Antenna structure and electronic device

An antenna structure includes a first radiator, a second radiator, an antenna ground, and a conductor. The first radiator for resonating at a high frequency band includes a feeding end. The second radiator is connected to the first radiator and resonates at a low frequency band with a part of the first radiator. The antenna ground is located on one side of the first radiator and the second radiator. The conductor is located between the second radiator and the antenna ground in a first direction and connected to the first radiator and the antenna ground. A slit having at least one bending portion is formed among the second radiator, and the conductor and the antenna ground. An electronic device is further provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 108141751, filed on Nov. 18, 2019. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technology Field

The disclosure relates to an antenna structure and an electronic device, and in particular to an antenna structure applicable to a device with a thin bezel and an electronic device having the antenna structure.

Description of Related Art

Currently, there are increasing demands for electronic devices with the design of a thin bezel. The design of a thin bezel makes the space for antennas of such electronic devices smaller and smaller and also makes it difficult to design.

SUMMARY

The disclosure provides an antenna structure, which can be applied to a device with a thin bezel.

The disclosure provides an electronic device having the antenna structure.

The antenna structure of the disclosure includes a first radiator, a second radiator, an antenna ground, and a conductor. The first radiator includes a feeding end. The first radiator is configured for resonating at a high frequency band. The second radiator is connected to the first radiator and resonates at a low frequency band with a portion of the first radiator. The antenna ground is located on one side of the first radiator and the second radiator. The conductor is located between the second radiator and the antenna ground in a first direction and connects the first radiator with the antenna ground. A slit having at least one bending portion is formed among the second radiator, the conductor, and the antenna ground.

In an embodiment of the disclosure, the slit has two bending portions and is Z-shaped.

In an embodiment of the disclosure, a length of the slit ranges from 11 mm to 20 mm, and a width of the slit ranges from 0.3 mm to 1.5 mm.

In an embodiment of the disclosure, the conductor has a first part and a second part, the first part is connected to the first radiator, and the second part is connected to the antenna ground. A length of the first part is less than a length of the second part in the first direction, and a length of the second part in a second direction ranges from 7 mm to 11 mm.

In an embodiment of the disclosure, the antenna structure further includes a substrate, a coaxial transmission line, and a conductor grounding layer. The substrate includes a first surface and a second surface opposite to each other. The first radiator, the second radiator, the conductor, and the antenna ground are disposed on the first surface. The coaxial transmission line is located on the second surface and electrically connected to the antenna ground.

In an embodiment of the disclosure, the antenna structure further includes a conductor grounding layer. A portion of the conductor grounding layer is disposed on the first surface and connected to the antenna ground, another portion of the conductor grounding layer extends beyond the substrate and is connected to a system ground, and a length of the conductor grounding layer ranges from 27 mm to 33 mm.

In an embodiment of the disclosure, a total length of the first radiator and the second radiator ranges from 23 mm to 27 mm; and a total width of the first radiator, the second radiator, and the conductor ranges from 3 mm to 5 mm.

In an embodiment of the disclosure, a length of the antenna ground ranges from 27 mm to 33 mm; a width of the antenna ground ranges from 1.5 mm to 4 mm; and a total width of the first radiator, the second radiator, the conductor, and the antenna ground ranges from 6 mm to 8.5 mm.

An electronic device of the disclosure includes housing and the antenna structure.

The housing includes an insulation area; and the antenna structure is disposed in the housing and beside the insulation area.

In an embodiment of the disclosure, the electronic device is a large-sized display device. The electronic device further includes a screen fixed on and exposed from the housing. A length of the screen is greater than 170 cm. The housing includes an insulating back cover and a metal side shell. The insulation area is formed on an opening of the metal side shell, and a total width of the antenna structure ranges from 6 mm to 8.5 mm.

In an embodiment of the disclosure, the electronic device further includes a system ground and a conducting element located in the housing. The conducting element connects the antenna structure and the system ground. A distance between the antenna structure and the system ground ranges from 3.5 mm to 6 mm.

In an embodiment of the disclosure, the electronic device further includes a screen fixed on and exposed from the housing. The housing includes a metal back cover and an insulating side shell. The insulation area is located in the insulating side shell. The metal back cover extends to the insulating side shell and partially covers the insulating side shell. The antenna structure is disposed beside the insulating side shell, and a projection of the metal back cover with respect to the screen covers a projection of the antenna structure with respect to the screen.

In an embodiment of the disclosure, the antenna structure further includes a substrate and a conductor grounding layer. The first radiator, the second radiator, the conductor, and the antenna ground are disposed on the substrate. A portion of the conductor grounding layer is disposed on the substrate and connected to the antenna ground. Another portion of the conductor grounding layer extends beyond the substrate in a bending manner and is connected to the metal back cover. The conductor grounding layer and a portion of the metal back cover together form a resonance chamber.

In an embodiment of the disclosure, a distance between the antenna structure and the insulating side shell ranges from 2 mm to 4 mm.

In an embodiment of the disclosure, a distance between the antenna structure and the metal back cover ranges from 6.5 mm to 8 mm.

In an embodiment of the disclosure, the slit has two bending portions and is Z-shaped, a length of the slit ranges from 11 mm to 20 mm, and a width of the slit ranges from 0.3 mm to 1.5 mm.

In an embodiment of the disclosure, the conductor has a first part and a second part. The first part is connected to the first radiator, and the second part is connected to the antenna ground. A length of the first part is less than a length of the second part in the first direction, and a length of the second part ranges from 7 mm to 11 mm.

In an embodiment of the disclosure, the electronic device further includes a substrate, a coaxial transmission line and a conductor grounding layer. The substrate includes a first surface and a second surface opposite to each other. The first radiator, the second radiator, the conductor, and the antenna ground are disposed on the first surface. The coaxial transmission line is located on the second surface and electrically connected to the antenna ground.

In an embodiment of the disclosure, a total length of the first radiator and the second radiator ranges from 23 mm to 27 mm, and a total width of the first radiator, the second radiator, and the conductor ranges from 3 mm to 5 mm.

In an embodiment of the disclosure, a length of the antenna ground ranges from 27 mm to 33 mm; a width of the antenna ground ranges from 1.5 mm to 4 mm; and a total width of the first radiator, the second radiator, the conductor, and the antenna ground ranges from 6 mm to 8.5 mm.

Based on the above, the antenna structure of the disclosure configures the first radiator for resonating at a high frequency band. The second radiator and a portion of the first radiator are configured for resonating at a low frequency band. The slit is formed between the second radiator and the conductor and between the second radiator and antenna ground. The slit can be configured as a π-type matching circuit, which makes a smaller-sized antenna structure possible, and thereby can be applied to electronic devices with slim border and improve the antenna.

DESCRIPTION OF THE EMBODIMENTS

FIG.1is a schematic view of an antenna structure according to an embodiment of the disclosure. Referring toFIG.1, an antenna structure100of the embodiment includes a first radiator110, a second radiator120, an antenna ground140, and a conductor130. Specifically, the first radiator110is approximately at positions A3, A2, A1, and B1; the second radiator120is connected to the first radiator110and is approximately at positions B1, A4, A5, A6, A7, A8, and A9; the conductor130is approximately at positions B1, B2, B3, B5, and B4; and the antenna ground140is approximately at position C1to position C2.

In the embodiment, the antenna structure100at a feeding end (the position A1) of the first radiator110extends leftward to the positions A2and A3and rightward to the positions A4, A5, A6, A7, A8, and A9in two respective radiation paths. The two radiation paths and ground paths of the positions B1, B2, B3, B4, and B5form PIFA antenna architecture and resonate at two antenna bands.

In detail, in the embodiment, the first radiator110(the positions A3, A2, A1, and B1) is configured for resonating at a high frequency band. The second radiator120(the positions B1, A4, A5, A6, A7, A8, and A9) and a portion of the first radiator110(the positions A2and B1) are configured for resonating at a low frequency band. In the embodiment, the low frequency band is a frequency band for Wi-Fi 2.4 GHz, and the high frequency band is a frequency band for Wi-Fi 5 GHz, but the range of the frequency band at which the antenna structure100resonates is not limited thereto.

In addition, the antenna ground140is located on one side of the first radiator110and the second radiator120. In the embodiment, a length L6of the antenna ground140ranges from 27 mm to 33 mm and, for example, may be 30 mm. A width of the antenna ground140(i.e., a length L3in a first direction D1) ranges from 1.5 mm to 4 mm and, for example, may be 2 mm.

The conductor130is located between the second radiator120and the antenna ground140along the first direction D1(i.e., the vertical direction ofFIG.1) and connects the first radiator110with the antenna ground140. As can be seen inFIG.1, in the embodiment, the conductor130has a first part and a second part. The first part (the positions B1and B2) is connected to the first radiator110, and the second part (the positions B2, B3, B5, and B4) is connected to the antenna ground140. In the first direction D1, the length of the first part (the positions B1and B2) is less than the length of the second part (the positions B2, B3, B5, and B4). Certainly, in other embodiments, the conductor130may have only a single length in the first direction D1or have more lengths, which is not limited thereto.

Generally, a conventional planar PIFA antenna architecture requires a length of 30 mm and a width of 10 mm to achieve better wireless transmission. However, the conventional planar PIFA antenna architecture is difficult to apply to devices with thin bezel due to its large size. In the embodiment, the width of an antenna pattern102(a length in the first direction D1), that is, a total width of the first radiator110, the second radiator120, the conductor130, and the antenna ground140(i.e., a total length, which is a sum of a length L2and the length L3, in the first direction D1) ranges from 6 mm to 8.5 mm and, for example, may be 6 mm. Therefore, the antenna pattern102has a smaller size and can be applied to devices with thin bezel.

In the embodiment, the reason that the antenna pattern102may have a smaller width is that the antenna structure100has a slit115, which has at least one bending portion and is formed among the second radiator120, the conductor130, and the antenna ground140(i.e., the portion between the positions B1, B2, B3, B5, and B6and the positions B1, A4, A5, A6, and A7). The slit115can be configured as a it-type matching circuit. The slit115has two bending portions and is Z-shaped, but the shape of the slit115is not limited thereto.

FIG.2is a schematic view of an equivalent circuit of a slit of the antenna structure inFIG.1. Referring toFIGS.1and2together, in the embodiment, the portion of the slit115(seeFIG.1) between the position A4and the position B2has the capacitance effect in the circuit, functioning as a capacitor172disposed between the position A4and the position B2. The path of the slit115at the positions A4, A5, A6, and A7(i.e., the path of the Z-shaped slit115) has the inductance effect in the circuit, functioning as an inductor174disposed between the position A4and the position A7. The portion of the slit115between the position A7and the position B6has the capacitance effect in the circuit, functioning as a capacitor176disposed between the position A7and the position B6.

In this way, by changing the equivalent circuit of the slit115and a width of the second part of the conductor130, the impedance matching of the high frequency band and the low frequency band can be adjusted, the peak gain can be reduced, and the antenna efficiency can be improved.

Specifically, a total length L1of the first radiator110and the second radiator120ranges from 23 mm to 27 mm in the first direction D1and, for example, 25 mm. A total width of the first radiator110, the second radiator120, and the conductor130(i.e., the length L2taken up by the first radiator110, the second radiator120, and the conductor130in the second direction D2) ranges from 3 mm to 5 mm and, for example, 4 mm. In other words, in the embodiment, an area occupied by the first radiator110, the second radiator120, and the conductor130is reduced to an area of 25 mm×4 mm.

In the embodiment, a length of the slit115ranges from 11 mm to 20 mm, and for example, 17 mm. A width L5of the slit115ranges from 0.3 mm to 1.5 mm, and for example, 0.5 mm. Certainly, the length and the width L5of the slit115are not limited thereto.

Note that, in the embodiment, the designer can use the equivalent circuit of the slit115and a length L4(which ranges from 7 mm to 11 mm and, for example, 9 mm) of the second part (i.e., the portion at the positions B2, B4, B3, and B5) of the conductor130to adjust the impedance matching of its dual frequency (Wi-Fi 2.4 GHz and Wi-Fi 5 GHz), reduce the peak gain, and improve the antenna efficiency. In addition, in the embodiment, a portion of the second radiator120bends at the positions A5, A6, A7, and A8and forms a notch117, whose length of the notch117is 2 mm, and whose width is 1 mm. The notch117can be configured to adjust the frequency to Wi-Fi 2.4 GHz.

As can be seen inFIG.1, the antenna structure100further includes a substrate105and a coaxial transmission line160. A length, width, and height of the substrate105roughly ranges from 27 mm to 33 mm (e.g. 30 mm), 6 mm to 8.5 mm (e.g. 6 mm), and 0.3 mm to 0.5 mm (e.g. 0.4 mm), but the disclosure is not limited thereto. In the embodiment, the substrate105is a double-sided circuit board; the substrate105includes a first surface106and a second surface107opposite to each other. The first radiator110, the second radiator120, the conductor130, and the antenna ground140are disposed on the first surface106while the coaxial transmission line160is located on the second surface107and is electrically connected to the antenna ground140.

In the embodiment, since the coaxial transmission line160is located on the second surface107, a portion of the antenna structure100at the position A1goes through a via hole (not shown) of the substrate105and is electrically connected to a positive end of the coaxial transmission line160. The antenna ground140of the antenna structure100(i.e., the path between the positions C1and C2) goes through a via hole (not shown) of the substrate105and is electrically connected to a negative end of the coaxial transmission line160at the ground terminal (i.e., the portion between the position C3and the position C4). Certainly, in other embodiments, the substrate105may be a single sided circuit board, and the first radiator110, the second radiator120, the conductor130, the antenna ground140, and the coaxial transmission line160may be on the same surface.

In addition, the antenna structure100further includes a conductor grounding layer14, a portion of the conductor grounding layer14is disposed on the first surface106and connected to the antenna ground140, and another portion of the conductor grounding layer14extends beyond the substrate105and is connected to a system ground (not shown). The conductor grounding layer14is, for example, a copper foil, but the disclosure is not limited thereto. The conductor grounding layer14may be welded to a portion of the antenna ground140(i.e., the path between the positions C1, B4, B5, B6, and C2), for example, a position at a width of 1 mm, and another portion of the conductor grounding layer14is connected to the system ground. In the embodiment, a length of the conductor grounding layer14is equal to the length L6of the antenna ground and ranges from 27 mm to 33 mm and, for example, 30 mm, but the disclosure is not limited thereto.

FIGS.3A to3Care schematic views of different antenna structures according to different embodiments of the disclosure. Referring toFIG.3AtoFIG.3C, antenna structures100a,100b, and100have respective slits115a,115b, and115in different lengths. In detail, the antenna structure100aofFIG.3Ais the antenna structure100ofFIG.1, but with a copper foil112disposed on the slit115. A length of the copper foil112is 6 mm so that the slit115ahas a smaller length, for example, 11 mm. The antenna structure100bofFIG.3Bis the antenna structure100ofFIG.1, but a copper foil114disposed on the slit115. A length of the copper foil114is 3 mm so that the length of the slit115bcan be 14 mm. The antenna structure100ofFIG.3Cis the same as the antenna structure100ofFIG.1, and the length of the slit115is 17 mm.

FIG.3Dis a schematic view of the frequency-voltage standing wave ratios of the antenna structure ofFIGS.3A to3C. Referring toFIG.3D, the antenna structures100a,100b, and100have better performance at a frequency band of Wi-Fi 5G, and the antenna structure100ofFIG.3Chas better performance at a frequency band of Wi-Fi 2.4G.

FIG.3Eis a Smith chart of the antenna structures ofFIGS.3A to3C. As can be seen inFIG.3E, the Smith chart of the antenna structure100aofFIG.3A, the antenna structure100bofFIG.3B, and the antenna structure100ofFIG.3Cshows a gradually moving-up and enlarging spiral in a clockwise manner, and the antenna structures have a characteristic of inductance in series. The greater the length of the slits115a,115band115, the closer the frequency of Wi-Fi 2.4 GHz can be adjusted to the quasi-frequency. In other words, the antenna structure100ofFIG.3Ccan have the best performance.

FIGS.4A to4Care schematic views of antenna structures according to different embodiments of the disclosure. Referring toFIG.4AtoFIG.4C, antenna structure100c,100d, and100have slits115c,115d, and115in respective widths L7, L8, and L5. In detail, in the antenna structure100cofFIG.4Aand the antenna structure100ofFIG.1, with a copper foil116added to the first radiator110and a copper foil122added between a portion121and a portion123of a second radiator120c, the width of the first radiator is increased and the width L7of the slit115cis increased to 1.5 mm. Similarly, in the antenna structure100dofFIG.4Band the antenna structure100ofFIG.1, with a copper foil118added to the first radiator110and a copper foil124added between the two portions121and123of a second radiator120d, the width L8of the slit115dis increased to 1 mm. The antenna structure100ofFIG.4Cis the same as the antenna structure100ofFIG.1, and the width L5of the slit115is 0.5 mm.

FIG.4Dis a schematic view of the frequency-voltage standing wave ratios of the antenna structures ofFIGS.4A to4C. Referring toFIG.4D, the antenna structure100c,100d,100have better performance at a frequency band of Wi-Fi 5G, and the antenna structure100ofFIG.4Chas the best performance at a frequency band of Wi-Fi 2.4G.

FIG.4Eis a Smith chart of the antenna structures ofFIGS.4A to4C. As can be seen inFIG.4E, the Smith chart of the antenna structure100cofFIG.4A, the antenna structure100dofFIG.4B, and the antenna structure100ofFIG.4Cshows a gradually moving-down and enlarging spiral in a clockwise manner, and the antenna structures have a characteristic of capacitance in series. The smaller the width of the slits115c,115dand115, the closer the frequency of Wi-Fi 2.4 GHz can be adjusted to the quasi-frequency. In other words, the antenna structure100ofFIG.4Ccan have the best performance.

FIG.5Ais a partial schematic view of the interior of an electronic device according to an embodiment of the disclosure.FIGS.5B and5Care partial enlarged views ofFIG.5A.FIG.6is a partial cross-sectional view of the electronic device ofFIG.5A. Referring toFIG.5AtoFIG.6, in the embodiment, the electronic device10is exemplified as a large-sized display device, such as a large-sized electronic whiteboard or a television. The electronic device10includes a screen15(seeFIG.6), and a length of the screen15is greater than 170 cm. In an embodiment, the screen15is, for example, 86 inches, its length is about 189.5 cm, and its width is about 106.5 cm. Certainly, the sizes of electronic device10and screen15are not limited thereto.

Generally, a large-sized device is limited by its large system ground, which tends to have the higher directivity of the antenna, and its peak gain tends to be too high, for example, greater than 5 dBi. In the embodiment, the slit115is used to reduce the width of the antenna pattern102to less than 6 mm. Because the antenna pattern102has a smaller width, its peak gain can be reduced. Hence, the requirements of a Bluetooth module card17and a Wi-Fi module card19are met.

As can be seen inFIGS.5A to5C, the electronic device10is configured with three antenna structures100disposed on an edge of a housing. The antenna structure100(serves as a Bluetooth antenna) shown on the left side ofFIG.5Ais connected to the Bluetooth module card17through the coaxial transmission line160(seeFIG.5B). The two antenna structures100(serve as Wi-Fi Main antenna and Wi-Fi AUX antenna) shown on the right side ofFIG.5Aare connected to the Wi-Fi module card19through the coaxial transmission line160(seeFIG.5C). In an embodiment, the coaxial transmission line160has a length of, for example, 350 mm and is a low loss transmission line with a diameter of 1.13 mm.

As shown inFIG.6, the housing includes an insulating back cover13and a metal side shell (not shown). The metal side shell has an insulation area12. The insulation area12is, for example, a plastic window, which is an opening (not shown) of the metal side shell injection molded with plastic. The screen15is shown at the bottom ofFIG.6, and the antenna structure100is arranged in the housing, beside the insulation area12, and above the screen15. The electronic device10further includes a system ground18and a conducting element16located in the housing. The antenna structure100is disposed on an insulation bracket11, and the antenna structure100is connected to the system ground18through the conductor grounding layer14and the conducting element16(e.g., a conductive foam).

In the embodiment, a total width L9of the antenna structure100(the sum of the lengths L2and L3in the first direction D1inFIG.1) ranges from 6 mm to 8.5 mm, for example, 6 mm. A distance L10(close to a thickness of the conducting element16) between the antenna structure100and the system ground18ranges from 3.5 mm to 6 mm, for example, 4.5 mm.

FIG.7is a schematic view of the frequency-voltage standing wave ratios of the antenna structure of the electronic device ofFIG.5Awith different widths. Referring toFIG.7, the width L9of the antenna structure100is 6 mm, 7 mm, and 8 mm which are indicated by dotted lines, thick lines, and thin lines, respectively. When the width L9of the antenna structure100is 6 mm, 7 mm, and 8 mm, the voltage standing wave ratios (VSWR) of Wi-Fi 2.4G and Wi-Fi 5G can be less than 3. In addition, when the width L9of the antenna structure100is smaller, its impedance matching gradually degrades, and therefore the width L9of the antenna structure100is favorably equal to or greater than 6 mm.

FIG.8is a schematic view of the frequency-antenna efficiency of the antenna structure of the electronic device ofFIG.5Awith different widths. Referring toFIG.8, when the width L9of the antenna structure100is 6 mm, the antenna efficiency of Wi-Fi 2.4 GHz has reached between −5.2 dBi and −5.5 dBi, and the antenna efficiency of Wi-Fi 5 GHz can be greater than −4 dBi. In addition, when the width L9of the antenna structure100is 7 mm and 8 mm, the antenna efficiency of Wi-Fi 2.4G and Wi-Fi 5G is more favorable.

FIG.9is a schematic view of the frequency-peak gains of the antenna structure of the electronic device ofFIG.5Awith different widths. Referring toFIG.9, when the width L9of the antenna structure100is below 8 mm, its peak gain can meet the requirements of the module cards. In addition, as can be seen inFIG.8, when the width L9of the antenna structure100is 8 mm, the antenna efficiency of Wi-Fi 2.4G is between −3.2 dBi and −4.2 dBi, and the antenna efficiency of Wi-Fi 5G is between −2.6 dBi and −3.1 dBi. Therefore, when the width L9of the antenna structure100is between 6 mm and 8 mm, both peak gain and antenna efficiency can have better performance.

FIG.10is a partial schematic view of the interior of an electronic device according to another embodiment of the disclosure.FIG.11is a partial cross-sectional view of the electronic device ofFIG.10.FIG.12is a simplified structural view ofFIG.11. Referring toFIG.10toFIG.12, in the embodiment, an electronic device20is, for example, a tablet device. A length L11of the whole device is 292 mm, its width L12is 201 mm, and its height is 8.45 mm.

The electronic device20includes two antenna structures100L and100R, and a distance L13between the two antenna structures is 67 mm. The two antenna structures100L and100R are connected to a Wi-Fi module card26through two coaxial transmission lines160L and160R. The antenna structure100L on the left inFIG.10is the Wi-Fi Main antenna, and the length of the coaxial transmission line160L of the antenna structure100L is 70 mm. The antenna structure100R on the right inFIG.10is the Wi-Fi AUX antenna, and the length of the coaxial transmission line160R of the antenna structure100R is 140 mm. In the embodiment, both coaxial transmission lines160L and160R use a low loss transmission line with a diameter of 1.13 mm.

As can be seen inFIG.11, in the embodiment, a screen25of the electronic device20is shown at the top inFIG.11. The housing includes a metal back cover22and an insulating side shell21. An insulation area is located at the insulating side shell21, and the metal back cover22is L-shaped, extends rightward and bends upward to the insulating side shell21, and partially covers the insulating side shell21. The antenna structure100is disposed on the insulation bracket23, beside the insulating side shell21and close to the screen25. A projection of the metal back cover22onto the screen25overlaps with a projection of the antenna structure100onto the screen25.

In the embodiment, the substrate105of the antenna structure100is a double-sided circuit board, and its length, width, and height are 25 mm, 6 mm, and 0.4 mm, respectively. As can be seen inFIG.11andFIG.12, the antenna pattern is printed on the first surface106of the substrate105, and the conductor grounding layer14and the coaxial transmission line160are disposed on the second surface107of the substrate105. InFIG.11, the conductor grounding layer14of the antenna structure100is Z-shaped and extends from the antenna pattern102to the outside of the substrate105in a bending manner and is connected to the metal back cover22in a bending manner. The antenna structure100is connected to the L-shaped metal back cover22through the Z-shaped conductor grounding layer14. The conductor grounding layer14and a portion of the metal back cover22together form a resonance chamber29. The conductor grounding layer14, the portion of the metal back cover22and a motherboard24of the system integrate into a complete ground surface. The shape of the resonance chamber29is close to a shape of J or a shape of U.

In the embodiment, a distance L14between the first surface106of the substrate105of the antenna structure100and the metal back cover22ranges from 6.5 mm to 8 mm, and the distance L14may be, for example, 6.9 mm. The U-shaped metallic resonance chamber29can concentrate an antenna radiation energy of the antenna pattern102toward a vertical direction ofFIG.11and reduce the antenna radiation energy flowing to the direction of the insulating side shell21(the right side ofFIG.11). Therefore, the value of edge Specific Absorption Rate (edge SAR) can be effectively reduced. In addition, because the conductor grounding layer14is Z-shaped, it may work as a barricade in the vertical direction. The antenna pattern102of the antenna structure100is separated from the motherboard24, which can reduce or block the noise source on the motherboard24, which directly affects the wireless transmission of the antenna structure100.

In addition, a distance L15between the antenna pattern102of the antenna structure100and the insulating side shell21ranges from 2 mm to 3 mm, for example, 3 mm. The distance L15is a preset safety distance when the value of edge SAR is being measured, so the antenna pattern102may not be disposed within the distance L15. Compared with a conventional electronic device20, in order to reduce the electromagnetic wave, it is required to reduce the antenna emission energy to 10 dBm so that the value of electromagnetic wave can comply with regulatory requirements. With the above design, the electronic device20of the embodiment does not need to reduce the transmission energy of the antenna, the value of electromagnetic wave can comply with the regulatory requirements, and the electronic device has favorably high antenna efficiency.

The practical test results of edge SAR are shown in Table 1. Compared with the antenna structure of the conventional electronic device with a transmit power of only 10 dBm at Wi-Fi 5 GHz, the antenna structures100L and100R of the electronic device20of the embodiment can transmit power of 13 dBm at Wi-Fi 5 GHz, which is an increase of 3 dBm.

FIG.13is a schematic view of the frequency-antenna efficiency of the two antenna structures of the electronic device ofFIG.10. Referring toFIG.13, the antenna efficiency of the two antenna structures100L and100R at a frequency band of Wi-Fi 2.4G is between −4.9 dBi and −5.5 dBi, and the antenna efficiency at a frequency band of Wi-Fi 5G is between −2.1 dBi and −3.5 dBi. Therefore, the two antenna structures have good antenna efficiency performance.

Based on the above, the antenna structure of the disclosure uses the first radiator for resonating at the high-frequency band and the second radiator and a portion of the first radiator for resonating at the low frequency band. The slit is formed between the second radiator and the conductor and between the second radiator and the antenna ground. The slit can be configured as a π-type matching circuit, which makes a smaller-sized antenna structure possible, and thereby it can be applied to electronic devices with thin bezel and improve the antenna.