Small implantable broadband microstrip antenna applied to wireless body area network

Abstract

The invention discloses a small-sized implantable broadband microstrip antenna applied to a wireless body area network. The small-sized implantable broadband microstrip antenna comprises a covering layer, a first metal layer, a dielectric substrate and a second metal layer which are stacked in sequence, a radiation patch is formed on the first metal layer, the edge of the radiation patch is flush with the edge of the dielectric substrate, and an S-shaped zigzag groove, an F-shaped zigzag groove and a rectangular groove are formed in the radiation patch; the S-shaped zigzag groove is a closed groove, and the upper half part of the radiation patch is cut into a special-shaped annular first structure part; the F-shaped zigzag groove and the rectangular groove are open grooves, the F-shaped zigzag groove is matched with the rectangular groove, and the lower half part of the radiation patch is cut into a zigzag structure; one end of the zigzag structure is an antenna feeding point, and the other end is connected with the first structure part; a metal ground plane is formed on the second metal layer, the left edge, the right edge and the bottom edge of the metal ground plane are flush with the dielectric substrate, and a certain gap is formed between the upper edge of the metal ground plane and the upper edge of the dielectric substrate.

Description

Technical Field

[0001] The invention relates to the field of microstrip antennas, and in particular to a small implantable broadband microstrip antenna applied to a wireless body area network. Background Art

[0002] Wireless body area network (WBAN) was first proposed in 2001. In recent years, the research focus of WBAN has been on implantable devices. As an important part of the fifth-generation mobile communication system, it has been widely used in medical, sports and military fields. With the continuous development and progress of science and technology, implantable devices have also been greatly developed. As the most important component of such devices, the performance of implantable antennas will directly affect the efficiency and stability of wireless communication of such devices. The working scene of implantable antennas is inside the human body. Each layer of human tissue has a different dielectric constant. The inhomogeneity of this dielectric constant will cause the propagation of electromagnetic waves inside the human body to be unstable and cause signal attenuation, which in turn affects the performance of the antenna. In addition, with the increase of age, the characteristics of each layer of tissue in the human body change, which will also cause the frequency of the antenna to shift.

[0003] Therefore, when designing implantable antennas, antenna size, bandwidth, biocompatibility and safety need to be considered.

[0004] Invention patent CN116505233A discloses a dual-frequency implantable antenna for wireless biomedical telemetry, which can work at both 915MHz and 2.45GHz frequencies, thus realizing wireless medical telemetry. However, the bandwidths of the two working frequency bands are relatively narrow, and no biocompatible materials are used.

[0005] Utility model patent CN214336911U discloses an ultra-wideband implantable antenna. The author invented an ultra-wideband antenna with biocompatibility, but its overall size is slightly larger, with a volume of 15×15×0.508mm 3 . Summary of the invention

[0006] The present invention aims to provide a small implantable broadband microstrip antenna for use in a wireless body area network. To this end, the specific technical solutions adopted by the present invention are as follows:

[0007] A small implantable broadband microstrip antenna for use in a wireless body area network comprises a cover layer, a first metal layer, a dielectric substrate and a second metal layer stacked in sequence;

[0008] A radiation patch is formed on the first metal layer, the edge of the radiation patch is flush with the edge of the dielectric substrate, and an S-shaped zigzag groove, an F-shaped zigzag groove and at least one rectangular groove are arranged thereon, the S-shaped zigzag groove is a closed groove, which is arranged in the middle of the upper half of the radiation patch, and the upper half of the radiation patch is cut into a first structural part in the shape of an irregular ring; the F-shaped zigzag groove and the rectangular groove are open grooves, which are arranged in the lower half of the radiation patch; the opening of the F-shaped zigzag groove is arranged on the left or right side of the radiation patch; the opening of the rectangular groove is arranged in the middle of the bottom of the radiation patch; the upper edge of the F-shaped zigzag groove is flush, and the lower edge cooperates with the rectangular groove to form a second structural part of a zigzag structure; the zigzag structure includes a second structural part, a third structural part and a fourth structural part connected in sequence; one end of the second structural part is an antenna feeding point, and the other end is connected to the first structural part;

[0009] A metal ground plane is formed on the second metal layer. The left and right edges and the bottom edge of the metal ground plane are flush with the dielectric substrate, and a certain gap is set between the upper edge of the metal ground plane and the upper edge of the dielectric substrate.

[0010] Furthermore, the dielectric substrate is made of Rogers RO5880 material with a relative dielectric constant of 2.2 and a loss tangent of 0.0009.

[0011] Furthermore, the thickness of the dielectric substrate is 0.127 mm or 0.254 mm.

[0012] Furthermore, the size of the dielectric substrate is 6mm*6mm.

[0013] Furthermore, the F-type zigzag groove is an F-type zigzag groove; and the number of the rectangular groove is 1.

[0014] Furthermore, the length of the S-shaped zigzag groove is 4.4 mm; the width is 0.4 mm, and the spacing is 0.3 mm; the length of the rectangular groove is 2.8 mm, and the width is 0.3 mm; the width of the zigzag structure part in the middle of the second structural part is 0.2 mm; and the gap between the upper edge of the metal grounding surface and the upper edge of the dielectric substrate is 1.5 mm.

[0015] Furthermore, a feeding hole is provided on the feeding point, the central conductor of the coaxial feed line is welded to the feeding point through the feeding hole, and the outer conductor of the coaxial feed line is welded to the metal grounding surface.

[0016] Furthermore, the covering layer is made of polydimethylsiloxane material.

[0017] Furthermore, the covering layer is made of silica gel.

[0018] The small implantable broadband microstrip antenna of this embodiment uses F-shaped and S-shaped zigzag grooves and rectangular grooves to achieve miniaturization of the antenna. By using polymer materials such as PDMS (polydimethylsiloxane) and silica gel as a covering layer, the antenna is made biocompatible. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0020] Figure 1 is a side view of the implantable broadband microstrip antenna of the present invention;

[0021] Figure 2 It is a schematic diagram of the radiation patch structure of the implantable broadband microstrip antenna of the present invention;

[0022] Figure 3 It is a schematic diagram of the metal ground plane structure of the implantable broadband microstrip antenna of the present invention;

[0023] Figure 4 It is a curve diagram of the simulation results of the reflection coefficient of the designed antenna;

[0024] Figure 5 is the XOZ radiation pattern of the antenna in the embodiment at a frequency of 2450 MHz;

[0025] Figure 6 It is the YOZ radiation pattern of the antenna described in the embodiment at the frequency point of 2450 MHz. DETAILED DESCRIPTION

[0026] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.

[0027] like Figure 1 As shown, this embodiment provides a small implantable broadband microstrip antenna for use in a wireless body area network, which is composed of a cover layer 1, a radiation patch layer 2, a dielectric substrate 3, and a metal ground layer 4 stacked in sequence.

[0028] The cover layer 1 is preferably made of PDMS (polydimethylsiloxane) material, which is biocompatible. Adding a cover layer 1 on the radiation patch layer 2 can achieve impedance matching of the antenna and make the antenna biocompatible. By using slotting technology on the radiation patch layer 2 and the metal ground layer 4, the antenna can be miniaturized and its bandwidth can be increased.

[0029] In this embodiment, the dielectric substrate 3 is a square dielectric substrate, and the length L and width W of the substrate are both 6 mm. Preferably, the dielectric substrate 3 adopts RogersRO5880 material with a relative dielectric constant of 2.2 and a loss tangent of 0.0009, and a thickness of h=0.127 mm. RO5880 material is a high-frequency substrate with extremely low dielectric constant and dielectric loss factor (loss tangent), which can effectively reduce signal loss and delay, ensure the efficiency and stability of data transmission, and its mechanical properties are also excellent, with good dimensional stability and chemical resistance, can maintain stable performance in various harsh environments, and has biocompatibility. In specific applications, substrates of Rogers RO5880 material of other thicknesses can also be selected, such as 0.254 mm.

[0030] like Figure 2 As shown, the radiation patch layer 2 is a metal layer, and a radiation patch 21 is formed by etching. The radiation patch 21 is square in shape, and its edge is flush with the edge of the dielectric substrate 3. An F-shaped meandering groove 22, an S-shaped meandering groove 23 and a rectangular groove 24 are provided on the radiation patch 21 to expand the current path of the antenna.

[0031] In this embodiment, the S-shaped meandering groove 22 is a closed groove, and the upper half of the radiation patch 21 is cut into a special-shaped ring structure with two radiation protrusions.

[0032] In the present embodiment, the F-shaped meandering groove 23 is an open groove, whose opening is located on the left side of the radiation patch 21, and whose upper edge is flush. The rectangular groove 24 is an open groove, whose opening is set in the middle of the bottom of the radiation patch 21. The rectangular groove 24 cooperates with the lower edge of the F-shaped meandering groove 23 to cut the lower half of the radiation patch 21 into a meandering structure, which includes a square structure part, a "J"-shaped structure part and a long strip structure part connected in sequence. In the present embodiment, the square structure part is located at the lower left corner of the radiation patch 21, which is used for antenna feeding and is provided with a coaxial feeding hole 25; the "J"-shaped structure part is located at the bottom of the radiation patch 21; the long strip structure part is located on the right side of the radiation patch 21, and is connected to the special-shaped annular structure part of the upper half of the radiation patch 21.

[0033] In practical applications, the S-shaped meandering groove 22 and the F-shaped meandering groove 23 may be mirrored left and right to form different patterns, but the radiation performance of the antenna will not be changed as a whole.

[0034] In specific applications, the F-shaped meandering groove 23 can also be changed to a quasi-F-shaped meandering groove, whose upper edge is flush and whose lower edge forms more than two protrusions, and multiple rectangular grooves 24 are provided at the same time, and N rectangular grooves and N+1 protrusions cooperate to form a super "S"-shaped meandering structure. This method can further expand the current path of the antenna.

[0035] A rectangular opening slot 41 is cut into the upper portion of the metal grounding layer 4 on the back of the dielectric substrate 3 to form a rectangular metal grounding surface 42 for impedance matching and frequency band adjustment. Specifically, the left and right edges and the bottom edge of the metal grounding surface 42 are flush with the dielectric substrate 3, and a certain gap is set between the upper edge and the upper edge of the dielectric substrate 3.

[0036] The central conductor of the coaxial feed line passes through the dielectric substrate 3 and the square structure part through the coaxial feed hole 25 and is welded and connected; the outer conductor (shielded wire) of the coaxial feed line is welded and connected to the metal ground plane 42.

[0037] In this embodiment, the dimensions of each structural part are shown in Table 1.

[0038] Table 1 Structural dimensions list

[0039]

[0040] On the radiation patch 21, an F-shaped meandering slot 22, an S-shaped meandering slot 23 and a rectangular slot 24 are introduced to expand the current path of the antenna, increase the bandwidth of the antenna, and effectively reduce the resonant frequency of the antenna to achieve antenna tuning. In order to enable the antenna to cover the required ISM frequency band (2.4-2.48GHz) and also have good impedance matching, a rectangular opening slot 41 is cut in the metal grounding layer 4 to form a gap between the metal grounding surface 42 and the upper edge of the dielectric substrate 3. The present invention uses a coaxial feeding method to feed the antenna. The coaxial feeding method can make the antenna have good shielding performance and can reduce the interference of human tissue to the antenna.

[0041] The implantable broadband microstrip antenna of this embodiment uses F-shaped and S-shaped zigzag grooves and rectangular grooves to achieve the miniaturization of the antenna. By using polymer materials such as PDMS (polydimethylsiloxane) and silicone as the covering layer, the antenna is made biocompatible. Therefore, the present invention can better adapt to the deformation of human tissue, reduce the damage of the antenna to the surrounding tissue, and thus improve the safety and comfort of the antenna, so that the antenna has good robustness. At the same time, silicone also has good corrosion resistance, and can extend the life of the antenna while ensuring safety. By using slotting technology on the radiation patch layer and the metal grounding layer of the antenna, the working bandwidth of the antenna is further increased, so that the working bandwidth of the antenna can cover the required ISM frequency band (2.4-2.48GHz). It can be seen that the peak gain of the antenna described in this embodiment at the frequency point of 2450MHz can reach -19dBi, the working bandwidth of the antenna reaches 23.8%, and the resonant frequency of the antenna is also optimized. Figure 4 - Figure 6As shown in the figure, the antenna is easier to integrate and implant, has higher security and stronger anti-interference ability. In addition, the antenna has low design cost, simple manufacturing process and good robustness, which can well meet the performance requirements of implantable devices. This also provides technical support for the development of implantable devices in WBAN applications, and also provides new design ideas and references for antennas with high requirements for miniaturization and biocompatibility.

[0042] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A small implantable broadband microstrip antenna for use in a wireless body area network, characterized in that: It includes a cover layer, a first metal layer, a dielectric substrate and a second metal layer stacked in sequence; A radiation patch is formed on the first metal layer, the edge of the radiation patch is flush with the edge of the dielectric substrate, and an S-shaped zigzag groove, an F-shaped zigzag groove and at least one rectangular groove are arranged thereon, the S-shaped zigzag groove is a closed groove, which is arranged in the middle of the upper half of the radiation patch, and the upper half of the radiation patch is cut into a first structural part in the shape of an irregular ring; the F-shaped zigzag groove and the rectangular groove are open grooves, which are arranged in the lower half of the radiation patch; the opening of the F-shaped zigzag groove is arranged on the left or right side of the radiation patch; the opening of the rectangular groove is arranged in the middle of the bottom of the radiation patch; the upper edge of the F-shaped zigzag groove is flush, and the lower edge cooperates with the rectangular groove to form a second structural part of a zigzag structure; the zigzag structure includes a second structural part, a third structural part and a fourth structural part connected in sequence; one end of the second structural part is an antenna feeding point, and the other end is connected to the first structural part; A metal ground plane is formed on the second metal layer. The left and right edges and the bottom edge of the metal ground plane are flush with the dielectric substrate, and a certain gap is set between the upper edge of the metal ground plane and the upper edge of the dielectric substrate.

2. The small implantable broadband microstrip antenna for wireless body area network according to claim 1, characterized in that: The dielectric substrate is made of Rogers RO5880 material with a relative dielectric constant of 2.2 and a loss tangent of 0.0009.

3. The small implantable broadband microstrip antenna for wireless body area network according to claim 2, characterized in that: The thickness of the dielectric substrate is 0.127 mm or 0.254 mm.

4. The small implantable broadband microstrip antenna for use in a wireless body area network according to claim 1, characterized in that: The size of the dielectric substrate is 6mm*6mm.

5. The small implantable broadband microstrip antenna for wireless body area network according to claim 4, characterized in that: The F-type zigzag groove is an F-type zigzag groove; the number of the rectangular groove is 1.

6. The small implantable broadband microstrip antenna for use in a wireless body area network as claimed in claim 5, characterized in that: The length of the S-shaped zigzag groove is 4.4 mm, the width is 0.4 mm, and the spacing is 0.3 mm; the length of the rectangular groove is 2.8 mm, and the width is 0.3 mm; the width of the zigzag structure part in the middle of the second structural part is 0.2 mm; the gap between the upper edge of the metal grounding surface and the upper edge of the dielectric substrate is 1.5 mm.

7. The small implantable broadband microstrip antenna for use in a wireless body area network according to claim 1, characterized in that: The feeding point is provided with a feeding hole, the central conductor of the coaxial feed line is welded to the feeding point through the feeding hole, and the outer conductor of the coaxial feed line is welded to the metal grounding surface.

8. The small implantable broadband microstrip antenna for wireless body area network according to claim 1, characterized in that: The covering layer is made of polydimethylsiloxane.

9. The small implantable broadband microstrip antenna for wireless body area network according to claim 1, characterized in that: The material of the covering layer is silica gel.

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