JP3361838B2 - Microstrip antenna for portable radio - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna for a portable radio such as a portable telephone, a cordless telephone and a personal communication telephone, and more particularly to the structure of an antenna suitable for a small portable radio.

[0002]

2. Description of the Related Art Taking a wireless line for a mobile phone as an example, a conventional band of 800 MHz is considered as an analog line, and a band of 900 MHz, 1.5 GHz, etc. is considered as a digital line including future problems. As a portable wireless device used in such a band, considering the convenience of carrying it and using it, there is a tendency to pursue more and more weight reduction and downsizing, and one example is currently 230 g and 150 cc. In the case of this portable wireless device, a whip antenna and a built-in inverted F antenna are mounted as antennas, but the built-in antenna has a reduced antenna gain due to its miniaturization, and in order to achieve further downsizing, a built-in inverted F There was a need for the invention of a high-efficiency antenna that replaces the antenna. Therefore, the present inventors have
Previously, the inventors invented and filed an antenna integrated with the housing, which utilizes a part of the housing as an antenna (Japanese Patent Application No. 3-1203).
No. 12). The previous invention was an invention utilizing the wavelength shortening effect of the dielectric constant, and was therefore an invention relating to a microstrip antenna using a dielectric substrate having a dielectric constant of 5 or more. The dielectric loss tangent is 2.5 × 10
~ ³ . However, considering the use in the future frequency band,
Further miniaturization is demanded.

The values of the dielectric constant and the dielectric loss tangent generally differ depending on the frequency. However, since there is no large variation in the above 800 MHz to 1.5 GHz band, all the characteristic values at 900 MHz in this specification. Shall be represented.

[0004]

In the case of an integrated antenna in which a part of the antenna is used in common with the case, when the case is large to some extent, the antenna can be made large and a large gain can be obtained. The smaller the housing, the smaller the antenna and the lower the gain. On the other hand, if the dielectric loss tangent is large, the efficiency of the antenna decreases. Therefore, it is particularly important that the dielectric loss tangent is small in order to further reduce the size of the portable wireless device.

The present inventors have conducted a search for a substrate material having a small dielectric loss tangent that does not reduce the gain, and found that there are some ceramics. However, since ceramics have drawbacks such as heavy weight and poor moldability,
Conventionally, it has not been practically used as a substrate material for a microstrip antenna. In the range of several hundred MHz to several GHz, the relative dielectric constant is 5 or more and the dielectric loss tangent is 2.5 × 1.
So far, polymer materials and composite materials of 0 to ³ or less do not exist. A first object of the present invention is to produce a dielectric material having a dielectric constant of 5 or more and a dielectric loss tangent of 2.5 × 10 ³ or less in a band of 800 MHz to 1.5 GHz, and using the same, a high gain mobile phone. An object is to provide a microstrip antenna for a wireless device. Further, in addition to the first object, a second object of the present invention is to provide a microstrip antenna for a portable wireless device in which an antenna is integrated, which does not hinder the reduction of the antenna gain particularly when a finger is touched during a call. Especially.

[0006]

In order to achieve the first object, the microstrip antenna for portable radio of the present invention is used in the band of 800 MHz to 1.5 GHz.
A microstrip antenna according to claim 1, wherein the dielectric substrate of the antenna is composed of a composite material containing Sr-containing BaTiO ₃ ceramic particles as a main component in a weight ratio and a polyolefin polymer matrix mixed therewith. By doing so, for example, a high gain as shown by A ₁ by the material 1 on the characteristic A of FIG. 1 is obtained.

Alternatively, in order to achieve the above first object,
The microstrip antenna for a portable wireless device of the present invention is
Microphone used in the 800MHz to 1.5GHz band
A losstrip antenna, wherein the dielectric substrate of the antenna is composed of a composite material in which ceramic particles of titania TiO ₂ are used as a main component in a weight ratio, and this is mixed with a polyolefin polymer matrix. . In this case, for example, as indicated by A ₂ of the material 2 on the characteristic A in FIG. 1, the gain is slightly inferior to the above A ₁ , but the high gain is secured while the weight is reduced as described later. It has the advantage of.

Here, in any of the above cases, the composite material is realized by a composition having a weight ratio of ceramics of 90% or less and a polyolefin polymer matrix of 10% or more.

A microstrip antenna for a portable wireless device of the present invention for achieving the above second object is arranged on the outer surface of the folding part of a portable wireless device having a folding part in a part of a housing, and A part of the antenna is integrated with the housing. Thus, as will be described later, for example, correspond to the characteristics A _1, A ₂ in FIG. 1, when a call is on characteristic B of what some reduction in gain due to a human body proximity as described below B _1, the B ₂ High gain is secured.

[0010]

[Function] Ceramics are not practical when they are in particle form and their characteristics cannot be evaluated, and they are usually used in a sintered state. And, as the sintered one, there is one that has a large dielectric constant and a small dielectric loss tangent, but as described above,
The disadvantage is that it is heavy and has poor moldability.

In the present invention, it is important to use BaTiO ₃ ceramic particles containing Sr as a main component in a weight ratio and to mix this with a polyolefin polymer matrix to form a composite material. . (Here, conceptually, the matrix is referred to as the B matrix when mixed with the B material when the A material is mixed with the B matrix. Also, the A on the mixed side is referred to as the A filler. (1) A ceramic powder having a large permittivity and a small dielectric loss tangent and a polymer material having a small permittivity and a small dielectric loss tangent are mixed and compounded as described above so that the ceramic particles are the main components in the weight ratio. As a result, a composite material having a large dielectric constant and a small dielectric loss tangent can be formed. (2) In this case, Sr functions to lower the dielectric loss tangent. (3) By mixing and compositing the ceramic particles as the main component in the weight ratio as described above, the secondary workability such as injection molding, compression molding, and punching is improved, and also as a dielectric substrate of the antenna. It becomes easy to form. (4) Since the polymer material has a specific gravity of about 1 and the ceramics has a specific gravity of 4 to 7, it is possible to reduce the weight of the composite material to about half. (5) Then, by using a composite material having excellent dielectric properties and molding processability as described above as the dielectric substrate, it is possible to configure the antenna of high gain as described above.

[0012] In the present invention as a main component ceramic particles of TiO ₂ in weight ratio, the case of a composite material by mixing a polyolefin-based polymer matrix which, as above SL except the effects of the Sr It has a meaning. Moreover, especially in this case, since the TiO ₂ ceramic particles themselves are lighter than the BaTiO ₃ ceramic particles,
Although the characteristics of the dielectric material are slightly inferior in terms of electrical properties, it is possible to form an antenna that has an advantage of being lightweight.

In addition to electrical dielectric properties, the above-mentioned problems such as workability and weight are important for a composite material as a dielectric substrate for an antenna. From such a viewpoint, 90% by weight of ceramics is used. Hereinafter, it can be realized by using a polyolefin polymer matrix having a composition of 10% or more. However, as will be described later as an example from the viewpoint of sufficiently utilizing the high dielectric constant of ceramics and improving the workability of a polymer material, (a) Ba containing Sr is used.
The weight ratio of the TiO ₃ ceramic particles is 83%,
With a composite material obtained by mixing this with a polyolefin polymer matrix of 17%, a dielectric material having a dielectric constant of 15.8 and a dielectric loss tangent of 4.4 × 10 to ⁴ can be obtained.
The weight ratio of the ceramic particles of TiO ₂ is 83%,
A composite material obtained by mixing this with 17% of a polyolefin-based polymer matrix has a dielectric constant of 10.3 and a dielectric loss tangent of 2.4 × 10 ⁻³ . That is, excellent characteristics exceeding the achievement of the first object of the present invention can be obtained.

Needless to say, if the antenna is integrated with the housing of the wireless device, the convenience of handling will be extremely high. However, in this type of portable wireless device of a box type, Your hand may touch the antenna during a call,
It tends to cover the antenna part, which causes instability so that the call is easily disturbed. However, the microstrip antenna for a portable wireless device of the present invention is arranged on the outer surface of the folding part of the portable wireless device having the folding part in a part of the housing, and a part of the antenna is integrated with the housing. By adopting the configuration, for example, as can be seen from the configuration of FIG. 3, it is possible to configure the folding unit to be used in an upright state, which enables communication without touching the antenna even during a call. Become natural. As a result, although there is some unavoidable gain reduction due to the proximity effect of the human body, high gain characteristics such as those shown by the B ₁ and B ₂ characteristics in FIG. 1 can be obtained with high stability.

[0015]

1 is a characteristic diagram of the dielectric loss tangent and the antenna gain of an embodiment of the present invention, FIG. 2 is a structural diagram of the microstrip antenna of the present invention, and FIG. 3 is a portable device of the present invention. It is a figure showing an example of appearance of a microstrip antenna for radios, and a foldable portable radio. Fig. 2 shows a microstrip antenna using a dielectric substrate made of a composite material of ceramic particles and a polyolefin-based polymer matrix, having a relative dielectric constant of 5 or more and a dielectric loss tangent of 2.5 × 10 ³ or less. It shows the configuration of. The radiation plate conductor 1 and the substrate conductor 3 (ground) are made of low loss metal, and the dielectric substrate 2 is inserted between these conductors,
The radiating plate conductor 1 is connected to the inner conductor of the feeder 4 of the coaxial cable. FIG. 3 shows an example of the external configuration of a portable wireless device as a mobile phone with a microstrip antenna, which uses the substrate conductor 3 of the microstrip antenna of FIG. 2 described above as a part of the casing. Is. Although the details will be described later, it is characterized by having a structure of a folded portion in part and mounting the antenna of the present invention on the outer surface of the folded portion.

In FIG. 1, the horizontal axis represents the dielectric loss tangent of the dielectric material of the dielectric substrate 2, and the vertical axis represents the gain as an antenna. The gain is dBd, where the relative gain with respect to the gain of the (1/2) wavelength dipole antenna is used as a standard dBd.
Is displayed in. In addition, there are indications of characteristics A and B in the figure. Characteristic A is a characteristic when the folded portion of the portable wireless device of FIG. 3 is set upright and placed in a free space that does not particularly disturb the characteristic of the antenna, and characteristic B is the characteristic of this portable wireless device. Shows the characteristics of the state when talking with the phone. Further, the point characteristics A ₁ and A _{2 in the} characteristic A are characteristics of the _first and _second embodiments of the present invention, respectively, and the point characteristic A ₃ is only a characteristic example different from the example. B ₁ ,
B ₂ and B ₃ correspond to A ₁ , A ₂ and A ₃ , respectively. In the characteristic of FIG. 1, the gain characteristic desired by the present inventors is −11.
When the target is equal to or higher than dBd and the gain is suitable for this, it is treated as a high gain in this specification.

In FIG. 1, the features to be noted are as follows. (1) Although the dielectric constants of the dielectric substrates used for A ₁ , A ₂ , and A ₃ are added, the characteristic A shows that the dielectric loss tangent effectively contributes to the improvement of the gain characteristic. (2) Since the human body approaches the antenna during a call, the gain is reduced by several dBd due to the influence. Although not shown in the figure, when the hand touches the antenna during a call, the characteristic B further easily and unstablely deteriorates by several dBd or more. In the case of the present invention, even though the portable wireless device is small, since the antenna is attached to the folding portion as described above, it is naturally eliminated that the hand touches the antenna portion during a call, and it is stable like the characteristic B. Various characteristics can be obtained. (3) In each of the first and second embodiments, high gain characteristics are obtained even if the decrease in gain due to the proximity effect of the human body during a call is taken into consideration.

Next, FIG. 1 for the first and second embodiments.
Will be explained together. Example 1: 83 wt% BaTiO ₃ -based powder containing Sr as a ceramic filler and 17 wt% polypropylene copolymer as a polymer matrix were roll-kneaded to obtain a dielectric property measurement sample having a length of 10 mm, an inner diameter of 3 mm, and an outer diameter of 7 mm. Is prepared and 80 by the S-parameter method
Dielectric properties from 0 MHz to 1.5 GHz were measured. As a result, the dielectric constant was 15.8 and the dielectric loss tangent was 4.4 × 10 ⁴ as a typical value at 900 MHz. Using this composite material, a microstrip antenna substrate having a thickness of 2 mm, a width of 35 mm and a length of 45 mm was produced. A radiating plate conductor and a substrate conductor (earth plate) were formed on this, and a feeding line was attached to the microstrip antenna. This was integrated with the casing of the casing radio and the antenna gain was measured. As a result, the antenna gain is -4.9 dBd in the case of vertical holding in free space, and the antenna gain is -9.0 dBd in the case of a call held by a human hand, which shows good characteristics of high gain. It was

Example 2: T as a ceramics filler
Using 83 wt% of io ₂ powder and 17 wt% of polypropylene copolymer as a polymer matrix, roll kneading was performed to prepare a dielectric property measurement sample having a length of 10 mm, an inner diameter of 3 mm, and an outer diameter of 7 mm.
Dielectric properties from z to 1.5 GHz were measured. As a result, 9
As a typical value of 00 MHz, the dielectric constant was 10.3 and the dielectric loss tangent was 2.4 × 10 ⁻³ . Using this composite material, a microstrip antenna substrate having a thickness of 2 mm, a width of 55 mm and a length of 60 mm was produced. A radiating plate conductor and a substrate conductor (earth plate) were formed on this, and a feeding line was attached to the microstrip antenna. This is integrated with the housing,
The antenna gain was measured. As a result, the antenna gain is -6.5 dBd in the case of vertical holding in free space, which is held by a person by hand, and the antenna gain is
It was −10.9 dBd, which showed good characteristics of high gain. The gain in this case is inferior to that in the first embodiment because the dielectric loss tangent of the dielectric substrate is large, but the gain characteristic is T.
Since the TiO ₂ powder material is lighter than the BaTiO ₃ system powder, there is an advantage that a lightweight antenna can be constructed.

In the above-mentioned embodiment, a roll-kneading composition was used in which 83 wt% of the ceramic filler and 17 wt% of the polymer matrix were used, but the composition ratio is not limited to this, and the ceramic filler may be used. 90 wt% or less, and the polymer matrix may be selected in the constitution of 10 wt% or more.

FIG. 3A is an external view showing a state in which the folding part on which the integrated antenna is mounted is closed, and FIG.
[Fig. 3] is an external view when the folding portion is opened for a call. As an example of a telephone, a push button unit and a microphone are provided on a fixed unit, and a display unit and a speaker are mounted on the inner surface of the folding unit. With such a structure, even if the overall size of the portable wireless device is small, the antenna naturally does not touch the antenna during a call, and a stable call can be secured.

[0022]

As described above, according to the present invention, a dielectric material having a dielectric constant of 5 or more and a dielectric loss tangent of 2.5 × 10 to ³ or less can be obtained.
It is possible to realize an integrated microstrip antenna with a high-gain housing for a small portable wireless device that can support the frequency band of Hz. The dielectric substrate for the antenna has practically excellent characteristics in terms of moldability, processability, and weight. Since this antenna is mounted on the outer surface of the small housing having the folding portion, stable communication characteristics with high gain can be obtained despite the small size. Further, since the output from the antenna can be reduced by improving the gain of the antenna, advantages such as a small capacity, a small size, and a long life of the battery are brought about, which is useful for making the portable wireless device small and lightweight.

[Brief description of drawings]

FIG. 1 is a characteristic diagram of a dielectric loss tangent and an antenna gain according to an embodiment of the present invention.

FIG. 2 is a structural diagram of a microstrip antenna.

FIG. 3 is an external view of a microstrip antenna for a portable wireless device and a foldable portable wireless device according to the present invention.

[Explanation of symbols]

1 ... Radiant plate conductor 2 ... Dielectric substrate 3 ... Board conductor 4 ... power supply line 5: Microstrip antenna 6 ... speaker 7 ... Display 8 ... Push button part 9 ... Mike

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shiro Nishi 1-6-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (56) Reference JP 3-162003 (JP, A) JP JP 3-216910 (JP, A) Actual Kaihei 4-85836 (JP, U) Technical report of IEICE, Vol. 90, No. 258 (1990) p. 113-118 “Composite Dielectric Journal of Apply d Polymer Science, Vol. 22, No. 8 (197 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01B 3/00 H01Q 13/08 H04Q 7 / 32

Claims (4)

(57) [Claims] 1. A microstrip antenna having a substrate conductor, a radiation plate conductor, and a dielectric substrate as a medium between these conductors is arranged in a part of a portable radio device, and has a frequency of 800 MHz to 1.5 MHz.
A microstrip antenna for portable radio equipment for use in a band of GHz, the dielectric substrate, the ceramic particles of BaTiO ₃ containing Sr as main components at a weight ratio, mixed with a polyolefin polymer matrix which A microstrip antenna for a portable wireless device, characterized in that it is made of a composite material. 2. A microstrip antenna having a substrate conductor, a radiation plate conductor, and a dielectric substrate as a medium between these conductors is arranged in a part of a portable radio device, and has a frequency of 800 MHz to 1.5 MHz.
A microstrip antenna for portable radio equipment for use in a band of GHz, the dielectric substrate, the ceramic particles of TiO ₂ as a main component at a weight ratio, formed by combining an polyolefin-based polymer matrix which composite A microstrip antenna for a portable wireless device, which is made of a material. 3. The microstrip antenna for a portable wireless device according to claim 1 or 2, wherein the composite material has a weight ratio of ceramics of 90% or less and a polyolefin polymer matrix of 10% or more. A microstrip antenna for a portable wireless device, which is characterized by being a thing. 4. The microstrip antenna for a portable wireless device according to claim 1, wherein the microstrip antenna has a folding part in a part of a housing of a folding part of the portable wireless device. A microstrip antenna for a portable wireless device, characterized in that it is arranged on the outer surface and part of the antenna is integrated with a housing.