Miniaturized five-frequency-band wearable antenna based on flexible fabric and manufacturing method thereof

Abstract

The invention belongs to the technical field of wearable antennas, and particularly relates to a miniaturized five-frequency-band wearable antenna based on flexible fabric and a manufacturing method thereof.The miniaturized five-frequency-band wearable antenna comprises a radiation patch, a first substrate, a second substrate and a grounding panel, and the second substrate is provided with a feed structure; the feed structure is provided with two short-circuit pins and a square notch resonance ring, the multiband wearable antenna has five working bands, and each working band has an edge emission directional diagram pointing to the normal direction. The preparation method comprises the following steps: step 1, designing the radiation patch of the microstrip patch antenna according to design requirements; and 2, selecting a corresponding feed mode and designing a feed structure according to the size of the radiation patch and a design target. The multiband wearable antenna designed by the invention has the advantages of multiple frequency bands, miniaturization, low profile, low SAR (Synthetic Aperture Radar), easiness in manufacturing, simple structure and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of wearable antennas, and particularly relates to a miniaturized five-band wearable antenna based on flexible fabric and a manufacturing method thereof. Background Art

[0002] In the context of the information age, wearable devices have received extensive attention due to their convenience and functional diversity. As a key part connecting these devices to the wireless network, wearable antennas must meet several requirements, including light weight, soft texture, miniaturization, low profile, and good biocompatibility and electromagnetic safety. At the same time, the demand for frequency bands in modern application scenarios is also becoming more and more diverse. Multi-band antennas can support communication protocols of different frequencies, enabling devices to flexibly cope with different network environments and providing more stable connections. And this integrated design can eliminate the mutual coupling problem of the multi-antenna structure and reduce the size and weight of the device, meeting the requirements of modern wearable devices for portability. However, achieving broadside radiation patterns in multiple frequency bands within a limited size is one of the main challenges for wearable antennas.

[0003] Therefore, it is necessary to provide a miniaturized five-band wearable antenna based on flexible textile and a manufacturing method thereof to solve the above technical problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a miniaturized five-band wearable antenna based on flexible fabric and a manufacturing method thereof, which can achieve broadside radiation patterns in five frequency bands within a limited size.

[0005] The technical solutions adopted by the present invention are specifically as follows:

[0006] A miniaturized five-band wearable antenna based on flexible fabric includes a radiation patch, a first substrate, a second substrate, and a ground plane. A feeding structure is provided on the second substrate, and two shorting pins and a square slot resonator are provided on the feeding structure. The five-band wearable antenna realizes five operating frequency bands under the conditions of smaller size and profile, and each operating frequency band has a broadside direction pattern pointing to the normal direction.

[0007] A manufacturing method of a miniaturized five-band wearable antenna based on flexible fabric, the manufacturing method includes the following steps:

[0008] Step 1: Design the radiation patch of the microstrip patch antenna according to the design requirements;

[0009] The said Step 1 specifically includes the following steps:

[0010] Step 101: Design the size of the radiation patch of the rectangular microstrip patch antenna at the corresponding center frequency point;

[0011] Step 102: Cut a U-shaped slot on the microstrip patch;

[0012] Step 103: Cut a pair of symmetric J-shaped slots inside the U-shaped slot.

[0013] Step 2: Select the corresponding feeding method and design the feeding structure according to the size of the radiating patch and the design objectives.

[0014] The said Step 2 includes the following steps:

[0015] Step 201: Based on the microstrip patch in Step 1, select the adjacent coupling feeding method according to the factors of bandwidth and the mode excited by the feeding.

[0016] Step 202: Design a T-shaped feeding structure according to the adjacent coupling feeding method.

[0017] Step 203: Add a pair of shorting pins at specific positions on the T-shaped feeding structure.

[0018] Step 204: Add a square-notch resonator ring at specific positions on the T-shaped feeding structure.

[0019] The technical effects achieved by the present invention are as follows:

[0020] 1. The present invention adopts the form of a microstrip patch antenna. The existence of its fully grounded plane enables the antenna to have a high front-to-back ratio, minimizing the radiation of the antenna to the human body while reducing the influence of the human body on the antenna performance, and having the advantage of low SAR.

[0021] 2. Cut a pair of J-shaped slots inside the traditional U-shaped slot, and excite three modes of the patch through the coupling feeding method, thereby generating three resonant frequencies. This operation of improving the U-shaped slot can reduce the resonant frequencies of the antenna, playing a role in miniaturization to a certain extent. At the same time, the existence of the J-shaped slots enables the currents inside the U-shaped slot of the patch to cancel each other out in the higher-order modes, thus improving the radiation pattern at the frequencies corresponding to the higher-order modes.

[0022] 3. Add two shorting pins on the T-shaped feeding structure, introducing additional inductive components, which are mutually coupled with the gap capacitance between the T-shaped branch and the patch, adding a new LC resonant circuit to the antenna, triggering the splitting of the original mode, and introducing a mode similar to it near the second resonant mode of the microstrip patch, thereby realizing the four-band operation of the antenna.

[0023] 4. Add a square-notch resonator ring on the shorted T-shaped feeding structure, which is mutually coupled with the higher-order mode of the patch to form a hybrid resonant mode, and as a distributed capacitance, cancels the excessive inductance introduced by the shorting pins in the high-frequency part, optimizing the impedance matching in the high-frequency part, thereby realizing the five-band operation of the antenna.

[0024] In summary, the five-band wearable antenna designed by the present invention has many advantages such as a large number of frequency bands, miniaturization, low profile, low SAR, easy manufacturing, and simple structure, so as to meet the requirements of high-speed communication and long-distance communication in mountainous and dense forest environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the structural diagram of the microstrip patch antenna; Figure 1 in which (a) three-dimensional view, (b) side view, (c) patch size, (d) feed structure size;

[0026] Figure 2 is the simulated curve of the reflection coefficient of four antennas during the design evolution process;

[0027] Figure 3 is the current distribution diagram of four antennas during the design evolution process;

[0028] Figure 4 is the simulated and measured diagram of the reflection coefficient of the wearable antenna under free space or human body loading;

[0029] Figure 5 is the radiation pattern of the wearable antenna under free space or human body loading; Figure 5 in which (a) 1.13 GHz, (b) 1.62 GHz, (c) 2.06 GHz, (d) 2.62 GHz, (e) 2.86 GHz; DETAILED DESCRIPTION OF THE INVENTION

[0030] In order to make the purpose and advantages of the present invention more clear, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific implementation manners of the present invention, and does not strictly limit the specific protection scope claimed by the present invention.

[0031] As Figure 1 shown, a miniaturized five-band wearable antenna based on a flexible fabric includes a radiation patch, a first substrate, a second substrate, and a ground plane. A feed structure is provided on the second substrate, and two shorting pins and a square-notch resonator are provided on the feed structure. The five-band wearable antenna realizes five working frequency bands under the conditions of a smaller size and profile, and each working frequency band has an edge radiation pattern pointing in the normal direction. The structural diagram of the microstrip patch is as Figure 1 shown. It should be noted that Figure 1 substrate 1 in Figure 1 is the first substrate, and

[0032] A manufacturing method of a miniaturized five-band wearable antenna based on a flexible fabric, the preparation method includes the following steps:

[0033] Step 1: Design the radiation patch of the microstrip patch antenna according to the design requirements.

[0034] The said Step 1 includes the following specific steps:

[0035] Step 101: Design the size of the radiation patch of the rectangular microstrip patch antenna at the corresponding center frequency point.

[0036] Step 102: Cut a U-shaped slot on the microstrip patch.

[0037] Step 103: Cut a pair of symmetric J-shaped slots inside the U-shaped slot.

[0038] In the simulation, Kevlar fiber fabric is used as the substrate of the designed patch antenna, and its measured relative permittivity ε r = 2.1 and dielectric loss tangent tanδ = 0.025 in the frequency band of 1 - 3 GHz. The microstrip patch is made of conductive fabric with copper and nickel coated on its surface, and the surface impedance is 0.03 Ω / sq. The detailed size parameters of the microstrip patch are shown in Table 1.

[0039] Table 1: Size parameter table of the designed multi-band antenna (unit: mm)

[0040]

[0041] Step 2: Select the corresponding feeding method and design the feeding structure according to the size of the radiation patch and the design goal.

[0042] The said Step 2 includes the following steps:

[0043] Step 201: Based on the microstrip patch in Step 1, select the near-field coupling feeding method according to the factors of bandwidth and the mode excited by the feeding.

[0044] Step 202: Design a T-shaped feeding structure according to the near-field coupling feeding method.

[0045] Step 203: Add a pair of shorting pins to the T-shaped feeding structure.

[0046] Step 204: Add a square-notch resonator ring to the T-shaped feeding structure.

[0047] The thicknesses of the first substrate and the second substrate are H 1 = 1.8 mm and H 2 = 1.8 mm respectively. The two shorting pins are made of copper wires with a diameter of 0.6 mm. The detailed size parameters of the feeding structure are shown in Table 1.

[0048] In the present invention, Figure 2The simulation curves of the reflection coefficients of four antennas during the design process are shown. It can be seen that the resonant frequencies of the "U-shaped slot_T-shaped feed" antenna are 1.25 GHz, 2.07 GHz, and 3.05 GHz, as Figure 2 indicated by the middle dotted line. By improving the operation of the U-shaped slot, the three resonant frequencies of the antenna are reduced to 1.19 GHz, 1.91 GHz, and 2.64 GHz respectively, as Figure 2 indicated by the middle dash-dotted line. At the same time, the presence of the J-shaped slot cancels out the currents inside the U-shaped slot in the higher-order modes of the patch, thereby improving the radiation pattern at the frequencies corresponding to the higher-order modes. Adding a shorting pin to the T-shaped feed structure enables the antenna to have a new resonant frequency, that is, a total of four resonant frequencies, which are 1.11 GHz, 1.63 GHz, 2.16 GHz, and 2.73 GHz respectively, as Figure 2 shown by the double dash-dotted line in Figure 2 . Adding a notched square resonator ring to the shorted T-shaped feed structure increases new resonant frequencies again, that is, a total of five resonant frequencies, which are 1.12 GHz, 1.60 GHz, 2.06 GHz, 2.62 GHz, and 2.86 GHz respectively, as

[0049] In the present invention, Figure 3 the current distribution diagrams of the above four antennas are shown, which can illustrate the working principle of the antennas. It can be seen from the figure that the "U-shaped slot_T-shaped feed" antenna is excited to three working modes, corresponding to the cases where the current path lengths are one and a half wavelengths, two and a half wavelengths, and three and a half wavelengths respectively. After improving the U-shaped slot, the three current paths of the antenna are all extended, so the three resonant frequencies of the antenna are reduced. By adding a shorting pin, an inductive component is introduced, which is mutually coupled with the gap capacitance between the T-shaped branch and the patch, adding a new LC resonant circuit to the antenna, triggering the splitting of the original mode (mode two), and adding a new resonant frequency to the antenna. The role of the resonator ring is similar to that of the shorting pin. It is mutually coupled with the higher-order mode of the patch to form a mixed resonant mode, triggering the splitting of the original mode three. At the same time, the resonator ring acts as a distributed capacitor, canceling out the inductance introduced by the shorting pin at high frequencies and forming a good impedance match near the frequency corresponding to mode three, thereby adding another new operating frequency.

[0050] In the present invention, Figure 4Simulated and measured curves of the reflection coefficient of the proposed wearable antenna in free space or under human loading. In the free space environment, the frequency bands with measured reflection coefficients lower than -10 dB are: 1.125 - 1.148 GHz, 1.565 - 1.660 GHz, 2.002 - 2.116 GHz, 2.578 - 2.660 GHz, and 2.847 - 2.905 GHz, and the corresponding relative bandwidths are: 2.02%, 5.89%, 5.54%, 3.13%, and 2.02% respectively; under human loading conditions, the frequency bands with measured reflection coefficients lower than -10 dB are 1.131 - 1.149 GHz, 1.576 - 1.666 GHz, 2.019 - 2.127 GHz, 2.583 - 2.659 GHz, and 2.851 - 2.905 GHz, and the corresponding relative bandwidths are 1.58%, 5.55%, 5.21%, 2.90%, and 1.87% respectively. It can be seen that the measured values of the reflection coefficient of the proposed multi-band antenna are in good agreement with the simulated values. At the same time, the measured and simulated values under human loading conditions are very close to the corresponding values in free space.

[0051] In the present invention, Figure 5 The radiation pattern of the proposed wearable antenna in free space or under human loading. It can be seen that the proposed antenna can achieve a directional broadside radiation pattern in all five frequency bands. Tables 2 and 3 are the simulated and measured gain values of the proposed antenna in free space and under human loading conditions respectively. The measurement and simulation show good agreement. Table 4 is the average SAR simulation value of the proposed antenna in each frequency band, which is lower than the national security standard of 2 W / kg (average of 10 g tissue).

[0052] Table 2: Gain table of the wearable antenna in each frequency band in free space

[0053]

[0054] Table 3: Gain table of the wearable antenna in each frequency band under human loading

[0055]

[0056] Table 4: Average SAR simulation value table of the proposed antenna in each frequency band

[0057]

[0058] In summary, the five-band wearable antenna designed in the present invention has many advantages such as a large number of frequency bands, miniaturization, low profile, low SAR, easy to manufacture, and simple structure, so as to meet the requirements of high-speed communication and long-distance communication in mountainous and forested environments.

[0059] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. The structures, devices, and operation methods not specifically described and explained in the present invention are implemented according to the conventional means in the art without special explanation and limitation.

Claims

1. A miniaturized five-band wearable antenna based on flexible fabric, characterized by: It includes a radiation patch, a first substrate, a second substrate and a ground panel, the second substrate is provided with a feeding structure, the feeding structure is provided with two short-circuit pins and a square notch resonant ring, the multi-band wearable antenna has five working frequency bands and each working frequency band has a side-fire radiation pattern pointing in the normal direction.

2. A method for manufacturing a miniaturized five-band wearable antenna based on flexible fabric, characterized in that: The five-band wearable antenna is the five-band wearable antenna in claim 1, and the preparation method comprises the following steps: Step 1: Design the radiation patch of the microstrip patch antenna according to the design requirements; Step 2: Select the corresponding feeding method and design the feeding structure according to the size and design objectives of the radiating patch.

3. The method for manufacturing a miniaturized five-band wearable antenna based on flexible fabric according to claim 2, characterized in that: The step 1 comprises the following specific steps: Step 101: Design the size of the radiating patch of the rectangular microstrip patch antenna at the corresponding center frequency; Step 102: Cut a U-shaped groove on the microstrip patch; Step 103: Cut a pair of symmetrical J-shaped grooves inside the U-shaped groove.

4. The method for manufacturing a miniaturized five-band wearable antenna based on flexible fabric according to claim 2, characterized in that: The step 2 comprises the following steps: Step 201: Based on the microstrip patch in step 1, a proximity-coupled feeding mode is selected according to factors of bandwidth and a mode excited by the feeding; Step 202: designing a T-type feeding structure according to a proximity coupling feeding method; Step 203: adding a pair of short-circuit pins at specific positions of the T-shaped feeding structure; Step 204: Add a square notch resonant ring at a specific position of the T-type feeding structure.

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