CN110890625A - Square-ring-shaped capacitive loading implantation type circularly polarized antenna with double-bending resonant ring - Google Patents

Square-ring-shaped capacitive loading implantation type circularly polarized antenna with double-bending resonant ring Download PDF

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CN110890625A
CN110890625A CN201911391870.5A CN201911391870A CN110890625A CN 110890625 A CN110890625 A CN 110890625A CN 201911391870 A CN201911391870 A CN 201911391870A CN 110890625 A CN110890625 A CN 110890625A
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ring
antenna
square
double
branch
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CN110890625B (en
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欧仁侠
齐秋菊
鲍捷
杨风健
张光雷
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Jilin Medical College
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Jilin Medical College
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00Details of, or arrangements associated with, antennas
    • H01Q1/36Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00Details of, or arrangements associated with, antennas
    • H01Q1/36Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H01Q1/38Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00Details of, or arrangements associated with, antennas
    • H01Q1/48Earthing means; Earth screens; Counterpoises
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00Details of, or arrangements associated with, antennas
    • H01Q1/50Structural association of antennas with earthing switches, lead-in devices or lightning protectors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00Details of, or arrangements associated with, antennas
    • H01Q1/52Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure
    • H01Q1/526Electromagnetic shields
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04Resonant antennas
    • H01Q9/0485Dielectric resonator antennas
    • H01Q9/0492Dielectric resonator antennas circularly polarised

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  • Electromagnetism (AREA)
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Abstract

The invention designs a square-ring capacitive loading implanted circular polarized antenna with a double-bent resonant ring, an additional mode close to the resonant frequency of a main mode can be excited by the outer square ring by using the electromagnetic coupling effect, the impedance bandwidth is widened, the interdigital capacitor is added between the outer square ring and the inner square ring, the capacitive loading characteristic is generated, and the size of the antenna is reduced. The circular polarizer with array layout formed by the double-bending resonant rings has a more compact structure and can concentrate stronger electromagnetismAnd energy is used for exciting two degenerate orthogonal modes with equal amplitudes and 90-degree phase difference, so that circular polarization radiation is realized, the rectangular branch with increased gaps is formed in the middle of the U-shaped branch, and the circular polarization purity of the antenna can be adjusted and enhanced. The volume of the antenna is only 9 x 0.635mm3The antenna has the characteristics of miniaturization, wide band, circular polarization, interference resistance and the like, is suitable for the ISM 2.45GHz frequency band, and meets the working requirements of miniaturization and circular polarization of the antenna after being implanted into a human tissue environment.

Description

Square-ring-shaped capacitive loading implantation type circularly polarized antenna with double-bending resonant ring
Technical Field
The invention relates to the technical field of implanted antennas, in particular to a square-ring capacitive loading implanted circularly polarized antenna with a double-bending resonant ring, which is suitable for an implanted circularly polarized wireless biomedical device in an ISM 2.45GHz frequency band.
Background
The bioelectromagnetism covers a plurality of fields such as biology, medical technology, electromagnetism and the like, is concerned by researchers, and is more and more widely applied to medical diagnosis, treatment and the like. The application of the bioelectromagnetism in a medical system can not only help doctors diagnose and prevent diseases, but also monitor the change of human physiological parameters in real time, thereby providing a great deal of convenience for patients. The implanted antenna is a key link of a remote medical monitoring system, is a carrier for information transmission, and is very important for the design and research of the implanted antenna. The performance of the implanted antenna directly affects the working efficiency and stability of the remote medical monitoring system. The implanted antenna transmits the physiological parameters monitored by the sensor to the in-vitro receiving device, and a doctor analyzes the parameters to complete the diagnosis process. Common wireless medical equipment includes wearing formula, the formula of taking into and implanted, and the wireless medical equipment work of wearing formula is in free space, and is lower to the antenna requirement, and the formula of taking into and the work of implanted wireless medical equipment is in the human body, and the electromagnetic characteristic of wireless medical equipment can be influenced to the strong coupling between wireless medical equipment and the human body, and how to design the implanted antenna that the performance is good, the operation is stable is a problem that needs to solve urgently in the biological electromagnetism field. The circularly polarized antenna can receive and transmit linearly polarized waves in any direction or circularly polarized waves in the same rotating direction, has the advantages of easiness in conformality, strong anti-interference capability, low error rate, multipath interference resistance and the like, is suitable for environments with frequently changed relative positions of an external antenna and an implanted antenna, and the implanted antenna needs to have a wider working frequency band, a smaller design size, a reduced SAR value absorbed by a human body and the like. The method for widening the frequency band of the implanted antenna comprises the following steps: reducing the Q value of the equivalent resonant circuit; a multi-resonance coupling structure is added to replace a simple resonance structure, such as a parasitic patch; designing a plurality of patches on the same plane, increasing resonance points through the coupling of the patches and widening the bandwidth; the antenna adopts a multilayer stacked structure, adopts multilayer patches and multilayer dielectric substrates in the antenna, and feeds power in an electromagnetic coupling or aperture coupling mode; by adopting a fractal technology and adopting fractal antenna elements or arranging the array units according to a fractal rule, the fractal antenna can widen the bandwidth of the antenna and reduce the size of the antenna at the same time. The method for miniaturizing the implanted antenna mainly comprises the following steps: increasing the relative dielectric constant; the meander technology, which is to open a slot or a slit on a radiation patch and guide current to be distributed along the slit, thereby extending the current path on the surface of the antenna and enabling the resonant frequency to shift to the low frequency direction; an antenna loading technology is adopted, wherein a short-circuit probe, a short-circuit sheet or a short-circuit surface is introduced between a radiation patch and a floor to form a quarter-wavelength structure, so that the size of an antenna is reduced; the capacitive inductive loading technology can offset inductive impedance, and the miniaturization and impedance matching of the antenna are realized. The main method for realizing the circular polarization characteristic comprises the following steps: adopting a caliber coupling feed method; setting a short-circuit probe; introducing a perturbation structure on the radiation patch, namely introducing a gap or a loading branch on the radiation patch or the floor; loading a circular polarizer composed of an open resonant ring, and the like. The split ring resonator is a sub-wavelength magnetic resonator, has negative dielectric constant property, can inhibit surface waves, reduce mutual coupling and reduce the size of an antenna, and can generate weaker left-handed material characteristics when an implanted antenna is loaded with the split ring resonator to form an array.
Disclosure of Invention
The invention aims to provide a square-ring capacitive loading implanted circular polarized antenna with a double-bending resonant ring, which has the characteristics of miniaturization, wide frequency band, circular polarization, interference resistance, good biocompatibility and the like, is convenient to integrate with an implanted wireless biomedical device, is suitable for an ISM (industrial scientific medical) 2.45GHz frequency band, and can meet the requirements of the implanted wireless biomedical device on the performance of the antenna.
The technical scheme of the invention is as follows: introduce two square ring capacitive loading implanted circular polarized antenna who buckles the resonant ring, constitute its characterized in that by dielectric substrate 1, the square ring capacitive loading radiating element 2, short circuit probe 3, short circuit probe 4, coaxial joint 5, the floor 6 that introduce two resonance rings:
a. the square ring capacitive loading radiation unit 2 introduced with the double-bending resonance ring consists of an outer square ring 2-1, an inner square ring 2-2 and a double-bending resonance ring 2-3, the outer square ring 2-1 can excite an additional mode close to the resonance frequency of a main mode by utilizing the electromagnetic coupling effect so as to widen the impedance bandwidth of the antenna, an interdigital capacitor 2-4, an interdigital capacitor 2-5, an interdigital capacitor 2-6 and an interdigital capacitor 2-7 are added between four radiation edges of the outer square ring 2-1 and the inner square ring 2-2 to generate the capacitive loading characteristic, the size of the implanted antenna is reduced, the miniaturization of the antenna is realized, the double-bending resonance ring 2-3 is loaded in the inner square ring 2-2, and the circular polarizer structure of the array formed by the double-bending resonance rings 2-3 is more compact, stronger electromagnetic energy can be concentrated, a single bending resonance ring is formed by bending a square ring by half, the inner part of the bending resonance ring is disconnected and two U-shaped branches are symmetrically placed, a gap is formed between the two U-shaped branches, an E-shaped groove is formed in the single bending resonance ring, the rectangular branch is additionally arranged in the gap and is connected with the upper edge of the E-shaped groove, a circular polarizer consisting of double bending resonance rings 2-3 can excite two degenerate orthogonal modes with equal amplitudes and 90-degree phase difference, so that circular polarization radiation is realized, the circular polarization purity of the implanted antenna can be adjusted and enhanced by the added rectangular branch, the double bending resonance rings 2-3 are connected with the inner square ring 2-2 through rectangular conduction bands, and the two single bending resonance rings are symmetrical about the transverse symmetrical axis of the dielectric substrate 1;
b. the short circuit probe 3 and the short circuit probe 4 are arranged at the lower left corner and the upper left corner of an inner square ring 2-2 in the square-ring capacitive loading radiation unit 2 introduced with the double-bent resonance ring, the short circuit probe 3 and the short circuit probe 4 are symmetrical about the transverse axis of the antenna dielectric substrate 1, the short circuit probe 3 and the short circuit probe 4 are added to form a standing wave structure, and the size of the antenna is further reduced;
c. the coaxial connector 5 is positioned on the right side of an inner square ring 2-2 in the square annular capacitive loading radiation unit 2 introduced with the double-bending resonance ring and positioned on a transverse symmetrical axis of the dielectric substrate 1, an inner core of the coaxial connector 5 is connected with the inner square ring 2-2 in the square annular capacitive loading radiation unit 2 introduced with the double-bending resonance ring, and an outer core of the coaxial connector 5 is connected with the floor 6;
d. the floor 6 is a square complete metal patch structure, and can form a shielding layer to isolate the electronic device of the wireless biomedical device from the implanted circularly polarized antenna, reduce the interference of the antenna on other electronic devices, and improve the electromagnetic compatibility.
The length L of the dielectric substrate 1 is 8 mm-10 mm, and the width W is 8 mm-10 mm.
The distance W between the square ring capacitive loading radiating element 2 with the double-bending resonant ring and the edge of the dielectric substrate 110.2 mm-0.3 mm, the square ring capacitive loading radiation unit 2 introduced with the double-bending resonance ring consists of an outer square ring 2-1, an inner square ring 2-2 and a double-bending resonance ring 2-3, and the outer side length of the outer square ring 2-1 is W38.4 mm-8.6 mm, side length W of the inner side137.8 mm-8 mm, the outer side length of the inner square ring 2-1 is W126.2 mm-6.4 mm, side length W of the inner side114.4 mm-4.6 mm, the distance L between the outer square ring 2-1 and the inner square ring 2-220.7 mm-0.9 mm, the length L of the upper and lower branches in the interdigital capacitor 2-5, 2-6 and 2-710.6 mm-0.7 mm, width W20.1 mm-0.2 mm, and the width W of the space between the upper branch knot and the lower branch knot40.1 mm-0.2 mm, the double-bending resonance ring 2-3 is connected with the inner square ring 2-2 through a rectangular conduction band with width W of the rectangular conduction band50.2 mm-0.4 mm, length L30.2 mm-0.4 mm, length L of single bending resonance ring71.7 mm-1.8 mm, width W63.8 mm-4 mm, and the ring width W of the single bending resonance ring70.2 mm-0.4 mm, the width W of the branch connected with the U-shaped branch100.9 mm-1.1 mm, length L80.3 mm-0.4 mm, and the length L of the left branch of the U-shaped branch50.8 mm-0.9 mm, length L of right branch60.9 mm-1.1 mm, upper branch length W90.9 mm-1.1 mm, and the width W of the U-shaped branch140.3 mm-0.4 mm, and rectangular branches are added in the middle of the splitPitch length L41.1 mm-1.3 mm, width W8Is 0.1 mm-0.3 mm.
The short circuit probe 3 and the short circuit probe 4 have a radius R10.2 mm-0.4 mm, and the distance R between the centers of the short- circuit probes 3 and 4 and the center of the dielectric substrate 123.5 mm-3.9 mm, and the included angles a between the short- circuit probes 3 and 4 and the longitudinal symmetry axis of the dielectric substrate 11The radius of the short-circuit probe 3 and the radius of the short-circuit probe 4 are equal to the radius of the inner core of the coaxial connector 5, and the radius is 42-47 degrees.
The distance W between the center of the coaxial connector 5 and the center of the dielectric substrate 10Is 2.5 mm-2.9 mm.
The floor 6 is a complete square metal patch, the size of the floor 6 is the same as that of the medium substrate 1, L is 8 mm-10 mm, and W is 8 mm-10 mm in width.
The square-ring capacitive loading implanted circular polarized antenna with the double-bending resonant ring introduced is coated with a layer of ultrathin biocompatible film alumina on the outer surface, has small influence on the reflection coefficient and the antenna gain, is close to the dielectric constant of the dielectric substrate 1, and has the dielectric constant epsilonr9.2, loss tangent tan delta of 0.008 and coating thickness of 0.03mm, and can isolate implanted circular polarization from human tissue of the antenna, prevent the conductive patch of the antenna from directly contacting with the human tissue, and reduce the influence of the human tissue on the performance of the implanted circular polarization antenna.
The invention has the following effects: the invention designs a square-ring capacitive loading implanted circular polarized antenna with a double-bending resonant ring, an additional mode close to the resonant frequency of a main mode can be excited by the outer square ring by using the electromagnetic coupling effect, so that the impedance bandwidth of the antenna is widened, the interdigital capacitor is added between the outer square ring and the inner square ring, the capacitive loading characteristic is generated, the size of the implanted antenna is reduced, and the miniaturization of the antenna is realized. The circular polarizer with the array layout formed by the double-bent resonant rings is more compact in structure, can concentrate stronger electromagnetic energy and can excite two degenerate orthogonal modes with equal amplitudes and 90-degree phase difference, so that circular polarization radiation is realized, rectangular branches with increased gaps are formed in the middle of the U-shaped branches, and the circular polarization purity of the implanted antenna can be adjusted and enhanced. The floor is oneThe square complete metal patch structure can form a shielding layer to isolate the electronic device of the wireless biomedical device from the implanted circularly polarized antenna, reduce the interference of the antenna on other electronic devices and improve the electromagnetic compatibility. The addition of the short-circuit probe can form a standing wave structure, and the size of the antenna is further reduced. The implanted circularly polarized antenna is of a planar structure, and the volume of the antenna is only 9 multiplied by 0.635mm3The antenna has the characteristics of miniaturization, wide band, circular polarization, interference resistance, good biocompatibility and the like, is suitable for the ISM 2.45GHz frequency band, and meets the working requirements of miniaturization and circular polarization of the antenna after being implanted into a human tissue environment.
Drawings
Fig. 1 is a schematic front view of an embodiment of the present invention.
Fig. 2 is a schematic side view of an embodiment of the present invention.
Fig. 3 is a schematic diagram of a back structure according to an embodiment of the invention.
FIG. 4 illustrates the effect of embodiments of the present invention on the impedance bandwidth and axial ratio bandwidth of an antenna before and after introducing capacitive loading between the outside quad-ring and the inside quad-ring.
FIG. 5 shows an embodiment of the present invention forming a split between U-shaped branches to increase the length L of the rectangular branches4Width W of8The effect on the antenna impedance bandwidth and the axial ratio bandwidth.
FIG. 6 is a schematic illustration of the depth of implantation into a skin layer in accordance with an embodiment of the present invention.
Fig. 7 illustrates the effect of different implant depths H on the antenna impedance bandwidth and axial ratio bandwidth for embodiments of the present invention.
Fig. 8 is a plot of simulated and measured impedance bandwidth for an embodiment of the present invention.
FIG. 9 is an E-plane radiation pattern for an embodiment of the present invention at a frequency of 2.45 GHz.
Fig. 10 is an H-plane radiation pattern for an embodiment of the present invention at a frequency of 2.45 GHz.
Detailed Description
The specific implementation mode of the invention is as follows: as shown in fig. 1, the square-ring capacitive loading implanted circular polarized antenna with the double-bending resonant ring introduced comprises a dielectric substrate 1, a square-ring capacitive loading radiation unit 2 with the double-bending resonant ring introduced, a short-circuit probe 3, a short-circuit probe 4, a coaxial connector 5 and a floor 6, and is characterized in that: the square ring capacitive loading radiation unit 2 introduced with the double-bending resonance ring consists of an outer square ring 2-1, an inner square ring 2-2 and a double-bending resonance ring 2-3, the outer square ring 2-1 can excite an additional mode close to the resonance frequency of a main mode by utilizing the electromagnetic coupling effect so as to widen the impedance bandwidth of the antenna, an interdigital capacitor 2-4, an interdigital capacitor 2-5, an interdigital capacitor 2-6 and an interdigital capacitor 2-7 are added between four radiation edges of the outer square ring 2-1 and the inner square ring 2-2 to generate the capacitive loading characteristic, the size of the implanted antenna is reduced, the miniaturization of the antenna is realized, the double-bending resonance ring 2-3 is loaded in the inner square ring 2-2, and the circular polarizer structure of the array formed by the double-bending resonance rings 2-3 is more compact, stronger electromagnetic energy can be concentrated, a single bending resonance ring is formed by bending a square ring by half, the inner part of the bending resonance ring is disconnected and two U-shaped branches are symmetrically placed, a gap is formed between the two U-shaped branches, an E-shaped groove is formed in the single bending resonance ring, the rectangular branch is additionally arranged in the gap and is connected with the upper edge of the E-shaped groove, a circular polarizer consisting of double bending resonance rings 2-3 can excite two degenerate orthogonal modes with equal amplitudes and 90-degree phase difference, so that circular polarization radiation is realized, the circular polarization purity of the implanted antenna can be adjusted and enhanced by the added rectangular branch, the double bending resonance rings 2-3 are connected with the inner square ring 2-2 through rectangular conduction bands, and the two single bending resonance rings are symmetrical about the transverse symmetrical axis of the dielectric substrate 1; the short circuit probe 3 and the short circuit probe 4 are arranged at the lower left corner and the upper left corner of an inner square ring 2-2 in the square-ring capacitive loading radiation unit 2 introduced with the double-bent resonance ring, the short circuit probe 3 and the short circuit probe 4 are symmetrical about the transverse axis of the antenna dielectric substrate 1, the short circuit probe 3 and the short circuit probe 4 are added to form a standing wave structure, and the size of the antenna is further reduced; the coaxial connector 5 is positioned on the right side of an inner square ring 2-2 in the square annular capacitive loading radiation unit 2 introduced with the double-bending resonance ring and positioned on a transverse symmetrical axis of the dielectric substrate 1, an inner core of the coaxial connector 5 is connected with the inner square ring 2-2 in the square annular capacitive loading radiation unit 2 introduced with the double-bending resonance ring, and an outer core of the coaxial connector 5 is connected with the floor 6; the floor 6 is a square complete metal patch structure, and can form a shielding layer to isolate the electronic device of the wireless biomedical device from the implanted circularly polarized antenna, reduce the interference of the antenna on other electronic devices, and improve the electromagnetic compatibility.
The length L of the dielectric substrate 1 is 8 mm-10 mm, and the width W is 8 mm-10 mm.
The distance W between the square ring capacitive loading radiating element 2 with the double-bending resonant ring and the edge of the dielectric substrate 110.2 mm-0.3 mm, the square ring capacitive loading radiation unit 2 introduced with the double-bending resonance ring consists of an outer square ring 2-1, an inner square ring 2-2 and a double-bending resonance ring 2-3, and the outer side length of the outer square ring 2-1 is W38.4 mm-8.6 mm, side length W of the inner side137.8 mm-8 mm, the outer side length of the inner square ring 2-1 is W126.2 mm-6.4 mm, side length W of the inner side114.4 mm-4.6 mm, the distance L between the outer square ring 2-1 and the inner square ring 2-220.7 mm-0.9 mm, the length L of the upper and lower branches in the interdigital capacitor 2-5, 2-6 and 2-710.6 mm-0.7 mm, width W20.1 mm-0.2 mm, and the width W of the space between the upper branch knot and the lower branch knot40.1 mm-0.2 mm, the double-bending resonance ring 2-3 is connected with the inner square ring 2-2 through a rectangular conduction band with width W of the rectangular conduction band50.2 mm-0.4 mm, length L30.2 mm-0.4 mm, length L of single bending resonance ring71.7 mm-1.8 mm, width W63.8 mm-4 mm, and the ring width W of the single bending resonance ring70.2 mm-0.4 mm, the width W of the branch connected with the U-shaped branch100.9 mm-1.1 mm, length L80.3 mm-0.4 mm, and the length L of the left branch of the U-shaped branch50.8 mm-0.9 mm, length L of right branch60.9 mm-1.1 mm, upper branch length W90.9 mm-1.1 mm, and the width W of the U-shaped branch140.3 mm-0.4 mm, and the length L of the rectangular branch is increased in the middle of the split41.1 mm-1.3 mm, width W8Is 0.1 mm-0.3 mm.
The short circuit probe 3 and the short circuit probeNeedle 4 radius R10.2 mm-0.4 mm, and the distance R between the centers of the short- circuit probes 3 and 4 and the center of the dielectric substrate 123.5 mm-3.9 mm, and the included angles a between the short- circuit probes 3 and 4 and the longitudinal symmetry axis of the dielectric substrate 11The radius of the short-circuit probe 3 and the radius of the short-circuit probe 4 are equal to the radius of the inner core of the coaxial connector 5, and the radius is 42-47 degrees.
The distance W between the center of the coaxial connector 5 and the center of the dielectric substrate 10Is 2.5 mm-2.9 mm.
The floor 6 is a complete square metal patch, the size of the floor 6 is the same as that of the medium substrate 1, L is 8 mm-10 mm, and W is 8 mm-10 mm in width.
The square-ring capacitive loading implanted circular polarized antenna with the double-bending resonant ring introduced is coated with a layer of ultrathin biocompatible film alumina on the outer surface, has small influence on the reflection coefficient and the antenna gain, is close to the dielectric constant of the dielectric substrate 1, and has the dielectric constant epsilonr9.2, loss tangent tan delta of 0.008 and coating thickness of 0.03mm, and can isolate implanted circular polarization from human tissue of the antenna, prevent the conductive patch of the antenna from directly contacting with the human tissue, and reduce the influence of the human tissue on the performance of the implanted circular polarization antenna.
Example (b): the specific manufacturing process is as described in the embodiment. Selecting Rogers RO3210 dielectric substrate with dielectric constant ∈r10.2, loss tangent tan delta 0.003, thickness H0.635 mm, coaxial joint using standard SMA joint. The dielectric substrate had a length L of 9mm and a width W of 9 mm. The outer square ring 2-1 can excite an additional mode close to the resonance frequency of the main mode by utilizing the electromagnetic coupling effect, so that the impedance bandwidth of the antenna is widened, interdigital capacitance is increased between the outer square ring 2-1 and the inner square ring 2-2 to generate a capacitive loading characteristic, the size of the implanted antenna is reduced, the miniaturization of the antenna is realized, and the distance W between the square-ring-shaped capacitive loading radiation unit 2 of the double-bent resonance ring and the edge of the dielectric substrate 1 is introduced10.25mm, the square ring capacitive loading radiation unit 2 introduced with the double-bending resonance ring consists of an outer square ring 2-1, an inner square ring 2-2 and a double-bending resonance ring 2-3, and the outer side length of the outer square ring 2-1 is W38.5mm, inner side length W137.9mm, the outer side length of the inner square ring 2-1 is W126.3mm, inner side length W11Is 4.5mm, and the distance L between the outer square ring 2-1 and the inner square ring 2-220.8mm, the length L of upper and lower branches in the interdigital capacitors 2-4, 2-5, 2-6 and 2-71Is 0.66mm, width W20.14mm, and the width W of the space between the upper branch and the lower branch4Is 0.14 mm. The circular polarizer with the array layout formed by the double-bending resonant rings 2-3 is more compact in structure, can concentrate stronger electromagnetic energy and can excite two degenerate orthogonal modes with equal amplitudes and 90-degree phase difference, so that circular polarization radiation is realized, the double-bending resonant rings 2-3 are connected with the inner square ring 2-2 through the rectangular conduction band, and the width W of the rectangular conduction band is larger5Is 0.3mm and has a length L30.3mm, length L of single bending resonance ring7Is 1.75mm and has a width W63.9mm, ring width W of single bending resonance ring70.3mm, a branch width W of the branch connected with the U-shaped branch101.02mm, length L80.32mm, the length L of the left branch of the U-shaped branch50.85mm, the length of the right branch is L61.05mm, upper branch length W90.96mm, the width of the U-shaped branch140.32mm, and the length L of a rectangular branch section is increased in the middle of the gap4Is 1.2mm, width W8The diameter of the rectangular branch is 0.2mm, and the rectangular branch with increased gaps is formed in the middle of the U-shaped branch, so that the circular polarization purity of the implanted antenna can be adjusted and enhanced. The short-circuit probe is added to form a standing wave structure, the size of the antenna is further reduced, and the radius R of the short-circuit probe 3 and the short-circuit probe 410.3mm, and the distance R between the centers of the short- circuit probes 3 and 4 and the center of the dielectric substrate 123.7mm, and the included angles a between the short- circuit probes 3 and 4 and the longitudinal symmetry axis of the dielectric substrate 11The radius of the short- circuit probes 3 and 4 is equal to the radius of the inner core of the coaxial connector 5 at 45 degrees. The distance W between the center of the coaxial connector 5 and the center of the dielectric substrate 10Is 2.7 mm. The floor 6 is a square complete metal patch structure, and can form a shielding layer to isolate the electronic device of the wireless biomedical device from the implanted circularly polarized antenna, reduce the interference of the antenna on other electronic devices, and improve the electromagnetic compatibilityThe floor board 6 has the same size as the dielectric substrate 1, and has a width W of 9mm and an L of 9 mm. The square-ring capacitive loading implanted circular polarized antenna with the double-bending resonant ring is plated with a layer of ultrathin biocompatible film alumina on the outer surface, has small influence on the reflection coefficient and the antenna gain, is close to the dielectric constant of the dielectric substrate 1, and has the dielectric constant epsilonr9.2, loss tangent tan delta of 0.008 and coating thickness of 0.03mm, and can isolate implanted circular polarization from human tissue of the antenna, prevent the conductive patch of the antenna from directly contacting with the human tissue, and reduce the influence of the human tissue on the performance of the implanted circular polarization antenna.
Analyzing the influence on the impedance bandwidth and the axial ratio bandwidth of the antenna before and after capacitive loading is introduced between the outer square ring and the inner square ring is shown in fig. 4, and it can be seen from the figure that the resonant frequency of the antenna is shifted to the low frequency direction by introducing the capacitive loading, the resonance degree is not changed greatly, the influence on the impedance bandwidth and the axial ratio bandwidth is small, the axial ratio performance optimum point is shifted accordingly, the size of the antenna before and after the capacitive loading is increased is reduced by 68%, which shows that the interdigital capacitance is increased between the outer square ring and the inner square ring, the capacitive loading characteristic is generated, the size of the implanted antenna is reduced, and the miniaturization of the antenna is realized.
The method selects a gap formed in the middle of the U-shaped branch to increase the length L of the rectangular branch4Width W of8The analysis of the effect on the antenna impedance bandwidth and axial ratio bandwidth is shown in FIG. 5, where L is selected4=1.1mm、W8=0.1mm、L4=1.2mm、W80.2mm and L4=1.3mm、W8The performance of the antenna is analyzed under three conditions of 0.3mm, and as can be seen from fig. 5, the resonant frequency of the antenna slightly shifts towards the high-frequency direction, the resonant degree increases and then decreases, the lowest value of the axial ratio performance decreases and then increases, and the point with the optimal axial ratio performance shifts, which indicates that the impedance matching and the circular polarization purity of the antenna are improved, because the rectangular branch with increased gap is formed in the middle of the U-shaped branch, and the circular polarization purity of the implanted antenna can be adjusted and enhanced.
The implanted circularly polarized antenna designed by the invention is mainly applied to a skin layer, a single-layer skin model with a simulation environment of 100mm multiplied by 28mm is adopted, the antenna is arranged in the center of the single-layer skin model, the implantation depth of the antenna is H, a schematic diagram of the depth of the implanted skin layer is shown in figure 6, the influence of different implantation depths H on the impedance bandwidth and the axial ratio bandwidth of the antenna is shown in figure 7, the initial value of the implantation depth is 4mm, and when the implantation depth H changes by +/-2 mm, the impedance bandwidth and the axial ratio bandwidth of the implanted circularly polarized antenna can still cover the required ISM 2.4 GHz-2.48 GHz frequency band, which indicates that the implanted circularly polarized antenna has higher stability.
The implanted circularly polarized antenna is placed in a solution simulating human skin for testing, wherein the skin solution comprises 36.7% of polyethylene glycol octyl phenyl ether, 5.1% of diethylene glycol monobutyl ether and 58.2% of deionized water. The impedance bandwidth of an implanted circularly polarized antenna is tested by using a network vector analyzer, the circular polarization characteristic of the antenna is tested in an indirect mode of matching an external linearly polarized dipole antenna, the simulation result and the test result of the impedance bandwidth and the axial ratio bandwidth are shown in fig. 8, the simulation impedance bandwidth of the implanted circularly polarized antenna is 2.18 GHz-2.82 GHz, the resonance frequency point in a frequency band is 2.45GHz, the simulation axial ratio bandwidth is 2.29 GHz-2.59 GHz, the actually measured impedance bandwidth is 2.15 GHz-2.78 GHz, the resonance frequency point in the frequency band is 2.43GHz, the actually measured axial ratio bandwidth is 2.26 GHz-2.52 GHz, the impedance bandwidth and the axial ratio bandwidth can cover the required working frequency, the resonance degree is increased to a certain extent, the test result and the simulation result are basically consistent, good resonance can be realized in the frequency band of 2.4 GHz-2.48 GHz, the resonance frequency and the axial ratio coefficient are slightly shifted to the low frequency direction, and the reasons for frequency shift of the implanted circularly polarized antenna are mainly ISM (industrial, The influence of the existence of bubbles on the antenna test and the simulation test environment dielectric constant are different between the simulated human body tissue and the simulated human body tissue.
E-plane and H-plane radiation patterns of the implanted circularly polarized antenna at a frequency point of 2.45GHz are tested, the radiation characteristics of the antenna are checked, and the actually measured patterns are shown in figures 9 and 10. The radiation pattern shows that the antenna has better directivity, the maximum radiation direction of the implanted circularly polarized antenna is along the Z-axis direction, namely towards the outer side of a human body, the main polarization is right-hand circular polarization, the maximum value of the actual gain along the Z-axis direction is-17.5 dBi, the difference between the main polarization and the cross polarization is 29.6dBi, the circularly polarizer mainly formed by the double-bent resonant rings in an array layout has a more compact structure, stronger electromagnetic energy can be concentrated, two degenerate orthogonal modes with equal amplitudes and 90-degree phase difference can be excited, so that the circularly polarized radiation is realized, the implanted circularly polarized antenna has wider axial ratio wave beams in a working frequency band, and the radiation characteristic is better.
In order to meet the safety requirement of the implanted circular polarized antenna after the antenna is implanted into human tissue, the safety of the implanted circular polarized antenna is comprehensively analyzed, the input power of the implanted circular polarized antenna is set to be 1W, the safety range of the human model for absorbing energy is evaluated by utilizing an average SAR value, through simulation calculation, the maximum average SAR value of the implanted circular polarized antenna at 2.45GHz when the human tissue is 1g is 235.8W/kg, the maximum average SAR value of the implanted circular polarized antenna at 10g is 51.3W/kg, in order to meet the safety standards of IEEEC95.1-1999 and IEEEC95.1-2005 on the SAR value, the maximum input power corresponding to the implanted circular polarized antenna is 8.7mW and 46.8mW respectively, and the implanted circular polarized antenna meets the requirement that the electromagnetic radiation under the conditions is safe and harmless to the human tissue.

Claims (7)

1. Introduce square ring shape capacitive loading implanted circular polarized antenna of two resonance rings of buckling, by dielectric substrate (1), introduce square ring shape capacitive loading radiating element (2) of two resonance rings of buckling, short circuit probe (3), short circuit probe (4), coaxial joint (5), floor (6) constitute, its characterized in that:
a. the square ring capacitive loading radiation unit (2) with the double-bending resonance ring introduced is composed of an outer square ring (2-1), an inner square ring (2-2) and a double-bending resonance ring (2-3), the outer square ring (2-1) can excite an additional mode close to the resonance frequency of a main mode by utilizing the electromagnetic coupling effect, so that the impedance bandwidth of the antenna is widened, interdigital capacitors (2-4), interdigital capacitors (2-5), interdigital capacitors (2-6) and interdigital capacitors (2-7) are added between four radiation edges of the outer square ring (2-1) and the inner square ring (2-2), the capacitive loading characteristic is generated, the size of the implanted antenna is reduced, the miniaturization of the antenna is realized, the double-bending resonance ring (2-3) is loaded in the inner square ring (2-2), the circular polarizer with array layout formed by the double-bending resonance rings (2-3) has more compact structure and can concentrate stronger electromagnetic energy, a single bending resonance ring is formed by bending a square ring by half, the inner part of the bending resonance ring is disconnected and two U-shaped branches are symmetrically arranged, a gap is formed between the two U-shaped branches, so that an E-shaped groove is formed in the single bending resonance ring, the rectangular branch is added in the middle of the split and is connected with the upper edge of the E-shaped groove, a circular polarizer consisting of the double-bending resonance ring (2-3) can excite two degenerate orthogonal modes with equal amplitudes and 90-degree phase difference, therefore, circularly polarized radiation is realized, the added rectangular branch can adjust and enhance the circularly polarized purity of the implanted antenna, the double-bent resonance ring (2-3) is connected with the inner square ring (2-2) through a rectangular conduction band, and the two single-bent resonance rings are symmetrical about the transverse symmetry axis of the dielectric substrate (1);
b. the short-circuit probe (3) and the short-circuit probe (4) are arranged at the left lower corner and the left upper corner of an inner square ring (2-2) in the square-ring-shaped capacitive loading radiation unit (2) with the double-bent resonance ring introduced, the short-circuit probe (3) and the short-circuit probe (4) are symmetrical about the transverse axis of the antenna dielectric substrate (1), the short-circuit probe (3) and the short-circuit probe (4) are added to form a standing wave structure, and the size of the antenna is further reduced;
c. the coaxial connector (5) is positioned on the right side of an inner square ring (2-2) in the square-ring-shaped capacitive loading radiation unit (2) for introducing the double-bending resonance ring and positioned on a transverse symmetrical axis of the dielectric substrate (1), an inner core of the coaxial connector (5) is connected with the inner square ring (2-2) in the square-ring-shaped capacitive loading radiation unit (2) for introducing the double-bending resonance ring, and an outer core of the coaxial connector (5) is connected with the floor (6);
d. the floor (6) is a square complete metal patch structure, a shielding layer can be formed, the electronic device of the wireless biomedical device and the implanted circularly polarized antenna are isolated, the interference of the antenna on other electronic devices is reduced, and the electromagnetic compatibility is improved.
2. The square-ring-shaped capacitive-loading implantable circularly polarized antenna with the double-bent resonant ring introduced according to claim 1, wherein the length L of the dielectric substrate (1) is 8 mm-10 mm, and the width W of the dielectric substrate is 8 mm-10 mm.
3. The square-ring-shaped capacitively-loaded implantable circularly polarized antenna with the double-bent resonant ring introduced therein according to claim 1, wherein the distance W between the square-ring-shaped capacitively-loaded radiating element (2) with the double-bent resonant ring introduced therein and the edge of the dielectric substrate (1)10.2 mm-0.3 mm, the square ring capacitive loading radiation unit (2) introduced with the double-bending resonance ring consists of an outer square ring (2-1), an inner square ring (2-2) and the double-bending resonance ring (2-3), and the outer side length of the outer square ring (2-1) is W38.4 mm-8.6 mm, side length W of the inner side137.8 mm-8 mm, the outer side length of the inner square ring 2-1 is W126.2 mm-6.4 mm, side length W of the inner side114.4 mm-4.6 mm, the distance L between the outer square ring (2-1) and the inner square ring (2-2)20.7 mm-0.9 mm, interdigital capacitance (2-4), interdigital capacitance (2-5), interdigital capacitance (2-6) and upper and lower branch length L in interdigital capacitance (2-7) added by outer square ring (2-1) and inner square ring (2-2)10.6 mm-0.7 mm, width W20.1 mm-0.2 mm, and the width W of the space between the upper branch knot and the lower branch knot40.1 mm-0.2 mm, the double-bending resonance ring (2-3) is connected with the inner square ring (2-2) through a rectangular conduction band, and the width W of the rectangular conduction band50.2 mm-0.4 mm, length L30.2 mm-0.4 mm, length L of single bending resonance ring71.7 mm-1.8 mm, width W63.8 mm-4 mm, and the ring width W of the single bending resonance ring70.2 mm-0.4 mm, the width W of the branch connected with the U-shaped branch100.9 mm-1.1 mm, length L80.3 mm-0.4 mm, and the length L of the left branch of the U-shaped branch50.8 mm-0.9 mm, length L of right branch60.9 mm-1.1 mm, upper branch length W90.9 mm-1.1 mm, and the width W of the U-shaped branch140.3 mm-0.4 mm, and the length L of the rectangular branch is increased in the middle of the split41.1 mm-1.3 mm, width W8Is 0.1 mm-0.3 mm.
4. The square-ring-shaped capacitively-loaded implantable circularly polarized antenna with the double-bent resonant ring introduced according to claim 1, wherein the short-circuit probes (3) and (4) have a radius R1Is 0.2mm &0.4mm, and the distance R between the centers of the short-circuit probe (3) and the short-circuit probe (4) and the center of the dielectric substrate (1)23.5 mm-3.9 mm, and the included angles a of the short-circuit probes (3) and (4) and the longitudinal symmetry axis of the dielectric substrate (1)1The radius of the short-circuit probe (3) and the radius of the short-circuit probe (4) are equal to the radius of the inner core of the coaxial connector (5) and are 42-47 degrees.
5. The square-ring-shaped capacitively-loaded implantable circularly polarized antenna with the introduction of the double-meander resonant ring according to claim 1, wherein the distance W between the center of the coaxial connector (5) and the center of the dielectric substrate (1) is0Is 2.5 mm-2.9 mm.
6. The square-ring capacitive-loading implanted circularly polarized antenna with the double-bent resonant ring introduced into the claim 1 is characterized in that the floor (6) is a complete square metal patch, the size of the floor (6) is the same as that of the dielectric substrate (1), L is 8 mm-10 mm, and W is 8 mm-10 mm.
7. The square-ring capacitive loading implantable circular polarized antenna with the double-bending resonant ring introduced into the claim 1, characterized in that the outer surface of the square-ring capacitive loading implantable circular polarized antenna with the double-bending resonant ring is coated with a layer of ultrathin biocompatible thin-film alumina, which has small influence on reflection coefficient and antenna gain, and has a dielectric constant close to that of the dielectric substrate (1), and the dielectric constant epsilon isr9.2, loss tangent tan delta of 0.008 and coating thickness of 0.03mm, and can isolate implanted circular polarization from human tissue of the antenna, prevent the conductive patch of the antenna from directly contacting with the human tissue, and reduce the influence of the human tissue on the performance of the implanted circular polarization antenna.
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