JP4405051B2 - Multi-frequency antenna system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-frequency shared base station antenna apparatus used for land mobile communication and the like.
[0002]
[Prior art]
Conventionally, with regard to this type of multi-frequency shared antenna apparatus, three frequency bands of 800 MHz band, 1.5 GHz band and 2 GHz band are assigned to land mobile communications used for automobile mobile phones and the like.
[0003]
A conventional monopole antenna used for each frequency band is shown in FIG.
That is, the antenna shown in FIG. 7 is a perspective view of a quarter-wave monopole antenna, and the quarter-wave monopole antenna 1 is suspended from the center of the circular ground plate 2 and the circular ground plate 2. The power feeding element 1a as an antenna element having a quarter wavelength of the used frequency is representative of an antenna having non-directional directivity in the horizontal plane.
Further, the directivity in the vertical plane varies depending on the size of the ground plate 2. As the ground plate 2 is larger, the wraparound to the rear of the ground plate 2 is reduced.
[0004]
Base station antenna devices used for land mobile communications, etc. Especially for base station antenna devices used in places with ceilings, such as indoors, the ceiling surface and antenna grounding plate can be installed on the same surface. It is desirable to realize an antenna such as the ¼ wavelength monopole antenna 1 that is almost unaffected by the above and can maintain omnidirectionality. However, there is a need for an inconspicuous antenna with a posture as low as possible due to an aesthetic problem when it is installed.
[0005]
Therefore, as shown in FIG. 8, the upper part of the antenna element 1a of the quarter-wave monopole antenna 1 is transformed into a conductive disk (or disk) 3a, and a capacity is provided therefor, thereby reducing the A so-called capacity-loaded monopole antenna 3 is often used.
In this case, the height can be about ¼ of the ¼ wavelength monopole antenna 1. The disk 3a parallel to the ground plate 2 is close to the ground plate 2, and the current on the disk 3a is canceled by the image current, and the radiation from the disk 3a does not contribute. Only the element component 3b perpendicular to the ground plate 2 contributes to radiation.
Therefore, the directivity is almost the same as that of the quarter-wave monopole antenna 1.
[0006]
[Problems to be solved by the invention]
By the way, with the spread of mobile communication in recent years, frequency bands to be used have been studied and various frequency bands have been proposed. In addition, due to the difficulty of securing frequency resources, it is necessary to use many different frequency bands in one system. In addition, it is expected that the use of a new frequency band will be studied for each generation of the system, and the use of a new frequency band is expected to be determined. Support for the previous generation frequency band is also required during the system transition period.
[0007]
This type of antenna basically requires a size corresponding to the frequency, and if the frequency band to be used is different, an antenna corresponding to that frequency is required.
Therefore, in the mobile communication using a plurality of frequency bands as described above, the base station antenna apparatus needs to cover all the frequency bands to be used. Therefore, an antenna corresponding to each frequency band must be prepared. Don't be.
For this reason, when the frequency band to be used increases, the number of antennas increases, the installation area of the antennas increases, and the cost of installation work and the poor appearance of the antennas become problems.
[0008]
In order to solve this problem, a method of using the antenna as a multi-frequency antenna can be considered. FIG. 9 is a perspective view of a typical dual-frequency antenna. This is an example of the dual use of the patch antenna, which is different from the monopole antenna shown in FIGS. 7 and 8, but is generally well known and suitable for explanation. It was taken up as a conventional example.
In this dual-frequency patch antenna 6, a small disk-shaped patch antenna 8 corresponding to a high frequency band is superimposed on a large disk-shaped patch antenna 7 corresponding to a low frequency band in parallel to the patch antenna 7. It is the structure arranged in.
[0009]
The patch antenna 8 in the high frequency band is a so-called disk-shaped parasitic element 8a that is not directly fed. The patch-shaped feeding element 7a of the patch antenna 7 in the low frequency band operates as if it is a ground plate. It can be said that. This structure is a method that is also used to widen the frequency band of the antenna. By changing the size (diameter) of the feeding element 7a and the parasitic element 8a, each element 7a, 8a is separately provided. This is a method of resonating at the frequency.
As a result, it is apparent that only one dual-frequency patch antenna 6 is required, and it is not necessary to prepare a separate antenna, so that the area occupied by the antenna 6 can be reduced.
[0010]
However, this structure employs a structure in which the patch antenna 8 corresponding to a high frequency is arranged so as to overlap the patch antenna 7 corresponding to a low frequency. There is a problem that the volume increases in the height direction. This means that the height increases as the number of antennas having frequencies to be shared increases. This increase in height has a problem in the aesthetics of the antenna 6.
On the other hand, even in other types of antennas, parasitic elements are often installed in an upward or lateral direction, and there is a problem in that the volume of the antenna is often increased compared to a single frequency case. .
[0011]
The present invention has been made in view of the above points, and its purpose is to solve the above-described problems, enable multi-frequency sharing, and reduce the height, so-called low posture, and the occupied volume thereof is higher than in the past. An object of the present invention is to provide a multi-frequency shared antenna device which does not become large.
[0012]
Another object of the present invention is to provide a plurality of frequency bands higher than the lowest frequency band between the plate-shaped feeding element of the antenna corresponding to the lowest frequency band and the ground plate among the plurality of frequency bands used. An object of the present invention is to provide a multi-frequency shared antenna apparatus that can accommodate the antenna elements.
[0013]
[Means for Solving the Problems]
The present invention includes a ground plate, a vertical element component suspended from the ground plate in a form insulated from the ground plate, and a plate-like antenna element connected to the vertical element component in a form parallel to the ground plate. A minimum frequency band capacity loaded monopole antenna corresponding to the lowest frequency band of the plurality of frequency bands, and first, second, ... having a frequency higher than the lowest frequency band. A pair of first frequency band antennas, a pair of second frequency band antennas corresponding to frequency bands of nth (n is an integer of 2 or more), and a pair of nth frequency band antennas. And comprising.
Of the antenna pairs, the i-th (i is 1, 2,... N) frequency band antenna pair is parallel to the vertical element component of the lowest frequency band capacity-loaded monopole antenna. And a pair of parallel element components parallel to the ground plate, and the i-th frequency band antenna pair is for the lowest frequency band. Between the ground plate and the plate-like antenna element of the capacity-loaded monopole antenna, they are symmetrically arranged around the vertical element component of the capacity-loaded monopole antenna for the lowest frequency band.
Further, the first frequency band antenna pair, the second frequency band antenna pair,..., The nth frequency band antenna pair are the vertical element component to which the parallel element component corresponds. The parallel element components are configured to have the same height with respect to the grounding plate so as to form a fan shape extending from the side toward the tip side.
And it is comprised so that it may feed with respect to the said capacity loading type | mold monopole antenna for minimum frequency bands, and, thereby, said objective is achieved.
[0014]
The capacitance loading type monopole antenna for the lowest frequency band may include an impedance matching short pin interposed between the plate antenna element and the ground plate.
[0015]
The ground plate and the plate-shaped antenna element of lowest frequency band for capacity loaded monopole antenna, it is preferable that each formed in a circular shape.
[0017]
Each of the antenna pairs may be any one of a capacity-loaded monopole antenna, a half-wavelength loop antenna, and an F-type antenna.
[0018]
The multi-frequency shared antenna apparatus of the present invention is configured as described above, and its basic configuration is shown in FIG.
According to FIG. 1, the multi-frequency antenna device 11 includes a disk (or disk) -shaped capacitively loaded monopole antenna 3 as a feeding element 3 a of the antenna having the lowest frequency among a plurality of frequencies used. The feed element 3a is substantially concentric with the ground plate through a vertical element component 3b penetrating the through hole 2a formed at the center position of the ground plate 2 and suspended from the ground plate 2. And arranged in parallel and fed by a coaxial cable or the like.
A plurality of (two in the figure) capacitively loaded monopole antennas 12 that resonate in the first and second frequency bands having frequencies higher than the lowest frequency in the vicinity of the vertical element component 3b of the antenna 3. Reference numeral 13 denotes a structure in which no power is supplied and which is disposed on the ground plate 2.
[0019]
Here, the plurality of capacity-loaded monopole antennas 12 and 13 use L-type monopole elements having a structure in which a quarter-wave monopole antenna of each frequency used is bent halfway, The vertical element components 12 b and 13 b of the antennas 12 and 13 are installed substantially parallel to the vertical element component 3 b of the antenna 3.
[0020]
In FIG. 1, the capacity-loaded monopole antenna 3 is fed and the capacity-loaded monopole antennas 12 and 13 in the first and second frequency bands are not fed. Regardless of this, one of the monopole antenna 3 and the monopole antennas 12 and 13 may be fed. That is, it is sufficient that one of the entire monopole antennas including the antenna corresponding to the lowest frequency band is fed. In this case, electric power in a corresponding frequency band is fed to the antenna to be fed.
[0021]
The elements of the antennas 12 and 13 that resonate in the first and second frequency bands of the high frequency can be structurally smaller than the feeding element 3a of the antenna 3 of the lowest frequency, so that the lowest The antenna is completely housed and hidden inside the feeding element 3a of the antenna 3 having the frequency. For this reason, the total volume of the multi-frequency shared antenna 11 does not increase at all.
The lengths of the parallel element components (element components parallel to the ground plate 2) 12a and 13a and the vertical element components 12b and 13b of the first and second frequency antennas 12 and 13 can be freely selected according to circumstances. Can be set.
[0022]
Furthermore, even if the number of use frequency bands higher than the lowest frequency is increased, it is possible to cope with the problem by increasing the number of passively loaded capacitively loaded monopole antennas having different lengths.
At this time, since the element component contributing to radiation is an element component perpendicular to the ground plate 2, the influence on the directivity in other frequency bands of each element is small. Therefore, omnidirectionality can be obtained in the same horizontal plane in any frequency band.
[0024]
In addition, each antenna element in a plurality of frequency bands higher than the lowest frequency does not necessarily need to be a capacity-loaded monopole antenna, and the plate-like feeding element 3a of the antenna 3 corresponding to the lowest frequency A normal quarter-wave monopole antenna may be used as long as it fits between the ground plate 2.
Furthermore, as for the types of the antennas in the plurality of frequency bands higher than the lowest frequency, a half-wave loop antenna, an F-type antenna, or the like can be used in addition to the above. Further, the directly fed element is not necessarily an element corresponding to the lowest frequency band, and can be changed to an element corresponding to another frequency depending on the situation as described above.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the drawings.
2 to 6 are diagrams showing an embodiment of the multi-frequency antenna device according to the present invention. FIG. 2 is a perspective view showing the configuration of the antenna device in which three frequency bands of 800 MHz, 1.5 GHz, and 2 GHz are shared. FIG. 3 is a diagram showing the return loss (return loss) with respect to the frequency of the antenna device of FIG. 2, and FIGS. 4 to 6 are the respective frequencies of the antenna device of FIG. 2, 800 MHz, 1.5 GHz, and 2 GHz. It is a figure which shows each directivity of a vertical surface and a horizontal surface.
[0026]
In FIG. 2, a three-frequency shared antenna device 31 includes a disk-type capacitively loaded monopole antenna 32 for the 800 MHz band, an L-shaped deformed capacitively loaded monopole antenna 33 for the 1.5 GHz band, and an L for the 2 GHz band. It consists of a monodeformation antenna 34 with a deformed capacity loading type.
[0027]
Among the three frequency bands to be used, the lowest disk-shaped capacitively loaded monopole antenna 32 for the 800 MHz band is formed at a disk-shaped ground plate 2 having a relatively large radius and at the center position of the ground plate 2. The through-hole 2a is formed through a vertical element component 32b penetrating the grounding plate 2 through insulation and a feed element 32a conducting therethrough. The power feeding element 32a is disposed concentrically with the ground plate 2 in parallel with the ground plate 2 at a certain interval by two conductive short pins (also serving as a support member) 26. The disc is made of a conductive material such as a metal and has a relatively small radius, and the vertical element component 32b is connected to the center of the disc.
The antenna 32 is directly supplied with required power from the lower end of the vertical element component 32b via a feed line (for example, a coaxial cable).
[0028]
Two short pins 26 are provided between the power supply element 32a and the ground plate 2 in order to match the impedance on the power supply element 32a side with the characteristic impedance 50Ω of the power supply line. At this time, the height of the vertical element component 32b, that is, the height of the antenna 32 is about 25 mm from the ground plate 2 and is about 0.067 wavelength when converted in the 800 MHz band, which is an extremely low height. The diameter of the feeding element 32a is about 80 mm, and the volume of the entire antenna 32 is kept small.
[0029]
The two L-shaped deformable capacity loaded monopole antennas 33 for the 1.5 GHz band and the 2 GHz for the non-feeding so as to surround the vertical element component 32b of the antenna 32 for the 800 MHz band. A total of six L-shaped deformable capacity loaded monopole antennas 34 for the band are symmetrically arranged around the vertical element component 32b. The vertical element components 33b and 34b of the respective antennas 33 and 34 are directly erected on the ground plate 2 in parallel with the vertical element component 32b for the 800 MHz band, and the respective vertical element components. Fan-shaped parallel element components 33a and 34a connected to the ends of 33b and 34b are formed in parallel to the ground plate 2, respectively.
[0030]
The fan-shaped parallel element component 33a of the antenna 33 for the 1.5 GHz band is larger than the fan-shaped parallel element component 34a of the antenna 34 for the 2 GHz band. Within the radius range, it is long in the radial direction and has a small central angle, and both the parallel element components 33a and 34a resonate in their respective frequency bands.
[0031]
1 . Of the antennas 33 and 34 in the 5 GHz band and the 2 GHz band, the length of the vertical element components 33b and 34b is about ½ of the length of the vertical element component 32b in the 800 MHz band, and the parallel component element 33a. , 34a is equal to or less than the radius of the feed element 32a in the 800 MHz band, so that the antennas 33 and 34 in the 1.5 GHz band and the 2 GHz band are inside the feed element 32a in the 800 MHz band, that is, in FIG. The space 27 shown by the alternate long and short dash line is completely accommodated and has a hidden structure.
[0032]
Here, the reason why the lengths of the vertical component elements 33b and 34b of the antennas 33 and 34 in the 1.5 GHz band and the 2 GHz band are the same is that the parallel element components 33a and 34a have the same height. This is because it is possible to manufacture in a batch with a printed circuit board or the like, and the number of parts can be reduced. Further, by arranging the positional relationships of the antennas 33 and 34 in the 1.5 GHz band and the 2 GHz band symmetrically with the vertical element component 32b in the 800 MHz band as the center, the directivity symmetry is improved. I'm doing better.
[0033]
FIG. 3 shows an example of the return loss characteristic (frequency vs. return loss characteristic) of the multi-frequency antenna device 31 of the present embodiment. According to FIG. 3, resonance is observed at three frequencies of 800 MHz band, 1.5 GHz band, and 2 GHz band. In addition, the resonance in the lowest 1.5 GHz band is lower than in other frequency bands, and the expected characteristics are obtained.
[0034]
Furthermore, examples of the directivity of the vertical plane and the horizontal plane of the antenna device 31 are shown in FIGS. Horizontal plane omnidirectionality is obtained at three frequencies of 800 MHz, 1.5 GHz, and 2 GHz. In addition, the same directivity is obtained in any frequency band without disturbing the directivity of the vertical plane.
[0035]
In the above description, the antenna 32 in the 800 MHz band is fed and the antennas 33 and 34 in the 1.5 GHz band and the 2 GHz band are not fed. However, the multi-frequency shared antenna device 31 of the present embodiment is not concerned with this. Instead, it is sufficient that one of the antennas 32, 33, and 34 is fed. Then, the power of the corresponding frequency band is fed to the one antenna to be fed.
[0036]
Note that the technology of the present invention is not limited to the technology in the above-described embodiment, and may be implemented by means of other modes that perform the same function, and the technology of the present invention may be variously modified within the scope of the above-described configuration. Addition is possible.
[0037]
【The invention's effect】
As is clear from the above description, according to the multi-frequency shared antenna device of the present invention, the antenna corresponding to the lowest frequency band among the plurality of frequency bands to be used is a capacity loaded monopole antenna, In addition, it is arranged so that a plurality of antennas corresponding to other frequency bands to be used are accommodated, and one of the antenna corresponding to the lowest frequency band and the plurality of antennas is fed. Multi-frequency sharing is possible, and it has an excellent effect that its height is low and its occupied volume does not become larger than the conventional one. In addition, the antenna corresponding to the lowest frequency band among the frequency bands to be used There is an effect that a plurality of antenna elements in a frequency band higher than the lowest frequency band can be accommodated between the plate-shaped feeding element and the ground plate so as to be hidden. .
[0038]
That is, among the frequency bands to be used, the antenna corresponding to the lowest frequency band is a capacitively loaded monopole antenna, and the antenna element corresponding to another high frequency band is set to a posture as low as possible, By accommodating and installing inside the antenna of the lowest frequency band so as to be completely hidden, the size of the antenna can be made within the size of the antenna corresponding to the lowest frequency band, so it is very easy to have a low posture. A frequency sharing antenna device can be realized.
[0039]
In addition, since a parasitic element that does not need to be directly fed is used except for one frequency band, the structure can be simplified. Furthermore, the design method according to the priority of resonance in the frequency band has been clarified, and the multi-frequency shared antenna apparatus can cope with various requirements.
At the same time, various types of antenna elements can be used, and the degree of design freedom is high.
[Brief description of the drawings]
FIG. 1 is a perspective view of a three-frequency shared antenna apparatus showing a basic configuration of the multi-frequency shared antenna apparatus of the present invention.
FIG. 2 (a) is a perspective view showing a configuration of an antenna device in which three frequency bands of 800 MHz, 1.5 GHz, and 2 GHz are shared, showing an embodiment of the multi-frequency shared antenna device of the present invention; FIG. 2B is an enlarged view of a portion A in FIG.
3 is a diagram showing a frequency versus return loss characteristic of the antenna apparatus of FIG. 2. FIG.
4 is a diagram showing directivity at a frequency of 800 MHz of the antenna apparatus of FIG. 2, FIG. 4 (a) is a diagram showing the directivity on the vertical plane, and FIG. 4 (b) is a diagram showing the directivity on each horizontal plane. It is.
5 is a diagram showing directivity at 1.5 GHz of the antenna apparatus of FIG. 2, FIG. 5 (a) is a diagram showing directivity on a vertical plane, and FIG. 5 (b) is a diagram showing directivity on each horizontal plane. FIG.
6 is a diagram showing directivity at 2 GHz of the antenna apparatus of FIG. 2, FIG. 6 (a) is a diagram showing vertical plane directivity, and FIG. 6 (b) is a diagram showing respective directivities on a horizontal plane. is there.
FIG. 7 is a perspective view showing a conventional quarter-wave monopole antenna.
FIG. 8 is a perspective view showing a conventional capacity-loaded monopole antenna.
FIG. 9 is a perspective view showing a conventional dual-frequency batch antenna.
[Explanation of symbols]
1 1/4 wavelength monopole antenna 2 Ground plate 3, 12, 13 Capacity loaded monopole antenna 3a Disk (feeding element)
3b, 12b, 13b, 32b, 33b, 34b Vertical element component 11 Multi-frequency shared antenna device 12a, 13a, 33a, 34a Parallel element component 26 Short pin 27 Space 31 Three-frequency shared antenna device 32 Disc type capacity loaded monopole antenna 33, 34 L-type deformed capacity loaded monopole antenna 32a Feeding element

Claims (4)

A ground plate, a vertical element component suspended from the ground plate in a form insulated from the ground plate, and a plate-like antenna element connected to the vertical element component in a form parallel to the ground plate, A capacity loaded monopole antenna for the lowest frequency band corresponding to the lowest frequency band of
A first frequency band antenna pair each corresponding to a first, second,..., Nth (n is an integer of 2 or more) frequency band having a frequency higher than the lowest frequency band; A pair of antennas for two frequency bands, and a pair of antennas for the nth frequency band;
Of the antenna pairs, the i-th (i is 1, 2,... N) frequency band antenna pair is parallel to the vertical element component of the lowest frequency band capacity-loaded monopole antenna. And a pair of parallel element components parallel to the ground plate, and the i-th frequency band antenna pair is for the lowest frequency band. Between the ground plate and the plate-like antenna element of the capacity-loaded monopole antenna, symmetrically arranged around the vertical element component of the capacity-loaded monopole antenna for the lowest frequency band,
Further, the first frequency band antenna pair, the second frequency band antenna pair,..., The nth frequency band antenna pair are the vertical element component to which the parallel element component corresponds. It is configured so as to form a fan shape that spreads from the side toward the tip side, and the parallel element components have the same height with respect to the ground plate,
A multi-frequency shared antenna apparatus configured to feed power to the minimum frequency band capacity-loaded monopole antenna.   2. The multi-frequency according to claim 1, wherein the minimum frequency band capacity-loaded monopole antenna includes an impedance matching short pin interposed between the plate antenna element and the ground plate. Shared antenna device.   The multi-frequency shared antenna apparatus according to claim 1, wherein a ground plate and a plate-like antenna element of the capacity loaded monopole antenna for the lowest frequency band are each formed in a circular shape. The multi-frequency shared antenna apparatus according to claim 1, wherein the pair of antennas is a pair of capacitively loaded monopole antennas.

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