Microlens array antenna

Abstract

To provide a microlens array antenna capable of reducing a ripple generated in a directional pattern, increasing an antenna gain, and in addition, reducing deterioration of a side lobe.SOLUTION: A microlens array antenna 1A comprises: patch antennas 3 formed onto a substrate 2; and dielectric lenses 4. The patch antennas 3 are closed to a y direction, and are arranged so as to be arranged onto the substrate 2. The dielectric lenses 4 have a column-like shape having a shaft direction to the y direction where the patch antennas 3 are arranged, and is provided on the upper part of each patch antenna 3. The dielectric lenses 4 include a dielectric constant distribution of which a dielectric constant ε becomes smaller toward an outer periphery of a radial direction from a shaft center. At least two or more both of the patch antennas 3 and the dielectric lenses 4 constructing a microlens antenna are arranged to an x direction orthogonal to the y direction where the patch antennas 3 are arranged so that each patch antenna 3 makes a row.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a microlens array antenna having an array structure of microlens antennas composed of a planar antenna arranged on a substrate and a dielectric lens provided above the planar antenna. [Background technology]

[0002] A conventional radar device equipped with this type of microlens array antenna is disclosed in, for example, Patent Document 1. As shown in Fig. 3 of the document, this microlens array antenna includes transmitting antennas 2a-2d and receiving antennas 3a-3d formed in a front region of a circuit board 1, which are configured as an antenna section of a phased array antenna that changes the transmission and reception directions of electromagnetic waves by electronic scanning. In front of this antenna section, a semi-cylindrical dielectric lens 7 is disposed so as to extend along the array direction.

[0003] 3 of Patent Document 2 shows a microlens array antenna 1C in which planar array antennas 3 each made of a dielectric lens 4 are arranged in multiple rows on a substrate 2. Each dielectric lens 4 has a shape that bulges out in a spindle shape on the side opposite to the patch antenna 3a, and a dielectric plate 5 is provided upright between each of the dielectric lenses 4 in each planar array antenna 3. The patch antennas 3a are arranged side by side on the substrate 2 in close proximity to and offset from the focal point c of the dielectric lens 4. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-60485 A [Patent Document 2] International Publication No. 2023 / 276606 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional microlens array antenna disclosed in Patent Document 1, multiple reflections of radio waves occur between the radiation electrode and antenna ground of the antenna part, which act as the primary wave source, and the surface of the dielectric lens 7 facing them, causing ripples in the directional characteristics of the antenna part in the array direction.

[0006] Furthermore, in order to increase the antenna gain by narrowing the directivity of the antenna unit in a direction perpendicular to the circuit board 1, which is orthogonal to the array direction of the antenna unit, it becomes necessary to increase the size of the dielectric lens 7 by increasing the radius of the dielectric lens 7 in the direction perpendicular to the circuit board 1, and to increase the distance between the dielectric lens 7 and the antenna unit on the surface of the circuit board 1 according to the focal length. This results in an increase in the overall size of the microlens array antenna.

[0007] In addition, in the microlens array antenna disclosed in the above-mentioned conventional Patent Document 2, in the direction of the AA line shown in FIG. 3(b) of the same document, where a dielectric plate 5 is arranged between each of the dielectric lenses 4, as shown in FIG. 1 of the same document, radio waves radiated from the patch antenna 3a at a low elevation angle and directed upward toward the adjacent patch antenna 3a are reflected by the dielectric plate 5 erected on the substrate 2 between the dielectric plates 5. Also, the radio waves are reflected by the surface of the dielectric lens 4 provided above the adjacent patch antenna 3a, and a part of the radio waves is bounced back toward the substrate 2. Therefore, the radio waves radiated at a low elevation angle are blocked from entering the dielectric lens 4 provided above the adjacent patch antenna 3a by the dielectric plate 5 and the surface of the dielectric lens 4 provided above the adjacent patch antenna 3a, making it possible to suppress radio waves that have adverse effects due to reflection and scattering. However, the energy of the radio waves radiated at a low elevation angle is wasted. [Means for solving the problem]

[0008] The present invention has been made to solve such problems, The microlens array antenna has an array structure in which at least two planar antennas are arranged in a row in a direction perpendicular to the direction in which the planar antennas are arranged, and a microlens antenna is composed of a dielectric lens having a columnar shape with an axial direction in which the planar antennas are arranged, which is provided above each planar antenna and has a dielectric constant distribution in which the dielectric constant decreases from the axis toward the outer periphery in the radial direction.

[0009] According to this configuration, the dielectric lens has a dielectric constant distribution in which the dielectric constant decreases from the axis toward the outer periphery in the radial direction, and since the dielectric constant near the outer periphery of the dielectric lens is small, the radio waves reflected on the lens surface of the dielectric lens can be reduced and the radio waves can be reflected at the axis of the dielectric lens, which has a large dielectric constant. Therefore, the reflection of the radio waves between the planar antenna on the substrate surface and the dielectric lens mainly occurs between the planar antenna on the substrate surface and the axis of the dielectric lens, and multiple reflections occurring between the planar antenna on the substrate surface and the surface of the dielectric lens can be reduced. In addition, the distance between the planar antenna on the substrate surface and the axis of the dielectric lens is longer than the distance between the planar antenna on the substrate surface and the surface of the dielectric lens. Therefore, due to attenuation due to the propagation distance of the radio waves, the multiple reflections of the radio waves between the former, which is a long distance, are weaker than those between the latter, which is a short distance.

[0010] As a result, it is possible to reduce ripples in the directional characteristics of the microlens array antenna in the array direction of the planar antenna, which is the axial direction of the dielectric lens, caused by multiple reflections of radio waves between the planar antenna on the surface of the substrate and the surface of the dielectric lens.

[0011] Also, according to this configuration, the microlens antenna is composed of planar antennas arranged adjacent to each other on the substrate, and a dielectric lens having a columnar shape with an axial direction in the direction in which the planar antennas are arranged, which is provided above each planar antenna and has a dielectric constant distribution in which the dielectric constant decreases from the axis to the outer periphery in the radial direction, and at least two of these microlens antennas are arranged in a direction perpendicular to the direction in which the planar antennas are arranged. Therefore, by arranging at least two of these microlens antennas, which can reduce ripples occurring in the directivity characteristics in the array direction of the planar antennas as described above, in a direction perpendicular to the array direction in which the planar antennas are arranged, the directivity of each microlens antenna in the direction perpendicular to the array direction in which the planar antennas are arranged becomes sharp, and the antenna gain also increases synergistically.

[0012] Therefore, it is possible to increase the antenna gain by narrowing the directivity in the direction in which the dielectric lenses are arranged, which is perpendicular to the array direction, without increasing the diameter of the dielectric lens and making the dielectric lens larger as in the conventional case.

[0013] According to this configuration, the radio waves radiated at a low elevation angle from one of the planar antennas arranged in a row below the adjacent dielectric lenses and directed toward the top of the other adjacent planar antenna are incident on the dielectric lens arranged above the other planar antenna. At this time, the dielectric lens has a dielectric constant distribution in which the dielectric constant decreases from the axis toward the outer periphery in the radial direction, and the dielectric constant near the outer periphery of the dielectric lens is small, so that the radio waves reflected on the lens surface of the dielectric lens can be reduced. In addition, the directivity of the radio waves incident on the dielectric lens arranged above the other planar antenna at a low elevation angle is narrowed in the direction in which the dielectric lenses are arranged as described above, and the radio waves reflected on the lens surface of the dielectric lens are small, so that the influence of blocking caused by being reflected on the surface of the dielectric lens and bounced back to the substrate side as in the conventional case, or being blocked by an object such as a dielectric plate as in the conventional case, is reduced.

[0014] As a result, the deterioration of the side lobes of the microlens array antenna can be reduced. Also, the energy of the radio waves radiated from the planar antenna at low elevation angles is not wasted as in the conventional case. Effect of the Invention

[0015] According to the present invention, it is possible to provide a microlens array antenna that can reduce ripples that occur in the directional characteristics in the array direction in which closely spaced planar antennas are arranged, can narrow the directivity in the direction in which the dielectric lenses are arranged without increasing the size of the dielectric lenses, can increase the antenna gain, and can also reduce degradation of the side lobes. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1A is a perspective view of a microlens array antenna according to a first embodiment of the present invention, and FIG. 1B is a perspective view of a patch antenna seen through a dielectric lens shown in FIG. [Diagram 2] FIG. 2 is a front view of the microlens array antenna according to the first embodiment. [Diagram 3] FIG. 5A is a perspective view of a microlens array antenna according to a second embodiment of the present invention, and FIG. 5B is a perspective view of a patch antenna seen through a dielectric lens and a horn shown in FIG. [Figure 4] FIG. 11 is a front view of a microlens array antenna according to a second embodiment. [Diagram 5] FIG. 10A is an oblique view of a comparative microlens array antenna for comparison with the directional characteristics of the microlens array antenna according to the second embodiment, and FIG. 10B is an oblique view of a patch antenna seen through the dielectric lens shown in FIG. [Figure 6] 6A is a graph showing the directivity characteristic of the microlens array antenna according to the second embodiment, and FIG. 6B is a graph showing the directivity characteristic of the microlens array antenna of the comparative example shown in FIG. [Figure 7]11 is a perspective view of a patch antenna seen through a dielectric lens of a microlens array antenna according to a third embodiment of the present invention. FIG. [Figure 8] 13 is a perspective view of a patch antenna seen through a dielectric lens of a microlens array antenna according to a fourth embodiment of the present invention. FIG. [Figure 9] FIG. 13(a) is a front view of a microlens array antenna according to a fourth embodiment, and (b) is a front view of a microlens array antenna assumed to reduce the size of the microlens array antenna. [Figure 10] FIG. 13(a) is a perspective view of a dielectric lens that constitutes a microlens array antenna according to a fifth embodiment of the present invention, and FIG. 13(b) is a perspective view of a dielectric lens that constitutes a microlens array antenna according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Next, an embodiment of a microlens array antenna according to the present invention will be described. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

[0018] FIG. 1(a) is a perspective view of a microlens array antenna 1A according to a first embodiment of the present invention, and FIG. 2 is a front view.

[0019] The microlens array antenna 1A includes a patch antenna 3 formed on a substrate 2 and a dielectric lens 4 provided above the patch antenna 3. The patch antennas 3 form a planar antenna and are arranged side by side on the substrate 2, close to each other in the y direction and spaced at intervals of 0.5 or a wavelength close to the wavelength of the radio waves transmitted by the patch antennas 3. The dielectric lens 4 has a columnar shape with its axial direction in the y direction in which the patch antennas 3 are arranged, and is provided above each patch antenna 3. "Above" here refers to the z direction in which each patch antenna 3 radiates radio waves. The dielectric lens 4 is a Luneburg lens having a dielectric constant distribution in which the dielectric constant ε decreases from the axis toward the radial periphery.

[0020] In this embodiment, the dielectric lens 4 has a cylindrical shape. In this embodiment, the dielectric constant ε r 1 is 1.8, and the relative dielectric constant ε of the first cylindrical layer 4b, which is one outside the cylindrical layer 4a, is r 2 is 1.4, and the relative dielectric constant ε of the second cylindrical layer 4c, which is the outermost layer immediately outside the first cylindrical layer 4b, is r 3 is 1.2, and the magnitude relationship between them is ε r 1>ε r 2>ε r The relative dielectric constant ε r The values ​​are merely examples and are not limited to these values.

[0021] The patch antennas 3 arranged closely in the y direction and the dielectric lens 4 above them constitute a microlens antenna. In this embodiment, the microlens antenna has an array structure in which at least two patch antennas 3 (four in this embodiment) are arranged in two rows in the x direction perpendicular to the y direction in which the patch antennas 3 are arranged, as shown in Fig. 1(b), to constitute a microlens array antenna 1A. Fig. 1(b) is a perspective view of each patch antenna 3 on a substrate 2 seen through the dielectric lens 4 shown in Fig. 1(a).

[0022] According to the microlens array antenna 1A of the present embodiment, the dielectric lens 4 has a dielectric constant distribution in which the dielectric constant ε decreases from the axis toward the outer periphery in the radial direction, similar to a spherical Luneburg lens. r 3 is small, 1.2, and the relative dielectric constant of air, ε r (≒1), the relative dielectric constant ε rThe radio waves can be reflected by the cylindrical layer 4a at the axial center of the dielectric lens 4, which has the largest 1 at 1.8. Therefore, the reflection of the radio waves between the patch antenna 3 on the substrate surface and the dielectric lens 4 occurs mainly between the patch antenna 3 on the substrate surface and the cylindrical layer 4a at the axial center of the dielectric lens 4, and the multiple reflections occurring between the patch antenna 3 on the substrate surface and the surface of the dielectric lens 4 can be reduced.

[0023] 2, the distance Lb between the patch antenna 3 on the substrate surface and the cylindrical layer 4a of the dielectric lens 4 is longer than the distance La between the patch antenna 3 on the substrate surface and the surface of the dielectric lens 4. For this reason, due to attenuation caused by the propagation distance of radio waves, the multiple reflections of radio waves between the former, which is the longer distance Lb, are weaker than those between the latter, which is the shorter distance La.

[0024] As a result, it is possible to reduce ripples in the directional characteristic of microlens array antenna 1A in the array direction of patch antenna 3, which is the axial direction of dielectric lens 4, i.e., the y direction, caused by multiple reflections of radio waves between patch antenna 3 on the surface of the substrate and the surface of dielectric lens 4.

[0025] According to the microlens array antenna 1A of the present embodiment, the microlens antenna is composed of patch antennas 3 arranged in the y direction on the substrate 2 in close proximity to each other, and dielectric lenses 4 that are shaped like a column with an axial direction from the y direction in which the patch antennas 3 are arranged, are provided above each patch antenna 3, and have a dielectric constant distribution in which the dielectric constant ε decreases from the axis to the radial outer periphery, and at least two of these microlens antennas are arranged in the x direction perpendicular to the y direction in which the patch antennas 3 are arranged. Therefore, by arranging at least two of these microlens antennas, which can reduce ripples in the directivity characteristics in the y direction, which is the array direction of the patch antennas 3, in the x direction perpendicular to the y direction, as described above, the directivity of each microlens antenna in the x direction becomes sharp, and the antenna gain also increases synergistically. Therefore, it is possible to increase the antenna gain by narrowing the directivity in the x direction in which the dielectric lenses 4 are arranged perpendicular to the array direction, without increasing the diameter of the dielectric lens 4 to make it larger, as in the conventional case.

[0026] According to the microlens array antenna 1A of the present embodiment, the radio wave α radiated at a low elevation angle from one of the patch antennas 3 arranged in a row in the x direction below the adjacent dielectric lenses 4 and directed upward to the other adjacent patch antenna 3 as shown in FIG. 2 is incident on the dielectric lens 4 above the other patch antenna 3. At this time, the dielectric lens 4 has a dielectric constant distribution in which the dielectric constant ε decreases from the axis toward the outer periphery in the radial direction, and the dielectric constant ε of the second cylindrical layer 4c near the outer periphery of the dielectric lens 4 is small, so that the radio wave reflected on the lens surface of the dielectric lens 4 can be reduced. Moreover, the radio wave α incident on the dielectric lens 4 arranged above the other patch antenna 3 at a low elevation angle as shown in FIG. 2 has a narrowed directivity in the x direction as described above, and the radio wave reflected on the lens surface of the dielectric lens 4 is small, so that the influence of blocking caused by being reflected on the surface of the dielectric lens 4 and bounced back to the substrate 2 side as in the conventional case, or being blocked by an object such as a dielectric plate as in the conventional case, is reduced.

[0027] As a result, it is possible to reduce degradation of the side lobes of the microlens array antenna 1 A. Also, the energy of the radio wave α radiated from the patch antenna 3 at a low elevation angle is not wasted as in the conventional case.

[0028] Furthermore, according to the microlens array antenna 1A of this embodiment, the dielectric lens has a simple cylindrical shape, so that the dielectric lens 4 can be easily manufactured.

[0029] FIG. 3(a) is a perspective view of a microlens array antenna 1B according to a second embodiment of the present invention, and FIG. 4 is a front view.

[0030] Microlens array antenna 1B according to the second embodiment differs from microlens array antenna 1A according to the first embodiment in that metal blocks are provided as horns 5 on substrate 2 sandwiching each patch antenna 3 below both sides of each dielectric lens 4. Other features of microlens array antenna 1B according to the second embodiment are the same as those of microlens array antenna 1A according to the first embodiment. Also, Fig. 3(b) is a perspective view of each patch antenna 3 on substrate 2 seen through dielectric lens 4 and horn 5 shown in Fig. 3(a).

[0031] The horn 5 is erected on the substrate 2 along the lower sides of each dielectric lens 4, as shown in Figure 4, with surfaces 5a facing the lower sides of each dielectric lens 4, and with a cross-section in the shape of a mountain or semi-mountain.

[0032] Since the main function of dielectric lens 4 is to align only the phase of radio waves and it cannot control the aperture distribution of the antenna, it is necessary to control the aperture distribution by the directivity of patch antenna 3. According to microlens array antenna 1B of the second embodiment, metal horns 5 erected on substrate 2 sandwiching each patch antenna 3 below both sides of each dielectric lens 4 make it easy to control the directivity of radio waves radiated from patch antenna 3 in the y direction, which is the axial direction of dielectric lens 4.

[0033] Therefore, the horn 5 controls the aperture distribution of the patch antenna 3 by the directivity in the axial direction of the dielectric lens 4 of the radio waves radiated from the patch antenna 3, and weakens the electric field distribution in the axial center of the dielectric lens 4 adjacent to the dielectric lens 4 located above the patch antenna 3, thereby suppressing the radio waves α that are irradiated from the patch antenna 3 to the axial center of the adjacent dielectric lens 4 and bounce back to the substrate 2 side. As a result, the microlens array antenna 1B according to the second embodiment achieves the same effects as the microlens array antenna 1A according to the first embodiment, and further suppresses the side lobes of the microlens array antenna 1B.

[0034] A comparative simulation was performed to confirm the side lobe characteristics of the microlens array antenna 1B according to the second embodiment. Fig. 5(a) is a perspective view of a microlens array antenna 11 of a comparative example used in the comparative simulation. Unlike the dielectric lens 4, which is a Luneburg lens, the microlens array antenna 11 includes a dielectric lens 44 that has a uniform dielectric constant and is integrally formed by connecting dielectric bodies having a cylindrical shape similar to a semi-cylindrical shape in the x direction. Except for the dielectric lens 44, the microlens array antenna 11 of the comparative example has a similar configuration to the microlens array antenna 1B according to the second embodiment.

[0035] Fig. 5(b) is a perspective view of each patch antenna 3 on the substrate 2 seen through the dielectric lens 44 shown in Fig. 5(a). Like the microlens array antenna 1B according to the second embodiment, this microlens array antenna 11 also has an array structure in which four microlens antennas each consisting of two patch antennas 3 closely arranged in the y direction and a columnar portion of a dielectric lens 44 above them are arranged in two rows in the x direction perpendicular to the y direction in which the patch antennas 3 are arranged.

[0036] The comparative simulation was performed by simulating the directivity of each of the microlens array antennas 1B and 11 for one row 3a when four patch antennas 3 were arranged closely together in two rows like this. The graph shown in Fig. 6 is a graph showing the results of this comparative simulation.

[0037] The graph shown in Fig. 6(a) shows the directivity calculation results for microlens array antenna 1B according to the second embodiment using dielectric lens 4 which is a Luneburg lens, and the graph shown in Fig. 6(b) shows the directivity calculation results for microlens array antenna 11 of the comparative example using dielectric lens 44 with a uniform dielectric constant. In addition, characteristic line A connecting the plots of white circles ○ in each graph shows the directivity calculation result in the y direction which is the lens axial direction, and characteristic line B connecting the plots of black circles ● shows the directivity calculation result in the x direction which is the direction in which the columnar portions of dielectric lens 4 and dielectric lens 44 are aligned.

[0038] The horizontal axis of each graph, for characteristic line A, represents the angle θ [deg] at which the assumed measurement point of each plot is inclined in the y direction with respect to the z direction, which is the direction perpendicular to the substrate surface of the substrate 2, around the center of the y direction length of the dielectric lenses 4, 44. The horizontal axis of each graph, for characteristic line A, represents the angle θ [deg] at which the assumed measurement point of each plot is inclined in the x direction with respect to the z direction, which is the direction perpendicular to the substrate surface of the substrate 2, around the center of the x direction length of the dielectric lenses 4, 44. The vertical axis of each graph, for both characteristic lines A and B, represents the antenna gain GAIN [dB] at the assumed measurement point of each plot.

[0039] From these graphs, it can be seen that, in the graph shown in FIG. 6(b) showing the characteristics of the comparative example, the gain deviation in the angular direction increases due to multiple reflections between the surface of the dielectric lens 44 and the patch antenna 3 on the substrate 2, resulting in a bias in the directivity. In contrast, in the graph shown in FIG. 6(a) showing the characteristics of the microlens array antenna 1B of the second embodiment, it can be seen that the dielectric constant ε of the surface of the dielectric lens 4 is small, and multiple reflections between the surface of the dielectric lens 4 and the patch antenna 3 on the substrate 2 can be reduced, resulting in a small gain deviation in the angular direction and a small bias in the directivity. In addition, in the graph shown in FIG. 6(a) showing the characteristics of the second embodiment, ... side lobes in the ±50° direction of the directivity in the x direction, where the dielectric lenses 4 are lined up, can be reduced compared to those shown in FIG. 6(b) of the comparative example.

[0040] Therefore, from the above comparative simulation results, it was confirmed that the microlens array antenna 1B of the second embodiment has higher directional gain and suppressed side lobes compared to the microlens array antenna 11 of the comparative example.

[0041] FIG. 7 is a perspective view of a microlens array antenna 1C according to a third embodiment of the present invention, showing a patch antenna 3 on a substrate 2 seen through a dielectric lens 4. FIG.

[0042] The microlens array antenna 1C according to the third embodiment differs from the microlens array antenna 1A according to the first embodiment in that at least three patch antennas 3, four in this embodiment, are arranged on the substrate 2 at intervals of 0.5 wavelengths or close to that wavelength of the radio waves transmitted by the patch antennas 3 in the y direction which is the axial direction of the dielectric lens 4. All other points are the same as the microlens array antenna 1A according to the first embodiment.

[0043] In the conventional microlens array antenna disclosed in Patent Document 2, the patch antennas 3a are arranged in pairs closely below each spindle-shaped dielectric lens 4, and in the direction along line BB shown in Figure 3(c) of the document, the arrangement position of the patch antennas 3a is shifted from the focal point c. For this reason, when three or more patch antennas 3a are arranged closely, distortion occurs in the antenna directivity in the direction along line BB, and the antenna gain is reduced.

[0044] The microlens array antenna 1C according to the third embodiment is different from the conventional microlens array antenna in that the dielectric lens 4 has a columnar shape with its axis in the y direction, which is the array direction of the closely arranged patch antennas 3, and is provided over each patch antenna 3. In addition, since the dielectric constant of the surface of the dielectric lens 4 is small, reflection on the lens surface is small, and the arrangement position of the patch antenna 3 does not shift from the focal position of the dielectric lens 4 as in the conventional case. Therefore, it is possible to arrange three or more patch antennas 3 closely in an array in the y direction without causing directional distortion in the y direction of the microlens array antenna 1C or reducing the antenna gain. This makes it easy to arrange an antenna layout compatible with MIMO (Multi Input Multi Output) by arranging the patch antennas 3 in the x and y directions.

[0045] Fig. 8 is a perspective view of a microlens array antenna 1D according to a fourth embodiment of the present invention, showing a patch antenna 3 on a substrate 2 through a dielectric lens 4A. Fig. 9(a) is a front view of the microlens array antenna 1D.

[0046] The micro-lens array antenna 1D according to the fourth embodiment is different from the micro-lens array antenna 1A according to the first embodiment in that the dielectric lens 4A has an elliptical columnar cross-section with a thickness t in the z direction perpendicular to the substrate 2 being smaller than the width D in the x direction horizontal to the substrate 2 (t < D), as shown in FIG. 9(a). Other points are the same as those of the micro-lens array antenna 1A according to the first embodiment.

[0047] The elliptical columnar dielectric lens 4A is also set such that the relative dielectric constant ε of each layer decreases from the axis center toward the outer periphery in the radial direction. For example, as an example, similar to the columnar dielectric lens 4, the relative dielectric constant ε r 1 of the elliptical column layer 4a1 including the axis center of the dielectric lens 4A is 1.8, and the relative dielectric constant ε r 2 of the first elliptical cylinder layer 4b1 one outside the elliptical column layer 4a1 is 1.4, and the relative dielectric constant ε r 3 of the outermost second elliptical cylinder layer 4c1 one outside the first elliptical cylinder layer 4b1 is 1.2, and their magnitude relationship is ε r 1 > ε r 2 > ε r 3.

[0048] According to the micro-lens array antenna 1D according to the fourth embodiment, compared with the micro-lens array antenna 1A according to the first embodiment, without changing the distance Lb (see FIG. 9(a) and FIG. 2) between the elliptical column layer 4a1 at the axis center of the dielectric lens 4A with a large relative dielectric constant ε where radio waves are reflected and the patch antenna 3 on the surface of the substrate 2, the height Hb (see FIG. 9(a)) of the dielectric lens 4A from the surface of the substrate 2 can be made lower than the height Ha (see FIG. 2) of the dielectric lens 4 from the surface of the substrate 2. Thereby, the dimension in the z direction perpendicular to the surface of the substrate 2 of the micro-lens array antenna 1D can be reduced, and miniaturization (thinning) of the micro-lens array antenna 1D can be achieved.

[0049] On the one hand, in order to miniaturize (thin down) the microlens array antenna 1A, if the dielectric lens 4 is simply miniaturized to provide the microlens array antenna 12 with the dielectric lens 45 having a small diameter shown in Fig. 9(b), the distance Lc between the cylindrical layer 4a2 at the axial center of the dielectric lens 45, where the relative permittivity ε is large and the radio wave reflection is large, and the patch antenna 3 on the surface of the substrate 2 becomes smaller than the above distance Lb (Lc < Lb). Here, the relative permittivity ε of the cylindrical layer 4a2 at the axial center r 1. The relative permittivity ε of the first cylindrical layer 4b2 on the outside of the cylindrical layer 4a2 r 2. The relative permittivity ε of the outermost second cylindrical layer 4c2 on the outside of the first cylindrical layer 4b2 r 3. Their magnitude relationship is ε r 1 > ε r 2 > ε r 3 is set.

[0050] Therefore, due to the decrease in the distance Lc, the distance attenuation of the multiple reflected radio waves between the cylindrical layer 4a2 of the dielectric lens 45 and the patch antenna 3 on the surface of the substrate 2 becomes smaller. For this reason, the reflected waves between them strengthen or weaken each other, and distortion appears in the directivity of the microlens array antenna 12.

[0051] Fig. 10(a) is a perspective view of the dielectric lens 4B used in the microlens array antenna according to the fifth embodiment of the present invention.

[0052] The microlens array antenna according to the fifth embodiment is different from the microlens array antenna 1A according to the first embodiment in that the dielectric lens 4B is made of a material having a single relative permittivity ε, and a plurality of cylindrical holes 4d1, 4d2, 4d3 whose diameters increase from the axis toward the outer periphery in the radial direction are formed in the y direction, which is the axial direction of the material having a single relative permittivity ε, and the elliptical columnar shape having a flat cross-section with the thickness in the z direction perpendicular to the substrate 2 being smaller than the width in the x direction horizontal to the substrate 2. Other points are the same as those of the microlens array antenna 1A according to the first embodiment.

[0053] FIG. 10(b) is a perspective view of a dielectric lens 4C used in a microlens array antenna according to the sixth embodiment of the present invention.

[0054] The microlens array antenna according to the sixth embodiment differs from the microlens array antenna 1A according to the first embodiment in that a dielectric lens 4C is made of a material having a single dielectric constant ε, a plurality of slit-like gaps (grooves) 4e1, 4e2, 4e3, 4e4 whose radial width increases from the axis center toward the radial periphery are formed in the y direction which is the axial direction of the material having a single dielectric constant ε, and that the microlens array antenna according to the sixth embodiment has an elliptical cylindrical shape with a flattened cross section whose thickness in the z direction perpendicular to the substrate 2 is smaller than its width in the x direction parallel to the substrate 2. Other points are the same as those of the microlens array antenna 1A according to the first embodiment.

[0055] According to each of the microlens array antennas of the fifth and sixth embodiments, cylindrical holes 4d1, 4d2, 4d3 whose diameters increase from the axis center toward the radial periphery, or gaps 4e1, 4e2, 4e3, 4e4 whose radial widths increase from the axis center toward the radial periphery, are formed in the axial direction of a material having a single dielectric constant, thereby obtaining dielectric lenses 4B, 4C having a columnar shape with a dielectric constant distribution in which the dielectric constant ε decreases from the axis center toward the radial periphery. These cylindrical holes 4d1, 4d2, 4d3 and gaps 4e1, 4e2, 4e3, 4e4 are formed by drilling a material having a single dielectric constant ε in the axial direction.

[0056] Therefore, it is not necessary to form the columnar dielectric lenses 4, 4A by bonding different kinds of strip-shaped dielectrics with different dielectric constants ε so that the dielectric constant ε decreases from the axis center toward the radial periphery, and radio waves are not unintentionally reflected by gaps that occur at the bonding portion of the strip-shaped dielectrics. Moreover, it is possible to manufacture the columnar dielectric lenses 4B, 4C with the dielectric constant ε decreasing from the axis center toward the radial periphery by simply processing the same material without the need to prepare strip-shaped dielectric materials of different kinds or to bond these different strip-shaped dielectrics together. This allows the cost of the microlens array antenna to be reduced.

[0057] Furthermore, by forming the cylindrical dielectric lenses 4B, 4C into an elliptical cylindrical shape, the dimension of the microlens array antenna in the z direction perpendicular to the surface of the substrate 2 can be reduced, as in the microlens array antenna 1D of the fourth embodiment, and the microlens array antenna can be made smaller (thinner).

[0058] In the microlens array antennas according to the fifth and sixth embodiments, the dielectric lenses 4B, 4C are formed in an elliptical cylindrical shape, but they may be formed in a cylindrical shape as in the microlens array antenna 1A according to the first embodiment. In this case, the microlens array antenna cannot be made smaller (thinner), but the cost of the microlens array antenna can be reduced as in the microlens array antennas according to the fifth and sixth embodiments.

[0059] Furthermore, in each of the microlens array antennas 1C and 1D according to the third and fourth embodiments, and each of the microlens array antennas according to the fifth and sixth embodiments, similar to the microlens array antenna 1B according to the second embodiment, a horn 5 may be provided on the substrate 2 sandwiching each patch antenna 3, below both sides of each dielectric lens 4, 4A, 4B, 4C, along both sides of each dielectric lens 4, 4A, 4B, 4C, with surfaces 5a facing the lower both sides of each dielectric lens 4, 4A, 4B, 4C.

[0060] With this configuration, in each of the microlens array antennas 1C and 1D according to the third and fourth embodiments, and each of the microlens array antennas according to the fifth and sixth embodiments, further side lobe suppression is possible, similar to the microlens array antenna 1B according to the second embodiment.

[0061] In addition, in the above first, second and third embodiments, the shape of the dielectric lens 4 is described as being cylindrical, and in the fourth, fifth and sixth embodiments, the shape of the dielectric lenses 4A, 4B, 4C is described as being elliptical cylindrical, but the shape is not limited to these and may be any shape as long as it is cylindrical.

[0062] In the above first and second embodiments, an array structure in which two adjacent patch antennas 3 are arranged in two rows and four dielectric lenses 4 are arranged has been described, and in the third, fourth, fifth and sixth embodiments, an array structure in which four adjacent patch antennas 3 are arranged in four rows and four dielectric lenses 4, 4A, 4B and 4C are arranged has been described. However, the number of adjacent patch antennas 3, the number of rows in which the patch antennas 3 are arranged, and the number of dielectric lenses 4, 4A, 4B and 4C arranged are not limited to these and may be set to any value.

[0063] In addition, in each of the above embodiments, the planar antenna is described as a patch antenna. However, the planar antenna is not limited to a patch antenna, and may be, for example, a meander line antenna in which a conductor is bent into a crank shape, a slot antenna, or other planar antennas.

[0064] To summarise the above, the present invention can be expressed as follows.

[0065] <1> The microlens array antenna has an array structure in which at least two of the planar antennas are arranged in a row in a direction perpendicular to the direction in which the planar antennas are arranged, the microlens antennas being composed of dielectric lenses having a columnar shape with an axial direction in which the planar antennas are arranged, the dielectric lenses being provided above each of the planar antennas and having a dielectric constant distribution in which the dielectric constant decreases from the axis toward the outer periphery in the radial direction.

[0066] <2> At least three of the planar antennas are arranged on the substrate at intervals of 0.5 wavelengths or close to the wavelengths in the axial direction. <1> The microlens array antenna according to claim 1 .

[0067] <3> The dielectric lens is characterized in that it has a cylindrical shape. <1> or <2> The microlens array antenna according to claim 1 .

[0068] <4> The dielectric lens is characterized in that it has an elliptical cylindrical shape with a flat cross section in which the thickness in a direction perpendicular to the substrate is smaller than the width in a direction parallel to the substrate. <1> or <2> The microlens array antenna according to claim 1 .

[0069] <5> The dielectric lens is characterized in that a plurality of cylindrical holes whose diameter increases from the axis center toward the radial periphery, or a plurality of voids whose radial width increases from the axis center toward the radial periphery are formed in the axial direction of the material having a single dielectric constant. <1> or <2> The microlens array antenna according to claim 1 .

[0070] <6> The present invention is characterized in that a metal block is provided on the substrate sandwiching the planar antennas below both sides of each of the dielectric lenses, along both sides of each of the dielectric lenses, with the metal block being erected with the surfaces facing the lower both sides of each of the dielectric lenses. <1> from <5> 13. The microlens array antenna according to claim 12, [Explanation of symbols]

[0071] 1A, 1B, 1C, 1D...Microlens array antenna 2...Substrate 3...Patch antenna (flat antenna) 3a…row of patch antenna 3 4, 4A, 4B, 4C...Dielectric lenses 4d1, 4d2, 4d3...Cylindrical hole 4e1,4e2,4e3,4e4...Void 5…Horn (metal block)

Claims

1. The microlens array antenna has an array structure in which at least two of the planar antennas are arranged in a row in a direction perpendicular to the direction in which the planar antennas are arranged, the microlens antennas being composed of dielectric lenses having a columnar shape with an axial direction in which the planar antennas are arranged, the dielectric lenses being provided above each of the planar antennas and having a dielectric constant distribution in which the dielectric constant decreases from the axis toward the outer periphery in the radial direction.

2. 2. The microlens array antenna according to claim 1, wherein at least three of the planar antennas are arranged on the substrate at intervals of 0.5 wavelengths or wavelengths close thereto in the axial direction.

3. 3. The microlens array antenna according to claim 1, wherein the dielectric lens has a cylindrical shape.

4. 3. The microlens array antenna according to claim 1, wherein the dielectric lens has an elliptical cylindrical shape with a flattened cross section whose thickness in a direction perpendicular to the substrate is smaller than its width in a direction horizontal to the substrate.

5. The microlens array antenna according to claim 1 or claim 2, characterized in that the dielectric lens is formed in the axial direction of a material having a single dielectric constant, with a plurality of cylindrical holes whose diameter increases from the axis center to the radial outer periphery, or a plurality of voids whose radial width increases from the axis center to the radial outer periphery.

6. The microlens array antenna as described in claim 1 or claim 2, characterized in that a metal block is provided on the substrate sandwiching each of the planar antennas below both sides of each of the dielectric lenses, the metal block being erected along both sides of each of the dielectric lenses with its surfaces facing the lower both sides of each of the dielectric lenses.

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