Antenna device and radar device

Abstract

Provided are: an antenna device in which the minimum detection distance is shortened; and a radar device.　The antenna device comprises: a waveguide having a first opening, a second opening that is larger than the first opening when observed in a planar view of the opening, and an inner wall surface connecting the first opening and the second opening; an antenna that is provided inside the first opening so as to be positioned, when observed in a planar view of the opening, inside the first opening, directed toward the inside of the waveguide; and a radio wave lens provided inside the waveguide, the radio lens having a first surface located on the first opening side and located more toward the inside of the waveguide than the first opening, a second surface located on the second opening side and located more toward the inside of the waveguide than the second opening, and an outer edge part which is sized so as to close a gap between the inner wall surface and the outer edge part when observed in a planar view of the opening.

Description

Antenna device and radar device

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

[0002] Conventionally, there has been a sensor having an antenna. The antenna includes a substrate, a radiating portion formed on the substrate, and a waveguide that propagates electromagnetic waves radiated from the radiating portion and radiates them as a beam. The waveguide has a radiation-side opening that is longer in a second direction than in a first direction that are orthogonal to each other, and the radiation-side opening is larger than the opening on the opposite side to the radiation-side opening. The opening on the opposite side to the radiation-side opening is disposed so that an edge of the opening encloses the radiating portion on the side of the substrate on which the radiating portion is formed. The sensor includes a dielectric lens at the radiation-side opening, and the electric field plane direction of the radiating portion is the second direction (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2019-054546

[0004] However, part of the radio waves transmitted from the antenna are reflected by the surface of the dielectric lens facing the antenna, resulting in multiple reflections between the antenna and the dielectric lens. This makes it difficult to detect signals in areas close to the sensor, increasing the minimum detection distance that the sensor can detect.

[0005] The dielectric lens of a conventional sensor is provided at the radiation side opening, which is the farthest position from the antenna, and the distance between the dielectric lens and the antenna is long, resulting in a long minimum detection distance.

[0006] Therefore, an object of the present invention is to provide an antenna device and a radar device that have a reduced minimum detection distance.

[0007] An antenna device according to an embodiment of the present disclosure includes a waveguide having a first opening, a second opening larger than the first opening when viewed from the opening plane, and an inner wall surface connecting the first opening and the second opening; an antenna provided at the first opening facing the inside of the waveguide so as to be located inside the first opening when viewed from the opening plane; and a radio wave lens provided inside the waveguide, the radio wave lens having a first surface located on the first opening side and located inside the waveguide relative to the first opening, a second surface located on the second opening side and located inside the waveguide relative to the second opening, and an outer edge portion sized to close a gap between the first opening and the inner wall surface when viewed from the opening plane.

[0008] It is possible to provide an antenna device and a radar device with a reduced minimum detection distance.

[0009] 1 is a diagram showing an example of the configuration of a radar device of an embodiment; FIG. 2 is a diagram showing an example of the configuration of a radar device of an embodiment; FIG. 3 is a diagram showing an example of the configuration of a radio wave lens of the radar device of an embodiment; FIG. 4 is a diagram explaining an example of a propagation path in the radar device of an embodiment; FIG. 5 is a diagram showing an example of an experimental result of a minimum detection distance in the radar device of an embodiment; FIG. 6 is a diagram showing an example of an experimental result of a minimum detection distance in a radar device for comparison; FIG. 7 is a diagram showing a modified example of the radar device of an embodiment; FIG. 8 is a diagram showing a modified example of the radar device of an embodiment;

[0010] Hereinafter, an embodiment to which the antenna device and radar device of the present disclosure are applied will be described.

[0011] In the following, the XYZ coordinate system will be defined and explained. For convenience of explanation, the -Z direction side will be referred to as the lower side or bottom, and the +Z direction side will be referred to as the upper side or top, but this does not represent a universal up-down relationship. Also, viewing from the XZ plane will be referred to as a planar view. Also, viewing an opening from the XZ plane will be referred to as an opening plane view.

[0012] 1A and 1B are diagrams illustrating an example of the configuration of a radar device 100 according to an embodiment. Fig. 1A is a perspective view, Fig. 1B is a diagram illustrating a cross section parallel to the YZ plane, and Fig. 1C is a perspective view illustrating an example of the configuration of a radio wave lens 130.

[0013] The radar device 100 includes a substrate 101, a waveguide 110, a transmitting / receiving unit 120, and a radio wave lens 130. The radar device 100 excluding the transmitting / receiving circuit included in the transmitting / receiving unit 120 constitutes an antenna device 100A of the embodiment. The antenna device 100A includes the substrate 101, the waveguide 110, a transmitting antenna 120Tx, a receiving antenna 120Rx, and the radio wave lens 130.

[0014] 1B is a cross section obtained by cutting the waveguide 110 along the YZ plane including the central axis C of the waveguide 110 (the optical axis of the radio wave lens 130). 1A and 1B also show an enlarged view of the substrate 101 and the transceiver unit 120 on the left side.

[0015] The antenna device 100A is a horn antenna. The waveguide 110 shown in FIGS. 1A and 1B is, for example, a rectangular waveguide that widens into a pyramidal shape, and therefore the antenna device 100A shown in FIGS. 1A and 1B is a rectangular horn antenna. Furthermore, the waveguide 110 is narrow in width (thickness) in the X direction and flat, and therefore the antenna device 100A is a flat rectangular horn antenna. Here, a configuration in which the waveguide 110 is a rectangular waveguide that widens into a pyramidal shape will be described as an example. However, the waveguide 110 may also be a circular waveguide that widens into a conical shape, in which case the antenna device 100A becomes a circular horn antenna.

[0016] The radar device 100 is a device that measures the distance to an object by transmitting and receiving radio waves, and uses a radio wave lens 130 to narrow the radiation pattern of the transmitted waves and also to focus the received radio waves.

[0017] As an example, such a radar device 100 can be used as a radar device that receives reflected waves from a measurement target and measures the distance to the measurement target. The distance to the measurement target can be measured based on the round-trip time between transmitting radio waves as transmission waves and receiving the reflected radio waves. Generally, in a radar device that measures the distance to a measurement target, the closer the measurement target is, the lower the detection accuracy becomes due to the influence of multiple reflections. This is because the closer the measurement target is, the shorter the round-trip time becomes, making it difficult to distinguish between received waves that are not multiple reflections and multiple reflected waves. When detection accuracy decreases, the shortest detectable distance (minimum detectable distance) becomes longer. The radar device 100 of this embodiment solves this problem.

[0018] A multiple-reflected wave is a radio wave that is reflected two or more times within the space surrounded by the substrate 101, the waveguide 110, the transmitting / receiving unit 120, and the radio wave lens 130. For radio waves transmitted in the +Y direction from the transmitting / receiving unit 120, multiple-reflected waves may occur, for example, by being reflected by the surface on the -Y direction side of the radio wave lens 130 without passing through the radio wave lens 130. For radio waves that have passed through the radio wave lens 130 in the -Y direction, multiple-reflected waves may occur, for example, by being reflected by the inner wall surface 113 of the waveguide 110 without directly reaching the transmitting / receiving unit 120.

[0019] The radio waves transmitted and received by the radar device 100 are, for example, radio waves in the millimeter wave band. 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 radar device 100 may be radio waves with frequencies belonging to a band other than the millimeter wave band.

[0020] <Configuration of substrate 101> The substrate 101 is a substrate on which the transceiver unit 120 is mounted, and may be, for example, a wiring substrate conforming to the FR-4 (Flame Retardant type 4) standard. The substrate 101 is fixed to the −Y direction side of the waveguide 110.

[0021] <Configuration of Waveguide 110> The waveguide 110 is, for example, a rectangular waveguide that widens into a pyramidal shape. The waveguide 110 is made of metal (conductor). The waveguide 110 has an opening 111, an opening 112, and an inner wall surface 113. The inside of the waveguide 110 is a waveguide through which radio waves propagate. The opening 111 is an example of a first opening, and the opening 112 is an example of a second opening. The centers of the openings 111 and 112 are aligned when viewed from the opening surface. The +Y direction is an example of the radiation direction of the transmitting antenna 120Tx of the transceiver unit 120.

[0022] 1A and 1B, the origin of the XYZ coordinate system coincides with the center of the opening 111, and the central axis C of the waveguide 110 coincides with the Y axis. The center of the opening 111 is the center of the opening 111 when viewed from the opening surface. The central axis C also coincides with the optical axis of the radio wave lens 130. In the figures, the central axis C and the Y axis are shown shifted from each other to make it easier to see. Note that the XYZ coordinate system is also shown in FIG. 1C.

[0023] Opening 111 is located at the end of waveguide 110 on the -Y direction side, and opening 112 is located at the end of waveguide 110 on the +Y direction side. The section that functions as waveguide 110 through which radio waves propagate is the section between openings 111 and 112. Opening 112 is larger than opening 111 when viewed from the surface of the opening. The center of opening 112 when viewed from the surface of the opening is located on the Y axis and central axis C, similar to the center of opening 111 when viewed from the surface of the opening.

[0024] The width of the opening 111 in the X direction is constant regardless of the position in the Z direction. The width of the opening 112 in the X direction is constant regardless of the position in the Z direction. The widths of the openings 111 and 112 in the X direction are equal. The length of the opening 112 in the Z direction is longer than the length of the opening 111 in the Z direction. The centers of the lengths of the openings 111 and 112 in the Z direction are aligned.

[0025] A transceiver unit 120 mounted on the substrate 101 is provided on the opening 111 side. The opening 111 surrounds the transmitting antenna 120Tx and the receiving antenna 120Rx when viewed from the opening surface. Here, as an example, the opening 111 surrounds the transceiver unit 120 having the transmitting antenna 120Tx and the receiving antenna 120Rx when viewed from the opening surface.

[0026] The inner wall surface 113 connects the openings 111 and 112. The inner wall surface 113 is rectangular in the opening plane view and widens so that the opening area increases from the opening 111 side to the opening 112 side. More specifically, the inner wall surface 113 has two surfaces parallel to the YZ plane and two surfaces that have a width in the X direction between the two surfaces and are inclined with respect to the Y and Z axes. The two surfaces parallel to the YZ plane have an isosceles trapezoidal shape in the YZ plane view, with the opening 111 side corresponding to the upper base and the opening 112 side corresponding to the lower base. The two hypotenuses of each trapezoid of the two surfaces parallel to the YZ plane are straight lines. The lengths of the two hypotenuses are equal, and the angles that the two hypotenuses make with the central axis C in the YZ plane view are equal.

[0027] The two surfaces having a width in the X direction are surfaces formed by connecting the hypotenuses of the trapezoids of the two surfaces parallel to the YZ plane in the X direction, and are rectangular when viewed from the normal direction of each of the two surfaces having a width in the X direction.

[0028] A radio wave lens 130 is attached to the inner wall surface 113. When the radio wave lens 130 is attached to the inner wall surface 113, no gap is formed between the outer edge of the radio wave lens 130 and the inner wall surface 113 when viewed from the opening surface. This is to prevent radio waves from passing through the gap between the inner wall surface 113 and the outer edge of the radio wave lens 130.

[0029] <Configuration of the Transmitter / Receiver 120> The transmitter / receiver 120 is mounted on the surface of the substrate 101 on the +Y direction side. The transmitter / receiver 120 is an example of an integrated circuit chip. The transmitter / receiver 120 has a transmitting antenna 120Tx and a receiving antenna 120Rx. The transmitting antenna 120Tx and the receiving antenna 120Rx are mounted on the surface of the transmitter / receiver 120 on the +Y direction side. The transmitter / receiver 120 incorporates a transmitting / receiving circuit connected to the transmitting antenna 120Tx and the receiving antenna 120Rx.

[0030] The transmitting / receiving unit 120 is smaller than the substrate 101 in a plan view, and is, for example, square in shape. The transmitting / receiving unit 120 is provided so as to be located at the center of the opening 111 in a plan view (opening surface view), and more specifically, is arranged so that the center of the transmitting / receiving unit 120 in a plan view is located on the central axis C. Furthermore, the Y-direction position of the surface on the +Y-direction side of the transmitting / receiving unit 120 coincides with the Y-direction position of the opening 111.

[0031] The transmitting antenna 120Tx and the receiving antenna 120Rx are provided on the surface on the +Y direction side of the transceiver unit 120, spaced apart in the Z direction. The transmitting antenna 120Tx and the receiving antenna 120Rx are, for example, antennas of the same 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.

[0032] The transmitting antenna 120Tx and the receiving antenna 120Rx are arranged so as to be point-symmetrical 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 synonymous with viewing the transmitting antenna 120Tx and the receiving antenna 120Rx from the opening surface of the opening 111 (plan view).

[0033] The transmitting antenna 120Tx and the receiving antenna 120Rx being point-symmetric with respect to the central axis C in a planar view means that the center of the transmitting antenna 120Tx in a planar view and the center of the receiving antenna 120Rx in a planar view are arranged point-symmetric with respect to the central axis C in a planar view. The center of the transmitting antenna 120Tx in a planar view and the center of the receiving antenna 120Rx in a planar view are both located on the Z axis. Because the central axis C coincides with the optical axis of the radio wave lens 130, the transmitting antenna 120Tx and the receiving antenna 120Rx are arranged offset from the optical axis of the radio wave lens 130.

[0034] Furthermore, the center of the transmitting antenna 120Tx in a planar view and the center of the receiving antenna 120Rx in a planar view are both located on the Z axis, and are arranged in a planar view so as to be point-symmetric with respect to the central axis C. Therefore, in a cross section (see FIG. 1B ) obtained by cutting the waveguide 110 in the YZ plane including the optical axis of the radio wave lens 130, the transmitting antenna 120Tx and the receiving antenna 120Rx are arranged so as to be point-symmetric with respect to the central axis C.

[0035] 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 wave lens 130), they are placed in this manner to align 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 realized by, for example, a loop antenna, a patch antenna, a monopole antenna, a dipole antenna, or the like.

[0036] Furthermore, the position in the Y direction of the surface on the +Y direction side of the transmitting / receiving unit 120 coincides with the position in the Y direction of the opening 111 .

[0037] 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 wave lens 130. 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 wave lens 130. The center of the radio wave lens 130 is located on the optical axis of the radio wave lens 130 (the central axis C of the waveguide 110) and at the center of the thickness of the radio wave lens 130 in the Y direction.

[0038] <Configuration of Radio Wave Lens 130> The radio wave lens 130 is fixed to the inner wall surface 113 of the waveguide 110. The radio wave lens 130 may be fixed to the inner wall surface 113 using adhesive, double-sided tape, a jig, or the like. The radio wave lens 130 is made of glass or resin, for example. The radio wave lens 130 may be any lens that can focus radio waves transmitted and received by the transmitting antenna 120Tx and the receiving antenna 120Rx in both directions, and is, for example, a biconvex lens that is rectangular in plan view. However, the radio wave lens 130 may also be a single-convex lens. A biconvex lens and a single-convex lens are examples of a convex lens.

[0039] The radio wave lens 130 has surfaces 131 and 132. The surface 131 is an example of a first surface and is the surface on the −Y direction side of the radio wave lens 130. The surface 132 is an example of a second surface and is the surface on the +Y direction side of the radio wave lens 130.

[0040] 1B , radio wave lens 130, which is composed of a biconvex lens that is rectangular in plan view, has surfaces 131 and 132 that protrude symmetrically and are curved with respect to the XZ plane that passes through the center in the Y direction of radio wave lens 130. The center of the length of surface 131 in the Z direction protrudes the most toward the −Y direction, and the center of the length of surface 132 in the Z direction protrudes the most toward the +Y direction. Surfaces 131 and 132 have shapes that are symmetrical on the +Z direction side and the −Z direction side with respect to the center of the length in the Z direction, and have shapes that are not curved in the X direction.

[0041] Furthermore, as an example, the surfaces 131 and 132 are provided with unevenness to suppress reflection of radio waves. As an example, the unevenness is provided from the end on the -Z direction side to the end on the +Z direction side along the curved shape of the surfaces 131 and 132 in the YZ plane view. If the wavelength within the lens of the radio waves emitted by the radar device 100 is λe, then the depth of the unevenness may be set to λe / 4, for example. The phase of the radio waves reflected by the concave portions and the radio waves reflected by the convex portions is shifted by 180 degrees, so that the reflected waves can be canceled out. Note that the radio wave lens 130 does not have to have unevenness.

[0042] The surface 131 is located more inward in the waveguide 110 than the opening 111. "The surface 131 is located more inward in the waveguide 110 than the opening 111" means that the portion of the surface 131 that protrudes most in the -Y direction is located more inward (more in the +Y direction) in the waveguide 110 than the opening plane, which is a plane that includes the opening edge and center of the opening 111. The portion of the surface 131 that protrudes most in the -Y direction is a portion that extends in the X direction at the center of the surface 131 in the Z direction.

[0043] The surface 132 is located inside the waveguide 110 with respect to the opening 112. "The surface 132 is located inside the waveguide 110 with respect to the opening 112" means that the portion of the surface 132 that protrudes most toward the +Y direction is located inside the waveguide 110 (on the -Y direction side) with respect to the opening plane, which is a plane including the opening edge and center of the opening 112. The portion of the surface 132 that protrudes most toward the +Y direction is a portion of the surface 132 that extends in the X direction at the center of the surface 132 in the Z direction. Note that the surface 132 does not come into direct contact with the outside air. The surface 132 is exposed inside the waveguide 110 when viewed from the opening 112.

[0044] When attached to the inner wall surface 113, the radio wave lens 130 is configured so that no gap is created between the outer edge of the radio wave lens 130 and the inner wall surface 113 when viewed from the opening surface from the −Y direction side and the +Y direction side. This is to ensure that all transmission waves radiated from the transmitting antenna 120Tx are incident on the radio wave lens 130, and that no transmission waves are generated that propagate toward the opening 112 without entering the radio wave lens 130. Also, this is to ensure that all reflected waves reflected toward the −Y direction by the opening 112 are incident on the radio wave lens 130, and that no reflected waves are propagated toward the opening 111 without entering the radio wave lens 130.

[0045] To achieve this configuration, the outer edge of the radio wave lens 130 has a size that closes the gap between it and the inner wall surface 113 when viewed from the opening side. The position of the radio wave lens 130 in the Y direction is predetermined. Therefore, by matching the width in the X direction and the length in the Z direction of the outer edge of the radio wave lens 130 to the width in the X direction and the length in the Z direction of the portion of the inner wall surface 113 where the radio wave lens 130 is disposed, it is possible to prevent a gap from occurring between the outer edge of the radio wave lens 130 and the inner wall surface 113. Note that the outer edge of the radio wave lens 130 refers to a portion that includes the outer surface connecting the surfaces 131 and 132 of the radio wave lens 130 and the edge portions of the surfaces 131 and 132 along the outer surfaces. The position of the outer edge of the radio wave lens 130 corresponds to the position of the outer surface connecting the surfaces 131 and 132 when the radio wave lens 130 is viewed from above.

[0046] Furthermore, if the length of the waveguide 110 in the Y direction is L (see FIG. 1B), the distance P in the Y direction from the transmitting antenna 120Tx and the receiving antenna 120Rx of the transceiver unit 120 of the radio lens 130 is 2 / 3 or less of the distance L. That is, P≦2L / 3. In FIG. 1B, as an example, P is L / 3. Note that the length L of the waveguide 110 in the Y direction corresponds to the distance between the openings 111 and 112.

[0047] By offsetting the radio wave lens 130 in the −Y direction from the opening 112 and providing it inside the waveguide 110, it is possible to shorten the distance P while ensuring a certain length L of the waveguide 110. By ensuring a certain length L of the waveguide 110, it is possible to increase the opening area of ​​the opening 112 to a certain extent, thereby increasing the gain of the waveguide 110. Furthermore, by shortening the distance P, the propagation distance of radio waves traveling back and forth between the transmitter / receiver 120 and the surface 131 of the radio wave lens 130 due to multiple reflections is shortened, and by narrowing the range in which reflected waves due to multiple reflections occur, it is possible to shorten the minimum detection distance. Furthermore, by using the radio wave lens 130 in this manner, it is possible to focus the radio waves that have passed through the radio wave lens 130 and narrow the beam emitted from the radar device 100.

[0048] Furthermore, radio wave lens 130 is configured so that the phase of the radio waves is aligned over the entire area from the end of opening 112 on the -Z direction side to the end on the +Z direction side (the entire aperture plane of opening 112) in order to convert the beam radiated from opening 112 in the +Y direction into a plane wave. More specifically, the thickness and relative dielectric constant of radio wave lens 130 in the Y direction are configured so that the phase of the radio waves that are transmitted from transmitting antenna 120Tx, pass through radio wave lens 130, and reach the aperture plane of opening 112 is aligned over the entire aperture plane. This will be described using FIG. 1D .

[0049] 1D is a diagram illustrating an example of propagation paths A to C in the radar device 100. Propagation path A is an example of a first propagation path, propagation path B is an example of a second propagation path, and propagation path C is an example of a third propagation path.

[0050] Propagation path A is a path along which, in the YZ plane view, radio waves (transmission waves) radiated from the transmitting antenna 120Tx pass through the radio wave lens 130 and reach the end of the opening 112 on the +Z direction side. Note that, in the YZ plane view, propagation path A is also the path along which radio waves radiated from the transmitting antenna 120Tx pass through the radio wave lens 130 and reach the end of the opening 112 on the −Z direction side. The end of the opening 112 on the +Z direction side or the −Z direction side is the part of the opening edge of the opening 112 along which the distance over which the radio waves radiated from the transmitting antenna 120Tx propagate within the waveguide 110 is the longest.

[0051] Propagation path B is a path along which, in the YZ plane view, radio waves (transmission waves) radiated from the transmitting antenna 120Tx propagate in the +Y direction (front direction), pass through the radio wave lens 130, and reach the center of the aperture 112. That is, propagation path B is a path along which waves propagate in a straight line from the transmitting antenna 120Tx in the front direction, pass through the radio wave lens 130, and reach the center of the aperture 112. Note that, because the transmitting antenna 120Tx is slightly offset from the central axis C, when waves propagate in a straight line from the transmitting antenna 120Tx in the front direction, they arrive at a point on the aperture plane of the aperture 112 that is slightly offset from the aperture center. However, because this difference can be ignored, here, the path along which waves propagate in a straight line from the transmitting antenna 120Tx in the front direction and reach the aperture plane of the aperture 112 is treated as propagation path B.

[0052] Propagation path C is a path along which, in the YZ plane view, radio waves (transmission waves) radiated from the transmitting antenna 120Tx propagate linearly in an arbitrary direction within the waveguide 110, pass through the radio wave lens 130, and reach an arbitrary point on the aperture plane of the opening 112. In other words, propagation path C is a path from the transmitting antenna 120Tx to an arbitrary point on the aperture plane including the edge and center of the opening 112.

[0053] Here, the phase delay amount of the radio wave along propagation path A is denoted by φa, the phase delay amount of the radio wave along propagation path B is denoted by φb, and the phase delay amount of the radio wave along propagation path C is denoted by φc. The phase delay amount φa is an example of a first phase delay amount and is the phase delay amount of the radio wave that travels through transmission path A and arrives at the end of the aperture 112 on the +Z direction side relative to the phase of the radio wave transmitted from the transmitting antenna 120Tx. The phase delay amount φb is an example of a second phase delay amount and is the phase delay amount of the radio wave that travels through transmission path B and arrives at the center of the aperture 112 relative to the phase of the radio wave transmitted from the transmitting antenna 120Tx. The phase delay amount φc is an example of a third phase delay amount and is the phase delay amount of the radio wave that travels through transmission path C and arrives at an arbitrary point on the aperture plane of the aperture 112 relative to the phase of the radio wave transmitted from the transmitting antenna 120Tx.

[0054] Also, as shown in FIG. 1D , La1 is the distance from the transmitting antenna 120Tx to the surface 131 on the propagation path A, Lae is the distance within the radio wave lens 130 from the surface 131 to the surface 132 on the propagation path A, and La2 is the distance from the surface 132 to the edge of the opening 112 on the propagation path A.

[0055] Furthermore, Lb1 is the distance from the transmitting antenna 120Tx to the surface 131 on the propagation path B, Lbe is the distance within the radio wave lens 130 from the surface 131 to the surface 132 on the propagation path B, and Lb2 is the distance from the surface 132 to the opening edge of the opening 112 on the propagation path B.

[0056] Furthermore, Lc1 is the distance from the antenna (transmitting antenna 120Tx) to surface 131 on propagation path C, Lce is the distance within radio wave lens 130 from surface 131 to surface 132 on propagation path C, and Lc2 is the distance from surface 132 to the opening edge of opening 112 on propagation path C.

[0057] The phase delay amounts φa, φb, and φc can be expressed by the following equations (1) to (3), respectively: εr is the relative dielectric constant of the radio wave lens 130, and λ is the wavelength in the waveguide.

[0058]

[0059]

[0060]

[0061] As an example, the radio wave lens 130 is configured so that the phase difference between the phase delay amount φb and the phase delay amount φa, and the phase difference between the phase delay amount φb and the phase delay amount φc are within ±45 degrees. Note that, as an example, the phase difference is expressed as a positive value when a phase that lags the phase delay amount φb is used as a reference, and a phase that leads the phase delay amount φb is expressed as a negative value.

[0062] Here, the phase difference between the phase delay amount φb and the phase delay amount φa, and the phase difference between the phase delay amount φb and the phase delay amount φc being within ±45 degrees has the following meaning: That is, even if the transmission wave radiated from the transmitting antenna 120Tx reaches any point other than the aperture center on the aperture plane of the aperture 112, the phase difference with the phase of the transmission wave that reaches the aperture center via propagation path B is within a certain range, and is within a range in which the phases can be considered to be approximately equal.

[0063] When the phase of the transmission wave radiated from the transmitting antenna 120Tx and arriving on the aperture plane of the aperture 112 is perfectly aligned, the beam radiated from the aperture 112 becomes a completely phase-aligned plane wave. If the beam radiated from the aperture 112 is a plane wave, a beam with high gain can be obtained, and by irradiating the object to be measured with the plane wave beam and receiving the wave reflected by the object to be measured, the distance from the radar device 100 to the object to be measured can be detected with high accuracy.

[0064] However, in reality, it is not easy to radiate a perfect plane wave beam from the opening 112, so the radio wave lens 130 is configured so that the phase difference between the phase delay amount φb and the phase delay amount φa, and the phase difference between the phase delay amount φb and the phase delay amount φc are within the allowable range of ±45 degrees.

[0065] It is more preferable that the phase difference between the phase delay amount φb and the phase delay amount φa, and the phase difference between the phase delay amount φb and the phase delay amount φc, are as small as possible. For this reason, it is more preferable that this phase difference is within ±30 degrees, and even more preferably within ±20 degrees, and therefore it is more preferable to configure the radio wave lens 130 so that such a phase difference can be realized.

[0066] <Experimental Results> Figure 2A is a diagram showing an example of experimental results of the minimum detection distance in the radar device 100. Figure 2B is a diagram showing an example of experimental results of the minimum detection distance in a comparative radar device. The comparative radar device has a configuration in which the radio wave lens 130 of the radar device 100 is attached to the opening 112. Attaching the radio wave lens 130 to the opening 112 means that the center of the thickness of the radio wave lens 130 in the Y direction is located at the opening 112, and the half of the radio wave lens 130 on the +Y direction side protrudes outward beyond the opening 112.

[0067] The frequency of the radio waves emitted from the transmitting antenna 120Tx was set to 60 GHz, and the length L of the waveguide 110 was set to 120 mm to achieve a narrow beam with a beam width of 1 to 3 degrees. Also, the distance P representing the position of the radio wave lens 130 was set to 40 mm. In other words, P = L / 3.

[0068] 2A and 2B, the horizontal axis represents the distance (mm) between the surface of the transceiver 120 on the +Y direction side of the radar device 100 and the comparative radar device and the object to be measured, and the vertical axis represents the output strength (unitless) of the radar detection signal of the radar device 100 and the comparative radar device. The output strength of the radar detection signal is not limited to the strength of the received wave alone, but may also include the strength of multiple reflected waves. The dashed line at the value of 500 on the vertical axis indicates the threshold level at which the radar device 100 and the comparative radar device determine the presence of an object to be measured based on the output strength of the radar detection signal.

[0069] 2A and 2B show, as an example, the output strength of the radar detection signal received by the receiving antenna 120Rx of the radar device 100 and a comparative radar device when the measurement target is placed at a distance of 2050 mm to show the output strength of the radar detection signal when the measurement target is present. 2A and 2B show the output strength of the radar detection signal on the long-distance side, from 0 mm to 2200 mm.

[0070] 2A and 2B, it can be seen that the output strength of the radar detection signal of the radar device 100 of the embodiment shown in Fig. 2A is lower at short distances than the output strength of the radar detection signal of the comparative radar device shown in Fig. 2B. As an example, it is assumed that a measurement target can be detected if the output strength of the radar detection signal is 500 or less.

[0071] As shown in Figure 2B, the comparative radar device was affected by multiple reflections up to approximately 800 mm. Specifically, multiple reflections were observed, ranging from a first reflected wave occurring at a distance of approximately 150 mm to a fifth reflected wave occurring at a distance of approximately 800 mm. The minimum detection distance of the comparative radar device was approximately 800 mm.

[0072] 2A, in the radar device 100 of the embodiment, multiple reflections were observed, from the first reflected wave occurring at a distance of about 30 mm to the fifth reflected wave occurring at a distance of about 220 mm. The interval from the first reflected wave to the fifth reflected wave was shorter than in the comparative radar device because the distance between the transmitter / receiver 120 and the radio wave lens 130 was shorter.

[0073] In the radar device 100 of the embodiment, the influence of multiple reflections occurred up to about 230 mm, and the minimum detection distance was about 230 mm. In other words, it was confirmed that the radar device 100 of the embodiment can measure up to a short distance of about 230 mm.

[0074] As described above, the radar device 100 of the embodiment can significantly shorten the distance affected by multiple reflections compared to the comparative radar device. This is because the radio wave lens 130 is disposed closer to the transmitter / receiver 120. Furthermore, because the waveguide 110 is the same size as that of the comparative radar device, the gain of the beam emitted from the waveguide 110 can be maintained at the same level as that of the comparative radar device. This was confirmed by the fact that the output level of a measurement target occurring at a distance of approximately 2050 mm was the same for the radar device 100 of the embodiment ( FIG. 2A ) and the comparative radar device ( FIG. 2B ).

[0075] <Modification> FIGS. 3A to 3C are diagrams showing modifications of the radar device 100 of the embodiment.

[0076] <Fig. 3A> As shown in Fig. 3A, the radio wave lens 130 may be a Fresnel lens. The radio wave lens 130 shown in Fig. 3A is a Fresnel lens and has concave and convex surfaces 131 and 132, but the concave and convex surfaces do not have to be provided. By configuring the radio wave lens 130 as a Fresnel lens, it is possible to reduce the thickness of the radio wave lens 130.

[0077] < Figure 3B > As shown in Figure 3B , the end of waveguide 110 on the +Y direction side where opening 112 is located may be curved when viewed in the YZ plane. The positions of the -Z direction end and the +Z direction end of the +Y direction end of waveguide 110 shown in Figure 3B are equal to the positions of the -Z direction end and the +Z direction end of the +Y direction end of waveguide 110 shown in Figures 1A to 1D . The +Y direction end of waveguide 110 shown in Figure 3B is curved so as to protrude from the -Z direction end and the +Z direction end toward the center in the Z direction (the position of central axis C when viewed in the YZ plane).

[0078] The curved shape of the +Y direction end of the waveguide 110 is a continuous curve between the −Z direction end and the +Z direction end when viewed in the YZ plane. The +Y direction end of the waveguide 110 shown in FIG. 3B protrudes furthest toward the +Y direction at the center in the Z direction (the position of the central axis C when viewed in the YZ plane). Therefore, the distance from the transmitting antenna 120Tx to the center in the Z direction of the +Y direction end of the waveguide 110 is longer than the distance from the transmitting antenna 120Tx to the −Z direction end and the +Z direction end of the +Y direction end of the waveguide 110.

[0079] 1A to 1D is used, the phase delay amount of the radio wave at the opening 112 varies more depending on the position in the Z direction. Therefore, when the waveguide 110 shown in FIG. 3B is used, the phase shift of the reflected wave that propagates in the +Y direction within the waveguide 110 and is reflected in the -Y direction at the opening 112 varies more than when the waveguide 110 shown in FIGS. 1A to 1D is used, and the output level of the reflected wave due to multiple reflections can be reduced. As a result, the minimum detection distance can be shortened.

[0080] <Fig. 3C> In the radar device 100 shown in Fig. 3C, the waveguide 110 is conical, and the radio wave lens 130 is a biconvex lens that is circular when viewed from the aperture surface. The radio wave lens 130 does not need to have unevenness on the surfaces 131 and 132, and may also be a monoconvex lens. When the waveguide 110 is conical, it can emit a beam with a substantially circular radiation cross section. The waveguide 110 may also be an elliptical cone or a pyramid. The radio wave lens 130 may also be a Fresnel lens.

[0081] <Effects> Antenna device 100A includes: waveguide 110 having opening 111, opening 112 that is larger than opening 111 in a plan view of the opening; and inner wall surface 113 that connects openings 111 and 112; an antenna (transmitting antenna 120Tx) that is provided in opening 111 facing the inside of waveguide 110 so as to be located inside opening 111 in a plan view of the opening; and radio wave lens 130 that is provided inside waveguide 110, and has surface 131 that is located on the opening 111 side and is located more inside waveguide 110 than opening 111, surface 132 that is located on the opening 112 side and is located more inside waveguide 110 than opening 112, and an outer edge portion that is sized to close a gap between inner wall surface 113 in a plan view of the opening. Therefore, the distance between the antenna (transmitting antenna 120Tx) and the radio wave lens 130 is shortened, and the range in which reflected waves due to multiple reflections occur is narrowed, thereby shortening the minimum detection distance.

[0082] Therefore, it is possible to provide the antenna device 100A with a reduced minimum detection distance.

[0083] The radio wave lens 130 may be configured so that the phase of the radio waves emitted from the transmitting antenna (transmitting antenna 120Tx) is aligned at the opening 112. A high-gain plane wave beam can be emitted from the opening 112, and the distance from the radar device 100 to the measurement target can be detected with high accuracy.

[0084] If the first phase delay of the radio wave on propagation path A from the antenna (transmitting antenna 120Tx) to the opening edge of the opening 112 is φa, the second phase delay of the radio wave on propagation path B from the antenna (transmitting antenna 120Tx) to the opening center of the opening 112 is φb, and the third phase delay of the radio wave on propagation path C from the antenna (transmitting antenna 120Tx) to an arbitrary point on the opening plane including the opening edge and the opening center of the opening 112 is φc, the first phase delay φa, the second phase delay φb, and the third phase delay φc are respectively expressed by the following equations (1) to (3), and the radio wave lens 130 may be configured so that the phase difference between the second phase delay φb and the first phase delay φa, and the phase difference between the second phase delay φb and the third phase delay φc are within ±45 degrees.

[0085]

[0086]

[0087] where εr is the relative dielectric constant of the radio wave lens 130, and λ is the wavelength within the waveguide. Furthermore, La1 is the distance from the antenna (transmitting antenna 120Tx) to the surface 131 on propagation path A, Lae is the distance from the surface 131 to the surface 132 on propagation path A, and La2 is the distance from the surface 132 to the edge of the opening 112 on propagation path A. Furthermore, Lb1 is the distance from the antenna (transmitting antenna 120Tx) to the surface 131 on propagation path B, Lbe is the distance from the surface 131 to the surface 132 on propagation path B, and Lb2 is the distance from the surface 132 to the edge of the opening 112 on propagation path B. Furthermore, Lc1 is the distance from the antenna (transmitting antenna 120Tx) to surface 131 on propagation path C, Lce is the distance from surface 131 to surface 132 on propagation path C, and Lc2 is the distance from surface 132 to the opening edge of opening 112 on propagation path C.

[0088] By keeping the phase difference between the second phase delay φb and the first phase delay φa, and the phase difference between the second phase delay φb and the third phase delay φc within ±45 degrees, a high-gain plane wave beam can be emitted from the opening 112, and the distance from the radar device 100 to the object to be measured can be detected with high accuracy.

[0089] Furthermore, the distance between the radio wave lens 130 and the antenna (transmitting antenna 120Tx) may be equal to or less than two-thirds of the distance between the opening 111 and the opening 112 of the waveguide 110. By shortening the distance between the antenna (transmitting antenna 120Tx) and the radio wave lens 130, the range in which reflected waves due to multiple reflections occur is narrowed, thereby shortening the minimum detection distance.

[0090] The radio wave lens 130 may be a Fresnel lens, which allows the radio wave lens 130 to be made thinner.

[0091] The antenna device 100A may further include a substrate 101 on which an antenna (transmitting antenna 120Tx) is mounted, thereby making it possible to provide an antenna device 100A on which an antenna (transmitting antenna 120Tx) can be easily mounted.

[0092] The radar device 100 includes the above-described antenna device 100A, an antenna (transmitting antenna 120Tx), and a transmitting / receiving circuit connected to the antenna (transmitting antenna 120Tx), and includes a transmitting / receiving unit 120 mounted on a substrate 101.

[0093] Therefore, it is possible to provide a radar device 100 with a reduced minimum detection distance.

[0094] The above describes exemplary embodiments of an antenna device and a radar device according to the present disclosure. However, the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0095] This international application claims priority based on Japanese Patent Application No. 2024-009028, filed on January 24, 2024, the entire contents of which are incorporated herein by reference.

[0096] REFERENCE SIGNS LIST 100 Radar device 100A Antenna device 101 Substrate 110 Waveguide 111 Opening (an example of a first opening) 112 Opening (an example of a second opening) 113 Inner wall surface 120 Transmitting / receiving unit (an example of an integrated circuit chip) 120Tx Transmitting antenna 120Rx Receiving antenna 130 Radio wave lens 131 Surface (an example of a first surface) 132 Surface (an example of a second surface)

Claims

1. A waveguide having a first opening, a second opening that is larger than the first opening when viewed from the opening surface, and an inner wall surface connecting the first opening and the second opening, An antenna is provided in the first opening so as to be located inside the first opening when viewed from the opening surface, and facing the inside of the waveguide. A radio wave lens provided inside the waveguide, comprising: a first surface located on the first opening side and positioned inside the waveguide beyond the first opening; a second surface located on the second opening side and positioned inside the waveguide beyond the second opening; and an outer edge having a size that closes the gap between it and the inner wall surface when viewed from the opening surface. Antenna equipment, including

2. The antenna device according to claim 1, wherein the radio wave lens is configured such that the phase of the radio waves radiated from the antenna is aligned at the second aperture.

3. If φa is the first phase delay of the radio wave in the first propagation path from the antenna to the aperture edge of the second aperture, φb is the second phase delay of the radio wave in the second propagation path from the antenna to the aperture center of the second aperture, and φc is the third phase delay of the radio wave in the third propagation path from the antenna to any point on the aperture plane including the aperture edge and the aperture center of the second aperture, The first phase delay φa, the second phase delay φb, and the third phase delay φc are expressed by the following equations (1) to (3), The antenna device according to claim 1, wherein the radio wave lens is configured such that the phase difference between the second phase delay φb and the first phase delay φa, and the phase difference between the second phase delay φb and the third phase delay φc are within ±45 degrees. [Math 1] [Math 2] [Math 3] Here, εr is the relative permittivity of the radio wave lens, and λ is the wavelength inside the waveguide. La1 is the distance from the antenna to the first surface on the first propagation path, Lae is the distance from the first surface to the second surface on the first propagation path, and La2 is the distance from the second surface to the aperture edge of the second aperture on the first propagation path. Lb1 is the distance from the antenna to the first surface on the second propagation path, Lbe is the distance from the first surface to the second surface on the second propagation path, and Lb2 is the distance from the second surface to the aperture edge of the second aperture on the second propagation path. Lc1 is the distance from the antenna to the first surface on the third propagation path, Lce is the distance from the first surface to the second surface on the third propagation path, and Lc2 is the distance from the second surface to the aperture edge of the second aperture on the third propagation path.

4. The antenna device according to any one of claims 1 to 3, wherein the distance between the radio wave lens and the antenna is 2 / 3 or less of the distance between the first opening and the second opening of the waveguide.

5. The antenna device according to claim 1, wherein the radio wave lens is a Fresnel lens.

6. The antenna device according to claim 1, further comprising a substrate on which the antenna is mounted.

7. The antenna device according to claim 6, The integrated circuit chip mounted on the substrate has the antenna and a transmitting / receiving circuit connected to the antenna. Radar equipment, including

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