Slot array antenna

Abstract

To provide a slot array antenna capable of suppressing a side lobe.SOLUTION: A slot array antenna 1 including a waveguide 2 and a horn 3 is provided. The waveguide 2 has a slot 22 for emitting a radio wave on a first surface 21. The horn 3 is fixed to the waveguide 2 while oriented so as to emit the radio wave to the first surface 21, and has a first narrow aperture 31 which is formed by bending upper and lower portions 32 and 33 inwardly in a short-side direction of the first surface 21. The aperture width of the first narrow aperture 31 is shorter than the width of the first surface 21 in the short-side direction. The horn has a second narrow aperture 34 formed by further inwardly bending the upper and lower portions 32 and 33 in the radial direction beyond the first narrow opening 31. The aperture width of the second narrow aperture 34 is 2 / 5 or less of the wavelength of the radio wave.SELECTED DRAWING: Figure 1

Description

Technical Field

[0007] ,

[0001] The present invention mainly relates to a marine radar for ship navigation, and more specifically, to a slot array antenna of a marine radar.

Background Art

[0002] A slot array antenna provided with a waveguide is a mainstream antenna used for marine antennas. And the slot array antenna uses a rectangular waveguide provided with a horn and a plurality of slots to improve directivity. Further, in a marine slot array antenna, an edge shunt system (horizontal polarization) is mainly used.

[0003] In an edge shunt type slot array antenna, a grating is generally provided to suppress the side lobe of the vertical polarization which is cross polarization.

[0004] On the other hand, when a longitudinal shunt type slot array antenna with different slot orientations is used, side lobes of horizontal polarization occur, but it is not easy to create a grating to suppress them. Therefore, in the longitudinal shunt type, it is necessary to efficiently suppress the side lobes of cross polarization (horizontal polarization) with a simple configuration.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In Patent Document 1, side lobes are suppressed by surrounding each slot of a longitudinal shunt type antenna with metal.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention provides a longitudinal shunt type slot array antenna that suppresses side lobes and is easy to manufacture. [Means for solving the problem]

[0008] The present invention provides a slot array antenna including a waveguide and a horn. The waveguide has a slot on its first surface for radiating radio waves. The horn is fixed to the waveguide in a direction that radiates radio waves toward the first surface and has a first narrow aperture formed by the upper and lower parts curving inward in the direction of the short side of the first surface. The aperture width of the first narrow aperture is shorter than the width of the first surface in the direction of the short side. The horn has a second narrow aperture formed by the upper and lower parts on the radiation direction side of the first narrow aperture curving inward even further. The aperture width of the second narrow aperture is 2 / 5 or less of the wavelength of the radio wave. With the above configuration, side lobes generated due to horizontal polarization are suppressed with a simple configuration and without using a grid for cross-polarization suppression.

[0009] Furthermore, the aperture width of the second narrow aperture may be less than or equal to 1 / 5 of the wavelength of the radio wave. With the above configuration, the propagation of horizontal polarization into the antenna is further suppressed by the second narrow aperture with an even narrower aperture, and side lobes are suppressed.

[0010] Furthermore, the upper and lower parts may form a horn shape on the radial side of the end of the second narrow opening.

[0011] Furthermore, the upper and lower parts may include a first bend that curves inward along the edge of the first surface and a second bend that curves radially, and the first narrow opening may be an opening formed when the upper and lower parts face each other on the radial side from the second bend.

[0012] Furthermore, the upper and lower parts may include a third bend that curves inward in the width direction of the first surface on the radial side of the second bend, and a fourth bend that curves radially on the radial side of the third bend, and the second narrow opening may be an opening formed with the upper and lower parts facing each other on the radial side from the fourth bend.

[0013] Furthermore, the upper and lower parts of the horn may overlap with a portion of the first surface of the waveguide near the first bend, thereby fixing the horn in the radial direction.

[0014] Furthermore, the waveguide may also have a long, slender, hollow structure.

[0015] Furthermore, the hollow structure may also be rectangular.

[0016] In another embodiment, a method for assembling a slot array antenna is provided. This method includes the steps of forming a waveguide having slots on a first surface for radiating radio waves, and forming a horn fixed to the waveguide in a direction that radiates radio waves toward the first surface, and having a first narrow aperture formed by the upper and lower parts curving inward in the short-side direction of the first surface. Furthermore, the aperture width of the first narrow aperture is shorter than the width of the first surface in the short-side direction. By shortening the distance between the upper and lower parts of the horn near the slots, horizontal polarization cannot propagate, and side lobes due to horizontal polarization are suppressed. Furthermore, by making the distance between the upper and lower parts of the horn near the slots 2λ / 5 or less, horizontal polarization can be further suppressed. Therefore, a low-side-lobe vertically polarized slot antenna can be realized without using a grid for cross-polarization suppression. [Brief explanation of the drawing]

[0017] The drawings are intended to facilitate understanding of the embodiments and are not intended to limit the configuration or results disclosed. [Figure 1] Figure 1 is a side view of a slot array antenna. [Figure 2] Figure 2 is a perspective view of a slot array antenna. [Figure 3] Figure 3 is a graph showing the radiation pattern of a slot array antenna. [Figure 4] Figure 4 shows the slot offset error for multiple slots in a slot array antenna. [Figure 5] Figure 5 is a graph showing the radiation pattern of a slot array antenna. [Figure 6]FIG. 6 is a graph showing the relationship between the intensity of the side lobe and the wavelength of different slot offset errors. [Figure 7] FIG. 7 is a flowchart showing a method of assembling a slot array antenna. BEST MODE FOR CARRYING OUT THE INVENTION

[0018] The present invention is not limited to other exemplary embodiments or features, and various modifications are possible within the scope of the technical idea presented in this specification. In the following detailed description, reference is made in part to the accompanying drawings.

[0019] The present invention can be arranged, replaced, combined, separated, and designed in a variety of different configurations within the scope described in this specification and shown in the drawings.

[0020] FIG. 1 shows a side view of a slot array antenna 1 according to an embodiment of the present disclosure. FIG. 2 shows a perspective view of the slot array antenna 1 according to an embodiment of the present disclosure. The slot array antenna 1 includes a waveguide 2 made of a metal material and a horn 3, which form the slot array antenna 1 when assembled.

[0021] The waveguide 2 is a rectangular elongated hollow structure. The waveguide 2 has a first surface 21 including a plurality of slots 22 arranged at a predetermined interval for radiating a plurality of radio waves. The plurality of slots are in the longitudinal direction and are arranged on the first surface 21 parallel to the length of the first surface 21. The width of the first surface 21 is greater than 1 / 4 of the wavelength (λ) of the radio wave. The slot array antenna 1 further has second, third, and fourth surfaces 23, 24, 25 such that the first to fourth surfaces 21 and 23-25 form the walls of the waveguide 2. Here, the wavelength is assumed to be the wavelength in free space, but when the effect is high when using the electrical length depending on the structure of the antenna, the electrical length is used.

[0022] The predetermined intervals do not necessarily have to be equal, and the design includes well-known techniques for efficiently radiating radio waves. For example, there are shapes designed so that the radiated wavefronts from each slit are in phase.

[0023] The width of the first surface 21 is suitable for radio waves to be emitted from the slit, and is preferably greater than 1 / 4 of the wavelength. The width of the first surface 21 can be any suitable width with respect to wavelength without departing from the scope of this disclosure.

[0024] The upper and lower parts of the horn 3 are fixed to the waveguide 2, opening in the direction of radiation of multiple radio waves. The horn 3 is bent inward relative to the width of the first surface 21 to form a first narrow aperture 31. The width of the first narrow aperture 31 is shorter than the short side of the first surface so as not to interfere with the slot. As a result, horizontal polarization cannot propagate through the first narrow aperture 31, and side lobes generated by the horizontal polarization of multiple radio waves are suppressed. Furthermore, the horn is fixed to the waveguide side in the direction of radiation, making positioning and fixing easier.

[0025] The aperture width of the first narrow aperture 31 can be any suitable width with respect to wavelength without departing from the scope of this disclosure.

[0026] The horn 3 is bent inward twice along the width of the first surface 21 to form an upper part 32 and a lower part 33 that form a first narrow opening 31 and a second narrow opening 34. The opening width of the second narrow opening 34 is less than or equal to 2 / 5 of the wavelength. The upper and lower parts 32 and 33 form a horn shape along the radial direction from the second narrow opening 34 onward. Each of the upper and lower parts 32 and 33 has a first bend 35a or 35b that curves inward along the width of the first surface 21 and a second bend (36a or 36b) along the radial direction at the end of the first surface 21, thus forming the first narrow opening 31.

[0027] In this embodiment, the aperture width of the second narrow aperture 34 is 2 / 5 or less of the wavelength, but is not limited thereto. The aperture width of the second narrow aperture 34 can be any appropriate width with respect to the wavelength without departing from the scope of this disclosure.

[0028] The upper and lower parts 32 and 33 have third bends 37a and 37b at a predetermined distance from the second bend (36a or 36b), such that the third bend (37a or 37b) is inward along the width of the first surface 21 and the fourth bend (38a or 38b) is inward along the radial direction, thereby forming the second narrow opening 34. The upper and lower parts 32 and 33 of the horn 3 partially overlap with the first surface 21 of the waveguide 2. The upper and lower parts 32 and 33 of the horn 3 further overlap with the second and third surfaces 23 and 24 of the waveguide 2, respectively. The fourth bend from the beginning is a 90-degree bend.

[0029] Waveguides 2 and horns 3 are metal sheets that have been bent and punched to form the desired design of their respective plates. Waveguides 2 and horns 3 are made of the same metal. In another embodiment, waveguides 2 and horns 3 are made of different metals. Waveguides 2 and horns 3 have the same thickness.

[0030] When the slot array antenna 1 is used to radiate multiple radio waves through the first narrow aperture 31, the side lobe suppression effect was insufficient when processing errors occurred. Therefore, including the second narrow aperture 34, a two-stage folded shape in the radiation direction is formed so that the gap between the horns in the second narrow aperture 34 is less than 1 / 5 of the wavelength. In a configuration where the upper and lower parts are each bent only once in the radiation direction, the plate between the first and second bends contacts the first surface and interferes with the slot 22, making it impossible to narrow the aperture width of the first narrow aperture 31 between the upper and lower parts 32 and 33 of the horn 3. On the other hand, a two-step bend is included in the slot array antenna 1.

[0031] Figure 3 is graph 300, which shows the radiation pattern of slot array antenna 1. Graph 300 shows the radio wave intensity for vertical and horizontal polarization with respect to the orientation of a conventional slot array antenna and slot array antenna 1. By setting the aperture width of the second narrow aperture 34 of the horn 3 near multiple slots 22 to 1 / 5 or less of the wavelength, horizontal polarization cannot propagate, and side lobes are suppressed. Thus, a low-side-lobe vertically polarized slot array antenna 1 can be realized without using a grating for cross-polarization suppression as shown in Figure 3.

[0032] Figure 4 shows the slot offset error for multiple slots 22 of the slot array antenna 1. The multiple slots 22 include the first to third slots 41 to 43. The second slot 42 has a slot offset error with respect to the first and third slots 41 and 43, as shown in Figure 4. The second slot 42 is positioned above the first and third slots 41 and 43 because the difference in positioning is the slot offset error.

[0033] As shown in Figure 4, if there are slot offset errors in multiple slots 22, the side lobes worsen as shown in Figure 5. Figure 5 is graph 500 showing the radiation pattern of the slot array antenna 1. Graph 500 shows the intensity of radio waves associated with various slot offset errors of the slot array antenna 1 against the azimuth angle.

[0034] Side lobes are suppressed by setting the aperture width between the upper and lower 32 and 33 of horn 3, i.e., the aperture width of the second narrow aperture, to 2 / 5 or less of the wavelength (0.4λ), preferably 1 / 5 or less of the wavelength (0.2λ), as shown in Figure 6. Figure 6 is a graph 600 showing the relationship between the intensity of the side lobes and the wavelength for different slot offset errors.

[0035] Figure 7 is a flowchart showing method 7 for assembling the slot array antenna 1.

[0036] In step 71, a waveguide 2 is formed having a first surface 21 containing a plurality of slots 22 arranged at predetermined intervals for emitting a plurality of radio waves. In step 72, the horn 3 is formed by bending inward relative to the width of the first surface 21 to form a first narrow opening 31.

[0037] In step 73, the horn 3 is fixedly attached to the waveguide 2 so as to open in the direction of radiation of multiple radio waves, forming the slot array antenna 1. The width of the first surface 21 is greater than 1 / 4 of the wavelength of the multiple radio waves. The aperture width of the first narrow aperture 31 is less than half of the wavelength of the multiple radio waves, suppressing the side lobes generated due to the horizontal polarization of the multiple radio waves. [Explanation of symbols]

[0038] 1 slot array antenna 2 waveguide 22 slots 3 horns 31 First narrow opening 32, 33 Upper and lower parts of the horn 34. Second narrow opening

Claims

1. A waveguide having a slot on its first surface for emitting radio waves, It is fixed to the waveguide in a direction that radiates radio waves toward the first surface, and in the direction of the short side of the first surface A horn having a first narrow opening formed by the upper and lower parts curving inward, Equipped with, The opening width of the first narrow opening is shorter than the width of the first surface in the short-side direction. The horn has a second narrow opening formed by the upper and lower parts on the radial side of the first narrow opening being further curved inward. The aperture width of the second narrow aperture is 2 / 5 or less of the wavelength of the radio wave. Slot array antenna.

2. The slot array antenna according to claim 1, wherein the aperture width of the second narrow aperture is 1 / 5 or less of the wavelength of the radio wave.

3. The slot array antenna according to claim 2, wherein the upper and lower parts are horn-shaped along the radiation direction on the radiation direction side of the end of the second narrow opening.

4. The upper and lower parts have a first bent portion that curves inward along the edge of the first surface and a second bent portion that curves radially, Equipped with, The first narrow opening is an opening formed with the upper and lower parts facing each other in the radial direction from the second bent portion. The slot array antenna according to claim 1.

5. The upper and lower parts are provided with a third bend that curves inward in the width direction of the first surface on the radial side of the second bend, and a fourth bend that curves radially on the radial side of the third bend. The second narrow opening is an opening formed with the upper and lower parts facing each other in the radial direction from the fourth bend. The slot array antenna according to claim 4.

6. The upper and lower portions of the horn overlap with a portion of the first surface of the waveguide near the first bend, and the horn is fixed in the radial direction. The slot array antenna according to claim 5.

7. The waveguide has a long, slender, hollow structure. The slot array antenna according to claim 6.

8. The aforementioned hollow structure is rectangular. The slot array antenna according to claim 7.

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