JPH11274840A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device with which the power feeding point position of an antenna can be set to a position offset from the contact position of a radio equipment casing and the antenna. SOLUTION: The linear part of a linear antenna element 21. adding a loading coil 22 to its top end is covered with an outer coaxial. conductor 23 through an insulator 24 and a coaxial structure with the part of the antenna element 21 as a core wire is provided. A sleeve constitutive part 25 is provided while being connected to the terminal part of the outer coaxial conductor 23 on the side of the loading coil so as to cover at least one part of the outer coaxial conductor 23 through the insulator 26. When the terminal part of the antenna element 21 on the opposite side of the loading coil 22 is defined as the contact part with radio equipment, a connecting part 42 of the antenna element 21 and the loading coil 22 is effectively used as a power feeding point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device called a whip antenna, which is used for an antenna device such as a mobile phone.

[0002]

2. Description of the Related Art As an antenna for a portable telephone, a whip antenna is mounted so as to be housed in a housing thereof, and the whip antenna is pulled out when used.

[0003] Conventionally, a feeding point when the whip antenna of this type is used in a state of being pulled out is a contact portion with a radio device housing, and a dipole structure is formed by an antenna element portion and a ground plate of the radio device housing. It has become.

[0004]

However, as in the prior art, when the power supply point at the time of use in a state where the antenna is pulled out is a contact portion with the case of the radio device, the high-frequency current is supplied to the radio device case. It also flows to the body. For this reason, in the case where the housing is used by holding it like a mobile phone, the influence of a human hand occurs.

On the other hand, in a portable telephone, during a call,
The user holds the housing in his hand and uses it close to the ears of the head. For this reason, in this call state, various characteristics of the antenna are deteriorated due to the influence of the human hand or head on the contact portion between the antenna element serving as the feeding point and the wireless device housing.

Further, when the portable telephone is held close to the ears of the head during use during a call, the power supply point, which is the maximum point of the high-frequency current, is located closest to the head. However, due to the problem of exposure of the head to radio waves, it is desirable that the position of the feeding point, which is the maximum point of the high-frequency current, be as far away from the head as possible.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an antenna device in which the position of the feeding point of the antenna can be offset from the contact position between the antenna of the radio unit and the antenna.

[0008]

In order to solve the above-mentioned problems, an antenna device according to the first aspect of the present invention comprises a linear antenna element having a loading coil added to a tip thereof, and a linear portion of the antenna element. Covered via an insulator, a coaxial outer conductor for forming a coaxial structure with the antenna element portion as a core wire, and connected to the loading coil side end of the coaxial outer conductor,
A sleeve component provided to cover at least a part of the coaxial outer conductor via an insulator.

In the configuration of the first aspect, even when the end of the antenna element opposite to the loading coil side is a contact portion with a radio device,
The connection point between the antenna element and the loading coil can be effectively set as a feeding point.

The invention according to claim 2 is the antenna device according to claim 1, wherein the antenna device can be pulled out and stored in a housing of the wireless device. In addition to the direct power supply, a contact point with the housing of the wireless device is configured such that the coaxial portion forming the stub has high impedance at a used frequency.

According to the second aspect of the present invention, since the power is directly supplied to the loading antenna and the element side has a high impedance, it is possible to prevent a high-frequency current from flowing to the element side.

The antenna element may be made of a conductor having elasticity, and the surface of the conductor may be plated with copper to reduce the high-frequency resistance.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a case where an embodiment of an antenna device according to the present invention is applied to a whip antenna of a portable telephone such as a portable telephone or a PHS will be described.

FIG. 2 shows an example of a housing of a portable telephone. An opening 12h for a receiver (speaker) and a transmitter (microphone) are provided on a front face 10f of the housing 10.
13h, a dial key 14 and various function control keys 15 are provided. Further, the liquid crystal display element 16 is provided at the center of the front face 10f.

An arc-shaped overhang 10c is formed on the upper left side of the housing 10 to prevent the housing 10 from being dropped during use. An operation knob for function control is provided so as to be in contact with the periphery of the overhang portion 10c, and when the user holds the housing 10 with the left hand, the periphery of the knob 21 is driven upward or downward by the thumb, The knob 21 is rotated clockwise or counterclockwise.

On the upper surface 10t of the casing 10, a flexible monopole antenna, a so-called whip antenna 18 having a length of 1/4 of the wavelength λ corresponding to the transmission / reception frequency, is provided.
The whip antenna 18 is pulled out during use.

At the tip of the whip antenna 18, a loading coil 19 having an electrical length of 1/4 of the wavelength λ corresponding to the transmission / reception frequency is added.

FIG. 1 shows an example of the configuration of a whip antenna 18 as an antenna device according to this embodiment.

As shown in FIG. 1, a top loading coil 22 is added to the tip of an antenna element 21 composed of a linear conductor. The element 21 is made of an elastic conductor, and its surface is plated with copper in order to increase high-frequency electrical conductivity.

The length of the linear element 21 is １ ／ of the wavelength λ corresponding to the transmission / reception frequency. The electrical length of the top loading coil 22 is also set to be １ ／ of the wavelength λ corresponding to the transmission / reception frequency.

The portion of the linear element 21 is
It has a coaxial structure with this element 21 as a core wire. That is, the element 21 is disposed at the center line position of the cylindrical coaxial outer conductor 23 and is covered with the coaxial inner insulator 24 except for the end opposite to the loading coil 22 side. The element 21, the coaxial inner insulator 24, and the coaxial outer conductor 23 form a coaxial transmission line.

In this example, an insulator having a dielectric constant er of about 4.0 is used as the coaxial internal insulator 24. This is to reduce the wavelength of the high-frequency current flowing through the element 21 so that the electrical length of the element 21 is close to half a wavelength. That is, the element 21
This is because the length of the transmission / reception wave is １ ／ wavelength on the element 21 since the length of the transmission / reception frequency is １ ／ wavelength.

Outside the coaxial outer conductor 23, a tubular sleeve component 25 is provided. This sleeve component 25
Are connected to the coaxial external conductor 23 at the end on the top loading coil 22 side, and are substantially integrally formed with the coaxial external conductor 23.

The sleeve holding insulator 26 is filled between the sleeve constituting portion 25 and the coaxial outer conductor 23. As the sleeve holding insulator 26,
An insulator having a dielectric constant er around 1.0 is used. this is,
This is for operating the sleeve constituting section 25 as a super top.

Next, a description will be given of the electrical connection structure in the housing when the antenna device of the embodiment is pulled out and stored in the case of a portable telephone.

FIG. 3 shows a connection structure when the antenna is pulled out. As shown in FIG. 3, when the antenna is pulled out, the high-frequency current generated by the transmission signal generator shown by the internal oscillator 31 is applied to the contact member 3.
2, power is supplied to the end of the element 21 opposite to the top loading coil 22 side.

The supplied high-frequency current travels through a coaxial transmission line having a coaxial structure in which the impedance of the contact member 32 and the contact portion 41 with the element 21 is the characteristic impedance while suppressing the matching loss. 2
1 reaches the connection portion 42 with the top loading coil 22. Here, the top loading coil 22
Is supplied to the dipole antenna constituted by the sleeve constituting section 25. Therefore, the feeding point at this time is the connecting portion 42 and is a position offset from the contact portion 41 corresponding to the feeding point of the conventional whip antenna.

At this time, the contact member 33 electrically connected to the housing base plate 30 of the portable telephone is connected to the coaxial outer conductor 2 on the open end side of the sleeve constituting portion 25 at the contact portion 43.
Touch 3. As a result, the potential of the oscillator 31 and the potential of the coaxial external conductor 23 are shared.

Next, the connection structure when the antenna is housed is shown in FIG.
This will be described with reference to FIG. When the antenna is housed, the contact member 32 comes into contact with the connection portion 42 of the element 21 with the top loading coil 22, and the high-frequency current from the oscillator 31 is directly supplied to the top loading coil 22.

At this time, the coaxial portion on the element 21 side forms a stub, but the coaxial internal insulator 24 has a dielectric constant of 4.
Since the element 21 is made of an insulator of zero, the wavelength of the high-frequency current flowing through the element 21 is shortened, and the electric length of the element 21 becomes close to １ ／ wavelength. At this time, the end of the element 21 opposite to the top loading coil 22 is an open end. Therefore, in the contact portion 42, the coaxial portion on the element 21 side constituting the stub has a high impedance, and the outflow of the high-frequency current to the element 21 side can be prevented.

When the antenna is stored,
A contact member 34 electrically connected to the housing base plate 30 of the mobile phone contacts the sleeve constituting portion 25 at the contact portion 44 and is electrically connected to the housing base plate 30 of the mobile phone. The contact member 35 that is
And at the contact portion 44.

As a result, the coaxial outer conductor 23 and the housing base plate 30 can be set to the same potential, and the influence of a human body such as a user's hand or head approaching the element 21 can be reduced. Can be.

The high-frequency current supplied at the contact portion 42 flows through the contact portion 44 to the housing base plate 30 through the contact member 34, and the top loading coil 22
The case base plate 30 forms a dipole antenna configuration. This is a configuration similar to a conventional whip antenna.

As described above, according to the antenna device of this embodiment, when the antenna is pulled out, the feeding point is located on the top loading coil side offset from the contact point between the portable telephone case and the antenna element. Therefore, the maximum point of the current distribution occurs at a position away from the user's head.

Therefore, as compared with the conventional antenna, the influence of the human body on the antenna characteristics is reduced, and the antenna radiation efficiency and the radiation directivity are improved. In addition, as described above, since the high-frequency current does not flow through the housing of the mobile phone, the influence of the user holding the device is reduced.

In the above description, a case has been described in which the present invention is applied to a portable telephone, but it goes without saying that the present invention can also be applied to a transceiver or the like.

[0037]

As described above, according to the present invention, the position of the feeding point of the antenna can be set to a position offset from the contact position between the radio unit housing and the antenna. For this reason, even in the case of a wireless device such as a mobile phone that is held and used by a user, deterioration of antenna characteristics can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a main part of an embodiment of an antenna device according to the present invention.

FIG. 2 is a diagram showing a portable telephone as an example of a wireless device to which the antenna device according to the present invention is applied;

FIG. 3 is a diagram showing a connection structure when the antenna is pulled out of the embodiment of the antenna device according to the present invention.

FIG. 4 is a diagram showing a connection structure when the antenna is housed in the embodiment of the antenna device according to the present invention.

[Explanation of symbols]

21: antenna element, 22: top loading coil, 23: coaxial outer conductor, 24: coaxial inner insulator,
25 ... Sleeve constituent part, 26 ... Sleeve part holding insulator,
Reference numeral 30: housing base plate, 31: oscillator, 32: contact member, 33
... contact member, 34 ... contact member, 35 ... contact member

Claims (3)

[Claims] 1. A linear antenna element having a loading coil added to a tip thereof, and a linear portion of the antenna element is covered with an insulator to form a coaxial structure having the antenna element as a core wire. A coaxial external conductor, and a sleeve component connected to an end of the coaxial external conductor on the loading coil side and provided so as to cover at least a part of the coaxial external conductor via an insulator. Even when the end of the antenna element on the side opposite to the loading coil side is a contact portion with a wireless device, a connection point between the antenna element and the loading coil is effectively set as a feeding point. Antenna device. 2. An antenna device capable of being pulled out and housed in a housing of a wireless device, wherein in the housed state, power is directly supplied to the loading coil unit and the coaxial unit constituting a stub is provided. The antenna device according to claim 1, wherein a contact point with a housing of the wireless device is configured such that the impedance becomes high at a use frequency. 3. The antenna according to claim 1, wherein the antenna element is formed of a conductor having elasticity, and a surface of the conductor is plated with copper to reduce a high-frequency resistance value. Antenna device.