High-gain circularly polarized ultra-wideband flexible wearable siw antenna array and applications thereof

Abstract

The application discloses a high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array and application thereof, and belongs to the field of wearable antennas. The application comprises a central array element and a plurality of circumferential array elements uniformly distributed in a circumferential array around the central array element. The central array element and the circumferential array elements form a symmetrical arrangement structure to improve the overall gain of the array through the superposition effect of the array element radiation energy. Meanwhile, a rotating feeding mode is adopted for the central array element and all the circumferential array elements. During the feeding process, the excitation amplitudes of the central array element and the circumferential array elements are kept consistent, and the excitation phases are in a preset gradient distribution. The high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array and application thereof have the characteristics of ultra-wideband, circular polarization, miniaturization and high-gain directional radiation, and can realize high-speed data transmission, effective transmission and reception of external long-distance signals, alleviate polarization mismatch problems in dynamic scenes, facilitate seamless integration of clothing, and still maintain stable performance under the influence of human body load.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wearable antenna, and particularly relates to a high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array and application thereof. BACKGROUND

[0002] With the rapid penetration of human-centric wireless communication systems in the fields of health care, emergency support, military coordination, etc., the performance requirements for the core element, i.e., flexible wearable antenna, are becoming increasingly stringent. Such an antenna not only needs to adapt to the complex link architecture of wireless body area networks (WBANs) to meet the functional requirements of health monitoring data collection, emergency rescue signal interaction, military operation instruction coordination, etc., but also needs to take into account the practicality of wearable scenarios (such as small size, light weight, seamless integration with clothing), and even can be extended to fashion accessory product forms. Among them, the extracorporeal communication antenna, as the key interface for the interaction between WBANs and external devices, needs to meet four core performance indicators: first, it needs to have wideband working capability to support high-speed data transmission; second, it needs to have high-gain broadside radiation characteristics to ensure effective transmission and reception of extracorporeal long-distance signals; third, it needs to have polarization diversity function to alleviate the polarization mismatch problem caused by human dynamic movement; and fourth, it needs to have excellent flexibility and environmental adaptability, and still maintain stable performance under the condition of human body load (such as skin, fat, muscle, etc. tissue contact or antenna self-bending).

[0003] However, the special electromagnetic properties of human tissues (such as high dielectric constant, high loss) bring significant challenges to wearable antenna design. At present, the human-centric wireless communication system mainly uses the industrial, scientific and medical (ISM, Industrial, Scientific and Medical) frequency band, among which 2.4 GHz is a global universal frequency band (widely used in Bluetooth, Wi-Fi technology), 5.8 GHz frequency band is suitable for high-speed wireless communication scenarios in some countries / regions, and 915 MHz frequency band is commonly used in the Americas; however, the existing technical solutions are difficult to meet the above four requirements of the extracorporeal communication antenna in the frequency band.

[0004] From the existing technical path, the current wearable antenna is mainly developed through three types of schemes, and each has obvious defects: 1. Narrowband antenna scheme: This type of scheme is mostly designed for specific links, such as quasi-omnidirectional radiation structure for body surface links and directional radiation structure for body outside links; but the narrowband characteristic fundamentally cannot meet the wideband demand of the body outside communication system for high-speed data transmission, and it is difficult to adapt to the bandwidth demand in multiple service scenarios. 2. Wideband / ultra-wideband antenna scheme: Although this type of scheme greatly improves the bandwidth through structural optimization, it generally adopts single polarization design, which is prone to polarization mismatch during human body movement (such as limb swinging and posture change), resulting in a decline in communication quality; some schemes attempt to solve the mismatch problem through multi-polarization or circular polarization design, but they face the inherent contradiction between bandwidth and thickness - wider bandwidth needs to rely on multi-layer substrate structure, and multi-layer design increases the thickness and weight of the antenna, violating the lightweight and low-profile requirements of wearability. 3. Special structure optimization scheme: Some researches achieve multi-frequency band operation through fractal geometry structure, but such structure is prone to resonance frequency shift when loaded on a curved human body (such as fitting a curved limb), resulting in performance detuning; another scheme uses radio frequency (RF) switches to achieve polarization or frequency reconfiguration, which significantly increases system complexity and power consumption, conflicting with the low-energy consumption constraint of wearable devices; in addition, multi-input multi-output (MIMO) design can improve channel capacity, but it requires a large antenna aperture and strict element spacing, which is difficult to adapt to the miniaturization demand of wearable scenarios, and is limited in practical application.

[0005] In summary, the existing technology has not solved the core technical pain points in the field of wearable antennas: how to simultaneously achieve ultra-wideband, circular polarization (polarization diversity), and low-profile characteristics within the ISM frequency band, and ensure the performance stability and flexible wearability of the antenna under human body load (contacting human tissues or bending). SUMMARY

[0006] The purpose of the present application is to provide a high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array and its application, which solves the above technical problems.

[0007] To achieve the above purpose, the present application provides a high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array, which includes a central element and a plurality of circumferential elements uniformly distributed around the central element in a circumferential array. The central element and the circumferential elements form a symmetrical arrangement structure to improve the overall gain of the array through the superposition effect of element radiation energy.

[0008] At the same time, the central element and all circumferential elements adopt a rotating feeding method, and the excitation amplitudes of the central element and the circumferential elements are kept consistent during the feeding process, and the excitation phases are distributed in a preset gradient.

[0009] Preferably, the central array element and the circumferential array element both adopt a layered flexible structure, which comprises, from top to bottom, a radiation layer, an upper FPC flexible dielectric layer, a silicone rubber dielectric layer, a lower FPC flexible dielectric layer, and a ground layer; wherein the radiation layer integrates a polarization control component for realizing circular polarization, a bandwidth expansion component for expanding the working bandwidth, and a resonant cavity radiation part of a SIW resonant component for forming a directional radiation beam, each component realizing circular polarization, ultra-wideband, and directional radiation functions through resonant coupling and electromagnetic mode superposition.

[0010] Preferably, the polarization control component includes a cross-dipole composed of two pairs of radiation arms, each pair of radiation arms including mutually orthogonal long and short radiation arms, and a quarter-circle connecting segment for connecting the long and short radiation arms; one pair of radiation arms is connected with one end of the center conductor of the coaxial line, the other end of the center conductor is welded with the center pin of the SMA connector, and the other pair of radiation arms is connected with a ground short probe.

[0011] The orthogonal positions of the long and short radiation arms are located at the center of the radiation layer, so as to form an orthogonal electric field with a phase difference of 90° through the orthogonal long and short radiation arms, and meet the circular polarization forming condition in combination with the impedance matching effect of the quarter-circle connecting segment.

[0012] Preferably, the bandwidth expansion component includes four 1 / 4 circular parasitic patches arranged in the fan-shaped region surrounded by the long radiation arms, the short radiation arms, and the quarter-circle connecting segment, the parasitic patches excite their own resonances through electromagnetic coupling with the cross-dipole.

[0013] Preferably, the resonant cavity radiation part of the SIW resonant component includes a plurality of rectangular slots uniformly distributed in a circumferential array around the center of the radiation layer, one end of the rectangular slot is connected with the 1 / 4 circular parasitic patch, and the other end extends to the edge of the radiation layer.

[0014] Preferably, the upper and lower FPC flexible dielectric layers both adopt polyimide material with a dielectric constant of 3.5 and a loss tangent of 0.004, to play a supporting and insulating role.

[0015] The silicone rubber dielectric layer has a dielectric constant of 3.2 and a loss tangent of 0.02, and a metallized via of the SIW resonant component is embedded in the silicone rubber dielectric layer.

[0016] The silicone rubber dielectric layer, together with the upper and lower FPC flexible dielectric layers, forms a low-loss flexible substrate, and provides a structural carrier for the metallized via.

[0017] The ground layer is an etched metal floor, one end of the outer conductor of the coaxial line is welded with the etched metal floor, and the other end of the outer conductor is welded with the outer pin of the SMA joint to realize signal input.

[0018] Preferably, the characteristic impedance of the coaxial line is 50Ω.

[0019] Preferably, the circumferential side of the central element is provided with 6 circumferential elements, and the 6 circumferential elements are distributed at the vertices of a regular hexagon around the periphery of the central element, and are sequentially located at the 0°, 60°, 120°, 180°, 240° and 300° directions of the radial direction of the central element, and taking the structure of the central element as the reference, the 6 circumferential elements are rotated counterclockwise by 90°, 150°, 210°, 270°, 330° and 30° around the center of the circumferential element respectively, so as to cooperate with the excitation phases of 0°, 90°, 150°, 210°, 270°, 330° and 30°.

[0020] Preferably, the resonant cavity radiation part includes 8 rectangular slots uniformly distributed in a circumferential array around the center of the radiation layer.

[0021] The application of the high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array on the surface of the human body has the following advantages: under the condition of loading on the human body plane or loading with a bending radius of 150mm, the impedance bandwidth of the high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array is ≥26.3%, the axial ratio is ≤3dB, and the unit gain is ≥5dBi.

[0022] Therefore, the application of the high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array has the following advantages:

[0023] 1. Ultra-wideband characteristics, meeting high-speed data transmission: through the cooperation of the cross-dipole, four 1 / 4 circular parasitic patches and the SIW resonant cavity with 8 equally spaced rectangular slots, wide impedance bandwidth is realized, which can support ultra-high-speed data transmission and adapt to the high-speed data interaction demand of wireless body area network extracorporeal communication.

[0024] 2. Circular polarization function, alleviating polarization mismatch: the cross-dipole is composed of orthogonal long and short radiation arms and a quarter circular ring connection section, which can generate a phase difference of 90° of orthogonal electric field, and through array rotation feeding (each array element excitation phase presents a preset gradient) optimization, 3dB axial ratio bandwidth is realized, which can effectively alleviate the polarization mismatch problem caused by human dynamic movement (such as limb swing and posture change), and ensure communication stability.

[0025] 3. High-gain directional radiation, realizing long-distance signal transceiving: 7 array elements are arranged at the end points of a regular hexagon and the center, and the radiation energy is superimposed to improve the gain (the unit gain is > 5dBi in the working bandwidth, and the array gain is > 10dBi); at the same time, the SIW resonant cavity restricts the electromagnetic wave propagation direction through the metalized via and the etched gap, forms a directional beam, and can realize effective transmission and reception of long-distance signals outside the body, and adapts to the long-distance communication needs of health monitoring, emergency rescue and the like scenes;

[0026] 4. Flexible wearable, adapting to human body scenes and stable performance: the dielectric layer adopts PI material FPC (dielectric constant 3.5) and silicone rubber (dielectric constant 3.2), and the conductive part is flexible material, the antenna can be bent (such as bending radius 150mm) and is small in size and light in weight, and can be seamlessly integrated with clothes; at the same time, under the conditions of human body plane loading or bending loading, the changes of the core performances such as antenna impedance bandwidth, axial ratio and gain are small, so that the stable working state can be maintained.

[0027] The technical solutions of the present application will be further described in detail below by means of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a schematic diagram of the arrangement of the high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array of the present application;

[0029] Figure 2 It is a schematic diagram of the array element structure of the high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array of the present application, wherein (a) is a perspective view, (b) is a top view, and (c) is a side view;

[0030] Figure 3 It is a schematic diagram of the application of the high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array of the present application, wherein (a) is a plane loading schematic diagram, and (b) is a bending loading schematic diagram;

[0031] Figure 4 It is the radiation pattern of the array element at each frequency point described in the example, wherein (a) is the xoz plane radiation pattern of the array element at 5.30GHz, (b) is the xoz plane radiation pattern of the array element at 5.55GHz, (c) is the xoz plane radiation pattern of the array element at 5.80GHz; (d) is the yoz plane radiation pattern of the array element at 5.30GHz, (e) is the yoz plane radiation pattern of the array element at 5.55GHz, and (f) is the yoz plane radiation pattern of the array element at 5.80GHz;

[0032] Figure 5 It is a reflection coefficient curve diagram of the array element described in the example;

[0033] Figure 6The axial ratio curve of the array element described in the embodiment;

[0034] Figure 7 The gain curve of the antenna array described in the embodiment;

[0035] Figure 8 The antenna array performance curve described in the embodiment, wherein (a) is a reflection coefficient and isolation curve, (b) is an axial ratio curve, and (c) is a gain curve; in Figure 8 In (a) of the figure, it should be noted that S11 represents the reflection coefficient of port 1 when port 2 is matched; S22 represents the reflection coefficient of port 2 when port 1 is matched; S12 represents the reverse transmission coefficient of port 2 to port 1 when port 1 is matched; S23 represents the reverse transmission coefficient of port 3 to port 2 when port 2 is matched; S24 represents the reverse transmission coefficient of port 4 to port 2 when port 2 is matched; S25 represents the reverse transmission coefficient of port 5 to port 2 when port 2 is matched; wherein port 1 is the center element, and ports 2-5 are four circumferential elements;

[0036] Figure 9 The antenna array radiation pattern of each frequency point described in the embodiment, wherein (a) is the xoz plane radiation pattern of the antenna array at 5.30 GHz, (b) is the xoz plane radiation pattern of the antenna array at 5.55 GHz, (c) is the xoz plane radiation pattern of the antenna array at 5.80 GHz; (d) is the yoz plane radiation pattern of the antenna array at 5.30 GHz, (e) is the yoz plane radiation pattern of the antenna array at 5.55 GHz, and (f) is the yoz plane radiation pattern of the antenna array at 5.80 GHz.

[0037] 1, radiation layer; 11, long radiation arm; 12, short radiation arm; 13, quarter circular ring connecting section; 14, parasitic patch; 15, rectangular slot; 2, upper layer FPC flexible dielectric layer; 3, silicone rubber dielectric layer; 4, lower layer FPC flexible dielectric layer; 5, ground layer; 6, ground short circuit probe; 7, center conductor; 8, metallized via. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the embodiments of the present application are further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present application and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application. The examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout.

[0039] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0040] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0041] like Figures 1-3 As shown, the high-gain circularly polarized ultrawideband flexible wearable SIW antenna array includes a central array element and multiple circumferential array elements uniformly distributed in a circular array around the central array element. The central array element and the circumferential array elements form a symmetrical arrangement structure to improve the overall gain of the array through the superposition effect of the radiated energy of the array elements. At the same time, the central array element and all circumferential array elements are fed by a rotating method. During the feeding process, the excitation amplitude of the central array element and the circumferential array elements are kept consistent, and the excitation phase is distributed with a preset gradient. The polarization interference is canceled by phase coordination, thereby improving the axial ratio performance and radiation stability of the array.

[0042] Both the central array element and the circumferential array element adopt a layered flexible structure. The layered flexible structure includes, from top to bottom, a radiation layer 1, an upper FPC flexible dielectric layer 2, a silicone rubber dielectric layer 3, a lower FPC flexible dielectric layer 4, and a grounding layer 5. Among them, the radiation layer 1 integrates a polarization control component for realizing circular polarization, a bandwidth expansion component for expanding the working bandwidth, and the resonant cavity radiation part of the SIW resonant component for forming a directional radiation beam. Each component achieves circular polarization, ultra-wideband, and directional radiation functions through resonant coupling and electromagnetic mode superposition.

[0043] The polarization control assembly includes a cross dipole consisting of two radiating arms. Each radiating arm comprises a long radiating arm 11 and a short radiating arm 12 that are orthogonal to each other, and a quarter-circular ring connecting segment 13 for connecting the long radiating arm 11 and the short radiating arm 12. One radiating arm is connected to one end of the central conductor 7 of the coaxial line, and the other end of the central conductor 7 is soldered to the central pin of the SMA connector. The other radiating arm is connected to the grounding short-circuit probe 6. The orthogonal positions of the long radiating arm 11 and the short radiating arm 12 are located at the center of the radiating layer 1, thereby forming an orthogonal electric field with a phase difference of 90° through the orthogonal long radiating arm 11 and the short radiating arm 12. Combined with the impedance matching effect of the quarter-circular ring connecting segment 13, the conditions for circular polarization formation are met, thereby realizing the circular polarization function of the antenna and alleviating the polarization mismatch problem in the dynamic motion scenario of the human body.

[0044] The bandwidth expansion component includes four 1 / 4 circular parasitic patches 14 arranged in the sector area surrounded by the long radiation arm 11, the short radiation arm 12 and the quarter circular connecting segment 13. The parasitic patches 14 are excited to resonate by electromagnetic coupling with the cross dipole, and form superposition with the resonant mode of the SIW resonant component and the cross dipole, further expanding the working bandwidth of the antenna to meet the demand of ultra-wideband data transmission.

[0045] The resonant cavity radiation part of the SIW resonant component includes a plurality of rectangular slots 15 evenly distributed in a circumferential array around the center of the radiation layer 1. One end of the rectangular slot 15 is connected with the 1 / 4 circular parasitic patch 14, and the other end extends to the edge of the radiation layer 1.

[0046] The upper FPC flexible dielectric layer 2 and the lower FPC flexible dielectric layer 4 are both made of polyimide material, with a dielectric constant of 3.5 and a loss tangent of 0.004, to play a supporting and insulating role.

[0047] The silicon rubber dielectric layer 3 has a dielectric constant of 3.2 and a loss tangent of 0.02, and the metallized via 8 of the SIW resonant component is embedded in the silicon rubber dielectric layer 3.

[0048] The silicon rubber dielectric layer 3, the upper FPC flexible dielectric layer 2 and the lower FPC flexible dielectric layer 4 together form a low-loss flexible substrate, which provides a structural carrier for the metallized via 8 and enhances the flexible adaptability of the antenna.

[0049] The ground layer 5 is an etched metal floor, which is welded to one end of the outer conductor of the coaxial line and the outer pin of the SMA connector to realize signal input. At the same time, through the reflection of electromagnetic waves, the SIW resonant component realizes the function of directional radiation.

[0050] The characteristic impedance of the coaxial line is 50Ω.

[0051] The circumferential side of the central element is provided with six circumferential elements, and the six circumferential elements are distributed in the vertices of a regular hexagon along the periphery of the central element, and are located at 0°, 60°, 120°, 180°, 240° and 300° positions of the central element in sequence, and with the structure of the central element as a reference, the six circumferential elements are rotated counterclockwise by 90°, 150°, 210°, 270°, 330° and 30° around their own centers respectively, so as to cooperate with the excitation phases of 0°, 90°, 150°, 210°, 270°, 330° and 30° in sequence, further optimize the polarization consistency of the whole array, and ensure that there is no polarization interference when the radiation energy of each element is superimposed, so as to stably improve the directional radiation gain and axial ratio performance of the array.

[0052] The resonant cavity radiation part includes eight rectangular slots 15 evenly distributed in a circumferential array around the center of the radiation layer 1.

[0053] Application of high-gain circularly polarized ultrawideband flexible wearable SIW antenna array on human body surface: Under human body plane loading or 150mm bending radius loading conditions, the high-gain circularly polarized ultrawideband flexible wearable SIW antenna array has an impedance bandwidth ≥26.3%, axial ratio ≤3dB, and unit gain ≥5dBi.

[0054] Example

[0055] In this embodiment, the high-gain circularly polarized ultrawideband flexible wearable SIW antenna array described in this invention is adopted. Its basic antenna array element (i.e., the single structure of the central array element and the circumferential array element) adopts a layered flexible structure, which includes, from top to bottom, a radiating layer, an upper FPC flexible dielectric layer, a silicone rubber dielectric layer, a lower FPC flexible dielectric layer and a grounding layer.

[0056] Furthermore, the specific arrangement and feeding method of the high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array are as follows:

[0057] Array element arrangement: The 7 antenna array elements are arranged with the endpoints and center of a regular hexagon. Array element #1 (center array element) is located at the axis, and array elements #2 to #7 (circumferential array elements) are located at 0°, 60°, 120°, 180°, 240° and 300° azimuths of the center array element, respectively.

[0058] Array element rotation: Taking array element #1 as a reference, array elements #2 to #7 rotate counterclockwise around their own center by 90°, 150°, 210°, 270°, 330°, and 30° respectively;

[0059] Rotational feeding: The excitation amplitudes of the 7 array elements are all equal, and the excitation phases are 0°, 90°, 150°, 210°, 270°, 330°, and 30° respectively.

[0060] like Figures 4-7 As shown, the performance parameters of the array elements are as follows:

[0061] Reflection coefficient and isolation: Element #1 (center element): impedance bandwidth 4.52~6.37GHz, fractional bandwidth 40.0%; Element #2 (circumferential element, with symmetry): impedance bandwidth 4.60~6.35GHz, fractional bandwidth 32.0%;

[0062] Isolation: The isolation between array element #1 and array element #2 is greater than 26dB, and the isolation between array element #2 and array elements #3~#5 is greater than 27dB, 31dB, and 30dB respectively, with low crosstalk between ports.

[0063] Axial ratio: The axial ratio of the antenna array is less than 3dB in the simulation range, and the axial ratio bandwidth covers the narrowest impedance bandwidth (4.60~6.35GHz, fractional bandwidth 32.0%).

[0064] Gain: The gain of the array is greater than 10dBi in the operating bandwidth, realizing high gain characteristics.

[0065] Radiation pattern: At 5.20GHz, 5.55GHz and 5.80GHz, the array radiation beam is a directional beam; the left-handed circular polarization (LHCP) is the main polarization, and the right-handed circular polarization (RHCP) is the cross-polarization, with a difference of more than 10dB, and the polarization is stable.

[0066] Table 1 Array element structure parameters (unit: mm)

[0067]

[0068] It should be noted that in Table 1, , and respectively represent the radius of the radiation layer, the outer radius of the parasitic patch and the inner radius of the parasitic patch; , and respectively represent the length of the long radiation arm, the short radiation arm and the rectangular slot; , and respectively represent the width of the long radiation arm, the short radiation arm and the rectangular slot; and respectively represent the thickness of the silicone rubber dielectric layer and the upper layer FPC flexible dielectric layer.

[0069] The high-gain circularly polarized ultra-wideband flexible wearable SIW antenna array configured as shown in Table 1 is applied to two scenarios of plane loading and bending loading, wherein the bending loading considers bending along the x-axis and bending along the y-axis, and the bending radius is 150mm. In the 5.85GHz frequency band of the target application, the human tissue is divided into three layers from top to bottom, and the electrical parameters are as follows: skin: relative permittivity 35.36, bulk conductivity 3.46, loss tangent 0.32; fat: relative permittivity 4.98, bulk conductivity 0.27, loss tangent 0.18; muscle: relative permittivity 48.89, bulk conductivity 4.61, loss tangent 0.31.

[0070] The results are as follows: Figure 8 and Figure 9As shown, (I) reflection coefficient (-10 dB impedance bandwidth): free space: impedance bandwidth 4.71~6.34 GHz, fractional bandwidth 29.5%; human body plane loading: impedance bandwidth 4.71~6.35 GHz, fractional bandwidth 29.7%; human body bending along x-axis (150 mm radius): impedance bandwidth 4.65~6.08 GHz, fractional bandwidth 26.7%; human body bending along y-axis (150 mm radius): impedance bandwidth 4.63~6.03 GHz, fractional bandwidth 26.3%. It can be seen that the impedance bandwidth consistency of the array element under free space and human body loading is good.

[0071] (II) Axial ratio (3 dB axial ratio bandwidth): free space: axial ratio bandwidth 5.22~5.92 GHz, fractional bandwidth 12.3%; human body plane loading: axial ratio bandwidth 5.23~5.95 GHz, fractional bandwidth 12.9%; human body bending along x-axis (150 mm radius): axial ratio bandwidth 5.17~5.97 GHz, fractional bandwidth 14.4%; human body bending along y-axis (150 mm radius): axial ratio bandwidth 5.25~5.99 GHz, fractional bandwidth 13.2% (with slight fluctuations). The axial ratio bandwidth consistency of the array element under different scenarios is excellent, meeting the circular polarization performance requirements.

[0072] (III) Gain: the gain consistency of the array element under free space and human body loading conditions is good, and the gain is greater than 5 dBi within the working bandwidth.

[0073] (Four) radiation pattern: select 5.20 GHz, 5.55 GHz, 5.80 GHz in the 3 dB axial ratio bandwidth to analyze: the maximum radiation direction in the xoz plane and yoz plane is 0°, realizing directional radiation; left-handed circular polarization is the main polarization, right-handed circular polarization is cross polarization, and the difference between the two is greater than 10 dB, with excellent polarization stability.

[0074] It can be seen that the antenna array has excellent consistency and stability of core performance parameters in the free space, human body plane loading and bending loading (along the x-axis, along the y-axis, bending radius 150mm) scenarios: first, the -10dB impedance bandwidth of the antenna unit is ≥29.5% in the free space and human body plane loading, and ≥26.3% in the bending loading; at the array level, the fractional bandwidth of the central element impedance bandwidth is 40.0%, the fractional bandwidth of the circumferential element is ≥32.0%, and the isolation between elements is >26dB, meeting the requirements of ultra-wideband data transmission and multi-element cooperative work. Second, the 3dB axial ratio bandwidth of the antenna unit covers the 5.17~5.99GHz interval in each scenario, and the array axial ratio bandwidth is <3dB in the simulation range, with high circular polarization purity, effectively alleviating the polarization mismatch caused by human dynamic movement. Third, the antenna unit gain is >5dBi within the working bandwidth, the array gain is >10dBi, and the maximum radiation direction is stably directed to 0° in the xoz and yoz planes, realizing directional high-gain radiation and adapting to long-distance signal transmission in vitro. Fourth, the left-handed circular polarization is the main polarization, and the right-handed circular polarization is the cross-polarization, with an isolation >10dB, and excellent polarization stability.

[0075] In summary, the antenna array described in the present application has excellent performance stability in ultra-wideband, circular polarization, high gain and human body load, and can efficiently adapt to the multi-dimensional requirements of the human-centered wireless communication system in vitro communication scenarios (such as health monitoring, emergency rescue, etc.).

[0076] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements also cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A high-gain circularly polarized ultrawideband flexible wearable SIW antenna array, characterized in that: It includes a central array element and multiple circumferential array elements evenly distributed in a circular array around the central array element. The central array element and the circumferential array elements form a symmetrical arrangement structure to enhance the overall gain of the array through the superposition effect of the radiated energy of the array elements. Meanwhile, a rotating feeding method is used for the central array element and all circumferential array elements. During the feeding process, the excitation amplitude of the central array element and the circumferential array elements is kept consistent, and the excitation phase is distributed in a preset gradient. Both the central array element and the circumferential array element adopt a layered flexible structure. The layered flexible structure includes, from top to bottom, a radiation layer, an upper FPC flexible dielectric layer, a silicone rubber dielectric layer, a lower FPC flexible dielectric layer, and a grounding layer. Among them, the radiation layer integrates a polarization control component for achieving circular polarization, a bandwidth expansion component for expanding the working bandwidth, and the resonant cavity radiation part of the SIW resonant component for forming a directional radiation beam. Each component achieves circular polarization, ultra-wideband, and directional radiation functions through resonant coupling and electromagnetic mode superposition. The polarization control assembly includes a cross dipole consisting of two radiating arms, each radiating arm comprising a long radiating arm and a short radiating arm that are orthogonal to each other, and a quarter-circular connecting segment for connecting the long radiating arm and the short radiating arm; one radiating arm is connected to one end of the center conductor of the coaxial line, the other end of the center conductor is soldered to the center pin of the SMA connector, and the other radiating arm is connected to the ground short-circuit probe. The orthogonal positions of the long and short radiation arms are located at the center of the radiation layer, thus forming an orthogonal electric field with a phase difference of 90° through the orthogonal long and short radiation arms. Combined with the impedance matching effect of the quarter-circular ring connecting section, the conditions for circular polarization formation are met. The bandwidth extension component includes four 1 / 4 circular parasitic patches located in a fan-shaped area enclosed by the long radiating arm, the short radiating arm, and the quarter-circular connecting section. The parasitic patches generate electromagnetic coupling with the cross dipole, which excites the parasitic patches to resonate on their own. The resonant cavity radiation section of the SIW resonant component includes multiple rectangular slots evenly distributed in a circular array around the center of the radiation layer. One end of each rectangular slot is connected to a 1 / 4 circular parasitic patch, and the other end extends towards the edge of the radiation layer.

2. The high-gain circularly polarized ultrawideband flexible wearable SIW antenna array according to claim 1, characterized in that: Both the upper and lower FPC flexible dielectric layers are made of polyimide with a dielectric constant of 3.5 and a loss tangent of 0.004, serving as support and insulation. The silicone rubber dielectric layer has a dielectric constant of 3.2 and a loss tangent of 0.02, and its interior is embedded with metallized vias for SIW resonant components; The silicone rubber dielectric layer, together with the upper FPC flexible dielectric layer and the lower FPC flexible dielectric layer, constitutes a low-loss flexible substrate, providing a structural carrier for metallized vias; The ground plane is an etched metal ground plane, which is soldered to one end of the outer conductor of the coaxial line, and the other end of the outer conductor is soldered to the outer pin of the SMA connector to realize signal input.

3. The high-gain circularly polarized ultrawideband flexible wearable SIW antenna array according to claim 2, characterized in that: The characteristic impedance of the coaxial cable is 50Ω.

4. The high-gain circularly polarized ultrawideband flexible wearable SIW antenna array according to claim 1, characterized in that: Six circumferential array elements are arranged on the circumferential side of the central array element, and the six circumferential array elements are distributed in a regular hexagonal shape around the periphery of the central array element. They are located at 0°, 60°, 120°, 180°, 240° and 300° radially from the central array element. With the structural orientation of the central array element as a reference, the six circumferential array elements rotate counterclockwise around their own center by 90°, 150°, 210°, 270°, 330° and 30° respectively, so as to coordinate with the excitation phases of 0°, 90°, 150°, 210°, 270°, 330° and 30° respectively.

5. The high-gain circularly polarized ultrawideband flexible wearable SIW antenna array according to claim 4, characterized in that: The resonant cavity radiation section includes eight rectangular slots evenly distributed in a circular array around the center of the radiation layer.

6. The application of the high-gain circularly polarized ultrawideband flexible wearable SIW antenna array as described in any one of claims 1-5 on the human body surface, characterized in that: Under human body plan loading or 150mm bending radius loading conditions, the high-gain circularly polarized ultrawideband flexible wearable SIW antenna array has an impedance bandwidth of ≥26.3%, an axial ratio of ≤3dB, and a unit gain of ≥5dBi.

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