JP5261628B2 - Waveguide slot array antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waveguide slot array antenna in which a band center frequency is shifted by exchanging a slot plate, and a frequency bandwidth at the center frequency is widened. <P>SOLUTION: The waveguide slot array antenna adopts a center feeding system for feeding power to a radiation waveguide and implements techniques for suppressing reflection from a slot by reducing the interval of slots 2 smaller than 1/2 intra-radiation-waveguide wavelength at a center frequency to be used. In order to correct inclinations, caused by reduction of the interval, of radiation beams to the side of a feed waveguide 4 on both sides of the feed waveguide 2 and in order to prevent radiation in an unwanted direction from being increased even if slots having great offset is increased by adopting the center feeding system, the slot plate 1 is inclined in such a way that the height of a partition wall 8 is inclined downward from a coupling part 10 to a termination part 9. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  According to the present invention, a base body provided with a feeding waveguide groove and a radiation waveguide groove and a slot plate in which slots as antenna elements are formed in rows at positions corresponding to the radiation waveguide groove are screwed or It belongs to the technical field of a waveguide slot array antenna that is in close contact by means of adhesion or the like and is mainly used in the millimeter wave band or the microwave band.

Such a waveguide slot array antenna has a relatively narrow frequency bandwidth.
Therefore, the use center frequency is limited to one. However, there is an economical problem because an antenna must be prepared for each different use center frequency. Therefore, a waveguide slot array antenna has been proposed that can shift the center frequency of use by changing only the slot plate without changing the expensive base body (for example, see Patent Document 1).

FIG. 2 is a perspective view of such a waveguide slot array antenna before the slot plate is mounted. FIG. 3 shows three slot plates having different center frequencies ((a), (b) and (c) in FIG. )) And a plan view of the base body ((d) in the figure).
By attaching a slot plate having a desired center frequency to the base body, a waveguide slot array antenna of the frequency band can be obtained.

The base body (d) is provided with a feed waveguide 4 in the lateral direction of the lower side and has a feed port 7 in the center thereof.
A plurality of rows of radiating waveguides 5 are provided in the direction perpendicular to the feeding waveguide 4 (upward) with a partition wall 8 therebetween. This is called one-sided power feeding because the feeding waveguide groove is provided on one side of the base body.

In such an antenna, when power is supplied from the power supply port 7, an electromagnetic wave is radiated from each slot to the space.
At this time, a part of the electromagnetic wave is reflected toward the feed waveguide without being radiated from the slot to the space. Since this reflection is a loss, measures are taken to make it as small as possible.

As a countermeasure, the longitudinal interval of the slots of the slot plate 1 is set to be larger or smaller than a half of the guide wavelength λ _g of the use center frequency, and the slot interval is set to the guide wavelength λ at the use center frequency. Instead, it is set to be 1/2 of _g , and instead, an inductive wall is provided on the partition wall surface opposite to the offset of the slot so as to correspond to each slot, and the reflection from this cancels the reflection from the slot.
In this case, the distance between the inductive walls in the waveguide axis direction is also determined by the guide wavelength λ _g at the operating frequency in the same manner as the slot.

FIG 2, the antenna of FIG. 3, also different course guide wavelength lambda _g from central frequency used is changed by replacing the different slot plate slotted interval.
However, since the inductive wall is formed in the partition wall and cannot be changed in accordance with λ _g , the reflection canceling measure by the inductive wall cannot be adopted, and the slot interval is set to the guide wavelength at the center frequency used. by less than one-half of the lambda _g, thereby suppressing reflection at the slot. As a result, the radiation beam from the slot plate is inclined from the normal direction of the surface of the slot plate 1 toward the feed waveguide as shown in FIG.

However, there is no particular problem in using the antenna of FIGS. 2 and 3 as long as the radiation beam is set so as to be directed in a desired direction.
In addition, the slot arrangement is a so-called staggered arrangement in which the width of the feed waveguide is offset alternately left and right with respect to the center line of the width of the feed waveguide.

  The reason is that the radiation phase of adjacent slots differs slightly by π radians at a distance of a little less than a half wavelength in the length direction of the radiation waveguide, and differs by π radians by being located on the opposite side of the center line. The reason is to emit near 2π radians, that is, near in-phase.

And this offset amount becomes large gradually as it goes to the termination | terminus side from the electric power feeding end side of a radiation waveguide.
The reason is that the electromagnetic wave input from the feeding end is sequentially emitted from the slot, so that the level of the electromagnetic wave propagating in the waveguide decreases as the end approaches.
However, since it is desirable to make the radiation intensity from each slot as uniform as possible, the amount of offset from the center of the tube width is gradually increased in order to perform radiation at the same level as the slot on the feeding end side from the reduced electromagnetic wave level in the tube. Is going.
However, there is a problem that radiation in an unnecessary direction increases as the number of slots having a large offset amount increases.

On the other hand, as a technique for widening the frequency bandwidth of such a waveguide slot array antenna, the feeding waveguide is placed at the center of the base body as shown in FIG. 4 instead of the one-side feeding as shown in FIGS. A so-called central feeding system in which radiation waveguides are provided on both sides is known (for example, see Non-Patent Document 1).
However, in FIG. 4, since the shift of the center frequency due to the replacement of the slot plate is not considered, the reflection from the slot is suppressed by providing an inductive wall on the melting wall, and the slot interval is two times the guide wavelength. 1 is assumed. Therefore, there is no problem that the beam is tilted.

Therefore, the inventors have changed the slot frequency with different slot spacings, such as the antennas of FIGS. 2 and 3, by changing the center frequency of the waveguide slot array antenna at each selected center frequency. We aimed to realize a center-fed waveguide slot array antenna with a wide frequency bandwidth.
JP 2007-336659 A (paragraphs [0036] to [0043], FIGS. 1 and 3 to 5) Park Seok, Jiro Hirokawa, Makoto Ando, “Design of Cross-branch for Single-layer Waveguide Antenna Feeding”, IEICE 2001 Communication Society Conference Proceedings 1, IEICE, 2001 8 May 29, P.I. 173

However, since the use center frequency is shifted by changing the slot plate, as a means for suppressing reflection at the slot, the slot interval of each slot plate is used as the center of use as in the antenna of FIGS. It must be employed a technique called smaller than the guide wavelength lambda 1 half of _g in the frequency.
As a result, in the central feed type, the direction of the radiation beam formed by the slot plates on both sides of the feed waveguide is fed from the normal direction of the slot plate as shown in FIG. It tilts so as to be close to the waveguide side. However, there is a problem that such a beam tilt adversely affects the radiation directivity of the entire antenna.

Another problem is the amount of slot offset.
In the case of single-side power feeding as shown in FIGS. 2 and 3, there is one termination of one radiation waveguide. However, this one waveguide is divided into two by adopting the central feeding system, and the termination is 2 At the location, there is a problem that the number of slots with a large offset amount is doubled, and radiation in an unnecessary direction increases, so that side lobes increase and aperture efficiency decreases.

  The problem to be solved by the present invention is that, in view of the above-mentioned problems of the prior art, there is no problem of beam tilt and unnecessary radiation increase, and the center frequency can be shifted by replacing the slot plate with a central feed type, In addition, a waveguide slot array antenna having a wide bandwidth around each frequency is realized.

The present invention has the following means in order to solve the above problems.
The configuration of the present invention includes a feed waveguide groove extending linearly and a radiation waveguide groove coupled to both sides of the feed waveguide groove by a coupling window so as to extend in a direction perpendicular to the longitudinal direction of the feed waveguide groove. Are formed, and the height of the partition wall separating the adjacent radiation waveguide grooves is highest at the coupling portion and lowest at the end portion of the radiation waveguide groove, and the top portion of the partition wall is inclined downward toward the termination portion. A base plate, and a slot plate that can be attached and removed so as to be in close contact with the top of the partition wall so as to cover the entire waveguide groove of the base body, and the slot for radiation at a position corresponding to each radiation waveguide groove The slot has an interval in the direction of the radiation waveguide that is shorter than one half of the wavelength in the radiation waveguide at the center frequency of use defined in the slot plate, and slots adjacent to each other in the column direction are radiation waveguides. Opposite sides of the width center axis Offset, the offset amount is a waveguide slot array antenna, wherein the slot plate gradually increasing as it approaches to the end portion of the radiation waveguide trench, in that it consists of.

  In the waveguide slot array antenna of the present invention, as described in the problem solving means, the slot plate is inclined downward from the central feeding waveguide portion toward the end of the radiation waveguide. The direction of the radiation beam tilted toward the feeding waveguide can be made closer to the front direction, and by making the inclination angle of the slot plate coincide with the inclination angle of the radiation beam in FIG. The tilting has an effect that the adverse effect on the radiation directivity can be greatly improved.

  Further, since the slot plate is inclined downward toward the end of the radiation waveguide, the distance between the slot plate and the bottom surface of the radiation waveguide groove decreases as the end approaches, and as a result, the coupling between the waveguide and the slot is reduced. The intensity increases and the radiation power from the slot increases. In the slot array antenna, the reason why the offset amount of the slot increases as it advances toward the end is that the electromagnetic wave in the radiation waveguide advances while radiating from the side-by-side slots, so its strength decreases as it approaches the end. Go. This is because radiation with the same level as the slot on the feeding end side is performed from the lowered electromagnetic wave level.

  However, in the present invention, as described above, since the slot plate is inclined, the degree of coupling of the slot increases as it approaches the end, so that the amount of offset can be reduced accordingly, and as a result, There is an effect that electromagnetic radiation in an unnecessary direction caused by a large offset amount is reduced, and the antenna can be made low in side lobe and highly efficient.

  In the waveguide slot array antenna of the present invention, the inclination of the radiation beam is determined by how much the loss due to reflection at the slot during transmission is suppressed. On the other hand, the inclination angle of the slot plate is determined depending on how much the offset amount of the slot is increased toward the end. Therefore, the extent to which the inclination angle of the radiation beam and the inclination angle of the slot plate are matched, and the extent to which the radiation in the unnecessary direction determined by the allowable reflection loss and offset amount is allowable. The best embodiment is the one determined together.

  In addition, since the use frequency band may be shifted by replacing the slot plate when the slot plate is attached to the base body, replaceable screwing is the best embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a side sectional view of a waveguide slot array antenna according to an embodiment of the present invention as viewed from the tube axis direction of a feed waveguide.
A feeding waveguide 4 extending in a straight line is formed in the center of the plate-like base body, and a plurality of radiation waveguides 5 are parallel to each other in a direction perpendicular to the longitudinal direction of the feeding waveguide. It is provided and coupled to the feed waveguide 4. The radiation waveguides 5 adjacent to each other in the direction perpendicular to the paper surface are separated by a partition wall 8.

  In the present invention, the height of the partition wall 8 is a downward slope from the coupling portion 10 to the terminal portion 9. By this inclination, the beam direction inclined toward the feeding waveguide 4 as shown in FIG. 6 can be directed to the boresight direction like the beam shown in FIG.

  Next, since the slot plate 1 is inclined, the distance h between the slot plate 1 and the bottom surface of the radiation waveguide decreases as the distance from the coupling portion 10 to the terminal portion 9 increases. When the distance is reduced, the degree of coupling of the slot 2 is increased, and the ratio of the radiation intensity from the slot to the electromagnetic field intensity in the radiation waveguide is increased.

Therefore, when the conventional h is constant, the electromagnetic wave intensity in the radiating waveguide decreases as the terminal approaches the terminal, but the terminal tries to obtain the same radiated electromagnetic field intensity from the slot. Although the offset amount of the slot is increased as the distance approaches, the distance h is changed to become smaller, and it is not necessary to increase the offset amount as much as in the prior art.
As a result, electromagnetic radiation in an unnecessary direction due to a large offset amount can be suppressed, and low side lobe and high efficiency can be realized.

  As described above, the waveguide slot array antenna of the present invention can be replaced with a central feed type having a wide frequency bandwidth and a slot plate having a different slot arrangement by tilting the slot plate 1 as shown in FIG. Thus, a waveguide slot array antenna capable of shifting the center frequency is obtained.

  The base body 3 is manufactured by die casting in which a molten alloy is press-fitted into a mold. The slot plate 1 is provided with a slot 2 in a metal plate by punching so that the base body 3 can be inclined after punching. It is bent and processed.

It is sectional drawing seen in the axial direction of the feed waveguide which shows that the slot plate of the waveguide slot array antenna of this invention inclines. FIG. 6 is a perspective view of a conventional waveguide slot array antenna that can shift a use center frequency by changing a slot plate in a single-side feeding type. FIG. 3 is a plan view of a slot plate and a base body of the waveguide slot array antenna of FIG. 2, in which three slot plates having different center frequencies are prepared. FIG. 6 is a plan view of a slot plate and a base body of a conventional center-fed waveguide slot array antenna. FIG. 4 is a side sectional view showing the inclination of a radiation beam in the antennas of FIGS. 2 and 3. FIG. 4 is a side sectional view showing an inclination of a beam when the antennas of FIGS. 2 and 3 are configured as a central feeding type.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slot plate 2 Slot 3 Base body 4 Feeding waveguide 5 Radiation waveguide 6 Inductive wall 7 Feeding port 8 Bulkhead 9 Termination part 10 Coupling part

Claims (1)

A plurality of linear waveguide feed waveguide grooves and a plurality of radiation waveguide grooves coupled with coupling windows so as to extend in a direction perpendicular to the longitudinal direction of the feed waveguide groove on both sides of the feed waveguide groove; The height of the partition wall separating adjacent radiation waveguide grooves is the highest at the coupling portion, the lowest at the end portion of the radiation waveguide groove, and the top of the partition wall is inclined downward toward the termination portion; and
A slot plate that can be attached and removed so as to be in close contact with the top of the partition wall so as to cover the entire waveguide groove of the base body, and has a slot slot for radiation at a position corresponding to each radiation waveguide groove, The distance between the slots in the direction of the radiation waveguide is shorter than one half of the wavelength in the radiation waveguide at the use center frequency defined for the slot plate, and the slots adjacent in the column direction are relative to the central axis of the radiation waveguide width. The slot plate is offset to the opposite side, and the amount of the offset gradually increases as it approaches the terminal end of the radiation waveguide groove ,
A waveguide slot array antenna comprising:

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