Patent Grant
7106256
The present invention relates to an antenna device, in particular an antenna device in a microwave range (3 GHz to 30 GHz) and a millimeter wave range (30 to 300 GHz) used for communication, distance measuring equipment or broadcast.
Heretofore, a disc monopole antenna, which is disclosed in M. Hammoud et al, “Matching The Input Impedance of A Broadband Disc Monopole”, Electron. Lett., Vol. 29, No. 4, pp. 406–407, 1993, has been known as an antenna having an operating frequency band in a wide band.
Additionally, an antenna, which is shown in
Sung-Bae Cho et.al., “ULTRA WIDEBAND PLANAR STEPPED-FAT DIPOLE ANTENNA FOR HIGH RESOLUTION IMPULSE RADAR”, 2003 Asia-Pacific Microwave Conference, discloses another planar dipole antenna, which has an operating frequency band in a wide band. This planar antenna has a structure wherein a pair of metal conductors having a similar shape, which serves as a radiating conductor, is disposed on a dielectric member so as to be separated from each other with a certain distance, and power is fed to the paired metal conductors from a region between the separated conductors.
Each of the antenna devices shown in
The antennas shown in
Additionally, the antenna device shown in
Although the planar dipole antenna disclosed in the second non-patent document has an operating frequency band in a wide band, this planar antenna is not an antenna having a high degree of freedom in design since the paired metal conductors forming a radiating element need to have a stepped shape.
From these viewpoints, it is an object of the present invention to provide a high gain antenna device, which has a small size of antenna without having an occupied volume as a three-dimensional structure as in prior art, and which has an operating frequency band in a wider range than the prior art and has a high degree freedom in design.
Means for Solving the Problems
In order to attain the problem stated earlier, the present invention provides an antenna device comprising a dielectric member including a planar radiating conductor and a feeder; the radiating conductor comprising a first forming element and a second forming element disposed so as to have a portion common to each other; the first element being formed in a shape selected among a polygon, a substantial polygon, a circle, a substantial circle, an oval and a substantial oval; the second element having at least one portion formed in a shape selected among a polygon, a substantial polygon, a circle, a substantial circle, an oval, a substantial oval, a trapezoid and a substantial trapezoid; and the feeder being connected to the radiating conductor.
The shape of the second forming element may contain not only the entire shape of a polygon, a substantial polygon, a circle, a substantial circle, an oval, a substantial oval, a trapezoid or a substantial trapezoid, but also a portion of a shape selected among these configurations. For example, a semi-circle, a semi-oval, a half configuration of a polygonal or a trapezoid, or another configuration is also applicable.
For example, the feeder is connected to the radiating conductor at a peripheral portion of the second forming element in a peripheral portion of the radiating conductor, which is located on a side of the second forming element as seen from the first forming element. In this case, the feeder is disposed on the same plane as the radiating conductor and is connected to the radiating conductor on this plane.
Or, the feeder may be connected to the radiating conductor from a direction inclined with respect to or from a direction substantially perpendicular to the plane just stated. In this case, the second forming element is not limited to be connected to the radiating conductor at the peripheral portion.
It is preferred that the antenna device have the radiating conductor and the feeder disposed on the dielectric member or in the dielectric member to form an antenna body, that the antenna body be mounted to an insulating substrate; that the insulating substrate has a ground conductor disposed on a surface thereof remote from the dielectric member or disposed therein; and that the antenna body be mounted to the insulating substrate so that the dielectric member is disposed with the radiating conductor being parallel with or substantially parallel with the ground conductor.
In this case, the insulating substrate may include a signal line forming a transmission line along with the ground conductor, the signal line being connected to the feeder. For example, the signal line is connected to the feeder through a via formed in the dielectric member. The dielectric member may have a pair of ground patterns disposed at symmetrical positions with respect to, e.g., the feeder.
The antenna body, which is mounted to the insulating substrate, may be disposed and fixed on a region on an opposite surface of the insulating substrate remote from an exposed portion of the insulating substrate without the ground conductor disposed thereon. In other words, the antenna body is disposed at such a position to avoid confrontation with the ground conductor and to be parallel with the ground conductor.
Additionally, it is preferred that the antenna device further comprise a reflecting member disposed away from the insulating substrate, the reflecting member being configured to reflect a radio wave radiated from the radiating conductor. The reflecting member may comprise, e.g., a metal plate having a flat reflecting surface, or be a reflecting member, which has a configuration containing, e.g., a cylindrical shape, a portion of a cylindrical shape, a spherical shape or a portion of a spherical shape so as to have a reflecting surface formed in a curved surface. For example, the reflecting member comprises a flat plate and is disposed in parallel with or substantially parallel with the ground conductor of the insulating substrate.
Additionally, it is preferred that the antenna device further comprise an air layer disposed between the reflecting member and the insulating substrate. Additionally, it is also preferred that the antenna device further comprise a dielectric layer disposed between the reflecting member and the insulating substrate. In this case, the dielectric layer comprises preferably a dielectric material having a relative dielectric constant in a range from 1.5 to 20, and more preferably a dielectric material having a relative dielectric constant in a range from 2 to 10.
When both of the dielectric layer and the air layer are disposed, it is preferred that the dielectric layer be disposed on a surface of the reflecting member so that the insulating substrate, the air layer, the dielectric layer and the reflecting member are disposed in this order.
In the planar radiating conductor according to the antenna device of the present invention, the first forming element, which is formed in a shape selected among a polygon, a substantial polygon, a circle, a substantial circle, an oval and a substantial oval, and the second forming element, which has at least one portion formed in a shape selected among a polygon, a substantial polygon, a circle, a substantial circle, an oval, a substantial oval, a trapezoid and a substantial trapezoid, are disposed so as to have a portion common to each other. The feeder is connected to the radiating conductor. By this arrangement, it is possible to realize an antenna device, which has an operating frequency band adapted for a wider band than the conventional antennas, provides good impedance matching and has a high degree freedom in design.
Since the antenna body, which comprises the dielectric member, the radiating conductor disposed on or in the dielectric member, and the feeder, has a planar structure, it is possible to provide a surface mount antenna device, wherein the antenna body is mounted to a surface of an insulating substrate, such as a circuit board.
In accordance with the present invention, the exposed portion without the ground conductor disposed thereon may be formed on a portion of a surface of the insulating substrate, and the antenna body may be mounted to a region on the opposite surface of the insulating substrate remote from the exposed portion. In particular, the exposed portion may be formed so as to have contact with an end portion of the insulating substrate, and the antenna body may be disposed in the vicinity of the end portion of the insulating substrate. By this arrangement, the exposed portion of the insulating substrate, which is necessary for the antenna body, can be minimized, and it is possible to provide an antenna device, which is smaller than prior art and has a wider operating frequency band.
When the antenna body is disposed in the vicinity of the end portion of a circuit board, the region for provision of a peripheral circuit can be increased, and the entire communication equipment can be made smaller.
Additionally, when the reflecting member, which reflects a radio wave radiated from the radiating conductor, is disposed away from the insulating substrate, it is possible to provide a high gain antenna device. When the dielectric layer is disposed between the reflecting member and the insulting substrate, and when the air layer is additionally disposed between the dielectric layer and the insulting substrate, it is possible to provide a higher gain antenna device. In particular, by disposing the antenna body having a planar structure, the insulating substrate, the dielectric layer and the reflecting member in parallel or substantially parallel with one another, it is possible to provide a small and high gain antenna device.
Now, the antenna device according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
The antenna body 10 functions as a surface-mount antenna to be mounted to a surface of an insulating substrate 17, such as a circuit board. The antenna body is configured to include a radiating conductor 11, a feeder 14 and a dielectric member 16.
The radiating conductor 11 is a planar metal conductor, which is disposed in the dielectric member 16.
The radiating conductor 11 is configured so that a first forming element 12 having a circular shape and a second forming element 13 having a semi-oval shape with an oval shape partly included are disposed so as to share a portion. The radiating conductor 11 and the feeder 14 are connected together at a peripheral portion of the second forming element 13. The peripheral portion of the second forming element 13, where the connecting position exists, is located on a side of the second forming element 13 remote from the first forming element 12.
As shown in
The radiating conductor 11 and the feeder 14, which are thus configured, are disposed on the same plane in the dielectric member 16.
The dielectric member 16 includes ground patterns 15a and 15b in order to ensure a potential of 0 at symmetrical positions with respect to the feeder 14 and to effectively provide impedance matching for the antenna. These ground patterns 15a and 15b are configured so as to be connected to a ground conductor 18 through auxiliary patterns and vias, which are disposed in, e.g., the insulating substrate 17 and are not shown.
The first forming element 12 of the radiating conductor 11 is formed in a circular disc shape, and the second forming element 13 of the radiating conductor is formed in a semi-oval shape having a part of an oval shape. In
In the radiating conductor 11 shown in
In order to delimit the shape of the radiating conductor 11 by a longitudinal length ratio α stated later, a longitudinal length L31 of the first forming element and a longitudinal length L32 of a portion of the second forming element projected from the first forming element are defined in
As shown in
As shown in
The antenna device 1 thus figured is formed in such a shape that the first forming element 12 in a circular shape and the second forming element 13 in a semi-oval shape are combined so as to share a portion as stated earlier. By this arrangement, the antenna device can have an improved fractional bandwidth and a wider operating frequency band as shown in Examples stated later.
The radiating conductor of the antenna according to the present invention may be formed in any shape as long as the first forming element, which has a shape selected among a polygon, a substantially polygon, a circle, a substantially circle, an oval and a substantially oval, and the second forming element, which has at least one portion of a shape selected among a polygon, a substantially polygon, a circle, a substantially circle, an oval, a substantially oval, a trapezoid and a substantially trapezoid, are disposed so as to have a portion common to each other.
Although the radiating conductor 11 and the feeder 14 are disposed in the dielectric member 16 in
When the dielectric member 16 comprises a laminated member, the laminated member may be formed by laminating similar dielectric layers having a single relative dielectric constant or may be formed by laminating dielectric layers having at least two kinds of different relative dielectric constants as shown in
By disposing the radiating conductor 11 in the dielectric member 16 to utilize a wavelength shortening effect of a dielectric material, the antenna body 10 can be made small. In this case, it is possible to determine an effective relative dielectric constant in accordance with the position of the radiating conductor 11, the relative dielectric constant of the dielectric member 16 or a combination of at least two kinds of relative dielectric constants of the dielectric member. Thus, it is possible to obtain a wavelength shortening effect according to an effective relative dielectric constant. By properly selecting and adjusting the effective relative dielectric constant, it is possible to provide the antenna body 10 with a wide operating frequency band.
Although the first forming element 12 and the second forming element 13 are disposed on the same plane, the feeder 14, and the ground patterns 15a and 15b may be disposed on the same plane as or a different plane from the first forming element 12 and the second forming element 13. When the feeder and the ground patterns are disposed on a different plane from the first and second forming elements, the connection between the second forming element 13 and the feeder 14, and the feeder 14 and the signal line 19 of the strip line may be made by vias in the dielectric member 16, an example of the vias being shown in
The connection from the signal line 19 of the strip line to the feeder 14 may be made by the via 20 shown in
The antenna device 1 is configured by surface-mounting the antenna body 10 on the insulating substrate 17 with the ground conductor 18 disposed thereon. The ground conductor 18 may be disposed on a rear surface of the insulating substrate 17 made of, e.g., a dielectric material, by printing. In this case, the transmission line for feeding power to the antenna body 10, e.g., the signal line of a strip line, such as a micro-strip transmission line, may be disposed on a surface of the insulating substrate 17 by printing.
The insulating substrate 17 may comprise a laminated substrate. In this case, the ground conductor 18 may be configured to be disposed in an inner layer of the laminated member, such as a second layer or a third layer, instead of a surface layer, and have an insulating layer disposed thereon.
The transmission line, which is formed on the insulating substrate 17 to feed power to the antenna body 10, is not limited to a micro-strip transmission line and may comprise a coplanar line, wherein the ground conductor and the signal line are disposed on the same surface of the insulating substrate 17. In this case, the ground conductor of the coplanar line functions as the ground conductor 18. The antenna body 10 may be mounted to a surface with the coplanar line disposed thereon or the opposite surface thereof.
The antenna body 10 and the ground conductor 18 may be disposed on the same plane of a single substrate. In this case, it is not necessary to provide an additional member, such as the dielectric member 16 forming the antenna body 10. The antenna device may be configured so that the antenna body 10 is disposed on the opposite region of the exposed portion 24, and the strip line is disposed on the rear surface of the substrate to feed power the antenna body 10 through a via. In other words, the antenna body 10 may be disposed so that the plane; where the ground conductor 18 is disposed, is parallel with the plane, where the radiating conductor 11 of the antenna body 10 is disposed.
A portion of the dielectric member 16, which forms the antenna body 10, or the insulating substrate 17, which has the ground conductor 18 formed thereon, may have a terminal disposed thereon so as to fixedly mount the antenna body 10 to the insulating substrate 17 by, e.g. soldering. By disposing such a terminal at plural positions, it is possible to prevent the antenna body 10 from falling out of the insulating substrate 17 during handling even when the antenna device is employed in communication equipment, such as radio communication equipment. Such a terminal may be employed to connect between the signal line 19 of the strip line formed on the insulating substrate 17 and the feeder 14 formed in the dielectric member 16 by, e.g. soldering for instance. In this case, prevention against falling-out and electrical connection can be simultaneously realized.
In order to dispose such a terminal, the distance L1 between an end of the antenna element 11 (an end of the dielectric member 16) and the ground conductor 18 (see
The antenna device 1 thus configured may be appropriately employed as an antenna device for transmission and reception of a linearly polarized wave.
Now, transmission and reception characteristics of the antenna device 1 thus configured will be explained.
In the frequency characteristic of VSWR shown in
Fractional bandwidth=2·(fH−fL)/(fH+fL)×100(%)
It is meant that a wider fractional bandwidth has a wider operating frequency bandwidth.
The frequency characteristics of VSWR in the antenna device 1 shown in
The antenna device according to the present invention has a fractional bandwidth of not less than 40% when using a frequency bandwidth having VSWR of less than 2.0. The antenna device according to the present invention preferably has a fractional bandwidth of not less than 75% when using a frequency bandwidth having. VSWR of less than 2.2, more preferably has a fractional bandwidth of not less than 85% when using a frequency bandwidth having VSWR of less than 2.4, particularly preferably has a fractional bandwidth of not less than 90% when using a frequency bandwidth having VSWR of less than 2.6, and most preferably has a fractional bandwidth of not less than 100% when using a frequency bandwidth having VSWR of less than 3.0.
Now, the antenna devices according to other embodiments of the present invention will be described.
In the antenna device 2, the antenna body 10 is mounted to a surface of the insulating substrate 17, such as a circuit board, as in the antenna device 1. Additionally, the reflector 41 and the dielectric layer 51 are disposed along the insulating substrate 17 on the side of the surface of the insulating substrate 17 with the ground conductor 18 disposed thereon.
The antenna body 10 is a surface-mount antenna, which is mounted to a surface of the insulating substrate 17 as stated earlier. Explanation of the antenna body 10 and the insulating substrate 17 is omitted since both parts have been stated earlier.
The reflector 41 comprises a flat metal plate and has a function to improve a gain by providing a radio wave radiating from the antenna body 10 with a sharp radiation pattern in a normal line direction of a surface of the reflector 41. A radio wave radiated from the antenna body 10 is reflected in a direction of Z since the reflector 41 is disposed along the insulating substrate 17 as shown in
The material for the reflector 41 is not limited to metal. The reflector may be made of any material, which reflects a radio wave. For example, it is acceptable to employ one wherein a transparent conductive film is disposed on a dielectric substrate, such as a glass plate. It is also acceptable to employ an EBG (Electromagnetic Band Gap) structure, which functions as an artificial magnetic conductor.
The dielectric layer 51 is disposed on the surface of the reflector 41.
The dielectric layer 51 comprises a dielectric member, which is provided between the insulating substrate 17 and the reflector 41. The dielectric layer has a function to provide the antenna device 2 with a high gain by being employed along with the reflector 41. Although the dielectric layer 51 is disposed on the surface of the reflector 41 in this embodiment, the dielectric layer may be provided at a desired position between the insulating substrate 17 and the reflector 41 in the present invention. However, in order to maintain a high gain for a low frequency in the operating frequency band of the antenna device 2, it is preferred that the dielectric layer 51 be disposed on the surface of the reflector 41 so that the insulating substrate 17, an air layer 61, the dielectric layer 51 and the reflector 41 are provided in this order. Although the relative dielectric constant of the dielectric layer 51 is not particularly limited, the relative dielectric constant preferably ranges from 1.5 to 20, more preferably ranges from 2 to 10.
Although the reflector 41 is provided along the insulating substrate 17 in this embodiment, the reflector 41 is not necessarily provided along the insulating substrate 17 in the present invention. The direction of the reflector 41 and the dielectric layer 51 to the insulating substrate 17 may be modified according to a direction to reflect a radio wave. For example, in order to obtain the maximum radiation intensity of a radio wave in a direction inclined at an angle of θ=20 deg from the Z-axis toward the Y-axis in
It is preferred that the insulating substrate 17, the reflector 41 and the dielectric layer 51 be disposed parallel or substantially parallel with one another. By this arrangement, the antenna device can be configured in a substantially planar shape and can be provided as a small size antenna device. The reflector 41 and the dielectric layer 51 may be disposed on the side of the insulating substrate 17 remote from the antenna body 10 or the same side of the insulating substrate as the antenna body 10.
In
The dimensions of the reflector 41 (lengths L41 and L42) are set so that the flat metal plate can function as a reflection plate for a radio wave. When the reflector 41 has smaller dimensions than a certain value, the reflector cannot function as a reflection plate. The lengths L41 and L42 are set so that the reflector 41 can perform the required function in a frequency band in a wide band to provide the antenna device 2 with a characteristic having a high gain over the wide band. For example, it is sufficient that the length L41 and/or the length L42 is 30 mm or longer in the antenna device 2. Although it is preferred that the length L41 of the reflector 41 in the transverse direction and/or the length L42 of the reflector in the vertical direction be equal to or longer than the lengths of the insulating substrate 17 in the corresponding direction, it is sufficient that at least one of the length L41 of the reflector 41 in the vertical direction and the length L42 of the reflector in the vertical direction is equal to or longer than the length of the insulating substrate 17 in the corresponding direction. For example, even if the length L41 of the reflector 41 in the transverse direction is shorter than the length of the insulating substrate 17 in the transverse direction, it is sufficient that the length L42 of the reflector 41 in the vertical direction is longer than the length of the insulating substrate 17 in the vertical direction. It is preferred that the length L41 and/or the length L42 be 1.3 times or more the length of the insulating substrate 17 in the transverse direction and/or the length of the insulating substrate 17 in the vertical direction, e.g., 40 mm or longer.
By adjusting the distance L43, the reflector 41 can perform the required function in a frequency band in a wide band to provide the antenna device with a high gain over a wide band. The distance L43 in the antenna device 2 preferably ranges from 5 to 25 mm, more preferably ranges from 7 to 22 mm. In both ranges, the antenna device exhibits high gain characteristics in a wide operating frequency band from 3 to 5 GHz.
The shape of the dielectric layer 51 is defined by representing the length of the dielectric layer 51 in the transverse direction and the length of the dielectric layer in the vertical direction by L51 and L52, respectively, in
When the dielectric layer 51 has a smaller size than a certain size, the gain of the antenna device 2 is lowered. The dielectric layer can function so as to provide the antenna device 2 with high gain characteristics in a frequency band in a wide band by setting the length L51 and the length L52 in a certain range.
For example, it is sufficient that the length L51 and/or the length L52 is 30 mm or longer in the antenna device 2. It is preferred that the length L51 of the dielectric layer 51 in the transverse direction and/or the length L52 of the dielectric layer in the vertical direction be equal to or longer that the length of the insulating substrate 17 in the corresponding direction. However, it is sufficient that at least one of the length L51 of the dielectric layer 51 in the transverse direction and the length L52 of the dielectric layer in the vertical direction is equal to or longer than the length of the insulating substrate 17 in the corresponding direction. For example, even if the length L51 of the dielectric layer 51 in the transverse direction is shorter than the length of the insulating substrate 17 in the transverse direction, it is sufficient that the length L52 of the dielectric layer 51 in the vertical direction is longer than the length of the insulating substrate 17 in the vertical direction. It is preferred that the length L51 and/or the length L52 is 1.3 times or more the length of the insulating substrate 17 in the transverse direction and/or the length of the insulating substrate in the vertical direction, e.g., 40 mm or longer.
By setting the thickness L53 of the dielectric layer 51 in a certain range, the dielectric layer can function so as to provide the antenna device 2 with high gain characteristics over a frequency band in a wide band.
The range of the thickness L53 of the dielectric layer 51 will be described later.
Now, characteristics of the antenna device according to the present invention will be specifically described based on various examples.
Example 1 is an example wherein the antenna device 1 having the antenna body 10 shown in
In each of Example 1 and Example 7, the antenna body 10 or 110 is mounted to one of both surfaces of the insulating substrate 17, and the ground conductor 18 is disposed on the other surface as shown in
Table 1 shows the dimensions of main parts of the antenna device 1 in Example 1 along with those in Examples 2 to 7, which will be stated later. The words “length” and “width” in items of “ground pattern”, “dielectric member”, “insulating substrate” and “ground conductor” in Table 1 mean the length in the vertical direction and the length in the transverse direction in
As shown in
This reveals that it is possible to provide optimum impedance matching over a wide band by appropriately adjusting the shape of the second forming element 13 in accordance with the size of the first forming element 12 in the radiating conductor 11. Additionally, it is possible to provide good matching in a wider frequency band by appropriately adjusting the major axis radius and the minor axis radius of the oval shape in the second forming element 13.
Additionally, the length of the feeder 14 in Example 2 is 0.7 mm. The thickness of the dielectric member 16 is 1.2 mm, and the radiating conductor 11 is disposed in the dielectric member 16. The dielectric member 16 is configured so that the radiating conductor 11 is disposed in two sets of dual dielectric layers (first dielectric layer 32 and second dielectric layer 33) having different relative dielectric constants as shown in
The fractional bandwidth found from the frequency characteristic of VSWR shown in
Specifically, the dielectric member 16 is formed by two sets of dual dielectric layers (first dielectric layer 32 and second dielectric layer 33) having different relative dielectric constants as in Example 2. In the dielectric member 16, the radiating conductor 11 and the feeder 14, which formed the antenna body 10, were disposed on a single plane in a substantially central portion in the thickness direction of the dielectric member 16. The first dielectric layer 32 has a relative dielectric constant of 22.7 and a thickness of 0.3 mm, and the second dielectric layer 33 has a relative dielectric constant of 7.6 and a thickness of 0.3 mm.
The dimensions of main parts of the antenna device 1 in Example 3 are shown in Table 1.
With respect to other dimensions, the dielectric member 16 has a thickness of 1.2 mm as a whole. The insulating substrate 17 has a thickness of 0.8 mm. Both forming elements were disposed so that a portion of the semi-oval shape of the second forming element 13, which had the smallest radius of curvature, was located in the vicinity of the center of the circular shape of the first forming element 12, and that a linear portion of the semi-oval shape of the second forming element 13 (a portion that is obtained by cutting the oval shape in half) was disposed so as to project from the first forming element 12. The feeder 14, which is connected to a peripheral portion on a side of the second forming element 13 as seen from the first forming element 12, has a length of 0.9 mm and a width of 0.2 mm. The other peripheral portion of the feeder 14, which is not connected to the second forming element 13, is located at a position away from an end of the dielectric member 16 (a lower end of the dielectric member 16 in
Additionally, the ground patterns 15a and 15b were disposed on a side of the dielectric member 16 in contact with the insulating substrate 17, and an unshown feeding pad is disposed between the ground patterns 15a and 15b. The unshown feeding pad has dimensions of 1.1 mm in length and 1.4 mm in width. The distance between the unshown feeding pad and each of the ground patterns 15a and 15b is 0.5 mm. The feeding pad was connected to an end of the feeder 14 through the via 20.
The insulating substrate 17 having the ground conductor 18 was fabricated by employing a resin substrate, which had a thickness of 0.8 mm and had both sides covered with copper foil having a thickness of 0.018 mm (R-1766T manufactured by Matsushita Electric Works, Ltd. and having a relative dielectric constant of 4.7). The insulating substrate 17 had one of the surfaces formed with the signal line 19 and the other surface formed with the ground conductor 18, and the dielectric member 16 was mounted to an end of the surface of the insulating substrate 17 with the signal line 19 formed thereon (an upper right end of the insulating substrate 17 shown in
The signal line 19 of the transmission line is formed as a signal line of a micro-strip transmission line and has a transverse width of 1.4 mm. Conductor patterns, such as the ground conductor 18, the signal line 19 and an unshown connection pad (a pad connected to the feeding pad), were disposed by etching. These conductors were subjected to gold-flush treatment, and the surface portions of the conductors except for the connection pad were covered with a solder-resist.
A lead-free cream (M705 manufactured by Senju Metal Industry Co., Ltd.) was printed at the position of the connection pad of the insulating substrate 17 by using a metal mask. The dielectric member 16 was located at a certain position and was put on the insulating substrate 17, and the dielectric member 16 and the insulating substrate 17 were heated at a temperature of 250° C. to be melt-bonded together by soldering. Thus, the signal line 19 was connected to the feeding pad of the dielectric member 16, and the ground patterns 15a and 15b were connected to the ground conductor 18 through connection pads and vias, which were formed at the insulating substrate 17 but not shown.
Measurements of VSWR were conducted in connection with the antenna device thus fabricated, and measurement results shown in
Additionally, when an antenna device, which had the second forming element 13 formed in a rectangular shape, was fabricated, it was affirmed that this antenna device also had a similar fractional bandwidth.
An antenna device 1 employing a radiating conductor 11 shown in
The dimensions of main parts of the antenna devices 1 in Example 4 shown in
In each of Example 4 and Example 5, the radiating conductor 11 is disposed by combining a first forming element 12 and a second forming element 13 so that both forming elements shares a portion having the smallest radius of curvature in the semi-oval shape of the second forming element 13. The first forming element 12 in Example 4 is disposed so as to have the major axis extending in a transverse direction in
From now on, explanation will be made, making such a distinction that the antenna body 10 shown in
In
The length and the width in the hexagonal shape (item of the first forming element 12) in Example 6 in Table 1 mean the length in the vertical direction in FIG. 12 and the length in the transverse direction in
Additionally,
As stated earlier, the combination of the first forming element 12 and the second forming element 13 in the radiating conductor 11 according to the present invention is not limited to the combination of a circular shape and a semi-oval shape as shown in
Example 7 is an antenna device, which employs an antenna body 110 (see
The antenna 110 shown in
The dimensions of main parts of the antenna device in Example 7 shown in
The fractional bandwidth in Example 7 shown in
In the antenna device 1 according to the present invention, it is not always necessary to dispose the ground patterns 15a and 15b.
As shown in
The dimensions of main parts of the antenna device 1 in each of Examples 9 to 11 are shown in Table 2. As shown in
The portion where the antenna body 10 is mounted to the insulating substrate 17 is the opposite region of the exposed portion 24 where the insulating substrate 17 is exposed without the ground conductor 18 being disposed as shown in
As seen from
Although the antenna body 10 shown in
The dimensions of main parts of the antenna device 1 of Example 13 are shown in Table 2. In Example 12, the antenna element 10 is disposed on a right end portion of the opposite region opposite the exposed portion of the insulating substrate 17. Even Example 13 exhibits a good characteristic as in Example 12. However, the fractional bandwidth is slightly decreased in comparison with Example 12. From this viewpoint, it is preferred that the antenna body 10 be disposed on an end portion of the opposite region opposite the exposed portion of the insulating substrate 17. It is more preferred that the antenna body be disposed at one of the four corners of the insulating substrate 17. Although the antenna body 10 is disposed at an upper right end in
Although in the present invention, the antenna body 10 is disposed on the opposite region opposite the exposed portion of the insulating substrate 17, a second ground conductor 15 may be disposed so as to have an end portion located at a position away from an end of the antenna body 10 (an end of the dielectric member 16) by a distance L2 as shown in
Example 14 has a fractional bandwidth of 50%, providing a wide fractional bandwidth and an operating frequency band in a wide band. Example 15 has a fractional bandwidth decreasing to about 42%, almost half. From this viewpoint, it is preferred that the second ground conductor 15 be disposed so as to have a distance L2 of 3 mm or longer in the antenna device with the antenna body 10 mounted thereto.
The insulating substrate 17 with the ground conductor 10 disposed thereon may comprise a circuit board with another circuit element disposed thereon. In this case, the ground conductor of the circuit board serves as the ground conductor 18. The antenna body 10 is disposed on an opposite region opposite an exposed portion of the circuit board, i.e. a region of an opposite surface opposite the exposed portion 24 of the insulating substrate 17. This means that the region of the circuit board except for the exposed portion can be utilized as a space for disposing another circuit element or the like. When the second ground conductor 15 is disposed, it is possible to increase the space for disposing such a circuit element or the like.
By disposing the second ground conductor 15 as stated earlier, the exposed portion 24 can be made smaller, providing an antenna device having a small structure and a wide operating frequency band.
Now, a relationship between the shape and the fractional bandwidth of the radiating conductor 11 shown in
As an index representing the shape of the radiating conductor 11, a longitudinal length ratio is determined according to the following formula (1) using the vertical length L31 of the first forming element 12 and the vertical length L32 of the projected portion of the second forming element 13 projecting from the first forming element 12 in the radiating conductor 11 as shown in
Vertical length ratio α=L31/(L31+L32) (1)
Although a portion having the smallest radius of curvature in the semi-oval shape of the second forming element 13 is located in the vicinity of substantially the center of the circular shape of the first forming element 12 in the radiating conductor 11 shown in
The antenna device 1 of Example 16 has a structure similar to Examples 1 and 2, and the dimensions of main parts are shown in Table 2.
The radiating conductor 11 is disposed in two sets of dual electric layers having different related dielectric constants, as shown in
The feeder 14, which is connected to a peripheral portion of the second forming element 13 remote from the first forming element 12, has a length of 0.9 mm and a width of 0.2 mm. The other peripheral portion of the feeder 14, which is not connected to the second forming element 13, is located at a position away from an end of the dielectric member 16 (the lower end of the dielectric member 16 in
Additionally, the ground patterns 15a and 15b are disposed on a surface of the dielectric member 16 in contact with the insulating substrate 17, and an unshown feeding pad is disposed between the ground patterns 15a and 15b. The unshown feeding pad has dimensions of 1.1 mm in length and 1.4 mm in width. The distance between the feeding pad and each of the ground patterns 15a and 15b is 0.5 mm. The feeding pad is connected to an end of the feeder 14 through the via 20.
The insulating substrate 17 has a thickness of 0.8 mm and a relative dielectric constant of 4.7. The insulating substrate 17 has the signal line 19 disposed on one of the surfaces thereof and the ground conductor 18 disposed on the other surface. As shown in
The first forming element 12 and the second forming element 13 of the radiating conductor 11, and the feeder 14 are disposed on the same plane in the dielectric member 16 (at a substantially central portion in the thickness direction). The linear portion in the semi-oval shape (a portion obtained by cutting the oval shape in half) in the second forming element 13 is disposed so as to project from the first forming element 12. The length of the first forming element 12 in the transverse direction is 8.6 mm, the entire length of L31+L32 of the radiating conductor 11 in the vertical direction is 8.2 mm, and the longitudinal length ratio α is modified by changing the length L31. Thus, the first forming element 12 is modified into an oval shape or a circular shape according to a longitudinal length ratio α.
According to
Additionally, an antenna device 1 which included a radiating conductor 11 wherein the longitudinal length ratio α was 64%, was fabricated as Example 17, and VSWR was measured.
The antenna device 1 of Example 17 was fabricated, using a fabricating method similar to Example 3.
The dimensions of main parts of the antenna device 1 of Example 17 are shown in Table 2.
In this case, the entire length of L31+L32 in the vertical direction, which is represented as the pattern shape of the radiating conductor 11, is 8.1 mm. The antenna device had the same structure as Example 16 except for the shape of the radiating conductor 11.
The fractional bandwidth of Example 17 shown in
Even when the second forming element 13 was formed in a rectangular shape, when the length L32 was 2.9 mm and when the length in the transverse direction was 0.8 mm, it was verified that a similar fractional bandwidth was able to be obtained.
An antenna device wherein the shape of the radiating conductor 11 is modified will be explained as Example 18.
The dimensions of main parts of the antenna device of Example 18 are shown in Table 2. The phrase “square shape one side: 2 mm” of the second forming element 13 of Example 18 means that the shape of the second forming element projecting from the first forming element 12 has a square shape having sides of 2 mm.
The feeder 14 has a length of 0.7 mm and a width of 0.2 mm. The distance between the right edge of the feeder 14 and the left edge of the ground pattern 15a, and the distance between the left edge of the feeder 14 and the right edge of the ground pattern 15b are 2 mm. The antenna body 10 is mounted to an upper surface of the insulating substrate 17b as shown in
The fractional bandwidth of Example 18 shown in
Now, an antenna device 2 wherein, as shown in
The radiating conductor 11 of the antenna body 10, which is employed in the antenna device 2 in Example 19, is disposed in a dielectric member 16, which comprises two sets of dielectric layers having different relative dielectric constants, as shown in
The dimensions of main parts of the antenna device 2 of Example 19, as well as dimensions of Examples 20 and 21 stated below, are shown in Table 3 below. The words “length” and “width” in items of “ground pattern”, “dielectric member”, “insulating substrate” and “ground conductor” in Table 3 mean the length in the vertical direction and the length in the transverse direction in
The length L32 of a portion of the second forming element 13 in the vertical direction, which projects from the first forming element 12 of the radiating conductor 11, is 1.8 mm. The insulating substrate 17 is disposed in the vicinity of substantially the center of the reflector 41, and the insulating substrate 17 and the reflector 41 are configured to be substantially parallel with each other. The reflector 41 is disposed away from the insulating substrate by a desired distance (distance L43)
As shown in
On the other hand,
As shown in
By adjusting the length L41, the length L42 and the distance L43 of the reflector 41, it is possible to effectively operate the metal plate as the reflector.
Now, an antenna device 2, wherein only the shapes of the first forming element 12 and the second forming element 13 of the radiating conductor 11 in the antenna device 2 of Example 19 were modified, will be explained as Example 20.
The dimensions of main parts of the antenna device 2 of Example 20 are shown in Table 3.
The entire length L31+L32 in the vertical direction, which appears as the outline of the pattern shape of the radiating conductor 11, is 8.1 mm, and the length L32 is 2.9 mm.
As shown in
Even when the second forming element 13 is formed in a rectangular shape, when the length L32 is 2.9 mm and when the length in the transverse direction is 0.8 mm, it was verified that the antenna device has a radiation pattern similar to
Additionally, a characteristic of the dielectric layer 51 in the antenna device 2 shown in
The antenna device 2 is configured so that in an assembly comprising an antenna body 10 and an insulating substrate 17 formed in the same structure and the same dimensions as Example 19, the reflector 41 having a flat metal surface is disposed in the vicinity of substantially the center of the insulating substrate 17, and the reflector 41 and the insulating substrate 17 are disposed substantially in parallel with each other.
The dimensions of main parts of the antenna device 2 in Example 21 are shown in Table 3.
The insulating substrate 17, the air layer 61, the dielectric layer 51 and the reflector 41 are provided in this order, and the air layer 61 and the dielectric layer 51 are substantially in parallel with the reflector 41.
In the antenna device 2 thus configured, the dielectric layer 51 performs a required function in a wide band of frequency range by setting the thickness L53 of the dielectric layer 51 in a certain range, and the antenna device 2 exhibits high gain characteristics over a wide band.
The ratio β is represented by the following formula (2).
Ratio β=L53/L43×100 (2)
As shown in
As shown in
Even when the second forming element 13 is formed in a rectangular shape, when the length L32 is 2.9 mm and when the length in the transverse direction is 0.8 mm, it is verified to obtain a radiation pattern similar to
Although explanation of the monopole antenna, wherein the radiating conductor 11 is connected to an unbalanced line, such as a micro-strip line, has been made, the present invention is not limited to the monopole antenna, and two pairs of radiating conductors 11 and antenna bodies 10 may be disposed to employ the antenna according to the present invention as a dipole antenna. In this case, one signal line of the balanced lines is connected to one of the radiating conductor 11 or one of the antenna body 10, and the other signal line of the balanced lines is connected to the other radiating conductor 11 or the other antenna body 10. Unbalanced lines may be modified into balanced lines through baluns, and the respective balanced lines may be connected to the respective radiating conductors 11 or the respective antenna bodies 10.
Although the antenna device according to the present invention has been described in detail, the present It is to be understood that modification and variation of the present invention may be made without departing from the sprit and scope of the present invention.
The present application claims priorities under 35 U.S.C. §119 to Japanese patent application number 2003-384324 filed Nov. 13, 2003 and Japanese patent application number 2004-156357 filed May 26, 2004. The contents of these applications are incorporated therein by reference in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-384324 | Nov 2003 | JP | national |
| 2004-156357 | May 2004 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6512488 | Schantz | Jan 2003 | B1 |
| 6809687 | Yuanzhu | Oct 2004 | B1 |
| 6897808 | Murch et al. | May 2005 | B1 |
| 6897811 | Asai et al. | May 2005 | B1 |
| 20040100406 | Hironori | May 2004 | A1 |
| 20040100407 | Hironori | May 2004 | A1 |
| 20040100408 | Hironori | May 2004 | A1 |
| 20040100409 | Okado | May 2004 | A1 |
| 20050156788 | Lin | Jul 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| 10-150318 | Jun 1998 | JP |
| 10-276033 | Oct 1998 | JP |
| 3273463 | Feb 2002 | JP |
| 2002-164731 | Jun 2002 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20060038723 A1 | Feb 2006 | US |
