Microlens array antenna

Abstract

Provided is a microlens array antenna that makes it possible to increase antenna efficiency and does not cause deterioration in side lobe characteristic. A microlens array antenna 1A is provided with a planar array antenna 3 formed on a substrate 2, and a multifocal dielectric lens 4 provided above the planar array antenna. In the planar array antenna 3, patch antennas 3a each constituting a planar antenna are formed at approximately equal intervals of one wavelength or longer in a first direction x on the surface of the substrate 2. The multifocal dielectric lens 4 is provided above the planar array antenna 3, and a plurality of dielectric lenses 4a respectively focused on the patch antennas 3a are integrally formed. The multifocal dielectric lens 4 has, between the adjacent dielectric lenses 4a, an overlap portion 4b in which the respective opening diameters Dn of the dielectric lenses 4a overlap each other in the first direction x.

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.

Background Art

[0002] Conventionally, as an array antenna of this type, for example, there is one disclosed in Non-Patent Document 1. As shown in Fig. 2 of this document, this array antenna is formed by arranging horn antennas above a microstrip antenna in an array, and a dielectric lens is attached to the opening of each horn antenna.

[0003] Also conventionally, as an array antenna of this type, for example, there is one disclosed in Patent Document 1. As shown in FIG. 1 of this document, this array antenna is composed of a planar array antenna 3 formed on a substrate and a plurality of dielectric lenses 4a, 4b1, 4b2, 4c1, 4c2 provided above it. The area of the opening surface parallel to the surface of the substrate of each dielectric lens 4a, 4b1, 4b2, 4c1, 4c2 becomes smaller from the dielectric lens 4a located above the planar antenna 3a at the center of the array toward the dielectric lenses 4c1, 4c2 located above the planar antennas 3c1, 3c2 at both ends of the array.

[0004] Also conventionally, as an array antenna of this type, for example, there is one disclosed in Patent Document 2. As shown in FIG. 1 of this document, this array antenna is configured as a lens array 100 which is an antenna system including a plurality of lens sets 110. Each lens set 110 includes a lens 112 and at least one feed element 152. At least one feed element 152 is aligned with the lens 112 and is configured to guide a signal in a desired direction through the lens 112.

Prior Art Documents

Non-Patent Documents

[0005] [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) [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2021 / 241125 [Patent Document 2] Japanese Patent Publication No. 2018-157541 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in the conventional array antenna disclosed in Non-Patent Literature 1, radio waves radiated by the antenna leak through the gap between the outer edge of the dielectric lens and the inner edge of the aperture end of the horn. This leakage of radio waves acts as a wave source, affecting adjacent antennas and degrading the antenna's sidelobe characteristics. Furthermore, in the conventional array antenna disclosed in Non-Patent Literature 1, if the horn height H is reduced relative to the aperture diameter D in order to align the phase on the aperture surface, the thickness of the dielectric lens increases, degrading the aperture efficiency of the antenna. Also, if the number of sets n of horns, dielectric lenses, and microstrip antennas is increased to reduce the thickness of the dielectric lens, the feed loss increases. For this reason, there is a limit to how low the horn height H can be reduced relative to the aperture diameter D in order to align the phase on the aperture surface.

[0008] Furthermore, in the conventional array antenna disclosed in Patent Document 1, radio waves incident from the diagonal front of the array antenna are blocked by the dielectric lens 4a located in the center of the array, which is higher than the substrate, making it difficult for them to enter the dielectric lenses 4b1 and 4b2 located on either side of it, which are one level lower than the substrate. As a result, it becomes difficult to align the phase of the radio waves passing through the dielectric lens 4a located in the center of the array with the radio waves passing through the dielectric lenses 4b1 and 4b2 located on either side of it, which degrades the overall aperture efficiency of the array antenna and also degrades the sidelobe characteristics.

[0009] Furthermore, in the conventional array antenna disclosed in Patent Document 2, it is conceivable that radio waves passing through one lens 112 may leak into the other lens 112. As a result, the lens sets 110 interfere with each other, causing deterioration of aperture efficiency and side lobe characteristics. [Means for solving the problem]

[0010] This invention was made to solve these problems. At approximately equal intervals of one wavelength or more in the radio waves being transmitted and received , transmits and receives radio waves with a single element A planar array antenna is formed on a substrate in an array shape in a first direction, A multifocal dielectric lens is provided above a planar array antenna, and is formed by integrating multiple dielectric lenses, each having a focal point for one of the planar antennas, and having an overlapping portion where the aperture diameters of each dielectric lens overlap in a first direction. A microlens array antenna was constructed that included the following features:

[0011] In this configuration, the aperture surfaces of adjacent dielectric lenses are connected in the overlapping portion where the aperture diameters overlap in the first direction, improving aperture efficiency and forming a region with a uniform dielectric constant between adjacent dielectric lenses via the overlapping portion. Therefore, among the radio waves radiated from each planar antenna, those radiated at a low elevation angle and directed toward the overlapping portion do not refract in the space between dielectric lenses, as would occur if there were no such overlapping portion between the dielectric lenses and independent dielectric lenses were arranged in an array with space in between. Instead, they pass through the overlapping portion into the adjacent dielectric lens and into the adjacent dielectric lens. As a result, it becomes possible to design lenses with a shape that does not produce large phase errors between radio waves passing through the dielectric lens directly above the planar antenna and radio waves passing through the overlapping portion into the adjacent dielectric lens, making it possible to align the phases of each radio wave on the aperture surface.

[0012] Therefore, as a whole, the radio waves emitted from each planar antenna are radiated from the microlens array antenna with less loss between dielectric lenses due to blocking by adjacent dielectric lenses, as in conventional designs, making it possible to increase the antenna efficiency of the microlens array antenna.

[0013] Furthermore, unlike conventional array antennas, sidelobe characteristics are not degraded by interference caused by radio waves leaking between adjacent antennas becoming wave sources, or by the blocking of radio waves incident at an oblique angle, which prevents the phase of radio waves passing through each dielectric lens from being aligned.

[0014] Furthermore, the present invention is At approximately equal intervals of one wavelength or more in the radio waves being transmitted and received , transmits and receives radio waves with a single element A planar array antenna is formed on a substrate in an array shape in one direction, A Luneberg lens integrated dielectric lens is formed by integrating multiple Luneberg lenses, each with an effective dielectric constant decreasing from the center toward the outer space, in one direction above each planar antenna, and having an overlapping portion where adjacent ends with low effective dielectric constants of each Luneberg lens overlap in one direction. A microlens array antenna was constructed that included the following features:

[0015] In this configuration, adjacent Luneberg lenses are connected by an overlapping region with a low effective dielectric constant, and a region with a low and uniform dielectric constant is formed between adjacent Luneberg lenses across the overlapping region. Therefore, among the radio waves radiated from each planar antenna, those radiated at low elevation angles pass through the overlapping region with low dielectric constant with minimal reflection and are incident on the adjacent Luneberg lens, passing through the adjacent Luneberg lens. As a result, it becomes possible to design lenses with a shape that does not produce large phase errors between the radio waves passing through the Luneberg lens directly above the planar antenna and the radio waves passing through the overlapping region and the adjacent Luneberg lens, making it possible to align the phases of each radio wave on the aperture surface.

[0016] Therefore, as a whole, the radio waves emitted from each planar antenna are radiated from the microlens array antenna with less loss between dielectric lenses due to blocking by adjacent dielectric lenses, as in conventional designs, making it possible to increase the antenna efficiency of the microlens array antenna.

[0017] Furthermore, unlike conventional array antennas, sidelobe characteristics are not degraded by interference caused by leaking radio waves between adjacent antennas, or by the blocking of radio waves incident at an oblique angle, which prevents the phase of radio waves passing through each Luneberg lens from being aligned. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a microlens array antenna that can increase antenna efficiency and does not deteriorate side lobe characteristics.

Brief Description of the Drawings

[0019] [Figure 1] (a) is a side view of a microlens array antenna according to the first embodiment of the present invention, and (b) is a side view of a conventional microlens array antenna. [Figure 2] (a) and (b) are a plan view and a side view of a conventional microlens array antenna, and (c) and (d) are a plan view and a side view of the microlens array antenna of the first embodiment. [Figure 3] It is a graph showing the comparison results of each characteristic by simulation between the conventional microlens array antenna shown in FIGS. 2(a) and (b) and the microlens array antenna of the first embodiment shown in FIGS. 2(c) and (d). [Figure 4] (a) is a partial side view of a microlens array antenna according to the second embodiment of the present invention, and (b) is a diagram schematically showing the situation of each radio wave in the overlapping portion shown in (a) in an enlarged manner. [Figure 5] It is a cross-sectional view of a microlens array antenna according to the third embodiment of the present invention. [Figure 6] It is a plan view of a microlens array antenna according to the fourth embodiment of the present invention. [Figure 7] (a) is a plan view of a microlens array antenna according to the fifth embodiment of the present invention, (b) is a side view, and (c) is a front view. <00001​​​​​​​​Next, embodiments for implementing the microlens array antenna of the present invention will be described.

[0021] Figure 1(a) is a side view of a microlens array antenna 1A according to a first embodiment of the present invention.

[0022] The microlens array antenna 1A comprises a planar array antenna 3 formed on a substrate 2 and a multifocal dielectric lens 4 provided above it. The planar array antenna 3 is formed on the surface of the substrate 2 at approximately equal intervals in a first direction x, with each patch antenna 3a constituting the planar antenna being formed. In this embodiment, each patch antenna 3a is formed at approximately equal intervals of one wavelength or more of the radio waves transmitted and received by the microlens array antenna 1A. Preferably, each patch antenna 3a is set at approximately equal intervals of one to two wavelengths of the radio waves to be transmitted and received, and is formed in an area of ​​0.5 wavelengths square. This is because each dielectric lens 4a constituting the multifocal dielectric lens 4 collects radio wave energy in an area of ​​at least one wavelength square. A ground pattern 5 is formed on the back surface of the substrate 2 to provide a reference potential to each patch antenna 3a.

[0023] The multifocal dielectric lens 4 is positioned above the planar array antenna 3 and is formed by integrating multiple dielectric lenses 4a, each having a focal point for each patch antenna 3a, and having an elliptical shape in plan view. Here, "above" refers to the direction z in which each patch antenna 3a radiates radio waves. The multifocal dielectric lens 4 has overlapping portions 4b between adjacent dielectric lenses 4a, where the aperture diameters Dn of each dielectric lens 4a overlap in the first direction x. The focal point formed for each patch antenna 3a is determined by describing each wave by expanding the wave number of the radio waves radiated from each patch antenna 3a, which is the primary wave source. The focal point is set so that each wave is in phase in front of the lens when it is irradiated by the dielectric lens 4a, refracted, and transmitted through the front surface of the lens. In this case, the focal point is calculated from the lens surface (including the focal position) and the dielectric constant of the lens.

[0024] In this embodiment, each dielectric lens 4a has a spindle-shaped bulge on the side opposite the patch antenna 3a and is provided for the purpose of focusing the radio waves radiated from the patch antenna 3a. In order to shorten the focal length and control the radio waves radiated at a low elevation angle, the lens shape on the side opposite the patch antenna 3a bulges out to become convex. The multifocal dielectric lens 4, which is formed by integrating each dielectric lens 4a into one, has multiple focal points at each focal point of each dielectric lens 4a. The directivity of the microlens array antenna 1A is controlled by combining the power of the radio waves transmitted and received by each patch antenna 3a.

[0025] In this embodiment of the microlens array antenna 1A, the aperture surfaces of adjacent dielectric lenses 4a are connected in the overlapping portion 4b where the aperture diameters Dn overlap in the first direction x, improving aperture efficiency and forming a region with a uniform dielectric constant between adjacent dielectric lenses 4a via the overlapping portion 4b. Therefore, among the radio waves radiated from each patch antenna 3a, those radiated at a low elevation angle toward the overlapping portion 4b do not refract in the space between the dielectric lenses 4a, as in the case of the conventional microlens array antenna 6 shown in Figure 1(b), but instead pass through the overlapping portion 4b to the adjacent dielectric lens 4a and into the adjacent dielectric lens 4a.

[0026] In the conventional microlens array antenna 6 shown in Figure 1(b), there is no such overlapping portion 4b between the dielectric lenses 4a; instead, independent, individual dielectric lenses 4a are arranged in an array with space in between. Note that in Figure 1(b), parts identical or corresponding to those in Figure 1(a) are denoted by the same reference numerals, and their descriptions are omitted.

[0027] Therefore, with the microlens array antenna 1A according to this embodiment, it becomes possible to design a lens shape that does not produce a large phase error between the radio wave α1 shown by the solid line in Figure 1(a), which passes through the dielectric lens 4a directly above the patch antenna 3a, and the radio wave α2 shown by the dotted line in Figure 1(a), which passes through the adjacent dielectric lens 4a via the overlap portion 4b, making it possible to align the phases of each radio wave α1 and α2 on the aperture surface.

[0028] Therefore, overall, the radio waves emitted from each patch antenna 3a are radiated from the microlens array antenna 1A with less loss between dielectric lenses due to blocking by adjacent dielectric lenses, as in conventional designs, making it possible to increase the antenna efficiency of the microlens array antenna 1A.

[0029] Furthermore, unlike conventional array antennas, sidelobe characteristics are not degraded by interference caused by radio waves leaking between adjacent antennas becoming wave sources, or by the blocking of radio waves incident at an oblique angle, which prevents the phase of radio waves passing through each dielectric lens from being aligned.

[0030] Figure 2 shows the microlens array antenna 1A of this embodiment and a conventional microlens array antenna 6, which were used to confirm the effects of this embodiment. Figures (a) and (b) are a plan view and a side view of the conventional microlens array antenna 6, and Figures (c) and (d) are a plan view and a side view of the microlens array antenna 1A of this embodiment. In Figure 2, the same reference numerals are used for parts that are the same as or corresponding to those in Figure 1, and their descriptions are omitted.

[0031] The conventional microlens array antenna 6 shown in Figures (a) and (b) consists of independent, individual dielectric lenses 4a arranged in an array across space, as shown in Figure 1(b). The microlens array antenna 1A of this embodiment, shown in Figures (c) and (d), consists of multiple dielectric lenses 4a integrated to form a single multifocal dielectric lens 4, as shown in Figure 1(a). The multifocal dielectric lens 4 is formed by integrating the aperture diameters Dn (n=4,3,2,1) of individual dielectric lenses 4a in the array direction, overlapping with the aperture diameter Dn-1 of adjacent dielectric lenses 4a. Furthermore, the array length L is set to be the same for both the microlens array antenna 1A of this embodiment and the conventional microlens array antenna 6.

[0032] Figure 3 is a graph showing the results of a simulation comparison of the characteristics of the microlens array antenna 1A of this embodiment shown in Figure 2 and a conventional microlens array antenna 6. Figure 3(a) is a graph showing the overall directivity of each microlens array antenna 1A and 6. Figure 3(b) is a graph showing the difference in directivity gain of each microlens array antenna 1A and 6, and is a magnified view of the area around the maximum gain of the main lobe in the graph shown in Figure 3(a). The vertical axis of each graph represents the antenna gain [dBi], and the horizontal axis represents the antenna directivity angle [deg]. Furthermore, the solid line characteristic A represents the characteristics of the microlens array antenna 1A of this embodiment, and the dotted line characteristic B represents the characteristics of the conventional microlens array antenna 6.

[0033] From the graph shown in Figure (a), it can be seen that the gain difference between the main lobe and the first sub-lobe is 14.5 (=17.5-3) [dBi] for the microlens array antenna 1A of this embodiment, and 13 (=17-4) [dBi] for the conventional microlens array antenna 6. From this, it can be understood that the microlens array antenna 1A of this embodiment has smaller side lobes compared to the conventional microlens array antenna 6, and the side lobe characteristics are improved by 1.5 (=14.5-13) [dBi].

[0034] Furthermore, from the graph shown in Figure (b), it can be seen that the maximum gain of the main lobe in the microlens array antenna 1A of this embodiment is 17.1 [dBi], while the maximum gain of the main lobe in the conventional microlens array antenna 6 is 16.7 [dBi], and the difference in directional gain is 0.4 (=17.1-16.7) [dBi]. From this, it can be understood that the microlens array antenna 1A of this embodiment has a higher main lobe gain compared to the conventional microlens array antenna 6, and the directional gain of the main lobe is improved by 0.4 [dBi].

[0035] From the above simulation results, it can be confirmed that the microlens array antenna 1A according to this embodiment has the effect of reducing the loss of radio wave energy due to blocking when radiated from the patch antenna 3a at a low elevation angle and irradiated onto the adjacent dielectric lens 4a, thereby increasing antenna efficiency, and without degrading the sidelobe characteristics.

[0036] Figure 4(a) is a side view of a part of a microlens array antenna 1B according to a second embodiment of the present invention. In this figure, parts that are the same as or corresponding to those in Figure 1 are denoted by the same reference numerals and their descriptions are omitted.

[0037] In the second embodiment, the microlens array antenna 1B has a thickness d in the direction perpendicular to the substrate 2 of the overlap portion 4b of the multifocal dielectric lens 4, as shown in (1) below.

number

[0038] According to the microlens array antenna 1B of the second embodiment, when each dielectric lens 4a constituting the multifocal dielectric lens 4 is a short-focus lens, the thickness d of the overlap portion 4b in the direction perpendicular to the substrate 2 is set to the above range, so that radio waves in the overlap portion 4b where the incident angle θ to the dielectric lens 4a is in the range of greater than 60° and less than 75° (60° < θ < 75°) can be phase-aligned on the aperture surface of the multifocal dielectric lens 4. By phase-aligning radio waves in this angular range on the aperture surface, the directivity of the patch antenna 3a can be increased and the sidelobe characteristics can be improved.

[0039] The radio wave α3, shown as a thin solid line in the diagram, radiated from the patch antenna 3a at a low elevation angle, is partially reflected towards the substrate 2 at the point where it exits from the upper end of the diagonally upward overlap portion 4b into the space on the opposite side of the substrate 2, as indicated by the dotted arrow in the diagram. Subsequently, a portion of this reflected wave becomes a reflected wave α4, which bounces back to the opposite side of the substrate 2 at the substrate 2-side surface of the adjacent dielectric lens 4a. The phase of this reflected wave α4 and the phase of the radio wave α3 exiting from the upper end of the overlap portion 4b into the space on the opposite side of the substrate 2 are adjusted so that the propagation lengths of each radio wave α3 and α4 within the overlap portion 4b are approximately in phase on the aperture surface, by setting the thickness d of the overlap portion 4b to the above range. This adjustment of propagation length is performed by setting the propagation lengths of each radio wave α3 and α4 within the overlap portion 4b to be equal, as follows. For the sake of simplicity in explaining the fundamental principles, the propagation length x3 passing through the dielectric of the dielectric lens 4a (see Figure 4(b)) will not be considered here, assuming that the dielectric constant of the lens is low.

[0040] Figure 4(b) is a schematic, enlarged view illustrating the situation of radio waves α3 and α4 in the overlap portion 4b. Radio wave α3 radiated from the patch antenna 3a is incident on the overlap portion 4b at the incident angle θ shown in the figure, passes through the overlap portion 4b, and exits into space from its upper end. At the point where it exits into space, a portion is reflected, and the reflected wave α4, which bounces off the surface of the adjacent dielectric lens 4a, travels back and forth within the overlap portion 4b as shown in the figure. The propagation lengths x1 and x2 of each radio wave α3 and α4 within the overlap portion 4b at this time are expressed by equations (2) and (3) below, respectively.

number

[0041] In order to align the phases of each radio wave α3 and α4 on the aperture surface of the multifocal dielectric lens 4, a propagation length λ0 of one wavelength is added to the propagation length x1 of radio wave α3 in the overlap portion 4b, thereby delaying radio wave α3 by one wavelength. This makes the propagation length of radio wave α3 in the overlap portion 4b equal to the propagation length x2 of radio wave α4 in the overlap portion 4b. This condition for each radio wave α3 and α4 to be in phase is expressed by the following equation (4).

number

[0042] By moving the propagation length x1 in the left side of equation (4) to the right side, we obtain equation (5), and solving equation (5) for thickness d yields equation (6).

number

[0043] When the angle of incidence θ is 60°, cosθ is 1 / 2, and when the angle of incidence θ is 75°, cosθ is approximately 1 / 4. Therefore, from equation (6), the thickness d when the angle of incidence θ is 60° is given by equation (7), and the thickness d when the angle of incidence θ is 75° is given by equation (8).

number

[0044] Therefore, if the thickness d of the overlap portion 4b is greater than the thickness d shown in equation (8) when the incident angle θ is 75°, and less than the thickness d shown in equation (7) when the incident angle θ is 60°, that is, if the thickness d is within the range of the inequality shown in (1), the directivity of the patch antenna 3a can be increased and the phases of each radio wave α3 and α4 can be aligned on the aperture surface of the multifocal dielectric lens 4 without degrading the sidelobe characteristics.

[0045] Furthermore, the radio wave α5, shown as a thick solid line in Figure 4(a), which passes through the adjacent dielectric lens 4a without being reflected at the upper end of the overlap portion 4b, can be aligned in phase with the radio wave α1 shown in Figure 1, which passes through the dielectric lens 4a directly above the patch antenna 3a, by designing the lens to have a shape that does not produce a large phase error, as explained in the first embodiment. This makes it possible to align the phases of each radio wave α1 and α5 on the aperture surface of the multifocal dielectric lens 4.

[0046] Therefore, the phase of the reflected wave α4, which is partially reflected at the upper edge of the overlap portion 4b where it exits to the space on the opposite side of the substrate 2 and bounced back to the opposite side of the substrate 2 at the substrate 2 side surface of the adjacent dielectric lens 4a, and the phase of the radio wave α3 that exits from the upper edge of the overlap portion 4b to the space on the opposite side of the substrate 2 are in opposite phase, thus preventing power loss of the radio wave. As a result, the antenna efficiency of the multifocal dielectric lens 4 as a whole can be improved.

[0047] Figure 5 is a cross-sectional view of a microlens array antenna 1C according to a third embodiment of the present invention. In this figure, parts that are the same as or corresponding to those in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0048] The micro-lens array antenna 1C according to the third embodiment is different from the micro-lens array antenna 1B according to the second embodiment in that a support block 4c is integrally formed as a support substrate on the outer edge of the multi-focus dielectric lens 4. Other points are the same as those of the micro-lens array antenna 1B according to the second embodiment.

[0049] The support block 4c fixes the distance between the multi-focus dielectric lens 4 and the substrate 2 to the focal length of each dielectric lens 4a. This support block 4c has a thickness d2 in the first direction, that is, in the direction parallel to the substrate 2, and the overlapping portion 4b has a thickness d in the second direction, that is, in the direction perpendicular to the substrate 2. The thickness d2 of the support block 4c is thinner than the thickness d of the overlapping portion 4b. Also, the support block 4c is formed of the same dielectric material as the multi-focus dielectric lens 4.

[0050] According to the micro-lens array antenna 1C according to the third embodiment, the distance between the multi-focus dielectric lens 4 and the substrate 2 is fixed to the focal length of each dielectric lens 4a by the support block 4c integrally formed on the multi-focus dielectric lens 4, so the optical characteristics of the multi-focus dielectric lens 4 are stabilized.

[0051] Also, the support block 4c has a thickness d2 (d2 < d) thinner than the thickness d of the overlapping portion 4b, that is, less than or equal to 1 / 4 of the wavelength in the dielectric lens 4a of the radio wave to be transmitted and received (see equation (1)), and is integrally formed on the outer edge of the multi-focus dielectric lens 4 from the same material as the multi-focus dielectric lens 4. Therefore, the influence on the micro-lens array antenna 1C from the reflected wave of the radio wave in the support block 4c is reduced.

[0052] This is because the first reflected wave α6, shown as a solid line in the figure, is formed when radio waves emitted from the patch antenna 3a at a low elevation angle are reflected off one side of the support block 4c on the patch antenna 3a side, and the second reflected wave α7, shown as a dotted line in the figure, is formed when radio waves emitted from the patch antenna 3a at a low elevation angle propagate through the support block 4c and are reflected off the other side of the support block 4c opposite to the first side, appearing on the side with a predetermined phase difference. In other words, the phase difference causes the first reflected wave α6 and the second reflected wave α7 to be out of phase, weakening the intensity of their combined wave incident on each dielectric lens 4a. As a result, the overall characteristics of the microlens array antenna 1C are less likely to deteriorate, and the distance between the multifocal dielectric lens 4 and the substrate 2 can be fixed to the focal length of each dielectric lens 4a by the support block 4c.

[0053] Figure 6 is a plan view of microlens array antennas 1A', 1B', and 1C' according to a fourth embodiment of the present invention. In this figure, parts that are the same as or corresponding to those in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0054] The microlens array antennas 1A', 1B', and 1C' according to the fourth embodiment are characterized by the feeding method to each patch antenna 3a1, 3a2, 3a3, and 3a4 that constitute the planar array antenna 3 in each of the above microlens array antennas 1A, 1B, and 1C.

[0055] In other words, in the microlens array antennas 1A', 1B', 1C' according to the fourth embodiment, power is supplied to each patch antenna 3a1, 3a2, 3a3, 3a4 via a feed line 7 supplied from feed position 7a. The feed position 7b on the feed line 7 for each patch antenna 3a1, 3a2, 3a3, 3a4 is set to be outside the space between adjacent patch antennas 3a2, 3a3, and inside the space between adjacent pairs of patch antennas 3a1, 3a2 and patch antennas 3a3, 3a4. That is, the feed positions 7b of adjacent elements are set to be opposite in the array direction. As a result, adjacent patch antennas 3a2, 3a3, 3a1, 3a2, and 3a3, 3a4 are excited in approximately opposite phases. Each microlens array antenna 1A', 1B', and 1C' is the same as the microlens array antennas 1A, 1B, and 1C according to the above embodiments, except for this point.

[0056] According to the microlens array antennas 1A', 1B', 1C' of the fourth embodiment, for adjacent patch antennas 3a2, 3a3, 3a1, 3a2, and 3a3, 3a4, the feeding direction of the feeding line 7 to each patch antenna 3a1, 3a2, 3a3, 3a4 is in a direction facing each other for patch antennas 3a2, 3a3 where the feeding position 7b is set on the outside between them, and in a direction moving away from each other for patch antennas 3a1, 3a2 and 3a3, 3a4 where the feeding position 7b is set on the inside between them.

[0057] Therefore, regardless of whether the feed position 7b on the feed line 7 is set outside the space between the patch antennas 3a2 and 3a3, or inside the space between the patch antennas 3a1, 3a2 and 3a3, 3a4, adjacent patch antennas 3a2, 3a3, 3a1, 3a2, and 3a3, 3a4 are fed with currents that are approximately 180° out of phase. As a result, each patch antenna is fed with a current in opposite phase, and the magnetic field effect of each feed current on the radio waves entering and leaving the patch antennas 3a1, 3a2, 3a3, and 3a4 is canceled out. This makes it possible to suppress the side lobes caused by the feed current in the directivity of the microlens array antennas 1A', 1B', and 1C' in the feed direction.

[0058] Figure 7(a) is a plan view of a microlens array antenna 1D according to the fifth embodiment of the present invention, Figure 7(b) is a side view, and Figure 7(c) is a front view. In these figures, parts that are the same as or correspond to those in Figures 1 and 6 are denoted by the same reference numerals, and their descriptions are omitted. The x-direction is defined as the first direction, and the y-direction is defined as the second direction perpendicular to the first direction.

[0059] In the fifth embodiment, the microlens array antenna 1D is configured by arranging multiple planar antenna rows 3b of patch antennas 3a, which are formed in an array in the x-direction, in the y-direction to form a planar array antenna 3. The intervals between each planar antenna row 3b in the y-direction are set to approximately equal intervals of half wavelengths of the radio waves transmitted and received by the microlens array antenna 1D. Furthermore, in the microlens array antenna 1D, multiple dielectric lens rows 4d of dielectric lenses 4a, whose aperture diameters overlap and are integrated in the x-direction, are arranged in the y-direction, and the aperture diameters of each dielectric lens 4a overlap and are integrated in the y-direction to form a multifocal dielectric lens 4. Each dielectric lens 4a constituting the dielectric lens row 4d has a focal point on each patch antenna 3a of each planar antenna row 3b above each planar antenna row 3b which is arranged in multiple locations in the y-direction.

[0060] According to the fifth embodiment of the microlens array antenna 1D, a beam with a slightly sharp directionality in the x-direction and a wide angle of directivity in the y-direction can be emitted from the microlens array antenna 1D. This makes it possible to perform beamforming at a wide angle in the y-direction and to arrange the antennas in an array configuration for MIMO (Multiple Input Multiple Output) operation, where the transmitting and receiving antennas are arranged in a matrix in the x and y directions.

[0061] Figure 8(a) is a cross-sectional view of a microlens array antenna 1E according to a sixth embodiment of the present invention. In this figure, parts that are the same as or corresponding to those in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0062] The microlens array antenna 1E according to the sixth embodiment comprises a planar array antenna 3, a Luneberg lens integrated dielectric lens 8, and a metal block 10.

[0063] The integrated Luneberg lens dielectric lens 8 is formed by integrating multiple Luneberg lenses 8a, each with an effective dielectric constant decreasing from the center outward, in one direction above each patch antenna 3a. In this embodiment, each Luneberg lens 8a is spherical, and its effective dielectric constant ε is 1.8 at the center, 1.5 around it, and 1.3 at the outer edge, decreasing from the center outward. The integrated Luneberg lens dielectric lens 8 has an overlapping portion 8b where the adjacent ends of each Luneberg lens 8a, where the effective dielectric constant ε is smallest at 1.3, overlap in one direction.

[0064] The metal block 10 has a concave shape and is installed on the substrate 2, surrounding each patch antenna 3a located below each Luneberg lens 8a.

[0065] According to the microlens array antenna 1E of the sixth embodiment, adjacent Luneberg lenses 8a are connected by an overlapping portion 8b with a small effective dielectric constant ε, and a region with a small and uniform dielectric constant is formed between adjacent Luneberg lenses 8a via the overlapping portion 8b. Therefore, among the radio waves radiated from each patch antenna 3a, radio waves radiated at a low elevation angle pass through the overlapping portion 8b with little reflection and are incident on the adjacent Luneberg lens 8a, and pass through the adjacent Luneberg lens 8a. As a result, it becomes possible to design a lens shape that does not produce a large phase error between the radio wave α8, shown by the solid arrow in the figure, which passes through the Luneberg lens 8a directly above the patch antenna 3a, and the radio wave α9, shown by the dotted arrow in the figure, which passes through the adjacent Luneberg lens 8a via the overlapping portion 8b, and it becomes possible to align the phases of each radio wave α8 and α9 on the aperture surface of the microlens array antenna 1E.

[0066] Therefore, overall, the radio waves emitted from each patch antenna 3a are radiated from the microlens array antenna 1E with less loss between dielectric lenses due to blocking by adjacent dielectric lenses, as in conventional designs, making it possible to increase the antenna efficiency of the microlens array antenna 1E.

[0067] Furthermore, unlike conventional array antennas, sidelobe characteristics are not degraded by interference between adjacent antennas caused by leaking radio waves between them, or by the blocking of radio waves incident at an oblique angle, which prevents the phase of radio waves passing through each Luneberg lens 8a from being aligned.

[0068] Furthermore, because the focal point of the Luneberg lens 8a is located near its outer edge, radio waves passing through the Luneberg lens 8a and heading towards the patch antenna 3a directly below it spread out toward the patch antenna 3a directly below it. Therefore, radio waves passing through the Luneberg lens 8a and heading towards the patch antenna 3a directly below it may also affect the adjacent patch antenna 3a positioned opposite the adjacent Luneberg lens 8a. However, according to the microlens array antenna 1E of the sixth embodiment, radio waves passing through the Luneberg lens 8a and spreading toward the patch antenna 3a directly below it are prevented from entering the adjacent patch antenna 3a by the metal block 10 provided between each patch antenna 3a. Therefore, the metal block 10 isolates adjacent patch antennas 3a, preventing deterioration of the sidelobe characteristics.

[0069] Figure 8(b) is a cross-sectional view of a microlens array antenna 1E' according to a modified example of the sixth embodiment. In this figure, parts that are the same as or corresponding to those in Figure 8(a) are denoted by the same reference numerals, and their descriptions are omitted.

[0070] In the above-described microlens array antenna 1E, we explained the case where the integrated dielectric lens 8 is constructed from a Runeberg lens 8a, where the dielectric material changes from the center outwards, resulting in a decrease in the effective dielectric constant ε from the center outwards. However, the microlens array antenna 1E' may also be constructed using an integrated dielectric lens 9 made up of each of the Runeberg lenses 9a shown in Figure 8(b).

[0071] Each Luneberg lens 9a is configured such that, in a spherical dielectric with a uniform effective dielectric constant ε, vacancies 9b are formed, the diameter of which increases sequentially from the center toward the outer space, so that the effective dielectric constant ε decreases from the center toward the outer space. In this case, an overlap portion 9c is formed between adjacent Luneberg lenses 9a, where the vacancies 9b with the largest diameters overlap in one direction.

[0072] Even when a microlens array antenna 1E' is constructed using such a Luneberg lens-integrated dielectric lens 9, adjacent Luneberg lenses 9a are connected in overlapping portions 9c where the effective dielectric constant ε is small, and a region with a small dielectric constant and uniformity is formed between adjacent Luneberg lenses 9a via the overlapping portions 9c. Therefore, among the radio waves radiated from each patch antenna 3a, radio waves radiated at low elevation angles pass through the overlapping portions 9c with a small effective dielectric constant ε with minimal reflection and are incident on the adjacent Luneberg lens 9a, passing through the adjacent Luneberg lens 9a.

[0073] Therefore, the microlens array antenna 1E' obtained by this modification also produces the same effects as the microlens array antenna 1E according to the sixth embodiment described above.

[0074] Furthermore, the Runeberg lens constituting the integrated Runeberg lens dielectric lens does not necessarily have to be spherical; it may be egg-shaped, semi-circular, cylindrical, or other shapes, and these configurations will also produce the same effects as the microlens array antenna 1E according to the sixth embodiment.

[0075] Furthermore, in the above embodiments and modifications, the number of planar antennas constituting the planar array antenna 3, and the number of dielectric lenses 4a and Luneberg lenses 8a and 9a to be integrated were described as being 4 each. However, it is not limited to 4; 2 or more is sufficient.

[0076] Furthermore, in each of the embodiments and modifications described above, the case in which the planar antenna is a patch antenna was explained. However, except for the fourth embodiment which is characterized by the feeding method of the patch antenna 3a, the planar antenna is not limited to a patch antenna, and may be a planar antenna such as a meander line antenna made by bending a conductor into a crank shape, or a slot antenna.

[0077] In summary, the present invention can be described as follows:

[0078] <1> A planar array antenna is formed on a substrate in an array-like manner in a first direction, with planar antennas spaced at equal intervals of one wavelength or more of the radio waves to be transmitted and received, A multifocal dielectric lens is provided above the planar array antenna, and is formed by integrating a plurality of dielectric lenses, each of which has a focal point on the planar antenna, and having an overlap portion where the aperture diameters of each dielectric lens overlap in the first direction. A microlens array antenna equipped with this feature. <2> The multifocal dielectric lens is such that, when the thickness d of the overlap portion perpendicular to the substrate is λ0, the wavelength of the transmitted and received radio waves in free space is θ, the angle of incidence of the transmitted and received radio waves to the dielectric lens in the overlap portion is θ, and the dielectric constant of the multifocal dielectric lens is ε, then the following equation (1)

number

[0079] 1A, 1B, 1C, 1D, 1E, 1A', 1B', 1C', 1E'... Microlens array antennas 2… Circuit board 3…Planar array antenna 3a... Patch antenna (planar antenna) 3b…Planar antenna array 4…Multifocal dielectric lenses 4a…Dielectric lens 4b, 8b, 9c... overlapping sections 4c...Support block (support base) 4d... Dielectric lens array 5…Ground Pattern 7…Power supply line 7a, 7b... Power supply locations 8,9…Luneberg lens-integrated dielectric lens 8a, 9a... Reneberg Lens 9c…Vacancy 10…Cross-references of applications related to metal blocks

[0080] This application claims priority over Japanese Patent Application No. 2023-041715, filed with the Japan Patent Office on 16 March 2023, all of which disclosures are incorporated herein by reference in their entirety.

Claims

1. A planar array antenna is formed on a substrate in an array-like manner in a first direction, with planar antennas that transmit and receive radio waves using one element at approximately equal intervals of one wavelength or more of the radio waves to be transmitted and received, A multifocal dielectric lens is provided above the planar array antenna, and is formed by integrating a plurality of dielectric lenses, each of which has a focal point on the planar antenna, and having an overlap portion where the aperture diameters of each dielectric lens overlap in the first direction. A microlens array antenna equipped with this feature.

2. The multifocal dielectric lens has a thickness d in the overlap portion perpendicular to the substrate, where λ is the wavelength of the radio waves transmitted and received in free space. ０ When the angle of incidence to the dielectric lens in the overlap portion of the transmitted and received radio waves is θ and the dielectric constant of the multifocal dielectric lens is ε, then the following equation (1) [Math 1] A microlens array antenna according to claim 1, characterized in that it is within the range shown.

3. The microlens array antenna according to claim 1 or 2, wherein the multifocal dielectric lens is provided with a support base that fixes the distance between the support base and the substrate to the focal length of each dielectric lens, the support base being integrally formed on the outer edge of the multifocal dielectric lens using the same material as the multifocal dielectric lens, and the thickness of the support base in the direction parallel to the substrate is thinner than the thickness d of the overlap portion.

4. The planar array antenna is characterized in that the planar antennas are patch antennas, the feed position in the feed line to each planar antenna is set to a position outside the space between adjacent planar antennas or inside the space between adjacent planar antennas, and each adjacent planar antenna is excited in substantially opposite phase, as described in claim 1 or 2.

5. The aforementioned planar array antenna is configured such that multiple rows of planar antennas, each of which is formed in an array in the first direction, are arranged in a second direction perpendicular to the first direction at approximately equal intervals of half wavelengths of the radio waves to be transmitted and received. The multifocal dielectric lens is formed such that the dielectric lens rows of each dielectric lens, whose aperture diameters overlap and are integrated in the first direction, are arranged in a second direction above each of the planar antenna rows, with each dielectric lens constituting the dielectric lens row having a focal point for each planar antenna in each of the planar antenna rows, and the aperture diameters of each dielectric lens constituting the dielectric lens row overlap and are integrated in the second direction as well. A microlens array antenna as described in claim 1 or 2.

6. A planar array antenna is formed on a substrate in an array-like manner in one direction, with planar antennas that transmit and receive radio waves using one element at approximately equal intervals of one wavelength or more of the radio waves to be transmitted and received, A Luneberg lens integrated dielectric lens is formed by integrating multiple Luneberg lenses, each with an effective dielectric constant decreasing from the center toward the outer space, in one direction above each planar antenna, and having overlapping portions where the portions with small effective dielectric constants at adjacent ends of each Luneberg lens overlap in one direction. A microlens array antenna equipped with this feature.

7. The microlens array antenna according to claim 6, characterized in that a metal block is provided between each of the planar antennas.

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