Dual-frequency implantable antenna based on winding line structure

Abstract

The invention provides a dual-frequency implantable antenna based on a winding line structure. The dual-frequency implantable antenna is used for solving the technical problem that an existing implantable antenna cannot realize high-frequency-ratio dual-frequency work. Comprising an upper layer substrate used for isolating a radiator and biological tissue, a middle layer substrate used for installing a winding line radiation patch, and a bottom layer substrate reserved with a rectification circuit integration space. The upper layer substrate, the middle layer substrate and the bottom layer substrate are sequentially arranged in a stacked mode from top to bottom, a winding line radiation patch is attached to the middle layer substrate, and the winding line radiation patch comprises more than two asymmetrical winding patch units. And the plurality of winding patch units used for increasing the length of a current path so as to realize a dual-frequency resonant mode are connected in sequence. Synchronous work of a 915 MHz frequency band wireless energy receiving mode and a 2.5 GHz frequency band data telemetering mode can be achieved, and the power supply circuit is suitable for implantable medical equipment needing continuous power supply such as intracranial pressure monitoring and cardiac pacemakers.

Description

Technical Field

[0001] This invention relates to the field of biomedical electronics and wireless power transmission, and in particular to a dual-frequency implantable antenna based on a meandering line structure. Background Technology

[0002] With the widespread application of implantable medical devices in areas such as physiological parameter monitoring, nerve stimulation, and drug delivery, their power supply has become a key bottleneck restricting the long-term operation of these devices. Traditional implantable devices rely on battery power, but battery capacity is limited and replacement requires invasive surgery, increasing patient suffering and medical costs, as well as posing risks of tissue damage and infection due to battery leakage. Furthermore, battery size limits the miniaturization of devices, while large implants increase the risk of tissue inflammation and device rejection. Therefore, developing battery-free wireless power transfer (WPT) technology to achieve continuous power supply and data telemetry for implantable devices has become a research hotspot in the field of biomedical engineering.

[0003] Existing wireless power transfer technologies are mainly divided into two categories: near-field magnetic coupling and far-field radiation. The former has higher efficiency but is sensitive to positional shifts, while the latter has a longer transmission distance but its efficiency is generally less than 1%. In implantable antenna design, achieving both miniaturization and dual-band operation has always been a technical challenge. Winding wire structures, by increasing the current path length, achieve size reduction and have been widely used in implantable antenna design. However, when achieving dual-band operation with a high frequency ratio is required, how to simultaneously excite the resonant modes of two frequency bands within a compact size through reasonable radiator layout and grounding structure design, while ensuring good impedance matching and radiation efficiency in both bands, remains a pressing technical problem to be solved.

[0004] An invention patent with authorization announcement number CN119944284B discloses an implantable WPT system based on a planar electrically coupled loop antenna. However, this design only operates in a single frequency band and cannot simultaneously meet the dual requirements of energy reception and data telemetry, necessitating the integration of an additional communication antenna, which increases system complexity. Therefore, developing an implantable antenna system capable of achieving dual-frequency operation with a high frequency ratio on a single compact antenna element is of great significance for improving the integration and reliability of implantable medical devices. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-band implantable antenna based on a meandering line structure. This addresses the technical problem that existing implantable antennas cannot achieve dual-band operation with a high frequency ratio.

[0006] A dual-band implantable antenna based on a meandering line structure includes an upper substrate for isolating the radiator from biological tissue, a middle substrate for mounting the meandering line radiating patch, and a bottom substrate with reserved space for rectifier circuit integration.

[0007] The upper substrate, middle substrate, and bottom substrate are stacked sequentially from top to bottom. A meandering radial patch is attached to the middle substrate. The meandering radial patch includes two or more asymmetrical meandering patch units. Several meandering patch units are connected in sequence to increase the current path length and thus realize the dual-frequency resonant mode.

[0008] Optionally, the dual-frequency resonant mode includes a wireless power receiving mode in the 915 MHz band and a data telemetry mode in the 2.5 GHz band;

[0009] The 915 MHz band is a quarter-wavelength monopole mode, in which the current flows in the same direction; the 2.5 GHz band is a half-wavelength monopole mode, in which the current flows in the opposite direction.

[0010] Optionally, the meandering patch unit includes a first meandering patch unit, a second meandering patch unit, and a third meandering patch unit arranged in parallel at intervals in sequence;

[0011] One end of the first meandering patch unit is connected to one end of the second meandering patch unit via a first connecting plate, and the other end of the second meandering patch unit is connected to one end of the third meandering patch unit via a second connecting plate.

[0012] Optionally, the meandering radial patch may further include an inverted L-shaped connecting plate;

[0013] The vertical edge of the inverted L-shaped connecting plate is located on the side of the first meandering patch unit away from the second meandering patch unit. The vertical edge of the inverted L-shaped connecting plate is connected to the other end of the first meandering patch unit through a third connecting plate. The horizontal edge of the inverted L-shaped connecting plate is connected to the first vertical plate.

[0014] Optionally, the first, second, and third meandering patch units are all planar meandering folded structures with the horizontal and vertical sides connected end to end.

[0015] Optionally, it also includes a bottom ground plane disposed on the bottom substrate, the bottom ground plane being connected to the meandering radial patch via a short-circuit pin, the upper end of the short-circuit pin passing through the middle substrate and connected to the corner position of the inverted L-shaped connecting plate.

[0016] Optionally, it also includes a coaxial feed structure, wherein the inner conductor of the coaxial feed structure passes through the middle layer substrate and is connected to the second meandering patch unit.

[0017] Optionally, the width of the first, second, and third serpentine patch units is 1.5 mm.

[0018] The spacing between the first and second wavy patch units and between the second and third wavy patch units is 1 mm, and the spacing between the first, second, and third wavy patch units and the inverted L-shaped connecting plate is 0.3 mm.

[0019] Optionally, the width of the horizontal and vertical sides of the first, second, and third serpentine patch units, as well as the width of the first, second, and third connecting plates, is 0.5 mm, and the width of the first vertical plate is 0.7 mm.

[0020] Optionally, the end face length of the upper substrate, the middle substrate, and the bottom substrate is 9mm, and the width is 8mm.

[0021] The thickness of the upper and lower substrates is 0.25 mm, the thickness of the middle substrate is 0.5 mm, and the material of the upper, middle and lower substrates is Rogers 3010, with a dielectric constant of 10.2 and a loss tangent of 0.0023.

[0022] Because of the adoption of the above technical solution, the present invention has the following advantages:

[0023] 1. This application enables simultaneous operation of the 915 MHz band wireless power receiving mode and the 2.5 GHz band data telemetry mode, and is applicable to implantable medical devices that require continuous power supply, such as intracranial pressure monitoring and cardiac pacemakers.

[0024] 2. This application adopts a three-layer Rogers3010 high dielectric constant substrate stack structure. The overall size of the antenna is 8mm×9mm×1mm, and the volume is only 72 mm³. It achieves dual-band operation with a large frequency ratio (2.73:1) within a compact size, while meeting the dual requirements of wireless power reception and data telemetry.

[0025] 3. The antenna of this application achieves a resonant frequency drift of less than 30 MHz within the implantation depth range of 2mm to 8mm, and obtains excellent impedance matching characteristics of -32.66dB and -31.75dB in the two operating frequency bands, respectively. It also complies with the IEEE C95.1 international safety standard, providing an effective wireless power supply and communication solution for implantable medical devices such as cardiac pacemakers and intracranial pressure monitoring.

[0026] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0027] The accompanying drawings of this invention are described below.

[0028] Figure 1 This is a schematic diagram of the structure of the middle layer substrate and the meandering line radiating patch of the present invention.

[0029] Figure 2 This is a front view of the dual-frequency implanted antenna of the present invention.

[0030] Figure 3 This is a schematic diagram of the simulation environment for the antenna implanted in the uniform skin model of the present invention.

[0031] Figure 4 The antenna reflection coefficient |S of this invention 11 Frequency response curve.

[0032] Figure 5 The antenna reflection coefficient |S| at different implantation depths according to the present invention 11 | Comparison curves.

[0033] Figure 6 This is the radiation pattern of the antenna's E-plane in the 915 MHz band of this invention.

[0034] Figure 7 This is the radiation pattern of the antenna H-plane in the 915 MHz band of this invention.

[0035] Figure 8 This is the radiation pattern of the antenna E-plane in the 2.5 GHz band of this invention.

[0036] Figure 9 This is the radiation pattern of the antenna H-plane in the 2.5 GHz band of this invention.

[0037] Figure 10 This is a SAR distribution map of the 915 MHz band within the 1g organization range of the present invention.

[0038] Figure 11 This is a SAR distribution map of the 915 MHz band within the 10g organization range of this invention.

[0039] Figure 12 This is a SAR distribution map of the 2.5 GHz band within the 1g organization range of the present invention.

[0040] Figure 13 This is a SAR distribution map of the 2.5 GHz band within the 10g organization range of the present invention.

[0041] In the diagram: 1-Upper substrate; 2-Middle substrate; 3-Bottom substrate; 4-Waving line radial patch; 401-First wavy patch unit; 402-Second wavy patch unit; 403-Third wavy patch unit; 404-Inverted L-shaped connecting plate; 405-First vertical plate; 5-Short circuit pin; 6-Coaxial feeder structure; 7-Bottom ground plane. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Example:

[0044] like Figure 1 and Figure 2 The dual-band implantable antenna based on a meandering line structure shown includes an upper substrate 1 for isolating the radiator from biological tissue, a middle substrate 2 for mounting the meandering line radiating patch, and a bottom substrate 3 with reserved space for rectifier circuit integration.

[0045] The upper substrate 1, the middle substrate 2 and the bottom substrate 3 are stacked sequentially from top to bottom. A meandering radial patch 4 is attached to the middle substrate 2. The meandering radial patch includes two or more asymmetrical meandering patch units, which are connected sequentially to increase the current path length and thus realize the dual-frequency resonant mode.

[0046] In this embodiment, the dual-frequency resonant mode includes a wireless power receiving mode in the 915 MHz band and a data telemetry mode in the 2.5 GHz band; the 915 MHz band is a quarter-wavelength monopole mode, in which the current flows in the same direction; the 2.5 GHz band is a half-wavelength monopole mode, in which the current flows in the opposite direction. The antenna of this application is suitable for implantable medical devices requiring continuous power supply, such as intracranial pressure monitoring devices and pacemakers.

[0047] In this embodiment, the material of the meandering radial patch 4 is copper. The end face lengths of the upper substrate 1, the middle substrate 2, and the bottom substrate 3 are all 9 mm and the widths are all 8 mm. The thicknesses of the upper substrate 1 and the bottom substrate 3 are 0.25 mm, the thickness of the middle substrate 2 is 0.5 mm, and the material of the upper substrate 1, the middle substrate 2, and the bottom substrate 3 is Rogers 3010, with a dielectric constant of 10.2 and a loss tangent of 0.0023.

[0048] like Figure 1 and Figure 2 As shown, the meandering patch unit includes a first meandering patch unit 401, a second meandering patch unit 402 and a third meandering patch unit 402 arranged in parallel at intervals in sequence;

[0049] One end of the first meandering patch unit 401 is connected to one end of the second meandering patch unit 402 via a first connecting plate, and the other end of the second meandering patch unit 402 and one end of the third meandering patch unit 402 are connected via a second connecting plate.

[0050] like Figure 1 and Figure 2 As shown, the meandering radial patch 4 also includes an inverted L-shaped connecting plate 404;

[0051] The vertical edge of the inverted L-shaped connecting plate 404 is located on the side of the first meandering patch unit 401 away from the second meandering patch unit 402. The vertical edge of the inverted L-shaped connecting plate 404 is connected to the other end of the first meandering patch unit 401 through a third connecting plate. The horizontal edge of the inverted L-shaped connecting plate 404 is connected to the first vertical plate 405.

[0052] like Figure 1 , Figure 2 and Figure 3 As shown, the first meandering patch unit 401, the second meandering patch unit 402 and the third meandering patch unit 402 are all planar meandering folded structures with the horizontal and vertical sides connected end to end.

[0053] like Figure 1 and Figure 2 As shown, it also includes a bottom ground plane 7 disposed on the bottom substrate 3. The bottom ground plane 7 is connected to the meandering line radial patch 4 through a short-circuit pin 5. The upper end of the short-circuit pin 5 passes through the middle substrate 2 and is connected to the corner position of the inverted L-shaped connecting plate 404.

[0054] like Figure 1 and Figure 2 As shown, it also includes a coaxial feed structure 6, the inner conductor of which passes through the middle substrate 2 and is connected to the second meandering patch unit 402.

[0055] In this embodiment, the bottom ground plane 7 is a complete metal ground plane (with the same dimensions as the substrate). The coaxial feed structure 6 is connected to the metal ground plane, and impedance matching is achieved through the coaxial feed structure 6. The short-circuit pin 5 is used to adjust the impedance matching of the antenna in the low-frequency band, improving the reflection coefficient characteristics in the 915 MHz band. The application achieves resonance in the 915 MHz and 2.5 GHz bands by optimizing the layout of the meandering line radiating patch 4 and the position of the short-circuit pin.

[0056] like Figure 1 and Figure 2 As shown, the widths of the first meandering patch unit 401, the second meandering patch unit 402, and the third meandering patch unit 403 are all 1.5 mm;

[0057] The spacing between the first meandering patch unit 401 and the second meandering patch unit 402, and between the second meandering patch unit 402 and the third meandering patch unit 402, is 1 mm. The spacing between the first meandering patch unit 401, the second meandering patch unit 402, and the third meandering patch unit 403 and the inverted L-shaped connecting plate 404 is 0.3 mm.

[0058] like Figure 1 and Figure 2 As shown, the width of the horizontal and vertical sides of the first meandering patch unit 401, the second meandering patch unit 402, and the third meandering patch unit 403, as well as the width of the first, second, and third connecting plates, are all 0.5 mm, and the width of the first vertical plate 405 is 0.7 mm.

[0059] Experimental simulation:

[0060] like Figure 3 As shown, this embodiment performs electromagnetic simulation analysis on a uniform skin model (HSP). The skin model has dimensions of 150 mm × 150 mm × 80 mm to simulate the actual human tissue environment. The antenna implantation depth ds is set to 2 mm, meaning the top of the antenna is 2 mm from the surface of the skin model. According to the literature, the frequency-dependent dielectric properties of skin tissue are: εr = 41.3 and σ = 0.87 S / m at 915 MHz; and εr = 38.7 and σ = 1.44 S / m at 2.5 GHz.

[0061] Through simulation, the antenna's reflection coefficient |S 11 Simulation results are as follows Figure 4 As shown, at an implantation depth of 2 mm, the antenna achieves excellent impedance matching characteristics of -32.66 dB and -31.75 dB in the 915 MHz and 2.5 GHz dual-band frequencies, respectively, corresponding to -10 dB bandwidths of 70 MHz and 200 MHz. The results of the study on the influence of different implantation depths (2 mm, 4 mm, 6 mm, and 8 mm) on the antenna reflection coefficient are as follows... Figure 5 As shown, as the implantation depth increased from 2 mm to 8 mm, the resonant frequency drift in the 915 MHz band was less than 30 MHz, and the resonant frequency in the 2.5 GHz band remained stable, demonstrating that the antenna design has good robustness.

[0062] Figure 6 and Figure 7 The radiation patterns of the antenna in the E-plane and H-plane of the 915 MHz band are shown respectively; as follows: Figure 6 As shown, in the E-plane radiation pattern of the 915 MHz band, the antenna exhibits directional radiation characteristics, with the maximum radiation direction pointing outwards (0° direction), a peak gain of -38.8 dBi, a moderate main lobe width, and good sidelobe suppression. Figure 7 As shown, in the H-plane radiation pattern of the 915 MHz band, the radiation pattern maintains good symmetry, and the radiated energy is mainly concentrated in the upper half space, verifying the stable radiation performance of the antenna in this frequency band. Figure 8 and Figure 9 The radiation patterns of the antenna in the E-plane and H-plane of the 2.5 GHz band are shown respectively; as follows: Figure 8 As shown, in the E-plane radiation pattern of the 2.5 GHz band, the antenna achieves a peak gain of -33.5 dBi, and the radiation pattern exhibits more concentrated directional radiation characteristics, which is beneficial for achieving efficient data telemetry communication; as Figure 9 As shown, in the H-plane radiation pattern of the 2.5 GHz band, the radiation pattern exhibits good symmetry and stability, with the main lobe direction aligning with the E-plane, ensuring a reliable communication link with external devices. Both frequency band radiation patterns indicate that the antenna's maximum radiation direction points outwards, effectively reducing electromagnetic radiation to deep tissues. This facilitates efficient wireless power transmission and data communication while minimizing potential impacts on human tissues.

[0063] Based on international standards IEEE C95.1-1999 and IEEE C95.1-2005, the specific absorption rate (SAR) of implantable antennas was assessed for patient safety. These standards specify SAR limits of 1.6 W / kg and 2.0 W / kg for 1g and 10g of human tissue, respectively. SAR simulation analysis was performed under an input power of 1W. Figure 10 The SAR distribution of the 915 MHz band within the 1g organization range is shown, with an average SAR peak value of 29.83 W / kg. Figure 11 The SAR distribution of the 915 MHz band within the 10g organization range is shown, with an average SAR peak value of 3.101 W / kg in 10g. Figure 12 The SAR distribution of the 2.5 GHz band within the 1g organization range is shown, with an average SAR peak value of 60.246 W / kg. Figure 13 The SAR distribution of the 2.5 GHz band within the 10g organization range is shown, with an average SAR peak value of 6.428 W / kg in 10g.

[0064] In practical implantable medical device applications, the antenna's input power is limited to 25 μW. Through normalized calculations, under actual operating conditions, the average SAR values ​​for 1g and 10g in the 915 MHz band drop to approximately 0.75 mW / kg and 0.078 mW / kg, respectively; and the average SAR values ​​for 1g and 10g in the 2.5 GHz band drop to approximately 1.51 mW / kg and 0.16 mW / kg, respectively, both far below the safety limits specified in the IEEE C95.1 standard. Based on the above SAR analysis, the implantable antenna system proposed in this invention will not pose an electromagnetic radiation safety risk to patients in practical applications.

[0065] In summary, the compact dual-band implantable antenna system based on a meandering line structure provided in this application successfully achieves dual-band operation with a high frequency ratio (2.73:1), simultaneously meeting the requirements for 915MHz wireless power reception and 2.5GHz data telemetry in an ultra-compact size (72 mm³), and maintaining stable performance at different implantation depths, providing a reliable wireless power supply and communication solution for implantable medical devices.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A dual-band implantable antenna based on a meander line structure, characterized by, It comprises an upper layer substrate (1) for isolating the radiator and the biological tissue, a middle layer substrate (2) for mounting the meander line radiation patch, and a bottom layer substrate (3) reserved for the integrated space of the rectifier circuit; The upper layer substrate (1), the middle layer substrate (2) and the bottom layer substrate (3) are sequentially stacked from top to bottom, the meander line radiation patch (4) is attached to the middle layer substrate (2), the meander line radiation patch comprises two or more asymmetric meander patch units, and a plurality of meander patch units for increasing the length of the current path to realize a double-frequency resonance mode are sequentially connected.

2. The dual-band implantable antenna based on meander line structure according to claim 1, wherein, The double-frequency resonance mode includes a wireless energy receiving mode of 915 MHz frequency band and a data telemetry mode of 2.5 GHz frequency band.

3. The dual-band implantable antenna based on meander line structure according to claim 1 or 2, characterized in that, The meander patch unit comprises a first meander patch unit (401), a second meander patch unit (402) and a third meander patch unit (402) which are sequentially and spaced apart in parallel; One end of the first meander patch unit (401) and one end of the second meander patch unit (402) are connected by a first connecting plate, and the other end of the second meander patch unit (402) and one end of the third meander patch unit (402) are connected by a second connecting plate.

4. The dual-band implantable antenna based on meander line structure according to claim 3, wherein, The meander line radiation patch (4) further comprises an inverted L-shaped connecting plate (404); The vertical edge of the inverted L-shaped connecting plate (404) is located on the side of the first meander patch unit (401) away from the second meander patch unit (402), the vertical edge of the inverted L-shaped connecting plate (404) is connected to the other end of the first meander patch unit (401) through a third connecting plate, and the horizontal edge of the inverted L-shaped connecting plate (404) is connected with a first vertical plate (405).

5. The dual-band implantable antenna based on meander line structure according to claim 3, wherein, The first meander patch unit (401), the second meander patch unit (402) and the third meander patch unit (402) are all planar meander folding structures with horizontal edges and vertical edges connected in sequence.

6. The dual-band implantable antenna based on meander line structure according to claim 4, wherein, It further comprises a bottom grounding plate (7) provided on the bottom layer substrate (3), the bottom grounding plate (7) is connected to the meander line radiation patch (4) through a short-circuit pin (5), and the upper end of the short-circuit pin (5) is connected to the corner position of the inverted L-shaped connecting plate (404) through the middle layer substrate (2).

7. The dual-band implantable antenna based on meander line structure according to claim 3, wherein, It further comprises a coaxial feed line structure (6), the inner conductor of the coaxial feed line structure (6) is connected to the second meander patch unit (402) through the middle layer substrate (2).

8. The dual-band implantable antenna based on meander line structure according to claim 3, wherein, The width of the first meander patch unit (401), the second meander patch unit (402) and the third meander patch unit (403) is 1.5 mm; The spacing between the first meander patch unit (401) and the second meander patch unit (402) and the spacing between the second meander patch unit (402) and the third meander patch unit (402) are both 1 mm, and the spacing between the first meander patch unit (401), the second meander patch unit (402) and the third meander patch unit (403) and the inverted L-shaped connecting plate (404) is 0.3 mm.

9. The dual-band implantable antenna based on meander line structure according to claim 3, wherein, The width of the horizontal and vertical edges of the first, second and third meandered patch units (401, 402, 403) and the first, second and third connecting plates is 0.5 mm, and the width of the first vertical plate (405) is 0.7 mm.

10. The dual-band implantable antenna based on meander line structure according to claim 1, wherein, The length of the end face of the upper substrate (1), the middle substrate (2) and the bottom substrate (3) is 9 mm, and the width is 8 mm. The thickness of the upper substrate (1) and the bottom substrate (3) is 0.25 mm, the thickness of the middle substrate (2) is 0.5 mm, and the material of the upper substrate (1), the middle substrate (2) and the bottom substrate (3) is Rogers 3010, the dielectric constant is 10.2, and the loss tangent is 0.0023.

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