CN104681988A - Near field communication antenna - Google Patents

Abstract

A near field communication antenna. The near field communication antenna comprises: a dielectric substrate, a coil and a coupling structure; the coil is arranged on the dielectric substrate; the coupling structure comprises at least one coupling branch, wherein two ends of the coupling branch are respectively connected to two different connection points on the coil. The coupling structure of the present invention can average the coupling current of the near field communication antenna, thereby improving the omnidirectionality of the near field communication antenna.

Description

near field communication antenna

technical field

The invention relates to a near field communication (Near Field Communication, NFC) antenna, in particular to an isotropic and high-efficiency near field communication antenna.

Background technique

With the development of mobile communication technology, mobile devices have become more and more common in recent years, such as portable computers, mobile phones, multimedia players and other portable electronic devices with mixed functions. In order to meet people's needs, mobile devices generally have a wireless communication function. Some cover long-distance wireless communication ranges, for example: mobile phones use 2G, 3G, LTE (Long Term Evolution, Long Term Evolution) systems and use 700MHz, 850MHz, 900MHz, 1800MHz, 1900MHz, 2100MHz, 2300MHz and 2500MHz for communication , while some cover short-range wireless communication ranges, such as: Wi-Fi, Bluetooth (Bluetooth) and WiMAX (Worldwide Interoperability for Microwave Access, Microwave Access Global Interoperability) systems use 2.4GHz, 3.5GHz, 5.2GHz and 5.8GHz frequency band for communication.

Taking a mobile device with near-field communication function as an example, since its near-field communication antenna usually has to be set in a rectangular card and conforms to its shape, this design method will cause the related reader to be unable to read at various angles. Get good reception. For example, when the angle between the reader and the long side of the NFC antenna is 90 degrees or 270 degrees, the electric field strength received by the reader will be relatively weak, thus reducing the near field The communication quality of the communication antenna.

Therefore, it is necessary to provide a near field communication antenna to solve the above problems.

Contents of the invention

In order to solve the problems of the prior art, the present invention provides a near field communication antenna, the near field communication antenna includes: a dielectric substrate; a coil, the coil is arranged on the dielectric substrate; and a coupling structure, the coupling structure includes at least A coupling branch, wherein the two ends of the coupling branch are respectively connected to two different connection points on the coil. The coupling structure is used to improve the omnidirectionality of the near field communication antenna.

The coupling structure of the present invention can average the coupling current of the near-field communication antenna, thereby effectively improving the overall omnidirectionality of the near-field communication antenna.

Description of drawings

FIG. 1 is a top view showing a near field communication antenna according to an embodiment of the present invention;

2A is a perspective view showing a near field communication antenna according to another embodiment of the present invention;

2B is a perspective view showing a near field communication antenna according to yet another embodiment of the present invention;

3 is a perspective view showing a near field communication antenna according to a preferred embodiment of the present invention;

FIG. 4A is a perspective view showing a coupling structure according to an embodiment of the present invention;

4B is a perspective view showing a coupling structure according to an embodiment of the present invention;

FIG. 4C is a perspective view showing a coupling structure according to an embodiment of the present invention;

FIG. 5A is a perspective view showing a coupling structure according to an embodiment of the present invention;

5B is a perspective view showing a coupling structure according to an embodiment of the present invention;

FIG. 5C is a perspective view showing a coupling structure according to an embodiment of the present invention;

5D is a perspective view showing a coupling structure according to an embodiment of the present invention;

FIG. 6A is a diagram showing the relative orientation of the near field communication antenna and the measuring device according to an embodiment of the present invention;

6B is a diagram showing the relative orientation of the NFC antenna and the measurement device according to another embodiment of the present invention; and

FIG. 7 is a graph showing the relationship between the electric field strength and the test angle of the near field communication antenna according to an embodiment of the present invention.

Description of main component symbols:

100, 200, 250, 300 Near Field Communication Antenna

110 Dielectric Substrate

111 Left Area

112 Central Area

113 Right Area

120, 320 Coil

121, 122, 321, 322 End of Coil

130, 230, 235, 330, 410, 420, 430, 510, coupling structure

520, 530, 540

131, 231, 232, 331, 531, 532, 533, 534 Coupling branches

241, 242, 243, 244, 340 Conductive vias

325 Center Clearance Area of Coil

610 Measuring device

CC0, CC1, CC2, CC3, CC4 Curves

D1 Distance between two adjacent coupling branches

E1, E2 The surface of the dielectric substrate

H1 Thickness of dielectric substrate

L1, L2 Length

P1, P2, P3, P4 Connection point

Detailed ways

In order to make the purpose, features and advantages of the present invention more comprehensible, specific embodiments of the present invention are listed below, together with the accompanying drawings, for detailed description as follows.

FIG. 1 is a top view showing a near field communication antenna 100 according to an embodiment of the present invention. The NFC antenna 100 can be installed in a mobile device, such as a smart phone (Smart Phone), a tablet computer (Tablet Computer), or a notebook computer (Notebook Computer). As shown in FIG. 1 , the NFC antenna 100 includes: a dielectric substrate 110 , a coil 120 and a coupling structure 130 . The dielectric substrate 110 may be an FR4 (Flame Retard4) substrate. The coil 120 and the coupling structure 130 can be made of conductors, such as copper, silver, aluminum, iron or alloys thereof. The coil 120 is disposed on the dielectric substrate 110 . In some embodiments, the coil 120 serves as a main radiation portion of the NFC antenna 100 , and the two ends 121 , 122 of the coil 120 are respectively connected to a positive pole and a negative pole of a signal source (not shown). The signal source may be a radio frequency (Radio Frequency, RF) module, and is used to excite the near field communication antenna 100 . The total number of turns of the coil 120 can be 1, 2, 3, 4 or more. In some embodiments, either end of the coil 120 can also be connected to a matching circuit (not shown) to adjust its resonance length. Under this design, the coil 120 can work at the near field communication frequency of 13.56MHz. The coupling structure 130 includes at least one coupling branch 131 , wherein two ends of the coupling branch 131 are respectively connected to two different connection points P1 and P2 on the coil 120 . In some embodiments, the coil 120 is approximately a rectangle with two long sides and two short sides, and the connection points P1 and P2 are respectively located approximately on the long sides of the rectangle. In some other embodiments, the connection points P1 and P2 may also be located roughly on a long side and a short side of the rectangle, respectively. The coupling branch 131 of the coupling structure 130 can be regarded as a resistor and a capacitor connected in series. When the coupling branch 131 is connected to the coil 120 , its impedance characteristic can enhance the coupling energy of the NFC antenna 100 , thereby improving the omnidirectionality of the NFC antenna 100 .

In the embodiment of FIG. 1 , the coil 120 and the coupling structure 130 may both be disposed on the same surface E1 of the dielectric substrate 110 . However, the present invention is not limited thereto. FIG. 2A is a perspective view showing a near field communication antenna 200 according to another embodiment of the present invention. In the embodiment shown in FIG. 2A , the coil 120 and a coupling structure 230 of the NFC antenna 200 are respectively disposed on two opposite surfaces E1 and E2 of the dielectric substrate 110 . The NFC antenna 200 further includes two conductive through holes 241, 242 formed in the dielectric substrate 110, wherein the two ends of at least one coupling branch 231 of the coupling structure 230 are respectively connected to the coil 120 through the conductive through holes 241, 242. The two connection points P1 and P2 on .

FIG. 2B is a perspective view showing a near field communication antenna 250 according to yet another embodiment of the present invention. Figure 2B is similar to Figure 2A. In the embodiment shown in FIG. 2B , the coil 120 and a coupling structure 235 of the NFC antenna 250 are also disposed on two opposite surfaces E1 , E2 of the dielectric substrate 110 . The NFC antenna 250 further includes four conductive vias 241 , 242 , 243 , 244 formed in the dielectric substrate 110 . The two ends of a coupling branch 231 of the coupling structure 235 are respectively connected to the two connection points P1 and P2 on the coil 120 through the conductive through holes 241 and 242, and the two ends of the other coupling branch 232 of the coupling structure 235 are respectively It is connected to the other two connection points P3 and P4 on the coil 120 through the conductive through holes 243 and 244 . Compared with FIG. 2A , the NFC antenna 250 shown in FIG. 2B exhibits better symmetry, so it can provide higher omnidirectionality. It must be noted that the shape of the aforementioned coupling branch is not particularly limited in the present invention. For example, each of the aforementioned coupling branches may be approximately straight, a square bracket, a zigzag, a semicircle or a smooth curve.

FIG. 3 is a perspective view showing a near field communication antenna 300 according to a preferred embodiment of the present invention. As shown in FIG. 3 , the NFC antenna 300 includes: a dielectric substrate 110 , a coil 320 and a coupling structure 330 . The coil 320 and the coupling structure 330 are respectively disposed on two opposite surfaces E1 and E2 of the dielectric substrate 110 . Compared with the foregoing embodiments, the coupling structure 330 of the NFC antenna 300 includes more coupling branches 331 , and the total number of turns of the coil 320 of the NFC antenna 300 is also larger. In some embodiments, the total number of the coupling branches 331 may be exactly twice the total number of turns of the coil 320 to facilitate their symmetrical connection with each other. For example, the total number of the coupling branches 331 can be 8, and the total number of turns of the coil 320 can be 4, but not limited thereto. The near field communication antenna 300 may further include a plurality of conductive through holes 340 (for example: sixteen conductive through holes 340 separated from each other) formed in the dielectric substrate 110, wherein the two ends of each coupling branch 331 can be respectively connected via their respective The two conductive vias 340 are connected to the respective two connection points on the coil 320 . In more detail, the coil 320 can include multiple loops of different sizes, and the coupling structure 330 can include multiple coupling branches 331 of different lengths, wherein longer coupling branches 331 are connected to larger loops, and shorter coupling branches 331 are connected to larger loops. The coupling branch 331 of is connected to a smaller loop, and so on. Under this design, each loop of the coil 320 can just be connected to two respective coupling branches 331 of equal length.

The surface E2 of the dielectric substrate 110 can be further divided into a left area 111 , a central area 112 and a right area 113 , wherein the central area 112 can completely separate the left area 111 from the right area 113 . In some embodiments, the coupling branches 331 of the coupling structure 330 are symmetrically disposed in the left area 111 and the right area 113 . For example, if there are four coupling branches 331 disposed in the left region 111 , there will be another four coupling branches 331 mirrored in the right region 113 . The coil 320 may have a central clearance area 325 . In some embodiments, the vertical projections of the coupling branches 331 on the coil 320 can be roughly located in the central clearance area 325 , but the vertical projections cannot overlap with the central point of the coil 320 . In some embodiments, the coupling branches 331 are arranged substantially parallel to each other. For example, the coil 320 can be roughly a rectangle with two long sides and two short sides, and the coupling branches 331 can be arranged roughly parallel to the short sides of the rectangle. In order to increase the coupling energy, the total length L2 of the coupling structure 330 is usually smaller than the length L1 of the long side of the rectangular coil 320 . For example, the total length L2 of the coupling structure 330 may be approximately 50% to 80% of the length L1 of the long side of the rectangular coil 320 .

In the embodiment of FIG. 3 , the total number of the coupling branches 331 of the coupling structure 330 is 8, and each coupling branch 331 is roughly in the shape of a square bracket. However, the present invention is not limited thereto. In other embodiments, the coupling structure 330 may include more or less coupling branches 331 , and each coupling branch 331 may also have a different shape. In other embodiments, the coupling branches 331 may also be asymmetrically disposed on the surface E2 of the dielectric substrate 110 . For example, one coupling branch 331 may be disposed in the left region 111 of the dielectric substrate 110 , but three coupling branches 331 may be disposed in the right region 113 of the dielectric substrate 110 . Some variable configurations of the NFC antenna of the present invention can be described in the following embodiments.

FIG. 4A is a perspective view showing a coupling structure 410 according to an embodiment of the present invention. In the embodiment of FIG. 4A , the coupling structure 410 includes two coupling branches 331 symmetrically disposed on the surface E2 of the dielectric substrate 110 . FIG. 4B is a perspective view showing a coupling structure 420 according to an embodiment of the present invention. In the embodiment of FIG. 4B , the coupling structure 420 includes four coupling branches 331 symmetrically disposed on the surface E2 of the dielectric substrate 110 . FIG. 4C is a perspective view showing a coupling structure 430 according to an embodiment of the invention. In the embodiment of FIG. 4C , the coupling structure 430 includes six coupling branches 331 symmetrically disposed on the surface E2 of the dielectric substrate 110 . It should be understood that, the two ends of each of the above-mentioned coupling branches can be respectively connected to a respective primary loop of a coil. For example, longer coupling branches connect to larger loops, while shorter coupling branches connect to smaller loops, and so on. The coupling structures 410 , 420 , and 430 shown in FIGS. 4A , 4B, and 4C can all be used to replace the coupling structure 330 in FIG. 3 .

FIG. 5A is a perspective view showing a coupling structure 510 according to an embodiment of the present invention. In the embodiment of FIG. 5A , the coupling structure 510 includes two coupling branches 531 , and each coupling branch 531 is substantially straight. FIG. 5B is a perspective view showing a coupling structure 520 according to an embodiment of the present invention. In the embodiment of FIG. 5B , the coupling structure 520 includes two coupling branches 532 , and each coupling branch 532 is roughly in the shape of a zigzag line. FIG. 5C is a perspective view showing a coupling structure 530 according to an embodiment of the invention. In the embodiment of FIG. 5C , the coupling structure 530 includes two coupling branches 533 , and each coupling branch 533 is approximately semicircular. FIG. 5D is a perspective view showing a coupling structure 540 according to an embodiment of the present invention. In the embodiment of FIG. 5D , the coupling structure 540 includes two coupling branches 534 , and each coupling branch 534 is approximately a smooth curve. It must be understood that each of the aforementioned coupling structures may include more coupling branches, and the two ends of each coupling branch may be respectively connected to a respective primary loop of a coil. For example, longer coupling branches connect to larger loops, while shorter coupling branches connect to smaller loops, and so on. The coupling structures 510 , 520 , 530 , and 540 shown in FIGS. 5A , 5B, 5C, and 5D can all be used to replace the coupling structure 330 in FIG. 3 .

FIG. 6A is a diagram showing the relative orientation of the NFC antenna 300 and the measuring device 610 according to an embodiment of the present invention. FIG. 6B is a diagram showing the relative orientation of the NFC antenna 300 and the measuring device 610 according to another embodiment of the present invention. The measuring device 610 can be used to detect the electromagnetic wave transmitted by the NFC antenna 300 and analyze the electric field intensity of the electromagnetic wave. The measuring device 610 may be roughly a rectangle. When the long side of the measuring device 610 is parallel to the long side of the near-field communication antenna 300, it can be considered that the test angle between the measuring device 610 and the near-field communication antenna 300 is 0 degrees or 180 degrees (as shown in FIG. 6A ); and when the long side of the measuring device 610 is perpendicular to the long side of the near-field communication antenna 300, it can be considered that the test angle between the measuring device 610 and the near-field communication antenna 300 is 90 degrees or 270 degrees (as shown in 6B).

FIG. 7 is a graph showing the relationship between the electric field intensity and the test angle of the near field communication antenna 300 according to an embodiment of the present invention. As mentioned above, the measurement device 610 can detect the electric field strength of the NFC antenna 300 at different test angles, and the measurement results are shown in FIG. 7 . Curve CC0 represents the electric field strength detected when the coupling structure 330 is removed; curve CC1 represents the electric field strength detected when the coupling structure 330 includes two coupling branches 331 (as shown in FIG. 4A ); curve CC2 represents When the coupling structure 330 includes four coupling branches 331 (as shown in Figure 4B) the detected electric field strength; Curve CC3 represents when the coupling structure 330 includes six coupling branches 331 (as shown in Figure 4C) detected and the curve CC4 represents the detected electric field intensity when the coupling structure 330 includes eight coupling branches 331 (as shown in FIG. 3 ). According to the measurement results in FIG. 7 , if the coupling structure 330 includes more coupling branches 331 connected to the coil 320 , the NFC antenna 300 can provide an electric field with a more uniform intensity at each test angle. The coupling structure of the present invention can more evenly couple the coupling current of the near-field communication antenna, thereby effectively improving the overall omnidirectionality of the near-field communication antenna.

Please refer to Figure 3 again. In some embodiments, the component dimensions and component parameters of the present invention may be as follows. The thickness H1 of the dielectric substrate 110 is less than 2mm. The coil 320 works at a frequency of 13.56MHz. The total area of the coil 320 is about 60x40mm ² . The distance D1 between two adjacent coupling branches 331 is less than 1 mm. The vertical projections of the coupling branches 331 on the coil 320 are approximately located in the central clear area 325 , and the central area of the central clear area 325 that does not overlap with the vertical projections has an area of about 20×20 mm ² .

It should be noted that the above component parameters, component shapes and frequency ranges are not limitations of the present invention. Antenna designers can adjust these settings according to different needs. The near field communication antenna of the present invention is not limited to the states shown in FIGS. 1-7 . The present invention may only include any one or more features of any one or more of the embodiments of FIGS. 1-7 . In other words, not all the features shown in the figures must be implemented in the NFC antenna of the present invention at the same time.

Ordinal numbers within the scope of this specification and claims, such as "first", "second", "third", etc., have no sequential relationship with each other, and are only used to mark and distinguish between two Different components with the same name.

Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the scope of the present invention. Any person skilled in the art should be able to make some changes and modifications without departing from the spirit and scope of the present invention. Modification, therefore, the scope of protection of the present invention should be defined by the scope of the appended claims.

Claims (17)

1. A near-field communication antenna, the near-field communication antenna comprising: a dielectric substrate; a coil disposed on the dielectric substrate; and A coupling structure, the coupling structure includes at least one coupling branch, wherein the two ends of the coupling branch are respectively connected to two different connection points on the coil. 2. The near field communication antenna as claimed in claim 1, wherein the coil serves as a main radiation portion of the near field communication antenna, and two ends of the coil are respectively connected to a positive pole and a negative pole of a signal source. 3 . The near field communication antenna as claimed in claim 1 , wherein the coil is substantially a rectangle, the rectangle has two long sides and two short sides, and the connection points are approximately located on the long sides. 4 . 4. The near field communication antenna as claimed in claim 1, wherein the coil and the coupling structure are both disposed on the same surface of the dielectric substrate. 5. The near field communication antenna as claimed in claim 1, wherein the coil and the coupling structure are respectively disposed on two opposite surfaces of the dielectric substrate. 6. The near field communication antenna as claimed in claim 5, wherein at least two conductive vias are formed in the dielectric substrate, and the ends of the coupling branch are respectively connected to the coils on the coil through the conductive vias. Wait for connection points. 7. The near field communication antenna as claimed in claim 5, wherein the coupling structure comprises a plurality of coupling branches, the dielectric substrate comprises a left region, a central region and a right region, and the coupling branches are symmetrical It is disposed in the left area and the right area, and the central area completely separates the left area from the right area. 8 . The near field communication antenna as claimed in claim 7 , wherein the coil has a central clearance area, and the vertical projections of the coupling branches on the coil are substantially located within the central clearance area. 9. The near field communication antenna as claimed in claim 7, wherein the total number of the coupling branches is twice the total number of turns of the coil. 10. The near field communication antenna as claimed in claim 7, wherein the total number of the coupling branches is 2, 4, 6 or 8. 11. The near field communication antenna as claimed in claim 7, wherein each of the coupling branches is approximately straight, a square bracket, a zigzag, a semicircle or a smooth curve. 12. The near field communication antenna as claimed in claim 7, wherein the coupling branches are arranged substantially parallel to each other. 13. The near field communication antenna as claimed in claim 12, wherein the coil is substantially a rectangle, the rectangle has two long sides and two short sides, and the coupling branches are substantially parallel to the short sides. 14. The near field communication antenna as claimed in claim 7, wherein the distance between adjacent two of the coupling branches is less than 1mm. 15. The near field communication antenna as claimed in claim 1, wherein the dielectric substrate is an FR4 substrate. 16. The near field communication antenna as claimed in claim 1, wherein the thickness of the dielectric substrate is less than 2mm. 17. The near field communication antenna as claimed in claim 1, wherein the coil operates at a frequency of 13.56MHz.