JPH0486107A - Cross feeding type square waveguide slot array antenna - Google Patents

Abstract

PURPOSE:To make the frequency characteristic broad by using two orthogonal independent electric fields so as to feed in a square waveguide space in a way that each electric field is propagated symmetrically in the basic mode. CONSTITUTION:Power fed to a coaxial cable as a feeding part 6 is propagated in square waveguides 5a, 5b and the power is fed in a square waveguide space in phase from feeding slots 4a, 4b, propagated from the feeding slot 4a in the basic mode of an electric field Ea in the X direction in the square waveguide space S and propagated from the feeding slot 4b in the basic mode of an electric field Eb in the Y direction in the square waveguide space S. In this case, the feeding power from the feeding slot 4a excites the power radiation slot 1a to allow the power in phase whose electric field direction is Ea to radiate into a free space. Similarly, the feeding power from the feeding slot 4b excites the power radiation slot 1b to allow the power in phase whose electric field direction is Eb to radiate into a free space.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a rectangular waveguide slot array antenna suitable for use in communication antennas, broadcasting antennas, and the like.

[Conventional technology]

The propagation mode in a conventional rectangular waveguide is shown in the explanatory diagram of radio wave propagation in the orthogonal coordinate system of Fig. 5 ((a) shows the t magnetic field distribution, and (b) shows the current distribution). As such, the least attenuated fundamental mode (TEI, T E or wave) expressed in the orthogonal coordinate system is used. Therefore, the rectangular waveguide has a cutoff frequency (the cutoff frequency is fl,
If the speed of light is a, the long side of the C1 rectangular waveguide is ft=
c/2a) to the frequency (f, (20]-c/a) that is the attenuation range of other higher-order modes, so the long side a is defined by λ as the free space wavelength. Then a-
It is in the range of λ/1.06 to 1.56, and the short side is approximately a
/ 2 is common.

A conventional slot array antenna is a rectangular waveguide with slots cut into the wall of the rectangular waveguide as described above. In this antenna, as shown in the perspective view of Figure 6, the current in the wall of the tube is reduced by half. Since the direction is reversed every wavelength λg/2 (λg is the tube wavelength), the inclination directions of the slots are also alternately reversed accordingly. As a result, the Z components of the combined electric fields of the radio waves emitted from the pair of slots are in phase and added together, and the Y components are in antiphase and cancel each other out. Therefore, in the case of the arrangement shown in FIG. 6, linearly polarized waves are emitted.

[Invention or problem to be solved]

By the way, the conventional slot array antenna as mentioned above is suitable as a radar antenna, or it has a vertical plane, and its width is as wide as 16° to 20°, so its gain is small and it is not suitable for communication antennas, broadcasting antennas, etc. Not suitable.

In addition, since it is a traveling wave antenna, as shown in FIG.
If it is shorter, the phase of the power radiated from slot b' is smaller than the phase of the power radiated from slot b'.
Since the main lobe P moves by λg, as shown in FIG. 7(b), it tilts in the direction a, and conversely, as the wavelength becomes longer, it tilts in the direction b, and the directivity changes as the frequency changes.

Note that if multiple slot array antennas are arranged side by side, the beam width can be narrowed and linearly polarized waves that are orthogonal to each other can be radiated, but the structure becomes complicated and the weight increases.
Production cost becomes higher.

There are some problems.

Although the present invention attempts to solve these problems, σ
), the hour wheel structure is lightweight and can reduce production costs, and prevents deviations in directivity due to changes in the main T-hoop.
The purpose of this invention is to provide a cross-fed rectangular waveguide slot/l,h array anti-→ that can widen the frequency band.

[Means to solve the problem]

Therefore, the cross-fed rectangular waveguide slot array antenna of the present invention includes a pair of substantially rectangular metal plates arranged facing each other with a distance of l, and one of the pair of metal plates. A large number of power radiation slots arranged in rows and columns
/h, and a power feeding part capable of supplying power to the rectangular waveguide, the electric field direction of the feeding part is parallel to the pair of metal plates, and It is characterized by being configured with two orthogonal independent power feeding means that can feed power as substantially plane waves of two orthogonal independent fundamental modes.

[For production]

In the above-described cross-fed rectangular waveguide linear/door array antenna of the present invention, when power is supplied to the rectangular waveguide space by the power feeding means, almost the same phase power is transmitted independently through the power radiation slot. and are radiated into free space as mutually orthogonal polarized waves.

Further, the effect of preventing fluctuations in the main lobe due to changes in frequency is performed.

〔Example〕

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
1 to 4(c) show a cross-fed rectangular waveguide slot array antenna as an embodiment of the present invention. An explanatory diagram of the arrangement of the slots, Figures 3 (a) and (b) are explanatory diagrams explaining the directivity, and Figures 4 (a), (b), (
e) is a diagram showing a modification of the power feeding means to the rectangular waveguide space.

1.2 Figure 1 As shown, the width W is 8 or more (here λ is the free space wavelength) and the length is 8 or 6 so that they face each other with a distance of d. The above is a pair of 1 and 5 shaped metal plates 1. A waveguide space S is formed. On the metal plate 1, power radiation slots 1b75 are arranged in rows vertically and horizontally. In addition, as explained in the prior art, two rectangular waveguides Sa and Sb provided on the pipe wall are used as power feeding slots ia and 4b at a cross section near the center of the metal plate 1.2. They are connected in the shape of a rectangular waveguide space S.

Furthermore, a dielectric material such as a slow wave circuit is disposed within the rectangular waveguide space S.

In addition, at the center of the junction of the two waveguides Sa and 5b of the power feeding means, there is a coaxial center conductor as the power feeding part 6 and a dielectric material that is an insulator around it or a material that matches the waveguide. It is attached so that it protrudes into the waveguide by its length.

With the above-mentioned configuration, in this embodiment, the coaxial I as the power feeding unit 6: the fed power is transmitted through the rectangular waveguides Sa, S.
The power propagates through power supply throwers Ha, l
Power is fed into the rectangular waveguide space S in the same phase from the power supply slot 4a in the same phase as shown in FIG. From the power feeding slot z 4b, the electric field Eb propagates in the Y direction in the rectangular waveguide space S in the fundamental mode.

At this time, the power supplied from the power supply slot 43 is
As shown in the figure, the power radiation slot la whose slot spacing Sa is set to λga (in-line wavelength of the power fed from the power feeding slot 4a) is excited, and in-phase power whose electric field direction is Ea is excited. radiates into free space. However, the power radiation slot 1b is not excited.

Similarly, as shown in FIG. 2, the feeding power from the feeding throat tib is transmitted to the power radiating throat Hb whose slot interval sb is set to λgb (the wavelength within the channel of the power fed from the feeding throat Hb). is excited, and radiates in-phase power into free space with an electric field direction of Eh. However, the power radiation slot 1a is not excited. Therefore, slot la
, lb can each independently radiate orthogonal linearly polarized waves such as electric fields Ea and Eb.

Since a large number (for example, several dozen) of these I slots la and Ib are provided vertically and horizontally, the directivity becomes sharp,
Furthermore, as shown in FIGS. 3(a) and 3(b), by making the propagation directions of the power fed into the rectangular waveguide space S from the power feeding means 5a and 5b symmetrical, the power feeding is increased. Even if the power frequency changes, the left main lobe P1 and the right main lobe P
2 means that the main lobes PI and P2 are tilted in mutually symmetrical directions, and the direction of the main lobe P of the antenna as a whole, which is created by combining the two main lobes PI and P2, is constant.

Furthermore, by using a slow wave circuit, the tube wavelength λg is converted to the free space wavelength λ. Since it is shortened compared to , the generation of grating lobes can be suppressed.

Next, a modification of the power feeding means will be explained. In the above-mentioned embodiment, power is fed by a slot array antenna having a slot arrangement as explained in the prior art. In this case, a thrower Hc is arranged on the tube wall of the rectangular waveguide 95c.

At this time, the slot interval Sc is equal to the guide wavelength λg in the rectangular waveguide sC. With this structure, an electric field similar to that in the above embodiment can be generated within the rectangular waveguide space S.

In addition, as a power feeding means, in-phase power feeding can be performed using a microstrip line 7 as shown in FIG. 4(b) or FIG. 4(C).

In FIG. 4(C), reference numeral 8 indicates a conductor plate, 8a indicates a slot, and 9 indicates a dielectric material.

〔Effect of the invention〕

As detailed above, according to the cross-fed rectangular waveguide slot array antenna of the present invention, power is fed to the rectangular waveguide space with two orthogonal and independent electric fields, and each electric field is symmetrical as the fundamental mode. By feeding the power so that it propagates, it is possible to radiate mutually orthogonal linearly polarized waves from the radiation slot, and it is also possible to prevent the main lobe of the antenna as a whole from shifting in the direction due to frequency changes in the feeding power. If a gain equivalent to that of a normal traveling wave antenna is obtained, the effect or advantage that the frequency characteristic can be made wider can be obtained.

[Brief explanation of drawings]

Figures 1 to 3 and Figures 4 and 4 (a), (b), and (C) show a cross-fed rectangular waveguide slot array antenna as an embodiment of the present invention, and Figure 1 shows the cross-fed rectangular waveguide slot array antenna. FIG. 2 is an explanatory diagram of the arrangement of the power radiation slots, FIG. 3(a) and (b) are explanatory diagrams of the directivity, and FIG. 4(a) is a perspective view of the whole. (b) and (c) are both diagrams showing modified examples of the power feeding means to the rectangular waveguide space, and FIGS. 5 to 7 show conventional techniques, and FIG. (b) is an explanatory diagram of radio wave propagation in the orthogonal coordinate system, FIG. 6 is a perspective view of the slot array antenna, and FIG. 7(a). (b) is an explanatory diagram explaining the directivity. 1.2...Metal plate, Ia, Ib, Ib'...Slot for power radiation, 3...Metal wall, 4a, 4b, 4c...
- Power supply slot, 5a. 5b, Sc...Square waveguide, 6...Coaxial pin of power feeding section, S...Square waveguide space, S a, S b,
S c, S p...slot spacing, d...height of the rectangular waveguide, W...width of the rectangular waveguide, L...length of the rectangular waveguide, P, Pl, P2・Lord'-", 7・
・・Michaelostri・17', 8・・Conductor plate, 83・
・Also, "Foot, 9...Dielectric. Agent: Yoshihiko Iinuma, Patent Attorney, Isao Adachi, Figure (b) Figure (b) Figure (a) (b) Figure Figure 7 (a) / ! (b)

Claims (1)

[Claims] A rectangular shape consisting of a pair of substantially rectangular metal plates arranged to face each other and separated from each other, and a large number of power radiation slots arranged in rows and columns in either direction of the pair of metal plates. It is equipped with a waveguide line and a power feeding section capable of supplying power to the isogonal waveguide line, and the feeding section generates two independent fundamental modes whose electric field directions are parallel to and orthogonal to the pair of metal plates. A cross-fed rectangular waveguide slot array antenna comprising two orthogonal and independent power feeding means capable of feeding substantially as a plane wave.