An implantable slot antenna radiated by a magnetic source

Abstract

The present invention discloses an implantable slot antenna radiated by a magnetic source. The antenna consists of two square Rogers dielectric substrates with the same size, a metal ground plane located between the two dielectric substrates, and a rectangular metal feeder located above the upper dielectric substrate. The size of the metal ground plane is the same as that of the dielectric substrate, and a bowtie-shaped slot is etched in the middle, and is fed coaxially from the bottom. The present invention utilizes the characteristic that human tissues have no magnetic loss, and realizes magnetic source radiation by opening a bowtie-shaped slot on the metal ground plane, improves the radiation efficiency of the antenna, and enables the antenna to achieve a relatively high bandwidth and gain under the condition of a small size.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and particularly relates to an implantable slot antenna radiated by a magnetic source. Background Art

[0002] In today's society, hospitals are overcrowded, and it has become a common phenomenon that it is difficult to see a doctor. People's demand for being able to self-detect their health conditions and pay attention to the development of their diseases in real time is becoming stronger and stronger. Under this social phenomenon, implantable medical devices based on mobile medical services have developed rapidly, and wireless data transmission is widely used in implantable medical devices. Its function is to implant an antenna into the human body, transmit the collected data through the implanted antenna, and then receive the data through an external antenna to monitor the health condition of the human body.

[0003] The key component of wireless data transmission is an implantable antenna. The internal organizational structure of the human body is complex and has characteristics such as high relative permittivity, inhomogeneity, and high loss. And during the design process, factors such as the size of the antenna, working bandwidth, radiation efficiency, system compatibility, and the impact of radiation on the human body (SAR) need to be considered. Therefore, how to design a high-performance miniaturized implantable antenna is the current research difficulty and hotspot.

[0004] The information disclosed in this background art section is only intended to increase the understanding of the overall background of the present invention, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies in the prior art and provide an implantable slot antenna radiated by a magnetic source operating in the ISM band to solve the problem that the performance of traditional implantable antennas is limited in lossy human tissues.

[0006] To achieve the above functions, the present invention designs an implantable slot antenna radiated by a magnetic source. The implantable slot antenna includes a first dielectric plate, a copper metal ground plane, a second substrate, a coaxial probe, and a shorting post;

[0007] Wherein, the height of the shorting post is the same as the thickness of the first dielectric plate; the first dielectric plate, the metal ground plane, and the second substrate are rectangular and have the same size. The first dielectric plate includes a first substrate and a rectangular metal feeder. The rectangular metal feeder is located on the upper surface of the first substrate, and the symmetry axes of the rectangular metal feeder and the first substrate coincide; the rectangular metal feeder is provided with a first shorting hole and a first feeding hole. The first shorting hole and the first feeding hole are respectively located on both sides of the symmetry axis opposite to the short side of the rectangular metal feeder, and the centers of the first shorting hole and the first feeding hole are located on the axis of the symmetry axis opposite to the long side of the rectangular metal feeder;

[0008] The first dielectric plate, the metal ground plate, and the second substrate are stacked in sequence. An axially symmetric bowtie-shaped slot is provided on the metal ground plate. The bowtie-shaped slot is surrounded by two straight edges and two concave pentagonal broken lines. The axis of symmetry of the bowtie-shaped slot coincides with the axis of symmetry of the metal ground plate. Second feeding holes and second short-circuit holes are provided on both sides of the concave pentagonal broken lines of the bowtie-shaped slot, and the centers of the second short-circuit holes and the second feeding holes are located on the axis of the axis of symmetry of the metal ground plate.

[0009] The radii of the first short-circuit hole and the second short-circuit hole are the same as the radius of the short-circuit post. The coaxial probe is composed of a first probe and a second probe that are columnar and have collinear axes. The lower end of the first probe is fixedly butted with the upper end of the second probe, and the height of the first probe is the same as the thickness of the first dielectric plate. The radius of the second probe is greater than that of the first probe.

[0010] The radius of the first feeding hole is the same as the radius of the first probe of the coaxial probe, and the radius of the second feeding hole is the same as the radius of the second probe of the coaxial probe.

[0011] Through holes are provided on the first substrate, and their positions and sizes correspond to the first short-circuit hole and the first feeding hole on the rectangular metal feeder respectively. The upper end of the short-circuit post penetrates through the through hole on the first substrate, is butted with the rectangular metal feeder through the first short-circuit hole on the rectangular metal feeder, and the lower end is butted with the metal ground plate through the second short-circuit hole on the metal ground plate. The upper end of the first probe of the coaxial probe penetrates through the through hole on the first substrate, is butted with the rectangular metal feeder through the first feeding hole on the rectangular metal feeder, and the upper end of the second probe of the coaxial probe is butted with the metal ground plate through the second feeding hole on the metal ground plate.

[0012] A through hole is provided on the second substrate, and its radius is the same as that of the second probe of the coaxial probe. The center point coincides with the center point of the second feeding hole on the metal ground plate. The second probe of the coaxial probe penetrates through the through hole on the second substrate, and the upper end is butted with the metal ground plate.

[0013] As a preferred technical solution of the present invention: The first substrate and the second substrate are square substrates with a side length of 8 mm and a thickness of 0.635 mm.

[0014] As a preferred technical solution of the present invention: The first substrate and the second substrate are Rogers dielectric substrates with a dielectric constant of 10.2.

[0015] As a preferred technical solution of the present invention: The long side of the rectangular metal feeder is 5 mm, the short side is 2 mm, and the distance between the short side corresponding to the first short-circuit hole on the rectangular metal feeder and the edge of the first substrate it faces is 2 mm.

[0016] As a preferred technical solution of the present invention: the radii of the first short - circuit hole and the second short - circuit hole are 0.3 mm, and the radius of the first feeding hole is 0.33 mm.

[0017] As a preferred technical solution of the present invention: the total length of the bow - tie - shaped slot on the metal ground plane is 6 mm, the length of the straight side is 1.4 mm, each straight side is 1 mm away from the edge of the metal ground plane it faces, and the two concave penta - fold lines are respectively composed of the first fold line, the second fold line, the third fold line, the fourth fold line, and the fifth fold line connected end to end;

[0018] One end of the first fold line is connected to the end of the straight side and is perpendicular to the straight side. The length of the first fold line is 0.88 mm. The first fold line and the second fold line form an inward - concave obtuse angle. The third fold line is parallel to the first fold line, and the length of the third fold line is 1 mm. The third fold line and the fourth fold line form an outward - concave obtuse angle. The fifth fold line is parallel and collinear with the first fold line, the fifth fold line is connected to the end of the other straight side of the bow - tie - shaped slot, and is perpendicular to this straight side. The length of the fifth fold line is 0.88 mm; the distance between the third fold lines of the two concave penta - fold lines is 0.3 mm.

[0019] As a preferred technical solution of the present invention: the vertical distance between the edge of the second short - circuit hole and the third fold line of the bow - tie - shaped slot it faces is 0.85 mm, and the vertical distance between the edge of the second feeding hole and the third fold line of the bow - tie - shaped slot it faces is 1.85 mm.

[0020] As a preferred technical solution of the present invention: the height of the short - circuit post is 0.635 mm, and the vertical distance between the upper edge of the short - circuit post and the axis of the symmetry axis of the first substrate is 1 mm.

[0021] As a preferred technical solution of the present invention: the vertical distance between the upper edge of the second probe of the coaxial probe and the axis of the symmetry axis of the first substrate is 2 mm.

[0022] Advantageous effects: Compared with the prior art, the advantages of the present invention include:

[0023] (1) By utilizing the characteristic that human tissues have no magnetic loss, a bow - tie - shaped slot is arranged on the metal ground plane, and magnetic source radiation is realized through the 180 - degree phase difference formed by the short - circuit posts and the coaxial probe on both sides of it.

[0024] (2) Energy coupling is carried out between the rectangular metal feeder placed above the first substrate and the bow - tie - shaped slot on the metal ground plane, improving the radiation efficiency of the antenna.

[0025] (3) By placing the second substrate under the metal ground plane, it is avoided that the radiation slot is in direct contact with lossy tissues, resulting in a short - circuit effect, and the radiation performance is further improved. Description of the Drawings

[0026] Figure 1 is a three - dimensional view of an implantable slot antenna radiated by a magnetic source according to an embodiment of the present invention;

[0027] Figure 2 is a side view of an implantable slot antenna radiated by a magnetic source according to an embodiment of the present invention;

[0028] Figure 3 is a top view of a first dielectric plate according to an embodiment of the present invention;

[0029] Figure 4 is a top view of a metal ground plane according to an embodiment of the present invention;

[0030] Wherein: 1. First dielectric plate; 2. First substrate; 3. Rectangular metal feeder; 4. Metal ground plane; 5. Bow - tie slot; 6. Second substrate; 7. Coaxial probe; 8. First short - circuit hole; 9. Short - circuit post; 10. First feeding hole; 11. Second short - circuit hole; 12. Second feeding hole;

[0031] Figure 5 is a schematic diagram of a simulation environment of an implantable slot antenna radiated by a magnetic source according to an embodiment of the present invention;

[0032] Figure 6 is the input return loss of the present invention when the implantation depths are 3mm, 9mm, and 15mm respectively;

[0033] Figure 7 is the simulation result of the main polarization gain and cross - polarization gain of the present invention at an implantation depth of 3mm at 2.45GHz in the Phi = 0° (xoz plane);

[0034] Figure 8 is the simulation result of the main polarization gain and cross - polarization gain of the present invention at a depth of 3mm at 2.45GHz in the Phi = 90° (yoz plane);

[0035] Figure 9 is the simulation result of the gain - frequency variation curve of the present invention when the implantation depths are 3mm, 9mm, and 15mm respectively;

[0036] Figure 10 is the simulation and measurement result of the input return loss of the present invention at an implantation depth of 3mm. Detailed implementation manners

[0037] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention.

[0038] Refer toFigure 1 , Figure 2 , an implantable slot antenna radiated by a magnetic source provided by an embodiment of the present invention. The implantable slot antenna includes a first dielectric plate, a copper metal ground plane, a second substrate, a coaxial probe, and a shorting post;

[0039] Wherein, the height of the shorting post is the same as the thickness of the first dielectric plate; the first dielectric plate, the metal ground plane, and the second substrate are rectangular and have the same size. The first dielectric plate includes a first substrate and a rectangular metal feeder. The rectangular metal feeder is located on the upper surface of the first substrate, and the symmetry axes of the rectangular metal feeder and the first substrate coincide; the rectangular metal feeder is provided with a first shorting hole and a first feeding hole. The first shorting hole and the first feeding hole are respectively located on both sides of the symmetry axis opposite to the short side of the rectangular metal feeder, and the centers of the first shorting hole and the first feeding hole are located on the axis of the symmetry axis opposite to the long side of the rectangular metal feeder;

[0040] The first dielectric plate, the metal ground plane, and the second substrate are stacked in sequence. The metal ground plane is provided with an axially symmetric bowtie-shaped slot. The bowtie-shaped slot is surrounded by two straight edges and two concave pentagonal broken lines. The symmetry axis of the bowtie-shaped slot coincides with the symmetry axis of the metal ground plane; second feeding holes and second shorting holes are provided on both sides of the concave pentagonal broken line of the bowtie-shaped slot, and the centers of the second shorting hole and the second feeding hole are located on the axis of the symmetry axis of the metal ground plane;

[0041] The radii of the first shorting hole and the second shorting hole are the same as the radius of the shorting post. The coaxial probe is composed of a first probe and a second probe with a cylindrical shape and collinear axes. The lower end of the first probe is fixedly butted with the upper end of the second probe, and the height of the first probe is the same as the thickness of the first dielectric plate. The radius of the second probe is larger than that of the first probe.

[0042] The radius of the first feeding hole is the same as the radius of the first probe of the coaxial probe, and the radius of the second feeding hole is the same as the radius of the second probe of the coaxial probe;

[0043] Through holes with positions and sizes corresponding to the first shorting hole and the first feeding hole on the rectangular metal feeder are provided on the first substrate. The upper end of the shorting post penetrates through the through hole on the first substrate, is butted with the rectangular metal feeder through the first shorting hole on the rectangular metal feeder, and the lower end is butted with the metal ground plane through the second shorting hole on the metal ground plane; the upper end of the first probe of the coaxial probe penetrates through the through hole on the first substrate, is butted with the rectangular metal feeder through the first feeding hole on the rectangular metal feeder, and the upper end of the second probe of the coaxial probe is butted with the metal ground plane through the second feeding hole on the metal ground plane;

[0044] A through hole is provided on the second substrate, whose radius is the same as that of the second probe of the coaxial probe, and whose center point coincides with the center point of the second feeding hole on the metal ground plate. The second probe of the coaxial probe passes through the through hole on the second substrate, and the upper end is connected to the metal ground plate.

[0045] The first substrate and the second substrate are Rogers medium, a square substrate with a dielectric constant of 10.2, a side length of 8 mm and a thickness of 0.635 mm.

[0046] Reference Figure 3 The long side of the rectangular metal feeder is 5 mm, the short side is 2 mm, and the distance between the short side opposite to the first short-circuit hole on the rectangular metal feeder and the edge of the first substrate opposite to it is 2 mm.

[0047] The radius of the first short-circuit hole and the second short-circuit hole is 0.3 mm, and the radius of the first feeding hole is 0.33 mm.

[0048] Reference Figure 4 The total length of the bow tie-shaped gap on the metal grounding plate is 6 mm, the length of the straight edge is 1.4 mm, and each straight edge is 1 mm away from the edge of the metal grounding plate to which it corresponds. The two inward concave five-fold lines are respectively composed of the first fold line, the second fold line, the fifth fold line, the fourth fold line, and the fifth fold line connected end to end;

[0049] One endpoint of the first fold line is connected to the endpoint of the straight edge, and the first fold line and the straight edge are perpendicular to each other, the length of the first fold line is 0.88mm, the first fold line and the second fold line form an obtuse angle concave inward, the third fold line is parallel to the first fold line, the length of the third fold line is 1mm, the third fold line and the fourth fold line form an obtuse angle concave outward, the fifth fold line is parallel to the first fold line and is colinear, the fifth fold line is connected to another endpoint of the straight edge of the bow tie-shaped gap, and the fifth fold line and the straight edge are perpendicular to each other, the length of the fifth fold line is 0.88mm; the distance between the third fold lines of the two concave five-fold lines is 0.3mm.

[0050] The vertical distance between the edge of the second short-circuit hole and the third fold line of the bow-tie-shaped gap it faces is 0.85 mm, and the vertical distance between the edge of the second feeding hole and the third fold line of the bow-tie-shaped gap it faces is 1.85 mm.

[0051] The height of the short-circuit column is 0.635 mm, and the vertical distance between the upper edge of the short-circuit column and the axis of the first substrate symmetry axis is 1 mm. The vertical distance between the upper edge of the second probe of the coaxial probe and the axis of the first substrate symmetry axis is 2 mm.

[0052] The implantable slot antenna radiated by a magnetic source provided by an embodiment of the present invention realizes magnetic source radiation by opening a bowtie-shaped slot on a metal ground plane. On the one hand, a rectangular metal feeder is placed above the first substrate to achieve energy coupling with the bowtie-shaped slot on the metal ground plane. In addition, a 180-degree phase difference formed by shorting posts and coaxial probes on both sides of the bowtie-shaped slot is used to excite slot radiation. On the other hand, a second substrate is placed below the metal ground plane to avoid the short-circuit effect caused by the direct contact between the radiation slot and lossy tissues, thereby improving the radiation efficiency.

[0053] As Figure 5 shown, the performance of the implantable slot antenna radiated by a magnetic source designed by the present invention is simulated. The center frequency of the antenna is 2.45 GHz. During the simulation process, the antenna is placed in simulated skin tissue (size: 80 mm × 80 mm × 60 mm), and the implantation depth h of the antenna is set to 3 mm, 9 mm, and 15 mm respectively, and the input return loss S 11 of the antenna is simulated to obtain Figure 6 .

[0054] It can be seen from Figure 6 that at 2.45 GHz, there are obvious resonances in the antenna at the three implantation depths. In addition, due to the enhanced tissue loss during propagation, as the implantation depth h of the antenna increases, the S 11 curve gradually deepens.

[0055] Figure 10 Shown is the simulation and measurement results of the input return loss S 11 of the present invention with an implantation depth of 3 mm. It can be observed that the measured impedance bandwidth (|S 11 | < -10 dB) is 23.9% (2.28 - 2.9 GHz). Compared with the simulated impedance bandwidth of 23.7% (2.2 - 2.78 GHz), the agreement is good.

[0056] Figures 7-8 Shown is the simulation of the radiation pattern of the implantable slot antenna radiated by a magnetic source designed by the present invention at 2.45 GHz with an implantation depth of 3 mm. It can be seen from the figure that the antenna exhibits good lateral radiation performance, and the maximum actual gain is -23 dBi.

[0057] Figure 9 Shown are the simulation results of the gain vs. frequency curves of the implantable slot antenna radiated by a magnetic source designed by the present invention when the implantation depths h are 3 mm, 9 mm, and 15 mm respectively. It can be seen that as the implantation depth increases, due to the increased loss brought by human tissues, the antenna gain decreases significantly.

[0058] An implantable slot antenna radiated by a magnetic source provided by the present invention effectively utilizes the loss characteristics of human tissues, improves the radiation efficiency of the antenna while having a small size, achieves a relatively high bandwidth and gain, and still has relatively stable performance under different implantation depths. The simulation and measurement results of the antenna have high consistency and have important application significance in the field of biomedicine.

[0059] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. An implantable slot antenna radiated by a magnetic source, characterized in that The implantable slot antenna includes a first dielectric plate, a copper metal ground plane, a second substrate, a coaxial probe, and a short - circuit metal post; Among them, the height of the short - circuit metal post is the same as the thickness of the first dielectric plate; the first dielectric plate, the copper metal ground plane, and the second substrate are rectangular and have the same size. The first dielectric plate includes a first substrate and a rectangular copper metal feeder line. The rectangular metal feeder line is located on the upper surface of the first substrate, and the longitudinal symmetry axes of the rectangular metal feeder line and the first substrate coincide; the rectangular metal feeder line is provided with a first short - circuit hole and a first feeding hole. The first short - circuit hole and the first feeding hole are respectively located on both sides of the symmetry axis opposite to the short side of the rectangular metal feeder line, and the center points of the first short - circuit hole and the first feeding hole are located on the axis of the symmetry axis opposite to the long side of the rectangular metal feeder line; The first dielectric plate, the copper metal ground plane, and the second substrate are stacked in sequence. The copper metal ground plane is provided with an axially symmetric bow - tie - shaped slot. The bow - tie - shaped slot is surrounded by two straight edges and two concave pentagonal broken lines. The symmetry axis of the bow - tie - shaped slot coincides with the symmetry axis of the copper metal ground plane; second feeding holes are provided on both sides of the concave pentagonal broken lines of the bow - tie - shaped slot, and the center points of the second short - circuit hole and the second feeding hole are located on the axis of the symmetry axis of the copper metal ground plane. This symmetry axis passes through the two concave pentagonal broken lines of the bow - tie - shaped slot and is parallel to the two straight edges of the bow - tie - shaped slot; The radii of the first short - circuit hole and the second short - circuit hole are the same as the radius of the short - circuit metal post. The coaxial probe is composed of a first probe and a second probe with cylindrical shapes and collinear axes. The lower end of the first probe is fixedly butted with the upper end of the second probe, and the height of the first probe is the same as the thickness of the first dielectric plate. The radius of the second probe is larger than that of the first probe. The radius of the first feeding hole is the same as the radius of the first probe of the coaxial probe, and the radius of the second feeding hole is the same as the radius of the second probe of the coaxial probe; The first substrate is provided with through - holes whose positions and sizes correspond to the first short - circuit hole and the first feeding hole on the rectangular metal feeder line respectively. The upper end of the short - circuit metal post passes through the through - hole on the first substrate, and through the first short - circuit hole on the rectangular metal feeder line, it is butted with the rectangular metal feeder line. The lower end passes through the second short - circuit hole on the copper metal ground plane and is butted with the copper metal ground plane; the upper end of the first probe of the coaxial probe passes through the through - hole on the first substrate, and through the first feeding hole on the rectangular metal feeder line, it is butted with the rectangular metal feeder line. The upper end of the second probe of the coaxial probe passes through the second feeding hole on the copper metal ground plane and is butted with the copper metal ground plane; The second substrate is provided with a through - hole whose radius is the same as that of the second probe of the coaxial probe, and the center point coincides with the center point of the second feeding hole on the copper metal ground plane. The second probe of the coaxial probe passes through the through - hole on the second substrate, and the upper end is butted with the copper metal ground plane.

2. The implantable slot antenna radiated by a magnetic source according to claim 1, wherein The first substrate and the second substrate are square substrates with a side length of 8 mm and a thickness of 0.635 mm.

3. The implantable slot antenna radiated by a magnetic source according to claim 1, wherein The first substrate and the second substrate are Rogers dielectric substrates with a dielectric constant of 10.

2.

4. The implantable slot antenna radiated by a magnetic source according to claim 1, wherein The long side of the rectangular metal feeder line is 5 mm, the short side is 2 mm, and the distance between the short side opposite to the first short - circuit hole on the rectangular metal feeder line and the edge of the first substrate opposite to it is 2 mm.

5. An implantable slot antenna radiated by a magnetic source according to claim 1, characterized in that, The radii of the first short - circuit hole and the second short - circuit hole are 0.3 mm, and the radius of the first feeding hole is 0.33 mm.

6. The implantable slot antenna radiated by a magnetic source according to claim 1, wherein The total length of the bow - tie - shaped slot on the copper metal ground plane is 6 mm, the length of the straight side is 1.4 mm, and each straight side is 1 mm away from the edge of the copper metal ground plane it faces. The two concave five - fold lines are respectively composed of the first fold line, the second fold line, the third fold line, the fourth fold line, and the fifth fold line connected end to end. One end of the first fold line is connected to the end of the straight side, and the first fold line is perpendicular to the straight side. The length of the first fold line is 0.88 mm. The first fold line and the second fold line form an obtuse angle that is concave inward. The third fold line is parallel to the first fold line, and the length of the third fold line is 1 mm. The third fold line and the fourth fold line form an obtuse angle that is concave outward. The fifth fold line is parallel and collinear with the first fold line, the fifth fold line is connected to the end of the other straight side of the bow - tie - shaped slot, and the fifth fold line is perpendicular to this straight side. The length of the fifth fold line is 0.88 mm. The distance between the third fold lines of the two concave five - fold lines is 0.3 mm.

7. An implantable slot antenna radiated by a magnetic source according to claim 6, characterized in that The vertical distance between the edge of the second short - circuit hole and the third fold line of the bow - tie - shaped slot it faces is 0.85 mm, and the vertical distance between the edge of the second feeding hole and the third fold line of the bow - tie - shaped slot it faces is 1.85 mm.

8. An implantable slot antenna radiated by a magnetic source according to claim 6, wherein The height of the short - circuit metal post is 0.635 mm. The vertical distance between the upper edge of the short - circuit metal post and the axis of the first substrate symmetry axis is 1 mm, and this symmetry axis is opposite to the two short sides of the rectangular metal feeder.

9. An implantable slot antenna radiated by a magnetic source according to claim 6, characterized in that, The vertical distance between the upper edge of the second probe of the coaxial probe and the axis of the first substrate symmetry axis is 2 mm, and this symmetry axis is opposite to the two short sides of the rectangular metal feeder.

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