JP2007006062A - Omnidirectional antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a further reduction in diameter, structural simplification and inexpensiveness without deteriorating performance as an omnidirectional antenna. <P>SOLUTION: In order to approximate a horizontal direction distances of two dipole elements 20 as much as possible, the respective dipole elements are cross fed by a feedline conductor 40 and a grounded line conductor 50 running on a longitudinal axial line of a dielectric substrate 10-1 and unnecessary wave radiation from the respective dipole elements 20 are suppressed by first and second Sperrtop 30 which are provided in a configuration that they clamp the respective dipole elements 20 vertically. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed omnidirectional antenna suitable for use in a base station such as a mobile communication system.

A base station such as a mobile communication system often forms a circular communication area. In this case, an omnidirectional antenna is used in a horizontal plane in order to transmit radio waves uniformly around the base station.
As this kind of antenna, a collinear antenna is well known. However, this collinear antenna has the advantage that the diameter can be reduced, but has the disadvantage that the usable frequency band is narrow. For example, in a collinear antenna formed on a dielectric substrate, when a band where the voltage standing wave ratio is 1.5 or less is set as a usable frequency band, the band is about 2% of the use center frequency.

In a cellular phone base station, since the frequency bands for transmission and reception are separated, a broadband antenna applicable to both the transmission and reception bands is required. However, since the collinear antenna has a narrow usable frequency band as described above, it is not effective as an antenna for a mobile phone base station.
On the other hand, in recent mobile communication systems, a beam tilt variable function in a vertical plane is essential. However, in the collinear antenna, since the feeding method to the radiating element is a series feeding method, it is difficult to control the feeding phase and amplitude for each radiating element necessary for beam tilt.
In order to solve the problems of the collinear antenna, a printed omnidirectional antenna using a dipole element has been proposed (for example, see Patent Document 1).

JP 2003-32034 A

  However, the printed omnidirectional antenna described in Patent Document 1 has a configuration in which two dielectric substrates formed with a pair of dipole antenna patterns and one dielectric substrate formed with a feed circuit pattern are three-dimensionally combined. Therefore, the outer diameter is increased, and the horizontal plane directivity is slightly biased.

  Ideally, an omnidirectional antenna used in a base station such as a mobile communication system can be further reduced in diameter and can be beam tilted by parallel feeding. It is also important that the internal structure can be simplified and inexpensive, and that there is little deviation in directivity in the horizontal plane.

  In view of such circumstances, an object of the present invention is to provide an omnidirectional antenna capable of further reducing the diameter, simplifying the structure, and reducing the cost without impairing the performance as an omnidirectional antenna. It is said. It is another object of the present invention to provide an omnidirectional antenna having an array configuration capable of reducing the diameter and the like and changing the beam tilt in the vertical plane.

  In order to achieve the above object, an omnidirectional antenna according to the present invention has a long dielectric substrate and a shape parallel to the longitudinal axis at a symmetrical position about the longitudinal axis of the dielectric substrate. And first and second dipole elements printed in a form in which one and the other element conductors are positioned on one and the other surfaces of the dielectric substrate, respectively, and the first and second dipole elements Connected to the one element conductor in the above, connected to the feeder line conductor extending along the longitudinal axis on one surface of the dielectric substrate, and to the other element conductor in the first and second dipole elements, A ground line conductor extending along the longitudinal axis on the other surface of the dielectric substrate and the other of the dielectric substrate in a form sandwiching the first and second dipole elements vertically First and second super tops, one end of which is printed on the surface and short-circuited to the ground line conductor, respectively, via a feed circuit configured by the feed line conductor and the ground line conductor The first and second dipole elements are configured to perform cross feeding.

  Further, the omnidirectional antenna according to the present invention has two omnidirectional antennas having the above-described configuration arranged vertically as an antenna block for arraying, and a two-distributed parallel feeding circuit by the feeding circuit of those antenna blocks. Is configured.

Furthermore, in the omnidirectional antenna according to the present invention, the arrayed omnidirectional antennas are arranged in a plurality of stages as antenna blocks, and a feeding phase and amplitude are arranged in the two distributed parallel feeding circuits of the antenna blocks. A variable phase shifter is inserted for changing each.
Each of the omnidirectional antennas is preferably housed in a cylindrical cover and used particularly when used outdoors.

  According to the omnidirectional antenna according to the present invention, in order to make the horizontal distance between the two half-wave dipole elements as close as possible, each dipole element is provided by a feed line conductor and a ground line conductor that respectively pass on the longitudinal axis of the dielectric substrate. Since the first and second super tops that are cross-fed and sandwiched between the dipole elements are prevented from emitting unnecessary radio waves from the dipole elements, The diameter can be reduced without impairing the performance, and the internal structure can be simplified and reduced in price.

  In addition, according to the omnidirectional antenna having the array configuration according to the present invention in which two antenna blocks each including the omnidirectional antenna are arranged above and below, the phase and amplitude of power feeding to the dipole element of each antenna block Therefore, the vertical in-plane directivity (low side lobe, setting of the beam tilt angle) with good characteristics can be obtained.

  Furthermore, according to the omnidirectional antenna according to the present invention in which a plurality of antenna blocks each including the omnidirectional antenna having the above array configuration are arranged in a vertical direction, the feeding phase to the dipole element of each antenna block is changed by the variable phase shifter. Thus, it is possible to easily change the beam tilt angle in the vertical plane.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A, 1B, and 1C are a front view, a side view, and a rear view, respectively, showing an embodiment of an omnidirectional antenna according to the present invention.
This omnidirectional antenna A1 has a pair of dipole elements 20 and a pair of super-tops 30 on a long dielectric substrate 10-1 having a lateral width w set to about 0.11λ (λ is a wavelength of a used frequency). Is formed by printing.

Each dipole element 20 is set to have a length of about 0.4λg (λg is a wavelength of a use frequency on the dielectric substrate 10-1), and is symmetric about the longitudinal axis of the dielectric substrate 10-1. The positions are formed in parallel so as to be separated from each other by about 0.08λ.
Of the element conductors 21 and 22 constituting the dipole element 20, one element conductor 21 is provided on the front surface of the dielectric substrate 10-1, and the other element conductor 21 is provided on the back surface of the dielectric substrate 10-1. Yes.

A feed line conductor 40 and a ground line conductor 50 extending on the longitudinal axis of the dielectric substrate 10-1 are printed on the front surface and the back surface of the dielectric substrate 10-1.
The feed line conductor 40 is formed so as to extend from the lower end of the dielectric substrate 10-1 to the height portion of the center point of the dipole element 20, and the left and right dipole elements via the feed line conductors 41 extending left and right from the upper end. It is connected to the feeding point of 20 element conductors 21. On the other hand, the ground line conductor 50 is formed so as to extend from the lower end to the upper end of the electric substrate 10 and feeds the element conductors 22 of the left and right dipole elements 20 via the respective feed line conductors 51 extending left and right from the upper and lower intermediate points. Connected to a point.

Each of the super tops 30 has a length of about 0.3λg, and is formed on the back surface of the dielectric substrate 10-1.
One super top 30 is short-circuited to the ground line conductor 60 at a position approximately 0.22λ above the height of the center point of the dipole element 20, and extends along both sides of the ground line conductor 60 from the short-circuited portion. Extending upward. Further, the other super top 30 is short-circuited to the ground line conductor 60 at a position separated by about 0.22λ from the height of the center point of the dipole element 20, and both sides of the ground line conductor 50 from the short-circuited part. Extending downward. The other super top 30 is short-circuited at one end to the ground line conductor 60 at a position about 0.22λ below the height of the center point of the dipole element 20, and both sides of the ground line conductor 50 from the short-circuited part. Extending downward.

  In the omnidirectional antenna A <b> 1 according to this embodiment, a central conductor of a coaxial feed line (not shown) is connected to the feed line conductor 40, and an external conductor of the coaxial feed line is connected to the ground line conductor 50. Can be used to send and receive.

  Usually, a dipole antenna is omnidirectional in a horizontal plane. Here, considering a two-dipole antenna in which two dipole elements are arranged in parallel at intervals in the horizontal direction, if the arrangement distance of these dipole elements becomes as small as possible with respect to the wavelength λ of the operating frequency, this 2 The dipole antenna is also omnidirectional in the horizontal plane, as is the case with a single antenna.

In the omnidirectional antenna A1 according to the above-described embodiment, in order to make the horizontal distance between the two half-wave dipole elements 20 as close as possible, the central portions of the half-wave dipole elements 20 are respectively passed (dielectric substrate 10- A feed circuit is constituted by the feed line conductor 40 and the ground line conductor 50 formed of a microstrip line (passing on one longitudinal axis).
The half-wave dipole elements 20 of the antenna A1 are cross-fed through the feed circuit without using a frequency-dependent balanced / unbalanced conversion circuit. The positioned super-top 30 acts to reduce or eliminate unnecessary radio wave radiation from the dipole element 20.

Therefore, according to the omnidirectional antenna A1 according to this embodiment, the diameter can be reduced without impairing the performance as the omnidirectional antenna.
In addition, since the omnidirectional antenna according to this embodiment does not have accessory parts such as parasitic elements and is configured using the dielectric substrate 10-1, the structure thereof is greatly simplified and moved. Performance capable of covering the transmission band and the reception band in the body communication system is obtained.

  When the omnidirectional antenna A1 of this embodiment is used outdoors, it is desirable to store it in a cover (not shown) made of fiber reinforced plastic or the like. This cover may be a cylindrical cover having an inner diameter of about 0.115λ and an outer diameter of about 0.13λ in view of the structure of the omnidirectional antenna A1, and thus can be a structure having a small wind receiving load. is there.

  2A, 2B, and 2C are a front view, a side view, and a rear view, respectively, showing an embodiment of an omnidirectional antenna according to the present invention that is arrayed. This arrayed omnidirectional antenna A2 has a configuration in which two antenna blocks b1 having substantially the same configuration as the omnidirectional antenna A1 shown in FIG. 1 are connected in the vertical direction. Therefore, the dielectric substrate 10-2 of the antenna A2 has a length that is approximately twice the length of the dielectric substrate 10-1 shown in FIG.

  In this arrayed omnidirectional antenna A2, the feed line conductor 40 of the upper antenna block b1 and the feed line conductor 40 of the lower antenna block b1 are at a point P at the substantially central portion in the vertical direction of the dielectric substrate 10-2. Similarly, the ground line conductors 50 of both antenna blocks b1 are also coupled to each other.

  According to the omnidirectional antenna A2 having this array configuration, the feed line conductor 40 and the ground line conductor 50 of each antenna block b1 function as a parallel feed line having the coupling point P as a feed end. Therefore, by adjusting the position of the coupling point P and appropriately setting the phase and amplitude of power feeding to the dipole element 20 of each antenna block b1, it is possible to reduce the side lobe and achieve a good vertical angle with a desired beam tilt angle. In-plane directivity can be obtained.

  3A, 3B, and 3C are a front view, a side view, and a rear view, respectively, showing another example of the arrayed omnidirectional antenna according to the present invention. This arrayed omnidirectional antenna A3 has a configuration in which four antenna blocks b1 having substantially the same configuration as the omnidirectional antenna A1 shown in FIG. 1 are connected in the vertical direction, in other words, shown in FIG. It has a configuration in which two antenna blocks b2 having the same configuration as the omnidirectional antenna A2 are connected in the vertical direction. Therefore, the dielectric substrate 10-3 of the antenna A3 has a length that is approximately twice the length of the dielectric substrate 10-2 shown in FIG.

  In this arrayed omnidirectional antenna A3, the ground line conductors of both antenna blocks b2 are coupled to each other, and the feeding end P of the upper antenna block b2 and the feeding end P of the lower antenna block b2 are respectively connected to the cable 60. And 70 are connected to a distributor 80 or a variable phase shifter 90.

In the antenna A3, when the distributor 80 is used, the directivity in the vertical plane is fixed. On the other hand, when the variable phase shifter 90 is used, the variable phase shifter 90 is inserted into the parallel feeding circuit of each antenna block b2. By changing the feeding phase for each of the dipole elements, the beam tilt angle in the vertical plane can be easily changed.
The arrayed omnidirectional antenna shown in FIGS. 2 and 3 can also be accommodated in a cylindrical cover or the like.

4, 5 and 6 illustrate the VSWR characteristics, horizontal plane directivity and vertical plane directivity of the arrayed omnidirectional antenna shown in FIG. 3, respectively.
As is apparent from FIG. 4, according to this arrayed omnidirectional antenna, it is possible to obtain a wide band characteristic that the frequency band where the VSWR is 1.5 or less is about 18%.
Further, as apparent from FIG. 5, this arrayed omnidirectional antenna has a very small level deviation of the directivity in the horizontal plane (within a deviation of 1 dB).
The VSWR characteristics and horizontal directivity of the antenna A1 shown in FIG. 1 and the antenna A2 shown in FIG. 2 are also similar to those of the antenna A3 shown in FIG.

(A), (b) and (c) are the front view, the side view, and the rear view which respectively show one Embodiment of the omnidirectional antenna which concerns on this invention. (A), (b) and (c) are the front view, the side view, and the rear view which respectively show embodiment of the omnidirectional antenna which concerns on the present invention made into the array. (A), (b) and (c) are the front view, side view, and back view which show the other example of the arrayed omnidirectional antenna based on this invention, respectively. It is the graph which illustrated the VSWR characteristic of the arrayed omnidirectional antenna shown in FIG. It is the graph which illustrated the directivity in the horizontal surface of the arrayed omnidirectional antenna shown in FIG. 4 is a graph illustrating the in-plane directivity of the arrayed omnidirectional antenna shown in FIG. 3.

Explanation of symbols

10-1, 10-2, 10-3 Dielectric substrate 20 Dipole element 21, 22 Element conductor 30 Super top 40 Feed line conductor 50 Ground line conductor 60, 70 Cable 80 Divider 90 Variable phase shifter

Claims (4)

A long dielectric substrate;
The first and second element conductors are positioned on one and the other surfaces of the dielectric substrate in a form parallel to the longitudinal axis at symmetrical positions about the longitudinal axis of the dielectric substrate. First and second dipole elements printed in the form;
A feed line conductor connected to the one element conductor in the first and second dipole elements and extending along the longitudinal axis on one surface of the dielectric substrate;
A ground line conductor connected to the other element conductor in the first and second dipole elements and extending along the longitudinal axis on the other surface of the dielectric substrate;
First and second super tops printed on the other surface of the dielectric substrate in a form sandwiching the first and second dipole elements up and down, each having one end short-circuited to the ground line conductor; With
An omnidirectional antenna configured to perform cross-feeding with respect to the first and second dipole elements via a feeding circuit constituted by the feeding line conductor and the ground line conductor.   For arraying, two omnidirectional antennas according to claim 1 are vertically arranged as antenna blocks, and a two-distributed parallel feeding circuit is constituted by the feeding circuits of these antenna blocks. Sex antenna.   The omnidirectional antenna according to claim 2 is arranged in a plurality of stages as antenna blocks, and variable phase shifters for changing the feeding phase and amplitude are respectively inserted in the two distributed parallel feeding circuits of the antenna blocks. An omnidirectional antenna characterized by   The omnidirectional antenna according to any one of claims 1 to 3, wherein the omnidirectional antenna is housed in a cylindrical cover.

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