Antenna equipment and radar module

Abstract

The objectives are ease of manufacturing, broad bandwidth, and obtaining good antenna characteristics even when the substrate thickness is relatively large relative to the wavelength. [Solution] The antenna 1a comprises a substrate 10 as a multilayer substrate. The antenna 1a comprises a feed line portion 22, a conductor layer 30 as a GND layer, and a fence-shaped conductor F1. The feed line portion 22 is located on one first main surface of the substrate 10. The conductor layer 30 is a first inner layer of the multilayer substrate and has a slot 32 located opposite and intersecting the feed line portion 22. The fence-shaped conductor F1 has a plurality of vias V1 and conductor layers 40, 50, 60, 70 connected to each other via the plurality of vias V1, and surrounds the slot 32.

Description

Technical Field

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

Background Art

[0002] In recent years, radar modules (radar sensors) for indoor installation assuming use cases such as vital sensing and human presence sensors have begun to spread. Antennas provided in radar modules for indoor installation are required to be broadband, small-sized, and inexpensive.

[0003] Also, a general method of simply configuring a patch antenna for a radar module with a substrate is known. For example, by using a feeding structure by microstrip, a patch antenna having a two-layer structure of GND (Ground), a patch element, and a feeding line without using vias in the feeding structure is known (see Non-Patent Document 1).

[0004] However, it has been difficult to give the patch element in the above two-layer patch antenna a sufficient bandwidth. Therefore, a patch antenna having a parasitic element (non-fed element) arranged in the vicinity of the patch element and realizing broadband is known (see Non-Patent Document 1 and Patent Document 1).

[0005] However, the patch antenna having the above parasitic element requires the dimension in the width direction of the patch element to be a certain value or more. For this reason, when trying to form an array of parasitic elements with a pitch of about half wavelength in the width direction, the parasitic elements may interfere with each other and may not function properly. Therefore, a stacked patch antenna is known as a method of achieving broadband while keeping the occupied area of the antenna in a plan view small (see Non-Patent Document 1). The stacked patch antenna has a structure in which a plurality of patch elements are stacked in the stacking direction.

[0006] However, the above-mentioned stacked patch antenna required blind vias to drive the driven patch (the fed patch element), making substrate manufacturing difficult. Therefore, a slot-fed patch antenna is known as a feeding method that does not use vias (see Non-Patent Literature 1). The slot-fed patch antenna has a microstrip on one main surface of the substrate and a patch element on the other main surface, with a GND plane having a slot pattern in the inner layer. The slot-fed patch antenna feeds power to the patch element by feeding power from the microstrip to the slot pattern, utilizing the electromagnetic coupling between the slot pattern and the patch element. As a result, the slot-fed patch antenna can be fed without vias, and it is relatively easier to secure bandwidth compared to the above-mentioned two-layer antenna. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-93711 [Non-patent literature]

[0008] [Non-Patent Document 1] Jean-Francois Zurcher,Fred E. Gardiol,"BROADBAND PATCH ANTENNAS",Artech House Publishers,February 1st 1995 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, in slot-fed patch antennas, the patch element is configured on the front surface of the substrate, and the feed line is configured on the back surface. Power is fed by electromagnetic coupling from the slot pattern opening on the back surface to the patch element on the front surface. Therefore, when the substrate thickness is relatively thick relative to the wavelength, for example, when using an FR4 (Flame Retardant Type 4) substrate (dielectric constant 4.4) with a substrate thickness of about 1 mm for an antenna operating at 60 GHz (wavelength 5 mm), the distance between the patch element and the slot is large relative to the wavelength, making power feeding difficult and potentially resulting in insufficient performance.

[0010] The objective of the present invention is to provide an antenna that is easy to manufacture, has a wide bandwidth, and exhibits good antenna characteristics even when the substrate thickness is relatively large relative to the wavelength. [Means for solving the problem]

[0011] To solve the above problems, the antenna of the present invention is An antenna comprising a multilayer substrate, A power supply line portion is arranged on one of the first main surfaces of the multilayer substrate, The first inner layer of the multilayer substrate, having a GND layer with a slot positioned opposite and intersecting the power supply line portion, The device comprises a fence-shaped conductor surrounding the slot, having a plurality of vias and a conductor layer connected to each other via the plurality of vias. [Effects of the Invention]

[0012] According to the present invention, manufacturing is easy, a wide bandwidth can be achieved, and good antenna characteristics can be obtained even when the substrate thickness is relatively large relative to the wavelength. [Brief explanation of the drawing]

[0013] [Figure 1] This is a partially transparent perspective view showing an antenna according to the first embodiment of the present invention. [Figure 2] This is a perspective view showing the antenna device. [Figure 3]It is a schematic side view showing an antenna. [Figure 4] It is a plan view showing the lowermost conductor layer. [Figure 5] It is a plan view showing the second conductor layer from the lowermost layer. [Figure 6] It is a plan view showing the third conductor layer from the lowermost layer. [Figure 7] It is a plan view showing the fourth, fifth, and sixth conductor layers from the lowermost layer. [Figure 8] It is a diagram showing the frequency characteristics of the return loss of the antenna device. [Figure 9] It is a diagram showing the frequency characteristics of the radiation efficiency of the antenna device. [Figure 10] It is a plan view showing the radar module of the second embodiment. [Figure 11] It is a diagram showing the horizontal angle characteristics of the gain of the antenna device. [Figure 12] It is a diagram showing the vertical angle characteristics of the gain of the antenna device.

Mode for Carrying Out the Invention

[0014] Hereinafter, the first and second embodiments of the present invention will be described in detail in order with reference to the accompanying drawings. However, the scope of the invention is not limited to the illustrated examples.

[0015] (First Embodiment) Referring to FIGS. 1 to 9, the first embodiment of the present invention will be described. First, referring to FIGS. 1 to 7, the device configuration of this embodiment will be described. FIG. 1 is a partially transparent perspective view showing the antenna 1a of this embodiment. FIG. 2 is a perspective view showing the antenna devices 2a and 2b. FIG. 3 is a schematic side view showing the antenna 1a. FIG. 4 is a plan view showing the conductor layer 20. FIG. 5 is a plan view showing the conductor layer 30. FIG. 6 is a plan view showing the conductor layer 40. FIG. 7 is a plan view showing the conductor layers 50, 60, and 70.

[0016] As shown in Figure 1, the antenna 1a in this embodiment is an antenna used for a radar module 3 (Figure 10), which will be described later. The radar module 3 is a radar sensor module, which is installed, for example, indoors in a facility, and transmits and receives millimeter waves to detect the distance and angle (position information) and speed of people inside the room. Antenna 1a is, for example, an antenna for transmitting and receiving radio waves in the 60 GHz band (57-64 GHz) allocated to Japan as millimeter waves for the radar module. However, the frequency band of antenna 1a is not limited to the 60 GHz band. Also, in Figure 1, the three-dimensional XYZ axes are taken with antenna 1a as the reference, and the same applies to the other figures.

[0017] As shown in Figure 2, antenna 1a is actually used in the radar module 3 as an antenna device 2a, which includes antennas 1a and 1b arranged in an array. Antenna device 2b includes antennas 1c and 1d arranged in an array. Antennas 1b, 1c, and 1d have the same configuration as antenna 1a, but differ in the orientation and arrangement of each component. For this reason, antenna 1a will be described primarily. Note that antennas 1a to 1d can each be configured as an antenna device individually. This antenna device can be used, for example, for transmitting / receiving radio waves from the radar module.

[0018] As shown in Figure 1, antenna 1a is a multilayer substrate antenna comprising a substrate 10. Substrate 10 is a laminated substrate having a base material 10A, a conductor 10B, and vias V1. Base material 10A has base material layers 11, 12, 13, 14, and 15. Conductor 10B has conductor layers 20, 30, 40, 50, 60, and 70. In substrate 10, the conductor layer 20, base material layer 11, conductor layer 30, base material layer 12, conductor layer 40, base material layer 13, conductor layer 50, base material layer 14, conductor layer 60, base material layer 15, and conductor layer 70 are stacked in order from the -X direction to the +X direction.

[0019] Base layers 11, 13, and 15 are core layers of an insulator (dielectric), and are composed of, for example, FR4. Base layers 12 and 14 are adhesive layers of an insulator (dielectric), and have a structure in which, for example, a prepreg has been cured. A prepreg is an intermediate substrate of a composite material in which reinforcing fibers are pre-impregnated with a resin matrix. Base layers 11 to 15 shall be made of a material with a relative permittivity εr = 4.4, for example. However, the composition of base layers 11 to 15 is not limited to the above configuration. For example, base layers 11 to 15 may all be made of FR4.

[0020] In antenna 1a, the conductor layer 20 is made of a conductor such as copper foil and is formed on the lower side (-X direction side) of the base layer 11. The conductor layer 20 has microstrip lines formed on it that are electrically connected to the radar IC (Integrated Circuit) 4 (Figure 10), which will be described later. As shown in Figures 3 and 4, the conductor layer 20 has a GND section 21 and a feed line section 22 formed in the hole M1. The feed line section 22 has a line section 221, a branch section 222, and a feed line 223.

[0021] The GND section 21 is a conductor section that is grounded by being connected to the GND section 31, which is the reference conductor of the signal line, via via V1. Via V1 is a via pad of a through-hole via made of conductor material that penetrates from conductor layer 20 to conductor layer 70, and is electrically connected to and grounded to the GND section 21.

[0022] The line section 221 is a microstrip line connected to the radar IC 4 side, through which the antenna current flows. The hole M1 is a rectangular section without a conductor. The branch section 222 is a λ / 4 transformer for impedance matching. One end of the branch section 222 is connected to the line section 221, and the other end is branched into two and connected to the feed line 223. The feed line 223 is a fork-shaped open stub composed of microstrip lines. One end of the feed line 223 is connected to the branch section 222, and the tip is open and extends in the +Z direction.

[0023] In antenna 1a, the conductor layer 30 is made of a conductor such as copper foil and is formed on the upper side (+X direction side) of the base layer 11. As shown in Figures 3 and 5, the conductor layer 30 has a GND section 31 and a slot 32. The GND section 31 is a grounded conductor section to which via V1 is electrically connected. The via V1 of the GND section 31 is arranged to surround the slot 32 from the side. The slot 32 is formed in the XY plane at a position opposite the feed line 223 on the GND section 31, and its longitudinal direction extends in the Y axis direction. Viewed from the +X axis direction, the slot 32 intersects with the feed line section 22. The dotted line in Figure 4 corresponds to the slot 32.

[0024] Viewed from the +X direction, the power supply line section 22 is branched symmetrically from the center of the slot by a branching section 222 just before it intersects the slot 32. By adjusting the distance between the two branched power supply line sections 22, the position where it crosses the slot 32 can be adjusted while maintaining the symmetry of the power supply structure. In this way, the electromagnetic coupling between the slot 32 and the power supply line section 22 can be adjusted without changing the size of the slot 32. This makes it possible to independently adjust the degree of coupling, simplifying the design. If the power supply line section 22 did not have a fork-shaped branching structure and consisted of a single power supply line passing through the center of the slot, the degree of coupling would have to be adjusted by the size of the slot 32, and in that case the resonant frequency would change along with the degree of coupling, making the adjustment somewhat difficult.

[0025] In antenna 1a, the conductor layer 40 is made of a conductor such as copper foil and is formed on the lower side (-X direction side) of the base material layer 13. As shown in Figures 3 and 6, the conductor layer 40 has a GND portion 41 and a patch element 42.

[0026] The GND section 41 is a grounded conductor, to which via V1 is electrically connected. The patch element 42 is a rectangular antenna element of conductor formed within the hole M2. The hole M2 is a rectangular area without a conductor, and is approximately rectangular in size, about λ / 2 square. λ is the wavelength of the radio waves to be transmitted and received. In this embodiment, for example, since the outer perimeter of the via V1 row is a square of λ / 2 square, the conductor layer 40 is designed with dimensions such that the hole M2 is strictly speaking slightly smaller than λ / 2. When viewed from the +X side, the hole M2 is the same size as the hole M1 and is located in the same YZ plane position. The via V1 of the GND section 41 is arranged to surround the hole M2.

[0027] Unlike conventional patch elements, which are formed on the surface, the patch element 42 is formed in the inner layer. As a result, the wavelength shortening due to the dielectric of the formed substrate layer 13 (and substrate layer 12) is strongly at work, resulting in a significantly smaller size than conventional patch elements. The patch element 42 electromagnetically couples with the slot 32 and functions as a resonator.

[0028] In antenna 1a, the conductor layer 50 is made of a conductor such as copper foil and is formed on the upper side (+X direction side) of the base material layer 13. As shown in Figures 3 and 7, the conductor layer 50 has a GND portion 51.

[0029] The GND section 51 is a grounded conductor, to which via V1 is electrically connected, forming a hole M3. The hole M3 is a rectangular section without a conductor, approximately rectangular in size with a square area of ​​about λ / 2. Viewed from the +X side, hole M3 is the same size as holes M1 and M2 and is located in the same YZ plane position. Via V1 of the GND section 51 is positioned to surround hole M3 from the side.

[0030] In antenna 1a, the conductor layer 60 is made of a conductor such as copper foil and is formed on the lower side (-X direction side) of the base layer 15. As shown in Figures 3 and 7, the conductor layer 60 has a GND portion 61. The GND portion 61 is a grounded conductor portion to which vias V1 are electrically connected and holes M3 are formed. The vias V1 of the GND portion 61 are arranged to surround the holes M3 from the side.

[0031] In antenna 1a, the conductor layer 70 is made of a conductor such as copper foil and is formed on the upper side (+X direction side) of the base material layer 15. As shown in Figures 3 and 7, the conductor layer 70 has a GND portion 71. The GND portion 71 is a grounded conductor portion to which vias V1 are electrically connected and holes M3 are formed. The vias V1 of the GND portion 71 are arranged to surround the holes M3 from the side.

[0032] In antenna 1a, the GND sections 41, 51, 61, 71 and via V1 form a fence-like conductor F1 that acts as a GND conductor, surrounding the slot 32 and patch element 42 from the side. The space S1 is a space (cavity) surrounded by the conductor layer 30 and the fence-like conductor F1. The space S1 is a roughly rectangular three-dimensional spatial region containing the base material layers 12-15 and the patch element 42. As shown in Figures 1 and 3, the portion of the conductor layer 30 surrounded by the fence-like conductor F1 is defined as the cavity conductor C1. The patch element 42 has the function of strengthening the electromagnetic coupling between the slot 32, which is a box-shaped resonator structure with one of its six faces (composed of the cavity conductor C1 and the fence-like conductor F1) open, and the feed line section 22. As shown in Figures 1 and 3, this box-shaped resonator structure is defined as the cavity resonator C0. The hole M0 is an open hole on the upper surface (+X direction) side of the cavity resonator C0, and corresponds to the hole M3 of the conductor layer 70.

[0033] As shown in Figure 1, the length of the hole M0 in the Z-axis direction is denoted as length L. The length of the hole M0 in the Y-axis direction is denoted as width W. The distance between the cavity conductor C1 (GND section 31) and the GND section 71 is denoted as distance H. In this way, the frequency of the cavity resonator C0 can be finely adjusted by widening or narrowing the width of the hole M0 without changing the thickness of the substrate or the position of the via V1, and this adjustment is actually performed in this manner. However, it is assumed that the Z-axis direction length and Y-axis direction length of the outer circumference of via V1 are approximately the same size as the length L and width W of the hole M0. The length L and width W of the hole M0 are configured to be slightly smaller than the Z-axis direction length and Y-axis direction length created by the fence-shaped conductor F1. Antenna 1a is designed such that the width W [m] and distance H [m] satisfy the following equation (1).

number

[0034] Antenna 1a is appropriately designed to satisfy equation (1). This causes the cavity resonator C0 to produce a resonant mode similar to that of a waveguide cavity resonator at the desired frequency, and to function as a radio wave radiator.

[0035] As shown in Figures 2 to 7, the antenna devices 2a and 2b integrally include antennas 1a, 1b, 1c, and 1d, and a shield case 80. Antennas 1b, 1c, and 1d have the same configuration as antenna 1a. However, antenna 1b is adjacent to the -Z side of antenna 1a, and is positioned so that the extending direction of the tip of the feed line 223 is in the +Z direction. Antenna 1c is adjacent to the +Y side of antenna 1a, and is positioned so that the extending direction of the tip of the feed line 223 is in the +Z direction. Antenna 1d is adjacent to the -Z side of antenna 1c, and is positioned so that the tip of the feed line 223 is in the +Z direction.

[0036] As shown in Figure 2, the shield case 80 is made of a conductor such as metal and has an opening on one side. Conductors are arranged to cover the entire surface of the base layer 11 and the conductor layer 20 from the -X direction, and are connected to 20 at the corners and other ends (partially open on the sides). The shield case 80 is electrically connected to the GND section 21 and grounded. The shield case 80 may also be configured to cover the entire surface of the base layer 11 and the conductor layer 20 from the -X direction in each of the antennas 1a, 1b, 1c, and 1d, as well as in the radar module 3 described later. The shield case 80 may also be configured to cover at least the areas corresponding to the feed line section 22, the slot 32, and the patch element 42 from the -X direction.

[0037] As shown in Figure 4, in the antenna device 2a, the conductor layer 20 has a line section 25 and a power distribution section 26 for connecting the feed line section 22 of antenna 1a and the feed line section 22 of antenna 1b. The line section 25 is, for example, a microstrip line connected to the radar IC 4, which will be described later, and through which antenna current flows. One end of the line section 25 is connected to the radar IC 4, and the other end is connected to the power distribution section 26. The power distribution section 26 is a T-junction distributor that distributes the power input from the line section 25 to the feed line section 22 of antenna 1a and the feed line section 22 of antenna 1b. The power distribution section 26 branches the line section 25 into two, with one branched end connected to the feed line section 22 of antenna 1a and the other branched end connected to the feed line section 22 of antenna 1b. Similarly, in the antenna device 2b, the conductor layer 20 has a line section 25 and a power distribution section 26 for connecting the feed line section 22 of antenna 1c and the feed line section 22 of antenna 1d.

[0038] Next, the antenna characteristics of antenna device 2a will be explained with reference to Figures 8 and 9. Figure 8 shows the frequency characteristics of the return loss of antenna device 2a. Figure 9 shows the frequency characteristics of the radiation efficiency of antenna device 2a.

[0039] Here, the radio waves of the radar module 3 are in the 60 GHz band, and the relative permittivity εr of the substrate 10 is 4.4. In the antenna device 2a, the thicknesses (length in the X-axis direction) of the base material layers 11, 12, 13, 14, and 15 are 0.1 [mm], 0.15 [mm], 0.3 [mm], 0.15 [mm], and 0.1 [mm], respectively. Similarly, the thicknesses (length in the X-axis direction) of the conductor layers 20, 30, 40, 50, 60, and 70 are 0.035 [mm], 0.012 [mm], 0.012 [mm], 0.012 [mm], 0.012 [mm], and 0.035 [mm], respectively. In this case, the total thickness (substrate thickness) of the conductor layer 20, base material layer 11...conductor layer 70 is 0.918 [mm]. Note that Figure 3 is a schematic diagram, and some parts do not precisely correspond to the thickness of each component described above.

[0040] As shown in Figure 8, the return loss [dB] of antenna device 2a with respect to frequency [GHz] was simulated under the above conditions. In the 60 GHz band (approximately 57 to 64 [GHz] on the graph), antenna 1a has a small return loss and is in resonance.

[0041] Furthermore, as shown in Figure 9, the radiation efficiency [dB] of antenna device 2a with respect to frequency [GHz] was simulated under the above conditions. Antenna 1a achieved high radiation efficiency in the 60 GHz band (approximately 57 to 64 [GHz] on the graph). The results in Figures 8 and 9 show that even when the substrate thickness of antenna device 2a is relatively large at 0.918 [mm] with respect to wavelength λ, good antenna characteristics (return loss, radiation efficiency) can be obtained with a simple manufacturing method using only through-hole vias.

[0042] As described above, according to this embodiment, the antenna 1a has a substrate 10 as a multilayer substrate. The antenna 1a comprises a feed line section 22, a conductor layer 30 as a GND layer, and a fence-shaped conductor F1. The feed line section 22 is located on one of the first main surfaces of the substrate 10 in the -X direction. The conductor layer 30 is a first inner layer of the substrate 10 and has a slot 32 that is located opposite and intersecting the feed line section 22. The fence-shaped conductor F1 has a plurality of vias V1 and conductor layers 40, 50, 60, 70 that are connected to each other via the plurality of vias V1, and surrounds the slot 32. The plurality of vias V1 are through-hole vias.

[0043] Therefore, in antenna 1a, the fence-shaped conductor F1 fed from the feed line section 22 via the slot 32 functions as a waveguide antenna. Thus, a broadband antenna can be constructed, and good antenna characteristics can be obtained even when the substrate thickness is relatively large relative to the wavelength. Furthermore, since it can be constructed without using blind vias such as laser vias, antenna 1a can be realized with a simple structure, and its manufacturing can be easily done.

[0044] The conductor layer 30 has a cavity conductor C1, which is the portion surrounded by a fence-shaped conductor F1. The cavity resonator C0 having the cavity conductor C1 and the fence-shaped conductor F1, and the open hole M0 of the cavity resonator C0 satisfy equation (1). Here, W is the length of the hole M0 in the direction parallel to the longitudinal direction of the slot 32. H is the distance from the cavity conductor C1 to the conductor layer 70 as the second main surface on the other +X side of the substrate 10. f is the lower limit of the operating frequency of antenna 1a. Therefore, the cavity resonator C0 satisfies the dimensions necessary for it to resonate as a waveguide cavity resonator with one side open. Thus, the cavity resonator C0 allows antenna 1a to function clearly as an antenna, making it possible to realize a wider bandwidth antenna.

[0045] Antenna 1a includes a patch element 42. The patch element 42 is located on the second inner layer of the multilayer substrate, which is positioned on the +X side of the first inner layer, the conductor layer 30, and is positioned opposite the slot 32. As a result of the addition of the patch element 42, the slot 32 and the fence-shaped conductor F1 become electromagnetically coupled via the patch element 42. Therefore, the electromagnetic coupling is strengthened, and a wider bandwidth antenna characteristic can be achieved.

[0046] The substrate 10 includes FR4. This allows the antenna 1a to be made inexpensively.

[0047] The antenna device 2a(2b) is equipped with antennas 1a, 1b(1c,1d) on the substrate 10. The antenna device 2a(2b) is positioned on the first main surface in the -X direction and includes a power distribution unit 26 that supplies power to antennas 1a, 1b(1c,1d). Therefore, since antennas 1a, 1b(1c,1d) are arranged in an array, a higher gain can be achieved.

[0048] The antenna devices 2a and 2b are equipped with a shield case 80 that covers the feed line section 22 and the power distribution section 26 and serves as a grounded shield. Therefore, the antenna devices 2a and 2b are less susceptible to the influence of the surrounding installation environment on the antenna surface of the first main surface on the +X direction side and the second main surface on the opposite -X direction side.

[0049] (Second Embodiment) A second embodiment of the present invention will be described with reference to Figures 10 to 12. Figure 10 is a plan view showing the radar module 3 of this embodiment. Figure 11 is a diagram showing the horizontal angle characteristics of the gain of the antenna device 2a. Figure 12 is a diagram showing the vertical angle characteristics of the gain of the antenna device 2a.

[0050] Figure 10 shows the planar configuration of the radar module 3 of this embodiment. However, the XYZ axes in Figure 10 differ from those in Figure 4 when the antenna 1a is used as the reference. Also, for the antenna, the layers above the conductor layer 20 (-X direction) are omitted from the illustration. The radar module 3 includes antenna devices 2a, 2b, 2c, 2d, 2e and a radar IC 4. Antenna devices 2a and 2b are antenna devices for transmitting radio waves for the radar. Antenna devices 2c, 2d, and 2e are antenna devices for receiving radio waves for the radar.

[0051] Antenna devices 2a and 2b are arranged at intervals of λ / 2 in the Y-axis direction. Antenna devices 2c, 2d, and 2e are arranged at intervals of λ in the Y-axis direction. Furthermore, antenna devices 2a to 2e are arranged so that their polarization planes are equal. Radar IC 4 generates the radar transmission signal and outputs this transmission signal to antenna devices 2a and 2b to radiate radio waves. Radar IC 4 also receives the radar reception signal received from antenna devices 2c, 2d, and 2e as input and processes the received signal.

[0052] With this configuration, the radar module 3 can form a virtual array equivalent to an antenna device consisting of a single transmitting antenna and six receiving antennas arranged at λ / 2 intervals. This configuration allows for improved angular resolution with a small number of elements. Furthermore, since the spacing between elements in the receiving antenna is only λ, interference between adjacent elements in the feed line section 22 is prevented.

[0053] Here, the manufacturing method of the radar module 3 will be briefly explained. First, conductive layers 20 and 30 are formed on the base layer 11, conductive layers 40 and 50 are formed on the base layer 13, and conductive layers 60 and 70 are formed on the base layer 15. Then, the base layer 11 on which conductive layers 20 and 30 are formed and the base layer 13 on which conductive layers 40 and 50 are formed are bonded and cured with a prepreg base layer 12. Then, the base layers 11 to 13 on which conductive layers 20 to 50 are formed and the base layer 15 on which conductive layers 60 and 70 are formed are bonded and cured with a prepreg base layer 14. Finally, vias V1 are formed on the base layers 11 to 15 on which conductive layers 20 to 70 are formed, the radar IC 4 is mounted, and the shield case 80 is connected.

[0054] Referring to Figures 11 and 12, the antenna characteristics of the antenna device 2a of the radar module 3 will be explained. Here, the radar module 3 is assumed to be installed, for example, at a high position indoors, and to be positioned so that the X-axis and Y-axis directions are horizontal. Therefore, the XY plane is a horizontal plane parallel to the ground. The XZ plane is a vertical plane perpendicular to the horizontal plane.

[0055] In antenna device 2a, the length of the transmission line 221 from the power distribution unit 26 to the branching unit 222 is not equal for antennas 1a and 1b. The transmission line 221 of antenna 1a is about 400 μm longer than the transmission line 221 of antenna 1b. As a result, the phase of the signal fed to antenna 1a lags behind the phase of the signal fed to antenna 1b by about 40 to 60 degrees. Therefore, antenna device 2a can configure an antenna beam that is tilted slightly downward (-Z direction) from the horizontal (XY plane).

[0056] As shown in Figure 11, the gain [dBi] of antenna device 2a with respect to the horizontal angle [° (degrees)] in the horizontal plane (XY plane) was simulated. A horizontal angle of 0 [°] corresponds to the +X direction. The gain of antenna device 2a is symmetrical with respect to the horizontal angle and exhibits a good waveform pattern with little ripple.

[0057] As shown in Figure 12, the gain [dBi] of antenna device 2a was simulated with respect to the vertical angle [°] of the vertical plane (XZ plane). A vertical angle of 0 [°] corresponds to the +Z direction. The gain of antenna device 2a takes a large value in the downward direction (-Z direction) relative to the vertical angle in the horizontal direction (90 [°]), showing a good tilt pattern.

[0058] Similarly, in antenna device 2b, the transmission line 221 of antenna 1c is approximately 400 μm longer than the transmission line 221 of antenna 1d. Likewise, in each of antenna devices 2c to 2e, the transmission line 221 of the antenna on the +Z direction side is approximately 400 μm longer than the transmission line 221 of the antenna on the -Z direction side. As a result, antenna devices 2b to 2e can each configure an antenna beam tilted slightly downward (-Z direction) from the horizontal (XY plane).

[0059] As described above, according to this embodiment, the radar module 3 comprises multiple antennas of antenna devices 2a to 2e and a radar IC 4 as a circuit section. The radar IC 4 receives the radar transmission signals from the multiple antennas and processes the radar reception signals. Therefore, the radar module 3 can be easily manufactured, has a wide bandwidth, and can obtain good antenna characteristics even when the substrate thickness is relatively large relative to the wavelength.

[0060] The antennas 1a, 1b (1c, 1d, etc.) of the antenna device 2a (2b, etc.) have a line section 221 with a line length set so that the phase difference between adjacent antennas is 40 to 60 degrees. Therefore, when the radar module 3 is installed in a high position indoors, it is possible to achieve an antenna beam with a slightly downward tilt that is suitable for illuminating the interior of the room.

[0061] The above embodiments and descriptions are merely examples of antenna devices and radar modules according to the present invention, and are not limited thereto.

[0062] For example, in the above embodiment, the antennas 1a to 1d and antenna devices 2a to 2e are configured to be applied to a radar module, but the configuration is not limited to this. The antennas 1a to 1d and antenna devices 2a to 2e may also be configured to be applied to equipment for purposes other than radar.

[0063] Furthermore, the detailed configuration and operation of the radar module 3 in the above embodiment can also be modified as appropriate without departing from the spirit of the present invention. [Explanation of Symbols]

[0064] 3. Radar Module 2a, 2b, 2c, 2d, 2e Antenna equipment 1a, 1b, 1c, 1d antennas 10 circuit boards 10A base material 11,12,13,14,15 Base material layer 10B conductor 20, 30, 40, 50, 60, 70 Conductor layers 21,31,41,51,61,71 GND section 22 Power line section 221,25 Track section 222 Branch section 223 Feed line 26 Power distribution section 32 slots 42 patch elements C0 Cavity Resonator M0,M1,M2,M3 Hole C1 Cavity conductor F1 Fence-shaped conductor S1 space 4 Radar IC

Claims

1. An antenna device comprising a multilayer substrate, A power supply line portion is arranged on one of the first main surfaces of the multilayer substrate, The first inner layer of the multilayer substrate is a GND layer having a slot positioned opposite and intersecting the power supply line portion, An antenna device comprising a fence-shaped conductor surrounding the slot, having a plurality of vias and a conductor layer connected to each other via the plurality of vias.

2. The antenna device according to claim 1, wherein the plurality of vias are through-hole vias.

3. The GND layer has a cavity conductor which is the portion surrounded by the fence-shaped conductor, The antenna device according to claim 1, wherein when W is the length in the direction parallel to the longitudinal direction of the slot in the open hole of the cavity resonator having the cavity conductor and the fence-shaped conductor, H is the distance from the cavity conductor to the other second main surface of the multilayer substrate, and f is the lower limit of the operating frequency of the antenna device, the antenna device satisfies the following equation (1). [Math 1]

4. The antenna device according to claim 1, further comprising a patch element disposed in the second inner layer of the multilayer substrate and positioned opposite the slot.

5. The antenna device according to claim 1, wherein the multilayer substrate includes FR4.

6. The multilayer substrate is provided with a plurality of antenna devices as described in claim 1, An antenna device comprising a power distribution unit arranged on the first main surface and supplying power to the plurality of antenna devices.

7. The antenna device according to claim 6, wherein the plurality of antenna devices have a line section with a line length set such that the phase difference between adjacent antenna devices is 40 to 60 degrees.

8. The antenna device according to claim 6, comprising a grounded shield portion arranged on the first main surface, covering the power supply line portion and the power distribution portion.

9. An antenna device according to any one of claims 1 to 8, A radar module comprising a circuit section that performs at least one of the following: input of a radar transmission signal and processing of a radar reception signal.

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