JP2016021704A - Array antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an array antenna device capable of preventing reduction of antenna gain in a wide-angle direction even when the frequency of an electric wave for power supplying is changed.SOLUTION: The array antenna device is arranged so that a metal pole 7 erects vertically relative to the surface of a ground conductor plate 1 being positioned between neighboring cavity antennas 6 in a Y-direction (or, between an edge of the ground conductor plate 1 and a cavity antenna 6). The metal pole 7 is arranged so that the height dimension thereof is set to a length which is longer than a quarter of a wavelength corresponding to the band end at the low frequency side in the frequency bandwidth in the wavelength corresponding to the frequency bandwidth of the electric wave supplied by the feeding probe 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an array antenna device in which cavity antennas are periodically arranged.

In recent years, an array antenna apparatus in which a plurality of element antennas are arrayed or a phased array in which a phase shifter is connected to each element antenna in order to cope with higher functionality and higher performance of information communication equipment and radar. Antenna devices are widely used.
For example, when an array antenna apparatus is mounted on an aircraft, an automobile, or the like, the loading space and the loading weight are limited. Therefore, the array antenna apparatus is required to be small or low in posture and lightweight.

The following Patent Documents 1 and 2 disclose a cavity antenna as a low-profile and lightweight antenna.
When this cavity antenna is periodically arranged as an element antenna and a phase shifter is connected to each cavity antenna to configure a phased array antenna device, mutual coupling between the cavity antennas is required when scanning the beam. The active impedance of the array antenna device changes due to the influence of surface waves and leakage waves generated due to the periodic structure of the antenna aperture.
As a result, depending on the frequency of the radio wave used and the beam scanning angle, the active impedance may deteriorate, resulting in an increase in mismatch loss (decrease in antenna gain).

Patent Document 3 below discloses an array antenna device that improves a decrease in antenna gain during beam scanning.
FIG. 7 is a perspective view showing an array antenna device disclosed in Patent Document 3. As shown in FIG.
In this array antenna apparatus, a dipole antenna 101 is used as an element antenna, and the dipole antenna 101 is periodically arranged on the ground conductor plate 100.
The dipole antenna 101 includes a radiating portion 101a and a feed line portion 101b. The height dimension of the feed line portion 101b corresponds to approximately ¼ wavelength of the frequency of the radio wave to be used. It is provided at a position of approximately ¼ wavelength from the conductor plate 100.
Note that the dipole antennas 101 are periodically arranged at intervals determined from the condition that no grating lobe is generated even when the beam is scanned in the wide-angle direction (a direction away from the Z direction).

In this array antenna apparatus, a pole 102 is provided adjacent to the dipole antenna 101.
The poles 102 are metal pillars installed substantially vertically on the ground conductor plate 100 and are arranged with the same period as the period when the dipole antennas 101 are arranged.

Here, when a radio wave is fed to any one dipole antenna 101 among the plurality of dipole antennas 101 arranged on the ground conductor plate 100, the radio wave is radiated into the space from the dipole antenna 101. A part of the radio wave radiated to the space is irradiated to another dipole antenna 101 adjacent to the dipole antenna 101.
As a result, the induced current is excited in the other dipole antenna 101 irradiated with the radio wave (particularly, the induced current is excited in the feed line portion 101b), so that the radio wave is radiated from the other dipole antenna 101 into the space. Radio wave re-emission occurs.

As a result, the radio wave radiation pattern in the array antenna apparatus includes a radio wave radiated into the space from one dipole antenna 101 fed with the radio wave and a radio wave radiated into the space from another adjacent dipole antenna 101. It will be superimposed.
For this reason, the pattern shape of the radio wave radiation pattern in the array antenna apparatus generally has a narrow beam width, and the antenna gain in the wide-angle direction (the direction away from the Z direction) decreases.

In this array antenna apparatus, the pole 102 is disposed adjacent to the dipole antenna 101 in order to improve the decrease in antenna gain in the wide-angle direction.
When a radio wave is fed to any one dipole antenna 101, a part of the radio wave radiated from the dipole antenna 101 to the space is also irradiated to the pole 102, and an induced current is excited in the pole 102. Re-radiation of radio waves that are radiated from 102 to space occurs.
The pattern shape of the radio wave re-radiated by the induced current in the pole 102 has a low gain in the Z direction and a high gain in the wide-angle direction (a direction away from the Z direction) in the figure.

In this array antenna apparatus, the pole 102 is combined so that the radio wave radiated to the space from one dipole antenna 101 fed with the radio wave and the radio wave re-radiated by the induced current in the pole 102 are combined in substantially the same phase. The height of the is adjusted.
As a result, the radiation pattern of one dipole antenna 101 to which radio waves are fed becomes a radiation pattern that has a wider beam width and a smaller decrease in antenna gain in the wide-angle direction than when the pole 102 is not disposed.

In the array antenna device disclosed in Patent Document 3, a dipole antenna 101 is used as an element antenna. However, an array antenna device using a waveguide aperture antenna as an element antenna is described in Non-Patent Document 1 below. It is disclosed.
In this array antenna apparatus, a part of the radio wave radiated into the space from the waveguide aperture antenna may have a large change in active impedance due to the effect of interelement coupling that enters the adjacent waveguide aperture antenna. .
Therefore, in order to prevent a part of the radio wave radiated into the space from the waveguide opening antenna from entering the adjacent waveguide opening antenna, between the adjacent waveguide opening antennas, A metal wall that shields radio waves is provided. The height of the metal wall is determined by the frequency of the radio wave used.

JP 58-168304 A (FIG. 1) Japanese Patent Laid-Open No. 2-57002 (FIG. 1) JP 2002-185245 A (paragraph number [0013], FIG. 1)

Mailloux, R.J., "Surface waves and anomalous wave radiation nulls on phased arrays of TEM waveguides with fences," Antennas and Propagation, IEEE Transactions on, vol.20, no.2, pp.160,166, Mar 1972

Since the conventional array antenna apparatus is configured as described above, in the case of Patent Document 3, the radio wave radiated to the space from the dipole antenna 101 to which the radio wave is fed and the re-radiated radio wave generated from the pole 102 are substantially the same. If the height of the pole 102 is adjusted so as to be synthesized in the same phase, it is possible to suppress a decrease in antenna gain in the wide angle direction (a direction away from the Z direction). However, the height of the pole 102 cannot be adjusted as appropriate according to the frequency of the radio wave fed to the dipole antenna 101, and is a fixed height, so when the frequency of the radio wave fed to the dipole antenna 101 is changed, There has been a problem that it is impossible to sufficiently suppress a decrease in antenna gain in the wide-angle direction.
Further, in the case of Non-Patent Document 1, when the frequency of the radio wave fed to the waveguide aperture antenna is changed, the effect of the metal wall shielding the radio wave is reduced, and the reduction of the antenna gain in the wide angle direction is sufficiently suppressed. There was a problem that it was impossible.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an array antenna device that can suppress a decrease in antenna gain in a wide-angle direction even if the frequency of a radio wave to be fed is changed. And

  An array antenna device according to the present invention is applied to a ground conductor plate having a plurality of openings, a conductive cavity that is a recess formed in the plurality of openings in the ground conductor plate, and a side wall of the conductive cavity. A feeding member that feeds radio waves into the inside of the conductive cavity, a conductive flat plate provided inside the conductive cavity, and a metal column that stands on the surface of the ground conductive plate The height dimension of the metal column is longer than one quarter of the wavelength corresponding to the frequency band of the low frequency side in the frequency band among the wavelengths corresponding to the frequency band of the radio wave fed by the power supply member. It is made to be set to.

  According to this invention, the height dimension of the metal pillar standing on the surface of the ground conductor plate is a band on the low frequency side in the frequency band among the wavelengths corresponding to the frequency band of the radio wave fed by the power feeding member. Since the length is set to be longer than a quarter of the wavelength corresponding to the end, even if the frequency of the radio wave fed from the feeding member is changed, the reduction of the antenna gain in the wide angle direction is suppressed. There is an effect that can.

It is a perspective view which shows the array antenna apparatus by Embodiment 1 of this invention. It is a top view which shows the array antenna apparatus of FIG. It is AA sectional drawing of the array antenna apparatus of FIG.1 and FIG.2. It is a schematic diagram which shows the electric field distribution of the electromagnetic wave in the antenna opening vicinity in case the metal pillar 7 is not provided. It is a schematic diagram which shows the electric field distribution of the electromagnetic wave in the antenna opening vicinity in case the metal pillar 7 is provided. It is a top view which shows the array antenna apparatus by Embodiment 2 of this invention. It is a perspective view which shows the array antenna apparatus currently disclosed by patent document 3. FIG.

Embodiment 1 FIG.
1 is a perspective view showing an array antenna apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a top view showing the array antenna apparatus of FIG. 1, and FIG. 3 is a cross-sectional view of the array antenna apparatus of FIG. 1 and FIG.
1 to 3, the ground conductor plate 1 is periodically provided with rectangular openings. 1 and 2 show an example in which nine openings are provided, the number of openings is not limited to nine, and may be eight or less or ten or more.

The conductive cavity 2 is a recess formed in the opening of the ground conductor plate 1.
That is, the conductive cavity 2 is formed of a conductive chassis having a rectangular cross-sectional shape, and the open surface 2a (the upper side of the conductive cavity 2 in FIG. 3) coincides with the opening of the ground conductor plate 1. .
The end surface 2b (the lower side of the conductive cavity 2 in FIG. 3) opposite to the open surface 2a in the conductive cavity 2 is blocked by a short-circuit conductor wall made of a plate-like conductor and is electrically short-circuited. .
In addition, the side wall 2c of the conductive cavity 2 is provided with a hole 3 for inserting a feeding probe.

The power feeding probe 4 is inserted into a hole 3 provided in the side wall 2c of the conductive cavity 2 (inserted perpendicularly to the central axis (Z direction in FIG. 3) of the conductive cavity 2), and conductive. It is a power supply member that supplies radio waves to the inside of the cavity 2.
The conductor flat plate 5 is a metal plate having a rectangular cross-sectional shape, and is disposed inside the conductive cavity 2 so as to be perpendicular to the central axis of the conductive cavity 2 (Z direction in FIG. 3).
In addition, the cavity antenna 6 is comprised from the electroconductive cavity 2, the electric power feeding probe 4, and the conductor flat plate 5, and FIG.1 and FIG.2 shows the example by which nine cavity antennas 6 are arrange | positioned periodically. . However, the number of the cavity antennas 6 is not limited to 9, and may be 8 or less, or 10 or more. However, when scanning the beam within a predetermined beam scanning range, the period is set at an interval at which no grating lobe appears. Are arranged.

The metal pillar 7 stands vertically with respect to the surface of the ground conductor plate 1 so as to be positioned between the cavity antennas 6 adjacent in the Y direction (or between the end face of the ground conductor plate 1 and the cavity antenna 6). It has been.
The height dimension of the metal column 7 is longer than a quarter of the wavelength corresponding to the frequency band of the radio wave fed by the power feeding probe 4 and corresponding to the lower frequency band end of the frequency band. Is set to
In addition, each metal pillar 7 is arranged with the same period as the period when the cavity antenna 6 is arranged.

  FIG. 4 is a schematic diagram showing the electric field distribution of the radio wave near the antenna opening when the metal column 7 is not provided, and FIG. 5 is the electric field of the radio wave near the antenna opening when the metal column 7 is provided. It is a schematic diagram which shows distribution.

Next, the operation will be described.
First, the case where the metal pillar 7 is not provided will be described.
When the feeding probe 4 feeds radio waves into the inside of the conductive cavity 2, the radio waves are transmitted through the inside of the conductive cavity 2 and radiated into the space from the open surface 2 a of the conductive cavity 2.
At this time, since the conductive flat plate 5 is disposed inside the conductive cavity 2 so as to block the electric field, the conductive flat plate 5 has a capacitive and inductive component in parallel to the input impedance of the feeding probe 4. It acts as an addition and operates as a so-called resonance circuit. That is, the conductor flat plate 5 operates as a non-excitation element that realizes impedance matching over a wide band.

As shown in FIG. 4, the electric field distribution inside the conductive cavity 2 is mainly a TE01 mode, which is a so-called fundamental mode of a rectangular waveguide, and mainly has an electric field component parallel to the Y direction. A radio wave radiated into space (a radio wave irradiated in the Z direction) also has a polarization parallel to the Y direction as a main polarization.
However, since the opening of the cavity antenna 6 (the open surface 2a of the conductive cavity 2) is a discontinuous surface between the cavity antenna 6 and the external space, the so-called higher-order mode TM11 mode of the rectangular waveguide is used. An electric field (an electric field having a Y-direction component and a Z-direction component) is also generated.
When a discontinuous surface with the cavity antenna 6 is viewed from an external space, it has a predetermined surface impedance, and the conductor flat plate 5 can be regarded as a structure having the surface impedance periodically.
On the conductor flat plate 5 having such a surface impedance periodically, a radio wave called a surface wave or a leak wave can be propagated.

Here, consider the case of performing beam scanning (E-plane beam scanning) on the YZ plane.
When performing E-plane beam scanning, it is generally known that surface waves or leakage waves are generated only when the surface impedance has an inductive reactance component. , A distribution having a Y-direction component and a Z-direction component.
Since the opening of the cavity antenna 6 (the open surface 2a of the conductive cavity 2) is excited by a TM11 mode electric field (an electric field having a Y direction component and a Z direction component) as described above, the TM11 mode is excited. This electric field induces surface waves or leakage waves.

The cavity antenna 6 adjacent in the Y direction is fed with radio waves having a phase difference corresponding to the beam scanning angle for beam scanning.
There is a phase difference between radio waves fed to the cavity antenna 6 adjacent in the Y direction and a phase difference generated when the surface wave or leakage wave propagates between the cavity antennas 6 adjacent in the Y direction. When they are the same, the surface wave or leakage wave is strongly excited.
When the surface wave or the leaky wave is strongly excited, the power radiated to the space is reduced and the antenna gain is greatly reduced.
Therefore, the generation of surface waves or leakage waves propagating on the antenna aperture is one of the causes of a decrease in antenna gain when performing E-plane beam scanning with an array antenna apparatus in which the cavity antennas 6 are periodically arranged. it can.

Next, the case where the metal pillar 7 is provided will be described.
When the feeding probe 4 feeds radio waves into the inside of the conductive cavity 2, the radio waves are transmitted through the inside of the conductive cavity 2 and radiated into the space from the open surface 2 a of the conductive cavity 2.
As shown in FIG. 5, the electric field distribution inside the conductive cavity 2 is mainly a TE01 mode, which is a fundamental mode of the rectangular waveguide, and mainly has an electric field component parallel to the Y direction. A radio wave radiated into space (a radio wave irradiated in the Z direction) also has a polarization parallel to the Y direction as a main polarization.
However, at the opening of the cavity antenna 6 (the open surface 2a of the conductive cavity 2), similarly to the case where the metal column 7 is not provided, the electric field (Y direction) of the TM11 mode, which is a higher-order mode of the rectangular waveguide. And an electric field having a component and a Z-direction component) are generated.

The electric field distribution of the surface wave or leakage wave propagating on the antenna opening surface is a distribution having a Y-direction component and a Z-direction component, but a metal column 7 (parallel to the Z direction) that stands perpendicular to the ground conductor plate 1. Since the metal column 7) is arranged, generation of an electric field parallel to the extending direction of the metal column 7 (Z-direction component electric field) is suppressed. This is because the electric field in the direction parallel to the metal surface is zero on the metal surface, and the generation of an electric field parallel to the extending direction of the metal column 7 (electric field of the Z direction component) is suppressed. Is done.
In the first embodiment, the metal column 7 is set up at a position where the electric field of the Y direction component is strong (near the center of the X direction in the cavity antenna 6), and the position where the electric field of the Y direction component is weak (X in the cavity antenna 6). The metal column 7 is not set up in the vicinity of the end of the direction), but the electric field at the position where the metal column 7 is not set up (the electric field near the end of the cavity antenna 6 in the X direction) is set up by the metal column 7. The generation of the electric field of the Z direction component is suppressed by the metal column 7 in such a manner that it is dragged by the electric field at the position (the electric field in the cavity antenna 6 near the center in the X direction).

As described above, the generation of the electric field parallel to the extending direction of the metal pillar 7 (the electric field of the Z direction component) is suppressed, so that the generation of the surface wave or the leakage wave is suppressed. Therefore, even if E-plane beam scanning is performed, generation of surface waves or leakage waves that cause a decrease in antenna gain is suppressed, so that a decrease in antenna gain can be prevented.
The height of the metal pillar 7 is longer than one quarter of the wavelength corresponding to the frequency band of the radio wave fed by the power feeding probe 4 and corresponding to the lower frequency band end of the frequency band. Therefore, if the frequency of the radio wave fed by the power feeding probe 4 is within the range of the frequency band (a radio wave with a frequency outside the frequency band is not normally used), the frequency of the radio wave is Even if it changes, generation | occurrence | production of the electric field of a Z direction component can be suppressed.

As apparent from the above, according to the first embodiment, the height dimension of the metal pillar 7 standing on the surface of the ground conductor plate 1 corresponds to the frequency band of the radio wave fed by the power feeding probe 4. Since the wavelength is set to be longer than a quarter of the wavelength corresponding to the lower frequency band end in the frequency band, the frequency of the radio wave fed from the feeding probe 4 is Even if it is changed within the range of the frequency band, it is possible to suppress the decrease in the antenna gain in the wide angle direction.
Further, since the metal pillar 7 is merely raised from the surface of the ground conductor plate 1, the weight of the array antenna device is not significantly increased, and the array antenna device is not increased in size. For this reason, it is possible to prevent deterioration in mountability on an aircraft, an automobile, or the like.

Embodiment 2. FIG.
In the first embodiment, the metal column 7 is set up at a position where the electric field of the Y direction component is strong (near the center in the X direction in the cavity antenna 6). The position is not limited to a position where the electric field of the Y direction component is strong (near the center of the cavity antenna 6 in the X direction).
For example, as shown in FIG. 6A, a metal pillar 7 may be erected near the center of the cavity antenna 6 in the Y direction between the cavity antennas 6 adjacent in the X direction. .
Further, as shown in FIG. 6B, metal pillars 7 may be erected at the four corners of the opening of the cavity antenna 6.
Further, as shown in FIG. 6C, a metal pillar 7 may be erected in the vicinity of the end portion in the X direction of the cavity antenna 6.
6A to 6C, when the metal column 7 is erected, the metal column 7 is erected at a position where the electric field of the Y direction component is strong (near the center in the X direction in the cavity antenna 6). Compared to the case, there is a possibility that the degree of the effect of suppressing the generation of the electric field of the Z direction component may be different, but similarly, the generation of the electric field of the Z direction component can be suppressed.

  In the first embodiment, the conductive cavities 2 and the conductor flat plates 5 have a rectangular cross-sectional shape. However, the cross-sectional shape is not limited to a rectangular shape. For example, the cross-sectional shape is a square shape. Or a circular shape.

In the first embodiment, an example in which the metal column 7 is a columnar metal has been described. However, the present invention is not limited to a columnar metal, and for example, a metal having a prismatic shape or a plate shape may be used. Good.
In the first embodiment, it is assumed that all the metal columns 7 periodically arranged have the same height and the same thickness. The height may be different, and the thickness of each metal column 7 may be different.
In the first embodiment, one metal column 7 is provided between the adjacent cavity antennas 6. However, a plurality of metals are provided between the adjacent cavity antennas 6. A pillar 7 may be provided.

In the first embodiment, the metal pillar 7 is shown to stand vertically with respect to the surface of the ground conductor plate 1. However, the ground conductor plate 1 and the metal pillar 7 are made of metal integrally formed. Alternatively, the metal pillar 7 may be attached to the surface of the ground conductor plate 1.
When the metal pillar 7 is attached to the surface of the ground conductor plate 1, the metal pillar 7 is formed so that the end of the metal pillar 7 has a shaft structure for fitting, and the ground conductor plate A fitting hole may be provided on the surface of 1. Thereby, the metal pillar 7 can be stood on the surface of the ground conductor plate 1 by press-fitting the shaft structure at the end of the metal pillar 7 into the fitting hole formed on the surface of the ground conductor plate 1. .

  Further, the metal column 7 may be formed so that the end portion of the metal column 7 has a shaft structure provided with a screw thread, and a screw hole may be provided on the surface of the ground conductor plate 1. Thereby, the metal pillar 7 can be stood on the surface of the ground conductor plate 1 by screwing the shaft structure at the end of the metal pillar 7 into the screw hole formed in the surface of the ground conductor plate 1.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 ground conductor plate, 2 conductive cavity, 2a open surface of conductive cavity, 2b end surface opposite to open surface, 2c side wall of conductive cavity, 3 hole for feeding probe insertion, 4 feeding probe (feeding member), 5 conductor flat plate, 6 cavity antenna, 7 metal pillar, 100 ground conductor plate, 101 dipole antenna, 101a radiation part, 101b feed line part, 102 pole.

Claims (6)

A ground conductor plate having a plurality of openings;
A conductive cavity that is a recess formed in a plurality of openings in the ground conductor plate;
A power supply member that is inserted into a hole provided in a side wall of the conductive cavity, and feeds radio waves into the conductive cavity;
A conductor flat plate provided inside the conductive cavity;
A metal pillar standing on the surface of the ground conductor plate,
The height dimension of the metal column is longer than a quarter of the wavelength corresponding to the low frequency side band edge in the frequency band among the wavelengths corresponding to the frequency band of the radio wave fed by the power feeding member. An array antenna apparatus characterized by being set to   2. The array antenna apparatus according to claim 1, wherein each of the conductive cavities and the metal pillars are periodically arranged.   3. The array antenna apparatus according to claim 2, wherein the metal pillars are respectively disposed between the conductive cavities arranged in the same direction.   The array antenna device according to any one of claims 1 to 3, wherein the metal pillar is a metal having a cylindrical shape, a prismatic shape, or a flat plate shape.   The end of the metal column has a fitting shaft structure, and the shaft structure at the end of the metal column is press-fitted into a fitting hole formed on the surface of the ground conductor plate. The array antenna device according to claim 1, wherein the metal pillar is erected on a surface of the ground conductor plate.   The end of the metal column has a shaft structure with a thread, and the shaft structure at the end of the metal column is screwed into a screw hole formed on the surface of the ground conductor plate. The array antenna device according to claim 1, wherein the metal pillar is erected on a surface of the ground conductor plate.

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