JP3021316B2 - Unwanted electromagnetic wave absorption structure of mobile phone - Google Patents

Abstract

PURPOSE: To absorb spurious electromagnetic waves (harmonics) leaking from a portable telephone without attenuating basic waves of the telephone to minimize adverse affects by microwaves to a human body. CONSTITUTION: An absorbing structure for spurious electromagnetic waves from a portable telephone comprises an absorbing body 14 molded of a mixture of magnetic powder and rubber or resin into a ring wherein the body 14 is mounted at a foot of an antenna 12 of a housing 10 of the telephone. The magnetic powder may be iron powder, but preferably may be ferrite powder of manganese-zinc, nickel-zinc or magnesium-zinc. The ring-like absorbing body for spurious electromagnetic waves may be adhered to the housing or attracted to the housing at the foot of the antenna with a permanent magnet integrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for shielding and absorbing unnecessary electromagnetic waves such as harmonics leaking from a portable telephone, and more particularly, to a ring-shaped structure made of a mixture of magnetic powder and rubber or resin. The present invention relates to an unnecessary electromagnetic wave absorbing structure of a mobile phone in which an unnecessary electromagnetic wave absorber is attached to a base of an antenna.

[0002]

2. Description of the Related Art It has been pointed out that unnecessary electromagnetic waves such as harmonics leaking from various wireless devices such as mobile phones may cause malfunctions of other electronic devices or adversely affect the human body. It has been demanded.
In particular, in the case of a mobile phone, not only is it always carried, but it operates near the user's head (ears / mouth) during a call, so the leaked unnecessary electromagnetic waves are considered to have a large adverse effect on the human body. .

At present, there is an EMI regulation as a regulation concerning unnecessary electromagnetic waves (noise), but the upper limit of the regulated frequency is 1 GHz. Therefore, in the conventional technology, the leakage of unnecessary electromagnetic waves from the housing is prevented by covering the inside of the housing of the mobile phone with metal foil or applying conductive paint, and attaching a shielding material to the housing joint. are doing.

[0004]

However, even if electromagnetic shielding of a portable telephone is performed with the conventional structure, it is impossible to shield the transmitting and receiving antenna. Therefore, the radiation of unnecessary electromagnetic waves from the periphery of the antenna cannot be prevented. These radiated unnecessary electromagnetic waves (harmonics, microwaves) have an adverse effect on the human body. For this reason, the upper limit of the frequency for regulation on unnecessary electromagnetic waves is going to be raised from 1 GHz to more than ten GHz. In this case, if a general absorber that removes (attenuates) these unnecessary electromagnetic waves from several GHz to several tens of GHz is used, the fundamental wave (here, 1.5 GHz used in a mobile phone) is also attenuated. It cannot be used in practice.

SUMMARY OF THE INVENTION It is an object of the present invention to absorb unnecessary electromagnetic waves (harmonics) leaking from a mobile phone without attenuating a fundamental wave in the mobile phone, thereby minimizing adverse effects on the human body due to microwaves. An object of the present invention is to provide an unnecessary electromagnetic wave absorbing structure for a mobile phone.

[0006]

According to the present invention, an unnecessary electromagnetic wave absorber formed by molding a mixture of magnetic powder and rubber or resin into a ring is provided at the base of an antenna of a housing of a portable telephone. This is an unnecessary electromagnetic wave absorbing structure of a mobile phone mounted so as to penetrate inside the ring of the electromagnetic wave absorber.
As the magnetic powder, iron powder may be used, but manganese-zinc based,
Nickel-zinc or magnesium-zinc ferrite powders are preferred. The ring-shaped unnecessary electromagnetic wave absorber may be adhered to the housing, fixed with a double-sided adhesive sheet, or adsorbed to the housing at the base of the antenna by a ring-shaped permanent magnet. May be.

[0007] The frequency-impedance characteristic is adjusted by the mixing ratio of the magnetic powder and the rubber or resin. For example, manganese-zinc ferrite powder is converted to EPDM (ethylene
1200 ph against propylene diene monomer) based rubber
r (per hundred rubber: mixing ratio with respect to 100 parts by weight of rubber), mixed and molded into a ring, the material exhibits low impedance at 1 to several GHz,
It exhibits high impedance in a high frequency region of several tens of GHz, and attenuates and absorbs electromagnetic waves at that frequency.

The mixing ratio of the ferrite powder and the rubber (resin) is such that the ferrite powder is 800 to 1200 ph with respect to the rubber.
r is preferable. The upper limit is set to 1200 phr because it is the maximum amount that can be mixed into rubber, and if the amount is more than this, molding cannot be performed. The lower limit is 80
The reason for setting it to 0 phr is that if it is less than this, the frequency region that can be absorbed moves to the higher frequency side (the frequency region where the impedance becomes higher becomes the higher frequency side), and the fundamental wave and unnecessary electromagnetic waves therebetween are not absorbed.

[0009]

The ring-like unnecessary electromagnetic wave absorber made of a mixture of the magnetic powder and rubber or resin as described above has a low impedance at a frequency of about 1.5 GHz, which is a fundamental wave of a mobile phone, but has a higher harmonic. The impedance is high for certain unnecessary electromagnetic waves. The impedance is composed of a resistance component R and an inductance component jωL. The increase in the impedance in the high frequency region is mainly due to the increase in the resistance component R. The resistance component R has a function of converting electric energy into heat energy.

When transmitting a radio wave from a portable telephone, the radio wave (current) flows from the base of the antenna toward the tip. When a ring-shaped unnecessary electromagnetic wave absorber made of a mixture of magnetic powder and rubber or resin is attached to the base of the antenna, the current flowing through the antenna, which is the fundamental wave of the mobile phone, is 1.
At a frequency of about 5 GHz, the impedance is low so that it is not attenuated. However, unnecessary electromagnetic waves, which are harmonics thereof, are absorbed and attenuated because of its high impedance. Thus, unnecessary electromagnetic waves radiated from the antenna can be reduced.

[0011]

EXAMPLE A manganese-zinc ferrite powder was prepared by EPDM.
(Ethylene / propylene diene monomer) rubber
1200 phr (Per Hundred Rubber: Rubber 100
(Mixing ratio to parts by weight) and mix. This 120
The value of 0 phr is a value close to the limit value at which rubber can be packed. The mixture is vulcanized and pressed into a ring to form an unnecessary electromagnetic wave absorber, which is mounted on the base of the antenna of a mobile phone.

FIG. 1 is an explanatory view showing an embodiment of an unnecessary electromagnetic wave absorbing structure of a portable telephone according to the present invention. The unnecessary electromagnetic wave absorber 14 formed in a ring shape as described above is mounted on the base of the telescopic antenna 12 of the housing 10 of the mobile phone so that the antenna 12 penetrates the inside of the ring. Details of this mounting structure are shown in FIGS.

In FIG. 2, the structure of the unnecessary electromagnetic wave absorber 20 is shown in FIG.
It has a ring shape such that the flange portions 24 are located at both ends of the central small-diameter portion 22, and is held between both flange portions 24 so that the edges of the housing 10 are fitted from both sides.
The antenna 12 extends and contracts through the ring-shaped unnecessary electromagnetic wave absorber 20. The example shown in FIG. 3 is a structure in which an extremely simple ring-shaped unnecessary electromagnetic wave absorber 14 is attached to the inner wall surface of the housing 10 with an adhesive. Each of these examples has a configuration in which the mobile phone is attached during a process of assembling the mobile phone.

The present invention can be retrofitted to a portable telephone. An example is shown in FIGS. FIG. 4 shows an example in which the ring-shaped unnecessary electromagnetic wave absorber 14 is attached to the outer wall surface of the housing 10 with a double-sided adhesive sheet 27. It is preferable to use a double-sided adhesive sheet because the release paper may be peeled off and pressure-bonded, so that the double-sided adhesive sheet can be easily attached. However, it is also possible to use an adhesive instead of the double-sided adhesive sheet. When the base portion of the antenna 12 of the housing 10 is made of an iron plate (magnetic material) or the like, as shown in FIG. It can also be adsorbed selectively.

The ring-shaped unnecessary electromagnetic wave absorber attached to the base of the antenna has a low impedance at a frequency of about 1.5 GHz, which is a fundamental wave of a portable telephone, due to adjustment of a filling ratio of magnetic powder, and the like. In this case, it is possible to exhibit such a characteristic that the impedance is sharply increased and a peak occurs at ten to several tens of GHz. Such a frequency-
With the impedance characteristic, it is possible to absorb and attenuate only the higher harmonics (unwanted electromagnetic waves) without attenuating the 1.5 GHz fundamental wave of the current flowing through the antenna. As a result, when transmitting a mobile phone, unnecessary electromagnetic waves are hardly radiated from the antenna, so that problems such as malfunction of various electronic devices can be prevented, and adverse effects on the human body can be eliminated. Also in the case of reception by a mobile phone, noise can be reduced and the SN ratio can be improved.

The magnetic powder to be mixed with the rubber may be nickel-zinc-based, magnesium-zinc-based ferrite, or a mixture of two or more thereof in addition to the manganese-zinc-based ferrite. Further, iron powder and the like can be used. The filling ratio with respect to resin or rubber is appropriately adjusted according to the required impedance characteristics.

Further, the ring-shaped unnecessary electromagnetic wave absorber is not limited to a portable telephone, but may be, for example, a wireless LAN (LAN).
The present invention is also applicable to other electronic devices, and is effective in preventing malfunction of other various electronic devices.

[0018]

According to the present invention, as described above, the unnecessary electromagnetic wave absorber formed by molding a mixture of magnetic powder and rubber or resin into a ring shape is mounted on the base of the antenna of the housing of the portable telephone. Therefore, it can be easily and easily implemented, and can be retrofitted to a completed mobile phone. Further, according to the present invention, only the unnecessary wave can be shielded without attenuating the fundamental wave, so that the adverse effect on the human body due to the unnecessary electromagnetic wave (microwave) can be reduced, and the malfunction of other various electronic devices can be prevented. And the like can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of an unnecessary electromagnetic wave absorbing structure of a mobile phone according to the present invention.

FIG. 2 is an explanatory view showing an example of a mounting structure of an unnecessary electromagnetic wave absorber.

FIG. 3 is an explanatory view showing another example of the mounting structure of the unnecessary electromagnetic wave absorber.

FIG. 4 is an explanatory view showing another example of the mounting structure of the unnecessary electromagnetic wave absorber.

FIG. 5 is an explanatory view showing another example of the mounting structure of the unnecessary electromagnetic wave absorber.

[Explanation of symbols]

 Reference Signs List 10 Housing for mobile phone 12 Antenna 14 Ring-shaped unnecessary electromagnetic wave absorber

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-299873 (JP, A) JP-A-53-52339 (JP, A) JP-A-6-45781 (JP, A) JP-A-6-45781 291711 (JP, A) JP-A-7-336081 (JP, A) JP-A 62-79319 (JP, U) JP-A 4-85838 (JP, U) JP-A 60-175490 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 9/00

Claims (4)

(57) [Claims] 1. An unnecessary electromagnetic wave absorber obtained by molding a mixture of magnetic powder and rubber or resin into a ring shape is provided at the base of an antenna of a housing of a mobile phone, and the antenna penetrates the inside of the ring of the unnecessary electromagnetic wave absorber. An unnecessary electromagnetic wave absorbing structure for a mobile phone, wherein the structure is attached to the mobile phone. 2. The magnetic powder is one of manganese-zinc, nickel-zinc, and magnesium-zinc ferrites or a mixture of two or more thereof.
Unnecessary electromagnetic wave absorption structure described. 3. The unnecessary electromagnetic wave absorbing structure according to claim 2, wherein the mixing ratio of the ferrite powder and the rubber is a ratio of adding the ferrite powder to the rubber in an amount of 800 to 1200 phr. 4. The unnecessary electromagnetic wave absorbing structure according to claim 1, wherein the ring-shaped unnecessary electromagnetic wave absorber is attracted to a housing of the mobile phone at a base of the antenna by a ring-shaped permanent magnet.