CN110808451A - Square resonant ring loaded implanted circularly polarized antenna for wireless biomedical - Google Patents

Abstract

The invention designs a loaded square resonant ring implanted circularly polarized antenna for wireless biomedicine, and adding a meandering structure around the radiation patch can make the antenna surface current meander along the meandering structure, thereby increasing the antenna surface current path, reducing the resonant frequency of the antenna. The square complementary split resonator loaded at the center of the loaded square resonator radiating patch is a metamaterial structure array with negative magnetic permeability, which can further enhance the efficiency produced by a single complementary split resonator and reduce the overall size of the antenna. By adjusting the size of the square complementary split resonator, two orthogonal modes can be excited, resulting in circular polarization. The size of the antenna is only 11×11×0.635mm ³ , and it has the characteristics of miniaturization, circular polarization, frequency bandwidth, anti-interference, and excellent biocompatibility. and circular polarization work requirements.

Description

Loaded square resonant ring implantable circularly polarized antenna for wireless biomedicine

technical field

The invention relates to the technical field of implantable antennas, in particular to a loaded square resonant ring implanted circularly polarized antenna for wireless biomedicine, which is suitable for an implantable circularly polarized wireless biomedical device in the ISM 2.45GHz frequency band.

Background technique

With the improvement of medical level and the continuous growth of economy, the trend of population aging has become irreversible on a global scale, which has brought huge pressure to the medical industry. Using wireless technology to carry out telemedicine will be a low-cost, high-efficiency s solution. The advantage of wireless biomedical technology is that the distance between the hospital and the patient is not limited, and the doctor can remotely monitor and detect the physiological parameters of the patient. Compared with the traditional diagnosis and treatment method, the wireless biomedical technology can provide comprehensive and accurate data in real time to provide the doctor with the basis for diagnosis. , doctors can analyze and diagnose data more quickly and efficiently, and patients can get examination and diagnosis and treatment without going to the hospital in person. In daily life, commonly used wireless biomedical devices include: pacemakers, cochlear implants, cardioverter defibrillators, blood glucose monitors, temperature monitors, retinal implants, etc. Wireless biomedical technology mainly collects human physiological parameters through various sensors, and transmits the collected physiological parameters to the analysis system and storage device through the transmission unit. The doctor makes diagnosis and treatment suggestions through the original data or analysis data provided by the analysis system. The data transmission between the data acquisition system, the analysis system and the storage device needs to pass through the implantable antenna. Therefore, the implantable antenna is an important part of the wireless biomedical device and the core device in the data transmission system. Implantable antennas need to be implanted in human organs or tissues. Therefore, comfort is a key factor in implanting human organs or tissues, which requires implantable antennas to have low profile and miniaturization characteristics. The electrical characteristics in human organs and tissues are quite different from those in free space, which requires implantable antennas to have broadband characteristics to reduce the impact of the complex environment of the human body on the antenna, which requires linearly polarized antennas to have a wider impedance bandwidth , the circularly polarized antenna has a wider axial ratio bandwidth. The circularly polarized antenna has the advantages of low bit error rate, anti-multipath interference and strong anti-interference ability. The main method to realize the circular polarization characteristic: open a specific structure slot on the radiating patch, so that the surface current flows meanderingly along the slot, thereby increasing the current path on the antenna surface, and opening a specific structure slot on the antenna surface can produce a phase difference of 90 degrees The degenerate mode of polarization makes the antenna produce circular polarization characteristics; the circular polarization characteristic can be achieved by using the aperture coupling feeding method, the feeding position of this method is more flexible, and the floor can well isolate the feeder and the radiating element; Feeding on the diagonal of the radiating element and introducing slice resistors can achieve circular polarization performance; the radiating element adopts aperture coupling or slotting technology, and the circular polarization performance can be achieved by feeding through multiple feeding points, and the gap is approximately A resonant structure close to the resonant frequency of the radiating element can broaden the bandwidth. The complementary split resonator ring is a geometrical mutual couple structure. The complementary split resonant structure can be obtained by exchanging the slot part and the metal part. The complementary split resonant structure is a metamaterial structure with negative magnetic permeability, and its dielectric constant is far When the wavelength is smaller than the wavelength at resonance, the circular polarization performance of the antenna can be achieved by adjusting the position and size of the split resonator ring, and the use of complementary split resonator rings can meet the design requirements of the antenna for miniaturization and circular polarization. Non-patent document 1 discloses a circularly polarized antenna loaded with a complementary split resonator. The center of the radiating element is loaded with a split resonator, which is a metamaterial structure with negative magnetic permeability, which reduces the size of the antenna. By adjusting the split resonance The position of the ring opening and the size of the resonant ring can achieve circular polarization performance. Four C-shaped slots are added around the radiating element, which can increase the effective current path and further reduce the size of the antenna. Non-patent document 2 discloses a square-ring circularly polarized implantable antenna. Rectangular slots of different sizes are opened at the four edges of the radiation unit to achieve circular polarization characteristics, and a square slot is opened in the center of the radiation patch. Two triangles are added to the corners to form geometric perturbations, which further reduce the size of the antenna by introducing short-circuit probes.

Citation List

Non-Patent Document 1: X.Y.Liu, Z.T.Wu, Y.Fan, and E.M.Tentzeris.A miniaturizedCSRR loaded wide-beam width circularly polarized implantable antenna for subcutaneous real-time glucose monitoring[J].IEEE Antennas WirelessPropag.Lett.,2017,16 :577-580.

Non-patent document 2: Z. Yang, S. Xiao, L. Zhu, B. Zhang, and H. Tu. A circularlypolarized implantable antenna for 2.4-GHz ISM band biomedical applications [J]. IEEE Antennas Wireless Propag. Lett., 2017, 16:2554-2557.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a loaded square resonant ring implanted circularly polarized antenna for wireless biomedicine. It is integrated with implantable wireless biomedical devices, suitable for ISM 2.45GHz frequency band, and can meet the antenna performance requirements of wireless biomedical devices.

The technical scheme of the present invention is: an implanted circularly polarized antenna with a loaded square resonator ring for wireless biomedicine, which is composed of a dielectric substrate 1, a loaded square resonant ring radiation patch 2, a short-circuit probe 3, a short-circuit probe 4, and the same The shaft joint 5 and the floor 6 are constituted, and are characterized in that:

a. The loading square resonator ring radiation patch 2 is to open a rectangular groove around the radiation patch, and add a meandering structure 2-1, meandering structure 2-2, meandering structure 2- in the rectangular groove 3. The meandering structure 2-4, the meandering structure 2-1 is respectively rotated 90 degrees with the dielectric substrate 1 as the center to obtain the meandering structure 2-2, the meandering structure 2-3, and the meandering structure 2 -4, adding a meandering structure 2-1, meandering structure 2-2, meandering structure 2-3, meandering structure 2-4 around the radiation patch can make the antenna surface current along the meandering structure meandering flow, thereby increasing the current path on the surface of the antenna, reducing the resonant frequency of the antenna, and adjusting the size of the meandering structure 2-1, meandering structure 2-2, meandering structure 2-3, and meandering structure 2-4 The impedance matching can be further optimized. A square slot is opened in the middle of the loaded square resonator radiating patch 2, and the square complementary split resonator 2-5, the square complementary split resonator 2-6, and the square complementary split resonator 2 are loaded in the square slot. -7. Square complementary split resonator 2-8, square complementary split resonator 2-5, square complementary split resonator 2-6, square complementary split resonator 2-7, square complementary split resonator 2-8 by two The square ring is composed of a square patch, and is connected to the loaded square resonant ring radiation patch 2 through three rectangular conduction bands. 2-6. The angle difference between the square complementary split resonator ring 2-7 and the center of the square complementary split resonator ring 2-8 is 90 degrees, and the square complementary split resonator ring 2-5, Square Complementary Slit Resonator 2-6, Square Complementary Slit Resonator 2-7, Square Complementary Slit Resonator 2-8 is an array of metamaterial structures with negative permeability that can further enhance the By adjusting the square complementary split resonator 2-5, square complementary split resonator 2-6, square complementary split resonator 2-7, square complementary split resonator The size of the split resonator ring 2-8 can excite two orthogonal modes, resulting in circular polarization characteristics;

b. The short-circuit probe 3 and the short-circuit probe 4 are arranged on the lower left side and the upper left side of the loaded square resonant ring radiation patch 2. The short-circuit probe 3 and the short-circuit probe 4 are symmetrical about the horizontal axis of the antenna dielectric substrate 1, and the increase The short-circuit probe 3 and the short-circuit probe 4 can increase the resonance point, thereby widening the impedance bandwidth of the antenna;

c. The coaxial joint 5 is located on the diagonal line on the upper right side of the loaded square resonant ring radiating patch 2, the inner core of the coaxial joint 5 is connected with the loaded square resonant ring radiating patch 2, and the The outer core is connected to the floor 6;

d. The floor 6 is a square complete metal patch structure without additional slots or gaps, and a shielding layer is formed between the implantable circularly polarized antenna and the underlying wireless biomedical device electronic device, which can reduce the implantation. The interference of the implanted circularly polarized antenna to other electronic devices is improved, and the electromagnetic compatibility performance of the implanted circularly polarized antenna is improved.

The length L of the dielectric substrate 1 is 10 mm to 12 mm, and the width W is 10 mm to 12 mm.

The said loaded square resonant ring radiation patch 2 has a rectangular groove around the radiation patch with a length L ₂ of 1.3mm-1.5mm, a width W ₄ of 5.5mm-5.7mm, a meandering structure 2-1, meandering The width W ₂ of the structure 2-2, the meandering structure 2-3, and the meandering structure 2-4 is 0.15mm~0.25mm, and the distance W3 from the left side _of the rectangular groove is 0.25mm~0.3mm, and the lower side of the rectangular groove is 0.25mm~0.3mm. _The distance L1 is 0.25mm~0.35mm, the width W6 of the square slot in the middle of the loaded square resonant ring radiation patch ₂ is 4.9mm~5.1mm, the square complementary opening resonator ring 2-5 loaded in the square slot, the square complementary opening Resonator ring 2-6, square complementary split resonator ring 2-7, square complementary split resonator ring 2-8 The width W ₁₂ of the outer square ring is 2.2mm to 2.3mm, and the distance W ₇ between the outer square ring and the left side of the square groove is 0.1 mm～0.2mm, the width _W11 of the middle square ring is 1.6mm～1.7mm, the distance W8 between the middle square ring and the outer square ring is 0.1mm～0.2mm, and the width _W10 of the inner side _patch is 1mm～1.2mm , the distance W ₉ between the inner side patch and the middle square ring is 0.1mm-0.2mm, and the width W ₅ of the three rectangular conducting strips connecting two square rings and one square patch is 0.1mm-0.3mm.

The radius R ₁ of the short-circuit probe 3 and the short-circuit probe 4 is 0.2 mm to 0.4 mm, and the distance R ₂ between the center of the short-circuit probe 3 and the short-circuit probe 4 from the center of the dielectric substrate 1 is 5.8 mm to 6.2 mm. The angle a ₁ between the needles 3 and the short-circuit probes 4 and the longitudinal symmetry axis of the dielectric substrate 1 is 40 to 50 degrees.

The distance L ₀ from the center of the coaxial joint 5 to the transverse axis of symmetry of the dielectric substrate 1 is 2.8 mm˜3.2 mm, and the distance W ₀ from the longitudinal axis of symmetry of the dielectric substrate 1 is 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 dielectric substrate 1 , the length L is 10mm-12mm, and the width W is 10mm-12mm.

The outer surface of the loaded square resonant ring implantable circularly polarized antenna for wireless biomedicine is coated with a layer of ultra-thin biocompatible thin-film alumina that has little effect on the antenna gain and reflection coefficient, and the dielectric of the dielectric substrate 1 The constants are similar, the dielectric constant _εr is 9.2, the loss tangent tanδ is 0.008, and the coating thickness is 0.02mm, which isolates human tissue from the implanted circularly polarized antenna, prevents direct contact between human tissue and the conductive patch of the antenna, and reduces the incidence of human tissue. Effects on the performance of implanted circularly polarized antennas.

The effect of the present invention is: the present invention designs a square resonant ring implanted circularly polarized antenna for wireless biomedicine, and adding a meandering structure around the radiation patch can make the surface current of the antenna flow meanderingly along the meandering structure , thereby increasing the current path on the surface of the antenna, reducing the resonant frequency of the antenna, and adjusting the size of the meandering structure can further optimize the impedance matching. The square complementary split resonator loaded at the center of the loaded square resonator radiating patch is a metamaterial structure array with negative magnetic permeability, which can further enhance the efficiency produced by a single complementary split resonator, making the antenna resonant frequency lower to low frequencies The direction is shifted to reduce the overall size of the antenna. By adjusting the size of the square complementary split resonator ring, two orthogonal modes can be excited, thereby generating circular polarization characteristics. The floor is a square complete metal patch structure without additional slots or gaps, and a shielding layer is formed between the implantable circularly polarized antenna and the underlying wireless biomedical device electronics, which can reduce the level of the implanted circularly polarized antenna. Interference to other electronic devices, improving the electromagnetic compatibility performance of the implanted circularly polarized antenna. Adding shorting probes can increase the resonance point, thereby broadening the impedance bandwidth of the antenna. The implanted circularly polarized antenna is a plane structure, the size of the antenna is only 11×11×0.635mm ³ , it has the characteristics of miniaturization, circular polarization, wide frequency band, anti-interference, excellent biocompatibility, etc. It is suitable for ISM 2.45 The GHz frequency band meets the requirements of miniaturization and circular polarization after implantation in the human tissue environment.

Description of drawings

FIG. 1 is a schematic diagram of a front structure of an embodiment of the present invention.

FIG. 2 is a schematic side structure diagram of an embodiment of the present invention.

FIG. 3 is a schematic diagram of a rear structure of an embodiment of the present invention.

FIG. 4 shows the influence of the width W ₂ of the meandering structure on the antenna impedance bandwidth and the axial ratio bandwidth according to the embodiment of the present invention.

5 shows the influence of the width W _{12 of the outer square ring, the width W 11 of the middle square ring, and the width W 10 of the} side patch on the antenna impedance bandwidth and the axial ratio bandwidth of the square complementary split resonator ring according to the embodiment of the present invention.

FIG. 6 is a schematic diagram of the depth of the implanted skin layer according to an embodiment of the present invention.

FIG. 7 shows the effects of different implantation depths H on the antenna impedance bandwidth and the axial ratio bandwidth according to the embodiment of the present invention.

FIG. 8 is a simulated and measured impedance bandwidth curve according to an embodiment of the present invention.

FIG. 9 is an E-plane radiation pattern at a frequency of 2.45 GHz according to an embodiment of the present invention.

FIG. 10 is an H-plane radiation pattern at a frequency of 2.45 GHz according to an embodiment of the present invention.

Detailed ways

The specific embodiment of the present invention is as follows: as shown in FIG. 1 , an implanted circularly polarized antenna with a loaded square resonant ring for wireless biomedicine is composed of a dielectric substrate 1 , a loaded square resonant ring radiation patch 2 , and a short-circuit probe 3 . , a short-circuit probe 4, a coaxial joint 5, and a floor 6, and is characterized in that: the said loaded square resonant ring radiation patch 2 is a rectangular groove around the radiation patch, and a meandering structure 2 is added in the rectangular groove. -1. The meandering structure 2-2, the meandering structure 2-3, the meandering structure 2-4, the meandering structure 2-1 is respectively rotated 90 degrees with the dielectric substrate 1 as the center to obtain the meandering structure 2-2, meandering structure 2-3, meandering structure 2-4, add meandering structure 2-1, meandering structure 2-2, meandering structure 2-3 around the radiation patch, The meandering structure 2-4 can make the surface current of the antenna flow meanderingly along the meandering structure, thereby increasing the current path of the antenna surface, reducing the resonant frequency of the antenna, and adjusting the meandering structure 2-1, meandering structure 2-2, The size of the meandering structure 2-3 and meandering structure 2-4 can further optimize the impedance matching. A square slot is opened in the middle of the loaded square resonator radiating patch 2, and a square complementary split resonator 2- is loaded in the square slot. 5. Square complementary split resonator 2-6, square complementary split resonator 2-7, square complementary split resonator 2-8, square complementary split resonator 2-5, square complementary split resonator 2-6, square complementary split The resonant ring 2-7 and the square complementary split resonator ring 2-8 are composed of two square rings and a square patch, which are connected to the loaded square resonator ring radiation patch 2 through three rectangular conduction bands. The angle difference relative to the center of the square complementary split resonator 2-5, the square complementary split resonator 2-6, the square complementary split resonator 2-7, and the square complementary split resonator 2-8 is 90 degrees. The square complementary split resonator 2-5, the square complementary split resonator 2-6, the square complementary split resonator 2-7, and the square complementary split resonator 2-8 loaded in the center of the ring radiation patch 2 are a kind of The high-efficiency metamaterial structure array can further enhance the efficiency of a single complementary split resonator ring, shift the antenna resonant frequency to the low frequency direction, and reduce the overall size of the antenna. By adjusting the square complementary split resonator ring 2-5, the square complementary split The size of the resonator ring 2-6, the square complementary split resonator ring 2-7, and the square complementary split resonator ring 2-8 can excite two orthogonal modes, thereby generating circular polarization characteristics; the short-circuit probe 3, short-circuit The probes 4 are arranged on the lower left side and the upper left side of the loaded square resonant ring radiation patch 2. The short-circuit probe 3 and the short-circuit probe 4 are symmetrical about the horizontal axis of the antenna dielectric substrate 1. Adding the short-circuit probe 3 and the short-circuit probe 4 can increase the Resonance point, thereby broadening the impedance bandwidth of the antenna; the coaxial joint 5 is located on the diagonal line on the upper right side of the loaded square resonator ring radiation patch 2, and the inner core of the coaxial joint 5 is connected to the loaded square resonance ring radiation patch 2. connected, the outer core of the coaxial connector 5 is connected to the floor 6 The floor 6 is a square complete metal patch structure, no additional slots or gaps are added, and a shielding layer is formed between the implantable circularly polarized antenna and the underlying wireless biomedical device electronic device, which can reduce implantation. The interference of the implanted circularly polarized antenna to other electronic devices is improved, and the electromagnetic compatibility performance of the implanted circularly polarized antenna is improved.

The length L of the dielectric substrate 1 is 10 mm to 12 mm, and the width W is 10 mm to 12 mm.

The said loaded square resonant ring radiation patch 2 has a rectangular groove around the radiation patch with a length L ₂ of 1.3mm-1.5mm, a width W ₄ of 5.5mm-5.7mm, a meandering structure 2-1, meandering The width W ₂ of the structure 2-2, the meandering structure 2-3, and the meandering structure 2-4 is 0.15mm~0.25mm, and the distance W3 from the left side _of the rectangular groove is 0.25mm~0.3mm, and the lower side of the rectangular groove is 0.25mm~0.3mm. _The distance L1 is 0.25mm~0.35mm, the width W6 of the square slot in the middle of the loaded square resonant ring radiation patch ₂ is 4.9mm~5.1mm, the square complementary opening resonator ring 2-5 loaded in the square slot, the square complementary opening Resonator ring 2-6, square complementary split resonator ring 2-7, square complementary split resonator ring 2-8 The width W ₁₂ of the outer square ring is 2.2mm to 2.3mm, and the distance W ₇ between the outer square ring and the left side of the square groove is 0.1 mm～0.2mm, the width _W11 of the middle square ring is 1.6mm～1.7mm, the distance W8 between the middle square ring and the outer square ring is 0.1mm～0.2mm, and the width _W10 of the inner side _patch is 1mm～1.2mm , the distance W ₉ between the inner side patch and the middle square ring is 0.1mm-0.2mm, and the width W ₅ of the three rectangular conducting strips connecting two square rings and one square patch is 0.1mm-0.3mm.

The radius R ₁ of the short-circuit probe 3 and the short-circuit probe 4 is 0.2 mm to 0.4 mm, and the distance R ₂ between the center of the short-circuit probe 3 and the short-circuit probe 4 from the center of the dielectric substrate 1 is 5.8 mm to 6.2 mm. The angle a ₁ between the needles 3 and the short-circuit probes 4 and the longitudinal symmetry axis of the dielectric substrate 1 is 40 to 50 degrees.

The distance L ₀ from the center of the coaxial joint 5 to the transverse axis of symmetry of the dielectric substrate 1 is 2.8 mm˜3.2 mm, and the distance W ₀ from the longitudinal axis of symmetry of the dielectric substrate 1 is 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 dielectric substrate 1 , the length L is 10mm-12mm, and the width W is 10mm-12mm.

The outer surface of the loaded square resonant ring implantable circularly polarized antenna for wireless biomedicine is coated with a layer of ultra-thin biocompatible thin-film alumina that has little effect on the antenna gain and reflection coefficient, and the dielectric of the dielectric substrate 1 The constants are similar, the dielectric constant _εr is 9.2, the loss tangent tanδ is 0.008, and the coating thickness is 0.02mm, which isolates human tissue from the implanted circularly polarized antenna, prevents direct contact between human tissue and the conductive patch of the antenna, and reduces the incidence of human tissue. Effects on the performance of implanted circularly polarized antennas.

Example: The specific production process is as described in the embodiment. Select Rogers RO3210 dielectric substrate, dielectric constant ε _r =10.2, loss tangent tanδ = 0.003, thickness H = 0.635mm, and the coaxial connector adopts standard SMA connector. The length L of the dielectric substrate is 11 mm, and the width W is 11 mm. Adding a meandering structure around the radiation patch can make the antenna surface current meander along the meandering structure, thereby increasing the current path on the antenna surface and reducing the antenna resonant frequency. Adjusting the meandering structure size can further optimize impedance matching. Loading the square resonator ring radiation patch 2 The length L ₂ of the rectangular groove around the radiation patch is 1.4mm, the width W ₄ is 5.67mm, the meandering structure 2-1, the meandering structure 2-2, the meandering structure 2-3. The width W ₂ of the meandering structure 2-4 is 0.21 mm, the distance W ₃ from the left side of the rectangular groove is 0.27 mm, and the distance L ₁ from the lower side of the rectangular groove is 0.27 mm. The square complementary split resonator loaded at the center of the loaded square resonator radiating patch is a metamaterial structure array with negative magnetic permeability, which can further enhance the efficiency produced by a single complementary split resonator, making the antenna resonant frequency lower to low frequencies The direction is shifted to reduce the overall size of the antenna. By adjusting the size of the square complementary split resonator ring, two orthogonal modes can be excited, thereby generating circular polarization characteristics. The width W ₆ of the square slot in the middle of the loaded square resonator radiating patch 2 is 5mm, and the square complementary split resonator 2-5, the square complementary split resonator 2-6, the square complementary split resonator 2-7 loaded in the square slot, Square complementary split resonator ring 2-8 The width W ₁₂ of the outer square ring is 2.22mm, the distance W ₇ between the outer square ring and the left side of the square groove is 0.14mm, the width W ₁₁ of the middle square ring is 1.66mm, the middle square ring and the outer The distance W ₈ of the square ring is 0.14mm, the width W ₁₀ of the inner direction patch is 1.1mm, and the distance W ₉ between the inner direction patch and the middle square ring is 0.14mm. The width W ₅ of each rectangular conduction band is 0.14 mm. Adding shorting probes can increase the resonance point, thereby broadening the impedance bandwidth of the antenna. The radius R ₁ of the short-circuit probe 3 and the short-circuit probe 4 is 0.3mm, the distance R ₂ between the center of the short-circuit probe 3 and the short-circuit probe 4 and the center of the dielectric substrate 1 is 6mm, and the short-circuit probe 3, the short-circuit probe 4 and the dielectric substrate are 1. The included angle a ₁ of the longitudinal axis of symmetry is 46 degrees, and the radius of the short-circuit probe 3 and the short-circuit probe 4 is equal to the radius of the inner core of the coaxial joint 5 . The distance L ₀ from the center of the coaxial joint 5 to the transverse symmetry axis of the dielectric substrate 1 is 3 mm, and the distance W ₀ from the longitudinal symmetry axis of the dielectric substrate 1 is 3 mm. The floor is a square complete metal patch structure without additional slots or gaps, and a shielding layer is formed between the implantable circularly polarized antenna and the underlying wireless biomedical device electronics, which can reduce the level of the implanted circularly polarized antenna. Interference with other electronic devices, and improve the electromagnetic compatibility performance of the implanted circularly polarized antenna. 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 11mm, and the width W is 11mm. The outer surface of the implanted circularly polarized antenna loaded with a square resonant ring for wireless biomedicine is coated with an ultra-thin biocompatible thin-film alumina that has little effect on the antenna gain and reflection coefficient, and the dielectric constant is similar to that of the dielectric substrate 1 , the dielectric constant _εr is 9.2, the loss tangent tanδ is 0.008, and the coating thickness is 0.02mm, which isolates human tissue from the implanted circularly polarized antenna, prevents direct contact between human tissue and the conductive patch of the antenna, and reduces the impact of human tissue on implantation. impact on the performance of the immersed circularly polarized antenna.

The influence of the width W ₂ of the meandering structure on the antenna impedance bandwidth and the axial ratio bandwidth is shown in Figure 4. The three cases of W ₂ =0.15mm, W ₂ =0.21mm and W ₂ =0.25mm are selected respectively. The performance of the antenna is analyzed. It can be seen from Figure ₄ that with the increase of the width W of the meander structure, the resonant frequency of the antenna shifts to the low frequency direction, the resonance degree gradually increases, and the axial ratio coefficient also shifts. The reason is that Adding a meandering structure around the radiation patch can make the antenna surface current meander along the meandering structure, thereby increasing the current path on the antenna surface and reducing the antenna resonant frequency. Adjusting the meandering structure size can further optimize impedance matching. When W ₂ =0.21mm, the performance of the antenna is the best, and both the impedance bandwidth and the axial ratio bandwidth cover the required ISM2.45GHz frequency band.

Select the width W ₁₂ of the outer square ring of the square complementary split resonator ring, the width W ₁₁ of the middle square ring, and the width W ₁₀ of the side patch to analyze the influence on the antenna impedance bandwidth and the axial ratio bandwidth as shown in Figure 5. _W12 =2.2mm, W11=1.6mm, _W10 =1mm, W12= _2.22mm , _W11 = _1.66mm , _W10 =1.1mm and _W12 =2.3mm, _W11 =1.7mm, _W10 = The performance of the antenna is analyzed in the three cases of 1.2mm. It can be seen from Figure 5 that with the increase of the size of the square complementary split resonant ring, the resonant frequency of the antenna shifts to the low frequency direction, and the resonance degree first increases and then decreases. The ratio coefficient also shifts to low frequencies because the square complementary split resonator loaded at the center of the loaded square resonator radiating patch is an array of metamaterial structures with negative permeability that can further enhance a single complementary opening The efficiency produced by the resonant ring shifts the resonant frequency of the antenna to the low frequency direction, reducing the overall size of the antenna. By adjusting the size of the square complementary split resonator ring, two orthogonal modes can be excited, thereby generating circular polarization characteristics. When W ₁₂ =2.22mm, W ₁₁ =1.66mm, W ₁₀ =1.1mm, the antenna performance is the best, and both the impedance bandwidth and the axial ratio bandwidth cover the required ISM 2.45GHz frequency band.

The application environment of the implanted circularly polarized antenna designed by the present invention is mainly the skin layer, the simulation environment is a single-layer skin model of 90mm×90mm×25mm, the antenna is placed in the center of the single-layer skin model, and the distance between the upper layer of the skin model and the upper surface of the antenna is is H, the schematic diagram of the implanted skin layer depth is shown in Figure 6, and the effects of different implantation depths H on the antenna impedance bandwidth and axial ratio bandwidth are shown in Figure 7. The implantation depth H is in the range of 3mm to 7mm, and the implant The reflection coefficient and axial ratio coefficient of the circularly polarized antenna are relatively stable, and each performance has good robustness, which can well cover the required ISM 2.45GHz frequency band.

The implanted circularly polarized antenna was placed in a solution simulating human skin for testing. The skin solution included deionized water 58.2%, diethylene glycol monobutyl ether 5.1% and polyethylene glycol octyl phenyl ether 36.7%. The impedance bandwidth of the antenna is tested by a vector network analyzer, and the circular polarization characteristics of the antenna are tested indirectly through the coordination of the external linearly polarized dipole antenna. The simulation results and test results of the impedance bandwidth and the axial ratio bandwidth are shown in Figure 8. The simulated impedance bandwidth of the implanted circularly polarized antenna is 2.26GHz～2.71GHz, the resonant frequency is 2.45GHz, the simulated axial ratio bandwidth is 2.28GHz～2.52GHz, the measured impedance bandwidth is 2.29GHz～2.75GHz, and the resonance frequency is 2.46GHz , the degree of resonance has increased significantly, the measured axial ratio bandwidth is 2.30GHz ~ 2.56GHz, the axial ratio bandwidth can cover the required operating frequency, the gap between the simulation results and the test results is small, and good resonance can be achieved in the ISM frequency band. The impedance characteristics and axial ratio characteristics of the circularly polarized antenna in the working frequency band are good, and the resonant frequency and axial ratio coefficient are slightly shifted to the high frequency direction. , the effect of air bubbles on the antenna test and the difference in the dielectric constant of the simulated test environment.

The radiation patterns of the implanted circularly polarized antenna at the 2.45GHz frequency point of the E and H surfaces are tested to check the radiation characteristics of the antenna. The measured patterns are shown in Figure 9 and Figure 10. It can be seen from the radiation pattern that the antenna has good directivity. The maximum radiation direction of the implanted circularly polarized antenna is along the Z-axis direction, that is, toward the outside of the human body. The main polarization is left-handed circular polarization. The actual gain value is -28.8dBi, and the difference between the main polarization and the cross-polarization is 32.1dBi. The main reason is that two orthogonal modes can be excited by adjusting the size of the square complementary split resonator ring, thereby generating circular polarization characteristics. The axial ratio beam in the working frequency band is wider and the radiation characteristics are excellent. It is suitable for the ISM 2.45GHz working frequency band and can meet the needs of complex implantation environments.

Considering the safety factors of implantation in human tissue, the safety of implantable circularly polarized antenna is comprehensively analyzed. The input power of the implanted circularly polarized antenna is set to 1W, and the average SAR value is used to evaluate the safe range of energy absorbed by the human body model. , after simulation calculation, the maximum average SAR value of the implanted circularly polarized antenna at 2.45GHz is 392.5W/kg for 1-g human tissue, and the maximum average SAR value for 10-g human tissue is 82.7W/kg, which is in line with IEEEC95. .1-1999 and IEEEC95.1-2005 safety standards for SAR values, the maximum input power corresponding to the implanted circularly polarized antenna is 3.1mW and 21.6mW respectively, and the implanted circularly polarized antenna meets the electromagnetic Radiation is safe and harmless to human tissue.

Claims (7)

1. A loaded square resonant ring implanted circularly polarized antenna for wireless biomedicine, consisting of a dielectric substrate (1), a loaded square resonator radiating patch (2), a short-circuit probe (3), and a short-circuit probe (4) ), a coaxial joint (5), and a floor (6), characterized in that: a. The loading square resonator ring radiation patch (2) is to open a rectangular groove around the radiation patch, and add a meandering structure (2-1), a meandering structure (2-2), The meandering structure (2-3), the meandering structure (2-4), and the meandering structure (2-1) are respectively rotated by 90 degrees with the dielectric substrate (1) as the center to obtain the meandering structure (2- 2), meandering structure (2-3), meandering structure (2-4), adding meandering structure (2-1), meandering structure (2-2), meandering structure around the radiation patch The meandering structure (2-3) and the meandering structure (2-4) can make the surface current of the antenna flow meanderingly along the meandering structure, thereby increasing the current path on the surface of the antenna, reducing the resonant frequency of the antenna, and adjusting the meandering structure ( 2-1), meandering structure (2-2), meandering structure (2-3), meandering structure (2-4) size can further optimize impedance matching, when the square resonator ring radiation patch is loaded (2) A square slot is opened in the middle, and the square complementary split resonator ring (2-5), the square complementary split resonator (2-6), the square complementary split resonator (2-7), and the square complementary split resonator are loaded into the square slot. Resonant ring (2-8), square complementary split resonator (2-5), square complementary split resonator (2-6), square complementary split resonator (2-7), square complementary split resonator (2-8 ) consists of two square rings and a square patch, which are connected to the loaded square resonator ring radiating patch (2) through three rectangular conduction bands, and the three rectangular conduction bands are opposite to the square complementary split resonator ring (2- 5) The angle difference between the centers of the square complementary split resonator ring (2-6), the square complementary split resonator ring (2-7), and the square complementary split resonator ring (2-8) is 90 degrees. Square complementary split resonator (2-5), square complementary split resonator (2-6), square complementary split resonator (2-7), square complementary split resonator (2-8) centrally loaded on plate (2) It is a metamaterial structure array with negative magnetic permeability, which can further enhance the efficiency of a single complementary split resonator ring, shift the antenna resonant frequency to the low frequency direction, and reduce the overall size of the antenna. By adjusting the square complementary split resonator ring (2-5), square complementary split resonator (2-6), square complementary split resonator (2-7), square complementary split resonator (2-8) are dimensioned to excite two orthogonal modes, thereby Generate circular polarization characteristics; b. The short-circuit probe (3) and the short-circuit probe (4) are arranged on the lower left side and the upper left side of the loaded square resonant ring radiation patch (2). The short-circuit probe (3) and the short-circuit probe (4) With respect to the transverse axis symmetry of the antenna dielectric substrate (1), adding a short-circuit probe (3) and a short-circuit probe (4) can increase the resonance point, thereby broadening the impedance bandwidth of the antenna; c. The coaxial joint (5) is located on the diagonal line on the upper right side of the loaded square resonator ring radiation patch (2), and the inner core of the coaxial joint (5) is connected to the loaded square resonance ring radiation patch (2) connected, the outer core of the coaxial joint (5) is connected with the floor (6); d. The floor (6) is a square complete metal patch structure without additional slots or gaps, and a shielding layer is formed between the implanted circularly polarized antenna and the underlying wireless biomedical device electronic device, which can The interference of the implanted circularly polarized antenna to other electronic devices is reduced, and the electromagnetic compatibility performance of the implanted circularly polarized antenna is improved. 2. The implanted circularly polarized antenna with a loaded square resonator ring for wireless biomedicine according to claim 1, characterized in that the length L of the dielectric substrate (1) is 10mm-12mm, and the width W is 10mm ~12mm. 3. The loaded square resonant ring implantable circularly polarized antenna for wireless biomedicine according to claim 1, wherein the loaded square resonator radiating patch (2) has a rectangular groove around the radiating patch _The length L2 is 1.3mm~1.5mm, the width W4 is 5.5mm~ _5.7mm , the meandering structure (2-1), the meandering structure (2-2), the meandering structure (2-3) The width W2 of the meandering structure ( _2-4 ) is 0.15mm～0.25mm, the distance W3 from the left side _of the rectangular groove is 0.25mm～0.3mm, and the distance L1 from the lower side _of the rectangular groove is 0.25mm～0.35mm , the width W ₆ of the square groove in the middle of the square resonator ring radiating patch (2) is 4.9mm to 5.1mm, and the square complementary split resonator ring (2-5) and the square complementary split resonator ring (2-6) loaded in the square groove ), square complementary split resonator ring (2-7), square complementary split resonator ring (2-8) The width W ₁₂ of the outer square ring is 2.2mm～2.3mm, and the distance W ₇ between the outer square ring and the left side of the square groove is 0.1 mm～0.2mm, the width _W11 of the middle square ring is 1.6mm～1.7mm, the distance W8 between the middle square ring and the outer square ring is 0.1mm～0.2mm, and the width _W10 of the inner side _patch is 1mm～1.2mm , the distance W ₉ between the inner side patch and the middle square ring is 0.1mm-0.2mm, and the width W ₅ of the three rectangular conducting strips connecting two square rings and one square patch is 0.1mm-0.3mm. 4. The implanted circularly polarized antenna with a square resonant ring for wireless biomedicine according to claim ₁ , wherein the radius R of the short-circuit probe (3) and the short-circuit probe (4) is 0.2mm～0.4mm, the distance R2 from the center of the short-circuit probe (3) and the short-circuit probe (4) to the center of the dielectric substrate ( ₁ ) is 5.8mm～6.2mm, the short-circuit probe (3), the short-circuit probe (4) ) and the longitudinal axis of symmetry of the dielectric substrate ( ₁ ) and the included angle a1 is 40 degrees to 50 degrees, and the radius of the short-circuit probe (3) and the short-circuit probe (4) is equal to the inner core radius of the coaxial joint (5). 5. The implanted circularly polarized antenna with a loaded square resonant ring for wireless biomedicine according to claim 1, characterized in that the center of the coaxial joint (5) is separated from the transverse axis of symmetry of the dielectric substrate (1). The distance L ₀ is 2.8 mm˜3.2 mm, and the distance W ₀ from the longitudinal symmetry axis of the dielectric substrate (1) is 2.8 mm˜3.2 mm. 6. The implanted circularly polarized antenna with a loaded square resonator ring for wireless biomedicine according to claim 1, wherein the floor (6) is a complete square metal patch, and the floor (6) The size is the same as that of the dielectric substrate (1), the length L is 10mm-12mm, and the width W is 10mm-12mm. 7. The implanted circularly polarized antenna with a loaded square resonator for wireless biomedicine according to claim 1, characterized in that the implanted circularly polarized antenna with a loaded square resonator for wireless biomedicine The outer surface is coated with a layer of ultra-thin biocompatible thin-film alumina that has little effect on the antenna gain and reflection coefficient. The dielectric _constant is similar to that of the dielectric substrate (1). The thickness is 0.02mm, which isolates human tissue from the implanted circularly polarized antenna, prevents direct contact between human tissue and the conductive patch of the antenna, and reduces the impact of human tissue on the performance of the implanted circularly polarized antenna.

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