JP4447766B2 - Electromagnetic radiation suppressor and earphone provided with electromagnetic radiation suppressor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic radiation suppressor for suppressing an electromagnetic wave radiated from a cord of an earphone used for a portable communication device such as a cellular phone, and an earphone provided with the electromagnetic radiation suppressor.
[0002]
[Prior art]
In recent years, mobile phones, which are one type of portable communication device, have become a necessity for daily life, regardless of gender, and will become more important in the future as the information society advances. On the other hand, with the widespread use of mobile phones, there is a growing concern that electromagnetic waves radiated from mobile phones may adversely affect the human body.
[0003]
That is, the mobile phone is used in a high frequency band of, for example, 800 MHz to over 2 GHz, and its output also has a high value of 600 to 800 mW. In addition, since the earpiece disposed in the casing is used in a state where it is directed to the auricle and close to the head of the caller, it is radiated from an antenna disposed in the vicinity of the earpiece. It has been pointed out that there is a possibility that the incidence of brain tumors may be increased because electromagnetic waves are directly applied to the caller's head. For this reason, it is recommended not to use the mobile phone in the state close to the head of the caller by connecting the microphone and the earphone.
[0004]
[Problems to be solved by the invention]
However, the operation of the antenna of the mobile phone is not only the antenna portion but also the housing, and a part of the housing is responsible. When the earphone 102 is attached to the mobile phone 101 as shown in FIG. 7, it is attached to the earphone main body 103. The cord (cable) 104 may be irradiated with electromagnetic waves. That is, in the finite-length cord 104, when the electrical length (electric length) is an odd multiple of a quarter wavelength of the electromagnetic wave, resonance occurs and a standing wave SW is generated. The head 104 is radiated and irradiated to the head.
[0005]
The electrical length here is not the physical length of the cord 104, but the various cases such as the case of the mobile phone 101, the hand holding the cord 104, the shape of the cord 104, the type of covering material, the state of the cord 104 being routed, etc. The elements of are involved and determined. For this reason, it is difficult to determine when standing waves are generated and electromagnetic waves are radiated, and it is difficult to suppress the generation of electromagnetic waves effectively by suppressing the generation of standing waves. There is a problem with it.
[0006]
The present invention has been made in view of such circumstances, and provides an electromagnetic radiation suppressor capable of effectively suppressing electromagnetic waves radiated from the earphone cord and an earphone provided with the electromagnetic radiation suppressor. The purpose is to do.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is an electromagnetic radiation suppressor for suppressing an electromagnetic wave radiated from the cord by being provided on a cord of an earphone used in a portable communication device, It is characterized by comprising a magnetic body that covers a part, and a lossy dielectric disposed so as to cover the magnetic body.
[0008]
According to this configuration, the electromagnetic wave is effectively absorbed by the action of the magnetic substance and the lossy dielectric, and even if a standing wave is generated, the electromagnetic wave radiated from the earphone cord is effectively suppressed. be able to.
[0009]
The invention of claim 2 is characterized in that, in the invention according to claim 1, the lossy dielectric is extended so as to cover a region adjacent to the magnetic body of the cord.
[0010]
According to this configuration, the electromagnetic wave is absorbed by the lossy dielectric material even in a portion where the magnetic material of the cord does not exist, and the electromagnetic wave radiated from the cord of the earphone can be more effectively suppressed.
[0011]
The invention of claim 3 is characterized in that, in the invention according to claim 2, the lossy dielectric is made of a flexible material.
[0012]
According to this configuration, the electromagnetic wave radiated from the cord of the earphone can be effectively suppressed, while the end portion of the cord with respect to the magnetic body can be reinforced, and the cord is cut at the end portion of the magnetic body. It is effectively prevented from being easily done.
[0013]
According to a fourth aspect of the present invention, there is provided the lowest carrier frequency according to any one of the first to third aspects, wherein an equivalent electric length obtained by synthesizing the magnetic body and the lossy dielectric body is a target for suppressing a standing wave. It is characterized by having a length of at least 1/4 wavelength.
[0014]
According to this configuration, it can be applied to all portable communication devices such as mobile phones used in a frequency region above the minimum carrier frequency, and can be excellent in versatility.
[0015]
The invention of claim 5 is characterized in that the electromagnetic radiation suppressor according to any one of claims 1 to 4 is provided in a part of a cord of an earphone used for a portable communication device.
[0016]
According to this configuration, the electromagnetic wave is effectively absorbed due to the action of the magnetic body and the lossy dielectric, and even if a standing wave is generated, the electromagnetic wave radiated from the cord can be effectively suppressed. Earphone can be realized.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing an earphone to which an electromagnetic radiation suppressor according to a first embodiment of the present invention is attached. In this figure, an earphone 10 is used by being attached to a mobile phone which is one of portable communication devices, and includes a cord (cable) 12, an earphone main body 14 connected to one end of the cord 12, and a cord 12. A connector 16 connected to the other end of the wire, a magnetic body 18 with loss (hysteresis loss and dielectric loss) disposed so as to cover the cord 12 at a position near the earphone main body 14 in the cord 12, and a magnetic body 18 And a lossy dielectric 20 disposed so as to cover.
[0018]
The earphone 10 is one in which a bone-ear microphone composed of a condenser microphone or the like is built in the earphone main body 14. Further, the cord 12 is formed by covering a signal line disposed inside with an insulating outer skin 121. The magnetic body 18 and the lossy dielectric body 20 constitute an electromagnetic radiation suppressor 22.
[0019]
The magnetic body 18 is composed of a ferrite core (for example, an outer diameter of 8.5 mm and a length of 16 mm) that is a cylindrical soft magnetic body having a through-hole 181 in the center, and the through-hole 181 serves as a cord 12. The cord 12 is disposed so as to cover the cord 12 by being inserted in a close state. The magnetic body 18 may be provided in the cord 12 by inserting the cord 12 through the through hole 181 before attaching the earphone main body 14 or the connector 16 to the end portion of the cord 12, or 2 along the axial direction. A split structure such as splitting may be used, and the respective divided pieces (divided portions) may be integrated by being abutted from the outer periphery of the cord 12 and bonded or fixed by winding a tape.
[0020]
The lossy dielectric 20 is made of a non-woven sheet (for example, 50 mm in length) having flexibility and having a surface resistance of about 40Ω / □ by including carbonized fibers and the like. In addition to covering the magnetic body 18, the area adjacent to the area covered with the magnetic body 18 of the cord 12, and disposed so as to cover the cord 12 on the opposite side of the earphone main body 14.
[0021]
FIG. 2 shows an electromagnetic radiation suppression characteristic of the electromagnetic radiation suppressor 20 provided in the earphone 10 configured as described above together with other comparative examples in the frequency range of 800 to 2300 MHz. In this figure, symbol A is the one of the present invention in which the magnetic body 18 and the lossy dielectric 20 are provided, symbol B is that of the first comparative example in which only the lossy dielectric 20 is provided, and symbol C is the lossy dielectric of the magnetic material 18. The thing of the 2nd comparative example of only the code | cord | chord 12 which does not provide the body 20 is each shown. The horizontal axis in FIG. 2 indicates the frequency (MHz), and the vertical axis indicates the attenuation from the maximum resonance point (maximum radiation point).
[0022]
The suppression characteristic of electromagnetic wave radiation shown in FIG. 2 is obtained as follows. That is, as shown in FIGS. 3A and 3B, the earphone main body 14 is attached to the auricle ER of the polystyrene foam head HD, and the cord 12 is fixed at a predetermined position so as not to move. On the other hand, a 3 mm square micro loop antenna LA made of a metal wire is disposed at a substantially central position P in the head HD (position separated from the pinna ER by a dimension d). Then, a predetermined level of electromagnetic waves is radiated from the cable 12 in a frequency range of 800 to 2300 MHz in a predetermined step, and a high frequency voltage induced in the minute loop antenna LA at this time is measured with an RF level meter LM. The amount of attenuation from the maximum resonance point (maximum radiation point) is obtained.
[0023]
As can be seen from FIG. 2, the reference numeral A according to the present invention shows excellent suppression characteristics in the entire measurement frequency range as compared with the first and second comparative examples indicated by reference numerals B and C. Yes. For this reason, the first generation mobile phone having a use frequency (carrier frequency) of 840 to 970 MHz, the second generation mobile phone having a use frequency of, for example, 1500 to 1900 MHz, and the third generation mobile phone having a use frequency of 1800 to 2200 MHz. It can be applied to any mobile phone.
[0024]
For example, at the resonance point of 900 MHz, the code A of the present invention is improved by 12 dB over the code C of the second comparative example, and has a sufficient suppression characteristic. On the other hand, the code B of the first comparative example is only 8 dB better than the code C of the second comparative example, and the suppression characteristic is not sufficient. At 1360 MHz, which is another resonance point, the code A has an improvement of 16 dB over the code C, and has sufficient suppression characteristics. On the other hand, the code B is only 10 dB better than the code C, which is not necessarily sufficient. At 1800 MHz, which is another resonance point, the code A has an improvement of 13 dB over the code C, and has a sufficient suppression characteristic. On the other hand, the code B has only 6 dB improvement over the code C, and the suppression characteristic is insufficient.
[0025]
Thus, the reason why the loss dielectric 20 provided so as to cover the magnetic body 18 is excellent in suppression characteristics is as follows. That is, the standing wave is periodically generated in the wavelength direction at the electric field maximum point (magnetic field minimum point) and the electric field minimum point (magnetic field maximum point). When the cable 12 is covered with the magnetic body 18, the maximum magnetic field is obtained. The point effectively absorbs the magnetic field, but does not function at the maximum electric field point (minimum magnetic field point). However, in the present invention, since the magnetic body 18 is covered with the loss dielectric 20, the magnetic body 18 functions as a dielectric at the maximum electric field and absorbs the electromagnetic wave together with the loss dielectric 20. It has excellent suppression characteristics. Since the lossy dielectric 20 has no effect on the magnetic field, a sufficient suppression characteristic cannot be obtained by simply covering the lossy dielectric 20 with the lossy dielectric 20.
[0026]
Further, a predetermined calculation is performed on the relationship between the characteristic impedance between the insulating sheath 121 of the cable 12 and the magnetic body 18 and the lossy dielectric 20 and the equivalent resistance in the thickness direction (radial direction) of the magnetic body 18 and the lossy dielectric 20. As a result of theoretical analysis based on the equation and the like, the ratio of the equivalent resistance in the thickness direction of the magnetic body 18 and the loss dielectric 20 to the characteristic impedance between the insulating shell 121 and the magnetic body 18 and the loss dielectric 20 is 100 ±. It was revealed that excellent suppression characteristics were exhibited when the ratio was 60% (preferably 100 ± 50%).
[0027]
In addition, as a result of analyzing the relationship between the equivalent electrical length formed by combining the magnetic body 18 and the lossy dielectric body 20 and the carrier frequency (use frequency) that is the object of suppression of the standing wave based on a predetermined calculation formula, It is clear that the equivalent electrical length formed by combining the magnetic body 18 and the lossy dielectric body 20 exhibits excellent suppression characteristics when it has a length equal to or longer than ¼ wavelength of the carrier frequency to be suppressed for standing waves. It became.
[0028]
Therefore, in order to make the earphone to which the electromagnetic radiation suppressor 20 according to the present invention is applied and the earphone provided with the electromagnetic radiation suppressor 20 applicable to a plurality of mobile phones having different carrier frequencies, the magnetic body 18 and the loss dielectric It is only necessary that the equivalent electrical length formed by combining 20 and the length of the minimum carrier frequency to be suppressed by the standing wave has a length of at least ¼ wavelength. For example, if the lowest carrier frequency to be suppressed is 840 MHz of the first generation mobile phone, the equivalent electrical length is set to have at least a quarter wavelength of this frequency. It can be applied to each frequency of the first generation, second generation, and third generation. Of course, in the case where it is applicable only to the frequency of the second generation or the frequency of the third generation, the length of the magnetic body 18 and the loss dielectric 20 can be made shorter than that of the embodiment.
[0029]
The equivalent electrical length is the physical length when the complex permeability μ of the magnetic body 18 is represented by μ = μ′−jμ ″, and the complex permittivity ε of the loss dielectric 20 is represented by ε = ε′−jε ″. × Re√ (μr × εr). Here, Re represents the complex permeability and the real number of the complex permittivity, μr represents the equivalent complex permeability, and εr represents the equivalent complex permittivity.
[0030]
FIG. 4 is a diagram showing an earphone 10 ′ according to a second embodiment of the present invention. This earphone 10 'differs from the earphone 10 of the first embodiment only in that an electromagnetic radiation suppressing body 22 comprising a magnetic body 18 and a lossy dielectric body 20 is attached in the vicinity of the connector 16 of the cord 12. Are the same and will not be described in detail.
[0031]
FIG. 5 shows the suppression characteristics of the electromagnetic radiation of the earphone 10 ′ configured as described above in comparison with the electromagnetic radiation suppressing body 22 not provided in the frequency range of 800 to 2300 MHz. In this figure, the symbol D indicates the one of the present invention provided with the magnetic body 18 and the lossy dielectric 20, and the symbol E indicates only the cord 12 without the electromagnetic radiation suppressing body 22. As is apparent from FIG. 5, the device according to the present invention indicated by the symbol D has excellent suppression characteristics in the entire frequency range as compared with the device without the electromagnetic radiation suppressor 22 indicated by the symbol E. . The suppression characteristic of electromagnetic wave radiation shown in FIG. 5 is obtained by the same method as in the first embodiment, and the horizontal axis indicates the frequency (MHz) and the vertical axis indicates the same as in FIG. It shows the amount of attenuation from the maximum resonance point (maximum radiation point).
[0032]
As shown in FIG. 6, when the relationship between the frequency of electromagnetic waves in the head HD and the degree of attenuation is approximately calculated within the frequency allocation range of the cellular phone, the electric field indicated by the chain line is greatly attenuated. The magnetic field indicated by the solid line is not attenuated so much. For this reason, it can be said that the influence of the electromagnetic wave on the head is larger in the magnetic field than in the electric field. The attenuation characteristic in the head HD shown in FIG. 6 is that a mobile phone is placed at a position 5 mm away from the head HD, and the attenuation at the position of 5 mm in the head HD is the specific resistance ρ in the brain ρ = 200Ω. · Cm, the dielectric constant ε of which is calculated with ε = 50 and εr = 50−j (1 / ωερ).
[0033]
The electromagnetic radiation suppressor 22 and the earphones 10 and 10 'provided with the electromagnetic radiation suppressor 22 according to the present invention include a magnetic body 18 covering a part of the cord 12 of the earphone and the magnetic body as in the above embodiment. Since the lossy dielectric 20 is disposed so as to cover 18, the action of the magnetic body 18 and the lossy dielectric 20 can be combined to effectively suppress electromagnetic waves radiated from the cord 12. Can do.
[0034]
In addition, the earphone provided with the electromagnetic radiation suppressor and the electromagnetic radiation suppressor according to the present invention is not limited to the above-described embodiment, and various modifications as described below can be adopted.
[0035]
(1) In the above embodiment, ferrite is used as the magnetic body 18, but it may be made of another magnetic material. Further, it is preferable that the magnetic body 18 is disposed in close contact with the cord 12 as in the embodiment from the viewpoint of improving the suppression characteristic of electromagnetic wave radiation, but it is configured so that a slight gap is generated. Also good.
[0036]
(2) In the above embodiment, the lossy dielectric 20 is made of a nonwoven fabric, but is not limited thereto. For example, various materials such as ferrite rubber (rubber mixed with ferrite powder) and carbon rubber (rubber mixed with carbon powder) can be used. When a material having flexibility (flexibility) such as a nonwoven fabric or rubber is used, the end portion of the magnetic body 18 in the cord 12 can be reinforced, and the end portion of the magnetic body 18 is provided with the cord 12. Can be effectively prevented from being easily cut. Of course, it is not limited to what has flexibility, and it cannot be overemphasized that it can be used even if it does not have flexibility.
[0037]
Further, the lossy dielectric 20 has a divided structure such as being divided into two along the axial direction, and each divided piece (divided portion) is abutted from the outer periphery of the magnetic body 18 to be integrated. Good. In this case, the magnetic body 18 may be divided in the same manner, and the magnetic body 18 and the loss dielectric 20 may be integrated by an insulating case that covers the outer periphery of the loss dielectric 20.
[0038]
(3) In the above embodiment, the earphones 10 and 10 'are described as being used for a mobile phone which is one of portable communication devices, but can also be used for other communication devices such as a car phone. It is. Further, the communication system to be used is not limited to a specific one.
[0039]
(4) In the above embodiment, the earphones 10 and 10 ′ are described as so-called earphone microphones in which the ear-ear microphone is built in the earphone main body 14, but the present invention is not limited to this. For example, an earphone microphone in which an appropriate microphone such as a condenser microphone is attached in the middle of the cord 12 (a portion corresponding to the position of the mouth when the earphone main body 14 is attached to the auricle) may be used. It is also possible to make the earphone and the microphone independent of each other. For this reason, in this invention, what included the microphone in the earphone main body 14, the thing which attached the microphone in the middle of the code | cord | chord 12, the thing of a single earphone, etc. are named generically.
[0040]
(5) In the above embodiment, the lossy dielectric 20 covers the magnetic body 18 and covers the cord 12 that is adjacent to the region covered with the magnetic body 18 of the cord 12 and is opposite to the earphone main body 14. However, it is not limited to this. For example, the lossy dielectric 20 may be extended so as to cover the cords 12 in the regions on both sides adjacent to the region covered with the magnetic body 18 of the cord 12. Further, the lossy dielectric 20 may be disposed so as to substantially cover only the magnetic body 18. In short, the ratio of the equivalent resistance in the thickness direction of the magnetic body 18 and the lossy dielectric 20 to the characteristic impedance between the insulating sheath 121 of the cord 12 and the magnetic body 18 and the lossy dielectric 20 is in the range of 100 ± 60%. It only has to be set to be.
[0041]
(6) In the above embodiment, the electromagnetic radiation suppressing body 22 is described as being provided on the earphone body 14 side of the cord 12 and provided on the connector 16 side of the cord 12. Even if it is provided in the section, the suppression characteristic is also excellent. In short, it may be provided at least in part of the cord 12. In terms of characteristics, it is preferable to provide the electromagnetic radiation suppressor 22 on the side of the earphone main body 14 of the cord 12, but in this case, the weight on the earphone main body 14 side increases even if it is small. Become. For this reason, in terms of ease of use, it is preferable to provide the electromagnetic radiation suppressor 22 on the connector 16 side of the cord 12.
[0042]
【The invention's effect】
As described above, according to the electromagnetic radiation suppressing body of claim 1, since the magnetic body covering a part of the cord and the loss dielectric disposed so as to cover the magnetic body are provided, Even when electromagnetic waves are effectively absorbed by the action of the body and the lossy dielectric, and standing waves are generated, the electromagnetic waves radiated from the earphone cord can be effectively suppressed.
[0043]
According to the electromagnetic radiation suppressing body of the second aspect, since the lossy dielectric is extended so as to cover the area adjacent to the magnetic body of the cord, the electromagnetic wave is also generated by the lossy dielectric even in a place where the magnetic body does not exist. Is absorbed, and electromagnetic waves radiated from the earphone cord can be more effectively suppressed.
[0044]
According to the electromagnetic radiation suppressing body of the third aspect, since the loss dielectric is made of a flexible material, the end portion of the cord with respect to the magnetic body can be reinforced, and the cord is made of the magnetic body. It is possible to effectively prevent the end edge portion from being easily cut.
[0045]
According to the electromagnetic radiation suppressing body of claim 4, the equivalent electric length formed by combining the magnetic body and the lossy dielectric is at least 1/4 wavelength of the lowest carrier frequency to be suppressed for the standing wave. Therefore, it can be applied to all portable communication devices used at a frequency equal to or higher than the minimum carrier frequency, and can be excellent in versatility.
[0046]
According to the fifth aspect of the present invention, since the electromagnetic radiation suppressing body according to any one of the first to fourth aspects is provided in a part of the cord, the action of the magnetic body and the lossy dielectric body can be considered. Thus, the electromagnetic wave is effectively absorbed and the electromagnetic wave radiated from the cord can be effectively suppressed.
[Brief description of the drawings]
FIG. 1 is a diagram showing an earphone provided with an electromagnetic radiation suppressor according to a first embodiment of the present invention.
FIG. 2 is a characteristic diagram for explaining suppression characteristics of an electromagnetic radiation suppressor provided in the earphone shown in FIG. 1;
3A and 3B are diagrams for explaining a method of measuring the suppression characteristic of the electromagnetic radiation suppressor provided in the earphone shown in FIG. 1, wherein FIG. 3A is an external view of a head attached with the earphone, and FIG. It is a figure for demonstrating arrangement | positioning of a micro loop antenna.
FIG. 4 is a diagram showing an earphone provided with an electromagnetic radiation suppressor according to a second embodiment of the present invention.
FIG. 5 is a characteristic diagram for explaining suppression characteristics of an electromagnetic radiation suppressor provided in the earphone shown in FIG. 4;
FIG. 6 is a diagram illustrating the attenuation characteristics of electromagnetic waves in the head.
FIG. 7 is a diagram for explaining a relationship between a cord of an earphone attached to a mobile phone and a standing wave.
[Explanation of symbols]
10, 10 'Earphone 12 Cord 14 Earphone main body 16 Connector 18 Magnetic body 20 Loss dielectric 121 Insulation skin

Claims (5)

An electromagnetic radiation suppressor for suppressing an electromagnetic wave radiated from the cord by being provided on a cord of an earphone used in a portable communication device, the magnetic body covering a part of the cord, and covering the magnetic body An electromagnetic radiation suppressor comprising: a lossy dielectric disposed on the substrate. 2. The electromagnetic radiation suppressor according to claim 1, wherein the lossy dielectric is extended so as to cover a region adjacent to the magnetic body of the cord. 3. The electromagnetic radiation suppressor according to claim 2, wherein the lossy dielectric is made of a flexible material. The equivalent electric length formed by combining the magnetic substance and the lossy dielectric substance has a length of at least 1/4 wavelength of the lowest carrier frequency to be suppressed for standing waves. The electromagnetic radiation suppression body in any one. An earphone comprising the earphone cord used in a portable communication device provided with the electromagnetic radiation suppressor according to any one of claims 1 to 4.

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