JP2013034118A - Array antenna - Google Patents

Abstract

An array antenna is provided in which the arrangement interval of sub-array antennas can be made smaller than an external dimension required for a wide wall surface of a rectangular waveguide connected to a feeding portion.
A plurality of sub-array antennas 3 are arranged in a longitudinal direction so that a feeding unit 6 provided at substantially the center in the longitudinal direction of each feeding line 5 does not interfere with a feeding unit of a feeding line in another adjacent sub-array antenna. Are alternately displaced. Thereby, the arrangement interval of the subarray antennas 3 can be set to about 0.6 wavelength which is smaller than 0.9 wavelength which is the outer dimension required for the wide wall surface of the rectangular waveguide connected to the feeding portion. .
[Selection] Figure 1

Description

  The present invention relates to an array antenna used in a microwave band or a millimeter wave band.

  There are various types of array antennas used in the microwave band and the millimeter wave band, such as a microstrip array antenna and a coaxial slot array antenna. These array antennas are configured by arranging a plurality of subarray antennas in parallel on a plane with a predetermined interval (array interval). Each subarray antenna includes a plurality of element antennas arranged substantially linearly at a predetermined interval, and a feed line to which the plurality of element antennas are respectively connected.

  A power feeding section is provided on the power feeding line of each subarray antenna. In many cases, the feeding section of each subarray antenna and the transmission system and reception system outside the antenna are connected via a rectangular waveguide. In the example of transmission, a microwave band or millimeter wave band high-frequency signal output from the transmission system is input from the rectangular waveguide to the power feeding unit, and from the power feeding unit to one side and the other side in the longitudinal direction of the power feeding line. The power is sequentially supplied to the plurality of element antennas on the feeding lines on each side, and the respective element antennas are excited. In general, the power feeding unit is provided at approximately the center in the longitudinal direction of the power feeding line.

  By the way, in the array antenna, in order to reduce the grating lobe which is a problem in the directivity pattern and to expand the beam scanning range that determines the angle measurement capability, it is necessary to make the array interval of the subarray antennas as narrow as possible. Specifically, if a plurality of subarray antennas can be arranged at intervals of, for example, about 0.6 wavelengths, the maximum scanning angle can be set to 40 degrees while suppressing grating lobes.

  In this case, a microstrip array antenna using a patch antenna as an element antenna will be described as an example. A feed line in each subarray antenna is, for example, a microstrip line, a triplate line, a post wall waveguide, or the like. The line width is smaller than the wide area width of the rectangular waveguide, and is usually not a restriction in reducing the juxtaposition interval between the subarray antennas.

  However, each rectangular waveguide connecting the feeding section of each subarray antenna to the transmission system and the reception system has its wide wall surface orthogonal to the arrangement surface of each subarray antenna and the arrangement direction of each subarray antenna. It is connected with each electric power feeding part in the parallel state. That is, each power feeding portion has a rectangular waveguide cross-sectional opening shape to which the external shape is connected, and each subarray antenna faces each other between the power feeding portions adjacent to each other on the end surface in the longitudinal direction of each power feeding portion. The feed lines are arranged in parallel. Therefore, the length in the longitudinal direction of each power feeding portion is approximately the same as the outer dimension (0.9 wavelength or more) required for the wide wall width of the rectangular waveguide.

  In this way, in the configuration in which the power supply lines are arranged in the center in the center where the power supply lines are arranged at both ends in the longitudinal direction, each power supply is performed with the side surfaces in the longitudinal direction in contact with each other between the adjacent power supply parts. When the line is arranged, the arrangement configuration is such that the arrangement interval of the subarray antennas can be minimized. This indicates that the arrangement interval of the subarray antennas cannot be 0.9 wavelengths or less. This problem occurs similarly in the coaxial slot array antenna.

  To deal with this problem, for example, Patent Document 1 is a countermeasure example using a microstrip array antenna. However, the first feeding line (which is an original feeding line to which a plurality of element antennas are connected, and a feeding unit is provided at substantially the center. In addition to the antenna board on which the second feed line made of a dielectric line having a wavelength shortening effect is arranged in order to make the interval between adjacent feed parts on the antenna board less than or equal to 0.6 wavelengths An array antenna has been proposed in which a substrate is provided and interference between rectangular waveguides in the power feeding portion is avoided.

JP 2010-212946 A

  In the array antenna proposed in Patent Document 1, the array interval of the subarray antennas can be reduced to about 0.6 wavelengths. However, since a power supply substrate is required in addition to the antenna substrate, there is a problem that the manufacturing cost increases. Further, the technique proposed in Patent Document 1 cannot be applied to a coaxial slot array antenna.

  The present invention has been made in view of the above, and is an array antenna that can reduce the arrangement interval of the subarray antennas to be smaller than the external dimensions required for the wide wall surface width of the rectangular waveguide connected to the feeding portion. The purpose is to obtain.

  In order to solve the above-described problems and achieve the object, the present invention includes a plurality of element antennas arranged substantially linearly at a predetermined interval, and the plurality of element antennas connected to each other, A plurality of sub-array antennas having a feed line provided with a feed section connected to a transmission system and a reception system via a rectangular waveguide are arranged on a plane, and the shape of the rectangular rectangular cross section of the rectangular waveguide to be connected In the array antenna arranged such that the respective feeding lines are arranged in parallel so that the end faces in the longitudinal direction of the feeding part having an external shape matched to each other face each other between the feeding parts, the plurality of sub-array antennas, The power supply section provided in the power supply line is arranged such that the end faces on the longitudinal direction side of adjacent power supply sections do not face each other, but the end faces on the short side face each other.

  According to the present invention, each of the subarray antennas is arranged such that the feeding parts in the neighboring feeding lines are arranged so that the end faces on the long side do not face each other and the end faces on the short side face each other. Can be made smaller than the external dimensions (0.9 wavelength) required for the wide wall width of the rectangular waveguide connected to the. Specifically, regardless of whether the array antenna is a microstrip array antenna or a coaxial slot array antenna, the arrangement interval of the subarray antennas can be reduced to about 0.6 wavelengths near the limit. Therefore, the beam scanning range can be expanded while suppressing the grating lobe. Even if the array antenna is a microstrip array antenna, a feeding substrate or the like is not used in addition to the antenna substrate as in the invention described in Patent Document 1, so that the manufacturing cost can be reduced. It is done.

FIG. 1 is a conceptual diagram showing an external configuration of an array antenna according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view taken along line A-A ′ for explaining the relationship between the power feeding unit and the rectangular waveguide shown in FIG. 1. FIG. 3 is a plan view illustrating details of the microstrip line / waveguide converter provided in the power feeding unit shown in FIG. 4 is a cross-sectional view taken along line B-B ′ shown in FIG. 3. FIG. 5 is a conceptual diagram showing an external configuration of the array antenna according to the second embodiment of the present invention.

  Embodiments of an array antenna according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram showing an external configuration of an array antenna according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view taken along line AA ′ for explaining the relationship between the power feeding section and the rectangular waveguide shown in FIG. FIG. 3 is a plan view illustrating details of the microstrip line / waveguide converter provided in the power feeding unit shown in FIG. FIG. 4 is a cross-sectional view taken along line BB ′ shown in FIG.

  In FIG. 1, an array antenna 1 according to the first embodiment is, for example, a microstrip array antenna, and includes a plurality of subarray antennas 3 arranged in parallel at a predetermined interval (array interval) on an antenna substrate 2. The

  The plurality of sub-array antennas 3 constituting the microstrip array antenna are a plurality of element antennas 4 which are patch antennas arranged on the antenna substrate 2 at a predetermined interval and substantially linearly, and a plurality of element antennas 4, respectively. Are respectively connected to the feeder line 5. Since the feed line 5 is disposed along the arrangement direction of the plurality of element antennas 4, it is similarly arranged in a substantially straight line. The power supply line 5 is, for example, a microstrip line, a triplate line, a post wall waveguide, or the like, and a power supply unit 6 is provided at the approximate center in the longitudinal direction.

  Since the power feeding unit 6 and the transmission system and the reception system outside the antenna are connected via a rectangular waveguide, the power feeding unit 6 is, for example, a microstrip line / rectangular conductor as shown in FIGS. The wave tube converter is configured.

  In FIG. 1, the feed lines 5 are alternately shifted in the longitudinal direction, and therefore, every other feed section 6 and every other feed line 5 are shown in FIG. 2. As shown in FIG. 2, in each feeding portion 6 formed on the antenna substrate 2, the rectangular rectangular open end 8 a of the rectangular waveguide 8 is connected to the ground conductor pattern 7 that covers the back surface of the antenna substrate 2. . Specifically, the power supply unit 6 which is a microstrip line / waveguide conversion unit is configured as shown in FIGS. 3 and 4, for example. 3 and 4, the illustration of the wall thickness of the rectangular waveguide 8 is omitted.

  3 and 4, the ground conductor pattern 7 has an elongated rectangular coupling slot 9 similar to the rectangular shape of the rectangular opening end 8a of the rectangular waveguide 8 to be connected. It is formed in parallel with the long side of the rectangular opening end 8a. A conductor pattern 10 is formed on the surface region of the antenna substrate 2 corresponding to the connection position of the rectangular waveguide 8, and from this conductor pattern 10, the strip conductor 5 a constituting the feed line 5 is connected to the coupling slot 9. It is pulled out in both directions from the position directly above. The plurality of connecting conductors 11 that connect the outer periphery of the conductor pattern 10 and the ground conductor pattern 7 are arranged so as to surround the outer periphery of the rectangular open end 8 a of the rectangular waveguide 8.

  Since the plurality of connection conductors 11 constitute a metal wall, a pseudo rectangular waveguide is formed in the antenna substrate 2. The quasi-rectangular waveguide in the antenna substrate 2 and the rectangular waveguide 8 connected to the feeding portion 6 are electromagnetically coupled via the coupling slot 9, so that the transmission mode and the rectangular shape in the feeding line 5 are obtained. Conversion to the transmission mode in the waveguide 8 is performed.

  As described above, the outer shape of the power feeding portion 6 is a shape (in many cases, a rectangular shape) that matches the shape of the rectangular opening of the rectangular waveguide 8 to be connected. In addition, although the shape of the rectangular opening of the cross section of the rectangular waveguide 8 to be connected is shown in FIG. 3 in the case where the four corners are right angles, there may be a rounded shape.

  Now, in an electronic scanning antenna such as a phased array antenna or digital beam forming (DBF), if the arrangement interval of a plurality of subarray antennas is not appropriate, a grating lobe is generated in addition to the original main beam. For example, in the case of a radar antenna, when the grating lobe catches the target, a serious problem such as erroneous detection of the direction of the target occurs. Therefore, it is necessary to design so that no grating lobe is generated.

The conditions for preventing the generation of grating lobes are as follows, assuming that the arrangement interval of a plurality of subarray antennas is d, the wavelength is λ, and the maximum beam scanning angle is θm:
d ≦ λ / (1+ | sin θm |) (1)
Given in.

  As can be understood from Equation (1), in order to increase the maximum beam scanning angle θm, it is necessary to narrow the array interval d. For example, if the maximum beam scanning angle θm is 40 °, the array interval d needs to be set to 0.6λ or less. However, since the external dimension of a patch antenna normally used as an element antenna is about 0.5λ, it is difficult to make the arrangement interval d close to 0.5λ, and d = 0.6λ is the limit.

  The external configuration of a general array antenna will be described with reference to the reference numerals shown in FIG. 1. In a general array antenna, a plurality of subarray antennas 3 are provided on an antenna substrate 2 as shown in FIG. The line 5 was arranged with both ends aligned.

  At this time, as shown in FIGS. 2 to 4, each rectangular waveguide 8 connected to the feeding section 6 of each subarray antenna has its wide wall surface orthogonal to the arrangement surface of each subarray antenna, and each Each feeder 6 is connected in parallel with the arrangement direction of the subarray antennas. Therefore, the external shape of each power feeding portion 6 is similar to the rectangular cross-section opening of the rectangular waveguide 8 to be connected (in many cases, a rectangular shape).

  In short, in a general array antenna, each sub-array antenna is arranged with both ends of each feed line 5 aligned, so that each feed is made with the end faces in the longitudinal direction of the feed section 6 facing each other between adjacent feed sections. The tracks 5 were arranged in parallel. Therefore, the dimension in the longitudinal direction of the power feeding section 6 is the same as the outer dimension required for the wide wall width of the connected rectangular waveguide 8.

  Here, the dimensions of the rectangular waveguide are determined by public standards for each frequency. For example, the dimensions of the millimeter wave band 76.5 GHz rectangular waveguide have an inner diameter of 2.54 × 1.27 mm. When 0.5 mm is added to the tube as the thickness of the tube, the outer dimension becomes 3.54 × 2.27 mm. When expressed by the wavelength λ, the inner diameter becomes 0.648λ × 0.324λ, and the outer dimension becomes 0.903λ. × 0.579λ. That is, the external dimension required for the wide wall width of the rectangular waveguide used in the microwave band and the millimeter wave band is 0.9 wavelength or more.

  Therefore, in a general array antenna, if the arrangement interval of the sub-array antennas is to be narrowed to 0.9 wavelength or less, the longitudinal end surfaces of the adjacent feeding units 6 interfere with each other. It cannot be narrowed below 9 wavelengths.

  As a method for solving this problem, if the feed lines 5 of each of the plurality of subarray antennas 3 can be arranged so that the end faces on the side in the longitudinal direction of the adjacent feed sections 6 do not face each other, the end faces on the short side face each other. The arrangement intervals of the subarray antennas can be narrowed to 0.9 wavelengths or less without causing the end faces on the longitudinal direction side of the feeding section 6 to interfere with each other. Embodiment 1 and Embodiment 2 are shown as configuration examples of such an arrangement mode.

  In the first embodiment, as shown in FIG. 1, when the power feeding unit 6 is provided at substantially the center of the power feeding line 5, the power feeding lines 5 are alternately shifted in the longitudinal direction. . Then, between the feed lines 5, the feed portions 6 are arranged such that the end surfaces on the longitudinal direction side of the adjacent feed portions 6 do not face each other, and the end surfaces on the short side direction of the feed portions 6 adjacent to each other face each other. Since arrangement is possible, the arrangement interval can be narrowed to the limit of about 0.6 wavelength.

  Next, the operation will be described. When the present array antenna 1 is used for transmission, a microwave band or a millimeter wave band high-frequency signal is input to each of the feeding units 6 of the plurality of subarray antennas 3 from a rectangular waveguide 8 connected to an external transmission system. Is done. The input high-frequency signal is converted from the transmission mode to the transmission mode in the feeder line 5 in each feeder unit 6. The high-frequency signal whose transmission mode has been converted is distributed to one side and the other side in the longitudinal direction of the feed line 5, and is sequentially fed to the plurality of element antennas 4 in the feed line 5 on each side, and electromagnetic waves are generated in the space. Is emitted.

  When the array antenna 1 is used for reception, electromagnetic waves coming from space are received by the plurality of element antennas 4 in each of the plurality of subarray antennas 3 and synthesized by the feed line 5 and the feed unit 6. The signal is output to a rectangular waveguide 8 connected to an external receiving system. Since the antenna is generally reciprocal, the array antenna 1 can be used for both transmission and reception.

  Here, according to the first embodiment, in the microstrip array antenna in which the power feeding section 6 is provided at substantially the center in the longitudinal direction of each feed line 5, as shown in FIG. 1, the subarray antennas 3 are alternately arranged in the longitudinal direction. They are staggered. For this reason, the adjacent feeders 6 can be arranged close to each other so that the lateral end faces face each other without causing the longitudinal end faces to interfere with each other. Can be narrowed to the limit of about 0.6 wavelength.

  Therefore, the effect that the beam scanning range can be expanded while suppressing the grating lobe can be obtained. In addition, unlike the invention described in Patent Document 1, since a power supply substrate or the like is not used in addition to the antenna substrate, an effect that manufacturing costs can be suppressed is also obtained.

Embodiment 2. FIG.
FIG. 5 is a conceptual diagram showing an external configuration of the array antenna according to the second embodiment of the present invention. In FIG. 5, the same reference numerals are given to components that are the same as or equivalent to those shown in FIG. 1 (Embodiment 1). In FIG. 5, the description will be focused on the portion related to the second embodiment.

  As shown in FIG. 5, the array antenna 20 according to the second embodiment is provided with a subarray antenna 21 instead of the subarray antenna 3 in the configuration shown in FIG. 1 (first embodiment). The subarray antenna 21 is configured by alternately arranging a first subarray antenna provided with a feed line 22a and a second subarray antenna provided with a feed line 22b.

  As shown in FIG. 5, the array antenna 20 according to the second embodiment includes a sub-array antenna (first sub-array antenna) 21 provided with a feed line 22a and a sub-array antenna (second output) provided with a feed line 22b. Subarray antennas) 21 are alternately arranged with both ends aligned.

  Here, like the feed line 5 in the first embodiment, the feed lines 22a and 22b are configured by a microstrip line, a triplate line, a post wall waveguide, and the like. Although the wave tube is connected, the conversion unit is configured in the same way, and the external shape has the same dimensions, the arrangement position of the power feeding unit 6 is different from that of the first embodiment. That is, the power supply unit 6 in the power supply line 22a is provided at a position shifted from the approximate center of the length in the longitudinal direction of the power supply line 22a to one end in the longitudinal direction, and the power supply unit 6 in the power supply line 22b is supplied with power. The line 22b is provided at a position shifted from the approximate center in the longitudinal direction length to the other end side in the longitudinal direction by a predetermined distance.

  Since the adjacent feed line 22a and feed line 22b are arranged by shifting the feed part 6 in the opposite longitudinal directions, the feed lines 22a and 22b are alternately arranged with both ends aligned, as shown in FIG. If it arrange | positions, between the adjacent electric power feeding parts 6, it can arrange | position close together so that a mutual longitudinal direction end surface may not interfere, and a mutual short direction side end surface may face, and feed line 22a, 22b The arrangement interval can be narrowed to 0.9 wavelength or less.

  Therefore, according to the second embodiment, the arrangement interval of the sub-array antennas 21 can be narrowed to the limit of about 0.6 wavelengths, so that the beam scanning is performed while suppressing the grating lobe as in the first embodiment. The range can be expanded.

  Here, in the first embodiment, as shown in FIG. 1, the adjacent feed lines 5 are arranged so as to be shifted from each other in the longitudinal direction, so that the phase centers of the plurality of subarray antennas 3 are substantially linear in the arrangement direction. There is a possibility that orthogonal components are mixed at the time of angle measurement and the angle measurement accuracy is lowered.

  On the other hand, in the second embodiment, as shown in FIG. 5, since there is no shift in the longitudinal direction between the adjacent feed lines 22a and 22b, the phase centers of the plurality of subarray antennas 21 are substantially in the arrangement direction. They are arranged on a straight line, so that orthogonal components are not mixed during angle measurement, and a decrease in angle measurement accuracy can be prevented.

  Therefore, according to the second embodiment, in addition to the actions and effects obtained in the first embodiment, it is possible to prevent a decrease in angle measurement accuracy that is a problem in the first embodiment.

  As the array antenna used in the microwave band and the millimeter wave band, the first and second embodiments have shown application examples to the microstrip array antenna. However, the present invention is similarly applied to, for example, a coaxial slot array antenna. can do.

  As described above, the array antenna according to the present invention is useful as an array antenna that can make the array spacing of the subarray antennas smaller than the external dimensions required for the wide wall surface of the rectangular waveguide connected to the feeder. It is.

DESCRIPTION OF SYMBOLS 1,20 Array antenna 2 Antenna board 3,21 Subarray antenna 4 Element antenna 5,22a, 22b Feed line 5a Strip conductor which comprises feed line 6 Feed part 7 Ground conductor pattern 8 Rectangular waveguide 8a Cross section of rectangular waveguide Rectangular open end 9 Coupling slot 10 Conductor pattern 11 Connection conductor

Claims (3)

A plurality of element antennas arranged in a substantially straight line with a predetermined interval, and a power feeding unit to which the plurality of element antennas are respectively connected, and a transmission system and a reception system are connected via a rectangular waveguide A plurality of sub-array antennas each having a feed line provided with a plurality of sub-array antennas are adjacent to each other on the plane in the longitudinal direction end face of the feed section having an external shape that matches the shape of the rectangular opening of the rectangular waveguide to be connected. In the array antenna arranged so that the feeding lines face each other between the feeding parts in parallel,
The plurality of subarray antennas are:
The array antenna, wherein the power feeding portions provided in each of the power feeding lines are arranged so that end surfaces on the longitudinal direction side of adjacent power feeding portions do not face each other and end surfaces on the short side face each other. The plurality of subarray antennas are:
The feeding section is provided at substantially the center of the length in the longitudinal direction of each of the feeding lines, the end faces on the short side face each other between adjacent feeding sections, and the other longitudinal feeding side between the other feeding sections. The array antenna according to claim 1, wherein the feed lines are arranged so as to be shifted from each other in the longitudinal direction so that the end faces face each other. The plurality of subarray antennas are:
A first subarray antenna in which the power feeding unit is provided at a position shifted from a substantially center of the longitudinal length of the feed line to one end side in the longitudinal direction by a predetermined distance;
A second sub-array antenna in which the power feeding unit is provided at a position deviated by a predetermined distance from the approximate center of the length in the longitudinal direction of the feed line to the other end side in the longitudinal direction;
The first sub-array antenna and the second sub-array antenna are alternately arranged in the arrangement direction with both ends of the feed line aligned, and are arranged with the end faces on the short direction side of the adjacent feed parts facing each other. The array antenna according to claim 1, wherein:

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