating branch 231 are arranged approximately symmetrically on both sides of the center of the radiator A2. That is, the position of the second feeding point 222 and the position of the third feeding point 232 are both deviated from the center of the radiator A2.

[0103] The working principle and antenna performance of the antenna structure 203 shown in FIG. 3 are analyzed below, taking the first antenna unit 21, the second antenna unit 22 and the third antenna unit 23 of the antenna structure 203 all working in the N78 frequency band with a resonant frequency of 3.5 GHz as an example. Figure 10 The working principle and antenna performance of the antenna structure 203 shown in FIG. 3 are analyzed below, taking the first antenna unit 21, the second antenna unit 22 and the third antenna unit 23 of the antenna structure 203 all working in the N78 frequency band with a resonant frequency of 3.5 GHz as an example.

[0104] As shown in FIG. 13(a) and FIG. 13(b), taking the single port P with a bias feed on the radiator B as an example, in one excitation mode, the left branch b1 on the left side of the port is excited to generate a radiation mode, while the right branch b2 on the right side of the port is not excited to generate a radiation mode, a strong current is generated on the left branch b1, and only a weak current is generated on the right branch b2. Among them, the position on the right side of the port P is a current small point, the right end of the right branch b2 is an open end, and there is a strong electric field, which is the strongest electric field point and the smallest current point. From the right end of the right branch b2 to the port P, the current changes slightly, but the electric field changes significantly. That is, the position of the right branch b2 close to the port P is a position where the current and electric field are relatively small. Since the potential difference between the current small point and the relatively small electric field point is close to 0, loading a short-circuit or open-circuit branch at this position has little effect on the main resonance frequency, current distribution and radiation pattern of the original antenna, thereby realizing a self-decoupling antenna.

[0105] Based on the above principle, the antenna structure 203 sets the second feed point 222 and the third feed point 232 close to each other, as shown in FIG. 14(a), when the second feed point 222 is in an excited state, a strong current is generated on the second radiation branch 221 on the left side of the second feed point 222, and the third radiation branch 231 on the right side of the second feed point 222 is not excited to generate a radiation mode. The position on the right side of the second feed point 222 is a current small point, and the position near the right side of the second feed point 222 is a current small point and a relatively small electric field point. Since the third feed point 232 is close to the second feed point 222, according to the above analysis, the third feed point 232 is located at the current small point and the relatively small electric field point, and the potential difference between the third radiation branch 231 and the ground plane at the third feed point 232 is 0 or close to 0, therefore, the current in the third feed point 232 is also close to 0, thereby realizing self-decoupling between the second feed point 222 and the third feed point 232.

[0106] Similarly, as shown in FIG14( b), when the third feed point 232 is in an excited state, a strong current is generated on the third radiating branch 231 on the right side of the third feed point 232, while the second radiating branch 221 on the left side of the third feed point 232 is not excited to radiate. The position to the left of the third feed point 232 is a point with low current, and the position near the left side of the third feed point 232 is a point with low current and a relatively low electric field. Since the second feed point 222 is located near the third feed point 232, according to the above analysis, the second feed point 222 is located at a point with low current and a relatively low electric field. At the second feed point 222, the potential difference between the second radiating branch 221 and the ground is 0, or close to 0. Therefore, the current in the second feed point 222 is also close to 0, thereby achieving self-decoupling between the third feed point 232 and the second feed point 222.

[0107] It can be seen that for the second antenna unit 22 and the third antenna unit 23 of the common radiator, the interval between the feeding points of the two will affect the isolation effect between the two. The closer the distance between the feeding points of the two, the better the decoupling effect between the two, and accordingly, the higher the isolation between the two.

[0108] Figure 15(a) shows Figure 10 Schematic diagram of S-parameter curves of the three-port antenna structure 203. Reference numerals S11, S22, and S33 respectively indicate the reflection coefficient curves of the first antenna unit 21, the second antenna unit 22, and the third antenna unit 23. Reference numeral S21 indicates the transmission coefficient curve between the first antenna unit 21 and the second antenna unit 22. Reference numeral S13 indicates the transmission coefficient curve between the first antenna unit 21 and the third antenna unit 23. Reference numeral S32 indicates the transmission coefficient curve between the second antenna unit 22 and the third antenna unit 23.

[0109] It can be seen from the S-parameter curve shown in Figure 15(a) that within the operating frequency band (3.4-3.6GHz), the reflection coefficient S11 of the first antenna unit 21, the reflection coefficient S22 of the second antenna unit 22, and the reflection coefficient S33 of the third antenna unit 23 are all less than -6dB, and the isolation between the ports is higher than 12.5dB, which is very good.

[0110] In addition, by comparing the transmission coefficient curves shown in Figure 7(b) and Figure 15(a), it can be seen that since the antenna structure 203 is loaded with the third radiating branch 231 on the right side of the second feeding point 222, the symmetry of the first radiating branch 211 and the second radiating branch 221 relative to the gap 24 is destroyed. Therefore, the deepest point of the isolation between the first feeding point 212 and the second feeding point 222 will deteriorate, but the sideband isolation will not deteriorate.

[0111] Since the first feeding point 212 and the third feeding point 232 are physically far apart, there is a high degree of isolation between the two mainly due to the effect of the increased physical distance.

[0112] Figure 15(b) shows Figure 10 The schematic diagram of the S parameter and antenna efficiency curve of the three-port antenna structure 203 is shown. Among them, the reference numerals S11, S22, and S33 are used to indicate the reflection coefficient curves of the first antenna unit 21, the second antenna unit 22, and the third antenna unit 23, respectively; the reference numerals Rad_P1, Rad_P2, and Rad_P3 are used to indicate the radiation efficiency curves of the first antenna unit 21, the second antenna unit 22, and the third antenna unit 23; and the reference numerals Tot_P1, Tot_P2, and Tot_P3 are used to indicate the system efficiency curves of the first antenna unit 21, the second antenna unit 22, and the third antenna unit 23. As can be seen from Figure 15(b), within the operating frequency band (3.4-3.6GHz), the antenna efficiency of each antenna unit is high, and no efficiency pit occurs. It can be seen that the antenna structure 203 provided in the embodiment of the present application improves the isolation between the ports while also simultaneously improving the antenna efficiency.

[0113] Figure 16(a) shows Figure 10 The 3D directional pattern at 3.5 GHz frequency when the first feeding point 212 of the antenna structure 203 is in the excited state is shown in FIG16(b). Figure 10 The 3D directional pattern at 3.5 GHz frequency when the second feeding point 222 of the antenna structure 203 is in the excited state is shown in FIG16(c). Figure 10 The 3D directional pattern of the third feeding point 232 of the antenna structure 203 shown in FIG. 2 is at a frequency of 3.5 GHz when the third feeding point 232 is in an excited state. Figure 16(a)-Figure 16(c) It can be seen from the 3D directional pattern shown that the antenna structure 203 provided in the embodiment of the present application improves the isolation between the three ports while maintaining the stability of the antenna's radiation pattern and polarization directional pattern characteristics.

[0114] Figure 17 for Figure 10An envelope correlation coefficient diagram of the three-port antenna structure 203 is shown. In the diagram, reference ECC_S12 is used to indicate an ECC curve between the first antenna unit 21 and the second antenna unit 22, reference ECC_S13 is used to indicate an ECC curve between the first antenna unit 21 and the third antenna unit 23, and reference ECC_S23 is used to indicate an ECC curve between the second antenna unit 22 and the third antenna unit 23. It can be seen that, in the working frequency band 3.4GHz-3.6GHz, the ECC between the ports of the antenna structure 203 is less than 0.1, and the antenna structure 203 has good diversity performance. Figure 17 It can be seen that, in the working frequency band 3.4GHz-3.6GHz, the ECC between the ports of the antenna structure 203 is less than 0.1, and the antenna structure 203 has good diversity performance.

[0115] In summary, the antenna structure 203 provided by the embodiments of the present application is a three-port MIMO antenna with self-coupling characteristics. Since the first antenna unit 21, the second antenna unit 22, and the third antenna unit 23 share the radiator A2, the integration of the antenna structure 203 can be improved, and the space occupied by the antenna structure 203 can be reduced.

[0116] In addition, since the inductive decoupling element 25 is arranged between the first antenna unit 21 and the second antenna unit 22, and the first antenna unit 21 and the second antenna unit 22 are spaced apart by the interdigital-shaped gap 24, the decoupling between the first antenna unit 21 and the second antenna unit 22 is achieved by the gap 24 and the inductive decoupling element 25, and the size of the inductive decoupling element 25 is reduced by the interdigital-shaped gap 24, thereby facilitating further miniaturization of the antenna structure 203 to further reduce the space occupied by the antenna structure 203.

[0117] In addition, since the inductive decoupling element 25 is arranged between the first antenna unit 21 and the second antenna unit 22, and the first antenna unit 21 and the second antenna unit 22 are spaced apart by the interdigital-shaped gap 24, the decoupling between the first antenna unit 21 and the second antenna unit 22 is achieved by the gap 24 and the inductive decoupling element 25, and the size of the inductive decoupling element 25 is reduced by the interdigital-shaped gap 24, thereby facilitating further miniaturization of the antenna structure 203 to further reduce the space occupied by the antenna structure 203.

[0118] In summary, the antenna structure 203 can achieve good isolation between the ports of the MIMO antenna system, and has the characteristics of high efficiency, miniaturization, simple structure, etc., can meet the performance requirements of antennas in the field of intelligent terminal communication, is also conducive to application to small-sized terminal devices 100 with small clearances, and can improve the communication performance of the terminal device 100.

[0119] The above description is only specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any changes or alternatives that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application shall be covered in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An antenna structure, comprising: a first antenna element comprising a first radiating branch and a first feed point provided at a first end of the first radiating branch; a second antenna element comprising a second radiating branch and a second feed point, a first end of the second radiating branch and a second end of the first radiating branch forming a slot, a second end of the second radiating branch being provided with the second feed point; wherein the slot is in a meander shape, and the slot forms an equivalent capacitance between the second end of the first radiating branch and the first end of the second radiating branch; and an inductive decoupling element electrically connected between the second end of the first radiating branch and the first end of the second radiating branch, wherein the inductive decoupling element forms an equivalent inductance between the second end of the first radiating branch and the first end of the second radiating branch; wherein the equivalent capacitance and the equivalent inductance form an LC resonant structure, and the LC resonant structure is configured to achieve decoupling between the first antenna element and the second antenna element; the antenna structure further comprises a first decoupling branch provided between the second end of the first radiating branch and the first end of the second radiating branch, wherein a first end of the first decoupling branch and the second end of the first radiating branch form a first sub-slot in a meander shape, a second end of the first decoupling branch and the first end of the second radiating branch form a second sub-slot in a meander shape, and the slot comprises the first sub-slot and the second sub-slot; the first sub-slot forms a first equivalent sub-capacitance between the second end of the first radiating branch and the first end of the first decoupling branch, the second sub-slot forms a second equivalent sub-capacitance between the second end of the first decoupling branch and the first end of the second radiating branch, the first equivalent sub-capacitance and the second equivalent sub-capacitance are connected in series between the second end of the first radiating branch and the first end of the second radiating branch, and the equivalent capacitance comprises the first equivalent sub-capacitance and the second equivalent sub-capacitance connected in series.

2. The antenna structure of claim 1, wherein, the antenna structure further comprises a third antenna element comprising a third radiating branch, a first end of the third radiating branch being provided with a third feed point, and a second end of the third radiating branch being free; wherein the second radiating branch and the third radiating branch are formed on a same radiator, the second end of the second radiating branch is adjacent to the first end of the third radiating branch, and the second feed point and the third feed point are close to each other to achieve self-decoupling between the second antenna element and the third antenna element.

3. The antenna structure of claim 1, wherein, the inductive decoupling element comprises a second decoupling branch, an inductive element, and a third decoupling branch, wherein the second decoupling branch extends from the second end of the first radiating branch, and a free end of the second decoupling branch is electrically connected to a first end of the inductive element; the third decoupling branch extends from the first end of the second radiating branch, and a free end of the third decoupling branch is electrically connected to a second end of the inductive element.

4. The antenna structure of claim 3, wherein, The gap and the inductive decoupling element are configured to adjust the CM impedance between the first antenna unit and the second antenna unit to be similar or equal to the DM impedance between the first antenna unit and the second antenna unit, so as to adjust the resonant frequency of the LC resonant structure to be the same as the decoupling frequency between the first antenna unit and the second antenna unit.

5. The antenna structure of any one of claims 1-2, wherein, The first antenna unit and the second antenna unit are same-frequency antenna units, or the operating frequency bands of the first antenna unit and the second antenna unit at least partially overlap. The first radiating branch and the second radiating branch are symmetrically arranged on both sides of the gap.

6. The antenna structure of claim 2, wherein, The second antenna unit and the third antenna unit are same-frequency antenna units, or the operating frequency bands of the second antenna unit and the third antenna unit at least partially overlap. The second radiating branch and the third radiating branch are symmetrically arranged on both sides of the center of the radiator.

7. The antenna structure of claim 6, wherein, The electrical length of the second radiating branch is equal to one fourth of the electromagnetic wave length of the resonant frequency of the second antenna unit. The electrical length of the third radiating branch is equal to one fourth of the electromagnetic wave length of the resonant frequency of the third antenna unit. The second feeding point and the third feeding point are spaced apart by a preset distance, and the preset distance is smaller than the length of the second radiating branch and the length of the third radiating branch.

8. The antenna structure of claim 2, wherein, The first antenna unit, the second antenna unit and the third antenna unit are formed on the same radiator, and the radiator is any one of a flexible circuit board antenna, a printed circuit board antenna or a microstrip antenna.

9. A terminal device comprising a housing and the antenna structure according to any one of claims 1-8, wherein the antenna structure is arranged in the housing.

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