Graphene-based circularly polarized ingestible antenna for capsule endoscopy device

Abstract

The present invention discloses a graphene-based circularly polarized ingestible antenna for a capsule endoscope device. The materials of the radiation units and the floor of each layer of the antenna are copper-clad graphene film. The copper-clad graphene film material has a high carrier density and can increase the working bandwidth and gain of the ingestible antenna. The graphene double S combined structure radiation patch (4) and the graphene double S combined structure radiation patch (5) are connected through four short-circuit probes to form a composite spiral structure, thereby generating circular polarization characteristics, reducing the bit error rate while suppressing multipath interference. The hook-shaped combined structure of the graphene hook-shaped combined structure radiation patch can reduce the resonant frequency of the antenna and increase the impedance bandwidth of the antenna. The volume of the antenna is only π×(4.5) 2 mm 3 It has the characteristics of wide bandwidth, circular polarization, anti-interference, good electromagnetic compatibility and small size. It is suitable for ISM 2.4GHz frequency band and can meet the working requirements after being taken into complex environment.

Description

Technical Field

[0001] The present invention relates to the technical field of capsule endoscope device ingestible antennas, and in particular to a graphene-based circularly polarized ingestible antenna for a capsule endoscope device, which is suitable for a circularly polarized ingestible capsule endoscope device in an ISM 2.4 GHz frequency band. Background Art

[0002] With the rapid development of intelligent biomedical technology, capsule endoscopes have gradually changed from traditional wired methods to wireless methods. The intelligence and miniaturization of capsule endoscopes have become a hot topic in current research. Compared with traditional endoscopes, wireless endoscopes can achieve real-time data transmission with an image transmission rate of more than 2Mbps through an external base station, and realize imaging detection of the digestive system and gastrointestinal system, which is not only conducive to providing doctors with accurate and fast diagnosis and treatment data, but also greatly reduces the pain of patients. Wireless capsule endoscope devices usually include cameras, light sources, batteries, transceivers, antennas, etc. In the design process of wireless capsule endoscopes, it is usually necessary to consider system power consumption, transmission distance, operating frequency, image frame number, image resolution, battery capacity, overall size, etc. The antenna is the core component of the wireless capsule endoscope device, and the performance of the antenna directly affects the accuracy and real-time transmission of image data. In order to obtain high-resolution images to diagnose the location of lesions, it is necessary to increase the frame rate of data transmission to improve the accuracy of diagnosis. At the same time, the working performance of the capsule endoscope in different environments after being ingested must also be considered. This requires the antenna to have a wider bandwidth and stronger anti-interference ability. Designing a broadband, circularly polarized, and miniaturized antenna can well meet the above requirements. The circularly polarized antenna can suppress the polarization mismatch caused by the capsule in different digestive organ internal environments and movements. The conformal antenna mainly attaches the antenna to the outer surface of the capsule and becomes part of the outer surface of the capsule. The curved ring structure can realize the miniaturization of the antenna. The conformal antenna can reduce the use of the internal volume of the capsule, improve the system integration, and improve the gain and radiation efficiency at the same time. However, the conformal antenna does not have a complete floor, and the anti-interference performance and electromagnetic compatibility between other devices are weaker than other types of antennas. Non-patent document 1 designs a circularly polarized antenna for a capsule endoscope device. The antenna is conformal to the outer wall of the capsule to form a self-encapsulation structure, which improves the radiation efficiency and gain of the antenna. The conformal antenna has a complete floor and forms a shielding layer in the internal area of ​​the capsule to improve the anti-interference and electromagnetic compatibility performance, but the antenna design and debugging are relatively complicated. Designing the antenna inside the capsule can avoid contact between the antenna and human tissue and prevent corrosion from tissue fluid. Helical antennas have characteristics such as wide bandwidth and easy circular polarization, but conventional helical antennas are large in size. Non-patent document 2 designs a new type of helical antenna, which realizes a planar helical antenna structure through multi-layer open rings combined with metal via connections, and improves the circular polarization performance of the antenna by adjusting the angle and radius of the open ring, but the size of the antenna is still large. The composite antenna is composed of a conformal antenna on the surface of the capsule and an antenna inside the capsule. Both linear polarization and circular polarization characteristics can be achieved, but the disadvantage of this type of antenna is that the design and processing are relatively complicated.Non-patent document 3 designs an antenna composed of a conformal offset-fed dipole on the surface of a capsule and an inverted spiral structure inside the capsule. The conformal offset-fed dipole on the surface of the capsule improves impedance matching by adjusting the arm length. The conformal offset-fed dipole antenna has circular polarization characteristics. The inverted spiral structure antenna adjusts impedance matching by adjusting the spiral structure radius and spiral structure height. The inverted spiral structure antenna has linear polarization characteristics. The conductivity of graphene materials is 50 times that of ordinary materials. The honeycomb structure of graphene can produce a higher carrier density, making it excellent in conductivity. The use of graphene materials in printed antennas can greatly improve antenna performance, achieve efficient dynamic adjustment, high transparency, improve transmission efficiency and reduce losses, meet the miniaturization requirements of antennas in ingestible wireless communication systems, and also greatly increase communication distance. Domestic and foreign scholars' research on graphene materials in the field of antennas mainly focuses on terahertz antennas, reconfigurable antennas, filtering antennas, flexible antennas, and wearable antennas, and there is relatively little research on graphene in ingestible antennas.

[0003] Citation list

[0004] Non-patent literature 1: Yang Xiantao, Research on circularly polarized antennas for implantable medical devices, Master's thesis of South China University of Technology, 2017: 62-74.

[0005] Non-patent literature 2: Liu Changrong, Research on the application of implantable antennas in biomedicine, PhD dissertation of University of Electronic Science and Technology of China, 2015:64-76.

[0006] Non-patent literature 3: Rajagopalan H., Rahmat-Samii Y.. Wireless medical telemetry characterization for in-gestible capsule antenna designs. IEEE Antennas and Wireless Propagation Letters, 2012, 11(4): 1679–1682. Summary of the invention

[0007] The purpose of the present invention is to provide a graphene-based circularly polarized intake antenna for a capsule endoscope device, which has the characteristics of wide bandwidth, circular polarization, anti-interference, good electromagnetic compatibility, small size, etc., is easy to be integrated into a wireless capsule endoscope device, is suitable for the ISM 2.4GHz frequency band, and can meet the working requirements after intake in a complex environment.

[0008] The technical solution of the present invention is: a graphene-based circularly polarized ingestible antenna for a capsule endoscope device, comprising a dielectric substrate (1), a dielectric substrate (2), a dielectric substrate (3), a graphene double S combined structure radiation patch (4), a graphene double S combined structure radiation patch (5), a graphene hook-shaped combined structure radiation patch (6), a graphene floor (7), a coaxial connector (8), a short-circuit probe (5-1), a short-circuit probe (5-2), a short-circuit probe (5-3), and a short-circuit probe (5-4); the graphene double S combined structure radiation patch (4), the graphene double S combined structure radiation patch (5), the graphene hook-shaped combined structure radiation patch (6), and the graphene floor (7) are all made of copper-clad graphene film, and the copper-clad graphene film material has a high carrier density, so that it has excellent electrical conductivity, can increase the working bandwidth and gain of the ingestible antenna, improve transmission efficiency and reduce loss; and the characteristics are:

[0009] a. The dielectric substrate (1), dielectric substrate (2), and dielectric substrate (3) are respectively located at the upper layer, middle layer, and lower layer of the antenna;

[0010] b. The graphene double S combined structure radiation patch (4) is located on the upper surface of the dielectric substrate (1). The graphene double S combined structure radiation patch (4) is composed of two S shapes, the S shape is composed of two upper and lower notched circular rings, one of the S shapes is obtained by rotating the other S shape by 90 degrees through the central axis. The double S combined structure can effectively increase the current path and reduce the size of the antenna to meet the miniaturization requirements. A circular impedance matching adjustment is added between the two S-shaped combined structures. Four circular rings are set at the top of the S shape for connecting short-circuit probes to ensure that the connection between the graphene double S combined structure radiation patch (4) and the graphene double S combined structure radiation patch (5) is stable and reliable;

[0011] c. The graphene double S combined structure radiation patch (5) is located on the upper surface of the dielectric substrate (2), the overall structural size of the double S combined structure radiation patch (5) is consistent with the graphene double S combined structure radiation patch (4), and a circular hole is opened on the center circle of the double S combined structure for connecting the inner core of the coaxial connector (8);

[0012] d. The graphene hook-shaped combined structure radiation patch (6) is located on the upper surface of the dielectric substrate (3). The graphene hook-shaped combined structure radiation patch (6) is composed of four notched circular ring patches, a central circular ring patch and a connecting conductive strip. The central circular ring patch is connected to the four notched circular ring patches through the connecting conductive strip to form a hook-shaped combined structure. The circular hole of the central circular ring patch is used to connect the inner core of the coaxial connector (8). The hook-shaped combined structure of the graphene hook-shaped combined structure radiation patch (6) can reduce the resonant frequency of the antenna, further reduce the size of the antenna, and increase the impedance bandwidth of the antenna. Adjusting the size of the graphene hook-shaped combined structure radiation patch (6) can further optimize the circular polarization purity of the antenna.

[0013] e. The graphene floor (7) is located on the lower surface of the dielectric substrate (3). The graphene floor (7) adopts a complete circular structure to form a shielding layer inside the wireless endoscope capsule, which can effectively prevent the antenna from interfering with other electronic devices inside the capsule and improve the anti-interference performance and electromagnetic compatibility performance of the antenna;

[0014] f. The coaxial connector (8) is located on the lower side of the lower surface of the dielectric substrate (3), the inner core of the coaxial connector (8) is connected to the central circular holes of the graphene double S combined structure radiation patch (5) and the graphene hook-shaped combined structure radiation patch (6), and the outer cylindrical conductor of the coaxial connector (8) is connected to the center of the graphene floor (7);

[0015] g. The short-circuit probe (5-1), short-circuit probe (5-2), short-circuit probe (5-3), and short-circuit probe (5-4) are located between the graphene double S combination structure radiation patch (4) and the graphene double S combination structure radiation patch (5). The graphene double S combination structure radiation patch (5) and the graphene double S combination structure radiation patch (4) are connected to the upper and lower ends of the short-circuit probe (5-1), short-circuit probe (5-2), short-circuit probe (5-3), and short-circuit probe (5-4) through four rings arranged at the top of the S shape to form a composite spiral structure, thereby generating circular polarization characteristics, reducing the bit error rate while suppressing multipath interference.

[0016] The copper-clad graphene film has a thickness of 0.01 mm to 0.03 mm, and the radius R1 of the dielectric substrate (1), the dielectric substrate (2), and the dielectric substrate (3) is 4 mm to 5 mm.

[0017] The outer diameter R3 of the notched ring of the graphene double S combined structure radiation patch (4) is 2.1 mm to 2.4 mm, the inner diameter R4 is 1.8 mm to 2.0 mm, the height L1 of the notch is 2.0 mm to 2.5 mm, the outer diameter R7 of the four rings arranged at the top of the S shape is 0.25 mm to 0.35 mm, and the inner diameter R8 is 0.15 mm to 0.25 mm.

[0018] The overall structural dimensions of the graphene double S combined structure radiation patch (5) are consistent with those of the graphene double S combined structure radiation patch (4), the radius R6 of the circular hole of the central circle of the double S combined structure is 0.25 mm to 0.35 mm, and the distance R5 from the center of the four circular rings arranged at the top of the S shape to the center of the graphene double S combined structure radiation patch (5) is 1.9 mm to 2.1 mm.

[0019] The outer diameters R of the four notched rings of the graphene hook-shaped combined structure radiation patch (6) are 10 The inner diameter R9 is 1.3mm to 1.5mm, the notch height L2 is 0.7mm to 1.1mm, the width W1 of the connecting guide band between the notch ring and the center ring is 0.4mm to 0.7mm, the length L3 is 0.4mm to 0.6mm, and the outer diameter R 11 It is 0.7mm~0.9mm.

[0020] The outer surface of the circularly polarized ingestion antenna is coated with a layer of biocompatible material polyetheretherketone with a thickness of 0.04 mm and a dielectric constant of ε r The loss tangent tanδ is 3.2 and 0.01, which realizes the biocompatibility of the circularly polarized intake antenna with the human body and prevents the circularly polarized intake antenna from directly contacting the human digestive organs to cause short circuit, corrosion or rejection.

[0021] The effect of the present invention is that the present invention designs a circularly polarized intake antenna based on graphene for capsule endoscope device, and the materials of each layer of radiation unit and floor of the antenna are copper-clad graphene film, and the copper-clad graphene film material has a high carrier density, so that it has excellent conductivity, can increase the working bandwidth and gain of the intake antenna, improve transmission efficiency and reduce loss. The graphene double S combined structure radiation patch (4) and the graphene double S combined structure radiation patch (5) adopt a double S combined structure, which can effectively increase the current path and reduce the size of the antenna to meet the miniaturization requirements. The graphene double S combined structure radiation patch (4) and the graphene double S combined structure radiation patch (5) are connected by four short-circuit probes to form a composite spiral structure, thereby generating circular polarization characteristics, while suppressing multipath interference and reducing the bit error rate. The hook-shaped combined structure of the graphene hook-shaped combined structure radiation patch can reduce the resonant frequency of the antenna, further reduce the size of the antenna, and increase the impedance bandwidth of the antenna. Adjusting the size of the graphene hook-shaped combined structure radiation patch can further optimize the circular polarization purity of the antenna. The graphene floor adopts a complete circular structure, forming a shielding layer inside the wireless endoscope capsule, which can effectively prevent the antenna from interfering with other electronic devices inside the capsule and improve the anti-interference performance and electromagnetic compatibility performance of the antenna. The circularly polarized intake antenna is a three-layer planar combination structure, and the volume of the antenna is only π×(4.5) 2 mm3 It has the characteristics of wide bandwidth, circular polarization, anti-interference, good electromagnetic compatibility and small size. It is suitable for ISM 2.4GHz frequency band and can meet the working requirements after being taken into complex environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the three-dimensional structure of an embodiment of the present invention.

[0023] Figure 2 It is a schematic structural diagram of a graphene double S combined structure radiation patch (4) according to an embodiment of the present invention.

[0024] Figure 3 It is a schematic diagram of the structure of a graphene double S combined structure radiation patch (5) according to an embodiment of the present invention.

[0025] Figure 4 It is a schematic structural diagram of a graphene hook-shaped combined structure radiation patch (6) according to an embodiment of the present invention.

[0026] Figure 5 It is a schematic diagram of the side structure of an embodiment of the present invention.

[0027] Figure 6 The invention discloses an embodiment of the invention in which the outer diameter R3 and the inner diameter R4 of the notched ring of the graphene double-S combined structure radiation patch (4) affect the antenna impedance bandwidth and the axial ratio bandwidth.

[0028] Figure 7 is the outer diameter R of the four notched rings of the graphene hook-shaped combined structure radiation patch (6) of the embodiment of the present invention. 10 , the influence of inner diameter R9 on antenna impedance bandwidth and axial ratio bandwidth.

[0029] Figure 8 This is the influence of the thickness T of the copper-clad graphene film on the antenna performance in the embodiment of the present invention.

[0030] Fig. 9 This is the effect of different digestive organs of the human body on the antenna performance in the embodiment of the present invention.

[0031] Fig.10 Gain and axial ratio curves of a circularly polarized ingestion antenna ingested into the stomach.

[0032] Fig.11 Gain and axial ratio curves of a circularly polarized intake antenna into the small intestine.

[0033] Fig.12 Gain and axial ratio curves of the circularly polarized intake antenna for the intake colon.

[0034] Fig.13 The impedance bandwidth and axial ratio bandwidth curves of the embodiment of the present invention are simulated and measured. DETAILED DESCRIPTION

[0035] The specific implementation mode of the present invention is: Figure 1As shown, a graphene-based circularly polarized ingestible antenna for a capsule endoscope device is composed of a dielectric substrate (1), a dielectric substrate (2), a dielectric substrate (3), a graphene double S combined structure radiation patch (4), a graphene double S combined structure radiation patch (5), a graphene hook-shaped combined structure radiation patch (6), a graphene floor (7), a coaxial connector (8), a short-circuit probe (5-1), a short-circuit probe (5-2), a short-circuit probe (5-3), and a short-circuit probe (5-4), wherein the graphene double S combined structure radiation patch (4), the graphene double S combined structure radiation patch (5), the graphene hook-shaped combined structure radiation patch (6), and the graphene floor (7) are made of The materials are all copper-clad graphene films. The copper-clad graphene film material has a high carrier density, which makes it have excellent conductivity, can increase the working bandwidth and gain of the intake antenna, improve transmission efficiency and reduce loss; it is characterized in that: the dielectric substrate (1), the dielectric substrate (2), and the dielectric substrate (3) are respectively located in the upper layer, middle layer and lower layer of the antenna; the graphene double S combined structure radiation patch (4) is located on the upper surface of the dielectric substrate (1), and the graphene double S combined structure radiation patch (4) is composed of two S shapes, the S shape is composed of two upper and lower notched circular rings, one of which is obtained by rotating the other S shape by 90 degrees through the central axis, and the double S The combined structure can effectively increase the current path and reduce the size of the antenna to meet the miniaturization requirements. A circular impedance matching adjustment is added between the two S-shaped combined structures. Four circular rings are arranged at the top of the S shape for connecting a short-circuit probe to ensure a stable and reliable connection between the graphene double S combined structure radiation patch (4) and the graphene double S combined structure radiation patch (5). The graphene double S combined structure radiation patch (5) is located on the upper surface of the dielectric substrate (2). The overall structural size of the double S combined structure radiation patch (5) is consistent with that of the graphene double S combined structure radiation patch (4). A circular hole is opened on the center circle of the double S combined structure for connecting the inner core of the coaxial connector (8). The graphene hook-shaped combined structure radiation patch (6) is located on the upper surface of the dielectric substrate (3). The graphene hook-shaped combined structure radiation patch (6) is composed of four notched circular ring patches, a central circular ring patch and a connecting conductive strip. The central circular ring patch is connected to the four notched circular ring patches via the connecting conductive strip to form a hook-shaped combined structure. The circular hole of the central circular ring patch is used to connect the inner core of the coaxial connector (8). The hook-shaped combined structure of the graphene hook-shaped combined structure radiation patch (6) can reduce the resonant frequency of the antenna, further reduce the size of the antenna, and increase the impedance bandwidth of the antenna at the same time. The size of the graphene hook-shaped combined structure radiation patch (6) can be adjusted to further optimize the circular polarization purity of the antenna.The graphene floor (7) is located on the lower surface of the dielectric substrate (3). The graphene floor (7) adopts a complete circular structure and forms a shielding layer inside the wireless endoscope capsule, which can effectively prevent the antenna from interfering with other electronic devices inside the capsule, thereby improving the anti-interference performance and electromagnetic compatibility performance of the antenna; the coaxial connector (8) is located on the lower side of the lower surface of the dielectric substrate (3), the inner core of the coaxial connector (8) is connected to the central circular hole of the graphene double S combined structure radiation patch (5) and the graphene hook-shaped combined structure radiation patch (6), and the outer cylindrical conductor of the coaxial connector (8) is connected to the center of the graphene floor (7); The short-circuit probe (5-1), the short-circuit probe (5-2), the short-circuit probe (5-3), and the short-circuit probe (5-4) are located between the graphene double S combined structure radiation patch (4) and the graphene double S combined structure radiation patch (5). The graphene double S combined structure radiation patch (5) and the graphene double S combined structure radiation patch (4) are connected to the upper and lower ends of the short-circuit probe (5-1), the short-circuit probe (5-2), the short-circuit probe (5-3), and the short-circuit probe (5-4) through four rings arranged at the top of the S shape to form a composite spiral structure, thereby generating circular polarization characteristics, reducing the bit error rate while suppressing multipath interference. ;

[0036] The copper-clad graphene film has a thickness of 0.01 mm to 0.03 mm, and the radius R1 of the dielectric substrate (1), the dielectric substrate (2), and the dielectric substrate (3) is 4 mm to 5 mm.

[0037] The outer diameter R3 of the notched ring of the graphene double S combined structure radiation patch (4) is 2.1 mm to 2.4 mm, the inner diameter R4 is 1.8 mm to 2.0 mm, the height L1 of the notch is 2.0 mm to 2.5 mm, the outer diameter R7 of the four rings arranged at the top of the S shape is 0.25 mm to 0.35 mm, and the inner diameter R8 is 0.15 mm to 0.25 mm.

[0038] The overall structural dimensions of the graphene double S combined structure radiation patch (5) are consistent with those of the graphene double S combined structure radiation patch (4), the radius R6 of the circular hole of the central circle of the double S combined structure is 0.25 mm to 0.35 mm, and the distance R5 from the center of the four circular rings arranged at the top of the S shape to the center of the graphene double S combined structure radiation patch (5) is 1.9 mm to 2.1 mm.

[0039] The outer diameters R of the four notched rings of the graphene hook-shaped combined structure radiation patch (6) are 10 The inner diameter R9 is 1.3mm to 1.5mm, the notch height L2 is 0.7mm to 1.1mm, the width W1 of the connecting guide band between the notch ring and the center ring is 0.4mm to 0.7mm, the length L3 is 0.4mm to 0.6mm, and the outer diameter R 11It is 0.7mm~0.9mm.

[0040] The outer surface of the circularly polarized ingestion antenna is coated with a layer of biocompatible material polyetheretherketone with a thickness of 0.04 mm and a dielectric constant of ε r The loss tangent tanδ is 3.2 and 0.01, which realizes the biocompatibility of the circularly polarized intake antenna with the human body and prevents the circularly polarized intake antenna from directly contacting the human digestive organs to cause short circuit, corrosion or rejection.

[0041] Example: The specific manufacturing process is as described in the embodiment. Rogers RO3210 dielectric substrate is selected, and the dielectric constant ε r =10.2, loss tangent tanδ=0.003, thickness H=0.635mm, and the coaxial connector adopts a standard SMA connector. The materials of each layer of the radiation unit and the floor of the circularly polarized intake antenna are copper-clad graphene film. The copper-clad graphene film material has a high carrier density, which makes it have excellent conductivity, can increase the working bandwidth and gain of the intake antenna, improve transmission efficiency and reduce loss. The thickness of the copper-clad graphene film is 0.03mm, and the radius R1 of the dielectric substrate (1), the dielectric substrate (2), and the dielectric substrate (3) is 4.5mm. The graphene double S combined structure radiation patch (4) and the graphene double S combined structure radiation patch (5) adopt a double S combined structure to effectively increase the current path and reduce the antenna size to meet the miniaturization requirements. The graphene double S combined structure radiation patch (4) and the graphene double S combined structure radiation patch (5) are connected by four short-circuit probes to form a composite spiral structure, thereby generating circular polarization characteristics, while suppressing multipath interference and reducing the bit error rate. The outer diameter R3 of the notch ring of the graphene double S combined structure radiation patch (4) is 2.25 mm, the inner diameter R4 is 1.9 mm, the height L1 of the notch is 2.3 mm, the outer diameter R7 of the four rings arranged at the top of the S shape is 0.3 mm, and the inner diameter R8 is 0.2 mm. The overall structural dimensions of the graphene double S combined structure radiation patch (5) are consistent with those of the graphene double S combined structure radiation patch (4), the radius R6 of the circular hole of the center circle of the double S combined structure is 0.3 mm, and the distance R5 from the center of the four rings arranged at the top of the S shape to the center of the graphene double S combined structure radiation patch (5) is 2.08 mm. The graphene floor adopts a complete circular structure to form a shielding layer inside the wireless endoscope capsule, which can effectively prevent the antenna from interfering with other electronic devices inside the capsule, thereby improving the anti-interference performance and electromagnetic compatibility performance of the antenna. The hook-shaped structure of the graphene hook-shaped structure radiation patch can reduce the resonant frequency of the antenna, further reduce the size of the antenna, and increase the impedance bandwidth of the antenna. Adjusting the size of the graphene hook-shaped structure radiation patch can further optimize the circular polarization purity of the antenna. The outer diameter R of the four notched rings of the graphene hook-shaped structure radiation patch (6) is 10The inner diameter R9 is 1.4mm, the notch height L2 is 0.85mm, the width W1 of the connecting band between the notch ring and the center ring is 0.55mm, the length L3 is 0.5mm, and the outer diameter R 11 The outer surface of the circularly polarized intake antenna is coated with a layer of biocompatible material polyetheretherketone with a thickness of 0.04mm and a dielectric constant of ε r The loss tangent tanδ is 3.2 and 0.01, which realizes the biocompatibility of the circularly polarized intake antenna with the human body and prevents the circularly polarized intake antenna from directly contacting the human digestive organs to cause short circuit, corrosion or rejection.

[0042] The influence of the outer diameter R3 and inner diameter R4 of the notched ring of the graphene double S composite structure radiation patch (4) on the antenna impedance bandwidth and axial ratio bandwidth is shown in the figure. Figure 6 As shown, three cases of R3 = 2.15mm, R4 = 1.8mm, R3 = 2.25mm, R4 = 1.9mm, R3 = 2.35mm, and R4 = 2.0mm are selected to analyze the antenna performance. Figure 6 It can be seen that with the increase of the outer diameter R3 and the inner diameter R4 of the notched ring, the resonant frequency of the circular polarization intake antenna shifts toward the low frequency direction, and the optimal point of the axial ratio performance also moves toward the low frequency correspondingly with the change of the ring size, which has little effect on the impedance matching of the antenna. The reason is that the increase in the ring size causes the increase in the electrical size of the composite spiral structure, which causes the resonant frequency band to shift toward the low frequency direction, and the axial ratio performance of the antenna is still good. When R3 = 2.25mm and R4 = 1.9mm, the impedance bandwidth and axial ratio bandwidth of the intake circular polarization antenna both cover the required ISM2.4GHz frequency band.

[0043] Select the outer diameters R of the four notched rings of the graphene hook-shaped composite structure radiation patch (6) 10 , the influence of inner diameter R9 on antenna impedance bandwidth and axial ratio bandwidth, such as Figure 7 As shown, select R 10 =1.3mm, R9=0.95mm, R 10 =1.4mm, R9=1.05mm, R 10 The antenna performance is analyzed in the following three cases: R9 = 1.5mm, R9 = 1.15mm. Figure 7 As can be seen, with the outer diameter R of the notched ring 10 , the inner diameter R9 increases, the resonant frequency and the best point of the axial ratio performance of the circularly polarized intake antenna shift toward the low frequency direction, and the resonance degree gradually increases. The reason is that the introduction of the hook-shaped combined structure radiation patch can adjust the impedance matching and polarization purity of the intake antenna. 10When R = 1.4mm and R9 = 1.05mm, the impedance bandwidth and axial ratio bandwidth of the intake circularly polarized antenna both cover the required ISM 2.4GHz frequency band.

[0044] The thickness T of the copper-clad graphene film is selected as 0.02mm, 0.03mm, and 0.04mm, and the influence of the thickness of the copper-clad graphene film on the antenna performance is analyzed. Figure 8 As shown in the figure, it can be seen that with the increase of the thickness of the copper-clad graphene film, the resonant frequency offset of the circularly polarized intake antenna is small, and the resonance degree is significantly increased, indicating that the impedance matching of the circularly polarized intake antenna is significantly improved. The reason is that with the increase of the thickness of the copper-clad graphene film, the conductivity of the copper-clad graphene film is improved, thereby reducing the loss of the copper-clad graphene film and optimizing the impedance matching of the circularly polarized intake antenna. When the thickness T of the copper-clad graphene film is selected as 0.03mm, the performance of the circularly polarized intake antenna meets the working requirements of the ISM2.4GHz frequency band.

[0045] The application of capsule endoscopy device determines that the intake circularly polarized antenna will be taken into different human digestive organs. In order to analyze the influence of the intake position and environment of the circularly polarized intake antenna on the antenna impedance bandwidth, the designed antenna is taken into different human digestive organs using the CST human high-precision model. The circularly polarized intake antenna is taken into the stomach, small intestine and colon for comparison and testing. The influence of the circularly polarized intake antenna taking into different digestive organs on the antenna impedance bandwidth and axial ratio bandwidth is shown in the figure. Fig. 9 As shown in the figure, the distances of the circularly polarized ingestion antenna from the body surface in the stomach, small intestine, and colon are 21 mm, 32 mm, and 48 mm, respectively. The circularly polarized ingestion antenna has a wide impedance bandwidth and good impedance matching in the three ingestion positions. The resonant frequency shifts toward the high frequency direction, but the impedance bandwidth and axial ratio bandwidth can still cover the required working frequency band, mainly because of the dielectric constant ε of the stomach. r is 65.02, the dielectric constant of the small intestine ε r is 57.86, the dielectric constant of the colon ε r It is 53.92, and the dielectric constants of the three digestive organs gradually decrease, causing the resonant frequency to shift toward the high frequency direction.

[0046] The radiation characteristics of circularly polarized intake antennas at different intake positions are analyzed. The gain and axial ratio curves of circularly polarized intake antennas for the stomach, small intestine, and colon are shown in Figure 2. Fig.10 , 11As shown in Figure 12, it can be seen from the figure that the maximum gain and the best axial ratio angle of the circular polarization intake antenna after intake into the stomach are -45 degrees, the maximum gain and the best axial ratio angle of the circular polarization intake antenna after intake into the small intestine are -18 degrees, and the maximum gain and the best axial ratio angle of the circular polarization intake antenna after intake into the colon are 22 degrees. The maximum gain of the circular polarization intake antenna in the stomach, small intestine, and colon are -22.8dBic, -28.6dBic, and -35.2dBic, respectively. The maximum gain of the circular polarization intake antenna gradually decreases. The main reason is that different intake depths affect the loss of electromagnetic energy and different digestive tissues cause different dielectric losses. The axial ratios of the corresponding three positions are 2.8dB, 3.9dB, and 5.2dB, respectively. The polarization purity has different degrees of deterioration, which is caused by the large changes in the human tissue model. Further optimization of the tissue model can improve the axial ratio performance.

[0047] A comprehensive analysis was conducted on the safety performance of the circularly polarized intake antenna. By setting the input power of the circularly polarized intake antenna to 1W, the distribution of the average SAR value of the human body was analyzed. After simulation calculation, the maximum 1- / 10-gSAR values ​​of the circularly polarized intake antenna at the stomach, small intestine and colon were 142.3 / 23.2W / kg, 172.3 / 32.8W / kg and 125.3 / 24.6W / kg. After calculation, it can be concluded that in order to meet the FCC and IEEE safety standards for SAR values, the maximum allowable input power of the intake antenna is 9.2mW and 47.8mW, and the electromagnetic radiation of the circularly polarized intake antenna under normal operation is safe and harmless to the human digestive tissue.

[0048] The circularly polarized ingestible antenna is placed in an environment simulating human digestive tissue. The impedance bandwidth of the antenna is tested using a vector network analyzer. The axial ratio bandwidth of the antenna is tested indirectly by using an in vitro antenna. The simulation results of the impedance bandwidth and axial ratio bandwidth are consistent with the test results. Fig.13 As shown in the figure, the simulated impedance bandwidth of the intake antenna is 2.31GHz~2.58GHz, the resonant frequency is 2.45GHz, the simulated axial ratio bandwidth is 2.35GHz~2.49GHz, the measured impedance bandwidth is 2.16GHz~2.42GHz, the resonant frequency is 2.28GHz, and the measured axial ratio bandwidth is 2.17GHz~2.38GHz. The axial ratio bandwidth can cover the working frequency, and the measured and simulated results are consistent. The circularly polarized intake antenna has a wide working bandwidth, and the impedance characteristics and axial ratio characteristics within the working frequency band are good. The resonant frequency and axial ratio bandwidth center are shifted to the low frequency direction to a certain extent. The frequency shift is mainly caused by simulating the human digestive environment and processing test errors.

Claims

1. A graphene-based circularly polarized ingestion antenna for a capsule endoscope device, comprising a first dielectric substrate (1), a second dielectric substrate (2), a third dielectric substrate (3), a first graphene double S combined structure radiation patch (4), a second graphene double S combined structure radiation patch (5), a graphene hook-shaped combined structure radiation patch (6), a graphene floor (7), a coaxial connector (8), a first short-circuit probe (5-1), a second short-circuit probe (5-2), a third short-circuit probe (5-3), and a fourth short-circuit probe (5-4), wherein the graphene double S combined structure radiation patch (4), the graphene double S combined structure radiation patch (5), the graphene hook-shaped combined structure radiation patch (6), and the graphene floor (7) are all made of copper-clad graphene film; characterized in that: a. The first dielectric substrate (1), the second dielectric substrate (2), and the third dielectric substrate (3) are respectively located at the upper layer, the middle layer, and the lower layer of the antenna; b. The first graphene double S combined structure radiation patch (4) is located on the upper surface of the first dielectric substrate (1), and the first graphene double S combined structure radiation patch (4) is composed of two S-shaped combinations, the S-shape is composed of two upper and lower notched circular rings, one of the S-shapes is obtained by rotating the other S-shape by 90 degrees through the central axis, a circular adjustment impedance matching is added between the two S-shaped combined structures, and four circular rings are arranged at the top of the S-shape for connecting short-circuit probes to ensure that the connection between the first graphene double S combined structure radiation patch (4) and the second graphene double S combined structure radiation patch (5) is stable and reliable; c. The second graphene double S combined structure radiation patch (5) is located on the upper surface of the second dielectric substrate (2), the overall structural size of the second graphene double S combined structure radiation patch (5) is consistent with the first graphene double S combined structure radiation patch (4), and a circular hole is opened on the center circle of the double S combined structure for connecting the inner core of the coaxial connector (8); d. The graphene hook-shaped combined structure radiation patch (6) is located on the upper surface of the third dielectric substrate (3). The graphene hook-shaped combined structure radiation patch (6) is composed of four notched circular patches, a central circular patch and a connecting conductive strip. The central circular patch is connected to the four notched circular patches through the connecting conductive strip to form a hook-shaped combined structure. The circular hole of the central circular patch is used to connect the inner core of the coaxial connector (8). e. The graphene floor (7) is located on the lower surface of the third dielectric substrate (3), and the graphene floor (7) adopts a complete circular structure to form a shielding layer inside the wireless endoscope capsule; f. The coaxial connector (8) is located on the lower side of the lower surface of the third dielectric substrate (3), the inner core of the coaxial connector (8) is connected to the central circular holes of the second graphene double S combined structure radiation patch (5) and the graphene hook-shaped combined structure radiation patch (6), and the outer cylindrical conductor of the coaxial connector (8) is connected to the center of the graphene floor (7); g. The first short-circuit probe (5-1), the second short-circuit probe (5-2), the third short-circuit probe (5-3), and the fourth short-circuit probe (5-4) are located between the first graphene double S combination structure radiation patch (4) and the second graphene double S combination structure radiation patch (5), and the second graphene double S combination structure radiation patch (5) and the first graphene double S combination structure radiation patch (4) are connected to the upper and lower ends of the first short-circuit probe (5-1), the second short-circuit probe (5-2), the third short-circuit probe (5-3), and the fourth short-circuit probe (5-4) by setting four rings at the top of the S shape to form a composite spiral structure; The outer diameter R3 of the notched ring of the first graphene double S combined structure radiation patch (4) is 2.1 mm to 2.4 mm, the inner diameter R4 is 1.8 mm to 2.0 mm, the height L1 of the notch is 2.0 mm to 2.5 mm, the outer diameter R7 of the four rings arranged at the top of the S shape is 0.25 mm to 0.35 mm, and the inner diameter R8 is 0.15 mm to 0.25 mm.

2. The graphene-based circularly polarized ingestion antenna for capsule endoscopy device according to claim 1, characterized in that The copper-clad graphene film has a thickness of 0.01 mm to 0.03 mm, and the radius R1 of the first dielectric substrate (1), the second dielectric substrate (2), and the third dielectric substrate (3) is 4 mm to 5 mm.

3. The graphene-based circularly polarized ingestion antenna for capsule endoscopy device according to claim 1, characterized in that The overall structural dimensions of the second graphene double S combined structure radiation patch (5) are consistent with those of the first graphene double S combined structure radiation patch (4), the radius R6 of the circular hole of the center circle of the double S combined structure is 0.25 mm to 0.35 mm, and the distance R5 from the center of the four circular rings arranged at the top of the S shape to the center of the second graphene double S combined structure radiation patch (5) is 1.9 mm to 2.1 mm.

4. The graphene-based circularly polarized ingestion antenna for capsule endoscopy device according to claim 1, characterized in that The outer diameters R of the four notched rings of the graphene hook-shaped combined structure radiation patch (6) are 10 The inner diameter R9 is 1.3mm to 1.5mm, the notch height L2 is 0.7mm to 1.1mm, the width W1 of the connecting guide band between the notch ring and the center ring is 0.4mm to 0.7mm, the length L3 is 0.4mm to 0.6mm, and the outer diameter R 11 It is 0.7mm~0.9mm.

5. The graphene-based circularly polarized ingestion antenna for capsule endoscopy device according to claim 1, characterized in that The outer surface of the circularly polarized ingestion antenna is coated with a layer of biocompatible material polyetheretherketone with a thickness of 0.04 mm and a dielectric constant of ε r is 3.2, and the loss tangent tanδ is 0.01.

Images