CN110808451A - Square resonant ring loaded implanted circularly polarized antenna for wireless biomedical - Google Patents
Square resonant ring loaded implanted circularly polarized antenna for wireless biomedical Download PDFInfo
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Abstract
The invention designs a loading square resonance ring implanted circular polarized antenna for wireless biomedical treatment, and the winding structure is added around the radiation patch to enable the surface current of the antenna to flow along the winding structure in a winding manner, so that the surface current path of the antenna is increased, and the resonant frequency of the antenna is reduced. The square complementary open resonant ring loaded in the center of the radiation patch loaded with the square resonant ring is a metamaterial structure array with negative magnetic conductivity, and can further enhance the single sheetThe performance of the complementary split ring resonator reduces the overall size of the antenna, and two orthogonal modes can be excited by adjusting the size of the square complementary split ring resonator to generate circular polarization characteristics. The volume of the antenna is only 11 multiplied by 0.635mm3The micro-strip-type micro-strip antenna has the characteristics of miniaturization, circular polarization, wide frequency band, interference resistance, excellent biocompatibility and the like, is suitable for the ISM2.45GHz frequency band, and meets the working requirements of miniaturization and circular polarization after being implanted into a human tissue environment.
Description
Technical Field
The invention relates to the technical field of implanted antennas, in particular to an implanted circularly polarized antenna loaded with a square resonant ring for wireless biomedical use, which is suitable for an implanted circularly polarized wireless biomedical device in ISM2.45GHz frequency band.
Background
With the rise of medical level and the continuous increase of economy, the trend of population aging is irreversible in the global scope, which brings huge pressure to the medical industry, and the development of remote medical treatment by utilizing wireless technology is a low-cost and high-efficiency solution. The wireless biomedical technology has the advantages that the hospital and the patient can not be limited by distance, the doctor can remotely monitor and detect the physiological parameters of the patient, compared with the traditional diagnosis and treatment mode, the wireless biomedical technology can provide comprehensive and accurate data in real time to provide diagnosis basis for the doctor, the doctor can analyze and diagnose the data more quickly and efficiently, and the patient can be checked and treated without personally going to the hospital. In daily life, a common wireless biomedical device includes: cardiac pacemakers, cochlear implants, cardioverter defibrillators, blood glucose monitors, temperature monitors, retinal implants, and the like. The wireless biomedical technology is mainly characterized in that various sensors are used for collecting human physiological parameters, the collected physiological parameters are transmitted to an analysis system and a storage device through a transmission unit, and a doctor makes diagnosis and treatment suggestions through original data or analysis data provided by the analysis system. Data transmission between the data acquisition system and the analysis system and between the data acquisition system and the storage device needs to pass through the implanted antenna, so the implanted antenna is an important component in the wireless biomedical device and is a core device in the data transmission system. The implantable antenna needs to be implanted into a human organ or tissue, and thus, comfort is a key factor for implantation into a human organ or tissue, which requires the implantable antenna to have a low profile and a small size. Compared with the free space, the electrical characteristics of human organs and tissues are greatly different, so that the implanted antenna is required to have broadband characteristics, the influence of the human complex environment on the antenna is reduced, the linear polarization antenna is required to have wider impedance bandwidth, and the circular polarization antenna has wider axial ratio bandwidth. The circularly polarized antenna has the advantages of low error rate, multipath interference resistance, strong anti-interference capability and the like. The main method for realizing the circular polarization characteristic comprises the following steps: opening a gap with a specific structure on a radiation patch, so that surface current flows in a winding way along the gap, and further increasing the surface current path of the antenna, and opening the gap with the specific structure on the surface of the antenna can generate a polarization degenerate mode with a phase difference of 90 degrees, so that the antenna generates a circular polarization characteristic; the circular polarization characteristic can be realized by adopting a caliber coupling feed method, the feed position of the method is more flexible, and the floor can well separate a feed line from a radiation unit; the feed is carried out on the diagonal line of the radiation unit, and the slice resistance is introduced, so that the circular polarization performance can be realized; the radiation unit adopts caliber coupling or slotting technology, circular polarization performance can be realized through feeding of a plurality of feed points, a gap is similar to a resonance structure, and the bandwidth can be widened by being close to the resonance frequency of the radiation unit. The complementary split resonant ring is a geometric mutual coupling structure, a gap part and a metal part are exchanged to obtain the complementary split resonant structure, the complementary split resonant structure is a metamaterial structure with negative magnetic conductivity, the dielectric constant of the metamaterial structure is far smaller than the wavelength of resonance, the position and the size of the split resonant ring are adjusted to realize the circular polarization performance of the antenna, and the complementary split resonant ring can meet the requirements of miniaturization and circular polarization design of the antenna. Non-patent document 1 discloses a complementary split ring loaded circularly polarized antenna, the center of a radiating element is loaded with a split ring, the split ring is a metamaterial structure with negative magnetic conductivity, the size of the antenna is reduced, the circular polarization performance is realized by adjusting the split ring opening position and the size of the split ring, four C-shaped grooves are additionally arranged around the radiating element, the effective current path can be increased, and the size of the antenna is further reduced. Non-patent document 2 discloses a square-ring circularly polarized implanted antenna, in which rectangular grooves of different sizes are formed at four edges of a radiation unit to realize circular polarization characteristics, a rectangular groove is formed at the center of a radiation patch, two triangles are added to the diagonal of the square to form geometric perturbation, and the size of the antenna is further reduced by introducing a short-circuit probe.
List of cited documents
Non-patent document 1: X.Y.Liu, Z.T.Wu, Y.Fan, and E.M.Tentzeri.A minor dCSRR loaded with wide-beam with wide circulation polarized with available anti-gene for use in the treatment of time glucose monitoring [ J ]. IEEE antibodies Wireless Probe.Lett., 2017,16:577-580.
Non-patent document 2: yang, S.Xiao, L.Zhu, B.Zhang, and H.Tu.A circular polarized implantable antenna for 2.4-GHz ISM band biological applications [ J ]. IEEE extensions Wireless application, Lett.,2017,16: 2554-.
Disclosure of Invention
The invention aims to provide a square resonance ring loaded implanted circular polarization antenna for wireless biomedical treatment, which has the characteristics of miniaturization, circular polarization, wide frequency band, interference resistance, excellent biocompatibility and the like, is conveniently integrated 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 wireless biomedical device on the performance of the antenna.
The technical scheme of the invention is as follows: a implanted circular polarized antenna of square resonance ring of loading for wireless bio-medical treatment comprises medium substrate 1, loading square resonance ring radiation paster 2, short circuit probe 3, short circuit probe 4, coaxial joint 5, floor 6, its characterized in that:
a. the loaded square resonant ring radiation patch 2 is characterized in that a rectangular groove is formed in the periphery of the radiation patch, a meandering structure 2-1, a meandering structure 2-2, a meandering structure 2-3 and a meandering structure 2-4 are added in the rectangular groove, the meandering structure 2-1 rotates for 90 degrees by taking a dielectric substrate 1 as a center to obtain the meandering structure 2-2, the meandering structure 2-3 and the meandering structure 2-4, the meandering structure 2-1, the meandering structure 2-2, the meandering structure 2-3 and the meandering structure 2-4 are added in the periphery of the radiation patch, so that the antenna surface current can meander along the meandering structure, the antenna surface current path is increased, the antenna resonant frequency is reduced, and the meandering structure 2-1 is adjusted, The sizes of the meandering structure 2-2, the meandering structure 2-3 and the meandering structure 2-4 can further optimize impedance matching, a square groove is formed in the middle of the square resonance ring radiation patch 2, a square complementary open resonance ring 2-5, a square complementary open resonance ring 2-6, a square complementary open resonance ring 2-7 and a square complementary open resonance ring 2-8 are loaded in the square groove, the square complementary open resonance ring 2-5, the square complementary open resonance ring 2-6, the square complementary open resonance ring 2-7 and the square complementary open resonance ring 2-8 are composed of two square rings and one square patch, the meandering structure 2-3 and the meandering structure 2-4 are connected with the square resonance ring radiation patch 2 through three rectangular conduction bands, and the three rectangular conduction bands are connected with the square resonance ring radiation patch 2-5 relative to the square complementary open resonance ring 2-5, The angle difference between the centers of the square complementary open-ended resonant ring 2-6, the square complementary open-ended resonant ring 2-7 and the square complementary open-ended resonant ring 2-8 is 90 degrees, the square complementary open-ended resonant ring 2-5, the square complementary open-ended resonant ring 2-6, the square complementary open-ended resonant ring 2-7 and the square complementary open-ended resonant ring 2-8 loaded in the center of the square resonant ring radiation patch 2 are metamaterial structure arrays with negative magnetic conductivity, the efficiency generated by a single complementary open-ended resonant ring can be further enhanced, the resonant frequency of the antenna is shifted to the low frequency direction, the overall size of the antenna is reduced, two orthogonal modes can be excited by adjusting the sizes of the square complementary open-ended resonant ring 2-5, the square complementary open-ended resonant ring 2-6, the square complementary open-ended resonant ring 2-7 and the square complementary open-ended resonant ring 2-8, thereby generating a circular polarization characteristic;
b. the short- circuit probes 3 and 4 are arranged on the left lower side and the left upper side of the loading square resonant ring radiation patch 2, the short- circuit probes 3 and 4 are symmetrical about the transverse axis of the antenna dielectric substrate 1, and the short- circuit probes 3 and 4 are added to increase resonance points, so that the impedance bandwidth of the antenna is widened;
c. the coaxial connector 5 is positioned on a diagonal line of the upper right side of the loading square resonant ring radiation patch 2, an inner core of the coaxial connector 5 is connected with the loading square resonant ring radiation patch 2, 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, no slot or gap is added, a shielding layer is formed between the implanted circularly polarized antenna and the lower-layer wireless biomedical device electronic device, the interference of the implanted circularly polarized antenna to other electronic devices can be reduced, and the electromagnetic compatibility of the implanted circularly polarized antenna is improved.
The length L of the dielectric substrate 1 is 10 mm-12 mm, and the width W is 10 mm-12 mm.
The radiation patch 2 loaded with the square resonance ring is provided with a rectangular groove around the length L21.3 mm-1.5 mm, width W45.5mm to 5.7mm, a width W of the meandering structure 2-1, the meandering structure 2-2, the meandering structure 2-3, and the meandering structure 2-420.15 mm-0.25 mm, and a distance W from the left side of the rectangular groove30.25 mm-0.3 mm, and the distance L from the lower edge of the rectangular groove10.25 mm-0.35 mm, and the width W of the middle square groove of the square resonant ring radiation patch 264.9 mm-5.1 mm, square complementary open resonant ring 2-5, square complementary open resonant ring 2-6, square complementary open resonant ring 2-7, square ring width W of square ring outside square ring 2-8122.2 mm-2.3 mm, the distance W between the outer square ring and the left side of the square groove70.1 mm-0.2 mm, width W of middle square ring111.6 mm-1.7 mm, the distance W between the middle square ring and the outer square ring80.1 mm-0.2 mm, width W of the patch in the inner direction 101 mm-1.2 mm, the distance W between the patch in the inner side direction and the middle square ring90.1 mm-0.2 mm, width W of three rectangular conduction bands connecting two square rings and one square patch5Is 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 125.8 mm-6.2 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 40-50 degrees.
The distance L between the center of the coaxial connector 5 and the transverse symmetrical axis of the dielectric substrate 102.8 mm-3.2 mm, and a distance W from the longitudinal symmetry axis of the dielectric substrate 10Is 2.8 mm-3.2 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, the length L is 10 mm-12 mm, and the width W is 10 mm-12 mm.
The external surface of the square resonance ring-loaded implanted circular polarization antenna for wireless biological medical treatment is plated with a layer of ultrathin biocompatible thin-film alumina which has little influence on antenna gain and reflection coefficient, the dielectric constant of the ultra-thin biocompatible thin-film alumina is similar to that of the dielectric substrate 1, and the dielectric constant epsilonr9.2, loss tangent tan delta of 0.008 and coating thickness of 0.02mm, and can isolate human tissue from the implanted circularly polarized antenna, prevent direct contact between the human tissue and the conductive patch of the antenna, and reduce the influence of the human tissue on the performance of the implanted circularly polarized antenna.
The invention has the following effects: the invention designs a loading square resonance ring implanted circular polarized antenna for wireless biomedical treatment, and the winding structure is added around the radiation patch to enable the surface current of the antenna to flow along the winding structure in a winding way, so that the surface current path of the antenna is increased, the resonance frequency of the antenna is reduced, and the size of the winding structure is adjusted to further optimize impedance matching. The square complementary open-ended resonant ring loaded at the center of the radiation patch loaded with the square resonant ring is a metamaterial structure array with negative magnetic conductivity, can further enhance the efficiency generated by a single complementary open-ended resonant ring, enables the resonant frequency of an antenna to shift towards the low-frequency direction, reduces the overall size of the antenna, and can excite two orthogonal modes by adjusting the size of the square complementary open-ended resonant ring, thereby generating the circular polarization characteristic. The floor is a square complete metal patch structure, no slot or gap is added, a shielding layer is formed between the implanted circularly polarized antenna and the lower-layer electronic device of the wireless biomedical device, the interference of the implanted circularly polarized antenna to other electronic devices can be reduced, and the electromagnetic compatibility of the implanted circularly polarized antenna is improved. The addition of the shorting probe can increase the resonance point, thereby broadening the impedance bandwidth of the antenna. The implanted circularly polarized antenna is of a planar structure, and the volume of the antenna is only 11 multiplied by 0.635mm3Has the characteristics of miniaturization, circular polarization, wide frequency band, interference resistance, excellent biocompatibility and the like, is suitable for the ISM2.45GHz frequency band, and meets the requirement of being implanted into a human tissue ringThe miniaturization and circular polarization work requirements are met.
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 is a width W of a serpentine structure according to an embodiment of the present invention2The effect on the antenna impedance bandwidth and the axial ratio bandwidth.
FIG. 5 shows the width W of the outer square ring of the square complementary split resonant ring in accordance with the embodiment of the present invention12Width W of middle square ring11Width W of inner and side direction patches10The 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 resonance ring loaded implanted circularly polarized antenna for wireless biomedical treatment is composed of a dielectric substrate 1, a square resonance ring loaded radiation patch 2, a short-circuit probe 3, a short-circuit probe 4, a coaxial connector 5 and a floor 6, and is characterized in that: the loaded square resonant ring radiation patch 2 is characterized in that a rectangular groove is formed in the periphery of the radiation patch, a meandering structure 2-1, a meandering structure 2-2, a meandering structure 2-3 and a meandering structure 2-4 are added in the rectangular groove, the meandering structure 2-1 rotates for 90 degrees by taking a dielectric substrate 1 as a center to obtain the meandering structure 2-2, the meandering structure 2-3 and the meandering structure 2-4, the meandering structure 2-1, the meandering structure 2-2, the meandering structure 2-3 and the meandering structure 2-4 are added in the periphery of the radiation patch, so that the antenna surface current can meander along the meandering structure, the antenna surface current path is increased, the antenna resonant frequency is reduced, and the meandering structure 2-1 is adjusted, The sizes of the meandering structure 2-2, the meandering structure 2-3 and the meandering structure 2-4 can further optimize impedance matching, a square groove is formed in the middle of the square resonance ring radiation patch 2, a square complementary open resonance ring 2-5, a square complementary open resonance ring 2-6, a square complementary open resonance ring 2-7 and a square complementary open resonance ring 2-8 are loaded in the square groove, the square complementary open resonance ring 2-5, the square complementary open resonance ring 2-6, the square complementary open resonance ring 2-7 and the square complementary open resonance ring 2-8 are composed of two square rings and one square patch, the meandering structure 2-3 and the meandering structure 2-4 are connected with the square resonance ring radiation patch 2 through three rectangular conduction bands, and the three rectangular conduction bands are connected with the square resonance ring radiation patch 2-5 relative to the square complementary open resonance ring 2-5, The angle difference between the centers of the square complementary open-ended resonant ring 2-6, the square complementary open-ended resonant ring 2-7 and the square complementary open-ended resonant ring 2-8 is 90 degrees, the square complementary open-ended resonant ring 2-5, the square complementary open-ended resonant ring 2-6, the square complementary open-ended resonant ring 2-7 and the square complementary open-ended resonant ring 2-8 loaded in the center of the square resonant ring radiation patch 2 are metamaterial structure arrays with negative magnetic conductivity, the efficiency generated by a single complementary open-ended resonant ring can be further enhanced, the resonant frequency of the antenna is shifted to the low frequency direction, the overall size of the antenna is reduced, two orthogonal modes can be excited by adjusting the sizes of the square complementary open-ended resonant ring 2-5, the square complementary open-ended resonant ring 2-6, the square complementary open-ended resonant ring 2-7 and the square complementary open-ended resonant ring 2-8, thereby generating a circular polarization characteristic; the short- circuit probes 3 and 4 are arranged on the left lower side and the left upper side of the loading square resonant ring radiation patch 2, the short- circuit probes 3 and 4 are symmetrical about the transverse axis of the antenna dielectric substrate 1, and the short- circuit probes 3 and 4 are added to increase resonance points, so that the impedance bandwidth of the antenna is widened; the coaxial connector 5 is positioned on a diagonal line of the upper right side of the loading square resonant ring radiation patch 2, an inner core of the coaxial connector 5 is connected with the loading square resonant ring radiation patch 2, 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, no slot or gap is added, a shielding layer is formed between the implanted circularly polarized antenna and the lower-layer wireless biomedical device electronic device, the interference of the implanted circularly polarized antenna to other electronic devices can be reduced, and the electromagnetic compatibility of the implanted circularly polarized antenna is improved.
The length L of the dielectric substrate 1 is 10 mm-12 mm, and the width W is 10 mm-12 mm.
The radiation patch 2 loaded with the square resonance ring is provided with a rectangular groove around the length L21.3 mm-1.5 mm, width W45.5mm to 5.7mm, a width W of the meandering structure 2-1, the meandering structure 2-2, the meandering structure 2-3, and the meandering structure 2-420.15 mm-0.25 mm, and a distance W from the left side of the rectangular groove30.25 mm-0.3 mm, and the distance L from the lower edge of the rectangular groove10.25 mm-0.35 mm, and the width W of the middle square groove of the square resonant ring radiation patch 264.9 mm-5.1 mm, square complementary open resonant ring 2-5, square complementary open resonant ring 2-6, square complementary open resonant ring 2-7, square ring width W of square ring outside square ring 2-8122.2 mm-2.3 mm, the distance W between the outer square ring and the left side of the square groove70.1 mm-0.2 mm, width W of middle square ring111.6 mm-1.7 mm, the distance W between the middle square ring and the outer square ring80.1 mm-0.2 mm, width W of the patch in the inner direction 101 mm-1.2 mm, the distance W between the patch in the inner side direction and the middle square ring90.1 mm-0.2 mm, width W of three rectangular conduction bands connecting two square rings and one square patch5Is 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 125.8 mm-6.2 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 40-50 degrees.
The coaxial connector 5 is spaced from the medium in the centerDistance L of transverse symmetry axis of substrate 102.8 mm-3.2 mm, and a distance W from the longitudinal symmetry axis of the dielectric substrate 10Is 2.8 mm-3.2 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, the length L is 10 mm-12 mm, and the width W is 10 mm-12 mm.
The external surface of the square resonance ring-loaded implanted circular polarization antenna for wireless biological medical treatment is plated with a layer of ultrathin biocompatible thin-film alumina which has little influence on antenna gain and reflection coefficient, the dielectric constant of the ultra-thin biocompatible thin-film alumina is similar to that of the dielectric substrate 1, and the dielectric constant epsilonr9.2, loss tangent tan delta of 0.008 and coating thickness of 0.02mm, and can isolate human tissue from the implanted circularly polarized antenna, prevent direct contact between the human tissue and the conductive patch of the antenna, and reduce the influence of the human tissue on the performance of the implanted circularly polarized 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 11mm and a width W of 11 mm. The winding structure added around the radiating patch can enable the antenna surface current to flow along the winding structure in a winding mode, so that the antenna surface current path is increased, the antenna resonant frequency is reduced, and the impedance matching can be further optimized by adjusting the size of the winding structure. Rectangular groove length L is opened around loading square resonant ring radiation paster 2 radiation paster2Is 1.4mm, width W45.67mm, width W of the meandering structure 2-1, the meandering structure 2-2, the meandering structure 2-3, and the meandering structure 2-42Is 0.21mm, and is spaced from the left side of the rectangular groove by a distance W3Is 0.27mm and is spaced from the lower edge of the rectangular groove by a distance L1Is 0.27 mm. The square complementary open-ended resonant ring loaded at the center of the radiation patch loaded with the square resonant ring is a metamaterial structure array with negative magnetic conductivity, can further enhance the efficiency generated by a single complementary open-ended resonant ring, enables the resonant frequency of the antenna to shift towards the low-frequency direction, reduces the overall size of the antenna, and can excite two complementary open-ended resonant rings by adjusting the size of the square complementary open-ended resonant ringOrthogonal modes, thereby creating circular polarization characteristics. Width W of middle square groove of loading square resonant ring radiation patch 265mm, square complementary open resonant ring 2-5 loaded in the square groove, square complementary open resonant ring 2-6, square complementary open resonant ring 2-7, square complementary open resonant ring 2-8 outside square ring width W12Is 2.22mm, and the distance W between the outer square ring and the left side of the square groove70.14mm, width W of the middle square ring11Is 1.66mm, the distance W between the middle square ring and the outer square ring80.14mm, width W of the patch in the inner direction10Is 1.1mm, and the distance W between the patch in the inner side direction and the middle square ring9Width W of three rectangular conduction bands of 0.14mm connecting two square rings and one square patch5Is 0.14 mm. The addition of the shorting probe can increase the resonance point, thereby broadening the impedance bandwidth of the antenna. Short circuit probe 3, short circuit probe 4 radius R10.3mm, and the distance R between the centers of the short- circuit probes 3 and 4 and the center of the dielectric substrate 126mm, 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 46 degrees. The distance L between the center of the coaxial connector 5 and the transverse symmetrical axis of the dielectric substrate 10Is 3mm, and is spaced from the longitudinal symmetry axis of the dielectric substrate 1 by a distance W0Is 3 mm. The floor is a square complete metal patch structure, no slot or gap is added, a shielding layer is formed between the implanted circularly polarized antenna and the lower-layer electronic device of the wireless biomedical device, the interference of the implanted circularly polarized antenna to other electronic devices can be reduced, and the electromagnetic compatibility of the implanted circularly polarized antenna is improved. 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, the length L is 11mm, and the width W is 11 mm. The outer surface of the square resonance ring-loaded implanted circular polarized antenna for wireless biological medical treatment is plated with a layer of ultrathin biocompatible thin-film alumina which has little influence on the gain and the reflection coefficient of the antenna and has the dielectric constant similar to that of the dielectric substrate 1, and the dielectric constant epsilonr9.2, loss tangent tan delta of 0.008, and coating thickness of 0.02mm, and can isolate human tissue from implanted circularly polarized antenna and prevent human tissue from contacting implanted circularly polarized antennaThe conductive patches of the antenna are in direct contact, so that the influence of human tissues on the performance of the implanted circularly polarized antenna is reduced.
Selecting width W of meandering structure2The analysis of the effect on the antenna impedance bandwidth and axial ratio bandwidth is shown in FIG. 4, where W is selected separately2＝0.15mm、W20.21mm and W2The antenna performance was analyzed for the three cases of 0.25mm, and it can be seen from fig. 4 that the width W of the meander structure is as wide as W2The antenna has the advantages that the resonance frequency shifts towards the low-frequency direction, the resonance degree gradually increases, and the axial ratio coefficient also shifts along with the shift of the resonance frequency, because the winding structure is added around the radiation patch, the surface current of the antenna can flow along the winding structure in a winding mode, so that the surface current path of the antenna is increased, the resonance frequency of the antenna is reduced, and the size of the winding structure is adjusted to further optimize impedance matching. When W is2When the antenna is 0.21mm, the antenna performance is best, and the impedance bandwidth and the axial ratio bandwidth both cover the required frequency band of ISM 2.45GHz.
Selecting the width W of a square ring outside a square complementary open resonant ring12Width W of middle square ring11Width W of inner and side direction patches10Analysis of the effects on the antenna impedance bandwidth and axial ratio bandwidth is shown in FIG. 5, where W is selected separately12＝2.2mm、W11＝1.6mm、W10＝1mm、W12＝2.22mm、W11＝1.66mm、W101.1mm and W12＝2.3mm、W11＝1.7mm、W10The performance of the antenna is analyzed under three conditions of 1.2mm, as can be seen from fig. 5, along with the increase of the size of the square complementary open-ended resonant ring, the resonant frequency point of the antenna shifts towards the low-frequency direction, the resonant degree increases first and then decreases, and the axial ratio coefficient also shifts towards the low-frequency position, because the square complementary open-ended resonant ring loaded at the center of the radiation patch of the square resonant ring is loaded, the square complementary open-ended resonant ring is a metamaterial structure array with negative magnetic permeability, the efficiency generated by a single complementary open-ended resonant ring can be further enhanced, the resonant frequency of the antenna shifts towards the low-frequency direction, the overall size of the antenna is reduced, two orthogonal modes can be excited by adjusting the size of the square complementary open-ended resonant ring, and therefore the circular polarization characteristic is generated. When W is12＝2.22mm、W11＝1.66mm、W10When the antenna is 1.1mm, the antenna performance is optimal, and the impedance bandwidth and the axial ratio bandwidth both cover the needed ISM2.45GHz frequency band.
The application environment of the implanted circularly polarized antenna designed by the invention is mainly a skin layer, the simulation environment is a single-layer skin model with the thickness of 90mm multiplied by 25mm, the antenna is arranged in the center of the single-layer skin model, the distance between the upper layer of the skin model and the upper surface 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 implantation depth H is within the range of 3mm to 7mm, the reflection coefficient and the axial ratio coefficient of the implanted circularly polarized antenna are relatively stable, each performance has good robustness, and the required ISM2.45GHz frequency band can be well covered.
The implanted circularly polarized antenna is placed in a solution simulating human skin for testing, wherein the skin solution comprises 58.2% of deionized water, 5.1% of diethylene glycol monobutyl ether and 36.7% of polyethylene glycol octyl phenyl ether. The impedance bandwidth of the antenna is tested by using a vector network analyzer, the circular polarization characteristic of the antenna is tested in an indirect mode of matching an in-vitro 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 circular polarization antenna is 2.26 GHz-2.71 GHz, the resonance frequency is 2.45GHz, the simulation axial ratio bandwidth is 2.28 GHz-2.52 GHz, the actually measured impedance bandwidth is 2.29 GHz-2.75 GHz, the resonance frequency is 2.46GHz, the resonance degree is obviously increased, the actually measured axial ratio bandwidth is 2.30 GHz-2.56 GHz, the axial ratio bandwidth can cover the required working frequency, the difference between the simulation result and the test result is small, good resonance can be realized in an ISM frequency band, the impedance characteristic and the axial ratio characteristic of the implanted circular polarization antenna in the working frequency band are good, the resonance frequency and the axial ratio coefficient are slightly shifted to the high frequency direction, and the causes of frequency shift are mainly the processing test error of the implanted, The influence of the air bubbles between the coaxial cable and the simulated human body tissue on the antenna test and the difference of the dielectric constant of the simulation test environment are caused.
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 directivity of the antenna is good, 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 left-hand circular polarization, the actual gain value along the Z-axis direction is-28.8 dBi, the difference between the main polarization and the cross polarization is 32.1dBi, two orthogonal modes can be excited mainly by adjusting the size of a square complementary open resonant ring, so that the circularly polarized characteristic is generated, the axial ratio wave beam of the antenna in a working frequency band is wider, the radiation characteristic is excellent, the antenna is suitable for an ISM2.45GHz working frequency band, and the requirement of a complex implantation environment can be met.
Considering the safety factors of implanted human tissues, comprehensively analyzing the safety of the implanted circularly polarized antenna, setting the input power of the implanted circularly polarized antenna to be 1W, evaluating the safety range of the human model for absorbing energy by using an average SAR value, and performing simulation calculation to obtain the maximum average SAR value of 1-g human tissues at 2.45GHz of the implanted circularly polarized antenna to be 392.5W/kg, the maximum average SAR value of 10-g human tissues to be 82.7W/kg, wherein the maximum input powers corresponding to the implanted circularly polarized antenna are respectively 3.1mW and 21.6mW in order to meet the safety standards of IEEEC95.1-1999 and IEEEC95.1-2005 on SAR values, and the implanted circularly polarized antenna meets the condition that the electromagnetic radiation under the above conditions is safe and harmless to the human tissues.
Claims (7)
1. A implanted circular polarized antenna of square resonance ring of loading for wireless bio-medical treatment comprises medium base plate (1), square resonance ring radiation paster (2) of loading, short circuit probe (3), short circuit probe (4), coaxial connector (5), floor (6), its characterized in that:
a. the loaded square resonant ring radiation patch (2) is characterized in that a rectangular groove is formed in the periphery of the radiation patch, a winding structure (2-1), a winding structure (2-2), a winding structure (2-3) and a winding structure (2-4) are added in the rectangular groove, the winding structure (2-1) respectively rotates for 90 degrees by taking a dielectric substrate (1) as a center to obtain the winding structure (2-2), the winding structure (2-3) and the winding structure (2-4), the winding structure (2-1), the winding structure (2-2), the winding structure (2-3) and the winding structure (2-4) are added in the periphery of the radiation patch, so that the antenna surface current can flow along the winding structure in a winding manner, and the antenna surface current path is increased, the antenna resonant frequency is reduced, the sizes of the meandering structure (2-1), the meandering structure (2-2), the meandering structure (2-3) and the meandering structure (2-4) are adjusted to further optimize impedance matching, a square groove is formed in the middle of a loaded square resonant ring radiation patch (2), a square complementary open resonant ring (2-5), a square complementary open resonant ring (2-6), a square complementary open resonant ring (2-7) and a square complementary open resonant ring (2-8) are loaded in the square groove, the square complementary open resonant ring (2-5), the square complementary open resonant ring (2-6), the square complementary open resonant ring (2-7) and the square complementary open resonant ring (2-8) are composed of two square rings and one square patch, the antenna is connected with a loading square resonant ring radiation patch (2) through three rectangular conduction bands, the angle difference between the three rectangular conduction bands relative to the centers of a square complementary open resonant ring (2-5), a square complementary open resonant ring (2-6), a square complementary open resonant ring (2-7) and a square complementary open resonant ring (2-8) is 90 degrees, the square complementary open resonant ring (2-5), the square complementary open resonant ring (2-6), the square complementary open resonant ring (2-7) and the square complementary open resonant ring (2-8) loaded at the center of the loading square resonant ring radiation patch (2) are a metamaterial structure array with negative magnetic permeability, the efficiency generated by a single complementary open resonant ring can be further enhanced, and the resonant frequency of the antenna is shifted to the low-frequency direction, the overall size of the antenna is reduced, and two orthogonal modes can be excited by adjusting the sizes of the square complementary open-ended resonant ring (2-5), the square complementary open-ended resonant ring (2-6), the square complementary open-ended resonant ring (2-7) and the square complementary open-ended resonant ring (2-8), so that the circular polarization characteristic is generated;
b. the short-circuit probe (3) and the short-circuit probe (4) are arranged on the left lower side and the left upper side of the loading square resonant ring radiation patch (2), the short-circuit probe (3) and the short-circuit probe (4) are symmetrical about a transverse axis of the antenna dielectric substrate (1), and resonance points can be increased by adding the short-circuit probe (3) and the short-circuit probe (4), so that the impedance bandwidth of the antenna is widened;
c. the coaxial connector (5) is positioned on the diagonal line of the right upper side of the loading square resonant ring radiation patch (2), the inner core of the coaxial connector (5) is connected with the loading square resonant ring radiation patch (2), and the outer core of the coaxial connector (5) is connected with the floor (6);
d. the floor (6) is of a square complete metal patch structure, no slot or gap is added, a shielding layer is formed between the implanted circularly polarized antenna and the lower-layer electronic device of the wireless biomedical device, the interference of the implanted circularly polarized antenna to other electronic devices can be reduced, and the electromagnetic compatibility of the implanted circularly polarized antenna is improved.
2. The loaded square resonance ring implanted circular polarized antenna for wireless bio-medical treatment according to claim 1, wherein the length L of the dielectric substrate (1) is 10mm to 12mm, and the width W is 10mm to 12 mm.
3. The implanted circularly polarized antenna with square resonance ring for wireless biomedical use according to claim 1, wherein the radiating patch of the radiating patch (2) with square resonance ring has a rectangular slot length L around the radiating patch21.3 mm-1.5 mm, width W45.5mm to 5.7mm, a width W of the meandering structure (2-1), the meandering structure (2-2), the meandering structure (2-3), and the meandering structure (2-4)20.15 mm-0.25 mm, and a distance W from the left side of the rectangular groove30.25 mm-0.3 mm, and the distance L from the lower edge of the rectangular groove10.25 mm-0.35 mm, and the width W of the middle square groove of the square resonant ring radiation patch (2) is loaded64.9 mm-5.1 mm, square complementary open resonant ring (2-5), square complementary open resonant ring (2-6), square complementary open resonant ring (2-7), square complementary open resonant ring (2-8) and width W of square ring outside square ring122.2 mm-2.3 mm, the distance W between the outer square ring and the left side of the square groove70.1 mm-0.2 mm, width W of middle square ring111.6 mm-1.7 mm, the distance W between the middle square ring and the outer square ring80.1 mm-0.2 mm, width W of the patch in the inner direction101 mm-1.2 mm, the distance W between the patch in the inner side direction and the middle square ring90.1 mm-0.2 mm, connecting two squaresWidth W of three rectangular conduction bands of ring and one square patch5Is 0.1 mm-0.3 mm.
4. The loaded square resonance ring implanted circularly polarized antenna for wireless bio-medical treatment according to claim 1, wherein 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 probe (3) and the short-circuit probe (4) and the center of the dielectric substrate (1)25.8 mm-6.2 mm, and the included angles a between 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) within 40-50 degrees.
5. The loaded square resonance ring implanted circularly polarized antenna for wireless biomedical applications according to claim 1, wherein the distance L between the center of the coaxial connector (5) and the transverse symmetry axis of the dielectric substrate (1)02.8 mm-3.2 mm, and the distance W from the longitudinal symmetry axis of the dielectric substrate (1)0Is 2.8 mm-3.2 mm.
6. The loaded square resonance ring implanted circular polarized antenna for wireless biomedical use according to claim 1, wherein 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), the length L is 10mm to 12mm, and the width W is 10mm to 12 mm.
7. The square resonance ring loaded implanted circular polarized antenna for wireless biomedical use according to claim 1, wherein the outer surface of the square resonance ring loaded circular polarized antenna for wireless biomedical use is coated with a layer of ultra-thin biocompatible thin film alumina having little influence on antenna gain and reflection coefficient, and the dielectric constant of the ultra-thin biocompatible thin film alumina is similar to that of the dielectric substrate (1), and the dielectric constant is epsilonr9.2, loss tangent tan delta of 0.008, coating thickness of 0.02mm, isolation of human tissue from implanted circularly polarized antenna, prevention of direct contact between human tissue and conductive patch of antenna, and reduction of implantation of human tissueImpact of the performance of an in-line circularly polarized antenna.
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