Ism band broadband antenna for metamaterial fabric wireless body area network near field communication

Abstract

The application discloses an ISM frequency band broadband antenna for near field communication of a metamaterial fabric wireless body area network, and belongs to the wireless communication field.The ISM frequency band broadband antenna comprises a dielectric substrate, the bottom layer of the dielectric substrate is etched with a coupling structure, the top layer is etched with a first feed line structure, a second feed line structure, a third feed line structure and a fourth feed line structure, the current antinode of the third feed line structure and the fourth feed line structure is respectively provided with a first far field suppression resistor and a second far field suppression resistor, and the junction of the first feed line structure and the third feed line structure and the junction of the second feed line structure and the fourth feed line structure are respectively provided with a first impedance matching resistor and a second impedance matching resistor.The ISM frequency band broadband antenna for near field communication of the metamaterial fabric wireless body area network effectively solves the data security problem caused by electromagnetic wave far field radiation leakage in a WBAN system constructed by the metamaterial fabric, and improves the information security of a WBAN application scene.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, and particularly relates to an ISM frequency band wideband antenna for near field communication of a metamaterial fabric wireless body area network. BACKGROUND

[0002] A wireless body area network (WBAN) is composed of various sensors and communication devices, is a wireless communication network designed around the human body, and is used for collecting, transmitting and processing physiological behavior data related to the human body. With the progress and development of science and technology, people's attention and research on the wireless body area network (WBAN) are gradually deepening, especially in the medical fields of disease prevention, health management and early diagnosis.

[0003] For wireless communication between data in the WBAN system, the antenna is usually relied on to transmit electromagnetic waves carrying information to the next node device through radiation, and the physical layer working mechanism of this process has a security risk, that is, the data transmission relies on far-field electromagnetic wave radiation, so that the electromagnetic wave signal carrying sensitive physiological information is easy to be intercepted by non-authorized equipment when propagating in free space. The human physiological data carried by the WBAN is highly sensitive private information, especially in the field of medical health monitoring. Once these information is stolen or tampered with, it may cause the patient's privacy to be disturbed, cause false diagnosis or treatment decisions, and even cause serious medical accidents and other risks. Although existing research can rely on security encryption means of the protocol layer and the link layer to protect data, such a scheme still has limitations, that is, the encryption process needs to rely on complex algorithms, which will increase the energy consumption of the node, and the low energy consumption requirement of the WBAN is difficult to meet the deployment of algorithm and storage resources, in addition, even if the encrypted data packet is intercepted, the attacker can still attack through subsequent advanced persistent threats (APTs).

[0004] In [Wireless body sensor networks based on metamaterial textiles], a metamaterial textile technology combining artificial surface plasmonic transmission lines with fabrics is proposed, which provides a new way to solve the data security problem in WBAN. The field confinement characteristics of artificial surface plasmonic transmission lines can confine electromagnetic waves on the surface of metamaterial fabrics, reducing electromagnetic wave leakage caused by far-field radiation, thereby reducing the risk of data interception. However, there are still many sensor nodes in the WBAN system composed of metamaterial fabrics, and when these nodes transmit data wirelessly to the metamaterial fabric transmission line, the antenna at the sensor end also has the possibility of electromagnetic wave leakage. Therefore, it is necessary to design near-field devices with electromagnetic wave near-field focusing characteristics, so as to further improve the data security of the WBAN system composed of metamaterial fabrics.

[0005] In [Low-Profile All-Textile Multiband Microstrip Circular Patch Antenna for WBAN Applications], a low-profile all-textile multiband microstrip circular patch antenna is proposed, which activates multiple modes through various slot structures to achieve multi-band operation in WBAN applications. In [A Miniaturized Circularly Polarized Implantable RFID Antenna for Biomedical Applications], a miniaturized circularly polarized implantable RFID antenna is proposed, which uses an extended ring and a curved line design to reduce the size of the antenna, and uses an improved T-shaped matching network to achieve good impedance matching between the chip and the antenna. In [Design and Analysis of a Quad-Band Antenna for IoT and Wearable RFID Applications], a quad-band antenna suitable for wearable applications is proposed, which uses a comb-shaped slot structure to achieve miniaturization and ensure good impedance matching in multiple frequency bands.

[0006] However, the above prior art lacks research on data security caused by far-field electromagnetic wave leakage of the antenna, and the maximum gain of the antenna in the above prior art is greater than -10dB, which will inevitably increase the probability of data interception, so it is necessary to reduce the risk of information interception from the source. In addition, the antenna also needs to have a wide bandwidth to adapt to the complex working environment of the human body. Therefore, there is an urgent need for a near-field antenna that can realize safe and efficient signal transmission in a WBAN constructed by a metamaterial fabric. The antenna should have the characteristics of lightness, miniaturization, and strong compatibility, and can ensure high-quality signal transmission without interfering with the normal physiological functions of the human body. In addition, the antenna should have low far-field radiation and strong anti-interference ability to ensure the safety and reliability of information transmission. SUMMARY

[0007] The purpose of the present application is to provide an ISM frequency band wideband antenna for near-field communication of a metamaterial fabric wireless body area network to solve the problems in the background art.

[0008] To achieve the above-mentioned purpose, the present application provides an ISM frequency band wideband antenna for near-field communication of a metamaterial fabric wireless body area network, which comprises a dielectric substrate, the bottom layer of the dielectric substrate is etched with a coupling structure, the top layer of the dielectric substrate is etched with a first feed line structure, a second feed line structure, a third feed line structure and a fourth feed line structure, the current antinode of the third feed line structure and the fourth feed line structure is respectively provided with a first far-field suppression resistor and a second far-field suppression resistor, the intersection of the first feed line structure and the third feed line structure is provided with a first impedance matching resistor, and the intersection of the second feed line structure and the fourth feed line structure is provided with a second impedance matching resistor.

[0009] Preferably, the first feed line structure and the second feed line structure are symmetrically arranged in Y shape, and the third feed line structure and the fourth feed line structure are semicircular structures symmetrically arranged.

[0010] Preferably, the first feed line structure, the second feed line structure, the third feed line structure and the fourth feed line structure together form a circular loop radiation structure, wherein the length of the first feed line structure and the second feed line structure is one quarter of the wave length, and the length of the third feed line structure and the fourth feed line structure is one half of the wave length.

[0011] Preferably, the coupling structure is a Y-shaped structure.

[0012] Preferably, the central operating frequency and the impedance matching degree are adjusted by changing the resistance value of the first impedance matching resistor and the second impedance matching resistor and the opening degree number of the Y-shaped coupling structure. ​​

[0013] Preferably, the far field radiation gain is adjusted by changing the resistance value of the first far field suppression resistor and the second far field suppression resistor.

[0014] Preferably, the medium substrate material is FR4 hard board, and flexible medium materials such as PI can also be used.

[0015] Therefore, the present application has the following beneficial effects by using the ISM frequency band wideband antenna for the metamaterial fabric wireless body area network near field communication:

[0016] (1) The loop structure formed by the top layer of feed line structure makes the current on the loop present the same clock direction, thereby generating a strong and uniform near field magnetic field;

[0017] (2) The method of adding resistance at the wave crest is used to realize the far field radiation gain of the antenna less than -10dB, reduce the electromagnetic wave far field radiation leakage, thereby reducing the risk of information interception in the propagation process;

[0018] (3) The method of adding matching resistance at the wave node and the bottom Y-shaped coupling structure is used, and the antenna realizes the wideband impedance matching of 2.14-2.67GHz S 11 <-10dB), the antenna size is 21mmx26.5mmx0.8mm, which takes into account the requirements of miniaturization and wideband characteristics of WBAN system application;

[0019] (4) The far field radiation gain of the antenna can be further adjusted by changing the resistance value of the far field suppression resistor; the impedance matching of the antenna can be further controlled by adjusting the size of the impedance matching resistor and the opening degree of the Y-shaped coupling structure θ to adapt to the complex working environment of the human body.

[0020] 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

[0021] Figure 1 The top layer structure diagram of the medium substrate of the embodiment of the present application is shown in the figure;

[0022] Figure 2 The bottom layer structure diagram of the medium substrate of the embodiment of the present application is shown in the figure;

[0023] Figure 3 The current flow distribution diagram of the antenna at the center frequency of 2.4GHz in the embodiment of the present application is shown in the figure; wherein, (a) is the top layer current flow distribution diagram, and (b) is the bottom layer current flow distribution diagram;

[0024] Figure 4It is a current amplitude distribution diagram of the antenna in the embodiment of the application at a 2.4 GHz center frequency; wherein, (a) is a top layer current amplitude distribution diagram, and (b) is a bottom layer current amplitude distribution diagram;

[0025] Figure 5 It is a simulation return loss S11 curve diagram of the antenna in the embodiment of the application when R3=R4=62 Ω and the opening degree of the Y-shaped coupling structure is It is a simulation return loss S11 curve diagram of the antenna in the embodiment of the application when R3=R4=62 Ω and the opening degree of the Y-shaped coupling structure is

[0026] Figure 6 It is a simulation return loss S11 curve diagram of the antenna in the embodiment of the application when R3=R4=62 Ω, R1=R2=140 Ω and the opening degree of the Y-shaped coupling structure is

[0027] Figure 7 It is a far field radiation gain diagram of the antenna in the embodiment of the application at a 2.4 GHz center frequency when R1=R2=140 Ω and the opening degree of the Y-shaped coupling structure is It is a far field radiation gain diagram of the antenna in the embodiment of the application at a 2.4 GHz center frequency when R1=R2=140 Ω and the opening degree of the Y-shaped coupling structure is

[0028] Figure 8 It is a magnetic field distribution diagram of the antenna in the embodiment of the application at a 2.4 GHz center frequency on an x-y plane at different heights z; the heights z are 5 mm, 10 mm, 15 mm and 20 mm in sequence; wherein, (a) is a magnetic field distribution diagram of the x-y plane when the height z is 5 mm, (b) is a magnetic field distribution diagram of the x-y plane when the height z is 10 mm, (c) is a magnetic field distribution diagram of the x-y plane when the height z is 15 mm, and (d) is a magnetic field distribution diagram of the x-y plane when the height z is 20 mm;

[0029] Figure 9 It is a magnetic field distribution diagram of the antenna in the embodiment of the application at a 2.4 GHz center frequency on a y-z plane when x=0 mm;

[0030] Figure 10 It is a simulation and actual measurement return loss S11 curve diagram of the antenna in the embodiment of the application;

[0031] Reference signs

[0032] 1, first feeding line structure; 2, second feeding line structure; 3, third feeding line structure; 4, fourth feeding line structure; 5, first impedance matching resistance; 6, second impedance matching resistance; 7, first far field suppression resistance; 8, second far field suppression resistance; 9, coupling structure. DETAILED DESCRIPTION

[0033] The following detailed description of embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the application as claimed, but merely represents selected embodiments of the application. Based upon the embodiments in the application, all other embodiments that a person of ordinary skill in the art obtains without creative work are within the scope of the application.

[0034] Referring to Figure 1 An ISM frequency band broadband antenna for metamaterial fabric wireless body area network near field communication, comprising a dielectric substrate, a coupling structure 9 is etched on the bottom layer of the dielectric substrate, and the coupling structure 9 is a Y-shaped structure.

[0035] A first feed line structure 1, a second feed line structure 2, a third feed line structure 3 and a fourth feed line structure 4 are etched on the top layer of the dielectric substrate, and a first far field suppression resistor 7 and a second far field suppression resistor 8 are respectively arranged at the current antinodes of the third feed line structure 3 and the fourth feed line structure 4, a first impedance matching resistor 5 is arranged at the intersection of the first feed line structure 1 and the third feed line structure 3, and a second impedance matching resistor 6 is arranged at the intersection of the second feed line structure 2 and the fourth feed line structure 4. The intersection of the first feed line structure 1 and the third feed line structure 3, and the intersection of the second feed line structure 2 and the fourth feed line structure 4 are current node positions.

[0036] The first impedance matching resistor 5 and the second impedance matching resistor 6 are R 1 and R 2, the first far field suppression resistor 7 and the second far field suppression resistor 8 are R 3 and R 4; as shown in the figure, the coupling structure 9 forms a Y-shaped structure on the bottom layer, the opening degree of the Y-shaped structure is Figure 2 , and other parameter values in the figure are as follows: θ 1=0.8mm, w 2=3mm, w 3=5.1mm, w 1=0.3mm, g 2=0.5mm, g 3=1.5mm, g 1=10.5mm, r 1=8.4mm, r 4=16mm. w The first feed line structure 1 and the second feed line structure 2 are symmetrically arranged in a Y shape, and the third feed line structure 3 and the fourth feed line structure 4 are semicircular structures and are symmetrically arranged.

[0037]

[0038] ​The first feeding line structure 1, the second feeding line structure 2, the third feeding line structure 3 and the fourth feeding line structure 4 together form a circular loop radiation structure, wherein the length of the first feeding line structure 1 and the second feeding line structure 2 is one quarter , and the length of the third feeding line structure 3 and the fourth feeding line structure 4 is one half , wherein is the guided wave wavelength.

[0039] The central operating frequency and the impedance matching degree of the antenna are adjusted by changing the resistance values of the first impedance matching resistor 5 and the second impedance matching resistor 6 and the opening degree of the Y-shaped coupling structure 9 .

[0040] The far field radiation gain of the antenna is adjusted by changing the resistance values of the first far field suppression resistor 7 and the second far field suppression resistor 8.

[0041] Figure 3 is the current flow distribution diagram of the top layer and the bottom layer structure of the antenna at the central frequency of 2.4 GHz in this embodiment. It can be seen from Figure 3 that the current flow direction is reversed at the junction of the first feeding line structure 1 and the third feeding line structure 3, and at the junction of the second feeding line structure 2 and the fourth feeding line structure 4, and the current flow direction on the third feeding line structure 3 and the fourth feeding line structure 4 does not change, so the current flow direction on the entire circular loop radiation structure presents the same direction, and the loop current will help to form a strong and uniform near field magnetic field;

[0042] Figure 4 is the current amplitude distribution diagram of the top layer and the bottom layer structure of the antenna at the central frequency of 2.4 GHz in this embodiment. It can be seen from Figure 4 that the current amplitude reaches the minimum (the area with blue color) at the junction of the first feeding line structure 1 and the third feeding line structure 3, and at the junction of the second feeding line structure 2 and the fourth feeding line structure 4, which is the current wave node. The current amplitude is maximum (the area with green color) on the third feeding line structure 3 and the fourth feeding line structure 4, which is the current wave crest. Therefore, the first far field suppression resistor 7 and the second far field suppression resistor 8, R3 and R4 respectively, are placed in the current wave crest area to consume energy and reduce far field radiation. The first impedance matching resistor 5 and the second impedance matching resistor 6, R1 and R2 respectively, are placed in the current wave node area to adjust the impedance matching degree. In addition, the current amplitude of the first feeding line structure 1 and the second feeding line structure 2 near the feeding end is large, so the Y-shaped coupling structure 9 is added to the bottom layer of the dielectric substrate. The top layer current excites the Y-shaped coupling structure 9 on the bottom layer to generate a current opposite to the top layer current flow direction, which is used to guide the electromagnetic field to concentrate in the near field area, adjust the near field magnetic field distribution, and further weaken the far field radiation;

[0043] Figure 5 For the embodiment, R3=R4=62Ω, Y-shaped coupling structure 9 opening degree θ=90°, the simulation return loss S11 curve of the antenna with different R1, R2 (R1=R2) resistance values. As can be seen from the figure, as the resistance values of R1 and R2 gradually increase from 120Ω, 130Ω, 140Ω, 150Ω, 160Ω, the center frequency of the antenna gradually moves to high frequency, and the impedance matching degree gradually decreases.

[0044] Figure 6 For the embodiment, R3=R4=62Ω, R1=R2=140Ω, the simulation return loss S11 curve of the antenna with different Y-shaped coupling structure 9 opening degrees θ. As can be seen from the figure, as the degrees θ increase from 82°, 86°, 90°, 94°, 98°, the center frequency and impedance matching degree of the antenna decrease with the increase of the degree θ. Therefore, the center frequency of the antenna can be controlled by changing the resistance values of R1 and R2 and the value of the Y-shaped coupling structure 9 opening degree θ, and the impedance matching of the antenna can be adjusted;

[0045] Figure 7 For the embodiment, R1=R2=140Ω, Y-shaped coupling structure 9 opening degree θ=90°, the E-plane and H-plane far-field radiation gain diagram of the antenna at 2.4GHz center frequency with different R3, R4 (R3=R4) resistance values. As can be seen from the E-plane and H-plane radiation gain in the figure, as the resistance values of R3 and R4 increase from 30Ω to 60Ω, the maximum far-field radiation gain of the antenna decreases from-8.61dB to-10.45dB, so the far-field radiation gain of the antenna can be suppressed by increasing the resistance values of R3 and R4;

[0046] Figure 8 For the embodiment, the magnetic field distribution diagram of the antenna in the x-y plane at different heights z above the 2.4GHz center frequency, the height z is 5mm, 10mm, 15mm, 20mm respectively.

[0047] Figure 9 For the embodiment, the magnetic field distribution diagram of the antenna in the y-z plane when x=0mm at 2.4GHz center frequency. As can be seen from Figure 8 and Figure 9 , the antenna produces strong and uniform vertical magnetic field in the range of 0mm to 20mm from the upper surface of the antenna, and the magnetic field strength reaches or exceeds 0.01 A / m, and as the distance above the antenna increases, the magnetic field strength gradually weakens, and the area of high intensity (red and yellow) gradually shrinks, which is a typical near-field antenna characteristic, which indicates that the magnetic field strength is mainly concentrated near the antenna, and rapidly attenuates with the increase of distance;

[0048] Figure 10 The following is a graph of the simulated and measured return loss S11 of the antenna in this embodiment. Parameter settings: two impedance matching resistors R1 = R2 = 140Ω, two far-field suppression resistors R3 = R4 = 62Ω, and a Y-shaped coupling structure with an opening angle θ = 90°. Based on these parameters, the antenna was simulated and tested physically. It can be seen that the simulated and measured center operating frequencies are basically consistent. The simulated S11 at the operating frequency (2.40GHz) is -28.5dB, while the measured S11 at the operating frequency (2.43GHz) is -19.1dB. Furthermore, compared to the simulated S11 < -10dB impedance bandwidth (2.12GHz to 2.66GHz), the actual measured -10dB impedance bandwidth is extended, indicating that the fabricated antenna has good impedance matching and is applicable over a wider frequency range.

[0049] Therefore, the present invention adopts the above-mentioned ISM band broadband antenna for near-field communication of metamaterial fabric wireless body area network, realizes low far-field radiation of the antenna by loading resistors at the antinode points, and also realizes low far-field radiation of the antenna by loading resistors at the node points and adjusting the opening of the underlying Y-shaped coupling structure. θ The size of the antenna is adjusted to control the central operating frequency of the antenna and adjust the impedance matching. This invention offers advantages such as miniaturization, wide bandwidth, and low radiation. It focuses on resolving data security issues caused by far-field electromagnetic radiation leakage in WBAN systems constructed with metamaterial fabrics. It also addresses issues such as insufficient antenna bandwidth, impedance matching difficulties, and operating frequency control in WBAN systems operating under human conditions. This near-field antenna can be effectively applied to metamaterial fabric WBAN applications that require high data transmission security.

[0050] According to the YD / T 1644 standard, the power per unit mass absorbed by 10 grams of human tissue under radio electromagnetic radiation (10-gSAR) must not exceed 2 W / kg to meet the required electromagnetic radiation safety standards. Using the electromagnetic simulation software Ansys HFSS, the human body specific absorption rate (SAR) analysis of the ISM-band near-field communication broadband antenna provided by this invention was conducted. The antenna was placed 1.5 mm above human tissue, with an input power setting of 100 mW. The simulation showed that the antenna's maximum 10-gSAR value at 2.4 GHz was 0.95 W / kg, which is lower than the standard value. Therefore, under these conditions, the antenna can be safely used in metamaterial fabric WBAN systems.

[0051] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. An ISM band broadband antenna for near-field communication of a metamaterial fabric wireless body area network, characterized by: The invention comprises a dielectric substrate, wherein a coupling structure is etched on a bottom layer of the dielectric substrate, and a first feeder structure, a second feeder structure, a third feeder structure, and a fourth feeder structure are etched on a top layer of the dielectric substrate. A first far-field suppression resistor and a second far-field suppression resistor are respectively provided at the current antinodes of the third feeder structure and the fourth feeder structure. A first impedance matching resistor is provided at the intersection of the first feeder structure and the third feeder structure, and a second impedance matching resistor is provided at the intersection of the second feeder structure and the fourth feeder structure. The coupling structure is a Y-shaped structure; By changing the resistance of the first impedance matching resistor and the second impedance matching resistor and the opening degree of the Y-shaped coupling structure To adjust the central operating frequency and impedance matching; The far-field radiation gain is adjusted by changing the resistance values ​​of the first far-field suppression resistor and the second far-field suppression resistor.

2. The ISM band broadband antenna for near-field communication of a metamaterial fabric wireless body area network according to claim 1, characterized in that: The first feeder line structure and the second feeder line structure are symmetrically arranged in a Y shape, and the third feeder line structure and the fourth feeder line structure are semicircular structures and are symmetrically arranged.

3. The ISM band broadband antenna for near-field communication of a metamaterial fabric wireless body area network according to claim 2, characterized in that: The first feeder structure, the second feeder structure, the third feeder structure and the fourth feeder structure together form a circular loop radiation structure, wherein the lengths of the first feeder structure and the second feeder structure are both one-quarter The lengths of the third and fourth feeder structures are both half ,in is the guided wave wavelength.

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