CN109286077B

CN109286077B - Mobile device

Info

Publication number: CN109286077B
Application number: CN201810234411.5A
Authority: CN
Inventors: 陈静雯; 张家豪
Original assignee: Wistron Neweb Corp
Current assignee: Wistron Neweb Corp
Priority date: 2017-07-19
Filing date: 2018-03-21
Publication date: 2021-10-22
Anticipated expiration: 2038-03-21
Also published as: CN109286077A; TW201909478A; TWI659565B

Abstract

A mobile device is provided. The mobile device includes: a metal back cover, a grounding metal part, a feed-in radiation part and a dielectric substrate; the metal back cover is provided with a slotted hole; the grounding metal part is coupled to the metal back cover; the feed-in radiation part is provided with a feed-in point and comprises a first feed-in branch, a second feed-in branch and a third feed-in branch, wherein the second feed-in branch and the first feed-in branch extend towards opposite directions, and the third feed-in branch and the first feed-in branch extend towards the same direction; the vertical projection of the feed-in radiation part on the metal back cover is at least partially overlapped with the slotted hole; the dielectric substrate is adjacent to the metal back cover, wherein the grounding metal part and the feed-in radiation part are both arranged on the dielectric substrate; wherein the slot holes of the feed radiation part and the metal back cover together form an antenna structure. The invention has the advantages of small size, wide frequency band, high efficiency of high and low frequency antenna, increased stability of the device and beautification of the appearance of the device, and is suitable for various mobile communication devices.

Description

Mobile device

Technical Field

The present invention relates to a mobile device, and more particularly, to a mobile device and an Antenna Structure (Antenna Structure) thereof.

Background

With the development of mobile communication technology, mobile devices have become increasingly popular in recent years, such as: portable computers, mobile phones, multimedia players and other portable electronic devices with mixed functions. To meet the demand of people, mobile devices generally have a function of wireless communication. Some cover long-range wireless communication ranges, such as: the mobile phone uses 2G, 3G, LTE (Long Term Evolution) system and its used frequency bands of 700MHz, 850MHz, 900MHz, 1800MHz, 1900MHz, 2100MHz, 2300MHz and 2500MHz for communication, while some cover short-distance wireless communication ranges, for example: Wi-Fi and Bluetooth systems use frequency bands of 2.4GHz, 5.2GHz, and 5.8GHz for communication.

In order to pursue the aesthetic appearance, designers nowadays often add elements of metal components to mobile devices. However, the added metal elements tend to adversely affect the antenna supporting wireless communication in the mobile device, thereby reducing the overall communication quality of the mobile device. Therefore, there is a need for a new mobile device and antenna structure to overcome the problems encountered in the conventional technology.

Therefore, it is desirable to provide a mobile device to solve the above problems.

Disclosure of Invention

In a preferred embodiment, the present invention provides a mobile device, comprising: a metal back cover, the metal back cover having a slot; a grounding metal portion coupled to the metal back cover; a feed-in radiation part having a feed-in point, wherein the feed-in radiation part comprises: a first feeding branch, wherein one end of the first feeding branch is coupled to the feeding point, the first feeding branch has a first polygon, the first polygon has at least a major axis and a minor axis, and the major axis of the first polygon extends along a first direction; a second feeding branch, wherein one end of the second feeding branch is coupled to the feeding point, the second feeding branch has a second polygon, the second polygon has at least a long axis and a short axis, the long axis of the second polygon extends along a second direction, and the second direction is opposite to the first direction; and a third feeding-in branch, wherein one end of the third feeding-in branch is coupled to the feeding-in point, the third feeding-in branch has a third polygon, the third polygon has at least a long axis and a short axis, and the long axis of the third polygon extends along the first direction; and a dielectric substrate, the dielectric substrate is adjacent to the metal back cover, wherein the grounding metal part and the feed-in radiation part are both arranged on the dielectric substrate; wherein the vertical projection of the feed-in radiation part on the metal back cover is at least partially overlapped with the slot; wherein the feed-in radiation part and the slot of the metal back cover together form an antenna structure.

In some embodiments, the slot is a closed slot and has a rectangular shape, and a long axis of the slot is parallel to the long axis of the first feeding branch, the long axis of the second feeding branch, and the long axis of the third feeding branch.

In some embodiments, the other end of each of the first feeding branch, the second feeding branch, and the third feeding branch is an open end.

In some embodiments, the first polygon exhibits a rectangle.

In some embodiments, the second polygon appears as a rectangle or an L-shape.

In some embodiments, the third polygon is a rectangle, an L-shape, or a U-shape.

In some embodiments, the grounding metal portion is a grounding copper foil and extends from the dielectric substrate to the metal back cover.

In some embodiments, a first coupling gap is formed between the first feeding branch and the third feeding branch, and a width of the first coupling gap is smaller than or equal to a width of the slot.

In some embodiments, a second coupling gap is formed between the second feeding branch and the grounding metal portion, and the width of the second coupling gap is smaller than or equal to the width of the slot.

In some embodiments, the antenna structure covers a first frequency band between 2400MHz and 2500MHz and a second frequency band between 5150MHz and 5875 MHz.

In some embodiments, the length of the slot is equal to 0.5 wavelengths of the center frequency of the first frequency band.

In some embodiments, the length of the first feeding branch is equal to 0.25 times the wavelength of the center frequency of the first frequency band.

In some embodiments, the first feeding branch and the slot of the metal back cover are excited to generate the first frequency band.

In some embodiments, the length of the second feeding branch is equal to 0.25 times the wavelength of the center frequency of the second frequency band.

In some embodiments, the second feeding branch is excited to generate the second frequency band.

In some embodiments, the length of the third feeding branch is between 0.125 and 0.25 wavelengths of the center frequency of the first frequency band.

In some embodiments, the third feeding branch is used for increasing the radiation efficiency and the operating bandwidth of the first frequency band and the second frequency band.

Compared with the traditional design, the invention at least has the advantages of small size, wide frequency band, high-low frequency antenna efficiency, device stability increase and device appearance beautification, so the invention is suitable for various mobile communication devices.

Drawings

FIG. 1A shows a top view of a mobile device according to an embodiment of the invention.

FIG. 1B shows a side view of a mobile device according to an embodiment of the invention.

Fig. 2 is a voltage standing wave ratio diagram of an antenna structure of a mobile device according to an embodiment of the invention.

Fig. 3 shows a top view of a mobile device according to an embodiment of the invention.

Fig. 4 shows a top view of a mobile device according to an embodiment of the invention.

Fig. 5 shows a top view of a mobile device according to an embodiment of the invention.

Fig. 6 shows a top view of a mobile device according to an embodiment of the invention.

Description of the main component symbols:

100. 300, 400, 500, 600 mobile device

110 metal back cover

Edge of 111 metal back cover

120 slotted hole

121. Closed end of 122 slotted hole

130. 330, 430 and 530 feed radiation part

140. 340, 540 first feed-in branch

141. 341, 541 open end of first feeding branch

150. 350, 450, 550 second feeding branch

151. 351, 451, 551 open end of the second feeding branch

160. 360, 560 third feeding branch

161. 361, 561 open end of the third feeding branch

170 dielectric substrate

180. 680 ground metal part

365 third feeding branch

455 end bent portion of second feeding branch

First surface of E1 dielectric substrate

Second surface of E2 dielectric substrate

FB1 first frequency band

FB2 second frequency band

FP feed-in point

GC1 first coupling gap

GC2 second coupling gap

W1, W2 Width

X X axle

Y Y axle

Z Z axle

Detailed Description

In order to make the objects, features and advantages of the present invention comprehensible, specific embodiments accompanied with figures are described in detail below.

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. The present specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The term "substantially" means within an acceptable error range, within which a person skilled in the art can solve the technical problem to achieve the basic technical result. In addition, the term "coupled" is used herein to encompass any direct or indirect electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

FIG. 1A shows a top view of a mobile device 100 according to an embodiment of the invention. FIG. 1B shows a side view of the mobile device 100 according to an embodiment of the invention. Please refer to fig. 1A and fig. 1B together. The mobile device 100 may be a Smart Phone (Smart Phone), a Tablet Computer (Tablet Computer), or a Notebook Computer (Notebook Computer). In the embodiment of fig. 1A, 1B, the mobile device 100 comprises: a Metal Back Cover (Metal Back Cover)110, a Feeding Radiation Element (Feeding Radiation Element)130, a Dielectric Substrate (Dielectric Substrate)170, and a Ground Metal Element (Ground Metal Element) 180. It must be understood that although not shown in fig. 1A, 1B, in practice the mobile device 100 may also comprise other elements, such as: a Processor (Processor), a Touch Control Panel (Touch Panel), a Speaker (Speaker), a Battery Module (Battery Module), and a Housing (Housing). In other embodiments, the mobile Device 100 is implemented in a Deformable Device (Deformable Device) that can switch between a Tablet Mode (Tablet Mode) and a Notebook Mode (Notebook Mode).

The metal back cover 110 has a Slot (Slot)120, wherein the Slot 120 may be a substantially straight strip-shaped opening or a rectangular opening. In detail, the Slot 120 is a Closed Slot (Closed Slot) having two Closed ends (Closed ends) 121, 122 away from each other. However, the present invention is not limited thereto. In other embodiments, the Slot 120 may be a Monopole Slot (Open Slot) having an Open End and a closed End that are away from each other. If the mobile device 100 is implemented in a notebook computer or a deformable device, an edge 111 of the metal back cover 110 may be adjacent to a Hinge assembly (not shown) of the notebook computer or the deformable device. For example, the spacing between the edge 111 of the metal back cover 110 and the hinge member may be less than 10 mm.

The feeding radiation part 130 can be made of metal material, such as: copper, silver, aluminum, iron, or alloys thereof. The dielectric substrate 170 may be an FR4 (film resistor 4) substrate, a Printed Circuit Board (PCB), or a Flexible Circuit Board (FCB). The dielectric substrate 170 may have a first surface E1 and a second surface E2 opposite to each other, wherein the feeding radiating element 130 and the grounding metal element 180 are disposed on the first surface E1 of the dielectric substrate 170, and the second surface E2 of the dielectric substrate 170 may be close to or directly attached to the metal back cover 110 (adjacent to the slot 120), such that the dielectric substrate 170 almost completely covers the slot 120 of the metal back cover 110. It should be noted that the term "adjacent" or "adjacent" in this specification may refer to a distance between two corresponding elements being less than a predetermined distance (e.g., 5mm or less), and may also include the case where two corresponding elements are in direct contact with each other (i.e., the distance is shortened to 0).

The grounding metal portion 180 is coupled to the metal back cover 110, and both of them can provide a Ground Voltage (Ground Voltage) of the mobile device 100. For example, the grounding metal portion 180 may be a grounding Copper Foil (Ground Copper Foil), which may extend from the dielectric substrate 170 to the metal back cover 110. The feeding radiating portion 130 has a feeding point FP, which is coupled to a Positive Electrode (Positive Electrode) of a Signal Source (not shown), and a Negative Electrode (Negative Electrode) of the Signal Source is coupled to the grounding metal portion 180. For example, the signal source may be a Radio Frequency (RF) module, which can be used to generate a transmission signal or process a reception signal. In some embodiments, the positive pole of the signal source is coupled to the feed point FP through a center wire of a Coaxial Cable (Coaxial Cable), and the negative pole of the signal source is coupled to the grounding metal portion 180 through a conductive shell of the Coaxial Cable. The feeding radiating part 130 extends across the slot 120 of the metal back cover 110. That is, the Vertical Projection (Vertical Projection) of the feeding radiating portion 130 (including the first feeding branch 140, the second feeding branch 150, and the third feeding branch 160) on the metal back cover 110 at least partially overlaps the slot 120.

In detail, the Feeding radiating portion 130 includes a first Feeding Branch (Feeding Branch)140, a second Feeding Branch 150, and a third Feeding Branch 160. The combination of the first feeding branch 140, the second feeding branch 150, and the third feeding branch 160 may include a Y-shaped connection portion surrounding the feeding point FP. The first feeding branch 140 has a first Polygon (Polygon) which may substantially present a rectangle or an L-shape. One End of the first feeding branch 140 is coupled to the feeding point FP, and the other End of the first feeding branch 140 is an Open End (Open End) 141. The first polygon of the first feeding branch 140 has at least a Long Axis (Long Axis) and a Short Axis (Short Axis), wherein the Long Axis of the first polygon extends along a first direction, for example: and + X-axis direction. For example, the major axis of the first polygon may be a first virtual straight line passing through the open end 141 and parallel to the + X axis. The second feeding branch 150 has a second polygon, which may substantially present a rectangle or an L-shape. One end of the second feeding branch 150 is coupled to the feeding point FP, and the other end of the second feeding branch 150 is an open end 151. The second polygon of the second feeding branch 150 has at least a long axis and a short axis, wherein the long axis of the second polygon extends along a second direction, for example: -X-axis direction. For example, the major axis of the second polygon may be a second virtual straight line passing through the open end 151 and parallel to the-X axis. In other words, the second direction may be opposite to the first direction, such that the first feeding branch 140 and the second feeding branch 150 may extend in substantially opposite directions. For example, the open end 141 of the first feeding branch 140 may extend toward the + X axis, and the open end 151 of the second feeding branch 150 may extend toward the-X axis. The third feeding branch 160 may have a third polygon, which may substantially present a rectangle or an L-shape. One end of the third feeding branch 160 is coupled to the feeding point FP, and the other end of the third feeding branch 160 is an open end 161. The third polygon of the third feeding branch 160 at least has a major axis and a minor axis, wherein the major axis of the third polygon also extends along the first direction, for example: and + X-axis direction. For example, the major axis of the third polygon may be a third virtual straight line passing through the open end 161 and parallel to the + X axis. In other words, the first feeding branch 140 and the third feeding branch 160 may extend in substantially the same direction. For example, the open end 141 of the first feeding branch 140 may extend toward the + X axis, and the open end 161 of the third feeding branch 160 may also extend toward the + X axis. Each of the first feeding branch 140, the second feeding branch 150, and the third feeding branch 160 is at least partially parallel to the slot 120 of the metal back cover 110. In some embodiments, a long axis of the slot 120 (passing through the two closed ends 121, 122) is parallel to the long axis of the first feeding branch 140, the long axis of the second feeding branch 150, and the long axis of the third feeding branch 160. In addition, a first Coupling Gap GC1 may be formed between the first feeding branch 140 and the third feeding branch 160, and a second Coupling Gap GC2 may be formed between the second feeding branch 150 and the grounding metal portion 180. In the preferred embodiment, the metal back cover 110, the slot 120, and the feeding radiating portion 130 together form an Antenna Structure (Antenna Structure).

Fig. 2 shows a Voltage Standing Wave Ratio (VSWR) diagram of an antenna structure of the mobile device 100 according to an embodiment of the invention, wherein the horizontal axis represents an operating frequency (MHz) and the vertical axis represents the VSWR. According to the measurement results shown in fig. 2, the antenna structure of the mobile device 100 can cover a first frequency band FB1 and a second frequency band FB2 when receiving or transmitting wireless signals, wherein the first frequency band FB1 can be approximately between 2400MHz and 2500MHz, and the second frequency band FB2 can be approximately between 5150MHz and 5875 MHz. Thus, the antenna structure of the mobile device 100 can support at least 2.4GHz/5GHz broadband operation for Bluetooth and WLAN (Wireless Local Area network). According to the practical measurement results, the Antenna Efficiency (Antenna Efficiency) of the Antenna structure of the mobile device 100 in the first frequency band FB1 can reach about-3.78 dB, and the Antenna Efficiency in the second frequency band FB2 can reach about-3.95 dB (which is about 2 to 4dB higher than the Antenna Efficiency of the conventional slot Antenna), which can meet the practical application requirements of the general mobile communication device.

In some embodiments, the principles of operation of the antenna structure of the mobile device 100 may be as follows. The first feeding branch 140 and the slot 120 of the metal back cover 110 are used for exciting and generating the aforementioned first frequency band FB 1. The second feeding branch 150 is used for exciting and generating the aforementioned second frequency band FB 2. The third feeding branch 160 can also be coupled and excited by the first feeding branch 140 to simultaneously increase the Radiation Efficiency (Radiation Efficiency) and the operating Bandwidth (Operation Bandwidth) of the first frequency band FB1 and the second frequency band FB 2. Since the feeding radiating portion 130 has a Meandering Shape (e.g., three feeding branches), the overall area of the antenna structure of the mobile device 100 can be greatly reduced.

In some embodiments, the dimensions of the elements of the mobile device 100 may be as follows. The length of the slot 120 (i.e., the length from the closed end 121 to the other closed end 122) may be substantially equal to 0.5 times the wavelength (λ/2) of the center Frequency (Central Frequency) of the first Frequency band FB 1. The length of the first feeding branch 140 (i.e., the length from the feeding point FP to the open end 141) may be substantially equal to 0.25 times the wavelength (λ/4) of the center frequency of the first frequency band FB 1. The length of the second feeding branch 150 (i.e., the length from the feeding point FP to the open end 151) may be substantially equal to 0.25 times the wavelength (λ/4) of the center frequency of the second frequency band FB 2. The length of the third feeding branch 160 (i.e., the length from the feeding point FP to the open end 161) may be between 0.125 and 0.25 wavelengths (λ/8- λ/4) of the center frequency of the first frequency band FB 1. In order to enhance the coupling effect between the elements, the width of the first coupling gap GC1 can be smaller than or equal to the width W1 of the slot 120, and the width of the second coupling gap GC2 can also be smaller than or equal to the width W1 of the slot 120. The above element size range is found from a plurality of experimental results, which is helpful for optimizing the operating band and Impedance Matching (Impedance Matching) of the antenna structure of the mobile device 100.

It should be understood that the shape of the above feeding radiating portion 130 can be finely adjusted according to different requirements. For example, the Y-shaped connection portion (i.e., the vicinity of the feed point FP) between the first feeding branch 140, the second feeding branch 150 and the third feeding branch 160 can be modified to a smoother shape to remove the discontinuous saw-tooth edges, but the effect of the present invention is not affected. The following embodiments will describe different configurations of the proposed antenna structure, but the figures and the description thereof are only illustrative and not intended to limit the scope of the present invention.

Fig. 3 shows a top view of a mobile device 300 according to an embodiment of the invention. Fig. 3 is similar to fig. 1A. In the embodiment of fig. 3, a feeding radiating portion 330 of the mobile device 300 includes a first feeding branch 340, a second feeding branch 350, and a third feeding branch 360, wherein the third feeding branch 360 further includes an end bending portion 365, such that an open end 361 of the third feeding branch 360 is closer to an open end 341 of the first feeding branch 340. The terminal bent portion 365 may be substantially perpendicular to the rest of the third feeding branch 360. The third feeding branch 360 (i.e., the third polygon) having the terminal bent portion 365 may substantially have a U-shape. The addition of the terminal bent portion 365 can reduce the equivalent width of the first coupling gap GC1 between the first feeding branch 340 and the third feeding branch 360 to enhance the coupling effect between the first feeding branch 340 and the third feeding branch 360. With this design, the radiation efficiency of the antenna structure of the mobile device 300 in the first frequency band FB1 can be further improved. The remaining features of the mobile device 300 of fig. 3 are similar to those of the mobile device 100 of fig. 1A and 1B, so that similar operations can be achieved in both embodiments.

Fig. 4 shows a top view of a mobile device 400 according to an embodiment of the invention. Fig. 4 is similar to fig. 3. In the embodiment of fig. 4, a second feeding branch 450 of a feeding radiating part 430 of the mobile device 400 further includes an end bent portion 455, such that an open end 451 of the second feeding branch 450 is closer to the grounding metal part 180. Terminal bent portion 455 may be substantially perpendicular to the rest of second feeding branch 450. The second feeding branch 450 (i.e., the second polygon) having the terminal bent portion 455 may substantially have an L-shape. The addition of the terminal bent portion 455 can reduce the equivalent width of the second coupling gap GC2 between the second feeding branch 450 and the grounding metal part 180, so as to fine-tune the impedance matching between the second feeding branch 450 and the grounding metal part 180. With this design, the radiation efficiency of the antenna structure of the mobile device 400 in the second frequency band FB2 can be further improved. The remaining features of the mobile device 400 of fig. 4 are similar to those of the mobile device 300 of fig. 3, so that similar operations can be achieved in both embodiments.

Fig. 5 shows a top view of a mobile device 500 according to an embodiment of the invention. Fig. 5 is similar to fig. 1A. In the embodiment of fig. 5, a feeding radiation portion 530 of the mobile device 500 includes a first feeding branch 540, a second feeding branch 550, and a third feeding branch 560, wherein a width W2 of the first feeding branch 540 is significantly increased (e.g., the width W2 of fig. 5 may be about twice as large as the width W2 of fig. 1A), so that a vertical projection of the first feeding branch 540 on the metal back cover 110 at least partially overlaps the slot 120. For example, the width W2 of the first feeding branch 540 may be greater than or equal to the width W1 of the slot 120, but is not limited thereto. The widening of the first feeding branch 540 may reduce the equivalent width of the first coupling gap GC1 between the first feeding branch 540 and the third feeding branch 560 to enhance the coupling effect between the first feeding branch 540 and the third feeding branch 560. With this design, the radiation efficiency of the antenna structure of the mobile device 500 in the first frequency band FB1 can be further improved. The remaining features of the mobile device 500 of fig. 5 are similar to those of the mobile device 100 of fig. 1A and 1B, so that similar operations can be achieved in both embodiments.

Fig. 6 shows a top view of a mobile device 600 according to an embodiment of the invention. Fig. 6 is similar to fig. 5. In the embodiment of fig. 6, a grounding metal part 680 of the mobile device 600 moves closer to the second feeding branch 550, so that a vertical projection of the grounding metal part 680 on the metal back cover 110 at least partially overlaps the slot 120. The movement of the ground metal part 680 may reduce the equivalent width of the second coupling gap GC2 between the second feeding branch 550 and the ground metal part 680 to fine-tune the impedance matching between the second feeding branch 550 and the ground metal part 680. With this design, the radiation efficiency of the antenna structure of the mobile device 600 in the second frequency band FB2 can be further improved. The remaining features of the mobile device 600 of fig. 6 are similar to those of the mobile device 500 of fig. 5, so that similar operations can be achieved in both embodiments.

The invention provides a novel antenna structure, which comprises a slotted hole, and when the antenna structure is applied to a mobile device with a metal back cover, the metal back cover can be regarded as an extension part of the antenna structure, so that the metal back cover can be effectively prevented from generating negative influence on the communication quality of the mobile device. It should be noted that the present invention can further improve the design of the mobile device without digging any Antenna Window (Antenna Window) on the metal back cover. Compared with the traditional design, the invention at least has the advantages of small size, wide frequency band, high-low frequency antenna efficiency, device stability increase and device appearance beautification, so the invention is suitable for various mobile communication devices.

It is noted that the sizes, shapes and frequency ranges of the above-mentioned components are not limitations of the present invention. The antenna designer can adjust these settings according to different needs. The mobile device and the antenna structure of the present invention are not limited to the states illustrated in fig. 1A to 6. The present invention may include only any one or more features of any one or more of the embodiments of fig. 1A-6. In other words, not all illustrated features may be implemented in the mobile device and antenna structure of the present invention.

Ordinal numbers such as "first," "second," "third," etc., in the specification and claims are not to be given a sequential order, but are merely used to identify two different elements having the same name.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A mobile device, comprising:

a metal back cover, the metal back cover having a slot;

a grounding metal portion coupled to the metal back cover;

a feed-in radiation part having a feed-in point, wherein the feed-in radiation part comprises:

a first feeding branch, wherein one end of the first feeding branch is coupled to the feeding point, the first feeding branch has a first polygon, the first polygon has at least a major axis and a minor axis, and the major axis of the first polygon extends along a first direction;

a second feeding branch, wherein one end of the second feeding branch is coupled to the feeding point, the second feeding branch has a second polygon, the second polygon has at least a long axis and a short axis, the long axis of the second polygon extends along a second direction, and the second direction is opposite to the first direction; and

a third feeding-in branch, wherein one end of the third feeding-in branch is coupled to the feeding-in point, the third feeding-in branch has a third polygon, the third polygon has at least a long axis and a short axis, and the long axis of the third polygon extends along the first direction; and

a dielectric substrate adjacent to the metal back cover, wherein the grounding metal part and the feed-in radiation part are both arranged on the dielectric substrate;

wherein the vertical projection of the feed-in radiation part on the metal back cover is at least partially overlapped with the slot;

wherein the feed-in radiation part and the slot of the metal back cover form an antenna structure together;

wherein the other end of each of the first feeding branch, the second feeding branch and the third feeding branch is an open end;

wherein the slot is a closed slot;

wherein a first coupling gap is formed between the first feeding branch and the third feeding branch.

2. The mobile device according to claim 1, wherein the slot has a rectangular shape, and a major axis of the slot is parallel to the major axis of the first feeding branch, the major axis of the second feeding branch, and the major axis of the third feeding branch.

3. The mobile device of claim 1, wherein the first polygon represents a rectangle.

4. The mobile device of claim 1, wherein the second polygon has a rectangular shape or an L-shape.

5. The mobile device of claim 1, wherein the third polygon has a rectangular shape, an L-shape, or a U-shape.

6. The mobile device as claimed in claim 1, wherein the grounding metal portion is a grounding copper foil and extends from the dielectric substrate to the metal back cover.

7. The mobile device as claimed in claim 1, wherein the width of the first coupling gap is smaller than or equal to the width of the slot.

8. The mobile device according to claim 1, wherein a second coupling gap is formed between the second feeding branch and the grounding metal portion, and a width of the second coupling gap is smaller than or equal to a width of the slot.

9. The mobile device of claim 1, wherein the antenna structure covers a first frequency band between 2400MHz and 2500MHz and a second frequency band between 5150MHz and 5875 MHz.

10. The mobile device as claimed in claim 9, wherein the length of the slot is equal to 0.5 wavelength of the center frequency of the first frequency band.

11. The mobile device according to claim 9, wherein the length of the first feeding branch is equal to 0.25 times the wavelength of the center frequency of the first frequency band.

12. The mobile device according to claim 9, wherein the slot of the first feeding branch and the metal back cover are excited to generate the first frequency band.

13. The mobile device according to claim 9, wherein the length of the second feeding branch is equal to 0.25 times the wavelength of the center frequency of the second frequency band.

14. The mobile device as claimed in claim 9, wherein the second feeding branch is excited to generate the second frequency band.

15. The mobile device according to claim 9, wherein the length of the third feeding branch is between 0.125 and 0.25 wavelengths of the center frequency of the first frequency band.

16. The mobile device as claimed in claim 9, wherein the third feeding branch is used for increasing radiation efficiency and operating bandwidth of the first frequency band and the second frequency band.