TREA

Chip antenna

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Information

  • Patent Grant
  • 6583769
  • Patent Number
    6,583,769
  • Date Filed
    Thursday, June 28, 2001
    24 years ago
  • Date Issued
    Tuesday, June 24, 2003
    22 years ago
Information
Abstract
A chip antenna capable of reducing the spiral pitch of an antenna line to be smaller than that of a conventional one. Conductor patterns are electrically connected sequentially in series through via holes so as to form a spiral antenna line. The antenna line has a winding axis which is arranged either in a zigzag manner or along a straight line. Adjacent wound portions have an equal diameter or width or the adjacent portions may have unequal widths. Since adjacent via holes are arranged in a staggered arrangement with each other, the distance between the adjacent via holes is larger than the spiral pitch of the antenna line, allowing the adjacent portions to be closer together than a conventional chip antenna, thereby allowing the resonance frequency to be reduced.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to chip antennas, and in particular relates to a chip antenna for mobile communication units such as portable telephone terminals and pagers and a chip antenna for local area networks (LANs).




2. Description of the Related Art




It is important for antennas for use in mobile communication units and LANs to be small-sized. As one of the antennas satisfying such a demand, a helical-type chip antenna is known.




An example of a conventional helical-type chip antenna is shown in

FIGS. 9 and 10

. A chip antenna


100


comprises a rectangular-solid dielectric base body


121


, an antenna line


130


disposed in the dielectric base body


121


, a feed terminal


110


, and a fixing terminal


111


. One end


134


of the antenna line


130


is electrically connected to the feed terminal


110


and the other end


135


is unconnected.




The antenna line


130


is formed by alternately connecting a conductor pattern


131


and a via hole


132


in series. The antenna line


130


has a helical structure having a uniform width and height (or diameter) and the pitch P, and is wound about a straight axis CL in the horizontal direction (direction of arrow X in the drawing).




In order to enable a chip antenna also to be used at low frequencies, the chip antenna is generally required to reduce the resonance frequency. One of the methods for reducing the resonance frequency of the chip antenna is to decrease the spiral pitch of the antenna line.




However, since in the conventional chip antenna


100


, adjacent via holes


132


are close to each other, there is a problem that the spiral pitch of the antenna line


130


cannot be reduced much due to limitation in manufacturing.




SUMMARY OF THE INVENTION




Accordingly, it is an object of the present invention to provide a chip antenna capable of reducing the spiral pitch of an antenna line so that it is smaller than that of a conventional chip antenna.




In order to achieve the above-mentioned object, in accordance with a first aspect of the present invention, a chip antenna comprises a base body, an antenna line disposed in the base body and being spirally wound, and a feed terminal disposed on a surface of the base body and being electrically connected to one end of the antenna line, wherein the antenna line has a winding axis which curves in a zigzag manner.




In accordance with a second aspect of the present invention, a chip antenna comprises a base body, an antenna line disposed in the base body and being spirally wound, and a feed terminal disposed on a surface of the base body and being electrically connected to one end of the antenna line, wherein the antenna line has a substantially straight winding axis, and adjacent wound portions have a different width or diameter.




More specifically, the antenna line may be formed by electrically connecting a plurality of conductor patterns disposed in the base body in series by via holes which are arranged in the base body in a staggered arrangement.




By the structures described above, the minimum spiral pitch of the antenna line can be smaller than that of a conventional antenna, thereby enabling the resonance frequency of the chip antenna to be reduced to less than that of a conventional chip antenna.




A chip antenna according to the present invention may further comprise an opposing conductor for adjusting the resonance frequency, wherein the opposing conductor opposes at least one of the plurality of conductor patterns forming the antenna line and is electrically connected to part of the plurality of conductor patterns. Thereby, when the area of the opposing conductor for adjusting the resonance frequency is changed, the resonance frequency of the chip antenna can be adjusted without changing the number of winding turns of the antenna line.











BRIEF DESCRIPTION OF THE DRAWING(S)





FIG. 1

is an assembly view of a chip antenna according to a first embodiment of the present invention;





FIG. 2

is a perspective view of the chip antenna shown in

FIG. 1

;





FIG. 3

is a plan view of the chip antenna shown in

FIG. 1

;





FIG. 4

is an assembly view of a chip antenna according to a second embodiment of the present invention;





FIG. 5

is a perspective view of the chip antenna shown in

FIG. 4

;





FIG. 6

is a plan view of the chip antenna shown in

FIG. 4

;





FIG. 7

is a plan view of a chip antenna according to a third embodiment of the present invention;





FIG. 8

is a plan view of a chip antenna according to another embodiment of the present invention;





FIG. 9

is a perspective view of a conventional chip antenna; and





FIG. 10

is a plan view of the chip antenna shown in FIG.


9


.











DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION




Embodiments according to the present invention will be described below with reference to the attached drawings.




First Embodiment, FIGS.


1


to


3







FIG. 1

is an assembly view showing a chip antenna


1


;

FIG. 2

is an external perspective view of the chip antenna


1


shown in

FIG. 1

; and

FIG. 3

is a plan view of the chip antenna


1


shown in FIG.


1


.




As is shown in

FIG. 1

, the chip antenna


1


comprises a dielectric sheet


16


having conductor patterns


25




b


,


25




d


,


25




f


,


25




h


,


25




j


, and


25




l


and via holes


12




a


to


121


formed thereon, a dielectric sheet


17


having the via holes


12




a


to


121


formed thereon, and a dielectric sheet


18


having conductor patterns


25




a


,


25




c


,


25




e


,


25




g


,


25




i


,


25




k


, and


25




m


formed on the top face of the dielectric sheet


18


.




The conductor patterns


25




a


to


25




m


are formed on the surfaces of the respective dielectric sheets


16


and


18


by a method such as printing, sputtering, vapor deposition, pasting, or plating. As a material of the conductor patterns


25




a


to


25




m


, Ag, Ag—Pd, Au, Pt, Cu, Ni, etc., are used. As a material of the dielectric sheets


16


to


18


, a resin such as a fluorocarbon resin, ceramic containing barium oxide, aluminum oxide, silica, etc. as principal ingredients, and a mixture of ceramic and a resin are used. The via holes


12




a


to


12




l


may be formed by filling holes formed on the dielectric sheets


16


and


17


with conductive paste.




The conductor patterns


25




a


to


25




m


are electrically connected sequentially in series by the via holes


12




a


to


12




l


formed on the dielectric sheets


16


and


17


so as to form a spiral antenna line


20


. One end of the spiral antenna line


20


(i.e., the conductor pattern


25




a


) is exposed to the left side of the conductor sheet


18


and the other end (i.e., the conductor pattern


25




m


) is exposed to the right side of the conductor sheet


18


.




The conductor patterns


25




b


,


25




d


,


25




f


,


25




h


,


25




j


, and


25




l


formed on the surface of the dielectric sheet


16


have an equal length and are arranged in parallel to each other at intervals of a predetermined pitch. The conductor patterns


25




b


,


25




f


, and


25




j


and the conductor patterns


25




d


,


25




h


, and


25




l


are each alternately arranged in a staggered arrangement. Similarly, the conductor patterns


25




a


,


25




c


,


25




e


,


25




g


,


25




i


,


25




k


, and


25




m


formed on the top surface of the dielectric sheet


18


also have an equal length and are arranged in parallel to each other at intervals of a predetermined pitch. Furthermore, the via holes


12




a


,


12




c


,


12




e


,


12




g


,


12




i


, and


12




k


are alternately arranged in a staggered arrangement, and the via holes


12




b


,


12




d


,


12




f


,


12




h


,


12




j


, and


12




l


are alternately arranged in a staggered arrangement.




The dielectric sheets


16


to


18


described above, as shown in

FIG. 1

, are sequentially deposited and unitarily burned so as to form a dielectric base body


11


as shown in FIG.


2


. At both ends of the dielectric base body


11


, terminals


21


and


22


are respectively disposed. The terminal


21


is electrically connected to the conductor pattern


25




a


while the terminal


22


is electrically connected to the conductor pattern


25




m


. Any one of the terminals


21


and


22


is used as a feed terminal and the other is for as a fixing terminal. The terminals


21


and


22


may be formed of conductive paste such as Ag, Ag—Pd, Cu, or Ni by a method such as coating, burning, or further wet plating thereon.




In the chip antenna


1


formed as described above, as shown in

FIG. 3

, the antenna line


20


has a winding axis CL which curves in a zigzag manner, and adjacent spiral portions have an equal diameter. Since adjacent via holes (the via holes


12




a


,


12




c


,


12




e


,


12




g


,


12




i


, and


12




k


, for example) are arranged in a staggered arrangement with each other, the distance P


2


between adjacent via holes (the via holes


12




a


and


12




c


, for example) is larger than the spiral pitch P


1


of the antenna line


20


. Therefore, even when the spiral pitch P


1


of the antenna line


20


is reduced to be smaller, the distance P


2


between the adjacent via holes


12




a


and


12




c


can be larger than that of a conventional antenna line, so that limitation in manufacturing may be circumvented. Consequently, the minimum spiral pitch of the antenna line


20


can be smaller than that of a conventional one, thereby enabling the resonance frequency of the chip antenna


1


to be reduced approximately 20% smaller than that of a conventional chip antenna.




Second Embodiment, FIGS.


4


to


6







FIG. 4

is an assembly view of a chip antenna


2


;

FIG. 5

is an exterior perspective view of the chip antenna


2


shown in

FIG. 4

;

FIG. 6

is a plan view of the chip antenna


2


shown in

FIG. 4

; however, in

FIG. 6

, an opposing conductor


23


for adjusting the resonance frequency and a via hole


32




m


are not shown.




As is shown in

FIG. 4

, the chip antenna


2


comprises a dielectric sheet


15


having the opposing conductor


23


for adjusting the resonance frequency and the via hole


32




m


formed thereon, a dielectric sheet


16


having conductor patterns


45




b


,


45




d


,


45




f


,


45




h


,


45




j


, and


45




l


and via holes


32




a


to


32




l


formed thereon, a dielectric sheet


17


having the via holes


32




a


to


321


formed thereon, and a dielectric sheet


18


having conductor patterns


45




a


,


45




c


,


45




e


,


45




g


,


45




i


,


45




k


, and


45




m


formed on the top face of the dielectric sheet


18


.




The conductor patterns


45




a


to


45




m


are electrically connected sequentially in series via the via holes


32




a


to


32




l


formed on the dielectric sheets


16


and


17


so as to form a spiral antenna line


40


. One end of the spiral antenna line


40


(i.e., the conductor pattern


45




a


) is exposed to the left side of the conductor sheet


18


and the other end (i.e., the conductor pattern


45




m


) is exposed to the right side of the conductor sheet


18


.




The conductor patterns


45




b


,


45




f


, and


45




j


formed on the top surface of the dielectric sheet


16


have an equal length and are arranged alternately with and in parallel to the conductor patterns


45




d


,


45




h


, and


45




l


having a smaller length than that of the conductor patterns


45




b


,


45




f


, and


45




j


at intervals of a predetermined pitch. Similarly, the conductor patterns


45




a


,


45




c


,


45




e


,


45




g


,


45




i


,


45




k


, and


45




m


formed on the top surface of the dielectric sheet


18


also have an equal length and are arranged at intervals of a predetermined pitch. Furthermore, the via holes


32




a


,


32




c


,


32




e


,


32




g


,


32




i


, and


32




k


are alternately arranged in a staggered arrangement, and the via holes


32




b


,


32




d


,


32




f


,


32




h


,


32




j


, and


32




l


are alternately arranged in a staggered arrangement.




The opposing conductor


23


for adjusting the resonance frequency is formed in a position opposing the conductor patterns


45




h


to


45




l


and is electrically connected to the conductor pattern


45




l


via the via hole


32




m.






The dielectric sheets


15


to


18


described above, as shown in

FIG. 4

, are sequentially deposited and unitarily burned so as to form a dielectric base body


11


a as shown in FIG.


5


. At both ends of the dielectric base body


11




a,


terminals


21


and


22


are respectively disposed. The terminal


21


is electrically connected to the conductor pattern


45




a


while the terminal


22


is electrically connected to the conductor pattern


45




m.






In the chip antenna


2


formed as described above, as shown in

FIG. 6

, the antenna line


40


has a straight winding axis CL, and adjacent wound portions thereof have a different diameter. Since adjacent via holes (the via holes


32




a


,


32




c


,


32




e


,


32




g


,


32




i


, and


32




k


, for example) are arranged in a staggered arrangement, the distance P


2


between adjacent via holes (the via holes


32




a


and


32




c


, for example) is larger than the spiral pitch P


1


of the antenna line


40


. Therefore, even when the spiral pitch P


1


of the antenna line


40


is reduced to be smaller, the distance P


2


between the adjacent via holes


32




a


and


32




c


can be larger than that of a conventional antenna line, so that limitation in manufacturing may be circumvented. Consequently, the minimum spiral pitch of the antenna line


40


can be smaller than that of a conventional one, thereby enabling the resonance frequency of the chip antenna


2


to be reduced approximately 20% smaller than that of a conventional chip antenna.




As is shown in

FIG. 5

, the opposing conductor


23


for adjusting the resonance frequency formed on the top surface of the dielectric base body


1


a is cut by forming a slit


23




a


on the opposing conductor


23


using a laser, sandblasting, etching, a knife, etc. The area of the opposing conductor


23


for adjusting the resonance frequency being connected to the antenna line


40


is thereby reduced, enabling the resonance frequency of the chip antenna


2


to be changed. Accordingly, even after forming the dielectric base body


11




a,


the resonance frequency can be adjusted to be a desired value, thereby improving the yield of the chip antenna


2


.




Third Embodiment, FIG.


7







FIG. 7

is a plan view of a chip antenna


3


according to a third embodiment. In the third embodiment, a spiral antenna line


60


is arranged in a dielectric base body


11




b


, in which the diameter of the spiral line


60


increases gradually as the winding proceeds.




Conductor patterns


65




a


to


65




m


formed in the dielectric base body


11




b


are electrically connected sequentially in series through via holes


52




a


to


52




l


formed in the dielectric base body


11




b


so as to form a spiral antenna line


60


. The conductor patterns


65




b


,


65




f


, and


65




j


and the conductor patterns


65




d


,


65




h


, and


65




l


are arranged at intervals of a predetermined pitch and each length thereof increases gradually in order. The via holes


52




b


,


52




d


,


52




f


,


52




h


,


52




j


, and


52




l


are arranged in a staggered arrangement. The via holes


52




a


,


52




c


,


52




e


,


52




g


,


52




i


, and


52




k


are also arranged in a staggered arrangement.




In the chip antenna


3


formed as described above, just like in the second embodiment, the antenna line


60


has a straight winding axis CL, and adjacent wound portions thereof have a different diameter. Since adjacent via holes (the via holes


52




a


,


52




c


,


52




e


,


52




g


,


52




i


, and


52




k


, for example) are arranged in a staggered arrangement, the distance P


2


between adjacent via holes (the via holes


52




a


and


52




c


, for example) is larger than the spiral pitch P


1


of the antenna line


60


. Therefore, even when the spiral pitch P


1


of the antenna line


60


is reduced to be smaller, the distance P


2


between the adjacent via holes


52




a


and


52




c


can be larger than that of a conventional antenna line, so that limitation in manufacturing may be circumvented. Consequently, the minimum spiral pitch of the antenna line


60


can be smaller than that of a conventional one, thereby enabling the resonance frequency of the chip antenna


3


to be reduced smaller than that of a conventional chip antenna.




Other Embodiments




The present invention is not limited to the above-described embodiments, however. Various modifications can be made within the scope of the invention. For example, in the embodiments, the cross-section of the spiral antenna line is rectangular; however it may have an arbitrary shape such as a substantially track shape having straight portions and curved portions or a semi-cylindrical shape. The dielectric base body may be spherical, cubic, cylindrical, conical, or pyramidal as well as being rectangular solid. The entire or part of the antenna line may be embedded into the base body. Also, the entire conductor patterns may be formed on a surface of the base body


11


by using the dielectric sheet


19


shown in

FIG. 8

instead of the dielectric sheet


18


according to the first embodiment shown in FIG.


1


. Furthermore, the base body may be formed from a magnetic material. One end of the antenna line may be open as shown in FIG.


9


.




Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.



Claims
  • 1. A chip antenna comprising:a base body; an antenna line disposed on or in the base body and being spirally wound; and a feed terminal disposed on a surface of the base body and being electrically connected to one end of the antenna line, wherein the antenna line has a winding axis which is arranged in a zigzag manner.
  • 2. The chip antenna of claim 1, wherein the base body comprises a plurality of laminations, at least two of the laminations having conductors disposed thereon with conductive via holes connecting the conductors on a first lamination to conductors on a second lamination thereby forming the spirally wound antenna line having a rectangular cross section and having a defined pitch and wherein a distance between adjacent through holes is greater than the pitch.
  • 3. A chip antenna of claim 1, further comprising:a plurality of conductor patterns disposed in the base body; and via holes, wherein the antenna line is formed by electrically connecting the plurality of conductor patterns in series by the via holes which are arranged in the base body in a staggered arrangement.
  • 4. The chip antenna of claim 1, further comprising an opposing conductor for adjusting the resonance frequency, wherein the opposing conductor opposes at least one of the plurality of conductor patterns forming the antenna line and is electrically connected to part of the plurality of conductor patterns.
  • 5. The chip antenna of claim 3, further comprising an opposing conductor for adjusting the resonance frequency, wherein the opposing conductor opposes at least one of the plurality of conductor patterns forming the antenna line and is electrically connected to part of the plurality of conductor patterns.
  • 6. The chip antenna of claim 1, wherein the antenna line has a substantially rectangular cross section.
  • 7. The chip antenna of claim 3, wherein the antenna line has a substantially rectangular cross section.
  • 8. The chip antenna of claim 1, wherein the base body comprises one of a dielectric and a magnetic element.
  • 9. The chip antenna of claim 3, wherein the base body comprises one of a dielectric and a magnetic element.
  • 10. The chip antenna of claim 2, wherein adjacent conductors on at least one of the laminations have equal lengths.
  • 11. The chip antenna of claim 1, wherein the antenna line has a terminal for connection to a power feed at one end.
  • 12. The chip antenna of claim 11, wherein the antenna line has a second end that is provided to a second terminal or left unconnected.
  • 13. A chip antenna comprising:a base body; an antenna line disposed on or in the base body and being spirally wound; and a feed terminal disposed on a surface of the base body and being electrically connected to one end of the antenna line; wherein the antenna line has a substantially straight winding axis, and adjacent wound portions of the antenna line have a different length, where the length is defined as a distance extending in one direction from the substantially straight winding axis to each of the adjacent wound portions.
  • 14. The chip antenna of claim 13, wherein the base body comprises a plurality of laminations, two of the laminations having conductors disposed thereon with conductive via holes connecting the conductors on a first lamination to conductors on a second lamination thereby forming the spirally wound antenna line having a rectangular cross section and having a defined pitch and wherein a distance between adjacent through holes is greater than the pitch.
  • 15. A chip antenna of claim 13, further comprising:a plurality of conductor patterns disposed in the base body; and via holes, wherein the antenna line is formed by electrically connecting the plurality of conductor patterns in series by the via holes which are arranged in the base body in a staggered arrangement.
  • 16. The chip antenna of claim 13, further comprising an opposing conductor for adjusting the resonance frequency, wherein the opposing conductor opposes at least one of the plurality of conductor patterns forming the antenna line and is electrically connected to part of the plurality of conductor patterns.
  • 17. The chip antenna of claim 13, wherein the antenna line has a substantially rectangular cross section.
  • 18. The chip antenna of claim 13, wherein the base body comprises one of a dielectric and a magnetic element.
  • 19. The chip antenna of claim 14, wherein adjacent conductors on both laminations have unequal lengths.
  • 20. The chip antenna of claim 14, wherein the width of adjacent conductors on at least one of the laminations increases from a first end of the base body to a second end.
  • 21. The chip antenna of claim 13, wherein the antenna line has a terminal for connection to a power feed at one end.
  • 22. The chip antenna of claim 21, wherein the antenna line has a second end that is provided to a second terminal or left unconnected.
Priority Claims (1)
Number Date Country Kind
2000-231117 Jul 2000 JP
US Referenced Citations (2)
Number Name Date Kind
4644366 Scholz Feb 1987 A
5541610 Imanishi et al. Jul 1996 A
Foreign Referenced Citations (4)
Number Date Country
0863570 Sep 1998 EP
2702091 Sep 1994 FR
4242911 Aug 1992 JP
8316725 Nov 1996 JP
Non-Patent Literature Citations (3)
Entry
Patent Abstracts of Japan vol. 2000, No. 04, Aug. 31, 2000 & JP 2000 013132 A (TDK Corp), Jan. 14, 2000.
Patent Abstracts of Japan vol. 1998, No. 08, Jun. 30, 1998 & JP 10 084216 (Saitama Nippon Denki KK), Mar. 31, 1998.
Cardosa et al. “A Spherial Helical Antenna” Antennas and Propagation Society International Symposium, 1993. AP-S. Digest Ann Arbor, MI, USA Jun. 28-Jul. 2 1993, New York, NY IEEE, Jun. 28, 1993 pp. 1558-1561.