Antenna equipment

Abstract

To provide an antenna device that reduces an effect of multiple reflections and improves detection performance.SOLUTION: An antenna device includes: a substrate; an integrated circuit chip having a transmitting antenna and a receiving antenna and mounted on the substrate; a waveguide having a first aperture that is provided on the substrate side and surrounds the transmitting antenna and the receiving antenna in an aperture surface view, a second aperture that is provided further back than the first aperture in a radiation direction of the transmitting antenna, and a first inner wall surface connecting the first and second apertures; a radio wave lens fixed to the second aperture; and a cylindrical radio wave absorber provided inside the first inner wall surface. The radio wave absorber has a third aperture that is provided on the first aperture side, is smaller than the first aperture and the substrate in the aperture surface view of the first aperture, and surrounds the transmitting and receiving antennas, a fourth aperture that is provided further back than the third aperture in the radiation direction and larger than the third aperture, and a second inner wall surface connecting the third and fourth apertures.SELECTED DRAWING: Figure 1B

Description

Technical Field

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

Background Art

[0002] Conventionally, there is a millimeter-wave radar device including an antenna that transmits and receives radio waves, a radome that covers the antenna, and a radio wave absorber disposed on the surface of the radome, wherein the radio wave absorber is configured to reduce reflected radio waves that are transmitted from the antenna and become side lobes (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since a conventional millimeter-wave radar device (antenna device) does not consider multiple reflections that are reflected a plurality of times inside the millimeter-wave radar device without passing through the radio wave passing end portion of the radome, there is a possibility that radio waves of multiple reflections cannot be absorbed by the radio wave absorber. Radio waves due to multiple reflections are generated, for example, by being reflected by the radio wave passing end portion or the substrate of the antenna, or by being reflected by the radio wave absorber, and deteriorate the detection performance of the device.

[0005] Therefore, an object is to provide an antenna device that reduces the influence of multiple reflections and improves detection performance.

Means for Solving the Problems

[0006] An antenna device according to an embodiment of the present disclosure includes a substrate, an integrated circuit chip mounted on the substrate 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, and a radio wave lens fixed to the second opening. The device comprises a cylindrical radio wave absorber provided on the inside of the first inner wall surface, the radio wave absorber having a third opening provided on the first opening side, which 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 provided further back than the third opening in the radiation direction and larger than the third opening, and a second inner wall surface connecting the third opening and the fourth opening. [Effects of the Invention]

[0007] This allows us to provide an antenna device that reduces the effects of multiple reflections and improves detection performance. [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 3]This figure shows an example of the results of an experiment conducted using the antenna device of the embodiment. [Figure 4A] This figure shows an example of the configuration of an antenna device in the first modified embodiment. [Figure 4B] These figures show examples of the configuration of the radio wave absorber in the antenna device of the first modified embodiment. [Figure 5A] This figure shows an example of the configuration of an antenna device in a second modified embodiment. [Figure 5B] These figures show examples of the configuration of the radio wave absorber in the antenna device of the second modified embodiment. [Figure 6A] This figure shows an example of the configuration of an antenna device in a third modified embodiment. [Figure 6B] These figures show examples of the configuration of the radio wave absorber in the antenna device of the third modified embodiment. [Modes for carrying out the invention]

[0009] The following describes embodiments to which the antenna device of this disclosure is applied.

[0010] <Embodiment> <Configuration of antenna device 100> Figures 1A, 1B, and 1C show an antenna device 100 according to an embodiment. Figure 1D is a perspective view showing the radio wave absorber 140 of the antenna device 100 according to the embodiment. Figure 1A is a perspective view, Figure 1B is a diagram showing a partial half-section, and Figure 1C is a front view. Figure 2A shows a cross-section in the direction of arrow AA in Figure 1A, and is a diagram showing a cross-section obtained by cutting the waveguide 110 in the YZ plane containing the optical axis of the radio wave lens 130. Here, unless otherwise specified, the configuration of the antenna device 100 will be described using Figures 1A, 1B, 1C, 1D, and 2A.

[0011] Hereinafter, an explanation will be given by defining an XYZ coordinate system. For the sake of convenience in the explanation, the -Z direction side is referred to as the lower side or bottom, and the +Z direction side is referred to as the upper side or top, but this does not represent a universal up-and-down relationship. Also, viewing 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] The antenna device 100 includes a substrate 101, a waveguide 110, a transceiver unit 120, a radio lens 130, and a radio wave absorber 140. The antenna device 100 is a device for transmitting and receiving radio waves. The radio lens 130 narrows the radiation pattern of the transmitted wave and focuses the received radio waves with the lens. Also, the antenna device 100 absorbs the multiple reflection waves generated by multiple reflections inside with the radio wave absorber 140.

[0013] Such an antenna device 100 can be used, for example, as a radar device that receives a reflected wave in which a transmitted wave is reflected by a measurement object and returns, and measures the distance to the measurement object. Based on the round-trip time from transmitting the radio wave as a transmitted wave to receiving the radio wave as a reflected wave, the distance to the measurement object can be measured. Generally, in a radar device that measures the distance to a measurement object, the closer the measurement object is, the lower the detection accuracy due to the influence of multiple reflections. This is because the closer the measurement object is, the shorter the round-trip time, and it becomes difficult to distinguish between the received wave that is not a multiple reflection and the multiple reflection wave. When the detection accuracy decreases, the shortest detectable distance (shortest detection distance) becomes longer. The antenna device 100 of the present embodiment solves such a problem.

[0014] The multiple reflection wave is a radio wave that has been reflected two or more times within the space surrounded by the substrate 101, the waveguide 110, the transceiver unit 120, the radio lens 130, and the radio wave absorber 140. For example, for the radio wave transmitted from the transceiver unit 120 in the +Y direction, a multiple reflection wave may occur when it is reflected by the surface on the -Y direction side of the radio lens 130 without passing through the radio lens 130. For the radio wave that has passed through the radio lens 130 in the -Y direction, for example, a multiple reflection wave may occur when it is reflected by the inner wall surface 110A of the waveguide 110 or the like without directly reaching the transceiver unit 120.

[0015] The radio wave transmitted and received by the antenna device 100 is, for example, a radio wave in the millimeter wave band. The millimeter wave is a radio wave in the frequency band of 30 GHz to 300 GHz and behaves substantially the same as light. Note that the radio wave transmitted and received by the antenna device 100 may be a radio wave having a frequency belonging to a band other than the millimeter wave band.

[0016] <Configuration of the substrate 101> The substrate 101 is a substrate on which the transmission / reception unit 120 is mounted, and for example, a wiring substrate conforming to the FR-4 (Flame Retardant type 4) standard can be used. The substrate 101 is fixed to the -Y direction side of the waveguide 110.

[0017] <Configuration of the waveguide 110> The waveguide 110 is, for example, a cylindrical and hollow circular waveguide. The waveguide 110 has an opening 111, an opening 112, an inner wall surface 110A, and a mounting portion 115. The inside of the waveguide 110 is a waveguide through which radio waves propagate. The inner wall surface 110A is an example of a first inner wall surface, the opening 111 is an example of a first opening, and the opening 112 is an example of a second opening. The -Y direction side of the waveguide 110 is an example of the first opening side, and the +Y direction side is an example of the second opening side. Also, the +Y direction is an example of the radiation direction of the transmission antenna 120Tx of the transmission / reception unit 120.

[0018] In FIGS. 1A, 1B, 1C, and 2A, the origin of the XYZ coordinates coincides with the center of the opening 111, and the central axis C of the waveguide 110 coincides with the Y axis. Also, the central axis C coincides with the optical axis of the radio wave lens 130. In the figures, for the sake of clarity, the central axis C and the Y axis are shown shifted from each other.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] <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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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 point-symmetrically with respect to the central axis C.

[0031] 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.

[0032] 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).

[0033] 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).

[0034] <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.

[0035] <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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The inner wall surface 143 is an inner wall surface that connects the openings 141 and 142. The inner wall surface 143 has inner wall surfaces 143A, 143B, and 143C, which are arranged from the -Y direction side to the +Y direction side.

[0040] The -Y-direction end of the inner wall surface 143A is the opening 141. The inner wall surface 143A is a wall surface (corresponding to the outer surface of the frustum of a cone) that extends in a frustum-like shape from the opening 141 toward the +Y-direction, and the inner wall surface 143B is connected to the +Y-direction end of the inner wall surface 143A. As an example, the inner wall surface 143A is provided over a section that is approximately half the length of the radio wave absorber 140 in the Y-direction.

[0041] The inner wall surface 143B is a cylindrical wall surface with a constant diameter (a wall surface corresponding to the inner circumference of a cylinder). For example, the inner wall surface 143B is provided over a section of approximately 1 / 3 of the length of the radio wave absorber 140 in the Y direction. The inner wall surface 143C is connected to the +Y direction end of the inner wall surface 143B.

[0042] The end of the inner wall surface 143C on the +Y direction side is the opening 142. The inner wall surface 143C is a wall surface (corresponding to the outer surface of the frustocone) that extends in a frustoconical shape from the opening 142 toward the -Y direction, and the inner wall surface 143B is connected to the end of the inner wall surface 143C on the -Y direction side. For example, the length of the inner wall surface 143C in the Y direction is shorter than that of the inner wall surfaces 143A and 143B, and it is provided over a section that is approximately 1 / 10 of the length of the radio wave absorber 140 in the Y direction.

[0043] 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 the radio wave radiated from the transmitting antenna 120Tx that propagates without being reflected. Details of this configuration will be explained using Figure 2B.

[0044] <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.

[0045] 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.

[0046] 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.

[0047]

number

[0048] 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.

[0049] 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. Similarly, as shown by the thick dashed line, the received waves pass through the radio lens 130 and reach the receiving antenna 120Rx without reaching the inner wall surface 143.

[0050] 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).

[0051] 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.

[0052]

number

[0053] <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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] However, in reality, as shown in Figure 2C, the radio wave absorber 140 is positioned to absorb most of the multiple reflected waves. 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.

[0059] 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.

[0060] 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.

[0061] <Experimental Results> Figure 3 shows an example of the results of an experiment conducted using the antenna device 100. The experimental results in Figure 3 show an example of the received signal strength of the receiving antenna 120Rx as a function of the distance between the antenna device 100 and the object being measured. Figure 3 also shows an example of the experimental results for a comparative antenna device. The comparative antenna device has a configuration in which the radio wave absorber 140 is omitted from the antenna device 100.

[0062] In Figure 3, the horizontal axis represents the distance (mm) between the antenna device 100 and the comparison antenna device and the object being measured, and the vertical axis represents the received signal strength (unitless) of the receiving antenna 120Rx of the antenna device 100 and the comparison antenna device. The received signal strength of the receiving antenna 120Rx is not limited to the signal strength of the received wave alone, but may also include the signal strength of multiple reflected waves.

[0063] Figure 3 shows the received signal strength of the receiving antenna 120Rx of antenna device 100 with a solid line, and the received signal strength of the receiving antenna 120Rx of the comparison antenna device with a dashed line. The noise level is shown with a dashed line.

[0064] Furthermore, Figure 3 shows the reception strength threshold as a dashed line. The reception strength threshold is used by the computer connected to the antenna device 100 or the comparison antenna device to determine the presence or absence of the object to be measured. When the reception strength exceeds the threshold, it is determined that the object to be measured is present. In Figure 3, the threshold is, as an example, 200, which is the output data value of the ADC (Analog to Digital Converter) installed between the antenna device 100 and the computer.

[0065] Furthermore, Figure 3 shows, as an example, the received signal strength when the object to be measured is located at a position of 2000 mm, and the received signal strength is shown by the receiving antenna 120Rx of the antenna device 100. As a result, the received signal strength characteristic of the solid line shows a peak in the ADC output data at a position of 1600 mm, and the output data increases to approximately 1600.

[0066] Comparing the received signal strength of antenna device 100 and the comparison antenna device, both are below the threshold at longer distances, but increase as the distance decreases. The received signal strength of the comparison antenna device increases sharply from a distance of about 400 mm, peaking at approximately 9500. This is due to the effect of multiple reflected waves. In fact, the shortest detection distance for the comparison antenna device was 400 mm. That is, with the comparison antenna device, the received signal strength of receiving antenna 120Rx is above the threshold at a distance of 400 mm. Note that the shortest detection distance is the shortest distance at which detection is possible. In other words, the detectable distance for the comparison antenna device is limited to 400 mm or more.

[0067] In contrast, the received signal strength of antenna device 100 remained below the threshold even at distances shorter than 400 mm, and the received signal strength only exceeded the threshold at a distance of 160 mm. In other words, the shortest detection distance for antenna device 100 was 160 mm. Furthermore, even at distances shorter than 160 mm, the peak signal strength was approximately 2100, which was significantly lower than the peak signal strength of the comparison antenna device (approximately 9500).

[0068] As shown above, the experimental results in Figure 3 demonstrate that the antenna device 100, with the addition of the radio wave absorber 140 compared to the comparative antenna device, significantly reduced the effects of multiple reflected waves, and the shortest detection distance was drastically shortened from 400 mm to 160 mm. In other words, it was confirmed that detection performance can be significantly improved by absorbing multiple reflected waves with the radio wave absorber 140. Detection performance is expressed as the shortest detection distance as an example.

[0069] <Effects> The antenna device 100 comprises 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 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 provided further back than the opening 111 in the radiation direction of the transmitting antenna 120Tx, and an inner wall surface 110A connecting the openings 111 and 112, a radio wave lens 130 fixed to the opening 112, and a cylindrical radio wave absorber 140 provided inside the inner wall surface 110A. The radio wave absorber 140 is provided on the side of the opening 111 and has an opening 141 that is smaller than the opening 111 and the substrate 101 when viewed from the opening surface of the opening 111 and surrounds the transmitting antenna 120Tx and the receiving antenna 120Rx, an opening 142 that is located further back than the opening 141 in the radiation direction and is larger than the opening 141, and an inner wall surface 143 that connects the openings 141 and 142. Therefore, reflection from the surface of the substrate 101 can be suppressed and the generation of multiple reflected waves can be suppressed.

[0070] Therefore, it is possible to provide an antenna device 100 that reduces the effects of multiple reflections and improves detection performance.

[0071] Furthermore, since the aperture 142 of the radio wave absorber 140 is located closer to the aperture 111 than the aperture 112 of the waveguide 110 in the radiation direction, a configuration can be achieved in which the radio wave absorber 140 is not located on the radiation path of the primary radiation wave emitted from the transmitting antenna 120Tx on the side closer to the radio wave lens 130, thereby reducing the effects of multiple reflections and providing an antenna device 100 with improved detection performance.

[0072] Furthermore, since the inner wall surface 143 of the radio wave absorber 140 is located outside the radiation path of the primary radiation waves emitted from the transmitting antenna 120Tx, a configuration in which the radio wave absorber 140 is not located on the radiation path of the primary radiation waves emitted from the transmitting antenna 120Tx can be more reliably achieved, thereby more reliably reducing the effects of multiple reflections and providing an antenna device 100 with more reliably improved detection performance.

[0073] Furthermore, the transmitting antenna 120Tx and the receiving antenna 120Rx are positioned on either side of the optical axis of the radio wave lens 130. Therefore, under the constraint that it is difficult to position the transmitting antenna 120Tx and the receiving antenna 120Rx on the central axis C, by positioning the transmitting antenna 120Tx and the receiving antenna 120Rx symmetrically with respect to the central axis C, it is possible to provide an antenna device 100 that more reliably reduces the effects of multiple reflections of transmitted and received waves and more reliably improves detection performance.

[0074] Furthermore, the aperture angle α of the radio wave lens 130 as seen from the focal point of the radio wave lens 130 is expressed by the following equation (3), where D is the diameter of the radio wave lens 130 and FP is the focal length of the radio wave lens 130, and the inner wall surface 143 of the radio wave absorber 140 is located outside the region represented by the aperture angle α.

[0075]

number

[0076] Therefore, the radio wave absorber 140 is positioned outside the region represented by the aperture angle α (see Figure 2B), so as not to obstruct the path between the primary radiation wave (transmitted wave) radiated from the transmitting antenna 120Tx and the radio wave (received wave) that passes through the radio wave lens 130 from outside the antenna device 100 and is received by the receiving antenna 120Rx. As a result, the antenna device 100 does not suffer a decrease in detection sensitivity due to attenuation of the transmitted and received waves within the radiation path, and can detect the object to be measured with high accuracy. Furthermore, when the aperture angle α of the radio wave lens 130 is smaller than the opening 112 of the waveguide 110 when viewed from the focal point of the radio wave lens 130, the antenna device 100 can be provided with an antenna that more reliably reduces the effects of multiple reflections and more reliably improves detection performance by using the radio wave absorber 140 having an inner wall surface 143 located outside the region represented by the aperture angle α of the radio wave lens 130.

[0077] Furthermore, the aperture angle β of the aperture 112 as viewed from the intersection point of the optical axis of the radio wave lens 130 and the surface of the transmitting / receiving unit 120 satisfies the following equation (4), where Dd is the diameter of the aperture 112 and L is the distance between the intersection point and the center of the aperture 112.

[0078]

number

[0079] Therefore, when 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 transmitting / receiving unit 120, is smaller than the aperture angle α of the radio wave lens 130, an antenna device 100 can be provided that more reliably reduces the effects of multiple reflections and more reliably improves detection performance by using a radio wave absorber 140 having an inner wall surface 143 located outside the region represented by the aperture angle β of the aperture 112.

[0080] <First variation> Figures 4A and 4B show examples of the configurations of the antenna device 100M1 and the radio wave absorber 140M1 of the first modified embodiment, respectively. The antenna device 100M1 has a configuration in which the radio wave absorber 140 of the antenna device 100 of the embodiment is replaced with a radio wave absorber 140M1. Since the other configurations are the same, the radio wave absorber 140M1 will be described here.

[0081] The radio wave absorber 140M1 has openings 141 and 142 and an inner wall surface 143M1. The openings 141 and 142 are rectangular in shape when viewed from the opening surface, with opening 141 being smaller than opening 142. The opening size of opening 141 is matched to the size of the outer edge of the transmitting / receiving unit 120, and opening 141 is provided to surround the outer edge of the transmitting / receiving unit 120 with a small gap between it and the outer edge.

[0082] The inner wall surface 143M1 has inner wall surfaces 143A and 143B extending from the -Y direction side to the +Y direction side. The -Y direction end of inner wall surface 143A is an opening 141, and inner wall surface 143A has a shape corresponding to the inner surface of a rectangular tube, with inner wall surface 143B connected to the +Y direction end.

[0083] The inner wall surface 143B is a side surface that extends in a truncated square pyramidal shape from the +Y direction end of the inner wall surface 143A, and the +Y direction end of the inner wall surface 143B is the opening 142.

[0084] An antenna device 100M1 using such a radio wave absorber 140M1 can suppress reflection on the surface of the substrate 101 and suppress the generation of multiple reflected waves, similar to the antenna device 100 of the embodiment.

[0085] Therefore, an antenna device 100M1 can be provided that reduces the effects of multiple reflections and improves detection performance. Furthermore, since the aperture size of the opening 141 is matched to the size of the outer edge of the transmitting / receiving unit 120, reflections on the surface of the substrate 101 between the opening 141 and the transmitting / receiving unit 120 can be reduced, and multiple reflections can be effectively suppressed. In addition, the radio wave absorber 140M1 is located outside the region represented by the aperture angle α (see Figure 2B), so as not to obstruct the path between the primary radiation wave (transmitted wave) radiated from the transmitting antenna 120Tx and the radio wave (received wave) that passes through the radio wave lens 130 from outside the antenna device 100 and is received by the receiving antenna 120Rx. For this reason, the antenna device 100M1 does not suffer a decrease in detection sensitivity due to attenuation of the transmitted and received waves within the radiation path, and can detect the object to be measured with high accuracy.

[0086] <Second variation> Figures 5A and 5B show examples of the configurations of the antenna device 100M2 and the radio wave absorber 140M2 of a second modified embodiment, respectively. The antenna device 100M2 has a configuration in which the radio wave absorber 140 of the antenna device 100 of the embodiment is replaced with a radio wave absorber 140M2. Since the other configurations are the same, the radio wave absorber 140M2 will be described here.

[0087] The radio wave absorber 140M2 has openings 141 and 142 and an inner wall surface 143M2. Opening 141 is rectangular in a view from the opening surface, and opening 142 is circular in a view from the opening surface, with opening 141 being smaller than opening 142. The centers of openings 141 and 142 in a view from the opening surface are located on the central axis C. The opening size of opening 141 is matched to the size of the outer edge of the transmitting / receiving unit 120, and opening 141 is provided so as to surround the outer edge of the transmitting / receiving unit 120 with a small gap between it and the outer edge.

[0088] The inner wall surface 143M2 has inner wall surfaces 143A, 143B, 143C, 143D, and 143E from the -Y direction side to the +Y direction side. The -Y direction end of inner wall surface 143A is an opening 141, and inner wall surface 143A has a shape corresponding to the inner surface of a rectangular tube, with inner wall surface 143B connected to the +Y direction end.

[0089] The inner wall surface 143B is a side surface that extends in a truncated square pyramidal 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 a plane parallel to the XZ plane, with a circular outer edge, and the +Y direction end of the inner wall surface 143B is connected as an opening at the center of the aperture view of the radio wave absorber 140M2. The inner wall surface 143D is connected to the outer edge of the inner wall surface 143C.

[0090] The inner wall surface 143D is a side surface that extends cylindrically from the outer edge of the inner wall surface 143C, and its diameter is constant in the Y direction. The inner wall surface 143E is connected to the +Y direction end of the inner wall surface 143D.

[0091] The inner wall surface 143E is a side surface that extends in a frustoconical shape from the +Y direction end of the inner wall surface 143D, and the +Y direction end of the inner wall surface 143E is the opening 142.

[0092] An antenna device 100M2 using such a radio wave absorber 140M2 can suppress reflection on the surface of the substrate 101 and suppress the generation of multiple reflected waves, similar to the antenna device 100 of the embodiment.

[0093] Therefore, an antenna device 100M2 can be provided that reduces the effects of multiple reflections and improves detection performance. Furthermore, since the aperture size of the opening 141 is matched to the size of the outer edge of the transmitting / receiving unit 120, reflections on the surface of the substrate 101 between the opening 141 and the transmitting / receiving unit 120 can be reduced, and multiple reflections can be effectively suppressed. In addition, the radio wave absorber 140M2 is located outside the region represented by the aperture angle α (see Figure 2B), so as not to obstruct the path between the primary radiation wave (transmitted wave) radiated from the transmitting antenna 120Tx and the radio wave (received wave) that passes through the radio wave lens 130 from outside the antenna device 100 and is received by the receiving antenna 120Rx. For this reason, the antenna device 100M2 does not suffer a decrease in detection sensitivity due to attenuation of the transmitted and received waves within the radiation path, and can detect the object to be measured with high accuracy.

[0094] <Third variation> Figures 6A and 6B show examples of the configurations of the antenna device 100M3 and the radio wave absorber 140M3 of a third modified embodiment, respectively. The antenna device 100M3 has a configuration in which the radio wave absorber 140 of the antenna device 100 of the embodiment is replaced with a radio wave absorber 140M3. Since the other configurations are the same, the radio wave absorber 140M3 will be described here.

[0095] The radio wave absorber 140M3 has openings 141 and 142 and an inner wall surface 143M3. Openings 141 and 142 are circular when viewed from the opening surface, with opening 141 being smaller than opening 142. The centers of openings 141 and 142 when viewed from the opening surface are located on the central axis C.

[0096] The inner wall surface 143M3 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 an opening 141, and inner wall surface 143A has a shape corresponding to the inner surface of a cylinder, with inner wall surface 143B connected to the +Y direction end.

[0097] The inner wall surface 143B is a side surface 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 140M3, 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.

[0098] 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.

[0099] 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.

[0100] An antenna device 100M3 using such a radio wave absorber 140M3 can suppress reflection on the surface of the substrate 101 and suppress the generation of multiple reflected waves, similar to the antenna device 100 of the embodiment.

[0101] Therefore, it is possible to provide an antenna device 100M3 that reduces the effects of multiple reflections and improves detection performance. Furthermore, the inner wall surface 143M3 extends further away from the central axis C than the inner wall surfaces 143M1 and 143M2 of the radio wave absorbers 140M1 and M2 of the first and second modified examples, and is located outside the region represented by the aperture angle α shown in Figure 2B. For this reason, the antenna device 100M3 of the third modified example can suppress multiple reflections more effectively than the antenna devices 100M1 and 100M2 of the first and second modified examples, further reducing the effects of multiple reflections and providing an antenna device 100M3 with improved detection performance. In addition, the radio wave absorber 140M3 is located outside the region represented by the aperture angle α (see Figure 2B), so as not to obstruct the path between the primary radiated wave (transmitted wave) emitted from the transmitting antenna 120Tx and the radio wave (received wave) that passes through the radio wave lens 130 from outside the antenna device 100M3 and is received by the receiving antenna 120Rx. Therefore, the antenna device 100M3 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.

[0102] Furthermore, the radio wave absorber 140 of the antenna device 100 in this embodiment extends further away from the central axis C than the radio wave absorber 140M3 of the antenna device 100M3 of the third modified example, and is located outside the region represented by the aperture angle α shown in Figure 2B. For this reason, the antenna device 100 in this embodiment can suppress multiple reflections more effectively than the antenna device 100M3 of the third modified example, thereby reducing the effects of multiple reflections and providing an antenna device 100 with improved detection performance.

[0103] 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.

[0104] The following additional information is disclosed regarding the embodiments described above. (Note 1) circuit board and An integrated circuit chip having a transmitting antenna and a receiving antenna, mounted on the substrate, A waveguide having a first opening on the substrate side that surrounds the transmitting antenna and the receiving antenna when viewed from the opening surface, 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 aperture, A cylindrical radio wave absorber provided on the inside of the first inner wall surface and Equipped with, The aforementioned 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 in the radial direction, located further back than the third opening, and is larger than the third opening. The second inner wall surface connecting the third opening and the fourth opening and An antenna device having the following features. (Note 2) The antenna device according to Appendix 1, wherein the fourth opening of the radio wave absorber is located on the first opening side of the waveguide than the second opening in the radiation direction. (Note 3) The antenna device according to Appendix 1 or 2, wherein the second inner wall surface of the radio wave absorber is located outside the radiation path of the primary radiation wave radiated from the transmitting antenna. (Note 4) The antenna device according to any one of the appendices 1 to 3, wherein the transmitting antenna and the receiving antenna are arranged on either side of the optical axis of the radio wave lens. (Note 5) The aperture angle α of the radio wave lens as viewed from the focal point of the radio wave lens is given by the following equation (1), where D is the diameter of the radio wave lens and FP is the focal length of the radio wave lens. The antenna device as described in Appendix 4, wherein the second inner wall surface of the radio wave absorber is located outside the region represented by the aperture angle α.

[0105]

number

[0106]

number

[0107] 100, 100M1, 100M2, 100M3 Antenna Equipment 101 circuit board 110 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) 120 Transmitter / Receiver Unit (Example of an Integrated Circuit Chip) 120Tx Transmitting Antenna 120Rx receiving antenna 121 circuit boards 130 Radio-controlled lens 140, 140M1, 140M2, 140M3 Radio wave absorbers 141 Opening (Example of the third opening) 142 Opening (Example of the fourth opening) 143, 143M1, 143M2, 143M3 Inner wall surface (Example of the second inner wall surface)

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 first opening on the substrate side that surrounds the transmitting antenna and the receiving antenna when viewed from the opening surface, 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 aperture, A cylindrical radio wave absorber provided on the inside of the first inner wall surface and Equipped with, The aforementioned 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 in the radial direction, located further back than the third opening, and is larger than the third opening. The second inner wall surface connecting the third opening and the fourth opening and An antenna device having the following features.

2. The antenna device according to claim 1, wherein the fourth opening of the radio wave absorber is located on the first opening side of the waveguide than the second opening in the radiation direction.

3. The antenna device according to claim 1, wherein the second inner wall surface of the radio wave absorber is located outside the radiation path of the primary radiation wave radiated from the transmitting antenna.

4. The antenna device according to any one of claims 1 to 3, wherein the transmitting antenna and the receiving antenna are arranged on either side of the optical axis of the radio wave lens.

5. The aperture angle α of the radio wave lens as viewed from the focal point of the radio wave lens is given by the following equation (1), where D is the diameter of the radio wave lens and FP is the focal length of the radio wave lens. The antenna device according to claim 4, wherein the second inner wall surface of the radio wave absorber is located outside the region represented by the opening angle α. [Math 1]

6. The antenna device according to claim 4, wherein the aperture angle β of the second aperture, as viewed from the intersection point of the optical axis of the radio wave lens and the surface of the integrated circuit chip, satisfies the following equation (2), where Dd is the diameter of the second aperture and L is the distance between the intersection point and the center of the second aperture. [Math 2]

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