Antenna element and antenna module

Abstract

An antenna element according to one embodiment of the present technology comprises a dielectric substrate, a conductor portion, a dielectric waveguide, a power supply portion, and a plurality of opening grooves. The conductor portion includes a line conductor layer provided along the dielectric substrate. In the dielectric waveguide, an end surface of the dielectric substrate serves as an antenna opening. The power supply portion is formed in the line conductor layer and comprises a coplanar line, a slot line that opens toward the dielectric waveguide, and a line converting portion that connects the coplanar line and the slot line. The plurality of opening grooves are formed in the conductor portion and are provided on both sides of the slot line so as to open toward the dielectric waveguide.

Description

Antenna Element and Antenna Module

[0001] The present technology relates to an antenna element and an antenna module that transmit and receive electromagnetic waves.

[0002] Conventionally, a slot antenna has been developed as an antenna having a relatively small and simple configuration. Patent Document 1 describes a slot antenna configured using a conductor pattern at the edge of a substrate. Patent Document 2 also describes a system that performs beamforming and the like using an antenna array combining a slot antenna and a trough antenna.

[0003] Japanese Unexamined Patent Application Publication No. 2007-311944, Japanese Patent Application Publication No. 2021-503227

[0004] Generally, since the gain of a slot antenna alone is small, for example, a method of improving the gain by arraying a plurality of slot antennas is used. Also, by arraying, it is possible to suppress the deviation of the beam of a single slot antenna. On the other hand, an antenna formed by arraying slot antennas becomes large as a single element. For example, in applications such as MIMO (Multi Input Multi Output) radar, by arranging a plurality of antenna elements at intervals of 1 / 2 of the radar wavelength, it is possible to maximize the phase estimation angle. However, as described above, when each antenna becomes large, it is considered difficult to achieve an optimal arrangement.

[0005] In view of the above circumstances, an object of the present technology is to provide an antenna element and an antenna module that are small and easily arrayed while improving the gain and beam width in a single unit.

[0006] To achieve the above objective, an antenna element according to one embodiment of this technology comprises a dielectric substrate, a conductor portion, a dielectric waveguide, a power supply portion, and a plurality of opening grooves. The conductor portion includes a transmission line conductor layer provided along the dielectric substrate. The dielectric waveguide has an antenna opening at the end face of the dielectric substrate. The power supply portion is formed in the transmission line conductor layer and has a coplanar transmission line, a slot transmission line opening toward the dielectric waveguide, and a transmission line conversion portion connecting the coplanar transmission line and the slot transmission line. The plurality of opening grooves are formed in the conductor portion and are provided on both sides of the slot transmission line so as to open toward the dielectric waveguide.

[0007] In this antenna element, a coplanar transmission line formed in the transmission line conductor layer is connected to a slot transmission line that opens toward the dielectric waveguide via a transmission line conversion section. Furthermore, multiple opening grooves formed in the conductor portion, including the transmission line conductor layer, are provided on both sides of the slot transmission line, opening toward the dielectric waveguide. This allows for efficient propagation of electromagnetic waves excited by the slot transmission line to the dielectric waveguide while suppressing beam polarization. Additionally, by sharing the opening grooves, the slot transmission lines can be arranged at short intervals. This makes it possible to realize a compact antenna element that is easy to array while improving the gain and beamwidth of a single unit.

[0008] The line conductor layer may have a first grounding conductor. In this case, the coplanar line may have a line conductor surrounded by the first grounding conductor. The line conversion section may also have a conversion conductor spaced apart from the first grounding conductor and connected to the line conductor, and a gap formed between the tip of the conversion conductor and the first grounding conductor. The slot line may also be a line in which the first grounding conductor is open facing the conversion conductor.

[0009] The line conductor may extend inward toward the end edge of the first grounding conductor. In this case, the conversion conductor and the gap portion may be provided along the end edge of the first grounding conductor. The first grounding conductor may also have a tab portion that forms its end edge and extends to the opening of the slotted line.

[0010] The conversion conductor may be a conductor obtained by bending the line conductor to one side along the edge of the first grounding conductor. In this case, the slot line may be provided facing the connection position between the line conductor and the conversion conductor.

[0011] The conductor portion may include the line conductor layer and an adjacent conductor layer provided on the same side of the dielectric substrate as the line conductor layer. In this case, the adjacent conductor layer may have a second ground conductor with an opening formed in a region that overlaps with the line conversion portion and the slot line in a plan view.

[0012] The aforementioned line conductor layer may be provided between the dielectric substrate and the adjacent conductor layer.

[0013] The conductor portion may include the line conductor layer and a plurality of opposing conductor layers provided on the dielectric substrate opposite to the line conductor layer. In this case, the plurality of opposing conductor layers may form stepped portions that extend toward the antenna opening of the dielectric waveguide in the region that overlaps with the line conversion portion and the slot line in a plan view.

[0014] The conductor portion may have a plurality of conductor layers, including the line conductor layer, and a plurality of connecting conductors that connect the plurality of conductor layers. In this case, each of the plurality of opening grooves may be partitioned by a conductor wall through which the plurality of conductor layers are connected by the plurality of connecting conductors.

[0015] The plurality of opening grooves may have a depth corresponding to the wavelength of the electromagnetic wave used in the dielectric waveguide.

[0016] The plurality of opening grooves may be provided parallel to the track direction of the slotted track.

[0017] The plurality of opening grooves may be provided in a concave shape so as to surround the dielectric waveguide in front of the slot line, with the slot line as the bottom.

[0018] The dielectric waveguide may be configured such that the length from the slot line to the antenna aperture is 1 / 4 or more of the wavelength of the electromagnetic wave used in the dielectric waveguide.

[0019] The dielectric waveguide may have a length from the slot line to the antenna aperture that is an integer multiple of half the wavelength of the electromagnetic wave used in the dielectric waveguide.

[0020] An antenna module according to one embodiment of this technology comprises a dielectric substrate, a conductor portion, and a plurality of antenna elements. The conductor portion includes a transmission line conductor layer provided along the dielectric substrate. The plurality of antenna elements comprises a power supply portion having a dielectric waveguide with the end face of the dielectric substrate as an antenna opening, a coplanar transmission line formed in the transmission line conductor layer, a slot transmission line formed in the transmission line conductor layer and opening toward the dielectric waveguide, and a transmission line conversion portion connecting the coplanar transmission line and the slot transmission line, and a plurality of opening grooves formed in the conductor portion and provided on both sides of the slot transmission line so as to open toward the dielectric waveguide.

[0021] The plurality of antenna elements may be arranged such that the spacing between each of the slot lines is half the wavelength of the electromagnetic wave used in the dielectric waveguide.

[0022] The plurality of antenna elements may share the opening groove with adjacent antenna elements.

[0023] This is a perspective view showing an example of the configuration of an antenna element according to the first embodiment of this technology. This is a plan view showing an example of the configuration of the antenna element shown in Figure 1. This is a schematic cross-sectional view illustrating the layer structure of the antenna element. This is an enlarged perspective view showing an example of the configuration of the feeding section. This is a plan view showing an example of the conductor pattern of the feeding section. This is a schematic diagram illustrating the electric field in a coplanar line and a slot line. This is a schematic diagram illustrating an example of the operation of the feeding section. This is an enlarged plan view showing an example of the configuration of an opening groove. This is a graph showing the angular distribution of antenna gain in an antenna element provided with multiple opening grooves. This is a schematic diagram illustrating an example of the operation of a dielectric waveguide. This is a graph showing the relationship between the length of the dielectric waveguide and VSWR. This is a graph showing the relationship between the length of the dielectric waveguide and antenna gain. This is a plan view showing an example of an antenna array using the antenna element. This is a graph showing the frequency characteristics of VSWR in the antenna array. This is a graph showing the frequency characteristics of absolute gain in the antenna array. This is a plan view showing a modified example of the antenna element. This is a plan view showing another modified example of the antenna element. This is a perspective view showing an example of the configuration of an antenna module according to the second embodiment. This is a plan view showing an example of the configuration of the antenna module shown in Figure 18. This is a block diagram showing a functional configuration example of the antenna module. This is a schematic diagram illustrating the arrangement of antenna elements in an antenna module. This is a graph showing the horizontal radiation characteristics of the antenna module. This is a graph showing the phase difference characteristics of the antenna module. This is a plan view showing an example of the conductor pattern of the feed point according to another embodiment. This is a plan view showing an example of the conductor pattern of the feed point according to another embodiment.

[0024] The embodiments of this technology will be described below with reference to the drawings.

[0025] [Antenna Element] Figure 1 is a perspective view showing an example of the configuration of an antenna element according to the first embodiment of this technology. Figure 2 is a plan view showing an example of the configuration of the antenna element shown in Figure 1. Figure 3 is a schematic cross-sectional view illustrating the layer structure of the antenna element.

[0026] In each figure, the X, Y, and Z axes represent three mutually orthogonal axes, corresponding to the length (front-to-back direction), width (left-to-right direction), and thickness (height direction) of the antenna element 10, respectively. In addition, the upper and lower sides in the Z direction in each figure may be referred to as the upper and lower sides of the antenna element 10. Note that the terms "upper side" and "lower side" describe the relative positional relationship of the antenna element 10 and do not limit the orientation in which the antenna element 10 is used.

[0027] The antenna element 10 is an element that, for example, converts between an RF (Radio Frequency) signal of a predetermined frequency and an electromagnetic wave of a predetermined frequency to transmit (radiate) or receive (detect) electromagnetic waves. The antenna element 10 is used, for example, in antenna modules that perform object detection or communication using millimeter waves or microwaves. Beyond this, the applications of the antenna element 10 are not particularly limited. Hereinafter, the electromagnetic waves used by the antenna element 10 may be referred to as the electromagnetic waves used by the antenna element 10.

[0028] In this embodiment, the antenna element 10 is made of a dielectric multilayer substrate 11 having a thickness direction in the Z-axis direction. First, the configuration of the dielectric multilayer substrate 11 will be described. As shown in Figure 3, the dielectric multilayer substrate 11 has a plurality of dielectric layers 12, a plurality of conductor layers 13, and a plurality of connecting conductors 14.

[0029] Multiple dielectric layers 12 are each composed of a dielectric material and are arranged with the conductive layer 13 in between. Each dielectric layer 12 is typically made of an insulating dielectric material and functions as an insulating layer. Examples of such materials include insulating organic materials such as epoxy resins and fluororesins such as polytetrafluoroethylene, and insulating inorganic materials such as ceramics. Each dielectric layer 12 may be composed of the same dielectric material, or each layer may be composed of a different dielectric material.

[0030] The multiple dielectric layers 12 include an inner dielectric layer M1, an upper dielectric layer M2, and a lower dielectric layer M3. The upper dielectric layer M2 and the lower dielectric layer M3 are provided above and below the inner dielectric layer M1, respectively, with the conductor layer 13 in between.

[0031] The inner dielectric layer M1 is a substrate made of dielectric material and is the core material responsible for the rigidity of the dielectric multilayer substrate 11. In this embodiment, the inner dielectric layer M1 corresponds to a dielectric substrate. The thickness of the inner dielectric layer M1 is greater than that of the upper dielectric layer M2 and the lower dielectric layer M3. The upper dielectric layer M2 and the lower dielectric layer M3 are constructed using a prepreg or the like made of dielectric material and are laminated above and below the inner dielectric layer M1 by a build-up method.

[0032] The following explanation will primarily use the case where the frequency (operating frequency) of the electromagnetic wave or RF signal used by the antenna element 10 is in the 24 GHz band as an example. In this case, for example, the thickness of the inner dielectric layer M1 is set to 1.26 mm, the thickness of the upper dielectric layer M2 is set to 0.07 mm, and the thickness of the lower dielectric layer M3 is set to 0.07 mm. The dielectric constant of each dielectric layer 12 is set to, for example, 4. Of course, the thickness and dielectric constant of each dielectric layer 12 are not limited to the example above and may be set appropriately according to the operating frequency, etc.

[0033] The multiple conductor layers 13 are layered conductors provided along each dielectric layer 12, forming wiring and conductor patterns. Copper is typically used as the conductor material, but other metals may also be used.

[0034] The multiple conductor layers 13 include a first conductor layer L1, a second conductor layer L2, a third conductor layer L3, and a fourth conductor layer L4. The first conductor layer L1 is provided above the upper dielectric layer M2. The second conductor layer L2 is provided between the upper dielectric layer M2 and the inner dielectric layer M1. The third conductor layer L3 is provided between the inner dielectric layer M1 and the lower dielectric layer M3. The fourth conductor layer L4 is provided below the lower dielectric layer M3. The thickness of each conductor layer 13 is set to, for example, about 40 μm. In addition, the thickness and material of each conductor layer 13 are not limited to the examples described above.

[0035] The multiple connecting conductors 14 are columnar conductors that connect the multiple conductor layers 13 to each other. The connecting conductors 14 penetrate the dielectric layer 12 provided between each conductor layer 13, electrically connecting each conductor layer 13. The connecting conductors 14 may be hollow structures with a metal film formed on the inner circumference of a through-hole, or they may be configured as metal columns filled with a conductor such as metal plating or a metal plug. Furthermore, each connecting conductor 14 may be configured to connect only two conductor layers 13, or it may be configured to connect three or more conductor layers 13.

[0036] Multiple conductor layers 13 and multiple connecting conductors 14 constitute the conductor portion 15 of the antenna element 10. Here, the conductor portion 15 is the part of the dielectric multilayer substrate 11 that is made of a conductor material. As will be described later, in this embodiment, the second conductor layer L2 of the conductor portion 15 becomes a line conductor layer on which a power supply section 21 consisting of a coplanar line 30, a slot line 31, and a line conversion section 32 is formed. Thus, the conductor portion 15 includes a line conductor layer (second conductor layer L2) provided along the dielectric substrate (inner dielectric layer M1).

[0037] A protective film may be provided on the dielectric multilayer substrate 11. The protective film is a film for protecting the surface of the conductive layers 13 (first conductive layer L1 and fourth conductive layer L4) arranged on the outside of the dielectric multilayer substrate 11. A gold film layer or solder resist can be used as the protective film. The configuration of the dielectric multilayer substrate 11 is not limited to this.

[0038] As shown in Figures 1 and 2, the antenna element 10 has a dielectric waveguide 20, a power supply section 21, and a plurality of opening grooves 22.

[0039] The dielectric waveguide 20 is a waveguide in which the end face of the inner dielectric layer M1, which is a dielectric substrate, is an antenna aperture 23. The antenna aperture 23 is, for example, the part that serves as the outlet or inlet for electromagnetic waves in the antenna element 10. The dielectric waveguide 20 is made of a dielectric material including the inner dielectric layer M1 and propagates electromagnetic waves between the power supply section 21 and the antenna aperture 23.

[0040] In this embodiment, the planar shape of the dielectric multilayer substrate 11 is rectangular with edges along the X and Y directions. The plurality of conductor layers 13 are arranged so that the front edges of each layer are aligned along a predetermined line (edge ​​24 of the conductor layer 13) in the Y direction. In the antenna element 10, a dielectric waveguide 20 is formed in the region from the edge 24 of each conductor layer 13 to the X-direction front end face (antenna opening 23) of the dielectric multilayer substrate 11. In this embodiment, the dielectric waveguide 20 is composed of a laminate of an inner dielectric layer M1 and an upper dielectric layer M2 and a lower dielectric layer M3 provided above and below it.

[0041] The power supply section 21 is formed in the second conductor layer L2, which is a conductor layer for the transmission line. Here, the power supply section 21 is provided in a region including the front edge 24 of the second conductor layer L2. In the antenna element 10, for example, electromagnetic waves corresponding to the RF signal input to the power supply section 21 propagate through the dielectric waveguide 20 and are radiated from the antenna aperture 23. Alternatively, electromagnetic waves incident on the dielectric waveguide 20 from the antenna aperture 23 are converted into an RF signal in the power supply section 21. The power supply section 21 includes a coplanar transmission line 30, a slot transmission line 31, and a transmission line conversion section 32.

[0042] The coplanar line 30 is a line that transmits an RF signal of a predetermined frequency and is formed in the second conductor layer L2, which is a conductor layer for lines. In the example shown in Figures 1 and 2, the coplanar line 30 is schematically shown by a dotted line. The rear end of the coplanar line 30 (line conductor 34, described later) provided in the second conductor layer L2 is connected to a connection terminal 25 provided in the first conductor layer L2 via a connecting conductor 14 that penetrates the upper dielectric layer M2, and the front end is connected to the line conversion unit 32. The connection terminal 25 is a terminal for connecting to an IC circuit (not shown) or the like that transmits or receives an RF signal.

[0043] The slot line 31 is a line that opens toward the dielectric waveguide 20. In this embodiment, the slot line 31 is formed by a gap formed in the ground conductor (ground conductor 33b, described later) of the second conductor layer L2. The slot line 31 excites the dielectric waveguide 20 with electromagnetic waves corresponding to the RF signal, or generates an RF signal corresponding to the electromagnetic waves that have reached the slot line 31 from the dielectric waveguide 20.

[0044] The line conversion section 32 connects the coplanar line 30 and the slot line 31. That is, the line conversion section 32 functions as a converter that mutually converts two types of lines (the coplanar line 30 and the slot line 31) through which RF signals are transmitted. The line conversion section 32 is formed on the same second conductor layer L2 as the coplanar line 30 and the slot line 31.

[0045] The plurality of opening grooves 22 are formed in the conductor portion 15 and provided so as to open toward the dielectric waveguide 20 on both sides of the slot line 31. In the present embodiment, the slit-shaped conductor structure formed in the thickness direction by the conductor portion 15 (the plurality of conductor layers 13 and the plurality of connection conductors 14) provided on the dielectric multilayer substrate 11 becomes the opening groove 22. Each opening groove 22 radiates, for example, electromagnetic waves excited by the slot line 31 toward the dielectric waveguide 20.

[0046] Hereinafter, each part of the antenna element 10 will be specifically described.

[0047] [Power feeding portion] FIG. 4 is an enlarged perspective view showing a configuration example of the power feeding portion. FIG. 5 is a plan view showing an example of the conductor pattern of the power feeding portion. FIGS. 5A and 5B are the conductor patterns of the first conductor layer L1 and the second conductor layer L2.

[0048] As described above, in the present embodiment, on the upper side of the inner dielectric layer M1, the second conductor layer L2 serving as a line conductor layer and the first conductor layer L1 are provided. That is, the first conductor layer L1 is an adjacent conductor layer provided on the same side as the second conductor layer L2 of the inner dielectric layer M1. The first conductor layer L1 is the conductor layer closest to the second conductor layer L2, and together with the second conductor layer L2, constitutes the power feeding portion 21.

[0049] Also, in the present embodiment, the second conductor layer L2 is provided between the inner dielectric layer M1 and the first conductor layer L?. That is, the main part constituting the power feeding portion 21 is arranged in the lower layer of the first conductor layer L1, which is the outermost (upper side) in the antenna element 10, and becomes an inner-layered pattern. Thus, by inner-layering the coplanar line 30 and the like, it is possible to avoid a situation where the transmission performance of RF signals deteriorates due to, for example, a protective film provided on the surface.

[0050] As shown in Figure 5A, the first conductor layer L1 has a grounding conductor 33a. Also, as shown in Figure 5B, the second conductor layer L2 has a grounding conductor 33b. Both grounding conductors 33a and 33b are connected to the ground potential (GND) at the antenna element 10 and are electrically grounded conductors. In this embodiment, the grounding conductor 33b provided in the second conductor layer L2 corresponds to the first grounding conductor, and the grounding conductor 33a provided in the first conductor layer L1 corresponds to the second grounding conductor.

[0051] As shown in Figure 5B, the coplanar line 30 has a line conductor 34 and a slit portion 35. The line conductor 34 is a conductor surrounded by the ground conductor 33b and functions as a signal line (microstrip line) of the coplanar line 30. As the line conductor 34, a line-shaped conductor pattern formed with a predetermined line width in the second conductor layer L2 is used, and one end thereof is connected to the connection terminal 25 shown in Figures 1 and 2. The slit portion 35 is a slit-shaped opening pattern formed on both sides of the line conductor 34 and functions as a gap separating the line conductor 34 and the ground conductor 33b.

[0052] In this embodiment, the line conductor 34 is configured to extend inward toward the end edge 24 of the grounding conductor 33b. Specifically, a line conductor 34 is formed that extends linearly along the X direction, and linear slit portions 35 are formed on both sides of the line conductor 34. The shape of the line conductor 34 is not limited, and for example, a line conductor 34 that is inclined with respect to the X direction or a curved line conductor 34 may be formed.

[0053] As shown in Figure 5A, the region of the first conductor layer L1 that overlaps with the coplanar line 30 is covered by the grounding conductor 33a. In other words, the line conductor 34 is shielded by the grounding conductor 33a. This prevents external noise from entering the coplanar line 30 and blocks noise radiated from the coplanar line 30.

[0054] As shown in Figure 5B, the line conversion section 32 has a conversion conductor 37 and a gap section 38. The conversion conductor 37 is a conductor that is spaced apart from the ground conductor 33b and connected to the line conductor 34. In other words, the conversion conductor 37 can be said to be a conductor pattern that constitutes the end of the line conductor 34 in the second conductor layer L2. The gap section 38 is formed between the tip of the conversion conductor 37 and the ground conductor 33b. Here, the opening pattern formed in the region extending the conversion conductor 37 toward its tip functions as the gap section 38. The conversion conductor 37 and the gap section 38 are structures for generating a phase difference in the electric field generated on both sides of the coplanar line 30 (line conductor 34).

[0055] In this embodiment, the conversion conductor 37 and the gap portion 38 are provided along the edge 24 of the grounding conductor 33b. Here, the edge 24 of the grounding conductor 33b is formed along the Y direction. Therefore, the conversion conductor 37 and the gap portion 38 are also formed along the Y direction. This makes it possible to reduce the size of the line conversion unit 32 in the front-to-back direction (X direction), so that, for example, a coplanar line 30 can be converted to a slot line 31 over a relatively short distance.

[0056] In this embodiment, the conversion conductor 37 is a conductor obtained by bending the line conductor 34 to one side along the edge 24 of the ground conductor 33b. That is, the line conductor 34 has a predetermined line width and is bent into an L-shape, forming a conductor pattern. As shown in Figure 5B, the conversion conductor 37 is bent in a direction that is to the right of the line conductor 34 when viewed in the forward X direction (lower side in the figure). Of course, the conversion conductor 37 may also be bent in a direction that is to the left of the line conductor 34 (upper side in the figure). By making the line conversion section 32 a pattern bent to one side in this way, the size of the line conversion section 32 in the left-right direction (Y direction) can be reduced.

[0057] As shown in Figure 5B, the slot line 31 is a line in which the grounding conductor 33b is open facing the conversion conductor 37. That is, the gap in the grounding conductor 33b that forms the slot line 31 is provided at a position opposite to the conversion conductor 37. In this way, because the slot line 31 faces the conversion conductor 37, an electric field with a phase difference can be efficiently generated on the slot line 31.

[0058] Furthermore, the grounding conductor 33b has a tab portion 39 that forms its edge 24 and extends to the opening of the slot line 31. The tab portion 39 is a line-shaped conductor pattern extending in the Y direction from the right side (lower side in the figure) where the gap portion 38 of the line conversion section 32 is provided. Of the slit portions 35 formed on both sides of the line conductor 34, the left slit portion 35 that does not intersect with the conversion conductor 37 extends in the X direction and reaches the edge 24 of the grounding conductor 33. Therefore, the slot line 31 is formed between the grounding conductor 33b that demarcates the left slit portion 35 and the tab portion 39 extending from the right side.

[0059] In the following, the tip of the tab portion 39 will be referred to as the slot end 40a, and the end of the grounding conductor 33b on the opposite side of the slot end 40a will be referred to as the slot end 40b. The opening sandwiched between the slot end 40a and the slot end 40b becomes the slot line 31.

[0060] Furthermore, as shown in Figures 4 and 5A, an opening (hereinafter referred to as a power supply opening 41) is formed in the grounding conductor 33a provided in the first conductor layer L1 in a region that overlaps with the line conversion unit 32 and the slot line 31 in a plan view. The power supply opening 41 is an opening pattern provided in the first conductor layer L1 so as not to obstruct the patterns of the line conversion unit 32 and the slot line 31. As a result, even if the first conductor layer L1 is provided adjacent to the second conductor layer L2, the line conversion unit 32 and the slot line 31 can be operated properly.

[0061] Here, the planar shape of the grounding conductor 33a, including the power supply opening 41, is set to be the same as that of the grounding conductor 33b of the second conductor layer L2, except for the portion that becomes the coplanar line 30. Therefore, as shown in Figure 4, the power supply opening 41 becomes a window that exposes the conversion conductor 37. The grounding conductor 33a also has a tab portion 39 along the edge 24, a slot end 40a which is the tip of the tab portion 39, and a slot end 40b which is opposite to the slot end 40a, similar to the grounding conductor 33b. The opening sandwiched between the slot end 40a and the slot end 40b of the grounding conductor 33a also functions as a slot line 31.

[0062] Furthermore, as shown in Figures 4 and 5, the power supply unit 21 is equipped with connecting conductors 14 (conductor posts) that connect all the conductor layers 13 (L1 to L4) so ​​as to surround the RF signal transmission section consisting of the coplanar line 30, the line conversion unit 32, and the slot line 31. These connecting conductors 14 constitute a conductor wall (post wall) that shields the line conversion unit 32, etc. This suppresses the influence of surrounding conductors and other antenna elements, making it possible to properly convert between the coplanar line 30 and the slot line 31.

[0063] Figure 6 is a schematic diagram illustrating the electric field in a coplanar transmission line and a slotted transmission line. Figures 6A and 6B schematically show cross-sections of the coplanar transmission line 30 and the slotted transmission line 31 along the YZ plane. Here, the electric field 5 generated when each transmission line transmits an RF signal is schematically illustrated using black arrows.

[0064] As shown in Figure 6A, in the coplanar transmission line 30, an electric field 5 is generated between the transmission line conductor 34 and the surrounding grounding conductors (the grounding conductors 33b on both sides arranged between the transmission line conductor 34 and the slit portion 35, and the grounding conductor 33a arranged above the transmission line conductor 34). These electric fields 5 are alternating current electric fields with equal phase.

[0065] As shown in Figure 6B, in the slot line 31, an electric field 5 is generated between the grounding conductors of the same layer facing each other across a gap (slot end 40a and slot end 40b). In this embodiment, the slot line 31 is formed across two layers: the grounding conductor 33a of the first conductor layer L1 and the grounding conductor 33b of the second conductor layer L2. In this case, the electric field 5 generated in the gap of the grounding conductor 33a and the electric field 5 generated in the gap of the grounding conductor 33b are alternating electric fields with equal phase.

[0066] Figure 7 is a schematic diagram illustrating an example of the operation of the power supply unit. In Figure 7, the image current 6 generated on both sides of the line conductor 34 when an RF signal is applied to the line conductor 34 of the coplanar line 30 is schematically illustrated by dotted arrows. The electric field 5 generated in the slot line 31 is also schematically illustrated by black arrows. Here, we will explain the case in which an RF signal is transmitted from the coplanar line 30 to the slot line 31.

[0067] The image current 6 is an alternating current that oscillates with a period similar to that of an RF signal, for example. For example, the phase of the electric field 5 generated in each line, as explained with reference to Figure 6, corresponds to the phase of the image current 6 flowing at the location where the electric field 5 is generated.

[0068] The image current 6a shown in Figure 7 is an image current that occurs on the right side (lower side in the figure) of the line conductor 34 and flows through a path bent into a U shape by the conversion conductor 37. The image current 6b is an image current that occurs on the left side (upper side in the figure) of the line conductor 34 and flows through a path that travels straight toward the slot line 31. Because the image currents 6a and 6b travel through these different paths, they acquire a phase difference by the time they reach the slot line 31.

[0069] For example, in the coplanar transmission line 30, the image currents 6a and 6b are in phase, creating an in-phase electric field distribution with respect to the transmission line conductor 34 as shown in Figure 6A. On the other hand, in the slot transmission line 31, the image current 6a passing through the path that wraps around the conversion conductor 37 generates an electric field 5a between the right slot end 40a and the conversion conductor 37, and the image current 6b traveling straight through the left slit portion 35 generates an electric field 5b between the left slot end 40b and the conversion conductor 37.

[0070] At this time, since the image currents 6a and 6b have a phase difference, the electric fields 5a and 5b also have a phase difference. Here, we assume that the phase difference between the electric fields 5a and 5b is 180°. In this case, for example, with the electric field 5b generated in the direction from the conversion conductor 37 toward the slot end 40b, the electric field 5a is generated in the direction from the slot end 40a toward the conversion conductor 37. As a result, an electric field 5c is generated in the slot line 31 from the slot end 40a toward the slot end 40b. This results in an electric field distribution in the slot line 31 as shown in Figure 6B.

[0071] In the slotted transmission line 31, an electromagnetic wave 7 (indicated by the white arrow) having the same frequency as the RF signal is excited in the dielectric waveguide 20 located in front of it by the electric field 5c generated along the Y direction. Therefore, the region where the slotted transmission line 31 and the dielectric waveguide 20 are connected functions as an excitation section 42 in the power supply section 21 where the electromagnetic wave 7 is excited. By using the slotted transmission line 31, the size of the excitation section 42 in the X direction can be reduced to less than 1 / 4 of the wavelength of the electromagnetic wave used in the dielectric waveguide 20. The electromagnetic wave 7 excited in the slotted transmission line 31 (excitation section 42) propagates through the dielectric waveguide 20 and is radiated from the antenna aperture 23, which is not shown in the figure.

[0072] In this way, the power supply unit 21 includes a process of converting from the coplanar line 30 to the slot line 31, and then the electromagnetic waves 7 are radiated from the slot line 31 to the substrate end which becomes the antenna aperture 23. This makes it possible to significantly reduce the size of the conductors (line conversion unit 32 and slot line 31) required to excite the electromagnetic waves 7.

[0073] Furthermore, the slot line 31 is provided facing the connection point between the line conductor 34 and the conversion conductor 37. This creates a bypass path that provides a phase difference to the image current 6b across the entire line conductor 34. As a result, it is possible to realize a bypass path of the required length without unnecessarily increasing the length of the line conductor 34, and the size of the line conversion unit 32 in the Y direction can be made sufficiently small.

[0074] Furthermore, if electromagnetic waves 7 are incident from the antenna aperture 23, the process described above proceeds in reverse. That is, the RF signal generated in the slot line 31 that receives electromagnetic waves 7 is transmitted to the coplanar line 30 via the line conversion unit 32.

[0075] Here, we will explain the dimensions of each part of the feed unit 21 when the operating frequency of the antenna element 10 is in the 24 GHz band. Note that the dimensions described below are merely examples, and the dimensions of each part of the feed unit 21 can be appropriately set according to the application and operating frequency of the antenna element 10.

[0076] The dimensions of the coplanar transmission line 30 are optimally determined based on, for example, the relative permittivity of the dielectric layers 12 used (particularly the inner dielectric layer M1 and the upper dielectric layer M2) and the distance between the first conductor layer L1 and the second conductor layer L2 (the thickness of the upper dielectric layer M2). Here, the width (line width W) of the transmission line conductor 34 and the width (gap width G) of the slit portion 35 that constitute the coplanar transmission line 30 are both set to 0.10 mm.

[0077] In the line conversion unit 32, the path length through which the image current 6b passes can be adjusted by changing the lengths of the line conductor 34 and the gap portion 38. This makes it possible to appropriately adjust the phase difference between the image current 6a and the image current 6b (electric field 5a and electric field 5b). In other words, the conversion efficiency between the coplanar line 30 and the slot line 31 can be adjusted by changing the lengths of the line conductor 34 and the gap portion 38. Here, the length C1 of the line conductor 34 is set to 0.95 mm, and the length C2 of the gap portion 38 is set to 0.43 mm. The values ​​of C1 and C2 are set, for example, using simulation, to maximize the conversion efficiency between each line.

[0078] Furthermore, it is preferable that dimensions other than C1 and C2 in the track conversion section 32 (such as the track width and the gap width with the grounding conductor 33b) be set to match the dimensions of the coplanar track 30. For example, the width of the conversion conductor 37 (line width C3) is set to 0.10 mm, the same as the line width W of the track conductor 34. Also, the width of the gap formed on the front and rear sides of the conversion conductor 37 in the X direction (gap width C4) is set to 0.10 mm, the same as the gap width G of the slit section 35.

[0079] The dimensions of the power supply opening 41 provided in the first conductor layer L2 (grounding conductor 33a) are set to match the dimensions of the line conversion section 32. For example, the width of the power supply opening 41 in the X direction is set to C3 + 2 × C4 = 0.30 mm, and the width in the Y direction is set to C1 + C2 + G = 1.48 mm.

[0080] The dimensions of the slot line 31 are optimized, for example, using simulations, so that the electromagnetic wave 7 can be excited most efficiently with respect to the dielectric waveguide 20. Here, the width S1 of the slot line 31 (the distance between the slot ends 40a and 40b) is set to 0.40 mm, and the length S2 of the slot line 31 (the length of the slot line 31 in the X direction) is set to 0.10 mm. The length of the tab portion 39 along the Y direction is 1.08 mm.

[0081] Next, the configuration of the lower layer of the power supply unit 21 will be described. As described above, in this embodiment, a third conductor layer L3 and a fourth conductor layer L4 are provided below the inner dielectric layer M1. That is, the third conductor layer L3 and the fourth conductor layer L4 are a plurality of opposing conductor layers provided on the opposite side of the second conductor layer L2 of the inner dielectric layer M1.

[0082] As shown in Figures 1 and 4, in this embodiment, a stepped portion 44 is formed by multiple opposing conductor layers (L3 and L4) in the region that overlaps with the line conversion section 32 and the slot line 31 in a plan view, extending toward the antenna opening 23 of the dielectric waveguide 20. The stepped portion 44 is a stepped structure composed of a third conductor layer L3 and a fourth conductor layer L4.

[0083] Here, a rectangular notch is formed at the front edge 24 of the third conductor layer L3. The front edge 24 of the fourth conductor layer L4 is left as a straight line without any notches. This creates a stepped portion 44 that slopes downward toward the front in the X direction where the antenna opening 23 is located. The stepped portion 44 functions to spread the electromagnetic waves 7 in the Z direction, for example, like a horn antenna. This makes it possible to widen the elevation angle of the radiation range of the electromagnetic waves 7. Note that the stepped portion 44 is not necessarily required.

[0084] [Opening Grooves] Figure 8 is an enlarged plan view showing an example of the configuration of opening grooves. Hereinafter, with reference to Figures 8 and 1, a plurality of opening grooves 22 formed by the conductor portion 15 (conductor layer 13 and connecting conductor 14) of the antenna element 10 will be described. In the antenna element 10, three opening grooves 22 are provided on both sides of the slot line 31.

[0085] As described above, the multiple opening grooves 22 are slit-shaped grooves formed using the conductor portion 15. The wave-shaped structure in which multiple opening grooves 22 are arranged is also called corrugated. Linear opening grooves 22 are formed in the antenna element 10 from the edges 24 of all conductor layers 13 (first conductor layer L1 to fourth conductor layer L4) toward the inside. The opening grooves 22 are typically composed of ground conductors in each conductor layer 13.

[0086] As shown in Figure 8, in this embodiment, the multiple opening grooves 22 are provided parallel to the line direction of the slot line 31. The line direction of the slot line 31 is the direction in which the RF signal is transmitted in the slot line 31 (here, the X direction), and the direction in which the electromagnetic waves 7 are radiated. As will be described later, each opening groove 22 functions as a radiating end that radiates electromagnetic waves 7 along the opening groove 22. Therefore, by providing multiple opening grooves 22 parallel to the line direction of the slot line 31, it is possible to sufficiently improve the radiation efficiency of the electromagnetic waves 7 in the forward direction.

[0087] Furthermore, it is preferable that the pattern constituting the opening groove 22 is the same shape for all conductor layers 13 (the first conductor layer L1 to the fourth conductor layer L4). For example, Figure 8 shows the pattern of the opening groove 22 formed by the first conductor layer L1, but the opening groove 22 for the second conductor layer L2, the third conductor layer L3, and the fourth conductor layer L4 is also formed with a similar pattern. This makes it possible to maintain a high level of radiation efficiency of electromagnetic waves 7 from each opening groove 22.

[0088] As shown in Figure 1, it is preferable to provide vias (connecting conductors 14) that penetrate all the conductor layers 13 (the first conductor layer L1 to the fourth conductor layer L4) between adjacent opening grooves 22. Therefore, a conductor wall 45 composed of the conductor layers 13 and connecting conductors 14 is formed between adjacent opening grooves 22. Here, the conductor wall 45 is a structure in which, for example, columnar connecting conductors 14 provided in the Z direction of the substrate are arranged in a row and each connecting conductor 14 is electrically connected via the conductor layer 13. For example, if the spacing between the connecting conductors 14 is sufficiently small, electromagnetic waves 7 will not pass through the conductor wall 45. This makes it possible to control the propagation direction of electromagnetic waves 7.

[0089] In this way, each of the multiple opening grooves 22 is partitioned by a conductor wall 45 in which multiple conductor layers 13 are connected by multiple connecting conductors 14. In the example shown in Figure 8, each opening groove 22 is partitioned by a conductor wall 45 composed of three connecting conductors 14 (vias). This makes it possible to avoid situations such as leakage of electromagnetic wave components 7 to both sides of the opening groove 22, and to improve the efficiency of electromagnetic wave radiation forward.

[0090] Here, with reference to Figure 8, the basic operation of the opening groove 22 will be explained. The electromagnetic wave 7 (see Figure 7) excited by the slot line 31 includes a component that propagates in the Y direction along the front edge 24 of the multiple conductor layers 13. Of the electromagnetic wave 7 propagating in the Y direction, the electromagnetic wave component 8a (leftward arrow in the figure) that enters the opening groove 22 is reflected at the bottom of the opening groove 22 (the end opposite the opening of the opening groove 22). The electromagnetic wave component 8b (rightward arrow in the figure) reflected at the bottom of the opening groove 22 propagates toward the opening of the opening groove 22. When the phases of these electromagnetic wave components 8a and 8b are aligned, the electromagnetic wave 7 is efficiently radiated from the opening groove 22. This can also be described as the phenomenon in which the opening groove 22 resonates with the slot line 31 and radiates the electromagnetic wave 7.

[0091] In this embodiment, all of the multiple opening grooves 22 are formed to open toward the front of the antenna element 10. This makes it possible to efficiently radiate the electromagnetic waves 7 excited by the slot line 31 toward the front.

[0092] Next, the dimensions of the multiple opening grooves 22 will be described. In the following, it will be assumed that the antenna element 10 operates in the 24 GHz band. Note that the dimensions of each part of the multiple opening grooves 22 can be appropriately set according to the application and operating frequency of the antenna element 10.

[0093] The width G1 of the opening groove 22 is set to 0.10 mm. This is, for example, the minimum groove width in a conductor pattern. The width G2 of the conductor portion 15 separating the two opening grooves 22 is set to 0.55 mm. Therefore, the spacing G3 between adjacent opening grooves 22 is set to 0.65 mm. G2 and G3 are set to minimize the diameter of the connecting conductor 14 (via hole diameter or land diameter), for example. The width G2 of the conductor portion 15 may be set to a smaller value, for example, by reducing it to the same value as the width G1 of the opening groove 22, the radiation efficiency of the electromagnetic wave 7 can be further improved. For example, a configuration in which the width G2 of the conductor portion 15 is reduced without providing a conductor wall 45 (connecting conductor 14) may be adopted. Furthermore, by reducing the above-mentioned G1, G2, and G3, it is also possible to miniaturize the element size in the Y direction.

[0094] The depth G4 of the opening groove 22 is typically set to match the wavelength of the electromagnetic wave used in the dielectric waveguide 20. Here, the depth G4 of the opening groove 22 is set to 1.8 mm. This value is 1 / 4 of the wavelength of the electromagnetic wave used in the dielectric waveguide 20. In this way, multiple opening grooves 22 have depths corresponding to the wavelength of the electromagnetic wave used in the dielectric waveguide 20.

[0095] This makes it easier for the phases of the electromagnetic wave component 8a incident on the opening groove 22 and the electromagnetic wave component 8b reflected by the opening groove 22 to align, thereby significantly improving the radiation efficiency of the electromagnetic waves 7 from the opening groove 22. However, since interfaces between the dielectric layer 12 and free space exist on the upper and lower surfaces of the opening groove 22, the wavelength shortening effect due to the relative permittivity of the dielectric waveguide 20 may be slightly reduced. Therefore, for example, the depth G4 of the opening groove 22 may be set taking the wavelength shortening effect into consideration.

[0096] Furthermore, it is sufficient that at least one of the multiple opening grooves 22 be arranged on each side of the slot line 31, and the shape, position, number, etc., of each opening groove 22 are not particularly limited. Also, each opening groove 22 does not have to be symmetrical with respect to the slot line 31. In addition, the specific configuration of the multiple opening grooves 22 is not limited, and the opening grooves 22 may be provided as appropriate depending on the application of the antenna element 10, for example.

[0097] Figure 9 is a graph showing the angular distribution of antenna gain in an antenna element with multiple aperture grooves. Figure 9 shows the simulation results when using electromagnetic waves in the 24 GHz band, comparing the horizontal radiation characteristics of an antenna element 10 with multiple aperture grooves 22 (plot 48a) and an antenna element without aperture grooves 22 (plot 48b). The horizontal axis of the graph is the azimuth angle θ [deg] in the horizontal direction (XY plane), and the vertical axis is the absolute gain [dBi] relative to an isotropic antenna.

[0098] In Figure 9, an azimuth angle of 0° corresponds to the orientation of the central axis of the slot line 31 along the X direction (forward of the element). As shown in plot 48b, when multiple aperture grooves 22 are not provided, the absolute gain in the forward direction is low, indicating that electromagnetic waves 7 cannot be radiated forward. On the other hand, as shown in plot 48a, in the antenna element 10 with multiple aperture grooves 22, the absolute gain in the forward direction is improved, indicating that electromagnetic waves 7 can be radiated forward. Furthermore, it can be seen that an absolute gain equal to or greater than that in the forward direction is obtained in an angular range of ±60° or more. Thus, by providing multiple aperture grooves 22, it is possible to improve the radiation efficiency toward the forward direction (gain around an azimuth angle of 0°) and achieve a wide beam width.

[0099] [Dielectric Waveguide] Figure 10 is a schematic diagram illustrating an example of the operation of a dielectric waveguide. Figure 10 shows a cross-section of an antenna element 10 along the XZ plane. The part of the dielectric waveguide 20 connected to the left side in the figure is a conductor section 15 in which slot lines 31 etc. are formed, and the right end of the dielectric waveguide 20 is the antenna opening 23. Here, electromagnetic waves 7 propagating within the dielectric waveguide 20 and electromagnetic waves 7 radiated from the dielectric waveguide 20 are schematically shown.

[0100] The dielectric waveguide 20 is a rectangular waveguide provided in front of the slot line 31 and the multiple aperture grooves 22. The antenna element 10 propagates electromagnetic waves 7 along the dielectric waveguide 20 by utilizing reflection due to the difference in dielectric constant between free space and the dielectric. This improves the gain of the antenna. Below, the relationship between the length L_diel of the dielectric waveguide 20 and the radiation characteristics will be explained, with the distance in the X direction from the slot line 31 to the antenna aperture 23 being L_diel.

[0101] Figure 11 is a graph showing the relationship between the length of the dielectric waveguide and the VSWR. Figure 12 is a graph showing the relationship between the length of the dielectric waveguide and the antenna gain. Figures 11 and 12 are simulation results when using electromagnetic waves in the 24 GHz band.

[0102] Figure 11 plots the Voltage Standing Wave Ratio (VSWR) with L_diel [mm] on the horizontal axis. For example, a voltage standing wave ratio close to 1 indicates that the proportion of electromagnetic waves 7 reflected by the antenna aperture 23 is small, and the radiation characteristics are excellent. Figure 12 plots the absolute gain [dBi] with L_diel [mm] on the horizontal axis. A higher absolute gain value indicates a higher gain for the antenna.

[0103] In general, in dielectric waveguides, reflection of electromagnetic waves occurs at the radiating end face due to the difference in dielectric constant between the waveguide and free space. Furthermore, the degree of reflection at the radiating end face changes depending on the phase state of the electromagnetic wave, so there is a periodically optimal length for dielectric waveguides. This is a characteristic also seen in dielectric rod antennas, where the dielectric waveguide is installed in the radiating direction to improve gain.

[0104] In the dielectric waveguide 20 according to this embodiment, reflection at the front end face, which forms the antenna aperture 23, affects the radiation characteristics. If the reflection at the antenna aperture 23 is large, the proportion of electromagnetic waves 7 radiated from the surface of the dielectric waveguide 20, for example as shown in Figure 10, increases, which may lead to a decrease in gain. The proportion of such reflection changes periodically with the length L_diel of the dielectric waveguide 20.

[0105] As shown in Figure 11, the voltage standing wave ratio oscillates periodically with respect to L_diel. For example, the bottom portion where the voltage standing wave ratio approaches 1 appears at intervals of about 5 mm to 6 mm. The length of this oscillation period corresponds to approximately half the wavelength of the 24 GHz electromagnetic wave in the dielectric waveguide 20.

[0106] Furthermore, as shown in Figure 12, the absolute gain tends to increase with L_deel in the range from 0 mm to approximately 15 mm. A peak portion where the absolute gain is high occurs periodically with respect to L_deel. This period also corresponds to half the wavelength of the electromagnetic wave, as described above. The peak portion shown in Figure 12 roughly coincides with the bottom portion shown in Figure 11.

[0107] In this embodiment, the dielectric waveguide 20 is configured such that the length L_diel from the slot line 31 to the antenna aperture 23 is set to at least 1 / 4 of the wavelength of the electromagnetic wave used in the dielectric waveguide 20. This is the minimum length required for the dielectric waveguide 20 to function. In Figure 12, the length corresponding to the wavelength of the electromagnetic wave used is approximately 3 mm, but in the region where L_diel < 3 mm, sufficient gain is not obtained. Conversely, by setting L_diel to 3 mm or more, it is possible to significantly improve the gain.

[0108] More preferably, the length L_diel of the dielectric waveguide is set to an integer multiple of half the wavelength of the electromagnetic wave used in the dielectric waveguide. This length is such that the bottom portion of the voltage standing wave ratio appears in Figure 11 and the peak portion of the absolute gain appears in Figure 12. This makes it possible to sufficiently suppress the reflection of electromagnetic waves 7 at the antenna aperture 23 and to significantly improve the gain of the antenna element.

[0109] Furthermore, the gain improvement of the dielectric waveguide 20 slows down as its length increases. This means that the propagation mode HE 11 becomes dominant in the electromagnetic wave 7 propagating through the dielectric waveguide 20. For example, the results shown in Figure 12 show that in the antenna element 10, even if the dielectric waveguide 20 is made longer than 15 mm, no significant gain improvement effect is observed. For this reason, it is preferable to set the length L_diel of the dielectric waveguide 20 to 15 mm or less. This makes it possible to improve the gain without unnecessarily increasing the length of the dielectric waveguide 20.

[0110] [Antenna Array] The antenna element 10 according to this embodiment is an element that is easily arranged in an array due to the structure described above. Below, an antenna array configured using a plurality of antenna elements 10 will be described.

[0111] Figure 13 is a plan view showing an example of an antenna array using antenna elements. The antenna array 50 shown in Figure 13 has a structure in which two antenna elements 10a and 10b are arranged side by side. The basic structure of antenna elements 10a and 10b is the same as that of antenna element 10 described above.

[0112] Multiple antenna elements 10 constituting the antenna array 50 share an opening groove 22 between adjacent antenna elements 10. Here, three opening grooves 22 are provided between antenna elements 10a and 10b. These opening grooves 22 perform functions such as radiating electromagnetic waves 7 excited by the slot line 31 of antenna element 10a forward, and radiating electromagnetic waves 7 excited by the slot line 31 of antenna element 10b forward.

[0113] In this way, the multiple opening grooves 22 provided on the antenna element 10 can be shared with other antenna elements. This makes it possible to set the spacing between each antenna element 10 relatively freely, even when opening grooves 22 are provided on both sides of the slot line 31.

[0114] In the antenna array 50, the multiple antenna elements 10 are arranged such that the spacing between each slot line 31 is half the wavelength of the electromagnetic wave used in the dielectric waveguide 20. Here, the spacing between the central axes (distance in the Y direction) of each slot line 31 provided in antenna elements 10a and 10b is set to half the wavelength of the electromagnetic wave used. This enables an arrangement that maximizes the phase estimation angle in, for example, a MIMO radar module (see Figure 21, etc.). The spacing between the multiple antenna elements 10 may be set appropriately depending on the application of the antenna array 50.

[0115] Figure 14 is a graph showing the frequency characteristics of the VSWR in the antenna array. Figure 15 is a graph showing the frequency characteristics of the absolute gain in the antenna array. Figures 14 and 15 plot the simulation results for the antenna element 10 shown in Figure 1, etc., and the simulation results for the antenna elements 10a and 10b that constitute the antenna array 50 shown in Figure 13, respectively. The horizontal axis in Figures 14 and 15 is frequency [GHz]. Here, we focus on the operating bandwidth of the antenna element 10 in the region from 24 GHz to 24.25 GHz.

[0116] As shown in Figure 14, the VSWR characteristics of antenna elements 10a and 10b on the antenna array 50 are almost identical and generally match those of antenna element 10. Furthermore, the VSWR in the operating bandwidth is 2 or less. In other words, even with the antenna array 50, it is possible to suppress the reflection of electromagnetic waves 7 at the antenna aperture 23 to a low level.

[0117] Furthermore, as shown in Figure 15, the absolute gain of antenna elements 10a and 10b on the antenna array 50 is 4 dBi or more in the operating bandwidth, and no decrease in gain is observed compared to antenna element 10. For example, in applications such as radar, a gain of approximately 3 dBi to 4 dBi is required to detect an object 5 m away, and both the individual antenna element 10 and the antenna elements 10a and 10b on the antenna array 50 can be said to satisfy this condition. Thus, by using this technology, even when an antenna array 50 is configured, antenna elements 10a and 10b can achieve sufficiently high gain individually.

[0118] [Modified Antenna Element] Figure 16 is a plan view showing a modified antenna element. The antenna element 10c shown in Figure 16 is an example in which a conductor pattern is formed with a plurality of opening grooves 22 on the side in front of the slot line 31. In this case, if there is a region composed only of dielectric layer 12 in front of the slot line 31 (in the direction of electromagnetic wave radiation), that region functions as a dielectric waveguide 20.

[0119] In the antenna element 10c, the multiple opening grooves 22 are provided in a concave shape, with the slot line 31 as the bottom and surrounding the dielectric waveguide 20 in front of the slot line 31. With this configuration, it is possible to concentrate electromagnetic waves 7 in the dielectric waveguide 20 provided in front of the slot line 31, for example. In addition, the situation in which electromagnetic waves diffuse in the Y direction along the edge 24 of the conductor layer 13 is avoided, and isolation from other elements can be achieved.

[0120] Here, a conductor pattern including the opening grooves 22 is formed radially around the slot line 31. This makes it possible to widen the radial range, for example, in the azimuth direction. The opening grooves 22 formed in front of the slot line 31 are formed along the Y direction. Thus, the opening grooves 22 do not necessarily have to be formed along the line direction (X direction) of the slot line 31. For example, the opening grooves 22 may be provided so as to be inclined with respect to the X or Y direction. Furthermore, the depth of the opening grooves 22 is not limited, and as shown in Figure 16, multiple types of opening grooves 22 with different depths may be provided.

[0121] Figure 17 is a plan view showing another modified antenna element. The antenna element 10d shown in Figure 17 is an example in which the slot line 31 is longer compared to the antenna element 10 shown in Figure 1, etc. In this case, a longitudinal gap along the X direction is formed between the slot end 40a and the slot end 40b, and the slot line is formed by this gap.

[0122] Furthermore, notches 49 (areas indicated by dotted lines) are formed in the third conductor layer L3 and the fourth conductor layer L4 so as to overlap with the slot line 31 in a plan view. This suppresses unnecessary coupling between the slot line 31 and the lower conductor layer 13, making it possible to efficiently excite electromagnetic waves.

[0123] Furthermore, electromagnetic waves are basically excited at the front edge 24 of the slot line 31. For this reason, the multiple opening grooves 22 are each provided so as to open at the same position as the edge of the slot line 31 in the X direction. In the example shown in Figure 17, two opening grooves 22 are provided on each side of the slot line 31. Thus, the number of opening grooves 22 is not limited.

[0124] As described above, in the antenna element 10 according to this embodiment, a coplanar line 30 formed in the second conductor layer L2, which is a conductor layer for the transmission line, is connected to a slot line 31 that opens toward the dielectric waveguide 20 via a transmission line conversion unit 32. In addition, a plurality of opening grooves 22 formed in the conductor portion 15 are provided on both sides of the slot line 31 so as to open toward the dielectric waveguide 20. This makes it possible to efficiently propagate electromagnetic waves excited by the slot line 31 to the dielectric waveguide 20 and suppress beam bias. Furthermore, by sharing the opening grooves 22, for example, it becomes possible to arrange the slot lines 31 at short intervals. This makes it possible to realize a compact antenna element that is easy to array while improving the gain and beam width of a single unit.

[0125] Slot antennas, constructed from conductive patterns on a substrate, are small and easily implemented antennas. Known types include those that radiate electromagnetic waves from the surface of the substrate and those that radiate them from the edges of the substrate. Because individual slot antennas have low gain, methods have been proposed to improve gain by arranging multiple slot antennas in an array. Arraying is also expected to suppress beam width bias and other distortions.

[0126] However, it is expected that the size of the individual slot antennas will be large when they are arranged on a substrate. Therefore, when using them as independent antennas, the placement of the antennas will be limited by their size. For example, in cases where independent transmitting antennas or independent receiving antennas are arranged side by side, such as in MIMO radar, the spacing between each antenna is important, but if the above-mentioned array of slot antennas is used as a single antenna, it may be difficult to arrange the antennas at the required spacing.

[0127] In this embodiment, the coplanar line 30 and the slot line 31 are converted to each other using the line conversion unit 32. By using the slot line 31 in this way, it is possible to shorten the electromagnetic wave excitation section 42 in the antenna element 10, and the wavelength of the electromagnetic waves used in the dielectric waveguide 20 can be reduced to 1 / 4 or less. This makes it possible to reduce the element size in the X direction.

[0128] Furthermore, the electromagnetic waves excited by the slot lines 31 are propagated to the dielectric waveguide 20. This suppresses, for example, the radiation of electromagnetic waves from the surface of the dielectric waveguide 20, making it possible to efficiently propagate electromagnetic waves toward the antenna aperture 23, thereby improving the forward gain. In this way, the antenna element 10 can improve the gain without creating an array of slot antennas (slot lines 31).

[0129] Furthermore, opening grooves 22, composed of conductor sections 15 (conductor layer 13 and connecting conductor 14), are provided on both sides of the slot line 31. This makes it possible to concentrate electromagnetic waves into the dielectric waveguide 20 in front of the slot line 31, thereby significantly improving the gain of the antenna element 10. In addition, since each opening groove 22 functions as an electromagnetic wave radiation edge, beam width bias is suppressed, and the beam width can be widened.

[0130] In this way, the antenna element 10 takes advantage of the characteristics of a slot antenna, such as its small size and simple shape, while achieving high gain (for example, a gain of about 3 dBi-4 dBi) and a wide beam width with the antenna alone.

[0131] Furthermore, when an antenna array is constructed using the antenna elements 10, it is possible to share the opening grooves 22 between adjacent antenna elements 10. This allows multiple antenna elements 10 to be arranged at intervals of half the wavelength of the electromagnetic waves used in the dielectric waveguide 20, for example. For this reason, the antenna elements 10 can be suitably applied to MIMO radars and the like that radiate electromagnetic waves from the edge of the substrate.

[0132] <Second Embodiment> A second embodiment of the antenna module according to the present technology will be described. In the following description, parts that are similar to the configuration and operation of the antenna element 10 described in the above embodiment will be omitted or simplified.

[0133] Figure 18 is a perspective view showing an example configuration of an antenna module according to the second embodiment. Figure 19 is a plan view showing an example configuration of the antenna module shown in Figure 18. Figure 20 is a block diagram showing an example of a functional configuration of the antenna module.

[0134] The antenna module 100 is a thin circuit module equipped with a plurality of antenna elements 110. The plurality of antenna elements 110 use antennas having the same basic structure as the antenna element 10 described in the first embodiment.

[0135] The antenna module 100 is configured, for example, as a millimeter-wave radar module. A millimeter-wave radar module is a module that uses millimeter-wave electromagnetic waves to detect people and obstacles, and is beginning to become popular for automotive and home appliance applications. In addition to millimeter-wave radar modules, this technology may also be applied to other applications such as communication modules.

[0136] The dielectric multilayer substrate 111 constituting the antenna module 100 has a cross-sectional structure, for example, as described with reference to Figure 4, and is a substrate in which four conductor layers (L1 to L4) are stacked with three dielectric layers (M1 to M3) sandwiched in between. The dielectric multilayer substrate 111 as a whole is configured as a plate material that is long in the Y direction. Furthermore, a millimeter-wave radar IC 101 that outputs or detects millimeter-wave RF signals (millimeter-wave signals) is mounted on the first conductor layer L1, which is the upper surface layer of the antenna module 100.

[0137] As shown in Figure 20, the antenna module 100 is provided with a connector 102, a regulator 103, and an MCU (Micro Controller Unit) 104, in addition to the millimeter-wave radar IC 101 described above. Communication wiring and power wiring to external devices are connected to the connector 102. The regulator 103 and the MCU 104 are also connected to the connector 102. The regulator 103 is a power supply circuit that supplies power to the MCU 104 and the millimeter-wave radar IC 101 as needed. The MCU 104 is a calculation circuit that controls the millimeter-wave radar IC 101. The connector 102, regulator 103, and MCU 104 are appropriately mounted on the surface of the dielectric multilayer substrate 111 together with the millimeter-wave radar IC 101.

[0138] Returning to Figures 18 and 19, the antenna module 100 is provided with multiple transmission units 105 that connect multiple antenna elements 110 to the millimeter-wave radar IC 101. The transmission units 105 are lines that extend the coplanar lines 30 that constitute the power supply units 21 in the antenna elements 110. The coplanar lines 30 are provided in the second conductor layer L2 and are inner-layered lines. In Figure 19, each transmission unit 105 is schematically shown by a dotted line.

[0139] In this embodiment, the multiple antenna elements 110 include a transmitting antenna element TX1 and two receiving antenna elements RX1 and RX2. Therefore, the antenna module 100 functions as a MIMO radar antenna.

[0140] The transmitting antenna element TX1 is configured similarly to the antenna element 10c shown in Figure 16, for example. That is, in the transmitting antenna element TX1, a plurality of opening grooves 22 are arranged in a concave shape so as to surround the dielectric waveguide 20 provided in front of the slot line 31. The transmitting antenna element TX1 is connected to the transmitting terminal 106a via the transmission section 105a.

[0141] The two receiving antenna elements RX1 and RX2 are arranged adjacent to each other to form a receiving antenna array 150. The receiving antenna array 150 is configured similarly to the antenna array 50 shown in Figure 13, for example. Each receiving antenna element RX1 and RX2 is connected to the receiving terminals 106b and 106c, respectively, via the transmission units 105b and 105c.

[0142] In the antenna module 100, a dielectric waveguide 20a is provided for the transmitting antenna element TX1, and a common dielectric waveguide 20b is provided for the receiving antenna elements RX1 and RX2. Between the dielectric waveguides 20a and 20b, a recess is formed in which the entire dielectric layer is recessed in order to maintain isolation between the transmitting and receiving sides.

[0143] Figure 21 is a schematic diagram illustrating the arrangement of antenna elements in an antenna module. Here, the receiving antenna element RX1, the receiving antenna element RX2, and the transmitting antenna element TX1 are arranged in order from left to right.

[0144] In the antenna module 100 configured as a MIMO radar, electromagnetic waves transmitted from the transmitting antenna element TX1 are reflected by objects within the detection range and received by two receiving antenna elements RX1 and RX2. Now consider the reflection from an object located to the left and in front. In this case, as shown in Figure 2, an additional distance is required for the electromagnetic waves reflected by the object to reach the receiving antenna element RX2, compared to the distance required to reach the receiving antenna element RX1. Here, if the spacing between the receiving antenna elements RX1 and RX2 is d, and the angle of arrival of the electromagnetic waves reflected by the object is θ, then the additional distance is d × sin(θ).

[0145] This additional distance corresponds to the phase difference ω between the signals received by the receiving antenna elements RX1 and RX2. If the wavelength of the electromagnetic wave is λ, the phase difference ω is expressed as follows: ω = (2π / λ) × d × sin(θ) ... (1) Also, from equation (1), the angle of arrival θ is expressed as follows: θ = sin -1 (ωλ / 2πd) ...(2)

[0146] Here, the phase difference ω is uniquely determined only within the range -π ≤ ω ≤ π. Therefore, if ω = π, the maximum phase estimation angle θ_FOV can be expressed as follows: θ_FOV = ±sin -1 (λ / 2d) ... (3) From equation (3), it can be seen that when d = λ / 2, the maximum phase estimation angle θ_FOV = ±90°. In reality, the wavelength of electromagnetic waves is shortened due to the influence of the dielectric constant of the dielectric substrate, etc., so the maximum phase estimation angle is achieved by setting d to λ / 2 or less.

[0147] To perform angle estimation, at least two receiving antennas are required, but increasing the number of antennas improves the accuracy of angle estimation and enhances the angular resolution. The number of receiving antennas and transmitting antennas should be set to a number that can be handled by, for example, the millimeter-wave radar IC 101. In the example shown in Figure 21, one transmitting antenna element TX1 and two receiving antenna elements RX1 and RX2 are provided. In this case, to detect the arrival angle θ based on the phase difference ω, it is preferable to arrange the two receiving antenna elements RX1 and RX2 at an interval of half the wavelength.

[0148] For these reasons, the receiving antenna elements RX1 and RX2 are arranged such that the spacing d between their respective slot lines 31 is half the wavelength λ of the electromagnetic wave used in the dielectric waveguide 20. This makes it possible to set the maximum phase estimation angle θ_FOV to approximately ±90°, thereby maximizing the detection range as a radar.

[0149] Returning to Figures 18 and 19, in the receiving antenna array 150, similar to Figure 13, the opening groove 22 is shared between adjacent antenna elements 110 (receiving antenna elements RX1 and RX2). This allows for a high degree of freedom in setting the spacing between the receiving antenna elements RX1 and RX2. Therefore, the above-mentioned condition d = λ / 2 can be easily satisfied.

[0150] Figure 22 is a graph showing the horizontal radiation characteristics of the antenna module. Figure 23 is a graph showing the phase difference characteristics of the antenna module. Figures 22 and 23 are simulation results when using electromagnetic waves in the 24 GHz band.

[0151] Figure 22 plots the azimuth angle distribution of absolute gain for each of the transmitting antenna element TX1 and the two receiving antenna elements RX1 and RX2. In the antenna module 100, the azimuth angle range in which all antenna elements 110 (TX1, RX1, RX2) have an absolute gain of 3 dBi or more is approximately ±50°, indicating that it is possible to radiate electromagnetic waves over a wide area in the horizontal direction. Furthermore, each antenna element 110 achieves an absolute gain of 4 dBi or more individually, without the need to array the slot lines 31.

[0152] Figure 23 shows plot 48c, which represents the ideal value of the phase difference characteristics, and plot 48d, which represents the phase difference characteristics of the antenna module 100. The horizontal axis of the graph is the angle of arrival θ, and the vertical axis is the phase difference ω. For example, the closer plot 48d is to the ideal value (plot 48c), the higher the angle detection accuracy of the antenna module 100. Here, it can be seen that characteristics close to the ideal value are obtained in the range of ±60°. In other words, the antenna module 100 is capable of detecting the angle of arrival θ in the horizontal direction with high accuracy in the range of ±60°. This makes it possible to realize a high-precision radar module.

[0153] <Other Embodiments> This technology is not limited to the embodiments described above, and various other embodiments can be realized.

[0154] Figure 24 is a plan view showing an example of a conductor pattern of the power supply unit 21 according to another embodiment. The power supply unit 21a shown in Figure 24 is constructed without bending the conversion conductor 37 of the line conversion unit 32. In this case, the line conductor 34 of the coplanar line 30 is bent instead of the conversion conductor 37.

[0155] As shown in Figure 24B, the track conductor 34 extends from the inside of the second conductor layer L2 along the X direction and is bent along the Y direction just before the end edge 24. Also, as shown in Figure 24A, the upper side of the track conductor 34 is covered by the ground conductor 33a of the first conductor layer L1. This forms a coplanar track 30 with an L-shaped bend at the end. Here, an example of bending the coplanar track 30 at a right angle has been described, but for example, the coplanar track 30 may be bent more gently so that its end aligns with the end edge 24.

[0156] As shown in Figure 24B, a conversion conductor 37 extending in the Y direction is connected to the tip of the line conductor 34. A gap portion 38 is formed on the tip side of the conversion conductor 37. As shown in Figure 24A, a power supply opening 41 is formed in the first conductor layer L1 so as to overlap with the conversion conductor 37 and the gap portion 38. The slot line 31 is provided close to the connection point between the line conductor 34 and the conversion conductor 37.

[0157] Thus, in the power supply section 21a, the tip of the coplanar line 30 (line conductor 34) is formed along the edge 24, so there is no need to bend the conversion conductor 37. Even with this configuration, the path of the image current that bypasses the conversion conductor 37 becomes longer, making it possible to generate a phase difference in the electric field generated in the slot line 31.

[0158] Figure 25 is a plan view showing an example of a conductor pattern of the power supply unit 21 according to another embodiment. The power supply unit 21b shown in Figure 25 is configured as a T-shaped pattern in which the conversion conductor 37 of the line conversion unit 32 is branched in the Y direction.

[0159] As shown in Figure 25B, the conversion conductor 37 has a connection portion 55 that connects to the line conductor 34 of the coplanar line 30, and two branch portions 56a and 56b that branch off from the connection portion 55 in opposite directions along the Y direction. The branch portions 56a and 56b are provided in a direction that is to the right (lower side in the figure) and to the left (upper side in the figure) of the line conductor 34 when viewed in the forward X direction. A gap portion 38a is provided between the tip of branch portion 56a and the ground conductor 33b, and a gap portion 38b is provided between the tip of branch portion 56b and the ground conductor 33b. Furthermore, as shown in Figure 24A, a power supply opening 41 is formed in the first conductor layer L1 so as to overlap with the conversion conductor 37 and the two gap portions 38a and 38b.

[0160] The slot line 31 of the power supply section 21b is provided opposite the connection section 55 of the conversion conductor 37 (the branching position of branch section 56a and branch section 56b). For example, in the second conductor layer L2, a tab section 39a extending from the gap section 38a side and a tab section 39b extending from the gap section 38b side are formed along the end edge of the ground conductor 33b. Similarly, two tab sections 39a and 39b are formed in the first conductor layer L1. The slot line 31 of the power supply section 21b is formed between these tab sections 39a and 39b formed across the two layers.

[0161] Thus, the line conversion section 32 may be a conductor pattern that branches the line conductor 34 of the coplanar line 30 to the left and right. When branching the line conversion section 32, it is necessary to generate a phase difference in the electric field in the slot line 31, so it is necessary to make it an asymmetrical pattern. In this case, for example, the lengths of the branch sections 56a and 56b are set to different values. Alternatively, the lengths of the gap sections 38a and 38b may be set to different values. In addition, any structure that can create a phase difference in the electric field generated in the slot line 31 can be used as the line conversion section 32.

[0162] In the above embodiment, a configuration in which the power supply section is formed on the second conductor layer L2 has been described. However, the invention is not limited to this, and for example, the power supply section may be formed on the first conductor layer L1. In other words, the power supply section may be provided on the surface layer of the antenna element. In this case, for example, the power supply section can be provided on the surface layer of the antenna element by swapping the conductor pattern of the first conductor layer L1 shown in Figure 5A with the conductor pattern of the second conductor layer L2 shown in Figure 5B.

[0163] Furthermore, although the above embodiment described an example in which an antenna element is configured on a dielectric multilayer substrate in which multiple conductive layers are stacked, an antenna element may also be provided on a dielectric substrate in which a single conductive layer is formed. In this case, a conductive pattern of the second conductive layer L2, as shown in Figure 5B, is formed on the conductive layer on the dielectric substrate. Even in such a case, by applying this technology, it is possible to configure an antenna element that is compact and easy to array while improving the gain and beam width of a single unit.

[0164] It is also possible to combine at least two of the feature features of the present technology described above. In other words, the various feature features described in each embodiment may be combined arbitrarily, regardless of the specific embodiment. Furthermore, the various effects described above are merely examples and not limiting, and other effects may also be exhibited.

[0165] In this disclosure, "same," "equal," "orthogonal," etc., are concepts that include "substantially the same," "substantially equal," "substantially orthogonal," etc. For example, states that fall within a predetermined range (e.g., a range of ±10%) based on "exactly the same," "exactly equal," "exactly orthogonal," etc.

[0166] Furthermore, this technology can also be configured as follows: (1) An antenna element comprising: a dielectric substrate; a conductor portion including a transmission line conductor layer provided along the dielectric substrate; a dielectric waveguide with the end face of the dielectric substrate as an antenna opening; a power supply portion formed in the transmission line conductor layer and having a coplanar line, a slot line opening toward the dielectric waveguide, and a line conversion portion connecting the coplanar line and the slot line; and a plurality of opening grooves formed in the conductor portion and provided on both sides of the slot line so as to open toward the dielectric waveguide. (2) An antenna element according to (1), wherein the line conductor layer has a first grounding conductor, the coplanar line has a line conductor surrounded by the first grounding conductor, the line conversion section has a conversion conductor spaced apart from the first grounding conductor and connected to the line conductor, and a gap portion formed between the tip of the conversion conductor and the first grounding conductor, and the slot line is an antenna element in which the first grounding conductor is open facing the conversion conductor. (3) An antenna element according to (2), wherein the line conductor extends inward toward the edge of the first grounding conductor, the conversion conductor and the gap portion are provided along the edge of the first grounding conductor, and the first grounding conductor has a tab portion that forms its edge and extends to the opening of the slot line. (4) An antenna element according to (2) or (3), wherein the conversion conductor is a conductor obtained by bending the line conductor to one side along the edge of the first ground conductor, and the slot line is an antenna element provided facing the connection position between the line conductor and the conversion conductor. (5) An antenna element according to any one of (1) to (4), wherein the conductor portion includes the line conductor layer and an adjacent conductor layer provided on the same side of the dielectric substrate as the line conductor layer, and the adjacent conductor layer is an antenna element having a second ground conductor with an opening formed in a region that overlaps with the line conversion portion and the slot line in a plan view. (6) An antenna element according to (5), wherein the line conductor layer is an antenna element provided between the dielectric substrate and the adjacent conductor layer.(7) An antenna element according to any one of (1) to (6), wherein the conductor portion includes the line conductor layer and a plurality of opposing conductor layers provided on the dielectric substrate opposite to the line conductor layer, and the plurality of opposing conductor layers form a stepped portion that extends toward the antenna opening of the dielectric waveguide in a region that overlaps with the line conversion portion and the slot line in a plan view. (8) An antenna element according to any one of (1) to (7), wherein the conductor portion has a plurality of conductor layers including the line conductor layer and a plurality of connecting conductors that connect the plurality of conductor layers, and the plurality of opening grooves are each partitioned by a conductor wall through which the plurality of conductor layers are connected by the plurality of connecting conductors. (9) An antenna element according to any one of (1) to (8), wherein the plurality of opening grooves have a depth corresponding to the wavelength of the electromagnetic wave used in the dielectric waveguide. (10) An antenna element according to any one of (1) to (9), wherein the plurality of aperture grooves are provided parallel to the direction of the slot line. (11) An antenna element according to any one of (1) to (10), wherein the plurality of aperture grooves are provided in a concave shape so as to surround the dielectric waveguide in front of the slot line with the slot line as the bottom. (12) An antenna element according to any one of (1) to (11), wherein the dielectric waveguide is set so that the length from the slot line to the antenna aperture is 1 / 4 or more of the wavelength of the electromagnetic wave used in the dielectric waveguide. (13) An antenna element according to any one of (1) to (12), wherein the dielectric waveguide is set so that the length from the slot line to the antenna aperture is an integer multiple of 1 / 2 of the wavelength of the electromagnetic wave used in the dielectric waveguide.(14) An antenna module comprising: a dielectric substrate; a conductor portion including a line conductor layer provided along the dielectric substrate; a dielectric waveguide with the end face of the dielectric substrate as an antenna opening; a coplanar line formed in the line conductor layer; a power supply portion having a slot line formed in the line conductor layer and opening toward the dielectric waveguide, and a line conversion portion connecting the coplanar line and the slot line; and a plurality of antenna elements having a plurality of opening grooves formed in the conductor portion and provided on both sides of the slot line so as to open toward the dielectric waveguide. (15) An antenna module according to (14), wherein the plurality of antenna elements are arranged such that the spacing between each of the slot lines is half the wavelength of the electromagnetic wave used in the dielectric waveguide. (16) An antenna module according to (14) or (15), wherein the plurality of antenna elements share the opening grooves between adjacent antenna elements.

[0167] M1...Inner dielectric layer 10, 10a-10d, 110...Antenna element 12...Dielectric layer 13...Conductor layer 14...Connecting conductor 15...Conductor section 20, 20a, 20b...Dielectric waveguide 21, 21a, 21b...Feed section 22...Aperture groove 23...Antenna aperture 30...Coplanar line 31...Slot line 32...Line conversion section 100...Antenna module

Claims

1. An antenna element comprising: a dielectric substrate; a conductor portion including a line conductor layer provided along the dielectric substrate; a dielectric waveguide with the end face of the dielectric substrate as an antenna opening; a power supply portion formed in the line conductor layer and having a coplanar line, a slot line opening toward the dielectric waveguide, and a line conversion portion connecting the coplanar line and the slot line; and a plurality of opening grooves formed in the conductor portion and provided on both sides of the slot line so as to open toward the dielectric waveguide.

2. An antenna element according to claim 1, wherein the line conductor layer has a first ground conductor, the coplanar line has a line conductor surrounded by the first ground conductor, the line conversion section has a conversion conductor spaced apart from the first ground conductor and connected to the line conductor, and a gap formed between the tip of the conversion conductor and the first ground conductor, and the slot line is a line in which the first ground conductor is open facing the conversion conductor.

3. An antenna element according to claim 2, wherein the line conductor extends inward toward the end edge of the first ground conductor, the conversion conductor and the gap portion are provided along the end edge of the first ground conductor, and the first ground conductor has a tab portion that forms its end edge and extends to the opening of the slot line.

4. An antenna element according to claim 2, wherein the conversion conductor is a conductor obtained by bending the line conductor to one side along the edge of the first ground conductor, and the slot line is an antenna element provided facing the connection position between the line conductor and the conversion conductor.

5. An antenna element according to claim 1, wherein the conductor portion includes the line conductor layer and an adjacent conductor layer provided on the same side of the dielectric substrate as the line conductor layer, and the adjacent conductor layer has a second ground conductor with an opening formed in a region that overlaps with the line conversion portion and the slot line in a plan view.

6. An antenna element according to claim 5, wherein the line conductor layer is provided between the dielectric substrate and the adjacent conductor layer.

7. An antenna element according to claim 1, wherein the conductor portion includes the line conductor layer and a plurality of opposing conductor layers provided on the dielectric substrate opposite to the line conductor layer, and the plurality of opposing conductor layers form a stepped portion that extends toward the antenna opening of the dielectric waveguide in a region that overlaps with the line conversion portion and the slot line in a plan view.

8. An antenna element according to claim 1, wherein the conductor portion comprises a plurality of conductor layers including the line conductor layer and a plurality of connecting conductors connecting the plurality of conductor layers, and the plurality of opening grooves are each partitioned by a conductor wall through which the plurality of conductor layers are connected by the plurality of connecting conductors.

9. An antenna element according to claim 1, wherein the plurality of aperture grooves have a depth corresponding to the wavelength of the electromagnetic wave used in the dielectric waveguide.

10. An antenna element according to claim 1, wherein the plurality of aperture grooves are provided parallel to the line direction of the slot line.

11. An antenna element according to claim 1, wherein the plurality of aperture grooves are provided in a concave shape so as to surround the dielectric waveguide in front of the slot line with the slot line as the bottom.

12. An antenna element according to claim 1, wherein the dielectric waveguide is configured such that the length from the slot line to the antenna aperture is 1 / 4 or more of the wavelength of the electromagnetic wave used in the dielectric waveguide.

13. An antenna element according to claim 1, wherein the dielectric waveguide is configured such that the length from the slot line to the antenna aperture is an integer multiple of half the wavelength of the electromagnetic wave used in the dielectric waveguide.

14. An antenna module comprising: a dielectric substrate; a conductor portion including a transmission line conductor layer provided along the dielectric substrate; a dielectric waveguide with the end face of the dielectric substrate as an antenna opening; a coplanar transmission line formed in the transmission line conductor layer; a power supply portion having a slot transmission line formed in the transmission line conductor layer and opening toward the dielectric waveguide, and a transmission line conversion portion connecting the coplanar transmission line and the slot transmission line; and a plurality of antenna elements having a plurality of opening grooves formed in the conductor portion and provided on both sides of the slot transmission line so as to open toward the dielectric waveguide.

15. An antenna module according to claim 14, wherein the plurality of antenna elements are arranged such that the spacing between each of the slot lines is half the wavelength of the electromagnetic wave used in the dielectric waveguide.

16. An antenna module according to claim 14, wherein the plurality of antenna elements share the aperture grooves between adjacent antenna elements.

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