Patent Grant
8159404
This application is the U.S. National Phase under 35 U.S.C. §371 of International Application PCT Patent Application No. PCT/JP2007/069816, filed on Oct. 11, 2007, which claims priority to Japanese Patent Application No. 2007-120542, filed on May 1, 2007 and Japanese Patent Application No. 2006-334104, filed on Dec. 12. 2006; the contents of which are all herein incorporated by this reference in their entireties. All publications, patents, patent applications, databases and other references cited in this application, all related applications referenced herein, and all references cited therein, are incorporated by reference in their entirety as if restated here in full and as if each individual publication, patent, patent application, database or other reference were specifically and individually indicated to be incorporated by reference.
The present invention relates to a multi-frequency antenna preferably mounted on vehicles capable of receiving FM broadcasts and terrestrial digital broadcasts.
Prior antenna devices attached to vehicles are ordinarily arranged as antenna devices which can receive AM broadcasts and FM broadcasts. As these antenna devices, there is known a vehicle-mounted antenna device arranged as a helical antenna having an antenna rod portion around which a helical element is helically wound.
In the multi-frequency helical antenna 200 shown in
The antenna device 100 has a problem in that it cannot be operated in a plurality of frequency bands. To cope with the above problem, it is considered to apply a multi-frequency technology for operating the multi-frequency helical antenna 200 in a plurality of frequency bands so that the antenna device 100 is operated in the plurality of frequency bands. That is, a passive helical element is further disposed between the pitches of the helical element 111. With this arrangement, the antenna device 100 can be arranged as a multi-frequency antenna which is operated in the plurality of frequency bands. However, since the passive helical element must be further disposed between the pitches of the helical element 111, it is necessary to increase the pitches of the helical element 111. As a result, since the length L of the helical element 111 is increased, the antenna device is disadvantageous in the design and handling thereof.
Accordingly, an object of the present invention is to provide a multi-frequency antenna the length of which can be reduced as far as possible even when it is operated in a plurality of frequency bands.
To achieve the above object, the most important feature of the present invention is to provide a helical element, which is wound around the outer periphery of a support member and operated in a first frequency band, and a line-shaped element which is disposed in a groove portion formed on the outer periphery of the support member or in an accommodation hole formed in the support member and operated in a second frequency band.
According to the present invention, an antenna is provided with helical element, which is wound around the outer periphery of the support member and operated in the first frequency band, and the line-shaped element which is disposed in the groove portion formed on the outer periphery of the support member or in the accommodation hole formed in the support member and operated in the second frequency band, thereby the antenna can be arranged as a multi-frequency antenna. In this case, since what is operated in the second frequency band is the line-shaped element disposed in the groove portion or in the accommodation hole, the pitches of the helical element are not necessary to be increased and thus the overall length of the multi-frequency antenna can be. Further, the overall length of the multi-frequency antenna can be reduced with the effect of the helical element.
a) is a front elevational view of a line-shaped element of the multi-frequency antenna of the third embodiment according to the present invention.
b) is a partially enlarged view of the line-shaped element of the multi-frequency antenna of the third embodiment according to the present invention.
The multi-frequency antenna 1 shown in these drawings is composed of a rod-shaped insulation support member 10 which has an approximately circular cross section and a helical element 11 wound around the outer periphery thereof at pitches p. A metal element fitting 13 is fitted with the lower end of the support member 10 and electrically connected to the lower end of the helical element 11. The lower portion of the element fitting 13 is arranged as an attachment portion 14 having a reduced diameter to fix the multi-frequency antenna 1 to an antenna case and the like, and a male screw is formed on the attachment portion 14 so that it is threaded into the antenna case attached to, for example, a roof of a vehicle. The support member 10 is molded with resin and has flexibility, and a helical groove is formed around the outer periphery thereof. The helical element 11 having the pitches p is formed by winding a conductor in the helical groove. Further, although not shown, a portion from the extreme end of the support member 10, around which the helical element 11 is wound, to the element fitting 13 is molded with resin so as to cover the helical element 11.
Further, four groove portions, that are, a first groove portion 10a, a second groove portion 10b, a third groove portion 10c, and a fourth groove portion 10d are formed from the lower end of the support member 10 upward approximately in parallel with the central axis of the support member 10. The first groove portion 10a to the fourth groove portion 10d have approximately the same shape, which is a taper shape made narrower toward the extreme ends thereof, and the extreme ends of the groove portions are formed in a semicircular shape. A line-shaped element 12, which has a length slightly shorter than the length b of the first groove portion 10a, is disposed in the first groove portion 10a with an interval defined between it and the helical element 11. In this case, the line-shaped element 12 is disposed in the semicircular portion of the first groove portion 10a at the extreme end thereof so that at least about 1 mm of the interval can be secured between the line-shaped element 12 and the helical element 11. The line-shaped element 12 is covered with an insulation film of polyurethane and the like, and thus even if it comes into contact with the helical element 11 spaced apart therefrom, it is insulated therefrom in direct current. The lower end of the line-shaped element 12 is electrically connected to the element fitting 13, and thus power is supplied to the helical element 11 and the line-shaped element 12 from the element fitting 13. Note that the first groove portion 10a to the fourth groove portion 10d are formed at equal intervals so that when bending stress is applied to the support member 10, it is uniformly dispersed and thus the support member 10 is prevented from being broken by the bending stress even with the grooves formed.
Here, the helical element 11 is made to have a length L, which allows the helical element 11 to resonate with the frequency band of FM broadcast, and the line-shaped element 12 is made to have a length, which allows the line-shaped element 12 to resonate with the frequency band of terrestrial digital television broadcast. In this case, the diameter φ of the helical element 11 wound around the support member 10 is set to about 6.8 mm, the pitches p thereof are set to about 1.76 mm, the length L thereof is set to about 139 mm, and the length a of the line-shaped element 12 is set to about 80 mm. Note that the length b of the first groove portion 10a is set to about 85 mm, and the length L1 of the element fitting 13 is set to about 22.5 mm. Further, the interval between the helical element 11 and the line-shaped element 12 is set at least about 1 mm.
The frequency characteristics shown in
Further, the frequency characteristics shown in
Note that, in the prior antenna device 100 shown in
It is considered that this is because the electric length of the helical element 11 is equivalently increased with the effect of the line-shaped element 12.
As shown in
Further, in the multi-frequency antenna 1 of the first embodiment according to the present invention, the element fitting 13 is fitted with the lower portion of the support member 10 around which the helical element 11 is wound.
The multi-frequency antenna 2 shown in these drawings is composed of a rod-shaped insulation support member 20 which has an approximately circular cross section and a helical element 21 wound around the outer periphery thereof at predetermined pitches. A metal element fitting 23 is fitted with the lower end of the support member 20 and electrically connected to the lower end of the helical element 21. The lower portion of the element fitting 23 is arranged as an attachment portion 24 having a reduced diameter to fix the multi-frequency antenna 2 to an antenna case and the like, and a male screw is formed on the attachment portion 24 so that it is threaded into the an antenna case attached to, for example, a roof and the like of a vehicle. The support member 20 is molded with resin and has flexibility, and a helical groove is formed around the outer periphery thereof. The helical element 21 having the predetermined pitches is formed by winding a conductor in the helical groove. Although not shown, a portion from the extreme end of the support member 20, around which the helical element 21 is wound, to the element fitting 23, is molded with resin so as to cover the helical element 21.
Further, four groove portions having a predetermined length, that are, a first groove portion 20a, a second groove portion 20b, a third groove portion 20c, and a fourth groove portion 20d are formed from the lower end of the support member 20 upward approximately in parallel with the central axis thereof. The first groove portion 20a to the fourth groove portion 20d have approximately the same taper shape, which is a taper shape made narrower toward the extreme ends thereof, and the extreme ends of the groove portions are formed in a semicircular shape. Then, a line-shaped element 22a is disposed in the first groove portion 20a, a line-shaped element 22b is disposed in the second groove portion 20b, and a line-shaped element 22d is disposed in the fourth groove portion 20d with intervals between them and the helical element 21. In this case, the line-shaped elements 22a, 22b, 22d are disposed in the semicircular portions of the first groove portion 20a, the second grove portion 20b, and the fourth groove 20d at the extreme ends thereof so that at least about 1 mm of the interval can be secured between the line-shaped elements and the helical element 21. The line-shaped elements 22a, 22b, 22d are covered with an insulation film of polyurethane and the like, and thus even if they come into contact with the helical element 21 spaced apart therefrom, they are insulated therefrom in direct current. The lower ends of the line-shaped elements 22a, 22b, 22d are electrically connected to the element fitting 23, and thus power is supplied to the helical element 21 and the line-shaped elements 22a, 22b, 22d from the element fitting 23. Note that the first groove portion 20a to the fourth groove portion 20d are formed at equal intervals so that when bending stress is applied to the support member 20, it is uniformly dispersed and thus the support member 20 is prevented from being broken by the bending stress even with the grooves formed.
Here, the helical element 21 is made to have a length L, which allows the helical element 21 to resonate with the frequency band of FM broadcast, and the line-shaped element 22a is made to have a length, which allows the line-shaped element 22a to resonate with the frequency band of terrestrial digital television broadcast. Further, the line-shaped element 22b is made to have a length, which allows the line-shaped element 22b to resonate with frequency band of the 800 MHz mobile phone network, and the line-shaped element 22d is made to have a length, which allows the line-shaped element 22d to resonate with frequency band of the 1.8 GHz mobile phone network. With this arrangement, the multi-frequency antenna 2 of the second embodiment can be arranged as a multi-frequency antenna which is operated in the four frequency bands. However, the frequency bands in which the multi-frequency antenna 2 is operated are not limited to the above frequency bands except the frequency band of FM broadcast. That is, the multi-frequency antenna 2 can be operated in the frequency bands of terrestrial digital radio, the frequency bands of mobile phone network such as AMPS (Advanced Mobile Phone Service), GSM (Global System for Mobile Communications), DCS (Digital Communication System), PCS (Personal Communication Service), PDC (Personal Digital Cellular) and the like, and the frequency bands of a keyless system, a weather band, DAB (Digital Audio Broadcast) and the like. In this case, it is sufficient to set the lengths of the line-shaped elements 22a, 22b, 22d to the lengths corresponding to the frequency bands in which they are desired to be put into operation.
In the multi-frequency antenna 2 of the second embodiment, by using the helical element 21 as a voltage receiving device in the frequency band of AM broadcast, the helical element 21 can be also used as an antenna for receiving AM broadcast.
Note that the lower end of the helical element 21 is bent downward and connected to a connecting portion in which it is densely wound around the lower end of the support member 20 also in the multi-frequency antenna 2 of the second embodiment. Further, the lower ends of the line-shaped elements 22a, 22b, 22d are extended and the insulation film is removed only from the extended portions so as to connected to the connecting portion. In the state, the element fitting 23 is fitted with the lower end of the support member 20 so as to cover the connecting portion and caulked. With this arrangement, the helical element 21 and the line-shaped elements 22a, 22b, 22d are electrically connected to the element fitting 23.
Next,
The multi-frequency antenna 3 of the third embodiment according to the present invention shown in
The multi-frequency antenna 3 of the third embodiment is composed of a rod-shaped insulation support member 30 which has an approximately circular cross section and a helical element 31 is wound around the outer periphery thereof at pitches p. A metal element fitting 33 is fitted with the lower end of the support member 30 and electrically connected to the lower end of the helical element 31. The lower portion of the element fitting 33 is arranged as an attachment portion 34 having a reduced diameter to fix the multi-frequency antenna 3 to an antenna case and the like, and a male screw is formed on the attachment portion 34 so that it is threaded into the an antenna case attached to, for example, a roof of a vehicle. The support member 30 is molded with resin and has flexibility, and a helical groove is formed around the outer periphery thereof. The helical element 31 having pitches p is formed by winding a conductor in the helical groove. Further, as shown by a broken line in
Further, an accommodation hole 30a having a predetermined length is formed from the lower end of the support member 30 upward approximately along the central axis thereof. A line-shaped element 32 having a length a slightly shorter than the length of the accommodation hole 30a is accommodated in the accommodation hole 30a. In this case, the line-shaped element 32 is inserted into an insertion hole formed in an attachment portion 34 located under the element fitting 33 from below the attachment portion 34 and the lower portion of the line-shaped element 32 is inserted into the insertion hole under pressure, thereby the line-shaped element 32 is electrically connected to the element fitting 33 as well as mechanically fixed thereto. The element fitting 33 in this state is positioned below the support member 30 around which the helical element 31 is wound, the line-shaped element 32 is inserted into the accommodation hole 30a formed in the support member 30, a connecting portion 31, which is formed at the lower portion of the support member 30 and has a slightly smaller diameter, is fitted with the element fitting 33 from above it, and the element fitting 33 of the portion is caulked. Since the helical element 31 is densely wound around the outer periphery of the connecting portion 31a, the lower end of the helical element 31 is electrically connected to the element fitting 33 so that power is supplied to the helical element 31 and the line-shaped element 32 from the element fitting 33.
The helical element 31 is made to have a length L, which allows the helical element 31 to resonate with the frequency band of FM broadcast, and the line-shaped element 32 is made to have a length, which allows the line-shaped element 32 to resonate with the frequency band of terrestrial digital television broadcast. In this case, the diameter φ of the helical element 31 wound around the support member 30 is set to about 6.81 mm, the pitches p thereof are set to about 1.76 mm, and the length L thereof is set to about 139 mm and the length a of the line-shaped element 32 is set to about 82 mm. Note that the length L1 of the element fitting 33 is set to about 22.5 mm. Although the length of the accommodation hole 30a is set to about 85 mm, it may be formed so as to pass through the overall support member 30. Further, the interval S between the helical element 31 and the line-shaped element 32 (refer to
As shown in these drawings, the metal element fitting 33 is composed of a cylindrical portion 33a and the attachment portion 34 formed so as to project from the lower end of the cylindrical portion 33a. A plurality of (for example, six) projecting pieces 33b project from the outer periphery of the cylindrical portion 33a at the same interval in approximately the central portion of the element fitting 33. A lower cylindrical portion 33c is formed under the projecting pieces 33b, and the attachment portion 34, which has a thread formed around the outer periphery thereof, is formed under the lower cylindrical portion 33c. An insertion hole 33d is formed in the upper portion in the inside of the cylindrical portion 33a so that a connecting portion 31a formed in the lower portion of the support member 30 is inserted thereto and fitted, the diameter of the lower portion of the insertion hole 33d is slightly reduced, and an insertion hole 33e, which communicates with the insertion hole 33d and has a thin diameter, is formed passing through the attachment portion 34. The insertion hole 33e is formed approximately on the longer axis of the element fitting 33, and the line-shaped element 32 is inserted into the insertion hole 33e. Note that the widths of the plurality of projecting pieces 33b are increased toward the extreme ends thereof so that when the antenna cover 35 is molded, it can be securely molded to the element fitting 33.
a) is a front elevational view showing an arrangement of the line-shaped element 32, and
As shown in these drawings, the line-shaped element 32 is composed of a line-shaped metallic wire and has a flatly-pressed portion 32a pressed flat in the lower portion thereof. The line-shaped element 32 is inserted into the insertion hole 33e from below the attachment portion 34 of the element fitting 33. When the flatly-pressed portion 32a is abutted against the lower end of the insertion hole 33e, the flatly-pressed portion 32a is inserted into the insertion hole 33e under pressure using a tool. With this operation, the line-shaped element 32 is fixed to the element fitting 33 as well as electrically connected thereto.
In the multi-frequency antenna 3 of the third embodiment according to the present invention, the winding diameter φ of the helical element 31 is set to about 6.8 mm, the wire diameter C thereof is set to about 0.4 mm, the pitches p thereof are set to about 1.76 mm, and the length L thereof is set to about 139 mm, the length a of the line-shaped element 32 is set to about 82 mm and the diameter D thereof is set to about 0.8 mm, and the interval S between the helical element 31 and the line-shaped element 32 is set to about 2.6 mm.
Referring to
Further, in the prior antenna device 100 shown in
As described above, the multi-frequency antenna 3 of the third embodiment according to the present invention can be low-profiled even being allowed to operate in a plurality of frequency bands because the helical element 31 with the effect of the line-shaped element 32. Further, when the helical element 31 is used as a voltage receiving device in the frequency band of AM broadcast, the helical element 31 can be also used as an antenna for receiving AM broadcast. With this arrangement, the multi-frequency antenna 3 of the third embodiment according to the present invention can be arranged as a multi-frequency antenna capable of receiving AM/FM broadcast and terrestrial digital television broadcast.
Here, since the arrangement of a receiving system when the multi-frequency antenna 3 of the third embodiment according to the present invention is mounted on a vehicle and the like is the same as the arrangement shown in the block diagram shown in
Next,
Referring to
Further,
Referring to
Further,
Referring to
Further, even if the interval S between the helical element 31 and the line-shaped element 32 is narrowed, the multi-frequency antenna 3 can approximately resonate with 83 MHz which is the center frequency of FM broadcast by reducing the diameter D of the line-shaped element. As described above, in the multi-frequency antenna 3 of the third embodiment according to the present invention, desired electric characteristics can be obtained by combining the diameter D of the line-shaped element and the interval S between the helical element 31 and the line-shaped element 32 and adjusting the electric length of the helical element 31.
It is preferable from what has been described above to set the diameter D of the line-shaped element 32 to about 1 mm or less and to set the interval S between the helical element 31 and the line-shaped element 32 to about 1 mm or more in the multi-frequency antenna 3 of the third embodiment according to the present invention. Further, since desired electric characteristics can be obtained in the frequency bands of FM broadcast and terrestrial digital television broadcast by reducing the wire diameter C of the helical element 31, the wire diameter C of the helical element 31 is preferably set to about 1 mm or less.
Next,
Further,
As described above, in the multi-frequency antenna 3 of the third embodiment, even if the length a of the line-shaped element 32 is slightly reduced and the length L of the helical element 31 is increased, the multi-frequency antenna 3 is sufficiently operated in the frequency band of FM broadcast and the frequency band of terrestrial digital television broadcast. In this case, when the helical element 31 is used as a voltage receiving device in the frequency band of AM broadcast, the multi-frequency antenna 3 can be also used as a multi-frequency antenna capable of receiving AM/FM broadcast and terrestrial digital television broadcast.
In the multi-frequency antenna 3 of the third embodiment according to the present invention described above, the typical value of the diameter D of the line-shaped element 32 is set to about 0.8 mm, and the line-shaped element 32 having the dimension is accommodated in the accommodation hole 30a. Therefore, since the diameter of the accommodation hole 30a can be reduced (to about 1 mm), even if the support member 30 is formed in the pipe shape, it can be made flexible sufficiently, thereby even if bending stress is applied to support member 30, it is flexed without being broken. Further, when the interval S between the helical element 31 and the line-shaped element 32 is set to about 2.6 mm or less, the diameter of the support member 30 is reduced and thus the diameter of the multi-frequency antenna 3 is reduced. With this arrangement, the multi-frequency antenna 3 has flexibility.
It is preferable to set the interval between the helical element and the line-shaped element to at least about 1 mm to obtain the electric characteristics described above in the multi-frequency antenna devices of the first and second embodiments according to the present invention described above. Thus, when the line-shaped element is covered with an insulation tube having a thickness of about 1 mm or more and disposed in the taper-shaped groove formed on the support member, the outer periphery of the insulation tube can be caused to come into contact with the taper-shaped groove as well as to come into contact with the helical element, thereby the interval between the line-shaped element and the helical element can be set to a predetermined interval. With this arrangement, the electric characteristics of the multi-frequency antenna can be stabilized. Further, an insulation material having a low dielectric constant may be interposed between the helical element and the line-shaped element so that the interval between the helical element and the line-shaped element is set to a predetermined interval.
Note that although the four groove portions are formed on the outer periphery of the support member at the same interval in the multi-frequency antenna devices of the first and the second embodiments according to the present invention described above, the present invention is not limited thereto and the grooves may be formed as many as the line-shaped elements. In this case, when a plurality of groove portions are formed, it is preferable to form them at the same interval. Further, although the multi-frequency antenna according to the present invention is arranged so as to be attached to a roof and a trunk of a vehicle, the present invention is not limited thereto and can be applied to a multi-frequency antenna as long as it is operated in two or more frequency bands.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-334104 | Dec 2006 | JP | national |
| 2007-120542 | May 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/069816 | 10/11/2007 | WO | 00 | 10/5/2008 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2008/072415 | 6/19/2008 | WO | A |
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| 03-9375 | Aug 1991 | JP |
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| Number | Date | Country | |
|---|---|---|---|
| 20090284441 A1 | Nov 2009 | US |
