Multi-band high-gain low-specific absorption rate wearable antenna based on AMC

Abstract

The invention relates to a multi-band high-gain low-specific-absorption-rate wearable antenna based on an AMC. The multi-band high-gain low-specific-absorption-rate wearable antenna comprises a multi-band antenna fed by a coplanar waveguide, an AMC reflecting plate and a spacing layer, the multi-band antenna comprises a first dielectric substrate, a coplanar structure arranged on the first dielectric substrate, and a plurality of radiation branches connected with the coplanar structure. The AMC reflecting plate is composed of AMC reflecting modules based on a plurality of arrays; the AMC reflection module comprises a second dielectric substrate, a radiation assembly and a grounding plate, wherein the radiation assembly and the grounding plate are arranged on the two opposite sides of the second dielectric substrate respectively. The radiation assembly has in-phase reflection phase bandwidth covering all working frequency bands of the multi-frequency-band antenna; the radiation assembly comprises a plurality of radiation rings; on the side face of the second dielectric substrate, the multiple radiation rings are sequentially arranged from inside to outside in the radial direction, and the two radiation rings closest to the center are connected with each other. The wearable antenna of the scheme has more excellent gain and unidirectional radiation characteristics and lower human body specific absorption rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wearable devices, and particularly relates to a wearable antenna with AMC-based multi-band high gain and low specific absorption rate. BACKGROUND

[0002] With the rapid development of science and technology, as a kind of local communication network technology constructed around the human body and its surrounding space, wireless body area network has been widely used in intelligent communication, military and medical fields and many other fields. In this network system, the antenna is the core element for data interaction between electronic devices and the external environment, and its performance directly affects the stability, efficiency and user experience of the communication system.

[0003] In recent years, the wearable device market has shown explosive growth, which has also increased the demand for wearable antennas. However, compared with traditional antenna design, wearable antennas face many unique challenges. On the one hand, when the antenna is close to the human body tissue, the load on the human body will cause the antenna to have frequency shift or detuning phenomenon, and the radiation pattern will also be deteriorated. This is because the human body as a complex electromagnetic medium will have a significant impact on the electromagnetic properties of the antenna. For example, in wearable devices, the antenna is close to the human skin, and the sweat, fat and other tissue components of the human body will change the electromagnetic environment around the antenna, causing the originally set working frequency of the antenna to shift, thereby affecting the communication quality. On the other hand, the changes in human body movement and posture will cause the deformation of the antenna, leading to a decline in the performance of the antenna and failing to meet the actual application requirements. Taking a smart bracelet as an example, the frequent swinging, bending and other movements of the user's arm in daily activities will cause the deformation of the antenna on the bracelet, thereby affecting its signal transmission capability.

[0004] To adapt to the application of wearable devices, various types of wearable antennas have emerged, such as microstrip antennas, planar inverted F antennas, slot antennas, etc. However, most of these antennas work in a single frequency band, which cannot meet the demand of modern communication systems for multi-link communication. In today's communication environment, users often need to use multiple communication protocols at the same time, such as Bluetooth, WiFi, NFC, etc., and single-band antennas obviously cannot meet this demand. If single-band antennas are used for data interaction respectively, not only will there be coupling between multiple antennas, causing complex electromagnetic problems, but also the size and occupied space of the entire communication system will be increased, which is extremely disadvantageous for wearable devices that pursue lightness, thinness and portability.

[0005] Therefore, dual / multi-band wearable antennas become a research hotspot. At present, dual / multi-band wearable antennas have made some breakthroughs, most of which adopt planar antenna design to fit the human body curve. However, the radiation pattern of such antennas is mostly bidirectional, which has a greater impact on the human body and may lead to a higher specific absorption rate. To reduce the impact of antenna back radiation on the human body, some scholars propose to configure a complete ground plane on the back. However, the electromagnetic wave reflected by the ordinary complete metal ground plane is 180° out of phase with the incident electromagnetic wave, which needs to be adjusted to a specific distance, such as a quarter wavelength position, to reduce the back radiation of the antenna. However, such a structure has a narrow bandwidth and low gain, which limits its application in practice.

[0006] The artificial magnetic conductor (AMC) structure can make the forward-radiated electromagnetic wave of the antenna and the reflected wave in phase and superimposed, and the backward-radiated electromagnetic wave is strongly suppressed due to phase cancellation. At the same time, the high impedance characteristic of the AMC structure can constrain more energy in the radiation direction, thereby improving the antenna gain. Moreover, the distance between the AMC structure and the antenna does not need to be a specific quarter wavelength, and a distance much smaller than the distance can achieve the effect, which is conducive to realizing low profile and conformal design. Therefore, the AMC structure is a good choice for wearable antenna design, and has certain advantages in solving the challenges of low specific absorption rate, stability of performance on the human body, and conformal ability of wearable antenna design.

[0007] However, the wearable antennas based on AMC currently still have a demand for continuous optimization in terms of reducing specific absorption rate, improving gain, and reducing back radiation. In terms of specific absorption rate, although the existing design can meet the basic safety specifications, there is still room for optimization, and seeking further reduction of SAR is one of the important goals of current research. Low gain leads to limited signal transmission distance and unstable communication quality. The effect of reducing back radiation is not obvious, which also has a negative impact on the performance of the antenna.

[0008] In summary, although the AMC structure provides an effective way to improve the performance of wearable antennas, how to realize multi-band operation while synergistically optimizing the specific absorption rate, gain, and radiation pattern is still a key challenge in current research. Developing a wearable antenna that can balance wideband characteristics, low electromagnetic exposure risk, high radiation efficiency, and stable directivity has important research significance and application value for promoting the development of the next generation of high-performance and high-reliability wearable devices. SUMMARY

[0009] The technical problem to be solved by the present application is to provide a multi-band high-gain low-specific absorption rate wearable antenna based on AMC.

[0010] To achieve the above object, the application provides a wearable antenna with multi-band high gain and low specific absorption rate based on AMC, comprising a multi-band antenna fed by a coplanar waveguide, an AMC reflecting plate, and a spacer layer for connecting the multi-band antenna and the AMC reflecting plate. The multi-band antenna comprises a first dielectric substrate, a coplanar structure arranged on the first dielectric substrate, and a plurality of radiation branches connected to the coplanar structure. The AMC reflecting plate is composed of a plurality of arrayed AMC reflecting modules. The AMC reflecting module comprises a second dielectric substrate, a radiation assembly arranged on one side of the second dielectric substrate, and a ground plate arranged on the other side of the second dielectric substrate. The radiation assembly has a same-phase reflection phase bandwidth covering all working frequency bands of the multi-band antenna, wherein the radiation assembly comprises a plurality of radiation rings. On the side of the second dielectric substrate, the plurality of radiation rings are arranged along the radial direction from inside to outside, and the two radiation rings closest to the center are connected to each other.

[0011] According to an aspect of the application, the multi-band antenna is a three-band antenna, and the plurality of radiation branches are a first radiation branch, a second radiation branch, and a third radiation branch. The first radiation branch is a trifurcated branch. The second radiation branch is a rectangular branch. The third radiation branch is a rectangular spiral branch.

[0012] According to an aspect of the application, the first radiation branch is used to generate a low-frequency resonance point at a low frequency of 2.5 GHz. The second radiation branch is used to generate a high-frequency resonance point at a high frequency of 5 GHz. The third radiation branch is used to generate a medium-frequency resonance point at a medium frequency of 3.6 GHz.

[0013] According to an aspect of the application, the third radiation branch is composed of a plurality of rectangular structures rotated multiple times, wherein the lengths of the plurality of rectangular structures are different, and the widths of at least part of the rectangular structures are different.

[0014] According to an aspect of the application, the third radiation branch is composed of six rectangular structures rotated five times at an angle of 90°.

[0015] According to an aspect of the application, the coplanar structure comprises a microstrip feed line structure and a rectangular metal ground. The rectangular metal ground is arranged on both sides of the microstrip feed line structure in the width direction, and the side edges of the rectangular metal ground are flush with one end of the microstrip feed line structure. The first radiation branch is connected to the microstrip feed line structure at an end away from the rectangular metal ground; The second radiation branch and the third radiation branch are respectively connected on both sides of the width direction of the microstrip feed line structure, and the second radiation branch and the third radiation branch are located between the rectangular metal ground and the first radiation branch.

[0016] According to an aspect of the present application, the length and width of the rectangular structure connected to the microstrip feed line structure in the third radiation branch are greater than the length and width of the remaining rectangular structures.

[0017] According to an aspect of the present application, three radiation rings are provided, and are respectively: the first radiation ring, the second radiation ring, and the third radiation ring, which are sequentially reduced in radial size; The first radiation ring, the second radiation ring, and the third radiation ring respectively generate three sections of co-phase reflection phase bandwidth between +90° and -90°; The radially outer side of the first radiation ring is a circular edge, and the radially inner side is a cross-shaped stepped edge; The radially outer side and the radially inner side of the second radiation ring are both cross-shaped stepped edges; The radially outer side of the third radiation ring is a cross-shaped stepped edge, and the radially inner side is a circular edge; The radially outer side of the third radiation ring is connected to the radially inner side of the second radiation ring.

[0018] According to an aspect of the present application, the radially outer side of the second radiation ring is parallel to the radially inner side of the first radiation ring and is provided with a spacing; In the second radiation ring, the shape of the radially outer side is consistent with the shape of the radially inner side, and the area surrounded by the radially inner side is 0.75 times the area surrounded by the radially outer side; The corner of the third radiation ring based on the maximum size position of the radially outer side is connected to the radially inner side of the second radiation ring.

[0019] According to an aspect of the present application, the first dielectric substrate is a polyimide plate with a thickness of 0.13 mm; The second dielectric substrate is a polydimethylsiloxane with a thickness of 2 mm; The operating frequency bands of the multi-band antenna are respectively: 2.36 GHz-2.6 GHz, 3.56 GHz-3.68 GHz, and 4.91 GHz-5.2 GHz; The AMC reflection module is arranged in a 3x3 array.

[0020] According to one scheme of the application, the wearable antenna has excellent one-way radiation characteristics, and significantly reduces the specific absorption rate (SAR) of the human body, with SAR values of 0.0383 W / kg, 0.0101 W / kg, and 0.0427 W / kg at 2.5 GHz, 3.6 GHz, and 5.05 GHz, respectively. The peak gain in the frequency bands of 2.36-2.6 GHz, 3.56-3.68 GHz, and 4.91-5.2 GHz is 7.6 dBi, 8 dBi, and 9 dBi, respectively.

[0021] According to one scheme of the application, the scheme has multi-band characteristics, covering the frequency bands of 2.36-2.6 GHz, 3.56-3.68 GHz, and 4.91-5.2 GHz, and can play a multifunctional role in a wireless body area network system, reducing the complex electromagnetic problems caused by multi-antenna coupling.

[0022] According to one scheme of the application, the radiation assembly of the scheme has a same-phase reflection phase bandwidth covering all operating frequency bands of the multi-band antenna, thereby making it easier to combine the AMC reflector plate with the multi-band antenna, and making the wearable antenna of the scheme have more superior gain, one-way radiation characteristics, and lower specific absorption rate.

[0023] According to one scheme of the application, the scheme can generate corresponding reflection phase bandwidths at different operating frequency bands based on different radiation rings. The radiation ring at the outermost circle corresponds to the reflection phase bandwidth at the low frequency band, and the direction from the outside to the inside gradually corresponds to the change from low to high of the operating frequency band. In particular, by connecting the two radiation rings closest to the center to each other, the resonance points generated by the adjacent position radiation rings can be moved to high frequencies, thereby sufficiently expanding the same-phase reflection bandwidth of the previous frequency band while moving the same-phase reflection phase bandwidth of the high frequency band to the target frequency band, so that the AMC reflector plate has a more extensive same-phase reflection phase bandwidth, and realizes the ability to comprehensively cover all operating frequency bands of the multi-band antenna.

[0024] According to one scheme of the application, the wearable antenna combined with the multi-band antenna and the AMC reflector plate has superior gain, superior one-way radiation characteristics, and superior specific absorption rate.

[0025] According to one scheme of the application, the scheme has a simple structure and is easy to process, and has the advantages of large-scale and low-cost preparation.

[0026] According to one scheme of the application, the scheme can reduce the multi-antenna coupling problem caused by a single frequency point antenna in a wireless body area network, and has the characteristics of high gain and low specific absorption rate, and can be well applied to the fields of wearable antennas and communication.

[0027] According to one scheme of the present application, the scheme effectively solves the complex electromagnetic coupling problem caused by a large number of antennas in a wireless body area network by replacing a plurality of single-frequency antennas with a single multi-band antenna, simplifies system design, and improves device integration and reliability.

[0028] According to one scheme of the present application, the specific absorption rate value of the scheme is much lower than the limit value of most existing safety standards in the field, fully proving that the antenna has extremely high safety when used close to the human body, greatly reducing the potential electromagnetic radiation risk to human health, and fully embodying the excellent electromagnetic safety performance of the scheme.

[0029] According to one scheme of the present application, the scheme precisely controls the reflection phase characteristics of the artificial magnetic conductor by unique radiation ring layout and connection design (such as connecting the two inner rings), so that the in-phase reflection bandwidth perfectly covers all working frequency bands of the antenna, which is a key to ensure high-performance one-way radiation performance.

[0030] According to one scheme of the present application, the performance of the scheme has the advantages of predictability and controllability, and the correspondence between the radiation ring from the outside to the inside and the working frequency band from low to high is clear, which provides a clear and reliable guiding principle for performance tuning and subsequent modification design for different frequency band requirements of the antenna.

[0031] According to one scheme of the present application, the scheme has the characteristics of simple structure and easy processing, and in combination with excellent electrical performance, it has the potential to go from the laboratory to large-scale commercial application, and is cost controllable and easy to promote.

[0032] According to one scheme of the present application, the scheme has a more broad application prospect, based on its multi-band, high gain, low SAR and compact structure, it is not only suitable for wireless body area networks, but also can show great application potential and applicability in modern wearable communication fields such as medical monitoring and intelligent clothing. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a structural diagram of the wearable antenna based on AMC of the present application; Figure 2 is a side view of the wearable antenna based on AMC of the present application; Figure 3 is a structural diagram of the multi-band antenna of the present application; Figure 4 is a bottom structural diagram of the AMC reflection plate of the present application; Figure 5 is a structural diagram of the AMC reflection module of the present application; Figure 6S11 curve schematic diagram of the wearable antenna of the present application; Figure 7 Gain curve schematic diagram of the wearable antenna of the present application; Figure 8 Radiation direction schematic diagram of the wearable antenna of the present application at low frequency resonance point 2.5GHz, wherein, Figure 8 (a) represents E-plane radiation direction schematic diagram, Figure 8 (b) represents H-plane radiation direction schematic diagram; Figure 9 Radiation direction schematic diagram of the wearable antenna of the present application at middle frequency resonance point 3.6GHz, wherein, Figure 9 (a) represents E-plane radiation direction schematic diagram, Figure 9 (b) represents H-plane radiation direction schematic diagram; Figure 10 Radiation direction schematic diagram of the wearable antenna of the present application at high frequency resonance point 5.05GHz, wherein, Figure 10 (a) represents E-plane radiation direction schematic diagram, Figure 10 (b) represents H-plane radiation direction schematic diagram; Figure 11 Human body specific absorption rate schematic diagram of the wearable antenna of the present application at low frequency resonance point 2.5GHz; Figure 12 Human body specific absorption rate schematic diagram of the wearable antenna of the present application at middle frequency resonance point 3.6GHz; Figure 13 Human body specific absorption rate schematic diagram of the wearable antenna of the present application at high frequency resonance point 5.05GHz. DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described in the following are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0035] In the description of the embodiments of the present application, the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" express the orientation or positional relationship based on the orientation or positional relationship shown in the relevant drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation of the present application.

[0036] The application will be described in detail below with reference to the drawings and specific embodiments, which cannot be exhaustively listed here, but the embodiments of the application are not limited to the following embodiments.

[0037] In combination Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown in the drawings and specific embodiments, according to an embodiment of the application, a wearable antenna based on AMC and multi-band high gain and low specific absorption rate of the application includes: a multi-band antenna 1 fed by a coplanar waveguide, an AMC reflector 2, and a spacer layer 3 for connecting the multi-band antenna 1 and the AMC reflector 2; wherein the multi-band antenna 1 is used to provide different working frequency bands, realize the multi-functional connection function in the wireless body area network system, and reduce the complex electromagnetic problems caused by traditional multi-antenna coupling. The AMC reflector 2 is used to reduce the radiation influence of the multi-band antenna 1 on the human body, improve the gain and front-to-back ratio of the multi-band antenna 1, and reduce the influence of the complex electromagnetic characteristics of the human body on the performance of the multi-band antenna 1. Thus, in this embodiment, the multi-band antenna 1 includes: a first dielectric substrate 11, a coplanar structure 111 disposed on the first dielectric substrate 11, and a plurality of radiation branches 113 connected to the coplanar structure 111; in this embodiment, in order to realize the multi-band antenna 1 multi-band function, the resonant point of each radiation branch 113 is different. Further, the multi-band antenna 1 is fed by the coplanar waveguide based on the coplanar structure 111, and the port impedance of the feed is 50 ohms, which can be well matched with the SMA interface.

[0038] In this embodiment, the radiation branches 113 are made of metal materials, of course, other conductive materials can be selected according to specific application scenarios, such as graphene, conductive fabric and other excellent conductive materials.

[0039] In this embodiment, the AMC reflector 2 is composed of a plurality of arrayed AMC reflection modules 21; wherein the AMC reflection module 21 includes: a second dielectric substrate 211, a radiation assembly 212 and a ground plate 213 disposed on the opposite sides of the second dielectric substrate 211; wherein the radiation assembly 212 has a same-phase reflection phase bandwidth covering all working frequency bands of the multi-band antenna 1, thereby more easily realizing the combination of the AMC reflector 2 and the multi-band antenna 1, so that the wearable antenna of the present scheme has more superior gain, unidirectional radiation characteristics and lower specific absorption rate of the human body.

[0040] In the embodiment, the radiation assembly 212 comprises: a plurality of radiation rings 212a; wherein, on the side of the second dielectric substrate 211, the plurality of radiation rings 212a are arranged in the radial direction from inside to outside, and the two radiation rings 212a closest to the center are connected to each other. Specifically, different radiation rings 212a can be used to generate corresponding reflection phase bandwidths in different working frequency bands. The radiation ring 212a at the outermost position corresponds to the generation of the reflection phase bandwidth at the low frequency band, and the direction from the outside to the inside gradually corresponds to the change from low to high of the working frequency band. In particular, by connecting the two radiation rings 212a closest to the center to each other, the resonance points generated by the adjacent position radiation rings 212a can be moved to high frequency, thereby sufficiently expanding the in-phase reflection bandwidth of the previous frequency band, moving the in-phase reflection phase bandwidth of the high frequency band to the target frequency band, and enabling the AMC reflector 2 to have a more extensive in-phase reflection phase bandwidth, and realizing the ability to comprehensively cover all working frequency bands of the multi-band antenna 1.

[0041] In combination Figure 1 and Figure 3 As shown in FIGS. 1 to 3, according to an embodiment of the present application, the multi-band antenna 1 is a three-band antenna, and the plurality of radiation branches 113 are respectively a first radiation branch 113a, a second radiation branch 113b and a third radiation branch 113c; wherein the first radiation branch 113a is a three-pronged branch for generating a low frequency resonance point at a low frequency of 2.5 GHz; in the embodiment, the first radiation branch 113a comprises: a first transverse rectangular structure 113a1 and three first longitudinal rectangular structures 113a2; wherein the first longitudinal rectangular structure 113a2 is arranged vertically on the same side of the first transverse rectangular structure 113a1, and the three first longitudinal rectangular structures 113a2 are located at three equal positions of the first transverse rectangular structure 113a1, i.e. at both ends and the middle of the first transverse rectangular structure 113a1, thereby forming a symmetrical three-pronged structure. Further, the length of the first longitudinal rectangular structure 113a2 at the middle position is greater than that of the remaining first longitudinal rectangular structures 113a2. Thus, by adjusting the sizes of the first transverse rectangular structure 113a1 and the three first longitudinal rectangular structures 113a2, the resonance point offset can be adjusted, which is helpful for the multi-band antenna 1 to work at the set target frequency band in subsequent design. In the embodiment, the first transverse rectangular structure 113a1 has a length of 24.4 mm and a width of 1.1 mm; among the three first longitudinal rectangular structures 113a2, the first longitudinal rectangular structure 113a2 at the middle position has a length of 12.2 mm and a width of 1.1 mm, and the remaining first longitudinal rectangular structures 113a2 have a length of 6.1 mm and a width of 1.1 mm.

[0042] In the embodiment, the second radiation branch 113b is a rectangular branch, which is used to generate a high-frequency resonance point at a high frequency of 5.05 GHz; wherein, by adjusting the distance of the second radiation branch 113b from the feeding point and the length, the optimal result of the working frequency range adapted by the second radiation branch 113b can be obtained.

[0043] In the embodiment, the third radiation branch 113c is a rectangular spiral branch, which is used to generate a medium-frequency resonance point at a medium frequency of 3.6 GHz; wherein, the third radiation branch 113c is composed of multiple rectangular structures 113c1 rotated for multiple times, wherein, the lengths of the multiple rectangular structures 113c1 are different, and the widths of at least part of the rectangular structures 113c1 are different. In the embodiment, by adjusting the distance of the third radiation branch 113c from the feeding point, the number and size of the rectangular structures 113c1, the optimal result of the working frequency range adapted by the third radiation branch 113c can be obtained.

[0044] As shown in FIG. 6, according to an embodiment of the present application, the third radiation branch 113c is composed of 6 rectangular structures 113c1 rotated for 5 times at an angle of 90°. Figure 3 As shown in FIG. 6, according to an embodiment of the present application, the third radiation branch 113c is composed of 6 rectangular structures 113c1 rotated for 5 times at an angle of 90°.

[0045] As shown in FIG. 6, according to an embodiment of the present application, the third radiation branch 113c is composed of 6 rectangular structures 113c1 rotated for 5 times at an angle of 90°. Figure 3 As shown in FIG. 6, according to an embodiment of the present application, the third radiation branch 113c is composed of 6 rectangular structures 113c1 rotated for 5 times at an angle of 90°.

[0046] Furthermore, the first radiating stub 113a is connected to the end of the microstrip feeder structure 111a away from the rectangular metal ground 111b; while the second radiating stub 113b and the third radiating stub 113c are respectively connected on both sides of the microstrip feeder structure 111a in the width direction, and the second radiating stub 113b and the third radiating stub 113c are located between the rectangular metal ground 111b and the first radiating stub 113a in the length direction of the microstrip feeder structure 111a. In this embodiment, the second radiating branch 113b is located on the right side of the microstrip feeder structure 111a, while the third radiating branch 113c is located on the left side of the microstrip feeder structure 111a. Of course, in another embodiment, the second radiating branch 113b is located on the left side of the microstrip feeder structure 111a, while the third radiating branch 113c is located on the right side of the microstrip feeder structure 111a. This allows the second radiating branch 113b and the third radiating branch 113c to be interchanged on both sides of the width direction of the microstrip feeder structure 111a, effectively ensuring the flexibility of its arrangement.

[0047] Furthermore, along the length direction of the microstrip feeder structure 111a, the connection positions of the second radiating stub 113b and the third radiating stub 113c with the microstrip feeder structure 111a are staggered; wherein, the distance between the second radiating stub 113b and the feeder port is 18mm, while the distance between the third radiating stub 113c and the feeder port is 17mm.

[0048] like Figure 3 As shown, according to one embodiment of the present invention, in the third radiating branch 113c, the length and width of the rectangular structure 113c1 connected to the microstrip feeder structure 111a are both greater than the length and width of the other rectangular structures 113c1. In this embodiment, the third radiating stub 113c is constructed from six rectangular structures 113c1, which are arranged in the following directions from the connecting end of the third radiating stub 113c (i.e., the end connected to the microstrip feeder structure 111a) to the spiral extension end (i.e., the end not connected to the microstrip feeder structure 111a): a first rectangular structure, a second rectangular structure, a third rectangular structure, a fourth rectangular structure, a fifth rectangular structure, and a sixth rectangular structure. The first rectangular structure has a length of 16.5 mm and a width of 2.25 mm; the second rectangular structure has a length of 4.4 mm and a width of 1 mm; the third rectangular structure has a length of 4 mm and a width of 1 mm; the fourth rectangular structure has a length of 4 mm and a width of 1 mm; the fifth rectangular structure has a length of 2 mm and a width of 0.7 mm; and the sixth rectangular structure has a length of 2 mm and a width of 0.7 mm. In this embodiment, the size of the first rectangular structure is larger than the size of the second radiating stub 113b, where the second radiating stub 113b has a length of 10 mm and a width of 2.2 mm.

[0049] like Figure 5As shown, according to an embodiment of the present application, the radiation ring 212a is provided with three, and are respectively: the radial dimension is sequentially reduced to the first radiation ring 212a1, the second radiation ring 212a2 and the third radiation ring 212a3; wherein the first radiation ring 212a1, the second radiation ring 212a2 and the third radiation ring 212a3 respectively generate three segments of in-phase reflection phase bandwidth between +90° to -90°; in the present embodiment, the radially outer side of the first radiation ring 212a1 is a circular edge, and the radially inner side is a cross-shaped stepped edge; specifically, first prepare a circular radiation patch, and then remove a cross-shaped stepped area in the radiation patch to achieve the preparation of the first radiation ring 212a1 for generating the reflection phase bandwidth at the low frequency band.

[0050] In the present embodiment, the radius of the circular edge (i.e. the radially outer side) of the first radiation ring 212a1 is 13mm, and the cross-shaped stepped edge (i.e. the radially inner side) is realized by sequentially connecting the outer edges of the cross structure and the four identical rectangular portions arranged at the diagonal positions of the cross structure, wherein the length of the two vertically intersecting rectangles of the cross structure is 20mm, and the width is 9.5mm, and the length of the rectangular portion arranged at the diagonal position is 3.8mm, and the width is 3.2mm. In the present embodiment, the first radiation ring 212a1 can adopt a method of removing the middle part to form its ring structure, which will not be described here.

[0051] Further, the radially outer side and the radially inner side of the second radiation ring 212a2 are both cross-shaped stepped edges; specifically, first prepare a cross-shaped stepped radiation patch, and then remove a cross-shaped stepped area in the radiation patch to achieve the preparation of the second radiation ring 212a2, which has a very wide reflection phase bandwidth at the medium frequency band and can meet the needs of the antenna, but has a very narrow reflection phase bandwidth at the high frequency band and cannot meet the needs of the antenna. In the present embodiment, in the second radiation ring 212a2, the shape of the radially outer side is consistent with the shape of the radially inner side, and the area surrounded by the radially inner side is 0.75 times the area surrounded by the radially outer side. In the present embodiment, the shape of the radially outer side of the second radiation ring 212a2 is consistent with the shape of the radially inner side of the first radiation ring 212a1, but the size of the radially outer side of the second radiation ring 212a2 is smaller than the size of the radially inner side of the first radiation ring 212a1, thereby allowing the first radiation ring 212a1 and the second radiation ring 212a2 to be spaced apart. Thus, the radially outer side of the second radiation ring 212a2 and the radially inner side of the first radiation ring 212a1 can be arranged in parallel and with a spacing.

[0052] In the embodiment, the radially outer side of the second radiation ring 212a2 is realized by sequentially connecting the outer edges of a cross structure and four identical rectangular sections arranged at the diagonal positions of the cross structure, wherein the two vertically intersecting rectangles of the cross structure have a length of 17.8 mm and a width of 7.5 mm respectively, and the rectangular sections arranged at the diagonal positions have a length of 2.85 mm and a width of 2.28 mm. The radially inner side is determined based on the same shape and a 0.75 times surrounding area limit, and will not be described herein again. In the embodiment, the second radiation ring 212a2 can form a ring structure by removing the middle part, and will not be described herein again.

[0053] Further, the radially outer side of the third radiation ring 212a3 is a cross ladder-shaped side, and the radially inner side is a circular side; in the embodiment, the radially outer side of the third radiation ring 212a3 is connected to the radially inner side of the second radiation ring 212a2, and thus, based on the connection of the third radiation ring 212a3 and the second radiation ring 212a2, the equivalent inductance inherent to a single second radiation ring 212a2 is sufficiently reduced, so that the resonance point of the AMC reflecting module 21 is moved to a high frequency, and thus the zero reflection phase point of the high frequency band is right-shifted to the required frequency band of the antenna, and at the same time, due to the coupling effect between the resonance modes, the intermediate frequency band reflection phase bandwidth can be smoothly transitioned, achieving the effect of fully covering the intermediate frequency band and the high frequency band.

[0054] In the embodiment, the cross ladder-shaped side of the third radiation ring 212a3 outside forms four equally spaced extension arms in the circumferential direction, so that the right-angle positions of the extension arms can realize the connection with the second radiation ring 212a2, that is, the corner at the maximum size position of the radially outer side of the third radiation ring 212a3 is connected to the radially inner side of the second radiation ring 212a2. In the embodiment, to realize the connection of the third radiation ring 212a3 and the second radiation ring 212a2, the cross extension direction of the third radiation ring 212a3 is different from the cross extension direction of the second radiation ring 212a2, that is, the extension direction of the extension arm of the third radiation ring 212a3 is inclined relative to the cross extension direction of the second radiation ring 212a2, and in this arrangement, the third radiation ring 212a3 with the smallest size can still be sufficiently connected to the inner side of the second radiation ring 212a2.

[0055] In this embodiment, the cross-shaped stepped edge on the outer side of the third radial ring 212a3 is formed by sequentially connecting the outer edges of a cross structure and four identical first rectangular portions arranged diagonally along the cross structure. The cross structure is composed of two perpendicularly intersecting second rectangular portions. In this embodiment, the length of the second rectangular portion is 10.6 mm and the width is 2.2 mm, while the length and width of the first rectangular portion are both 1 mm and 1 mm.

[0056] In this embodiment, the radius of the circular edge (i.e. the radial inner edge) inside the third radiation ring 212a3 is 1.5 mm.

[0057] In this embodiment, the third radiation ring 212a3 is connected to the second radiation ring 212a2 by rotating the entire ring by 45°.

[0058] like Figure 1 As shown, according to one embodiment of the present invention, the first dielectric substrate 11 is a polyimide plate with a thickness of 0.13 mm; the second dielectric substrate 211 is polydimethylsiloxane with a thickness of 2 mm.

[0059] like Figure 1 As shown, according to one embodiment of the present invention, the operating frequency bands of the multi-band antenna 1 are 2.36GHz-2.6GHz, 3.56GHz-3.68GHz, and 4.91GHz-5.2GHz; the in-phase reflection phase bandwidth of the AMC reflection module 21 covers the range of 2GHz-2.6GHz, 2.71GHz-4.65GHz, and 4.9GHz-5.9GHz.

[0060] like Figure 1 As shown, according to one embodiment of the present invention, the AMC reflection module 21 is arranged in a 3×3 array.

[0061] like Figure 2 As shown, according to one embodiment of the present invention, the spacer layer 3 is made of foam plastic.

[0062] To further illustrate this plan, further examples will be provided.

[0063] Example 1 In this embodiment, the wearable antenna of this solution includes a multi-band antenna 1, an AMC reflector 2, and a spacer layer 3; wherein, the multi-band antenna 1 has a size of 44mm×44mm; the AMC reflector 2 has a size of 90×90mm and adopts a 3×3 array of AMC reflector modules 21; the spacer layer 3 is made of foam plastic with a dielectric constant similar to that of air, and its external dimensions are the same as those of the multi-band antenna 1.

[0064] Further, in the multi-band antenna 1, the first dielectric substrate 11 is made of polyimide material, with a thickness of 0.13 mm, a dielectric constant of 3.5, and a loss tangent of 0.0021. Further, the multi-band antenna 1 is implemented based on the coplanar structure 111 to realize coplanar waveguide feeding, with a port impedance of 50 ohms, to realize matching with an SMA interface.

[0065] Further, the second dielectric substrate 211 is made of polydimethylsiloxane, with a dielectric constant of 2.7 and a thickness of 2 mm.

[0066] In the embodiment, based on the foregoing structural arrangement, the multi-band antenna 1 has three operating frequency bands, namely 2.36-2.6 GHz (Bluetooth / WiFi), 3.56-3.68 GHz (5G n77 / n78), and 4.91-5.2 GHz (WiFi). Moreover, the multi-band antenna 1 has an omnidirectional radiation characteristic, and the gain range is 2.3-4.5 dBi in the 2-6 GHz frequency band, with gains of 2.3 dBi, 2.9 dBi, and 4.6 dBi at the resonant frequencies of 2.5 GHz, 3.6 GHz, and 5.05 GHz, respectively.

[0067] In the embodiment, the AMC reflector 2 is constructed based on the foregoing structural arrangement and is connected to the multi-band antenna 1. Since the dielectric constant of the spacing layer 3 is close to that of air, the gain of the multi-band antenna 1 loaded with the AMC reflector 2 is 6.1-9.1 dBi in the 2-6 GHz frequency band, with gains of 7.6 dBi, 8 dBi, and 9 dBi at the resonant frequencies of 2.5 GHz, 3.6 GHz, and 5.05 GHz, respectively, and the antenna has unidirectional radiation.

[0068] Further, a square three-layer skin tissue model with a length of 110 mm and a width of 110 mm is loaded below the AMC reflector 2, with the outermost layer being skin, the middle layer being muscle, and the innermost layer being fat. The skin tissue model is used to calculate the specific absorption rate (SAR) of the wearable antenna of the present scheme, and the results show that the SAR values at the resonant frequencies of 2.5 GHz, 3.6 GHz, and 5.05 GHz are 0.0383 W / kg, 0.0101 W / kg, and 0.0427 W / kg, respectively, which are far less than 1.6 W / kg, and the wearable performance is excellent.

[0069] Further, the electromagnetic full-wave simulation software CST is used to simulate, analyze, and optimize the foregoing wearable antenna, and the structural parameters, S11 parameters, gain, radiation pattern, and SAR value of the antenna are summarized.

[0070] As Figure 6As shown, the wearable antenna of the present application has a range of S11 parameters less than -10dB of 2.36-2.6GHz, 3.56-3.68GHz, 4.91-5.2GHz, has the characteristics of multiple frequency bands, and thus has multiple functions in the wireless body area network, and in terms of communication, can be used for Bluetooth, WiFi, and 5Gn78 frequency bands.

[0071] As shown, Figure 7 As shown, the wearable antenna of the present application has a working frequency band of 2.36-2.6GHz, 3.56-3.68GHz, 4.91-5.2GHz, and a peak gain of up to 7.6dBi, 8dBi, 9dBi.

[0072] As shown in combination with Figure 8 , Figure 9 and Figure 10 , the wearable antenna of the present application has the characteristics of one-way radiation at three resonance points of 2.5GHz, 3.6GHz, and 5.05GHz, and greatly reduces the back radiation.

[0073] As shown in combination with Figure 11 , Figure 12 and Figure 13 , the wearable antenna of the present application has SAR values of 0.0383W / kg, 0.0101W / kg, and 0.0427W / kg at three resonance points of 2.5GHz, 3.6GHz, and 5.05GHz, respectively.

[0074] As shown, the wearable antenna of the present application has a range of S11 parameters less than -10dB of 2.36-2.6GHz, 3.56-3.68GHz, 4.91-5.2GHz, has the characteristics of multiple frequency bands, and thus has multiple functions in the wireless body area network, and in terms of communication, can be used for Bluetooth, WiFi, and 5Gn78 frequency bands.

[0075] The above content is only an example of a specific solution of the present application, and for devices and structures not described in detail, it should be understood that general devices and general methods existing in the art are used to implement them.

[0076] The above only describes one solution of the present application and is not used to limit the present application, and for those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-band wearable antenna with high gain and low specific absorption rate based on AMC, characterized in that, The application relates to a multi-band antenna (1) fed by a coplanar waveguide, an AMC reflector plate (2), and a spacer layer (3) for connecting the multi-band antenna (1) and the AMC reflector plate (2). The multi-band antenna (1) comprises a first dielectric substrate (11), a coplanar structure (111) arranged on the first dielectric substrate (11), and a plurality of radiation branches (113) connected to the coplanar structure (111). The AMC reflector plate (2) is composed of a plurality of arrayed AMC reflection modules (21). The AMC reflection module (21) comprises a second dielectric substrate (211), a radiation assembly (212) and a ground plate (213) arranged on opposite sides of the second dielectric substrate (211). The radiation assembly (212) has a same-phase reflection phase bandwidth covering all working frequency bands of the multi-band antenna (1), and the radiation assembly (212) comprises a plurality of radiation rings (212a). On the side of the second dielectric substrate (211), the plurality of radiation rings (212a) are arranged in a radial direction from inside to outside, and the two radiation rings (212a) closest to the center are connected to each other. The multi-band antenna (1) is a three-band antenna, and the plurality of radiation branches (113) are respectively a first radiation branch (113a), a second radiation branch (113b) and a third radiation branch (113c).

2. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to claim 1, wherein, The first radiation branch (113a) is a trifurcated branch. The second radiation branch (113b) is a rectangular branch. The third radiation branch (113c) is a rectangular spiral branch. The first radiation branch (113a) is used for generating a low-frequency resonance point at a low frequency of 2.5 GHz.

3. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to claim 2, wherein, The second radiation branch (113b) is used for generating a high-frequency resonance point at a high frequency of 5 GHz. The third radiation branch (113c) is used for generating a medium-frequency resonance point at a medium frequency of 3.6 GHz. The third radiation branch (113c) is composed of a plurality of rectangular structures (113c1) rotated for multiple times, wherein the lengths of the plurality of rectangular structures (113c1) are different, and the widths of at least part of the rectangular structures (113c1) are different.

4. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to claim 3, wherein, The third radiation branch (113c) is composed of six rectangular structures (113c1) rotated at an angle of 90 degrees for five times.

5. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to claim 4, wherein, The coplanar structure (111) comprises a microstrip feed line structure (111a) and a rectangular metal ground (111b).

6. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to any one of claims 2 to 5, characterized in that, The rectangular metal ground (111b) is arranged on both sides of the microstrip feed line structure (111a) in the width direction, and the side edges of the rectangular metal ground (111b) are arranged flush with one end of the microstrip feed line structure (111a). The first radiation branch (113a) is connected to one end of the microstrip feed line structure (111a) away from the rectangular metal ground (111b). ​ The second radiation branch (113b) and the third radiation branch (113c) are connected on both sides of the microstrip feed line structure (111a) width direction, and the second radiation branch (113b) and the third radiation branch (113c) are located between the rectangular metal ground (111b) and the first radiation branch (113a).

7. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to claim 6, wherein, The length and width of the rectangular structure (113c1) connected with the microstrip feed line structure (111a) in the third radiation branch (113c) are greater than those of the remaining rectangular structures (113c1).

8. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to any one of claims 1 to 5, characterized in that, The radiation ring (212a) is provided with three, which are respectively: the first radiation ring (212a1), the second radiation ring (212a2) and the third radiation ring (212a3) whose radial dimensions decrease in turn; The first radiation ring (212a1), the second radiation ring (212a2) and the third radiation ring (212a3) generate three sections of in-phase reflection phase bandwidth between +90° to -90° respectively; The radially outer side of the first radiation ring (212a1) is a circular edge, and the radially inner side is a cross-step edge; The radially outer side and the radially inner side of the second radiation ring (212a2) are both cross-step edges; The radially outer side of the third radiation ring (212a3) is a cross-step edge, and the radially inner side is a circular edge; The radially outer side of the third radiation ring (212a3) is connected with the radially inner side of the second radiation ring (212a2).

9. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to claim 8, wherein, The radially outer side of the second radiation ring (212a2) is arranged in parallel with the radially inner side of the first radiation ring (212a1) with a spacing; In the second radiation ring (212a2), the shape of the radially outer side is consistent with that of the radially inner side, and the area surrounded by the radially inner side is 0.75 times the area surrounded by the radially outer side; The corner of the third radiation ring (212a3) based on the maximum size position of the radially outer side is connected with the radially inner side of the second radiation ring (212a2).

10. The AMC-based multi-band high-gain low specific absorption rate wearable antenna according to any one of claims 1 to 5, characterized in that, The first dielectric substrate (11) is a polyimide plate with a thickness of 0.13mm; The second dielectric substrate (211) is a polydimethylsiloxane with a thickness of 2mm; The working frequency bands of the multi-band antenna (1) are respectively: 2.36GHz-2.6GHz, 3.56GHz-3.68GHz, 4.91GHz-5.2GHz; The AMC reflection module (21) is arranged in a 3x3 array.

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