JP2002185245A - Array antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an array antenna in structure for spreading the beam width of an array element pattern by solving the problem that the beam width of the array element pattern becomes narrow for adversely affecting wide-angle beam scanning characteristics in the conventional array antenna. SOLUTION: In the array antenna, a dipole 2 operating at frequency f1 is arranged at an element position that is determined from conditions for preventing grating lobe from being generated even if scanning is made at a wide angle by beams at the frequency f1. A plurality of poles 3 with a specific length are arranged nearly vertically to a conductor bottom board 1 near each dipole 2, thus expanding the beam width of the array element pattern due to the influence of re-radiation from an induced current being distributed on the poles 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array antenna having a dipole as an element antenna and to a structure having an effect of expanding a beam width of an array element pattern.

[0002]

2. Description of the Related Art In mobile communication, for example, communication is performed between a plurality of mobile terminals and a base station antenna installed on the roof of a building or a tower. Recently, infrastructure development has progressed, and a plurality of communication systems have been mixed. For example, FIG. 7 shows the concept of mobile communication, where 20 is a base station antenna, and 21 is a terminal. Here, a system for removing radio waves (interference waves) from other communication systems or an array antenna for improving communication quality in a wide range is used as the base station antenna 20. The array antenna has an advantage that beam scanning and multi-beam configuration over a wide range can be performed instantaneously.

[0003] When beam scanning is performed at a wide angle with the above array antenna, it is necessary to arrange the element antennas with a small distance. Therefore, the coupling amount between the element antennas increases, the radiation pattern (array element pattern) of the element antennas is disturbed, and the antenna gain at the time of beam scanning decreases. Therefore, it is necessary to control the beam width to increase the beam width in the array element pattern.

In the field of mobile communications, a digital system called the second generation is currently the mainstream, but in a few years, the system is rapidly changing to a third generation and a fourth generation with a wider bandwidth. . Therefore, it is considered that a plurality of different communication systems are used together as described above. In this case, as the base station antenna, for example, in consideration of the next ten years, it is necessary to use a third-generation and fourth-generation system that can be commonly used in view of a reduction in installation space and cost. I think that the.

[0005] In order to improve communication quality, diversity reception is employed in the base station antenna for mobile communication as described above. As a diversity branch configuration method in such diversity, space diversity is often used, but there is a disadvantage that two antennas must be installed at a certain interval or more, and the antenna installation space becomes large. On the other hand, as a diversity branch with a small installation space, there is polarization diversity using the multi-propagation characteristics between different polarizations, and this is realized by configuring antennas with vertical polarization and antennas with horizontal polarization respectively. it can. At this time, in consideration of reducing the antenna installation space, each antenna may be installed in the same plane. In this case, the interval between the antennas becomes narrow, and there is a problem that the antennas are affected by adjacent antennas. The problems of the prior art will be described below using a general array antenna using a dipole as an element antenna as an example.

FIG. 8 shows, for example, Naoki Inagaki, Toshio Sekiguchi, "P
Hashed Array Antenna's Array
-Element Pattern and Active I
mpedance ”(Transactions of the Institute of Electronics, Information and Communication Engineers' 7
0/12 Vol. 53-BNo. FIG. 12 is a diagram showing a configuration of a conventional array antenna described with reference to an array antenna using a dipole shown in FIG. The array antenna is assumed to operate at the frequency f _1. 8, 31 is the conductive ground plane, 32 is a dipole operating at the frequency f _1, the radiation part of the 32a, and a feed line unit of 32b. 8A is a configuration diagram, and FIG. 8B is a cross-sectional view along AA.

Next, the operation will be described. In this array antenna, in the arrangement of dipoles 32 operating at a frequency f _1, so as not grating lobe is generated in the wide angle direction at a frequency f _1, to determine the element spacing of the dipole 32 operating at the f _1, conductive ground plane on frequency f ₁ arranged so that the radiation part 32a to a position of substantially 1/4 wavelength, to operate as the array antenna by exciting each dipole.

In order to know the properties of the array antenna at the time of beam scanning, there is a method in which only one element of interest is excited and the radiation pattern of the other element is dummy terminated (this is called an array element pattern). . This array element pattern includes an influence due to inter-element coupling between an element to be excited and its surrounding elements, and is different from a radiation pattern of a single element alone. In an array antenna that requires beam scanning, it is required that the array element pattern has a wide-angle beam width characteristic in order to prevent a decrease in gain during beam scanning to a wide angle.

Since the conventional array antenna using a dipole as an element antenna is configured as described above, in the case of having a wide-angle beam scanning characteristic, the element spacing is set to, for example, about half a wavelength in order to suppress the generation of grating lobes. Need to be narrower. Further, when the dual-polarized array antenna is realized on the same aperture, the element spacing for the other polarization is further increased because the other polarization element antennas are arranged on the same aperture. For this reason, the coupling between the elements is large, and the induced current due to the coupled wave is distributed on the element antenna (non-excitation element) adjacent to the element antenna (excitation element) of interest. Re-radiation occurs from the induced current, particularly the induced current distributed on the feed line of the adjacent element, and the array element pattern obtained by superposition with the direct wave from the excitation element has a narrow beam width radiation pattern. This is illustrated in FIG.
It is. In the figure, 33 is an excitation dipole element, 34
Is a radiation pattern of the excitation dipole element 33 alone, 35 is a non-excitation dipole element adjacent to the excitation dipole element 33, 36 is a re-radiation pattern from a two-element array composed of dummy-terminated non-excitation dipole elements 35, 37 is Reference numeral 38 denotes an array element pattern of a three-element array 37 composed of an excitation dipole element 33 and a non-excitation dipole element 35.

FIG. 9A shows a radiation pattern 34 (right figure) of the excitation dipole element 33 alone (left figure). The beam width at this time is assumed to be A. The phase of the radiation pattern 34 is used as a reference. Next, the left diagram of FIG.
7 shows the state of re-radiation from the induced current distributed particularly in the feed line portion of the non-excited dipole element 35 due to the coupling from the excited dipole element 33, and the right figure of (b) shows the non-excited dipole element two-element array. FIG. The re-emission pattern 36 has three beams, and the left and right beams have opposite phases with respect to the middle beam, and the left and right beams have the same phase. This is because the induced current on the feed line of the non-excited dipole 35 is in the monopole mode, and thus has a null point in the front direction of the antenna. However, there is some re-emission from the radiating portion, so that three beams are generated.
In addition, induced currents of opposite phases are distributed on the feed lines of the non-excitation dipoles 35 arranged on the left and right of the excitation dipole element 33, and the arrangement positions are different, so that an array factor is generated. This is because the phases of the left and right beams of the pattern are the same as shown in FIG. Also, assuming that the element interval from the excitation dipole element 33 is substantially half a wavelength, the phase of the re-emission pattern 36 is the same as the radiation pattern 34 of the direct wave from the excitation dipole element 33 ((a)). ) Is in a reversed phase relationship. Therefore, an array element pattern 38 of the three-element array 37 formed by superimposing the radiation patterns of (a) and (b) is as shown in the right diagram of (c). Radiation pattern 3
The beam width B of the array element pattern 38 becomes narrower than the beam width A because the phase 4 and the re-radiation pattern 36 are in an opposite phase relationship and cancel each other. FIG. 10 shows an example of the simulation. In this example, the array element pattern is calculated by exciting only the center element of an array in which three elements are arranged at 0.35 wavelength intervals (both elements are arranged orthogonal to the center element). It can be seen that the beam width of the array element pattern is narrower than the pattern of the element alone.

[0011]

As described above, in the conventional array antenna, the beam of the array element pattern is affected by the re-radiation of the non-excitation element adjacent to the excitation element, particularly from the induced current distributed on the feed line. There has been a problem that the width becomes narrow and adversely affects wide-angle beam scanning characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain an array antenna having a structure in which the beam width of an array element pattern is widened.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object,
The array antenna according to the first aspect of the present invention includes a conductor
Frequency f from ground plane₁At a position approximately 1/4 wavelength apart
Frequency f₁Dipole that resonates with the
F configured with a line for feeding ₁Move in
The element antenna to be made₁Beam run at
At element spacing where grating lobes do not occur during inspection
An array formed on one surface of a conductive ground plane
In an antenna, one or more elements of the above element antenna
The antenna is separated from the element antenna by a predetermined distance.
Place a pole consisting of a conductor of a predetermined length at the position
Are arranged almost vertically on one surface of the conductor ground plane.
It is provided.

[0014] array antenna of the present invention relating to claim 2, in the conductive ground plane position to place the pole, does not affect the array element pattern opening diameter smaller said array antenna with respect to wavelength at said frequency f ₁ A concave recess having a size is provided, the pole extends to the bottom of the concave recess, and the pole has a predetermined length.

According to a third aspect of the present invention, at least a part of the pole is formed in a meandering shape or a spiral shape.

According to a fourth aspect of the present invention, an end portion of the pole is provided with a bent portion having a shape bent at 90 degrees or at an acute angle.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Since the array antenna described here has wide-angle beam scanning characteristics, the element spacing is, for example, approximately 1/2.
It should be as narrow as the wavelength. Embodiment 1 FIG. FIG. 1A is a configuration diagram of an array antenna according to Embodiment 1 of the present invention. FIG. 1 (b)
FIG. 2 is a sectional view taken along a dotted line AA shown in FIG. In Figure 1, 1 is the conductive ground plane, 2 is a dipole operating at the frequency f ₁ (element antenna), 2a radiant section of the dipole, 2b is feed line unit of the dipole. In general, the radiation portion 2a of the dipole is provided approximately a quarter wavelength above the frequency f ₁ from the conductive ground plate 1. Reference numeral 3 denotes a pole which is installed substantially vertically on the conductor ground plate 1, has a certain length, and has a linear conductor or a conductor surface.

Next, the operation will be described. Are arranged dipoles 2 operating at frequency f ₁ to the element position determined from the occurrence conditions under which no grating lobes even when the beam scanning angle at the frequency f _1. And the frequency f ₁
In the case of the operation of the dipole, a signal from an input end (not shown in FIG. 1) provided on the back surface of the conductive ground plane 1 is transmitted through the feed line section 2b of the dipole and feeds the radiating section 2a of the dipole. Radiated from the radiation section 2a. Height from the ground conductor plate 1 of the radiating portion 2a of the dipole 2 is substantially a quarter wavelength at the frequency f _1, the radiation wave from each dipole is a maximum at the antenna front direction.

However, when looking at the array element pattern which is important in knowing the array characteristics, as it was in the prior art, the effect of re-radiation from the non-excited dipole element adjacent to the excited dipole element of interest, as described in the above-mentioned conventional example, is taken as it is. This causes a problem that the beam width becomes narrow, and the beam cannot be scanned at a wide angle. Therefore, this problem is solved by providing the pole 3. FIG. 2 shows this state. Here, a three-element array will be used to simplify the description. In the drawing, 4 is an excitation dipole element, 5 is a dummy-terminated non-excitation dipole element adjacent to the excitation dipole element 4, and 6 is a combination of the excitation dipole element 4 and the non-excitation dipole element 3.
Element array, 7 is an array element pattern of a three-element array,
Reference numeral 8 denotes a re-radiation pattern from an induced current distributed on the pole 3 caused by a coupled wave from the excitation dipole element 4, 9 denotes an array antenna composed of a three-element array 6 and the pole 3, and 10 denotes an array antenna. It is an array element pattern.

The effect of expanding the beam width of the array element pattern will be described with reference to FIG. The left figure of (a) shows the three-element array 6, and the right figure shows the array element pattern 7 when the center element of the three-element array 6 is excited. For convenience, the beam width at this time is B. The beam width B is the radiation pattern of the excitation dipole element 4 alone due to the effect of re-radiation from the induced current on the non-excitation dipole element 5 adjacent to the excitation dipole element 4 and particularly due to the coupled wave distributed in the feed line section. Is smaller than the beam width. Next, (b)
As shown in the left diagram, a plurality of poles 3 having a specific length are arranged in the vicinity of the excitation element.
The induced current is distributed by the coupled wave from the. The re-emission pattern from these induced currents has a pattern shape as shown in the right figure. That is, since the induced current on the pole 3 is in the monopole mode, it has a null point in the front direction of the antenna. Also, induced currents having opposite phases are distributed on the poles 3 arranged on the left and right sides of the excitation dipole element 4, and the arrangement positions are different between the poles 3 and an array factor is generated. Has the same phase on the left and right sides of the pattern. In addition, the re-radiation pattern has substantially the same phase as the array element pattern 7 because the pole 3 is arranged so as to be in phase near the excitation dipole element 4. Array element pattern 1 of an array antenna 9 ((c) left diagram) composed of a superposition of a re-radiation pattern 8 from the pole 3 and an array element pattern 7 in a three-element array
0 is shown on the right side of (c). Since the radiation patterns to be superposed are substantially in phase with each other, the beam width C of the array element pattern 10 is wider than the beam width B of the array element pattern 7. As shown in FIG. 1 (a), by providing the pawl 3 in the vicinity of that dipole 2 All operating at frequency f _1, it is possible to widen the beam width of all of the array element pattern of the dipole 2. FIG. 3 shows an example of the simulation. It can be seen that the provision of the pole has the effect of expanding the beam width.

As described above, according to the first embodiment, the array antenna having the dipole 2 operating at the frequency f ₁ as the element antenna and the pole 3 having a specific length in the vicinity of each dipole 2 are provided. Since the plurality of conductors are arranged substantially perpendicular to the conductor ground plane 1, there is an effect that the beam width of the array element pattern is widened by the influence of re-radiation from the induced current distributed on the pole 3.

In FIG. 1, the poles 3 are arranged regularly, but this is not always necessary. The position of the pole is a parameter for controlling the beam width. The length of the pole 3 is dependent on the wavelength at the frequency f _1, it is possible to finely tune the beam width by a change in length. Furthermore, the pole 3 and the feed line section 2b of the dipole need not be parallel, and the beam width can be finely adjusted by the inclination of the pole 3.

Embodiment 2 FIG. In the first embodiment, a plurality of poles having a specific length are provided in the array antenna. In the second embodiment, an array antenna in which the arrangement of the poles is changed will be described. FIG.
FIG. 4 is a cross-sectional view of the array antenna according to the second embodiment. In FIG. 4, reference numeral 11 denotes a concave recess provided at a position on the conductor ground plate 1 where the pole 3 is arranged.

Next, the operation will be described. The operation as an array antenna and the operation to increase the beam width of the array element pattern due to the re-radiation from the induced current distributed on the pole 3 due to the coupled wave are the same as those described in the first embodiment. Therefore, the description is omitted here.

In the second embodiment, the pole 3 can be extended to a predetermined length by the concave recess 11 provided at the position of the pole 3 on the conductive ground plane 1 while suppressing the pole 3 from extending upward. . Thus, it is possible to adjust the length of the pole 3 in easy length resonant at the operating frequency f ₁ of without any inconvenience array antenna on interference and fabrication of the radiation portion 2a of the dipole, an array element pattern beam width Has an adjustable effect. The size of the opening diameter of the concave recess 11 so that sufficiently small relative to the wavelength of the frequency f _1, the recess 11 does not affect the array element pattern. In addition, the concave recess 11 may be formed by depressing the conductor ground plate 1 or may be provided around the conductor ground plate 1.

Embodiment 3 In the second embodiment, the arrangement of the poles is changed. In the third embodiment, an array antenna in which the shape of the pole is changed will be described. FIG. 5A is a sectional view of an array antenna according to the third embodiment. FIG.
(B) and (c) show other pole shapes.
In the figure, 12a is a zigzag meandering pole, 1
2b is a meandering meandering pole, and 12c is a spiral pole.

Next, the operation will be described. The operation as the array antenna and the operation of expanding the beam width of the array element pattern due to the re-radiation from the induced current distributed on the pole caused by the coupled wave are the same as those described in the first embodiment. Therefore, the description is omitted here.

In the third embodiment, FIG.
As shown in the figure, a zigzag meandering pole 12a is arranged. Therefore, the length of the pole can be appropriately extended while keeping the posture low, and the magnitude of the induced current distributed on the pole can be changed. That is, the effect of widening the beam width at a low frequency can be realized with a low-profile pole. The same effect can be obtained by using a pole 12b meandering in a meander shape as shown in FIG. 5B and a spiral pole 12c as shown in FIG. 5C.

Embodiment 4 In the fourth embodiment, an array antenna in which the shape of the pole is bent at 90 degrees (Γ-shape) or when the angle formed with the conductor ground plane is smaller than 90 degrees will be described. FIG. 6 is a sectional view of the array antenna according to the fourth embodiment. In the drawing, reference numeral 13 denotes a pole whose tip is bent in a Γ shape.

Next, the operation will be described. By arranging the pole 13 whose tip is bent in a 先端 shape as shown in FIG. 6, the re-radiation pattern from the pole 13 does not become a sharp null point in the front direction of the antenna, and the gain in the front direction of the array element pattern. It has the effect of preventing the drop. This is because the re-emission from the induced current distributed in the Γ-shaped bent portion is directed toward the front of the antenna. Also,
By bending the tip, the height of the pole from the conductor ground plate 1 can be suppressed, the length can be increased, and the beam width can be adjusted.

Further, as shown in the figure, the tip is bent at a more acute angle than the Γ-shape, and the angle formed with the conductor ground plane is 90 °.
The same effect is obtained for a pole having a shape smaller than the degree. In this case, there is an advantage that the beam width can be controlled by adjusting the angle formed.

The same effect can be obtained even when two poles are arranged at substantially the same position and substantially in parallel, and the amount of current induced in the poles can be changed.

[0033]

As is evident from the foregoing description, according to the invention of claim 1, a dipole that resonates at a frequency f ₁ which is provided at a position away substantially quarter wavelength at the frequency f ₁ from the conductive ground plane, the dipole the antenna elements operating at a frequency f _1, which is configured with a line for feeding, and arrayed on one surface of the conductive ground plane in element spacing without occurrence of grating lobes when beam scanning at the frequency f ₁ is formed In the array antenna, for one or more element antennas of the element antenna, a pole made of a conductor of a predetermined length is provided at a position separated from the element antenna by a predetermined distance substantially perpendicularly to the conductor ground plane. Since a plurality of antennas are arranged on the surface, there is an effect that an array antenna having a wider beam width of the array element pattern can be obtained.

According to the second aspect of the present invention, the conductor base plate at the position where the pole is arranged has a small aperture diameter with respect to the wavelength at the frequency f ₁ and does not affect the array element pattern of the array antenna. Since a concave recess having a size is provided, the pole extends to the bottom of the concave recess, and the pole has a predetermined length, so that the pole extends to a predetermined length while suppressing upward extension of the pole. It can be an effect that can adjust the length of the pole easy length resonant at the operating frequency f ₁ of without any inconvenience array antenna on interference and fabrication of the radiation of the dipole.

According to the third aspect of the present invention, since at least a part of the pole is formed in a meandering shape or a spiral shape, the length of the pole can be appropriately extended while maintaining a low posture, and the pole can be extended. This has the effect of changing the magnitude of the induced current distributed in.

According to the fourth aspect of the present invention, since a bent portion having a shape bent at 90 degrees or at an acute angle is provided at the end of the pole, there is an effect of preventing a decrease in gain in the front direction of the array element pattern. . Further, there is an effect that the beam width can be adjusted by suppressing the height from the conductor ground plane and extending the length, and the beam width can be controlled by adjusting the angle.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an array antenna according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing that an effect of expanding a beam width of an array element pattern can be obtained in the array antenna of the present invention.

FIG. 3 is an explanatory diagram showing a simulation result showing that an effect of expanding a beam width of an array element pattern can be obtained in the array antenna of the present invention.

FIG. 4 is a configuration explanatory view of an array antenna according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating a configuration of a pole of an array antenna according to a third embodiment of the present invention.

FIG. 6 is a configuration explanatory view showing a shape of a pole of an array antenna according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram showing the concept of conventional mobile communication.

FIG. 8 is a configuration explanatory view showing a conventional array antenna using a dipole as an element antenna.

FIG. 9 is an explanatory diagram showing that a beam width of an array element pattern becomes narrower in a conventional array antenna.

FIG. 10 is an explanatory diagram showing a simulation result of a reduction in the beam width of an array element pattern in a conventional array antenna.

[Explanation of symbols]

1 conductor ground plate, 2 dipole, 2a radiation part, 2b
Feed line section, 3 poles, 4 excitation dipole element, 5
Non-excited dipole element, 63 element array, 7 array element pattern, 8 re-radiation pattern, 9 array antenna, 10 array element pattern, 11 concave depression, 12a zigzag meandering pole, 12b meandering pole , 12c spiral pole,
13 A pole bent in a Γ shape, 20 base station antennas, 21 terminals.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hirokatsu Okegawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term in Mitsubishi Electric Corporation (reference) 5J020 AA03 BA02 BA03 BC03 BC09 DA04 5J021 AA06 AA09 AB03 BA01 GA08 HA05 JA07

Claims (4)

[Claims] In claim 1. A dipole that resonates at a frequency f ₁ which is provided at a position away substantially quarter wavelength at the frequency f ₁ from the conductive base plate, the frequency f _1, which is configured with a line for feeding the dipole the antenna elements that operate in the array antenna formed by a plurality arranged in element spacing without occurrence of grating lobes when the beam is scanned on one surface of the conductive base plate of the frequency f _1, one or more elements of the element antennas The antenna is characterized in that a plurality of poles made of a conductor of a predetermined length are arranged at a predetermined distance from the element antenna and arranged on one surface of the conductor ground plane substantially perpendicular to the conductor ground plane. Array antenna. 2. The conductor ground at a position where the pole is arranged.
The frequency f ₁Aperture diameter is small for wavelength at
Does not affect the array element pattern of the above array antenna
A concave recess having a size is provided, and the pole is connected to the concave recess.
Extending to the bottom of the sole and making the pole the specified length
The array antenna according to claim 1, wherein: 3. The array antenna according to claim 1, wherein at least a part of the pole is formed in a meandering shape or a spiral shape. 4. The array antenna according to claim 1, wherein a bent portion having a shape bent at 90 degrees or at an acute angle is provided at an end of the pole.