A small implantable broadband microstrip antenna for wireless body area networks

Abstract

The present invention discloses a small implantable broadband microstrip antenna for use in a wireless body area network, comprising 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 a rectangular groove are provided on the first metal layer; the S-shaped zigzag groove is a closed groove, which cuts the upper half of the radiation patch into a first structural portion in the shape of an irregular ring; the F-shaped zigzag groove and the rectangular groove are open grooves, and the F-shaped zigzag groove cooperates with the rectangular groove to cut the lower half of the radiation patch into a zigzag structure; one end of the zigzag structure is an antenna feeding point, and the other end is connected to the first structural portion; 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 provided between the upper edge and the upper edge of the dielectric substrate.

Description

Technical Field

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

[0002] Wireless body area networks (WBANs) were first proposed in 2001. In recent years, research on WBANs has focused on implantable devices. As a key component of fifth-generation mobile communication systems, they have been widely used in fields such as medicine, sports, and the military. With the continuous advancement of science and technology, implantable devices have also seen significant growth. Implantable antennas, as the most critical component of these devices, directly impact the efficiency and stability of wireless communication. Implantable antennas operate within the human body, where each layer of tissue has a different dielectric constant. This uneven dielectric constant leads to unstable electromagnetic wave propagation and signal attenuation, which in turn affects antenna performance. Furthermore, as the characteristics of tissue layers change with aging, the antenna's frequency can shift.

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

[0004] Invention patent CN116505233A discloses a dual-band implantable antenna for wireless biomedical telemetry. This implantable antenna can operate simultaneously at both 915 MHz and 2.45 GHz frequencies, enabling wireless medical telemetry. However, both operating frequency bands have relatively narrow bandwidths and are not made of biocompatible materials.

[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 wireless body area networks. 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 provided thereon, the S-shaped zigzag groove is a closed groove, which is provided 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 provided in the lower half of the radiation patch; the opening of the F-shaped zigzag groove is provided on the left or right side of the radiation patch; the opening of the rectangular groove is provided 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 the 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-shaped zigzag groove is an F-shaped zigzag groove; and the number of the rectangular groove is 1.

[0014] Furthermore, the S-shaped zigzag groove has a length of 4.4 mm, a width of 0.4 mm, and a spacing of 0.3 mm; the rectangular groove has a length of 2.8 mm and a width of 0.3 mm; the width of the zigzag structure portion in the middle of the second structural portion is 0.2 mm; and the gap between the upper edge of the metal ground plane 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.

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

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

[0019] To further illustrate various embodiments, the present invention is provided with accompanying drawings. These drawings form part of the present disclosure and are primarily used to illustrate the embodiments and, in conjunction with the relevant description in the specification, to explain the operating principles of the embodiments. By referring to these drawings, one of ordinary skill in the art will understand other possible embodiments and the advantages of the present invention. The components in the figures are not drawn to scale, and similar reference numerals 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 Schematic diagram of the radiation patch structure of the implantable broadband microstrip antenna of the present invention;

[0022] Figure 3 Schematic diagram of the metal ground plane structure of the implantable broadband microstrip antenna of the present invention;

[0023] Figure 4 The reflection coefficient simulation result curve of the designed antenna;

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

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

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

[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] Covering layer 1 is preferably made of PDMS (polydimethylsiloxane), a biocompatible material. Adding a covering layer 1 to radiating patch layer 2 achieves impedance matching and biocompatibility. Slotting in radiating patch layer 2 and metal ground layer 4 minimizes the antenna's size and increases its bandwidth.

[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 is made of Rogers RO5880 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, ensuring the efficiency and stability of data transmission. At the same time, its mechanical properties are also excellent, with good dimensional stability and chemical resistance, and can maintain stable performance in various harsh environments, and has biocompatibility. In specific applications, substrates of Rogers RO5880 material of other thicknesses, such as 0.254 mm, can also be selected.

[0030] like Figure 2 As shown, the radiating patch layer 2 is a metal layer, which is etched to form a radiating patch 21. The radiating patch 21 has a square shape, and its edge is flush with the edge of the dielectric substrate 3. Radiating patch 21 is provided with an F-shaped meandering groove 22, an S-shaped meandering groove 23, and a rectangular groove 24 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 this embodiment, the F-shaped zigzag slot 23 is an open slot, its opening located on the left side of the radiating patch 21, and its upper edge is flush. The rectangular slot 24 is an open slot, its opening located in the middle of the bottom of the radiating patch 21. The rectangular slot 24 cooperates with the lower edge of the F-shaped zigzag slot 23 to cut the lower half of the radiating patch 21 into a zigzag structure, which includes a square structure portion, a "J"-shaped structure portion, and a long strip structure portion connected in sequence. In this embodiment, the square structure portion is located in the lower left corner of the radiating patch 21 and is used for antenna feeding. It is provided with a coaxial feeding hole 25; the "J"-shaped structure portion is located at the bottom of the radiating patch 21; and the long strip structure portion is located on the right side of the radiating patch 21 and is connected to the special-shaped ring structure portion in the upper half of the radiating patch 21.

[0033] In practical applications, the S-shaped meandering slot 22 and the F-shaped meandering slot 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 slot 23 can be replaced with a similar F-shaped meandering slot, with a flat upper edge and two or more protrusions on the lower edge. Multiple rectangular slots 24 can also be provided. N rectangular slots and N+1 protrusions combine to form a super-""-shaped meandering structure. This method can further expand the antenna's current path.

[0035] The metal ground layer 4 on the back of the dielectric substrate 3 has a rectangular slot 41 cut into its upper portion, forming a rectangular metal ground plane 42 for impedance matching and frequency band adjustment. Specifically, the left and right edges and bottom edge of the metal ground plane 42 are flush with the dielectric substrate 3, while its upper edge is spaced apart from 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 portion through the coaxial feed hole 25 and is welded to the square structure portion; the outer conductor (shielded wire) of the coaxial feed line is welded 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

[0039]

[0040] An F-shaped meandering slot 22, an S-shaped meandering slot 23, and a rectangular slot 24 are introduced into the radiating patch 21 to expand the antenna's current path, increase the antenna's bandwidth, and effectively reduce the antenna's resonant frequency, enabling antenna tuning. To ensure the antenna covers the required ISM frequency band (2.4-2.48 GHz) and provides good impedance matching, a rectangular open slot 41 is cut into the metal ground layer 4, creating a gap between the metal ground plane 42 and the upper edge of the dielectric substrate 3. The present invention uses coaxial feeding to feed the antenna, which provides excellent shielding performance and reduces interference from human tissue.

[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 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, such as Figure 4 - Figure 6As shown in the figure, this antenna is easier to integrate and implant, offers enhanced security, and possesses stronger anti-interference capabilities. Furthermore, it features low design costs, simple manufacturing processes, and excellent robustness, effectively meeting the performance requirements of implantable devices. This provides technical support for the development of implantable devices in WBAN applications and offers new design ideas and references for antennas requiring high miniaturization and biocompatibility.

[0042] Although the present invention has been particularly shown and described in conjunction with preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made to the present invention without departing from the spirit and scope of the invention as defined in the appended claims, and all such changes 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 by: 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 provided thereon, the S-shaped zigzag groove is a closed groove, which is provided 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 provided in the lower half of the radiation patch; the opening of the F-shaped zigzag groove is provided on the left or right side of the radiation patch; the opening of the rectangular groove is provided 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 the 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 use in a wireless body area network according to claim 1, wherein: 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 use in a wireless body area network according to claim 2, wherein: 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, wherein: The size of the dielectric substrate is 6mm*6mm.

5. The small implantable broadband microstrip antenna for use in a wireless body area network according to claim 4, wherein: The F-shaped zigzag groove is an F-shaped 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 according to claim 5, wherein: The S-shaped zigzag groove has a length of 4.4 mm, a width of 0.4 mm, and a spacing of 0.3 mm. The rectangular groove has a length of 2.8 mm and a width of 0.3 mm. The width of the zigzag structure portion in the middle of the second structural portion is 0.2 mm. The gap between the upper edge of the metal ground plane 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, wherein: 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 use in a wireless body area network according to claim 1, wherein: The covering layer is made of polydimethylsiloxane.

9. The small implantable broadband microstrip antenna for use in a wireless body area network according to claim 1, wherein: The covering layer is made of silica gel.

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