A compact dual-band multi-port implantable antenna for biomedical devices

Abstract

The application provides a compact dual-band multi-port implantable antenna for biomedical devices, which is composed of multiple single-input single-output antenna units arranged in a planar manner, each of which comprises a radiating patch, a substrate, an overlying dielectric layer, a ground plane, a feeding port and a short-circuit via; the radiating patch is provided with multiple slot structures to form an elongated current path, thereby realizing miniaturization and dual-band operation; the ground plane is provided with a slot structure to improve impedance matching and expand bandwidth. Four identical antenna units are arranged in an alternating direction, thereby realizing inherent isolation without additional decoupling structures. The antenna has stable performance and quasi-omnidirectional radiation characteristics in a biological tissue environment and can be reliably integrated into a compact implantable device.

Description

Technical Field

[0001] This invention relates to the field of wireless biomedical devices, specifically a compact dual-band multi-port implantable antenna for biomedical devices. Background Technology

[0002] Implantable biomedical devices, such as wireless capsule endoscopes and leadless pacemakers, have become essential medical equipment for continuous patient monitoring, early diagnosis, and therapeutic intervention. These devices require efficient and reliable wireless communication links to transmit physiological data and receive control signals from external monitoring systems.

[0003] The design of implantable antennas in implantable biomedical devices faces significant technical challenges, primarily due to the extremely limited device package size and the high losses and heterogeneous environment of human tissue. The antenna must maintain a resonant state in a specific frequency band to simultaneously achieve wireless power supply and high-speed data telemetry. Failure to meet these requirements will result in degraded signal quality, reduced data throughput, and decreased device operating efficiency.

[0004] While traditional single-input single-output antennas have been used in implantable biomedical devices, their intrinsic spectral efficiency is limited, failing to meet the demands of high-speed data telemetry. Furthermore, their design typically suffers from poor impedance matching, limited bandwidth, and directional radiation patterns, further reducing communication reliability in implanted environments.

[0005] Multiple-input multiple-output (MIMO) antenna systems can improve data throughput, enhance channel capacity, and improve spatial diversity performance, which is crucial for maintaining robust communication in high-loss implanted environments. However, existing implanted MIMO antenna designs have many limitations, including large size, insufficient isolation between closely packed antenna elements, high mutual coupling, and reliance on external decoupling structures (such as inductors, compensation lines, or defective grounding structures). These solutions increase device manufacturing complexity, system cost, and reduce overall reliability.

[0006] Therefore, there is a growing market demand for multi-input multi-output antennas that can simultaneously achieve miniaturization, multi-band operation, high isolation, low mutual coupling, and quasi-omnidirectional radiation, without requiring additional decoupling components. Furthermore, such antennas should be able to be integrated into various implantable devices, maintain stable performance in different tissue environments, meet specific absorption rate limits, and support long-distance, high-speed data telemetry.

[0007] Existing implantable multiple-input multiple-output (MIMO) antenna solutions often involve trade-offs between size, performance, and safety. There is an urgent need for a technical solution that can achieve an optimized combination of miniaturization, dual-band operation, high isolation, efficient radiation, and safety for human exposure, in order to meet the practical application needs of the implantable biomedical antenna field. Summary of the Invention

[0008] This invention proposes a compact dual-band multi-port implantable antenna for biomedical devices, aiming to solve the technical problems of existing implantable antennas, such as large size, high coupling between antenna elements, limited bandwidth, and significant radiation directivity. The disclosed antenna can operate simultaneously in the 1.4 GHz wireless medical telemetry service band and the 2.45 GHz industrial, scientific, and medical band, realizing wireless power supply and high-speed data telemetry in biological tissue environments. The technical solution provided by this invention is as follows:

[0009] In a first aspect, a compact dual-band multi-port implantable antenna for biomedical devices is provided, comprising a plurality of single-input single-output antenna elements arranged in a stacked configuration. Each single-input single-output antenna element includes a substrate, a radiating patch disposed on a first surface of the substrate, a ground plane disposed on a second surface of the substrate, a feed port electrically connected to the radiating patch, and a short-circuit via electrically connecting the radiating patch to the ground plane. The radiating patch, the substrate, and the ground plane are arranged in a stacked configuration, and a dielectric layer is disposed above the radiating patch to achieve electromagnetic isolation. The radiating patch and the ground plane have a plurality of slots.

[0010] Preferably, the radiating patch includes multiple sequentially connected longitudinal slots to form a zigzag structure, thereby increasing the effective current path length.

[0011] Preferably, the grounding plane includes a central slotted section and a laterally extended slotted section, forming a folded or inverted U-shaped current path to increase distributed capacitance and inductance, generate additional resonance, and expand the impedance bandwidth.

[0012] Preferably, the feed port and the short-circuit via are arranged at different positions on the radiating patch, wherein the feed port is used to excite the antenna, and the short-circuit via achieves resonant tuning and impedance matching by introducing an inductive-capacitive load.

[0013] Preferably, the four single-input single-output antenna elements are arranged in a planar configuration, with adjacent antenna elements arranged in alternating directions, so that the high-current region of one antenna element corresponds to the low-current region of the adjacent antenna element, thereby achieving inherent self-decoupling and reducing mutual coupling.

[0014] Preferably, the spacing between adjacent antenna elements is 0.5 mm.

[0015] Secondly, an implantable medical device includes a sensor, a processing circuit, and a power supply. The processing circuit uses a compact dual-band multi-port implantable antenna for biomedical devices to achieve dual-band wireless communication and quasi-omnidirectional radiation functions.

[0016] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention employs an ultra-miniaturized design suitable for capsule-shaped devices, enabling dual-band operation for wireless power supply and data telemetry. High isolation is achieved through inherent antenna self-decoupling; impedance matching and radiation performance are enhanced through a zigzag radiating patch and defective grounding structure; and reliable communication in high-loss biological tissues is ensured through quasi-omnidirectional coverage. This invention provides a safe, efficient, and robust technical solution for high-speed data telemetry in implantable medical devices. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This invention provides a single-input single-output antenna element for an implantable antenna, wherein... Figure 1 (a) is the dielectric layer covering the top of the antenna. Figure 1 (b) is the radiation patch beneath the overlying dielectric layer. Figure 1 (c) is the substrate below the radiating patch. Figure 1 (d) is the grounding plane on the bottom side of the substrate. Figure 1 (e) is a side view of the antenna;

[0019] Figure 2 This is a diagram of a four-port multiple-input multiple-output antenna configuration, where... Figure 2 (a) is a diagram showing the configuration of the radiating patch. Figure 2 (b) is a grounding plane configuration diagram;

[0020] Figure 3 The graph shows the reflection coefficient curves of a four-port multiple-input multiple-output antenna in uniform and non-uniform tissue models. Figure 3 (a) is a graph of the reflection coefficient in the large intestine model. Figure 3 (b) is a graph of the reflection coefficient in the cardiac model;

[0021] Figure 4 The figure shows the coupling coefficient curves for a four-port multiple-input multiple-output antenna. Figure 4 (a) is a graph of the coupling coefficient in the large intestine model. Figure 4 (b) is a graph of the coupling coefficient in the cardiac model;

[0022] Figure 5 The image shows the far-field radiation pattern of a four-port multiple-input multiple-output antenna in an implanted environment. Figure 5 (a) shows the radiation pattern at a frequency of 1.4 GHz. Figure 5 (b) shows the radiation pattern at a frequency of 2.45 GHz;

[0023] The figure shows: left first longitudinal slot 1a, right first longitudinal slot 1b, left second longitudinal slot 2a, right second longitudinal slot 2b, left third longitudinal slot 3a, right third longitudinal slot 3b, fourth longitudinal slot 4a, first transverse slot 4b, cylindrical feed port 5a, cylindrical shorting pin 5b, rectangular slot 6a, second transverse slot 6b, left fifth longitudinal slot 7a, right fifth longitudinal slot 7b, left sixth longitudinal slot 8a, right sixth longitudinal slot 8b, ground plane feed port 9a, ground plane shorting pin 9b, dielectric layer 10a, substrate 10b, radiating patch 11a, ground plane 11b, feed cylinder 12a, shorting pin cylinder 12b, feed position 13a, substrate feed cylinder 13b, substrate shorting pin cylinder 14a, and cross-sectional reference line 14b. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To make the above-mentioned objectives, features and effects of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1: A compact dual-band multi-port implantable antenna for biomedical devices, comprising multiple single-input single-output antenna elements arranged in a single array. Each single-input single-output antenna element includes a top dielectric layer, a radiating patch, a substrate, a ground plane, a feed port, and a short-circuit via. The radiating patch employs a partially folded current path configuration, extending the effective current path within a compact physical area. This structure achieves miniaturization of the antenna while maintaining the resonant characteristics at the target operating frequency. The substrate uses a high-dielectric-constant substrate, such as Rogers RT / duroid 6010, with a relative permittivity of 10.2 and a dielectric loss tangent of 0.0023. The top dielectric layer is made of the same material to provide electromagnetic isolation, reducing electromagnetic interference with surrounding biological tissues and internal device components, thereby stabilizing antenna performance in the implantation environment. The ground plane features a strategically arranged slot structure.

[0027] For a clear description of the antenna's structural configuration, see [link to documentation]. Figure 1The radiating patch 11a is located below the overlying dielectric layer 10a. It has a left first longitudinal slot 1a on its left side and a right first longitudinal slot 1b on its right side. The left second longitudinal slot 2a is located adjacent to the left first longitudinal slot 1a, and the right second longitudinal slot 2b is located adjacent to the right first longitudinal slot 1b. The left third longitudinal slot 3a is located adjacent to the left second longitudinal slot 2a, and the right third longitudinal slot 3b is located adjacent to the right second longitudinal slot 2b. The fourth longitudinal slot 4a is located at the center between the left third longitudinal slot 3a and the left third longitudinal slot 3b. Furthermore, the upper side of the radiating patch 11a is also provided with a cylindrical power supply port 5a and a cylindrical shorting pin 5b.

[0028] The substrate 10b is located below the radiating patch 11a, and a substrate feeding cylinder 13b and a substrate shorting pin cylinder 14a are provided on its upper side, with their positions consistent with the cylindrical feeding port 5a and the cylindrical shorting pin 5b.

[0029] The grounding plane 11b is located below the substrate 10b and adopts a defect grounding structure. It has a central slotted section consisting of a first transverse slot 4b, a sixth longitudinal slot 8a on the left and a sixth longitudinal slot 8b on the right, and a lateral extension slotted section consisting of a rectangular slot 6a, a fifth longitudinal slot 7a on the left, a fifth longitudinal slot 7b on the right and a second transverse slot 6b. Furthermore, a grounding plane feed port 9a and a grounding plane short-circuit pin 9b are also provided on the upper side of the grounding plane 11b, and their positions are consistent with those of the cylindrical feed port 5a and the cylindrical short-circuit pin 5b.

[0030] In this embodiment, the radiating patch 11a employs a plurality of rectangular vertical slots arranged to achieve dual-frequency operation and control current distribution. Specifically, the radiating patch has three vertical slots 1a, 2a, and 3a on the left side, three vertical slots 1b, 2b, and 3b on the right side, and one vertical slot 4a in the middle. The slot structure divides the surface current into multiple paths, thereby increasing the effective current path length and achieving low-frequency resonance without increasing the overall size of the antenna. The arrangement of the vertical slot structure forms folded current paths within the radiating patch. The extended current paths support resonance in the low-frequency band of approximately 1.4 GHz, while the short current paths formed between adjacent slot segments support resonance in the high-frequency band of approximately 2.45 GHz. This configuration enables dual-frequency synchronous operation in a compact size.

[0031] The shorting pin 12b electrically connects the radiating patch 11a to the ground plane 11b and is located in the upper right region of the patch. The shorting pin introduces an inductive load and creates an additional current path between the patch and the ground plane, thereby contributing to antenna miniaturization and impedance matching.

[0032] The feed port 9a is coupled to the radiating patch 11a through the feed post 12a, providing a conductive path between the ground plane and the radiating patch. The position of the feed point can effectively excite the antenna, while maintaining impedance matching in both frequency bands. The spatial separation between the feed port and the shorting pin generates a comprehensive inductor-capacitor effect, enabling fine adjustment of the resonant frequency.

[0033] Ground plane 11b contains multiple slot structures, including horizontal slots, vertical slots, and rectangular slots. These slots form a defective grounding structure, altering the current distribution on the ground plane. The resulting current paths resemble folded or inverted U-shaped structures, thereby increasing the effective inductance and capacitance of the antenna.

[0034] The interaction between the radiating patch slot and the ground plane slot generates multiple resonances and enhances the impedance bandwidth. This combined structure improves antenna radiation characteristics and ensures stable performance in high-loss biological environments. The radiating patch 11a is mounted on the substrate 10b and covered by a metamaterial layer 10a, forming a stacked structure. This configuration provides biocompatibility and electromagnetic isolation for internal components of the implanted device. Together, these components form a compact dual-band antenna structure suitable for biological implantation.

[0035] See Figure 2 A four-port multiple-input multiple-output (MIMO) antenna is constructed by arranging four single-input single-output (SSO) antenna elements in a planar configuration, with the antenna elements rotating alternately relative to adjacent elements. The spacing between adjacent antenna elements is approximately 0.5 mm. This configuration achieves compact integration while ensuring effective isolation between elements. The alternating rotation of the antenna elements corresponds high-current regions with low-current regions of adjacent elements, achieving inherent self-decoupling without the need for additional decoupling structures. The overall antenna assembly occupies a compact volume of 26.6 mm³, suitable for integration into capsule-shaped implantable devices. Despite the limited size, the four-port configuration still provides improved spatial diversity, reduced signal fading, and enhanced channel capacity. The antenna uses a 50Ω coaxial feed to ensure compatibility with standard implantable electronics. The feed points are precisely positioned to maximize dual-band return loss performance.

[0036] Figure 3 The reflection coefficients of the four-port multiple-input multiple-output antenna are shown in uniform and non-uniform tissue models. 、| , , ).

[0037] Figure 4 The coupling coefficients of the four-port multiple-input multiple-output antenna are shown in uniform and non-uniform tissue models. 、| , , , , ).

[0038] In colon and heart tissue models, all ports maintained stable resonance in the dual-band, with reflection coefficients ranging from −20.89 dB to −32.15 dB, verifying good impedance matching and multi-port consistency.

[0039] The mutual coupling coefficients between all ports are below -20dB, effectively suppressing inter-unit interference without requiring additional components. Symmetry ensures that the omitted coefficients ( (Their performance was consistent.)

[0040] Figure 5 The far-field radiation pattern of the four-port MIMO antenna shown indicates that each plane has approximately uniform quasi-omnidirectional coverage within the dual-band environment. The radiation characteristics of the individual antenna elements are identical due to their consistent geometry and load.

[0041] The simulated peak gain of the four-port antenna in the intestinal model is -27.5 dBi at 1.4 GHz and -17.5 dBi at 2.45 GHz; in the heart model, the values ​​are -26.3 dBi and -17.5 dBi, respectively. The lower gain at 1.4 GHz is mainly due to the higher media loss in biological tissue.

[0042] This invention employed specific absorption rate assessments to ensure patient safety, with the antenna performance significantly below the limits set by the IEEE C95.1–2019 standard in both 1g and 10g tissue models. Wireless telemetry performance was analyzed using link budget calculations, demonstrating that the four-port MIMO antenna supports reliable data transmission over distances exceeding 20 meters and up to 100 Mbps in both frequency bands. Envelope correlation coefficients and diversity gain were calculated using radiation patterns; the envelope correlation coefficients were below 0.5 in both frequency bands, indicating low correlation between antenna elements, and the diversity gain was close to 9.9 dB, showcasing high diversity performance. MIMO performance was evaluated by calculating channel capacity loss and total effective reflection coefficient; the channel capacity loss was below 0.4 b / sec / Hz, and the total effective reflection coefficient remained below −10 dB under phase excitation, verifying the stability of the multi-port operation.

[0043] The antenna design allows for integration with capsule-shaped devices, maintaining performance even with internal electronic components such as batteries and sensors. The planar four-port configuration enhances spatial diversity, reduces fading effects, and improves channel reliability, offering advantages over single-port designs. Partially folded patch and slot geometry enable antenna miniaturization while maintaining dual-frequency resonance, ensuring compatibility with small-volume implantable devices. The four-port MIMO antenna exhibits a quasi-omnidirectional radiation mode, ensuring reliable communication with external receivers from any direction within the capsule.

[0044] In summary, the four-port dual-band multi-input multi-output antenna proposed in the embodiments provides a compact, efficient, and safe solution for implantable medical devices. The combined effect of the radiating patch slot configuration, grounding plane slot structure, power supply and shorting pin layout, and multi-unit combination achieves dual-band operation, high isolation, quasi-omnidirectional radiation, and reliable in-vivo wireless communication.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compact dual-band multi-port implantable antenna for biomedical devices, characterized in that, It is composed of multiple single-input single-output antenna elements arranged in a row. The single-input single-output antenna element includes a substrate, a radiating patch disposed on a first surface of the substrate, a ground plane disposed on a second surface of the substrate, a feed port electrically connected to the radiating patch, and a short-circuit via electrically connecting the radiating patch to the ground plane. The radiating patch, substrate, and ground plane are arranged in a stacked configuration, and an overlay dielectric layer is provided on top of the radiating patch to achieve electromagnetic isolation; the radiating patch and ground plane have multiple slots.

2. The compact dual-band multi-port implantable antenna for biomedical devices according to claim 1, characterized in that, The radiating patch includes multiple sequentially connected longitudinal slots, forming a zigzag structure to increase the effective current path length.

3. A compact dual-band multi-port implantable antenna for biomedical devices according to claim 2, characterized in that, The grounding plane includes a central slotted section and lateral extended slotted sections, forming a folded or inverted U-shaped current path to increase distributed capacitance and inductance, generate additional resonance, and expand the impedance bandwidth.

4. A compact dual-band multi-port implantable antenna for biomedical devices according to claim 1, characterized in that, The feed port and short-circuit via are arranged at different locations on the radiating patch. The feed port is used to excite the antenna, while the short-circuit via achieves resonant tuning and impedance matching by introducing an inductive-capacitive load.

5. A compact dual-band multi-port implantable antenna for biomedical devices according to claim 1, characterized in that, The four single-input single-output antenna elements are arranged in a planar configuration, with adjacent antenna elements arranged in an alternating direction. This ensures that the high-current region of one antenna element corresponds to the low-current region of the adjacent antenna element, achieving inherent self-decoupling and reducing mutual coupling.

6. A compact dual-band multi-port implantable antenna for biomedical devices according to claim 1, characterized in that, The spacing between adjacent antenna elements is 0.5 mm.

7. An implantable medical device, comprising a sensor, a processing circuit, and a power supply, characterized in that, The processing circuit uses a compact dual-band multi-port implantable antenna for biomedical devices as described in any one of claims 1 to 6 to achieve dual-band wireless communication and quasi-omnidirectional radiation functions.

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