Ceramic chip antenna

Information

  • Patent Grant
  • 6825819
  • Patent Number
    6,825,819
  • Date Filed
    Wednesday, November 20, 2002
    22 years ago
  • Date Issued
    Tuesday, November 30, 2004
    20 years ago
Abstract
A ceramic chip antenna for use in ultra-high frequency communications. The ceramic chip antenna according to the present invention comprises a main body, first and second helical conductors, and a single power supply section for supplying power to the first and second helical conductors. The main body is produced by laminating a plurality of ceramic sheets made of a dielectric material. The first and second helical conductors are formed inside the main body by a screen-printing method. The first and second helical conductors have the same axis of helical rotation, as view from the power supply section.
Description




FIELD OF THE INVENTION




The present invention relates to a ceramic chip antenna, and more particularly, to a ceramic chip antenna of a helix structure with application to a wireless communication system.




BACKGROUND OF THE INVENTION




Ceramic chip antennas have been widely accepted as an antenna element in the field of wireless communications due to their compactness. Typically, as shown in

FIG. 1

, such ceramic chip antennas include a helical conductor of a single helix structure embedded by printing into a main body composed of a plurality of laminated ceramic sheets. The helical conductor comprises a plurality of first horizontal strip lines


4




a


and a plurality of second horizontal strip lines


4




b


, both of which are thickly printed on the ceramic sheets. The helical conductor further comprises a plurality of vertical strip lines


5




a


and


5




b


that are produced by filling via holes (formed in the ceramic sheets) with conductive material. First horizontal strip lines


4




a


, second horizontal strip lines


4




b


, and vertical strip lines


5




a


and


5




b


are electrically connected to form an integral structure.




However, this single helical conductor structure poses a problem in terms of bandwidth when applied to a wireless communication system. Ceramic chip antenna


100


in

FIG. 1

does not meet the wideband frequency characteristics required by a typical wireless communication system such as a mobile phone, WLAN, Bluetooth etc.




Alternatively, a ceramic chip antenna as shown in

FIG. 2A

is often used to meet the required wideband frequency characteristics of wireless telecommunication systems. Ceramic chip antenna


200


in

FIG. 2A

includes two helical conductors


7


and


8


, which have different axes of helical rotation A, B, respectively. The structure of ceramic chip antenna


200


is further described with reference to FIG.


2


B. First helical conductor


7


is formed by electrically connecting a plurality of first horizontal strip lines


7




a


, which are thickly printed on first ceramic sheet


6




a


, a plurality of vertical strip lines


7




b


, which are produced by filling via holes (not shown) formed in second ceramic sheet


6




b


and third ceramic sheet


6




c


with conductive materials, and a plurality of second horizontal strip lines


7




c


, which are thickly printed on fourth ceramic sheet


6




d


. Similarly, second helical conductor


8


is formed by connecting a plurality of third horizontal strip lines


8




a


, which are thickly printed on first ceramic sheet


6




a


, a plurality of vertical strip lines


8




b


, which are produced by filling via holes (not shown) formed in second ceramic sheet


6




b


and third ceramic sheet


6




c


with conductive materials, and a plurality of fourth horizontal strip lines


8




c


, which are also thickly printed on fourth ceramic sheet


6




d


. Power supplying terminals


9


and


10


are formed on first ceramic sheet


6




a.






As explained above, horizontal strip lines


7




a


,


7




c


,


8




a


and


8




c


are thickly printed on first and fourth ceramic sheets


6




a


and


6




d


to form the two helical conductors, so that the structure of ceramic chip antenna


200


avoids complexity in manufacturing. However, two problems are encountered with ceramic chip antenna


200


: the size of the antenna inevitably becomes large because helical conductors


7


and


8


have different axes of helical rotation A and B from each other; and the structure of the antenna becomes complicated as two power supplying terminals


9


and


10


must be provided.




Accordingly, a need in the art exists to provide a ceramic chip antenna with a simple structure, which can be manufactured in an efficient manner while meeting wideband frequency requirements.




SUMMARY OF THE INVENTION




Therefore, an object of the present invention is to provide a ceramic chip antenna meeting wideband frequency requirements and having a simple structure for efficient manufacturing.




In accordance with one aspect of the present invention, a ceramic chip antenna is provided that comprises a main body formed by laminating a plurality of ceramic sheets made of a ceramic dielectric material, first and second helical conductors formed inside the main body, and a power supply section coupled to the first and second helical conductors for supplying power thereto, wherein the first and second helical conductors have the same axis of helical rotation as viewed from the power supply section.











BRIEF DESCRIPTION OF DRAWING




The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiment given in conjunction with the accompanying drawing.





FIG. 1

shows a structure of a conventional ceramic chip antenna including a helical conductor having a single helix structure;





FIG. 2A

shows a structure of a conventional ceramic chip antenna including two helical conductors composed of two helices having different axes of helical rotation;





FIG. 2B

is an exploded view of the ceramic chip antenna shown in

FIG. 2A

;





FIG. 3

shows a structure of a ceramic chip antenna in accordance with one embodiment of the present invention;





FIG. 4A

is an exploded view of the ceramic chip antenna shown in

FIG. 3

;





FIG. 4B

is a detailed view of the power supply section of the ceramic chip antenna shown in

FIG. 4A

;





FIG. 5

is a graph of the frequency bandwidth characteristics of the ceramic chip antennas shown in

FIGS. 1 and 3

;





FIG. 6

shows a structure of a ceramic chip antenna in accordance with another embodiment of the present invention; and





FIG. 7

is a graph of the frequency bandwidth characteristic of the ceramic chip antenna shown in FIG.


6


.











DETAILED DESCRIPTION OF THE PRESENT INVENTION





FIG. 3

shows a structure of a ceramic chip antenna in accordance with one embodiment of the present invention. Ceramic chip antenna


300


comprises main body


105


having a rectangular parallelepiped shape, which is formed by laminating a plurality of ceramic sheets, first helical conductor


120


and second helical conductor


130


for forming a dual helix structure inside main body


105


, and a power supply section coupled to first and second helical conductors


120


and


130


for applying a supply voltage thereto. First and second helical conductors


120


and


130


share the same axis of helical rotation as viewed from the power supply section, which makes the structure of the ceramic chip antenna simple. Moreover, the power supply section applies a supply voltage to each of helical conductors


120


and


130


so that the structure of the ceramic chip antenna is as similarly simple as if one independent helical antenna were provided inside the chip.




The structure of ceramic chip antenna


300


will now be described in more detail with reference to

FIGS. 4A and 4B

.

FIG. 4A

is an exploded view of the ceramic chip antenna as shown in FIG.


3


. Ceramic chip antenna


300


comprises a plurality of laminated dielectric ceramic sheets


140


,


150


,


160


and


170


. On first ceramic sheet


140


, first horizontal strip lines


120




a


are thickly printed. The “thick printing” technique is a conventional technique for providing an electrode pattern on a thick ceramic sheet with a thickness of 50-300 μm by a screen printing method. To form first vertical strip lines


120




b


and


120




c


, via holes (not shown) are formed into second and third ceramic sheets


150


and


160


, which are filled with conductive material. Conductive material, like silver (Ag) paste, is preferably used to thickly print a plurality of metallic horizontal strip lines to fill the via holes. Second horizontal strip lines


120




d


are thickly printed on third ceramic sheet


160


. First horizontal strip lines


120




a


, first vertical strip lines


120




b


and


120




c


, and second horizontal strip lines


120




d


are electrically connected to form first helical conductor


120


of ceramic chip antenna


300


.




Second helical conductor


130


of ceramic chip antenna


300


is similarly produced. Third horizontal strip lines


130




a


are thickly printed on first ceramic sheet


140


, and via holes (not shown) are formed into second and third ceramic sheets


150


and


160


, which are filled with conductive material to form second vertical strip lines


130




b


and


130




c


. Fourth horizontal strip lines


130




d


are thickly printed on third ceramic sheet


160


. Third horizontal strip lines


130




a


, second vertical strip lines


130




b


and


130




c


, and fourth horizontal strip lines


130




d


are all electrically connected. Even though the plurality of horizontal strip lines


120




d


and


130




d


and vertical strip lines


120




c


and


130




c


are illustrated in

FIG. 4A

as being separated from each other on third ceramic sheet


160


, vertical strip lines


120




c


and


130




c


must be formed to abut horizontal strip lines


120




d


and


130




d


to provide electrical connection.




As previously explained, first horizontal strip lines


120




a


and third horizontal strip lines


130




a


constituting first and second helical conductors


120


and


130


are thickly printed on first ceramic sheet


140


in turn. Second and fourth horizontal strip lines


120




d


and


130




d


are thickly printed on third ceramic sheet


160


in turn. First vertical strip lines


120




b


and


120




c


constituting first helical conductor


120


, and second vertical strip lines


130




b


and


130




c


constituting second helical conductor


130


are formed in turn on second and third ceramic sheets


150


and


160


. Therefore, the process of thick printing and laminating the dielectric ceramic sheets can be simplified. Since the number and length of the metallic strip lines are identical for the two helical conductors, first and second helical conductors


120


and


130


shown in

FIG. 3

have the same length.




The T-type power supply section is connected to first and second helical conductors


120


and


130


to provide a supply voltage, which is input from the exterior of main body


300


, to first and second helical conductors


120


and


130


. This T-type power supply section is characterized by a T-shaped film


110




a


printed on the top surface of second ceramic sheet


150


to extend from one of the edges of second ceramic sheet


150


where the top surface of second ceramic sheet


150


meets a right end surface


150




a


of second ceramic sheet


150


, as shown in FIG.


4


A. T-shaped film


110




a


is arranged on second ceramic sheet


150


such that first end


110




b


of film


110




a


coincides with the afore-mentioned edge of second ceramic sheet


150


. The structure and method of formation of the T-type power supply section on first to third ceramic sheets


140


-


160


will be described in detail with reference to FIG.


4


B.




As shown in

FIG. 4B

, third vertical strip line


110




e


is formed in a recessed portion of end surface


150




a


of second ceramic sheet


150


such that the outer surface of third vertical strip line


110




e


is coplanar with end surface


150




a


of second ceramic sheet


150


. Likewise, fourth vertical strip line


110




f


is formed in a recessed portion of end surface


140




a


of first ceramic sheet


140


such that the outer surface of fourth vertical strip line


110




f


is coplanar with end surface


140




a


of first ceramic sheet


140


. The outer surfaces of third and fourth vertical strip lines


110




e


and


110




f


are exposed to the exterior. First end


110




b


of T-shaped film


110




a


is connected to the upper surface of third vertical strip line


110




e


in a vertical relationship, and the lower surface of third vertical strip line


110




e


is connected to the upper surface of fourth vertical strip line


110




f


. With this structure, the lower surface of fourth vertical strip line


110




f


is coplanar with the lower surface of first ceramic sheet


140


and is exposed to the exterior. Next, second end


110




c


and third end


110




d


of T-shaped film


110




a


are connected to first helical conductor


120


and second helical conductor


130


, respectively. Therefore, a voltage input from the exterior of main body


105


can be transmitted to first and second helical conductors


120


and


130


through fourth and third vertical strip lines


110




f


and


110




e.






The ceramic chip antenna may be used as an antenna element of a mobile phone. For such application, the ceramic chip antenna is usually mounted on, for example, the surface of the substrate of a mobile phone by a soldering method. In order to improve stability in surface-mounting, preferably a plating treatment is conducted over: a portion of the lower surface of first ceramic sheet


140


, including the externally exposed lower surface of fourth vertical strip line


110




f


; at least a central portion of end surface


140




a


of first ceramic sheet


140


, including the externally exposed outer surface of fourth vertical strip line


110




f


; at least a central portion of end surface


150




a


of second ceramic sheet


150


, including the externally exposed outer surface of third vertical strip line


110




e


; and at least a central portion of the end surface of third ceramic sheet


160


.





FIG. 5

is a graph of the frequency bandwidth characteristic curve


230


of conventional ceramic chip antennas


100


shown in FIG.


1


and the frequency bandwidth characteristic curve


240


of ceramic chip antenna


300


of

FIG. 3

according to the present invention. In

FIG. 5

, the ordinate and the abscissa represent the return loss of the antenna and the frequency, respectively. As described above, the ceramic chip antenna of the present invention is designed such that the length of the first helical conductor is equal to that of the second helical conductor. As a result, the first and second helical conductors resonate at the same center frequency fo. Accordingly, bandwidth


220


of ceramic chip antenna


300


, which is embodied by the helical conductors of a dual-helix type, is broader than bandwidth


210


of conventional ceramic chip antenna


100


, which is embodied by the helical conductor of the single-helix type.





FIG. 6

shows a structure of a ceramic chip antenna in accordance with another embodiment of the present invention. Ceramic chip antenna


600


comprises a main body


180


formed by laminating plural ceramic sheets, and two helical conductors


181


and


182


for forming a dual helix structure inside main body


180


, as in ceramic chip antenna


300


. The processes of forming the dual helix structure inside main body


180


are similar to those described in connection with ceramic chip antenna


300


, and the detailed explanation thereof is omitted herein. According to this embodiment, however, the numbers of horizontal strip lines and vertical strip lines are different for the two helical conductors. As a result, first helical conductor


181


and second helical conductor


182


have different lengths so that they resonate at the two different resonant frequencies fo


1


, fo


2


, as shown in FIG.


7


. Accordingly, bandwidth


250


for ceramic chip antenna


600


can be further extended as compared to that obtainable by ceramic chip antenna


300


.




As mentioned above, the ceramic chip antennas according to the present invention described in conjunction with

FIGS. 3-7

can meet the frequency bandwidth characteristics required by wireless communication systems such as a mobile phone, WLAN, Bluetooth etc. Particularly, the structure of the antenna can be made as similarly simple as if a single-helix type antenna were formed, because a plurality of helical conductors are connected to only one power supply section.




While the present invention has been shown and described with respect to the particular embodiment, it will be apparent to those skilled in the art that many exchanges and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.



Claims
  • 1. A ceramic chip antenna comprising:a main body formed by laminating a plurality of ceramic sheets made of a dielectric material; a first helical conductor and a second helical conductor formed inside the main body; and a power supply section coupled to the first and second helical conductors for supplying power thereto, wherein the first and second helical conductors have the same axis of helical rotation as viewed from the power supply section, and the power supply section comprises a T-shaped film having three ends thickly printed on a predetermined ceramic sheet.
  • 2. The ceramic chip antenna of claim 1, wherein the first helical conductor is produced by connecting first horizontal strip lines formed on the first ceramic sheet, first vertical strip lines formed on the second and third ceramic sheets, and second horizontal strip lines formed on the third ceramic sheet.
  • 3. The ceramic chip antenna of claim 2, wherein the second helical conductor is produced by connecting third horizontal strip lines formed on the first ceramic sheet, second vertical strip lines formed on the second and third ceramic sheets, and fourth horizontal strip lines formed on the third ceramic sheet.
  • 4. The ceramic chip antenna of claim 1, wherein the first helical conductor is connected to the second end of the T-shaped film, and the second helical conductor is connected to the third end of the T-shaped film.
  • 5. The ceramic chip antenna of claim 3, wherein the first and third horizontal strip lines are thickly printed on the first ceramic sheet.
  • 6. The ceramic chip antenna of claim 3, wherein the second and fourth horizontal strip lines are thickly printed on the third ceramic sheet.
  • 7. The ceramic chip antenna of claim 1, wherein the first and second helical conductors have the same length.
  • 8. The ceramic chip antenna of claim 1, wherein the first and second helical conductors have different lengths.
Priority Claims (1)
Number Date Country Kind
10-2002-30514 May 2002 KR
US Referenced Citations (4)
Number Name Date Kind
6023251 Koo et al. Feb 2000 A
6650303 Kim et al. Nov 2003 B2
20020067312 Hilgers Jun 2002 A1
20020118075 Ohwada Aug 2002 A1