The present invention relates to a wide bandwidth antenna and a communication card using the wide bandwidth antenna.
For example, JP-A-57-142003 discloses the following antennas. That is, it discloses a monopole antenna in which a flat-plate type radiation element 1001 having a disc shape is erected vertically to an earth plate or the ground 1002 as shown in
In addition, JP-A-55-4109 discloses the following antennas, for example. That is, a sheet-type elliptical antenna 1006 is erected vertically to a refection surface 1007 so that the major axis thereof is parallel to the reflection surface 1007, and power supply is carried out through a coaxial power feeder 1008, as shown in
Besides, a monopole antenna as shown in
The antennas described above pertain to a monopole antenna in which a flat-plate conductor having various shapes is erected vertically to the ground surface, and a symmetric dipole antenna using two flat-plate conductors having the same shape.
Besides, U.S. Pat. No. 6,351,246 discloses a symmetric dipole antenna having a special shape as shown in
In addition,
Furthermore, US-A-2002-122010A1 discloses an antenna 1020 in which a tapered clearance area 1023 and a driven element 1022 whose feed point 1025 is connected to a transmission line 1024 are provided within a ground element 1021 as shown in
As described above, though various antennas have been hitherto known, the conventional vertical mount type monopole antennas have problems that their sizes are large, and it is difficult to control the antenna characteristic since it is difficult to control the distance between the radiation conductor and the ground surface. Furthermore, the conventional symmetrical type dipole antennas also have a problem that it is difficult to control the antenna characteristic since the radiation conductors have the same shape, thereby it is difficult to control the distance between the radiation conductors.
Besides, the special symmetric dipole antenna described in U.S. Pat. No. 6,351,246 has a problem on the implementation, in which a lot of elements and two kinds of signals, which are supplied to the elements, must be prepared. In addition, the ground pattern 1103 is opposite to the balance element 1101 and 1102, but the sides of the ground element 1103, which are opposite to the balance element 1101 and 1102, are straight lines.
Furthermore, JP-A-8-213820 does not disclose and suggest that the outer shape of the ground pattern 1034 is processed.
In addition, though the antenna of US-A-2002-122010A1 aims at miniaturization, the structure that the driven element is provided within the ground element cannot achieve the sufficient miniaturization because of the shape of the ground element. Besides, the shape of the ground element does not have a tapered shape with respect to the driven element.
In view of the foregoing problems, an object of the present invention is to provide an antenna having a novel shape that can be miniaturized and widened in bandwidth, and a wireless communication card using that antenna.
Furthermore, another object of the present invention is to provide an antenna having a novel shape that can be miniaturized and make it easy to control the antenna characteristic, and a wireless communication card using that antenna.
An antenna according to a first aspect of the invention comprises a planar antenna element having a feed point; and a ground pattern being juxtaposed with the planar antenna element, and the ground pattern has a trimmed portion causing to continuously change a distance between the planar antenna element and the ground pattern.
By providing the trimmed portion, it is possible to appropriately adjust the coupling degree with the antenna element, thereby it is possible to widen the bandwidth. In addition, since the antenna element and the ground pattern are juxtaposed with each other, the miniaturization is achieved.
In addition, the trimmed portion may be formed from a point near the feed point toward a side being opposite to the planar antenna element. Moreover, the planar antenna element and the ground pattern may be formed extending along counter directions respectively. Furthermore, the ground element may be disposed without fully surrounding the planar antenna element.
Besides, the trimmed portion may be formed in a tapered shape with respect to the feed point of the planar antenna element. By providing the tapered shape for the ground pattern, it is possible to appropriately adjust the coupling degree with the antenna element, thereby it is possible to widen the bandwidth.
In addition, the tapered shape may be composed of any one of segments, curved lines being convex upwardly, and curved lines being convex downwardly. The tapered shape can be formed in accordance with the desired characteristic.
Furthermore, the tapered shape may be symmetric with respect to a straight line passing through the feed point of the antenna element. It is also possible to form a concavity accommodating a portion for feeding to the feed point of the antenna element at a tip of the tapered shape.
In addition, the antenna element may be formed on a dielectric substrate, the ground pattern may be formed in or on a resin board, and said dielectric substrate may be mounted on the resin board. When the antenna element is formed in or on the dielectric substrate, the size of the antenna can be further miniaturized. Incidentally, when the antenna element substrate is formed on the dielectric substrate, the coupling with the ground pattern becomes strong. However, by adopting the tapered shape, it is possible to appropriately adjust the coupling degree, thereby the wide bandwidth can be achieved.
Furthermore, the antenna element may have a cut-out portion formed from an edge portion farthest from the feed point toward the ground pattern. The cut-out portion may be formed at an edge portion being opposite to the ground pattern side of said antenna element. Even in a case where the antenna is miniaturized, by forming the cut-out portion, the length of the current path on the antenna element is sufficiently secured, thereby the bandwidth is widened in a low frequency side.
In addition, the antenna element may have a shape in which a bottom side thereof has a straight portion or a substantially straight portion adjacent to the ground pattern, lateral sides thereof are provided vertically or substantially vertically to the bottom side and the cut-out portion is provided in a top side thereof. Though there is a limit of the miniaturization of the antenna element in order to secure the characteristic of the low frequency range, the miniaturization and the wide bandwidth are enabled if the above-described structure of the antenna element is adopted. Incidentally, at that time, the tapered shape of the ground pattern enables to wholly enhance the impedance characteristics.
Furthermore, the dielectric substrate on which the antenna element is formed may be mounted at an upper end on the resin board.
In addition, the dielectric substrate on which the antenna element is formed may be mounted at an upper end on the resin board, and the ground pattern may be formed to have a region extending toward at least either of a right side and a left side of the dielectric substrate. By providing such a region, the bandwidth in the low frequency side can be widened.
Furthermore, the dielectric substrate on which the antenna element is formed may be mounted at at least either of a right upper end and a left upper end on the resin board, and the ground pattern may be formed to have a region extending toward an opposite side to a side in which the dielectric substrate is mounted.
An antenna according to a second aspect of this invention comprises: a dielectric substrate on which an antenna element is formed; and a board on which the dielectric substrate is mounted, and in or on which a ground pattern is formed to be juxtaposed with the dielectric substrate, and the ground pattern has a tapered shape with respect to a feed point of the antenna element, and the antenna element has a cut-out portion formed from an edge portion farthest from the feed point toward a side of the juxtaposed ground pattern.
In addition, the dielectric substrate may be mounted on an upper end on the board, and the ground pattern may be formed to provide a region extending toward at least either of the left and right of the dielectric substrate. Furthermore, a first dielectric substrate may be disposed on a right upper end on the board, a second dielectric substrate may be disposed on a left upper end on the board, and the ground pattern may have a region to separate the first and second dielectric substrate.
A wireless communication device according to a third aspect of this invention comprises: a dielectric substrate on which an antenna element is formed; a board on which the dielectric substrate is mounted, and in or on which a ground pattern juxtaposed with the dielectric substrate is formed; and a RF circuitry mounted on the ground pattern, and wherein the ground pattern has a trimmed portion causing to continuously change a distance between the planar antenna element and the ground pattern.
Incidentally, the ground pattern and the antenna element or dielectric substrate including the antenna element do not fully face each other, and both the planes thereof are parallel or substantially parallel to each other. Besides, the ground pattern and the antenna element or dielectric substrate including the antenna element do not completely overlap with each other, and both the planes thereof are parallel or substantially parallel to each other.
Preferred embodiments according to the present invention will be described with reference to the accompanying drawings.
In addition, the planar element 1 and the ground pattern 2 are designed to be symmetrical with respect to the line 4 passing through the feed point 1a. Accordingly, the cut-out portion 5 is also symmetrical with respect to the line 4. Furthermore, the length (hereinafter referred to as “distance”) of a line segment extending from any point on the bottom side 1b of the planar element 1 to the ground pattern 2 in parallel with the line 4 is also symmetric with respect to the line 4.
When the planar element 1 is formed to be covered by the dielectric substrate 7, the condition of the electromagnetic field around the planar element 1 is varied by the dielectric material. Specifically, since an effect of increasing the density of the electric field in the dielectric material and a wavelength shortening effect can be obtained, the planar element 1 can be miniaturized. Furthermore, the lift-off angle of the current path is varied by these effects, and an inductance component L and a capacitance component C in the impedance equivalent circuit of the antenna are varied. That is, the impedance characteristic is greatly affected. The shape of the planar element 1 is optimized so that a desired impedance characteristic can be achieved in a desired range in consideration for the effect on the aforementioned impedance characteristic.
In this embodiment, the upper edge portions 2a and 2b of the ground pattern 2 are downwardly inclined from the intersecting point with the line 4 by a height L2 (=2 to 3 mm) at the side edge portions of the grand pattern 2 in the case where the width of the grand pattern 2 is 20 mm. That is, the ground pattern 2 has a tapered shape formed of upper edge portions 2a and 2b with respect to the planar element 1. Since the bottom side 1b of the planar element 1 is vertical to the line 4, the distance between the bottom side 1b of the planar element 1 and the ground pattern 2 is linearly increased as approaching to the side edge portions. That is, the antenna according to this embodiment is equipped with a continuous varying portion at which the distance between the planar element 1 and the ground pattern 2 is continuously varied. By providing such a continuous varying portion, the coupling degree between the planar element 1 and the ground pattern 2 is adjusted. By adjusting the coupling degree, especially, the bandwidth at a high frequency side can be widened.
The planar element 1 according to this embodiment is designed to have a shape with a rectangular cut-out portion 5 in order to further enhance miniaturization and secure current paths 8 for achieving a desired frequency bandwidth, as shown in
Incidentally, the planar element 1 of this embodiment may be considered as a radiation conductor of a monopole antenna like the prior arts. On the other hand, since the ground pattern 2 of the antenna of this embodiment partially contributes to radiation, the antenna of this embodiment is also considered as a dipole antenna. However, since the dipole antenna normally uses two radiation conductors having the same shape, the antenna of this embodiment may be called as an asymmetrical dipole antenna. Furthermore, the antenna of this embodiment is considered as a traveling wave antenna. Such considerations can be applied to all the embodiments described below.
An antenna according to a second embodiment of the present invention comprises a dielectric substrate 17 that contains a planar element 11 therein and has a dielectric constant of about 20, a ground pattern 12 that is juxtaposed with the dielectric substrate 17 and has upper edge portions 12a and 12b that are upwardly convex curved lines, a board 16 such as a printed circuit board or the like, and a high-frequency power source 13 connected to a feed point 11a of the planar element 11 as shown in
The planar element 11 and the ground pattern 12 are designed symmetrically with respect to the line 14 passing through the feed point 11a. Furthermore, the length (hereinafter referred to as “distance”) of a line segment extending from any point on the bottom side 11b of the plan element 11 to the ground pattern 12 in parallel to the line 14 is also symmetric with respect to the line 14.
Since the upper edge portion 12a and 12b of the ground pattern 12 is designed to be an upwardly convex curved line (for example, arc), the distance between the planar element 11 and the ground pattern 12 is gradually increased as approaching to the side edge portions of the ground pattern 12. In other words, though the angle is not an acute angle, a tapered shape with respect to the feed point 11a of the planar element 11 is made to the ground pattern. The structure of the side surface is almost the same as
A desired impedance characteristic can be achieved in a desired frequency range by adjusting the curvature of the curved line of the upper edge portions 12a and 12b of the ground pattern 12.
As shown in
The planar element 11 and the ground pattern 12 are designed to be symmetric with respect to a line 24 passing through the feed point 11a. The length (hereinafter referred to as “distance”) of a line segment extending from any point on the bottom side 11b of the planar element 11 to the ground pattern 22 in parallel to the line 24 is also symmetric with respect to the line 24.
Since the upper edge portions 22a and 22b of the ground pattern 22 are downward saturation curves starting from the cross-point between each saturated curve and the line 24, that is, downwardly convex curved lines, the distance between the planar element 11 and the ground pattern 22 asymptotically approaches a predetermined value as approaching to the side edge portions of the grand pattern 22. In other words, the tapered shape with respect to the dielectric substrate 17 is formed to the ground pattern 22.
A desired impedance characteristic can be achieved in a desired frequency range by adjusting the curvature of each of the curved lines of the upper edge portions 22a and 22b of the ground pattern 22.
Though there is no problem in a case where the ground pattern 12 can be formed to be symmetric with respect to the straight line 14 passing through the feed point 11a like the antenna according to the second embodiment of the present invention, there is a case where the ground pattern cannot be formed to be symmetric when the dielectric substrate 17 is mounted on the corner of the board 15, for example. Here, an optimum example is shown in a case where the ground pattern 12 cannot be formed to be symmetric as described above. As shown in
By forming such the ground pattern 38, it becomes possible to obtain the impedance characteristic, which is almost similar to the structure having the symmetrical ground pattern.
Incidentally, the antenna structure to be compared is shown in
The impedance characteristic of the antenna of
The structure of an antenna according to an fifth embodiment of the present invention is shown in
The external electrode 46a is connected to a projecting portion 41a of the planar element 41, and extends to the back surface (i.e. dotted line portion of the back surface) of the dielectric substrate 46. The feed portion 48 contacts with the external electrode 46a that is provided on the end portion of the side surface and the back surface of the dielectric substrate 46, and the feed portion 48 and the external electrode 46a are overlapped in the dotted line portion.
The planar element 41 is equipped with a projecting portion 41a connected to the external electrode 46a, a side 41b opposite to sides 42a and 42b of the ground pattern 42, arm portions 41c for securing current paths for low frequencies, and a rectangular cut-out portion 45 formed so as to concave from the top portion 41d toward the ground pattern 42. Moreover, the side 41b and the lateral side portions 41g are connected to each other through sides 41h formed by splaying the side 41b. Incidentally, the dielectric substrate 46 containing the planar element 41 is juxtaposed with the ground pattern 42.
Incidentally, in this embodiment, the planar element 41 is formed inside the dielectric substrate 46. That is, the dielectric substrate 46 is formed by laminating ceramic sheets, and the conductive planar element 41 is formed as one layer of the laminate. Accordingly, when viewed from the upper side, the planar element 1101 is not actually viewed like
Since the recess 47 for accommodating the feed portion 48 is provided to the tip having the tapered shape and composed of the sides 42a and 42b in the ground pattern 42, the edge portion of the ground pattern 42 opposite to the side 41b of the planar element 41 is not straight, and are divided into two sides 42a and 42b. Incidentally, the antenna according to this embodiment is symmetric with respect to a line 44 passing through the center of the feed portion 48, which is the feed position. The rectangular cut-out portion 45 and the tapered shape of the ground pattern 42 are also symmetrical with respect to the line 44. The sides 42a and 42b are inclined so that the distance between the side 41b of the planar element 41 and the sides 42a or 42b of the ground pattern 42 is linearly increased as being farther away from the line 44. Incidentally, the structure of the side surface is almost the same as
From a sixth embodiment to a ninth embodiment, optimization examples of the ground shape and application examples to the wireless communication card will be shown. Basically, the dielectric substrate 46 and planar element 41, and the shape of the ground pattern 42, which were shown in the fifth embodiment (
In this embodiment,
In this embodiment, an example is explained in which the seventh embodiment is applied to a diversity antenna. Normally, the space diversity antenna is used by switching two antennas, which are disposed apart from each other by a quarter wavelength. Accordingly, as shown in
A first antenna includes a dielectric substrate 46, which is the same as the dielectric substrate in the fifth embodiment, a high frequency power source 73a connected with the feed point 41a, and a ground pattern 72. The dielectric substrate 46 is provided on the right upper end of the printed circuit board 76 and vertically apart from the ground pattern 72 by 1 mm. By the sides 72a and 72b of the ground pattern 72, the tapered shape is formed with respect to the feed point 41a of the planar element 41. The difference of the height between a point of the ground pattern 72, which is nearest to the feed point 41a, and an intersecting point of the right lateral edge portion of the printed circuit board 76 and the side 72a is 2 to 3 mm. Though the tapered shape formed by the sides 72a and 72b is symmetric with respect to the straight line passing through the feed point 41a, the side 72b is connected to a vertical side 72c, and the side 72c is connected to a horizontal side 72d. The side 72d is further connected to a vertical side 72e. That is, a region 72f opposite to the left side surface of the dielectric substrate 46 and provided to separate the dielectric substrate 46 from a second antenna is added to the ground pattern 72. Thus, the ground pattern 72 has a shape partially surrounding the dielectric substrate 46 by the sides 72e, 72d, 72c, 72b and 72a. That is, the ground pattern is formed so as not to fully surround all the edge portions of the planar element 41 and so as to provide an opening to at least a part, which includes the cut-out portion, of the edge portion of the planar element 41. In this embodiment, since the ground pattern 72 opposite to the top portion including the cut-out portion and the right side edge portion of the planar element 41 is not provided, it can be said that there is an opening if a cover for the printed circuit board 76 is not considered.
A second antenna includes a dielectric substrate 77, which is the same as the dielectric substrate 46, a high frequency power source 73b connected with the feed point 71a, and a ground pattern 72. The dielectric substrate 77 is provided on the left upper end of the printed circuit board 76 and vertically apart from the ground pattern 72 by 1 mm. By the sides 72g and 72h of the ground pattern 72, the tapered shape is formed with respect to the feed point 71a of the planar element. The difference of the height between a point of the ground pattern 72, which is nearest to the feed point 71a, and an intersecting point of the left lateral edge portion of the printed circuit board 76 and the side 72g is 2 to 3 mm. Though the tapered shape formed by the sides 72g and 72h is symmetric with respect to the straight line passing through the feed point 71a, the side 72h is connected to a vertical side 72i, and the side 72i is connected to a horizontal side 72j. The side 72j is further connected to a vertical side 72k. That is, the region 72f opposite to the right side surface of the dielectric substrate 77 and provided to separate the dielectric substrate 77 from the first antenna is added to the ground pattern 72. Thus, the ground pattern 72 has a shape partially surrounding the dielectric substrate 77 by the sides 72g, 72h, 72i, 72j and 72k. That is, the ground pattern 72 is formed so as not to fully surround all the edge portions of the planar element and so as to provide an opening to at least a part, which includes the cut-out portion, of the edge portion of the planar element. In this embodiment, since the ground pattern 72 opposite to the top portion including the cut-out portion and the left side edge portion of the planar element is not provided, it can be said that there is an opening if a cover for the printed circuit board 76 is not considered. Basically, the printed circuit board 76 of this wireless communication card is symmetric with respect to the straight line 75.
Thus, the space diversity antenna can be implemented in the wireless communication antenna.
Thus, if the dielectric substrate 46 is used, it is possible to implement it inside the small stick type wireless communication card.
Though examples in which the planar element is integrally formed into the dielectric substrate were explained in the above-described embodiments, the planar element is not necessarily formed into the dielectric substrate. Next, an example of an antenna that does not use the dielectric substrate is explained.
The structure of an antenna according to a tenth embodiment of the present invention is shown in
Besides, the planar element 91 and the ground pattern 92 are symmetrical with respect to a straight line 94 passing through the feed point 91a. Furthermore, the length (hereinafter referred to as “distance”) of a line segment extending from any point on the arc of the planar element 91 to the ground pattern 92 in parallel with the line 94 is also symmetric with respect to the line 94. That is, if the distances from the straight line 94 are the same, the distances D11 and D12 extending from any point of the arc of the planar element 91 to the ground pattern are the same.
In this embodiment, sides 92a and 92b of the ground pattern 92, which are opposite to the planar element 91, are declined so that the distance between the planar element 91 and the ground pattern 92 becomes longer as being farther away from the straight line 94. That is, the ground pattern 92 is formed to have a tapered shape with respect to the feed point 91a of the planar element 91. Incidentally, the inclination of the sides 92a and 92b must be adjusted to obtain a desired antenna characteristic. As compared with a case using the dielectric substrate, since the coupling degree with the ground pattern 92 is low, too much inclination causes aggravation of the characteristic in the low frequency range.
Thus, by changing the distance between the planar element 91 and the ground pattern 92, the capacitance component C in the impedance equivalent circuit of the antenna is changed. As shown in
Furthermore, according to this embodiment, the planar element 91 is disposed on the center line 95 of the ground pattern 92 as shown in
Furthermore, the shape of the planar element 91 is not limited to the circle, and a reverse triangle and a semicircle, in which the arc is opposite to the ground pattern and a rectangular cut-out portion is formed from the top diameter portion toward the ground pattern may be adopted. The semicircle is not limited to a shape formed by dividing a complete circle into two portions, but a shape formed by dividing an ellipse into two portions may be adopted. At that time, if the tapered shape with respect to the feed position of the planar element 91 is formed to the ground pattern, it is possible to adjust the impedance characteristic according to the shape.
Though the embodiments of the present invention were explained, this invention is not limited to these embodiments. For example, though the shape of the cut-out portion of the planar element is indicated to be a rectangle as a typical example, it may be designed in a trapezoidal shape or other polygonal shape. The corners of the cut-out portion may be rounded. As for the tapered shape of the ground pattern, though an example in which a recess for accommodating an electrode for feeding is provided was explained, it is not necessary to form an acute angle to the tip of the ground pattern. Moreover, the planar element and the ground pattern do not completely overlap with each other but may partially overlap.
Although the present invention has been described with respect to a specific preferred embodiment thereof, various change and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.
Number | Date | Country | Kind |
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2002-343290 | Nov 2002 | JP | national |
2003-056740 | Mar 2003 | JP | national |
2003-150376 | May 2003 | JP | national |
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