JP2003037426A - Multi-frequency helical antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure each necessary frequency band for two or more frequency bands. SOLUTION: The multi-frequency helical antenna 20 includes an excitation coil unit 17, wound around the side circumferential face of a base unit 20a in a helical form and operated in a high frequency band, a parasitic coil unit 16 and a second parasitic coil unit 19, wound among the space of windings of the excitation coil unit 17. The excitation coil unit 17 is fed in power from a power feeding point 21 via a base unit 20b, and the parasitic coil unit 16 and the second parasitic coil unit 19 are coupled electrically with the excitation coil unit 17 and are fed from the excitation coil unit 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-frequency helical antenna that can be used in different frequency bands, and more particularly to a multi-frequency helical antenna suitable for mounting on a mobile device in a mobile telephone network.

[0002]

2. Description of the Related Art The number of subscribers to mobile phones and PHSs is increasing year by year, and the number of subscribers to mobile telephone networks is becoming insufficient due to the increase in subscribers. In this way, when the available frequency is insufficient due to an increase in the number of subscribers, a frequency band that can be used in almost the entire frequency band of a mobile phone,
Two frequency bands, a frequency band that can be used in urban areas, may be allocated. For example, 900 in Europe
Although the GSM system mobile phone in the MHz band can be used throughout Europe, in addition, in the urban area, the DCS system mobile phone in the 1.8 GHz band can be used in order to make up for a lack of available frequencies. Also in Japan 8
Frequency bands of 00 MHz band and 1.5 GHz band are assigned to the mobile telephone network. In order to use the mobile phone in such two frequency bands, it is necessary to make the mobile phone operable in the two frequency bands. That is, it is necessary to have a built-in radio circuit capable of operating in each of the two frequency bands and to have a two-frequency antenna that operates in the two frequency bands.

[0003]

As a dual-frequency helical antenna of this type, a dual-frequency helical antenna 115 as shown in FIG. 11 has been proposed. The dual-frequency helical antenna 115 has a first coil shown in a solid line wound in a coil shape.
The coil unit 116 and the second coil unit 117 shown by a broken line are provided. The winding start end of the first coil portion 116 and the winding start end of the second coil portion 117 are connected to each other, and power is fed from the power feeding portion 118 to the winding start end. 1st coil part 1
16 operating frequency bands of 800 MH in mobile telephone network
The length of the first coil unit 116 is adjusted so as to be in the z band, and the length of the second coil unit 117 is adjusted so that the operating frequency band of the second coil unit 117 becomes the 1.5 GHz band in the mobile telephone network. The adjustment allows the dual-frequency helical antenna 115 to operate in the 800 MHz band and the 1.5 GHz band in the mobile telephone network.

At this time, the dual-frequency helical antenna 115
FIG. 13 shows the voltage standing wave ratio (VSWR) characteristics of the above. With reference to this figure, it is possible to secure only a band of about 20 MHz as a frequency band of 800 MHz, and VSWR is 3.0 or more, which is not a good characteristic. For example, in the 800 MHz band in PDC (Personal Digital Cellular), a frequency band of about 70 MHz is required as the frequency band for upstream and downlink, but the antenna characteristics shown in FIG.
The frequency band of 0 MHz is not secured. Also, FIG.
Referring to FIG. 3, a frequency band of about 30 MHz is secured in the 1.5 GHz band, and a good value of the best VSWR value of about 1.6 is obtained. However, even in the 1.5 GHz band in the PDC, a frequency band of about 70 MHz is required as the frequency band for upstream and downstream, but the antenna characteristics shown in FIG.
The frequency band of 0 MHz is not secured.

A dual-frequency helical antenna 215 as shown in FIG. 12 has also been proposed as a dual-frequency helical antenna. The two-frequency helical antenna 215 includes an excitation coil section 216 shown by a solid line and a parasitic coil section 217 shown by a broken line, which are wound in a coil shape. The parasitic coil part 217 is arranged so as to be electromagnetically coupled to the excitation coil part 216, and power is supplied from the power supply part 218 to the winding start end of the excitation coil part 216. The parasitic coil unit 217 is electromagnetically coupled to the excitation coil unit 216.
Will be excited by. Here, the excitation coil unit 2
16 operating frequency bands of 800 MH in mobile telephone network
The length of the excitation coil unit 216 is adjusted so as to be in the z band, and the length of the parasitic coil unit 217 is adjusted so that the operating frequency band of the parasitic coil unit 217 becomes the 1.5 GHz band in the mobile telephone network. By doing so, the dual-frequency helical antenna 215 can operate in the 800 MHz band and the 1.5 GHz band in the mobile telephone network.

In this case, the dual frequency helical antenna 215
14 shows the voltage standing wave ratio (VSWR) characteristics of the above. With reference to this figure, it is possible to secure only a band of about 30 MHz as a frequency band of 800 MHz, and VSWR is 3.0 or more, which is not a good characteristic. Therefore, the band of about 70 MHz which is the frequency band of 800 MHz band in the PDC is not secured. Further, referring to FIG. 14, in the 1.5 GHz band, 10
Only the frequency band around MHz is secured,
The VSWR value is 3.0 or more, which is not good. Therefore, the frequency band of about 70 MHz which is the frequency band of 1.5 GHz band in the PDC is not secured.

The reason why good antenna characteristics cannot be obtained in the conventional two-frequency helical antenna is considered as follows. A helical antenna mounted on a conventional mobile phone has a diameter of a small enough for a wavelength and is wound at intervals of several to several tens of turns, and power is supplied from one end and the other is opened. Since the total length of the windings that make up this helical antenna is generally around a quarter wavelength at a frequency with good reflection characteristics,
With respect to the electric characteristics in the case of considering the distribution constant, a band in which the reflection characteristics become good again appears at 3/4 wavelength (triple in frequency). This has been confirmed by actual measurement. Therefore, for example, when it is shared with the 2400 MHz band, which has a triple relationship with the 800 MHz band, a dual frequency helical antenna can be easily realized without any special assistance.

On the other hand, in the case where the total length of the winding is about 1/4 wavelength of the frequency with good reflection characteristics, in the frequency band corresponding to 1/2 wavelength, even considering the electrical characteristics,
The reflection characteristics are extremely deteriorated and are close to total reflection. This has been confirmed by actual measurement. By the way, the frequency bands of PDC currently used as a mobile phone network in Japan are 800 MHz band and 1500 MHz band. Since these two frequency bands are approximately doubled in relation to each other, if the 800 MHz band helical antenna is used in the 1500 MHz band for the above-mentioned reason,
Almost all reflection occurs, and good antenna characteristics cannot be obtained.

That is, 800 MHz band and 1.5 GHz
In the case where the frequency band ratio has a relation of about twice as in the case of operating at two frequencies in the band, theoretically good antenna characteristics cannot be obtained as described above. This is shown in FIG. 11 and FIG. 12 which consist of two coil portions having a length of 800 MHz band and 1.5 GHz band.
The same applies to the dual-frequency helical antenna shown in.
In order to solve this problem, 800MHz band and 1500
An antenna with the best reflection characteristics was created near 1200 MHz, which is an intermediate frequency between the MHz band and the 800 MHz band and 1500 MHz that are in a modest mismatch state.
It is conceivable to force both bands to match the desired impedance via a matching circuit. However, this method has a problem in miniaturization and reliability because the matching circuit becomes complicated, and the various characteristics of the antenna deteriorate due to the effects of the loss of the matching circuit and the compatibility between the matching circuit and the helical antenna. However, there is a problem that variations in antenna characteristics and a decrease in yield may occur during mass production.

Therefore, an object of the present invention is to provide a multi-frequency helical antenna which can secure the required frequency bands for two or more frequency bands without using a matching circuit.

[0011]

[Means for Solving the Problems]

In order to achieve the above object, the multi-frequency helical antenna of the present invention is fed to one end, and
An excitation coil unit operable in the first frequency band and a parasitic coil unit disposed close to each other so as to be electromagnetically coupled to the excitation coil unit and operable in the second frequency band. The first frequency band is higher than the second frequency band.

In the above-mentioned multi-frequency helical antenna of the present invention, a second parasitic coil section is further arranged in close proximity so as to be electromagnetically coupled to the excitation coil section,
The operable frequency band in the second parasitic coil unit is set in the vicinity of the second frequency band, and the second frequency band is set by the parasitic coil unit and the second parasitic coil unit. It may be covered. Furthermore, in the above-mentioned multi-frequency helical antenna of the present invention, a plurality of grooves are formed in a predetermined length on the side peripheral surface of the elongated insulating rod-shaped body, and a conductive layer is formed in the grooves. Each of the coil portions is formed, and only the lower end of the conductive layer forming the excitation coil portion is formed on the surface of the base portion having a reduced diameter formed in the lower portion of the rod-shaped body. It may be connected to the conductive layer. Furthermore, in the multi-frequency helical antenna of the present invention, the first frequency band and the second frequency band are different frequency bands in the mobile telephone network, and the frequency band ratio is about 2. Good.

According to the present invention as described above, the excitation coil unit operable in the first frequency band, which is higher than the second frequency band, enables the parasitic coil operable in the first frequency band. Since the section is excited, it becomes possible to sufficiently secure the operable frequency band even if the frequency band ratio of the first frequency band and the second frequency band is about 2. In addition, the parasitic coil unit is a first parasitic coil unit capable of operating in the low frequency band of the second frequency band,
By configuring the second parasitic coil unit that can operate in the high frequency band of the second frequency band, the second frequency band can have a sufficient frequency bandwidth. Further, by forming a conductive layer in a plurality of grooves formed on the side peripheral surface of the rod-shaped body to form an exciting coil section and a parasitic coil section, in a plurality of frequency bands in the mobile telephone network. It can be an antenna suitable for an operable mobile device. As described above, according to the present invention, only a plurality of coil parts are used without using a matching circuit, and matching (good reflection characteristics) is achieved with respect to two frequency bands having a relationship of about double.
Since the matching circuit becomes unnecessary, it becomes possible to eliminate the problems caused by the matching circuit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration of a portable wireless device equipped with a multi-frequency helical antenna according to an embodiment of the present invention.
Shown in. A portable radio device 1 capable of operating at multiple frequencies shown in FIG.
Is a compact radio housing 3 that is convenient to carry.
And the antenna part 2 attached to the upper part of the radio housing 3
It consists of The wireless device housing 3 has a built-in circuit such as a transmission / reception unit and a codec unit. Antenna part 2
Is composed of a multi-frequency helical antenna operating in two frequency bands. The two frequency bands are, for example, the PDC system (Pe
rsonal Digital Cellular telecommunication system)
800MHz band (870MHz ~ 940MH
z) and 1.5 GHz band (1429 MHz to 1501 MH)
z) and GSM (Global System for Mobile communica)
800MHz band (890MHz-960)
MHz) and DCS (Digital Cellular System) 1.7 GHz band (1710 MHz to 1880 MHz).

FIG. 2 shows an example of the external structure of such an antenna unit 2. As shown in FIG. 2, in the antenna unit 2 in which the multi-frequency helical antenna of the present invention is built in, a metal base metal fitting 12 is screwed or fitted into an opening of a cylindrical antenna cover unit 11 having one end closed. It is composed by wearing. The antenna cover portion 11 is formed by resin molding, and has a multi-frequency helical antenna according to the present invention, which will be described later, built therein. The lower end of this multi-frequency helical antenna is electrically connected to the base metal fitting 12, and a slender rod-shaped mounting portion 13 is extended from the lower end of the base metal fitting 12. A screw portion 13 a is formed in the middle of the mounting portion 13, and the mounting portion 13 is inserted into a mounting hole provided in the wireless device housing 3 so that the screw portion 1 a.
The antenna portion 2 is mechanically and electrically fixed to the radio housing 3 by screwing 3a into the mounting hole.

FIG. 3 schematically shows a first structure of the multi-frequency helical antenna according to the present invention built in the antenna cover portion 11. The multi-frequency helical antenna 15 is shown by the excitation coil portion 17 shown by a solid line in which the number of turns wound in a helical shape is reduced, and by a broken line in which the number of turns wound in a helical shape is increased. It is composed of a parasitic coil unit 16 which is provided. The winding start end of the parasitic coil portion 16 is set to be substantially at the same position as the winding start end of the excitation coil portion 17 so as to be located at substantially the same position, and the winding start end thereof is substantially parallel to the excitation coil portion 17. 16 are wound. Both ends of the parasitic coil part 16 are not connected to any other part, but the lower part of the parasitic coil part 16 is wound so as to be overlapped with the excitation coil part 17, so that both are electromagnetically coupled. As a result, the parasitic coil section 16 is fed by the excitation coil section 17. Note that the winding start end of the excitation coil unit 17 is supplied with power from the power supply unit 18 as illustrated.

In the multi-frequency helical antenna 15 shown in FIG. 3, the length of the parasitic coil unit 16 is set so that the operating frequency band of the parasitic coil unit 16 having a large number of turns is 800 MHz band in the mobile telephone network. By adjusting the length of the excitation coil unit 17 so that the operating frequency band of the excitation coil unit 17 that is adjusted and the number of turns is reduced to the 1.5 GHz band in the mobile telephone network,
The multi-frequency helical antenna 15 is 80 in the mobile telephone network.
It can operate in the 0 MHz band and the 1.5 GHz band. The characteristic configuration of the multi-frequency helical antenna 15 of the present invention described above is such that the number of turns of the excitation coil unit 17 is reduced so that it operates in a high frequency band.
In this configuration, the parasitic coil section 16 excited by 7 has a large number of turns to operate in a low frequency band. FIG. 8 shows an example of VSWR characteristics of the multi-frequency helical antenna 15 according to the present invention shown in FIG. Referring to FIG. 8, in the 800 MHz band, a bandwidth having a VSWR value of 3.0 or less is obtained at approximately 60 MHz,
In the 1.5 GHz band, a bandwidth of about 50 MHz is obtained with a VSWR value of 3.0 or less.

In the multi-frequency helical antenna 15 shown in FIG. 3, the excitation coil section 17 is operated in a high frequency band, and the parasitic coil section 16 excited by the excitation coil section 17 is operated in a low frequency band. Therefore, as shown in FIG. 8, it is possible to roughly cover the frequency bands in the frequency bands of 800 MHz and 1.5 GHz in the PDC. Next, FIG. 4 schematically shows a second configuration of the multi-frequency helical antenna 20 according to the present invention capable of further widening the frequency band. This multi-frequency helical antenna 20 can also be built in the antenna cover portion 11.

The multi-frequency helical antenna 20 shown in FIG.
Are the excitation coil section 17 shown by a solid line with a reduced number of helically wound turns, and the parasitic coil section shown by a broken line with a large number of helically wound turns. 16 and a second parasitic coil portion 19 which is shown by a thick broken line and has a slightly smaller number of turns than the parasitic coil portion 16. The winding start ends of the parasitic coil portion 16 and the second parasitic coil portion 19 are set to be substantially at the same position as the winding start end of the excitation coil portion 17 so that they are located at substantially the same position, and are substantially aligned with the excitation coil portion 17, respectively. The parasitic coil section 16 and the second parasitic coil section 19 are wound in parallel. The parasitic coil section 16 and the second parasitic coil section 19 are not connected to anywhere,
The lower portions of the parasitic coil portion 16 and the second parasitic coil portion 19 are wound so as to overlap with the excitation coil portion 17, and thus are electromagnetically coupled to the excitation coil portion 17. As a result, the excitation coil unit 17 supplies power to the parasitic coil unit 16 and the second parasitic coil unit 19. In addition, at the winding start end of the excitation coil unit 17,
As shown in the figure, power is supplied from the power supply unit 18.

In the multi-frequency helical antenna 20 shown in FIG. 4, the length of the parasitic coil unit 16 is set so that the operating frequency band of the parasitic coil unit 16 having a large number of turns is 800 MHz band in the mobile telephone network. The operating frequency band of the second parasitic coil unit 19, which is adjusted and the number of turns is slightly reduced, is 800 MHz in the mobile telephone network.
The length of the second parasitic coil portion 19 is adjusted so as to be in the vicinity of the z band. As a result, a sufficiently wide frequency band can be secured even in a low frequency band of 800 MHz. In addition, the excitation coil unit 17 is configured such that the operating frequency band of the excitation coil unit 17 having a small number of turns is the 1.5 GHz band in the mobile telephone network.
By adjusting the length of the multi-frequency helical antenna 20,
It can be operated in the z band.

The characteristic configurations of the above-mentioned multi-frequency helical antenna 20 of the present invention also include a configuration in which the number of turns of the excitation coil unit 17 is reduced so that it operates in a high frequency band, and a low frequency band. That is, the two parasitic coil units that operate in accordance with (4) are composed of the parasitic coil unit 16 and the second parasitic coil unit 19 having slightly different lengths. The parasitic coil section 16 and the second parasitic coil section 19 are excited by the exciting coil section 17. FIG. 9 shows the VSWR characteristics of the multi-frequency helical antenna 20 of the second configuration according to the present invention shown in FIG. Referring to FIG. 9, the resonance characteristic appears in the 800 MHz band, and the resonance characteristic also appears in the frequency band slightly above that due to the action of the second parasitic coil section 19. Also,
Resonance characteristics appear in a frequency band slightly higher than the 1.5 GHz band. Therefore, the wire diameters of the excitation coil unit 17, the parasitic coil unit 16, and the second parasitic coil unit 19 are set so as to match the 800 MHz band and the 1.5 GHz band,
By adjusting the winding diameter, the pitch, etc., the VSWR characteristics as shown in FIG. 10 could be obtained. Referring to FIG. 10, a bandwidth having a VSWR value of 2.0 or less is obtained in a wide band of about 140 MHz in the 800 MHz band, and a bandwidth of the VSWR value of 2.0 or less is about 75 MHz in the 1.5 GHz band. Has been obtained. As described above, in the multi-frequency helical antenna 20 having the configuration shown in FIG. 4, sufficient antenna characteristics can be obtained as a frequency band of two frequencies in which the frequency band ratio between 800 MHz and 1.5 GHz in the PDC is about 2. become able to.

Now, the principle of operation of the multi-frequency helical antenna 20 shown in FIG. 4 of the present invention which is capable of obtaining a wide band frequency characteristic will be described. The multi-frequency helical antenna 20 is expressed as a distributed constant as shown in FIG. That is, when the wavelength of the center frequency in the frequency band of 1.5 GHz is λ2, the length of the excitation coil unit 17 is approximately λ2 / 4. Further, when the wavelength of the center frequency in the frequency band of 800 MHz band is λ1, the length of the parasitic coil unit 16 is about λ1 / 4. And
The length of the second parasitic coil portion 19 is about ¼ of the wavelength λ1 ′ that is slightly shorter (higher frequency) than the wavelength λ1. The parasitic coil unit 16 and the second parasitic coil unit 19 are electromagnetically coupled (M-coupled) to the excitation coil unit 17 mainly near the feeding point where a large amount of current flows.

Here, it is assumed that the excitation coil unit 17 is supplied with power by a signal in the 1.5 GHz band having a wavelength λ2. In this case, the parasitic coil portion 16 and the second parasitic coil portion 19 in the 800 MHz band seen in the 1.5 GHz band have open ends and appear to have a length of about ½ wavelength. Therefore, the coupling with the excitation coil unit 17 becomes weak. This is because the parasitic coil section 16 and the second parasitic coil section 19 are indicated by a broken line in FIG.
However, this means that the influence on the excitation coil unit 17 is reduced, and as a result, the original characteristics of the excitation coil unit 17 which is the 1.5 GHz band helical antenna come to appear.

Next, the excitation coil unit 17 is set to 80 for the wavelength λ1.
It is assumed that power is supplied by a 0 MHz band signal. in this case,
Excitation coil part 1 in the 1.5 GHz band seen in the 800 MHz band
In No. 7, the tip is open and the length appears to be about ⅛ wavelength, so that the impedance is high impedance near the feeding point.
Further, the parasitic coil portion 16 and the second parasitic coil portion 19 seen in the 800 MHz band have open ends and a length of about 1
Since the wavelength is / 4 wavelength, the area around the feeding point looks low impedance. Therefore, most of the electric power supplied to the excitation coil unit 17 in the 1.5 GHz band is as shown in FIG.
It is considered that the power is supplied to the parasitic coil section 16 and the second parasitic coil section 19 that are equivalently coupled to the excitation coil section 17 with the capacitance Co in a state where the impedance is relatively low as shown in FIG. As described above, power is directly supplied to the excitation coil unit 17 in the high frequency band, and the excitation coil unit 1
Two parasitic coil units 16 and 19 in the low frequency band from 7
By feeding the electromagnetically, the characteristics of the original helical antennas possessed by each can be obtained.

Next, FIG. 5 shows a concrete example of the structure of the multi-frequency helical antenna according to the present invention having the schematic structure shown in FIG. 4 built in the antenna cover part 11 of the antenna part 2 shown in FIG. The multi-frequency helical antenna 20 shown in FIG. 5 includes an elongated rod-shaped main body 20a having a predetermined diameter and formed of an insulating resin having good high-frequency characteristics. Three helical grooves are formed on the side peripheral surface of the main body 20a. The length of each of the three grooves is a length required for the parasitic coil portion 16, the second parasitic coil portion 19 and the excitation coil portion 17 shown in FIG. 4, and the winding pitch thereof is a predetermined winding pitch. ing. A conductive layer is formed in each of the three grooves by sticking, vapor deposition, or the like. The parasitic coil portion 16 and the second parasitic coil portion 1 are formed by the conductive layers formed in the three grooves.
9 and the excitation coil unit 17 are created.

A base portion 20b having a slightly reduced diameter is formed from the lower end of the main body portion 20a, and a conductive layer is formed on the surface of the base portion 20b. The helical groove in which the excitation coil portion 17 is formed is formed at the bottom,
A groove forming the second parasitic coil portion 19 is formed thereon, and a groove forming the parasitic coil portion 16 is further formed thereon. The lower end of the groove forming the exciting coil portion 17 is bent toward the base portion 20b, and the conductive layer forming the exciting coil portion 17 is formed on the surface of the base portion 20b. It comes to be connected to the conductive layer. This connection point is the feeding point 21. The base portion 20b is screwed to the base metal fitting 12 shown in FIG.
Is attached to the wireless device housing 3 and electrically connected to the transmission / reception unit, so that the excitation coil unit 17 is connected to the transmission / reception unit via the base portion 20b to supply power.
Then, the parasitic coil section 16 and the second parasitic coil section 19 are excited by the electromagnetic coupling from the exciting coil section 17 that is wound closely.

In this case, the diameter of the main body portion 20a, the exciting coil portion 17, and the winding pitch and groove width of the parasitic coil portion 16 and the second parasitic coil portion 19 are VSW shown in FIG.
It is adjusted in advance so that the R characteristic is obtained. As a result, the VSWR characteristics of the multi-frequency helical antenna 20 are shown in FIG.
As shown in 0, 800MHz and 1.5G in PDC
The antenna characteristics are sufficient as a frequency band of two frequencies of Hz.

Next, another concrete example of the structure of the multi-frequency helical antenna according to the present invention having the schematic structure shown in FIG. 4 built in the antenna cover part 11 of the antenna part 2 shown in FIG. 2 is shown in FIG. Show. The multi-frequency helical antenna 30 shown in FIG. 6 includes an elongated rod-shaped main body 30a having a predetermined diameter and formed of an insulating resin having good high-frequency characteristics. Three helical grooves are formed on the side peripheral surface of the main body 30a. The length of each of the three grooves is a length required for the parasitic coil portion 16, the second parasitic coil portion 19 and the excitation coil portion 17 shown in FIG. 4, and the winding pitch thereof is a predetermined winding pitch. ing.
A conductive layer is formed in each of the three grooves by sticking, vapor deposition, or the like, and the parasitic coil portion 36, the second parasitic coil portion 39, and the second parasitic coil portion 39 are formed by the conductive layers formed in the three grooves. The excitation coil unit 17 is created.

A base portion 30b having a slightly smaller diameter is formed from the lower end of the main body portion 30a, and a conductive layer is formed on the surface of the base portion 30b. The helical groove in which the excitation coil portion 17 is formed is formed at the bottom,
A groove forming the second parasitic coil portion 39 is formed thereon, and a groove forming the parasitic coil portion 36 is further formed thereon. In this case, the length of the groove is formed so that the number of turns of the second parasitic coil section 36 is slightly longer than the number of turns of the parasitic coil section 36. The lower end of the groove forming the exciting coil portion 17 is bent toward the base portion 30b, and the conductive layer forming the exciting coil portion 17 is formed by the base portion 20b.
Will be connected to the conductive layer formed on the surface of the. This connection point is the feeding point 31. Base 30b
Is screwed to the base metal fitting 12 shown in FIG.
Since the mounting portion 13 integrated with the mounting portion 13 is mounted on the wireless device housing 3 and electrically connected to the transmitting / receiving portion,
The excitation coil unit 17 is connected to the transmission / reception unit via the base 30b to supply power.

Then, the parasitic coil section 36 and the second parasitic coil section 39 are excited by electromagnetic coupling from the exciting coil section 17 which is wound closely. As a result, the second parasitic coil unit 39 operates in the 800 MHz band in the mobile communication network, and the parasitic coil unit 36 operates in the vicinity of the 800 MHz band in the mobile communication network. Furthermore, the excitation coil unit 17 operates in the 1.5 GHz band in the mobile telephone network. In this case, the diameter of the main body portion 30a, the excitation coil portion 17,
And the parasitic coil section 36 and the second parasitic coil section 3
The winding pitch and groove width of 9 are adjusted in advance so that the VSWR characteristics shown in FIG. 10 can be obtained. As a result, the VSWR characteristic of the multi-frequency helical antenna 30 becomes a sufficient antenna characteristic as a frequency band of two frequencies of 800 MHz and 1.5 GHz in the PDC as shown in FIG.

In the above description, it has been explained that it operates in the frequency band of two frequencies, but it is also possible to operate in multiple frequencies by providing a parasitic element that operates in another frequency band. Also, although each coil portion of the multi-frequency helical antenna is made of a conductive layer, the present invention is not limited to this. By winding a wire material having a predetermined wire diameter in a coil shape with a predetermined winding pitch and a winding diameter. You may make it produce each coil part.

[0033]

As described above, according to the present invention, the exciting coil unit operable in the first frequency band, which is higher than the second frequency band, can operate in the first frequency band. Since the power feeding coil section is excited, the operable frequency band can have a sufficient frequency bandwidth even when the frequency band ratio of the first frequency band and the second frequency band is about 2. Like Further, the parasitic coil unit is composed of a first parasitic coil unit operable in the low frequency band of the second frequency band and a second parasitic coil unit operable in the high frequency band of the second frequency band. By the second
The frequency band of can be made a sufficient frequency bandwidth. Further, by forming a conductive layer in a plurality of grooves formed on the side peripheral surface of the rod-shaped body to create an excitation coil section and a parasitic coil section, in a plurality of frequency bands in the mobile telephone network. It can be an antenna suitable for an operable mobile device. As described above, according to the present invention, only a plurality of coil portions can be used for matching (good reflection characteristics) with respect to two frequency bands having a relationship of approximately double without using a matching circuit, and a matching circuit is unnecessary. From
It becomes possible to eliminate the problems caused by the matching circuit.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example in which an antenna unit, which is a multi-frequency helical antenna according to an embodiment of the present invention, is attached to a radio housing.

FIG. 2 is a diagram showing an external configuration of an antenna unit that is a multi-frequency helical antenna according to an embodiment of the present invention.

FIG. 3 is a diagram showing a schematic first configuration of a multi-frequency helical antenna according to an embodiment of the present invention.

FIG. 4 is a diagram showing a schematic second configuration of a multi-frequency helical antenna according to an embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a multi-frequency helical antenna embodying a schematic second configuration of the multi-frequency helical antenna according to the exemplary embodiment of the present invention.

FIG. 6 is a diagram showing another configuration of the multi-frequency helical antenna embodying the schematic second configuration of the multi-frequency helical antenna according to the exemplary embodiment of the present invention.

FIG. 7 is a diagram for explaining the operating principle of the multi-frequency helical antenna according to the embodiment of the present invention in a distributed constant manner.

FIG. 8 is a diagram showing a VSWR characteristic of the multi-frequency helical antenna having the first configuration according to the exemplary embodiment of the present invention.

FIG. 9 is a diagram showing a VSWR characteristic before adjustment of the multi-frequency helical antenna having the second configuration according to the exemplary embodiment of the present invention.

FIG. 10 is a diagram showing a VSWR characteristic after adjustment of the multi-frequency helical antenna having the second configuration according to the exemplary embodiment of the present invention.

FIG. 11 is a diagram showing a first configuration of a conventionally proposed dual-frequency helical antenna.

FIG. 12 is a diagram showing a second configuration of a conventionally proposed dual-frequency helical antenna.

FIG. 13 is a diagram showing a VSWR characteristic of a conventionally proposed dual-frequency helical antenna having a first configuration.

FIG. 14 is a diagram showing a VSWR characteristic of a conventionally proposed dual-frequency helical antenna having a second configuration.

[Explanation of symbols]

1 portable radio, 2 antenna section, 3 radio housing, 1
1 antenna cover part, 12 base metal parts, 13 mounting part, 13a screw part, 15 multi-frequency helical antenna,
16 parasitic coil part, 17 excitation coil part, 18 feeding part, 19 parasitic coil part, 20 multi-frequency helical antenna, 20a main part, 20b base part, 21 feeding point, 30 multi-frequency helical antenna, 30a main part,
30b base part, 31 feeding point, 36 parasitic coil part,
39 parasitic coil section, 115 two-frequency helical antenna, 116 first coil section, 117 second coil section, 1
18 Feeder, 215 Dual-frequency helical antenna, 2
16 excitation coil section, 217 parasitic coil section, 218
Power supply

Claims (4)

[Claims] 1. An excitation coil unit which is fed to one end and which is operable in a first frequency band, and which are arranged in proximity to each other so as to be electromagnetically coupled to the excitation coil unit, and a second unit. And a parasitic coil unit operable in the frequency band, wherein the first frequency band is higher than the second frequency band. 2. A second parasitic coil section is further arranged so as to be electromagnetically coupled to the excitation coil section, and the operable frequency band in the second parasitic coil section is the first frequency band. 2. The multi-frequency coil according to claim 1, wherein the second frequency band is covered by the parasitic coil unit and the second parasitic coil unit in the vicinity of the second frequency band. Frequency helical antenna. 3. A plurality of grooves having a predetermined length are formed on a side peripheral surface of an elongated insulating rod-shaped main body, and the coil portions are formed by forming a conductive layer in the grooves. Only the lower end of the conductive layer forming the excitation coil portion is connected to the conductive layer formed on the surface of the base having a reduced diameter formed in the lower portion of the rod-shaped body. The multi-frequency helical antenna according to claim 1 or 2, characterized in that: 4. The first frequency band and the second frequency band are different frequency bands in a mobile telephone network, and the frequency band ratio is about 2. Alternatively, the multi-frequency helical antenna described in 2.