JP2001230617A - Antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve electrical characteristics of an antenna to be used for portable radio equipment, and to attain miniaturization and light weight. SOLUTION: A multiband antenna is constituted, by combining the helical coil of a flat conductor and a monopole antenna, composed of metal pipes having respectively different resonance frequencies. In comparison with the case of using a conventional conductor having a circular cross section, lightening and electrical characteristics improvements are enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna used for a portable radio, and more particularly to an antenna suitable for a portable telephone.

[0002]

2. Description of the Related Art Recently, portable telephones have become widespread. This mobile phone is provided with an antenna for transmitting and receiving radio waves for a call. This antenna includes a telescopic antenna that can be stored in a housing of a mobile phone for convenience in carrying, and a fixed antenna. As the fixed antenna, a helical coil-shaped antenna element having a resin-molded outer peripheral portion is used.

FIG. 5 shows an example of the structure of a conventional fixed helical coil antenna for a portable telephone.
In this antenna, a helical coil 51 is connected to a holder 12, and the holder 12 is further connected to a circuit board (not shown) in a housing of the telephone. The electrical length of the helical coil 51 corresponds to the wavelength λ used for a mobile phone,
For example, it is λ / 4. Conventionally, a so-called round wire whose material is phosphor bronze and whose cross section is circular has been used as the wire. The helical coil 51 is provided with a helical guide 52.
And the outer periphery was resin-molded. FIG.
1 shows an example of a fixed antenna for a mobile phone in which an outer peripheral portion is resin-molded.

FIG. 6 shows a structure of a conventional fixed monopole antenna for a portable telephone. Also in this case, the antenna element 61 is connected to the holder 12 and the holder 1
2 is further connected to a circuit board (not shown) in the housing of the telephone. The electrical length of the antenna element 61 is, for example, λ / 4 with respect to the wavelength λ used for the mobile phone. Conventionally, copper was used as the material, and the shape was a rod having a circular cross section, that is, a round bar. Then, the outer periphery of the antenna element 61 is resin-molded to form a fixed antenna for a mobile phone having the same shape as that of the helical coil antenna as shown in FIG.

FIG. 7 shows the structure of a conventional multiband antenna for a portable telephone. In this example, the helical coil 51 and the antenna element 61 of the monopole antenna are connected to the holder 12. In this case, the electrical length of the helical coil 51 is _１ ／ of the wavelength λ ₁ at the frequency of 800 MHz of the mobile phone.
The electrical length of the antenna element 61 is １ ／ of the wavelength λ ₂ of the mobile phone at the frequency of 1.9 GHz. The helical coil 51 is a phosphor bronze round wire, and the antenna element 61 is a copper round bar.

[0006]

In designing an antenna using a helical coil, the wire diameter, coil pitch,
It is necessary to optimize the conditions based on the coil outer diameter. In a helical coil using a round wire, a smaller coil outer diameter has a wider bandwidth and higher radiation efficiency, but has a problem that the entire length of the helical coil is longer. Although the radiation efficiency is increased even if the coil pitch is increased, the overall length of the helical coil also increases as a result.

As described above, in a helical coil using a round wire, an improvement in the electrical characteristics leads to an increase in the overall length of the antenna, and there is a limit in application to a device such as a mobile phone. Further, the helical coil using the round wire has a serious problem that the bandwidth cannot be widened as compared with other structures. Further, in a monopole antenna using a round bar, the applicable frequency becomes lower due to an increase in the outer diameter of the round bar, so that the size can be reduced, but there is a problem that the weight increases.

An antenna using a helical coil and a monopole antenna have problems when used alone as described above, and thus may be used as the multi-band antenna shown in FIG. In that case,
For example, 800 MHz is used for a helical coil at 1.9 GHz.
These two types of antennas are used with different resonance frequencies, such as a monopole antenna, but the shape becomes large or the electrical characteristics are 800 MHz.
There was a problem that the band was narrow.

Accordingly, an object of the present invention is to reduce the size and weight of an antenna used in a portable wireless device, and to improve electrical characteristics.

[0010]

SUMMARY OF THE INVENTION The present invention has been made as a result of studying the structures of a helical coil and a monopole antenna in order to solve the above problems. That is, the present invention is a helical coil antenna characterized in that a rectangular conductor is formed in a helical coil.

Further, the present invention is characterized in that in the helical coil antenna, the helical coil is formed such that a width direction of the rectangular conductor is substantially perpendicular to a longitudinal direction of the helical coil. Antenna.

Further, according to the present invention, in the helical coil antenna, the helical coil is electrically connected to a holder for attaching the helical coil to a housing of a wireless device and connecting the helical coil to a circuit board. An antenna characterized in that at least an outer peripheral portion of a coil is resin-molded.

Further, the present invention is a fixed type monopole antenna characterized in that a pipe-shaped metal is formed in an antenna element.

Further, according to the present invention, in the above monopole antenna, the antenna element is electrically connected to a holder for attaching the antenna element to a radio device housing and connecting the antenna element to a circuit board. An antenna, wherein at least the outer peripheral portion of the element is formed by resin molding.

Further, according to the present invention, the monopole antenna according to claim 4 is provided substantially at the center axis of the helical coil antenna, and the helical coil antenna and the monopole antenna have different resonance frequencies. This is a two-resonant antenna.

The present invention also provides the dual-resonance antenna, wherein the helical coil antenna and the monopole antenna are mounted on a holder for attaching the helical coil antenna and the monopole antenna to a radio device housing and connecting to the circuit board. The pole antenna is electrically connected,
An antenna characterized in that at least the outer peripheral portion of the helical antenna is resin-molded.

[0017]

In the helical coil using the rectangular conductor according to the present invention, the helical coil is formed so that the width direction of the rectangular conductor is substantially perpendicular to the longitudinal direction of the helical coil, so that the sectional area of the conductor is increased. Is the same as the round wire, the electrical characteristics can be improved.

Further, since the frequency band used for the mobile phone is a high frequency band of 800 MHz and 1.9 GHz, only the surface of the conductor acts as a conductor due to a so-called skin effect. Therefore, by using a pipe-shaped metal as the monopole antenna, the antenna is reduced in weight,
Electrical characteristics can also be improved.

Further, by applying the helical coil and the monopole antenna having the above structure to a multi-mode antenna, it is possible to reduce the weight and improve the electrical characteristics of the multi-mode antenna.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described. FIG. 1 shows an antenna using a rectangular conductor helical coil of the present invention. This antenna has a structure in which a helical coil 11 of a rectangular conductor is connected to a holder 12, and the holder 12 has a function of attaching the helical coil 11 to a mobile phone housing and a power supply unit for a circuit (not shown) in the housing. The structure has a screw portion 13 having the following functions.

By molding the outer periphery of the helical coil 11 with a resin, a fixed antenna having the appearance as shown in FIG. 4 is obtained. Further, the helical coil 11 may be formed by fitting to a helical guide similar to that shown in FIG.

Table 1 shows data comparing the characteristics of this antenna and an antenna using a conventional round wire helical coil. These data are measured in a state where the outer peripheral portion is not resin-molded. The material of the round wire and the rectangular conductor is copper, and the cross-sectional shape of the round wire is 1.58 m in diameter.
m, a rectangular conductor is a rectangle of 0.55 mm × 3.7 mm. Therefore, their cross-sectional areas are substantially the same. The pitch of each of the helical coils is 6 mm, the inner diameter of the helical coil of a round wire is 10 mm, the inner diameter of the helical coil of a rectangular conductor is 6 mm, and the length of each straight extension is 90 mm.

[0023]

[Table 1]

According to Table 1, the rectangular conductor helical coil is
The specific bandwidth is wider and the radiation efficiency is higher than that of the round helical coil. It can be seen that the use of the rectangular conductor is effective for improving the electrical characteristics of the antenna using the helical coil. Note that VSWR in Table 1 is an abbreviation for Voltage Standing Wave Ratio, and is a numerical value derived from the antenna input impedance and the characteristic impedance of the feed line.

Next, the case of a monopole antenna will be described. FIG. 2 shows the structure of a monopole antenna using the metal pipe of the present invention. In this example, an antenna element 21 made of a metal pipe made of copper and having a length of 30 mm, an outer diameter of 3.0 mm, and an inner diameter of 2.0 mm is connected to the holder 12, and the holder 12 uses a helical coil. It has the same function as that of. Also, in this case, when actually used, the outer peripheral portion can be resin-molded to have the appearance shown in FIG.

Table 2 shows data comparing the characteristics of this antenna and the conventional round bar antenna. The round bar in this case is copper having a diameter of 3.0 mm. In addition, characteristics were evaluated in a state where neither antenna was molded with resin. From the results shown in Table 2, all the antennas have the same resonance frequency and specific bandwidth, but the use of pipes has higher radiation efficiency, and the use of pipes reduces the weight of monopole antennas and improves electrical characteristics. It turns out that there is an effect in improvement.

[0027]

[Table 2]

Next, the case of a multi-band antenna will be described. FIG. 3 shows an example of a multi-band antenna in which a helical coil 11 using a rectangular conductor according to the present invention and an antenna element 21 made of a metal pipe are connected to a holder 12. The material shapes of the helical coil 11 and the antenna element 21 are the same as those described above,
The holder 12 also has the same function as in the case described above. The electrical length of the antenna using the helical coil is adjusted to _１ ／ of the wavelength λ _{1 at} the frequency of 800 MHz, and the monopole antenna is adjusted to １ ／ of the wavelength λ ₂ of the frequency of 1.9 GHz.

The helical coil 11 may be fitted to a helical guide having a hollow structure so that the antenna element 21 can be housed. In actual use, the outer periphery is resin-molded so that the external appearance is as shown in FIG.
According to the evaluation results of this multi-band antenna, the bandwidth is wider and the radiation efficiency is higher in the 800 kHz band, and the weight of the antenna element can be reduced in the 1.9 GHz band, as compared with the case where each is evaluated alone. Radiation efficiency increased. In other words, it has become possible to reduce the size and weight of the fixed multiband antenna for mobile phones and to improve the electrical characteristics.

[0030]

As described above, according to the present invention, by using a rectangular conductor for a helical coil and a metal pipe for a monopole antenna, a fixed type suitable for a portable radio device such as a cellular phone is used. It is possible to reduce the size and weight of the multiband antenna and to improve the electrical characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing an antenna using a rectangular conductor helical coil according to the present invention.

FIG. 2 is a diagram showing a monopole antenna using a metal pipe according to the present invention.

FIG. 3 is a diagram showing a multi-band antenna according to the present invention.

FIG. 4 is a diagram showing an antenna provided with a resin mold.

FIG. 5 is a diagram showing a conventional antenna using a round helical coil.

FIG. 6 is a diagram showing a conventional monopole antenna using a round bar.

FIG. 7 is a diagram showing a conventional multiband antenna.

[Explanation of symbols]

 Reference Signs List 11 Helical coil using rectangular conductor 12 Holder 13 Screw part 21 Antenna element using metal pipe 51 Helical coil using round wire 52 Helical guide 61 Antenna element using round bar

Continued on the front page F term (reference) 5J046 AA00 AA03 AB06 AB12 PA02 PA04 QA03 5J047 AA00 AA03 AB06 AB12 FD01

Claims (7)

[Claims] 1. A helical coil antenna wherein a rectangular conductor is formed in a helical coil. 2. The helical coil antenna according to claim 1, wherein the helical coil is formed such that a width direction of the rectangular conductor is substantially perpendicular to a longitudinal direction of the helical coil. And antenna. 3. The helical coil antenna according to claim 1, wherein the helical coil is electrically connected to a holder for attaching the helical coil to a wireless device housing and connecting to a circuit board. Wherein the helical coil is resin-molded at least on an outer peripheral portion of the helical coil. 4. A fixed monopole antenna, wherein a pipe-shaped metal is formed in an antenna element. 5. The monopole antenna according to claim 4, wherein said antenna element is electrically connected to a holder for attaching said antenna element to a radio device housing and connecting to a circuit board, and An antenna, wherein at least the outer peripheral portion of the element is resin-molded. 6. The monopole antenna according to claim 4, wherein the monopole antenna according to claim 4 is provided at a position substantially at the center axis of the helical coil antenna according to claim 1. A two-resonant antenna, wherein the antennas have different resonance frequencies. 7. The two-resonant antenna according to claim 6, wherein the helical coil antenna and the monopole antenna are mounted on a radio device housing and are connected to a circuit board by a holder. An antenna, wherein a pole antenna is electrically connected and at least an outer peripheral portion of the helical antenna is molded with a resin.