Microlens array antenna, and radar device and vehicle equipped with same

Abstract

Provided are a microlens array antenna less subject to a decrease in antenna gain or degradation of side lobe characteristics, and a radar device and a vehicle having the same. A microlens array antenna 1A is provided with: a planar array antenna 3 formed on a substrate 2; dielectric lenses 4 provided over the planar array antenna 3; and a dielectric plate 5 vertically rising from the substrate 2 between the dielectric lenses 4. Each of the dielectric lenses 4 is provided over each of patch antennas 3a of which the planar array antenna 3 is composed. Each of the patch antennas 3a emits radio waves, of which radio waves α0 emitted at a low elevation angle and advancing toward the dielectric lens 4 provided over an adjacent patch antenna 3a are reflected by the dielectric plate 5 rising from the substrate 2 between the dielectric lenses 5.

Description

[Technical Field]

[0001] The present invention relates to a microlens array antenna in which a dielectric lens is provided above a planar array antenna, and to a radar device and a vehicle equipped with the same. [Background technology]

[0002] Conventional array antennas of this type are disclosed, for example, in Non-Patent Document 1. As shown in Fig. 2 of the document, this array antenna consists of horn antennas arranged above a microstrip antenna, and a dielectric lens attached to the opening of each horn antenna. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] “Horn and Lens Antenna with Low Hight and Low Antenna Coupling for Compact Automotive 77-GHz Long-Range Rader”IEICE TRANS. ELECTRON., VOL.E103-C, NO.10 OCTOBER 2020 (Hitachi) Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional array antenna disclosed in Non-Patent Document 1, radio waves emitted by the antenna leak from the gap between the outer periphery of the dielectric lens and the inner periphery of the horn's opening end. This radio wave leakage acts as a wave source, affecting adjacent antennas and reducing the side lobe characteristics of the horn antenna. Furthermore, in the conventional array antenna, the horn height H cannot be reduced relative to the opening diameter D in order to align the phase on the aperture surface. Furthermore, if the height H is reduced, the side of the dielectric lens opposite the antenna becomes convex, resulting in blocking by the adjacent dielectric lens, which results in a loss of side lobe characteristics and antenna gain. [Means for solving the problem]

[0005] The present invention has been made to solve such problems, a planar array antenna formed on a substrate; a dielectric lens provided above each planar antenna constituting the planar array antenna; The antenna is installed on the substrate between the dielectric lenses, and among the radio waves emitted from the planar antenna, the amount of radio waves directed toward the dielectric lens installed above the adjacent planar antenna is At least some a dielectric plate having a side surface that blocks and reflects light from traveling to a dielectric lens provided above an adjacent planar antenna; Equipped with 、 The dielectric plate has a thickness and a dielectric constant such that a first reflected wave, which is a radio wave emitted from the planar antenna and reflected by one side surface of the dielectric plate facing the planar antenna, and a second reflected wave, which is a radio wave propagating through the dielectric plate through the one side surface and reflected by the other side surface of the dielectric plate opposite to the one side surface and appears in the space on the one side surface side, are shifted in phase by a predetermined phase. A microlens array antenna was constructed using this.

[0006] According to this configuration, among the radio waves radiated from each planar antenna, those radiated at low elevation angles and directed toward the dielectric lens provided above the adjacent planar antenna are reflected by the dielectric plate provided on the substrate between the dielectric lenses. Therefore, the radio waves radiated at low elevation angles are blocked by the dielectric plate from traveling toward the dielectric lens provided above the adjacent planar antenna. Therefore, even if the height dimension of the microlens array antenna is reduced by shortening the focal length of the dielectric lens by making the dielectric lens convex on the side opposite the planar antenna, radio waves at low elevation angles directed outside the irradiation range of the dielectric lens above the planar antenna are suppressed. As a result, even if the height dimension of the microlens array antenna is reduced by shortening the focal length of the dielectric lens by making the dielectric lens convex on the side opposite the planar antenna, each planar antenna is less likely to be affected by the radio waves radiated from the adjacent planar antenna, resulting in a reduction in antenna gain and degradation of side lobe characteristics.

[0007] The present invention also provides a radar device including the microlens array antenna described above, and a vehicle including the radar device. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a microlens array antenna in which the antenna gain is less likely to decrease and the side lobe characteristics are less likely to deteriorate, and a radar device and a vehicle including the same. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side view of a microlens array antenna according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a side view of a portion of a microlens array antenna according to a second embodiment of the present invention. [Figure 3] 10A and 10B are a plan view and a side cross-sectional view of a microlens array antenna according to a third embodiment of the present invention. [Figure 4]4A to 4C are a plan view, a side view, and a front view of a vehicle equipped with a radar device including the microlens array antenna shown in FIG. [Figure 5] 10A and 10B are a plan view and a side view of a microlens array antenna according to a fourth embodiment of the present invention. [Figure 6] FIG. 1(a) is a cross-sectional view of a microlens array antenna according to a fifth embodiment of the present invention, and FIG. 1(b) is a cross-sectional view of a microlens array antenna according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, a description will be given of embodiments for carrying out the microlens array antenna of the present invention, and a radar device and a vehicle equipped with the same.

[0011] FIG. 1 is a side view of a microlens array antenna 1A according to a first embodiment of the present invention.

[0012] The microlens array antenna 1A comprises a planar array antenna 3 formed on a substrate 2, a dielectric lens 4 provided above the planar array antenna 3, and a dielectric plate 5 provided vertically on the substrate 2 between each of the dielectric lenses 4. The planar array antenna 3 comprises patch antennas 3a formed in one direction on the surface of the substrate 2 at regular intervals. A ground pattern 6 that applies a reference potential to each patch antenna 3a is formed on the back surface of the substrate 2. Each dielectric lens 4 is provided above each of the patch antennas 3a that make up the planar array antenna 3, and each patch antenna 3a is located at the focal position of the dielectric lens 4 provided above it. Here, "upward" refers to the direction in which each patch antenna 3a emits radio waves.

[0013] In this embodiment, each dielectric lens 4 has a spindle-shaped bulge on the side opposite the patch antenna 3a, and is provided for the purpose of converging the radio waves emitted from the patch antenna 3a. In order to shorten the focal length and control the radio waves α0 emitted at a low elevation angle, the lens shape of each dielectric lens 4 bulges outward to form a convex shape on the side opposite the patch antenna 3a. In the microlens array antenna 1A, the power of the radio waves received by each patch antenna 3a is combined to control its directivity.

[0014] In this specification, the term "dielectric plate 5" is used to refer to a concept that encompasses everything from a thin dielectric film to a thick dielectric block. As the frequency of the radio waves emitted from the patch antenna 3a increases, the thickness of the dielectric plate 5 generally becomes thinner and more film-like, and as the frequency decreases, the thickness of the dielectric plate 5 generally becomes thicker and more block-like.

[0015] According to the microlens array antenna 1A of this embodiment, of the radio waves radiated from each patch antenna 3a, radio waves α0 radiated at a low elevation angle and directed toward the dielectric lens 4 provided above the adjacent patch antenna 3a are reflected by the dielectric plate 5 provided upright on the substrate 2 between the dielectric lenses 5, as shown in the figure. Therefore, the radio waves α0 radiated at a low elevation angle are blocked by the dielectric plate 5 from traveling toward the dielectric lens 4 provided above the adjacent patch antenna 3a.

[0016] Therefore, in order to reduce the dimension of microlens array antenna 1A in the height direction h, the side of dielectric lens 4 opposite patch antenna 3a is made convex as shown in the figure, and even if the focal length of dielectric lens 4 is shortened, radio waves α0 at low elevation angles traveling outside the irradiation range of dielectric lens 4 above patch antenna 3a are suppressed. Furthermore, even if the distance between each dielectric lens 4 is shortened to reduce the dimension of microlens array antenna 1A in the extension direction w, each patch antenna 3a is less likely to be affected by radio waves α0 radiated from adjacent patch antennas 3a, resulting in a decrease in antenna gain and deterioration of side lobe characteristics.

[0017] 2 is a side view of a portion of a microlens array antenna 1B according to a second embodiment of the present invention, in which the same or corresponding parts as those in FIG.

[0018] The microlens array antenna 1B according to the second embodiment differs from the microlens array antenna 1A according to the first embodiment in that the thickness t and dielectric constant ε of the dielectric plate 5 are as follows: Each dielectric plate 5 of the microlens array antenna 1B has a thickness t and a dielectric constant ε such that the first reflected wave α1 and the second reflected wave α2 of the radio wave α0 are shifted in phase by a predetermined amount. The first reflected wave α1 is a reflected wave of the radio wave α0 emitted from the patch antenna 3a, reflected by one side surface 5a of the dielectric plate 5 facing the patch antenna 3a. The second reflected wave α2 is a reflected wave of the radio wave α0 propagating through the dielectric plate 5 through one side surface 5a, reflected by the other side surface 5b of the dielectric plate 5 opposite to the one side surface 5a, and emerging in the space on the one side surface 5a side.

[0019] In the microlens array antenna 1B according to the second embodiment, the radio waves α0 emitted from the patch antenna 3a are reflected by one side surface 5a of the dielectric plate 5 to produce a first reflected wave α1, and the second reflected wave α2 is reflected by the other side surface 5b of the dielectric plate 5 and appears in the space on the side surface 5a side, and the phases of these two waves are shifted by a predetermined phase, so that the intensity of the composite wave of the first reflected wave α1 and the second reflected wave α2 that is shifted in phase by the predetermined phase is weakened. In particular, when the phase of the second reflected wave α2 is opposite to that of the first reflected wave α1, the intensity of the composite wave of the first reflected wave α1 and the second reflected wave α2 is weakened to the greatest extent.

[0020] In order to make the phase of the second reflected wave α2 opposite to the phase of the first reflected wave α1, if the incident angle θ of the radio wave α0 incident on one side surface 5a is set to 0° for the sake of simplicity, the thickness t of the dielectric plate 5 is set to λ0, the wavelength of the radio wave α0 propagating through the space is set to λ1, and the wavelength of the radio wave α0 propagating inside the dielectric plate 5 is set to λ2. g If the dielectric constant of the dielectric plate 5 is ε, then it is expressed by the following equation (1). t≒λ g / 4=λ0 / (4·ε 1 / 2 ) …(1)

[0021] When the dielectric plate 5 has a thickness t expressed by this equation (1), the sum of the distance la that the radio wave α0 travels in the dielectric plate 5 from one side surface 5a to the other side surface 5b and the distance lb that the second reflected wave α2 travels in the dielectric plate 5 from the other side surface 5b to the one side surface 5a is λ as expressed by the following equation (2). g / 2, and the phase of the second reflected wave α2 appearing on the one side surface 5a is opposite to the phase of the first reflected wave α1. la+lb=λ g / 4+λ g / 4=λ g / twenty two)

[0022] Therefore, by adjusting the thickness t and dielectric constant ε of the dielectric plate 5, it is possible to reduce the influence of the first reflected wave α1 on the dielectric lens 4 provided above the patch antenna 3a that generates the first reflected wave α1. Furthermore, by adjusting the amount of phase shift between the first reflected wave α1 and the second reflected wave α2, it is possible to control the amount of reflection of the component of the first reflected wave α1 in a desired direction. Therefore, it is possible to effectively reduce the component of the first reflected wave α1 in a reflection direction that has a large influence on the dielectric lens 4 provided above the patch antenna 3a that generates the first reflected wave α1. This makes it possible to more effectively prevent a decrease in the antenna gain of the patch antenna 3a.

[0023] Fig. 3(a) is a plan view of a microlens array antenna 1C according to a third embodiment of the present invention, Fig. 3(b) is a side cross-sectional view taken along line AA, and Fig. 3(c) is a side cross-sectional view taken along line BB. In these figures, parts that are the same as or correspond to those in Fig. 1 are designated by the same reference numerals and their explanation will be omitted.

[0024] The microlens array antenna 1C according to the third embodiment differs from the microlens array antenna 1B according to the second embodiment in that the planar array antennas 3 are arranged in multiple rows adjacent to each other on the substrate 2, each dielectric lens 4 in the planar array antenna 3 is formed in an elliptical shape with its major axis in the long side direction of the illustrated substrate 2, which is perpendicular to the short side direction of the illustrated substrate 2 along which the rows of planar array antennas 3 are arranged, when the surface of the substrate 2 is viewed in plan, and at least two or more patch antennas 3a are formed on the substrate 2 in the long axis direction, centered on the focal point c of the dielectric lens 4, at a position a predetermined distance from the focal point c.

[0025] According to the microlens array antenna 1C of the third embodiment, it is possible to control the directivity of the microlens array antenna 1C in the long-side direction of the substrate 2 by switching the excitation of each of the patch antennas 3a formed on the substrate 2 in the long-axis direction of the dielectric lens 4, offset from the focal point c of the dielectric lens 4, or by changing the excitation phase of each patch antenna 3a to perform phase synthesis. Also, it is possible to control the directivity of the microlens array antenna 1C in the short-side direction of the substrate 2 by changing the excitation phase of each of the four patch antennas 3a that constitute the planar array antenna 3, which are arranged in the short-side direction of the substrate 2. Therefore, it is possible to calculate the direction of radio waves arriving at the microlens array antenna 1C from the radio waves received by the microlens array antenna 1C.

[0026] For example, as shown in Fig. 4(a) in a plan view, Fig. 4(b) in a side view, and Fig. 4(c) in a front view of a vehicle 21, a radar device 22 equipped with a microlens array antenna 1C is provided in front of the vehicle 21, and the short side of the substrate 2 is set to the height direction of the vehicle 21 and the long side of the substrate 2 is set to the width direction of the vehicle 21. This allows the radar device 22 to have directivity in the azimuth direction, which is the azimuth angle direction of the vehicle 21, and in the elevation direction, which is the elevation angle direction of the vehicle 21. Therefore, the beam B emitted from the radar device 22 can be controlled to the azimuth direction shown in Fig. 4(a) or the elevation direction shown in Fig. 4(b). This makes it possible to calculate the direction of radio waves arriving from the azimuth direction and the elevation direction from the radio waves received by the microlens array antenna 1C.

[0027] In this case, as shown in FIG. 1C, the planar array antenna 3 in the rightmost column of the microlens array antenna 1C is the transmitting antenna Tx, and the planar array antennas 3 in the column to the left of the transmitting antenna Tx are the receiving antennas Rx1, Rx2, and Rx3. The direction of the incoming radio waves is calculated by digital beamforming or the like from the phase difference of the radio waves received by the receiving antennas Rx1, Rx2, and Rx3. Therefore, the directivity of the microlens array antenna 1C can be tilted in the azimuth and elevation directions of the vehicle 21.

[0028] 5(a) is a plan view of a microlens array antenna 1D according to a fourth embodiment of the present invention, and FIG. 5(b) is a side view. In these figures, parts that are the same as or correspond to those in FIGS. 1 and 3 are designated by the same reference numerals and their description will be omitted.

[0029] The microlens array antenna 1D according to the fourth embodiment differs from the microlens array antenna 1C according to the third embodiment in that each dielectric plate 5 is also installed vertically between adjacent patch antennas 3a constituting the planar array antenna 3 in each row.

[0030] According to the microlens array antenna 1D of the fourth embodiment, radio waves α0 are radiated at a low elevation angle between adjacent patch antennas 3a in the long side direction of the substrate 2, just as they are between each patch antenna 3a in the short side direction of the substrate 2, and travel toward the dielectric lens 4 provided above the adjacent patch antenna 3a in the long side direction. The radio waves α0 are reflected by the dielectric plate 5 provided on the substrate 2 between the dielectric lenses 4 in each row, as shown in Fig. 1. Therefore, the radio waves α0 are blocked by the dielectric plate 5 from traveling toward the dielectric lens 4 provided above the adjacent patch antenna 3a in the long side direction.

[0031] Therefore, even in a microlens array antenna 1D in which planar array antennas 3 are arranged in multiple rows, the dimension in the height direction h of the microlens array antenna 1D can be reduced by making the dielectric lenses 4 convex. Furthermore, even if the dimension in the long side direction of the substrate 2 is reduced by shortening the distance between each dielectric lens 4 in the long side direction of the substrate 2, each patch antenna 3a is less likely to be affected by the radio waves α0 radiated from the adjacent patch antennas 3a, resulting in a decrease in antenna gain and degradation of side lobe characteristics.

[0032] 6(a) is a cross-sectional view of a microlens array antenna 1E according to a fifth embodiment of the present invention. In Fig. 6, parts that are the same as or correspond to those in Fig. 3 and Fig. 5 are given the same reference numerals and their description will be omitted.

[0033] The microlens array antenna 1E according to the fifth embodiment differs from the microlens array antenna 1C according to the third embodiment and the microlens array antenna 1D according to the fourth embodiment in that each dielectric lens 4 is integrally formed with each dielectric plate 5 and fixed onto the substrate 2.

[0034] According to the microlens array antenna 1E of the fifth embodiment, the microlens array antenna 1E can be assembled by fixing the integrated dielectric lenses 4 and dielectric plates 5 onto the substrate 2, thereby improving the ease of assembly of the microlens array antenna 1E. Furthermore, by integrally molding the dielectric lenses 4 and the dielectric plates 5, the cost of the components of the microlens array antenna 1E can be reduced. This makes it possible to provide an inexpensive microlens array antenna 1E that is less susceptible to antenna gain reduction and side lobe characteristic degradation. Note that the microlens array antenna 1A of the first embodiment and the microlens array antenna 1B of the second embodiment may also be configured such that the dielectric lenses 4 and the dielectric plates 5 are integrally molded, similar to the microlens array antenna 1E of the fifth embodiment. This configuration achieves the same effects as the microlens array antenna 1E of the fifth embodiment.

[0035] 6(b) is a cross-sectional view of a microlens array antenna 1F according to a sixth embodiment of the present invention, in which the dielectric lenses 4 are formed integrally with the dielectric plates 5 standing between the patch antennas 3a when the dielectric constants of the dielectric lenses 4 and the dielectric plates 5 cannot be made the same value. In this case, the dielectric plates 5 are supported by vias 5c that penetrate the substrate 2 and connect them, and the vias 5c are fixed to a dielectric layer 5d formed on the back surface of the substrate 2. The dielectric layer 5d and the vias 5c are made of the same material as the dielectric plates 5.

[0036] According to the microlens array antenna 1F of the sixth embodiment, it is possible to easily attach each dielectric lens 4 to the substrate 2, improving the ease of assembly and reducing the unit cost of the dielectric lens 4. Therefore, like the above-described microlens array antenna 1E, the microlens array antenna 1F can be provided at low cost.

[0037] In each of the microlens array antennas 1A to 1D and 1F, the dielectric plate 5 may be configured to have a larger dielectric constant than that of the dielectric lens 4.

[0038] According to this modified example of the configuration, the relative permittivity of dielectric lens 4 is set to, for example, about 2 to 3, and the relative permittivity of dielectric plate 5 is set to, for example, about 8 to 10, thereby ensuring that radio waves α0 emitted from patch antenna 3a can enter dielectric lens 4 located above it, while increasing the difference in permittivity between dielectric plate 5 and the space, thereby increasing the amount of reflection of first reflected wave α1, which is generated when radio waves α0 emitted from patch antenna 3a are reflected by one side surface 5a of dielectric plate 5. Therefore, the thickness of dielectric plate 5 provided on substrate 2 between dielectric lenses 4 can be reduced, which in turn reduces the gaps between dielectric lenses 4 and reduces the overall dimensions of microlens array antennas 1A to 1D and 1F.

[0039] Furthermore, in each of the above microlens array antennas 1A to 1F, the dielectric plate 5 may be further configured to have a dielectric constant that generates a predetermined dielectric loss that converts a portion of the electrical energy of the radio wave α0 emitted from the patch antenna 3a into thermal energy.

[0040] According to this modified configuration, the electric energy of radio waves α0 emitted at a low elevation angle from patch antenna 3a is weakened by dielectric loss occurring in dielectric plate 5. This reduces the influence of radio waves α0 emitted at a low elevation angle from patch antenna 3a on dielectric lens 4 provided above adjacent patch antenna 3a, as well as the influence of reflected waves α1 and α2 reflected by dielectric plate 5 on dielectric lens 4 provided above patch antenna 3a that emitted radio waves α0. This makes it possible to provide microlens array antennas 1A to 1F that can more effectively prevent a decrease in the antenna gain of patch antenna 3a and deterioration of side lobe characteristics.

[0041] In addition, in the above-described embodiments and modifications, the planar antenna has been described as a patch antenna. However, the planar antenna is not limited to this, and may be, for example, a meander line antenna in which a conductor is bent into a crank shape, or a slot antenna. Furthermore, the number of planar antennas constituting the planar array antenna 3 is not limited to the number in the above-described embodiments and modifications, and may be two or more. [Industrial Applicability]

[0042] A radar device may be provided with any of the microlens array antennas 1A to 1F described above or the microlens array antennas 1A to 1F according to any of the modifications described above, and the radar device may be mounted on a vehicle 21, as in the radar device 22 shown in FIG. 4. This configuration makes it possible to provide a radar device and a vehicle equipped with a microlens array antenna that is less susceptible to reduction in antenna gain and deterioration of side lobe characteristics. Furthermore, the radar device may be mounted not only on vehicles, but also on aircraft, ships, and the like. In this case, the same effects as when the radar device is mounted on a vehicle can be achieved. [Explanation of symbols]

[0043] 1A, 1B, 1C, 1D, 1E, 1F...Microlens array antenna 2...Substrate 3...Planar array antenna 3a...Patch antenna (flat antenna) 4...Dielectric lens 5...Dielectric plate 5a…one side 5b…other side 5c…Beer 5d...Dielectric layer 6...Ground pattern 21...Vehicle 22...Radar equipment c…Focus

Claims

1. a planar array antenna formed on a substrate; a dielectric lens provided above each of the planar antennas constituting the planar array antenna; a dielectric plate provided on the substrate between the dielectric lenses, the dielectric plate having a side surface that blocks and reflects at least a portion of radio waves, among radio waves radiated from the planar antenna and directed toward the dielectric lens provided above the adjacent planar antenna, from traveling toward the dielectric lens provided above the adjacent planar antenna; Equipped with The dielectric plate has a thickness and a dielectric constant such that the phases of a first reflected wave, which is formed when radio waves emitted from the planar antenna are reflected on one side of the dielectric plate facing the planar antenna, and a second reflected wave, which is formed when the radio waves propagate through the dielectric plate through the one side and are reflected on the other side of the dielectric plate opposite the one side, and appear in the space on the one side, are shifted by a predetermined phase.

2. the planar array antennas are formed adjacent to each other in a plurality of rows on the substrate, the dielectric lens is formed in an elliptical shape having a major axis in a direction perpendicular to a direction in which the planar array antennas are arranged when the surface of the substrate is viewed in plan; The planar antenna is formed in plurality on the substrate in the longitudinal direction at positions spaced a predetermined distance from the focal point of the dielectric lens as the center.

2. The microlens array antenna according to claim 1, wherein the antenna is a microlens array antenna.

3. 3. The microlens array antenna according to claim 2, wherein the dielectric plate is also provided between adjacent planar antennas constituting the planar array antenna in each row.

4. 2. The microlens array antenna according to claim 1, wherein each of the dielectric lenses is integrally formed with each of the dielectric plates and fixed onto the substrate.

5. 2. The microlens array antenna according to claim 1, wherein the dielectric plate has a dielectric constant greater than that of the dielectric lens.

6. 2. The microlens array antenna according to claim 1, wherein the dielectric plate has a dielectric constant that generates a predetermined dielectric loss that converts a portion of the electrical energy of the radio waves emitted from the planar antenna into thermal energy.

7. A radar device comprising the microlens array antenna according to claim 1.

8. A vehicle comprising the radar device according to claim 7.

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