WO2021100999A1 - Brain-implanted antenna utilizing ultrapure water-based insulator - Google Patents

Abstract

The present invention relates to a brain-implanted antenna utilizing an ultrapure water (UPW)-based insulator, in which a UPW-based dielectric is used as an insulating layer of a human body-implanted antenna so as to reduce the size of the implanted antenna and improve the radiation efficiency and gain characteristics of the antenna, and antenna matching characteristics covering the ultra-wideband can be obtained by a wideband power feeding line provided with an L-shaped open stub. A brain-implanted antenna utilizing a UPW-based insulator according to an embodiment of the present invention may comprise an upper end antenna housing, an insulating layer, a slot antenna, an RF substrate, a wideband power feeding line, and a lower end antenna housing. The upper end antenna housing and the lower end antenna housing are made of a biocompatible material and block the inflow of foreign substances. The insulating layer is made of a dielectric based on UPW or distilled water, which is an extremely low lossy medium, and disposed between the upper end antenna housing and the slot antenna. The slot antenna is made of circular conductive metal and disposed on the RF substrate, and a rectangular slot is provided inside the slot antenna. The wideband power feeding line is made of a microstrip line of conductive metal and disposed below the RF substrate so as to bring about impedance matching characteristics and an efficient radiating mode of the slot antenna, and two L-shaped open stubs are provided in left-right symmetry at an end portion of the line in order to bring about the impedance matching.

Description

Brain implanted antenna with ultrapure water based insulator

The present invention relates to a brain implanted antenna to which an ultrapure water-based insulator is applied, and an ultrapure water (UPW)-based dielectric is used as an insulating layer of a human body insertion antenna in order to reduce the size of the implantable antenna and improve the radiation efficiency and gain characteristics of the antenna. The present invention relates to a brain implanted antenna to which an ultrapure water-based insulator capable of securing matching characteristics of an antenna covering an ultra-wide band through a broadband feed line provided with a shaped open stub is applied.

With the increase of the elderly population, the size of the prevention and treatment market for degenerative brain diseases (dementia, Alzheimer's) is expected to continue to grow. For this, a technology for monitoring and analyzing the patient's brain signals in real time is required. In addition, a technology capable of stably transmitting a weak brain signal in the human body to an external monitoring system must be secured.

On the other hand, in order to secure the reliability of wireless communication of medical devices for implantation in the body, an implantable antenna technology is essential. For wireless communication of such implantable medical devices, MICS (Medical Implant Communication System) and MedRadio (Medical Device Radiocommunication Service) in the 400MHz band, Industrial Scientific and Medical (ISM) in the 900MHz or 2.4GHz band, and the 3~10GHz band. UWB (Ultra Wide Band) frequency band is mainly used.

However, the human body insertion type antenna is generally placed in an environment where it is difficult to radiate due to dielectric loss in the human body. In addition, the antenna inserted into the human body requires additional design conditions to the conventional antenna used in a free space. That is, miniaturization for insertion of the human body, broadband for securing personal matching characteristics, gain for stable communication reliability, and suitability for the human body are required.

In spite of these limited design conditions, it is essential to secure an implantable antenna technology as one of the core technologies for implementing various medical sensor devices for implantation in the body such as brain signal processing and wireless transmission systems in the body.

[Prior technical literature]

[Patent Literature]

Republic of Korea Patent Registration No. 10-1699130 (announced on January 23, 2017)

Accordingly, the technical problem to be achieved by the present invention is to solve the disadvantages of the prior art, and an object thereof is to improve the radiation efficiency and gain characteristics of the human body insertion type antenna. In addition, there is an object to improve the impedance matching characteristics of the human body insertion type antenna to secure the matching characteristics of the antenna covering an ultra-wide band.

The brain implanted antenna to which the ultrapure water-based insulator is applied according to an embodiment of the present invention for achieving this technical problem may include an upper antenna housing, an insulating layer, a slot antenna, an RF substrate, a broadband feed line, and a lower antenna housing.

The upper antenna housing is made of a biocompatible material to insulate the brain-inserted antenna from living tissue and protect it from the introduction of foreign substances. The insulating layer is formed of a dielectric based on ultrapure water (UPW) or distilled water, which is an extremely low lossy medium, and is disposed between the upper antenna housing and the slot antenna.

The slot antenna is formed of a circular conductive metal and is disposed on an RF substrate, and a rectangular slot is provided inside the slot antenna.

The broadband feed line is formed as a microstrip line of a conductive metal in order to induce an impedance matching characteristic and an efficient radiation mode of the slot antenna, and is disposed at the lower end of the RF substrate, and has an impedance For matching, two L-shaped open stubs are symmetrically provided at the end of the line.

In addition, the lower antenna housing is made of a biocompatible material at the lower end of the broadband feed line to block the inflow of foreign substances.

As described above, the brain-inserted antenna to which the ultrapure water-based insulator according to the present invention is applied uses the ultrapure water-based dielectric as an insulator or superstrate of the human body-inserted antenna, reducing the size of the implantable antenna and radiating efficiency and gain characteristics of the antenna There is an effect that can improve. In addition, there is an effect of securing matching characteristics of an antenna covering an ultra-wide band through a broadband feed line provided with an L-shaped open stub.

1 is a block diagram showing a brain implanted antenna to which an ultrapure water-based insulator is applied according to an embodiment of the present invention.

2 is a block diagram illustrating a slot antenna according to an embodiment of the present invention.

3 is a block diagram showing a broadband feed line according to an embodiment of the present invention.

4A and 4B are diagrams showing a real brain implanted antenna to which an ultrapure water-based insulator is applied according to an embodiment of the present invention.

5 is a diagram illustrating a Shell Problem Model (SPM) according to an embodiment of the present invention.

6A, 6B, and 6C are graphs showing the maximum transmission efficiency (MPTE) according to the size of the non-loss region.

7 is a graph showing antenna radiation efficiency according to dielectric constant of an insulating layer.

8 is a graph showing reflection coefficients and gain characteristics of an antenna depending on whether or not a broadband feed line is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary. In addition, terms such as "...unit", "...group", and "...module" described in the specification mean a unit that processes at least one function or operation, which is implemented by hardware or software, or a combination of hardware and software. Can be.

Hereinafter, the present invention will be described in detail by describing a preferred embodiment of the present invention with reference to the accompanying drawings.

The same reference numerals shown in each drawing indicate the same members.

1 is a block diagram showing a brain implantation antenna 10 to which an ultrapure water-based insulator is applied according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a slot antenna 300 according to an embodiment of the present invention, and FIG. 3 Is a configuration diagram showing a broadband feed line 500 according to an embodiment of the present invention.

In addition, FIGS. 4A and 4B are diagrams showing the real thing of the brain implantation antenna 10 to which an ultrapure water-based insulator is applied according to an embodiment of the present invention. That is, FIG. 4A is a plan view of the brain implantation antenna 10 to which an ultrapure water-based insulator is applied according to an embodiment of the present invention, and FIG. 4B is an ultrapure water-based insulator implemented in real life according to an embodiment of the present invention. It is a bottom view of the brain insertion antenna 10.

In general, the dielectric loss medium called the human body inevitably causes loss from the viewpoint of radiation from the antenna. In addition, as shown in FIG. 1, an insulating layer or housings 100 and 600 are essential for the antenna for implantation in the body to insulate from a living tissue and protect the implanted device.

The brain insertion antenna 10 to which the ultrapure water-based insulator is applied according to an embodiment of the present invention can minimize the loss that inevitably occurs according to the configuration of the housings 100 and 600. In addition, the brain insertion antenna 10 to which the ultrapure water-based insulator is applied according to an embodiment of the present invention is inserted into the human body and transmits a biological signal or a brain signal measured in the body to the receiving antenna 20 outside the biological tissue.

In this case, a radio frequency (RF) signal may be transmitted/received between the brain insertion antenna 10 and the reception antenna 20.

The brain insertion antenna 10 to which the ultrapure water-based insulator is applied according to an embodiment of the present invention includes an upper antenna housing 100, an insulating layer 200, a slot antenna 300, an RF substrate 400, a broadband feed line 500 And a lower antenna housing 600.

The upper antenna housing 100 is made of a biocompatible material to insulate the brain insertion antenna 10 from living tissues and protects it from the introduction of foreign substances. That is, the upper antenna housing 100 may prevent metal oxidation and an electrical short circuit.

Here, the biocompatible material may be a nylon-12-based material that satisfies the US Pharmacopeia-biological test class VI.

The insulating layer 200 is formed of a dielectric based on ultrapure water (UPW) or distilled water, which is an extremely low lossy medium, and is disposed between the upper antenna housing 100 and the slot antenna 300 to provide an improved antenna. Implement radiation characteristics.

In general, the ultrapure water (UPW) has a dielectric loss close to 0 and a relative dielectric constant of 80. That is, the insulating layer 200 may be formed by filling a container made of a biocompatible material with an ultrapure water (UPW) or a dielectric based on distilled water.

The slot antenna 300 is formed of a circular conductive metal and is disposed on the RF substrate 400. In addition, a rectangular slot 310 is provided inside the slot antenna 300. As shown in FIG. 2, the slot antenna 300 may include a radiation prevention layer 320 and a rectangular slot 310 formed inside the radiation prevention layer 320.

For example, the width (D, Depth) of the radiation prevention layer 320 may be 10 mm, and the length (L, Length) of the radiation prevention layer 320 may be 11 mm. In addition, the slot 310 may have a width Sw (Slot width) of 7.5 mm, and the slot 310 may have a length Sl (Slot length) of 1.5 mm. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

The RF substrate 400 may be a Rogers 4350B substrate. That is, the slot antenna 300 and the broadband feed line 500 may be disposed on the upper and lower ends of the RF substrate 400, respectively.

As shown in FIG. 3, the broadband feed line 500 is formed as a microstrip line of a conductive metal to cause a broadband matching of the slot antenna 300 and an efficient radiation mode. Is placed in In addition, the broadband feed line 500 may include a feed line 510 and a feed resonator 520.

That is, the broadband feed line 500 is applied for excitation of the slot 310 shown in FIG. 2.

The feed line 510 may be connected to the cable 700 to receive a signal transmitted through the cable 700. That is, the measuring unit (not shown) may measure a biological signal inside the biological tissue and transmit the measured signal to the feed line 510 through the cable 700.

The feed line 510 receives a signal transmitted from the cable 700 and transmits it to the feed resonator 520, and the feed resonator 520 generates resonance based on the received signal.

At this time, the power supply resonator 520 includes two L-shaped open stubs to improve the impedance matching characteristics of the microstrip line, and the two L-shaped open stubs Are formed symmetrically left and right, and are connected to form one body at the end of the feed line 510 or the microstrip line.

For example, the width fw of the feed line 510 may be 0.5 mm, and the length fl of the feed line 510 may be 8 mm. In addition, the width mw of the feed resonator 520 may be 5 mm, and the length (ml) of the feed resonator 520 may be 1.25 mm. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

The lower antenna housing 600 is made of a biocompatible material and is disposed under the RF substrate 400 and the broadband power supply line 500. That is, the lower antenna housing 600 may insulate the broadband feed line 500 from a living body tissue and block the inflow of foreign substances to protect it.

As described above, the brain-inserting antenna 10 to which an ultrapure water-based insulator is applied according to an embodiment of the present invention has an effect of securing a broadband matching characteristic of the antenna through a feed structure for efficient aperture radiation.

In addition, the features and effects of the brain implantation antenna 10 to which the ultrapure water-based insulator is applied according to an embodiment of the present invention can be confirmed as follows.

5 is a diagram illustrating a Shell Problem Model (SPM) according to an embodiment of the present invention. That is, FIG. 5 is a diagram showing a Shell Problem Model (SPM) for analyzing propagation characteristics in a human brain environment. Here, a configuration including all of a Tx antenna 301, an insulating layer 201, and a housing 101 excluding the outermost head model 800 is seen. Corresponds to the brain insertion antenna 10 of the invention.

That is, the Tx antenna 301 of FIG. 5 corresponds to the slot antenna 300 of FIG. 1, and the insulating layer 201 of FIG. 5 corresponds to the insulating layer 200 of FIG. , The housing 101 of FIG. 5 corresponds to the upper antenna housing 100 of FIG. 1, respectively.

When the insulating layer 201 has an appropriate thickness and dielectric constant, it is possible to minimize reflection loss and dielectric loss of power radiated from an antenna in an environment where radio waves are barren such as a human head tissue. That is, in FIG. 5, radiation characteristics of the antenna may be improved according to a combination of an appropriate thickness and dielectric constant of the insulating layer 201 and the housing 101.

Realizes highly reliable wireless communication in such a barren environment, and applies bio-telemetry technology to brain-computer-interface, deep-brain-simulation (DBS), etc. In order to do this, optimization of insulator design specifications is required.

On the other hand, when relying on full-wave electromagnetic simulation to analyze the antenna radiation characteristics according to the characteristics of the inserted insulating layers 200 and 201, it takes a lot of computation time, so its use is limited and there are difficulties in optimization.

As shown in FIG. 5, the radio wave environment in which the inserted antenna 10 and the receiving antenna 20 are present in the human body can be simplified into a model in the form of a shell problem.

The analytical solution using the spherical wave theory according to an embodiment of the present invention designs insulating layers 200 and 201 having an optimized dielectric constant and thickness to have high reliability in wireless signal transmission. can do.

In addition, the electrical characteristics of each hair tissue can be replaced with a homogeneous head model as shown in [Table 1] below.

[Table 1] Homogeneous head model

In the shell problem, the thickness of the insulating layer 201 (r1), the thickness of the housing 101 (τ ₁ ), the thickness of the head model 800 (τ ₂₎ ), Power transmission efficiency (PTE) according to the angle θ formed by the transmit antenna 301 and the receive antenna 20,

, Port 1: transmit antenna 301, Port 2: receive antenna (20)) It is possible to derive a calculation formula.

In this case, in the case of the insulating layer 201 and the head model 800 in FIG. 5, the dielectric constant, the permeability, and the dielectric loss as well as the thickness may be set as design variables.

In addition, since the brain implantation antenna 10 according to an embodiment of the present invention has a very small electrical size, it can be assumed that only _{the lowest order TM 10} and TE _{10 spherical models are radiated.} In addition, additional propagation scattering by the shell is not taken into account.

[Equation 1] below represents the magnetic vector potential that causes the TM mode in each region indicated in the shell problem of FIG. 5, and specific coefficients (a ₁ , b ₁ , c ₁ , d ₁ , e ₁ , f ₁ ) is divided into a multiplied traveling wave and a standing wave component.

[Equation 1]

Here, each term in [Equation 1] is as follows.

-

: Legendre function of the first kind

-

: Alternative spherical Hankel function of second kind

-

: Alternative Spherical Bessel function of the first and second kind

At this time, the E and H-field components of each region can be obtained through the vector potential, and coefficients (a _{1: TM} , b) as shown in [Equation 2] below through the boundary conditions between regions _1:TM , c _1:TM , d _1:TM , e _1:TM , f _1:TM ) system of equations can be derived.

[Equation 2]

_{The PTE (PTE TM} ) value between the transmitting and receiving antennas operating in the TM mode may be calculated as shown in [Equation 3] below using a coefficient obtained through [Equation 2].

[Equation 3]

In addition, as shown in [Equation 4] below, an equation for an electric vector potential that causes a TE mode can be extracted, and can be divided into a traveling wave and a standing wave component according to each region indicated in FIG. I can.

[Equation 4]

At this time, the E and H-field components of each region can be obtained through the vector potential, and the coefficients (a _1:TE , b) as shown in [Equation 5] below through the boundary conditions between the regions _1:TE , c _1:TE , d _1:TE , e _1:TE , f _1:TE ) system of equations can be derived.

[Equation 5]

_{In addition, the PTE (PTE TE} ) value between the transmitting and receiving antennas operating in the TE mode may be calculated as shown in [Equation 6] below.

[Equation 6]

In this way, the insulating layer 200 having a dielectric constant and thickness optimized for the brain implanted antenna 10 may be designed through power transmission efficiency (PTE).

6A, 6B, and 6C are graphs showing the maximum power transfer efficiency (MPTE) according to the size of a non-loss region in an antenna of the same size. That is, FIGS. 6A, 6B, and 6C show the maximum power transfer efficiency (MPTE) transmitted to the reception antenna 20 outside the living tissue when a free space, which is a non-loss medium, exists in the housing of the implantable antenna. Is the result of deriving.

FIG. 6A is 403.5 MHz corresponding to the MICS frequency band, FIG. 6B is 2.4 GHz corresponding to the ISM frequency band, and FIG. 6C shows the operation of 5.8 GHz corresponding to the UWB frequency band.

As shown in FIGS. 6A, 6B, and 6C, it can be seen that securing a non-loss region in all of the frequency bands of MICS, ISM, and UWB can obtain higher maximum power transfer efficiency (MPTE). .

_{In addition, when the size of the antenna is the same, it can be seen that the larger the size (r 1} ) of the non-loss region, which is the insulating layer 201, the higher the maximum transmission efficiency (MPTE) in a frequency band mainly used for implantable medical devices.

7 is a graph showing antenna radiation efficiency according to the dielectric constant of the insulating layer 200. That is, FIG. 7 is a graph showing comparison of antenna radiation efficiencies according to dielectric characteristics of a dielectric with low high dielectric constant, which is a non-loss medium inserted into the antenna.

In general, the implantable antenna requires a low-profile design for insertion into the human body. Therefore, securing a large size of the non-loss region is inevitably limited.

As shown in FIG. 7, the higher the dielectric constant of the dielectric inserted into the antenna, the higher the radiation efficiency. That is, it can be seen that the radiation efficiency of the antenna is improved as the dielectric constant of the non-loss region inserted into the antenna is increased, although the same is the same non-loss region. In the case of ultrapure water (UPW), the dielectric loss is close to 0 and the relative dielectric constant reaches 80.

Therefore, the brain implantation antenna 10 to which the ultrapure water-based insulator is applied according to the embodiment of the present invention uses an ultrapure water (UPW)-based dielectric as the insulating layer of the human body insertion antenna, so that about 50% compared to using the free space (Air). There is an effect that can improve the radiation efficiency of.

8 is a graph showing reflection coefficients and gain characteristics of an antenna according to whether or not a broadband feed line 500 is applied. That is, FIG. 8 is a diagram showing a reflection coefficient characteristic and a gain characteristic of an antenna according to the presence or absence of an L-shaped open stub of the broadband feed line 500 according to an embodiment of the present invention.

In FIG. 8, the blue solid line representing the reflection coefficient when the L-shaped open stub is not applied is not impedance matched below -10dB, but represents the reflection coefficient when the L-shaped open stub is applied. The blue dotted line shows that impedance matching is made below -10dB in the target ultra-wide band.

In addition, in FIG. 8, a red dotted line indicating a gain when an L-shaped open stub is applied is a red solid line indicating a gain when an L-shaped open stub is not applied. In comparison, it can be seen that the gain of 1dB or more appears higher over the entire band.

That is, it can be seen that the brain insertion antenna 10 to which the L-shaped open stub indicated by the dotted line in FIG. 8 is applied exhibits an impedance matching characteristic in the target band and an average gain of about -20 dB or more in the aiming region. .

As described above, the brain implanted antenna 10 to which the ultrapure water-based insulator is applied according to an exemplary embodiment of the present invention satisfies a broadband operating band and satisfies a gain characteristic of a very high level compared to a conventional implantable antenna. Accordingly, there is an effect of ensuring a high information transmission rate and stable transmission through securing a broadband/high gain characteristic.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and is easily changed from the embodiments of the present invention by those of ordinary skill in the art to which the present invention pertains. Includes all changes to the extent deemed acceptable.

[Explanation of code]

10: brain insertion antenna 20: receiving antenna

100: upper antenna housing 101: housing

200, 201: insulating layer 300: slot antenna

301: transmit antenna (Tx) 310: slot

320: anti-radiation layer 400: RF substrate

500: broadband feed line 510: feed line

520: feed resonance part 600: lower antenna housing

700: cable 800: head model

Claims (5)

1. An RF substrate;

   A slot antenna formed of a conductive metal and disposed on the RF substrate;

   An upper antenna housing made of a biocompatible material on the slot antenna to block the inflow of foreign substances;

   An insulating layer disposed between the upper antenna housing and the slot antenna to implement radiation characteristics of the antenna and prevent oxidation;

   A broadband feed line formed as a microstrip line of a conductive metal and disposed at the lower end of the RF substrate to cause an impedance matching characteristic and an efficient radiation mode of the slot antenna; And

   A brain insertion antenna to which an ultrapure water-based insulator is applied, including a lower antenna housing made of a biocompatible material at the lower end of the broadband feed line to block the inflow of foreign substances.
2. The method of claim 1,

   The insulating layer is an ultra-pure water-based insulator applied to the brain implanted antenna, characterized in that made of an ultra-pure water-based dielectric, which is an extremely low lossy medium.
3. The method of claim 1,

   The broadband feed line is an ultrapure water-based insulator-applied brain insertion antenna, characterized in that two L-shaped open stubs are symmetrically provided at the ends of the line to match impedance.
4. The method of claim 3,

   The broadband feed line provided with the L-shaped open stub includes MICS (Medical Implant Communication System) and MedRadio (Medical Device Radiocommunication Service), ISM (Industrial Scientific and Medical) based on the matching characteristics of the antenna covering the ultra-wide band. , Ultra-wide band (UWB), characterized in that for radiating radio waves in the frequency band, ultra-pure water-based insulator applied brain implanted antenna, characterized in that.
5. The method of claim 1,

   The slot antenna is formed of a circular antenna, a brain insertion antenna to which an ultrapure water-based insulator is applied, characterized in that a rectangular slot is provided inside.

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