JPH0766618A - Sleeve load type beam tilt antenna - Google Patents

Abstract

PURPOSE:To form a simple-structured sleeve load type beam tilt antenna provided with sufficient characteristics as a beam tilt antenna capable of being miniaturized and made light in weight whose construction and maintenance are easy. CONSTITUTION:When the wavelength of the radio waves of a using frequency band is defined as lambda, this antenna is provided with a linear antenna main body A whose total length is approximately 3lambda/2 and a sleeve load B loaded coaxially with the antenna main body A in a range from the maximum point of current wave distribution at the position of 3lambda/4 from the vertex of the antenna main body A to the position of lambda/2 from the vertex of the antenna main body A. By letting the phase of the second current wave 12 of lambda/2 for which the vertex of the sleeve load B is a base point lag behind the phase of the first current wave I1 of lambda/2 for which the vertex of the antenna main body A is the base point, a beam tilt angle thetat is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna applied to a mobile communication system such as a car phone and a mobile phone,
The present invention mainly relates to a sleeve load type beam tilt antenna suitable as a base station antenna.

[0002]

2. Description of the Related Art Recently, mobile communication systems have become extremely popular. In this mobile communication system, which is a so-called cellular system, it is necessary to limit one zone to a considerably small size in order to effectively use radio waves. If the zone gets smaller, the radio waves from the base station will
The chances of leaking outside the zone are increased. In order to prevent this, the directivity of the antenna in the base station is required to be downward from the horizontal direction, and so-called beam tilt is required.

FIG. 12 is a diagram showing an example of a conventional beam tilting means. In this example, two dipole antenna elements 1 and 2 are arranged vertically in a line, and the second antenna elements 2 arranged on the lower side with respect to the current wave phase of the first antenna element 1 arranged on the upper side. In order to delay the current wave phase and tilt the beam, the electrical length L2 of the power feeding cable 4 of the second antenna element 2 is required to the electrical length L1 of the power feeding cable 3 of the first antenna element 1, and the required beam tilt angle θ
It is lengthened according to t.

[0004]

The above-mentioned conventional beam tilt antenna is of a so-called parallel feeding system, and the excitation current I1 of the first antenna element 1 and the second antenna element 2 are used.
Since it is necessary to variably adjust the electrical lengths of the power supply cables 3 and 4 in order to have a phase difference with the excitation current I2 of, the structure is complicated, and much labor is required for assembly.
Problems also tend to occur in maintenance. Particularly when an array antenna is used to increase the gain of the antenna, it is apparent that the structure is further complicated in combination with the need to sufficiently improve the processing accuracy of the feeding cables 3 and 4.

An object of the present invention is to provide a sleeve load type beam tilt antenna which has sufficient characteristics as a beam tilt antenna, has a simple structure, can be reduced in size and weight, and can be manufactured and maintained easily. Especially.

[0006]

In order to solve the above problems and achieve the object, the following measures were taken in the present invention. (1) When the wavelength of the radio wave in the operating frequency band is λ, the linear antenna body with a total length of about 3λ / 2 and the current wave distribution at the position 3λ / 4 from the apex of this antenna body A sleeve that is coaxially loaded with the antenna body in a range from the maximum point to the position of λ / 2 from the apex of the antenna body, the first current of λ / 2 having the apex of the antenna body as a base point. A beam tilt is generated by delaying the phase of the second current wave of λ / 2 with the open end of the sleeve as a base point with respect to the phase of the wave.

(2) In the above antenna, the sleeve is
The open end side is located on the apex side of the antenna body, and the short-circuited end side is located on the base end side of the antenna body.

(3) In the above antenna, when the electric length of the sleeve is kλ / 4, k is set within the range of k ≦ 1. (4) In the above antenna, by adjusting the impedance of the sleeve, the amplitude ratio between the first current wave and the second current wave is changed, and the half-value angle of the radiation beam is variably set. (5) The antenna having the configuration described in (1) above is arranged concentrically in multiple stages.

[0009]

As a result of taking the above-mentioned means, the following effects occur. Since the one of the present invention is not the parallel power feeding system like the conventional one but the series power feeding system, the structure is simplified,
It is possible to reduce the weight, and it is possible to reduce the processing man-hours during production. Further, since it is a combination of the linear antenna body and the sleeve, no problem occurs in terms of mechanical strength, durability is high, and maintenance is easy.

[0010]

1 (a) and 1 (b) are views showing the structure of a sleeve load type beam tilt antenna according to a first embodiment of the present invention. As shown in FIG. 1A, in this embodiment, when a spell top C is attached to the base end of an antenna body A to form a non-grounded antenna, and the wavelength of radio waves in the operating frequency band is λ, The feeding point is λ / 4 from the base end of the antenna body A.
And the distance La from the apex of the antenna body A to the open end of the sleeve load B with the amplitude ratio close to 1,
It is adjusted and set in the range from λ / 2 to 11λ / 16. When the device of this example was actually measured, a result close to the theoretical value was obtained. The details will be specifically described below.

As shown in FIGS. 1 (a) and 1 (b), this antenna includes a first antenna section 10, a second antenna section 20, a spell top section 30 for blocking an unbalanced current, and a feeding coaxial cable 40. It consists of

The first antenna section 10 is formed mainly of an antenna element 11 made of a cylindrical conductor, and its lower end 12 is formed.
Is connected to the tip of the center conductor 41 of the power feeding coaxial cable 40.

The second antenna section 20 comprises a sleeve 21 and a pipe 24. The sleeve 21 has an open end 22 at the upper end and a short-circuit end 23 at the lower end,
The open end 22 is arranged so as to face the lower end of the antenna element 11 of the first antenna unit 10 with a small gap g, and the short-circuited end 23 is connected to the central conductor 41 of the coaxial cable 40. There is. The length of the sleeve 21 is set to kλ / 4 (k ≦ 1). Pipe 24
Has its upper end located at a small distance from the short-circuited end 23 of the sleeve 21, and its lower end at the coaxial cable 4
0 to the outer conductor 42.

The spell top portion 30 has an open end portion 32 at the upper end of the tubular body 31 and a short circuit end portion 33 at the lower end of the tubular body 31, and the short circuit end portion 33 is connected to the pipe 24. The open end 32 of the spell top portion 30 is located at a position λ / 2 apart from the open upper end 22 of the sleeve 21, where λ is the wavelength of the radio wave in the used frequency band. The short-circuited end 33 is fixed to the pipe 24.

From the top of the antenna element 11 to the sleeve 21
When the distance La to the open end 22 is about 3λ / 4, the current wave phase of the first antenna unit 10 and the current wave phase of the second antenna unit 20 are in phase. When La is about λ / 2, the current wave of the second antenna unit 20 is delayed by about 180 ° with respect to the current wave of the first antenna unit 10. La above is 3λ
By changing from / 4 to λ / 2, a predetermined phase difference occurs between the current wave of the first antenna unit 10 and the current wave of the second antenna unit 20, and the beam tilt angle θt corresponding thereto is obtained.

The impedance value of the sleeve 21 is determined by the outer diameter d1 of the central conductor 41 of the coaxial cable 40 and the sleeve 2
It is determined by the ratio "d1 / d2" to the inner diameter d2 of 1 and the electrical length kλ / 4 of the sleeve 21.

In the present embodiment, k ≦ 1, and the amplitude ratio of the first current wave I1 on the first antenna section 10 and the second current wave I2 on the second antenna section 20 is 1 The impedance is adjusted so that it approaches. When the impedance is high, the amplitude ratio becomes smaller than 1, and the beam half-value angle and the gain change. That is, the half-value angle becomes broad and the gain decreases.

Next, the operation of the first embodiment will be described with reference to FIGS. 2 and 3 as appropriate. First, a principle explanation will be given.
As shown in FIG. 2A, when the phase of the second current wave I2 in the second antenna unit 20 is delayed with respect to the first current wave I1 in the linearly arranged first antenna unit 10, A radiation beam is obtained which is downward with respect to the horizontal direction. Here, assuming that I1 and I2 have the same amplitude, I1
When the beam pattern was calculated by changing the phase difference between I2 and I2, a beam tilt angle of 8 ° to 20 ° with respect to the horizontal direction was obtained with a phase difference of 45 ° to 135 °.

As shown in FIG. 2B, by loading the sleeve load B on the antenna main body A, a current wave distribution having a phase and an amplitude as shown in FIGS. 2C and 2D is obtained. Then, the amplitude ratio and the phase difference are defined as amplitude ratio: | I1 | / | I2 | (1) Phase difference: FI1 -FI2 (2). In the above formula (2), FI1
-FI2 = 0 That is, when the sleeve 21 is loaded as the load B so as to be in phase, the state shown in FIG. 3B is obtained. That is, if the open end 22 of the sleeve 21 (hereinafter, this end position is represented by P) is located at the maximum point of the reverse phase current I3 in FIG.
The phase difference between I1 and I2 is zero, that is, in phase, and the beam is horizontal. At this time, if the length from the upper end of the antenna body A to the position P of the open end portion 22 of the sleeve 21 is La, this La becomes 3λ / 4 when the wavelength is λ.

When La is changed from 3λ / 4 shown in FIG. 3C to λ / 2 shown in FIG. 3D, I1
The phase difference between I2 and I2 changes from the in-phase state to about 180 °. When La was changed from λ / 2 to 9λ / 16, a current wave distribution with a phase difference of 45 ° to 135 ° could be obtained. By adjusting the length of La in this way, the phase difference of I2 with respect to I1 can be adjusted.

Further, the length of the sleeve 21 is set to kλ / 4 (k ≦
1), the impedance of the sleeve 21 can be adjusted by changing the value of k.
First, the antenna becomes capacitive when k> 1, and the antenna becomes inductive when k <1 so that the impedance can be adjusted.

Now, assuming that the value of k is changed in the range of k = 0.78 to 1.08 to obtain the impedance of the sleeve 21, and the lumped constant load having the impedance is loaded on the antenna. , Sleeve length is 0.
It was found that the amplitude ratio was close to 1.0 in the range of 86λ / 4 to 0.88λ / 4.

Thus, the phase difference is changed by adjusting the value of La, the impedance is changed by adjusting the length of the sleeve 21, and the gain is optimized by bringing the amplitude ratio of I1 and I2 close to 1. By doing,
The beam tilt angle θt can be adjusted and set to a required value.

Specifically, for example, La is λ / 2 to 9λ
/ 16 range and the length of the sleeve 21 is kλ / 4
When (k = 0.86 to 0.88) and the amplitude ratio is brought close to 1, a current wave distribution with a phase difference of 45 ° to 135 ° is obtained, and a beam tilt effect of about 10 ° to 25 ° is obtained. I was able to. The gain at this time was about 4 dBi.

The following table shows the cases (1) to (1) when La and k are changed when the frequency used is 900 MHz.
It is the table which calculated each theoretical value about (6). (1) (2) (3) (4) (5) (6) La [λ] ………… 16/32 17/32 18/32 19/32 21/32 22/32 k …………… ……… 0.88 0.88 0.86 0.82 0.78 0.74 Load Z [Ω] …… j330.8 j330.8 j278.1 j206.6 j164.1 j135.0 Amplitude ratio ……………… 0.79 0.69 0.77 0.95 0.78 0.77 Phase difference [°] ………… 108 71 47 26 13 6 Tilt angle [°] ………… 23 15 10 7 3 1 Gain [dBi] …… 3.96 4.24 4.57 4.81 4.57 4.14 Fig. 4 (a) (b) (c) ) -FIG. 9 (a) (b) (c)
Is the phase difference (a) corresponding to the cases (1) to (6) in the table above.
It is a figure which shows the measurement example of the amplitude ratio (b), and each vertical in-plane radiation pattern (c) corresponding to this.

10 (a) and 10 (b), the sleeve 21 is
Second invention of the present invention
It is a figure which shows the structure and vertical in-plane radiation pattern of an Example. In the second embodiment, the gain is 6.4 dBi,
An antenna having a tilt angle θt of 24 ° was obtained.

11 (a) and 11 (b) also show the sleeve 2
It is a figure which shows the structure and vertical in-plane radiation pattern of the 3rd Example of this invention used as the high gain antenna of 4 steps | paragraphs using 3 pieces. In the third embodiment, the values of La and k are the second.
It differs from the embodiment. In this third embodiment,
An antenna having a gain of 7.15 dBi and a tilt angle θt of 7 ° was obtained. The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0028]

Since the sleeve load type beam tilt antenna of the present invention is of the series feeding type, not the conventional parallel feeding type, the structure can be simplified and the weight can be reduced. The number of processing steps can be reduced. Further, since it is a combination of the linear antenna body and the sleeve, no problem occurs in terms of mechanical strength, durability is high, and maintenance is easy. Thus, according to the present invention, it is possible to provide a sleeve load type beam tilt antenna which has sufficient characteristics as a beam tilt antenna, has a simple structure, can be reduced in size and weight, and can be manufactured and maintained easily.

[Brief description of drawings]

1A and 1B are a perspective view and a sectional view showing a configuration of a sleeve load type beam tilt antenna according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory view of the sleeve load type beam tilt antenna according to the first embodiment.

FIG. 3 is an operation explanatory view of the sleeve load type beam tilt antenna according to the first embodiment.

FIG. 4 is a diagram showing characteristics of the sleeve load type beam tilt antenna according to the first embodiment.

FIG. 5 is a diagram showing characteristics of the sleeve load type beam tilt antenna according to the first embodiment.

FIG. 6 is a diagram showing characteristics of the sleeve load type beam tilt antenna according to the first embodiment.

FIG. 7 is a diagram showing characteristics of the sleeve load type beam tilt antenna according to the first embodiment.

FIG. 8 is a diagram showing characteristics of the sleeve load type beam tilt antenna according to the first embodiment.

FIG. 9 is a diagram showing characteristics of the sleeve load type beam tilt antenna according to the first embodiment.

10A and 10B are a side view and a vertical in-plane radiation pattern diagram showing a configuration of a sleeve load type beam tilt antenna according to a second embodiment of the present invention.

11A and 11B are a side view and a vertical in-plane radiation pattern diagram showing a configuration of a sleeve load type beam tilt antenna according to a third embodiment of the present invention.

FIG. 12 is a schematic diagram showing a configuration of a conventional example.

[Explanation of symbols] A ... Antenna body B ... Sleeve load
C ... Supertop 10 ... First antenna section 11 ... Antenna element 2
0 ... 2nd antenna part 21 ... Sleeve 22 ... Open end 2
3 ... Short-circuited end part 30 ... Spell top part 40 ... Coaxial cable 41 for feeding 41 ... Center conductor 42 ... Outer conductor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nobuyo Nakano 1 Honjo-cho, Saga City, Saga Prefecture, Department of Electronics Engineering, Faculty of Science and Engineering, Saga University (72) Yoshimizu Egashira 4-1713 Minamioi, Shinagawa-ku, Tokyo Harada Industry Co., Ltd.

Claims (5)

[Claims] 1. A linear antenna body having a total length of about 3λ / 2, where λ is a wavelength of a radio wave in a frequency band used, and a current wave at a position 3λ / 4 from the apex of the antenna body. A sleeve coaxially loaded with the antenna body in a range from the maximum point of the distribution to the position of λ / 2 from the apex of the antenna body, and λ / 2 with the apex of the antenna body as a base point.
A beam load is generated by delaying the phase of the second current wave of λ / 2 with the open end of the sleeve as the base point with respect to the phase of the first current wave of Beam tilt antenna. 2. The sleeve is mounted so that the open end side is located at the apex side of the antenna body and the short-circuited end side is located at the base side of the antenna body. The sleeve load type beam tilt antenna described in. 3. When the electrical length of the sleeve is kλ / 4,
The sleeve load type beam tilt antenna according to claim 1, wherein k is set in a range of k ≦ 1. 4. The half-value angle of the radiation beam is variably set by changing the amplitude ratio of the first current wave and the second current wave by adjusting the impedance of the sleeve. The described sleeve load type beam tilt antenna. 5. A sleeve load type beam tilt antenna, wherein the antenna according to claim 1 is arranged concentrically in a plurality of stages.