Single-line waveguide antenna

Abstract

A single-line waveguide antenna (10A) of one aspect of the present disclosure is provided with a first extending part (30), a second extending part (40), and a connecting part (50A). The first extending part extends in a predetermined direction, and is provided with a first upper surface (31) having a plurality of first slots (21a, 21b) arranged at one-wavelength (λg) intervals. The second extending part extends in a predetermined direction and is provided with a second upper surface (41) having a plurality of second slots (21c, 21d) lined up offset by a half-wavelength from the plurality of first slots. The connecting part (50A) links the first extending part to the second extending part. The distance (L) from a first center to a second center is (n+1 / 2) times the wavelength (where n is an integer 1 or greater), the first center and the second center being the center of the first slot (21b) and the second slot (21d) that are closest to the connecting part.

Description

A waveguide antenna of a line Cross-reference to related applications

[0001] This international application claims the benefit of Japanese Patent Application No. 2024-232486, filed with the Japan Patent Office on December 27, 2024, the entire disclosure of which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to a waveguide antenna.

[0003] Non-Patent Document 1 below discloses a two-line waveguide slot antenna. The position of the slot of the first waveguide antenna is shifted by a half wavelength from the position of the slot of the second waveguide antenna. As a result, grating lobes are suppressed. Consequently, a decrease in gain in front of the antenna is suppressed, and false detection of unnecessary signals is suppressed.

[0004] Yuichi Hirayama, et al., "Broadbanding of a Partially Tournament-Traveling-Wave-Excited Millimeter-Wave Planar Array Antenna with a Slot with a Cavity Cut in a Waveguide Narrow Wall," IEICE technical report, November 2015, Vol. 115, No. 286, pp. 41-46

[0005] When signals of the same phase are fed to the first and second waveguide antennas, the polarization directions of the radio waves radiated from the first and second waveguide antennas do not match. Therefore, there is a possibility that a desired directivity cannot be obtained.

[0006] By adding a structure for rotating the phase by 180° to the first or second waveguide antenna, the polarization directions of the radio waves radiated from the first and second waveguide antennas can be made to match. However, as a result of the inventors' detailed study, it was found that adding a phase rotation structure causes a path difference in the two lines, and when the frequency of the supplied signal fluctuates, beam tilt is likely to occur due to the influence of the path difference. Furthermore, it was found that adding a phase rotation structure increases the cost.

[0007] This disclosure provides a waveguide antenna that can match the polarization directions of radio waves radiated from a plurality of slots with a simple configuration and suppress grating lobes.

[0008] This disclosure provides a single-line waveguide antenna that receives power and radiates radio waves, comprising a first extension section, a second extension section, and a connecting section. The first extension section extends in a predetermined direction and has a first upper surface having a plurality of first slots. The second extension section extends in a predetermined direction and has a second upper surface having a plurality of second slots. The connecting section connects the first extension section to the second extension section. The plurality of first slots are arranged along a predetermined direction at intervals of one wavelength (λg), where wavelength is the wavelength of radio waves within the waveguide antenna. The plurality of second slots are aligned with a half-wavelength offset from the plurality of first slots. The distance from the first center to the second center is (n + 1 / 2) times the wavelength (where n is an integer of 1 or more). The first center is the center of the first slot closest to the connecting section among the plurality of first slots. The second center is the center of the second slot closest to the connecting section among the plurality of second slots.

[0009] The single-line waveguide antenna disclosed herein is constructed by bending a single waveguide, with multiple second slots arranged at half-wavelength offsets from multiple first slots. This suppresses grating lobes. Furthermore, the multiple first slots and multiple second slots are arranged at one-wavelength intervals, and the distance from the outermost first slot to the outermost second slot is 3n / 2 times the wavelength. As a result, the polarization directions of the radio waves radiated from each of the multiple first slots and multiple second slots coincide. Therefore, with a simple configuration, it is possible to match the polarization directions of the radio waves radiated from each of the multiple first slots and multiple second slots while suppressing grating lobes.

[0010] This is a perspective view of a waveguide antenna according to the first embodiment. This is a top view of the waveguide antenna according to the first embodiment. This is a diagram showing the array factor of the waveguide antenna according to the first embodiment. This is a top view of a waveguide antenna according to the first reference example. This is a diagram showing the array factor of the waveguide antenna according to the first reference example. This is a top view of a waveguide antenna according to the second reference example. This is a top view of a waveguide antenna according to the third reference example. This is a diagram showing the array factor of the waveguide antenna according to the third reference example. This is a top view of a waveguide antenna according to the second embodiment. This is a top view of a waveguide antenna according to the third embodiment.

[0011] (1. First Embodiment) <1-1. Configuration> The waveguide antenna 10A according to this embodiment will be described with reference to Figures 1 and 2. The waveguide antenna 10A is mounted on a moving object and transmits or receives radio waves. Examples of moving objects include vehicles, trains, aircraft, and ships. In this embodiment, the waveguide antenna 10A is mounted on a vehicle and transmits, for example, radio waves in the millimeter wave band. In another embodiment, the waveguide antenna 10A may be mounted on a stationary object.

[0012] The waveguide antenna 10A is a narrow-walled waveguide. That is, the width of the waveguide antenna 10A is smaller than the height of the waveguide antenna 10A. Hereinafter, the width direction of the waveguide antenna 10A will be referred to as the y-axis direction, and the height direction as the z-axis direction. The direction perpendicular to the y-axis direction and the z-axis direction will be referred to as the x-axis direction. In another embodiment, the waveguide antenna 10A may be a wide-walled waveguide whose width is greater than its height.

[0013] Waveguide antenna 10A is a single-line waveguide constructed by bending a single waveguide into a U-shape. More specifically, waveguide antenna 10A is a slot array antenna having a plurality of first slots 21a, 21b and a plurality of second slots 21c, 21d formed on a single line.

[0014] The waveguide antenna 10A comprises a first extension 30, a second extension 40, and a connecting portion 50A that connects the first extension 30 to the second extension 40. The first extension 30 extends in the x-axis direction and comprises a first end 11 and a first upper surface 31. The first end 11 receives a signal with frequency f and free-space wavelength λ, specifically a millimeter-wave signal. The signal supplied to the first end 11 has a wavelength λg, which is the wavelength inside the waveguide antenna 10A.

[0015] The first upper surface 31 is provided with a plurality of first slots 21a and 21b. The first slots 21a and 21b each extend in the x-axis direction. The length of the first slots 21a and 21b in the x-axis direction is half a wavelength (1 / 2) λg each. The first slots 21a and 21b are arranged along the x-axis direction at intervals of one wavelength λg. Here, the distance between two adjacent slots is the distance between the centers of the two slots. The first slots 21a and 21b are arranged such that the distance between the two slots is one wavelength λg. The position of the first slot 21a is closer to the first end 11 than to the connection 50A. The position of the first slot 21b is closer to the connection 50A than to the first end 11. In this embodiment, the first upper surface 31 is provided with two first slots 21a and 21b, but in another embodiment, the first upper surface 31 may be provided with three or more first slots.

[0016] The second extended portion 40 extends in the x-axis direction and is parallel to the first extended portion 30. The second extended portion 40 comprises a second end portion 12 and a second upper surface 41. The second upper surface 41 comprises a plurality of second slots 21c and 21d. The second slots 21c and 21d each extend in the x-axis direction and have the same shape as the first slots 21a and 21b. That is, the length of each of the second slots 21c and 21d in the x-axis direction is half a wavelength (1 / 2) λg.

[0017] The second slots 21c and 21d are arranged along the x-axis at intervals of one wavelength λg. The distance from the center of the second slot 21c to the center of the adjacent second slot 21d is one wavelength λg. The number of second slots is equal to the number of first slots. In this embodiment, the second upper surface 41 has two second slots. The position of the second slot 21c is closer to the second end 12 than to the connection 50A. The position of the second slot 21d is closer to the connection 50A than to the second end 12. In another embodiment, the second upper surface 41 may have three or more second slots.

[0018] Furthermore, the multiple second slots 21c and 21d are aligned with a half-wavelength (1 / 2) λg offset from the multiple first slots 21a and 21b. In the x-axis direction, one second slot 21c is positioned between two adjacent first slots 21a and 21b. Also, in the x-axis direction, one first slot 21b is positioned between two adjacent second slots 21c and 21d. Therefore, in the waveguide antenna 10A, the first slots 21a, second slots 21c, first slots 21b, and second slots 21d are aligned in the x-axis direction at half-wavelength (1 / 2) intervals.

[0019] The connecting portion 50A connects the first extension portion 30 to the second extension portion 40. The connecting portion 50A has a U-shaped third upper surface 51A. The third upper surface 51A does not have a slot. Therefore, on the transmission line through which the signal supplied to the first end portion 11 is transmitted, the first slot 21b is located next to the second slot 21d. That is, on the transmission line through which the signal is transmitted, the first slot 21b is located next to the second slot 21d. The first slot 21b is the slot closest to the connecting portion 50A among the multiple first slots 21a, 21b. The second slot 21d is the slot closest to the connecting portion 50A among the multiple second slots 21c, 21d.

[0020] The length of the connecting portion 50A is designed such that the distance L from the first center to the second center is (λg / 2) + nλg, where n is an integer greater than or equal to 1. The first center is the center in the extension direction of the first slot 21b. The second center is the center in the extension direction of the second slot 21d. In this embodiment, the length of the connecting portion 50A is designed such that the distance L is (3 / 2)λg.

[0021] <1-2. Operation> <1-2-1. First Embodiment> Figure 3 shows the simulation results of the array factor of the waveguide antenna 10A. The signal supplied to the first end 11 propagates from the first extension 30 to the connection 50A, and from the connection 50A to the second extension 40. The supplied signal is then radiated from the first slots 21a, 21b and the second slots 21c, 21d, respectively. Since the distance between the first slot 21a and the first slot 21b is one wavelength λg, the polarization direction of the radio waves radiated from the first slot 21a is the same as the polarization direction of the radio waves radiated from the first slot 21b. Similarly, the polarization direction of the radio waves radiated from the second slot 21c is the same as the polarization direction of the radio waves radiated from the second slot 21d.

[0022] Furthermore, since the distance L is (λg / 2) + nλg, the polarization direction of the radio waves radiated from the first slot 21b coincides with the polarization direction of the radio waves radiated from the second slot 21d. The waveguide antenna 10A is bent into a U shape, and the second extension 40 is reversed from the first extension 30 in the y-axis direction. Therefore, when the distance L is (λg / 2) + nλg, the polarization directions of the radio waves radiated from the first slot 21b and the second slot 21d coincide.

[0023] Therefore, the polarization directions of the radio waves radiated from all slots of the waveguide antenna 10A coincide. Consequently, the waveguide antenna 10A achieves the desired directivity. In Figure 3, the waveguide antenna 10A achieves directivity in the forward direction.

[0024] Furthermore, since the first slot 21a, second slot 21c, first slot 21b, and second slot 21d are arranged at half-wavelength (1 / 2) λg intervals, the generation of grating lobes is suppressed. Consequently, as shown in Figure 3, the ratio of main lobes to side lobes is good. Therefore, the waveguide antenna 10A can achieve the desired directivity while suppressing grating lobes with a simple configuration.

[0025] <1-2-2. Reference Example> Figure 4 shows a waveguide antenna 100 according to the first reference example. The top surface of the waveguide antenna 100 is provided with four slots 21. The four slots 21 are arranged at intervals of one wavelength λg. Figure 5 shows the simulation results of the array factor of the waveguide antenna 100. In the waveguide antenna 100, the interval between adjacent slots 21 is one wavelength λg or more. As a result, grating lobes are generated, and the ratio of main lobes to side lobes deteriorates. Therefore, the waveguide antenna 100 may result in a decrease in front gain and false detection of unwanted signals in the grating direction.

[0026] Figure 6 shows a waveguide antenna 200 according to the second reference example. The waveguide antenna 200 is a two-line antenna comprising a first waveguide 210 and a second waveguide 220. The first waveguide 210 has two slots 21. The two slots 21 are spaced one wavelength λg apart. The second waveguide 220 has two slots 22. The two slots 22 are spaced one wavelength λg apart. The two slots 22 are spaced half a wavelength (1 / 2) λg apart from the two slots 21. Therefore, when in-phase signals are fed to the ends of the first waveguide 210 and the second waveguide 220, the polarization direction of the radio waves radiated from the two slots 21 is shifted by 180° from the polarization direction of the radio waves radiated from the two slots 22. Consequently, the waveguide antenna 200 suppresses the generation of grating lobes, but does not provide the desired directivity.

[0027] Figure 7 shows that the waveguide antenna 300 according to the third reference example is a two-line antenna comprising a first waveguide 310 and a second waveguide 320. The first waveguide 310 has two slots 21, which are spaced one wavelength apart. The second waveguide 320 has a 180° phase rotation structure 330 and two slots 22, which are spaced one wavelength λg apart. The two slots 22 are offset by half a wavelength (1 / 2) λg from the two slots 21. The 180° phase rotation structure 330 is positioned closer to the fed end than the two slots 22.

[0028] When signals of the same phase are fed to the ends of the first waveguide 310 and the second waveguide 320, the phase of the signal propagating through the second waveguide 320 is shifted by 180° from the phase of the signal propagating through the first waveguide 310 due to the 180° phase rotation structure 330. Therefore, the polarization directions of the radio waves radiated from each of the two slots 21 and the two slots 22 coincide. Thus, as shown in Figure 8, the waveguide antenna 300 achieves forward directivity while suppressing the generation of grating lobes. However, the waveguide antenna 300 requires the 180° phase rotation structure 330, which increases the cost. Also, the waveguide antenna 300 has a path difference of 180° phase rotation structure 330 between the two lines. Therefore, when the frequency of the feed signal fluctuates, beam tilt is likely to occur due to the effect of the path difference.

[0029] <1-3. Effects> The first embodiment described in detail above provides the following effects.

[0030] (1) The waveguide antenna 10A is constructed by bending a single waveguide. Furthermore, the grating lobe is suppressed because the multiple second slots 21c and 21d are aligned with a half-wavelength (1 / 2) λg offset from the multiple first slots 21a and 21b. In addition, the multiple first slots 21a and 21b and the multiple second slots 21c and 21d are arranged at intervals of one wavelength λg, and the distance L is (3 / 2) times the wavelength λg. As a result, the polarization directions of the radio waves radiated from each of the multiple first slots 21a and 21b and the multiple second slots 21c and 21d coincide. Therefore, with a simple configuration, the polarization directions of the radio waves radiated from each of the multiple first slots 21a and 21b and the multiple second slots 21c and 21d can be matched, and the grating lobe can be suppressed.

[0031] (2) By designing the waveguide antenna 10A to have a distance L of (3 / 2)λg, the distance from the first slot 21b to the second slot 21d can be minimized, thereby making the waveguide antenna 10A smaller.

[0032] (3) By forming the third upper surface 51A of the connection portion 50A in a U shape, a single-line waveguide antenna 10A that achieves the desired directivity while suppressing grating lobes can be easily manufactured.

[0033] (2. Second Embodiment) <2-1. Differences from the First Embodiment> The second embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. Note that the same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0034] The waveguide antenna 10A according to the first embodiment described above comprises a first extension portion 30, a second extension portion 40, and a connecting portion 50A. In contrast, as shown in Figure 9, the waveguide antenna 10B according to the second embodiment differs from the first embodiment in that it comprises a first extension portion 30, a second extension portion 40, and a connecting portion 50B. That is, the waveguide antenna 10B according to the second embodiment has a connecting portion 50B instead of a connecting portion 50A.

[0035] The connecting portion 50B has a rectangular third upper surface 51B. The rectangular shape has two corners. That is, the third upper surface 51B has a shape in which the curved portion of the third upper surface 51A is replaced with corners. The length of the connecting portion 50B is designed such that the distance L is (λg / 2) + nλg (n≧1).

[0036] <2-3. Effects> The second embodiment described in detail above produces the same effects as the first embodiment described above (1) to (3).

[0037] (3. Third Embodiment) <3-1. Differences from the First Embodiment> The third embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. Note that the same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0038] The waveguide antenna 10A according to the third embodiment described above comprises a first extension portion 30, a second extension portion 40, and a connecting portion 50A. In contrast, as shown in Figure 10, the waveguide antenna 10C according to the third embodiment differs from the first embodiment in that it comprises a first extension portion 30, a second extension portion 40, and a connecting portion 50C. That is, the waveguide antenna 10C according to the third embodiment has a connecting portion 50C instead of a connecting portion 50A.

[0039] The connecting portion 50C has a polygonal third upper surface 51C. The polygon has four angles. The length of the connecting portion 50C is designed such that the distance L is (λg / 2) + nλg (n≧1). In another embodiment, the polygon may have three angles or five or more angles.

[0040] <3-2. Effects> The third embodiment described in detail above provides the same effects as the first embodiment described above (1) to (3), as well as the following effects.

[0041] (4) The third upper surface 51C has a polygonal shape, which makes it possible to reduce the length of the waveguide antenna 10A in the x-axis direction.

[0042] (4. Other Embodiments) (a) Multiple functions of one component in the above embodiment may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, some of the configurations of the above embodiment may be omitted. Furthermore, at least some of the configurations of the above embodiment may be added to or replaced with the configurations of other above embodiments.

Claims

1. A single-line waveguide antenna (10A, 10B, 10C) that receives power and radiates radio waves, comprising: a first extension (30) extending in a predetermined direction and having a first upper surface (31) having a plurality of first slots (21a, 21b); a second extension (40) extending in the predetermined direction and having a second upper surface (41) having a plurality of second slots (21c, 21d); and connecting parts (50A, 50B, 50C) connecting the first extension to the second extension, wherein the plurality of first slots are arranged along the predetermined direction at intervals of one wavelength (λg), the wavelength being the wavelength of the radio waves within the waveguide antenna, and the plurality of second slots are aligned with a half-wavelength offset from the plurality of first slots. A single-line waveguide antenna, wherein the distance (L) from the first center to the second center is (n+1 / 2) times the wavelength (where n is an integer of 1 or more), the first center is the center of the first slot (21b) closest to the connection point among the plurality of first slots, and the second center is the center of the second slot (21d) closest to the connection point among the plurality of second slots.

2. The single-line waveguide antenna according to claim 1, wherein the distance (L) is (3 / 2) times the wavelength (λg).

3. The single-line waveguide antenna according to claim 1 or 2, wherein the connecting portion (50A) has a U-shaped third upper surface (51A).

4. The single-line waveguide antenna according to claim 1 or 2, wherein the connecting portion (50B) has a rectangular third upper surface (50B).

5. The single-line waveguide antenna according to claim 1 or 2, wherein the connecting portion (50C) has a polygonal third upper surface (50C).

Images