Impedance matching device for improving the gain of multi-frequency implanted antennas

Abstract

This invention belongs to the fields of wireless power transmission and biomedical telemetry, specifically an impedance matching device for improving the gain of multi-frequency implantable antennas. The device includes a dielectric substrate and a metal layer on the substrate. The metal layer includes multiple concentric metal rings and a metal patch disposed within the smallest concentric metal ring. Adjacent metal rings do not contact each other, forming a first gap; the smallest metal ring and the metal patch do not contact each other, forming a second gap. By adjusting the dimensions of the first and second gaps, impedance matching adjustment for different operating frequency bands can be achieved. This enhances the gain of multi-frequency implantable antennas in the biomedical frequency band, enabling their application in multi-frequency implantable devices and improving their information and power transmission efficiency.

Description

Technical Field

[0001] This invention belongs to the fields of wireless power transmission and biomedical telemetry, specifically relating to an impedance matching device for improving the gain of multi-frequency implantable antennas. Background Technology

[0002] Implantable medical devices mainly consist of biosensors, power supply systems, and wireless communication systems. Due to their broad application prospects in fields such as bio-telemetry and wireless power transmission, implantable antennas for medical devices have attracted significant attention. Implantable antennas wirelessly transmit data monitored by medical devices inside the body to external devices, while simultaneously allowing external devices to wirelessly transmit energy back into the body, ensuring the long-term stable operation of internal devices. This plays a crucial role in health monitoring and extending the lifespan of wireless medical devices. The performance of these technologies largely depends on the efficiency of wireless transmission from the external terminal to the internal device. Typically, implantable antennas need to be integrated inside the medical device before being implanted into the body. Therefore, their size needs to be reduced to facilitate integration and minimize discomfort. However, miniaturization reduces antenna gain, and impedance mismatch at the air-to-human interface leads to significant reflection, accounting for over 80% of the total information and energy transmission loss, severely limiting transmission efficiency.

[0003] To enhance the gain of implantable antennas and thus improve the information and power transmission efficiency of implantable devices, current methods mainly fall into three categories. The first is to improve gain by modifying the structure of the implantable antenna itself. This method achieves relatively poor gain enhancement, typically around 3dB. For example, Chulhun Seo et al. increased the antenna gain by approximately 3.2dB in the ISM band by drilling holes in the antenna coating medium and arranging them at specific intervals; Hyoungsuk Yoo et al. achieved gain enhancements of approximately 2dB and 1.5dB at 915MHz and 2.45GHz, respectively, by introducing metasurfaces into the coating medium. The second method is to improve gain by adding a relay device between the external terminal device and the human body. For example, D Mitra et al. utilized the high refractive index of metasurfaces to improve the gain of implantable antennas, thereby improving the efficiency of wireless power transmission systems. However, this method increases system complexity and is easily misaligned due to human movement, leading to deterioration in performance. Third, placing metasurfaces or impedance matching layers on the body surface can reduce reflections at the interface between the human body and the air, thereby increasing the gain. For example, Xu Lijie et al. recently proposed an impedance matching layer based on the slow wave effect, which achieved a gain enhancement of up to about 5.7dB in the ISM band. However, this method only achieves gain enhancement in a single frequency band. Summary of the Invention

[0004] The purpose of this invention is to provide an impedance matching device for improving the gain of multi-frequency implantable antennas. This device has a simple structure, a low profile, and can reduce reflections between the skin and air interface in the commonly used frequency bands of implantable medical devices, thereby achieving impedance matching that enhances multi-frequency gain.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An impedance matching device for improving the gain of a multi-frequency implanted antenna includes a dielectric substrate and a metal layer on the dielectric substrate; the metal layer includes a plurality of concentric metal rings and a metal patch disposed within the smallest concentric metal ring; adjacent metal rings do not contact each other to form a first gap, and the smallest metal ring and the metal patch do not contact each other to form a second gap; by adjusting the size of the first gap and the second gap, impedance matching adjustment for different operating frequency bands can be achieved.

[0007] Furthermore, the metal is a circular ring, a square ring, or an elliptical ring, preferably a square ring.

[0008] Furthermore, the shape of the metal patch is the same as the shape of the area enclosed by the inner ring of the smallest metal ring.

[0009] Furthermore, the metal layer material is copper.

[0010] Furthermore, the dielectric layer material is F4B with a dielectric constant of 4.3, a loss tangent of 0.0025, and dimensions of 37mm*37mm*8mm.

[0011] By adopting the above technical solution, the present invention has the following beneficial effects:

[0012] The impedance matching device of this invention consists of a single unit, with a simple structure that is easy to implement. By adjusting the sizes of the first and second slits, impedance matching at the skin-air interface for different frequency bands is achieved using the field confinement effect, thereby enhancing the gain of multi-frequency implantable antennas in the biomedical frequency band, enabling their application in multi-frequency implantable devices and improving their information and energy transmission efficiency. Attached Figure Description

[0013] Figure 1 A schematic diagram of the impedance matching device provided in the embodiment;

[0014] Figure 2 A schematic diagram of the S-parameters of the impedance matching device at the skin-air interface in this embodiment;

[0015] Figure 3 The impedance matching device for the embodiment is placed on the surface of a skin model containing a dual-band implanted antenna in a simulated environment. (a) is a perspective view, (b) is a top view, and (c) is a side view.

[0016] Figure 4 A schematic diagram showing the gain variation with frequency for WMTS band with and without impedance matching devices;

[0017] Figure 5 A schematic diagram showing the gain variation with frequency for ISM band with and without an impedance matching device;

[0018] Figure 6 This diagram illustrates the gain variation with frequency when a dual-band implantable antenna deflects within the body, with and without an impedance matching device. (a) WMTS band; (b) ISM band.

[0019] Figure label:

[0020] 1. First square ring, 2. Second square ring, 3. Metal patch, 4. Dielectric substrate, 5. Dual-band implantable antenna, 6. Skin model. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0022] like Figure 1 An impedance matching device for improving the gain of a multi-frequency implanted antenna includes a dielectric substrate and a metal layer on the dielectric substrate. The metal layer includes multiple concentric metal rings and a metal patch disposed within the smallest concentric metal ring. Adjacent metal rings do not contact each other to form a first gap, and the smallest metal ring and the metal patch do not contact each other to form a second gap. By adjusting the size of the first gap and the second gap, impedance matching adjustment for different operating frequency bands can be achieved, thereby enhancing the gain of the multi-frequency implanted antenna.

[0023] The impedance matching device provided in this embodiment has a simple structure and a wide range of applications. Gain enhancement for implantable antennas in different frequency bands can be achieved by controlling the number of metal rings. When the number of metal rings is one, it can be applied to single-band implantable antenna gain enhancement. When the number of concentric metal rings is two, it is applied to dual-band implantable antenna gain enhancement. When the number of concentric metal rings is three, it is applied to tri-band implantable antenna gain enhancement. It should be noted that when the number of concentric metal rings is greater than one, the operating frequency bands corresponding to each concentric metal ring are, from the outside in, the first operating frequency band, the second operating frequency band, and so on; and the order of each operating frequency band in the spectrum is from low to high, that is, the first operating frequency band corresponds to the lowest spectrum. Specifically, the gap between the smallest concentric metal ring and the metal patch is used to adjust the impedance matching of the highest operating frequency band; the gaps between adjacent concentric metal rings are used to adjust the operating frequency bands for impedance matching, which increase sequentially from the outside in.

[0024] Example 1

[0025] The impedance matching device for improving the gain of a dual-band implanted antenna was fabricated using copper as the material for the metal structure, with a thickness of 0.035 mm. Both concentric metal rings are square rings, designated as the first square ring and the second square ring from the outside in. The metal patch is also square. The outer side length of the first square ring is 37 mm, and the inner side length is 34.5 mm; the outer side length of the second square ring is 33.5 mm, and the inner side length is 29 mm; the square patch has a side length of 23.4 mm; the dielectric substrate 4 is F4B with a dielectric constant of 4.3 and a loss of 0.0025, and its dimensions are 37 mm * 37 mm * 8 mm.

[0026] Simulation tests were performed on the impedance matching device of Example 1:

[0027] like Figure 3 (a) Figure 3 (b) Figure 3 As shown in (c), the dimensions of the skin model were set to 70mm*70mm*60mm during the simulation. The dual-band implanted antenna was placed 4mm below the skin model and operated in the WMTS (1.395-1.4GHz) and ISM (2.40-2.48GHz) bands. The impedance matching device from the embodiment was then placed on the skin surface, with its center aligned with the center of the dual-band implanted antenna. The simulation results are as follows:

[0028] Figure 2 The figure shows the S-parameters obtained from simulations where the impedance matching layer is placed on the skin-air interface. Figure 2 It can be seen that the transmission coefficients S12 and S21 are -0.91dB at 1.4GHz and -0.7dB at 2.45GHz, indicating that the reflection between the skin and the air is greatly reduced after the impedance matching layer is applied.

[0029] Figure 4 A schematic diagram showing the gain versus frequency for the WMTS band with and without impedance matching devices. Figure 4 As can be seen, compared with the implantable antenna without the impedance matching device of this embodiment, the implantable antenna with the impedance matching device of this embodiment has a gain increase of about 4.8dB in the entire WMTS band. This indicates that this embodiment can improve the impedance matching at the skin-air interface in the WMTS band, thereby improving the transmission efficiency of information and energy.

[0030] Figure 5The diagram illustrates the gain variation with frequency for the ISM band with and without an impedance matching device. As can be seen from the figure, compared to the implantable antenna without the impedance matching device of this embodiment, the implantable antenna with the impedance matching device of this embodiment exhibits a gain enhancement of over 9.3 dB across the entire ISM band, with a maximum gain enhancement of 9.8 dB at 2.40 GHz. This indicates that this embodiment can significantly enhance the transmission efficiency at the skin-air interface.

[0031] Figure 6 This diagram illustrates the gain versus frequency with and without an impedance matching device when a dual-band implantable antenna deflects within the body. (a) WMTS band (b) ISM band. Figure 6 As can be seen in (a), in the WMTS band, the impedance matching layer provides approximately 4 dB of gain enhancement when the antenna rotation angle is 40°; from Figure 6 As can be seen in (b), in the ISM band, the impedance matching layer has a gain enhancement of about 10dB when the antenna rotation angle is 40°, indicating that the proposed impedance matching layer can effectively achieve impedance matching between skin and air in both frequency bands and can accept a certain degree of angular misalignment.

[0032] In summary, the impedance matching device for improving the gain of multi-frequency implantable antennas in this embodiment greatly enhances the gain of dual-frequency implantable antennas in the WMTS band (1.395-1.4GHz) and ISM band (2.4-2.48GHz). This impedance matching layer has the characteristics of dual-frequency operation, easy manufacturing, simple structure, low profile, and strong practicality.

[0033] Those skilled in the art should understand that the functions of the present invention are not limited to the above embodiments. The specific embodiments and descriptions in the specification are only for further illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, various changes and improvements can be made to the functions that the present invention can achieve, and all such changes and improvements fall within the scope of the present invention as claimed.

Claims

1. An impedance matching device for improving the gain of a multi-frequency implanted antenna, comprising a dielectric substrate and a metal layer located on the dielectric substrate, characterized in that: The metal layer includes multiple concentric metal rings and a metal patch disposed within the smallest concentric metal ring. Adjacent metal rings do not contact each other to form a first gap, and the smallest metal ring and the metal patch do not contact each other to form a second gap. By adjusting the size of the first and second gaps, impedance matching adjustment for different operating frequency bands can be achieved. When the number of concentric metal rings is greater than 1, the operating frequency bands corresponding to each concentric metal ring are arranged in ascending order on the spectrum from the outside to the inside. The second gap between the smallest concentric metal ring and the metal patch is used to adjust the impedance matching of the highest operating frequency band. The first gap between adjacent concentric metal rings is used to adjust the operating frequency bands for impedance matching, which increase sequentially from the outside to the inside.

2. The impedance matching device for improving the gain of a multi-frequency implanted antenna as described in claim 1, characterized in that: The metal is a circular ring, a square ring, or an elliptical ring.

3. The impedance matching device for improving the gain of a multi-frequency implanted antenna as described in claim 1, characterized in that: The shape of the metal patch is the same as the shape of the area enclosed by the inner ring of the smallest metal ring.

4. An impedance matching device for improving the gain of a multi-frequency implanted antenna as described in claim 1, characterized in that: The metal layer material is copper.

5. An impedance matching device for improving the gain of a multi-frequency implanted antenna as described in any one of claims 1 to 4, characterized in that: The dielectric substrate material is F4B with a dielectric constant of 4.3, a loss tangent of 0.0025, and dimensions of 37mm*37mm*8mm.

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