Antenna device and radar device

Abstract

[Problem] To improve antenna characteristics for high-frequency radio waves. [Solution] An antenna device comprising: a first line antenna that is formed from a linear first power supply line and a plurality of first antenna elements, each of said antenna elements having one end connected to the first power supply line and extending perpendicularly from the first power supply line; and a second line antenna that is formed from a second power supply line and a plurality of second antenna elements, and is linearly symmetrical to the first line antenna with respect to a virtual line parallel to the first power supply line and serving as the axis of symmetry.

Description

Antenna device and radar device

[0001] The present invention relates to an antenna device and a radar device.

[0002] For example, Japanese Patent Application Laid-Open No. 2007-53656 (Patent Document 1) discloses the following microstrip array antenna. That is, in a microstrip array antenna formed of a dielectric substrate having a conductor ground plane formed on the back surface and strip conductors formed on the dielectric substrate, the strip conductors include a feeding strip line arranged linearly, and a plurality of rectangular radiation antenna elements connected and arranged at predetermined intervals along at least one of both sides of the feeding strip line from that side. Each of the radiation antenna elements has a rectangular shape with different lengths and widths, and is connected so that its longitudinal direction is approximately 90 degrees with respect to the feeding strip line, and has two or more feeding strip lines with different widths on one feeding strip line by means of at least one or more line width conversion structures.

[0003] Japanese Patent Application Laid-Open No. 2007-53656

[0004] When propagating high-frequency radio waves in an antenna, the gain reduction due to the propagation loss of the feeding line, as well as the characteristic deterioration caused by unnecessary radiation and reflection, becomes large. A technology capable of improving the antenna characteristics for high-frequency radio waves is desired.

[0005] This invention has been made to solve the above problems, and an object thereof is to provide an antenna device and a radar device capable of improving the antenna characteristics for high-frequency radio waves.

[0006] In order to solve the above problems, an antenna device according to an aspect of this invention includes a first line antenna including a linear first feeding line and a plurality of first antenna elements whose ends are connected to the first feeding line and extend perpendicularly from the first feeding line, and a second line antenna including a second feeding line and a plurality of second antenna elements that are line-symmetric with respect to the first line antenna with a virtual line parallel to the first feeding line as a symmetry axis.

[0007] In this configuration, connecting the ends of the antenna elements to the feed line suppresses losses due to current branching. Furthermore, in line antennas arranged in the width direction of the feed line, by reversing the orientation of corresponding antenna elements, the phases of the radio waves supplied to the two line antennas are reversed, or the phases of the radio waves propagating from the two corresponding line antennas are reversed. This allows for strengthening the polarization in the desired direction while weakening the polarization in the unwanted direction, thereby suppressing side lobes and the like. Consequently, the antenna characteristics for high-frequency radio waves can be improved.

[0008] According to the present invention, the antenna characteristics for high-frequency radio waves can be improved.

[0009] Figure 1 shows the configuration of Comparative Example 1 of the antenna device according to an embodiment of the present invention. Figure 2 shows the simulation results of the horizontal directivity of Comparative Example 1 of the antenna device according to an embodiment of the present invention. Figure 3 shows the configuration of Comparative Example 2 of the antenna device according to an embodiment of the present invention. Figure 4 shows the simulation results of the horizontal directivity of Comparative Example 2 of the antenna device according to an embodiment of the present invention. Figure 5 is a diagram for explaining the reason why horizontal polarization occurs in Comparative Examples 1 and 2 of the antenna device according to an embodiment of the present invention. Figure 6 shows the configuration of the line antenna in Comparative Example 3 of the antenna device according to an embodiment of the present invention. Figure 7 shows the simulation results of the horizontal directivity of Comparative Example 3 of the antenna device according to an embodiment of the present invention. Figure 8 is a diagram for explaining the reason why horizontal polarization occurs in Comparative Example 3 of the antenna device according to an embodiment of the present invention. Figure 9 shows the configuration of the antenna device according to an embodiment of the present invention. Figure 10 shows the configuration of the distributor in the antenna device according to an embodiment of the present invention. Figure 11 shows the simulation results of the horizontal directivity of the antenna device according to an embodiment of the present invention. Figure 12 is a diagram for explaining the reason why horizontal polarization cancels out in the antenna device according to an embodiment of the present invention. Figure 13 shows the configuration of Modified Example 1 of the antenna device according to an embodiment of the present invention. Figure 14 shows the configuration of Modified Example 2 of the antenna device according to an embodiment of the present invention. Figure 15 shows the configuration of Modification 3 of the antenna device according to an embodiment of the present invention. Figure 16 shows the configuration of Modification 4 of the antenna device according to an embodiment of the present invention. Figure 17 shows the configuration of Modification 5 of the antenna device according to an embodiment of the present invention. Figure 18 shows an example of the configuration of a radar device, which is an application example of the antenna device according to an embodiment of the present invention.

[0010] Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated. Furthermore, at least some of the embodiments described below may be combined in any way.

[0011] [Comparative Example 1] Figure 1 shows the configuration of Comparative Example 1 of the antenna device according to an embodiment of the present invention.

[0012] Referring to Figure 1, the antenna device 71 comprises a plurality of line antennas 51, a branching section 61, and a power supply section 62. Each line antenna 51 includes a plurality of antenna elements 1 and a straight power supply line 2.

[0013] Antenna device 101 is used, for example, in radar equipment on a vessel such as a fishing boat. Antenna device 71 performs at least one of the following: transmission and reception of high-frequency radio waves, such as millimeter waves. The radiation direction R in which antenna device 71 should radiate radio waves is, for example, a direction that penetrates the plane of the paper in Figure 1 and is upward from the plane of the paper.

[0014] Each line antenna 51 is arranged in the width direction of the power supply line 2. Each line antenna 51 is realized, for example, using a microstrip line formed on a substrate B.

[0015] The line antenna 51 is a comb line antenna. More specifically, in the line antenna 51, each antenna element 1 is connected so as to be aligned along the direction of extension of the feed line 2.

[0016] The antenna element 1 is, for example, rectangular in shape and has an open first end and a second end connected to the feed line 2. In other words, the line antenna 51 is a series-fed antenna. Each antenna element 1 is connected to one side of the feed line 2.

[0017] Each line antenna 51 contains the same number of antenna elements 1. Between each line antenna 51, corresponding antenna elements 1 face each other along the width direction of the feed line 2. Multiple antenna elements 1 in a line antenna 51 extend in the same direction.

[0018] For example, in adjacent line antennas 51, each line antenna 51 is arranged such that the distance between the centers of the antenna elements 1 in the width direction of the feed line 2 is equal.

[0019] The power supply unit 62 supplies power to each line antenna 51 via the branching unit 61. The power supply unit 62 includes, for example, a waveguide-microstrip line converter that electromagnetically couples the power supply line 2, which is a microstrip line, with a waveguide (not shown). This converter is, for example, a proximity-feeding type in which the microstrip line is connected to the waveguide via a substrate.

[0020] The branching section 61 branches the alternating current supplied from the power supply section 62 and supplies it to each line antenna 51.

[0021] The antenna device 71 employs a series-fed line antenna 51 that directly connects the antenna element 1 and the feed line 2. Compared to a parallel-fed type where a branching point occurs from the feed line 2 to the antenna element 1, this configuration suppresses losses due to current branching.

[0022] Figure 2 shows the simulation results of the horizontal directivity of Comparative Example 1 of the antenna device according to an embodiment of the present invention.

[0023] In Figure 2, the vertical axis represents gain [dB] and the horizontal axis represents azimuth angle [degrees]. In Figure 2, graphs G1 and G2 show the vertical and horizontal polarization directivity of the antenna device 71 equipped with a converter, respectively, while graphs G3 and G4 show the vertical and horizontal polarization directivity of the antenna device 71 not equipped with a converter, respectively. Furthermore, an azimuth angle of zero degrees corresponds to the center of the radiation direction R described above, and an azimuth angle of 90 degrees or minus 90 degrees corresponds to the extension direction of the feed line 2.

[0024] Referring to Figure 2, graphs G2 and G4 show that the horizontal polarization side lobes are larger in the antenna device 71, and that the side lobes are generally larger when a converter is provided.

[0025] Thus, because the antenna device 71 employs a proximity feeding method, there is a problem in that unwanted radiation from the waveguide-microstrip line converter is large, resulting in deterioration of the horizontal polarization side lobes.

[0026] [Comparative Example 2] Next, Comparative Example 2 of the antenna device will be described. Except for the contents described below, it is the same as Comparative Example 1. Figure 3 is a diagram showing the configuration of Comparative Example 2 of the antenna device according to an embodiment of the present invention.

[0027] Referring to Figure 3, the antenna device 72, compared to the antenna device 71, is equipped with a power supply unit 63 instead of a power supply unit 62.

[0028] The power supply unit 63 supplies power to each line antenna 51 via the branching unit 61. The power supply unit 63 includes, for example, a waveguide-microstrip converter that electromagnetically couples the power supply line 2, which is a microstrip line, with a waveguide (not shown).

[0029] This converter is a back-short type that, for example, places the short-circuit portion of the microstrip line at a distance of 1 / 4 of the effective wavelength from the short-circuit portion of the waveguide, and performs transmission mode conversion between the waveguide and the microstrip line. This converter includes a grounding section that forms the short-circuit portion of the dielectric waveguide. The grounding section is implemented, for example, by a metal case.

[0030] By employing a back-shorting method, the short-circuited portion of the microstrip line can be positioned at the location where the signal strength is maximum, thereby improving the efficiency of signal transmission mode conversion.

[0031] Figure 4 shows the simulation results of the horizontal directivity of Comparative Example 2 of the antenna device according to an embodiment of the present invention. In Figure 4, graphs G11 and G12 show the vertical and horizontal polarized directivity of the antenna device 72 equipped with a converter, respectively, and graphs G13 and G14 show the vertical and horizontal polarized directivity of the antenna device 72 not equipped with a converter, respectively. The way to read the figure is the same as in Figure 2.

[0032] Referring to Figure 4, the antenna device 72 can prevent unwanted radiation from the converter using a metal case or the like.

[0033] On the other hand, graphs G12 and G14 show that reflection in the metal case strengthens the horizontal polarization in the direction toward the end of the power supply line 2, i.e., at an azimuth angle of 90 degrees, resulting in larger side lobes of horizontal polarization. It can be seen that the side lobes are larger when a converter is provided.

[0034] Thus, the antenna device 72, like the antenna device 71, also suffers from the problem of deteriorating horizontal polarization side lobes.

[0035] Figure 5 is a diagram illustrating the reason why horizontal polarization occurs in Comparative Examples 1 and 2 of the antenna device according to an embodiment of the present invention.

[0036] Referring to Figure 5, in the line antenna 51, current flows diagonally from the feed line 2 to the antenna element 1, generating vertical and horizontal polarization. Since the directions of currents I1 and I2 are the same at a certain timing in the antenna elements 1 facing each other between the line antennas 51, the vertical polarizations V1 and V2 generated by each line antenna 51 reinforce each other, and the horizontal polarizations H1 and H2 generated by each line antenna 51 reinforce each other. In other words, the side lobes of the horizontal polarization from each line antenna 51 reinforce each other.

[0037] [Comparative Example 3] Next, Comparative Example 3 of the antenna device will be described. Except for the details described below, it is the same as Comparative Example 1.

[0038] Figure 6 shows the configuration of a line antenna in Comparative Example 3 of the antenna device according to an embodiment of the present invention.

[0039] Referring to Figure 6, the antenna device 73, compared to the antenna device 71, is equipped with a line antenna 52 instead of a line antenna 51.

[0040] The line antenna 52 is a comb line antenna. More specifically, in the line antenna 52, each antenna element 1 is arranged along the direction of extension of the straight feed line 2 and is alternately connected on both sides of the feed line 2.

[0041] FIG. 7 is a diagram showing simulation results of the horizontal directivity of Comparative Example 3 of the antenna device according to the embodiment of the present invention. In FIG. 7, graphs G21 and G22 are the directivities of the vertical polarization and horizontal polarization of the antenna device in which each antenna element 1 is connected to one side of the feed line 2, similar to the antenna devices 71 and 72, and graphs G23 and G24 are the directivities of the vertical polarization and horizontal polarization of the antenna device 73, respectively. The viewing method of the figure is the same as that of FIG. 2.

[0042] FIG. 8 is a diagram for explaining the reason why horizontal polarization occurs in Comparative Example 3 of the antenna device according to the embodiment of the present invention.

[0043] Referring to FIGS. 7 and 8, in the line antenna 52, the interval between adjacent antenna elements 1 along the extending direction of the feed line 2 across both sides of the feed line 2 is about 1 / 2 of the wavelength λs of the radio wave propagating through the substrate B forming the line antenna 52. Therefore, currents I1 and I2 with inverted phases are respectively supplied to adjacent antenna elements 1, so that the horizontal polarizations cancel each other out in the radiation direction R.

[0044] On the other hand, in the direction toward the end portion of the feed line 2, since the interval between the antenna elements 1 is about λs / 2, the phase rotates 180 degrees and becomes in-phase while the radio wave propagates to the next antenna element 1, and the horizontal polarizations reinforce each other.

[0045] Therefore, from graphs G22 and G24, it can be seen that in the antenna device 73, the side lobe of the horizontal polarization becomes larger in the direction toward the end portion of the feed line 2.

[0046] Thus, the antenna device 73 also has a problem that the side lobe of the horizontal polarization deteriorates, similar to the antenna devices 71 and 72.

[0047] Therefore, the antenna device according to the embodiment of the present invention solves the above problems by the following configuration.

[0048] [Configuration] FIG. 9 is a diagram showing the configuration of the antenna device according to the embodiment of the present invention.

[0049] Referring to Figure 9, the antenna device 101 comprises one or more antenna sets, a distributor 21, and a power supply unit 22. The antenna set consists of two line antennas 11. That is, the antenna set includes two line antennas 11.

[0050] In the example shown in Figure 9, the antenna device 101 comprises two antenna sets 31 and 32. Antenna set 31 includes line antennas 11A and 11B, which are line antennas 11. Antenna set 32 ​​includes line antennas 11C and 11D, which are line antennas 11. The line antenna 11 includes a plurality of antenna elements 1 and a straight feed line 2.

[0051] In other words, the antenna device 101 has a two-dimensional array configuration in which line antennas 11 are arranged in an even number of rows.

[0052] Two antenna sets are installed side by side in the width direction of the power supply line 2. One antenna set is positioned so as to sandwich the other antenna set.

[0053] The antenna device 101 is used, for example, in radar equipment on a vessel such as a fishing boat. The antenna device 101 performs at least one of the following: transmission and reception of high-frequency radio waves, such as millimeter waves. The radiation direction R in which the antenna device 101 should radiate radio waves is, for example, a direction that penetrates the plane of the paper in Figure 1 and is upward from the plane of the paper.

[0054] Each line antenna 11 is arranged in the width direction of the power supply line 2. Each line antenna 11 is realized, for example, using a microstrip line formed on a substrate B.

[0055] The line antenna 11 is a comb line antenna. More specifically, in the line antenna 11, each antenna element 1 is connected so as to be aligned along the direction of extension of the feed line 2. Each antenna element 1 extends perpendicularly from the feed line 2.

[0056] The antenna element 1 is, for example, rectangular in shape and has an open first end and a second end connected to the feed line 2. In other words, the line antenna 11 is a series-fed antenna. Each antenna element 1 in the line antenna 11 is connected to one side of the feed line 2, that is, all are connected to the same side of the feed line 2.

[0057] Note that the shape of the antenna element 1 is not limited to a rectangle; it may be any other shape. In other words, the line antenna 11 can be a series-fed type, in which the ends of each antenna element 1 are connected to the feed line 2.

[0058] In the antenna assembly, each line antenna 11 contains the same number of antenna elements 1. Between each line antenna 11, corresponding antenna elements 1 face each other along the width direction of the feed line 2. Furthermore, the extension directions of corresponding antenna elements 1 between each line antenna 11 are reversed. That is, the two line antennas 11 constituting the antenna assembly are positioned symmetrically with respect to the central axis of their own antenna assembly along the extension direction of the feed line 2. Specifically, the feed line 2 and multiple antenna elements 1 in one of the two line antennas 11 constituting the antenna assembly are symmetrical with respect to the other line antenna 11, with respect to a virtual line L parallel to the feed line 2 as the axis of symmetry.

[0059] Furthermore, for example, in two line antennas 11 that constitute an antenna assembly, each antenna element 1 extends toward the other line antenna 11, that is, it extends toward the virtual line L.

[0060] For example, in adjacent line antennas 11, each line antenna 11 is arranged such that the distance between the centers of the antenna elements 1 in the width direction of the feed line 2 is equal.

[0061] The power supply unit 22 supplies power to each line antenna 11 via the distributor 21. The power supply unit 22 includes a back-short type waveguide-microstrip line converter, similar to the power supply unit 63 in Comparative Example 2. The power supply unit 22 may also be configured to include a proximity-feed type waveguide-microstrip line converter.

[0062] The antenna device 101 employs a series-fed line antenna 11 that directly connects the antenna element 1 and the feed line 2. Compared to a parallel-fed type where a branching point occurs from the feed line 2 to the antenna element 1, this configuration suppresses losses due to current branching.

[0063] Figure 10 shows the configuration of a distributor in an antenna device according to an embodiment of the present invention.

[0064] Referring to Figure 10, the antenna device 101 includes, for example, a phase shifter that inverts the phases of the current supplied to the two line antennas 11 constituting the antenna set. That is, the phase shifter inverts the phases of the radio waves supplied to the two line antennas 11 constituting the antenna set, or inverts the phases of the radio waves propagating from the two line antennas 11 constituting the antenna set.

[0065] The phase shifter is implemented by the distributor 21. More specifically, the distributor 21 has lines 41 to 46. The AC current from the feed unit 22 is branched and supplied to line 41, and then further branched and supplied to lines 43 and 44 connected to line antennas 11C and 11A, respectively. The AC current from the feed unit 22 is branched and supplied to line 42, and then further branched and supplied to lines 45 and 46 connected to line antennas 11B and 11D, respectively.

[0066] In the distributor 21, the lengths of lines 41 and 42 are set such that Lu - Ld = λs / 2, where Lu is the length of line 41 and Ld is the length of line 42. In addition, the lengths of lines 43 to 46 are set to be equal.

[0067] This makes it possible to invert the phases of the alternating current supplied to the two corresponding line antennas 11 in each of the antenna sets 31 and 32.

[0068] In other words, in each of the antenna sets 31 and 32, the phases of the radio waves supplied to the two corresponding line antennas can be inverted relative to each other, or the phases of the radio waves propagating from the two line antennas can be inverted relative to each other.

[0069] Furthermore, the antenna device 101 is not limited to a configuration that includes a phase shifter; it may also be configured in which a phase shifter is provided in a transmitting / receiving unit or the like connected to the feed unit 22 via a waveguide.

[0070] Figure 11 shows the simulation results of the horizontal directivity of an antenna device according to an embodiment of the present invention. In Figure 11, graphs G31 and G32 show the vertical and horizontal polarized directivity of the antenna device 101 equipped with a converter, respectively, while graphs G33 and G34 show the vertical and horizontal polarized directivity of the antenna device 101 not equipped with a converter, respectively. The way to read the figure is the same as in Figure 2.

[0071] Figure 12 is a diagram illustrating the reason why horizontal polarization cancels out in an antenna device according to an embodiment of the present invention.

[0072] Referring to Figures 11 and 12, in the line antenna 11, as in Comparative Examples 1 to 3, current flows diagonally from the feed line 2 to the antenna element 1, resulting in the generation of vertical and horizontal polarization.

[0073] On the other hand, in the antenna device 101, the distributor 21 supplies alternating current with a phase difference of 180 degrees to the two line antennas 11 in the antenna assembly, and the extension directions of the corresponding antenna elements 1 between each line antenna 11 are reversed relative to each other.

[0074] With this configuration, in the two line antennas constituting the antenna set, for example line antennas 11A and 11B, the directions of currents I1 and I2 at a certain timing are, for example, in the upper right and upper left directions of the plane of Figure 12, respectively. As a result, the vertical polarizations V1 and V2 generated by line antennas 11A and 11B reinforce each other, while the horizontal polarizations H1 and H2 generated by line antennas 11A and 11B cancel each other out.

[0075] As a result, the antenna device 101 can strengthen the vertical polarization while suppressing the horizontal polarization side lobes using the two line antennas that make up the antenna assembly, thereby achieving good antenna characteristics even in the high-frequency range.

[0076] Specifically, from graph G34, it can be seen that the horizontal polarization side lobes in the direction toward the end of the power supply line 2, i.e., at an azimuth angle of 90 degrees, are suppressed compared to, for example, the characteristics of the antenna device 72 shown in graph G14 of Figure 4. Furthermore, from graph G32, it can be seen that even when a converter is provided, the above-mentioned horizontal polarization side lobes are suppressed compared to, for example, the characteristics of the antenna device 72 shown in graph G12 of Figure 4.

[0077] Furthermore, by using two antenna sets 31 and 32, the beam width of the main lobe can be set to approximately 20 to 30 degrees, as shown in Figure 11. To make the beam sharper, the antenna device 101 can be configured to include a larger number of antenna sets.

[0078] [Modification] Next, a modification of the antenna device will be described. Except for the details described below, it is the same as the antenna device 101 described above.

[0079] Figure 13 shows the configuration of a modified example 1 of the antenna device according to an embodiment of the present invention.

[0080] Referring to Figure 13, the antenna device 101 may be configured to include a single antenna assembly.

[0081] Figure 14 shows the configuration of a modified example 2 of the antenna device according to an embodiment of the present invention.

[0082] Referring to Figure 14, the antenna device 101 may be configured such that, in the two line antennas 11 constituting the antenna set, each antenna element 1 extends toward the other line antenna 51, that is, toward the opposite side of the virtual line L.

[0083] Figure 15 shows the configuration of a modified example 3 of the antenna device according to an embodiment of the present invention.

[0084] Referring to Figure 15, the antenna device 101 may be configured to include an antenna set in which each antenna element 1 of the two line antennas 51 extends toward the other line antenna 51, that is, toward the virtual line L, and an antenna set in which each antenna element 1 of the two line antennas 51 extends toward the opposite side of the other line antenna 51, that is, toward the virtual line L.

[0085] Figure 16 shows the configuration of a modified example 4 of the antenna device according to an embodiment of the present invention.

[0086] Referring to Figure 16, the antenna device 101 may be configured to include one or more antenna sets, including two line antennas 52, similar to Comparative Example 3.

[0087] In the example shown in Figure 16, the antenna device 101 includes one antenna assembly 33.

[0088] The antenna assembly 33 includes line antennas 52A and 52B, which are line antennas 52. Line antennas 52A and 52B each contain the same number of antenna elements 1. Between line antennas 52A and 52B, corresponding antenna elements 1 face each other along the width direction of the feed line 2. Furthermore, between line antennas 52A and 52B, the extension directions of corresponding antenna elements 1 are reversed.

[0089] Figure 17 shows the configuration of a modified example 5 of the antenna device according to an embodiment of the present invention.

[0090] Referring to Figure 17, the antenna device 101 may have a configuration in which the number of each antenna element 1 in the line antenna 11 differs between antenna sets.

[0091] [Radar device] Figure 18 shows an example of the configuration of a radar device, which is an example of the application of an antenna device according to an embodiment of the present invention.

[0092] Referring to Figure 18, the radar device 201 is used on a ship such as a fishing boat and comprises an antenna unit 99, a control unit 83, a display unit 84, and an operation unit 85. The antenna unit 99 includes an antenna device 101, a transmitting / receiving unit 81, and a signal processing unit 82. The transmitting / receiving unit 81 has a modulation unit 91, a transmitting unit 92, a transmit / receive switching unit 93, a frequency conversion / amplification unit 94, a detection unit 95, and a video amplification unit 96.

[0093] The antenna section 99 includes a drive unit (not shown) that rotates the antenna device 101. The transmitting / receiving unit 81 in the antenna section 99 transmits and receives radio waves using the antenna device 101.

[0094] More specifically, the control unit 83 receives operation information from the operation unit 85 indicating user operations received by the operation unit 85, and controls each unit in the radar device 201.

[0095] The signal processing unit 82 outputs a trigger signal to the modulation unit 91 in accordance with the control of the control unit 83.

[0096] The modulation unit 91 receives a trigger signal from the signal processing unit 82, creates a pulse voltage, and outputs it to the transmission unit 92.

[0097] The transmitting unit 92 generates radio waves corresponding to the pulse voltage received from the modulation unit 91 and outputs them to the antenna device 101 via the transmit / receive switching unit 93 and a waveguide (not shown).

[0098] The antenna device 101 radiates radio waves received from the transmitting unit 92. The antenna device 101 also receives reflected waves from a target and outputs them to the frequency conversion and amplification unit 94 via a waveguide and a transmit / receive switching unit 93 (not shown).

[0099] The frequency conversion and amplification unit 94 down-converts and amplifies the radio waves received from the antenna device 101, and outputs the amplified signal to the detection unit 95.

[0100] The detection unit 95 generates a video signal by detecting the signal received from the frequency conversion and amplification unit 94 and outputs it to the video amplification unit 96.

[0101] The video amplification unit 96 amplifies the video signal received from the detection unit 95 and outputs it to the signal processing unit 82.

[0102] The signal processing unit 82 performs predetermined signal processing on the video signal received from the video amplification unit 96 and outputs the processed digital signal to the control unit 83.

[0103] The control unit 83 converts the digital signal received from the signal processing unit 82 into video information and outputs it to the display unit 84 along with video information from other devices such as sensors connected to the radar device 201.

[0104] The display unit 84 displays video information received from the control unit 83, namely radar images and information from various sensors, on the screen.

[0105] The antenna device 101 may be used in a device that transmits radio waves only, or in a device that receives radio waves only.

[0106] Incidentally, when propagating high-frequency radio waves in an antenna, gain reduction due to propagation loss in the feed line, as well as performance degradation due to unwanted radiation and reflection, become significant. Technologies capable of improving antenna performance for high-frequency radio waves are desired.

[0107] In contrast, in the antenna device according to an embodiment of the present invention, the two line antennas 11 constituting the antenna assembly include a linear feed line 2 and a plurality of antenna elements 1 whose ends are connected to the feed line 2 and which extend perpendicularly from the feed line 2. The feed line 2 and the plurality of antenna elements 1 in one of the two line antennas 11 are symmetrical with respect to the other line antenna 11 with respect to a virtual line L parallel to the feed line 2 as the axis of symmetry.

[0108] Furthermore, the radar device according to an embodiment of the present invention comprises an antenna device 101 and a transmitting / receiving unit 81 that transmits and receives radio waves using the antenna device 101.

[0109] In this configuration, connecting the ends of the antenna elements to the feed line suppresses losses due to current branching. Furthermore, by configuring the two line antennas symmetrically, if the phases of the radio waves supplied to the two line antennas are inverted relative to each other, or if the phases of the radio waves propagating from the two corresponding line antennas are inverted relative to each other, the polarization in the desired direction can be strengthened while the polarization in the unwanted direction can be weakened between the corresponding antenna elements, thereby suppressing side lobes and the like.

[0110] Therefore, the antenna device and radar device according to the embodiment of the present invention can improve the antenna characteristics for high-frequency radio waves.

[0111] Furthermore, in the antenna device according to the embodiment of the present invention, the phases of the currents supplied to the two line antennas constituting the antenna set are inverted relative to each other.

[0112] With this configuration, the antenna device can easily invert the phase of radio waves in a specific direction between two line antennas.

[0113] Furthermore, in the antenna device according to the embodiment of the present invention, the distributor 21 inverts the phases of the current supplied to the two line antennas 11 that constitute the antenna set.

[0114] This configuration allows for the efficient implementation of phase shifter functionality using a distributor.

[0115] Furthermore, in the antenna device according to the embodiment of the present invention, each antenna element 1 in the line antenna 11 is connected to the same side of the feed line 2.

[0116] This configuration allows for a reduction in the size of the antenna device in the width direction of the power supply line, which in turn suppresses grating lobes and improves antenna characteristics.

[0117] Furthermore, in the antenna device according to the embodiment of the present invention, in the two line antennas 11 that constitute the antenna set, each antenna element 1 extends toward the virtual line L.

[0118] With this configuration, for example, in the case of two line antennas of an antenna set located towards the center in the width direction of the feed line, the antenna elements can be placed in the space between the feed lines that is provided to avoid interference between the feed lines. This allows the size of the antenna device in the width direction of the feed line to be further reduced, and for example, grating lobes can be further suppressed.

[0119] Furthermore, in the antenna device according to the embodiment of the present invention, two antenna sets are provided, with one antenna set positioned to sandwich the other antenna set.

[0120] This configuration allows for the achievement of a more appropriate beam width.

[0121] Furthermore, in the antenna device according to the embodiment of the present invention, the power supply unit 22 includes a back-short type waveguide-microstrip line converter and supplies power to each power supply line 2.

[0122] This configuration makes it possible to suppress side lobes and improve antenna characteristics in antenna devices where side lobes tend to become large due to reflection of radio waves from the metal case or other components that make up the grounding section.

[0123] The embodiments described above should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0124] 1 Antenna element 2 Feed lines 11A, 11B, 11C, 11D, 51, 52, 52A, 52B Line antenna 21 Distributor 22, 62, 63 Feed unit 31, 32, 33 Antenna assembly 41-46 Line 61 Branch unit 81 Transmit / receive unit 82 Signal processing unit 83 Control unit 84 Display unit 85 Operation unit 91 Modulation unit 92 Transmit unit 93 Transmit / receive switching unit 94 Frequency conversion / amplification unit 95 Detection unit 96 Video amplification unit 99 Antenna unit 71, 72, 73, 101 Antenna device 201 Radar device

Claims

1. An antenna device comprising: a first line antenna consisting of a linear first feed line; and a plurality of first antenna elements whose ends are connected to the first feed line and which extend perpendicularly from the first feed line; and a second line antenna consisting of a second feed line and a plurality of second antenna elements which are symmetrical to the first line antenna with an imaginary line parallel to the first feed line as the axis of symmetry.

2. The antenna device according to claim 1, wherein the phases of the currents supplied to said first line antenna and said second line antenna are opposite to each other.

3. The antenna device according to claim 1 or 2, further comprising a distributor that inverts the phases of the currents supplied to the first line antenna and the second line antenna.

4. An antenna device according to any one of claims 1 to 3, wherein the plurality of first antenna elements are all connected to the same side of the first feed line, and the plurality of second antenna elements are all connected to the same side of the second feed line.

5. An antenna device according to any one of claims 1 to 4, wherein the plurality of first antenna elements and the plurality of second antenna elements extend toward the axis of symmetry.

6. An antenna device according to any one of claims 1 to 5, comprising two antenna pairs when the first line antenna and the second line antenna are considered as one antenna pair, one of which is arranged to sandwich the other antenna pair.

7. The antenna device according to any one of claims 1 to 6, comprising a back-short type waveguide-to-microstrip line converter, and further comprising a power supply section that supplies power to the first power supply line and the second power supply line.

8. A radar device comprising: an antenna device according to any one of claims 1 to 7; and a transmitter / receiver unit that transmits and receives radio waves using the antenna device.

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