JP2002118408A - Shared antenna for multifrequencies - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate a tuning of frequencies. SOLUTION: This shared antenna for multifrequencies 1 is provided with a helical element 10, and a parasitic helical element 11 which is associated electromagnetically with helical element 10. A tip of parasitic helical element 11 is folded to form a linear return 11a, the length of which is changed to tune the frequency of parasitic helical element 11. At that time, return part 11a is not in dense combination with helical element 10, and frequency tuning can be operated without affecting helical element 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable telephone and a simplified portable telephone (PHS: personal handyphone system).
The present invention relates to a multi-frequency antenna that can be used in frequency bands separated from each other used in such a manner as described above.

[0002]

2. Description of the Related Art The number of subscribers of portable telephones and PHSs is increasing year by year, and the number of subscribers has led to a shortage of available frequencies. As described above, when the number of subscribers is insufficient due to the increase in the number of subscribers, two frequency bands, ie, a frequency band that can be used in almost all regions and a frequency band that can be used in urban areas are allocated as frequency bands for mobile phones. May have been. For example, in Europe, GS of 900MHz band
The M-type mobile phone can be used in all parts of Europe, but in an urban area, a 1.8 GHz band DCS-type mobile phone can be used in order to make up for a shortage of frequencies to be used. In order to use a mobile phone in two frequency bands, it is necessary to make the mobile phone operable in two frequency bands. That is, it is necessary to incorporate a radio circuit in each of the two frequency bands and to provide a dual-frequency antenna that operates in the two frequency bands.

[0003]

A multi-resonant antenna disclosed in Japanese Patent Application Laid-Open No. 10-242740 is known as this type of multi-frequency antenna. In this multi-resonant antenna, a parasitic antenna element that is electromagnetically coupled to a first antenna element to which power is supplied is provided, and the parasitic antenna element is helical. However, such a conventional multi-resonant antenna has a problem that, when realized as a specific antenna structure, it is difficult to adjust a frequency band in which the antenna resonates. Therefore, an object of the present invention is to provide a multi-frequency antenna that can easily adjust the frequency.

[0004]

In order to achieve the above object, a multi-frequency antenna according to the present invention comprises a helical element having one end serving as a feed point, and a helical element which is electromagnetically coupled to the helical element. A helical element and a parasitic helical element arranged substantially coaxially,
At the tip of the parasitic helical element, a folded portion is formed which is bent so as to extend linearly substantially along the central axis.

In the multi-frequency antenna according to the present invention, the helical element and the parasitic helical element are wound around an outer peripheral surface of an insulating bobbin having a substantially circular cross section. A lower end is connected to a conductive mounting portion on which a lower portion of the insulating bobbin is mounted, and the folded portion of the parasitic helical element is formed substantially along a central axis from an upper surface of the insulating bobbin. May be housed in the hole. Further, in the multi-frequency antenna according to the present invention, the helical element and the parasitic helical element may be formed on an outer peripheral surface of a cylindrical insulating bobbin having a through hole formed substantially along a central axis. And a lower end of the helical element is connected to a conductive film formed on a fixing portion formed at a lower end of the insulating bobbin, and the folded portion of the parasitic helical element is formed. May be formed by a conductive film formed in the through hole formed in the insulating bobbin.

Further, in the multi-frequency antenna according to the present invention, a whip antenna is disposed so as to be slidable in the through hole formed in the insulating bobbin, and the whip antenna is housed. When done,
An insulating portion formed above the whip antenna may be located in the through hole. Still further, in the multi-frequency antenna according to the present invention, the insulating bobbin is insulated and fixed to a tip of the whip antenna, and when the whip antenna is extended, power is supplied to the whip antenna. When the whip antenna is stored, a holder for supplying power to the helical element formed on the insulating bobbin may be provided.

[0007] According to the present invention, since the linear folded portion is formed in the parasitic helical element, the frequency can be adjusted by adjusting the length of the folded portion. Therefore, the frequency can be easily adjusted without changing the coupling relationship with the helical element.

[0008]

FIG. 1 shows a configuration showing the principle of a multi-frequency antenna according to the present invention. As shown in FIG. 1, the multi-frequency antenna 1 includes a helical element 10 and a parasitic helical element 11 electromagnetically coupled to the helical element 10. The power supply 2 is connected to the lower end of the helical element 10, and when power is supplied from the power supply 2, the helical element 10 is excited in its resonant frequency band. At the same time, a current flowing through the helical element 10 is induced in the parasitic helical element 11 arranged substantially coaxially with the helical element 10, and is excited in the resonating frequency band. Assuming that the helical element 10 resonates at the frequency f1 and the parasitic helical element 11 resonates at the frequency f2, the multi-frequency antenna 1 resonates at the frequencies f1 and f2 as shown in FIG. It operates in two different frequency bands centered on the frequency f1 and the frequency f2. The frequency f1 is, for example, a center frequency in an 800 MHz band, and the frequency f2 is, for example, 1.5 GHz.
It can be the center frequency of the band. Further, a matching circuit 3 for performing impedance matching between the power supply unit 2 and the multi-resonance antenna 1 may be inserted between the power supply unit 2 and the multi-resonance antenna 1 so as to achieve impedance matching between the two.

In the multi-frequency antenna 1 according to the present invention,
A characteristic configuration is a configuration in which the tip of the parasitic helical element 11 is bent to form a linear folded portion 11a. The folded portion 11a is not tightly coupled to the helical element 10 and the folded portion 11a
Even if the length of a is changed, the electromagnetic coupling relationship between the helical element 10 and the parasitic helical element 11 is maintained without change. Therefore, the folded portion 11a
By adjusting the length, the resonance frequency of the parasitic helical element 11 can be independently adjusted without affecting other elements. The folded portion 11a may be bent upward. If the length of the folded portion 11a is increased, the resonance frequency of the parasitic helical element 11 can be shifted to a lower side. If the length is reduced, the resonance frequency of the parasitic helical element 11 can be shifted to a higher frequency.

When the length of the lower end of the parasitic helical element 11 is increased,
Can be shifted to a lower frequency, and the coupling with the helical element 10 can be made denser. Conversely, the parasitic helical element 11
If the length of the lower end of the helical element 11 is reduced, the resonance frequency of the parasitic helical element 11 can be shifted to a higher direction, and the coupling with the helical element 10 can be reduced. Further, when the length of the upper end of the helical element 10 is increased, the resonance frequency of the helical element 10 can be shifted to a lower side, and the coupling with the parasitic helical element 11 can be made more dense. Conversely, if the length of the upper end of the helical element 10 is reduced, the resonance frequency of the helical element 10 can be shifted to a higher direction, and the coupling with the parasitic helical element 11 can be reduced.

The multi-frequency antenna 1 according to the embodiment of the present invention can be applied to an antenna of a mobile phone operating in a multi-frequency band. Therefore, FIG. 3 shows a configuration of a first application example in which the multi-frequency antenna 1 according to the embodiment of the present invention is applied to an antenna of a mobile phone.
(A) and (b). The mobile phone 50 shown in FIGS. 3A and 3B is operable in two frequency bands, for example, an 800 MHz band and 1.5 GHz. The mobile phone 50 includes a telephone antenna 51. The telephone antenna 51 includes the whip element 20 and the multi-frequency antenna 1 according to the present invention.

The whip element 20 is slidable through the inside of the multi-frequency antenna 1, and an antenna top 21 is provided at the tip thereof. FIG. 3 (a)
Shows a state in which the whip element 20 is stored in the mobile phone 50. In this state, the multi-frequency antenna 1 is in an operating state. FIG. 3B shows a state where the whip element 20 is extended, and in this state, the whip element 20 is in an operating state.

FIG. 4 shows a detailed configuration of the telephone antenna 51 described above. As shown in FIG. 4, an elongated insulating portion 22 is integrally formed at the tip of the whip element 20, and an antenna top 21 is formed at the tip of the insulating portion 22. The antenna top 21 and the insulating part 22
It is provided integrally with the tip of the whip element 20 by resin molding. The whip element 20 is formed by covering a wire made of a superelastic metal or the like with a resin tube, and a metal stopper 23 is fixed to a lower end thereof. The whip element 20 is slidably fitted in a through hole of the multi-frequency antenna 1.

The multi-frequency antenna 1 comprises a cylindrical insulating bobbin 12 and a resin cover 1a for accommodating the insulating bobbin 12, and a mounting portion 1b is provided below the cover. . This mounting portion 1b is shown in FIG.
As shown in (b), it is a mounting portion for mounting the multi-frequency antenna 1 to the mobile phone 50. In this case, the multi-frequency antenna 1 can be mechanically and electrically attached to the mobile phone 50 by screwing the screw formed on the mounting portion 1b to the mobile phone 50. When the whip element 20 is extended, the stopper 23
Is inserted into the mounting portion 1b, and the whip element 20
Is connected to the mounting portion 1b via the stopper 23. When the whip element 20 is stored, the insulating portion 22 is inserted into the through hole of the insulating bobbin 12, and the multi-frequency antenna 1 becomes operable.

The helical element 10 and the parasitic helical element 11 are formed on the insulating bobbin 12, and the detailed configuration of the insulating bobbin 12 is shown in FIGS.
Shown in However, FIG. 5A is a top view of the insulating bobbin 12, and FIG. 5B is a plan view thereof. As shown in these figures, a through hole 13 is formed substantially along the center axis of the insulating bobbin 12, and two helical grooves are formed on the outer peripheral surface of the insulating bobbin 12. A conductive film is formed in the two grooves, and the helical element 10 is formed by the conductive film formed in one groove, and the parasitic helical element 11 is formed by the conductive film formed in the other groove. Have been. The groove in which the passive helical element 11 is formed is
Is partially overlapped with the upper part of the groove where the groove is formed, and is formed substantially at the center between the grooves.

From the lower end of the insulating bobbin 12, a thread portion 14 having a small diameter and a thread formed on a peripheral side surface is formed to extend. A conductive film is formed on the surface of the screw portion 14 and the lower surface of the insulating bobbin 12,
This conductive film is connected to the conductive film formed in the groove where the helical element 10 is formed. Further, the diameter of the upper portion of the through hole 13 formed in the insulating bobbin 12 is slightly increased, and a conductive film is formed on the inner peripheral surface thereof.
A folded portion 11a is formed by this conductive film, and the folded portion 11a is formed in a groove in which the parasitic helical element 11 is formed by a groove formed on the upper surface of the insulating bobbin 12 as shown in FIG. Connected to the conductive film.

The conductive film is formed by depositing or applying a metal material. By cutting the conductive film formed in the through hole 13 from the lower end, the length of the folded portion 11a is reduced. Can be adjusted. Thereby, the resonance frequency of the parasitic helical element 11 can be adjusted independently without affecting other elements. Further, the screw portion 14 is screwed onto an upper portion of a metal mounting portion 1b formed integrally with the lower portion of the cover portion 1a, thereby connecting the helical element 10 to the mounting portion 1b.
Can be electrically connected to the insulation bobbin 1
2 can be fixed to the mounting portion 1b. When screwed, the insulating bobbin 12 is housed in the cover 1a. After the screw 14 is screwed on the upper part of the mounting portion 1b, the cover 1a is covered with the insulating bobbin 12. You may make it shape | mold.

Here, when the telephone antenna 51 constructed as shown in FIGS. 4 and 5 is attached to the portable telephone 50 as shown in FIGS. 3 (a) and 3 (b), the voltage of the telephone antenna 51 is measured. FIGS. 6 to 9 show the standing wave ratio (VSWR) and the impedance characteristics. However, the whip element 20 and the helical element 10 are 830 MH
It is for a cellular system using z to 925 MHz, and the parasitic helical element 11 is 1575.4.
GPS using 2MHz ± 1.023MHz (Global
Positioning System: Global positioning system). The VSWR characteristic shown in FIG. 6 and the impedance characteristic shown in FIG. 7 are the antenna characteristics of the whip element 20 in the telephone antenna 51 when the whip element 20 is extended. Referring to FIG. 6, the whip element 20 operates at 830 MHz.
In the frequency band of １925 MHz, the VSWR is about 1.
7 to about 1.9, and as shown in the Smith chart of FIG.
In the frequency band of Hz, the impedance is located near the center of the Smith chart, and has good impedance characteristics.

The VSWR characteristics shown in FIG.
The impedance characteristic shown in FIG.
4 shows the antenna characteristics of the multi-frequency antenna 1 in the telephone antenna 51 when the antenna is stored. Referring to FIG. 8, the multi-frequency antenna 1 has a frequency of 830 MHz to 925M.
VSWR in a frequency band of about 1.6 to about 2.
3 as well as frequency 1575.
At 42 MHz, the VSWR is a good value of about 1.7. Further, as shown in the Smith chart shown in FIG. 9, in the frequency band of 830 MHz to 925 MHz and the frequency of 1575.42 MHz, the impedances are all located near the center of the Smith chart,
It can be seen that the impedance characteristics are good.
As described above, the multi-frequency antenna 1 according to the present invention includes:
It can be seen that the device operates well in two frequency bands having greatly different frequencies.

Next, FIGS. 10A and 10B show the configuration of a second application example in which the multi-frequency antenna 1 according to the embodiment of the present invention is applied to an antenna of a portable telephone. FIG.
The mobile phone 60 shown in FIGS.
It can operate in two frequency bands of a Hz band and 1.5 GHz. The mobile phone 60 includes a telephone antenna 61.
Is provided. The telephone antenna 61 includes the whip element 20 and the antenna top 31 in which the multi-frequency antenna according to the present invention is built. The whip element 20 is extendable / storable with respect to the mobile phone 60, and an antenna top 31 is provided at a tip thereof. FIG. 10A shows a state in which the whip element 20 is stored in the mobile phone 60. In this state, the multi-frequency antenna built in the antenna top 31 is in an operating state. Also,
FIG. 10B shows a state in which the whip element 20 is extended. In this state, the whip element 20 is in an operating state.

FIG. 11 shows the telephone antenna 61 described above.
The detailed configuration of is shown. As shown in FIG. 11, an elongated insulating portion 32 is integrally formed at the tip of the whip element 20.
And the antenna top 31 are fixed so as to be arranged on one axis. The insulating part 32 penetrates through a pipe-shaped metal top plug 33 to form an antenna top 31.
Has reached within. The whip element 20 is formed by covering a wire made of a superelastic metal or the like with a resin tube, and a metal stopper 23 is fixed to a lower end thereof. A metal holder 24 attached to the mobile phone 60 is fitted into the whip element 20.

The antenna top 31 is composed of a cylindrical insulating bobbin 12 and a resin cover 31a for accommodating the insulating bobbin 12, and a top plug 33 extends from a lower end thereof. This top plug 33
The screw portion 14 of the insulating bobbin 12 is screwed on the upper portion of the upper portion, and the insulating bobbin 12 is fixed to the top plug 33. At the same time, the helical element 10 is electrically connected to the top plug 33. The holder 24 is screwed to a screw portion provided on the mobile phone 60, and when the whip element 20 is extended, the stopper 23 is inserted into the holder 24, and the whip element 20 is inserted into the holder via the stopper 23. 24. When the whip element 20 is stored, the top plug 33 is inserted into the holder 24, and the helical element 10 is electrically connected to the holder 24 via the top plug 33. The helical element 10 and the parasitic helical element 11 are formed on the insulating bobbin 12. Since the configuration of the insulating bobbin 12 is as shown in FIGS. 5A and 5B, the description thereof is omitted. I do.

The conductive film formed on the insulating bobbin 12 is formed by depositing or applying a metal material, and the conductive film formed in the through hole 13 is cut from the lower end. Thereby, the length of the folded portion 11a can be adjusted, whereby the resonance frequency of the parasitic helical element 11 can be adjusted independently without affecting other elements. The screw portion 14 is screwed onto the top plug 33, so that the helical element 10 can be electrically connected to the top plug 33. After the insulating bobbin 12 is screwed onto the top plug 33, the cover 31a is formed or mounted so as to cover the insulating bobbin 12 and the top plug 33.

Here, when the antenna 61 for a telephone constructed as shown in FIGS. 11 and 5 is attached to a portable telephone 60 as shown in FIGS. The standing wave ratio (VSWR) and the impedance characteristics are shown in FIGS. However, whip element 20 and helical element 10 are 8
It is for a cellular system using 30 MHz to 925 MHz.
GPS using 75.42MHz ± 1.023MHz
Antenna. VS shown in FIG.
The WR characteristics and the impedance characteristics shown in FIG. 13 are the antenna characteristics of the whip element 20 in the telephone antenna 61 when the whip element 20 is extended. Referring to FIG. 12, the whip element 20
Has a good VSWR of about 1.8 to about 2.0 in a frequency band of 830 MHz to 925 MHz. As shown in the Smith chart shown in FIG.
In the frequency band of 0 MHz to 925 MHz, the impedance is located near the center of the Smith chart,
It has good impedance characteristics.

The antenna characteristics of the telephone antenna 61 when the whip element 20 is stored are similar to the VSWR characteristics shown in FIG. 8 and the impedance characteristics shown in FIG. That is, the antenna top 31
The multi-frequency shared antenna built in
VSWR is about 1.6 to 25 MHz in the frequency band.
It has good characteristics of about 2.3 and a frequency of 1575.
At 42 MHz, the VSWR is a good value of about 1.7. Further, in the frequency band of 830 MHz to 925 MHz and the frequency of 1575.42 MHz, the impedance is located near the center of the Smith chart, and good impedance characteristics are obtained. Thus, it can be seen that the multi-frequency antenna according to the present invention built in the antenna top 31 operates well in two frequency bands having greatly different frequencies.

Next, FIG. 14 shows a configuration of a third application example in which the multi-frequency antenna 1 according to the embodiment of the present invention is applied to an antenna of a portable telephone. The mobile phone 70 shown in FIG. 14 is, for example, an 800 MHz band and a 1.5 GHz
It is operable in the frequency band. This mobile phone 70
Is provided with a telephone antenna 71. The telephone antenna 71 is fixed and fixed to the mobile telephone 70, and is constituted by the multi-frequency antenna according to the present invention.

FIG. 15 shows a detailed configuration of the telephone antenna 71 described above. As shown in FIG. 15, the telephone antenna 71 includes an insulating bobbin 42 and a cover 41a in which the insulating bobbin 42 is housed. A helical element 110 and a parasitic helical element 111 are provided by winding a wire on the outer peripheral surface of the elongated insulating bobbin 42 having a substantially circular cross section. A lower portion of the insulating bobbin 42 is provided with a metal mounting portion 43.
The lower end of the helical element 110 is electrically connected to the mounting portion 43. further,
The parasitic helical element 111 is located above the helical element 110 and is disposed between the elements. The upper portion of the parasitic helical element 111 is bent along the upper surface of the insulating bobbin 42, and the distal end portion is bent and disposed in a hole formed substantially along the center axis of the insulating bobbin 42. . The portion that is bent and disposed in the hole is a folded portion 111a. By adjusting the length of the folded portion 111a, the resonance frequency of the parasitic helical element 111 can be adjusted independently without affecting other elements. Also, the insulating bobbin 42 is attached to the mounting portion 43.
Then, the cover portion 41a is formed or mounted so as to cover the insulating bobbin 42 and the upper portion of the mounting portion 43.

As described above, when the telephone antenna 71 configured as shown in FIG. 15 is attached to the portable telephone 70 as shown in FIG. 14, the voltage standing wave ratio (VSWR) and impedance of the telephone antenna 71 are set. The characteristics are the same as the VSWR characteristics shown in FIG. 8 and the impedance characteristics shown in FIG. However, the helical element 11
0 is for a cellular system using 830 MHz to 925 MHz, and is a passive helical element 11.
1 is a GPS antenna using 1575.42 MHz ± 1.023 MHz. That is, the telephone antenna 71 to which the multi-frequency antenna according to the present invention is applied has a good VSWR of about 1.6 to about 2.3 in a frequency band of 830 MHz to 925 MHz and a frequency of 1575.42 MHz. VSWR is a good value of about 1.7. Also, 8
30 MHz to 925 MHz frequency band and frequency 1
At 575.42 MHz, all impedances are located near the center of the Smith chart, resulting in good impedance characteristics. Thus, it can be seen that the telephone antenna 71 to which the multi-frequency antenna according to the present invention is applied operates well in two frequency bands having greatly different frequencies.

The multi-frequency antenna according to the present invention has a cellular system using 830 MHz to 925 MHz and a frequency of 1575.42 MHz ± 1.023 M.
Hz / 800 MHz band (PDC, IS-54 / 1)
36, IS-95, GSM) and GPS. Further, the multi-frequency antenna according to the present invention has an 8
Any of the cellular systems in the 00/900 MHz band and the 1.7 / 1.8 / 1.9 GHz band (DCS180
0, DECT, PHS, PCS) in two frequency bands. Still further, the multi-frequency antenna according to the present invention has a GP
It can be operated in two frequency bands of S and any of the 1.7 / 1.8 / 1.9 GHz band cellular systems. Further, in the third application example, the insulating bobbin 12 shown in FIG. Further, in the first and second application examples, an insulating bobbin 42 shown in FIG. 15 may be used instead of the insulating bobbin 12.

[0030]

As described above, according to the present invention, since a linear folded portion is formed in the parasitic helical element, the frequency can be adjusted by adjusting the length of the folded portion. it can. Therefore, the frequency can be easily adjusted without changing the coupling relationship with the helical element.

[Brief description of the drawings]

FIG. 1 is a diagram showing a principle configuration of a multi-frequency antenna according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of frequency characteristics of the multi-frequency antenna according to the present invention.

FIG. 3 is a diagram illustrating a configuration of a first application example of the multi-frequency antenna according to the embodiment of the present invention.

FIG. 4 is a diagram showing a detailed configuration of a first telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied.

FIG. 5 is a diagram showing a detailed configuration of an insulating bobbin according to a first telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied.

FIG. 6 is a diagram illustrating VSWR characteristics of the first telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied, when the antenna is extended.

FIG. 7 is a diagram showing impedance characteristics of the first telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied when the antenna is extended.

FIG. 8 is a diagram illustrating VSWR characteristics when the first telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied is housed.

FIG. 9 is a diagram showing impedance characteristics when the first telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied is stored.

FIG. 10 is a diagram showing a configuration of a second application example of the multi-frequency antenna according to the embodiment of the present invention.

FIG. 11 is a diagram showing a detailed configuration of a second telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied.

FIG. 12 is a diagram illustrating VSWR characteristics of the second telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied, when the antenna is extended.

FIG. 13 is a diagram showing impedance characteristics of the second telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied, when the second telephone antenna is extended.

FIG. 14 is a diagram illustrating a configuration of a third application example of the multi-frequency antenna according to the embodiment of the present invention.

FIG. 15 is a diagram showing a detailed configuration of a third telephone antenna to which the multi-frequency antenna according to the embodiment of the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Multi-frequency antenna, 1a cover part, 1b mounting part, 2 feeding part, 3 matching circuit, 10 helical element, 11 parasitic helical element, 11a folded part, 12 insulating bobbin, 13 through hole, 14 screw part, 20 whip Element, 21 Antenna Top, 22 Insulation, 23 Stopper, 24 Holder,
31 antenna top, 31a cover part, 32 insulating part, 33 top plug, 41a cover part, 42 insulating bobbin, 43 mounting part, 50 mobile phone, 51 telephone antenna, 60 mobile phone, 61 telephone antenna, 70 mobile phone, 71 Telephone antenna, 1
10 helical element, 111 parasitic helical element, 111a folded part

Claims (5)

[Claims] A helical element having one end serving as a feeding point; and a parasitic helical element disposed substantially coaxially with the helical element so as to be electromagnetically coupled to the helical element. A multi-frequency antenna, wherein a folded portion is formed at the tip of the element so as to extend substantially linearly along a central axis. 2. The helical element and the parasitic helical element are wound around an outer peripheral surface of an insulating bobbin having a substantially circular cross section, and a lower end of the helical element is mounted on a lower portion of the insulating bobbin. And the folded portion of the parasitic helical element is housed in a hole formed substantially along the center axis from the upper surface of the insulating bobbin. The multi-frequency antenna according to claim 1, wherein: 3. The helical element and the parasitic helical element are formed in a helical groove formed on an outer peripheral surface of a cylindrical insulating bobbin having a through hole formed substantially along a central axis. A lower end of the helical element is connected to a conductive film formed on a fixing portion formed at a lower end of the insulating bobbin, and the folded portion of the parasitic helical element is formed on the insulating bobbin. The multi-frequency antenna according to claim 1, wherein the antenna is formed of a conductive film formed in the through hole. 4. A whip antenna is disposed so as to be slidable in the through hole formed in the insulating bobbin, and when the whip antenna is stored,
The multi-frequency antenna according to claim 3, wherein an insulating portion formed on an upper part of the whip antenna is located in the through hole. 5. The insulated bobbin is insulated and fixed to the tip of the whip antenna, and supplies power to the whip antenna when the whip antenna is extended and when the whip antenna is stored. 4. The multi-frequency antenna according to claim 3, further comprising a holder configured to supply power to the helical element formed on the insulating bobbin.