CN110994148A

CN110994148A - Small-size implanted rectenna

Info

Publication number: CN110994148A
Application number: CN201911238983.1A
Authority: CN
Inventors: 刘雄英; 徐超; 刘徐迅; 李忠心
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2019-12-06
Filing date: 2019-12-06
Publication date: 2020-04-10

Abstract

The invention belongs to the field of biomedical telemetering, and relates to a small implanted rectifying antenna, which comprises: dielectric substrate, antenna radiation unit, floor, rectifier circuit, short circuit probe and the coaxial probe of feed, wherein: the medium substrate comprises a first layer medium substrate, a second layer medium substrate and a third layer medium substrate, the antenna radiation unit is located on the lower surface of the first layer medium substrate, the floor is located on the lower surface of the second layer medium substrate, the rectification circuit is located on the lower surface of the third layer medium substrate, the antenna radiation unit is electrically connected with the rectification circuit through the feed coaxial probe, the rectification circuit is connected to the floor through the short circuit probe, and the antenna radiation unit and the rectification circuit share the floor. The antenna radiation unit forms a bending curve structure by loading a plurality of bending gaps, and the bandwidth of the rectification antenna is effectively expanded. The invention has the advantages of small size, high rectification efficiency under low-power input and the like, can be implanted into a human body, and can also be applied to the field of wireless energy transmission in the biomedical field.

Description

Small-size implanted rectenna

Technical Field

The invention belongs to the field of biomedical telemetry, and relates to a small implanted rectifying antenna.

Background

With the continuing advances in biomedical engineering and the level of personalized healthcare, implantable medical devices have grown enormously over the last decades and are moving to a commercial scale. The implantable medical device can transmit human body physiological data information to external medical devices, doctors can diagnose and treat the human body physiological data information remotely, and the implantable medical device is widely applied to medical devices such as cardiac pacemakers, cardiac defibrillators, cochlear implants, bladder pressure monitoring devices, nerve stimulators and the like. However, the conventional biomedical implantable device is powered by an internal battery, and the battery needs to be replaced through an operation when the battery is exhausted, so that unnecessary trouble and pain of a patient are increased.

Thus, the powering of biomedical devices is more prone to practical, efficient, non-invasive and safe wireless energy transfer approaches, and implantable rectennas for wireless energy transfer have become a focus of research in recent years. The implanted rectifying antenna can receive external radio frequency signals and convert the external radio frequency signals into direct current energy to supply power to the implanted medical equipment. To better receive the rf energy, a high efficiency rectenna needs to be designed. The rectifying antenna consists of a receiving antenna and a rectifying circuit, and occupies a larger space, which can cause the increase of the size of the implanted medical equipment. The current implanted rectifying antenna mainly has the problems of low rectifying efficiency, large size and the like.

Disclosure of Invention

Aiming at the defects of the existing implanted rectifying antenna, the invention provides a small implanted rectifying antenna.

The invention is realized by adopting the following technical scheme:

a compact implantable rectenna, comprising: dielectric substrate, antenna radiation unit, floor, rectifier circuit, short circuit probe and the coaxial probe of feed, wherein:

the medium substrate comprises a first layer medium substrate, a second layer medium substrate and a third layer medium substrate, the antenna radiation unit is located on the lower surface of the first layer medium substrate, the floor is located on the lower surface of the second layer medium substrate, the rectification circuit is located on the lower surface of the third layer medium substrate, the antenna radiation unit is electrically connected with the rectification circuit through the feed coaxial probe, the rectification circuit is connected to the floor through the short circuit probe, and the antenna radiation unit and the rectification circuit share the floor.

Preferably, the antenna radiation unit comprises a fifth sector-ring patch, respectively: first fan annular paster, second fan annular paster, third fan annular paster, fourth fan annular paster and fifth fan annular paster, wherein: the central angles of the first fan-shaped patch, the second fan-shaped patch, the third fan-shaped patch and the fourth fan-shaped patch are all 60 degrees, and the central angle of the fifth fan-shaped patch is 120 degrees.

Preferably, the first, second, third and fourth annular patches form a bending curve structure by loading a plurality of bending slits.

Preferably, the meander curve structure has a radial width of 0.2mm and an axial width of 0.15 mm.

Preferably, the end of the first fan-shaped patch far away from the center of the circle is connected with a section of matching stub for adjusting the impedance matching of the antenna.

Preferably, the third fan-shaped patch is connected to a bent limb for extending the effective path of the current.

Preferably, the width of the bent branch is 0.2mm, and the included angle between the tail end of the bent branch and the radial line of the edge of the third fan-shaped patch is 42 degrees.

Preferably, the rectification circuit adopts a voltage doubling rectification structure, and comprises: the device comprises a matching network, a blocking capacitor, a filter capacitor, a rectifier diode, a load resistor and 7 microstrip lines, wherein the microstrip lines are connected through the matching network, the blocking capacitor or the filter capacitor.

Preferably, the feed coaxial probe has a radius of 0.35mm and the shorting probe has a radius of 0.3 mm.

Preferably, the floor is circular with a radius of 4 mm.

The invention has the following beneficial effects:

(1) the meandering structure of the invention is beneficial to prolonging the effective path of current and reducing the size of the antenna; the two resonance points can be close to each other by adjusting the sizes of the bent branches and the gaps, so that the bandwidth of the rectification antenna is expanded; the rectification circuit is integrated on the back of the rectification antenna and is integrally designed with the rectification antenna, so that the volume occupied by the rectification antenna is reduced.

(2) The invention has the advantages of small size, high rectification efficiency under low-power input and the like, can be implanted into a human body, and can also be applied to the field of wireless energy transmission in the biomedical field.

Drawings

Fig. 1 is a schematic diagram of a small-sized implantable rectenna in an embodiment of the present invention, wherein: (a) the antenna is a radiation unit diagram of the small implanted rectifying antenna, (b) the bottom view of the small implanted rectifying antenna, and (c) the side view of the small implanted rectifying antenna;

FIG. 2 is a three-layer phantom simulation of the small implantable rectenna in accordance with an embodiment of the present invention;

fig. 3 is a graph of the reflection coefficient S11 of a small implanted rectenna in accordance with an embodiment of the present invention;

FIG. 4 is a gain pattern of the XOZ and YOZ planes at a frequency of 915MHz for a compact implantable rectenna in accordance with one embodiment of the present invention;

fig. 5 is a simulation graph of rectification efficiency and output dc voltage of a small implanted rectenna in accordance with an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

As shown in fig. 1(a) - (c), a small implantable rectenna comprises: dielectric substrate 1, antenna radiation unit 2, floor 3, rectifier circuit 4, short circuit probe 5 and feed coaxial probe 6, wherein:

the dielectric substrate 1 comprises a first layer dielectric substrate 1A, a second layer dielectric substrate 1B and a third layer dielectric substrate 1C, the antenna radiation unit 2 is positioned on the lower surface of the first layer dielectric substrate 1A, the floor 3 is positioned on the lower surface of the second layer dielectric substrate 1B, and the rectification circuit 4 is positioned on the lower surface of the third layer dielectric substrate 1C. The antenna radiation unit 2 is electrically connected with the rectification circuit 4 through the feed coaxial probe 6, the rectification circuit 4 is connected to the floor 3 through the short circuit probe 5, and the antenna radiation unit 2 and the rectification circuit 4 share the floor 3.

In a preferred embodiment, the antenna radiation unit 2 has a radius of 4mm and is composed of fan-shaped

annular patches

21, 22, 23, 24 and 25, the central angles of the fan-shaped

annular patches

21, 22, 23 and 24 are all 60 degrees, and the central angle of the fan-shaped annular patch 25 is 120 degrees. The interface of the antenna radiating element 2 and the feeding coaxial probe 6 is located on the fan-ring patch 21. Three bending gaps are etched at the end, close to the center of a circle, of the fan-shaped annular patch 21 to form a zigzag structure, the radial width of the zigzag structure is w 1-0.2 mm, and the axial width s 1-0.15 mm. The tail end of the fan-shaped annular patch 21 far away from the center of the circle is connected with a section of matching branch 26, so that the impedance matching of the antenna can be adjusted.

The fan-shaped patch 21 is electrically connected with the fan-shaped patch 22, a plurality of bending gaps are etched on the fan-shaped patch 22 to form a zigzag structure, the radial width of the zigzag structure is w 1-0.2 mm, and the axial width s 1-0.15 mm. The bending slot 28 on the fan-shaped annular patch 22 can tune the resonance point of the antenna, and the included angle between the tail end of the bending slot 28 and the radial line of the edge of the fan-shaped annular patch 22 is a 1-24 degrees.

The sector annular patch 22 is electrically connected with the sector annular patch 25 in the counterclockwise direction, the central angle of the sector annular patch 25 is 120 degrees, the inner radius of the sector annular patch 25 is 0.6mm, and the impedance matching of the antenna can be adjusted. The sector ring patch 25 is electrically connected to the sector ring patch 24 in the counterclockwise direction. The fan-ring patch 24 is similar to the fan-ring patch 22 in structure, the bending slot 29 on the fan-ring patch 24 can tune the resonance point of the antenna, and the included angle between the end of the bending slot 29 and the radial line of the edge of the fan-ring patch 24 is 55 degrees, a 2.

The fan-ring patch 24 is electrically connected to the fan-ring patch 23 in the counterclockwise direction. The fan-ring patch 23 is a meandering structure. The radial width w1 of the zigzag structure is 0.2mm, and the axial width s1 is 0.15 mm. The fan-shaped patch 23 is electrically connected with the bent branch 27, the width w1 of the bent branch 27 is 0.2mm, and the included angle a3 between the tail end and the radial line of the edge of the fan-shaped patch 23 is 42 degrees.

The antenna radiation unit is etched with a plurality of bent gaps, so that a winding and bending structure can be formed, an effective current path is prolonged, and the miniaturization effect of the antenna is realized.

The rectification circuit 4 adopts a voltage doubling rectification structure and comprises a matching network, a blocking capacitor, a filter capacitor, a rectifier diode, a load resistor and a plurality of microstrip lines. The antenna radiation unit 2 is connected to an input end microstrip line 41 of the rectification circuit 4 through a feed coaxial probe 6, and the microstrip line 41 is in a square structure with the side length of 1 mm. The microstrip line 41 is connected to a matching network, which is composed of inductive elements L1 and L2, through microstrip line 42 and microstrip line 43. The microstrip line 43 is connected to the microstrip line 47 through an inductance element L2. The microstrip line 42 is connected to the microstrip line 44 through the inductance element L1.

After passing through the matching network, the microstrip line 44 is connected to the microstrip line 45 through a dc blocking capacitor C1, and the microstrip line 45 is connected to the microstrip line 46 and the microstrip line 47 through a rectifier diode D1 packaged by the SOT23-3, respectively. The left end of the microstrip line 46 is connected to the microstrip line 47 through the filter capacitor C2, the right end of the microstrip line 46 is connected to the microstrip line 47 through the load resistor R1, the microstrip line 47 is connected to the floor 3 through the short-circuit probe 5, and the two ends of the load resistor R1 output direct-current voltage.

Inductance values of the inductance elements L1 and L2 were 24nH and 4.7nH, respectively. The capacitance values of the inductive elements C1 and C2 are 100pF and 330pF, respectively, the load resistor R1 is 7.5K Ω, and the encapsulation form is 0603. The rectifier diode is a Schottky diode packaged by SOT23-3, the model is HSMS-2852, and two diodes are contained in the package.

The radius of the feed coaxial probe 6 is 0.35mm and the radius of the shorting probe 5 is 0.3 mm.

The radius of the floor 3 is 4mm, and the floor is kept complete except the passing area of the feeding coaxial probe 6, so that the influence of the bottom rectifying circuit element on the performance of the antenna can be reduced.

The dielectric substrate 1 was Rogers Ro3210, the radius was 4mm, the thickness was 0.635mm, the relative dielectric constant was 10.2, and the loss tangent was 0.003.

The invention uses the dielectric substrate with high dielectric constant, and can reduce the resonant frequency of the antenna, thereby reducing the size of the antenna. The surface of the antenna radiation unit is covered with a layer of dielectric substrate, so that the antenna can be prevented from being in direct contact with human tissues.

The simulation of the small implanted rectenna of the present invention in a three-layer human tissue model is described below.

The small implanted rectifying antenna is placed in a three-layer tissue model simulating a human body, as shown in fig. 2, a skin layer, a fat layer and a muscle layer are sequentially arranged from top to bottom, the thicknesses of the skin layer, the fat layer and the muscle layer are respectively 4mm, 4mm and 50mm, the antenna is placed at the position dp which is 4mm below the muscle layer, and the distance from the periphery of the model is 50 mm. Since the electromagnetic properties of human tissue vary with frequency, the relative permittivity and conductivity of the three-layer tissue model need to be set at the center frequency of 915 MHz. The small implanted rectenna operates in the ISM band at 902-928 MHz. When the frequency is 915MHz, the relative dielectric constants of the skin layer, the fat layer and the muscle layer are 41.3, 5.46 and 55 respectively, and the electric conductivities are 0.87S/m, 0.051S/m and 0.948S/m respectively.

The small implantable rectenna was placed in a three-layer tissue model with a reflection coefficient S11, as shown in fig. 3, and fig. 3 shows a reflection coefficient S11 when the rectifier circuit-containing third dielectric substrate 1C was not added and the rectifier circuit-containing third dielectric substrate 1C was added. When the third dielectric substrate 1C with the rectifying circuit is not added, the-10 dB impedance bandwidth of the antenna is 0.79-1.11GHz (33.7%), and after the third dielectric substrate 1C with the rectifying circuit is added, the-10 dB impedance bandwidth of the antenna is 0.83-1.03GHz (21.5%), and the-10 dB impedance bandwidth covers 902-928MHz in the ISM frequency band.

The small implantable rectenna was placed in a three-layer tissue model with the radiation patterns in the XOZ and YOZ planes at 915MHz, as shown in fig. 4, and the peak gain of the small implantable rectenna was-28.9 dBi at 915 MHz.

As shown in fig. 5, the rectification efficiency and the output dc voltage curve of the rectification circuit of the small implanted rectification antenna under different powers can reach 81% at most, and the rectification efficiency of the rectification antenna under the input power of-15 dBm can reach 50%, so that the rectification circuit of the small implanted rectification antenna can reach higher rectification efficiency under the low input power.

The small implanted rectifying antenna of the invention integrally designs the receiving antenna and the rectifying circuit, thereby effectively reducing the volume occupied by the rectifying antenna; the antenna radiation unit is etched with a plurality of bent gaps, a winding structure can be formed, and an effective current path is prolonged, so that the size of the antenna is reduced; the two resonance points can be close to each other by adjusting the size of the bent branch, and the bandwidth of the antenna is expanded.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A compact implantable rectenna, comprising: dielectric substrate, antenna radiation unit, floor, rectifier circuit, short circuit probe and the coaxial probe of feed, wherein:

2. The small implantable rectenna of claim 1, wherein the antenna radiating element comprises a fifth sector-ring patch, respectively: first fan annular paster, second fan annular paster, third fan annular paster, fourth fan annular paster and fifth fan annular paster, wherein: the central angles of the first fan-shaped patch, the second fan-shaped patch, the third fan-shaped patch and the fourth fan-shaped patch are all 60 degrees, and the central angle of the fifth fan-shaped patch is 120 degrees.

3. The small implantable rectenna of claim 2, wherein the first, second, third, and fourth sector-annular patches are loaded with a plurality of curved slots to form a meander curve structure.

4. The compact implantable rectenna of claim 3, wherein the meander curve structure has a radial width of 0.2mm and an axial width of 0.15 mm.

5. The small implantable rectenna of claim 2, wherein the first sector loop patch has a matching stub connected to the end away from the center of the circle for adjusting the impedance matching of the antenna.

6. The small implantable rectenna of claim 2, wherein the third segment is connected to a bent branch for extending the effective path of current.

7. The small implantable rectenna of claim 6, wherein the width of the bent branches is 0.2mm, and the included angle between the ends of the bent branches and the radial line of the edge of the third sector patch is 42 degrees.

8. The small implantable rectenna of claim 1, wherein the rectifying circuit is a voltage-doubling rectifying structure, comprising: the device comprises a matching network, a blocking capacitor, a filter capacitor, a rectifier diode, a load resistor and 7 microstrip lines, wherein the microstrip lines are connected through the matching network, the blocking capacitor or the filter capacitor.

9. The small implantable rectenna of claim 1, wherein the feed coaxial probe has a radius of 0.35mm and the shorting probe has a radius of 0.3 mm.

10. The small implantable rectenna of claim 1, wherein the floor is circular with a radius of 4 mm.