Antenna equipment

Abstract

The present invention provides an antenna device in which an increase in EIRP is suppressed and which has good radio wave reception sensitivity.　The antenna device comprises: a substrate; an integrated circuit chip that has a transmission antenna and a reception antenna and that is mounted on the substrate; a waveguide that has a first opening which is provided to the substrate side and which surrounds the transmission antenna and the reception antenna in a view of the opening face, a second opening which is provided further back than the first opening in the radiation direction of the transmission antenna, and a first inner wall surface which connects the first opening and the second opening; a radio wave lens that is fixed in the second opening; and a first radio wave absorbent body that is disposed to the first opening side in the space surrounded by the first inner wall surface. At least part of the first radio wave absorbent body is positioned inward of a first route of first direct waves that are radiated from the transmission antenna, that reach the radio wave lens directly, and that pass through the radio wave lens. The first radio wave absorbent body is positioned outward of a second route of second direct waves that pass through the radio wave lens and that directly reach the reception antenna.

Description

Technical Field

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[0001] The present disclosure relates to an antenna device.

Background Art

[0002] Conventionally, there is a lens antenna including a first horn (conical horn) formed of a metal conductor, a second horn formed of a plastic material having a radio wave absorption effect, and a lens for controlling the power distribution at the opening of the second horn. Since a radio wave absorber is not attached to the inner wall of the first horn, there is nothing to shield microwaves and it does not affect the power density distribution at the opening of the lens (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003] <​​​​​​​​​​​​​​​​​​​​​​​​The antenna device of the embodiment of the present disclosure comprises a substrate; an integrated circuit chip mounted on the substrate and having a transmitting antenna and a receiving antenna; a waveguide having a first opening on the substrate side that surrounds the transmitting antenna and the receiving antenna in an aperture view; a second opening provided further back than the first opening in the radiation direction of the transmitting antenna; and a first inner wall surface connecting the first opening and the second opening; a radio wave lens fixed to the second opening; and a first radio wave absorber disposed on the first opening side within the space surrounded by the first inner wall surface, wherein at least a portion of the first radio wave absorber is located inside the first path of a first direct wave radiated from the transmitting antenna that directly reaches and passes through the radio wave lens, and the first radio wave absorber is located outside the second path of a second direct wave that passes through the radio wave lens and directly reaches the receiving antenna. [Effects of the Invention]

[0007] This makes it possible to suppress the increase in EIRP and provide an antenna device with good radio wave reception sensitivity. [Brief explanation of the drawing]

[0008] [Figure 1A] This is a diagram showing an antenna device according to an embodiment. [Figure 1B] This is a diagram showing an antenna device according to an embodiment. [Figure 1C] This is a diagram showing an antenna device according to an embodiment. [Figure 1D] This is a perspective view showing the radio wave absorber of the antenna device according to the embodiment. [Figure 2A] This figure shows a cross-section taken along the line AA in Figure 1A. [Figure 2B] This figure illustrates an example of the position of the inner wall surface of the radio wave absorber in the antenna device of the embodiment. [Figure 2C] This figure illustrates an example of reflected wave absorption by a radio wave absorber in an antenna device according to an embodiment. [Figure 2D] This figure shows an example of the first and second paths in the cross-section viewed from the direction of arrow AA in Figure 1A. [Figure 3A] This is a diagram showing an example of the radiation characteristics of an antenna device for comparison. [Figure 3B] This is a diagram showing an example of the radiation characteristics of an antenna device for comparison. [Figure 3C] This is a diagram showing an example of the radiation characteristics of the antenna device 100 of the embodiment. [Figure 3D] This is a diagram showing an example of the radiation characteristics of the antenna device 100 of the embodiment. [Figure 4A] This is a diagram showing an example of the configuration of the antenna device of the first modification of the embodiment. [Figure 4B] This is a diagram showing an example of the configuration of the antenna device of the first modification of the embodiment. [Figure 5A] This is a diagram showing an example of the configuration of the antenna device of the second modification of the embodiment. [Figure 5B] This is a diagram showing an example of the configuration of the antenna device of the second modification of the embodiment. [Figure 5C] This is a diagram showing an example of the configuration of the antenna device of the second modification of the embodiment. [Figure 5D] This is a diagram showing an example of the configuration of the antenna device of the second modification of the embodiment. <T000080>This is a diagram showing an example of the configuration of the antenna device of the third modification of the embodiment. [Figure 6B] This is a diagram showing an example of the configuration of the antenna device of the third modification of the embodiment. [Figure 6C] This is a diagram showing an example of the configuration of the antenna device of the third modification of the embodiment. **[Embodiments for Carrying Out the Invention]**

[0009] Hereinafter, embodiments to which the antenna device of the present disclosure is applied will be described.

[0010] <Embodiment> <Configuration of Antenna Device 100> FIG. 1A, FIG. 1B, and FIG. 1C are diagrams showing the antenna device 100 of the embodiment. FIG. 1D is a perspective view showing the radio wave absorber 140 of the antenna device 100 of the embodiment. FIG. 1A is a perspective view, FIG. 1B is a view showing a part in a half cross-section, and FIG. 1C is a front view. FIG. 2A is a view showing a cross-section taken along the line A-A in FIG. 1A, and is a view showing a cross-section obtained by cutting the waveguide 110 in the YZ plane including the optical axis of the radio wave lens 130. Here, unless otherwise specified, the configuration of the antenna device 100 will be described using FIGS. 1A, FIG. 1B, FIG. 1C, FIG. 1D, and FIG. 2A.

[0011] Hereinafter, the XYZ coordinate system will be defined and described. Also, for convenience of explanation, the -Z direction side is referred to as the lower side or below, and the +Z direction side is referred to as the upper side or above, but this does not represent a universal up and down relationship. Also, viewing in the XZ plane is referred to as a plan view. Also, viewing the opening in the XZ plane view is referred to as an opening plane view.

[0012] <8000101>The antenna device 100 includes a substrate 101, a waveguide 110, a transceiver unit 120, a radio wave lens 130, a radio wave absorber 140, and a radio wave absorber 150. The radio wave absorber 150 is an example of a first radio wave absorber, and the radio wave absorber 140 is an example of a second radio wave absorber. The antenna device 100 may not include the radio wave absorber 140, but here, the configuration in which the antenna device 100 includes the radio wave absorber 140 will be described.

[0013] The antenna device 100 is a device that transmits and receives radio waves. The radio wave lens 130 narrows the radiation pattern of the transmitted wave and focuses the received radio waves with the lens to improve the reception sensitivity. Also, the antenna device 100 suppresses an increase in EIRP by attenuating the transmitted wave with the radio wave absorber 150, and absorbs the multiple reflection waves generated by multiple reflections inside with the radio wave absorber 140. [[ID=十四]]

[0014] Such an antenna device 100 can, for example, be used as a radar device that receives reflected waves that are returned after a transmitted wave is reflected by an object to be measured, and measures the distance to the object. The distance to the object can be measured based on the round-trip time from when the radio waves are transmitted as a transmitted wave until when they are received as reflected waves.

[0015] In Japan, the Radio Law sets an upper limit for the EIRP (Equivalent Isotropically Radiated Power) of transmitted waves. Furthermore, international guidelines exist, and similar limits apply in other countries. In conventional antenna systems, the antenna gains for both transmitted and received waves are equal. Therefore, increasing the antenna gain to improve reception sensitivity in conventional antenna systems may cause the EIRP of the transmitted wave to exceed the upper limit set by the Radio Law. Conversely, reducing the antenna gain to suppress EIRP may result in insufficient reception sensitivity. The antenna system 100 of this embodiment solves this problem by attenuating the transmitted wave with a radio wave absorber 150 to suppress the increase in EIRP and improve reception sensitivity.

[0016] Furthermore, in general, with radar devices that measure the distance to an object, the closer the object, the lower the detection accuracy becomes due to the effects of multiple reflections. This is because the shorter the round-trip time when the object is close, the more difficult it becomes to distinguish between a received wave that is not a multiple reflection and a wave that is a multiple reflection. When detection accuracy decreases, the shortest detectable distance (shortest detection distance) becomes longer. The antenna device 100 of this embodiment solves this problem by using a radio wave absorber 140.

[0017] Multiple reflected waves are radio waves that have been reflected two or more times within the space enclosed by the substrate 101, waveguide 110, transmitting / receiving unit 120, radio wave lens 130, and radio wave absorber 140. For radio waves transmitted from the transmitting / receiving unit 120 in the +Y direction, multiple reflected waves may occur, for example, when they are reflected by the surface of the radio wave lens 130 on the -Y direction side without passing through the radio wave lens 130. For radio waves that have passed through the radio wave lens 130 on the -Y direction side, multiple reflected waves may occur, for example, when they are reflected by the inner wall surface 110A of the waveguide 110, etc., without directly arriving at the transmitting / receiving unit 120.

[0018] The radio waves transmitted and received by the antenna device 100 are, for example, millimeter-wave radio waves. Millimeter waves are radio waves in the frequency band of 30 GHz to 300 GHz and behave almost identically to light. However, the radio waves transmitted and received by the antenna device 100 may also be radio waves with frequencies belonging to bands other than the millimeter-wave band.

[0019] <Configuration of circuit board 101> The circuit board 101 is a board on which the transmitting and receiving unit 120 is mounted, and as an example, a wiring board conforming to the FR-4 (Flame Retardant type 4) standard can be used. The circuit board 101 is fixed to the -Y direction side of the waveguide 110.

[0020] <Configuration of waveguide 110> Waveguide 110 is, for example, a cylindrical, hollow circular waveguide. Waveguide 110 has an opening 111, an opening 112, an inner wall surface 110A, and a mounting portion 115. The inside of waveguide 110 is a waveguide through which radio waves propagate. Inner wall surface 110A is an example of a first inner wall surface, opening 111 is an example of a first opening, and opening 112 is an example of a second opening. The -Y direction side of waveguide 110 is an example of a first opening side, and the +Y direction side is an example of a second opening side. The +Y direction is also an example of the radiation direction of the transmitting antenna 120Tx of the transmitting / receiving unit 120.

[0021] In Figures 1A, 1B, 1C, and 2A, the origin of the XYZ coordinate system coincides with the center of the aperture 111, and the central axis C of the waveguide 110 coincides with the Y axis. Furthermore, the central axis C coincides with the optical axis of the radio lens 130. For clarity, the central axis C and the Y axis are shown offset in the figures.

[0022] The inner wall surface 110A is the inner wall surface of the cylindrical, hollow waveguide 110. The waveguide 110, for example, has a cylindrical shape in which the diameter of opening 111 and the diameter of opening 112 are equal. Therefore, the inner wall surface 110A has a cylindrical shape with a constant diameter. Note that the diameter of opening 111 may be larger than the diameter of opening 112, and vice versa.

[0023] The aperture 111 is an opening located at the -Y direction end of the waveguide 110. The aperture 111 is circular when viewed from the aperture surface.

[0024] Aperture 112 is an opening located at the +Y direction end of waveguide 110. The section that functions as waveguide 110 through which radio waves propagate is the section between aperture 111 and aperture 112.

[0025] The opening 112 is circular when viewed from the opening surface. The diameter of the opening 112 is, for example, equal to the diameter of the opening 111. The radio wave lens 130 is attached to the opening 112 by the mounting portion 117.

[0026] The mounting portion 115 is a part that extends outward in a plan view at the -Y direction end of the waveguide 110, and for example has a square outer edge in a plan view. The mounting portion 115 is provided for attaching the substrate 101 to the waveguide 110. The outer edge of the mounting portion 115 in a plan view is held by the frame portion 105B of the cover 105 that covers the back side (-Y direction side) of the substrate 101. The mounting portion 115 is made of resin, for example.

[0027] The mounting portion 117 is a frame-shaped member that attaches the radio wave lens 130 to the waveguide 110 at the +Y direction end of the waveguide 110. The mounting portion 117 is annular in plan view and is fitted onto the outer circumferential surface of the waveguide 110 on the +Y direction side, holding the radio wave lens 130 at the +Y direction position of the opening 112. With the radio wave lens 130 held by the mounting portion 117, the optical axis of the radio wave lens 130 coincides with the central axis C of the waveguide 110. The mounting portion 117 is made of resin as an example.

[0028] With the radio wave lens 130 attached to the waveguide 110 by the mounting part 117 as described above, the focal point of the radio wave lens 130 is located at the center of the aperture surface view of the aperture 111. In other words, the length of the waveguide 110 in the direction of extension of the central axis C is set so that the focal point of the radio wave lens 130 is located on the aperture surface of the aperture 111.

[0029] <Configuration of the transmitting / receiving unit 120> The transmitting / receiving unit 120 is mounted on the surface of the substrate 101 on the +Y direction side. The transmitting / receiving unit 120 is an example of an integrated circuit chip. The transmitting / receiving unit 120 includes a substrate 121, a transmitting antenna 120Tx, and a receiving antenna 120Rx. The substrate 121 is smaller than the substrate 101 in plan view and is, for example, square. The substrate 121 is positioned in the center of the opening 111 in plan view, and more specifically, the center of the substrate 121 in plan view is located on the central axis C. Also, the Y-direction position of the surface of the substrate 121 on the +Y direction side coincides with the Y-direction position of the opening 111.

[0030] The transmitting antenna 120Tx and the receiving antenna 120Rx are provided on the surface of the substrate 121 on the +Y side, spaced apart in the Z direction. For example, the transmitting antenna 120Tx and the receiving antenna 120Rx are identical in shape and size. The transmitting antenna 120Tx transmits radio waves via the waveguide 110, and the receiving antenna 120Rx receives radio waves via the waveguide 110.

[0031] The transmitting antenna 120Tx and the receiving antenna 120Rx are arranged so as to be point-symmetric with respect to the central axis C in a plan view. Viewing the transmitting antenna 120Tx and the receiving antenna 120Rx in a plan view is equivalent to viewing the transmitting antenna 120Tx and the receiving antenna 120Rx in a plan view of the aperture 111.

[0032] The transmitting antenna 120Tx and the receiving antenna 120Rx are said to be point-symmetric with respect to the central axis C in a plan view if the centers of the transmitting antenna 120Tx and the receiving antenna 120Rx in a plan view are positioned point-symmetrically with respect to the central axis C in a plan view. The centers of the transmitting antenna 120Tx and the receiving antenna 120Rx in a plan view are both located on the Z-axis. Since the central axis C coincides with the optical axis of the radio lens 130, the transmitting antenna 120Tx and the receiving antenna 120Rx are positioned offset from the optical axis of the radio lens 130.

[0033] Furthermore, the centers of the transmitting antenna 120Tx and the receiving antenna 120Rx in a plan view are both located on the Z axis and are arranged point-symmetrically with respect to the central axis C in a plan view. Therefore, in the cross-section obtained by cutting the waveguide 110 in the YZ plane containing the optical axis of the radio wave lens 130, the transmitting antenna 120Tx and the receiving antenna 120Rx are arranged symmetrically with respect to the central axis C in the +Z and -Z directions.

[0034] Since it is not possible to place both the transmitting antenna 120Tx and the receiving antenna 120Rx on the central axis C (the optical axis of the radio lens 130), they are arranged in this manner to match the transmission and reception characteristics of the transmitting antenna 120Tx and the receiving antenna 120Rx. The transmitting antenna 120Tx and the receiving antenna 120Rx can be implemented using, for example, a loop antenna, patch antenna, monopole antenna, or dipole antenna.

[0035] Since the length of the waveguide 110 in the direction of extension of the central axis C is set so that the focal point of the radio wave lens 130 is located on the aperture surface of the aperture 111, the position of the optical axis of the radio wave lens 130 (central axis C of the waveguide 110) of the transmitting antenna 120Tx and receiving antenna 120Rx in the direction of extension is equal to the focal position of the radio wave lens 130. Furthermore, since the position in the Y direction of the surface on the +Y direction side of the substrate 121 coincides with the position in the Y direction of the aperture 111, the focal point of the radio wave lens 130 coincides with the center of the centers of the transmitting antenna 120Tx and receiving antenna 120Rx on the surface on the +Y direction side of the substrate 121 (a point on the central axis C).

[0036] The intensity of the radio waves (transmitted waves) radiated from the transmitting antenna 120Tx is strongest in the direction connecting the center of the transmitting antenna 120Tx and the center of the radio lens 130, and the intensity of the radio waves (received waves) received by the receiving antenna 120Rx is strongest in the direction connecting the center of the receiving antenna 120Rx and the center of the radio lens 130. The center of the radio lens 130 is located at the center of the thickness of the radio lens 130 in the Y direction, on the optical axis of the radio lens 130 (central axis C of the waveguide 110).

[0037] <Configuration of radio wave lens 130> The radio wave lens 130 can be any lens capable of focusing radio waves transmitted and received by the transmitting antenna 120Tx and the receiving antenna 120Rx in both directions, and as an example, it is a biconvex lens that is circular in plan view. However, the radio wave lens 130 may also be a uniconvex lens. Biconvex and uniconvex lenses are examples of convex lenses. Furthermore, the radio wave lens 130 may also be a flat lens such as a flat lens having a Fresnel zone or a flat lens having a metamaterial, but here we will describe the form in which it is a biconvex lens.

[0038] <Configuration of radio wave absorber 140> The radio wave absorber 140 is located in approximately half of the space inside the waveguide 110 on the -Y side. The radio wave absorber 140 is, for example, a component molded from a resin mixed with magnetic material or dielectric powder, and is a component that causes radio wave loss. The radio wave absorber 140 has an opening 141, an opening 142, and an inner wall surface 143. Opening 141 is an example of a third opening, opening 142 is an example of a fourth opening, and inner wall surface 143 is an example of a second inner wall surface.

[0039] The radio wave absorber 140 is positioned such that its central axis, parallel to the Y-axis of the roughly frustoconical space enclosed by the inner wall surface 143 between the openings 141 and 142, coincides with the central axis C of the waveguide 110. Furthermore, since the central axis C of the waveguide 110 coincides with the optical axis of the radio wave lens 130, the central axis of the radio wave absorber 140 coincides with the central axis C of the waveguide 110 and the optical axis of the radio wave lens 130.

[0040] The opening 141 is located on the side of the opening 111 and is smaller than the opening 111 and the substrate 101 when viewed from the opening surface of the opening 111, and is an opening that surrounds the transmitting antenna 120Tx and the receiving antenna 120Rx. In addition, the opening 141 is smaller than the opening 142 when viewed from the opening surface and is arranged concentrically. For example, the position of the opening 141 in the Y direction is aligned with the opening 111 of the waveguide 110 (see Figure 2A), so that the centers of the opening 141 and the opening 111 coincide when viewed from the opening surface.

[0041] The opening 142 is located further back (towards opening 112) than opening 141 in the radiation direction and is larger than opening 141. When viewed from the opening surface, opening 142 is larger than opening 141 and is arranged concentrically. The position of opening 142 in the Y direction is slightly to the +Y direction from the center of openings 111 and 112 of the waveguide 110, as shown in Figure 2A. The length between openings 141 and 142 of the radio wave absorber 140 can be determined according to the length of the waveguide 110 in the Y direction and the shape of the inner wall surface 143, etc.

[0042] The inner wall surface 143 is the inner wall surface connecting openings 141 and 142. The inner wall surface 143 has inner wall surfaces 143A, 143B, 143C, 143D, 143E, and 143F from the -Y direction side to the +Y direction side. The -Y direction end of inner wall surface 143A is opening 141, and inner wall surface 143A is a cylindrical wall surface with a constant diameter (a wall surface corresponding to the inner circumference of a cylinder), and inner wall surface 143B is connected to the +Y direction end.

[0043] The inner wall surface 143B is a wall surface (corresponding to the outer surface of a frustocone) that extends in a frustoconical shape from the +Y direction end of the inner wall surface 143A, and the inner wall surface 143C is connected to the +Y direction end. The inner wall surface 143C is composed of planes parallel to the XZ plane and is annular in aperture view. In the aperture view of the radio wave absorber 140, the +Y direction end of the inner wall surface 143B is connected as an opening to the center of the inner wall surface 143C. The inner wall surface 143D is connected to the outer edge of the inner wall surface 143C.

[0044] The inner wall surface 143D is a side surface that extends in a frustoconical shape from the +Y direction end of the inner wall surface 143C, and the inner wall surface 143E is connected to the +Y direction end. The inner wall surface 143E is a side surface that extends in a cylindrical shape from the +Y direction end of the inner wall surface 143D, and its diameter is constant in the Y direction. The inner wall surface 143F is connected to the +Y direction end of the inner wall surface 143E.

[0045] The inner wall surface 143F is a side surface that extends in a frustoconical shape from the +Y direction end of the inner wall surface 143E, and the +Y direction end of the inner wall surface 143F is the opening 142.

[0046] The radio wave absorber 140 is configured such that the primary radiation wave radiated from the transmitting antenna 120Tx in the +Y direction (radiation direction) does not come into contact with the inner wall surface 143, by having a space surrounded by the inner wall surface 143 as described above. In other words, the inner wall surface 143 is located outside the radiation path of the primary radiation wave radiated from the transmitting antenna 120Tx. The primary radiation wave is a direct wave radiated from the transmitting antenna 120Tx that passes directly through the radio wave lens 130 without being reflected. The radiation path of the primary radiation wave radiated from the transmitting antenna 120Tx is the same as the first path P1 (see Figure 2D) through which the first direct wave, described later, passes, and the primary radiation wave radiated from the transmitting antenna 120Tx is the same as the first direct wave, described later. Details of this configuration will be explained using Figure 2B.

[0047] <Position of inner wall surface 143> Figure 2B illustrates an example of the position of the inner wall surface 143 of the radio wave absorber 140. Compared to Figure 2A, Figure 2B adds the radio waves radiated from the transmitting antenna 120Tx (transmitted wave), the radio waves received by the receiving antenna 120Rx (received wave), the aperture angle α of the radio wave lens 130, the diameter D of the radio wave lens 130, and the focal length FP of the radio wave lens 130. The radio waves radiated from the transmitting antenna 120Tx (transmitted wave) are primary radiation waves. Note that in Figure 2B, some symbols are omitted for clarity.

[0048] The aperture angle α of the radio lens 130 is the aperture angle of the radio lens 130 as seen from the focal point of the radio lens 130, and is the angle corresponding to the primary radio wave emission angle of the transmitting and receiving antenna, which acts as the primary radiator, when the transmitting and receiving antenna is placed at the focal point of the radio lens 130.

[0049] The aperture angle α of the radio lens 130 is expressed by the following equation (1), where D is the diameter of the radio lens 130 and FP is the focal length of the radio lens 130. The aperture angle α depends on the type and specific structure of the transmitting and receiving antennas (transmitting antenna 120Tx and receiving antenna 120Rx) of the transmitting and receiving unit 120.

[0050]

number

[0051] The inner wall surface 143 of the radio wave absorber 140 is located outside the region represented by the aperture angle α. Since the region represented by the aperture angle α is included in the radiation path of the primary radiation wave emitted from the transmitting antenna 120Tx, the inner wall surface 143 is located outside the radiation path of the primary radiation wave emitted from the transmitting antenna 120Tx. The radio wave absorber 140 is configured so as not to obstruct the radiation path of the primary radiation wave emitted from the transmitting antenna 120Tx by having an inner wall surface 143 that is located outside the region represented by the aperture angle α. Furthermore, the radio wave absorber 140 is configured so as not to obstruct the path of radio waves (received waves) that pass from outside the antenna device 100 through the radio wave lens 130 and are received by the receiving antenna 120Rx by being located outside the region represented by the aperture angle α. For this reason, the antenna device 100 does not experience a decrease in detection sensitivity due to attenuation of transmitted and received waves within the radiation path, and can detect the object to be measured with high accuracy.

[0052] Figure 2B shows the radio waves (transmitted waves) as primary radiation emitted from the transmitting antenna 120Tx with a thick dashed line, and the radio waves (received waves) received by the receiving antenna 120Rx with a thick dashed line. As shown by the thick dashed line, the primary radiation is emitted within the range of the aperture angle α of the radio lens 130 and passes through the radio lens 130 without reaching the inner wall surface 143. Also, as shown by the thick dashed line, the received waves are focused as they pass through the radio lens 130 and reach the receiving antenna 120Rx without reaching the inner wall surface 143.

[0053] In Figure 2B, the aperture angle of the radio wave lens 130 is smaller than the aperture angle of the waveguide 110 when viewed from the focal point of the radio wave lens 130. However, if the aperture angle of the aperture 112 of the waveguide 110 is smaller than the aperture angle of the radio wave lens 130 when viewed from the focal point of the radio wave lens 130, the inner wall surface 143 should have a shape that is located outside the region represented by the aperture angle β of the aperture 112, which can be determined by the following equation (2).

[0054] In Figure 2B, the focal point of the radio wave lens 130 is the intersection of the optical axis of the radio wave lens 130 and the surface of the substrate 121 of the transmitting / receiving unit 120. Therefore, the aperture angle β of the aperture 112 as viewed from the intersection of the optical axis of the radio wave lens 130 and the surface of the substrate 121 of the transmitting / receiving unit 120 must satisfy the following equation (2), where Dd is the diameter of the aperture 112 and L is the distance between the intersection and the center of the aperture 112.

[0055]

number

[0056] <Absorption of reflected waves by radio wave absorber 140> Figure 2C illustrates an example of reflected wave absorption by the radio wave absorber 140. In Figure 2C, the received wave and corner dimensions shown in Figure 2B are omitted, and some reference numerals are also omitted. Figure 2C shows transmitted wave 1, which is radiated from the transmitting antenna 120Tx and passes through the central part of the radio wave lens 130, and transmitted waves 2 and 3, which are radiated from the transmitting antenna 120Tx and pass through the area outside the central part of the radio wave lens 130.

[0057] Transmitted wave 1 is transmitted through the surface of the radio lens 130 on the -Y direction side with almost no reflection. Transmitted wave 2 is partially reflected as it passes through the outer part of the radio lens 130 beyond the center, generating reflected wave 2. Reflected wave 2 is reflected toward the inner wall surface 110A of the waveguide 110, but reaches the inner wall surface 143 of the radio wave absorber 140 and is absorbed by the radio wave absorber 140. If the radio wave absorber 140 is not present, reflected wave 2 may be reflected by the inner wall surface 110A of the waveguide 110 after being reflected by the surface of the radio lens 130 on the -Y direction side, as shown by the thin dashed line, and reach the transmitting / receiving unit 120 as a multiple reflected wave.

[0058] Furthermore, similar to the transmission wave 2, when the transmitted wave 3 passes outside the central part of the radio wave lens 130, a portion is reflected, generating a reflected wave 3. The reflected wave 3 is reflected toward the inner wall surface 110A of the waveguide 110, but reaches the inner wall surface 143 of the radio wave absorber 140 and is absorbed by the radio wave absorber 140. If the radio wave absorber 140 is not present, the reflected wave 3 may be reflected by the surface on the -Y direction side of the radio wave lens 130 and then reflected by the inner wall surface 110A of the waveguide 110, as shown by the thin dashed line, and reach the transmitting / receiving unit 120 as a multiple reflected wave.

[0059] In addition to these transmitted waves 2 and 3, there are cases where transmitted waves that reach the center of the radio lens 130 more than transmitted waves 2 and 3, such as transmitted wave 1, are reflected by the surface of the radio lens 130 on the -Y direction, or where transmitted waves that reach outside the radio lens 130 more than transmitted waves 2 and 3 are reflected by the surface of the radio lens 130 on the -Y direction. If the radio wave absorber 140 is not present, these reflected waves may be reflected again, resulting in multiple reflected waves that may reach the transmitting / receiving unit 120.

[0060] Furthermore, if the radio wave absorber 140 is not present, multiple reflected waves may occur due to reflection from the surface of the substrate 101.

[0061] However, in reality, as shown in Figure 2C, the radio wave absorber 140 is positioned so that most of the multiple reflected waves can be absorbed. In this way, since the multiple reflected waves can be absorbed by the radio wave absorber 140, the reception of multiple reflected waves by the receiving antenna 120Rx can be suppressed.

[0062] When multiple reflected waves are received by the receiving antenna 120Rx, they become indistinguishable from the received waves that pass through the radio lens 130 and arrive directly at the receiving antenna 120Rx, thus reducing the detection accuracy of the received waves that pass through the radio lens 130 and arrive directly at the receiving antenna 120Rx. The closer the object being measured, the greater the decrease in detection accuracy due to the effect of multiple reflections, resulting in a longer minimum detection distance.

[0063] Since the antenna device 100 of the embodiment includes the radio wave absorber 140 as described above, it can suppress the reception of multiple reflected waves by the receiving antenna 120Rx. The antenna device 100 of the embodiment can improve detection performance by improving the detection accuracy of the received wave at the receiving antenna 120Rx, thereby shortening the minimum detection distance.

[0064] <Configuration of the radio wave absorber 150> The radio wave absorber 150 will be explained using Figure 2D in addition to Figures 1A to 1D and Figures 2A to 2C. Figure 2D shows an example of the first path P1 and the second path P2 in the cross-section viewed by arrow AA in Figure 1A.

[0065] The radio wave absorber 150 is provided to attenuate the radio waves radiated from the transmitting antenna 120Tx. By attenuating the transmitted wave, the power of the transmitted wave is kept below the upper limit of the Radio Law, while the received wave is not attenuated, enabling high receiving sensitivity of the receiving antenna 120Rx. The radio wave absorber 150, like the radio wave absorber 140, is a component molded from a resin mixed with, for example, magnetic material or dielectric powder, and is a component that causes loss of radio waves.

[0066] The radio wave absorber 150 is located inside the opening 141 of the radio wave absorber 140 when viewed from the opening surface of the opening 111, and is provided on the upper (+Z) side of the inner wall surface 143A and 143B of the inner wall surface 143 of the radio wave absorber 140. Here, the configuration of the radio wave absorber 150 will be described using the radial direction of the opening 141 of the radio wave absorber 140.

[0067] The radially outer surface of the radio wave absorber 150 is in contact with the inner wall surfaces 143A and 143B. Therefore, the boundary between the radio wave absorber 150 and the radio wave absorber 140 is curved.

[0068] In the Y direction, the radio wave absorber 150 is formed from the surface of the radio wave absorber 140 on the -Y direction side to a position between the -Y direction end and the +Y direction end of the inner wall surface 143B. The position of the surface of the radio wave absorber 140 on the -Y direction side in the Y direction is equal to the position of the opening 141 in the Y direction. Therefore, in the view of the opening surface of the opening 111, the radio wave absorber 150 overlaps with a part of the substrate 101 and also overlaps with a part of the transmitting / receiving unit 120 mounted on the +Y direction surface of the substrate 101.

[0069] As shown in Figures 1C and 1D, the radio wave absorber 150 is C-shaped when viewed from the opening surface of the opening 111, and is provided on the upper side of the inner wall surface 143A and 143B of the inner wall surface 143, in a state as if the C shape had been rotated 90 degrees clockwise. In other words, as shown in Figure 1C, the radio wave absorber 150 is positioned above the transmitting antenna 120Tx, diagonally above the transmitting antenna 120Tx in the +X direction, and diagonally above the transmitting antenna 120Tx in the -X direction when viewed from the opening surface of the opening 111.

[0070] Furthermore, as shown in Figures 1C and 1D, the radio wave absorber 150 has a recess 151 that is recessed in the +Z direction so as to straddle the transmitting antenna 120Tx when viewed from the opening surface of the opening 111. The surface of the recess 151 facing the central axis C is composed of three planes, for example. In addition, a chamfered portion 151A is formed between the portion of the surface of the recess 151 facing the central axis C on the +Y direction side and the surface of the radio wave absorber 150 on the +Y direction side. The chamfered portion 151A is the portion where the corner between the surface of the recess 151 facing the central axis C side and the surface of the radio wave absorber 150 on the +Y direction side is beveled.

[0071] Furthermore, the recess 151 is not limited to a configuration consisting of three planes, as shown in Figures 1C and 1D, but may also be curved in an arc shape, for example. Also, the radio wave absorber 150 does not need to have a chamfered portion 151A.

[0072] For example, the radio wave absorber 150 is formed integrally with the radio wave absorber 140, but it may also be manufactured separately from the radio wave absorber 140 and attached to the radio wave absorber 140. When the radio wave absorber 150 is formed integrally with the radio wave absorber 140, for example, it can be manufactured by integral molding or machining. In the cross-sectional view of Figure 2D, the radio wave absorber 150 and the radio wave absorber 140 are shown with different types of hatching to distinguish them from each other.

[0073] As shown in Figure 2D, the radio wave absorber 150 is positioned on the side of the opening 111 within the space enclosed by the inner wall surface 110A of the waveguide 110. This is because the transmitting antenna 120Tx is located on the side of the opening 111. At least a portion of the radio wave absorber 150 is located inside the first path P1 of the first direct wave radiated from the transmitting antenna 120Tx and reaching the radio lens 130 directly. This is to attenuate the first direct wave. The radio wave absorber 150 is also located outside the second path P2 of the second direct wave that passes through the radio lens 130 and reaches the receiving antenna 120Rx directly. This is to achieve high and good receiving sensitivity of the receiving antenna 120Rx without attenuating the second direct wave.

[0074] Here, the first direct wave is the transmitted wave radiated from the transmitting antenna 120Tx, which reaches the radio lens 130 directly and passes through the radio lens 130. The first path P1 is the three-dimensional path through which the first direct wave can travel between the transmitting antenna 120Tx and the radio lens 130, and is the three-dimensional spatial region through which the first direct wave can travel. At least a portion of the radio wave absorber 150 is located inside the first path P1, meaning that at least a portion of the radio wave absorber 150 is located within the three-dimensional spatial region through which the first direct wave can travel. The first path P1 is the same as the radiation path of the primary radiation wave radiated from the transmitting antenna 120Tx. The primary radiation wave radiated from the transmitting antenna 120Tx is the same as the first direct wave.

[0075] The three-dimensional spatial region through which the first direct wave can pass is the spatial region connecting the outer edge of the radio lens 130 and the outer edge of the transmitting antenna 120Tx. However, if the opening 112 of the waveguide 110 is inward from the outer edge of the radio lens 130, the three-dimensional spatial region through which the first direct wave can pass is the spatial region connecting the opening 112 of the waveguide 110 and the outer edge of the transmitting antenna 120Tx.

[0076] The second direct wave is a received wave that arrives from outside the radio lens 130 (+Y direction side), passes through the radio lens 130, and directly reaches the receiving antenna 120Rx. The second path P2 is a three-dimensional path that the second direct wave can take between the receiving antenna 120Rx and the radio lens 130, and is a three-dimensional spatial region through which the second direct wave can pass. The radio wave absorber 150 being located outside the second path P2 of the second direct wave means that the entire radio wave absorber 150 is located outside the three-dimensional spatial region through which the second direct wave can pass, and that the entire radio wave absorber 150 is not located inside the three-dimensional spatial region through which the second direct wave can pass.

[0077] The three-dimensional spatial region through which the second direct wave can pass is the spatial region connecting the outer edge of the radio lens 130 and the outer edge of the receiving antenna 120Rx. However, if the opening 112 of the waveguide 110 is inward from the outer edge of the radio lens 130, the three-dimensional spatial region through which the second direct wave can pass is the spatial region connecting the opening 112 of the waveguide 110 and the outer edge of the receiving antenna 120Rx.

[0078] Furthermore, the radio wave absorber 150 is positioned on the transmitting antenna 120Tx side of the central axis C of the waveguide 110 when viewed from the aperture plane of the aperture 111. The radio wave absorber 150 attenuates the radio waves radiated by the transmitting antenna 120Tx and is not located inside the second path P2 of the radio waves received by the receiving antenna 120Rx. Therefore, it is positioned on the transmitting antenna 120Tx side of the central axis C of the waveguide 110 when viewed from the aperture plane of the aperture 111. The central axis C coincides with the optical axis of the radio wave lens 130.

[0079] It was explained that the radio wave absorber 140 may have a shape in which its inner wall surface 143 is located outside the region represented by the aperture angle α in equation (1), or outside the region represented by the aperture angle β of the opening 112 determined by equation (2). However, the radio wave absorber 140 may also have a configuration in which its inner wall surface 143 is located outside the first path P1 and the second path P2.

[0080] <Simulation Results> To verify the effectiveness of the radio wave absorber 150, simulations were performed on a comparative antenna device without the radio wave absorber 150 and on an antenna device 100 of an embodiment that includes the radio wave absorber 150, and the radiation characteristics of the transmitting antenna 120Tx and receiving antenna 120Rx were calculated. The comparative antenna device has a configuration in which the radio wave absorber 150 is removed from the antenna device 100 of the embodiment.

[0081] Figures 3A and 3B show examples of radiation characteristics of a comparative antenna device. Figures 3C and 3D show examples of radiation characteristics of the antenna device 100 of the embodiment. Figures 3A and 3C show radiation characteristics in an XY cross-section passing through the central axis C, and Figures 3B and 3D show radiation characteristics in a YZ cross-section passing through the central axis C. In Figures 3A to 3D, the central axis C is located on a straight line connecting -90 degrees and 90 degrees.

[0082] The radiation characteristics of the comparative antenna devices shown in Figures 3A and 3B were calculated by setting the receiving sensitivity of the receiving antenna 120Rx to a desired high level, and setting the configuration of the transmitting antenna 120Tx and the receiving antenna 120Rx similarly. The radiation characteristics of the transmitted wave are shown by a solid line, and the radiation characteristics of the received wave are shown by a dashed line.

[0083] In Figure 3A, the radiation characteristics of the transmitted and received waves are equal, and the radiation characteristics of the transmitted wave (solid line) and the radiation characteristics of the received wave (dashed line) completely overlap, so only the radiation characteristics of the transmitted wave, represented by the solid line, are shown. In Figure 3B, it can be seen that the radiation characteristics of the transmitted wave on the +Z direction and the radiation characteristics of the received wave on the -Z direction are misaligned. This is because the transmitting antenna 120Tx is located above the central axis C, and the receiving antenna 120Rx is located below the central axis C.

[0084] The gain (antenna gain) of both the transmitted and received waves in the comparative antenna setup was 15.4 dB. Because the receiving sensitivity of the receiving antenna 120Rx was set to the desired high level, the power of the transmitted wave (EIRP) exceeded the upper limit of power stipulated by the Radio Law.

[0085] Figure 3C shows that the radiation characteristics of the transmitted and received waves are different, and that the gain of the transmitted wave is smaller than the gain of the received wave. Figure 3D also shows that the gain of the transmitted wave is smaller than the gain of the received wave.

[0086] In the antenna device 100 of this embodiment, the gain of the transmitted wave was 12.1 dB, and the gain of the received wave was 15.3 dB. Although the receiving sensitivity of the receiving antenna 120Rx was set to a desired high level, the power of the transmitted wave could be kept below the upper limit of power stipulated by the Radio Law. Therefore, it was confirmed that by providing the radio wave absorber 150, it is possible to obtain high and good receiving sensitivity while keeping the power of the transmitted wave below the upper limit of power stipulated by the Radio Law.

[0087] <Effects> The antenna device 100 includes a substrate 101, a transmitting / receiving unit 120 mounted on the substrate 101 and having a transmitting antenna 120Tx and a receiving antenna 120Rx, a waveguide 110 having an opening 111 (first opening) on ​​the substrate 101 side that surrounds the transmitting antenna 120Tx and the receiving antenna 120Rx when viewed from the opening surface, an opening 112 (second opening) provided further back than the opening 111 (first opening) in the radiation direction of the transmitting antenna 120Tx, and an inner wall surface 110A (first inner wall surface) connecting the opening 111 (first opening) and the opening 112 (second opening), and the opening 112 The system comprises a radio wave lens 130 fixed to the (second opening) and a radio wave absorber 150 (first radio wave absorber) positioned on the opening 111 (first opening) side within the space surrounded by the inner wall surface 110A (first inner wall surface). At least a portion of the radio wave absorber 150 (first radio wave absorber) is located inside the first path of the first direct wave radiated from the transmitting antenna 120Tx, which directly reaches the radio wave lens 130 and passes through the radio wave lens 130, while the radio wave absorber 150 (first radio wave absorber) is located outside the second path of the second direct wave that passes through the radio wave lens 130 and directly reaches the receiving antenna 120Rx. Therefore, high reception sensitivity can be obtained while attenuating the transmitted wave without attenuating the received wave.

[0088] Therefore, it is possible to provide an antenna device 100 that suppresses the increase in EIRP and has good radio wave reception sensitivity.

[0089] Furthermore, the transmitting antenna 120Tx and the receiving antenna 120Rx are positioned on either side of the central axis C (the optical axis of the radio wave lens 130). As a result, the first path P1 of the first direct wave and the second path P2 of the second direct wave are offset above and below the central axis C, respectively, and the radio wave absorber 150 can be positioned inside the first path P1 and outside the second path P2. Therefore, by utilizing the difference in position between the first path P1 and the second path P2, it is possible to suppress the increase in EIRP and provide an antenna device 100 with good radio wave reception sensitivity.

[0090] Furthermore, the radio wave absorber 150 (first radio wave absorber) is positioned on the transmitting antenna 120Tx side of the central axis C (optical axis of the radio wave lens 130) when viewed from the aperture surface of the aperture 111 (first aperture). By positioning the radio wave absorber 150 on the first path P1 side, it is possible to attenuate the transmitted wave, suppress the increase in EIRP, and provide an antenna device 100 with good radio wave reception sensitivity.

[0091] Furthermore, the antenna device 100 is further provided with a cylindrical radio wave absorber 140 (second radio wave absorber) located inside the inner wall surface 110A (first inner wall surface). The radio wave absorber 140 (second radio wave absorber) is located on the side of the opening 111 (first opening) and has an opening 141 (third opening) that is smaller than the opening 111 (first opening) and the substrate 101 when viewed from the opening surface of the opening 111 (first opening) and surrounds the transmitting antenna 120Tx and the receiving antenna 120Rx; an opening 142 (fourth opening) that is located further back than the opening 141 (third opening) in the radiation direction and is larger than the opening 141 (third opening); and an inner wall surface 143 (second inner wall surface) that connects the opening 141 (third opening) and the opening 142 (fourth opening). Therefore, it is possible to reduce the effects of multiple reflections, improve detection performance, suppress the increase in EIRP, and provide an antenna device 100 with good radio wave reception sensitivity.

[0092] Furthermore, since the radio wave absorber 150 (first radio wave absorber) is integrally formed with the radio wave absorber 140 (second radio wave absorber), the number of parts can be reduced by manufacturing the radio wave absorbers 140 and 150 simultaneously, and the positioning of the radio wave absorbers 140 and 150 relative to the transmitting antenna 120Tx and the receiving antenna 120Rx can be performed simultaneously.

[0093] <First variation> Figures 4A and 4B show an example of the configuration of the antenna device 100M1 in the first modified embodiment. Here, the differences between the antenna device 100M1 and the antenna device 100 will be explained. Among the components of the antenna device 100M1, components that are the same as those of the antenna device 100 are denoted by the same reference numerals, and their descriptions are omitted.

[0094] Antenna device 100M1 has a configuration in which the radio wave absorber 140 is removed from antenna device 100 and a radio wave absorber 150 is attached to the surface of the substrate 101 on the +Y direction side. The position and size of the radio wave absorber 150 of antenna device 100M1 are the same as those of the radio wave absorber 150 of antenna device 100. For example, if the effect of multiple reflections is small, it is not necessary to include the radio wave absorber 140, as in antenna device 100M1.

[0095] Furthermore, in the antenna device 100M1, since the radio wave absorber 150 is attached to the substrate 101, higher positional accuracy of the radio wave absorber 150 relative to the transmitting antenna 120Tx can be obtained. For example, when mounting the antenna device 100 on a vehicle or the like, even if there is a misalignment between the substrate 101 and the cover 105 or waveguide 110, the position of the radio wave absorber 150 relative to the transmitting antenna 120Tx will not shift, so the transmitted wave can be attenuated with high precision.

[0096] Because the radio wave absorber 150 attenuates the transmitted wave while not attenuating the received wave, high reception sensitivity can be obtained, thus providing an antenna device 100M1 with good radio wave reception sensitivity. Furthermore, because the positioning accuracy of the radio wave absorber 150 relative to the transmitting antenna 120Tx is high, the transmitted wave can be attenuated with high precision.

[0097] <Second variation> Figures 5A to 5D show an example of the configuration of the antenna device 100M2, a second modified example of the embodiment. Here, the differences between the antenna device 100M2 and the antenna devices 100 and 100M1 will be explained. Among the components of the antenna device 100M2, components that are the same as those of the antenna devices 100 and 100M1 are denoted by the same reference numerals, and their descriptions are omitted.

[0098] First, let's explain using Figures 5A to 5C. Antenna device 100M2 has a configuration in which the radio wave absorber 140 is removed from antenna device 100 and a radio wave absorber 150M2 is attached to the surface of the substrate 101 on the +Y direction side. The radio wave absorber 150M2 differs from the radio wave absorber 150 of antenna devices 100 and 100M1 in that, when viewed from the opening surface of the opening 111, it covers the transmitting antenna 120Tx and is attached to the surface of the transmitting / receiving unit 120 by three legs 151M2 that protrude in the -Y direction. For example, if the effect of multiple reflections is small, it is not necessary to include the radio wave absorber 140, as in antenna device 100M2.

[0099] For example, when attenuating the transmitted wave from a state where the gains of the transmitting antenna 120Tx and the receiving antenna 120Rx are equal, so that the power is below the upper limit of power stipulated by the Radio Law, if it is better to cover the transmitting antenna 120Tx when viewed from the aperture surface of the aperture 111, then the radio wave absorber 150M2 that covers the transmitting antenna 120Tx when viewed from the aperture surface of the aperture 111 should be used.

[0100] Furthermore, in the antenna device 100M2, the radio wave absorber 150M2 is attached to the substrate 101, similar to the antenna device 100M1, thus achieving higher positional accuracy of the radio wave absorber 150M2 relative to the transmitting antenna 120Tx. For example, when mounting the antenna device 100 on a vehicle or the like, even if there is a misalignment between the substrate 101 and the cover 105 or waveguide 110, the position of the radio wave absorber 150M2 relative to the transmitting antenna 120Tx will not shift, allowing for high-precision attenuation of the transmitted wave.

[0101] Because the radio wave absorber 150M2 attenuates the transmitted wave while not attenuating the received wave, high reception sensitivity can be obtained, thus providing an antenna device 100M2 with good radio wave reception sensitivity. In addition, because the positioning accuracy of the radio wave absorber 150 relative to the transmitting antenna 120Tx is high, the transmitted wave can be attenuated with high precision.

[0102] Furthermore, the radio wave absorber 150M2 may cover a portion of the transmitting antenna 120Tx in an aperture-level view of the opening 111. In other words, the radio wave absorber 150M2 may be configured to cover at least a portion of the transmitting antenna 120Tx in an aperture-level view of the opening 111. Figure 5D shows a configuration in which the radio wave absorber 150M2 covers the upper half of the transmitting antenna 120Tx in an aperture-level view of the opening 111.

[0103] The radio wave absorber 150M2 can attenuate the transmitted wave by covering at least a portion of the transmitting antenna 120Tx in the aperture surface view of the aperture 111. Furthermore, the attenuation rate of the transmitted wave can be set by adjusting the vertical length of the radio wave absorber 150M2 to adjust the proportion that the radio wave absorber 150 covers the transmitting antenna 120Tx.

[0104] <Third variation> Figures 6A to 6C show an example of the configuration of the antenna device 100M3, a third modified example of the embodiment. Here, the differences between the antenna device 100M3 and the antenna device 100 will be explained. Among the components of the antenna device 100M3, components that are the same as those of the antenna device 100 are denoted by the same reference numerals, and their descriptions are omitted.

[0105] <Configuration of Antenna System 100M3> Antenna device 100M3 has a configuration in which the radio wave absorber 140 of antenna device 100 is omitted, a waveguide 110M3 is included instead of waveguide 110, and a radio wave absorber 150M3 is included instead of radio wave absorber 150 and fixed to waveguide 110 with holder 155.

[0106] <Configuration of waveguide 110M3> Waveguide 110M3 has an opening 111, an opening 112, a recess 113A, an inner wall surface 114A, an inner wall surface 115A, and an inner wall surface 116A. The central axes of each of the openings 111, 112, 113A, 114A, 115A, and 116A are located on the central axis C.

[0107] The openings 111 and 112 correspond to the openings 111 and 112 of the waveguide 110.

[0108] The recess 113A is located on the -Y side of the opening 111 and is the portion into which the holder 155 is fitted. The recess 113A is a cylindrical recess extending from the -Y side surface of the waveguide 110M3 toward the +Y side. The central axis of the recess 113A coincides with the central axis C. The radial length of the recess 113A is longer than the radius of the opening 111. Therefore, when viewing the waveguide 110M3 from the -Y side, the recess 113A is larger than the opening 111.

[0109] The inner wall surface 114A is a cylindrical wall surface with a constant diameter (a wall surface corresponding to the inner circumference of a cylinder) and communicates with the opening 111 on the +Y side. The diameter of the inner wall surface 114A is equal to the diameter of the opening 111.

[0110] The inner wall surface 115A is a wall surface (corresponding to the outer surface of the frustum of a cone) that extends in a frustum-like shape from the +Y direction end of the inner wall surface 114A, with the opening 112 located at the +Y direction end. The inner wall surface 115A is located outside the region represented by the opening angle α shown in equation (1). Furthermore, the inner wall surface 115A is located outside the first path P1 and the second path P2 shown in Figure 2D.

[0111] The inner wall surface 116A is a cylindrical wall surface (corresponding to the inner circumferential surface of a cylinder) located on the +Y direction side of the opening 112, and is larger than the opening 112 when viewed from the opening surface of the waveguide 110M3.

[0112] <Configuration of the radio wave absorber 150M3 and holder 155> The radio wave absorber 150M3 has a disc shape and a through-hole 151M3 located on the +Y direction side of the receiving antenna 120Rx. The through-hole 151M3 penetrates approximately half of the -Z direction side of the radio wave absorber 150M3 in the Y direction. The through-hole 151M3 has a cylindrical inner wall surface (a wall surface corresponding to the inner circumference of a cylinder) with a constant diameter.

[0113] The radio wave absorber 150M3, like the radio wave absorber 150, is a component molded from a resin mixed with, for example, a magnetic material or dielectric powder, and is a component that causes radio wave loss. The holder 155 is preferably nonmetallic and is made of a dielectric material. The holder 155 can be made from, for example, resin or ceramic.

[0114] The radio wave absorber 150M3, held by the holder 155, covers the transmitting antenna 120Tx when viewed from the opening surface of the waveguide 110M3, while exposing the receiving antenna 120Rx through the through-hole 151M3. The inner wall surface of the through-hole 151M3 is located outside the second path P2 shown in Figure 2D. Therefore, the first direct wave output from the transmitting antenna 120Tx is attenuated by the radio wave absorber 150M3, but the second direct wave reaching the receiving antenna 120Rx passes inside the through-hole 151M3 and is not attenuated by the radio wave absorber 150M3.

[0115] The holder 155 is a disc-shaped member larger than the radio wave absorber 150M3, and has a recess 155A formed along the central axis C from the -Y direction side, and an opening 155B provided on the +Y direction side of the recess 155A. The recess 155A and the opening 155B are circular with the central axis C as viewed from the -Y direction side of the holder 155. The recess 155A has a cylindrical inner wall surface (a wall surface corresponding to the inner circumferential surface of a cylinder) with a constant diameter, and the end on the +Y direction side is connected to the opening 155B, which has a smaller diameter than the recess 155A. The recess 155A and the opening 155B penetrate the holder 155 in the Y direction.

[0116] A radio wave absorber 150M3 is fitted into the cylindrical inner wall surface of recess 155A. In this state, the opening edge of opening 155B is located outside the transmitting antenna 120Tx and receiving antenna 120Rx when viewed from the opening surface of opening 111 of waveguide 110M3. That is, the opening edge of opening 155B is located outside the first path P1 and the second path P2 shown in Figure 2D.

[0117] By attaching the radio wave absorber 150M3 to such a holder 155 and fitting the holder 155 into the recess 113A of the waveguide 110M3, the radio wave absorber 150M3 can be attached to the waveguide 110M3 as shown in Figures 6A to 6C.

[0118] When the radio wave absorber 150M3 is attached to the waveguide 110M3, the radio wave absorber 150M3 is located inside the first path P1 of the first direct wave output from the transmitting antenna 120Tx, but outside the second path P2 of the second direct wave reaching the receiving antenna 120Rx. Therefore, it is possible to obtain high receiving sensitivity by attenuating the transmitted wave with the radio wave absorber 150M3 without attenuating the received wave, and an antenna device 100M3 with good radio wave receiving sensitivity can be provided.

[0119] Furthermore, in the antenna device 100M3, the radio wave absorber 150M3 is attached to the waveguide 110M3, which improves the positioning accuracy between the waveguide 110M3 and the radio wave absorber 150M3.

[0120] Furthermore, as mentioned above, the holder 155 only needs to be able to hold the radio wave absorber 150M3, so it is not limited to a disc shape and can take on various other shapes.

[0121] Although exemplary embodiments of antenna devices of this disclosure have been described above, this disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0122] This international application claims priority based on Japanese Patent Application No. 2022-200579, filed on 15 December 2022, the entire contents of which are incorporated herein by reference. [Explanation of Symbols]

[0123] 100, 100M1, 100M2, 100M3 Antenna Equipment 101 circuit board 110, 110M3 waveguide 110A Inner wall surface (an example of the first inner wall surface) 111 Opening (Example of the first opening) 112 Opening (Example of the second opening) 113A Recess 114A Inner wall surface 115A Interior wall surface 116A Interior wall surface 120 Transmitter / Receiver Unit (Example of an Integrated Circuit Chip) 120Tx Transmitting Antenna 120Rx receiving antenna 121 circuit boards 130 Radio-controlled lens 140 Radio wave absorber (an example of a second radio wave absorber) 141 Opening (Example of the third opening) 142 Opening (Example of the fourth opening) 143 Inner wall surface (an example of a second inner wall surface) 150, 150M2, 150M3 radio wave absorbers (an example of the first radio wave absorber) 151 recess 151A Chamfered section 151M3 Through hole 155 Holder

Claims

1. circuit board and An integrated circuit chip having a transmitting antenna and a receiving antenna, mounted on the substrate, A waveguide having a central axis, a first opening provided on the substrate side in the extending direction of the central axis and surrounding the transmitting antenna and the receiving antenna in an open-plane view, a second opening provided on the radiating side of the transmitting antenna than the first opening in the extending direction of the central axis, and a first inner wall surface connecting the first opening and the second opening, A radio wave lens fixed to the second aperture, A first radio wave absorber is disposed on the first opening side within the space enclosed by the first inner wall surface. Equipped with, At least a portion of the first radio wave absorber is located inside the first path of the first direct wave that reaches the radio wave lens directly and passes through the radio wave lens, The antenna device wherein the first radio wave absorber is located outside the second path of the second direct wave that passes through the radio wave lens and reaches the receiving antenna directly.

2. The antenna device according to claim 1, wherein the first radio wave absorber covers at least a portion of the transmitting antenna when viewed from the opening surface of the first opening.

3. The antenna device according to claim 1 or 2, wherein the transmitting antenna and the receiving antenna are arranged on either side of the optical axis of the radio wave lens.

4. The antenna device according to claim 3, wherein the first radio wave absorber is provided on the transmitting antenna side of the optical axis when viewed from the aperture surface of the first aperture.

5. The device further comprises a cylindrical second radio wave absorber provided on the inside of the first inner wall surface, The second radio wave absorber is A third opening is provided on the side of the first opening, and is smaller than the first opening and the substrate when viewed from the opening surface of the first opening, and surrounds the transmitting antenna and the receiving antenna. A fourth opening is provided on the radiating side of the transmitting antenna than the third opening in the extending direction of the central axis, and is larger than the third opening. The second inner wall surface connecting the third opening and the fourth opening and The antenna device according to claim 1, having the following features.

6. The antenna device according to claim 5, wherein the second inner wall surface of the second radio wave absorber is located outside the first path and the second path.

7. The antenna device according to claim 6, wherein the first radio wave absorber is integrally formed with the second radio wave absorber.

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