JPH04207207A - Leaky waveguide slot array antenna - Google Patents

Abstract

PURPOSE:To increase the aperture efficiency by arranging circularly polarized wave radiation slots on one wider face of a rectangular radiation waveguide so that the angle of intersection between two slots of each radiation slot is shifted from 90 deg.. CONSTITUTION:A radiation waveguide 1 has wide faces 1a and narrow faces 1b, and radiation slots 11 to 16 are provided on one wide face 1a in the axial direction of the waveguide at prescribed intervals. The angle of intersection between slots in two directions of each of radiation slots 11 to 16 is shifted from 90 deg.. That is, slots in the axial direction out of crossed slots between which the angle of intersection is 90 deg. are inclined at an angle theta which is different by the degree of shift of the phase difference from 90 deg.. Thus, the phase difference between two electric field components with respect to time is 90 deg..

Description

[Detailed description of the invention]

[Industrial application field 1

[Prior Art J] A waveguide slot array antenna is known as an antenna that transmits and receives radio waves of a relatively high frequency such as a microwave band with high efficiency. Conventionally, as a leaky wave type slot array antenna, for example, J. GETSINGER, "Ellipt"
icallyPolarized Leaky-Wav
e Array”, IRE TRANSACTIONS
ON ANTENNAS AND PROPAGATI
ON, pp165-172. March. There is one shown in 1962. This antenna has a rectangular waveguide with a uniform cross section, and a large 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 the rectangular waveguide. This is a one-dimensional array antenna for circularly polarized waves, in which a high frequency wave is inputted from one end using a waveguide adapter, and the other end has a non-reflection termination structure. This antenna is basically a beam tilt type, and although it is a series sequential feeding type, it also has a relatively wide bandwidth. By arranging the slots in a planar shape, it is possible to construct a high-performance and highly functional antenna for receiving satellite broadcasting, for example. That is, since the leaky wave type waveguide slot array antenna has a waveguide structure, it basically has less power feeding loss and can be highly efficient, and the entire antenna can be made smaller. In addition, by setting the tilt angle of the beam appropriately, it is possible to install it vertically or nearly horizontally when receiving stationary satellite radio waves, and it can be installed closely against the wall in a house, and it can be installed in a vehicle. It has the advantage of being able to be installed horizontally on the roof. [Problem to be Solved by the Invention] TE, which is the fundamental mode in a rectangular waveguide. When only the mode is being transmitted, the intensity of the component (X component) of the magnetic field in the waveguide in the direction across the waveguide is H, and the intensity of the component (Z component) along the waveguide axis direction is H2. When, HX, H2
are respectively expressed as follows. H,=H0(1-(λo/2al "l""x 5i
n(x x/al・(1)o2=−jHo (λa/2
a) xcos(ix/a) =12) Eh. : Free space wavelength a : Waveguide width H, : Maximum intensity of Mi field The direction of this magnetic field is constant in the height direction of the waveguide, and rotates with time. Therefore, when a one-dimensional radiation slot (- letter shape) is provided on the wide surface (H surface) of a rectangular waveguide in the direction of the tube axis, and when it is provided perpendicularly to the tube axis, the radiation slot is The period of the leaking electric field is temporally shifted by 90 degrees. Therefore, when these two radiation slots are combined to form a two-dimensional shape (cross slot), the radio waves leaking from this radiation slot become elliptically polarized waves, and the position X of the cross slot is 0<x<a/ 2
It is known that the polarization becomes anti-rotating depending on whether the polarization is in the direction of 0 or a/2<x<a. In this elliptically polarized wave, the electric field component leaking from the slot provided in the direction of the tube axis and the electric field component leaking from the slot provided perpendicular to the tube axis are out of phase by 90 degrees, so the electric field of each component is Circular polarization can be achieved by matching the intensities. For the radiating cross slot, the length of the slot in the tube axis direction of the rectangular waveguide and the length of the slot in the direction perpendicular to the tube axis can be independently changed, or the position where the radiating cross slot is formed in the rectangular waveguide. It is known that the intensities of the two electric field components can be made to match by changing the two electric field components or by combining these methods. These directions are also a method for changing the amount of coupling between the radiation slot and the electromagnetic field in the waveguide, so the radiation cross slot is actually used to receive and transmit circularly polarized waves. When creating an antenna, the strengths of the two electric field components must be made equal so that the amount of coupling reaches the desired strength. Up to now, we have discussed cross-shaped slots that are a combination of slots parallel to the long axis of the waveguide and slots perpendicular to the long axis of the waveguide. Radiation slot and 1 perpendicular to it
Like a two-dimensional slot (diagonal cross slot) consisting of a dimensional radiation slot, the intersection angle of the two is 90 degrees.
By combining dimensional-shaped slots, it is possible to realize a two-dimensional slot for circularly polarized wave radiation based on the same principle as a cross slot, which is a combination of slots parallel and perpendicular to the long axis direction of the waveguide. can. In a leaky wave type waveguide slot array antenna for circularly polarized waves, a plurality of two-dimensional radiation slots formed in this manner are arranged in a row in the longitudinal direction of a rectangular waveguide. A high frequency wave is input from one end of the waveguide to give a traveling wave inside the tube, and radio waves are leaked from each radiation slot to form an array. In principle, in this radiating waveguide, the maximum aperture efficiency can be obtained when all of the feeding power is radiated from the radiating slots, and the power radiated from each radiating slot is uniform. This is a true fact. However, the power inside the radiation tube waveguide gradually decreases as it moves away from the power supply side due to the 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 increase the strength of the coupling between the radiation slot and the electromagnetic field of the radiation conductive tube as the electric power inside the tube decreases as the distance from the radiation conductive tube increases. Because of this configuration, the conventional leaky wave type waveguide slot array antenna has the following problems. That is, in the two-dimensional radiation slot configured in this manner, the problem is that the temporal phase difference between the two electric field components actually deviates from 90 degrees depending on the amount of coupling. Originally, if the electromagnetic field inside the rectangular waveguide was not disturbed by opening the slots, opening two slots on the wide surface of the rectangular waveguide would increase the temporal phase difference between the two by 90 degrees. In order to obtain an electric field component of , it is necessary to arrange these two slots so that they intersect at 90 degrees. However, due to the effect of opening the slots on the electromagnetic field inside the rectangular waveguide, even if the two slots are arranged to intersect at 90 degrees, the temporal phase difference between the two electric field components will not be 90 degrees. No. If the temporal phase difference between the two electric field components deviates from 90 degrees, even if the two electric field strengths are adjusted, elliptically polarized waves will always result, and circularly polarized waves will not be realized. Generally, when two slots are arranged so as to intersect at 90 degrees, if the strengths of the two electric field components are the same, the larger the amount of coupling, the stronger the two electric field components in the radiation slot. The deviation of the temporal phase from 90 degrees becomes large. Therefore, in a radiating waveguide in which the radiated power from each radiating slot is uniform, the radiating slot farthest from the feeding side end has a deviation from 90 degrees in the temporal phase difference between the two electric field components. It is an obvious fact that the radiated radio waves after becoming large and arrayed become elliptically polarized waves, making it impossible to achieve circularly polarized waves, and that when receiving and transmitting circularly polarized waves, the aperture efficiency decreases. . In addition, if the radiation waveguide is configured only with radiation slots with a small coupling amount so that the temporal phase difference between the two electric field components S in the radiation slot S deviates from 90 degrees, it is possible to Obviously, this also reduces the aperture efficiency, since only a portion of the more injected radio waves can be radiated. In this way, in the conventional technology, consideration has been given to matching the intensities of two power components;
No consideration is given to the deviation of the phase difference from 90 degrees that actually occurs, which has been a problem in obtaining high aperture efficiency. An object of the present invention is to provide a leaky wave type waveguide slot array antenna that can solve the above problems and further increase the aperture efficiency. [Means for Solving the Problems 1] In order to achieve such an object, the present invention provides a method in which a circularly polarized wave radiation slot formed by intersecting two slots is connected to an electromagnetic field within a rectangular radiation waveguide. They are arranged in an array on the wide surface of the radiation waveguide according to the amount of coupling, and the intersection angle of the two circularly polarized wave slots is set to 2.
It is characterized by being shifted from 90 degrees according to the temporal phase difference between the two electric field components. [Function] In the present invention, the intersection angle of two circularly polarized wave radiation slots is set to 90° on the wide surface (H plane) of the rectangular radiation waveguide.
By arranging the slots at different angles, the temporal phase difference between the electric field components of 2-'' emitted from each slot is adjusted to 90 degrees, and the aperture efficiency is further increased. Embodiments of the invention will be described in detail with reference to the drawings. Fig. 1 shows Embodiment 1 of the invention, which is an example of a circularly polarized layer one-dimensional array antenna. In Fig. 1, 1 is Rectangular radiation waveguide with wide side 1
It consists of a narrow side 1b and a narrow side 1b, and radiation slots 11 to 16 are provided on one side of the wide side 1a at predetermined intervals in the tube axis direction. Although the end portion 2 is depicted as being open, it may be connected to a waveguide for power supply, or
Power is supplied by a coaxial-waveguide conversion structure, etc. The other end 3 preferably has a non-reflection termination structure or is filled with a radio wave absorber, but is open or closed (which may result in a substantial short circuit, but is intended to reflect radio waves). In some cases, it may be practical to do something (not a real thing). The overall structure is like this, but in order to properly form a one-dimensional array and obtain high efficiency with respect to the center frequency, the spacing between the radiation slots 11-16 is set to about 0 of the spatial wavelength.
．． In addition to the leaky wave type waveguide slot array antenna described above as 5 times or less, each radiation slot 11 to 16
The radiation power from each radiation slot 11 should be uniform.
The coupling amount of ~16 is increased sequentially in ascending order of numbers, and usually the vertical and horizontal lengths of the radiation slots 11-16 are as follows:
This is achieved by sequentially lengthening the length. Further, at this time, a combination of lengths is selected such that the intensities of the two electric field components leaking from each of the vertical and horizontal slots match when viewed from the radiation direction of the main beam. FIG. 2 is a view of one of the radiation slots formed on the wide surface (H surface) of the radiation waveguide shown in FIG. 1, viewed from the front of the wide surface (H surface). In the figure, C is an auxiliary line drawn parallel to the long axis of the tube, d is a slot perpendicular to the long axis of the tube, e is a line passing through the intersection of auxiliary line C and slot d, and the temporal phase of the two electric field components. The slot is inclined at an angle θ with respect to the auxiliary line C in order to align the angle θ to 90 degrees, and f is the center line in the longitudinal direction of this slot. In this embodiment, since the radiation slots 11 to 16 are arranged so that the intersecting angle of the slots in the two directions is different from 90 degrees, that is, the cross-shaped slot tubes with the intersecting angle of the slots of 90 degrees are arranged. Since the axial slot is tilted at different angles θ depending on the degree to which the phase difference deviates from 90 degrees, the temporal phase difference between the two electric field components becomes 90 degrees. Note that even if the slot in the direction of the tube axis of the waveguide is not tilted, and only the slot in the direction perpendicular to the tube axis is tilted, the temporal phase difference can be made 90 degrees. Furthermore, by tilting both slots, the temporal phase difference can be made 90 degrees, and the effects are essentially the same. FIG. 3 shows a second embodiment of the present invention. In comparison with Embodiment 1, this embodiment differs in the shape of the radiation slot. In this embodiment, diagonal cross slots 21 to 26 are provided on the wide surface (H surface) of the rectangular waveguide 4. Ta. The diagonal cross slot is a method of matching the intensities of the two electric field components seen from the radiation direction of the main beam by changing the position where the radiation cross slot is formed on the rectangular waveguide, and changing the amount of coupling. This is achieved by making the two one-dimensional slots of the diagonal cross slots the same length and reducing the time to zero. The principle of circularly polarized radiation in the diagonal cross-shaped slot is the same as that of the cross-shaped slot. In order to make the amount of radiation from the slots uniform, when the amount of coupling of the radiation slots is gradually increased from the feeding side, as the amount of coupling increases, the temporal phase difference of the electric field components leaking from each slot becomes The degree of deviation from 90 degrees increases. Therefore, depending on the degree of deviation, the slots in the two directions of the radiation slot were arranged so that their intersection angles were deviated from 90 degrees, and the temporal phase difference between the two electric field components was corrected to 90 degrees. FIG. 4 is a front view of one of the diagonal cross slots shown in FIG. 3, viewed from the wide side (H side). In the figure, g and h represent the one-dimensional radiation slot that is tilted at 45 degrees to the long axis direction of the waveguide before correcting the temporal phase difference between the two electric field components to 90 degrees, and the one-dimensional radiation slot that is perpendicular to it. This is an auxiliary line representing the center line in the longitudinal direction of each slot of diagonal slots consisting of one-dimensional radiation slots that intersect with each other. In order to correct the temporal phase difference of the electric field components to 90 degrees, i and j are each φ, and the intersection angle is 90 degrees in total by twice φ.
Slots k and 4, which are offset from 0 degrees, are the longitudinal center lines of slots i and j, respectively. In the second embodiment, in the diagonal cross slots 21 to 26, the temporal phase difference between the two electric field components that is caused by the slots being formed on the radiation waveguide is corrected to be shifted from 90 degrees. A unique different angle, twice φ, in each diagonal cross slot so that the phase difference is 90 degrees.
is only tilted. In this second embodiment, two 1
Although an example has been described in which the two-dimensional slots are tilted by the same angle, the temporal phase difference can be set to 90 degrees by tilting only one slot, and the effect is essentially the same. [Effect of the invention 1 As explained above, according to the present invention, the intersection angle of the two circularly polarized wave slots on the wide surface (H-plane) of the rectangular radiation waveguide is shifted from 90 degrees. This arrangement has the effect that the temporal phase difference between the two electric field components radiated from each slot can be adjusted to 90 degrees, and the aperture efficiency can be further increased.

[Brief explanation of the drawing]

Fig. 1 is an external view showing a leaky wave type waveguide slot array antenna according to Embodiment 1 of the present invention, Fig. 2 is a view of one of the slots shown in Fig. 1 viewed from the front of the wide side, and Fig. 3 is An external view showing a leaky wave type waveguide slot array antenna according to Embodiment 2 of the present invention. FIG. 4 is a front view of one of the slots shown in the third figure, viewed from the wide side. DESCRIPTION OF SYMBOLS 1... Radiation waveguide, 4... Radiation waveguide, 11-16... Radiation slot, 21-26... Radiation slot. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1) Circularly polarized wave radiation slots formed by intersecting two slots are arranged in an array on the wide surface of the rectangular radiation waveguide according to the amount of coupling with the electromagnetic field within the rectangular radiation waveguide. , the intersection angle of the two circularly polarized wave slots is set to 9 according to the temporal phase difference between the two electric field components.
A leaky wave type waveguide slot array antenna characterized by being shifted from 0 degrees.