TWI462394B - A multi-loop antenna system and an electronic device having the same - Google Patents

Description

Multi-loop antenna system and electronic device having the same

The present invention relates to an antenna system, and more particularly to a multi-loop antenna system with high gain and high directivity.

Conventionally, antenna structures used in wireless network access points (APs) are mostly in the form of Planar Inverted F Antenna (PIFA) and monopole antennas, for example, as disclosed in the Republic of China Patent No. M377714. "Multi-input and multi-output dual-frequency monopole antenna device" in which three monopole antennas are metal-cut or stamped on the antenna ground plane and installed in the bridge to form an applicable system. An antenna system for Multiple Input Multiple Output (MIMO) technology.

However, although the antenna structure can be built in the device, since the antenna has a three-dimensional structure, it occupies a large space, and the space available in the wireless network bridge is limited. Moreover, the maximum gain of the conventional antenna structure in the 2.4 GHz or 5 GHz operating band is usually only 3~5 dBi, and the directivity of the antenna radiation pattern is low, which does not satisfy the high gain required by the bridge antenna. And the characteristics of high directional radiation field type.

Accordingly, it is an object of the present invention to provide a multi-loop antenna system that achieves dual frequency operation and has high directivity and high gain.

Another object of the present invention is to provide a wireless network bridge (AP) that is simple in structure, small in size, low-profile, easy to manufacture, low in cost, and applicable to small outdoor wireless networks. Built-in dual-frequency multi-loop antenna system.

Therefore, the multi-loop antenna system of the present invention comprises an antenna module and a system module. The antenna module includes an antenna substrate and a plurality of loop antennas. The antenna substrate includes a first surface and a second surface opposite to the first surface. The loop antennas are disposed on the first surface or the second surface of the antenna substrate. On the surface, each loop antenna includes a first radiator that provides a first operating frequency band, and a second radiator that provides a second operating frequency band, the first radiator having a feed at both ends thereof And a ground end, and the feeding end is adjacent to and spaced apart from the ground end, so that the first radiator forms a loop, and the second radiator has a first end and a second end at the two ends thereof, One end is connected to the feed end, and the second end is connected to the ground end, so that the second radiator forms another loop, and the geometric center of each loop antenna is the same as the geometric center defined by the loop antennas. And the shortest distance between any two adjacent loop antennas is the same; the system module includes at least one ground plane facing the second surface of the antenna substrate, providing the RF circuit of the system circuit board, and the system module and the antenna substrate Second table Parallel spaced a distance, the reflected radiation and for such loop antennas. Such a symmetrical structure antenna maintains the same isolation between the antennas and allows each loop antenna to have a more symmetrical signal coverage space in space.

Preferably, the second radiator of each of the loop antennas is located in a loop formed by the first radiator.

Preferably, the geometric centers of any two adjacent loop antennas are respectively at the same angle as the line connecting the geometric centers defined by the loop antennas.

Preferably, the antenna substrate further includes a through hole at a geometric center defined by the loop antennas for passing through a plurality of signal transmission lines.

Preferably, the area of the antenna substrate is less than or equal to the area of the system module to ensure that the system module can completely reflect the radiation of each loop antenna.

One of the effects of the present invention is that a plurality of full-wavelength loop antennas are disposed on the antenna substrate, and the full-wavelength antenna is a balanced antenna having high-gain antenna characteristics, and the isolation between the antenna and the antenna is also It can be kept to a minimum, and the radiation of the loop antenna can be reflected through at least one system ground plane on the system module, so that the radiation pattern of the antenna module has high directivity and high antenna gain, which can improve communication coverage.

The second effect of the present invention is that the geometric center of each loop antenna in the multi-loop antenna system is the same as the geometric center defined by the loop antennas, and the shortest distance of any two adjacent loop antennas is the same. The better isolation between the loop antennas and the same radiation field and signal coverage.

The third effect of the present invention is that the loop antenna is made by using a printed circuit board, is simple to manufacture and low in cost, and has a low-profile appearance and a planar structure, and is very suitable for use in a small outdoor wireless network. On the bridge.

The fourth function of the present invention is that the opening direction (feeding position) of each loop antenna is set at 45 degrees (or 135 degrees) relative to the geometric center defined by the loop antennas, and the antenna radiation field is in the vertical radiation. The direction (ie, the positive Z-axis) can have dual-polarized radiation characteristics.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of FIG.

Before the present invention is described in detail, it is noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 1, a first preferred embodiment of a multi-loop antenna system 100 of the present invention is operable over a dual-band wireless local area network WLAN (2400-2484/5150-5825 MHz). In the loop antenna system 100, in the embodiment, the multi-loop antenna system 100 includes an antenna module 10 and a system module 20 disposed in parallel with the antenna module 10.

The antenna module 10 includes an antenna substrate 1 and a plurality of loop antennas 2 (three in the embodiment). The antenna substrate 1 (or dielectric substrate) is circular or arbitrarily polygonal, and is made of an insulating material (for example, glass fiber, FR4). The antenna substrate 1 has a first surface 11 , a second surface 12 opposite to the first surface 11 , and a through hole 13 through which a plurality of signal transmission lines 5 pass. It should be noted that the perforations 13 of the antenna substrate 1 are disposed at the geometric center positions defined by the loop antennas 2, so as to shorten the length of the signal transmission line 5 and prevent the signal transmission line 5 from being pressed to the loop antenna 2, resulting in The antenna characteristics are affected.

Referring to FIG. 2 , the loop antennas 2 are all-wavelength loop antennas 2 , and are disposed on the first surface 11 of the antenna substrate 1 , and the loop antennas are respectively disposed on the first surface 11 of the antenna substrate 1 . 2 includes a first radiator 3 that provides a first operating frequency band, and a second radiator 4 that provides a second operating frequency band. The first radiator 3 has a feed point 31 and a ground point 32 at its two ends, and the feed end 31 is adjacent to and spaced apart from the ground end 32, so that the first radiator 3 Forming a circular loop; the second radiator 4 has a first end 41 and a second end 42 at opposite ends thereof, and the first end 41 is connected to the feeding end 31, and the second end 42 is connected to the ground end 32, so that The second radiator 4 partially forms a circular loop.

In this embodiment, the second radiator 4 has a radiating section 40, and a first extending section 410 and a second extending section 420 extending in parallel from opposite ends of the radiating section 40, and the first extending section 410 The end is the first end 41 of the second radiator 4, the end of the second extension 420 is the second end 42 of the second radiator 4, and the radiating section 40 forms a circular loop. In addition, the second radiator 4 of each loop antenna 2 is located in a loop formed by the first radiator 3, and the first extension 410 and the second extension 420 define an opening 430.

Referring to FIG. 3, the loop antenna 2 of the present embodiment is distributed along the circumference of the circular antenna substrate 1, and the geometric center of each loop antenna 2 and the three loop antennas 2 are defined together ( That is, the distance of point A is the same, that is, La=Lb=Lc, and the shortest distance between any two adjacent loop antennas 2 is the same, that is, L1=L2=L3, of any two adjacent loop antennas 2 The angle between the geometric center and the geometric center (point A) defined by the three loop antennas 2 is also the same, that is, θ ₁ = θ ₂ = θ ₃ , that is, 120 degrees. An antenna of such a symmetrical structure can maintain the same isolation between the antennas, and each loop antenna 2 has a more symmetrical signal coverage space in space.

In particular, the second radiator 4 is located in the loop formed by the first radiator 3, so that the second radiator 4 is disposed by the space inside the first radiator 3, so that the space can be increased without additional space. Under the double loop antenna design. In this embodiment, the geometric center position of the first radiator 3 is different from the geometric center position of the radiation segment 40 of the second radiator 4, and the connection between the geometric centers of the two is parallel to the first extension 410 and The extending direction of the second extending portion 420 is such that the first radiator 3 and the second radiator 4 are bilaterally symmetric with the geometric center of the two.

In addition, in each loop antenna 2, the extending direction of the first extension section 410 and the second extension section 420 (ie, the direction of the opening 430) is a geometric center (point A) and each defined by the three loop antennas 2 The geometric center connection of the loop antenna 2 (ie, La, Lb, and Lc) is sandwiched by an angle α, which is preferably 45 degrees, that is, the feeding position of the loop antenna 2 is defined together with respect to the geometry of the three loop antennas 2 The center position is rotated by 45 degrees (or 135 degrees) so that the antenna radiation pattern can have dual-polarized radiation characteristics in the vertical radiation direction (i.e., the Z-axis).

Of course, the direction of the opening 430 defined by the first extension 410 and the second extension 420 may also be toward the geometric center defined by the loop antennas 2, that is, the extension of the first extension 410 and the second extension 420. The geometric center (point A) defined by the direction parallel to the three loop antennas 2 is connected to the geometric center of each loop antenna 2, as shown in FIG. 4 (the signal transmission line 5 is omitted), and the rotation angle is not Set limits. In addition, the loop formed by the radiating section 40 of the first radiator 3 and the second radiator 4 is not limited to a circle, and both of them may be rectangular loops (as shown in FIG. 5, wherein the signal transmission line 5 is omitted. ), or the first radiator 3 is a circular loop, the radiant section 40 is a rectangular loop, and the like, and the dual-frequency resonance of the present invention can also be achieved.

Referring to FIG. 1, the system module 20 is a system circuit board, which may be a circular or arbitrary polygon. The system module 20 has at least one ground plane 201 facing the second surface 12 of the antenna substrate 1 (for example: The metal surface), in addition to being the system ground plane of the RF circuit on the system board, can also be regarded as a reflector for reflecting the radiation of the loop antenna 2, thereby not only making the antenna The module 10 has a high degree of directivity, and can also increase the antenna gain of the antenna module 10 in a single direction (ie, the normal direction of the first surface 11 of the antenna substrate 1). The system module 20 can be a multi-layer structure, the uppermost layer is a thin metal layer, the lower layer is a dielectric substrate, or can be a circuit layer containing more layers. Moreover, a gap exists between the ground plane (which can be used as a reflective surface) 201 and the second surface 12, and is used as an effective space for electronic components (not shown) on the system module 20. In addition, the area of the antenna substrate 1 of the present embodiment is less than or equal to the area of the system module 20 to ensure that the system module 20 can completely reflect the radiation of each loop antenna 2.

Referring to FIG. 6, the multi-loop antenna system 100 of the present embodiment is installed in a housing 210 of an electronic device 200 such as a wireless network access point (AP) or a wireless broadband router. And feeding the signal to the feeding end 31 of the loop antenna 2 by using a mini-coaxial cable as the signal transmission line 5, so that the multi-loop antenna system 100 can be matched with the system module 20 of different applications (ie, The system board) improves the flexibility in the use of the multi-loop antenna system 100. Of course, the type of the signal transmission line 5 is not limited by this embodiment.

7 to FIG. 9 is a schematic diagram showing the actual size of the multi-loop antenna system 100 of the present embodiment, wherein FIG. 7 is a planar development view of the single loop antenna 2; FIG. 8 is a top view of the multi-loop antenna system 100; 9 is a side view between the antenna substrate 1 and the system module 20, the unit of the number in each figure is mm (mm), can refer to the data in the figure to know the actual size of the embodiment, but not This embodiment is limited.

In this embodiment, the first radiator 3 and the second radiator 4 can respectively resonate at a frequency of 2.4 GHz and 5 GHz, and the spacing between the antenna substrate 1 and the ground plane 201 of the system module 20 needs to be greater than 5 mm. (mm), for a wider variety of electronic components to be placed on the system module (system board) 20, and a distance of 8.4 mm (mm) between the embodiments will result in better antenna gain.

Referring to FIG. 10 and FIG. 11 , the measurement result of the 2-D radiation field type of the loop antenna 2 operating at 2442 MHz and 5490 MHz is respectively performed, and the direction of the opening 430 of the loop antenna 2 and the three loop antennas 2 are shown. The geometric center of the joint definition and the geometric center line of each loop antenna 2 have an angle α of 45 degrees. As can be seen from the figure, by the cooperation of the antenna module 10 and the system module 20, the multi-loop antenna system 100 has a high antenna gain in the positive Z-axis direction, that is, a high directivity, and the antenna radiation pattern It has dual-polarized radiation characteristics and is suitable for wireless network bridges (APs).

Referring to FIG. 12, a reflection coefficient (Measure Coefficient) measurement data diagram of each loop antenna 2 is used. For convenience of description, referring to FIG. 3, three loop antennas 2 are respectively defined as a first loop antenna 21, A second loop antenna 22 and a third loop antenna 23. While in FIG. 12, S _11, S ₂₂ and S ₃₃ are a first loop antenna 21, a second loop antenna 22 and the third loop antenna 23 of the reflection coefficient. It can be known from experiments that the center frequency of the first operating band provided by the first radiator 3 is 2.4 GHz, and the center frequency of the second operating band provided by the second radiator 4 is 5 GHz, and the two are respectively at 2.4 GHz and 5 GHz. The reflection coefficient is less than minus 10-dB, which conforms to the specifications of the 2.4 GHz and 5 GHz wireless local area network bands, so this embodiment is indeed applicable to the wireless local area network.

Referring to FIG. 13, is an Isolation measurement data map between each loop antenna 2, where S ₂₁ is the isolation between the first loop antenna 21 and the second loop antenna 22; S ₃₁ is the first The isolation between the loop antenna 21 and the third loop antenna 23; S ₃₂ is the isolation between the second loop antenna 22 and the third loop antenna 23. It can be known from experiments that the isolation between the respective loop antennas 2 is on average about minus 15-dB, which has good isolation.

14 is a radiation efficiency/antenna gain-frequency graph of the multi-loop antenna system 100 of the present embodiment. As can be seen from the figure, the maximum gain and radiation efficiency of the multi-loop antenna system 100 in the 2.4 GHz WLAN band can reach 7.6 dBi and 76%, respectively, and the maximum gain and radiation efficiency in the 5 GHz WLAN band can reach 9 dBi and 83% with high antenna gain and good radiation characteristics.

Referring to FIG. 15 , a second preferred embodiment of the multi-loop antenna system 100 of the present invention is substantially the same as the first preferred embodiment, except that the loop antennas 2 can be respectively disposed on the antenna substrate 1 . Different surfaces. In this embodiment, the first loop antenna 21 is disposed on the first surface 11 of the antenna substrate 1 , and the second loop antenna 22 and the third loop antenna 23 are disposed on the second surface 12 of the antenna substrate 1 . It is also possible to receive or transmit dual-frequency signals and achieve high antenna gain characteristics. The signal transmission line 5 is also omitted in FIG.

Referring to FIG. 16, a third preferred embodiment of the multi-loop antenna system 100 of the present invention is substantially the same as the first preferred embodiment, except that in the embodiment, the second radiator 4 has only A radiating section 40, and the opposite ends of the radiating section 40 are the first end 41 and the second end 42 of the second radiator 4. In other words, the second radiator 4 of the present embodiment omits the first extension 410 and the second extension 420 (see FIG. 2) compared to the second radiator 4 of the first preferred embodiment, and directly utilizes radiation. The opposite ends of the segment 40 are connected to the feeding end 31 and the grounding end 32 of the first radiator 3, so that the dual-frequency signal can be received or transmitted in the present case and has high antenna gain and high directivity. The signal transmission line 5 is also omitted in FIG.

In summary, the multi-loop antenna system 100 of the present invention has the following effects:

1. The multi-loop antenna system 100 applies multiple input multiple output (MIMO) technology by arranging a plurality of loop antennas 2 on the antenna substrate 1, and the lengths of the first radiator 3 and the second radiator 4 are each Relative to the full wavelength of the operating center frequency (2.4 GHz and 5 GHz), the full-wavelength antenna is a balanced antenna with high gain antenna characteristics, and the isolation between the antenna and the antenna can be kept to a minimum. Appropriately adjusting the antenna feed pitch (ie, the distance between the feed end 31 and the ground end 32) and the distance between the first radiator 3 and the second radiator 4 can effectively control the impedance characteristics of the loop antenna 2 so that Excellent impedance matching is achieved in the 2.4/5 GHz wireless local area network.

2. The geometric center of each loop antenna 2 in the multi-loop antenna system 100 is the same as the geometric center defined by the loop antennas 2, and the shortest distance of any two adjacent loop antennas 2 is the same, Each loop antenna 2 has the same isolation (less than minus 15-dB) and symmetric radiation pattern and signal coverage.

3. The antenna module 10 is integrated with the system module 20, and the radiation of the loop antenna 2 is reflected by at least one ground plane on the system module 20, so that the antenna module 10 can have high directivity (at least More than 6 dBi) can also increase the antenna gain of the antenna module 10 in a single direction (positive Z-axis direction).

4. The opening direction (feeding position) of each loop antenna 2 is rotated by 45 degrees (or 135 degrees) with respect to the geometric center defined by the loop antennas 2, so that the antenna radiation field is in the vertical radiation direction. (i.e., the positive Z-axis) can have dual-polarized radiation characteristics, so that the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

100‧‧‧Multi-loop antenna system

200‧‧‧Electronic device 200

210‧‧‧Shell

10‧‧‧Antenna Module

20‧‧‧System Module

201‧‧‧ ground plane

1‧‧‧Antenna substrate

11‧‧‧ first surface

12‧‧‧ second surface

13‧‧‧Perforation

2‧‧‧Circle antenna

21‧‧‧First loop antenna

22‧‧‧second loop antenna

23‧‧‧ Third loop antenna

3‧‧‧First radiator

31‧‧‧Feeding end

32‧‧‧ Grounding terminal

4‧‧‧second radiator

40‧‧‧radiation section

410‧‧‧First extension

41‧‧‧ first end

420‧‧‧Second extension

42‧‧‧second end

430‧‧‧ openings

5‧‧‧Signal transmission line

Figure 1 is a first preferred embodiment of the multi-loop antenna system of the present invention;

Figure 2 is a plan development view showing a single loop antenna in the first preferred embodiment;

3 is a plan development view of the antenna module in the first preferred embodiment, wherein the opening direction is rotated by 45 degrees with respect to the geometric center defined by the loop antennas;

4 is a plan development view of the antenna module in the first preferred embodiment, wherein the opening direction is toward a geometric center defined by the loop antennas;

Figure 5 is a diagram showing another embodiment of the loop antenna in the first preferred embodiment;

Figure 6 is an electronic device illustrating a built-in multi-loop antenna system;

Figure 7 is a diagram showing the actual size between a single loop antenna in the first preferred embodiment;

Figure 8 is a view showing the actual size of the specifications between the respective loop antennas in the first preferred embodiment;

Figure 9 is a view showing the actual size of the antenna substrate and the system module in the first preferred embodiment;

10 is a diagram showing the measurement results of the 2-D radiation pattern of the X-Z plane and the Y-Z plane of the loop antenna operating at 2442 MHz in the first preferred embodiment;

11 is a diagram showing the measurement results of the 2-D radiation field type of the X-Z plane and the Y-Z plane of the loop antenna operating at 5490 MHz in the first preferred embodiment;

Figure 12 is a diagram showing measurement data of reflection coefficients of respective loop antennas in the first preferred embodiment;

Figure 13 is a diagram showing the isolation measurement data of each of the loop antennas in the first preferred embodiment;

Figure 14 is a graph showing the radiation efficiency / antenna gain-frequency of the multi-loop antenna system of the first preferred embodiment;

Figure 15 is a diagram showing a second preferred embodiment of the multi-loop antenna system of the present invention; and

Figure 16 is a diagram showing a third preferred embodiment of the multi-loop antenna system of the present invention.

100. . . Multi-loop antenna system

10. . . Antenna module

20. . . System module

1. . . Antenna substrate

11. . . First surface

12. . . Second surface

13. . . perforation

2. . . Loop antenna

201. . . Ground plane

5. . . Signal transmission line

Claims (9)

A multi-loop antenna system includes: an antenna module, comprising: an antenna substrate, including a first surface and a second surface opposite to the first surface; and a plurality of loop antennas disposed on the antenna substrate On the first surface or the second surface, each of the loop antennas includes a first radiator capable of providing a first operating frequency band, and a second radiator capable of providing a second operating frequency band, the first radiation The body has a feed end and a ground end at both ends thereof, and the feed end is adjacent to and spaced apart from the ground end, so that the first radiator forms a loop, and the second radiator has two a first end and a second end of the end, the first end is connected to the feed end, and the second end is connected to the ground end, so that the second radiator forms another loop; wherein the loop antenna The geometric center has the same distance from the geometric center defined by the loop antennas, and the shortest distance between any two adjacent loop antennas is the same; and a system module including at least one opposite to the antenna substrate Ground surface of the second surface, and the system The group is parallel to the second surface of the antenna substrate at a distance for reflecting the radiation of the loop antennas; wherein the two ends of the first radiator of each loop antenna jointly define an opening, and a geometric center of the loop antenna and a line connecting the openings, and a geometric center defined by the loop antennas and the loop day The line connecting the geometric centers of the lines is typically 45 degrees or 135 degrees. The multi-loop antenna system according to claim 1, wherein the second radiator of each of the loop antennas is located in a loop formed by the first radiator. The multi-loop antenna system according to claim 2, wherein the second radiator has a radiating section, and a first extending section and a second extending section respectively extending from both ends of the radiating section. The end of the first extension is a first end of the second radiator, the end of the second extension is a second end of the second radiator, and the radiant section forms a loop. The multi-loop antenna system according to claim 2, wherein the second radiator has a radiating section, and the opposite ends of the radiating section are respectively the first end and the second end of the second radiator At the two ends, the radiant section forms a loop. A multi-loop antenna system according to claim 3, wherein the geometric centers of any two adjacent loop antennas are respectively connected to the geometric centers defined by the loop antennas The angle is the same. The multi-loop antenna system of claim 1, wherein at least one of the first radiator and the second radiator forms a rectangular or circular loop. The multi-loop antenna system of claim 1, wherein the antenna substrate further comprises a perforation at a geometric center defined by the loop antennas for passing a plurality of signal transmission lines. According to the multi-loop antenna system described in claim 1, the The area of the antenna substrate is less than or equal to the area of the system module. An electronic device having a multi-loop antenna system includes: a housing; an antenna module mounted in the housing, the antenna module comprising: an antenna substrate, including a first surface and a opposite a second surface of the first surface; a plurality of loop antennas disposed on the first surface or the second surface of the antenna substrate, each of the loop antennas including a first radiator capable of providing a first operating frequency band And a second radiator capable of providing a second operating frequency band, the first radiator having a feed end and a ground end at both ends thereof, and the feed end is adjacent to and spaced apart from the ground end, Forming a first loop of the first radiator, the second radiator having a first end and a second end at the two ends thereof, the first end being connected to the feed end, the second end and the ground end Connecting, the second radiator forms another loop; wherein the geometric center of each loop antenna is the same as the geometric center defined by the loop antennas, and between any two adjacent loop antennas The shortest distance is the same; and a system module is installed in the The system module includes at least one ground plane facing the second surface of the antenna substrate, and the system module is spaced apart from the second surface of the antenna substrate by a distance for reflecting the same Radiation of the loop antenna; wherein the two ends of the first radiator of each loop antenna jointly define an opening, and the geometric center of each loop antenna is connected with the opening The line, the geometric center defined by the loop antenna and the geometric center of the loop antenna are clamped at 45 degrees or 135 degrees.