Full-duplex antenna for wearable devices

Abstract

The application provides a full-duplex antenna applied to a wearable device, eight slit groups, six short stubs and a rectangular parasitic unit are formed on a radiation patch, so that the antenna is miniaturized, a first feeding point and a second feeding point are arranged at appropriate positions, polarization of +45 degrees and -45 degrees is realized in a single aperture, a cross-shaped first isolation groove is arranged to change current distribution, and unequal amplitude phase cancellation effects are generated in combination with first, second and third slits with different lengths, so that coupling between a transmitting port and a receiving port is effectively weakened, and isolation of the antenna is further improved, that is, the antenna size is significantly reduced, high isolation of more than 25dB is realized under a very small port spacing, technical problems of full-duplex antennas in the prior art when applied to wearable devices are solved, and the antenna in the application is manufactured by using a standard multilayer printed circuit board process, is easy to process, is low in cost and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a full-duplex antenna for wearable devices. Background Technology

[0002] With the widespread application of smart wearable devices in medical monitoring, body area networks, military operations, and personal entertainment, the demand for high-speed, low-latency wireless communication capabilities is increasing. In-band full-duplex technology enables simultaneous signal transmission and reception on the same frequency band and is typically used in systems achieving high spectral efficiency. However, wearable devices generally have portability and miniaturization requirements; given limited space, signal transmission and reception are best achieved on the same antenna aperture. This necessitates that the antenna transceiver of a full-duplex system possess a high degree of self-interference suppression capability between the transmit and receive signal ports. To effectively reduce self-interference, factors can be considered simultaneously in the propagation / antenna domain, radio frequency domain, and digital domain. Eliminating self-interference in the antenna domain, i.e., improving the isolation between the antenna transmit and receive ports, is the relatively low-cost and most easily implemented method.

[0003] In the prior art, various methods are usually used to improve port isolation, such as: spatial isolation method: reducing coupling by increasing the physical distance between the transmitting and receiving antennas, but it is difficult to meet the miniaturization requirements of wearable devices; decoupling structure method: such as defective ground structure, electromagnetic bandgap or loaded metallized via, although it can improve isolation, it often makes the antenna structure more complex, thereby increasing the antenna size or introducing additional losses.

[0004] To address the aforementioned issues, how to suppress self-interference between the transmitter and receiver within the limited space of wearable devices and achieve a high-isolation, in-band full-duplex antenna design with common aperture has become a problem that needs to be solved. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a full-duplex antenna for wearable devices, which solves the problem that the existing full-duplex antennas cannot simultaneously achieve both high isolation to suppress self-interference from the transmitter to the receiver and be applicable in the limited space of wearable devices.

[0006] To achieve the above and other related objectives, the present invention provides a full-duplex antenna for wearable devices, the antenna comprising a first substrate, an insulating layer, a second substrate, and a radiating patch, wherein...

[0007] The first substrate, the insulating layer, the second substrate, and the radiating patch are stacked sequentially.

[0008] The radiating patch is located at the center of the second substrate, and the shape of the radiating patch is a regular octagon. Eight slit groups are uniformly arranged on the radiating patch along the circumferential direction of the regular octagon. Six short stubs are loaded on the radiating patch, of which three of the short stubs and the other three short stubs are symmetrically distributed about the axis of symmetry of the radiating patch. Rectangular parasitic units are correspondingly arranged at the front end of the six short stubs.

[0009] The first feed point and the second feed point provided on the radiating patch are used to generate mutually orthogonal ±45° polarized waves and are configured as the transmitting port and receiving port of the antenna. The first feed point and the second feed point are connected to the microstrip line located in the second substrate through a coaxial feeding structure.

[0010] A first isolation groove is disposed between the first feed point and the second feed point to change the surface current path on the radiating patch to weaken the coupling between the ports;

[0011] The second isolation slot is located directly above the first feed point and the second feed point and at a distance of 1.362 mm from the first feed point and the second feed point. It is used to generate an unequal amplitude phase cancellation signal to eliminate the coupling signal.

[0012] Optionally, the dielectric constant of the insulating layer is 4.31, the dielectric constant of the first substrate is 4.34, and the dielectric constant of the second substrate is 4.37; the thickness of the insulating layer is 0.208 mm, the thickness of the first substrate is 0.2 mm, and the thickness of the second substrate is 0.8 mm.

[0013] Optionally, the eight slit groups are of the same size, and each slit group includes three horizontal slits and one vertical slit, wherein the vertical slit is arranged perpendicularly to the three horizontal slits and is located at the midpoint of the three horizontal slits, and one end of the vertical slit passes through one side of the radiating patch.

[0014] Optionally, the dimensions of the three transverse slits are 0.306mm × 1.73mm, and the distance between any two adjacent transverse slits is 0.408mm.

[0015] Optionally, the first isolation groove is a cross-shaped groove with a length of 3.9 mm.

[0016] Optionally, the second isolation groove includes at least a first slit, a second slit, and a third slit, wherein the widths of the first slit, the second slit, and the third slit are equal but their lengths are different, and the distance between the first slit, the second slit, and the third slit is 0.255 mm.

[0017] Optionally, the length of the first slit is 2.34 mm, the length of the second slit is 3.16 mm, the length of the third slit is 1.83 mm, and the distance between the first slit and the first feed point is the shortest.

[0018] Optionally, the distance between the first feed point and the second feed point is 1.5 mm, and the first feed point and the second feed point are symmetrically distributed about the axis of symmetry of the radiating patch.

[0019] Optionally, the distance between the rectangular parasitic unit and the stub is 0.39 mm, and the size of the rectangular parasitic unit is 0.35 mm × 1.02 mm.

[0020] Optionally, the overall dimensions of the antenna are 0.4 λ0 × 0.2 λ0 × 0.025 λ0, where λ0 is the free-space wavelength at a frequency of 5.8 GHz.

[0021] As described above, the full-duplex antenna for wearable devices of the present invention achieves miniaturization by forming eight slit groups, six stubs, and rectangular parasitic elements on the radiating patch. Furthermore, by setting appropriately positioned first and second feed points, ±45° polarization is achieved within a single aperture. A cross-shaped first isolation slot at the feed point forms a high-impedance parallel resonant path to alter the current distribution. Combined with the unequal lengths of the first, second, and third slits, an unequal amplitude phase cancellation effect is generated, effectively weakening the coupling between the transmitting and receiving ports and further improving the antenna's isolation. In other words, the present invention significantly reduces the antenna size while achieving a high isolation of better than 25dB with extremely small port spacing, solving the technical challenges faced by existing full-duplex antennas when applied to wearable devices. Moreover, the antenna of the present invention can be manufactured using standard multilayer printed circuit board processes, making it easy to process, low in cost, and suitable for mass production. Attached Figure Description

[0022] Figure 1 The image shown is a top view of the full-duplex antenna of the present invention applied to wearable devices.

[0023] Figure 2 The image shown is a top view of the radiating patch in the full-duplex antenna of the present invention, applied to a wearable device.

[0024] Figure 3 The image shown is a top view of the slit group in a full-duplex antenna for wearable devices according to the present invention.

[0025] Figure 4 The diagram shown is a cross-sectional view of the full-duplex antenna of the present invention applied to wearable devices.

[0026] Figure 5 The impedance bandwidth and port isolation of the full-duplex antenna of the present invention, applied to wearable devices, are shown.

[0027] Figure 6 The diagram shows the gain of the full-duplex antenna of the present invention applied to wearable devices.

[0028] Figure 7 The diagram shows the antenna pattern of the full-duplex antenna of the present invention applied to a wearable device, wherein (a) represents the excitation of the transmit port; and (b) represents the excitation of the receive port.

[0029] Component designation explanation

[0030] 10. First substrate; 11. Insulating layer; 12. Second substrate; 13. Radiation patch; 131. First slit group; 132. Second slit group; 133. Third slit group; 134. Fourth slit group; 135. Fifth slit group; 136. Sixth slit group; 137. Seventh slit group; 138. Eighth slit group; 1311. First horizontal slit; 1312. Second horizontal slit; 1313. Third horizontal slit; 1314. First vertical slit; 14. Short stub; 15. Rectangular parasitic unit; 16. Second isolation groove; 17. First isolation groove; 181. First feed point; 182. Second feed point. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] Please see Figures 1 to 7 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0033] like Figures 1 to 4 As shown, this embodiment discloses a full-duplex antenna for wearable devices. The full-duplex antenna can be applied to a human body local area network communication system. The antenna includes, from bottom to top, a first substrate 10, an insulating layer 11, a second substrate 12, and a radiating patch 13 stacked sequentially.

[0034] In embodiments of the present invention, such as Figure 4As shown, the first substrate 10 and the second substrate 12 are two substrates with different dielectric constants. The material of the first substrate 10 includes, but is not limited to, FR-4, ceramic, or metal, where the metal includes, but is not limited to, copper or aluminum. The insulating layer 11 is a prepreg, which can serve as an adhesive layer between the first substrate 10 and the second substrate 12. The prepreg can be made of epoxy resin impregnated glass fiber. The prepreg, in a semi-cured state, fills the surface gaps between the first substrate 10 and the second substrate 12, ensuring the flatness and mechanical strength of the printed circuit board. The second substrate 12 can be made of the same or different material as the first substrate 10. Radial patches 13 are provided on the second substrate 12, which can also be used to expand the circuit layout space.

[0035] Specifically, the dimensions of each component forming the antenna must be as small as possible while ensuring antenna performance in order to meet the miniaturization requirements of wearable devices within limited space. In this embodiment, the first substrate 10 and the second substrate 12 both adopt the S1141 type substrate from SYTECH. The dielectric constant of the first substrate 10 is 4.34 and the thickness of the first substrate 10 is 0.2 mm. The dielectric constant of the second substrate 12 is 4.37 and the thickness of the second substrate 12 is 0.8 mm. A prepreg is also provided between the first substrate 10 and the second substrate 12 as an insulating layer 11. The relative dielectric constant of the insulating layer 11 is 4.31 and the thickness of the insulating layer 11 is 0.208 mm.

[0036] In this embodiment, as Figure 1 As shown, the radiating patch 13 is located at the center of the second substrate 12, and the shape of the radiating patch 13 is a regular octagon. Eight slit groups are uniformly arranged on the radiating patch 13 along the circumferential direction of the regular octagon. Six short stubs 14 are loaded on the radiating patch 13, of which three of the short stubs 14 and the other three short stubs 14 are symmetrically distributed about the axis of symmetry of the radiating patch 13, and rectangular parasitic units 15 are correspondingly arranged at the front ends of the six short stubs 14.

[0037] like Figure 1 and Figure 2 As shown, eight slit groups are evenly arranged along the circumference of the regular octagon on the radiation patch 13 (namely, slit group 131, slit group 132, slit group 133, slit group 134, slit group 135, slit group 136, slit group 137, and slit group 138, respectively). These eight slit groups are located along the eight sides of the regular octagon and extend from the edges towards the center. The eight slit groups must be evenly placed, meaning that the included angle between any two adjacent groups is the same; otherwise, the radiation pattern will be affected. Specifically, as shown... Figure 2As shown, the eight slit groups are all the same size, and each slit group includes three horizontal slits and one vertical slit. The first slit group 131 is used as an example for illustration: Figure 3 As shown, the first slit group 131 includes a first horizontal slit 1311, a second horizontal slit 1312, a third horizontal slit 1313, and a first vertical slit 1314. The first horizontal slit 1311, the second horizontal slit 1312, and the third horizontal slit 1313 are arranged parallel to each other, and the distance between the first horizontal slit 1311, the second horizontal slit 1312, and the third horizontal slit 1313 is 0.408 mm. The length and width of the first horizontal slit 1311, the second horizontal slit 1312, and the third horizontal slit 1313 are all the same, and the dimensions are all 0.306 mm × 1.73 mm. In addition, the first vertical slit 1314 is perpendicular to the first horizontal slit 1311, the second horizontal slit 1312, and the third horizontal slit 1313, and the first vertical slit 1314 is located at the midpoint of the first horizontal slit 1311, the second horizontal slit 1312, and the third horizontal slit 1313.

[0038] Furthermore, the shapes and sizes of the second slit group 132, the third slit group 133, the fourth slit group 134, the fifth slit group 135, the sixth slit group 136, the seventh slit group 137, and the eighth slit group 138 are the same as those of the first slit group 101. The only difference is that the orientation of the vertical slits 1314 in each slit group is different, which will not be described in detail here.

[0039] In this embodiment, as Figure 1As shown, the radiating patch 13 has a first feed point 181 and a second feed point 182 symmetrically distributed about the axis of symmetry of the radiating patch 13. The first feed point 181 and the second feed point 182 are distributed in a ±45° direction to excite a ±45° polarization field mode. The first feed point 181 and the second feed point 182 are configured as the transmitting port and the receiving port of the antenna. For example, the first feed point 181 serves as the receiving port of the antenna, and the second feed point 182 serves as the transmitting port of the antenna. The distance between the first feed point 181 and the second feed point 182 is 1.5 mm. A microstrip line is formed at the bottom of the first substrate 10. One end of the microstrip line is electrically connected to the first feed point 181 and the second feed point 182 in the radiating patch 13 through a coaxial structure that passes through the first substrate 10, the insulating layer 11, and the second substrate 12. The other end can be interconnected with the test cable to power the antenna's transmitting and receiving ports, causing the first feed point 181 and the second feed point 182 to generate mutually orthogonal ±45° polarized waves. When the antenna is powered, the surface current flows around the eight slit groups as it flows toward the edge of the radiating patch 13. When the first feed point 181 and the second feed point 182 are formed only on the radiating patch 13, the initial resonant frequency of the antenna's transmitting and receiving ports is 8.23 ​​GHz. The function of the eight slit groups is to adjust the impedance matching and adjust the resonant point. That is, the eight slit groups can increase the additional capacitance, causing the antenna's resonant frequency to drop from 8.23 ​​GHz to 6.37 GHz. However, the isolation between the antenna's transmitting and receiving ports is only 6.9 dB. That is, the resonant frequency and isolation at this time cannot meet the reliable communication requirements of the full-duplex system of the human body local area network.

[0040] Furthermore, such as Figure 1 As shown, six stubs 14 are loaded on the radiating patch 13, and rectangular parasitic units 15 are correspondingly arranged at the front ends of the six stubs 14. The rectangular parasitic units 15 are connected to the vertical slits 1314 in each slit group. Three of the stubs 14 and the other three stubs 14 are symmetrically distributed about the axis of symmetry of the radiating patch 13. For example, the three stubs 14 are located directly in front of the second slit group 132, the third slit group 133 and the fourth slit group 134, respectively, and the other three stubs 14 are located directly in front of the sixth slit group 136, the seventh slit group 137 and the eighth slit group 138, thereby further reducing the resonant frequency of the antenna.

[0041] Specifically, in this embodiment, the distance between the rectangular parasitic element 15 and the stub 14 is 0.39 mm, and the size of the rectangular parasitic element 15 is 0.35 mm × 1.02 mm. Through capacitive coupling between each set of stubs 14 and the rectangular parasitic element 15, the equivalent electrical length of the antenna is increased, thereby reducing the resonant frequency. At this time, the resonant frequency of the antenna is further reduced from 6.37 GHz to 6.05 GHz, but it still does not reach the desired ideal frequency, and the isolation between the antenna's transmitting port and receiving port is still low.

[0042] Furthermore, such as Figure 1 As shown, a first isolation slot 17 is provided between the first feed point 181 and the second feed point 182. The first isolation slot 17 can change the current path between the antenna transmitting port and the receiving port, thereby weakening the energy of current coupling through the surface of the radiating patch 13. Preferably, the first isolation slot 17 is a cross-shaped slot, and the length of the two gaps forming the cross-shaped slot is 3.9 mm. A parallel resonant path with high impedance is formed between the antenna transmitting port and the receiving port. The parallel resonant path changes the current path between the antenna transmitting port and the receiving port, weakening the coupling between the antenna transmitting port and the receiving port. In addition, the parallel resonant path can also increase the length of the current path, thereby causing the resonant frequency to be further reduced.

[0043] Specifically, by setting a cross-shaped first isolation slot 17 between the first feed point 181 and the second feed point 182, the resonant frequency of the antenna is reduced from 6.05 GHz to 5.925 GHz, and the isolation between the antenna transmit port and the receive port is increased to 23.2 dB.

[0044] However, the isolation between the antenna transmit port and the receive port is not flat within the frequency bandwidth of 5.75~5.85GHz, with a minimum of only 18dB. Therefore, in order to further enhance the isolation between the antenna transmit port and the receive port and to achieve the desired resonant frequency of the antenna, in this embodiment, a second isolation groove 16 is provided directly above the first feed point 181 and the second feed point 182, at a distance of 1.362mm from the center line connecting the first feed point 181 and the second feed point 182. The second isolation groove 16 includes a first slit, a second slit, and a third slit that are parallel to each other. The widths of the first slit, the second slit, and the third slit are all equal and 0.204mm, but their lengths are different. The distance between the first slit, the second slit, and the third slit is 0.255mm. The first slit, the second slit, and the third slit are mainly used to generate unequal amplitude phase cancellation signals to eliminate coupling signals.

[0045] Specifically, in this embodiment, the length of the first slit is 2.34 mm, the length of the second slit is 3.16 mm, and the length of the third slit is 1.83 mm. The distance between the first slit and the center line connecting the first feed point 181 and the second feed point 182 is the shortest. Compared with the traditional setting of a single large slit, in this embodiment, by setting the first slit, the second slit, and the third slit with unequal lengths, it is easier to control the amplitude and phase characteristics of the desired signal, thereby achieving better isolation.

[0046] Specifically, such as Figure 5 As shown, by setting the second isolation slot 16, the resonant frequency of the antenna is reduced from 5.925 GHz to 5.8 GHz, and the isolation between the antenna transmitting port and the receiving port is higher than 25 dB. That is, the resonant frequency and isolation at this time can meet the reliable communication requirements of the full-duplex system of the human body local area network.

[0047] like Figure 6 As shown, the gain diagram of the full-duplex antenna applied to wearable devices in this embodiment is displayed. In the frequency range of 5.75~5.85GHz, the measured gain is 0.34dBi to 0.58dBi for +45° polarization and 0.52dBi to 0.63dBi for -45° polarization, further proving that the full-duplex antenna in this embodiment can meet the reliable communication needs of the full-duplex system of the human body local area network.

[0048] like Figure 7 As shown, the antenna pattern of the full-duplex antenna of the present invention applied to a wearable device is displayed, wherein (a) the figure shows the excitation of the transmit port, and when the transmit port of the antenna is excited, the beamwidths of the E-plane and the H-plane are 103° and 112°, respectively; (b) the figure shows the excitation of the receive port, and when the receive port of the antenna is excited, the beamwidths of the E-plane and the H-plane are 102° and 111°, respectively.

[0049] In summary, this invention provides a common-aperture in-band full-duplex antenna for wearable devices. By forming eight slit groups, six stubs, and a rectangular parasitic element on a radiating patch, the antenna achieves miniaturization. Furthermore, by strategically placing a first and second feed point, ±45° polarization is achieved within a single aperture. A cross-shaped first isolation slot at the feed point forms a high-impedance parallel resonant path, altering the current distribution. Combined with unequal-length first, second, and third slits, unequal-amplitude phase cancellation effects are generated, effectively weakening the coupling between the transmit and receive ports and further improving the antenna's isolation. In other words, this invention significantly reduces the antenna size while achieving a high isolation of better than 25dB with extremely small port spacing, solving the technical challenges faced by existing full-duplex antennas in wearable devices. Moreover, the antenna of this invention can be manufactured using standard multilayer printed circuit board processes, making it easy to process, low-cost, and suitable for mass production. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0050] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A full-duplex antenna for wearable devices, characterized in that, The antenna includes a first substrate, an insulating layer, a second substrate, and a radiating patch, wherein, The first substrate, the insulating layer, the second substrate, and the radiating patch are stacked sequentially. The radiating patch is located at the center of the second substrate, and the shape of the radiating patch is a regular octagon. Eight slit groups are uniformly arranged on the radiating patch along the circumferential direction of the regular octagon. Six short stubs are loaded on the radiating patch, of which three of the short stubs and the other three short stubs are symmetrically distributed about the axis of symmetry of the radiating patch. Rectangular parasitic units are correspondingly arranged at the front end of the six short stubs. The radiating patch has a first feed point and a second feed point for generating mutually orthogonal ±45° polarized waves. The first feed point is configured as the transmitting port of the antenna, and the second feed point is configured as the receiving port of the antenna, or the first feed point is configured as the receiving port of the antenna, and the second feed point is configured as the transmitting port of the antenna. The first feed point and the second feed point are connected to a microstrip line located at the bottom of the first substrate through a coaxial feeding structure. A first isolation groove is disposed between the first feed point and the second feed point to change the surface current path on the radiating patch to weaken the coupling between the ports; The second isolation slot is located directly above the first feed point and the second feed point and at a distance of 1.362 mm from the first feed point and the second feed point. It is used to generate an unequal amplitude phase cancellation signal to eliminate the coupling signal.

2. The full-duplex antenna for wearable devices according to claim 1, characterized in that: The dielectric constant of the insulating layer is 4.31, the dielectric constant of the first substrate is 4.34, and the dielectric constant of the second substrate is 4.37; the thickness of the insulating layer is 0.208 mm, the thickness of the first substrate is 0.2 mm, and the thickness of the second substrate is 0.8 mm.

3. The full-duplex antenna for wearable devices according to claim 1, characterized in that: The eight slit groups are of the same size, and each slit group includes three horizontal slits and one vertical slit. The vertical slit is arranged perpendicularly to the three horizontal slits and is located at the midpoint of the three horizontal slits. The vertical slit in the slit group with the short slit line passes through the radial patch and extends into the short slit line.

4. The full-duplex antenna for wearable devices according to claim 3, characterized in that: The dimensions of the three transverse slits are 0.306mm × 1.73mm, and the distance between any two adjacent transverse slits is 0.408mm.

5. The full-duplex antenna for wearable devices according to claim 1, characterized in that: The first isolation groove is a cross-shaped groove with a length of 3.9 mm.

6. The full-duplex antenna for wearable devices according to claim 1, characterized in that: The second isolation groove includes at least a first slit, a second slit, and a third slit, wherein the widths of the first slit, the second slit, and the third slit are equal but their lengths are different, and the distance between the first slit, the second slit, and the third slit is 0.255 mm.

7. The full-duplex antenna for wearable devices according to claim 6, characterized in that: The length of the first slit is 2.34 mm, the length of the second slit is 3.16 mm, the length of the third slit is 1.83 mm, and the distance between the first slit and the first feed point is the shortest.

8. The full-duplex antenna for wearable devices according to claim 1, characterized in that: The distance between the first feed point and the second feed point is 1.5 mm, and the first feed point and the second feed point are symmetrically distributed about the axis of symmetry of the radiation patch.

9. The full-duplex antenna for wearable devices according to claim 1, characterized in that: The distance between the rectangular parasitic unit and the stub is 0.39 mm, and the size of the rectangular parasitic unit is 0.35 mm × 1.02 mm.

10. The full-duplex antenna for wearable devices according to claim 1, characterized in that: The overall dimensions of the antenna are 0.4 λ0 × 0.2 λ0 × 0.025 λ0, where λ0 is the free space wavelength at a frequency of 5.8 GHz.

Images