JPH10126144A - Antenna for mobile radio system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means that employs one choke to block the leakage of an unbalanced current to a coaxial feeder, requires a small required space with a simplified structure in the case, when feeding is applied to a plurality of the coaxial feeders to a plurality of antenna elements of vertical diversity configuration. SOLUTION: A first coaxial feeder 14 is inserted through a sleeve 13 at a lower part of a 1st antenna 11 and energized almost in the middle of sleeves 12, 13. A 2nd coaxial feeder 24 is inserted through sleeves 13, 12, 23, energized nearly in the middle of sleeves 22, 23 of a 2nd antenna 21. A lower part of a choke 19 is connected to outer conductors 17, 27 of the coaxial feeders 14, 24 at the lower part of the 1st and 2nd antennas 11, 21, so as to constitute a distance between a feeding point of the 1st antenna 11 and a feeding point of the 2nd antenna 12 to be set to 0.5nλ, and a distance between the feeding point of the 1st antenna 11 and a connecting point of the choke 19 to the outer conductors 17, 27 to be set to 3λ/4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile radio antenna which can be used to prevent leakage current to a coaxial feed line in a mobile radio antenna having a vertical diversity configuration in which a plurality of antenna elements are vertically arranged. Things.

[0002]

2. Description of the Related Art Conventionally, as an antenna used for a fixed station for mobile radio, since the position of the mobile station is unspecified and the radio wave state changes every moment, a plurality of antennas are used to obtain a stable reception state. 2. Description of the Related Art A vertical diversity configuration in which two antennas are arranged vertically apart and the output of an antenna having a better radio wave reception state is switched and received is often used.

FIG. 2 is a cross-sectional view of a vertical diversity antenna for mobile radio according to the prior art. In FIG. 2, the coaxial feed line 34 for the first antenna 31 passes through the inside of the sleeve 33 below the first antenna 31, and the inner conductor 35 is connected to the upper sleeve 32 at the feed point 36. The outer conductor 37 is connected to the lower sleeve 33 at a feed point 38.

A coaxial feed line 44 for the second antenna 41 passes through the sleeves 33 and 32 of the first antenna 31, passes through a sleeve 43 below the second antenna 41, and an inner conductor 45 is connected to a feeding point 46. Is connected to the upper sleeve 42 at
The outer conductor 47 of the coaxial feed line 44 is connected to the lower sleeve 43 at a feed point 48. Further, an approximate interval considered to be sufficient to enhance the effect of space diversity is provided between the first antenna 31 and the second antenna 41.

A first choke 39 having a quarter wavelength is connected to the outer conductor 37 at a connection point 40 below the coaxial feed line 34 for the first antenna, and the coaxial feed line 34 for the second antenna is provided. A second choke 49 of a quarter wavelength is connected to the outer conductor 47 at a connection point 50 below the electric wire 44, and the respective positions will be described later.

The operation is described below, and its operation will be described below. The first antenna 31 is provided by the coaxial feed line 34.
Are fed, and the two sleeves 4 of the second antenna 41 are fed by the coaxial feed line 44.
2, 43 are powered.

At this time, a leakage current flows through the outer conductor 37 of the coaxial feed line 34 in accordance with the feeding to the first antenna 31. In addition, a leakage current similarly flows through the outer conductor 47 of the coaxial feeder line 44 with power feeding to the second antenna 41.

Hereinafter, the outer conductor 37 of the first antenna 31
This will be further described with a focus on the leakage current flowing through.

That is, the leakage current flowing through the outer conductor 37 is an unbalanced current when a balanced antenna symmetrical above and below the feed point is fed by an unbalanced coaxial feed line.
Although the sleeve 33 has the function of a balance-unbalance conversion circuit (balun), it leaks due to its imperfection. Since this leakage current has the following adverse effects, it is necessary to minimize the leakage current. (1) There is an uncertain factor in the antenna input impedance. (2) Unwanted radiation due to leakage current disturbs antenna radiation characteristics. (3) In the case of the receiving antenna, unnecessary radio waves such as noises propagate through the outer conductor and enter through the antenna terminal, so that the original purpose of the outer conductor, that is, shielding cannot be fulfilled.

The leakage current flowing through the outer conductor 37 is distributed as shown by a broken line 52 and is in phase with the current distribution 51 of the antenna. The first choke 39 of the quarter wavelength is the connection point 4
0, the outer conductor 3 is connected to the outer conductor 37.
The impedance is theoretically infinite at the open end of the coaxial line formed by regarding the first choke 39 as an inner conductor and the first choke 39 as an outer conductor, that is, the impedance becomes theoretically infinite. 39 indicates that the leakage current is blocked. Also, a broken line 5 is used to satisfy the boundary condition.
The leakage current distributed in the area No. 2 is originally distributed at a half wavelength between the nodal points, but is located on the outer conductor 37 at a quarter wavelength from the end of the sleeve 33 where the amplitude should be maximum. In this case, the first chalk 39 is folded at the open end, and is canceled. However, if the position of the first choke 39 deviates from the position of the quarter wavelength, the leakage current is not canceled, and as a result, the leakage current distribution shown by the broken line 52 becomes apparent. That is, in order to prevent the propagation of the leakage current below the first choke 39 in FIG. 2 and eliminate the leakage current in the quarter wavelength section above the first choke 39, as shown in FIG. It is necessary to maintain the relationship of a quarter wavelength interval. However, in FIG. Note that λ represents a wavelength.

When the feed line 44 of the second antenna 41 passes through the inside of the sleeves 32 and 33 of the first antenna 31, the feed lines are close to each other. If they are distributed, they affect each other and the original performance of the antenna is not exhibited.

Similarly, since the leakage current is also canceled in the area of the dashed line 102, the dimension from the feeding points 46, 48 of the second antenna 41 to the lower end of the second choke 49 is such that n ₂ is an integer of 1 or more. 3λ / 4 + 0.5n ₂ λ
Must be set to

[0013]

However, in the prior art mobile radio antenna as shown in FIG. 2, the unbalanced current is prevented from leaking to the coaxial feed line and leaking to a portion near the feed line as described above. Since a choke is inserted for each coaxial feed line so as to prevent the current from being distributed, two coaxial feed lines are required in the case shown in FIG. 2 because there are two coaxial feed lines in the case shown in FIG. Therefore, there is a disadvantage that it is necessary to keep a space between the chokes at the lower portion of the antenna so that the chokes do not influence each other and reduce the effect, and that a large space is required around the choke. It is well known that the thicker the choke, the wider the effective frequency band becomes. It is necessary to make the choke thicker in order to widen the used frequency band, so that there is a problem that the space is further increased.

The present invention has been made in view of such a conventional problem,
It is an object of the present invention to provide a mobile radio antenna capable of reducing the number of chokes and reducing the required space as compared with the related art.

[0015]

SUMMARY OF THE INVENTION According to the present invention, there is provided a first half-wave vertical sleeve dipole which is substantially centrally fed by a first coaxial feed line, and wherein k is equal to two.
A k-th half-wave vertical sleeve dipole fed substantially centrally by a k-th coaxial feed line passing through the sleeve of the first half-wave vertical sleeve dipole; Substantially four lower ends connected to outer conductors of the first and kth coaxial feed lines below the first and kth half-wave vertical sleeve dipoles.
A choke having a sleeve having a length of one-half wavelength, wherein λ is a wavelength and n is an integer of 1 or more.
The feed point of the 1 / wavelength vertical sleeve dipole and the k-th
The distance between the feeding point of the half-wavelength vertical sleeve dipole and the feeding point of the first half-wavelength vertical sleeve dipole is substantially 0.5 nλ. The mobile radio antenna is configured so that the distance between the coaxial feed line and the connection point with the outer conductor is substantially 3λ / 4.

According to a second aspect of the present invention, there are provided a plurality of halves.
Of the wavelength vertical sleeve dipoles, where t is an integer of 1 or more, a t-th half wavelength vertical sleeve dipole fed substantially at the center by a t-th coaxial feed line, and s is an integer of s> t An s-th half-wave vertical sleeve dipole fed substantially at the center by an s-th coaxial feed line passing through the sleeve of the t-th half-wave vertical sleeve dipole; A choke having a substantially quarter-wave length sleeve connected at its lower end to the outer conductor of said s-th and t-th coaxial feed lines below the t-th half-wave vertical sleeve dipole; Where λ is a wavelength, n is an integer of 1 or more, and n ₁ is 0 or an integer of 1 or more, and the feeding point of the s-th half wavelength vertical sleeve dipole and the t-th half wavelength Power supply for vertical sleeve dipole A connection point between the feed point of the t-th half-wavelength vertical sleeve dipole and the outer conductor of the s-th and t-th coaxial feed lines so that the distance to the point is substantially 0.5 nλ. Is a mobile radio antenna configured to have a distance of 3λ / 4 substantially.

According to a third aspect of the present invention, a plurality of halves are provided.
The first half of a wavelength vertical sleeve dipole
For the wavelength vertical sleeve dipole and any other half wavelength vertical sleeve dipole, the distance between the feeding points of both half wavelength vertical sleeve dipoles is substantially an integral multiple of 0.5λ. And the choke is a shared mobile radio antenna.

According to the first aspect of the present invention, the first half-wavelength vertical sleeve dipole is fed substantially centrally by the first coaxial feed line, and the k-th half-wavelength vertical sleeve dipole is provided. Is fed substantially centrally by a k-th coaxial feed line passing through the sleeve of the first half-wave vertical sleeve dipole, where k is an integer greater than or equal to 2,
A choke is provided substantially below the first and kth half-wavelength vertical sleeve dipoles, the lower end being connected to the outer conductor of the first and kth coaxial feed lines at the lower end.
A feeding point of the first half-wavelength vertical sleeve dipole, and a k-th half-wavelength vertical sleeve dipole, where λ is a wavelength and n is an integer of 1 or more. Between the feed point of the first half-wavelength vertical sleeve dipole and the outer conductors of the first and k-th coaxial feed lines of the choke so that the distance to the feed point is substantially 0.5 nλ. The distance from the connection point is substantially 3λ / 4.

According to the second aspect of the present invention, of the plurality of half-wavelength vertical sleeve dipoles, the t-th half-wavelength vertical sleeve dipole has a t-th coaxial length where t is an integer of 1 or more. Power is supplied substantially at the center by the power supply line,
The s-th half-wave vertical sleeve dipole gives s
> T is fed substantially in the middle by an s-th coaxial feed line passing through the sleeve of the t-th half-wave vertical sleeve dipole as an integer of t, and the choke is driven by the s-th and t-th half-waves. A one-quarter wavelength sleeve having a lower end connected to the outer conductor of the s-th and t-th coaxial feeder lines below the one-sleeve vertical sleeve dipole, wherein λ is the wavelength and n is the wavelength. an integer of 1 or more, the n ₁ 0 or an integer of 1 or more, the distance between the feeding point of the 1-wavelength vertical sleeve dipole half of the s-th half-wave vertical sleeve dipole feeding point and the second t Is substantially 0.5 nλ, and the distance between the feed point of the t-th half-wavelength vertical sleeve dipole and the connection point between the choke and the outer conductors of the s-th and t-th coaxial feed lines is changed. It is configured to be substantially 3λ / 4.

Thus, in order to solve the above-mentioned problem, the mobile radio antenna according to the present invention is provided with, for example, a plurality of half antennas.
At the approximate center of each of the wavelength vertical sleeve dipoles, power is supplied by a coaxial feed line and connected to a choke of one sleeve at the same point of each coaxial feed line, and at the upper end of the choke becomes a node of the leakage current distribution. By setting the length from the connection point with the choke to the feed point and the length between the antenna elements in a predetermined relationship, one choke can be used for a plurality of coaxial feed lines feeding a plurality of antennas. Leakage of unbalanced current to the coaxial feed line can be prevented,
In addition, the leakage current is not distributed in the vicinity of the power supply line, the required space is small, and the structure can be simplified.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a mobile radio antenna having a vertical diversity configuration according to an embodiment of the present invention.

In FIG. 1, the first coaxial feed line 14 for the first antenna 11 is a half-wavelength first antenna 1.
1, the inner conductor 15 is connected to the sleeve 12, which is an upper quarter-wavelength antenna element, at the feed point 16, and the outer conductor 17 of the coaxial feed line 14 is connected to the lower quarter. It is connected to a sleeve 13 which is a one-wavelength antenna element at a feeding point 18.

A second coaxial feed line 24 for the second antenna 21 passes through the sleeves 13 and 12 of the first antenna 11 and passes through a sleeve 23 below the second antenna 21 having a half wavelength. As shown, the inner conductor 25 is connected at the feeding point 26 to the upper quarter-wavelength sleeve 22 as the upper antenna element, and the outer conductor 27 of the coaxial feeder 24 is connected to the lower quarter-wavelength sleeve as the antenna element. 23 is connected to a feeding point 28.

As described above, it is necessary to increase the space between the first antenna 11 and the second antenna 21 to a certain extent in order to enhance the effect of the space diversity. The distance between the feeding points of both antennas is set to 0.5 nλ (where n is an integer of 1 or more).

That is, conventionally, the first antenna 11 and the second antenna
Attention has been paid only to how large the distance between the antenna 21 and the antenna 21 should be secured, and the distance between the feeding points of both antennas affects the number of chokes, which the present inventors have noticed. I wasn't even aware of that. Then, the inventors of the present invention set the interval to 0. 0, based on the awareness that the interval should be related to the wavelength.
It has been noticed that the choke can be made one by setting 5nλ. In this regard,
Further details will be described later.

In FIG. 1, a quarter-wave choke 19 surrounding both feeder lines is provided below the coaxial feeder lines 14 and 24 for the first and second antennas. , 27 are connected. When λ is a wavelength and n is an integer of 1 or more, the distance between the feeding points 16 and 18 of the first antenna 11 and the connecting points 20 and 30 where the choke 19 is connected to the outer conductors 17 and 27 is 3λ / 4. The distance between the feeding points 16 and 18 of the first antenna 11 and the feeding points 26 and 28 of the second antenna 12 is set to 0.5 nλ. Also, the sleeves 12, 13, 22, 23
Are substantially equal in length, but only the sleeve 22 is rod-shaped, for example, the inner conductor of the coaxial feed line 24 may be used as it is.

As described above, the distance between the feeding points between the first antenna 11 and the second antenna 21 is 0.5 n.
A theoretical explanation will be given on the fact that the choke can be united by setting λ.

That is, the region A shown in FIG. 1 is composed of the coaxial feed line 14 of the first antenna and the coaxial feed line 2 of the second antenna.
4 is a region which is close to each other. In this region A, since both coaxial feed lines 14 and 24 are coupled at a high frequency, if a leakage current is distributed here, they will affect each other and the original performance of the antenna will not be exhibited. Become. In order to avoid such a disadvantage, it is necessary to prevent both the leakage current of the coaxial feed line 14 of the first antenna and the leakage current of the coaxial feed line 24 of the second antenna from occurring in the region A. There is. That is, assuming that the distance between the feeding points 16 and 18 of the first antenna 11 and the connecting points 20 and 30 where the choke 19 is connected to the outer conductors 17 and 27 is adjusted to 3λ / 4, If the distance between the feeding points of the first antenna 11 and the second antenna 21 is set to 0.5 nλ, the above-described inconvenience can be avoided, and therefore, the number of chokes can be reduced to one.

Next, the operation of the above configuration will be described with reference to FIG. Two sleeves 1 of the antenna element of the first antenna 11 by the coaxial feed line 14
2 and 13 are fed, and the second
Two sleeves 22 of the antenna element of the antenna 21 of
23 is powered. At this time, not only the broken line 1 which is a current contributing to the original radiation of the antenna with the power supply to the first antenna 11 but also a leakage current like the broken line 2 is generated in the outer conductor 17 of the coaxial feed line 14. I do.

The current distribution indicated by the broken line 1 is a half wavelength,
The distribution phase of the leakage current indicated by broken line 2 is the same as that of broken line 1. However, the leakage current indicated by the broken line 2 is normally distributed at a half wavelength between the nodes, but is located on the outer conductor 17 at a quarter wavelength from the end of the sleeve 13 where the amplitude should be maximum. At the open end of the choke 19, is canceled and does not occur, and no leakage current is distributed after the choke 19.

Similarly, the two sleeves 22 and 23 of the antenna element of the second antenna 21 are fed by the coaxial feed line 24. At this time, the radiation current distribution of the second antenna 21 becomes as shown by a broken line 3 along with the power supply to the second antenna 21, and the outer conductor 27 of the coaxial feed line 24 has a distribution of a distribution as shown by the broken lines 4 to 6. An electric current is generated. The currents of the broken lines 3 to 5 have a half wavelength, and the leakage current of the broken line 4 is in phase with the current distribution of the broken line 3, the leakage current of the broken line 5 is in the opposite phase to the broken line 4, and the broken line 6 is the reverse of the broken line 5. It becomes a phase distribution.

However, since the distance between the feeding points between the first antenna and the second antenna is configured to be 0.5 nλ, the leakage current indicated by the broken line 6 is also equal to the leakage current indicated by the broken line 2. As in the case, it did not occur and choke 1
After 9 the leakage current due to feeding the second antenna does not distribute.

As described above, according to the mobile radio antenna of the above-described embodiment, power is supplied through the coaxial power supply line substantially at the center of each of the plurality of half-wavelength vertical sleeve dipoles, and the respective coaxial power supply lines are provided. Is connected to a choke with one sleeve at the same location, and the length from the connection point with the choke to the feeding point and the length between the antenna elements are determined so that the node of the leakage current distribution is at the upper end of the choke. Is set so that a plurality of antennas can be fed by a plurality of coaxial feeders.
It is possible to prevent the unbalanced current from leaking to the coaxial feeder line with the chokes, and to prevent the leakage current from being distributed in the vicinity of the feeder line, so that the required space is small and the structure can be simplified.

In the above description, the number of antennas is 2
However, even when the number of the antennas becomes three or more, the distance between the lowermost first antenna and the choke is 3λ / 4, and the feeding point between the antennas above the first antenna. Each interval between them is an integral multiple of a half wavelength, in other words, each interval between the feeding points of the first antenna and the other antennas is an integer of a half wavelength. It goes without saying that the same effect can be obtained if it is made according to the configuration of the above-described embodiment so as to be doubled.

As described above, according to the present embodiment, the distance between the antennas and the distance from the first antenna to the connection point of the choke to the coaxial feed line are set so as to satisfy the above relationship. By connecting a common choke to a plurality of coaxial feeder lines at the same location, a single choke for preventing leakage current can be used, thereby reducing material costs and processing time and space. it can. Also, as a result of the reduced space, it is easy to increase the diameter of the choke to achieve a wider band.

In the above embodiment, the case of vertical diversity has been described. However, the present invention is not limited to diversity and may be applied to a case where two antennas operate separately. The present invention is not limited to only the specific examples of the above embodiment.

Further, in the above embodiment, the case where the distance between the feeding points of the first antenna and the other antennas is set to be an integral multiple of a half wavelength has been described. For example, among a plurality of antennas,
The configuration may be such that the distance between the feeding points is an integral multiple of a half wavelength only for some of the antennas. In this case, since the chokes can be commonly used for some of the above-mentioned antennas, the effect that the number of chokes can be reduced as compared with the conventional configuration in which the chokes are required by the number of antennas is exhibited. .

In the above embodiment, the case where the choke is arranged further below the first antenna provided at the lowest position in the mobile radio antenna has been described. In the case where only some of the antennas are arranged such that the distance between their feeding points is an integral multiple of half the wavelength, the antenna provided at the bottom of the antennas , And the choke may be provided such that the distance between the feed point of the antenna and the connection point between the choke and the outer conductor of each coaxial feed line is substantially 3λ / 4. .

[0040]

As is apparent from the above description, the present invention has the advantage that the number of chokes can be reduced and the required space can be reduced as compared with the prior art.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mobile radio antenna according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional mobile radio antenna.

[Explanation of symbols]

11 first antenna (first half-wavelength vertical sleeve dipole) 12, 13, 22, 23 sleeve 14 first coaxial feed line 15, 25 inner conductor 16, 18, 26, 28 feed point 17, 27 Outer conductor 19 Choke 20, 20 Contact 21 Second antenna (second half-wavelength vertical sleeve dipole) 24 Second coaxial feeder

Claims (3)

[Claims] A first half-wavelength vertical sleeve dipole fed substantially centrally by a first coaxial feeder; and a first half-wavelength vertical dipole, where k is an integer greater than or equal to two. A k-th half-wave vertical sleeve dipole fed substantially centrally by a k-th coaxial feed through a sleeve of the sleeve dipole; and the first and k-th half-wave vertical sleeves. A choke having a substantially quarter-wavelength sleeve with a lower end connected to the outer conductor of the first and k-th coaxial feed lines below the dipole, where λ is the wavelength and n is 1 or more. The feed point of the first half-wavelength vertical sleeve dipole and the k-th 2
The distance from the feed point of the half-wavelength vertical sleeve dipole to the feed point is substantially 0.5 nλ, and the first half is
Feeding point of vertical sleeve dipole and first of choke
And a distance between the k-th coaxial power supply line and a connection point with an outer conductor is substantially 3λ / 4. 2. A t-th half-wave vertical power fed substantially at the center by a t-th coaxial feed line, where t is an integer of 1 or more among a plurality of half-wave vertical sleeve dipoles. A sleeve dipole; and s is an integer of s> t, where s is an integer of s> t. The s-th half-wave fed substantially centrally by the s-th coaxial feed line passing through the sleeve of the t-th half-wave vertical sleeve dipole. A one-wavelength vertical sleeve dipole, and substantially a quarter connected to a lower end of an outer conductor of the s-th and t-th coaxial feed lines below the s-th and t-th half-wave vertical sleeve dipoles. A choke having a sleeve having a length of one wavelength, wherein λ is a wavelength, n is an integer of 1 or more, and n ₁ is 0 or an integer of 1 or more, and power is supplied to the s-th half-wavelength vertical sleeve dipole. Point and the t-th half wave The distance between the feed point of the vertical sleeve dipole and the feed point of the t-th half-wavelength vertical sleeve dipole and the s-th and t-th coaxial feed lines of the choke are set so as to be substantially 0.5 nλ. An antenna for mobile radio, characterized in that the distance from a connection point with a conductor is substantially 3λ / 4. 3. The method according to claim 1, wherein the first half-wavelength vertical sleeve dipole and the other half-wavelength vertical sleeve dipole are included in a plurality of half-wavelength vertical sleeve dipoles. The distance between each feed point of both half-wave vertical sleeve dipoles is substantially 0.5λ
The mobile radio antenna according to claim 1, wherein the choke is shared by an integer multiple of the following.