Chip antenna element, antenna apparatus and communications apparatus comprising same

Information

  • Patent Grant
  • 6476767
  • Patent Number
    6,476,767
  • Date Filed
    Friday, April 13, 2001
    23 years ago
  • Date Issued
    Tuesday, November 5, 2002
    22 years ago
Abstract
A chip antenna element comprises (a) a radiation electrode formed on at least one surface of an insulating substrate, such that the radiation electrode extends from a first end of the substrate or its vicinity to a second end of the substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of the substrate and a narrow tip end on the side of the second end of the substrate, (b) a first grounding electrode connecting directly or via a gap to the rear end of the radiation electrode, (c) a second grounding electrode opposing the tip end of the radiation electrode via a gap, and (d) a feeding electrode formed on at least one surface of the substrate at a position facing an intermediate point of the radiation electrode, with or without contact with the radiation electrode.
Description




FIELD OF THE INVENTION




The present invention relates to a microstrip-line chip antenna element suitable for microwave wireless communications apparatuses such as portable wireless phones and wireless local area network LAN, and an antenna apparatus comprising such a chip antenna element and a communications apparatus comprising such an antenna apparatus.




PRIOR ART




In microwave wireless communications apparatuses, particularly portable communications apparatuses such as cellular phones, monopole antennas and microstrip-line antennas are generally used for achieving miniaturization and reduction in thickness. A microstrip-line antenna element put into practical use at present has, as described in Japanese Patent Laid-Open No. 10-209740, a radiation electrode formed on an upper surface of a dielectric, rectangular parallelepiped body, high-frequency electric signal being fed from below.

FIG. 36

schematically shows the structure of this microstrip-line antenna element. When operated as an antenna, the antenna element is mounted onto a printed circuit board having a ground conductor


96


, and a feeding line


94


is disposed on a lower surface of the printed circuit board. An electric line force F is generated between an open end


91


of a radiation electrode


90


and the ground conductor


96


, whereby a magnetic flux is generated in a perpendicular direction to the radiation electrode


90


, efficiently emitting electromagnetic wave to the space. The length D of the radiation electrode


90


is usually about ¼ of a wavelength, generating a magnetic flux in a perpendicular direction to the radiation electrode


90


at resonance, the direction of an electric line force F being in perpendicular to the magnetic flux emitted from the end surface


91


of the radiation electrode


90


. With respect to the shape of the radiation electrode


90


in a plan view, various shapes such as circle, pentagon, etc. are proposed in addition to rectangle, though vertically or horizontally symmetric shapes are mostly used.




Antennas used for portable communications apparatuses should be small, efficient in radiation and substantially omni-directional. For this purpose, a small antenna element has a structure in which a radiation electrode is disposed on an upper surface or inside of an insulating substrate, because the wavelength of electric current flowing through the radiation electrode is made shorter by influence of the insulating substrate. Because the same radiation effect can be kept even though the radiation electrode is made shorter, the antenna can be miniaturized. The necessary length d of the antenna is represented by the following equation (1):








d=c


/(2


f




0




∈r


)  (1),






wherein ∈r is a specific dielectric constant of the insulating substrate, f


0


is a resonance frequency, and c is the velocity of light.




As is clear from the equation (1), the length d of an antenna element having a microstrip-line structure can be made shorter as the insulating substrate has a larger specific dielectric constant ∈r at a constant resonance frequency f


0


. In other words, with a substrate having a high specific dielectric constant ∈r, a small microstrip-line antenna element can be obtained with the same performance. Because a small antenna element is indispensable particularly for cellular phones, etc., the development of smaller, high-performance antenna elements has been desired.




There is an inverted F antenna as an antenna applicable to portable communications apparatuses other than the microstrip-line antenna. The inverted F antenna is constituted by an F-shaped antenna conductor comprising a bent portion at an end connected to a ground conductor plate, a center bent portion connected to a feeding line via a gap. Because the antenna conductor needs only to be as long as about ¼ of a wavelength, it may be regarded as an antenna having a shape obtained by laterally expanding the microstrip-line antenna element.




The conventional microstrip-line antenna element has the following disadvantages in miniaturization. That is, when the radiation electrode is made smaller by increasing the specific dielectric constant ∈r of an insulating substrate, a resonance bandwidth of the resonance frequency f


0


becomes narrower, whereby the antenna is operable only in a narrow frequency range.




This means the restriction of a frequency range available for communications, not preferable for antenna for cellular phones, etc. Accordingly, to develop a practically useful antenna, it should have wide bandwidth characteristics. Particularly in multi-frequency antennas using two or more frequencies, the phenomenon of narrowing a bandwidth is a serious problem, which cannot be controlled only by the properties of the insulating substrate.




A resonance bandwidth BW, a resonance frequency f


0


and a Q value representing the performance of an antenna at resonance meet the following relation:








BW=f




0




/Q


  (2).






The height H a microstrip-line antenna element equal to the thickness of its insulating substrate and the Q value meet the following relation:








Q∝∈r/H


  (3).






Known as a small microstrip-line antenna is an antenna having a radiation electrode divided to two parts at center, one end of the divided radiation electrode is electrically connected to a ground conductor plate (Hiroyuki Arai, “New Antenna Engineering,” Sogo-Densi Shuppan, pp. 109-112). Because the length of the radiation electrode is about ¼ of a wavelength at resonance frequency, this antenna is as small as about 50% of the conventional antenna.




Japanese Patent Laid-Open No. 11-251816 discloses a microstrip-line antenna element operable at an expanded bandwidth with a radiation electrode formed on an edge region (adjacent two surfaces) of the substrate. When this microstrip-line antenna element is assembled in a portable communications apparatus, however, a radio wave emitted mainly from the end of the radiation electrode induces electric current in a nearby casing or in conductors on the circuit board, making the current-induced conductors function as an apparent antenna. Thus, the characteristics of this antenna is variable depending on ambient environment, causing impedance mismatching at a feed point and the variation of radiation directivity.




Further, because electronic circuit parts mounted near the antenna element are affected by a high-frequency electromagnetic wave emitted from the end of the radiation electrode, there arise problems of deteriorating communications performance such as noises, errors, irregular oscillation, etc. Conventional means for coping with such problems was to fully separate nearby circuit parts from the antenna element, failing to increase the mounting density of parts near the antenna, thus largely hindering the miniaturization of communications apparatuses.




OBJECT OF THE INVENTION




Accordingly, an object of the present invention is to provide a small microstrip-line antenna element having a sufficient Q value with high gain and broad bandwidth.




Another object of the present invention is to provide an antenna apparatus comprising such an antenna element mounted onto a circuit board with improved mounting density without affecting nearby parts.




A further object of the present invention is to provide a communications apparatus such as a portable information terminal, etc. comprising such an antenna apparatus.




SUMMARY OF THE INVENTION




As a result of investigation by simulation to achieve the miniaturization and increase in bandwidth of an antenna element, it has been found: (1) the antenna element can equivalently be provided with a plurality of resonance circuits by properly designing the shapes of a radiation electrode go and grounding electrodes; (2) radiation directivity can be achieved with high gain and without unnecessary field emission by properly designing the arrangement of electrodes; and (3) an area occupied by the antenna can be reduced while providing good antenna characteristics by properly designing the mounting of an antenna onto a ground conductor. The present invention is based on these findings.




Thus, the chip antenna element of the present invention comprises an insulating substrate and a radiation electrode formed on at least one surface of the insulating substrate, the radiation electrode extending from a first end of the substrate or its vicinity to a second end of the substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise.




The chip antenna element according to one embodiment of the present invention comprises (a) a grounding electrode formed on a first end surface and/or a nearby surface region of an insulating substrate, (b) a radiation electrode formed on at least one surface of the substrate, such that the radiation electrode extends from the grounding electrode with or without a gap to a second end of the substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of the substrate and a narrow tip end on the side of the second end of the substrate, and (c) a feeding electrode formed on at least one surface of the substrate at a position facing an intermediate point of the radiation electrode, with or without contact with the radiation electrode.




The chip antenna element according to another embodiment of the present invention comprises (a) a radiation electrode formed on at least one surface of an insulating substrate, such that the radiation electrode extends from a first end of the substrate or its vicinity to a second end of the substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of the substrate and a narrow tip end on the side of the second end of the substrate, and (b) a grounding electrode opposing the tip end of the radiation electrode via a gap, and (c) a feeding electrode formed on at least one surface of the substrate at a position facing an intermediate point of the radiation electrode, with or without contact with the radiation electrode.




The chip antenna element according to a further embodiment of the present invention comprises (a) a radiation electrode formed on at least one surface of an insulating substrate, such that the radiation electrode extends from a first end of the substrate or its vicinity to a second end of the substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of the substrate and a narrow tip end on the side of the second end of the substrate, (b) a first grounding electrode connecting directly or via a gap to the rear end of the radiation electrode, (c) a second grounding electrode opposing the tip end of the radiation electrode via a gap, and (d) a feeding electrode formed on at least one surface of the substrate at a position facing an intermediate point of the radiation electrode, with or without contact with the radiation electrode.




One of the first and second grounding electrodes is preferably in contact with the radiation electrode, whereby the intensity of a radiating electric field decreases in a longitudinal direction of the radiation electrode and increases in a direction perpendicular thereto.




The chip antenna element preferably father comprises an extension electrode connected to the tip end of the radiation electrode and formed on a second end surface of the substrate and/or its nearby region on at least one side surface adjacent thereto. The extension electrode preferably is narrower than the tip end of the radiation electrode.




The insulating substrate is preferably in the form of a rectangular parallelepiped. Also, a ratio W/S of a width W of the wide rear end of the radiation electrode to a width S of the narrow tip end of the radiation electrode is preferably 2 or more, more preferably 2-5. The radiation electrode is preferably formed on adjacent side surfaces of the insulating substrate. Further, the feeding electrode is preferably located at a position deviating from a center of the substrate toward the tip end of the radiation electrode.




The antenna apparatus of the present invention comprises the above chip antenna element mounted onto a circuit board, the radiation electrode of the chip antenna element being in parallel with the edge of a ground conductor of the circuit board, and an open tip end of the radiation electrode being not close to the ground conductor.




There preferably is a gap between the grounding electrode of the chip antenna element and the ground conductor of the circuit board. The feeding electrode is preferably located at a position deviating from a center of the substrate of the chip antenna element toward the tip end of the radiation electrode. The feeding electrode preferably is connected to a feeding line disposed between a pair of ground conductors on the circuit board.




The communications apparatus of the present invention comprises the above antenna apparatus. The communications apparatuses of the present invention may preferably be cellular phones, headphones, personal computers, note-size personal computers, digital cameras, etc. comprising antennas for bluetooth devices.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view showing a chip antenna element for explaining the principle of the present invention;





FIG. 2

is a perspective view showing a chip antenna element according to one embodiment of the present invention;




FIG.


3


(


a


) is a view showing an equivalent circuit of the chip antenna element shown in

FIG. 2

;




FIG.


3


(


b


) is a view showing an equivalent circuit of a conventional chip antenna element;





FIG. 4

is a perspective view showing the structure of a radiation electrode in the chip antenna element of the present invention;





FIG. 5

is a graph showing the relations between a ratio W/S of the width W of a rear end of the radiation electrode to the width S of a tip end of the radiation electrode and a resonance frequency f


0


in the chip antenna element shown in

FIG. 4

;





FIG. 6

is a graph showing the relations between a ratio W/S of the radiation electrode and a specific bandwidth BW/f


0


;





FIG. 7

is a graph showing the relations between W/S of the radiation electrode and a Q value in the chip antenna element shown in

FIG. 4

;





FIG. 8

is a perspective view showing an antenna apparatus comprising the chip antenna element of the present invention mounted onto a circuit board;





FIG. 9

is a perspective view showing an antenna apparatus comprising a chip antenna element of the present invention mounted onto another circuit board;





FIG. 10

is a perspective view showing an antenna apparatus comprising the chip antenna element of the present invention mounted onto another circuit board;




FIG.


11


(


a


) is a graph showing the relations between the length of a substrate and a bandwidth in the chip antenna element shown in

FIG. 10

;




FIG.


11


(


b


) is a graph showing the relations between the width of a substrate and a bandwidth in the chip antenna element shown in

FIG. 10

;




FIG.


11


(


c


) is a graph showing the relations between the dielectric constant of a substrate and a bandwidth in the chip antenna element shown in

FIG. 10

;





FIG. 12

is a perspective view showing a chip antenna element of the present invention to be evaluated;





FIG. 13

is a graph showing the directivity of the chip antenna element of

FIG. 12

with respect to a Z-axis;





FIG. 14

is a graph showing the directivity of the chip antenna element of

FIG. 12

with respect to an X-axis;





FIG. 15

is a graph showing the directivity of the chip antenna element of

FIG. 12

with respect to a Y-axis;





FIG. 16

is a graph showing the bandwidth characteristics of the chip antenna element of

FIG. 12

;





FIG. 17

is a perspective view showing a chip antenna element according to a further embodiment of the present invention;





FIG. 18

is a graph showing the bandwidth of the chip antenna element of

FIG. 17

;




FIG.


19


(


a


) is a perspective view showing an upper surface of a chip antenna element according to a still further embodiment of the present invention;




FIG.


19


(


b


) is a perspective view showing an upper surface of a chip antenna element according to a still further embodiment of the present invention from an opposite angle;




FIG.


19


(


c


) is a perspective view showing a lower surface of a chip antenna element according to a still further embodiment of the present invention;




FIG.


20


(


a


) is a perspective view showing an upper surface of a chip antenna element according to a still further embodiment of the present invention;




FIG.


20


(


b


) is a perspective view showing an upper surface of a chip antenna element according to a still further embodiment of the present invention from an opposite angle;




FIG.


20


(


c


) is a perspective view showing a lower surface of a chip antenna element according to a still further embodiment of the present invention;





FIG. 21

is a perspective view showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 22

is a perspective view showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 23

is a perspective view showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 24

is a perspective view showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 25

is a perspective view showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 26

is a perspective view showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 27

is a development showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 28

is a development showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 29

is a development showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 30

is a development showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 31

is a development showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 32

is a development showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 33

is a development showing a chip antenna element according to still further embodiment of the present invention;





FIG. 34

is a development showing a chip antenna element according to a still further embodiment of the present invention;





FIG. 35

is a view showing various shapes of radiation electrodes usable in the chip antenna element of the present invention; and





FIG. 36

is a schematic view showing an example of conventional microstrip-line antenna elements.











DESCRIPTION OF THE PREFERRED EMBODIMENTS





FIG. 1

shows a planar chip antenna element for explaining the principle of the present invention, and

FIG. 2

shows a chip antenna element according to one embodiment of the present invention. In the planar chip


6


antenna element shown in

FIG. 1

, a radiation electrode


13


is gradually narrowing from a rear end


13




a


connected to a grounding electrode


15


connected to a ground conductor


31


to an open tip end


13




b


opposing a grounding electrode


17


extending from the ground conductor


31


.




The chip antenna element


10


shown in

FIG. 2

comprises an insulating substrate


11


substantially in the form of a rectangular parallelepiped; a grounding electrode


15


covering one end surface of the substrate


1


land its nearby surface region; a radiation electrode


13


formed as a microstrip conductor on an upper surface of the substrate


11


, such that it is directly connected to the grounding electrode


15


and extends therefrom to the other end with a width continuously decreasing; and a feeding electrode


14


formed on the substrate


11


without contact with the radiation electrode


13


, such that it feeds electric current to the radiation electrode


13


at an intermediate point. Though

FIG. 2

shows a structure in which the grounding electrode


17


is opposite to the open tip end


13




b


of the radiation electrode


13


via a gap


12


, this structure is not indispensable.




The important feature of the present invention is that the radiation electrode extends from a rear end to a tip end with a width decreasing substantially continuously and/or stepwise. The tip end of the radiation electrode is preferably in contact with the grounding electrode via a gap (in capacitance coupling). Also, the chip antenna element of the present invention is preferably mounted onto a circuit board, such that a gap between the tip end of the radiation electrode and the grounding electrode is distant from the ground conductor of the circuit board.




The width (in a direction perpendicular to a high-frequency electric current) of the radiation electrode


13


is not constant but gradually decreasing as nearing the gap


12


. The high-frequency electric current fed from a feed source (high-frequency signal source)


19


via a feeding electrode


14


resonates at a frequency determined by the inductance of the radiation electrode


13


and the capacitance of a capacitor between the radiation electrode


13


and a ground, and emits to the space as an electromagnetic energy. In this case, there arises an electric current distribution mode having a node and an antinode at the grounding electrode


15


and the gap


12


, respectively. If the radiation electrode


13


had a constant width, there would be only one electric current distribution mode. However, because the radiation electrode


13


extending between the grounding electrodes


15


,


17


has a changing width, a plurality of electric current distribution modes are generated, equivalent to the formation of a plurality of resonance circuits. Because each resonance circuit has very close resonance frequency, the antenna element macroscopically provides resonance characteristics of wide bandwidth, resulting in decrease in the Q value of the antenna element.




FIG.


3


(


a


) shows an equivalent circuit of the chip antenna element of

FIG. 2. A

feed source


19


feeds electric current to a radiation electrode


13


via inductance Li and capacitance Ci generated by the feeding electrode


14


, etc. The fed power is consumed by a radiation resistor R at resonance for emission to the space as electromagnetic wave. In the equivalent circuit, portions encircled by dotted lines are a radiation electrode


13


on the right side of the feed source


19


, and a grounding electrode


17


and a gap


12


on the left side, with a capacitance Cg between the radiation electrode


13


and the grounding electrode


17


.




FIG.


3


(


b


) shows an equivalent circuit of the chip antenna element comprising a radiation electrode having a constant width. In this case, the radiation electrode can simply be represented by inductance L and capacitance C. On the other hand, in the case of the chip antenna element of the present invention comprising a radiation electrode having a changing width, the radiation electrode should be treated like a distributed constant. That is, the radiation electrode may be regarded as a combination of a large number of gradually changing inductance and a large number of gradually changing capacitance connected to each other. Accordingly, the equivalent circuit of the radiation electrode


13


is represented by a ladder circuit comprising a plurality of inductance Lr


1


, Lr


2


, Lr


3


, . . . and a plurality of capacitance Cr


1


, Cr


2


, . . . Because their resonance frequencies are extremely close to each other, it looks as if resonance takes place continuously, resulting in frequency characteristics of broad bandwidth.




Though the chip antenna element shown in

FIG. 2

has a trapezoidal radiation electrode, the radiation electrode is not restricted to be trapezoidal but may be in any shape. The crux of the present invention is that in place of a radiation electrode having a constant width, a radiation electrode having a width gradually changing continuously and/or stepwise is used to provide an inductance distribution and a capacitance distribution, thereby constituting a plurality of resonance circuits, so-called parallel, multi-resonance circuits.




To know the influence of the shape of an radiation electrode on the characteristics of the chip antenna element, relations between W/S and various characteristics are investigated, in the trapezoidal radiation electrode shown in

FIG. 4

, which comprises a wide rear end having a width W, a narrow tip end having a width S, and a length D.

FIG. 5

shows the relation between W/S and a resonance frequency f


0


. When W/S exceeds about 5, the resonance frequency f


0


tends to be saturated.

FIG. 6

shows the relation between W/S and a specific bandwidth BW/f


0


. It is clear from

FIG. 6

that when W/S becomes about 3 or more, the specific bandwidth BW/f


0


is saturated.

FIG. 7

shows the relation between W/S and a Q value. As W/S increases, the Q value decreases, resulting in a wider bandwidth. When W/S is less than 2, the curve of the Q value is too steep to control. On the other hand, when W/S exceeds about 5, the Q value tends to be saturated. W/S meeting the condition of Q≦29 is about 3 or more. The above results indicate that W/S is preferably 2 or more, more preferably 2-5.




If a radiation electrode is formed not only on an upper surface of the substrate but also on adjacent side surfaces of the substrate, the chip antenna element preferably is made smaller with improved radiation directivity. The tip end


13




b


of the radiation electrode


13


may be provided with an extension electrode extending to the second end surface and/or its nearby surface regions. The extension electrode functions as inductance or capacitance, making it easy to improve the radiation gain and control the frequency.





FIG. 8

shows an example in which the chip antenna element


10


of the present invention is mounted onto ground conductors


31


,


31


of the circuit board


30


. The insulating, rectangular parallelepiped substrate


11


is covered by the grounding electrode


15


on one end surface (first end surface) or its nearby surface regions, without ground electrode on a most area of the bottom surface. The feeding electrode


14


is formed on the substrate at a position of providing impedance matching. The grounding electrode


15


of the chip antenna element


10


is connected to the ground conductor


31


of the circuit board


30


, and the feeding electrode


14


is connected to a feeding line


32


between the ground conductors


31


,


31


. The chip antenna element


10


is mounted onto the circuit board


30


, such that a gap


12


between the tip end


13




b


of the radiation electrode


13


and the grounding electrode


17


is the most distant from the ground conductors


31


,


31


.




When the antenna emits a radio wave, electromagnetic energy is emitted to the space by an electromagnetic field generated between the radiation electrode


13


and the ground conductor


31


, providing an extremely weak electromagnetic field at the grounding electrode


17


on the same voltage level as that of the ground conductor


31


, and thus resulting in the radiation of extremely small electromagnetic energy. Therefore, parts may be mounted onto the circuit board at positions near the antenna element. For this reason, it is possible to eliminate the influence of conductors of the casing and the circuit board, thereby preventing errors from occurring in the parts and thus improving the stability and reliability of the antenna characteristics.





FIG. 9

shows a typical example of the antenna apparatus. Both grounding electrodes.


15


,


17


of the antenna element


10


are connected to the ground conductors


31


,


31


of the circuit board


30


, with a feeding electrode


14


connected to a feeding line


32


. The radiation electrode


13


is encircled by grounding electrodes


15


,


17


at both lateral ends and the ground conductors


31


,


31


at bottom, leaving an upper surface and two side surfaces of the antenna element


10


free from electrodes. Therefore, there is provided such a directivity that the intensity of an electromagnetic field radiated is low in the longitudinal direction of the radiation electrode


13


but high in the vertical direction of the radiation electrode


13


, resulting in higher gain. Because the influence of an electromagnetic wave in the longitudinal direction of the radiation electrode


13


is reduced by shield effects of the grounding electrodes


15


,


17


, there is no problem of errors or malfunction even though parts


51


are mounted outside both end surfaces of the substrate


11


of the antenna element


10


.




As shown in

FIG. 10

, the antenna element


10


is mounted onto ground conductors


31


,


31


of the circuit board


30


, such that the radiation electrode


13


is in parallel with the edges of the ground conductors


31


,


31


, in the present invention. Each grounding electrode


15


,


17


is preferably connected to each ground conductor extension


310


extending from each ground conductor


31


, and an electric field-radiating gap


12


between the radiation electrode


13


and the grounding electrode


17


is preferably located at the most distant position from the ground conductors


31


,


31


.




If image current generated in the ground conductors


31


,


31


of the circuit board


30


by resonance current of the antenna element


10


has an opposite phase to that of current in the substrate


11


, the radiation of an electromagnetic wave from the antenna element


10


is hindered, thereby likely causing decrease in gain and the shift of a resonance frequency. As shown in

FIG. 10

, if the radiation electrode


13


through which a resonance current most flows and the gap


12


are located at the most distant positions from the ground conductors


31


,


31


, an electromagnetic field can be generated at the most distant position from the ground conductors


31


,


31


, thereby remarkably reducing image current. Because a bottom surface of the insulating substrate


11


of the antenna element


10


is mostly free from grounding electrodes, image current is prevented from flowing through the ground conductor


31


.




When the antenna element


10


is disposed such that it is perpendicular to the edges of the ground conductors


31


,


31


as in conventional technologies, there is a large unoccupied space on the circuit board


30


. On the other hand, when the antenna element


10


is disposed in parallel with the edges of the ground conductors


31


,


31


as in the present invention, an area occupied by the antenna element


10


is drastically reduced, resulting in larger freedom of mounting layout and higher mounting density. When the antenna element


10


is disposed in parallel with the edges of the ground conductors


31


,


31


, decrease in gain should be compensated. For this purpose, the present invention utilizes the effects of the shape of the radiation electrode


13


and the arrangement of the grounding electrodes


15


,


17


. For instance, with the grounding electrode


15


covering all the end regions of the substrate


11


, an electromagnetic field can be concentrated on a region ranging from the grounded rear end


13




a


of the radiation electrode


13


to the tip end


13




b


facing the gap


12


. Further, the mounting of the feeding electrode


14


at an impedance-matching position connecting to the radiation electrode


13


with capacitance contributes to concentration of an electromagnetic field in the radiation electrode


13


.




The reason why the radiation electrode


13


of the antenna element


10


is disposed in parallel with the edges of the ground conductors


31


,


31


of the circuit board


30


is to obtain the maximum shape effect of the radiation electrode


13


, thereby maximizing the function of a capacitor formed between the radiation electrode


13


and the ground surface. It is clear from

FIGS. 9 and 10

that the function of a capacitor between the radiation electrode and the ground conductor is remarkably higher in the structure of the present invention, in which the radiation electrode


13


is disposed in parallel with the edges of the ground conductors


31


,


31


, than the conventional structure, in which the radiation electrode


13


is disposed in perpendicular to the edges of the ground conductors


31


,


31


.




Because the antenna element of the present invention radiates an electromagnetic field from a gap


12


between the radiation electrode


13


and the grounding electrode


17


not only in a radial direction around a longitudinal axis of the antenna element


10


but also in a direction perpendicular thereto, the antenna element can be omni-directional regardless of arrangement when mounted in a communications apparatus.




FIGS.


11


(


a


)-(


c


) show the relations of a bandwidth BW of the antenna element with the size (length L and width W) and specific dielectric constant of the insulating substrate


11


. Because the bandwidth BW changes depending on the size and material of the substrate


11


, the present invention can efficiently be carried out by determining the relations of the size and material of the substrate


11


and bandwidth as shown in FIG.


11


. It has been found that the insulating substrate


11


is preferably a rectangular parallelepiped body of 15 mm×3 mm×3 mm made of dielectric Al


2


O


3


ceramic having a specific dielectric constant ∈r of 8. An electrode made of Ag was formed on the insulating substrate


11


as shown in

FIG. 10. A

radiation electrode


13


was substantially trapezoidal, and a ratio W/S of the width W of the rear end


13




a


to the width S of the tip end


13




b


was 3. Also, a 1-mm-long gap (insulating substrate-exposing portion)


12


was provided between an open tip end of the radiation electrode


13


and a grounding electrode


17


. The rear end


13




a


of the radiation electrode


13


was directly connected to a grounding electrode


15


. A feeding electrode


14


was formed on a side surface of the substrate at a position deviating from a center toward the gap. The antenna element


10


of the above size having a resonance frequency of 2.4-2.5 GHz, a bandwidth of 100 MHz, a specific bandwidth of 3.5%, a gain of −5 dBi or more and a voltage standing wave ratio VSWR of 3 or less was designed for cellular phones or wireless LAN required to be omni-directional.




The above-described embodiment is simply an example, which may properly be changed with respect to size and shape depending on design conditions. For instance, a columnar dielectric substrate may be used in place of the rectangular parallelepiped dielectric substrate, and substrate materials may be magnetic materials, resins or laminates thereof.




To expand the bandwidth or adjust the frequency, the gap or the radiation electrode is effectively trimmed. A rectangular slit (insulating substrate-exposing portion), which is provided on a slanting side of the radiation electrode


13


near an open end, can be trimmed to easily achieve matching.




The tip end


13




b


of the radiation electrode


13


should be opposite to the grounding electrode


17


via a gap


12


, while the rear end


13




a


may be connected to the grounding electrode


15


directly or via a gap (capacity coupling).




What is necessary to suppress the radiation of an electromagnetic field from the end surfaces of the substrate


11


is to cover the end surfaces of the substrate


11


with grounding electrodes


15


,


17


that are grounded. However, to ensure the effects of the grounding electrodes


15


,


17


, it is preferable to cover not only the end surfaces of the substrate


11


but also nearby regions on side surfaces adjacent to the end surfaces.




The feeding electrode


14


may be formed on a side surface or a side surface+an upper surface of the substrate


11


at a position facing the radiation electrode


13


with or without contact.




The antenna element


10


may be produced according to the following method. First, a dielectric ceramic block is cut to a plurality of rectangular parallelepiped chips, and worked to a predetermined size. The resultant dielectric chip is screen-printed with Ag electrodes (radiation electrode, grounding electrodes and feeding electrode) of predetermined shapes, and baked to provide a rectangular parallelepiped antenna element of 15 mm in length, 3 mm in width and 3 mm in thickness, for instance. The antenna element is preferably as thin as possible, and with the same thickness and width, anisotropy in a lateral direction disappears, making it easy to print electrodes.





FIG. 12

shows an antenna apparatus comprising an antenna element mounted onto a circuit board. The antenna element


10


is disposed along the edges of the ground conductors


31


,


31


of the circuit board


30


, with a feeding electrode


14


connected to a feeding line


32


connected to a feed source


19


located between both ground conductors


31


,


31


. The radiation electrode


13


has a wide rear end


13




a


on the side of the grounding electrode


15


and extends to a narrow tip end


13




b


with a width decreasing continuously. The gap


12


between the tip end


13




b


and the grounding electrode


17


is located at the most distant position from the ground conductors


31


,


31


. The feeding electrode


14


is located at a position deviating longitudinally from a center toward the gap


12


, and a center of the antenna element


10


deviates from the center of the ground conductors


31


,


31


accordingly.




The characteristics evaluated are a voltage standing wave ratio VSWR, directivity and gain. VSWR was determined by connecting a network analyzer to a feeder terminal and measuring impedance when viewed from the terminal side. The gain was calculated from power received by a reference antenna and the gain of a reference antenna, when power radiated from a test antenna was received by the reference antenna in an anechoic chamber. The directivity was determined by measuring the intensity of an electromagnetic field radiated in the same manner as the measurement of the gain, while rotating the antenna element disposed on a rotatable table.





FIGS. 13-15

show the directivity of the antenna element of

FIG. 12

when rotated about an X-axis, Y-axis and Z-axis. As is clear from

FIGS. 13-15

, the graph of gain was substantially circle in any of the three directions, indicating that the antenna element was substantially omni-directional, though there was slight decrease in gain observed in the longitudinal direction of the antenna element. The reason therefor is that an electromagnetic field radiated in the longitudinal direction of the radiation electrode


13


was weakened.





FIG. 16

shows the bandwidth of the antenna element


10


of FIG.


12


. As compared to the conventional antenna elements, the antenna element of the present invention shown in

FIG. 12

is remarkably improved in bandwidth. The bandwidth at a voltage standing wave ratio VSWR of 3 was 100 MHz.




The same measurement was carried out with the position of the feeding electrode


14


changing from a position shown in

FIG. 12

, at which it deviated from a center of the radiation electrode


13


toward the tip end


13




b


, to a center of the radiation electrode


13


and further to a position on the side of the rear end


13




a


, thus with the position of the antenna element


10


changing relative to the ground conductor


31


. As a result, when the position of the feeding electrode


14


was changed from the position shown in

FIG. 12

, the antenna element


10


was poor in omni-directionality of bandwidth. This confirmed that the position of the feeding electrode


14


relative to the radiation electrode


13


and the position of the antenna element


10


relative to the ground conductor


31


had large influence on omni-directionality of bandwidth.




When the feeding electrode


14


for feeding electric current to an intermediate point of the radiation electrode


13


is not in contact with the radiation electrode


13


, the feeding electrode


14


can have capacitance matching with the radiation electrode


13


. Therefore, it can be disposed near the open tip end


13




b


having high impedance. On the other hand, when the feeding electrode


14


is in contact with the radiation electrode


13


, matching is difficult because there is only inductance matching, making it inevitable to dispose the feeding electrode


14


on the side of the wide rear end


13




a


having low impedance.




When a 2-mm gap is provided in the antenna element shown in

FIG. 17

, the bandwidth increased to 180 MHz at a voltage standing wave ratio VSWR of 3 as shown in FIG.


18


. Even with no gap, the bandwidth was 120 MHz, achieving wider bandwidth than the conventional one. Though an occupied area slightly increases, the positioning of the radiation electrode


13


with a gap of about 2 mm from the ground conductor


31


is advantageous in bandwidth and radiation gain.





FIGS. 19 and 20

show another embodiment of the present invention. In the embodiment of

FIG. 19

, a radiation electrode


13


is disposed not only on an upper surface of the substrate


11


but also on adjacent side surfaces thereof. With this structure, the radiation electrode


13


is substantially widened, improving the omni-directionality of radiation gain, increasing the bandwidth, and achieving the miniaturization of the antenna element. The radiation electrode


13


may be extended to a lower surface of the insulating substrate


11


. As is clear from FIG.


19


(


c


), the grounding electrodes


15


,


17


formed on both ends are not electrically connected.




The antenna element shown in

FIG. 20

has a direct feeding system, in which a feeding electrode


14


is connected to a trapezoidal radiation electrode


13


. Formed on a lower surface of the antenna element


10


is a conductor


18


connected to the grounding electrodes


15


,


17


.





FIGS. 21-23

show thin antenna elements each having a length of 15 mm, a width of 3 mm and a height of 2 mm. These antenna elements have various radiation electrodes


13


each connected directly or via a gap to a grounding electrode


15


covering an end surface of the substrate


11


or its nearby surface region. The feeding electrode (not shown) is formed on a rear surface of the substrate. In these embodiments, the radiation electrode


13


is formed not only on an upper surface but also on adjacent side surfaces.




In the embodiment of

FIG. 23

, the radiation electrode


13


is meandering. With this structure, the radiation electrode


13


is substantially expanded, thereby providing improved radiation gain in a radial direction and broader bandwidth, and achieving further miniaturization.




In the embodiment shown in

FIG. 21

, there is a gap


21


between the radiation electrode


13


and the grounding electrode


15


. Because the radiation electrode


13


is provided with gaps with grounding electrodes at both ends, an electromagnetic field generated from the gaps are spread widely, resulting in decrease in a Q value and thus broader bandwidth.




In the embodiment shown in

FIG. 22

, the radiation electrode


13


is partially connected to the grounding electrode


15


. A slit (substrate-exposing portion)


22


is formed by trimming, and by changing the length and/or width of the slit


22


, the resonance frequency of the antenna element can be adjusted. A tip end


13




b


of the radiation electrode


13


extends to the second end surface, and the resultant extension electrode can be used as an inductance component or a loaded capacitance component.




In the embodiment shown in

FIG. 23

, the radiation electrode


13


is formed in a meandering manner on two adjacent surfaces of the substrate


1


. Because a resonance current flows through the meandering radiation electrode


13


, the length of the meandering radiation electrode corresponds to about ¼ of electrical length. Accordingly, the radiation electrode can be made shorter, resulting in a further miniaturized antenna element.




The antenna elements shown in

FIGS. 24-26

are the same as those shown in

FIGS. 21-23

except that they have grounding electrodes


17


facing tip ends of radiation electrodes


13


via gaps.





FIGS. 27-34

are developments showing antenna elements according to further embodiments of the present invention. In each figure, a hatched portion is an electrode.




The antenna element shown in

FIG. 27

comprises a grounding electrode


15


formed on one end surface of the substrate


11


or its nearby surface region, a radiation electrode


13


formed on two adjacent surfaces of the substrate


11


such that it longitudinally extends from the grounding electrode


15


to the other end of the substrate


11


with a width decreasing, and an extension electrode


131


extending from the tip end of the radiation electrode


13


on an adjacent side surface. A feeding electrode


14


has impedance matching with the radiation electrode


13


. the grounding electrode


15


is provided with a slit


22


for trimming, by which the frequency of the antenna element can be widely adjusted.




The antenna element shown in

FIG. 28

comprises a relatively wide extension electrode


131


for capacitance extending from the tip end


13




b


of the radiation electrode


13


on an upper surface and a side surface.




The antenna element shown in

FIG. 29

comprises an extension electrode


131


extending from the tip end of the radiation electrode


13


to the second end surface. The extension electrode


131


may be formed on the entire second end surface as a capacitance electrode.




The antenna element shown in

FIG. 30

comprises a radiation electrode


13


extending on two adjacent surfaces, and a capacitance electrode


132


formed on the second end surface with a gap from the tip end of the radiation electrode


13


.




The antenna element shown in

FIG. 31

comprises a trimming portion


20


on one end of the radiation electrode


13


, and an extension electrode


131


on the other end. With a dummy electrode


133


for soldering, the antenna element


10


is more strongly bonded to the circuit board


30


.




The antenna element shown in

FIG. 32

is the same as that shown in

FIG. 27

, except that the grounding electrode


15


is formed on the first end surface and its nearby surface region on four side surfaces, and that the feeding electrode


14


crosses the lower surface of the substrate


11


. With this structure, a sufficient area for soldering can be obtained.




The antenna element shown in

FIG. 33

is the same as that shown in

FIG. 32

, except that a dummy electrode


133


is formed on the lower surface of the substrate


11


instead of extending a feeding electrode


14


on the lower surface.




The antenna element shown in

FIG. 34

is the same as that shown in

FIG. 32

, except that it is provided with a floating electrode


134


on the lower surface of the substrate


11


without extending the feeding electrode


14


. The floating electrode


134


increases capacitance between the radiation electrode


13


and a ground, making it easy to miniaturize the antenna element and adjust the frequency thereof.




In addition to the above, the antenna element of the present invention may be provided with a radiation electrode having such a shape as shown in FIG.


35


.




Though the dielectric substrate is made of insulating ceramics in the above embodiments, substrates made of resins may be used instead. In the case of a resin substrate, it may be provided with a through-hole for forming a feed point.




An antenna apparatus comprising the antenna element of the present invention mounted onto a circuit board may be assembled in a wireless communications apparatus such as a cellular phone, information terminal equipment, etc., to provide a substantially omni-directional communications apparatus having good antenna characteristics such as gain, bandwidth, etc. As a surface-mounting antenna element, the antenna element of the present invention can have high freedom in design with a small occupying area, providing high mounting density and thus miniaturizing an antenna apparatus and thus a communications apparatus comprising the antenna apparatus. In the antenna apparatus comprising an antenna element of 15 mm×3 mm×2-3 mm, for instance, the antenna element occupies an area of 50 mm


2


or less, ½ or less of a space in the conventional antenna apparatus.




As described above, the present invention provides a substantially omni-directional, small, high-performance chip antenna element having a wide bandwidth and a high gain and an antenna apparatus comprising such a chip antenna element. Because this antenna element occupies only an extremely small area on a circuit board to which it is mounted, a higher mounting density can be achieved. Accordingly, a portable communications apparatus comprising such an antenna apparatus can be miniaturized, exhibiting stable communications performance regardless of the position and direction of the apparatus.



Claims
  • 1. A chip antenna element comprising(a) a grounding electrode formed on at least a first end surface at said first end of an insulating substrate, (b) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from said grounding electrode with or without a gap to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, and (c) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode.
  • 2. The chip antenna element according to claim 1, further comprising an extension electrode connected to the narrow tip end of said radiation electrode and formed on a second end surface of said substrate and/or its nearby region on at least one side surface adjacent thereto.
  • 3. The chip antenna element according to claim 1, wherein said insulating substrate is in the form of a rectangular parallelepiped.
  • 4. The chip antenna element according to claim 1, wherein a ratio W/S of a width W of the wide rear end of said radiation electrode to a width S of the narrow tip end of said radiation electrode is 2 or more.
  • 5. The chip antenna element according to claim 4, wherein the ratio W/S is 2-5.
  • 6. The chip antenna element according to claim 1, wherein said radiation electrode is formed on adjacent side surfaces of said insulating substrate.
  • 7. The chip antenna element according to claim 1, wherein said feeding electrode is located at a position deviating from a center of said substrate toward the tip end of said radiation electrode.
  • 8. A chip antenna element comprising(a) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from a first end of said substrate or its vicinity to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, (b) a grounding electrode opposing a tip end of said radiation electrode via a gap, and (c) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode.
  • 9. The chip antenna element according to claim 8, further comprising an extension electrode connected to the narrow tip end of said radiation electrode and formed on a second end surface of said substrate and/or its nearby region on at least one side surface adjacent thereto.
  • 10. The chip antenna element according to claim 8, wherein said insulating substrate is in the form of a rectangular parallelepiped.
  • 11. The chip antenna element according to claim 8, wherein a ratio W/S of a width W of the wide rear end of said radiation electrode to a width S of the narrow tip end of said radiation electrode is 2 or more.
  • 12. The chip antenna element according to claim 8, wherein said radiation electrode is formed on adjacent side surfaces of said insulating substrate.
  • 13. The chip antenna element according to claim 8, wherein said feeding electrode is located at a position deviating from a center of said substrate toward the tip end of said radiation electrode.
  • 14. A chip antenna element comprising(a) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from a first end of said substrate or its vicinity to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, (b) a first grounding electrode connecting directly or via a gap to the rear end of said radiation electrode, (c) a second grounding electrode opposing the tip end of said radiation electrode via a gap, and (d) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode.
  • 15. The chip antenna element according to claim 14, wherein one of said first and second grounding electrodes is in contact with said radiation electrode, whereby the intensity of a radiating electric field decreases in a longitudinal direction of said radiation electrode and increases in a direction perpendicular thereto.
  • 16. The chip antenna element according to claim 14, further comprising an extension electrode connected to the narrow tip end of said radiation electrode and formed on a second end surface of said substrate and/or its nearby region on at least one side surface adjacent thereto.
  • 17. The chip antenna element according to claim 14, wherein said insulating substrate is in the form of a rectangular parallelepiped.
  • 18. The chip antenna element according to claim 14, wherein a ratio W/S of a width W of the wide rear end of said radiation electrode to a width S of the narrow tip end of said radiation electrode is 2 or more.
  • 19. The chip antenna element according to claim 14, wherein said radiation electrode is formed on adjacent side surfaces of said insulating substrate.
  • 20. The chip antenna element according to claim 14, wherein said feeding electrode is located at a position deviating from a center of said substrate toward the tip end of said radiation electrode.
  • 21. An antenna apparatus comprising a chip antenna element mounted onto a circuit board, said chip antenna element comprising(a) a grounding electrode formed on at least a first end surface at said first end of an insulating substrate, (b) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from said grounding electrode with or without a gap to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, and (c) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode, said radiation electrode being in parallel with an edge of a ground conductor of said circuit board, and an open tip end of said radiation electrode being not close to said ground conductor.
  • 22. The antenna apparatus according to claim 21, wherein there is a gap between the grounding electrode of said chip antenna element and the ground conductor of said circuit board.
  • 23. The antenna apparatus according to claim 21, wherein said feeding electrode is located at a position deviating from a center of said substrate of said chip antenna element toward the tip end of said radiation electrode, and wherein said feeding electrode is connected to a feeding line disposed between a pair of ground conductors on said circuit board.
  • 24. An antenna apparatus comprising a chip antenna element mounted onto a circuit board, said chip antenna element comprising(a) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from a first end of said substrate or its vicinity to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, (b) a grounding electrode opposing a tip end of said radiation electrode via a gap, and (c) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode, said radiation electrode being in parallel with an edge of a ground conductor of said circuit board, and an open tip end of said radiation electrode being not close to said ground conductor.
  • 25. The antenna apparatus according to claim 24, wherein there is a gap between the grounding electrode of said chip antenna element and the ground conductor of said circuit board.
  • 26. The antenna apparatus according to claim 24, wherein said feeding electrode is located at a position deviating from a center of said substrate of said chip antenna element toward the tip end of said radiation electrode, and wherein said feeding electrode is connected to a feeding line disposed between a pair of ground conductors on said circuit board.
  • 27. An antenna apparatus comprising a chip antenna element mounted onto a circuit board, said chip antenna element comprising(a) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from a first end of said substrate or its vicinity to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, (b) a first grounding electrode connecting directly or via a gap to the rear end of said radiation electrode, (c) a second grounding electrode opposing the tip end of said radiation electrode via a gap, and (d) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode, said radiation electrode being in parallel with an edge of a ground conductor of said circuit board, and an open tip end of said radiation electrode being not close to said ground conductor.
  • 28. The antenna apparatus according to claim 27, wherein there is a gap between the grounding electrode of said chip antenna element and the ground conductor of said circuit board.
  • 29. The antenna apparatus according to claim 27, wherein said feeding electrode is located at a position deviating from a center of said substrate of said chip antenna element toward the tip end of said radiation electrode, and wherein said feeding electrode is connected to a feeding line disposed between a pair of ground conductors on said circuit board.
  • 30. A communications apparatus comprising an antenna apparatus comprising a chip antenna element mounted onto a circuit board, said chip antenna element comprising(a) a grounding electrode formed on at least a first end surface at said first end of an insulating substrate, (b) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from said grounding electrode with or without a gap to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, and (c) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode, said radiation electrode being in parallel with an edge of a ground conductor of said circuit board, and an open tip end of said radiation electrode being not close to said ground conductor.
  • 31. A communications apparatus comprising an antenna apparatus comprising a chip antenna element mounted onto a circuit board, said chip antenna element comprising(a) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from a first end of said substrate or its vicinity to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, (b) a grounding electrode opposing a tip end of said radiation electrode via a gap, and (c) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode, said radiation electrode being in parallel with an edge of a ground conductor of said circuit board, and an open tip end of said radiation electrode being not close to said ground conductor.
  • 32. A communications apparatus comprising an antenna apparatus comprising a chip antenna element mounted onto a circuit board, said chip antenna element comprising(a) a radiation electrode formed on at least one surface of said substrate, such that said radiation electrode extends from a first end of said substrate or its vicinity to a second end of said substrate or its vicinity, with a width decreasing substantially continuously and/or stepwise, thereby having a wide rear end on the side of the first end of said substrate and a narrow tip end on the side of the second end of said substrate, (b) a first grounding electrode connecting directly or via a gap to the rear end of said radiation electrode, (c) a second grounding electrode opposing the tip end of said radiation electrode via a gap, and (d) a feeding electrode formed on at least one adjacent side surface of said substrate laterally with respect to a longitudinal direction of said radiation electrode, with or without contact with said radiation electrode, said radiation electrode being in parallel with an edge of a ground conductor of said circuit board, and an open tip end of said radiation electrode being not close to said ground conductor.
Priority Claims (3)
Number Date Country Kind
2000-113686 Apr 2000 JP
2000-353460 Nov 2000 JP
2001-45354 Feb 2001 JP
US Referenced Citations (5)
Number Name Date Kind
5696517 Kawahata et al. Dec 1997 A
5861854 Kawahata et al. Jan 1999 A
6297777 Tsubaki et al. Oct 2001 B1
6300909 Tsubaki et al. Oct 2001 B1
6323811 Tsubaki et al. Nov 2001 B1
Foreign Referenced Citations (4)
Number Date Country
1 003 240 May 2000 EP
10-107535 Apr 1998 JP
10-209740 Aug 1998 JP
11-251816 Sep 1999 JP
Non-Patent Literature Citations (2)
Entry
European Patent Office Search Report dated Aug. 20, 2001.
K. Kazuya, “Surface Mount Antenna”, Patent Abstracts of Japan of JP 10107535, published Apr. 24, 1998.