JP3695591B2 - Mobile phone - Google Patents

Description

  The present invention relates to a mobile phone, and more particularly to a mobile phone that suppresses the influence of electromagnetic waves on a human body and improves antenna efficiency.

Wang, Fujiwara “Realization of a low local SAR in the head by suppressing the surface current of the mobile phone housing”. IEICE technical report. The Institute of Electronics, Information and Communication Engineers. September 1998 EMCJ98-45 p.35-40 Hashimoto, Tsuchida, Nishizawa “Fundamental study on SAR reduction using shield material placed in front of human body”. IEICE Transactions. The Institute of Electronics, Information and Communication Engineers. August 1996 Vol. J79-B-II No.8 p.486-491 Hanpuku, Nakamura, Hashimoto “Examination of radiation efficiency of mobile phone with low loss magnetic plate”. IEICE technical report. The Institute of Electronics, Information and Communication Engineers. July 2001 EMCJ2001-31.p.7-12 Watanabe, Hashimoto “Study on Improving Radiation Efficiency of Mobile Phone with High Permeability Magnetic Sheet”. Proceedings of the 2002 IEEJ Fundamentals / Materials / Common Section Conference (September 12, 2002) p.121

Japanese Patent Laid-Open No. 11-31909 JP 2001-352388 A JP 2002-151881 A

  With the spread of mobile phones, discussions have been made on the improvement of antenna efficiency during communication and various effects of electromagnetic waves. In particular, SAR (Specific Absorption Rate) must be evaluated from the viewpoint of influence on the human body. The SAR represents the amount of energy absorbed per unit time by a unit mass of tissue when the human body is exposed to electromagnetic waves, and devices used in the vicinity of the human head, such as mobile phones, are used in Japan. A local SAR averaged over 10 g of any tissue local to the human body is used, and it is a guideline that the value does not exceed 2 W / kg. Therefore, when designing a mobile phone, the local SAR value of the electromagnetic wave (800 MHz to 900 MHz band) from the mobile phone used near the head must be within the allowable value.

  Non-patent document 1 mentioned above describes that the surface current density of metal is suppressed and the value of local SAR is reduced by attaching a ferrite sheet having a thickness of 2.5 mm to the head side casing of the mobile phone. Yes. In Non-Patent Document 2, although it is an analysis result for a virtual model, it is SAR to shield a electromagnetic wave by arranging a 30 mm-thick dielectric between a mobile phone housing and a human head. It is described that it is effective for reduction.

  In Non-Patent Document 3, it is effective to place a 5 mm thick magnetic plate with a small magnetic loss between the mobile phone case and the SAR value by a little over 10% in order to improve the radiation efficiency of the antenna. It describes what you can do. According to Non-Patent Document 4, the FDTD (Finite Difference Time Domain) analysis method shows that by improving the magnetic plate described in Non-Patent Document 3, the radiation efficiency is improved even with a 0.8 mm thick magnetic plate. It was reported that it was confirmed in.

  In Patent Document 1, a non-directional chip antenna mounted on a circuit board is placed spatially separated from each other with a conductive reflector facing it, and connected to a ground pattern on the circuit board. It is described that the antenna efficiency can be improved. Patent Documents 2 and 3 describe that by incorporating a radio wave absorber made of a magnetic loss material or the like into a mobile phone, it is effective in reducing SAR and preventing adverse effects of unnecessary radio waves on the surroundings. Yes.

  As described above, various studies have been made to improve the calling environment of mobile phones. However, the SAR is sufficiently reduced, the antenna efficiency is improved, and the size and weight are inevitably required. Considering the practicality of mobile phones, the various proposals so far are still unsatisfactory. For example, the methods of Non-Patent Documents 1 to 3 require a ferrite magnetic material or dielectric plate material with a thickness of 2.5 mm to 30 mm in order to reduce SAR or improve antenna efficiency, and the size and weight of current mobile phones. It is very difficult to incorporate these while keeping In the example described in Non-Patent Document 3, since the antenna efficiency is lowered when a lossy electromagnetic wave absorber is used to lower the SAR, the antenna efficiency can be increased by using a low-loss magnetic material. However, the increase in efficiency is only 14.7%, and even if the SAR value is reached, there is only a reduction effect of a dozen percent.

  Further, according to Non-Patent Document 4, an analysis result that a high-permeability magnetic sheet having a thickness of 0.8 mm is effective for improving the antenna efficiency by the FDTD method has been obtained. Based on the above calculation, there is no evaluation of other physical properties of the high permeability magnetic sheet itself, for example, the relative permittivity (> 1) inherent in the magnetic material, and there are almost no practical applications. There is no suggestion.

  Patent Document 1 aims to improve the directivity and reduce the SAR, but the effect of reducing the SAR value is at most about 10%. Although Patent Document 2 describes that SAR is reduced by the interaction between a 1 to 4 mm thick wave absorber and a conductive layer, it is required for a wave absorber as in Non-Patent Document 4. The correlation between the physical properties and the SAR reduction effect is unknown, and its effectiveness cannot be confirmed. Patent Document 3 describes the composition of the radio wave absorber itself, but it is not clear what physical properties of the radio wave absorber are effective for absorbing unwanted radio waves, while maintaining good antenna efficiency. There is no description of a specific configuration for reducing the SAR.

  The present invention has been made in view of the above background, and its object is to provide a mobile phone that can greatly improve the call environment by reducing the SAR and increasing the antenna efficiency without impairing the light weight and compactness. There is to do.

In the present invention, in order to achieve the above object, it is more effective to use a dielectric than a magnetic material. Therefore, the relative permittivity ε _r of the dielectric is _expressed as “ε _r using a real part and an imaginary part. = Ε _r '−jε _r ″ ”, the unique combination of the real part ε _r ′ and the imaginary part ε _r ″ represents the antenna efficiency of the mobile phone, that is, the reflectance and transmission of electromagnetic waves. It was made paying attention to being effective in controlling the rate and the absorption rate. The dielectric material used in the present invention has a thickness of at 1mm or less, from the cellular phone antennas are used spatially separated, the ratio of the dielectric constant epsilon _r real part epsilon _r 'value and the imaginary part epsilon _r' 'of the The combination with the value is characterized by being selected so as to belong to the region outside the characteristic line K in the characteristic table listed in [Table 1] of claim 1.

In particular, considering the application to a lightweight and compact mobile phone, it is preferable to keep the thickness of the dielectric to 1 mm or less. However, under such restrictions, it is desirable to use a general dielectric material as it is. It is difficult to achieve this goal. Therefore, in the present invention, the dielectric constant, which is a characteristic physical property of the dielectric, is analyzed as described above, and the cellular phone is assumed on the precondition that the thickness of the dielectric is 1 mm and the frequency of the electromagnetic wave from the mobile phone is 900 MHz. Characteristic table devised to correlate the antenna efficiency required according to the result of reflection, transmission and absorption of electromagnetic waves from a telephone by a dielectric and the amount of electromagnetic waves (SAR value) absorbed by the human body The characteristic line K is defined above, and the value of the real part ε _r ′ and the value of the imaginary part ε _r ″ of the relative permittivity are selected so as to belong to the outer region of the characteristic line K. To adjust the relative permittivity, resin, rubber, or elastomer is used as the base material of the dielectric, and the type and amount of the dielectric material or conductive material mixed in the base material, or the form such as particle size and aspect ratio By adjusting, flexible response is possible, and the degree of freedom of adjustment is high.

The characteristic line K is a continuous line, and a closed region is formed between the horizontal axis (real part axis) and the vertical axis (imaginary part axis). The combination of the values of _r ′ and imaginary part ε _r ″ is as shown in the table below.

  The dielectric is preferably used by being extended between an electromagnetic radiation source such as an antenna or an oscillation circuit and a speaker of a mobile phone. SAR (0) and AEFF (0) are measured values of the SAR and the antenna efficiency in a state where the dielectric is not used, and SAR (A), AEFF (0) are measured values of the SAR and the antenna efficiency in a state where the dielectric is used. When AEFF (A) is defined, the SAR relative value is defined as SAR (A) / SAR (0), and the AEFF relative value is defined as AEFF (A) / AEFF (0), the SAR relative value <1, and the AEFF relative value> It is a feature of the present invention that it is 1. The SAR and antenna efficiency measurement method will be described later.

  According to the present invention, by using a sheet-like dielectric material having unique dielectric characteristics, an effect of improving the antenna efficiency can be obtained while reducing the SAR value, and the thickness of the dielectric material can be suppressed to 1 mm or less. Therefore, it is possible to significantly improve the calling environment of a lightweight and compact mobile phone. In addition, since the SAR relative value <1 and the AEFF relative value> 1 by using the dielectric, both the SAR and the antenna efficiency can be improved, and the communication environment of the mobile phone can be reliably improved. . The dielectric of the present invention can be adjusted with a considerable degree of freedom by adding a dielectric material or a conductive material to a resin, rubber or elastomer as a base material. large.

  FIG. 1 schematically shows a mobile phone using the present invention. The mobile phone 2 is used in the vicinity of the user's head 3. A transmitter / receiver circuit board 4, a main circuit board 5, and a power supply circuit board 6 are incorporated in the casing of the mobile phone 2, and circuit components constituting the transmitter / receiver circuit, control circuit, and power supply circuit, and chips such as an IC and a memory, respectively. The component is mounted. A whip antenna 7 is assembled to the transmission / reception circuit board 4 and is pulled out as shown in the figure when in use, and can be stored inside the housing when not in use.

  The main circuit board 5 is provided with a speaker 9 and a microphone 10, and can listen to and send voice through respective call holes formed in the housing. The main circuit board 5 is further provided with a liquid crystal panel 12, a dial key operation unit 13, and the like. The monitor screen of the liquid crystal panel 12 is exposed to the outside of the housing, and displays various information during a call to the user. When the dial key operation unit 13 is pressed, the operation signal is input to the control circuit mounted on the main circuit board 5 via the keypad device 14. The power supply circuit board 6 is provided with a rechargeable battery loading section. Note that the functions and operations of these various circuit boards and circuit components are the same as those of conventionally known mobile phones, and thus detailed description thereof is omitted.

  A dielectric sheet 15 is attached to the inner wall of the casing on the side close to the user's head 3 for the purpose of suppressing the SAR small and improving the antenna efficiency. The dielectric sheet 15 is made of a flexible dielectric having a thickness of 1 mm, and is substantially parallel to the longitudinal direction of the whip antenna 7 and between the transmission / reception circuit board 4 in the housing and the user's head 3. It is extended so as to block out. And it acts as an electromagnetic wave control body that reflects, absorbs, or transmits electromagnetic waves radiated from the mobile phone 2.

As a specific example, the dielectric sheet 15 is made of silicone rubber as a base material, and carbon powder as a conductive material and carbon fibers having a length of several hundred μm are used as additives in the base material. The values of the real part ε _r ′ and imaginary part ε _r ″ of the relative permittivity “ε _r = ε _r ′ −jε _r ″” of the prepared and mixed dielectric are shown in the characteristic table of FIG. As shown in the graph, the point X (288, 124) belongs to the region outside the characteristic line K. By using the dielectric sheet 15 having such a dielectric characteristic, it is possible to radiate electromagnetic waves from the mobile phone 2 without loss while suppressing the SAR value.

  The effect of using the dielectric sheet 15 has been confirmed by the experimental equipment shown in FIG. The experimental equipment shown in FIG. 2 is equivalent to the conventional mobile phone 20 excluding the dielectric sheet 15 and the human body and electromagnetic wave characteristics (relative permittivity = 43.6, conductivity = 0.91 (S / m)). The phantom model 22 and a plate-like dielectric sample 24 arranged between the two are used, and antennas 25 and 26 for measuring electromagnetic wave energy are arranged on both sides thereof.

  The antenna 25 is separated from the whip antenna 7 of the mobile phone 20 by a distance L1 (= 100 mm) in the opposite direction to the phantom model 22, and is used for measuring electromagnetic wave energy radiated from the mobile phone 20, and the measured value is Corresponds to antenna efficiency. The other antenna 26 is a distance L2 (= 25 mm) away from the housing outer wall of the mobile phone 20 on the phantom model 22 side, and is used to measure the electromagnetic wave energy received through the dielectric sample 24. Corresponds to the SAR value. The dielectric sample 24 has a thickness L3 of 1 mm and is separated from the housing of the mobile phone 20 by a distance L4 (= 0.5 mm). The size of the dielectric sample 24 is 150 mm × 150 mm.

When the value of the real part ε _r ′ of the relative permittivity ε _r of the dielectric sample 24 is selected as “288” and the value of the imaginary part ε _r ″ is set to “124”, an electromagnetic wave of 900 MHz is radiated from the mobile phone 20. As a relative value when the dielectric sample 24 is not disposed, the electromagnetic wave energy measured by the antenna 25 (antenna efficiency) increases by at least 10% and the electromagnetic wave energy measured by the antenna 26 ( It was confirmed that the (SAR value) can be reduced by 50% or more. Accordingly, the SAR relative value is 0.5 and the AEFF relative value is 1.1, which indicates that the dielectric sample 24 is effective in achieving the object of the present invention. The relative dielectric constant ε _r was measured using HP85070B manufactured by Japan Hewlett-Packard Company.

When a dielectric is used for such a purpose, a characteristic line K shown in FIG. 3 is used in order to study a practical range of the dielectric characteristics. This characteristic line K corresponds to the dielectric characteristic that satisfies the condition that when the thickness of the dielectric sample 24 is 1 mm, the SAR value is lowered and the relative value of the antenna efficiency is not less than 1.0. In particular, it is plotted with a combination of the real part ε _r ′ and the imaginary part ε _r ″ of the relative permittivity ε _r , and some of the points are listed in [Table 2] above. is there.

Further, as shown in FIGS. 4A to 4D, each point on the characteristic line K indicates the value of the imaginary part ε _r ″, for example, “151”, “41”, When the relative value of the antenna efficiency is graphed by fixing the values to “11” and “1” and changing the real part ε _r ′, respectively, the imaginary part ε when the relative value of the antenna efficiency is “1.0”. _It can be considered as a combination of the value of _r ″ and the value of the real part ε _r ′ at that time. Further, as shown in FIGS. 5A to 5C, the value of the real part ε _r ′ is fixed to, for example, “101”, “11”, “1” with the index shown in FIG. 'when graphed changes in the relative values of the antenna efficiency while varying the imaginary part epsilon _r when the antenna efficiency is "1.0"' imaginary part epsilon _r 'and values of' the real part of the time The combination with the value of ε _r ′ is plotted on the characteristic line K.

As can be seen from the graph of FIG. 4, when the value of the imaginary part ε _r ″ is fixed and the value of the real part ε _r ′ is increased, the antenna efficiency changes almost until the value exceeds “10”. However, after that, the antenna efficiency tends to increase. In general, it can be seen that increasing the value of the real part of the relative permittivity increases the reflectivity of electromagnetic waves, which is advantageous for reducing the SAR value and improving the antenna efficiency.

On the other hand, when the value of the real part ε _r ′ is fixed and the value of the imaginary part ε _r ″ is increased, the antenna efficiency once decreases and becomes minimal as shown in FIG. Show. As the value of the imaginary part ε _r ″ of the relative permittivity increases, the absorption rate for electromagnetic waves increases, which is advantageous for reducing the SAR value. However, it is not preferable that the value of the imaginary part ε _r ″ takes an intermediate value in the graph because the antenna efficiency is suppressed.

As shown in FIG. 3, the characteristic line K obtained in this way creates a closed region I on the graph with the value of the real part ε _r ′ and the value of the imaginary part ε _r ″ as the coordinate axes. . The dielectric sheet 15 using the present invention belongs to the region II outside the characteristic line K. On the other hand, for example, in Non-Patent Document 2, as a 30 mm-thick shield material used for the same purpose as the present invention, the relative permittivity ε _r is “10-j10”, “20-j20” 2 Although examples have been introduced, these samples S1 and S2 belong to the region I in FIG. 3, and there is a great difference in their dielectric characteristics.

  In order to improve the antenna efficiency while using the samples S1 and S2 having these dielectric characteristics and further reducing the SAR value, it is necessary to increase at least the reflectivity with respect to the electromagnetic wave. For this purpose, the thickness must be further increased. In other words, it is difficult to apply to the current lightweight and compact mobile phone.

  By the way, the region I shown in FIG. 3 corresponds to “a portion where both the real part and the imaginary part are small”, and the region II is (1) “a part where the value of the real part is large and the value of the imaginary part is small”. There are three types: a part having a small real part and a large imaginary part, and (3) a part having both a real part and an imaginary part. Including the relative dielectric constant of the dielectric in the part (1) can be realized by devising the aspect ratio of barium titanate or PZT added as a high dielectric material to the base material. Has the property that the reflection on the surface is not so much, but the absorption inside is also small. The inclusion of the relative dielectric constant in the part (2) can be realized by adjusting the particle diameter and aspect ratio of the conductive material such as carbon and metal to be added, and the mixing ratio with the base material. In order to include the relative dielectric constant in the part (3), it is possible to mix the material realized in (1) with a highly conductive material such as carbon or metal. Similar to the dielectric of the part 2), it has the property that there are many reflections on the surface and absorption inside.

The use of a low-loss magnetic plate for the same purpose as that of the present invention is introduced in Non-Patent Document 3, and evaluation of samples A, B, C, and D is performed. In the case of using a low-loss magnetic plate, the characteristic of relative permeability μ _r (= μ _r '−jμ ″) is important. For the improvement of antenna efficiency, the real part μ _r ′ is It is concluded that a larger imaginary part μ ″ is advantageous. Relative permeability mu _r samples A~D has a thickness of 5 mm, were as electromagnetic wave frequency is below the under 900MHz conditions, the relative dielectric constant epsilon _r in accordance with the description of the document, either "1- j0 ".

Therefore, in order to show that the method of obtaining the characteristic line K in the dielectric of the present invention is valid even when applied to the magnetic material, the horizontal axis of the samples A to D described in Non-Patent Document 3 FIG. 6 shows a state plotted in the relative permeability characteristic table in which the value of the real part μ _r ′ of the magnetic permeability μ _r is taken and the value of the imaginary part μ ″ is taken on the vertical axis. The characteristic lines K ₁ , K ₂ , K ₃ , and K ₄ in the figure have the relative values of the antenna efficiency of “1.0”, “10% decrease”, “ This is a plot of the combination of the value of the real part μ _r ′ and the value of the imaginary part μ ″ of the relative permeability when “20% decrease” and “30% decrease”.

  According to FIG. 6, it can be seen that the antenna efficiency of samples A, B, and C is lower than that of sample D by about 10 to 20%. Non-Patent Document 3 describes the following data as the evaluation results of these samples, which are almost in agreement with the results shown in FIG. 6, and the validity of the idea of obtaining the characteristic line K in the present invention is non- This can also be confirmed from the correspondence with the magnetic material of Patent Document 3.

  Further, the absorbed power in the above table represents “phantom absorbed power” corresponding to SAR, and in the relative permeability characteristics table of FIG. 6, samples A, B, C, and D are respectively in the order of 43, 60, 100, 31, which is in good agreement with the results of [Table 4].

  Furthermore, the use of the dielectric material having the relative dielectric constant characteristics specified in the present invention can sufficiently reduce the thickness while achieving the intended purpose. Consider the comparison with S1 and S2.

Samples S1 (ε _r = 10−j10) and S2 (ε _r = 20−j20) whose relative dielectric constants are specified, respectively, and dielectric X of the present invention belonging to region II in FIG. 6 (ε _r = 288−) For j124), the transmission ratio when an electromagnetic wave of 900 MHz is irradiated is shown in FIG. The transmission ratio is preferably small in order to keep the SAR small, but in order to reduce the transmission ratio to 0.4, the samples S1 and S2 are 2.8 mm and 1.4 mm, respectively. On the other hand, in the dielectric X of the present invention, about 0.1 to 0.2 mm is sufficient.

The reason why the transmission ratio can be reduced even if the dielectric X is sufficiently thin compared to the samples S1 and S2 is that the dielectric X has a square root of the product of the relative permittivity and the relative permeability “√ (ε _r × μ _r ) ”is large and the wavelength compression effect is considered to be large. For the same reason, when the dielectric X of the present invention is used, not only the thickness but also the vertical and horizontal sizes can be reduced.

Next, the reflection characteristics for electromagnetic waves are similarly compared between the samples S1 and S2 and the dielectric X of the present invention. As shown in FIG. 8, when the thickness d is taken on the horizontal axis, in order to obtain a reflection ratio of 0.5 with respect to a reflection ratio of 1 (total reflection), the dielectric X needs only about 0.5 mm thick. On the other hand, the samples S1 and S2 cannot be realized even with a thickness of 10 times that of 5 mm. When the reflection ratio of the dielectric is increased, the antenna efficiency is expected to be improved together with the reduction of the SAR, so that the superiority of the dielectric X is clear. In order to increase the reflectivity of electromagnetic waves, it is related to making the absolute value of Z = √ (μ _r / ε _r ) sufficiently larger than 1, and in this respect, dielectric X is more than samples 1 and 2 in this respect. It seems to be advantageous.

Comparing the case of using a case with a dielectric using a magnetic material with a view to increasing the ratio of the molecular mu _r and denominator epsilon _r of the Z, magnetic material described in Non-Patent Document 1 and Non-Patent Document 3 In the case of, inevitably accompanied by a finite relative dielectric constant ε _r larger than “1”. In this respect, to be used as a material for incorporating materials exhibiting magnetism in a case of using a dielectric, to the relative permeability mu _r to "1" is possible to easily implement a high for electromagnetic waves In order to provide reflectivity, it is more advantageous to use a dielectric material than a magnetic material.

For example, in the case of sample D (μ _r = 6.28−j0.76) of the magnetic material of Non-Patent Document 3, if the relative dielectric constant ε _r is 1, the absolute value of the numerator μ _{r of} Z and the denominator ε _r Is about 2.52, and a certain degree of reflection can be expected. However, as an extreme case, if the value of the relative dielectric constant ε _r is “6.28−j0.76”, the absolute value of Z is 1, and the reflection of electromagnetic waves from the magnetic material is eliminated. Not only in such a special case, but also because the magnetic material is accompanied by a relative dielectric constant greater than 1, it can be seen that the material is more disadvantageous than the dielectric as a material that enhances the reflection of electromagnetic waves.

  FIG. 9 is a graph showing the absorption ratio with respect to the thickness d for the dielectric X and the samples S1 and S2. Increasing the absorption is disadvantageous in terms of antenna efficiency, but increases the effect of reducing the SAR value. In the samples S1 and S2, the thickness d can only be increased in order to increase the absorption. However, in the dielectric X, the absorption can be adjusted within the range where the thickness d is thin, and the transmission ratio and reflection shown in FIGS. It can be seen that a flexible response can be taken when considering the ratio together.

  Specific examples of dielectrics that can be effectively used in the mobile phone of the present invention will be described below. As shown in [Table 5] below, Examples 1 to 3 all have silicone rubber as a base material, and graphite fibers and several additives are added thereto. Of the substance names listed in [Table 5], graphite fiber and conductive carbon are mixed as a conductive material with silicone rubber as a base material, and dry silica is mixed as a dielectric material. Silicone oil acts as a softening agent, and organic peroxide acts as a crosslinking agent. In addition, the weight part “0” in the table indicates that no addition was made.

The correspondence between each substance name and the specific product name, and the manufacturers or distributors of these products are as follows.
・ Silicone rubber "DY32-152U"
Toray Dow Corning Silicone Co., Ltd.
・ Graphite fiber "MG II 244"
Osaka Gas Chemical Co., Ltd.
・ Conductive carbon "Ketjen Black EC600JD"
Kao Corporation
・ Dry silica “Aerosil 200”
Nippon Aerosil Co., Ltd.
・ Silicone oil "SH200cv110cs"
Toray Dow Corning Silicone Co., Ltd.
・ CaO “VESTAPP”
Inoue Lime Industry Co., Ltd.
・ Organic peroxide "RC-4 (50P)"
Toray Dow Corning Silicone Co., Ltd.

The dielectrics of Examples 1 to 3 are prepared as dielectric sheets having dimensions of 0.5 mm × 40 mm × 110 mm. In the preparation, first, each selected material is put into an open roll in each part by weight, and sufficiently mixed at room temperature (25 ° C.) to obtain a mixture. An appropriate amount of this mixture is charged into a mold having an opposing gap set to 0.5 mm when pressed, and pressed at a temperature of 170 ° C. for 10 minutes (pressure 180 kgf / cm ² ) to form a sheet. To form. The dielectric sheet of Examples 1 to 3 can be prepared by cutting the sheet-like molded body having a thickness of 0.5 mm thus obtained into a size of 40 mm × 110 mm.

The values of the real part ε _r ′ and the imaginary part ε _r ″ of the complex relative permittivity possessed by the dielectric sheets of Examples 1 to 3 are as shown in [Table 5]. It can be seen that it is distributed outside the line K and is suitable as a dielectric that reduces the SAR of the mobile phone and increases the antenna efficiency. Moreover, since these dielectrics can be manufactured relatively easily using materials that are easily available, they are also suitable for mass production.

  In addition, the composition of the dielectric suitable for the mobile phone of the present invention is not limited to the above Examples 1 to 3. For example, an epoxy resin, an olefin resin, an olefin-based thermoplastic elastomer, a styrene-based elastomer, or the like can be used as a base material instead of silicone rubber. In addition, carbon fiber having an appropriate length (about 700 μm) as a conductive substance, flake graphite having a particle diameter of 20 μm, or alumina powder or wet silica as a substance to be added as a non-conductive material should be used. Is also possible.

  Although the present invention has been described based on the illustrated embodiment or example, the present invention is applicable to various mobile phones. For example, not only a built-in pull-out type whip antenna as an antenna, but also a chip antenna that can be used without protruding outside the housing is mounted on a circuit board, or a built-in antenna called an inverted F antenna is used. For example, a sheet-like dielectric such as a folding unit of a receiving unit and a transmitting unit may be used between an electromagnetic wave source such as an antenna or an oscillation circuit and a human head. For example, the same effect can be obtained regardless of the form. In addition, the position where the dielectric is provided is not only fixed to the inner wall of the housing, but also to any circuit board, or to the inner surface of a display device such as a liquid crystal panel. It can be implemented in various forms such as using together.

  Furthermore, according to the present invention, the cellular phone can be made compact and resources can be saved by facilitating the high-density design associated with the reduction in the thickness of the dielectric material, and further the call environment can be improved. Furthermore, if the antenna efficiency decreases, the radio wave output at the time of transmission / reception is inevitably increased, and the life of the built-in battery of the mobile phone is shortened. However, as the antenna efficiency is improved by the present invention, the accompanying effect that the battery life is extended. Can also be expected.

It is a principal part schematic sectional drawing of the mobile telephone to which this invention is applied. It is a conceptual diagram of the experimental installation for electromagnetic wave measurement. FIG. 6 is a characteristic diagram illustrating antenna efficiency as a correlation between a real part and an imaginary part of relative permittivity. It is a graph which shows the change of the relative value of antenna efficiency when the value of the vertical axis | shaft in FIG. 3 is fixed and the value of a horizontal axis is changed. It is a graph which shows the change of the relative value of antenna efficiency when the value of a horizontal axis in FIG. 3 is fixed and the value of a vertical axis is changed. It is the characteristic view which represented the antenna efficiency of the conventional sample by the method similar to FIG. 3 with the correlation with the relative magnetic permeability. It is a graph which shows the change of the transmission ratio with respect to the thickness of a dielectric material. It is a graph which shows the change of the reflection ratio with respect to the thickness of a dielectric material. It is a graph which shows the change of the absorption ratio with respect to the thickness of a dielectric material.

Explanation of symbols

2 Cellular phone 7 Whip antenna 15 Dielectric sheet 20 Cellular phone 22 Phantom model 24 Dielectric sample 25, 26 Antenna for electromagnetic wave measurement

Claims (3)

An antenna and a sheet-like dielectric that is spatially separated from the antenna and has a thickness of 1 mm or less are provided. The complex relative permittivity εr of the dielectric is expressed as “εr = εr′−jεr ″”. When the combination of the values of the real part εr ′ and the imaginary part εr ″ at the use frequency of the mobile phone is outside the region surrounded by the characteristic line K, the real part axis, and the imaginary part axis shown in [Table 1] The mobile phone characterized by belonging to a region, wherein the characteristic line K is a curve obtained by smoothly connecting points obtained by combining the values of the real part εr ′ and the imaginary part εr ″ shown in [Table 2] .

The dielectric is provided so as to extend between the antenna and the speaker, and this dielectric has a measured value of the antenna efficiency when the dielectric is not used as AEFF (0), and the antenna efficiency when the dielectric is used. When the measured value of AEFF (A) is AEFF (A), the real part εr ′ and the imaginary part at the use frequency of the mobile phone so that the AEFF relative value represented by AEFF (A) / AEFF (0) is larger than 1. 2. The mobile phone according to claim 1 , wherein values of εr ″ are combined . The mobile phone according to claim 1 or 2, wherein the complex relative permittivity of the dielectric is adjusted by adding a dielectric material and / or a conductive material to a resin, rubber, or elastomer as a base material. Phone.

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