JPH11154822A - Radio antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the radiation pattern of a desired 'character 8' characteristic, without lowering the radiation efficiency of each antenna by erecting plural antenna elements vertically on a ground plate at prescribed intervals and fixing or integrally forming the ground plates to the ground plate to/with an insulating plate which is divided so that each of the antenna elements are located at the center. SOLUTION: Four ground plates 11 to 14 which are squares in which one side is L3 are arranged on an insulating plate 20 with a gap 'd', and antenna elements 21 to 24 with each antenna length 11 to 14 respectively are elected at the center of each plate 11 to 14. The plate 11 and the element 21 to the plate 14 and the element 24 are monopole antennas, which respectively have different frequency bands. For instance, in the monopole antenna, a radiation pattern (B) in x-z plane of the plate 11 and the element 21 suppresses the radiation in an x-direction while radiating well in a z-direction. Consequently, it is possible to reduce the disturbance of the radiation patterns and to make the antennas small and low attitude.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio antenna used for a radio base station or a relay device of a cellular phone system, a pager system, etc., and in particular, antennas in two or more different frequency bands operate simultaneously. The present invention relates to a wireless antenna configured as described above.

[0002]

2. Description of the Related Art For example, when a small radio base station or a booster (relay device) of a cellular phone system is installed in an underground shopping mall or a building, the radio antennas to be installed are provided for each operating frequency of a plurality of service companies and An antenna is provided for each transmission / reception frequency band, and a plurality of antennas are housed in one radio case.

For example, in an 800 MHz band and a 1.5 GHz band mobile phone system, the antenna element for each system and for each frequency band for transmission and reception is mounted by sharing the same ground plate, thereby facilitating manufacture and cost. In consideration of the down, the ground plate is configured to double as a part of the wireless device case.

FIG. 5 is a perspective view (A) showing a configuration example of a conventional radio antenna to which a plurality of antenna elements are attached, and FIG. In the configuration example of this conventional wireless antenna, a monopole antenna, which is the basis of various types of antennas using a ground plate (or ground plane), has been described as an example. In the figure, reference numeral 1 denotes a common ground plate for four monopole antennas, and reference numerals 21 to 24 denote antenna elements having different lengths corresponding to transmission / reception frequencies. For example, four monopole antenna elements 21 to 24 are arranged on a square ground plate 1 having a side L ₀ of 12 cm. Each of the antenna elements 21 to 24 to a position a distance L ₂ is about 4.2cm from the center point O of the ground plate 1, are arranged at mutual spacing L ₁ = 6 cm. The length of each antenna element is l
₁ = 50 mm, l ₂ = 52 mm, l ₃ = 79 mm, l ₄ = 91
mm, 820 MHz, 950 MHz, 1440 MHz, 149
It is a 1/4 wavelength monopole antenna element corresponding to the frequency band of 0 MHz. Although power is supplied between the base of each of the antenna elements 21 to 24 and the ground plate 1, illustration is omitted.

FIG. 5B shows the radiation characteristic of the antenna element 21 in the 1490 MHz band. Only the monopole antenna element 21 having a length l ₁ = 50 mm is fed, and the other three antennas are open (open). ).

Originally, a monopole antenna is an antenna in which a rod-shaped antenna element is set up vertically on a metal grounding plate and feeds power between the base of the antenna element and the grounding plate. The best radiation characteristics can be obtained when standing. That is, the radiation does not radiate in the axial direction (z direction) of the antenna, but is perpendicular to the axis (x of the coordinate axis in FIG. 5A).
It radiates best on the y-plane) and has the "figure eight" characteristic.

As described above, when the booster antenna is installed on the ceiling of an underground mall or the like, it is better to radiate in a direction parallel to the ceiling and to radiate as little as possible directly below the antenna for the sake of communication. The reason that the amount of radiation may be small just below the antenna is that when the mobile device approaches the vicinity immediately below the antenna, there is a reflection or a scattered wave, and transmission and reception can be sufficiently performed. Conversely, if there is a lot of radiation directly below the antenna, when the mobile unit approaches the antenna, the AGC of the booster will operate to reduce the transmission output, shorten the communication distance and allow other mobile units in the same zone to talk. May disappear.

As shown in FIG. 5B, the radiation pattern on the xz plane by the element 21 of the wireless antenna shown in FIG. 5A has a small ground plane and each monopole antenna element is located at the center of the ground plane. This indicates that the radiation pattern is significantly disturbed because of the lack of this, and that the original "eight-character" characteristic of the monopole antenna cannot be obtained.

FIG. 6 shows, for comparison, the same l ₀ = 50 mm as the antenna element 21 at the center (point O) of the ground plate 1 having the same size (L ₀ × L ₀ ) as that of FIG. FIG. 5A is a configuration diagram when one rod-shaped antenna element 2 is arranged, and FIG. 6B is a radiation pattern characteristic diagram on the xz plane. As shown in FIG.
If the antenna element 2 is located at the center of the ground plate 1, the radiation pattern on the xz plane has a "figure eight" characteristic.

[0010]

As described above, in the configuration of a conventional radio antenna having a plurality of antenna elements having different frequencies from each other, since the plurality of antenna elements share one ground plate, Is arranged at a position away from the center of the ground plate, and since the ground plate is asymmetric with respect to each antenna element, there is a disadvantage that the radiation pattern of each antenna is greatly disturbed and a desired radiation pattern cannot be obtained. .

On the other hand, since the above-mentioned radio antenna is mounted on the ceiling of an underground shopping mall or the like, it is desired that the height of the antenna be reduced to reduce the size and the posture. Therefore, for example, the shape of the antenna element is changed into a helical shape, surrounded by a dielectric coating, a capacitor plate is added, a short-circuit pin is added, or a matching circuit is provided to adjust the resonance (tuning) frequency. Accordingly, a device for shortening the antenna element to lower the height has been devised. However, even if the antenna element itself is miniaturized, in a configuration in which a plurality of antenna elements are mounted on one ground plate, as described above, the radiation efficiency of each antenna is poor, and there is a limit to miniaturization and low attitude. There is a problem.

An object of the present invention is to reduce the size of a plurality of antenna elements provided on one ground plate and having different frequency bands,
It is an object of the present invention to provide a wireless antenna that overcomes the limitation of lowering the attitude and obtains a radiation pattern having a desired “figure-eight” characteristic without reducing the radiation efficiency of each antenna.

[0013]

According to the radio antenna of the present invention, a plurality of antenna elements of mutually different frequency bands are set up vertically on a ground plate at a predetermined interval, and the base of the antenna element and the ground plate are connected to each other. In the wireless antenna for feeding power therebetween, the ground plate is divided so that each of the antenna elements is located at a central portion, and is fixed or integrally formed on an insulating plate.

Further, in the radio antenna according to the present invention, the ground plate is provided with a notch such that each of the antenna elements is located at the center.

Further, the shape of the cut is a cross shape, the shape of the cut is an "H" shape, or the shape of the cut is a "river" shape. is there.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view (A) showing a first embodiment of the present invention and a diagram (B) showing an example of radiation characteristics. In the figure, a square ground plate of each 11 to 14 with a side L _3, 20 denotes an insulating plate, 21 to 24 is a monopole antenna element erected on each of the central portion of the ground plate 11 to 14. l _{1 to} l ₄ are the lengths of the antenna elements 21 to 24 and are _１ ／ of the wavelength λ of the transmission / reception frequency band. d is a gap between the ground plates.

In the first embodiment, the conventional ground plate 1 shown in FIG. 5 is divided into four parts in a cross shape, and they are arranged on an insulating plate 20 with a gap d therebetween. Actually, specific examples of the four ground plates 11 to 14 are a method of providing a narrow gap d and fixing them to an insulating case made of plastic or the like. It is realized by a method of dividing and integrally forming.

Further, although the antenna element of the first embodiment is shown in FIG. 1 as monopole antenna elements 21 to 24, similar effects can be obtained with antenna elements of other shapes using a ground plate. It is clear that it can be obtained.

The specific dimensions of the first embodiment shown in FIG. 1 are four square ground plates 11 to 14 each having a side L ₃ of 6 cm.
Are arranged at intervals d of 5 mm, and each antenna length is l ₁ = 50 mm, l ₂ = 52 mm, l
The antenna elements 21 to 24 of ₃ = 79 mm and l ₄ = 91 mm were set up. The ground plate 11 and the antenna element 21 are 1.5 GHz
Band 1490MHz monopole antenna, ground plate 12
The antenna element 22 is a monopole antenna for 1.5 GHz band for 1440 MHz, the ground plate 13 and the antenna element 23 are a monopole antenna for 800 MHz band for 950 MHz, and the ground plate 14 and the antenna element 24 are 820 MHz band for 820 MHz.
This is a monopole antenna for z.

FIG. 1B is a radiation pattern diagram on the xz plane of the monopole antenna formed by the ground plate 11 and the antenna element 21 (l ₁ = 50 mm) in the radio antenna of FIG.
Power is supplied only to a 50 mm long monopole antenna, and the other 3
The antenna of the book has characteristics in an open state (open). The characteristics of the conventional antenna configuration shown in FIG.
Compared with (B)), the radiation in the axial direction (z direction) is greatly suppressed, and the radiation is best performed in the direction perpendicular to the axis (xy plane). The difference in radiation intensity between the direction of x <0 and the direction of x> 0 is due to the influence of the three non-feed antennas.

FIG. 2 is a perspective view (A) and a radiation characteristic example (B) showing a second embodiment of the present invention. In the figure, 10
Is a square ground plate having one side L ₀ , and 15 is a cross-shaped notch of length L ₄ provided on the ground plate 10. Reference numerals 21 to 24 denote monopole antenna elements, each of which is erected at the center of each of the four sections divided by the cross-shaped cut 15.

The second embodiment has a configuration in which a cross-shaped cut 15 is formed in the ground plate 1 having the conventional configuration shown in FIG. The longer the cut length L ₄ is, the better, but a small gap g is left so as not to separate into four. In the second embodiment, the same effect as that of the first embodiment in which the ground plate is divided into four is obtained, and the disturbance of the radiation pattern due to the asymmetric characteristic of the ground plate can be avoided. The configuration in which the notch is formed in the ground plate may simply be formed in the conventional ground plate without changing the configuration of the conventional wireless antenna. Another specific example of the ground plate can be realized by using a printed circuit board.

Also in the case of the second embodiment, it is apparent that similar effects can be obtained by using antenna elements 21 to 24 of other shapes using a ground plate instead of monopole antenna elements. .

The specific dimensions of the second embodiment of FIG. 2, the width side L ₀ is the center of the ground plate 10 of 12cm square d = 5
An mm cross-shaped cut 15 was made. It should be noted, was a 11cm the length L ₄ of the cut both vertically and horizontally. The gap g is about 5 mm. The four monopole antenna elements 2
1 to 24, and each antenna element is connected to the ground plate 1
It is arranged at a position of about 4.2 cm from the center of 0 and at intervals of 6 cm. The length of each antenna element is 50mm, 5
They are 2 mm, 79 mm, and 91 mm, and are monopole antennas for transmission and reception in different frequency bands.

FIG. 2B is a radiation pattern diagram on the xz plane of the antenna element 21 in the wireless antenna of FIG. 2A, in which power is supplied only to a monopole antenna having a length of 50 mm, and the other three antennas This is a characteristic in an open state (open). Compared to the characteristics of the conventional antenna configuration shown in FIG. 5 (FIG. 5B), the radiation in the axial direction (z direction) is greatly suppressed, and the radiation is best in the direction perpendicular to the axis (xy plane). ing. x <
The difference in radiation intensity between the direction of 0 and the direction of x> 0 is as follows.
This is the effect of three non-feed antennas.

The reason why the "figure eight" characteristic is slightly inclined to the left is that the ground plate 10 is not completely separated into four monopole antennas. That is, the length L ₄ of the cut 15 has a great effect on the effect of improving the radiation pattern, and therefore, the cut should be made as long as possible.

For example, FIG. 3 is a radiation pattern diagram on the xz plane when the length L ₄ of the cut 15 is 10 cm both vertically and horizontally. In this example, the length L ₄ of the cut 15 in FIG.
This is an example in which the inclination (counterclockwise rotation) of the “figure of eight” characteristic is slightly larger than in the case of FIG.

FIG. 4 is a plan view showing another embodiment of the present invention, which is another embodiment having a different cut shape from the cut of the second embodiment. (A), an H-shaped notch 16 is provided in the grounding plate 30, and monopole antenna elements 33 and 34 of, for example, a low frequency 800 _MHz band are provided in the center of the left and right portions having a large divided area. In this example, monopole antenna elements 31 and 32 of a high frequency band of 1.5 GHz are provided at the center of a small upper and lower central portion.

FIG. 4B shows an example in which river-shaped cuts 17 to 19 are provided in the ground plate 40, and antenna elements 41 to 44 are provided in the center of the four divided sections.

As described above, the above embodiment has been described with reference to the case of a monopole antenna. However, similar effects can be obtained in the case of an antenna element of another shape using a ground plate.

[0031]

According to the present invention, it is possible to reduce the disturbance of the radiation pattern caused by the antenna being located off the center on the ground plate, and to further reduce the size and the posture. There is an extremely large effect in practical use.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure and a characteristic example showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a structure and characteristic examples according to a second embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a second embodiment of the present invention.

FIG. 4 is a plan view showing another example of the second embodiment of the present invention.

FIG. 5 is a diagram showing an example of the structure and characteristics of a conventional antenna.

FIG. 6 shows a structural example and a characteristic example diagram of one monopole antenna.

[Explanation of symbols]

 1, 10, 11, 12, 13, 14 Ground plate 2, 21, 22, 23, 24 Antenna element 15 Cross cut 16 H cut 17, 18, 19 Cut 20 Insulating plate 30 Ground plate 31, 32, 33, 34 antenna element 40 ground plate 41, 42, 43, 44 antenna element

Claims (5)

[Claims] 1. A radio antenna in which a plurality of antenna elements of mutually different frequency bands stand vertically on a ground plate at a predetermined interval and feed power between a base of the antenna element and the ground plate. Is a radio antenna, wherein each of the antenna elements is divided so as to be located at a central portion and fixed or integrally formed on an insulating plate. 2. The wireless antenna according to claim 1, wherein the ground plate is provided with a notch such that each of the antenna elements is located at a central portion. 3. The wireless antenna according to claim 2, wherein the cut has a cross shape. 4. The wireless antenna according to claim 2, wherein the shape of the cut is an “H” shape. 5. The wireless antenna according to claim 2, wherein the shape of the cut is a “river” shape.