JPH02280504A - Leakage type waveguide slot array antenna - Google Patents

Abstract

PURPOSE:To correct the effect of reducing a guide wavelength with a radiation slot and to keep the guide wavelength constant by using a ridge waveguide as a radiation waveguide and varying the size of the ridge as being parted from a feeding side in the guide axis direction. CONSTITUTION:The height of the ridge is made constant and the width a' of the edge is made narrow as being parted from a feeding side. Thus, the guide wavelength reduced by the radiation slot is corrected to be kept constant in the waveguide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a leaky waveguide slot array antenna in which a large number of radiation slots are formed in a waveguide to form an array.

[Prior Art] Waveguide slot array antennas are known as antennas that transmit and receive high frequency radio waves such as microwave bands with high efficiency. Examples of leaky waveguide slot array antennas include W, J, GETS I NGER,'Ellip
ticallyPolarliged Lerky-W
ave Array I RE T
RAS-A[:Tl0NSON ANNTENAS A
ND PROPAGATION, PP165-172
, March 1962.

The above-mentioned antenna has a rectangular waveguide with a cross section, and a number of cross-shaped slots are formed at predetermined intervals in the longitudinal direction at positions offset from the center of the wide surface (H-plane) of a rectangular waveguide. High frequency power is supplied from one end of the antenna using a waveguide adapter, and the other end is configured as a circularly polarized wave-dimensional array antenna with a non-reflection termination structure. This antenna is basically a beam tilt type, and although it is a serial feed type, it also has a relatively wide bandwidth.By arranging it in a planar shape, it can be used for satellite broadcasting, for example. A high performance and highly functional antenna for reception can be constructed.

In other words, since the leaky waveguide slot array antenna has a waveguide structure, the loss is small and the entire antenna can be miniaturized, and by setting the tilt angle appropriately, it can be vertically or It has the advantage that it can be installed nearly horizontally, and can be installed relatively closely on the wall of a house, and can be installed flat on the roof of a vehicle.

[Problems to be Solved by the Invention] In a leaky waveguide slot array antenna, if the free space wavelength of the radio wave used is λ0, and the internal wavelength of the reflection waveguide in which the radiation slot is formed is 1g, then The spacing between the radiation slots is approximately 0.5λ. If it is smaller than , the main beam will be emitted in the direction of θ that satisfies the following equation (1), regardless of the spacing.

sinθ;λ. /λgo (1)
However, λg-in. / l-(io/2a)”
(2) θ: Angle formed from the direction perpendicular to the plane formed by the radiation slot. This assumes that the tube wavelength λg is uniform throughout the tube.

On the other hand, when a plurality of radiation slots are formed in a radiation waveguide to form at least a one-dimensional array antenna, maximum aperture efficiency can be obtained if the power radiated from each radiation slot is uniform. , the power inside the radiation waveguide gradually decreases as it moves away from the feeding side due to power radiation from each radiation slot, so in order to make the radiation power from each radiation slot uniform, it is necessary to It is necessary to strengthen the engagement between the free space created by the radiation slot and the electromagnetic field in the waveguide near the slot to the extent that the electric power in the tube decreases as the distance from the radiation slot decreases. Incidentally, the strength of the coupling can be determined fairly arbitrarily depending on the size and position of the radiation slot.

Due to this configuration, the conventional leaky waveguide slot array antenna has the following problems.

In other words, as the free space and the electromagnetic field in the radiation waveguide are coupled by the radiation slot, the internal wavelength in the radiation waveguide changes as shown in Equation (2) when there is no radiation slot.
The free space wavelength λ is greater than the tube wavelength λg0 given by . The waveguide is shifted to the side and shortened, and the degree of shortening increases as the coupling between the free space by the radiation slot and the electromagnetic field within the radiation waveguide becomes stronger. Therefore, if we try to make the amount of radiated power uniform from each radiation slot, the wavelength in the radiation waveguide becomes shorter as it moves away from the feeding side, which deviates from the principle of phase synthesis in a leaky waveguide slot array antenna. As a result, Sekiguchi efficiency decreases.

An object of the present invention is to provide a leaky waveguide slot array antenna that can solve the above-mentioned problems and further increase Sekiguchi efficiency.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a radiation waveguide that changes the size of the ridge as it moves away from the power feeding part side along the tube axis direction. It is characterized by using a waveguide.

[Function] In the present invention, by changing the size of the ridge of the ridge waveguide used as the radiation waveguide, the change in the wavelength in the tube due to the provision of the slot is corrected and the wavelength in the tube is kept constant. By controlling and aligning the maximum radiation direction from each slot, the aperture efficiency is increased.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

First, the principle of the present invention will be explained.

In general, the cutoff wavelength of a ridge waveguide. is known to change depending on the height and width of the ridge. On the other hand, the guide wavelength λg and the cutoff wavelength λ in the waveguide. is the free space wavelength λ
. is related by the following formula.

The present invention utilizes these principles and changes the size of the ridge of the ridge waveguide used as the radiation tube, that is, the height and width of the ridge, thereby increasing the cutoff frequency as it moves away from the power feeding section in the axial direction of the radiation tube. The aim is to correct the tube wavelength, which is shortened by the radiation slot, so as to keep it constant within the tube.

FIG. 1 is a perspective view showing an entire embodiment of the present invention.

Further, FIG. 2 is a reference diagram for explaining the slot in this embodiment, and FIG. 3 is a reference diagram for explaining the ridge in this embodiment.

Here, FIG. 2 shows a radiation tube with a --shaped rectangular cross section, with a cross-shaped slot cut in the wide side.

The shape of this slot is not limited to a cross shape, but may be a simple linear slot parallel to or perpendicular to the tube axis, or a combination of horizontal and vertical slots.

Further, FIG. 3 is a cross-sectional view of the ridge waveguide.

Here, in FIG. 3(^), the thickness of the waveguide plate constituting the ridge portion is thinner than in FIG. 3(B). Also, Figure 3 (
C) shows a structure in which a conductor plate is placed and glued inside a rectangular waveguide. In short, the shape of the hollow part inside the waveguide through which the electric waves propagate needs only to have a ridge-like continuous convex part. In Fig. 3, the ridge is one side of the wide surface (H surface). Although the ridges are shown only on both sides, they can be placed anywhere on the wide surface, but in order to not disturb the electromagnetic waves propagating within the waveguide and to allow only a single mode to pass through as much as possible. , it is best to place it in the center of a wide surface.

Returning to FIG. 1 again, one embodiment of the present invention will be described. 1st
In the embodiment shown in the figure, the height of the ridge is kept constant, and the width a° of the ridge is narrowed as it moves away from the power feeding section. In order to counteract the tendency of the wavelength in the tube to shorten due to the radiation slot as it moves away from the feeder side, it is important to decide whether to widen or narrow the width while keeping the height of the ridge constant.
It is determined by the width of the ridge closest to the power supply section. That is, when a'/a is changed while b/c is constant, the cutoff frequency has a peak at a certain constant value, and as it moves away from the peak, the cutoff frequency decreases and approaches the value when no ridge is provided. This peak value is approximately a'/a-0
, 5, and the width a° of the ridge closest to the power supply part is a
When '/a is set to be larger than the peak value, the width of the ridge may be made wider as it moves away from the power supply part side in the tube axis direction.

In either case of narrowing or widening the width of the ridge, the method of changing the width may be determined depending on the degree of coupling between the electromagnetic field in the radiation tube and the free space by the radiation slot. In this case, for example, even if the width of the ridge is narrowed from the feeder side and the width is finally eliminated, it may not be possible to compensate for the effect of shortening the wavelength in the pipe due to the radiation slot; By making the height C large or small, it is possible to sufficiently compensate for the effect of shortening the wavelength in the pipe due to the radiation slot.

Although FIG. 1 shows a case in which the width of the ridge is changed gradually in a tapered manner, it may be changed in a stepwise manner.

FIG. 4 is a diagram showing another embodiment of the present invention.

In this embodiment, the width of the ridge is kept constant, and the height Co of the ridge is gradually lowered. In this embodiment, the height of the ridge is also changed gradually in a tapered manner, but it is also possible to change it in a stepped manner.

In FIGS. 1 and 4, the ridge is provided on the surface opposite to the surface provided with the radiation slot. It is also possible to provide a ridge on the surface provided with the radiation slot. but,
In that case, the position and width of the ridge will be limited depending on the size of the radiation slot. Further, in both the embodiments shown in FIG. 1 and FIG. 4, the transverse resonance method, which is well known as a design method for a ridge waveguide, can be used to design the ridge with one height and one width.

In all of the embodiments described so far, the wavelength within the tube shortens as it moves away from the power supply side in the tube axis direction, but depending on the application, the aperture efficiency at the center frequency may be slightly sacrificed to widen the band. It is necessary to distribute the amount of radiation from each radiation slot without making it uniform. For example, the amount of radiation should be reduced near both ends along the length of the radiation tube, and the amount of radiation should be increased near the center. distribution is considered. In this case, after the channel wavelength is greatly shortened near the center, the degree of shortening decreases as you move away from the power supply side, and the channel wavelength may conversely increase.
Even in such a case, the wavelength within the tube can be kept constant by changing the width and height of the ridge.

[Effects of the Invention] As explained above, in the present invention, a ridge waveguide is used as a radiation waveguide, and the size of the ridge is changed as it moves away from the power feeding part side along the tube axis direction. , it is possible to correct the effect of shortening the wavelength in the tube due to the radiation slots and keep the wavelength in the tube constant, and as a result, it is possible to align the direction in which the radio waves emitted from each radiation slot are most intensified, and to improve the aperture efficiency. It has the effect of further increasing.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention, FIGS. 2 and 3 are reference views for explaining the first embodiment, and FIG. 4 is a second embodiment of the present invention. FIG. Figure 1 Figure 3 Figure 2

Claims (1)

[Claims] 1) A leaky waveguide slot array antenna characterized in that a ridge waveguide whose ridge size changes as it moves away from the feeder side along the tube axis direction is used as a radiation waveguide.