JP2008205588A - Array antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an array antenna scanning the direction of directivity of a beam even in the case of a microwave having a narrow bandwidth, and preventing deterioration of antenna efficiency as well as increase of the antenna size. <P>SOLUTION: The array antenna provided with a waveguide having a plurality of slots disposed on its wall has a configuration in which a plurality of structures movable in a normal line direction of the waveguide wall having the slots disposed thereon are disposed in the waveguide axis direction so that the movable structures can be close to a waveguide wall opposing the waveguide wall having the slots disposed thereon, to change the distance between the structures and the waveguide wall having the slots disposed thereon. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an array antenna for controlling a beam directing direction in a waveguide slot array antenna in which a plurality of slots are arranged on a tube wall of a waveguide.

An array antenna that forms a beam in a desired direction by arranging a plurality of element antennas is used as an antenna of a radar device, a radio wave monitoring device, or a communication device. In order to efficiently supply power to each element antenna, a microwave is used. There is a waveguide slot array antenna in which a plurality of notches are provided in a tube wall of a waveguide that is one of transmission lines to form a slot, and radio waves are radiated through the slot.
And since the slot which is a power coupling part from the waveguide which is the main line forms the element antenna as it is, radio wave radiation is possible with a simple structure. Since the waveguide slot array antenna radiates microwaves propagating through the waveguide through the slots, the beam directing direction is determined by the phase relationship of the respective parts in the waveguide exciting the slots. Therefore, the slot interval is set to ½ of the guide wavelength in the waveguide, and in-phase excitation is performed to form a beam orthogonal to the slot arrangement direction (see, for example, Non-Patent Document 1).

  Further, a frequency-scan antenna (frequency scanning antenna) that changes the beam directing direction according to the frequency change is proposed by utilizing the fact that the slot excitation condition of the waveguide slot array antenna depends on the guide wavelength. (For example, refer nonpatent literature 2).

  As another method of scanning the beam, since the slot arrangement of the waveguide slot array antenna is fixed, it is also proposed to provide a drive unit for the antenna and move the antenna itself to direct the beam in a desired direction. (For example, refer to Patent Document 1 and Patent Document 2).

  Also, when a signal with a wide frequency bandwidth is input to the waveguide slot array antenna, the problem is that the beam directing directions at the upper and lower frequencies are different. By providing a dielectric cover in which the plane and the inner plane have an inclination angle, there is an antenna in which the main beam that has passed through is refracted and faces in the front direction within the band (see, for example, Patent Document 3).

The Institute of Electronics, Information and Communication Engineers, “Antenna Engineering Handbook”, Ohmsha, 1980, October, p. 223 Richard C. Edited by Johnson, “Antenna Engineering Handbook” Third Edition, McGraw-Hill, Inc. 1992, December JP-A-7-111416 JP 2003-66134 A JP 2004-15408 A

However, in a waveguide slot array antenna, if a frequency change is used to control beam pointing, it is difficult for the radar operating in a narrow band to perform beam pointing.
Further, the method of providing a mechanical drive unit outside the antenna and rotating it to control the beam directivity has a problem that the entire antenna becomes large.
In addition, when beam control is performed using the refractive index of the dielectric cover provided at the opening of the waveguide slot array antenna, the inner and outer surfaces of the dielectric cover are used to cope with the wide band. There is a problem that the tilt angle of the cover increases, the transmission loss of the cover increases, and the antenna efficiency decreases.

  An object of the present invention is to provide an array antenna that can scan the beam directing direction even with a narrow-band microwave and that does not reduce the antenna efficiency without increasing the overall size of the antenna.

  An array antenna according to the present invention is an array antenna including a waveguide having a plurality of slots arranged on a tube wall, and is adjacent to a tube wall facing the tube wall on which the slot is arranged, and the tube on which the slot is arranged A plurality of movable structures that are movable in the normal direction of the tube wall in which the slots are arranged are arranged in the tube axis direction so that the gap between the walls is narrowed or expanded.

  The effect of the array antenna according to the present invention is that, by shortening the short side of the cross section in the waveguide, the capacitance becomes stronger, the slot is excited in the leading phase, and the beam is tilted to the opposite side with respect to the input side. By making the short side longer, the capacitance becomes weaker, the slot is excited with a lag phase, and the beam is tilted to the input side, so that only the movable structure arranged in the waveguide is moved. Therefore, it is not necessary to increase the bandwidth of the antenna, the entire antenna does not become large, and the antenna efficiency does not decrease.

Embodiment 1 FIG.
FIG. 1 is a perspective view of an array antenna according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view perpendicular to the tube axis direction of the array antenna according to Embodiment 1 of the present invention.
The array antenna 1 according to the first embodiment of the present invention is a waveguide slot array antenna, and includes a cylindrical waveguide 2 having a rectangular cross section in which a long side is am and a short side is bm. A plurality of slots 4 are provided on one tube wall 3 on the long side of the cross section.
Further, the movable structure 6 that is close to the tube wall 5 facing the tube wall 3 of the waveguide 2 and is movable in a short side direction (hereinafter referred to as “short side direction”) in a plane perpendicular to the tube axis. Are provided in the tube axis direction. The movable structure 6 is controlled by a control circuit 7 provided outside the waveguide 2, and the gap dm between the tube wall 3 and the movable structure 6 is variable. The microwave is input from the input side 8 of the waveguide 2.

In general, when a movable structure 6 that shortens the short-side direction of the cross section of the waveguide 2 is arranged, as shown by the equivalent susceptance expressed by the equation (1), the capacitance is exhibited. It should be noted that λ _g is the guide wavelength. Formula (1) is described in Masamitsu Nakajima, “Microwave Engineering”, Morikita Publishing, April 1975 (hereinafter referred to as “Reference Document 1”).
Then, the shorter the short side of the cross section, that is, the narrower the gap dm, the greater the capacitance.

FIG. 3 is a sectional view in the tube axis direction of the equivalent circuit of the array antenna and the waveguide according to the first embodiment of the present invention.
As shown in FIG. 3B, since the movable structure 6 that shortens the short side of the cross section of the waveguide 2 is arranged in the tube axis direction, the equivalent circuit of the waveguide 2 is shown in FIG. ). In the array antenna 1 in which the movable structure 6 is arranged so as to form a beam perpendicular to the tube axis direction, the movable structure 6 is moved by the control circuit 7 so that the gap dm is reduced. In the circuit, the capacity of the portion corresponding to the movable structure 6 increases, and the phase of the microwave propagating in the waveguide 2 advances. As a result, as shown in FIG. 4, each slot 4 is excited with a leading phase, and the beam directed in the direction indicated by the broken line before the movement of the movable structure 6 is directed to the direction indicated by the solid line, ie, the input side 8. The beam tilts to the opposite side.

  Further, in the array antenna 1 in which the movable structure 6 is disposed so as to form a beam in a direction perpendicular to the tube axis direction, the movable structure 6 is moved by the control circuit 7 as shown in FIG. When dm is increased, the capacity of the portion corresponding to the movable structure 6 in the equivalent circuit is reduced, and each slot 4 is excited with a lag phase, and is directed in the direction indicated by the broken line before the movable structure 6 is moved. The beam tilts in the direction indicated by the solid line, that is, the input side 8.

  The array antenna 1 according to the first embodiment of the present invention is more capacitive by shortening the short side of the cross section in the waveguide 2, the slot 4 is excited in the leading phase, and the beam is directed to the input side 8. The movable structure is arranged in the waveguide 2 so that it is tilted to the opposite side, and conversely, the capacitance is weakened by making the short side longer, and the slot 4 is excited with a delayed phase and the beam is tilted to the input side 8. Since only the object 6 is moved, the input microwave does not have to be wideband, the entire antenna does not become large, and the antenna efficiency does not decrease.

Embodiment 2. FIG.
FIG. 6 is a perspective view of an array antenna according to Embodiment 2 of the present invention. FIG. 7 is a cross-sectional view perpendicular to the tube axis direction of the array antenna according to the second embodiment of the present invention.
The array antenna 11 according to Embodiment 2 of the present invention is a waveguide slot array antenna, and includes a cylindrical waveguide 12 having a rectangular cross section with a long side of am and a short side of bm. A plurality of slots 14 are provided on one tube wall 13 on the long side of the cross section.
Further, it is movable close to one tube wall 15 on the short side of the cross section of the waveguide 12 and movable in the long side direction (hereinafter referred to as the long side direction) on a plane perpendicular to the tube axis direction. A plurality of structures 16 are provided in the tube axis direction. The movable structure 16 is controlled by a control circuit 18 provided outside the waveguide 12, and the gap fm between the other tube wall 17 on the short side of the cross section and the movable structure 16 is variable. The microwave is input from the input side 19 of the waveguide 12.

Generally, when a movable structure 16 that shortens the long-side direction of the cross section of the waveguide 12 is disposed, inductivity is exhibited as can be seen from the equivalent susceptance expressed by the equation (2). Note that Equation (2) is described in Reference Document 1.
And the inductivity increases as the long side of the cross section becomes shorter, that is, as the gap fm becomes narrower.

FIG. 8 is a sectional view in the tube axis direction of an equivalent circuit of the array antenna and the waveguide according to the second embodiment of the present invention.
As shown in FIG. 8B, since a plurality of movable structures 16 that shorten the long sides of the cross section of the waveguide 12 are arranged in the tube axis direction, an equivalent circuit of the waveguide 12 is shown in FIG. ). In the array antenna 11 in which the movable structure 16 is arranged so as to form a beam in a direction perpendicular to the tube axis direction, the movable circuit 16 is moved by the control circuit 18 so that the gap fm is narrowed. In the circuit, the reactance of the portion corresponding to the movable structure 16 is increased, and the phase of the microwave propagating in the waveguide 12 is delayed. As a result, as shown in FIG. 9, each slot 14 is excited with a lagging phase, and the beam directed in the direction indicated by the broken line before the movement of the movable structure 16 is directed in the direction indicated by the solid line, that is, the beam on the input side 19. Tilt.

  Further, in the array antenna 11 in which the movable structure 16 is arranged so as to form a beam in a direction perpendicular to the tube axis direction, the movable structure 16 is moved by the control circuit 18 as shown in FIG. Is made wider, the reactance of the portion corresponding to the movable structure 16 in the equivalent circuit becomes smaller, and the phase of the microwave propagating in the waveguide 12 advances. As a result, each slot 14 is excited with a leading phase, and the beam that has been directed in the direction indicated by the broken line before the movement of the movable structure 16 is tilted in the direction indicated by the solid line, that is, the side opposite to the input side 19.

  In the array antenna 11 according to the second embodiment of the present invention, the inductivity is enhanced by shortening the long side of the cross section in the waveguide 12, the slot 14 is excited with a delayed phase, and the beam is tilted to the input side 19. On the contrary, the inductivity is weakened by making the long side long, and the movable structure is arranged in the waveguide 12 so that the slot 14 is excited at the leading phase and the beam is tilted to the opposite side with respect to the input side 19. Since only the object 16 is moved, the input microwave does not have to be wideband, the entire antenna does not become large, and the antenna efficiency does not decrease.

Embodiment 3 FIG.
FIG. 11 is a perspective view of an array antenna according to Embodiment 3 of the present invention. FIG. 12 is a sectional view in the tube axis direction of a waveguide according to the third embodiment of the present invention.
The array antenna 31 according to the third embodiment of the present invention is a waveguide slot array antenna, and includes a cylindrical waveguide 32 having a rectangular cross section having a long side of am and a short side of bm. A plurality of slots 34 are provided in one tube wall 33 on the long side of the cross section.
In addition, a movable structure 36 that is movable in the tube axis direction is provided at the end portion 35 of the waveguide 32. The movable structure 36 is controlled by a control circuit 37 provided outside the waveguide 32, and the position where the microwave is terminated is varied.

  In the array antenna 31 in which the movable structure 36 is arranged so as to form a beam in a direction perpendicular to the tube axis direction, the antinode portion of the standing wave formed in the waveguide 32 is almost at the position of the slot 34. The positions at which the microwaves are terminated are set so that the electric power input from the input side 38 is supplied to the slot 34 efficiently. At this time, in the antinode portion of the standing wave, the forward wave 41 and the backward wave 42 are in phase with respect to the tube axis direction. Details are described in Reference 1.

  Therefore, in the array antenna 31 in which the movable structure 36 is arranged so as to form a beam in a direction perpendicular to the tube axis direction, the control circuit 37 moves the movable structure 36 with respect to the tube axis direction as shown in FIG. Then, when moving forward or backward, the position of the terminal end that has been the reflection point of the forward wave 41 moves, so that the antinode portion of the standing wave that has occurred so far moves from the position of the slot 34. Therefore, one of the phases of the forward wave 41 and the backward wave 42 in the slot 34 is advanced, and the other is delayed. Therefore, the beam formed by each wave is opposite to the beam tilted in the direction of the input side 38 and the input side 38. The beam tilts in the direction and forms a bidirectional beam 43.

Embodiment 4 FIG.
FIG. 14 is a perspective view of an array antenna according to the fourth embodiment of the present invention. FIG. 15 is a top view for explaining propagation of the microwave equiphase surface inside the parallel plate waveguide according to the fourth embodiment of the present invention.
The array antenna 51 according to the fourth embodiment of the present invention is a parallel plate waveguide slot array antenna including a parallel plate waveguide 52 having two flat plates 53 and 54 arranged in parallel. A plurality of slots 55 are arranged on one flat plate 53.
The array antenna 51 is close to the other flat plate 54 and is movable in the normal direction of the flat plate 54 and a control circuit 57 that controls the movable structure 56 outside the parallel plate waveguide 52. Is provided. When the movable structure 56 is moved, the gap between the flat plate 53 and the movable structure 56 is narrowed or expanded.

  The microwave input from the input side 58 travels in one direction from the input side 58 because it is non-reflective terminated on the opposite side. Here, the traveling direction of the microwave is referred to as a tube axis 61. The input microwave power is sequentially supplied to the slot 55 in the direction of the tube axis 61 and radiated to the space. In accordance with the microwave equiphase surface 62 propagating in the parallel plate waveguide 52, power is supplied to the slot 55 in the same phase in the direction orthogonal to the tube axis 61 direction, and is symmetrical to the tube axis 61, that is, includes the tube axis 61. Form a beam in-plane.

FIG. 16 shows a cross-sectional view of a plane parallel to the tube axis of a parallel plate waveguide according to Embodiment 4 of the present invention.
As shown in FIG. 16, when the control circuit 57 changes the gap between the flat plate 53 and the movable structure 56 so that the gap is inclined in the plane perpendicular to the tube axis 61, the gap is inputted to the narrower side than the wider side. Microwave advances in phase. The equiphase surface 62 at this time is shown in FIG.
As shown in FIG. 17, the equiphase surface 62 in the parallel plate waveguide 52 is perpendicular to the tube axis 61, and the slot 55 to which power is supplied by the traveling microwaves has a cross section. There is a phase gradient in the direction. As a result, a beam tilted in a direction orthogonal to the tube axis direction can be formed.

1 is a perspective view of an array antenna according to Embodiment 1 of the present invention. It is sectional drawing by the plane perpendicular | vertical to the tube axis | shaft of the waveguide by Embodiment 1 of this invention. It is sectional drawing by the plane containing the equivalent circuit of the waveguide by Embodiment 1 of this invention, and the tube axis | shaft of a waveguide. It is a figure for demonstrating an example of the beam radiated | emitted from the array antenna by Embodiment 1 of this invention. It is a figure for demonstrating another example of the beam radiated | emitted from the array antenna by Embodiment 1 of this invention. It is a perspective view of the array antenna by Embodiment 2 of this invention. It is sectional drawing by the plane perpendicular | vertical to the tube axis of the waveguide by Embodiment 2 of this invention. It is sectional drawing by the plane containing the equivalent circuit of the waveguide by Embodiment 2 of this invention, and the tube axis | shaft of a waveguide. It is a figure for demonstrating an example of the beam radiated | emitted from the array antenna by Embodiment 2 of this invention. It is a figure for demonstrating another example of the beam radiated | emitted from the waveguide slot array antenna by Embodiment 2 of this invention. It is a perspective view of the array antenna by Embodiment 3 of this invention. It is sectional drawing by the plane containing the tube axis | shaft of the waveguide by Embodiment 3 of this invention. It is a figure for demonstrating an example of the beam radiated | emitted from the array antenna by Embodiment 3 of this invention. It is a perspective view of the array antenna by Embodiment 4 of this invention. It is a top view for demonstrating propagation of the microwave equiphase surface inside the array antenna by Embodiment 4 of this invention. It is a figure for demonstrating the cross-sectional structure of the array antenna by Embodiment 4 of this invention. It is a top view for demonstrating that the equiphase surface of the microwave inside the parallel plate type waveguide slot array antenna by Embodiment 4 of this invention inclines and propagates.

Explanation of symbols

  1, 11, 31, 51 Array antenna 2, 2, 32 Waveguide 3, 5, 13, 15, 17, 33 Tube wall 4, 14, 34, 55 Slot, 6, 16, 36, 56 Movable Structure, 7, 18, 37, 57 control circuit, 8, 19, 38, 58 input side, 35 termination, 41 forward wave, 42 backward wave, 43 bidirectional beam, 52 parallel plate waveguide, 53, 54 flat plate, 61 tube axis, 62 equiphase surfaces.

Claims (4)

In an array antenna including a waveguide having a plurality of slots arranged on a tube wall,
A normal direction of the tube wall in which the slots are arranged so that a gap between the slot and the tube wall in which the slots are arranged is narrowed or widened in the vicinity of the tube wall facing the tube wall in which the slots are arranged. An array antenna comprising a plurality of movable structures movable in the tube axis direction. In an array antenna including a waveguide having a plurality of slots arranged on a tube wall,
Moves in the normal direction of the adjacent tube wall so that the slot between the adjacent one of the tube walls adjacent to the arranged tube wall is narrowed or widened. An array antenna comprising a plurality of movable structures arranged in the tube axis direction. In an array antenna including a waveguide having a plurality of slots arranged on a tube wall,
An array antenna, characterized in that a movable structure movable in the tube axis direction of the waveguide is disposed at a terminal portion of the waveguide. In an array antenna comprising a first flat plate in which a plurality of slots are arranged and a second flat plate arranged in parallel with the first flat plate,
A movable structure that is movable in the normal direction of the first flat plate so that the gap between the first flat plate and the gap between the first flat plate and the first flat plate is narrowed or widened on the second flat plate. An array antenna characterized in that a plurality of array antennas are arranged.

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