JP2008211326A - Waveguide with slot and waveguide slot antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waveguide with slots such that a width of a slot surface is smaller than an H plane width of the waveguide, intervals of slots are at intervals where no grating lobe appears, and a plane of radiation polarization is orthogonal to a waveguide axial direction, and a waveguide slot antenna using the waveguide with the slots. <P>SOLUTION: Plate-shaped ridges along the waveguide axial direction are stood in parallel to the H plane in the center of an E plane wall width in a rectangularly-sectioned waveguide, and slots which are long in the waveguide axial direction are provided at intervals a 1/2 as long as an in-waveguide wavelength in the waveguide axial direction so that adjacent slots are opposed each other across a ridge standing line. Consequently, the width of the slot surface is narrower than the H plane width, no grating lobe appears, and a plane of polarization is orthogonal to the waveguide axial direction. A circular polarization antenna is obtained by arranging the waveguide with the slots in parallel to a waveguide with slots whose plane of polarization is parallel to its waveguide axial direction, and a horizontal polarization nondirectional antenna is obtained by providing two waveguides with slots parallel and upright in opposite direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a slotted waveguide used for a waveguide slot antenna, and a slotted waveguide having a plane of polarization perpendicular to the tube axis direction even when all slots are arranged in a substantially straight line. And a waveguide slot antenna using the slotted waveguide.

  Slotted waveguides whose polarization planes are perpendicular to the tube axis can be used when vertical polarization is required with the slotted waveguide installed horizontally or when the slotted waveguide is installed vertically. In this case, horizontal polarization is required.

FIG. 7 is a diagram showing a conventional slotted waveguide whose polarization plane is orthogonal to the tube axis direction.
(A) shows a rectangular waveguide having an H-plane (wide wall surface) in the tube axis direction in such a manner that center lines are alternately sandwiched at intervals of ½ in-tube wavelength (λ _g / 2) in the tube axis direction. A long slot is provided.
Since the directions of currents flowing through the tube wall are opposite to each other on both sides of the center line, the radiated electric field in the slots opposite to each other on the center line and spaced by half the tube wavelength (λ _g ) in the tube axis direction. Are in phase.

Further, since the slot is cut so as to be orthogonal to the wall current, the direction orthogonal to the slot is the direction of the electric field. Therefore, the direction of the arrow indicating the direction of the electric field is the same in all slots.
Thus, the electric field plane radiated from each slot is orthogonal to the tube axis direction (see, for example, Non-Patent Document 1).

(B) is the E-plane of the rectangular waveguide (narrow wall), at intervals of 1 guide wavelength lambda _g in the axial direction of the tube, in which a long slot provided in the tube axis direction. Accordingly, the phase is in phase at each slot position, and the radiated electric field is orthogonal to the slot, so that the direction indicated by the arrow is present.
Thus, the electric field plane radiated from each slot is orthogonal to the tube axis direction.
Naohisa Goto, “Illustration / Antenna”, First Edition, The Institute of Electronics, Information and Communication Engineers, March 20, 1995, p. 291

However, the conventional slotted waveguides have the following problems when they are used for waveguide slot antennas.
First, the slotted waveguide of FIG. 7A is that the opening size of the antenna is increased because the slot is provided on the wide wall surface of the waveguide.
For example, when a slot array antenna or the like in which a plurality of the waveguides with slots are arranged in parallel with the slot surfaces facing in the same direction, this defect appears remarkably.

  In addition, when a circularly polarized wave waveguide slot antenna is configured in combination with another E-plane slotted waveguide having orthogonal polarization planes, there is a problem that the element spacing is increased.

Next, in the slotted waveguide of FIG. 7B, since the slot is cut in the E plane, there is no problem with the size as in FIG. 7A, but the radiation phase from each slot is in phase. In order to achieve this, the slot interval is the one-wavelength wavelength interval.
Meanwhile In the recess waveguide, since the guide wavelength lambda _g longer than the free space wavelength lambda _O, slot interval is longer than the free space wave lambda _O.

  However, in an antenna in which slots are arranged (slot array antenna), there is a problem that a grating lobe appears when the slot interval becomes a free space wavelength and it cannot be used as an antenna practically.

  In view of the above-mentioned problems of the prior art, the problem of the present invention is that the width of the slot surface is smaller than the width of the H surface of the waveguide and the interval between the slots is such that no grating lobe appears, and the polarization plane is in the tube axis direction. It is to realize a slotted waveguide and an antenna using the slotted waveguide.

The present invention has the following configurations in order to solve the above problems.
In the first configuration of the present invention, a plate-like ridge extending along the tube axis direction is erected on the E-plane wall in the rectangular cross-section waveguide, and the interval in the tube axis direction is a half-wavelength interval in the tube. A slotted waveguide characterized by having long slots in the tube axis direction at positions alternately sandwiching every other position where the erection is erected.

  According to a second configuration of the present invention, the slotted waveguide according to the first configuration is arranged as one or a plurality of waveguides arranged in parallel with the slot surfaces facing in the same direction, and a power feeding device that feeds electromagnetic waves to them. And a waveguide slot antenna.

  In the third configuration of the present invention, the slotted waveguide of the first configuration and the slot between the slots adjacent to each other on the one E-plane wall in the tube axis direction at a half-tube wavelength interval are reversed. A waveguide array in which slotted waveguides provided with slots are arranged in parallel with the slot surfaces facing in the same direction, and a power feeding device that feeds electromagnetic waves to both waveguides with a phase difference of 90 degrees A waveguide slot antenna having a polarization plane of circular polarization.

  A fourth configuration of the present invention is a waveguide array in which two slotted waveguides of the first configuration are adjacent to each other with the slot surfaces facing in opposite directions and the side surfaces without slots facing each other. A waveguide slot antenna having a directivity in a plane perpendicular to the tube axis.

The structure of the slotted waveguide of the first configuration is similar to a structure folded in half with respect to the center line in the tube axis direction of the H surface of the rectangular cross-section waveguide.
FIG. 6 is a diagram showing an approximate structure when the rectangular waveguide is folded in half along the tube axis direction center line of the H-plane tube width.
(A) is a figure which shows the pipe-axis direction cross section of a rectangular waveguide. On both sides of the E-plane, with the guide wavelength lambda _g intervals in the axial direction of the tube, a long slot in the tube axis direction is between the left and right sides is provided with a shift by lambda _{g /} 2.
(B) is an approximate structure which is bent in the direction of the arc arrow with the center of (a) as the boundary. The part where the left and right H surfaces at the center of (a) are folded corresponds to the ridge part of (b) (the length is drawn short).
(C) is E surface (side surface) which looked at (b) from the right side. As described in the explanation of (a), slots on the E planes on both sides are provided at intervals of the guide wavelength λ _g in the tube axis direction and shifted in the tube axis direction by λ _g / 2 between the left and right sides ( When it is folded as shown in b) and the left and right E planes are aligned, the arrangement is such that the ridge positions are alternately sandwiched at intervals of λ _g / 2 in the tube axis direction as shown in (c).

On the other hand, when focusing on the direction of the electric field in (b), the direction of the electric field is reversed between the upper side and the lower side of the ridge at the same position in the tube axis direction. That is, the upper electric field and the lower electric field are just in reverse phase. Accordingly, the electric field at any one slot position and the electric field at the slot position on the opposite side across the ridge position at the interval of λ _g / 2 in the tube axis direction are in phase.
Therefore, the direction of the radiation electric field cut in the direction orthogonal to the current flowing through the tube wall at that position is the same as shown by the arrow in (c).
Accordingly, the electric field surface radiated from the slot array as shown in FIG. 4C is a surface orthogonal to the tube axis direction.

Next, the waveguide dimensions will be described.
Since the H-plane width of the waveguide in FIG. 6A is a, the cutoff frequency of this waveguide is C / (2a). Where C is the speed of light.
When considering the waveguide having the structure (b) having the same cut-off frequency, A≈a / 2. That is, the width of the H plane is about half of the waveguide width of (a).
As described above, this is because the structure (b) is obtained by folding the structure (a) in half.

Next, since the dimension of the E surface is b in (a), B = 2b in (b).
If b <a / 2 in the waveguide (a),
B = 2b <a,
The slot surface width in (b) is smaller than the wide wall surface width in (a).
Since the dimension a directly relates to the cutoff frequency in the waveguide, when the cutoff frequency is determined, a is naturally determined, and this cannot be changed due to the convenience of the mounting space, but the dimension b has such a restriction. Not at all.
Therefore, it is possible to set b smaller than the ratio of a to b in the standard waveguide.

From what has been described above, the slotted waveguide according to the first configuration of the present invention has the same cutoff frequency as that of the conventional slotted waveguide of FIG. ), The width of the H surface can be nearly half (A≈a / 2), and the width of the slot surface (E surface) is also the slot surface (H surface) of FIG. ), The slot spacing is substantially in-phase radiation at λ _g / 2, and there is an effect that radiation of a polarization plane orthogonal to the tube axis direction is possible without generating a grating lobe.

  The second configuration of the present invention is an antenna device that feeds power from the power feeding device to the slotted waveguide of the first configuration. When the slotted waveguide is set up vertically, horizontal polarization is obtained. Vertical polarization can be obtained.

  According to a third configuration of the present invention, the slotted waveguide of the first configuration and the slotted waveguide having a plane of polarization that includes the tube axis and is orthogonal to the slot surface are parallel with the slot surface facing the same direction. Since they are arranged, the polarization planes of the waveguides with both slots are orthogonal. Since the feeding device feeds both waveguides with a phase difference of 90 degrees, the combined vector of the electric fields radiated from the waveguides with both slots rotates, so-called circular deviation. A waveguide slot antenna from which waves can be obtained is constructed.

According to a fourth configuration of the present invention, two slotted waveguides of the first configuration are arranged in parallel adjacent to each other so that the slot surfaces face each other and the H surfaces face each other. This slot row is like a rod-shaped antenna whose plane of polarization is a plane orthogonal to the tube axis direction and whose directivity in the plane is almost omnidirectional.
Therefore, by constructing a waveguide slot antenna in which the directivity in the orthogonal plane becomes omnidirectional by making the interval between the slot arrays of two parallel waveguides with slots smaller than a half wavelength. can do. This antenna is a horizontal polarization and horizontal plane omnidirectional antenna that is installed vertically.

  In the present invention, the ridge is provided on the center line of the E plane, and its thickness is best made as thin as possible in manufacturing, and the structure in which the slots are arranged in a state close to a straight line is best.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view of a slotted waveguide according to the present invention.
The ratio of the H plane width to the E plane width is about 1-2. The ridge 2 is provided parallel to the H surface 4 along the center line of the width of the right E surface 5. In-pipe arrows indicate lines of electric force. The direction of the electric field is reversed between the upper space and the lower space of the ridge 2. That is, the phase is exactly the same as 180 degrees.
Therefore, the phase of the slot 3 on the one side of the ridge 2 and the slot 3 on the other side of the ridge 2 away from the slot 3 by a distance of λ _g / 2 in the tube axis direction is in phase.
As a result, the radiated electric fields from the slots arranged at the intervals and positions shown in FIG. 1 are all in phase.

Further, since the current flowing through the E-plane tube wall flows in the vertical direction in the figure and the slot 3 is provided so as to cross this current, the direction of the radiated electric field is a direction orthogonal to each slot 3. As a result, the plane of polarization of the radiated electric field is a plane orthogonal to the tube axis direction.
Accordingly, the antenna using the slotted waveguide 1 in the horizontal direction is vertically polarized, and the antenna used in the vertical direction is horizontally polarized.

Although the ridge 2 is depicted with a thickness in the figure, the thickness does not contribute anything electrically, so it is desirable that the ridge 2 be as thin as possible within the range allowed for manufacturing and strength.
Further, since it is desirable that the positions of the slots 3 be as straight as possible, it is preferable to provide the slots 3 as close to the ridge 2 as possible.

In the case of a rectangular waveguide, the H-plane width determines the cut-off frequency. Therefore, if the operating frequency is determined, the H-plane width is determined and its selection is restricted, but the E-plane width is such a decisive factor. Since there is no particular restriction, there is a certain degree of freedom in the direction to be sandwiched, so there is a great possibility of miniaturization of the antenna.
However, since the impedance changes when the E-plane width is sandwiched from the standard dimension, it is necessary to consider and consider whether it is necessary to use an impedance transformer.

FIG. 2 shows a single-phase slotted waveguide 1 according to the present invention or a plurality of slotted waveguides 1 arranged in parallel with the slot surfaces facing in the same direction. It is a figure which shows the structure of the linearly polarized wave waveguide slot antenna made to do.
If the slotted waveguide 1 is installed horizontally, it becomes a vertically polarized antenna, and if installed vertically, it becomes a horizontally polarized antenna.

FIG. 3 is a diagram showing a configuration of a circularly polarized antenna in which the waveguide with a slot of the present invention and a conventional waveguide with an E-plane slot are combined.
1 is a slotted waveguide according to the present invention, and 6 is a known slotted slot provided with one slot on the E-plane wall in which the slopes of adjacent slots are opposite to each other at intervals of λ _g / 2 in the tube axis direction. It is a waveguide.
This is a circularly polarized waveguide slot antenna device in which the two slotted waveguides 1 and 6 are arranged in parallel with their slot surfaces facing in the same direction and are fed from the feeding device 8 with a phase difference of 90 degrees. .

The radiated electric field from the slot of the slotted waveguide 1 is perpendicular to the tube axis direction, whereas the direction of the radiated electric field of the slotted waveguide 6 is the tube axis direction. It will be orthogonal.
On the other hand, since both the slotted waveguides are fed with a phase difference of 90 degrees from the feeding device 8, the combined electric field of both electric fields becomes circularly polarized waves whose directions rotate.

FIG. 4 is a diagram showing a configuration of an omnidirectional antenna using two waveguides with slots according to the present invention.
The two waveguides with slots according to the present invention are arranged in a waveguide arrangement in which the slot surfaces face each other in opposite directions and the side surfaces without slots face each other. In-phase power is supplied to the tube. In this antenna, each slot row of the two slotted waveguides 1 can be considered as one rod-like radiation conductor.
That is, it can be considered that two non-directional bar-shaped radiation conductors are arranged in parallel at a certain interval in a plane orthogonal to the bar.

Such a combined directivity in a plane orthogonal to the rod-shaped direction of the antenna can be considered as a combined directivity when omnidirectional radiating elements are arranged at an interval d.
Such directivity can be obtained by calculating mathematical formulas as is well known.

FIG. 5 is a diagram showing the combined radiation directivity when two non-directional two radiating elements are placed on the left and right of the center of the horizontal axis (90-270) and excited.
The distance between the elements is 0.3 wavelength (solid line) and 0.5 wavelength (dotted line). As is well known in the case of 0.5 wavelength, it has an 8-character characteristic, whereas in the case of 0.3 wavelength, the levels at 90 and 270 degrees are the levels at 0 and 180 degrees. Although it is about -5 dB compared to the above, the overall shape is almost a circle and it can be said to be omnidirectional.

Therefore, in the antenna of FIG. 4 as well, if the distance between the slot array facing the front side and the slot array facing the opposite side is about 0.3 of the operating wavelength, the omnidirectionality about the solid line of FIG. 5 is obtained. Will be.
In the configuration shown in FIG. 4, when considering that the slotted waveguide 1 of the present invention has a structure that is folded in half at the center of the width of the H plane in principle, the cutoff wavelength λ _C is λ _C = 4A.
Since the wavelength used must be shorter than the cutoff wavelength, this is reduced to 1 / 1.2 of the cutoff wavelength λ _C.
That is, if λ _P = λ _C /1.2 is set,
Since λ _C = 4A,
The use wavelength λ _P is λ _P = 4A / 1.2, and when A is represented by λ _P , A = 0.3λ _P.

On the other hand by setting the distance C of the ridge line to about one 0.1 [lambda] _P-third of the A, interval B between the slots column regarded as rod-like radiation conductor is expressed by Equation 1 below.

  Therefore, it becomes approximately one third of the wavelength used, and omnidirectionality close to the solid line in FIG. 5 is obtained.

In FIG. 4, the two slotted waveguides are drawn apart from each other. However, when the waveguides are in close contact with each other, the ridge 2 is located at the center of the E-plane width of the slotted waveguide 1. From the standing position, C becomes equal to the E-plane width of the slotted waveguide 1.
The ratio of end slots Tsukeshirube wave tube 1 H-plane width A and E-plane width 0.3λ _P: 0.1λ _P namely 3: 1 becomes, H surface in a state where two slots Tsukeshirube wave tube 1 in close contact The ratio between the width and the E-plane width is 3: 2, which is considered to be an appropriate dimensional relationship.

It is a perspective view of the Example of the waveguide with a slot of the present invention. It is a figure which shows the structure of the waveguide slot antenna which arrange | positions the waveguide with a slot of this invention 1 or several in parallel, and is fed from a feeder. It is a figure which shows the structure of the circularly polarized wave antenna which combined the waveguide with a slot of this invention, and the waveguide with a conventional E surface slot. It is a figure which shows the structure of the omnidirectional antenna using two waveguides with a slot of this invention. It is a figure which shows synthetic | combination directivity at the time of arrange | positioning the omnidirectional 2 radiation | emission element at intervals. It is a figure which shows the approximate structure at the time of folding a rectangular waveguide in half by the pipe-axis direction centerline of the H surface pipe width. It is a figure which shows the conventional waveguide with a slot whose polarization plane is orthogonal to a tube-axis direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waveguide with a slot 2 Ridge 3 Slot 4 H surface 5 E surface 6 Waveguide with a slot 7 Feeder 8 Feeder

Claims (4)

  A plate-shaped ridge extending along the tube axis direction is erected on the E-plane wall in the cross-sectional rectangular waveguide, and the position where the ridge is erected is set at a wavelength interval in the tube of 1/2. A slotted waveguide characterized by having long slots in the tube axis direction at positions alternately sandwiched between the slots.   A slotted waveguide according to claim 1, or a waveguide array in which a plurality of slotted waveguides are arranged in parallel with a slot surface facing in the same direction, and a power feeding device that feeds electromagnetic waves to the waveguide array. Waveguide slot antenna.   2. A slotted waveguide according to claim 1, wherein the slotted waveguide is provided with a slot in which the slopes of adjacent slots are oppositely inclined at a wavelength interval of one-half in the tube axis direction in the tube axis direction on one E-plane wall. A waveguide array in which the wave guides are arranged in parallel with the slot surfaces facing in the same direction, and a feeding device that feeds electromagnetic waves to both waveguides with a phase difference of 90 degrees, and the polarization plane is circularly polarized A waveguide slot antenna.   A waveguide array in which the two waveguides with slots according to claim 1 are oriented so that the slot surfaces face each other in opposite directions and the side surfaces without slots face each other, and in-phase power feeding to each waveguide A waveguide slot antenna, wherein the directivity in a plane orthogonal to the tube axis is omnidirectional.

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