KR20220008459A - Dipole antenna for intraoral tongue drive system - Google Patents

Abstract

The present invention relates to a dipole antenna for use in an oral cavity. The dipole antenna includes: a dielectric substrate; a meander-shaped radiating patch disposed on the dielectric substrate and formed including at least one of at least one horizontal and vertical slot; a capacitor positioned under the dielectric substrate; and a coating layer which protects the dielectric substrate. Through this, the present invention can overcome a problem of spatial compatibility and detuning caused by various conditions of an oral environment.

Description

DIPOLE ANTENNA FOR INTRAORAL TONGUE DRIVE SYSTEM

The present invention relates to a dipole antenna included in an intraoral tongue drive system, and more particularly, to a dipole antenna having stable impedance matching characteristics for use in the oral cavity.

Quadriplegia can be caused by spinal cord injury, amyotrophic lateral sclerosis, or stroke, and it is not easy for a quadriplegic patient to control a computer, smart device, or wheeled mobility device without the help of a guardian. Therefore, it is necessary to improve the functional ability and independence of patients with quadriplegia using assistive technology.

One of the assistive technologies, the Tongue-Drive System (TDS), is a tongue-operated assistive technology that is non-invasive, secure, flexible and robust. Based on the characteristics of the human tongue, the tongue drive system can maintain motor ability by directly connecting with the brain through the pituitary nerve when a spinal cord injury or other neurological disease occurs.

The tongue drive system consists of an intraoral Tongue-Drive System (iTDS) that attaches to a dental retainer and an extraoral Tongue-Drive System (iTDS) based on magnetic sensors mounted on the outside of the mouth around the cheek. , eTDS). In the case of the intraoral tongue drive system, a small magnetic tracer is implanted at the tip of the tongue, and the magnetic sensor detects magnetic fluctuations generated around the tracer through tongue movement and is wirelessly transmitted to an external receiving device worn by the user by an intraoral antenna. works in a way The external receiving device may process the sensor signal to generate a control signal to control a wheelchair, a computer, a smart device, and the like.

However, the communication between the antenna of the tongue drive system in the oral cavity and the external receiving device is susceptible to signal degradation or loss due to the absorption of power into the mouth at radio frequency (RF), the dynamic operating environment due to the movement of the tongue and jaw, and exposure to saliva. There is a difficulty in that there is a high possibility of performance degradation due to generation, antenna size, and frequency-dependent problems.

An object of the present invention is to solve the above problems, and to provide a dipole antenna that can be used in a tongue drive system in the oral cavity.

Another object of the present invention is to provide a dipole antenna having a small size so as to provide stable input impedance and broadband characteristics, and to be implantable at the tip of the tongue.

The present invention for achieving this object, in a dipole antenna usable in the oral cavity, a dielectric substrate, a meander-shaped radiation patch formed including at least one of at least one of at least one horizontal and vertical slot located on the dielectric substrate, and a capacitor positioned under the dielectric substrate and a coating layer protecting the dielectric substrate.

According to the present invention as described above, it is possible to provide a dipole antenna that can be used in a tongue drive system in the oral cavity, the dipole antenna provides stable input impedance and broadband characteristics, and can be implanted at the tip of the tongue due to its small size. In addition, it is possible to overcome the problems of spatial fit and detuning caused by various conditions of the oral environment through the antenna.

1 is a view showing the configuration of a dipole antenna according to an embodiment of the present invention;
2 is a view showing a radiation patch of a dipole antenna according to an embodiment of the present invention;
3 is a diagram illustrating a current distribution in a 915 MHz band of a dipole antenna according to an embodiment of the present invention;
4 is a graph showing the experimental results of measuring the radiation efficiency for each thickness in order to adopt the thickness of the coating layer of the dipole antenna according to an embodiment of the present invention;
5 is a diagram illustrating an operation circuit of a dipole antenna according to an embodiment of the present invention;
6 is a view for explaining conditions for a performance test of a dipole antenna according to an embodiment of the present invention;
7 is a graph for comparing the reflection coefficient measured through simulation and the reflection coefficient measured in the real environment;
Fig. 8 shows the radiation pattern and propagation direction to meet the propagation direction requirement of the application of the tongue drive system in the oral cavity;
9 is a view showing the SAR distribution for 1g tissue in the 915MHz frequency band in the open state and the closed state of the oral cavity;
10 is a diagram illustrating a link budget analysis result for evaluating a communication range of a dipole antenna according to an embodiment of the present invention.

The above-described objects, features and advantages will be described below in detail with reference to the accompanying drawings, and accordingly, those of ordinary skill in the art to which the present invention pertains will be able to easily implement the technical idea of the present invention. In describing the present invention, if it is determined that a detailed description of a known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

In the drawings, the same reference numerals are used to indicate the same or similar elements, and all combinations described in the specification and claims may be combined in any manner. And unless otherwise provided, it is to be understood that references to the singular may include one or more, and references to the singular may also include plural expressions.

The terminology used herein is for the purpose of describing specific exemplary embodiments only and is not intended to be limiting. As used herein, singular expressions may also be intended to include plural meanings unless the sentence clearly indicates otherwise. The term “and/or,” “and/or” includes any and all combinations of the items listed therewith. The terms "comprises", "comprising", "comprising", "comprising", "having", "having", etc. have an implicit meaning, so that these terms refer to their described features, integers, It specifies steps, operations, elements, and/or components and does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The steps, processes, and acts of the methods described herein should not be construed as necessarily performing their performance in such a specific order as discussed or exemplified, unless specifically determined to be an order of performance thereof. . It should also be understood that additional or alternative steps may be used.

In addition, each of the components may be implemented as a hardware processor, the above components may be integrated into one hardware processor, or the above components may be combined with each other and implemented as a plurality of hardware processors.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

The dipole antenna according to an embodiment of the present invention is applied to an intraoral tongue-drive system (iTDS) designed to be used by users with severe disabilities, and has stable and wide bandwidth characteristics. Due to these characteristics, the dipole antenna can overcome the spatial suitability and detuning problems caused by various conditions of the oral environment.

1 is a diagram illustrating a configuration of a dipole antenna according to an embodiment of the present invention. Referring to FIG. 1 , the dipole antenna may include a dielectric substrate 10 , a radiation patch 20 , a capacitor 30 , and a coating layer 40 .

The dielectric substrate 10 is formed of flexible polyimide (εr = 4.3 and tanδ = 0.004). The dielectric substrate 10 using polyimide provides elasticity and rigidity against potential damage that may occur to the dipole antenna. can do. The material of the dielectric substrate 10 is not limited to polyimide, and alumina, zirconia, PMMA, Carbon-Ti, or the like may be used.

The size of the dielectric substrate 10 is 19.8 mm x 4.2 mm x 0.025 mm, which is formed to be very small so that it can be sufficiently attached to the dental retainer.

The radiation patch 20 is formed on the dielectric substrate 10 and is made of a conductive material. The radiation patch 20 includes at least one horizontal slot and a vertical slot, and each horizontal slot and the vertical slot may be connected to each other to form a meander shape as a whole. As a result, the radiation patch 20 may have a shape in which one slot is arranged in a serpentine shape, and may have a meander shape bent 20 times in total. The specific shape of the radiation patch may refer to FIG. 2 .

Shorting pins may be included at both ends of the slot of the radiation patch 20 , for attaching the capacitor 30 to the lower portion of the dielectric substrate 10 . The capacitor 30 according to an embodiment of the present invention is used to ensure a stable impedance, and the capacitor 30 may have a capacity of 11 pF, but is not limited thereto.

Due to the shape of the radiation patch 20, the current flow path is the same as that of the existing antenna, but has the effect of reducing the size of the dipole antenna.

Also, in general, the shape of the radiation patch included in the antenna has a great influence on the radiation efficiency of the antenna. Since the efficiency of the antenna largely depends on the surface area of the radiation patch, the dipole antenna of the present invention can have a stable radiation efficiency of -27.1 to -17.3 dB over a wide band due to the shape of the radiation patch 20, and operates in the 915 MHz band can do. The current distribution of the dipole antenna of the present invention in the 915 MHz band is shown in FIG. 3 . Referring to FIG. 3, it can be seen that the current distribution of the dipole antenna is very uniform, thereby stabilizing the input impedance of the antenna and achieving a wide band.

However, since the above-described numerical values are merely examples, the present invention is not limited to these numerical values.

The dipole antenna according to an embodiment of the present invention protects the antenna from direct contact with saliva, thereby preventing a short circuit when the radiation patch 20 is exposed, and a dielectric substrate to provide biocompatibility of the antenna. The entire surface of (10) may be coated with the coating layer (30). In this case, the coating layer 30 may be formed of a biocompatible material.

A biocompatible material refers to a material that does not exhibit a rejection reaction when in contact with a living tissue or body fluid, etc. In this case, the rejection reaction may be irritation, inflammation, allergy, cancer, destruction or transformation of blood components, thrombus formation, etc. have.

For the coating layer 30 according to an embodiment of the present invention, polydimethylsiloxane (PDMS) may be used as a biocompatible material, or other biocompatible materials may be used.

The coating layer 30 may be formed to a thickness of 0.1 mm. As the coating layer 30 has a thickness of 0.1 mm, the size of the dipole antenna may be further reduced.

If the coating layer 30 is formed thinner, the size of the dipole antenna can be further reduced, but the dipole antenna of the present invention adopts a thickness of 0.1 mm for long-term protection of the antenna. 4 is a graph showing the results of an experiment measuring radiation efficiency by varying the thickness of the coating layer 30 of the dipole antenna to adopt the thickness of the coating layer 30. Referring to FIG. 4, the thickness of the coating layer 30 As it increases, it shows broadband characteristics, but maintains wideband characteristics at all thicknesses and resonates in the 915MHz frequency band, indicating that 0.1mm was adopted for the stability of the dipole antenna.

Due to the configuration of the dipole antenna as described above, the dipole antenna according to an embodiment of the present invention is formed in a very small size of 20 mm × 4.4 mm × 0.025 mm, which provides sufficient bandwidth and gain to maintain stable operation in human tissues. can have

5 is a diagram illustrating an operation circuit of a dipole antenna according to an embodiment of the present invention. A dipole antenna can be viewed as a radiation element closely related to resonance in which parts of adjacent bands overlap. element) can be modeled.

However, in the case of broadband communication, multiple parallel RLC circuits are cascaded to adjacent bands. Referring to FIG. 5 (a), the dipole antenna is based on a degenerative Foster canonical model and was designed using ADS software. Lp and Cp shown in (a) of FIG. 5 mean inductance and capacitance when the dipole antenna is operating at a low frequency.

The remaining high resonance is realized using three RLC circuits connected in a cascade. The parameters R1, R2, R3 represent the radiation resistance of each resonance involved, the middle RLC circuit (R2, L2, C2) controls the broadband lower end, the right RLC circuit (R3, L3, C3) controls the high frequency, The left RLC circuit (R1, L1, C1) coordinates the match within the band. C4 represents the capacitor loaded when the dipole antenna is electrostatically loaded.

The numerical values of each component constituting the circuit shown in FIG. 5A are the same as those of FIG. 5B.

6 is a view for explaining conditions for a performance test of a dipole antenna according to an embodiment of the present invention.

In the dipole antenna according to an embodiment of the present invention, simulation was performed through Ansoft HFSS software. As shown in FIG. 6 , simulations were performed for each of the open state and the closed state of the oral cavity, and a three-dimensional head with saline having similar dielectric properties to that of a human mouth was used to measure the performance of the oral cavity open state. A model was created, and an air box having a size of 63 mm × 50 mm × 15 mm was used. On the other hand, to measure the performance of the closed oral cavity, a curved cavity was formed in minced pork and a dipole antenna was placed inside the cavity.

In such an environment, the performance of the dipole antenna was evaluated in terms of radiation pattern, reflection coefficient, and SAR.

For verification of the simulation results, the dipole antenna was coated with a thin layer of biocompatible PDMS as shown in Fig. 6(c), and as shown in Fig. 6(d) and (e), A vector network analyzer was used to measure the reflection coefficient of the dipole antenna in the subject's actual oral cavity.

The simulated and actually measured reflection coefficients can be confirmed through FIG. 7 . Referring to FIG. 7 , it can be seen that the oral cavity maintains broadband and stable impedance matching in both the open state and the closed state.

Hereinafter, the results of verifying the performance of the dipole antenna through the experimental results of the simulation will be described.

1) Bandwidth

The bandwidth of the dipole antenna measured through simulation is 151% (813-2,200MHz) when the mouth is open and 163% (700-2,194MHz) when the mouth is closed. It can be seen that the bandwidth of the dipole antenna measured in the oral cavity is similar to 142% (820-2,120 MHz) and 181% (720-2,380 MHz), respectively. That is, the dipole antenna according to an embodiment of the present invention will have excellent performance in various environments of the actual oral cavity.

2) Radiation pattern

8 is a view showing a radiation pattern and a propagation direction to meet the propagation direction requirements of the application of the tongue drive system in the oral cavity. Referring to FIGS. 8 (a) and (b), the signal of the dipole antenna is It can be seen that the conditions for the required application were satisfied when propagated to the outside, and FIGS. It can be seen that (c) and (d) have similar shapes to each other. Specifically, the maximum peak values observed in the simulation and actual measurement are very similar to -17.5 and -17.96 dBi in the case of the open mouth, and -18.94 and -19.42 dBi in the case of the closed oral cavity.

3) SAR (absorption rate)

The operation of the antenna located inside the oral cavity is difficult due to the direct contact with the oral tissue and the power absorbed by the oral tissue. is limited to less than 1.6 W, 2 W/kg. In this simulation, the input power was set to 1W by calculating the SAR and maximum allowable power for 1g of tissue. 9 is a view showing the SAR distribution for 1g tissue in the 915 MHz frequency band in the open state and the closed state of the oral cavity. The maximum SAR of 108.25W/kg at mW and the maximum allowable power value in the closed state of the oral cavity were set as the maximum SAR of 120.09W/kg at 13.3mW. This value satisfies both international and national safety guidelines, and it has been proven that the dipole antenna according to an embodiment of the present invention operates safely in various environments in the oral cavity.

4) Communication range

Link budget analysis may be used to evaluate a communication range in which the dipole antenna according to an embodiment of the present invention can efficiently communicate with an external receiving device. Communication range is greatly affected by reflection, scattering, absorption, path loss, and mismatch loss.

10 is a diagram illustrating a link budget analysis result for evaluating a communication range of a dipole antenna according to an embodiment of the present invention.

Figure 10 (a) shows the parameters of the conventional intraoral tongue drive system, the dipole antenna according to an embodiment of the present invention calculates a link budget based on the existing parameters to evaluate the communication range (link margin) can be fixed at 35dB). The calculated link budget is the same as that of FIG. 10 (b). Referring to this, the dipole antenna is effectively at a distance of at least 20 m at a data rate of 250 kbps and at least 36 m at a data rate of 24 kbps, even in the worst-case scenario (mouth is closed). It can be seen that communication is possible.

Simulation and actual measurement results prove that the dipole antenna according to an embodiment of the present invention is suitable for being applied to an intraoral tongue drive system that transmits data to an external receiving device in the oral cavity and has superior performance than the conventional antenna .

In conclusion, the dipole antenna according to an embodiment of the present invention requires a minimum installation space of 20 mm × 4.4 mm × 0.025 mm, and maintains stable wideband operation at an operating frequency of 915 MHz. The 915 MHz frequency band is less susceptible to power absorption by oral tissues, provides good radiation performance, and can provide improved availability compared to the congested 2.4 GHz band, which receives significant power absorption in the oral cavity.

Embodiments of the present invention disclosed in the present specification and drawings are merely provided for specific examples to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims (3)

In the dipole antenna usable in the oral cavity,
dielectric substrate;
a meander-shaped radiating patch disposed on the dielectric substrate and formed including at least one of at least one horizontal and vertical slot;
a capacitor positioned under the dielectric substrate; and
A dipole antenna comprising a coating layer for protecting the dielectric substrate.
The method of claim 1,
Shorting pins are formed at both ends of the slots included in the radiation patch,
The capacitor is a dipole antenna arranged to be connected to the dielectric substrate through the shorting pin.
The method of claim 1,
The coating layer is for protecting the dielectric substrate, the radiation patch, and the capacitor, the dipole antenna formed of a biocompatible material.

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