Dual-frequency tunable smart wearable device

Abstract

The invention discloses a dual-frequency tunable smart wearable device, which is a wristband microstrip patch printed dipole antenna and comprises an antenna radiator and a hollow ring cylinder dielectric substrate arranged in the antenna radiator. A radiator of the antenna is composed of two rectangular metal copper patches, the two rectangular metal copper patches are symmetrically distributed on the outer surface of an annular cylinder dielectric substrate, and rectangular groove arrays are symmetrically etched on the two patches to achieve dual-band communication. The wrist strap support with the dielectric substrate serving as the wearable device is composed of a hollow annular cylinder container and a liquid medium contained in the container, the container is made of transparent ABS plastic, and the liquid medium is insulating oil. According to the wearable device, the reconfigurable characteristic of the resonant frequency of the wearable antenna is achieved by flexibly changing the geometrical shape and the physical size of the liquid medium, and instability caused by the fluidity of the fluid antenna in the wearing process of the wearable device is overcome through container layering treatment.

Description

Technical Field

[0001] The present invention belongs to the field of smart wearable devices, and in particular relates to a dual-frequency tunable smart wearable device. Background Art

[0002] With the continuous development of wireless communication technology, the human body-centered wireless body area network, which is constructed by sensors and portable devices implanted in the human body or worn on the human body, has become one of the research focuses of scholars. As an important component of wireless body area network to achieve communication, wearable devices including smart bracelets, smart watches, VR glasses, Google glasses, Bluetooth headsets, etc. have gradually become popular and have been widely used in medical, military, daily life and other fields.

[0003] Due to the special application scenarios of wireless body area networks, wearable devices not only need to be comfortable and concealed, but also have good frequency reconfiguration capabilities. On the one hand, wireless body area networks can be divided into three modes: external communication, surface communication, and internal communication. Considering that low-frequency electromagnetic waves have strong diffraction ability, strong penetration ability, and good omnidirectionality, high-frequency electromagnetic waves have weak diffraction ability, weak penetration, and good directivity, usually internal communication is a low frequency band, surface communication is a medium frequency band, and external communication is a high frequency band. Different communication modes have different frequency bands. Wearable device frequency reconfiguration can switch between multiple frequency bands to meet the needs of users for different communication modes. Supporting multi-band communication improves the versatility and adaptability of the device. On the other hand, electromagnetic interference is a common problem. Frequency reconfigurable wearable antennas can dynamically select appropriate frequencies according to the surrounding electromagnetic environment to avoid interference frequency bands. On the other hand, human tissue is a complex electromagnetic system. Different human tissues have different electromagnetic characteristics that will have different effects on antenna performance, resulting in different degrees of offset in the resonant frequency. Frequency reconfigurable antennas can flexibly adjust the frequency of the antenna according to the differences of the human body to offset the frequency deviation caused by human tissue on the antenna. In short, good frequency reconfiguration capabilities can ensure the stability of wearable device communication.

[0004] The most commonly used technical means to achieve frequency reconfiguration is to load PIN diodes, micro-electromechanical system switches, varactor diodes, etc. Although the above technologies have been developed and mature, there are still several limitations: (1) Loading electronic devices on the antenna requires additional control circuits, which increases the difficulty of antenna design and introduces losses that affect the radiation performance of the antenna. It is also unable to work stably for a long time under high power conditions; (2) The RF "switch" can only achieve discrete state reconfiguration and cannot achieve continuous tuning characteristics, which limits the application scenarios of the antenna. Summary of the invention

[0005] The purpose of the present invention is to provide a dual-frequency tunable smart wearable device, which aims to solve the energy loss caused by the frequency reconfiguration process of wearable devices currently used in wireless body area networks by loading PIN diodes, micro-electromechanical system switches, varactor diodes, etc.

[0006] To achieve the above objectives, the present invention provides a dual-frequency tunable smart wearable device in the form of a fluid antenna and a liquid frequency reconfigurable manner.

[0007] The dual-frequency tunable smart wearable device itself is a wristband-type microstrip patch printed dipole antenna, including an antenna radiator and an annular cylindrical dielectric substrate arranged inside; the antenna radiator is composed of two identical rectangular metal patches and is symmetrically distributed on the outer surface of the annular cylindrical dielectric substrate, and rectangular groove arrays are symmetrically distributed on the two patches. The dielectric substrate acts as a wristband bracket of the wearable device, and is composed of a hollow annular cylindrical container and a liquid medium contained in the container. Dual-frequency communication is achieved by uniformly and symmetrically etching grooves on the radiator, and the reconfigurable characteristics of the resonant frequency are achieved by flexibly changing the geometric shape of the liquid medium and configuring the physical size, and the container is layered to overcome the unstable performance caused by the fluidity of the fluid antenna during wearing.

[0008] Preferably, the container is made of transparent ABS plastic as raw material and is additively manufactured based on 3D printing technology. The relative dielectric constant is 3, the loss tangent is 0.001, and the relative magnetic permeability is 1.

[0009] Preferably, the liquid medium is insulating oil, also known as transformer oil, with a relative dielectric constant of 2.224, a loss tangent of 0.005, and a relative magnetic permeability of 1.

[0010] Preferably, the metal patch is made of copper, and has a thickness of 0.035 mm, a length of 80 mm, and a width of 20 mm.

[0011] Preferably, the grooves are 13 mm long, 1 mm wide, 0.035 mm thick, and spaced 20 mm apart.

[0012] Preferably, the dual-band frequency bands are 1.8 GHz and 2.4 GHz.

[0013] Preferably, the antenna adopts center point feeding, and the input impedance is 50 ohms.

[0014] Preferably, the container is a hollow annular cylinder with a height of 30 mm, an inner radius of 30 mm, and an outer radius of 42 mm. The annular cylinder cavity has a height of 28 mm, an inner radius of 31 mm, and an outer radius of 41 mm.

[0015] Preferably, the layering adopts 4 cylindrical spacers, and the radii of the four cylindrical spacers from inside to outside are 33mm, 35mm, 37mm, and 39mm respectively.

[0016] Beneficial effects of the present invention: The container is made of wear-resistant, dielectrically stable, environmentally safe, flexible and conformable transparent ABS plastic, which has the best communication performance while ensuring comfortable wearing. The antenna adopts a printed microstrip dipole antenna with omnidirectional radiation characteristics to ensure that the antenna radiates and receives evenly when the posture and position of the user's body are constantly changing during use. The radiator uses the watch strap accessories as a carrier, which has the advantages of portability, ornamental, and concealment. Dual-frequency communication is achieved by uniformly and symmetrically etching grooves on the radiator, and the reconfigurable characteristics of the resonant frequency are achieved by flexibly changing the geometric shape of the liquid medium inside the watch strap container and configuring the physical dimensions. The container is layered to overcome the unstable performance caused by the fluidity of the fluid antenna during wearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a wireframe diagram of the overall structure of the embodiment of the present application; Figure 2 is a perspective view of the overall structure wireframe of an embodiment of the present application; Figure 3 is a side view of a radiator according to an embodiment of the present application; Figure 4 is an isometric wireframe diagram of a radiator according to an embodiment of the present application; Figure 5 is a front view of the radiator in an embodiment of the present application; Figure 6 This is a perspective view of the container structure wireframe of the embodiment of the present application Figure 7 It is a wireframe diagram of the hierarchical structure of an embodiment of the present application; Figure 8 This is a comparison diagram of return loss-frequency curves after groove engraving in an embodiment of the present application; Fig. 9 is a return loss-frequency curve diagram when the embodiment of the present application is not layered; Fig.10 is a return loss-frequency curve diagram after layering in the embodiment of the present application; Fig.11 is a gain-frequency curve diagram of this embodiment; Fig.12 is the directional diagram of this embodiment; Description of Figure Numbers: 1. Radiator; 2. Wristband dielectric substrate; 3. Groove; 4. Feeding point; 5. Container; 6. Fluid medium; 7. Cylindrical layered structure. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] It should be noted that, in order to avoid blurring the present invention due to some unimportant details, only the structures and processing steps closely related to the scheme of the present invention are shown in the drawings, and the remaining details that are not closely related to the present invention are omitted. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention.

[0020] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0021] Example: like Figure 1 As shown, the embodiment of the present invention is a microstrip patch printed dipole antenna, comprising an antenna radiator 1 and a hollow cylindrical dielectric substrate 2 arranged inside.

[0022] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the antenna radiator 1 is composed of two rectangular metal copper patches with a thickness of 0.035 mm, a length of 80 mm, and a width of 20 mm, and is symmetrically distributed on the outer surface of the annular cylindrical dielectric substrate 2. A rectangular groove array 3 with a length of 13 mm, a width of 1 mm, and a spacing of 20 mm is symmetrically etched on the two patches to achieve 1.8 GHz and 2.4 GHz dual-band communication performance.

[0023] The dielectric substrate 2 acts as a wristband bracket for a wearable antenna. Figure 6 The hollow cylindrical container 5 shown and the liquid medium 6 contained in the container are composed of a flexible, comfortable and wearable antenna. The container 5 is made of a flexible, transparent ABS plastic with a relative dielectric constant of 3 and a relative magnetic permeability of 1 as raw material. The container 5 is additively manufactured based on 3D printing technology. The container 5 is a hollow annular cylinder with a height of 30 mm, an inner radius of 30 mm, and an outer radius of 42 mm. The height of the annular cylinder cavity is 28 mm, the inner radius is 31 mm, and the outer radius is 41 mm. The fluid medium 6 is an insulating oil (transformer oil) with a relative dielectric constant of 2.224 and a relative magnetic permeability of 1.

[0024] The embodiment of the present invention uses a method of etching grooves to achieve dual-frequency characteristics. In a distributed parameter circuit, the dual-frequency achieved by etching grooves can be understood as breaking the original uniform distribution of current on the surface of the radiator, so that part of the current will be guided to the edge and bottom of the grooves, changing the current distribution on the surface of the radiator. Different current paths will cause the radiator to resonate at different frequencies. For example, a shorter current path may correspond to a higher frequency resonance, while a longer current path may correspond to a lower frequency resonance. Grooving makes the current distribution on the radiator more complex and increases the circuitous path of the current, thereby producing different radiation characteristics in different frequency bands. In a lumped parameter circuit, the dual-frequency mechanism lies in the introduction of equivalent capacitance and inductance by the grooves. A capacitance effect will be formed between the edge and bottom of the groove and other parts of the radiator, and the groove itself will also produce a certain inductance effect. The combination of inductance and capacitance can form a resonant circuit, resonate at a specific frequency, and achieve dual-frequency operation.

[0025] The embodiment of the present invention realizes the reconfigurable characteristics of the resonant frequency by flexibly changing the geometric shape of the liquid medium 6 and configuring the physical size. In order to overcome the unstable performance caused by the fluidity of the fluid antenna during the wearing process of the wearable device, the container is layered, that is, the hollow inner space of the container 5 is added with the following Figure 7 The four cylindrical layered structures 7 with radii showing an arithmetic progression distribution divide the container 5 into five parts. The radii of the four cylindrical partitions 7 from the inside to the outside are 33mm, 35mm, 37mm, and 39mm respectively. The insulating oil is filled in each part from the inside to the outside, and the size of the liquid medium is increased gradually, so as to achieve the frequency reconfiguration capability while overcoming the fluidity of the liquid.

[0026] In order to verify the feasibility of the above method theory, the embodiment of the present invention uses CST three-dimensional electromagnetic software to build a model and perform simulation experiments.

[0027] like Figure 8 As shown, after the grooves were engraved, two resonance points with return loss less than -10dB appeared. The impedance bandwidths were 120MHz (1.84GHz-1.96GHz) and 70MHz (2.45GHz-2.52GHz), the resonant frequencies were 1.90GHz and 2.49GHz, and the relative impedance bandwidths were 6.32% and 2.81%, respectively.

[0028] like Fig. 9As shown in the figure, the difference between the inner and outer radii of the insulating oil ring cylinder is defined as h_medium. h_medium takes six different values ​​from small to large, namely 0mm, 2mm, 4mm, 6mm, 8mm and 10mm. By comparing these six return loss frequency curves, it can be found that with the increase of the thickness of the insulating oil h_medium, the frequencies of the two resonance points of the antenna are shifted towards the low frequency direction. The sweep frequency range of the 1.8GHz band is 1.66GHz-1.91GHz, and the sweep frequency range of the 2.4GHz band is 2.16GHz-2.48GHz. Since the human body is a complex motion system and wearable antennas have special application scenarios, wearable antennas need to maintain stable communication performance during movement, which is easy for solid antennas but a great challenge for liquid antennas. In order to overcome the unstable performance caused by the fluidity of the fluid antenna during wearing, the embodiment of the present invention adopts a layered processing technology. Fig. 9 , 10 It can be found that after the container is added with 4 cylindrical layered structures, the input return loss will produce a small frequency shift toward the low-frequency direction. Generally speaking, it still has good frequency reconfigurability characteristics after adding the layered processing.

[0029] Fig.11 Five gain-frequency curves with h_medium = 0mm, 2mm, 4mm, 6mm, and 8mm are shown, and the dual-frequency characteristics of the antenna in the two frequency bands of 1.8GHz and 2.4GHz can also be seen. As the thickness of the insulating oil increases, the resonance point and the bandwidth move toward the low frequency direction, and the gain in the 1.8GHz band reaches more than 3dB, and the gain in the 2.4GHz band reaches more than 4dB. The far-field directional diagrams of the E-plane and the H-plane at 1.8GHz and 2.4GHz of the wearable device described in this embodiment are as follows: Fig.12 shown.

[0030] In summary, it can be concluded that the reasonable etching of grooves and layering technology processing in the embodiments of the present invention can achieve good dual-frequency liquid reconfigurable characteristics of the antenna.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should all be deemed to fall within the scope of protection determined by the claims submitted for the present invention.

Claims

1. A dual-frequency tunable smart wearable device, the wearable device itself is a wristband microstrip patch printed dipole antenna, characterized in that: It includes an antenna radiator and a hollow annular cylindrical dielectric substrate arranged inside; The antenna radiator is composed of two identical rectangular metal patches, which are symmetrically distributed on the outer surface of the cylindrical dielectric substrate. Rectangular groove arrays are symmetrically distributed on the two patches to achieve dual-frequency communication. The dielectric substrate acts as a wristband bracket of the wearable device, and is composed of a hollow cylindrical container and a liquid medium contained in the container. The resonant frequency can be reconfigured by changing the geometric shape of the liquid medium inside the strap container and configuring the physical dimensions.

2. A dual-frequency tunable smart wearable device according to claim 1, characterized in that: The container is additively manufactured using transparent ABS plastic as raw material based on 3D printing technology. The relative dielectric constant of the material is 3, the loss tangent is 0.001, and the relative magnetic permeability is 1.

3. A dual-frequency tunable smart wearable device according to claim 1, characterized in that: The liquid medium is insulating oil, also called transformer oil, with a relative dielectric constant of 2.224, a loss tangent of 0.005, and a relative magnetic permeability of 1.

4. The dual-frequency tunable smart wearable device according to claim 1, characterized in that: The metal patch is made of copper, and has a thickness of 0.035 mm, a length of 80 mm, and a width of 20 mm.

5. The dual-frequency tunable smart wearable device according to claim 1, characterized in that: The grooves have a length of 13 mm, a width of 1 mm, a thickness of 0.035 mm, and a spacing of 20 mm.

6. The dual-frequency tunable smart wearable device according to claim 1, characterized in that: The frequency bands of the dual-band are 1.8 GHz and 2.4 GHz.

7. The dual-frequency tunable smart wearable device according to claim 1, characterized in that: The antenna is fed by a central port, and the input impedance is 50 ohms.

8. The dual-frequency tunable smart wearable device according to claim 1, characterized in that: The container is a hollow annular cylinder with a height of 30 mm, an inner radius of 30 mm and an outer radius of 42 mm. The annular cylinder cavity has a height of 28 mm, an inner radius of 31 mm and an outer radius of 41 mm.

9. A dual-frequency tunable smart wearable device according to claim 1 or 8, characterized in that: The unstable performance caused by the fluidity of the fluid antenna during the wearing of the wearable device is overcome through container layering.

10. The dual-frequency tunable smart wearable device according to claim 1, characterized in that: The layering adopts 4 cylindrical spacers, and the radii of the four cylindrical spacers from inside to outside are 33mm, 35mm, 37mm and 39mm respectively.

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